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Carbon black filled shell of high density wood-polyethylene composites to balance the antistatic properties and mechanical properties
Liu, C., Mei, C., Wang, K., Jiang, M., Chen, W., and Liu, B. (2018). "Carbon black filled shell of high density wood-polyethylene composites to balance the antistatic properties and mechanical properties," BioRes. 13(3), 6356-6369.
Carbon black (CB) was used to fill the shell of wood high-density polyethylene (HDPE) composite to improve its antistatic properties and simultaneously maintain its mechanical properties. The conductivity analysis revealed that the percolation threshold of the CB in coextruded WPC was between 15% and 20%, and the surface resistivity of the sample containing 20% CB (CW-20) achieved the floor antistatic requirements of an electronic information system room and its support area according to GB/T 50174 (2017). The addition of CB into the shell of the coextruded WPC inhibited its crystallization. The mechanical properties of coextruded WPC were increased when the CB content was increased. The flexural strength, flexural modulus, and impact strength of the CW-20 sample were increased by 21.6%, 10.8%, and 26.1%, respectively. In addition, the dosage of CB in regular WPCs was 6.71 times as much as that of coextruded WPCs, which achieved similar antistatic and mechanical properties of the two structural WPCs. These results demonstrated that the low CB filled shell of HDPE composite exhibited a large reduction in its surface resistivity and a significant enhancement in its mechanical properties, which expands the application of coextruded WPCs in flammable and explosive uses while also improving the antistatic and mechanical properties.
Chaozheng Liu, Changtong Mei,* Ke Wang, Min Jiang, Weimin Chen, and Bo Liu
Keywords: Wood-flour composites; Coextrusion; Carbon black; Mechanical properties; Antistatic properties
Contact information: College of Materials Science and Engineering, Nanjing Forestry University, Nanjing 210037, China; *Corresponding author: mei@njfu.edu.cn
Wood plastic composites (WPCs), which have emerged as constructive and decorative materials, are rarely used in flammable and explosive applications due to their electrostatic discharge. Electrostatic charge is easily produced on the surface of WPCs by rubbing, as thermoplastics and lignocellulose fibers show excellent electrical insulation properties (Yossef et al. 2001; Gao et al. 2010). WPCs prepared by thermoplastics and wood flour are poor conductors of electricity, and they easily generate electrostatic accumulation to cause dust, electric shock (discharge), burning, and even explosions. It is necessary to conduct an antistatic treatment for WPCs before their use in certain applications, such as program-controlled equipment rooms, operating rooms, or electronic components production workshops (Luo et al. 2000). In addition, the antistatic properties of WPCs are crucial, especially for indoor environments such as conference rooms or costly computer rooms, because excessive accumulation of electrostatic charge is detrimental to human health and electronic devices (Yu et al. 2017). There is a large amount of research on antistatic polymers. In contrast, the antistatic properties of WPCs are rarely reported, and their products have not been widely used in the market (Pinto et al. 2004; Zheng et al. 2004; Zhang et al. 2010; Cao et al. 2013). To improve the antistatic properties of polymers, various conductive fillers have been added, including metal powder or fiber (Malliaris and Turner 1971; Aharoni 1972), carbon black (CB) (Abdel-Bary et al. 1979; Miyasaka et al. 1982; Narkis et al. 2010), and carbon fiber (Wang and Peng 1997; Wu et al. 1999).
CB is one of the most widely used conductive fillers because of its light weight, low cost, and permanent conductivity (Song and Zheng 2005; Chen et al. 2006; Liao and Wang 2014). CB has a strong electrical conductivity and can be dispersed in the composites in a relatively uniform fashion due to its small particle size, which can form a continuous conductive network in the matrix, thereby improving the conductivity of the composites (Liu et al. 2010). The addition of CB is effective for decreasing the volume resistivity of polypropylene (PP), epoxy, and glass fiber composites (Tchoudakovet al. 1996). The electrical conductivity of polymer/CB composites increases sharply at a critical filler concentration, called the percolation threshold, due to the formation of a three-dimensional conductive network throughout the polymer matrix (Yu et al. 2017). Previous research has shown the percolation values for the critical transition in filler-based composites are 6.2 wt% for PP/CB (Zois et al. 1999) and 9 wt% for nylon 6/CB (Pinto et al. 2004). However, high loadings of CB (15 wt% to 20 wt%) in the polymer matrix was required to achieve the conductive percolation threshold, leading to the high cost, poor mechanical properties, and complex processing of the composites (Narkis et al. 1999; Rosner 2001; Cheah et al. 2015). The CB distribution was affected by the surface tension (Sumita et al.1991; Tchoudakov et al. 1996) and interfacial free energy (Asai et al.1992). It also depends on the polymer crystallinity (Gubbels et al.1994), viscosity (Feng and Chan 2000; Mironi-Harpaz and Narkis 2001a; Mironi-Harpaz and Narkis 2001b), and processing (Gubbels et al. 1994; Cheah et al. 2015). When the CB concentration reaches the percolation level in the continuous CB-rich phase, double percolation is achieved, and the percolation threshold is lowered (Tchoudakov et al. 1997; Breuer et al. 2015; Foulger 2015). For instance, Gubbels et al. reported that the electrical percolation threshold can be lowered to 0.2 to 0.3 v/v% when the CB particles were selectively localized at the interface of a co-continuous polyethylene/polystyrene (PE/PS) blend (Jamshid 1998).
However, introducing conductive fillers into an immiscible polymer blend, due to its weak interfacial interactions, has caused a decline in mechanical properties, especially in tensile properties (Gao et al. 2012; Cheah et al. 2015). Therefore, it is essential to find an optimal balance between the antistatic and the mechanical properties for the design of the polymer composites. Coextrusion technology, a method to make a protective surface, can produce a multilayer board with different properties in the outer and inner layers. Since electrostatic charge primarily occurs at the surface of a material (Yossef et al. 2001; Gao et al. 2010), pursuing a cost-effective means to cope with electrostatic charge would not favor adding conductive fillers into the bulk of a material instead of the surface. The coextruded WPCs with a high-density polyethylene (HDPE) cap layer significantly optimized the water resistance and flexural strength in comparison to the regular WPCs (Jiang et al. 2007; Rauwendaal 2010; Liu et al. 2018). Adding 3% CB into the shell layer of PP based WPC improved the tensile strength and hardness by 45% and 25%, respectively (Turku and Kärki 2014). The addition of CB has been shown to be effective in enhancing the antistatic properties of virgin plastic (Mamunya et al. 1996; Ishigure et al. 1999; Dudler et al. 2000; Pinto et al. 2004), however, the addition of CB to the HDPE shell of coextruded WPC has not yet been demonstrated to simultaneously improve its antistatic and mechanical properties.
The objective of this study was to reduce the composite cost and balance the antistatic and the mechanical properties of the composites through adding CB into the shell of coextruded WPCs. To achieve this, the effects of CB (0%, 5%, 10%, 15%, and 20%) on the antistatic, thermal, and mechanical properties of the coextruded and regular WPCs were studied using an ultrahigh resistance meter, universal testing machine, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Comparative analysis of regular and coextruded WPCs was done to confirm the advantages of cost and properties in coextruded WPCs. The obtained results gave a comprehensive understanding of how to seek a balance between the antistatic properties and the mechanical properties, and to apply coextruded WPCs in flammable and explosive applications.
The wood flour (WF) passing through a sieve of 80-mesh, but retained on the 100-mesh sieve, was prepared by Pucheng Wood Industry Co. Ltd. (Xuzhou, China). The HDPE (density: 0.951 g/cm3, melt flow index: 0.095 g/min, grade: 5000 s) and the coupling agent (MAH-g-PE) were supplied by Yangzi Petrochemical Co. Ltd. (Nanjing, China). The CB (Type F900B) with a specific surface area of 0.75 to 1.1 m2/g and a particle size of 9 to 17 nm, as a conductive filler, was obtained from Yiborui Chemical Co. Ltd. (Tianjin, China). The anhydrous ethanol, with a density of 0.79 g/mL, was obtained from Nanjing Chemical Reagent Co. Ltd. (Nanjing, China). Talcum with a particle size of 500 mesh was supplied by Jinqiang Limestone Co. Ltd. (Nanjing, China) and its main components were SiO2 and MgO. The polyethylene wax was obtained from Hongsheng Chemical Co. Ltd. (Dongguan, China).
Preparation of Coextruded HDPE / Wood-Plastic Composites
The composition and the labeling of the studied formulations are shown in Table 1. CW denotes coextruded WPC, and RW denotes regular WPC. The modified CB was prepared by suction filtration after stirring 100 g CB, 3 mL KH-570, and 200 mL anhydrous ethanol in a 500 mL three-necked bottle for 1 h at 80 °C (Bai and Li 2014; Guo et al. 2015). WPC with a core-shell structure was prepared using coextrusion technology. The HDPE and the CB were dried in an oven at 103 ± 2 °C for 24 h, and then they were placed in an open mill (Zhenggong Electromechanical Equipment Technology Co. Ltd., Type ZG-160, the speed of the main engine at 8 rpm, Dongguan, China) to mix at 150 °C for 10 min. The mixed materials were disposed in a claw crusher (Nagin Machinery Co. Ltd., Type NPCY-50J, Dongguan, China) to break down the particles of the shell layer composites. The WF was dried in an oven at 103 ± 2 °C for 8 h. The formulation of the core layer composites contained 51.3% wood powder, 34.2% HDPE, 4.3% MAH-g-PE, 8.5% talcum, and 1.7% polyethylene wax, based on the total weight of the composites. The blended core layer composites were placed into the high-speed mixer (Huaming Machinery Co., Type SHR-10A, with the speed of the main engine at 1500 rpm, Zhangjiagang, China) for 10 min to disperse the particles uniformly, and then were put into a conical twin screw extruder (Jinwei Machinery Manufacturing Co., Type SJZ45/100, Shenzhen, China) for granulation. Then, the core layer composites particles were fed through the core layer extruder (Type SJZ45/100, the speed of the main engine at 5 rpm, the range of the temperature from 150 to 185 °C), and the particles of the shell layer composites were placed in the shell extruder (Type JWS35/25, the speed of the main engine at 8 rpm and the range of the temperature from 100 to 210 °C). The preparation of regular WPC was similar with the preparation of the core layer composites in coextruded WPC. The only difference was that different proportions of CB (0%, 5%, 10%, 15% and 20%) were added to the regular WPC, based on the total weight of the wood poplar and the HDPE. The cross-sectional dimension was 100 x 8 mm (length x width) and the shell thickness was 0.5 mm, as shown in Fig. 1.
Table 1. Compositions and Labeling of the Studied Formulations
Fig. 1. Schematics of the cross section of regular WPC and coextruded WPC
Characterization and Testing
According to GB/T 1410 (2006), the surface resistivity of the specimen was tested with a ultrahigh resistance meter (Guance Testing Instrument Co. Ltd., Type EST121, Beijing, China). The size of the specimen was 100 x 100 x 8 mm (length x width x height) and the results from three specimens were averaged. The formula for calculating the surface resistivity is shown in Eq. 1,
ρs = Rx (P/g) (1)
where ρs (Ω) is the surface resistivity, Rx (Ω) is the measured surface resistivity, P (cm) is the effective perimeter of a protected electrode in a particular electrode device, and g (cm) is the distance between the two electrodes
Tensile testing was conducted according to the GB/T 29418-2012 standard using an electronic universal testing machine (Sans Material Co. Ltd., Type CMT4204, Shenzhen, China). The specimen size was 210 x 20 x 8 mm (length x width x height), the two fulcrum span was 200 mm, and the loading speed of the machine was 2 mm/min. According to the GB/T 1043-2008 standard, the specimens in the impact strength test were cut using a die from a compression mold with dimensions of 100 x 10 x 8 mm (length x width x height) by a pendulum impact testing machine (Sans Material Co. Ltd., Type ZBC1251-1, Shenzhen, China). The experiment results were taken as the average of the six measurements.
