On the transverse compression response of Kevlar KM2 using fiber-level finite element model

Flexible textile composites like woven Kevlar fabrics are widely used in high velocity impact (HVI) applications. Upon HVI they are subjected to both longitudinal tensile and transverse compressive loads. To understand the role of transverse properties, the single fiber and tow transverse compression response (SFTCR and TTCR) of Kevlar KM2 fibers are numerically analyzed using plane strain finite element (FE) models. A finite strain formulation with a minimum number of 84 finite elements is determined to be required for the fiber cross section to capture the finite strain SFTCR through a mesh convergence study. Comparison of converged numerical solution to the experimental results indicates the dominant role of geometric stiffening at finite strains due to growth in contact width. The TTCR is studied using a fiber length scale FE model of a single tow comprised of 400 fibers transversely loaded between rigid platens. This study along with micrographs of yarn after mechanical compaction illustrates fiber spreading and fiber–fiber contact friction interactions are important deformation mechanisms at finite strains. The TTCR is also studied using homogenized yarn level models with properties from the literature. Comparison of TTCR between fiber length scale and homogenized yarn length scale models indicate the need for a nonlinear material model for homogenized approaches to accurately predict the transverse compression response of the fabrics.     

An Analysis of Partially Clairvoyant Scheduling

Real-time scheduling problems confront two issues not addressed by traditional scheduling models, viz., parameter variability and the existence of complex relationships constraining the executions of jobs. Accordingly, modeling becomes crucial in the specification of scheduling problems in such systems. In this paper, we analyze scheduling algorithms in Partially Clairvoyant Real-time scheduling systems and present a new dual-based algorithm for the feasibility problem in the case of strict relative constraints. We also study the problem of online dispatching in Partially Clairvoyant systems and show that the complexity of dispatching is logarithmically related to the complexity of the schedulability problem.     

Synthesis and Properties of Imidazole-Blocked Toluene Diisocyanates

Abstract

Imidazole-, 2-methyl imidazole-, and benzimidazole-blocked toluene diisocyanates (TDI) were prepared and characterized by elemental analysis, IR, and NMR spectroscopy. Simultaneous TGA/DTA results showed that the thermal stability of the adduct decreases in the following order: imidazole-TDI > 2-methylimidazole-TDI > benzimidazole-TDI. Gelation test involving imidazole-blocked adducts and hydroxyl-terminated polybutadiene were also carried out. The cure rate of the adduct increases from the imidazole- to the 2-methylimidazole- and to the benzimidazole-blocked adduct. It is also found that the benzimidazole-blocked adduct shows better solubility in the polyols.     

Chiral Phosphoric Acid Catalyzed Kinetic Resolution of 2‐Amido Benzyl Alcohols: Asymmetric Synthesis of 4H‐3,1‐Benzoxazines

An efficient method for the asymmetric synthesis of 4H‐3,1‐benzoxazines was developed by kinetic resolution of 2‐amido benzyl alcohols using chiral phosphoric acid catalyzed intramolecular cyclizations. A broad range of benzyl alcohols (both secondary and tertiary alcohols) were kinetically resolved with high selectivities, with an s factor of up to 94. Mechanistic studies were performed to elucidate the mechanism of these reactions, wherein the amide moieties reacted as the electrophiles. Gram‐scale reaction and facile transformations of the chiral products demonstrate the potential of this method in asymmetric synthesis of biologically active chiral heterocycles.     

Dripping-jetting transitions in a dripping faucet

Fascinating dynamics is known to result when the flow rate Q at which water drips from a faucet varies. Starting with simple (period-1) dripping, the system transitions as Q increases to complex dripping, where it exhibits period-n (n=2,4, em leader ) and chaotic responses, and then jets once Q exceeds a threshold. New experiments and simulations show that high viscosity (micro) liquids, e.g., syrup, transition directly from simple dripping to jetting as Q increases. Phase diagrams showing transitions between simple and complex dripping and jetting in (Q,micro) space are developed. Values of Q for transition from dripping to jetting are estimated from scaling arguments and shown to accord well with simulations.     

