LitCovid-sentences  

PMC:7796291 / 12303-26231 JSONTXT 2 Projects

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Id Subject Object Predicate Lexical cue
T106 0-2 Sentence denotes 3.
T107 3-25 Sentence denotes Results and Discussion
T108 26-145 Sentence denotes The influence of various disinfection methods on the filtration and bactericidal performance was investigated for Resp.
T109 146-157 Sentence denotes A and Resp.
T110 158-160 Sentence denotes B.
T111 161-286 Sentence denotes The 3D images of layer constructions for those respirators were analyzed by the X-ray computed tomography (Xμ-CT) (Figure 1).
T112 287-466 Sentence denotes Common components of respirators included: a spunbond coverweb, one or two layers of electrostatically charged meltblown filter webs, and a spunbond inner web. respirator A (Resp.
T113 467-533 Sentence denotes A) had an additional stiffener web and 2 layers of meltblown webs.
T114 534-627 Sentence denotes The meltblown filter web was comprised of very thin fibers <2.5 μm in a considerable portion.
T115 628-660 Sentence denotes In contrast, respirator B (Resp.
T116 661-757 Sentence denotes B) consisted of a single layer filter web of which fiber diameter ranged from 2.5 μm to 12.5 μm.
T117 758-913 Sentence denotes The thickness of each layer of the respirators was measured firsthand with a thickness gauge applying a pressure of 2.4 N, and is presented in Figure 1C,F.
T118 914-1039 Sentence denotes It is noted that the measurements by the gauge were smaller than those estimated from the specific locations of Xμ-CT images.
T119 1040-1138 Sentence denotes When analyzing the morphological changes in the later sections, first-hand measurements were used.
T120 1140-1144 Sentence denotes 3.1.
T121 1145-1203 Sentence denotes Filtration Performance with Varied Disinfection Treatments
T122 1204-1327 Sentence denotes Varied disinfection methods accessible to the general public were investigated for their effects on filtration performance.
T123 1328-1427 Sentence denotes Without disinfection treatments, both respirators showed very high filtration efficiency of ≥99.5%.
T124 1428-1643 Sentence denotes It should be noted that the filtration efficiency was measured after challenging the respective aerosols for 3 min (by the KF standard) [35], which corresponded to about 2.7 mg of NaCl and 8 mg of paraffin oil mass.
T125 1644-1826 Sentence denotes The filtration performance against NaCl and paraffin oil aerosols were comparable, and the effects of various treatments on filtration of either aerosol were very similar (Figure 2).
T126 1827-1983 Sentence denotes The resistances of respirators were mostly consistent regardless of treatments, except that laundering treatments slightly decreased the resistance of Resp.
T127 1984-1986 Sentence denotes A.
T128 1987-2102 Sentence denotes The physical characteristics of respirators before and after treatment were further investigated in later sections.
T129 2103-2264 Sentence denotes As for the filtration efficiency, the organic solvents such as IPA and EtOH, and detergent-laundering deteriorated the filtration efficiency of both respirators.
T130 2265-2358 Sentence denotes Particularly for IPA and EtOH treatments, up to ~28% of efficiency was lost after treatments.
T131 2359-2621 Sentence denotes Considering that the resistance of the solvent-treated samples was unchanged, it can be inferred that the solvents caused the reduction of filtration performance by affecting the electrostatic filtration capacity, rather than disrupting the structural integrity.
T132 2622-2711 Sentence denotes Similarly, the filtration efficiency was notably reduced after laundering with detergent.
T133 2712-2904 Sentence denotes As laundering with water barely affected the filtration efficiency, this indicates that the detergent negatively affected it, probably through an impact on the electrostatic capture mechanism.
T134 2905-3051 Sentence denotes Physical treatments employing UV irradiation, oven-dry, and microwave irradiation caused little impact on the filtration efficiency or resistance.
T135 3052-3309 Sentence denotes Previous studies reported the deteriorated performance with thermal treatment of electret filters [10,41], but most of the performance deterioration occurred with harsher conditions (120 °C, 48 h) and especially for materials with high dielectric constants.