The section morphology of the sample after impact testing was observed using a scanning electron microscope (SEM, FEI Co., Type Quanta 200, Hillsboro, OR, USA). The section of the sample was sprayed with gold before SEM observation at an acceleration voltage of 15 kV.
The crystallization and thermodynamic properties were measured with a differential scanning calorimeter (DSC, NETZSCH Co., Type DSC 200F3, Bavaria, Germany) in a N2 atmosphere (20 mL/min). The heating rate was 10 °C/min and temperature range from room temperature to 200 °C. In addition, the degree of crystallinity was determined from the total specific enthalpy of melting or crystallization, according to Eq. 2 (Gaur and Wunderlich 1982),
Xc=ΔHm/ ΔHm+ (2)
where ΔHm (J/g) is the specific enthalpy of melting and ΔHm+ is the specific enthalpy of melting for 100% crystalline polyethylene. The ΔHm+ value is 293 J·g-1 in the equation.
Conductivity analysis
Figure 2 shows that the surface resistivities of coextruded and regular WPCs varied with the CB content. The surface resistivities of all samples were decreased while the CB content increased, indicating that the addition of CB reduced the surface resistivity of the composites and thus resulted in the disappearance of the surface electrostatic discharge. The surface resistivity of the CW-0 sample was 1014 Ω, which was higher than that of the RW-0 sample by two orders of magnitude. This result was due to the hydrophobicity of the HDPE shell in coextruded WPC and the hydrophilicity of the wood fiber in regular WPC (Klason and Kubát 1984). In addition, the critical value of the conductive filler to form continuous conductive networks, causing a dramatic resistivity decrease is known as the percolation threshold (Li et al. 2005). According to the standard GB 50174-2008, the surface resistivity of the antistatic floor in the computer room and its support area was 2.5 x 104 to 1.0 x 109 Ω (i.e.below the dotted line in Fig. 2). The surface resistivity of the RW-15 sample was 108 Ω, which could achieve the antistatic requirements of the floor in the electronic information system room and its support area. However, the surface resistivity of the RW-20 sample was 104Ω, showing a dramatic decrease in comparison with that of the previous sample. These results indicated that the percolation threshold of the CB in regular WPC was between 15% and 20%, which could form continuous conductive networks to rapidly dissipate the charge, thereby decreasing its surface resistivity. Similar results were also observed in coextruded WPCs with added CB. Moreover, although the surface resistivity of the RW-20 sample was almost equal to that of the CW-20 sample, the dosages of CB added into the two structural WPCs were different. It can be seen from Fig. 1 that the thickness ratio of the shell to core layer in coextruded WPCs was 1:14. The dosages of CB in regular WPCs were much higher than those in coextruded WPCs under the premise of the same surface resistivity in the two structural WPCs. For instance, since the densities of the two structural WPCs were approximately equal, 71.1 g/m3 CB was required for coextruded WPCs while 476.8 g/m3 CB was required for regular WPCs. Therefore, to achieve the similar antistatic properties of the two structural WPCs, the dosage of CB in regular WPCs was 6.71 times as much as that of the coextruded WPCs.
Fig. 2. Effects of CB contents on the surface resistivity of the two structural WPCs
Figure 3 shows the endothermic heat flow peak for the two structural WPCs containing different CB contents. The eigenvalues obtained from the DSC curve are summarized in Table 2. The determination of the melting point (Tm) showed that the CB particles slightly influenced this parameter, which is caused by the change in lamellar thickness of the crystallites (Chodák 1998). However, this influence was not monotonic for coextruded WPCs. To a certain extent, CB was added to the matrix as a nucleating agent. The addition of CB narrowed the grain size of the crystal, and its crystals were more regular than before (Sever et al. 2013). Therefore, the crystals in coextruded WPCs with the addition of CB completed the melting process within a short range of temperatures, showing the Tm, and the full width at the high maximum (FWHM, i.e., ΔTm) of the crystalline peak decreasing with the increase in the CB content. The onset melting temperature (Tm-o), Tm, and ΔTm of the RW-0 sample were obviously decreased by 5.20 °C, 4.30 °C, and 2.45 °C in comparison with those of the CW-0 sample, respectively. The obtained results indicated that the presence of WF in the RW-0 sample led to the melting of the HDPE matrix in the smaller temperature range than the CW-0 samples (Yang et al. 2015). A decrease in the degree of crystallinity was observed with an increase in CB content in the case of the coextruded WPCs. The crystallinity of the CW-20 sample was decreased by 12.5% in comparison with that of the CW-0 sample, demonstrating that the addition of CB into the shell inhabited the crystallization of the HDPE matrix. This result also indicated that the CB particles represent defect centers, which impeded the folding of macromolecular chains, similar to crosslinking in polymers (Lazár et al. 1990). Simultaneously, the crystallinity of the HDPE matrix decreased greatly with the addition of wood flour, showing that the wood flour hindered crystallization. Also, the crystallinity of the RW-20 sample was the smallest value in all samples, showing that the combination of CB and wood flour hindered the crystallization of the HDPE matrix.
Fig. 3. DSC curves of coextruded WPCs with different CB contents (0%, 5%, 10%, 15% and 20%) and the two structural WPCs (coextruded WPCs and regular WPCs) with the same CB contents (0% and 20%)
Table 2. DSC Parameters for the Two Different Structural WPCs
Section morphology
Figure 4 shows the section morphology of the RW-20 sample and the shell of the coextruded WPC when 0%, 10%, and 20% of CB was added. Its magnification is 1200 times. For coextruded WPCs, the shell section morphology of the CW-0 sample demonstrated the appearance of the filament (i.e., the arrow in Fig. 4). With the addition of CB, the shell section morphology of the CW-10 sample changed significantly, showing a certain interval of the lamellar structure. Also, it can be seen from Fig. 4 that the small shape of the lamellar structure in the section morphology of the CW-10 sample disappeared when the CB content increased to 20%. The lamellar structure in the section morphology of the CW-20 sample became larger, which can effectively transfer the static electricity generated by the HDPE shell through the free moving electrons and reduce the electrostatic effect on the surface of the composites. The CB can conduct electricity since the carbon atoms in the crystal structure of CB formed 3 covalent bonds (i.e., a π bond), and each carbon was left with a free electron, which can transport electric charges (Yang et al.2015). The addition of CB into the composites can form a conductive path within the composites to transfer the redundant charges, thereby achieving the purpose of being antistatic. This result was consistent with the surface resistivity of the samples decreasing with the increase in the CB content in the conductivity analysis. The section morphology of the CW-20 sample had a large lamellar structure and its surface was rough. The fractured burr of the shell HDPE was small, as indicated by the white arrow in Fig. 4. The section morphology of the RW-20 sample had a more obvious lamellar structure and its fractured burr was larger than those of the CW-20 sample. These results indicated that CB was mainly combined with the HDPE matrix in the three-phase system of CB/HDPE/wood flour, which formed a lamellar structure at the section and a conductive network, thereby dissipating the redundant charge (Breuer et al.2015). In addition, it is only needed to build the conductive network in the shell HDPE matrix by adding CB to the coextruded WPCs; however, the addition of CB was much more in regular WPCs and thus met similar antistatic requirements.
Fig. 4. The section morphology of the coextruded WPCs added 0%, 10%, and 20% CB (CW-0, CW-10, CW-20), and the regular WPC added with 20% CB (RW-20)
Figure 5 shows the mechanical properties (flexural strength, flexural modulus, and impact strength) of the two structural WPCs added with different CB contents. The flexural strength and flexural modulus of the CW-0 sample were higher than these of the RW-0 sample by 1.9% and 5.9%, respectively. The impact strength of the CW-0 sample was also increased by 18.8% in comparison with that of the RW-0 sample. These results were due to the HDPE shell withstanding part of the external stress to effectively hinder the diffusion of the stress-induced cracks (Zhang et al. 2005). As shown in Fig. 5, the addition of CB into the shell of coextruded WPCs can improve the mechanical properties of the composites. The flexural strength, flexural modulus, and impact strength of the CW-20 sample were increased by 21.6%, 10.8%, and 26.1% in comparison with those of the CW-0 sample, respectively. This result is due to the HDPE through the coupling agent with the effective combination of CB (Chen et al. 2017), which was also consistent with the inhabitation in the crystallization of the HDPE matrix by adding CB into the shell in DSC analysis. In addition, the flexural strength and flexural modulus of the RW-20 sample was increased by 28.0% and 1.3%, respectively, in comparison with those of the CW-20 sample. This result is due to the silane coupling agent on the CB surface combined with the wood fiber and HDPE in the process of blending and melting, which led to the tight integration of each component (Sever et al. 2013; Gong et al. 2016). However, the impact strength of the RW-20 sample decreased by 14.7% in comparison with that of the CW-20 sample. This result was because the HDPE shell can effectively delay the diffusion of the stress-induced cracks, and thus, the regular WPCs were more brittle than the coextruded WPCs.
Fig. 5. Mechanical properties of the two structural WPCs (coextruded WPCs and regular WPCs)
The percolation threshold of the carbon black (CB) in regular wood-polymer composites (WPC) or coextruded WPC was between 15% and 20%, at which point the conductive filler can form continuous conductive networks to rapidly dissipate the charge, thereby causing the surface resistivity to decrease. The CW-20 sample had the lowest value of surface resistivity in coextruded WPCs and the RW-20 sample had the same results in regular WPCs, which can achieve the floor antistatic requirements of the electronic information system room and its support area.
The differential scanning calorimetry (DSC) analysis revealed that the crystallinity of the CW-20 sample decreased by 12.5% in comparison with that of the CW-0 sample, demonstrating the inhibition on the crystallization of the high-density polyethylene (HDPE) matrix by adding CB to the shell. This result is consistent with the large lamellar structure in the section morphology of the CW-20 sample, which formed a conductive network to eliminate the static electricity due to the uniform distribution of CB in the HDPE matrix.
The flexural strength, flexural modulus, and impact strength of the CW-20 sample were increased by 21.6%, 10.8%, and 26.1%, respectively, in comparison with those of the CW-0 sample. This is due to the HDPE through the coupling agent with the effective combination of CB, and thus improving the mechanical properties of the composite.
Adding CB into the shell of coextruded WPC can improve its antistatic properties and simultaneously maintain its mechanical properties. Moreover, under the premise of the similar antistatic and mechanical properties of the two structural WPCs, the dosage of CB in regular WPCs was 6.71 times as much as that in coextruded WPCs.
The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China (Grant No. 011330031), the Doctorate Fellowship Foundation of Nanjing Forestry University, and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).
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Article submitted: April 21, 2018; Peer review completed: June 15, 2018; Revised version received: June 25, 2018; Accepted: June 30, 2018; Published: July 5, 2018.


