QoS-based Joint User Selection and Scheduling for MU-MIMO WLANs, Journal of Telecommunications and Information Technology, 2017, nr 4

The shift in Multi-User Multiple Input Multiple Output (MU-MIMO) has gained attention due to its wide support in very high throughput Wireless Local Area Networks (WLANs) such as the 802.11ac. However, the full advantage of MU-MIMO can be utilized only with proper user selection and scheduling. Also, providing Quality of Service (QoS) support is a major challenge for these wireless networks. Generally, user scheduling is done with the acquisition of Channel State Information (CSI) from all the users. In MU-MIMO based WLANs, the number of CSI request increases with the number of users. This results in an increased CSI overhead and in degradation of the overall throughput. Most of the proposals in the literature have not addressed the contention in the CSI feedback clearly. Hence, in this paper a Joint User Selection and Scheduling (JUSS) scheme is discussed and its performance is evaluated in terms of throughput, delay, packet loss and fairness. In the performance comparison some wellknown Medium Access Control (MAC) protocols are considered. The proposed scheme not only enhances throughput, but also avoids contention during CSI feedback period

Quantifying range of motion and stress patterns at the transitional lumbosacral junction: Pilot study using a computational model for load-bearing at accessory L5-S1 articulation

© International Society for the Advancement of Spine Surgery. Background: Symptomatic or asymptomatic transitional anomalies at the lumbosacral junction are common occurrences in the population. Lumbosacral (L5-S1) accessory articulations are the most common presentations of transitional anomalies at this region. Such anatomical alterations are believed to be associated with biomechanical changes of load-bearing and movement restrictions leading to low back pain. This study attempts to use computational models of a normal and a lumbosacral transitional vertebrae (LSTV) accessory articulation to analyze and compare the range of motion and loading patterns at the lumbosacral articulations. Methods: Three-dimensional Finite Element computational models of normal and accessory L5-S1 articulated sacrum were created. These models were tested for range of motion and stress patterns generated at the lumbosacral articulations using similar loading and motion simulation to elicit different moments/excursions at the lumbosacral junctions. Results: Compared to the normal variant, the transitional model exhibited different range of motion and divergent patterns of stress generation at the lumbosacral and accessory articulations with equal and physiological magnitudes of loading applied to both the models. Conclusions: The finite element modeling approach can be used for biomechanical investigations in LSTV variants. However, larger sample studies with different LSTV models may be required to statistically compare movement and loading patterns at LSTV-affected lumbosacral and sacroiliac junctions, and to recommend definitive treatment strategies in these situations

Structural Organization of Pregenomic RNA and the Carboxy-Terminal Domain of the Capsid Protein of Hepatitis B Virus

<div><p>The Hepatitis B Virus (HBV) double-stranded DNA genome is reverse transcribed from its RNA pregenome (pgRNA) within the virus core (or capsid). Phosphorylation of the arginine-rich carboxy-terminal domain (CTD) of the HBV capsid protein (Cp183) is essential for pgRNA encapsidation and reverse transcription. However, the structure of the CTD remains poorly defined. Here we report sub-nanometer resolution cryo-EM structures of <em>in vitro</em> assembled empty and pgRNA-filled Cp183 capsids in unphosphorylated and phosphorylation-mimic states. In empty capsids, we found unexpected evidence of surface accessible CTD density partially occluding pores in the capsid surface. We also observed that CTD organization changed substantively as a function of phosphorylation. In RNA-filled capsids, unphosphorylated CTDs favored thick ropes of RNA, while the phosphorylation-mimic favored a mesh of thin, high-density strands suggestive of single stranded RNA. These results demonstrate that the CTD can regulate nucleic acid structure, supporting the hypothesis that the HBV capsid has a functional role as a nucleic acid chaperone.</p> </div

Spatial organization of the CTDs.

<p>Difference maps of CTD density were calculated by subtracting the low-pass filtered atomic model of Cp149 from the (A) Cp183_e-SSS and (B) Cp183_e-EEE. The resulting CTD density (red and green, respectively) was superimposed on the corresponding region of the interior of the Cp149 capsid. The bottom panels shows the enlarged views at the (C,E) threefold and (D,F) fivefold axes. The overall distributions of the CTDs in Cp183_e-SSS and Cp183_e-EEE are very similar except that the CTD density in Cp183_e-SSS is more scattered whereas the CTD density in Cp183_e-EEE forms a funnel-like shape under the fivefold vertex.</p

Evaluation of IgG Antibody Response to Severe Acute Respiratory Syndrome Coronavirus-2 in Healthcare Workers in a Tertiary Care Centre, Chennai, India

