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LitCovid-PD-FMA-UBERON

LitCovid-PD-UBERON

{"project":"LitCovid-PD-UBERON","denotations":[{"id":"T57","span":{"begin":417,"end":434},"obj":"Body_part"},{"id":"T58","span":{"begin":717,"end":734},"obj":"Body_part"},{"id":"T59","span":{"begin":2177,"end":2194},"obj":"Body_part"}],"attributes":[{"id":"A57","pred":"uberon_id","subj":"T57","obj":"http://purl.obolibrary.org/obo/UBERON_0000065"},{"id":"A58","pred":"uberon_id","subj":"T58","obj":"http://purl.obolibrary.org/obo/UBERON_0000065"},{"id":"A59","pred":"uberon_id","subj":"T59","obj":"http://purl.obolibrary.org/obo/UBERON_0000065"}],"text":"Nanotechnology-Based Solutions to Increase the Efficiency and Safety of Protective Devices\nCryoelectron microscopy (cryo-EM) studies show that SARS-CoV-2 virions are particles near the larger end of the NP size range (70–90 nm).21,201 However, when dispersed into the air, the infectious particles exist as functionally larger particles. Initially, liquid droplets containing coronavirus virions originating from the respiratory tract of infected patients are emitted during normal breathing, forced expiration (e.g., coughing and sneezing), or aerosol-generating medical procedures (e.g., intubation and suctioning). Liquid droplets emitted into the air through these mechanisms originate from points throughout the respiratory tract and carry within them virions as well as other materials associated with the airways, including bacterial cells and epithelial cells (Figure 5). Droplets are emitted over a wide size range, and their potential viral burden is a cubic function of particle diameter (Figure 6). Thus, larger droplets have the potential to carry a significantly larger burden of virions according to their size and are substantially more hazardous than small droplets. Once emitted into the air, water from droplets immediately begins to evaporate. Water loss is associated with a rapid decrease in both particle diameter and terminal settling velocity (the equilibrium rate of fall of a particle in still air). The rate of evaporation of the largest droplets (\u003e150 μm) is often insufficient to slow their swift descent in air, and they impact on nearby surfaces. However, the rapid water loss and sharp slowing of settling velocity of smaller droplets enables them to avoid a similar fate. Their constituent solid residues are instead drawn together during evaporation and cemented with dried respiratory secretions, and they remain aloft as droplet nuclei. Several epidemiological studies have supported the potential for droplet nuclei to be an important means of transmission for SARS-CoV-2.202,203\nFigure 5 Droplets and droplet nuclei as important mechanism for transmission of infection. Liquid droplets containing SARS-CoV-2 virions originating from the respiratory tract of infected patients are emitted into the air and carry other materials including bacterial cells and epithelial cells. They are reduced in size by evaporation to small, dry particles resulting in droplet nuclei.\nFigure 6 Maximum theoretical viral burden versus droplet nucleus size (nm). Assuming a median virion size of about 100 nm, a droplet nucleus of 1 μm diameter could contain up to 370 randomly packed virions. A similar 10 μm diameter droplet nucleus could contain up to 360,000. In practical terms, however, the size-defining element of a droplet nucleus is determined by the component item with the largest volume, which is often a bacterial cell or an epithelial cell. Thus, droplet nuclei in the 1–10 μm size range and above contain far fewer virions than this theoretical maximum.