text:
Twins Baseball News
Twins bringing back veteran Matt Belisle for bullpen help
The Associated Press - June 12, 2018
DETROIT — The Minnesota Twins have signed right-handed reliever Matt Belisle to an $800,000, one-year contract, bringing back the popular veteran after a stint with Cleveland.
The Twins made the move Tuesday before their game at Detroit and designated utility infielder Gregorio Petit for release or assignment to make room on the roster.
Belisle had a 5.06 ERA for the Indians in eight appearances earlier this season before being assigned to Triple-A Columbus. The 38-year-old posted a 4.03 ERA for the Twins in 2017 in 62 appearances. He moved from setup man to a ninth-inning role after closer Brandon Kintzler was traded.
Twins relievers rank 21st in the major leagues with a 4.15 ERA.
Petit had 26 at-bats for the Twins. He hit .308 and played all four infield positions.

redpajama_set_name: RedPajamaCommonCrawl


The performance was at the same time moving, enlightening, meditative and surprising. And it was great fun to have the opportunity to meet the performers in a participative workshop too where we could be given a deeper insight into the work and the time to collaborate with them in trying out new ideas with their scores. Would love to see more of their work in different spaces!
"Beautifully delivered and innovative work. I enjoyed very much the layered, rich quality of this multi-media piece. Together with the video, the interesting use of many 'forms' of sound- instrumental performance, spoken word, recorded sound- created a kind of unique sonic and visual 'environment'. The work inspired my reflections on the nature of 'image' in relation to physicality and time.
"Firstly, many congratulations on what was for me a gripping and most stimulating performance yesterday. The fusion of elements while each remained a thing apart was perfect, as was the way the whole piece worked simultaneously on intellectual, sensual and visceral levels. Lastly, the overall architecture was strong and lucid.
"I found the work to be a creative portrayal and expression of various themes from the writings of Lucretius and Negri, as well as perhaps the experience of Negri's imprisonment. One overreaching element I felt was that of time: in terms of the setting and visual images from the Museum of Classical Archaeology together with the text of Lucretius, on one hand, and a feeling of continuity, or repetitiveness, which may also express the time Negri spent incarcerated. Moreover, a feeling of eternity came through, perhaps by the themes of discussing matter, atoms, etc which transcend our own human lifespans and the voices repeating phrases on this subject proved a reminder of 'constant-ness'.
The element of harsh realities, or of suffering were expressed through the more abrasive or irregular vocal sounds, which juxtaposed with more regular or 'softer' instrumental tones at times, added to the overall disturbing nature of the work. Yet in some parts there were more contemplative or peaceful moments, and the sound of water seems to have added to this. This moment contrasted effectively with notions of pain or darkness at other times.
"I've experienced Recitativo as a live radio transmission and a live performance. Having experienced the radio transmission first before attending the live performance, I felt it enhanced my comprehension of the live performance because my memories of hearing the piece merged with my sensory perceptions of seeing as I watched the performance. It took me a long time to locate the soprano singer, who I thought was located in the balcony by the sound of her voice within the church. This temporal engagement with the location of the players was both disorienting and pleasurable as I tried to visually connect the player with the location of their sound.