Introduction: Globally, the Coronavirus Disease-2019 (COVID19) pandemic poses a high risk for Healthcare Workers (HCWs) who are among the population that is most vulnerable of being infected with Severe Acute Respiratory SyndromeCoronavirus-2 (SARS-CoV-2). With a prevailing pandemic such as COVID-19, it becomes important to understand the presence and persistence of antibodies in the serum of HCW, testing positive for COVID-19 on Reverse transcriptase Polymerase Chain Reaction (RT-PCR). An understanding of the prevalence of IgG antibodies against COVID-19 and the duration for which they are present in the serum will help in predicting the immune response of individuals against the disease. Aim: To study the prevalence of COVID-19 IgG antibodies in laboratory confirmed COVID-19 RT-PCR positive symptomatic, asymptomatic and RT-PCR negative subjects. Materials and Methods: The present longitudinal study was conducted from April 2020 to December 2020 with a sample size of 90 participants based on a pilot study. Blood sample was collected and serum was separated. Enzyme Linked Immunosorbent Assay (ELISA) was done to detect the presence of COVID-19 IgG antibody in serum. Chi-square test and Pearson correlation were used to find out the statistical significance of COVID-19 IgG antibodies in COVID-19 positive and negative HCWs and the relationship between Cycle threshold values (Ct) and antibody levels, respectively. Results: Fever with sore throat was the most common (33%) symptom. Chi-square test done to compare IgG among RT-PCR positive and negative subjects showed p-value of <0.00001 which was significant. However, statistical significance was not found (p-value 0.9973) with respect to COVID-19 IgG antibodies in RT-PCR positive COVID-19 asymptomatic and symptomatic subjects. Mean antibody index in symptomatic and asymptomatic was 3.7743±1.9834 and 3.571±1.7961, respectively. Average number of days, the antibodies persisted was 25 days-266 days. Conclusion: The prevalence of COVID-19 antibodies among RT-PCR positive symptomatic, asymptomatic and RT-PCR negative subjects was 88%, 67% and 27%, respectively. The maximum number of days antibodies persisted was 266 days. Further studies will elucidate whether these antibodies prevent re-infection

Cryo-EM 3D reconstructions of empty and pgRNA-filled Cp183 capsids.

<p>Surface shaded exterior maps of T = 4 (A) Cp183_e-SSS, (B) Cp183_e-EEE, (C) Cp183_RNA-SSS, (D) Cp183_RNA-EEE and their related central sections (E–H). Insets show enlarged views of the twofold (i.e. quasi-sixfold) vertex. All four maps have a similar external appearance with 120 spikes decorating a fenestrated capsid surface; the outer layer extends from a radius of 125 to 170 Å. In (A) Cp183_e-SSS and (B) Cp183_e-EEE, a thin layer of electron density partially occludes the central opening pore at the twofold axis (A, B, E, F, black arrows). This density is unique to the empty capsids. The pgRNA-filled capsids (C, D, G, H), on the other hand, lack the density across the twofold pore but display a substantial internal layer of density at the radii between 100–120 Å. In central sections (G, H), this density, corresponding to the co-assembled pgRNA, is clearly inhomogeneous indicating that the pgRNA has adopted a preferred conformation or constellation of conformations evident even though it has been icosahedrally averaged in these reconstructions. White arrows indicate the CTD tails tethered from the capsid inner surface. Oval, triangle, and pentagon indicate locations of twofold, threefold and fivefold axes, respectively.</p

Structural organization of pgRNA.

<p>The difference maps of the pgRNA from (A) Cp183_RNA-SSS (blue) and (B) Cp183_RNA-EEE (gold) superimposed on cutaway of their respective empty capsids. By subtracting the empty Cp183 capsids from their respective pgRNA-filled capsids, the CTD-RNA interaction is evident as a gap, particularly evident on the fivefold of the EEE mutant (B). The pgRNA density in the unphosphorylated Cp183_RNA-SSS forms an icosahedral cage, similar to the organization of rcDNA observed in the native virion. The pgRNA in the phosphorylation-mimic Cp183-EEE capsid shows a continuous mesh-like network density that appears to be composed of short segments of density.</p

Cryo-micrographs of frozen-hydrated HBV capsids.

<p>(A) Cp183_e-SSS (e for empty), (B) Cp183_e-EEE, (C) Cp183_RNA-SSS, and (D) Cp183_RNA-EEE particles are shown, frozen hydrated in vitreous ice. These particles show the typical morphology of HBV capsids with characteristic spikes. These samples all have a minor population of smaller, T = 3 particles (black arrow). Inserts show translationally averaged images. Empty capsids (A, B) show a single ring corresponding to the protein shell; pgRNA-filled capsids (C, D) show two concentric rings, indicating the presence of an layer of nucleic acid. Note that the RNA ring in Cp183_RNA-EEE is thicker than in Cp183_RNA-SSS.</p