50175 research outputs found
Sort by
Influence of ligand coordination, solvent, and non-covalent interaction on the structural outcomes in coordination polymers with direct Cd(II)-alkanesulfonate bonds: A combined experimental and computational study
No full textOne-pot three-component Arbuzov-type reaction, involving anhydrous cadmium acetate, dimethyl sulfite, and tetraethylammonium iodide, has produced the cadmate salt, Et4N](2)Cd(OMs)(4)] (1) revealing weakly-coordinating methanesulfonate (OMs) ligands inside the metal-coordination sphere. The `ate' salt 1 was found useful as a precursor in the preparation of coordination polymers with compositions, Cd(OMs)(2) (MeOH)](n) (2) and Cd(OMs)(2)(H2O)(2)](n) (3), when subjected to crystallization in a methanol/chloroform mixture, in dry and ambient conditions, respectively. Compounds 1-3 were characterized by spectroscopic H-1, C-13 NMR, FT-IR] techniques, and elemental and thermogravimetric analysis, while the structural attributes of 2 and 3 were investigated using single-crystal X-ray diffraction. The composition of 1 was further scrutinized by electrospray-ionization massspectrometry (ESI-MS). The crystal structure of 2 exhibits formation of a two-dimensional (2-D) layer facilitated by the bidentate (mu(2)) and tridentate (mu(3)) modes of coordination of sulfonate ligands around the metal center. The structure of 3 demonstrates the formation of 1-D linear chains, comprising of eight-membered cyclic -Cd-O-S-O-] rings, owing to the bridging bidentate (mu(2)) mode of coordination of the sulfonate ligands. The involvement of hydrogen-bond interactions in 2 and 3 further perpetuates the assemblies into 2-D and 3-D supramolecular coordination polymers, respectively. This paper reports noticeable features such as, (a) cadmate dianion was afforded by the in situ generation of methanesulfonate ligands and subsequent complexation to the Cd(II) atom; (b) ability of alkanesulfonate ligand to display flexible coordinating behaviour (mu(2) and uncommon (mu(3))] and prolific H-bond acceptor; (c) competitive ligation between strong coordinating solvents (MeOH and H2O) and weakly-coordinating methanesulfonate ligands; (d) effect of types and number of solvent molecules around the metal center with their participation in non-covalent interactions in bringing variation in the structural outcome; (e) the values of distances of Cd-O bonds in 1 and 2 fall in the range of 2.24 angstrom to 2.29 angstrom, suggesting the presence of direct metal-sulfonate interactions. The dispersion-corrected density functional theory (DFT-D) and Bader's quantum theory of atoms in molecule (QTAIM) (primary and secondary) studies explored the structures, electronics, and non-covalent interactions of compounds 2 and 3. Additionally, among different involved non-covalent interactions, Hirshfeld surface analysis emphasized the presence of O center dot center dot center dot H/H center dot center dot center dot O contacts as the dominant intermolecular non-covalent interactions as the consolidating factor in crystal packing, in both compounds
Pericytes enable effective angiogenesis in the presence of proinflammatory signals
No full textAngiogenesis frequently occurs in the context of acute or persistent inflammation. The complex interplay of proinflammatory and proangiogenic cues is only partially understood. Using an experimental model, permitting exposure of developing blood vessel sprouts to multiple combinations of diverse biochemical stimuli and juxtacrine cell interactions, we present evidence that a proinflammatory cytokine, tumor necrosis factor (TNF), can have both proangiogenic and antiangiogenic effects, depending on the dose and the presence of pericytes. In particular, we find that pericytes can rescue and enhance angiogenesis in the presence of otherwise-inhibitory high TNF doses. This sharp switch from proangiogenic to antiangiogenic effect of TNF observed with an escalating dose of this cytokine, as well as the effect of pericytes, are explained by a mathematical model trained on the biochemical data. Furthermore, this model was predictive of the effects of diverse combinations of proinflammatory and antiinflammatory cues, and variable pericyte coverage. The mechanism supports the effect of TNF and pericytes as modulating signaling networks impinging on Notch signaling and specification of the Tip and Stalk phenotypes. This integrative analysis elucidates the plasticity of the angiogenic morphogenesis in the presence of diverse and potentially conflicting cues, with immediate implications for many physiological and pathological settings