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Melis Karabulut February 13, 2022 Expat Entrepreneurs: The Story of Horus and Feteer2022-02-13T11:45:29+01:00 BD Magazine, Eating Out / Nightlife
Melis Karabulut's series profiles some of Brno's foreign entrepreneurs to explore the challenges of running a business in a foreign country. This week, she profiles Horus, an authentic piece of Egypt in the center of Brno. Photo credit: MK / BD.
The authentic Middle Eastern taste is only now getting some recognition in Brno's international gastronomy scene. Middle Eastern food is misunderstood by many as hard-to-digest and meat-based, and most people only know the most popular options available anywhere in Europe such as kebab or falafel. Being a Eurasian myself, I guarantee my readers that there is so much more to discover and appreciate about this type of cuisine, as it combines the fresh and light taste of the Mediterranean and the spicy-sweetness of the East with many variations unique to the different countries in the region. Islam Elshamy's new Egyptian restaurant Horus is in town to serve this aim and need, as the diners of Brno should not miss out on this Egyptian version of the inclusiveness and richness of Middle Eastern food!
Horus opened in late August 2021 in the city center, offering some of the most traditional Egyptian dishes like Feteer and several other well-known foods from the region such as kofta, grilled meat, kebab, hummus, mutabbal, and tzatziki, along with some traditional drinks and desserts. Horus has a well-balanced and tasteful combination of what belongs to Egypt, and what belongs to the broader region. Though the restaurant is small, it is still possible to order and eat directly at the premises, or to get food to take away. The prices are very reasonable and worth your money considering the size of the portions and the quality of the food.
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The restaurant's signature product is Feteer, a very traditional food to Egypt. Egyptians say that Feteer is one of the oldest recipes in the world, going back to Pharaonic times. "What pizza is to Italians, Feteer is to Egyptians," says Mr. Elshamy, emphasising its importance in local Egyptian culture. Feteer consists of a thin layer of phyllo dough filled with a choice of filling, and there are many different options. Mr. Elshamy's menu includes savoury Feteer with pastrami, cheese, minced meat, or salami, as well as sweet versions, prepared with dates, sugar, cream, and nutella. People of the region would definitely find a piece of home in Feteer as the taste is similar to Arabic, Turkish or Balkan food, and it truly deserves to be the next candidate of internationally acclaimed recipes!
"What pizza is to Italians, Feteer is to Egyptians." — Islam Elshamy. Credit: Horus.
Horus takes its name from Egyptian mythology, and symbolizes the God of the Sun, a symbol that owner Mr. Elshamy wears around his neck every day as a source of power and belief in his business. The story of Horus and Mr. Elshamy is, like the Egyptian God of the Sun, enchanting.
Mr. Elshamy is a well-trained, experienced chef from Alexandria, Egypt, who moved to the Czech Republic in 2013. His first motivation for relocation was to reunite with his ex-wife, who was Czech, but they separated a short while after Islam's arrival. Going through many difficulties with visa, documentation, jobhunting, and accommodation in Brno, and getting used to a new country without the possibility of returning to a successful life in Egypt, he has been through the hard mill. "Egypt already had a lot of problems of its own when I came to the Czech Republic. Once you lost your job, you lost everything. I made a choice to come to Europe, and going back to my country would mean being unemployed and in a lot of trouble. I had to stand on my own feet and fight," he says.
When he was struggling to find a job in Brno, he sought to connect with the Arab community in Brno to ask for suggestions or help to sustain his life here. To his luck, another Egyptian restaurant owner offered him a job and Islam started working there. Later on, he found a better position at a Syrian-owned restaurant where Lucia Horánska, his current fiancee, was working as a bartender. They have been in a dedicated, supportive relationship for the last eight years. "My life changed when I found my angel," he says, "she supported me in every step I took, and stood by me in ups and downs."
Islam and Lucie. Credit: MK / BD.
As the couple worked together at the same restaurant for a long while, they developed their dreams of bigger and better opportunities in the culinary industry. One day at the end of 2016, by complete surprise, they saw a job opening at the Brno Marriott Hotel for a senior position, and Islam encouraged Lucie to go for the job as he thought she would have a stronger chance for the position, as a speaker of the local language. As Lucie succeeded in her job at the Marriott while still a bachelor's student, she did not forget about her partner's career and got him a position at the Marriott as a chef, where he worked for five years.
Before he moved to Brno, Islam already had considerable experience as a chef working at big hotel chains in Egypt, such as Marriott, Hilton, Four Seasons and Sheraton. Accordingly he was quite familiar with the hotel industry and the workflow of a professional kitchen. His experience and Lucie's support helped him to thrive. "I owe Marriott a lot, as I learned so many things and I was welcomed and supported by the other employees there. Even though I fully appreciate my work experience there, deep down I still had the dream of opening up a restaurant and making it my own. At the same time, I didn't know exactly what kind of restaurant I would open and what I would offer to people, so it took me a long while to think about it, plan it, and put it into action. Later on I came up with the idea of the Feteer, which is something that is unique to Egypt, and not any other Middle Eastern country. Since we share a common culture, food and language and there were already some restaurants offering mainstream Arabic food, I wanted to be the person who brings something that has never been brought to the Czech Republic before," he says, underlining that he has always had the ideal of opening his own restaurant at some point in his career, and Horus became his first attempt, as something he deeply cares about.
The kitchen at Horus. Photo credit: MK / BD.
I ask Mr. Elshamy about the difficulties he has faced in making his business dreams come true: "During the lockdown, I started to test out various recipes of Feteer and share them with my Czech and international friends in Brno. Their very positive feedback gave me the motivation to start looking for a place to rent as a restaurant more seriously. I believed in the idea that it would be successful. Later on, we took a loan from a bank to start the business up, and we eventually did open the restaurant, though I cannot say that it has been easy. We have been through difficulties in finding a suitable place, finding products, attracting customers, and marketing the restaurant. I can say that the business has been going fine, but of course, we would like to see it thrive. Lucie and I have been working hard on all of these, and my fiance is still working at a hotel in a senior role, but we definitely would appreciate more customers tasting our products by visiting us in person," he says, mentioning a challenge that is troubling many business owners – the delivery issue.
Just like many other business owners that I have met in Brno, Mr. Elshamy's business has been negatively influenced by the increasing demand for food delivery options in the culinary sector due to the COVID-19 pandemic. While working with delivery partners is one of the backbones of foreign and Czech businesses, there are heartbreaking facts that should be understood by the consumers, which would eventually and gradually cause a change in their purchasing habits. "We spend thousands of Czech crowns for the packaging of our products per week for the delivery services, and we don't charge the customers for the packaging, as this would make people choose other restaurants that do not charge. And also, since we would like to keep the packaging as ecological as possible; we always order paper packaging, which is more expensive. In addition, considering the partnership share of the delivery services that many business owners like us are also troubled with, we are looking forward to welcoming customers back again to the premises of our business. We would be delighted to have a bigger place to host more customers, and we hope that this will happen in the near future. Until then, we invite the people of Brno to taste Feteer or any of the other Middle Eastern food we cook."
Horus can be found on Minoritská 476/12, just a few steps from Zelny Trh. The restaurant is open everyday except for Sundays, usually from 11 am to 9 pm.
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https://ww82.brnodaily.cz/2022/02/13/eating-out-nightlife/expat-entrepreneurs-the-story-of-horus-and-feteer/https://ww82.brnodaily.cz/wp-content/uploads/2022/02/horus-featured-MK-BD-1024x768.jpghttps://ww82.brnodaily.cz/wp-content/uploads/2022/02/horus-featured-MK-BD-150x113.jpg 2022-02-13T11:45:27+01:00 Melis KarabulutBD MagazineEating Out / NightlifeBrno,Brno Expats,Business,Food,ForeignersMelis Karabulut's series profiles some of Brno's foreign entrepreneurs to explore the challenges of running a business in a foreign country. This week, she profiles Horus, an authentic piece of Egypt in the center of Brno. Photo credit: MK / BD. The authentic Middle Eastern taste is only now getting...Melis KarabulutMelis Karabulutmeliskarabulut97@gmail.comAuthorA journalist from Turkey; an enthusiast of investigative stories on migration and politics in the Czech Republic. Writes about the journeys of inspirational expats living in Brno; and the bits of life that spark inspiration.Brno Daily
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About Melis Karabulut
A journalist from Turkey; an enthusiast of investigative stories on migration and politics in the Czech Republic. Writes about the journeys of inspirational expats living in Brno; and the bits of life that spark inspiration.
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text:
\section{Introduction}
Coronavirus disease 2019 (COVID-19) is an infectious disease that has affected more than one million individuals all over the world and caused more than 55,000 deaths, as of April 3 in 2020. The science community has been working very actively to understand this new disease and make diagnosis and treatment guidelines based on the findings. One major stream of efforts are focused on discovering the correlation between radiological findings in the lung areas and  COVID-19. There have been several works~\citep{liu2020clinical,li2020coronavirus} publishing such results. However, existing studies are mostly conducted separately by different hospitals and medical institutes. Due to geographic affinity, the populations served by different hospitals have different genetic, social, and ethnic characteristics. As a result, the radiological findings from  COVID-19 patient cases in different populations are different. This population bias incurs inconsistent or even conflicting conclusions regarding the correlation between radiological findings and  COVID-19. As a result, medical professionals cannot make informed decisions on how to use radiological findings to guide diagnosis and treatment of  COVID-19.