\nFilter media, such as those used in N95 masks and in mechanical ventilation systems, consist of myriad interwoven fibers through which air is moved. Their purpose is to arrest particles as they move through the matrix. Filters capture particles chiefly by three mechanisms: impaction, interception, and diffusion. Impaction occurs when the momentum of a particle propelled toward a filter fiber prevents the particle from diverging around the fiber along the flow lines of the air stream, causing the particle to collide with the fiber. Impaction is the primary mechanism responsible for removing particles greater than 500 nm in diameter. Interception occurs when a particle diverges around a fiber along the flow lines of the airstream, the distance between the vector of the airstream and the centroid of the particle is smaller than the radius of the particle, and the particle touches the fiber. Interception operates efficiently on particles greater than 200 nm in diameter. Diffusion is the final important mechanism of particle removal, and it is most effective at removing very fine particles less than 200 nm, especially at low flow rates. Particles around 300 nm in diameter are least subject to these three removal mechanisms, and they are considered the “most penetrating” particles for a majority of filter types.204\nWhen virus-laden droplet nuclei are deposited on filter media, they penetrate the filter matrix to different depths depending on their size characteristics: larger particles tend to become impacted or intercepted nearer the surface of the intake-facing side, whereas smaller particles penetrate more deeply into the fibrous matrix. In the case of filtering facepiece masks, cyclical breathing can cause changes in the physical characteristics of particles after they have been deposited. Humid exhaled air causes hygroscopic droplet nuclei to swell, becoming larger than they were when captured on filtration media. This size change can affect the ability of the filter fibers to retain particles and can lead to redistribution, shedding, or even breakthrough of particles.\nFrom the standpoint of COVID-19, there are many opportunities for nanotechnology-based solutions to increase the efficiency and safety of air filter and mask devices. Some specific opportunities include (i) improving particle capture and retention characteristics, particularly, in the 300 nm diameter size range; (ii) reducing the effects of exhaled humid air on particle redistribution; (iii) rapid inactivation of membrane-bound microbes including enveloped viruses upon capture; and (iv) thin, high-efficiency filtration media for personal masks that are able to be reused repeatedly without loss of efficiency (e.g., novel electrospun nanofibers). In this context, recent findings exploring the performance of several fabrics commonly used in cloth masks, alone or in combination, suggest that the combined mechanical and electrostatic effect observed in hybrids enabled enhanced performance with a filtration efficiency \u003e80 and \u003e90% for particle sizes \u003c300 and \u003e300 nm, respectively.205\nElectrospinning is a technique that is widely used to produce nanofibers with diameters smaller than a micrometer (typically, ∼100 nm). Even a micron-thin layer of nanofibers can capture the smallest droplets containing viruses and bacteria and prevent them from traveling through the mask. TiO2-coated nanofibers deposited on a filter surface by the electrospinning process can capture submicrometer droplets and destroy the virus upon UV irradiation or under natural sunlight. After a micrometer-thick film of polyamide 11 nanofibers was deposited on polypropylene filter fabric, TiO2 NPs were directly electrosprayed onto the nanofibers.206 Scanning electron microscopy (Figure 7) demonstrated that nanofibers were uniformly coated by TiO2 NPs without agglomeration. TiO2-coated filters showed excellent photocatalytic and bactericidal activity and photoinduced hydrophilicity.\nFigure 7 Scanning electron microscope images of electrospun nanofibers on polypropylene filter fabric (a) and titania-coated electrospun nylon nanofibers (b). Reprinted with permission from ref (206). Copyright 2010 Springer Nature."}

