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Isolation of base stabilized fluoroborylene and its radical cation
No full textHerein, we report the synthesis and characterization of the metal free low valent fluoroborylene (Me-cAAC)(2)BF] (1) stabilized by cyclic (alkyl)(amino) carbene (cAAC). The fluoroborylene 1 is obtained by the reductive defluorination of Me-cAAC:BF3 with 2.0 equivalents of KC8 in the presence of 1.0 equivalent of Me-cAAC. Due to its highly electron rich nature, 1 underwent one-electron oxidation with 1.0 equivalent of lithium tetrakis(pentafluorophenyl)borate LiB(C6F5)(4)] to form the radical cation (Me-cAAC)(2)BF](+)B(C6F5)(4)](-) (2). DFT studies suggested that the lone pair of electrons is localized on the boron atom in 1, which explains its unprecedented reactivity. Both compounds 1 and 2 were characterized by X-ray crystallography. The radical cation 2 was studied by EPR spectroscopy
Optimal Linear Broadcast Rates of Some Two-Sender Unicast Index Coding Problems
No full textThe two-sender unicast index coding problem consists of two senders, each having a different set of messages. Some messages may be common to both the senders. Each receiver demands a unique message and has a subset of messages known as its side-information. The senders transmit coded messages by availing the knowledge of the side-information of all the receivers, such that all the receivers are able to decode their demands. The aim is to find the optimal aggregate number of coded transmissions per message length (also called the optimal broadcast rate with finite length messages), and its limiting value as the message length tends to infinity (also called the optimal broadcast rate). In this paper, only linear coding schemes are considered. Optimal linear broadcast rate for any finite message length and optimal linear broadcast rate for a basic class of the two-sender unicast index coding problem are established. Optimal code-constructions are also provided. These results are given in terms of the corresponding results of three independent single-sender sub-problems of the two-sender unicast index coding problem. Proof techniques used to obtain the results for the two-sender problem are shown to be useful in obtaining the results for some classes of the multi-sender unicast index coding problem
Optimization of absorption/desorption parameters of Brownmillerite SrCoO2.5 for oxygen storage
No full textThe order-disorder transition of Brownmillerite (BM)-type oxides have gained attraction for oxygen enrichment applications. Herein, BM SrCoO2.5 is exploited for oxygen storage and separation across its order-disorder transition. Optimized temperature and duration of heat treatment in an oxygen atmosphere for obtaining maximum oxygen storage is explored. A maximum of 15.28 cm(3) of O-2 per gram of the material can be stored in the sample at STP by a heat-treatment at 673-693 K. A drastic increase in ionic conductivity of the sample above a certain temperature gave rise to a threshold temperature for oxygen absorption. Kinetics of oxygen release appeared to follow nucleation and growth model and the rate of desorption was found to increase with rise in temperature. The oxygen intake/release of BM SrCoO2.5 occurs within minutes in a completely reversible manner facilitating a low cost O-2 separation through vacuum swing adsorption
Degeneracy in hippocampal physiology and plasticity
No full textDegeneracy, defined as the ability of structurally disparate elements to perform analogous function, has largely been assessed from the perspective of maintaining robustness of physiology or plasticity. How does the framework of degeneracy assimilate into an encoding system where the ability to change is an essential ingredient for storing new incoming information? Could degeneracy maintain the balance between the apparently contradictory goals of the need to change for encoding and the need to resist change towards maintaining homeostasis? In this review, we explore these fundamental questions with the mammalian hippocampus as an example encoding system. We systematically catalog lines of evidence, spanning multiple scales of analysis that point to the expression of degeneracy in hippocampal physiology and plasticity. We assess the potential of degeneracy as a framework to achieve the conjoint goals of encoding and homeostasis without cross-interferences. We postulate that biological complexity, involving interactions among the numerous parameters spanning different scales of analysis, could establish disparate routes towards accomplishing these conjoint goals. These disparate routes then provide several degrees of freedom to the encoding-homeostasis system in accomplishing its tasks in an input- and state-dependent manner. Finally, the expression of degeneracy spanning multiple scales offers an ideal reconciliation to several outstanding controversies, through the recognition that the seemingly contradictory disparate observations are merely alternate routes that the system might recruit towards accomplishment of its goals