We aim to address this issue. Our research goal is to develop natural language processing methods to collectively analyze the study results reported by many hospitals and medical institutes all over the world, reconcile these results, and make a holistic and unbiased conclusion regarding the correlation between radiological findings and COVID-19. Specifically, we take the CORD-19 dataset~\citep{cord19}, which contains over 45,000 scholarly articles, including over 33,000 with full text, about COVID-19, SARS-CoV-2, and related coronaviruses. We develop sentence classification methods to identify all sentences narrating radiological findings from COVID-19. Then constituent parsing is utilized to identify all noun phrases from these sentences and these noun phrases contain abnormalities, lesions, diseases identified by radiology imaging such as X-ray and computed tomography (CT). We calculate the frequency of these noun phrases and select those with top frequencies for medical professionals to further investigate. Since these  clinical entities are aggregated from a number of hospitals all over the world, the population bias is largely mitigated and the conclusions are more objective and universally informative. From the CORD-19 dataset, our method successfully discovers a set of clinical findings that are closely related with COVID-19.

The major contributions of this paper include:
\begin{itemize}
    \item We develop natural language processing methods to perform unbiased study of the correlation between radiological findings and COVID-19.
    \item We develop a bootstrapping approach to effectively train a sentence classifier with light-weight manual annotation effort. The sentence classifier is used to extract radiological findings from a vast amount of literature.
    \item We conduct experiments to verify the effectiveness of our method. From the CORD-19 dataset, our method successfully discovers a set of clinical findings that are closely related with COVID-19.
\end{itemize}
The rest of the paper is organized as follows. In Section 2, we introduce the data. Section 3 presents the method. Section 4 gives experimental results. Section 5 concludes the paper.

\section{Dataset}
We used the COVID-19 Open Research Dataset (CORD-19)~\citep{cord19} for our study. In response to the COVID-19 pandemic, the White House and a coalition of research groups  prepared the CORD-19 dataset. It contains over 45,000 scholarly articles, including over 33,000 with full text, about COVID-19, SARS-CoV-2, and related coronaviruses.  These articles are contributed by hospitals and medical institutes all over the world. Since the outbreak of COVID-19 is after November 2019, we select articles published after November 2019 to study, which include a total of 2081 articles and about 360000 sentences.
Many articles report the radiological findings related to COVID-19. Table~\ref{dataset_example} shows some examples.

\begin{table}[htbp]
  \centering
  \caption{Example sentences describing radiological findings related with COVID-19}
  \begin{tabular}{|m{14cm}|}\hline
  \small The X-ray chest and Highresolution computed-tomography chest showed a progressively reduced bilateral pleural effusion, interstitial-alveolar edema with bilateral hilar congestion. \\ \hline
  \small Non-pleural effusion appeared in the first and second CT examination and a bilateral pleural effusion appeared in the third CTexamination. \\ \hline
  \small Chest CT scans revealed that the grade 2 lesion and one of the grade 3 lesions as areas of prominent breast tissue mimicking faint GGO and post-inflammatory focal atelectasis on chest radiography, respectively. \\ \hline
  \small A showed many CT features such as ground-glass opacification,cobblestone/reticular pattern(blue arrow and bule line around region), frbrosis and dilated bronchi with thickened wall (the enlarged image in the upper right corner, red arrow). \\ \hline
  \small The typical CT images show bilateral pulmonary parenchymal ground-glass and consolidative pulmonary opacities, sometimes with a rounded morphology and a peripheral lung distribution. \\ \hline
  \small The chest CT ( Figure 3 ) showed multi-focal GGO with parenchyma consolidation and subpleural effusion, predominantly involving upper lungs.\\ \hline

  \end{tabular}
  \label{dataset_example}
\end{table}

\section{Methods}
Our goal is to develop natural language processing (NLP) methods to analyze a large collection of COVID-19 literature and discover unbiased and universally informative  correlation between radiological findings and COVID-19. To achieve this goal, we need to address two technical challenges. First, in the large collection of COVID-19 literature, only a small part of sentences are about radiological findings. It is time-consuming to manually identify these sentences. Simple methods such as keyword-based retrieval will falsely retrieve sentences that are not about radiological findings and miss sentences that are about radiological findings. How can we develop NLP methods to precisely and comprehensively extract sentences containing radiological findings with minimum human annotation? Second, given the extracted sentences, they are still highly unstructured, which are difficult for medical professionals to digest and index. How can we further process these sentences into structured information that is more concise and easy to use?

To address the first challenge, we develop a sentence classifier to judge whether a sentence contains radiological findings. To minimize manual-labeling overhead, we propose easy ways of constructing positive and negative training examples, develop a bootstrapping approach to mine hard examples, and use hard examples to re-train the classifier for reducing false positives. To address the second challenge, we use constituent parsing to recognize noun phrases which contain critical medical information (e.g., lesions, abnormalities, diseases) and are easy to index and digest. We select noun phrases with top frequencies for medical professionals to further investigate.

\subsection{Extracting Sentences Containing Radiological Findings}
In this section, we develop a sentence-level classifier to determine whether a sentence contains radiological findings. To build such a classifier, we need to create positive and negative training sentences, without labor-intensive annotations. To obtain  positive examples, we resort to the MedPix\footnote{https://medpix.nlm.nih.gov/home} database, which contains radiology reports narrating radiological findings. MedPix is an open-access online database of medical images, teaching cases, and clinical topics. It contains more than 9000 topics, 59000 images from 12000 patient cases. We selected diagnostic reports for CT images and used sentences in the reports as  positive samples. To obtain negative sentences, we randomly sample some sentences from the articles and quickly screen them to ensure that they are not about radiological findings. Since most sentences in the literature are not about radiological findings, a random sampling can almost ensure the select sentences are negative. A manual screening is conducted to further ensure this and the screening effort is not heavy.