LitCovid-PD-MONDO

{"project":"LitCovid-PD-MONDO","denotations":[{"id":"T209","span":{"begin":143,"end":151},"obj":"Disease"},{"id":"T210","span":{"begin":277,"end":287},"obj":"Disease"},{"id":"T211","span":{"begin":417,"end":446},"obj":"Disease"},{"id":"T212","span":{"begin":1999,"end":2007},"obj":"Disease"},{"id":"T213","span":{"begin":2099,"end":2108},"obj":"Disease"},{"id":"T214","span":{"begin":2137,"end":2145},"obj":"Disease"},{"id":"T215","span":{"begin":2177,"end":2206},"obj":"Disease"},{"id":"T216","span":{"begin":5120,"end":5128},"obj":"Disease"}],"attributes":[{"id":"A209","pred":"mondo_id","subj":"T209","obj":"http://purl.obolibrary.org/obo/MONDO_0005091"},{"id":"A210","pred":"mondo_id","subj":"T210","obj":"http://purl.obolibrary.org/obo/MONDO_0005550"},{"id":"A211","pred":"mondo_id","subj":"T211","obj":"http://purl.obolibrary.org/obo/MONDO_0024355"},{"id":"A212","pred":"mondo_id","subj":"T212","obj":"http://purl.obolibrary.org/obo/MONDO_0005091"},{"id":"A213","pred":"mondo_id","subj":"T213","obj":"http://purl.obolibrary.org/obo/MONDO_0005550"},{"id":"A214","pred":"mondo_id","subj":"T214","obj":"http://purl.obolibrary.org/obo/MONDO_0005091"},{"id":"A215","pred":"mondo_id","subj":"T215","obj":"http://purl.obolibrary.org/obo/MONDO_0024355"},{"id":"A216","pred":"mondo_id","subj":"T216","obj":"http://purl.obolibrary.org/obo/MONDO_0100096"}],"text":"Nanotechnology-Based Solutions to Increase the Efficiency and Safety of Protective Devices\nCryoelectron microscopy (cryo-EM) studies show that SARS-CoV-2 virions are particles near the larger end of the NP size range (70–90 nm).21,201 However, when dispersed into the air, the infectious particles exist as functionally larger particles. Initially, liquid droplets containing coronavirus virions originating from the respiratory tract of infected patients are emitted during normal breathing, forced expiration (e.g., coughing and sneezing), or aerosol-generating medical procedures (e.g., intubation and suctioning). Liquid droplets emitted into the air through these mechanisms originate from points throughout the respiratory tract and carry within them virions as well as other materials associated with the airways, including bacterial cells and epithelial cells (Figure 5). Droplets are emitted over a wide size range, and their potential viral burden is a cubic function of particle diameter (Figure 6). Thus, larger droplets have the potential to carry a significantly larger burden of virions according to their size and are substantially more hazardous than small droplets. Once emitted into the air, water from droplets immediately begins to evaporate. Water loss is associated with a rapid decrease in both particle diameter and terminal settling velocity (the equilibrium rate of fall of a particle in still air). The rate of evaporation of the largest droplets (\u003e150 μm) is often insufficient to slow their swift descent in air, and they impact on nearby surfaces. However, the rapid water loss and sharp slowing of settling velocity of smaller droplets enables them to avoid a similar fate. Their constituent solid residues are instead drawn together during evaporation and cemented with dried respiratory secretions, and they remain aloft as droplet nuclei. Several epidemiological studies have supported the potential for droplet nuclei to be an important means of transmission for SARS-CoV-2.202,203\nFigure 5 Droplets and droplet nuclei as important mechanism for transmission of infection. Liquid droplets containing SARS-CoV-2 virions originating from the respiratory tract of infected patients are emitted into the air and carry other materials including bacterial cells and epithelial cells. They are reduced in size by evaporation to small, dry particles resulting in droplet nuclei.\nFigure 6 Maximum theoretical viral burden versus droplet nucleus size (nm). Assuming a median virion size of about 100 nm, a droplet nucleus of 1 μm diameter could contain up to 370 randomly packed virions. A similar 10 μm diameter droplet nucleus could contain up to 360,000. In practical terms, however, the size-defining element of a droplet nucleus is determined by the component item with the largest volume, which is often a bacterial cell or an epithelial cell. Thus, droplet nuclei in the 1–10 μm size range and above contain far fewer virions than this theoretical maximum.