Nanomechanical-atomistic insights on interface interactions in asphalt mixtures with various chloride ion erosion statuses.

Coastal asphalt pavements are highly susceptible to sea salt erosion, which leads to a significant decrease in road performance and durability. However, the interface micro-adhesion mechanism of the asphalt-aggregate composites under chloride ion erosion is still not fully understood. Herein, using the silica microsphere Atomic Force Microscopy (AFM) modified tip and asphalt sample with chloride ions as a surface, we report the effect mechanism of chloride ion erosion on the interface adhesion behavior of asphalt-silica composites by AFM from the atomistic scale. The chloride ion erosion mechanism was further supported by molecular dynamics (MD) simulations. Due to the erosion effect of chloride ions, the structure evolution of the asphalt film surface will occur, and the weak adhesion gradient zone will be formed on the surface of the asphalt film. The concentration effect of chloride ions accelerates the formation of adhesion gradient zones, which are unstable and evolve over erosion time. Due to the presence of these adhesion gradient zones, water molecules will more easily penetrate the asphalt membrane and enter the asphalt-silica interface through adsorption and diffusion, thereby weakening the interface adhesion ability between the asphalt and the aggregate. Furthermore, the distribution and diffusion of asphalt fractions on the aggregate surface also affect the adhesion behavior evolution of asphalt-silica composites induced by chloride ion erosion. The evolution in the spatial distribution of fractions may be related to the formation of interfacial adhesion gradient zones. This study outcome has important theoretical significance for promoting the sustainability of asphalt pavements and for guiding pavement deicing.

Burden of tuberculosis and hepatitis co-infection among people living with HIV in Nepal: a systematic review and meta-analysis.

People living with HIV (PLHIV) are prone to tuberculosis (TB) and hepatitis co-infections, which cause substantial burden on morbidity and mortality. However, data on the burden of HIV co-infection from a specific low- and middle-income country are limited. To address this gap in evidence, a meta-analysis of published literature and country surveillance report was conducted to estimate the burden of TB, hepatitis B (HBV) and hepatitis C (HCV) co-infection among PLHIV in Nepal. Twenty-three studies, including 5900 PLHIV, were included in the meta-analysis. The pooled prevalence of HIV-TB, HIV-HBV and HIV-HCV co-infection was 19% (95% CI, 10-28%), 3% (2-5%) and 19% (4-33%), respectively. Low CD4 cell count (pooled odds ratio [OR] 4.38, 95% CI 1.11-17.25), smoking (3.07, 1.48-6.37) and alcohol drinking (3.12, 1.52-6.43) were significantly correlated with HIV-TB co-infection. The odds of HCV co-infection was greater in PLHIV, who were male (5.39, 1.54-18.89) and drug users (166.26, 15.94-1734.44). PLHIV who were on antiretroviral therapy had a reduced risk of HCV co-infection (0.49, 0.36-0.66) than the general PLHIV population. The burden of TB and hepatitis co-infection among PLHIV in Nepal was high. Regular screening of PLHIV for co-infections and prompt initiation of treatment are essential to reduce the transmission of infection and improve quality of life.

Fear, Risk Perception, and Engagement in Preventive Behaviors for COVID-19 during Nationwide Lockdown in Nepal.

The world has faced huge negative effects from the COVID-19 pandemic between early 2020 and late 2021. Each country has implemented a range of preventive measures to minimize the risk during the COVID-19 pandemic. This study assessed the COVID-19-related fear, risk perception, and preventative behavior during the nationwide lockdown due to COVID-19 in Nepal. In a cross-sectional study, conducted in mid-2021 during the nationwide lockdown in Nepal, a total of 1484 individuals completed measures on fear of COVID-19, COVID-19 risk perception, and preventive behavior. A multiple linear regression analysis was used to identify factors associated with COVID-19 fear. The results revealed significant differences in the fear of COVID-19 in association with the perceived risk of COVID-19 and preventive behaviors. Age, risk perception, preventive behavior, and poor health status were significantly positively related to fear of COVID-19. Perceived risk and preventive behaviors uniquely predicted fear of COVID-19 over and above the effects of socio-demographic variables. Being female and unmarried were the significant factors associated with fear of COVID-19 among study respondents. Higher risk perception, poor health status, and being female were strong factors of increased fear of COVID-19. Targeted interventions are essential to integrate community-level mental health care for COVID-19 resilience.

Comparative analysis of COVID-19 case fatality rate between two waves in Nepal.

The first COVID-19 case in Nepal was reported on January 23, 2020. Then infection, then, started to spread gradually, and October marked the most devastating increase in COVID-19 cases of the year 2020. Compared with the October 2020 peak in Nepal, the May 2021 peak of COVID-19 observed 2- and 10-fold rise in new cases and deaths per day, respectively. Given that this surprising increase in the death rate was not observed in other countries, this study analyzed the COVID-19 case fatality rates between the two peaks in Nepal. We found an increase in death rates among younger adults and people without comorbidities.