T136 3310-3507 Sentence denotes Aging the electret filter at an extremely high temperature can trigger the mobility of polymer chains and charge carriers, leading to the loss of charges and increased particulate penetration [41].
T137 3508-3746 Sentence denotes In this study, the polypropylene electret filters were treated by the oven-dry condition that was relatively mild and short-term (90 °C, 1 h); and for this reason, the oven-dry treatment caused negligible effect on the performance change.
T138 3747-3992 Sentence denotes UV irradiation may influence the performance by causing the surface oxidation, turning the surface hydrophilic [42]; and the increased conductivity in a humid condition can lead to the loss of charges, reducing the filtration efficiency [43,44].
T139 3993-4140 Sentence denotes However, UV irradiation, at the level of 10 W power with 253.7 nm wavelength, of this study did not significantly affect the filtration efficiency.
T140 4141-4371 Sentence denotes The results in Figure 2 show that thermal (oven-dry and microwave) and UV treatments hardly affected the filtration performance, aside from the fact that microwaving is not recommended for the safety reasons with metal components.
T141 4372-4450 Sentence denotes Samples laundered with water maintained the performance as the untreated ones.
T142 4451-4569 Sentence denotes However, the probable structural change, the torn coverweb (Figure S3), during the laundering procedure is of concern.
T143 4570-4693 Sentence denotes Thickness and porosity of filter webs after treatments showed little differences compared to the untreated webs (Table S1).
T144 4694-4814 Sentence denotes The residues on fibers after detergent-laundering is also of concern in the regard of environmental impacts (Figure S5).
T145 4816-4820 Sentence denotes 3.2.
T146 4821-4833 Sentence denotes Charge Decay
T147 4834-4957 Sentence denotes To examine the cause of reduced performance, the surface potential of the filter web was measured (Figure 3 and Figure S6).
T148 4958-5171 Sentence denotes The surface charges of the filter media are not consistently positive or negative; instead, both positive and negative charges can exist simultaneously, compensating the overall charges on the filter surface [45].
T149 5172-5297 Sentence denotes Therefore, for such cases, the average surface potential over an area can be less meaningful than the variation of potential.
T150 5298-5472 Sentence denotes In Figure 3, the surface potential across the horizontal line was measured by line-scanning, and the fluctuation of the voltage values was observed as an important parameter.
T151 5473-5699 Sentence denotes The surface potential of the untreated filter webs from respirators A and B ranged from −1.6 kV to +4.4 kV, and these surface charges contributed to particle capture either by coulombic attraction or induced polarization [46].
T152 5700-5830 Sentence denotes When the electret media was exposed to IPA, EtOH, and detergent solution, the range of surface potential was considerably reduced.
T153 5831-5969 Sentence denotes In particular, IPA-treated respirator exhibited nearly 0 kV invariably across all areas, clearly indicating the loss of surface potential.
T154 5970-6153 Sentence denotes The EtOH or detergent-treated respirators showed a slightly larger variation than the IPA-treated ones, indicating that surface charges may not be completely lost by those treatments.
T155 6154-6375 Sentence denotes The remaining charges would contribute to electrostatic filtration mechanism, as indicated by the higher filtration efficiency of EtOH and detergent-treated respirators compared to that of the IPA-treated ones (Figure 2).
T156 6376-6550 Sentence denotes The charge decay occurred by the exposure to alcohol and detergent solution was probably due to the mobility of the charge carrier caused by the penetration of liquid [9,24].
T157 6551-6698 Sentence denotes Water has high surface tension and does not wet the polypropylene (PP) surface; therefore, the effect of water-immersion on PP media is negligible.
T158 6699-6927 Sentence denotes IPA and EtOH immediately wetted the PP media in each layer as represented by the contact angle ~0° (Figure 4); and penetration of solvents into PP molecules expedited the charge carrier mobility, quickly dissipating the charges.
T159 6928-7080 Sentence denotes In the case of 0.1% detergent solution, instantaneous contact angle was around 120°, then within 30~60 s, the PP web fully absorbed the liquid droplets.