Given these positive and negative training sentences, we use them to train a sentence classifier which predicts whether a sentence is about the radiological findings of COVID-19. We use the Bidirectional Encoder Representations from Transformers (BERT) \citep{devlin2018bert} model for sentence classification. BERT is a neural language model that learns contextual representations of words and sentences. BERT pretrains deep bidirectional representations from
unlabeled text by jointly conditioning on both
left and right context in all layers. To apply the pretrained BERT to a downstream task such as sentence classification, one can add an additional layer on top of the BERT architecture and train this newly-added layer using the labeled data in the target task. In our case, similar to \citep{lee2020biobert},
we pretrain the BERT model on a vast amount of biomedical literature to obtain semantic representations of words. A linear layer is added to the output of BERT for predicting whether this sentence is positive (containing radiological finding) or negative. The architecture and hyperparameters of the BERT model used in our method are the same as those in \citep{lee2020biobert}. Figure~\ref{BERT} shows the architecture of the classification model.

\begin{figure}[htbp]
  \centering
  \includegraphics[width=3in]{bert.png}
  \caption{Architecture of the sentence classification model.}
  \label{BERT}
\end{figure}

When applying this trained sentence classifier to unseen sentences, we found that it yields a lot of false positives: many sentences irrelevant to radiological findings of COVID-19 are predicted as being relevant. To solve this problem, we iteratively perform hard example mining in a bootstrapping way and use these hard examples to retrain the classifier for reducing false positives. At iteration $t$, given the classifier $C_t$, we apply it to make predictions on unseen sentences. Each sentence is associated with a prediction score where a larger score indicates that this sentence is more likely to be positive. We rank these sentences in descending order of their prediction scores. Then for the top-K sentences with the largest prediction scores, we read them and label each of them as either being positive or negative. Then we add the labeled pairs to the training set and re-train the classifier and get $C_{t+1}$. This procedure is repeated again to identify new false positives and update the classifier using the new false positives.

\subsection{Extracting Noun Phrases}

The extracted sentences containing radiological findings of COVID-19 are highly unstructured, which are still difficult to digest for medical professionals. To solve this problem, from these unstructured sentences, we extract structured information that is both clinically important and easy to use. We notice that important information, such as lesions, abnormalities, diseases, is mostly contained in noun phrases. Therefore, we use NLP to extract noun phrases and perform further analysis therefrom. First, we perform part-of-speech (POS) tagging to label each word in a sentence as being a noun, verb, adjective, etc. Then on top of these words and their POS tags, we perform constituent  parsing to obtain the syntax tree of the sentence. An example is shown in Figure~\ref{chunker}. From bottom to top of the tree, fine-grained linguistic units such as words are composed into coarse-grained units such as phrases, including noun phrases. We obtain the noun phrases by reading the node labels in the tree.

Given the extracted noun phrases, we remove stop words in them and perform lemmatization to eliminate non-essential linguistic variations. We count the frequency of each noun phrase and rank them in descending frequency. Then we select the noun phrases with top frequencies and present them to medical professionals for further investigation.

\begin{figure}[htbp]
  \centering
  \includegraphics[width=4 in]{tree.png}
  \caption{An example of constituent parse tree.}
  \label{chunker}
\end{figure}

\section{Experiment}

\subsection{Experimental Settings}

For building the initial sentence classifier (before hard-example mining), we collected 2350 positive samples from MedPix and 3000 negative samples from CORD-19.  We used 90\% sentences for training and the rest 10\% sentences for validation. The weights in the sentence classifier are optimized using the Adam~\cite{} algorithm with a learning rate of $2\times 10^{-5}$ and a mini-batch size of 4. In bootstrapping for hard example mining, we added 400 false positives in each iteration for classifier-retraining and we performed 4 iterations of bootstrapping.

\subsection{Results of Sentence Classification}

\iffalse
\begin{table}[htbp]
  \centering
  \caption{Number of negative in training set, validation accuracy and number positive sentences in result over each iteration}
  \begin{tabular}{|c|c|c|c|}\hline
    iteration&neg samples & Accuracy & pos result \\ \hline
    0 & 2700 & 0.9916 & 5211 \\ \hline
    1 & 3060 & 0.9902 & 4407 \\ \hline
    2 & 3420 & 0.9900 & 3308 \\ \hline
    3 & 3780 & 0.9889 & 2461 \\ \hline
    4 & 4140 & 0.9870 & 998 \\ \hline
  \end{tabular}
  \label{classifier}
\end{table}
\fi

Under the final classifier, 998 sentences are predicted as being positive. Among them, 717 are true positives (according to manual check). The classifier achieves a precision of 71.8\%. For the initial classifier (before adding mined hard examples using bootstrapping), among the top 100 sentences with the largest prediction scores, 53 are false positives. The initial classifier only achieves a precision of 47\%. The precision achieved by classifiers trained after round 1-3 in bootstrapping is 55\%, 57\%, and 69\% respectively, as shown in Table~\ref{precision_of_top100}. This demonstrates the effectiveness of hard example mining.  Table~\ref{cls_result_example} shows some example sentences that are true positives, true negatives, and false positives, under the predictions made by the  final classifier.

\begin{table}[htbp]
  \centering
  \caption{Precision at top-100 after each iteration}
  \begin{tabular}{|c|c|}\hline
    Iteration & Precision \\ \hline
    0 & 47\% \\ \hline
    1 & 55\% \\ \hline
    2 & 57\% \\ \hline
    3 & 69\% \\ \hline

  \end{tabular}
  \label{precision_of_top100}
\end{table}

\begin{table}[htbp]
  \centering
  \caption{Example sentences for true positive (TP), true negative (TN), and false positive (FP).}
  \begin{tabular}{|p{0.9cm}|p{13cm}|}\hline
    \multirow{4}*{\textbf{ TP}} & \small Her chest radiograph demonstrated no abnormalities, but a CT scan of her chest revealed bilateral multifocal infiltrates and mediastinal and hilar lymphadenopathy. \\ \cline{2-2}
    ~ & \small The predominant pattern was groundglass opacity, with illdefined margins, air bronchograms, smooth or irregular inter lobular or septal thickening, and thickening of the adjacent pleura. \\ \cline{2-2}
    ~ & \small The patient's chest CT showed pulmonary consolidation, interlobular septal thickening, and pleural effusion. \\ \cline{2-2}
    ~ & \small Dynamic imaging showed progressive multi-spot patchy shadows in both lungs. \\ \hline
    \multirow{4}*{\textbf{ TN}} &
    \small Fourth, leisure activities and training on how to relax were properly arranged to help staff reduce stress. \\ \cline{2-2}
    ~ & \small Uncertainties of discrete E. coli samples and flow measurements were N30 and 97\%, respectively. \\ \cline{2-2}
    ~ & \small Acute lower respiratory tract infections (ALRIs) are a common illness in children $<$ 5 years old, with significant morbidity and mortality in infants and young children under the age of two (1) (2) (3) \\ \cline{2-2}
    ~ & \small Bovine viral diarrhea (BVD), which is caused by BVD virus (BVDV) infection, is one of the most important viral diseases of cattle, causing enormous economic losses to the livestock industry worldwide (Suda et al., 2018) . \\ \hline
    \multirow{4}*{\textbf{ FP}} &
    \small Pathology: At necropsy, there is diffuse lymphoma affecting multiple organs that can include those noted above plus kidney, adrenal gland, tonsils, and lung. \\ \cline{2-2}
    ~ & \small The stoma site per se is an incisional hernia by definition as it is a defect in the abdominal fascia with protruding intra-abdominal contents. \\ \cline{2-2}
    ~ & \small He was diagnosed with coronary artery disease in last year and was stented in Left anterior descending artery. \\ \cline{2-2}
    ~ & \small Ultimately, the patient underwent mitral valve replacement following the stress test. \\ \hline

