55 research outputs found
The evaluation of acoustic characteristic performance on natural sound absorbing materials from cogon grass waste
In the past few decades, synthetic fibers are been used widely in the field of sound absorption due to their superior characteristics such as durable and chemical resistant. However, there are several disadvantages of synthetic fibers such as non-biodegradability and hazards to the health of human. In this research, the natural sound absorber from cogon grass was investigated. The objective of the research was to evaluate the performance of cogon grass physical characteristics on its acoustical behavior, to evaluate the effect of sodium hydroxide (NaOH) treatment times on physical and acoustical characteristics of cogon grass, to investigate the decay effects after it was left over for twelve months and lastly to compare and verify the acoustical results with theoretical models based on (Delany-Bazley and Miki Model). The measurement of acoustical characteristics which are sound absorption coefficient (SAC) and noise reduction coefficient (NRC) were done by using impedance tube method (ITM). The samples of cogon grass were tested in a way of the untreated and treated with NaOH in varied soaked hours which are one, two, three, four and five hours. Scanning electron microscope (SEM) and density kit were used to investigate physical characteristics. The research confirmed that physical characteristics of tortuosity and airflow resistivity values tend to increase with the increment of treatment times, but the density and porosity tend to decrease. Untreated samples were tested with varied thicknesses of 10, 20, 30, 40 and 50mm. The results show SAC value increases when the thickness of the sample was increased. Treated samples results show the least treated sample (1 hour) reached the maximum SAC value and indicated the highest value of NRC which is 0.50. The results also show a reduction in sound absorption value after the samples were left for twelve months. Verification parts demonstrated that Delany-Bazley and Miki Model can predict approximately pattern compared with ITM results because of the theoretical models are developed by a simple empirical model approach. Overall, cogon grass samples have the good characteristics to be an acoustic material component
The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance
INTRODUCTION
Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic.
RATIONALE
We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs).
RESULTS
Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants.
CONCLUSION
Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century
Trends in mobility in India: issues of labour market integration and exclusion of vulnerable sections of the population
Biophysical Characterization and Molecular Docking Studies of Imidazolium Based Polyelectrolytes–DNA Complexes: Role of Hydrophobicity
Nonviral gene delivery vectors are
acquiring greater attention
in the field of gene therapy by replacing the biological viral vectors.
DNA–cationic polymer complexes are one of the most promising
systems to find application in gene therapy. Hence, a complete insight
of their biophysical characterization and binding energy profile is
important in understanding the mechanism involved in nonviral gene
therapy. In this investigation, the interaction between calf thymus
DNA (ctDNA) and imidazolium-based polyÂ(ionic liquids) (PILs) also
known as polyelectrolytes with three different alkyl side chains (ethyl,
butyl, and hexyl) in physiological conditions using various spectroscopic
experiments with constant DNA concentration and varying polyelectrolyte
concentrations is reported. UV–visible absorption, fluorescence
quenching studies, gel electrophoresis, circular dichroism (CD), and
Fourier transform infrared spectroscopy (FTIR) have confirmed the
binding of polyelectrolytes with DNA. UV–vis absorption measurements
and fluorescence quenching revealed that the binding between DNA and
the polyelectrolyte is dominated by electrostatic interactions. Additionally,
CD and FTIR results indicated that the DNA retained its B-form with
minor perturbation in the phosphate backbone without significant change
in the conformation of its base pairs. Preference for alkyl side chains
(<i>K</i><sub>PIL‑Ethyl Br</sub> < <i>K</i><sub>PIL‑Butyl Br</sub> < <i>K</i><sub>PIL‑Hexyl Br</sub>) toward efficient binding between
the polyelectrolyte and DNA was inferred from the binding and quenching
constants calculated from the absorption and emission spectra, respectively.
Further, in silico molecular docking studies not only validated the
observed binding trend but also provided insight into the binding
mode of the polyelectrolyte–DNA complex
Medical display application for degraded image sharpness restoration based on the modulation transfer function: initial assessment for a five-megapixel mammography display monitor
Investigation of enhancement in planar fast neutron detector efficiency with stacked structure using Geant4
Fermentative hydrogen production from beet sugar factory wastewater treatment in a continuous stirred tank reactor using anaerobic mixed consortia
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