Tactical Surface Modification of a 3D Graphite Felt as an Electrode of Vanadium Redox Flow Batteries with Enhanced Electrolyte Utilization and Fast Reaction Kinetics

Three-dimensional porous carbon materials have great importance as electrode materials for vanadium redox flow batteries due to electrochemical stability over a wide potential window and low cost. However, sluggish electrode kinetics toward vanadium redox reactions makes electrode treatment vital before its use in a vanadium redox flow battery. Researchers have used different routes to modify the graphite electrode surface. This article presents a very simple (and known) but tactical procedure to treat a graphite felt. The modified electrode possesses large surface area having well-developed uniform pore structures and abundant oxygen-rich surface functional groups (11.2%), which offers a significant reduction in peak separation potential and charge-transfer resistance with a noteworthy improvement in the peak current density and redox reaction reversibility compared to a bare graphite felt. The modified graphite felt electrode enables 14- and 19-fold improvements in exchange current toward VO2+/VO2+ and V3+/V2+ redox reactions, respectively, than those of a bare graphite felt. The battery performance at 50 mA cm–2 of current density displays energy efficiency (89%) and electrolyte utilization (89%) nearly 12 and 98%, respectively, higher than that of a bare graphite felt. The long-term performance (200 cycles) of the battery assured stable behavior of the modified electrode. Moreover, the present modified approach improves the peak power density by 3-fold compared to that of the bare graphite felt

Low-Cost Pore-Filled PVDF–Nafion Composite Membrane for the Vanadium Redox Flow Battery

Nafion solution is used as the filler for the porous polyvinylidene fluoride (PVDF) membrane for reducing the crossover of vanadium species in the vanadium redox flow battery (VRFB). Scanning electron microscopy confirmed the uniform penetration of the Nafion solution throughout the membrane. Water uptake, Nafion consumption, and permeability of vanadium ions of the PVDF–Nafion membrane are significantly smaller than those of the Nafion117 membrane. Vanadium permeability of the PVDF–Nafion composite membrane is 18 times lower than that of the Nafion117 membrane. Furthermore, owing to the reduction in vanadium permeability, the PVDF–Nafion membrane retains 70% more capacity than the Nafion117 membrane. PVDF–Nafion-5% shows stable voltage efficiency, demonstrating the robustness of the synthesized membrane. On the flip side, the composite membrane shows reduced proton conductivity. Therefore, in this paper, a strategy is shown of how to tackle the additional overpotential due to reduced proton conductivity. Further, the economic advantage and feasibility is justified using techno-economic assessment for the 1 kW–1 kW·h VRFB system assembled with the PVDF–Nafion composite membrane. The results show that the developed PVDF–Nafion membrane is a good alternative to the Nafion117 membrane in the VRFB due to its low cost, low vanadium permeability, and better cyclability up to 800 charge–discharge cycles

Hydrogen Adsorption on Zn-BDC, Cr-BDC, Ni-DABCO, and Mg-DOBDC Metal–Organic Frameworks

This work reports hydrogen adsorption properties of four different metal–organic frameworks (MOFs) namely Zn-BDC, Cr-BDC, Ni-DABCO, and Mg-DOBDC. Gravimetric hydrogen adsorption measurements are performed over a wide range of temperature (90 K to 298 K) and pressure (0 bar to 100 bar). At the lowest experimental temperature (90 K to 100 K) all the isotherms are saturated and the adsorption capacity is governed by pore volume. On the other hand, at room temperature the isotherms closely follow Henry’s law. Modeling of the excess isotherms is also done. Net adsorption isotherms, which can directly indicate the efficiency of porous adsorbent for storage, are also presented. In terms of volumetric efficiency, Mg-DOBDC MOF exhibits best storage capacity out of all the MOFs considered in this study

Crystal structure of a novel conformational state of the flavivirus NS3 protein: Implications for polyprotein processing and viral replication

The flavivirus genome comprises a single strand of positive-sense RNA, which is translated into a polyprotein and cleaved by a combination of viral and host proteases to yield functional proteins. One of these, nonstructural protein 3 (NS3), is an enzyme with both serine protease and NTPase/helicase activities. NS3 plays a central role in the flavivirus life cycle: the NS3 N-terminal serine protease together with its essential cofactor NS2B is involved in the processing of the polyprotein, whereas the NS3 C-terminal NTPase/helicase is responsible for ATP-dependent RNA strand separation during replication. An unresolved question remains regarding why NS3 appears to encode two apparently disconnected functionalities within one protein. Here we report the 2.75-Å-resolution crystal structure of full-length Murray Valley encephalitis virus NS3 fused with the protease activation peptide of NS2B. The biochemical characterization of this construct suggests that the protease has little influence on the helicase activity and vice versa. This finding is in agreement with the structural data, revealing a single protein with two essentially segregated globular domains. Comparison of the structure with that of dengue virus type 4 NS2B-NS3 reveals a relative orientation of the two domains that is radically different between the two structures. Our analysis suggests that the relative domain-domain orientation in NS3 is highly variable and dictated by a flexible interdomain linker. The possible implications of this conformational flexibility for the function of NS3 are discussed. Copyright © 2009, American Society for Microbiology. All Rights Reserved

