Reprocessing N95 Respirators During the COVID-19 Pandemic: Moist Heat Inactivates SARS-CoV-2 and Maintains N95 Filtration

AbstractBackgroundThe unprecedented demand and consequent global shortage of N95 respirators during the COVID-19 pandemic have left frontline workers vulnerable to infection. To potentially expand the supply, we validated a rapidly applicable low-cost decontamination protocol in compliance with regulatory standards to enable the safe reuse of personalized, disposable N95-respirators.MethodsFour common models of N95-respirators were disinfected for 60 minutes at 70°C either at 0% or 50% relative humidity (RH). Effective inactivation of SARS-CoV-2 and E. coli was evaluated in inoculated masks. The N95 filter integrity was examined with scanning electron microscopy. The protective function of disinfected N95 respirators was tested against US NIOSH standards for particle filtration efficiency, breathing resistance and respirator fit.ResultsA single heat treatment inactivated both SARS-CoV-2 (undetectable, detection limit: 100 TCID50/ml) and E. coli (0 colonies at 50%RH) in all four respirator models. Even N95-respirators that underwent ten decontamination cycles maintained their integrity and met US-governmental criteria for approval regarding fit, filtration efficiency and breathing resistance. Scanning electron microscopy demonstrated maintained N95 fiber diameter compared to baseline.InterpretationThermal disinfection enables large-scale, low cost decontamination of existing N95 respirators using commonly sourced equipment during the COVID-19 pandemic. This process could be used in hospitals and long term care facilities and also provides a feasible approach to expand the N95 supply in low- and middle-income regions.

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Alternative Method of Rapid Drying Vascular Specimens for Scanning Electron Microscopy

Journal of Endovascular Therapy ◽

10.1177/152660280301000218 ◽

2003 ◽

Vol 10 (2) ◽

pp. 285-287 ◽

Cited By ~ 2

Author(s):

DáŠa Slížová ◽

Otakar Krs ◽

Blanka PospíŠilová

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Electron Micrographs ◽

Low Cost ◽

High Rate ◽

Drying Methods ◽

Scanning Electron Micrographs ◽

Air Drying ◽

Critical Point Drying ◽

Scanning Electron

Purpose: To report the use of hexamethyldisilazane (HMDS) as an alternative to critical point drying for preparing stented canine peripheral vessels for scanning electron microscopy (SEM). Technique: Vascular specimens were fixed in 4% formaldehyde overnight, dehydrated in a graded ethanol series, followed by immersion in 100% hexamethyldisilazane. After air drying, the specimens were mounted on stainless steel stubs, coated with gold, and examined in the SEM. The electron micrographs were of high quality, showing the layers of the vascular wall and the incorporated stent covered by a neointimal layer. The micrographs were comparable to corresponding histological sections, but detailed endothelial patterns were more visible. Conclusions: HMDS treatment and subsequent air drying provides good quality scanning electron micrographs that reveal both endothelial patterns and the layered architecture of stented vessels. The disadvantage of HMDS drying may be a shrinkage and distortion similar to other drying agents. Ease of handling, low cost, and a high rate of success are advantages that favor HMDS desiccation over other drying methods.

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A Magnetic Array Fabricated by a Novel Process Constructed with Photosensitive Polyimide-Ferrite Nanocomposite

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.499.3 ◽

2012 ◽

Vol 499 ◽

pp. 3-6

Author(s):

Yuan Xun Li ◽

Huai Wu Zhang ◽

Ying Li Liu ◽

Jie Li

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Magnetic Nanoparticles ◽

Barium Ferrite ◽

Low Cost ◽

Simple Process ◽

Micrometer Scale ◽

Scanning Electron

The authors report an approach to the fabrication of a periodic magnetic array using photosensitive polyimide-barium ferrite nanocomposite. These patterns are shaped by a some-like imprint technique, under the interactions between the magnetic nanoparticles and permanent magnetic mold. Scanning electron microscopy has been used to characterize the magnetic array and well-defined structures with magnetic arrays are obtained. The diameter of each dot is as small as 52um. The presented concept leads to a realization of a magnetic array, which offers advances in achieving micrometer-scale patterns with a very low cost and simple process.