\nFilter media, such as those used in N95 masks and in mechanical ventilation systems, consist of myriad interwoven fibers through which air is moved. Their purpose is to arrest particles as they move through the matrix. Filters capture particles chiefly by three mechanisms: impaction, interception, and diffusion. Impaction occurs when the momentum of a particle propelled toward a filter fiber prevents the particle from diverging around the fiber along the flow lines of the air stream, causing the particle to collide with the fiber. Impaction is the primary mechanism responsible for removing particles greater than 500 nm in diameter. Interception occurs when a particle diverges around a fiber along the flow lines of the airstream, the distance between the vector of the airstream and the centroid of the particle is smaller than the radius of the particle, and the particle touches the fiber. Interception operates efficiently on particles greater than 200 nm in diameter. Diffusion is the final important mechanism of particle removal, and it is most effective at removing very fine particles less than 200 nm, especially at low flow rates. Particles around 300 nm in diameter are least subject to these three removal mechanisms, and they are considered the “most penetrating” particles for a majority of filter types.204\nWhen virus-laden droplet nuclei are deposited on filter media, they penetrate the filter matrix to different depths depending on their size characteristics: larger particles tend to become impacted or intercepted nearer the surface of the intake-facing side, whereas smaller particles penetrate more deeply into the fibrous matrix. In the case of filtering facepiece masks, cyclical breathing can cause changes in the physical characteristics of particles after they have been deposited. Humid exhaled air causes hygroscopic droplet nuclei to swell, becoming larger than they were when captured on filtration media. This size change can affect the ability of the filter fibers to retain particles and can lead to redistribution, shedding, or even breakthrough of particles.\nFrom the standpoint of COVID-19, there are many opportunities for nanotechnology-based solutions to increase the efficiency and safety of air filter and mask devices. Some specific opportunities include (i) improving particle capture and retention characteristics, particularly, in the 300 nm diameter size range; (ii) reducing the effects of exhaled humid air on particle redistribution; (iii) rapid inactivation of membrane-bound microbes including enveloped viruses upon capture; and (iv) thin, high-efficiency filtration media for personal masks that are able to be reused repeatedly without loss of efficiency (e.g., novel electrospun nanofibers). In this context, recent findings exploring the performance of several fabrics commonly used in cloth masks, alone or in combination, suggest that the combined mechanical and electrostatic effect observed in hybrids enabled enhanced performance with a filtration efficiency \u003e80 and \u003e90% for particle sizes \u003c300 and \u003e300 nm, respectively.205\nElectrospinning is a technique that is widely used to produce nanofibers with diameters smaller than a micrometer (typically, ∼100 nm). Even a micron-thin layer of nanofibers can capture the smallest droplets containing viruses and bacteria and prevent them from traveling through the mask. TiO2-coated nanofibers deposited on a filter surface by the electrospinning process can capture submicrometer droplets and destroy the virus upon UV irradiation or under natural sunlight. After a micrometer-thick film of polyamide 11 nanofibers was deposited on polypropylene filter fabric, TiO2 NPs were directly electrosprayed onto the nanofibers.206 Scanning electron microscopy (Figure 7) demonstrated that nanofibers were uniformly coated by TiO2 NPs without agglomeration. TiO2-coated filters showed excellent photocatalytic and bactericidal activity and photoinduced hydrophilicity.\nFigure 7 Scanning electron microscope images of electrospun nanofibers on polypropylene filter fabric (a) and titania-coated electrospun nylon nanofibers (b). Reprinted with permission from ref (206). Copyright 2010 Springer Nature."}