T160 7081-7264 Sentence denotes As the affinity of detergent solution to PP was not as high as EtOH or IPA, the impact of detergent on the electrostatic filtration was not as significant as that of organic solvents.
T161 7265-7432 Sentence denotes Unlike the other test liquid, the ClO− droplet maintained the contact angle of 140° without spreading, and the electrostatic filtration was hardly affected (Figure 2).
T162 7433-7703 Sentence denotes Among the treatments, detergent treatment reduced the contact angle; this increased surface wettability of filter web would adversely influence the charge retention by increasing the electric conductivity, as evidenced from the surface potential measurement in Figure 3.
T163 7704-7803 Sentence denotes As a result, the filtration performance after detergent treatment significantly decreased (≥10.8%).
T164 7804-7974 Sentence denotes To examine whether UV-treated or detergent-laundered respirators changed their chemistry, contact angles and FTIR spectra from those surfaces were examined (Figure 4B,C).
T165 7975-8147 Sentence denotes Untreated PP media has C-H stretching (2906 cm−1), CH2/CH3 asymmetrical bending (around 2982 cm−1), and other carbon and hydrogen bonding (2835 to 2972 cm−1) peaks [47,48].
T166 8148-8275 Sentence denotes After UV irradiation, distinctive peaks were observed for: C-O-C (around 1058 cm−1) and O-H bending (around 1161 cm−1) [49,50].
T167 8276-8430 Sentence denotes The changed surface chemistry seemed to attribute to surface oxidation, but hardly affected the wettability and filtration performance after UV treatment.
T168 8431-8543 Sentence denotes Solvent treatments with IPA, EtOH, and ClO− showed neither noxious residues nor distinctive hydrophilic bonding.
T169 8545-8549 Sentence denotes 3.3.
T170 8550-8571 Sentence denotes Mechanical Filtration
T171 8572-8686 Sentence denotes The particle capture of an electret filter is contributed by both mechanical and electrostatic capture mechanisms.
T172 8687-8919 Sentence denotes An electrostatic capture mechanism significantly improves the quality factor (filtration performance per a unit resistance); and when the surface charges are decayed, filtration mostly depends on the mechanical capture of particles.
T173 8920-9153 Sentence denotes It is well accepted that IPA treatment removes the surface charges of filter media; therefore, the IPA-treated samples can be deemed as the mechanical filter (mechanical contribution noted as “mech. cont’n”) (Figure 2 and Figure 3B).
T174 9154-9309 Sentence denotes The performance above this level of filtration for the untreated respirators A and B is considered as the electrostatic capture mechanism (electr. cont’n).
T175 9310-9585 Sentence denotes Disinfection treatments such as solvent immersion, UV, oven-dry, and microwaving seemed to have negligible impacts on the structural integrity (Figures S3 and S4); accordingly, there were no apparent changes in the resistance and mechanical filtration after those treatments.
T176 9586-9703 Sentence denotes Notable fiber damage was found in the laundered samples by the external force imposed during laundering (Figure S3A).
T177 9704-9732 Sentence denotes The physical damage of Resp.
T178 9733-9881 Sentence denotes A resulted in the decrease of resistance and mechanical filtration performance, corresponding to the lower filtration efficiency compared with Resp.
T179 9882-9884 Sentence denotes B.
T180 9886-9890 Sentence denotes 3.4.
T181 9891-9942 Sentence denotes Bactericidal Performance of Disinfection Treatments
T182 9943-10075 Sentence denotes To investigate the disinfection efficacy, the number of survived colony on respirators after disinfection treatments was quantified.
T183 10076-10258 Sentence denotes The E. coli culture was loaded on the respirators applying physical pressure; the bacteria culture penetrated up to the stiffener, and did not penetrate beyond this layer (Figure 5).
T184 10259-10355 Sentence denotes Without the physical pressure, the loaded culture drop rolled around on the surface of coverweb.
T185 10356-10480 Sentence denotes The number of loaded E. coli by each layer was correlated with OD470 measurement and expressed as CFU/cm2 substrate surface.