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Damage of the Bacterial Cell Envelope by Antimicrobial Peptides Gramicidin S and PGLa as Revealed by Transmission and Scanning Electron Microscopy

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00124-10 ◽

2010 ◽

Vol 54 (8) ◽

pp. 3132-3142 ◽

Cited By ~ 250

Author(s):

Mareike Hartmann ◽

Marina Berditsch ◽

Jacques Hawecker ◽

Mohammad Fotouhi Ardakani ◽

Dagmar Gerthsen ◽

...

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Antimicrobial Peptides ◽

Lipid Membrane ◽

Ultrastructural Changes ◽

Morphological Alterations ◽

Bacterial Membranes ◽

E Coli ◽

Gramicidin S ◽

Scanning Electron

ABSTRACT Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the ultrastructural changes in bacteria induced by antimicrobial peptides (AMPs). Both the β-stranded gramicidin S and the α-helical peptidyl-glycylleucine-carboxyamide (PGLa) are cationic amphiphilic AMPs known to interact with bacterial membranes. One representative Gram-negative strain, Escherichia coli ATCC 25922, and one representative Gram-positive strain, Staphylococcus aureus ATCC 25923, were exposed to the AMPs at sub-MICs and supra-MICs in salt-free medium. SEM revealed a shortening and swelling of the E. coli cells, and multiple blisters and bubbles formed on their surface. The S. aureus cells seemed to burst upon AMP exposure, showing open holes and deep craters in their envelope. TEM revealed the formation of intracellular membranous structures in both strains, which is attributed to a lateral expansion of the lipid membrane upon peptide insertion. Also, some morphological alterations in the DNA region were detected for S. aureus. After E. coli was incubated with AMPs in medium with low ionic strength, the cells appeared highly turgid compared to untreated controls. This observation suggests that the AMPs enhance osmosis through the inner membrane, before they eventually cause excessive leakage of the cellular contents. The adverse effect on the osmoregulatory capacity of the bacteria is attributed to the membrane-permeabilizing action of the amphiphilic peptides, even at low (sub-MIC) AMP concentrations. Altogether, the results demonstrate that both TEM and SEM, as well as appropriate sample preparation protocols, are needed to obtain detailed mechanistic insights into peptide function.

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The biofilm inhibition and eradication activity of curcumin againts polymicrobial biofilm

BIO Web of Conferences ◽

10.1051/bioconf/20202804001 ◽

2020 ◽

Vol 28 ◽

pp. 04001

Author(s):

Hasyrul Hamzah ◽

Triana Hertiani ◽

Sylvia Utami Tunjung Pratiwi ◽

Titik Nuryastuti ◽

Yosi Bayu Murti

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Inhibitory Activity ◽

Drug Control ◽

Inhibition Activity ◽

Control Activity ◽

Biofilm Inhibition ◽

E Coli ◽

Inhibition Concentration ◽

Scanning Electron

Curcumin is a polyphenol compound that is a member of the ginger family (Zingiberaceae), which has potential as an antibacterial, antifungal, and polymicrobial antibiofilm on the catheter. Still, its inhibitory activity and eradication of non-catheter polymicrobial antibiotics against S. aureus, P. aeruginosa, E. coli, and C. albicans have never been reported. The discovery of a candidate polymicrobial anti-biofilm drug is indispensable for overcoming infections associated with biofilms. This study aims to determine the inhibitory activity and eradication of curcumin on polymicrobial biofilms. Inhibition testing and eradication activity of polymicrobial biofilms were performed using the microtiter broth method. The effectiveness of curcumin on polymicrobial biofilms was analyzed using minimum biofilm inhibition concentration (MBIC50) and minimum biofilm eradication concentration (MBEC50). The mechanism of action of curcumin against polymicrobial biofilms is tested using scanning electron microscopy (SEM). Curcumin 1 % b/v gives biofilm inhibition activity in the mid-phase and maturation of 62.23 % ± 0.01, 59.43 % ± 0.01, and can eradicate polymicrobial biofilms by 55.79 % ± 0.01 and not much different with nystatin drug control activity. The results also provide evidence that curcumin can damage the extracellular polymeric matrix (EPS) polymicrobial biofilms of S. aureus, P. aeruginosa, E. coli, and C. albicans and damage the morphology of polymicrobial biofilms. Therefore, curcumin can be developed as a candidate for new antibiofilm drugs against polymicrobial biofilms S. aureus, P. aeruginosa, E. coli dan C albicabs.