Assay Platform for Clinically Relevant Metallo-β-lactamases

Metallo-β-lactamases (MBLs) are a growing threat to the use of almost all clinically used β-lactam antibiotics. The identification of broad-spectrum MBL inhibitors is hampered by the lack of a suitable screening platform, consisting of appropriate substrates and a set of clinically relevant MBLs. We report procedures for the preparation of a set of clinically relevant metallo-β-lactamases (i.e., NDM-1 (New Delhi MBL), IMP-1 (Imipenemase), SPM-1 (São Paulo MBL), and VIM-2 (Verona integron-encoded MBL)) and the identification of suitable fluorogenic substrates (umbelliferone-derived cephalosporins). The fluorogenic substrates were compared to chromogenic substrates (CENTA, nitrocefin, and imipenem), showing improved sensitivity and kinetic parameters. The efficiency of the fluorogenic substrates was exemplified by inhibitor screening, identifying 4-chloroisoquinolinols as potential pan MBL inhibitors

SIVRNA localizes with immune clusters in brain and spleen.

(A) Genes enriched in TEM and TCM clusters in control and SIV brain (p.adj B) UMAP of immune clusters in brain and vRNA expression in clusters in control and SIV. (C) UMAP of immune clusters in spleen and vRNA expression in clusters in control and SIV. Acute 251 (n = 4) cohort assessed. (TIF)</p

CSF CCR5+ CD8 T cell frequencies do not decrease during acute SIV infection.

shows % CD8 T cells, % CD28- CD95+ CD8 T cells, �R5+ CD8 T cells, and % CD69+ CD8 T cells in CSF in Chronic 251 cohort (n = 6). Significant differences by one-tailed Wilcoxon matched-pairs signed rank test, *, p (TIFF)</p

T cell effector molecular programs induced within the SIV-Infected brain.

Differential gene expression (DGE) analysis of the immune clusters across conditions was performed using functions from Seurat; selection threshold of (adjusted p-value  0.25) based on Benjamini-Hochberg correction. (A) Heat map of DGE genes in controls (C) versus SIV for each immune cluster. (B) Venn diagram shows shared interferon stimulated genes upregulated post SIV across brain and spleen CD4 T cell and monocyte/macrophage immune clusters. (C) Chord plot show pathways and corresponding genes enriched in SIV versus control CD4 TCM cell cluster in brain. (D) Venn diagram shows shared genes downregulated post SIV in brain and spleen CD4 T cell clusters. We used the monocle3 based workflow to estimate lineage differentiation between the cell populations based on the experimental conditions. We extracted the subsets of identified cell types from our integrated Seurat object and further inferred the trajectory graphs. Using the defined root node (TCM), we chose lineages based on the shortest path connecting the root node and the leaf node. After establishing different lineages, we implemented a differential gene test to find genes that changed as a function of pseudotime based on a combination of Moran’s statistic and q-value and visualized using heatmaps and individual gene trajectory plots. (E) Heatmap (Lineage 3) shows changes in gene expression in lineage comprising of T cells. Along this trajectory was induction of genes associated with cell cycle progression (TK1, MKI67, EIF1, S100A10, S100A4), immune cell activation and differentiation (ZEB2, KLF2, CD52) [41], cytotoxic function (PFN1, GZMB, GZMH, NKG7, and CST7). Canonical TCM genes, such as IL7R and LTB, were downregulated in this lineage. (F) shows expression levels genes of select genes from heat map (ZEB2, LTB, GZMB) along pseudo-time as a function of infection. Schematics were generated using BioRender.</p

Gating strategy for CNS tissues in SIV unexposed controls.

Gating strategy for CNS tissues in SIV unexposed controls.</p

Decrease in vRNA in brain during antiretroviral therapy.

(A) Chronic 251 cohort (n = 6) assessed. (B) Kinetics of plasma (red lines) and CSF (blue lines) viral suppression and rebound (vRNA copies/mL fluid, measured by RT-qPCR) over the course of ART initiation and interruption. Green bars indicate periods of ART with FTC, TDF, and DTG. Horizontal dashed line indicates limit of detection (15 vRNA copies/ml). (C) Concentration of ARVs (ng/mL) in plasma and CSF quantified by LC-MS. (D) Concentration of ARVs (ng/mg) in PFC and colonic tissue. (E) shows active phosphorylated forms of TFV and FTC. Spearman correlation, two-tailed p value shown. Sampling was performed 2–4 weeks post ART initiation with last ARV dose administered 9–12 hours prior to necropsy, FTC = emtricitabine, TDF = tenofovir disoproxil fumarate, DTG = dolutegravir, Gray shaded area represents lower limit of quantification of assay. (F) SIV vRNA (G) SIV vDNA (copies/10^6 cells) in brain region (RT-qPCR on post-mortem punch biopsies from specified regions. Gray shaded area represents viral loads below threshold of detection. Significant differences by two tailed Wilcoxon matched-pairs signed rank test, * p< 0.05 in C-E. Schematics were generated using BioRender.</p