Exceptional Viscoelastic Properties in Graphene Oxide Films.

Materials that combine high stiffness with effective damping are in high demand across various industries. While polymers excel in damping, they often lack stiffness and thermal stability. Conversely, metals and ceramics boast high mechanical and thermal properties but lack damping. This study demonstrates that graphene oxide (GO) and reduced graphene oxide (rGO) films can achieve exceptional viscoelastic properties across a wide temperature range. Furthermore, it explains the damping mechanisms and structural characteristics that influence the unique viscoelastic behavior of GO and rGO films. Through comprehensive characterizations, this study correlates the structure and spatial variation in local strain (measured with in situ Raman microscopy) of GO and rGO films with their storage and loss moduli. This correlation links these properties to the water loss as a function of the temperature rise. GO and rGO films exhibited a damping coefficient of 0.2-0.4 while maintaining stiffness values of 10-20 GPa in the 30-120 °C range. These high damping values were attributed to intermittent slippage and hydrogen bond density between the constituent sheets. Numerical modeling was conducted to further elucidate the mechanisms responsible for the properties noted in these films. This study enhances our understanding of the viscoelastic properties of GO films and offers a new potential material for applications across various fields.

A fast, ultrasensitive SERS immunoassay to detect SARS-CoV-2 in saliva.

The COVID-19 pandemic has emphasized the need for accurate, rapid, point-of-care diagnostics to control disease transmission. We have developed a simple, ultrasensitive single-particle surface-enhanced Raman spectroscopy (SERS) immunoassay to detect the SARS-CoV-2 spike protein in saliva. This assay relies on the use of single chain Fv (scFv) recombinant antibody expressed in E. coli to bind the SARS-CoV-2 spike protein. Recombinant scFv labeled with a SERS-active dye in solution is mixed with unlabeled scFv conjugated to gold-coated magnetic nanoparticles and a sample to be tested. In the presence of the SARS-CoV-2 spike protein, immunocomplexes form and concentrate the labeled scFv close to the gold surface of the nanoparticles, causing an increased SERS signal. The assay detects inactivated SARS-CoV-2 virus and spike protein in saliva at concentrations of 1.94 × 103 genomes mL-1 and 4.7 fg mL-1, respectively, making this direct detection antigen test only 2-3 times less sensitive than some qRT-PCR tests. All tested SARS-CoV-2 spike proteins, including those from alpha, beta, gamma, delta, and omicron variants, were detected without recognition of the closely related SARS and MERS spike proteins. This 30 min, no-wash assay requires only mixing, a magnetic separation step, and signal measurements using a hand-held, battery-powered Raman spectrometer, making this assay ideal for ultrasensitive detection of the SARS-CoV-2 virus at the point-of-care.

Rapid, Point-of-Care scFv-SERS Assay for Femtogram Level Detection of SARS-CoV-2.

Rapid, sensitive, on-site identification of SARS-CoV-2 infections is an important tool in the control and management of COVID-19. We have developed a surface-enhanced Raman scattering (SERS) immunoassay for highly sensitive detection of SARS-CoV-2. Single-chain Fv (scFv) recombinant antibody fragments that bind the SARS-CoV-2 spike protein were isolated by biopanning a human scFv library. ScFvs were conjugated to magnetic nanoparticles and SERS nanotags, followed by immunocomplex formation and detection of the SARS-CoV-2 spike protein with a limit of detection of 257 fg/mL in 30 min in viral transport medium. The assay also detected B.1.1.7 ("alpha"), B.1.351 ("beta"), and B.1.617.2 ("delta") spike proteins, while no cross-reactivity was observed with the common human coronavirus HKU1 spike protein. Inactivated whole SARS-CoV-2 virus was detected at 4.1 × 104 genomes/mL, which was 10-100-fold lower than virus loads typical of infectious individuals. The assay exhibited higher sensitivity for SARS-CoV-2 than commercial lateral flow assays, was compatible with viral transport media and saliva, enabled rapid pivoting to detect new virus variants, and facilitated highly sensitive, point-of-care diagnosis of COVID-19 in clinical and public health settings.

Life expectancy after HIV diagnosis based on data from the counseling center for behavioral diseases.

BACKGROUND: Predicting life expectancy is an important component of public health, in that, it may affect policy making in fields such as social security and medical care., To estimate the life expectancy and the average years of life lost (AYLL) of the human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS)-infected population, compared with that of the general population, and also to assess the impact of the CD4 count, risk factors of transmission, marital status, and employment status on life expectancy. MATERIAL AND METHODS: This study is a population-based cohort study. The sample consisted of HIV/AIDS-infected patients receiving care from 2001-2011. The patients were all adults (20-64 years) who were recruited from the Counseling Center of Behavioral Diseases. Life expectancy was measured based on an abridged life table, according to age-specific mortality rates and average years of life lost (AYLL) during the study period. RESULTS: Forty-three of the 205 eligible patients died during 853 person-years follow-up. Compared to the general population, the life expectancy for patients with HIV infection at age 20 is about 36 years less. We have found that out a total of 1597 years of life lost during 2001-2011, compared to an overall AYLL for all HIV/AIDS, the deaths had occurred 36 years earlier than the life expectancy. CONCLUSION: Life expectancy in HIV/AIDS-infected patients is about 38 years less than that of the general population at the exact age of 20. The deaths caused by HIV/AIDS occurred about 36 years before what was expected in the general population at ages 20-64, and many of these years of life lost could be saved if the health care system was implemented against the risk factors of HIV/AIDS.