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Evidence for Escherichia coli O157:H7 Attachment to Water Distribution Pipe Materials by Scanning Electron Microscopy

Journal of Food Protection ◽

10.4315/0362-028x-65.12.1970 ◽

2002 ◽

Vol 65 (12) ◽

pp. 1970-1975 ◽

Cited By ~ 3

Author(s):

MAFU AKIER ASSANTA ◽

DENIS ROY ◽

MARIE-JOSÉE LEMAY ◽

DIANE MONTPETIT

Keyword(s):

Electron Microscopy ◽

Escherichia Coli ◽

Scanning Electron Microscopy ◽

Water Distribution ◽

Escherichia Coli O157 ◽

Exposure Condition ◽

Copper Surfaces ◽

E Coli ◽

Plastic Surfaces ◽

Scanning Electron

Scanning electron microscopy observation was used to investigate the adhesion of Escherichia coli O157:H7 on water distribution pipe surfaces such as copper and polyethylene plastic at different contact times and storage temperatures. Our results indicated that E. coli cells could easily attach to both surface types after exposures as short as 1 or 4 h at ambient (20°C) and refrigeration temperatures (4°C). Also, we found that copper surfaces have a higher number of attached E. coli cells than plastic surfaces. The number of cells attached to each type of material depended on the nature of the water distribution pipe surfaces and the length of contact time. In addition, the surface energy value of each surface estimated by contact angle measurements using water, ∝-bromonaphthalene, and dimethyl sulfoxide as wetting agents showed that both copper (41.2 megajoules [MJ]·m−2) and plastic (45.8 MJ·m−2) have a low energy surface. In no cases could evidence of extracellular material be observed on surfaces with either exposure condition.

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Synthesis of silica of rice husk modification (3-aminopropyl) trietoxysilane for adsorption methylene blue

MATEC Web of Conferences ◽

10.1051/matecconf/201819709009 ◽

2018 ◽

Vol 197 ◽

pp. 09009

Author(s):

Yusmaniar Yusmaniar ◽

Darsef Darwis ◽

Afrizal Afrizal ◽

Annisa Annisa

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Methylene Blue ◽

Surface Area ◽

Adsorption Process ◽

Low Cost ◽

Sol Gel ◽

Alkaline Ph ◽

Modified Silica ◽

Scanning Electron

In this study, modified silica (3-Amynopropyl) triethoxysilane (APTES) synthesis and adsorption test of MB dye were performed. Silica is synthesized by sol-gel method and modified with APTES. APTES modified silica is characterized using several instruments, scanning electron microscopy (SEM), fourier transform infrared (FTIR), surface area analyzer (SAA) and UV-Vis spectrophotometer. The composite has a large surface area and has a mesoporous shape. At alkaline pH, MB dye can adsorb well. In addition, MB absorption is also maximized with the longer time of adsorption. The APTES modified silica adsorption process follows the Langmuir isotherm pattern. Thus, APTES modified silica can be used as an alternative to environmentally friendly and low-cost adsorbents.

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Enterohemorrhagic Escherichia coli O157:H7 Present in Radish Sprouts

Applied and Environmental Microbiology ◽

10.1128/aem.64.4.1532-1535.1998 ◽

1998 ◽

Vol 64 (4) ◽

pp. 1532-1535 ◽

Cited By ~ 173

Author(s):

Yoshinori Itoh ◽

Yoshiko Sugita-Konishi ◽

Fumiko Kasuga ◽

Masaaki Iwaki ◽

Yukiko Hara-Kudo ◽

...

Keyword(s):

Electron Microscopy ◽

Escherichia Coli ◽

Scanning Electron Microscopy ◽

Outer Surface ◽

Immunofluorescence Microscopy ◽

Enterohemorrhagic Escherichia Coli ◽

Escherichia Coli O157 ◽

E Coli ◽

Radish Sprouts ◽

Scanning Electron

ABSTRACT Using cultivation, immunofluorescence microscopy, and scanning electron microscopy, we demonstrated the presence of viable enterohemorrhagic Escherichia coli O157:H7 not only on the outer surfaces but also in the inner tissues and stomata of cotyledons of radish sprouts grown from seeds experimentally contaminated with the bacterium. HgCl2 treatment of the outer surface of the hypocotyl did not kill the contaminating bacteria, which emphasized the importance of either using seeds free from E. coli O157:H7 in the production of radish sprouts or heating the sprouts before they are eaten.