LitCovid-PD-CLO

LitCovid-PD-CHEBI

LitCovid-PD-HP

{"project":"LitCovid-PD-HP","denotations":[{"id":"T44","span":{"begin":417,"end":446},"obj":"Phenotype"},{"id":"T45","span":{"begin":518,"end":526},"obj":"Phenotype"},{"id":"T46","span":{"begin":2177,"end":2206},"obj":"Phenotype"}],"attributes":[{"id":"A44","pred":"hp_id","subj":"T44","obj":"http://purl.obolibrary.org/obo/HP_0011947"},{"id":"A45","pred":"hp_id","subj":"T45","obj":"http://purl.obolibrary.org/obo/HP_0012735"},{"id":"A46","pred":"hp_id","subj":"T46","obj":"http://purl.obolibrary.org/obo/HP_0011947"}],"text":"Nanotechnology-Based Solutions to Increase the Efficiency and Safety of Protective Devices\nCryoelectron microscopy (cryo-EM) studies show that SARS-CoV-2 virions are particles near the larger end of the NP size range (70–90 nm).21,201 However, when dispersed into the air, the infectious particles exist as functionally larger particles. Initially, liquid droplets containing coronavirus virions originating from the respiratory tract of infected patients are emitted during normal breathing, forced expiration (e.g., coughing and sneezing), or aerosol-generating medical procedures (e.g., intubation and suctioning). Liquid droplets emitted into the air through these mechanisms originate from points throughout the respiratory tract and carry within them virions as well as other materials associated with the airways, including bacterial cells and epithelial cells (Figure 5). Droplets are emitted over a wide size range, and their potential viral burden is a cubic function of particle diameter (Figure 6). Thus, larger droplets have the potential to carry a significantly larger burden of virions according to their size and are substantially more hazardous than small droplets. Once emitted into the air, water from droplets immediately begins to evaporate. Water loss is associated with a rapid decrease in both particle diameter and terminal settling velocity (the equilibrium rate of fall of a particle in still air). The rate of evaporation of the largest droplets (\u003e150 μm) is often insufficient to slow their swift descent in air, and they impact on nearby surfaces. However, the rapid water loss and sharp slowing of settling velocity of smaller droplets enables them to avoid a similar fate. Their constituent solid residues are instead drawn together during evaporation and cemented with dried respiratory secretions, and they remain aloft as droplet nuclei. Several epidemiological studies have supported the potential for droplet nuclei to be an important means of transmission for SARS-CoV-2.202,203\nFigure 5 Droplets and droplet nuclei as important mechanism for transmission of infection. Liquid droplets containing SARS-CoV-2 virions originating from the respiratory tract of infected patients are emitted into the air and carry other materials including bacterial cells and epithelial cells. They are reduced in size by evaporation to small, dry particles resulting in droplet nuclei.\nFigure 6 Maximum theoretical viral burden versus droplet nucleus size (nm). Assuming a median virion size of about 100 nm, a droplet nucleus of 1 μm diameter could contain up to 370 randomly packed virions. A similar 10 μm diameter droplet nucleus could contain up to 360,000. In practical terms, however, the size-defining element of a droplet nucleus is determined by the component item with the largest volume, which is often a bacterial cell or an epithelial cell. Thus, droplet nuclei in the 1–10 μm size range and above contain far fewer virions than this theoretical maximum.