  \end{tabular}
  \label{cls_result_example}
\end{table}

\subsection{Results of Noun Phrase Extraction}
Table~\ref{NP} shows the extracted noun phrases with top frequencies that are relevant to radiology. Medical professionals can look at this table and select noun phrases indicating radiological findings for further investigation, such as consolidation, pleural effusion, ground glass opacity, thickening, etc. We mark such noun phrases with bold font in the table. To further investigate how a noun phrase is relevant to COVID-19, medical professionals can review the sentences mentioning this noun phrase. Table~\ref{noun_phrases_sentences_example_0},\ref{noun_phrases_sentences_example_1},\ref{noun_phrases_sentences_example_2} show some examples.
\begin{table}[htbp]
  \centering
  \caption{Extracted radiology-relevant noun phrases with top phrases. Noun phrases relevant to clinical findings are highlighted with bold font.}
  \begin{tabular}{|l|c|l|c|}\hline
  \textbf{Noun phrase} & \textbf{Frequency }& \textbf{Noun phrase} & \textbf{Frequency} \\ \hline
  ct & 103 & liver & 19 \\ \hline
  \textbf{consolidation} & 79 & \textbf{fibrosis} & 13 \\ \hline
  lung & 62 & \textbf{abscess} & 13 \\ \hline
  lobe & 61 & infection & 13 \\ \hline
  chest & 57 & \textbf{air bronchogram} & 12 \\ \hline
   \textbf{pleural effusion} & 54 & \textbf{lymphadenopathy} & 12 \\ \hline
   \textbf{ground glass opacity} & 53 & hrct & 11 \\ \hline
  lesion & 50 & interlobular septa & 11 \\ \hline
  chest x-ray & 38 & cxr & 10 \\ \hline
  pneumonia & 35 & trachea & 10 \\ \hline
  chest radiographs & 29 & \textbf{bronchiectasis} & 9 \\ \hline
  tomography & 27 & fever & 5 \\ \hline
  echocardiogram & 22 &\textbf{multiple sclerosis} & 3 \\ \hline
   \textbf{thickening} & 21 & & \\ \hline
  \end{tabular}
  \label{NP}
\end{table}
\begin{table}[htbp]
\centering
  \caption{Example sentences containing interested noun phrases}
  \begin{tabular}{|p{3cm}|p{12cm}|}\hline
  \multirow{5}*{\begin{minipage}{3cm}\textbf{consolidation}\end{minipage}} & \footnotesize Chest CT images showed diffuse irregular small diffuse ground-glass nodular opacities with partial \textbf{consolidation} in bilateral lungs on Day 10 ( Figure 1A. \\ \cline{2-2}
    ~ & \footnotesize Axial thin-section non-contrast CT scan shows diffuse bilateral confluent and patchy ground-glass, air-bronchogram and \textbf{consolidation}, characterized by peripheral distribution. \\ \cline{2-2}
    ~ & \footnotesize B showed \textbf{consolidation} (pink arrow) and mixed pattern (yellow arrow and yellow line around region) in the bilateral lower lobes. \\ \cline{2-2}
    ~ & \footnotesize Subsequent chest CT images showed bilateral groundglass opacity, whereas the \textbf{consolidation} was resolved. \\ \cline{2-2}
    ~ & \footnotesize CT scan revealed bilateral peribronchial \textbf{consolidation}, swollen jejunum lymph node with uniform distribution of contrast medium, and multiple prominent nodules of the liver. \\ \hline

    \multirow{5}*{\begin{minipage}{3cm}\textbf{pleural effusion}\end{minipage}} & \footnotesize The chest film is not helpful in making a specific etiologic diagnosis; however, lobar consolidation, cavitation, and large \textbf{pleural effusions} support a bacterial cause. \\ \cline{2-2}
    ~ & \footnotesize Inhalation anthrax is notable for its absence of pulmonary infiltrate on chest imaging, but the presence of extensive mediastinal lymphadenopathy, \textbf{pleural effusions}, and severe shortness of breath, toxemia, and sense of impending doom. \\ \cline{2-2}
    ~ & \footnotesize An echocardiogram showed severe reduction of the left ventricular (LV) ejection fraction (25\%) and a chest X-ray exhibited bilateral \textbf{pleural effusion} with pulmonary interstitial edema (Fig. \\ \cline{2-2}
    ~ & \footnotesize The patient received 2 g/kg IVIG and significant \textbf{pleural effusion} was noted on the chest radiography and computed tomography 48 h after the completion of therapy. \\ \cline{2-2}
    ~ & \footnotesize Chest computed tomography showed bilateral \textbf{pleural effusion}, bilateral consolidation with air bronchogram, and ground-glass opacities in her left lung (Fig. \\ \hline

    \multirow{5}*{\begin{minipage}{3cm}\textbf{ground-glass opacity}\end{minipage}} & \footnotesize Axial thin-section non-contrast CT image shows diffusion lesions in bilateral lung, mainly manifested as \textbf{ground-glass opacification} (red arrow and red line around region),and cobblestone/Reticular pattern( blue arrow and blue line around region). \\ \cline{2-2}
    ~ & \footnotesize Chest CT will show areas of \textbf{ground-glass opacity} and consolidation in involved segments. \\ \cline{2-2}
    ~ & \footnotesize CT findings included ground glass opacity, consolidation, air bronchogram and nodular opacities. \\ \cline{2-2}
    ~ & \footnotesize CT images were reviewed and scored for lesion distribution, lobe and segment involvement, \textbf{ground-glass opacities}, consolidation, and interstitial thickening. \\ \cline{2-2}
    ~ & \footnotesize The most frequent radiological patterns on plain chest radiography was airspace/\textbf{ground glass opacification} in various lobes. \\ \hline

    \multirow{5}*{\begin{minipage}{3cm}\textbf{thickening}\end{minipage}} & \footnotesize Most of the lesions were distributed along the bronchovascular bundle or the dorsolateral and subpleural part of the lungs and were seen with or without interlobular septal \textbf{thickening}.  \\ \cline{2-2}
    ~ & \footnotesize CT images were reviewed and scored for lesion distribution, lobe and segment involvement, ground-glass opacities, consolidation, and interstitial \textbf{thickening}.  \\ \cline{2-2}
    ~ & \footnotesize Chest radiographs often demonstrate peribronchial \textbf{thickening} and infiltrates, often with areas of atelectasis. \\ \cline{2-2}
    ~ & \footnotesize Other c-HRCT signs of bronchiectasis include abnormalities in the surrounding lung may include parenchyma loss, emphysema, scars and nodular foci, 150 a linear array or cluster of cysts, dilated bronchi in the periphery of the lung, and bronchial wall \textbf{thickening} (Box 26.1). \\ \cline{2-2}
    ~ & \footnotesize CT showed multiple peripheral lesions in bilateral lungs, mainly characterized by GGO, paving stones and vascular \textbf{thickening}. \\ \hline

  \end{tabular}
  \label{noun_phrases_sentences_example_0}
\end{table}

\begin{table}[htbp]

  \caption{Example sentences containing interested noun phrases}
  \begin{tabular}{|p{3cm}|p{11cm}|}\hline

    \multirow{5}*{\begin{minipage}{3cm}\textbf{fibrosis}\end{minipage}} & \footnotesize (D) Images obtained 5 days later showed partial absorption of the consolidation lesions in the right lower lobe, but \textbf{fibrosis}, bronchiectasis, and vascular thickening occurred. \\ \cline{2-2}
    ~ & \footnotesize High-resolution chest computer tomography (HRCT) presented diffuse ground glass opacities, intra-lobular reticulation and small cysts in the upper lobes, middle lobe and lingula, suggesting pulmonary \textbf{fibrosis} (Fig. \\ \cline{2-2}
    ~ & \footnotesize These findings indicated the appearance of interstitial changes, suggesting the development of \textbf{fibrosis}. \\ \cline{2-2}
    ~ & \footnotesize No other clinical or radiological changes of lung congestion, \textbf{fibrosis}, or cancer to explain these ground-glass lung changes, or any concomitant radiological changes of dense consolidation, pleural effusion, lymphadenopathy, or pneumomediastinum were seen. \\ \cline{2-2}
    ~ & \footnotesize If the diagnosis of idiopathic pulmonary \textbf{fibrosis} is not previously established this criterion can be met by the presence of radiologic and/or histopathologic changes consistent with usual interstitial pneumonia pattern on the current evaluation. \\ \hline

    \multirow{5}*{\begin{minipage}{3cm}\textbf{abscess}\end{minipage}} & \footnotesize A contrast-enhanced computed tomography scan is useful because it differentiates a fully developed \textbf{abscess} from cellulitis and delineates the full extent of the abscess.\\ \cline{2-2}
    ~ & \footnotesize The \textbf{abscess} pushes the adjacent tonsil downward and medially, and the uvula may be so edematous, as to resemble a white grape. \\ \cline{2-2}
    ~ & \footnotesize A CT of the neck was obtained to rule out other etiologies for respiratory distress, which was negative for peritonsillar or retropharyngeal \textbf{abscess}. \\ \cline{2-2}
    ~ & \footnotesize Abnormalities include bronchopneumonia, solitary or multiple lung nodes, miliary interstitial lung disease, lung \textbf{abscess}, and pleural effusion. \\ \cline{2-2}
    ~ & \footnotesize A lung abscess, like an \textbf{abscess} elsewhere, represents a localized collection of pus. \\ \hline