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Development of Sustainable and Eco-Friendly Materials from Termite Hill Soil Stabilized with Cement for Low-Cost Housing in Chad

Buildings ◽

10.3390/buildings11030086 ◽

2021 ◽

Vol 11 (3) ◽

pp. 86

Author(s):

Assia Aboubakar Mahamat ◽

Numfor Linda Bih ◽

Olugbenga Ayeni ◽

Peter Azikiwe Onwualu ◽

Holmer Savastano ◽

...

Keyword(s):

Electron Microscopy ◽

Mechanical Properties ◽

Fracture Toughness ◽

Scanning Electron Microscopy ◽

Low Cost ◽

Sub Saharan Africa ◽

Ex Situ ◽

Termite Mound ◽

X Ray ◽

Scanning Electron

This paper explores the effects of cement stabilization (5, 10, 15 and 20 wt%) on the structural and mechanical properties (compressive/flexural strengths and fracture toughness) of abandoned termite mound soil. The crystal structures and crystallinity of the constituents were determined using X-ray diffraction (XRD), while the microstructure was characterized via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The functional groups were also identified using Fourier transform infra-red spectroscopy (FTIR). The compressive/flexural strengths of the stabilized and un-stabilized termite mound soil were also studied after curing for 7, 14 and 28 days. The fracture toughness mechanism was analyzed with the aid of the R-curve method. Additionally, the underlying deformation and cracking mechanisms are elucidated via in-situ/ex-situ optical and scanning electron microscopy. The stabilized termite mound soil displayed the highest mechanical properties of 13.91 MPa, 10.25 MPa and 3.52 kPa·m1/2 for compressive strength, flexural strength and fracture toughness, respectively. Besides displaying good mechanical properties and being locally available at no cost, renewable and an eco-friendly material, the termite mound soil will contribute to lowering the cost of housing in Sub-Saharan Africa, particularly in Chad.

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Microstructural and mechanical characterization of novel AA7075 composites reinforced with rice husk ash and carbonized eggshells

Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications ◽

10.1177/14644207211031265 ◽

2021 ◽

pp. 146442072110312

Author(s):

Vivudh Gupta ◽

Balbir Singh ◽

RK Mishra

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Rice Husk ◽

Rice Husk Ash ◽

Low Cost ◽

Agricultural Waste ◽

Stir Casting ◽

Light Weight ◽

Weight Percentage ◽

Scanning Electron

This paper investigates microstructural and mechanical characteristics of novel AA7075 composites supplemented with agricultural waste, i.e. rice husk ash and poultry waste, i.e. carbonized eggshells. Both these wastes possess important constituents which make them potential reinforcement material for composites, and their utilization also reduces the problem of disposal to a certain extent. AA7075 composites with varying weight percentages of rice husk ash and carbonized eggshells were prepared through stir casting route. The sum of weight percentages of both reinforcements was kept constant at 5 wt.%. Composites were tested for density and different mechanical properties. Prior to these tests, composites were examined through scanning electron microscopy and energy-dispersive X-ray spectroscopy techniques, wherein uniform distribution of reinforcements was observed. Inclusion of light weight reinforcements decreased the density of composites. Among these composites, highest hardness value was shown by composite having 5 wt.% of rice husk ash with 24.47% enhancement over unreinforced AA7075. Maximum tensile strength and compression strength were exhibited by hybrid composite with 3.75 wt.% rice husk ash and 1.25 wt.% carbonized eggshells. This increment is 28.20% and 16%, respectively, over base composition. Impact strength decreased as the weight percentage of CES increased, thereby indicating brittleness in behaviour. Fractography analysis of tensile and impact test specimens was done through scanning electron microscopy to determine failure mode wherein presence of cracks, voids, dimples, debonding, etc. was observed. Hence, these light weight and low cost green AA7075 composites showed improved properties making them as an alternative as well as sustainable material for automotive and aerospace applications.

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