T186 10481-10762 Sentence denotes Bacteria inactivation or removal efficiency was calculated by: (B0−Bn)B×100 (%), where B0 is the number of live bacteria in the untreated sample area, and Bn is the number of live bacteria in the treated sample area (n = 1~8, each number indicating the eight disinfection methods).
T187 10763-10815 Sentence denotes Bactericidal or bacteria removal efficiency of Resp.
T188 10816-10853 Sentence denotes A is shown in Figure 6 and Figure S7.
T189 10854-11010 Sentence denotes In the 2.5 cm × 2.5 cm designated area of each web, non-treated samples showed ~1.46 × 106 and ~2.53 × 106 CFUs on the coverweb and stiffener, respectively.
T190 11011-11214 Sentence denotes Microwaving, oven-dry, and UV treatment showed similar bactericidal effect up to about 82%; in fact, this is inconsistent with previous studies [18,20], where 99.99% inactivation efficiency was achieved.
T191 11215-11366 Sentence denotes This discrepancy can be attributed to the different treatment conditions, such as irradiation intensity, treatment time, and amount of bacteria loaded.
T192 11367-11592 Sentence denotes In a previous study, 1.0 × 106 CFU of bacteria was loaded on the respirator with a nebulizer; and the UV irradiation (wavelength; 254 nm, 5 min) and microwaving (400 W, 10 min) resulted in complete inactivation of cells [18].
T193 11593-11773 Sentence denotes The case of an oven-dry treatment (100 °C, 15 min) also achieved 99.99% inactivation efficiency, when 5.0 × 104 CFU of bacteria was dropped onto the surface of the respirator [20].
T194 11774-11904 Sentence denotes Compared to previous studies, this study built a harsher experimental condition with a higher loading of bacteria (5.0 × 106 CFU).
T195 11905-12097 Sentence denotes As a result, the intensity of microwaving (750 W, 2 min), UV irradiation (wavelength; 253.7 nm, 2 h), and oven-dry (90 °C, 1 h) of this study were insufficient for complete sterilization [51].
T196 12098-12292 Sentence denotes Chemical solvents (ClO−, EtOH, and IPA) and laundering treatments showed no color change with cell staining, indicating 100% bactericidal or bacteria removal efficiency (Figure 6 and Figure S7).
T197 12293-12401 Sentence denotes The morphological state of loaded bacteria after disinfection treatments was analyzed by FE-SEM (Figure 6C).
T198 12402-12611 Sentence denotes With microwaving, oven-dry, and UV irradiation, disruption of E. coli membrane integrity was observed; on the contrary, IPA immersion and water-laundering resulted in both cell deformation and cell detachment.
T199 12612-12740 Sentence denotes Remaining bacteria on water-laundered media was observed in a tangled structure of cells with contaminants on the fiber surface.
T200 12741-12908 Sentence denotes Generally, microwaving and oven-drying rely solely on the heating effect to inactivate microorganisms [52], as heating triggers the denaturation of cell proteins [53].
T201 12909-13077 Sentence denotes Additionally, the UV irradiation breaks the strong bond of cell membranes, such as O-H, P-O, and N-H bonds of E. coli, or induces oxidation, leading to cell death [54].
T202 13078-13344 Sentence denotes The solvents and detergent laundering treatments have compound effect of bactericidal and bacteria removal activity, by accumulating in the lipid of membrane and degrading the membrane integrity while inducing suspension of bacterial droplet into the liquid [55,56].
T203 13345-13461 Sentence denotes Meanwhile, laundering effectively removed bacteria by detaching them from fibers, rather than sterilizing the cells.
T204 13462-13657 Sentence denotes The results of bactericidal performance test imply the chemical solvents and hypochlorite solution are effective disinfection agents, as they concurrently inactivate the cell and detach bacteria.
T205 13658-13798 Sentence denotes Even if it is not complete sterilization, UV irradiation, and oven-dry methods seem fairly applicable for inactivating cells to some extent.
T206 13799-13928 Sentence denotes Laundering treatment removed a considerable amount of loaded bacteria; additionally, even the remaining bacteria was inactivated.