\nFilter media, such as those used in N95 masks and in mechanical ventilation systems, consist of myriad interwoven fibers through which air is moved. Their purpose is to arrest particles as they move through the matrix. Filters capture particles chiefly by three mechanisms: impaction, interception, and diffusion. Impaction occurs when the momentum of a particle propelled toward a filter fiber prevents the particle from diverging around the fiber along the flow lines of the air stream, causing the particle to collide with the fiber. Impaction is the primary mechanism responsible for removing particles greater than 500 nm in diameter. Interception occurs when a particle diverges around a fiber along the flow lines of the airstream, the distance between the vector of the airstream and the centroid of the particle is smaller than the radius of the particle, and the particle touches the fiber. Interception operates efficiently on particles greater than 200 nm in diameter. Diffusion is the final important mechanism of particle removal, and it is most effective at removing very fine particles less than 200 nm, especially at low flow rates. Particles around 300 nm in diameter are least subject to these three removal mechanisms, and they are considered the “most penetrating” particles for a majority of filter types.204\nWhen virus-laden droplet nuclei are deposited on filter media, they penetrate the filter matrix to different depths depending on their size characteristics: larger particles tend to become impacted or intercepted nearer the surface of the intake-facing side, whereas smaller particles penetrate more deeply into the fibrous matrix. In the case of filtering facepiece masks, cyclical breathing can cause changes in the physical characteristics of particles after they have been deposited. Humid exhaled air causes hygroscopic droplet nuclei to swell, becoming larger than they were when captured on filtration media. This size change can affect the ability of the filter fibers to retain particles and can lead to redistribution, shedding, or even breakthrough of particles.\nFrom the standpoint of COVID-19, there are many opportunities for nanotechnology-based solutions to increase the efficiency and safety of air filter and mask devices. Some specific opportunities include (i) improving particle capture and retention characteristics, particularly, in the 300 nm diameter size range; (ii) reducing the effects of exhaled humid air on particle redistribution; (iii) rapid inactivation of membrane-bound microbes including enveloped viruses upon capture; and (iv) thin, high-efficiency filtration media for personal masks that are able to be reused repeatedly without loss of efficiency (e.g., novel electrospun nanofibers). In this context, recent findings exploring the performance of several fabrics commonly used in cloth masks, alone or in combination, suggest that the combined mechanical and electrostatic effect observed in hybrids enabled enhanced performance with a filtration efficiency \u003e80 and \u003e90% for particle sizes \u003c300 and \u003e300 nm, respectively.205\nElectrospinning is a technique that is widely used to produce nanofibers with diameters smaller than a micrometer (typically, ∼100 nm). Even a micron-thin layer of nanofibers can capture the smallest droplets containing viruses and bacteria and prevent them from traveling through the mask. TiO2-coated nanofibers deposited on a filter surface by the electrospinning process can capture submicrometer droplets and destroy the virus upon UV irradiation or under natural sunlight. After a micrometer-thick film of polyamide 11 nanofibers was deposited on polypropylene filter fabric, TiO2 NPs were directly electrosprayed onto the nanofibers.206 Scanning electron microscopy (Figure 7) demonstrated that nanofibers were uniformly coated by TiO2 NPs without agglomeration. TiO2-coated filters showed excellent photocatalytic and bactericidal activity and photoinduced hydrophilicity.\nFigure 7 Scanning electron microscope images of electrospun nanofibers on polypropylene filter fabric (a) and titania-coated electrospun nylon nanofibers (b). Reprinted with permission from ref (206). Copyright 2010 Springer Nature."}