Conforming and discontinuous Galerkin FEM in space for solving parabolic obstacle problem
No full textIn this article, we propose and analyze conforming and discontinuous Galerkin (DG) finite element methods for numerical approximation of the solution of the parabolic variational inequality associated with a general obstacle in R-d (d = 2, 3). For fully discrete conforming method, we use globally continuous and piecewise linear finite element space. Whereas for the fully-discrete DG scheme, we employ piecewise linear finite element space for spatial discretization. The time discretization has been done by using the implicit backward Euler method. We present the error analysis for the conforming and the DG fully discrete schemes and derive an error estimate of optimal order (h+ Delta t) in a certain energy norm defined precisely in the article. The analysis is performed without any assumptions on the speed of propagation of the free boundary but only assumes the pragmatic regularity that u(t) is an element of L-2 (0, T; L-2(Omega)). The obstacle constraints are incorporated at the Lagrange nodes of the triangular mesh and the analysis exploits the Lagrange interpolation. We present some numerical experiment to illustrate the performance of the proposed methods
Interactions between reward motivation and emotional processing
No full textMuch of the past research on how reward motivation and emotional information influence brain and behavior has been conducted separately. Recently, a few behavioral and brain imaging studies have investigated how reward and emotional information co-jointly impact brain and behavior. The present chapter reviews findings from this recent line of work to summarize our current knowledge about the influence of reward expectancy on brain and behavior in the context of emotional information. The available findings suggest that behaviorally reward counteracts the adverse impact of potent emotional distractors on task performance. Additionally, brain findings suggest that the ventral striatum plays an active role in upregulating attentional control processes to limit the influence of emotional distractors. Overall, task relevance seems to play an important role in shaping interactions between reward and emotional processing. We conclude by outlining a few open questions for future research
Enhanced shot noise at bilayer graphene-superconductor junction
No full textTransport properties of graphene-superconductor junction have been studied extensively to understand the interplay of the relativistic Dirac quasiparticles and superconductivity. Though shot noise measurements in graphene have been performed to realize many theoretical predictions, both at zero magnetic field as well as quantum Hall (QH) regime, its junction with superconductor remain unexplored. Here, we have carried out the shot noise measurements in an edge contacted bilayer graphene-niobium superconductor junction at zero magnetic field as well as QH regime. At the Dirac point we have observed a Fano factor similar to 1/3 above the superconducting gap (Delta) and a transition to an enhanced Fano factor similar to 0.5 below the superconducting gap. By changing the carrier density we have found a continuous reduction of Fano factor for both types of carriers; however, the enhancement of Fano factor within the superconducting gap by a factor of similar to 1.5 is always preserved. The enhancement of shot noise is also observed in the QH regime, where the current is carried by the edge state, below the critical magnetic field and within the superconducting gap. These observations clearly demonstrate the enhanced charge transport at the graphene-superconductor interface
Three-Component Aminoselenation of Arynes
No full textThe three-component coupling of tertiary amines, arynes, and aryl selenium bromide or diaryl diselenide as an electrophilic selenium source allowing the synthesis of 2-selanyl aniline derivatives is reported. This aminoselenation reaction of arynes installs a C-N and C-Se bond under mild conditions, and the products are formed in moderate to good yields. This reaction is compatible with various functional groups, and the preliminary studies on the mechanism of the reaction is also provided