Computational identification of novel piperidine derivatives as potential HDM2 inhibitors designed by fragment-based QSAR,molecular docking and molecular dynamics simulations

Tumor suppressor protein p53 maintains integrity of genome and regulates the genes responsible for DNA repair mechanism, apoptosis as well as cell cycle and growth arrest. As with murine double minute 2 (MDM2), the human homolog HDM2 is a principal cellular antagonist of p53. In unstressed cells, cellular levels of p53 and HDM2 are maintained in an autoregulatory manner in which both mutually control cellular levels of each other. About half of the human cancers express wild-type p53 protein that is antagonized by over-expressed HDM2. Restoring p53 function via HDM2 antagonists is a leading therapeutic approach for treating a variety of tumors. In this study, we have developed a novel statistically sound group-based QSAR (GQSAR) model using piperidine-derived compounds that have been validated experimentally to inhibit p53–HDM2 interaction. On the basis of developed GQSAR model, a combinatorial library of molecules was prepared and its activity was predicted. These molecules were then docked to HDM2, and two top-scoring molecules possessing a binding energy of ?6.639 and ?6.305 kcal/mol were selected for further study. These molecules and their binding poses were analyzed further via molecular dynamic simulations. In this study, we report two lead compounds as potent HDM2 inhibitors and also provide an insight into mechanism of interaction of the lead compounds to HDM2 target.

     

A first report on the crystal structure of hydrazine based solid solution precursor,Mn0.61Zn0.39(OOCCHNNH2)2(H2O)2

A novel mixed metal complex, [Mn_0.61Zn_0.39(OOCCHNNH₂)₂(H₂O)₂] has been synthesized and characterized by hydrazine and metal analyses, CHN analyses, infrared spectra, simultaneous TG-DTA and single crystal X-ray diffraction studies. The structure of the complex has been determined by X-ray single crystal study which clearly reveals that the octahedral site is occupied by two metal ions (viz., Mn and Zn) around which two hydrazoneglyoxylate ligands (OOCCHNNH₂) coordinate in a bidentate chelating fashion. Two water molecules occupy the remaining two other sites of a slightly distorted octahedron with C₂ axis of symmetry. The infrared spectrum reveals the monodentate coordination behavior of carboxylate ions and coordination of water molecules. The simultaneous TG-DTA traces are in accordance with the formation of mixed metal oxide (spinel oxide) as an end product. The high resolution scanning electron microscopy (HRSEM) images show the presence of irregularly shaped agglomerated particles of sub-micron size. The zeta potential value for mixed metal oxide is ?33.1 mV, which indicates the stability of the oxide.     

Model systems for flavoenzyme activity: intramolecular self-assembly of a flavin derivative via hydrogen bonding and aromatic interactions

We have synthesised a flavin derivative incorporating functionalities that promote intramolecular self-assembly via hydrogen bonding and aromatic interactions.     

A Cell-Culture Technique to Encode Glyco-Nanoparticles Selectivity

Nanoparticles (NPs) embedded with bioactive ligands such as carbohydrates, peptides, and nucleic acid have emerged as a potential tool to target biological processes. Traditional in vitro assays performed under statistic conditions may result in non-specific outcome sometimes, mainly because of the sedimentation and self-assembly nature of NPs. Inverted cell-culture assay allows for flexible and accurate detection of the receptor-mediated uptake and cytotoxicity of NPs. By combining this technique with glyco-gold nanoparticles, cellular internalization and cytotoxicity were investigated. Regioselective glycosylation patterns and shapes of the NPs could tune the receptors′ binding affinity, resulting in precise cellular uptake of gold nanoparticles (AuNPs). Two cell lines HepG2 and HeLa were probed with galactosamine-embedded fluorescent AuNPs, revealing significant differences in cytotoxicity and uptake mechanism in upright and invert in vitro cell-culture assay, high-specificity toward uptake, and allowing for a rapid screening and optimization technique.     

A Zero-Space algorithm for Negative Cost Cycle Detection in networks

This paper is concerned with the problem of checking whether a network with positive and negative costs on its arcs contains a negative cost cycle. The Negative Cost Cycle Detection (NCCD) problem is one of the more fundamental problems in network design and finds applications in a number of domains ranging from Network Optimization and Operations Research to Constraint Programming and System Verification. As per the literature, approaches to this problem have been either Relaxation-based or Contraction-based. We introduce a fundamentally new approach for negative cost cycle detection; our approach, which we term as the Stressing Algorithm, is based on exploiting the connections between the NCCD problem and the problem of checking whether a system of difference constraints is feasible. The Stressing Algorithm is an incremental, comparison-based procedure which is as efficient as the fastest known comparison-based algorithm for this problem. In particular, on a network with n vertices and m edges, the Stressing Algorithm takes O(mn) time to detect the presence of a negative cost cycle or to report that none exists. A very important feature of the Stressing Algorithm is that it uses zero extra space; this is in marked contrast to all known algorithms that require Ω(n) extra space. It is well known that the NCCD problem is closely related to the Single Source Shortest Paths (SSSP) problem, i.e., the problem of determining the shortest path distances of all the vertices in a network, from a specified source; indeed most algorithms in the literature for the NCCD problem are modifications of approaches to the SSSP problem. At this juncture, it is not clear whether the Stressing Algorithm could be extended to solve the SSSP problem, even if O(n) extra space is available.