Elucidating the functional role of Mycobacterium smegmatis recX in stress response
No full textThe RecX protein has attracted considerable interest because the recX mutants exhibit multiple phenotypes associated with RecA functions. To further our understanding of the functional relationship between recA and recX, the effect of different stress treatments on their expression profiles, cell yield and viability were investigated. A significant correlation was found between the expression of Mycobacterium smegmatis recA and recX genes at different stages of growth, and in response to different stress treatments albeit recX exhibiting lower transcript and protein abundance at the mid-log and stationary phases of the bacterial growth cycle. To ascertain their roles in vivo, a targeted deletion of the recX and recArecX was performed in M. smegmatis. The growth kinetics of these mutant strains and their sensitivity patterns to different stress treatments were assessed relative to the wild-type strain. The deletion of recA affected normal cell growth and survival, while recX deletion showed no significant effect. Interestingly, deletion of both recX and recA genes results in a phenotype that is intermediate between the phenotypes of the Delta recA mutant and the wild-type strain. Collectively, these results reveal a previously unrecognized role for M. smegmatis recX and support the notion that it may regulate a subset of the yet unknown genes involved in normal cell growth and DNA-damage repair
Paederia foetida induces anticancer activity by modulating chromatin modification enzymes and altering pro-inflammatory cytokine gene expression in human prostate cancer cells
No full textAberrant epigenetic modifications are responsible for tumor development and cancer progression; however, readily reversible. Bioactive molecules from diets are promising to cure cancer by modulating epigenetic marks and changing immune response. These compounds specifically target the activity of DNMTs and HDACs to cure various human cancers. In view of this, we investigated the anticancer and epigenetic regulatory activities of an edible-plant Paederia foetida. The efficacy of methanolic extract of P. foetida leaves (MEPL) was tested for the modulation of epigenetic factors in gene silencing, i.e. DNMT and HDAC and expression pattern of certain tumor suppressor genes. After treatment of prostate cancer cells (PC-3 and DU-145) with MEPL, lupeol and beta-sitosterol; induction of apoptosis, decrease in cellular-viability and inhibition of cellular-migration were noticed. Simultaneously there was inhibition of DNMT1, HDACs and pro-inflammatory, IL-6, IL1-beta, TNF-alpha and anti-inflammatory, IL-10 genes in cancer and THP1 cell lines. The DNMT1 protein content, enzyme activity and Bcl2 expression decreased significantly; however, expression of E-cadherin (CDH1) and pro-apoptotic gene Bax increased significantly after the treatment of cells with drugs. We conclude plant-derived compounds can be considered to target epigenetic machineries involved with malignant transformation and can open new avenues for cancer therapeutics provoking immune response
Polyelectrolyte complex membranes made of chitosan-PSSAMA for pervaporation separation of industrially important azeotropic mixtures