The ETS transcription factor ELF1 regulates a broadly antiviral program distinct from the type I interferon response
No full textInduction of vast transcriptional programs is a central event of innate host responses to viral infections. Here we report a transcriptional program with potent antiviral activity, driven by E74-like ETS transcription factor 1 (ELF1). Using microscopy to quantify viral infection over time, we found that ELF1 inhibits eight diverse RNA and DNA viruses after multi-cycle replication. Elf1 deficiency results in enhanced susceptibility to influenza A virus infections in mice. ELF1 does not feed-forward to induce interferons, and ELF1's antiviral effect is not abolished by the absence of STAT1 or by inhibition of JAK phosphorylation. Accordingly, comparative expression analyses by RNA-seq revealed that the ELF1 transcriptional program is distinct from interferon signatures. Thus, ELF1 provides an additional layer of the innate host response, independent from the action of type I interferons
A CTC-Cluster-Specific Signature Derived from OMICS Analysis of Patient-Derived Xenograft Tumors Predicts Outcomes in Basal-Like Breast Cancer
No full textCirculating tumor cell clusters (CTCcl) have a higher metastatic potential compared to single CTCs and predict long-term outcomes in breast cancer (BC) patients. Because of the rarity of CTCcls, molecular characterization of primary tumors that give rise to CTCcl hold significant promise for better diagnosis and target discovery to combat metastatic BC. In our study, we utilized the reverse-phase protein array (RPPA) and transcriptomic (RNA-Seq) data of 10 triple-negative BC patient-derived xenograft (TNBC PDX) transplantable models with CTCs and evaluated expression of upregulated candidate protein Bcl2 (B-cell lymphoma 2) by immunohistochemistry (IHC). The sample-set consisted of six CTCcl-negative (CTCcl-) and four CTCcl-positive (CTCcl+) models. We analyzed the RPPA and transcriptomic profiles of CTCcl- and CTCcl+ TNBC PDX models. In addition, we derived a CTCcl-specific gene signature for testing if it predicted outcomes using a publicly available dataset from 360 patients with basal-like BC. The RPPA analysis of CTCcl+ vs. CTCcl- TNBC PDX tumors revealed elevated expression of Bcl2 (false discovery rate (FDR) < 0.0001, fold change (FC) = 3.5) and reduced acetyl coenzyme A carboxylase-1 (ACC1) (FDR = 0.0005, FC = 0.3) in CTCcl+ compared to CTCcl- tumors. Genome-wide transcriptomic analysis of CTCcl+ vs. CTCcl- tumors revealed 549 differentially expressed genes associated with the presence of CTCcls. Apoptosis was one of the significantly downregulated pathways (normalized enrichment score (NES) = -1.69; FDR < 0.05) in TNBC PDX tumors associated with CTCcl positivity. Two out of four CTCcl+ TNBC PDX primary tumors had high Bcl2 expression by IHC (H-score > 34); whereas, only one of six CTCcl- TNBC PDX primary tumors met this criterion. Evaluation of epithelial-mesenchymal transition (EMT)-specific signature did not show significant differences between CTCcl+ and CTCcl- tumors. However, a gene signature associated with the presence of CTCcls in TNBC PDX models was associated with worse relapse-free survival in the publicly available dataset from 360 patients with basal-like BC. In summary, we identified the multigene signature of primary PDX tumors associated with the presence of CTCcls. Evaluation of additional TNBC PDX models and patients can further illuminate cellular and molecular pathways facilitating CTCcl formation
A Novel Technique to Investigate the Role of Traps in the Off-State Performance of AlGaN/GaN High Electron Mobility Transistor on Si Using Substrate Bias
No full textLeakage mediated by GaN buffer traps is identified and studied using a novel characterization technique. Through back-gating measurement, the effect of buffer trap states on the lateral leakage is determined by probing mesa-isolated Ohmic pads. Time-dependent leakage measurements are carried out to study the extent of the increase in buffer leakage due to the traps. It is observed that the mesa leakage is more prominent at very slow sweep rates and high substrate bias. The temperature-dependent measurements show that the mesa leakage and the substrate leakage are characterized by thermionic emission from the traps with an activation barrier of 0.34 and 0.2 eV, respectively