Methicillin-resistant Staphylococcus aureus in Nepal: A systematic review and meta-analysis.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is a significant health threat and public burden worldwide, particularly in developing countries, including Nepal, due to its low healthcare standards and irrational use of antibiotics. It is evident that MRSA strains are frequently detected in Nepalese hospitals; however, they remain underreported. Therefore, to provide a comprehensive and clear understanding of MRSA infection at the national level, this systematic review and meta-analysis evaluated the prevalence and antimicrobial susceptibility patterns of MRSA in Nepal. METHODS: PubMed, EMBASE, Cochrane CENTRAL, Google scholar, and Nepalese databases were searched for studies published between 1st January 2008 and 31st August 2020. A total of 26 original articles were selected for quantitative analysis. Data extraction was accomplished by three authors independently and meta-analysis was performed using MedCalc Version 19.5.1 and Comprehensive Meta-Analysis (CMA) software v.3.0. RESULT: The pooled prevalence of MRSA infections among 5951 confirmed S. aureus isolates was 38.2% (95% CI, 31.4%-45.2%). We found a significant heterogeneity (I2 = 96.7% for resistance proportion), and no evidence of publication bias (p = 0.256) among studies. MRSA strains showed a high level of resistance to beta-lactam antibiotics and the highest susceptibility profile was noted in vancomycin 98.0% followed by chloramphenicol 91.0%. CONCLUSION: The analysis revealed that the overall MRSA burden in Nepal is considerably high and the prevalence of MRSA infections is in the increasing trend. Sound legislation, definite antibiotic policy, and implementations of control interventions are indispensable for tackling MRSA infection and antimicrobial resistance as a whole.

Solid Phase Stepwise Synthesis of Polyethylene Glycols.

Polyethylene glycol (PEG) and derivatives with eight and twelve ethylene glycol units were synthesized by stepwise addition of tetraethylene glycol monomers on a polystyrene solid support. The monomer contains a tosyl group at one end and a dimethoxytrityl group at the other. The Wang resin, which contains the 4-benzyloxy benzyl alcohol function, was used as the support. The synthetic cycle consists of deprotonation, Williamson ether formation (coupling), and detritylation. Cleavage of PEGs from solid support was achieved with trifluoroacetic acid. The synthesis including monomer synthesis was entirely chromatography-free. PEG products including those with different functionalities at the two termini were obtained in high yields. The products were analyzed with ESI and MALDI-TOF MS and were found close to monodispersity.

Evidence of Splitting 1,2,3-Triazole into an Alkyne and Azide by Low Mechanical Force in the Presence of Other Covalent Bonds.

The cycloaddition reaction of an alkyne and azide to form a 1,2,3-triazole is widely used in many areas. However, the stability of the triazole moiety under mechanical stress is unclear. To see if a triazole could be selectively split into an alkyne and azide in the presence of other typical covalent bonds, a mica surface functionalized with a molecule containing a triazole moiety in the middle and an activated ester at the end was prepared. An atomic force microscope (AFM) tip with amino groups on its surface was ramped over the mica surface at predefined locations, which could temporarily link the tip to the surface through amide bond formation. During retraction, the triazole or another bond in the linkage broke, and a force was recorded. The forces varied widely at different ramps from close to 0 pN to 860 pN due to nonspecific adhesions and to the inherent inconsistency of single bond rupture. If some of the forces were from triazole cycloreversion, there would be alkynes at the predefined ramping locations. The surface was reacted with an azide carboxylic acid followed by labeling with amino Au nanoparticles (AuNPs). AFM imaging revealed AuNPs at the predicted locations, which provided evidence that under certain conditions triazole could be split selectively in the presence of other bonds at forces below 860 pN.

Modification of a single-molecule AFM probe with highly defined surface functionality.

Single-molecule force spectroscopy with an atomic force microscope has been widely used to study inter- and intramolecular interactions. To obtain data consistent with single molecular events, a well-defined method is critical to limit the number of molecules at the apex of an AFM probe to one or to a few. In this paper, we demonstrate an easy method for single-molecule probe modification by using the Cu-catalyzed alkyne-azide cycloaddition reaction. Excess terminal alkynes were covalently attached to the probe, and a bi-functional molecule containing an azide at one end and a carboxylic acid at the other was dissolved in the reaction solution. By simply contacting the probe and the Cu substrate, controlled carboxylation on the probe apex could be achieved, since the 'click' reaction requires the co-exist of alkyne, azide and Cu(I). The finite contact area would result in a highly defined surface functionality of the probe down to single molecule level with high reproducibility.