No full textChitosan-based polyelectrolyte complex membranes (PECMs) were developed by incorporating polystyrene sulfonic acid-co-maleic acid (PSSAMA) in the chitosan membrane matrix as a pervaporation membrane by employing a solution technique. Fourier transform infrared (FTIR) spectroscopy, wide-angle X-ray diffraction (WAXD), thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were used to characterize the membranes. PECMs were tested for their potentiality to separate various azeotropic mixtures; water/ter-butanol, water/isopropanol, water/n-propanol and water/l, 4 dioxane at their azeotropic point. The PECMs containing 9 mass% of PSSAMA manifest highest separation selectivity of 5352 with a flux of 4.145 x 10(-2) kg/m(2) h for the azeotropic mixture of water/ter-butanol at 30 degrees C. To confirm their stability at the higher temperature, the PECMs were assessed for pervaporation (PV) separation at 40, 50 and 60 degrees C. For all PECMs total flux and flux of water appeared to be coinciding each other, signifying that PECM5 could be used successfully to break the azeotropic point of various azeotropic mixtures. The Arrhenius activation parameters were determined by diffusion and permeation values. The activation energy values procured for water permeation (E-pw) were considerably lower than ter-butanol permeation (E-pTBOH). The heat of sorption (Delta Hs) values obtained for PECMs were negative, showing that Langmuir's mode of sorption is dominant. (C) 2019 The Korean Society of Industrial and Engineering Chemistry
Enhancing absorption dominated microwave shielding in Co@C-PVDF nanocomposites through improved magnetization and graphitization of the Co@C-nanoparticles
No full textUsing composites of polyvinylidene fluoride (PVDF) and carbon nanostructures embedded with Co-nanoparticles we demonstrate that electromagnetic shielding effectiveness depends strongly on the graphitic carbon concentration and the magnetic properties of Co-particles. Cobalt nanoparticles encapsulated by graphitic carbon embedded in an amorphous carbon-matrix were synthesized by a one-pot pyrolysis method at two different synthesis temperatures, T-S = 800 degrees C (Co-800) and 1000 degrees C (Co-1000). We demonstrate that T-S plays an important role in determining the structure, morphology and magnetic properties of the carbonaceous matrix, the graphite layer and the Co nanoparticles. Higher amounts of graphitic carbon and high saturation magnetization were observed for the Co-1000 sample than that for the Co-800 sample. We observed that the electromagnetic interference (EMI) shielding behavior of the PVDF-Co-1000 nanocomposite shows higher shielding effectiveness than that of the PVDF-Co-800 specimen. A more inhomogeneous dielectric medium in the PVDF-Co-1000 composite results in higher dielectric loss and impedance mismatch. A direct correlation between the shielding effectiveness with dielectric permittivity and magnetic permeability is demonstrated. The synergy between the multiple reflections at the interfaces and absorption of the microwave radiation in the conducting species confirms that a higher degree of graphitization and highly magnetic particles in nanocomposites are effectively superior for EMI shielding of microwave radiation
From a Binary to a Quaternary Cocrystal: An Unusual Supramolecular Synthon
No full textFormation of a stoichiometric quaternary cocrystal consisting of resorcinol (RES), tetramethylpyrazine (TMP), phenazine (PHE) and pyrene (PYR) is described. A closed tetrameric resorcinol-heterocycle synthon, unusual in that it has two different linker bases rather than just one, is observed in this four-component solid. The tetrameric synthon is formed by two RES molecules and the two pyridine bases TMP and PHE. The stoichiometric quaternary cocrystal grows in an epitaxial fashion on the surfaces of a RES.PHE binary cocrystal which is initially obtained from the mother liquor. By indexing the common crystal faces of the binary and quaternary cocrystals, and noting that no ternary solid is obtained, a plausible mechanism has been proposed for the formation of this rare supramolecular architecture
Oxidation studies of Al alloys: Part I Al-Cu (liquid phase) alloy
No full textThis unique investigation explores the nature and chemistry of the oxides on Al-Cu alloys in the liquid state and conducts thermodynamic simulations and kinetic studies of the oxidation process. The morphology, microstructural evolution and chemistry of the oxides were explained over different time intervals. Thermodynamic simulations were performed to explain the formation and stability of oxides in the Al-5Cu alloy; the oxidation mechanism was discussed and compared to that of pure Al. Between 450-650 degrees C, the oxidation kinetics of Al exhibit parabolic and Al-5Cu shows pseudo-parabolic behaviour whereas between 750-950 degrees C both follow linear rate equations with activation energies of 150-200 kJ mol(-1)