LitCovid-PD-GO-BP

{"project":"LitCovid-PD-GO-BP","denotations":[{"id":"T76","span":{"begin":482,"end":491},"obj":"http://purl.obolibrary.org/obo/GO_0007585"},{"id":"T77","span":{"begin":1821,"end":1831},"obj":"http://purl.obolibrary.org/obo/GO_0046903"},{"id":"T78","span":{"begin":4706,"end":4715},"obj":"http://purl.obolibrary.org/obo/GO_0007585"},{"id":"T79","span":{"begin":5335,"end":5344},"obj":"http://purl.obolibrary.org/obo/GO_0051235"}],"text":"Nanotechnology-Based Solutions to Increase the Efficiency and Safety of Protective Devices\nCryoelectron microscopy (cryo-EM) studies show that SARS-CoV-2 virions are particles near the larger end of the NP size range (70–90 nm).21,201 However, when dispersed into the air, the infectious particles exist as functionally larger particles. Initially, liquid droplets containing coronavirus virions originating from the respiratory tract of infected patients are emitted during normal breathing, forced expiration (e.g., coughing and sneezing), or aerosol-generating medical procedures (e.g., intubation and suctioning). Liquid droplets emitted into the air through these mechanisms originate from points throughout the respiratory tract and carry within them virions as well as other materials associated with the airways, including bacterial cells and epithelial cells (Figure 5). Droplets are emitted over a wide size range, and their potential viral burden is a cubic function of particle diameter (Figure 6). Thus, larger droplets have the potential to carry a significantly larger burden of virions according to their size and are substantially more hazardous than small droplets. Once emitted into the air, water from droplets immediately begins to evaporate. Water loss is associated with a rapid decrease in both particle diameter and terminal settling velocity (the equilibrium rate of fall of a particle in still air). The rate of evaporation of the largest droplets (\u003e150 μm) is often insufficient to slow their swift descent in air, and they impact on nearby surfaces. However, the rapid water loss and sharp slowing of settling velocity of smaller droplets enables them to avoid a similar fate. Their constituent solid residues are instead drawn together during evaporation and cemented with dried respiratory secretions, and they remain aloft as droplet nuclei. Several epidemiological studies have supported the potential for droplet nuclei to be an important means of transmission for SARS-CoV-2.202,203\nFigure 5 Droplets and droplet nuclei as important mechanism for transmission of infection. Liquid droplets containing SARS-CoV-2 virions originating from the respiratory tract of infected patients are emitted into the air and carry other materials including bacterial cells and epithelial cells. They are reduced in size by evaporation to small, dry particles resulting in droplet nuclei.\nFigure 6 Maximum theoretical viral burden versus droplet nucleus size (nm). Assuming a median virion size of about 100 nm, a droplet nucleus of 1 μm diameter could contain up to 370 randomly packed virions. A similar 10 μm diameter droplet nucleus could contain up to 360,000. In practical terms, however, the size-defining element of a droplet nucleus is determined by the component item with the largest volume, which is often a bacterial cell or an epithelial cell. Thus, droplet nuclei in the 1–10 μm size range and above contain far fewer virions than this theoretical maximum.\nFilter media, such as those used in N95 masks and in mechanical ventilation systems, consist of myriad interwoven fibers through which air is moved. Their purpose is to arrest particles as they move through the matrix. Filters capture particles chiefly by three mechanisms: impaction, interception, and diffusion. Impaction occurs when the momentum of a particle propelled toward a filter fiber prevents the particle from diverging around the fiber along the flow lines of the air stream, causing the particle to collide with the fiber. Impaction is the primary mechanism responsible for removing particles greater than 500 nm in diameter. Interception occurs when a particle diverges around a fiber along the flow lines of the airstream, the distance between the vector of the airstream and the centroid of the particle is smaller than the radius of the particle, and the particle touches the fiber. Interception operates efficiently on particles greater than 200 nm in diameter. Diffusion is the final important mechanism of particle removal, and it is most effective at removing very fine particles less than 200 nm, especially at low flow rates. Particles around 300 nm in diameter are least subject to these three removal mechanisms, and they are considered the “most penetrating” particles for a majority of filter types.204\nWhen virus-laden droplet nuclei are deposited on filter media, they penetrate the filter matrix to different depths depending on their size characteristics: larger particles tend to become impacted or intercepted nearer the surface of the intake-facing side, whereas smaller particles penetrate more deeply into the fibrous matrix. In the case of filtering facepiece masks, cyclical breathing can cause changes in the physical characteristics of particles after they have been deposited. Humid exhaled air causes hygroscopic droplet nuclei to swell, becoming larger than they were when captured on filtration media. This size change can affect the ability of the filter fibers to retain particles and can lead to redistribution, shedding, or even breakthrough of particles.\nFrom the standpoint of COVID-19, there are many opportunities for nanotechnology-based solutions to increase the efficiency and safety of air filter and mask devices. Some specific opportunities include (i) improving particle capture and retention characteristics, particularly, in the 300 nm diameter size range; (ii) reducing the effects of exhaled humid air on particle redistribution; (iii) rapid inactivation of membrane-bound microbes including enveloped viruses upon capture; and (iv) thin, high-efficiency filtration media for personal masks that are able to be reused repeatedly without loss of efficiency (e.g., novel electrospun nanofibers). In this context, recent findings exploring the performance of several fabrics commonly used in cloth masks, alone or in combination, suggest that the combined mechanical and electrostatic effect observed in hybrids enabled enhanced performance with a filtration efficiency \u003e80 and \u003e90% for particle sizes \u003c300 and \u003e300 nm, respectively.205\nElectrospinning is a technique that is widely used to produce nanofibers with diameters smaller than a micrometer (typically, ∼100 nm). Even a micron-thin layer of nanofibers can capture the smallest droplets containing viruses and bacteria and prevent them from traveling through the mask. TiO2-coated nanofibers deposited on a filter surface by the electrospinning process can capture submicrometer droplets and destroy the virus upon UV irradiation or under natural sunlight. After a micrometer-thick film of polyamide 11 nanofibers was deposited on polypropylene filter fabric, TiO2 NPs were directly electrosprayed onto the nanofibers.206 Scanning electron microscopy (Figure 7) demonstrated that nanofibers were uniformly coated by TiO2 NPs without agglomeration. TiO2-coated filters showed excellent photocatalytic and bactericidal activity and photoinduced hydrophilicity.\nFigure 7 Scanning electron microscope images of electrospun nanofibers on polypropylene filter fabric (a) and titania-coated electrospun nylon nanofibers (b). Reprinted with permission from ref (206). Copyright 2010 Springer Nature."}