    \multirow{5}*{\begin{minipage}{3cm}\footnotesize\textbf{air bronchogram}\end{minipage}} & \footnotesize CT findings included ground glass opacity, consolidation, \textbf{air bronchogram} and nodular opacities. \\ \cline{2-2}
    ~ & \footnotesize Chest CT on Jan 13 showed improved status (3B) with diffuse consolidation of both lungs, uneven density and \textbf{air bronchogram}. \\ \cline{2-2}
    ~ & \footnotesize Chest computed tomography showed bilateral pleural effusion, bilateral consolidation with \textbf{air bronchogram}, and ground-glass opacities in her left lung (Fig. \\ \cline{2-2}
    ~ & \footnotesize The predominant pattern was groundglass opacity, with illdefined margins, \textbf{air bronchograms}, smooth or irregular inter lobular or septal thickening, and thickening of the adjacent pleura. \\ \cline{2-2}
    ~ & \footnotesize Computed tomography axial (A) and coronal (B) plane revealed multiple lesions (arrows) of ground glass opacity accompanied with consolidation under or near the pleura in bilateral lower lobes, with \textbf{air bronchogram} and thickened interlobular septa. \\ \hline

    \multirow{5}*{\begin{minipage}{3cm}\footnotesize\textbf{lymphadenopathy}\end{minipage}} & \footnotesize Merely consolidation, central distribution only, pleural effusions or \textbf{lymphadenopathy} were relatively rarely seen. \\ \cline{2-2}
    ~ & \footnotesize Thoracic and abdominal radiographs may provide evidence of pulmonary lesions, \textbf{lymphadenopathy}, and/or hepatosplenomegaly. \\ \cline{2-2}
    ~ & \footnotesize Neither pleural effusion nor \textbf{lymphadenopathy} was found. \\ \cline{2-2}
    ~ & \footnotesize Neither patient showed pleural effusion or \textbf{lymphadenopathy}. \\ \cline{2-2}
    ~ & \footnotesize 3.1 presence of \textbf{lymphadenopathy} (defined as lymph node size of !10 mm in short-axis dimension); 3.2 presence of pericardial effusion; 3.3 ascending thoracic aorta diameter. \\ \hline

  \end{tabular}
  \label{noun_phrases_sentences_example_1}
\end{table}

\begin{table}[htbp]

  \caption{Example sentences containing interested noun phrases}
  \begin{tabular}{|p{3cm}|p{11cm}|}\hline

    \multirow{5}*{\begin{minipage}{3cm}\textbf{intralobular septa}\end{minipage}} & \footnotesize The lesion density was mostly non-uniform with air bronchogram and thickened interlobular or \textbf{intralobular septa}. \\ \cline{2-2}
    ~ & \footnotesize The lesion may be patchy, nodular, honeycomb, grid or strips, and the lesion density is mostly uneven with the primary presentation of ground glass opacity accompanied by thickening of interlobular or \textbf{intralobular septa}. \\ \cline{2-2}
    ~ & \footnotesize High-resolution CT might show ground glass opacities (figure 5B) in early CT findings (with or without consolidation) followed by \textbf{interlobular septal} and intralobular interstitial thickening with peripheral and lower lobe involvement 93, 94 within the first week of MERS-CoV infection. \\ \cline{2-2}
    ~ & \footnotesize Other findings included intralobular or \textbf{interlobular septal} thickening, and a crazy paving pattern. \\ \cline{2-2}
    ~ & \footnotesize Most of the lesions were distributed along the bronchovascular bundle or the dorsolateral and subpleural part of the lungs and were seen with or without \textbf{interlobular septal} thickening. \\ \hline

    \multirow{5}*{\begin{minipage}{3cm}\textbf{trachea}\end{minipage}} & \footnotesize A lateral neck radiograph may show a hazy \textbf{tracheal} air column, with multiple luminal soft tissue irregularities due to pseudomembrane detachment from the soft tissue, but radiographs should be taken only after the patient is stabilized and safe. \\ \cline{2-2}
    ~ & \footnotesize CT imaging demonstrated diffuse edema and narrowing of the glottis, subglottis, and upper \textbf{trachea} in keeping with croup.  \\ \cline{2-2}
    ~ & \footnotesize Tracheal intubation was seen in the \textbf{trachea} and the heart shadow outline was not clear.  \\ \cline{2-2}
    ~ & \footnotesize Black arrows in the \textbf{trachea} indicate cilia and necrosis loss. \\ \cline{2-2}
    ~ & \footnotesize A neck radiograph will show the traditional narrowing of the \textbf{trachea} known as a steeple sign. \\ \hline

    \multirow{5}*{\begin{minipage}{3cm}\textbf{bronchiectasis}\end{minipage}} & \footnotesize The timing of c-HRCT scans to diagnose \textbf{bronchiectasis} is important. \\ \cline{2-2}
    ~ & \footnotesize Other c-HRCT signs of \textbf{bronchiectasis} include abnormalities in the surrounding lung may include parenchyma loss, emphysema, scars and nodular foci, 150 a linear array or cluster of cysts, dilated bronchi in the periphery of the lung, and bronchial wall thickening (Box 26.1). \\ \cline{2-2}
    ~ & \footnotesize In particular, CT is much better at identifying the presence and extent of \textbf{bronchiectasis} compared with thoracic radiography. \\ \cline{2-2}
    ~ & \footnotesize (D) Images obtained 5 days later showed partial absorption of the consolidation lesions in the right lower lobe, but fibrosis, \textbf{bronchiectasis}, and vascular thickening occurred. \\ \cline{2-2}
    ~ & \footnotesize In the right upper lobe, there were ground glass densification areas, traction \textbf{bronchiectasis}, interlobular septa thickening and subpleural cystic lesions. \\ \hline

  \end{tabular}
  \label{noun_phrases_sentences_example_2}
\end{table}

For example, reading the five example sentences containing consolidation, one can judge that consolidation is a typical manifestation of COVID-19. This is in accordance with the conclusion in \citep{consolidation}: ``Consolidation becomes the dominant CT findings as the disease progresses." Similarly, the example sentences of pleural effusion, ground glass opacity, thickening, fibrosis, bronchiectasis, lymphadenopathy show that these abnormalities are closely related with COVID-19. This is consistent with the results reported in the literature:
\begin{itemize}
    \item \textbf{Pleural effusion}: ``In terms of pleural changes, CT showed that six (9.7\%) had pleural effusion." \citep{pleural}
    \item \textbf{Ground glass opacity}: ``The predominant pattern of abnormalities after symptom onset was ground-glass opacity (35/78 [45\%] to 49/79 [62\%] in different periods." \cite{GGO}
    \item \textbf{Thickening}: ``Furthermore, ground-glass opacity was subcategorized into: (1) pure ground-glass opacity; (2) ground-glass opacity with smooth interlobular septal  thickening." \citep{GGO}
    \item \textbf{Fibrosis}: ``In five patients, follow-up CT showed improvement with the appearance of fibrosis and resolution of GGOs.", \citep{fibrosis}
    \item
     \textbf{Bronchiectasis} and \textbf{lymphadenopathy}: ``The most common patterns seen on chest CT were ground-glass opacity, in addition to ill-defined margins, smooth or irregular interlobular septal thickening, air bronchogram , crazy-paving pattern, and thickening of the adjacent pleura. Less common CT findings were nodules, cystic changes, bronchiolectasis, pleural effusion , and lymphadenopathy."  \citep{air_bronchogram}
\end{itemize}

\section{Conclusions}
In this paper, we develop natural language processing methods to automatically extract unbiased radiological findings of COVID-19. We develop a BERT-based classifier to select sentences that contain COVID-related radiological findings and use bootstrapping to mine hard examples for reducing false positives. Constituent parsing is used to extract noun phrases from the positive sentences and those with top frequencies are selected for medical professionals to further investigate. From the CORD-19 dataset, our method successfully discovers radiological findings that are closely related with COVID-19.

redpajama_set_name: RedPajamaArXiv


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