LitCovid-sentences

LitCovid-PubTator

2_test

{"project":"2_test","denotations":[{"id":"32519842-32333836-158624","span":{"begin":228,"end":230},"obj":"32333836"},{"id":"32519842-32149036-158625","span":{"begin":231,"end":234},"obj":"32149036"},{"id":"32519842-31986261-158626","span":{"begin":2010,"end":2013},"obj":"31986261"},{"id":"32519842-32329337-158627","span":{"begin":6086,"end":6089},"obj":"32329337"}],"text":"Nanotechnology-Based Solutions to Increase the Efficiency and Safety of Protective Devices\nCryoelectron microscopy (cryo-EM) studies show that SARS-CoV-2 virions are particles near the larger end of the NP size range (70–90 nm).21,201 However, when dispersed into the air, the infectious particles exist as functionally larger particles. Initially, liquid droplets containing coronavirus virions originating from the respiratory tract of infected patients are emitted during normal breathing, forced expiration (e.g., coughing and sneezing), or aerosol-generating medical procedures (e.g., intubation and suctioning). Liquid droplets emitted into the air through these mechanisms originate from points throughout the respiratory tract and carry within them virions as well as other materials associated with the airways, including bacterial cells and epithelial cells (Figure 5). Droplets are emitted over a wide size range, and their potential viral burden is a cubic function of particle diameter (Figure 6). Thus, larger droplets have the potential to carry a significantly larger burden of virions according to their size and are substantially more hazardous than small droplets. Once emitted into the air, water from droplets immediately begins to evaporate. Water loss is associated with a rapid decrease in both particle diameter and terminal settling velocity (the equilibrium rate of fall of a particle in still air). The rate of evaporation of the largest droplets (\u003e150 μm) is often insufficient to slow their swift descent in air, and they impact on nearby surfaces. However, the rapid water loss and sharp slowing of settling velocity of smaller droplets enables them to avoid a similar fate. Their constituent solid residues are instead drawn together during evaporation and cemented with dried respiratory secretions, and they remain aloft as droplet nuclei. Several epidemiological studies have supported the potential for droplet nuclei to be an important means of transmission for SARS-CoV-2.202,203\nFigure 5 Droplets and droplet nuclei as important mechanism for transmission of infection. Liquid droplets containing SARS-CoV-2 virions originating from the respiratory tract of infected patients are emitted into the air and carry other materials including bacterial cells and epithelial cells. They are reduced in size by evaporation to small, dry particles resulting in droplet nuclei.\nFigure 6 Maximum theoretical viral burden versus droplet nucleus size (nm). Assuming a median virion size of about 100 nm, a droplet nucleus of 1 μm diameter could contain up to 370 randomly packed virions. A similar 10 μm diameter droplet nucleus could contain up to 360,000. In practical terms, however, the size-defining element of a droplet nucleus is determined by the component item with the largest volume, which is often a bacterial cell or an epithelial cell. Thus, droplet nuclei in the 1–10 μm size range and above contain far fewer virions than this theoretical maximum.\nFilter media, such as those used in N95 masks and in mechanical ventilation systems, consist of myriad interwoven fibers through which air is moved. Their purpose is to arrest particles as they move through the matrix. Filters capture particles chiefly by three mechanisms: impaction, interception, and diffusion. Impaction occurs when the momentum of a particle propelled toward a filter fiber prevents the particle from diverging around the fiber along the flow lines of the air stream, causing the particle to collide with the fiber. Impaction is the primary mechanism responsible for removing particles greater than 500 nm in diameter. Interception occurs when a particle diverges around a fiber along the flow lines of the airstream, the distance between the vector of the airstream and the centroid of the particle is smaller than the radius of the particle, and the particle touches the fiber. Interception operates efficiently on particles greater than 200 nm in diameter. Diffusion is the final important mechanism of particle removal, and it is most effective at removing very fine particles less than 200 nm, especially at low flow rates. Particles around 300 nm in diameter are least subject to these three removal mechanisms, and they are considered the “most penetrating” particles for a majority of filter types.204\nWhen virus-laden droplet nuclei are deposited on filter media, they penetrate the filter matrix to different depths depending on their size characteristics: larger particles tend to become impacted or intercepted nearer the surface of the intake-facing side, whereas smaller particles penetrate more deeply into the fibrous matrix. In the case of filtering facepiece masks, cyclical breathing can cause changes in the physical characteristics of particles after they have been deposited. Humid exhaled air causes hygroscopic droplet nuclei to swell, becoming larger than they were when captured on filtration media. This size change can affect the ability of the filter fibers to retain particles and can lead to redistribution, shedding, or even breakthrough of particles.\nFrom the standpoint of COVID-19, there are many opportunities for nanotechnology-based solutions to increase the efficiency and safety of air filter and mask devices. Some specific opportunities include (i) improving particle capture and retention characteristics, particularly, in the 300 nm diameter size range; (ii) reducing the effects of exhaled humid air on particle redistribution; (iii) rapid inactivation of membrane-bound microbes including enveloped viruses upon capture; and (iv) thin, high-efficiency filtration media for personal masks that are able to be reused repeatedly without loss of efficiency (e.g., novel electrospun nanofibers). In this context, recent findings exploring the performance of several fabrics commonly used in cloth masks, alone or in combination, suggest that the combined mechanical and electrostatic effect observed in hybrids enabled enhanced performance with a filtration efficiency \u003e80 and \u003e90% for particle sizes \u003c300 and \u003e300 nm, respectively.205\nElectrospinning is a technique that is widely used to produce nanofibers with diameters smaller than a micrometer (typically, ∼100 nm). Even a micron-thin layer of nanofibers can capture the smallest droplets containing viruses and bacteria and prevent them from traveling through the mask. TiO2-coated nanofibers deposited on a filter surface by the electrospinning process can capture submicrometer droplets and destroy the virus upon UV irradiation or under natural sunlight. After a micrometer-thick film of polyamide 11 nanofibers was deposited on polypropylene filter fabric, TiO2 NPs were directly electrosprayed onto the nanofibers.206 Scanning electron microscopy (Figure 7) demonstrated that nanofibers were uniformly coated by TiO2 NPs without agglomeration. TiO2-coated filters showed excellent photocatalytic and bactericidal activity and photoinduced hydrophilicity.\nFigure 7 Scanning electron microscope images of electrospun nanofibers on polypropylene filter fabric (a) and titania-coated electrospun nylon nanofibers (b). Reprinted with permission from ref (206). Copyright 2010 Springer Nature."}

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