Relativistic effects and gold site distributions: synthesis, structure, and bonding in a polar intermetallic Na6Cd16Au7

Na(6)Cd(16)Au(7) has been synthesized via typical high-temperature reactions, and its structure refined by single crystal X-ray diffraction as cubic, Fm ?3m, a = 13.589(1) ?, Z = 4. The structure consists of Cd(8) tetrahedral star (TS) building blocks that are face capped by six shared gold (Au2) vertexes and further diagonally bridged via Au1 to generate an orthogonal, three-dimensional framework [Cd(8)(Au2)(6/2)(Au1)(4/8)], an ordered ternary derivative of Mn(6)Th(23). Linear muffin-tin-orbital (LMTO)-atomic sphere approximation (ASA) electronic structure calculations indicate that Na(6)Cd(16)Au(7) is metallic and that ～76% of the total crystal orbital Hamilton populations (-ICOHP) originate from polar Cd-Au bonding with 18% more from fewer Cd-Cd contacts. Na(6)Cd(16)Au(7) (45 valence electron count (vec)) is isotypic with the older electron-richer Mg(6)Cu(16)Si(7) (56 vec) in which the atom types are switched and bonding characteristics among the network elements are altered considerably (Si for Au, Cu for Cd, Mg for Na). The earlier and more electronegative element Au now occupies the Si site, in accord with the larger relativistic bonding contributions from polar Cd-Au versus Cu-Si bonds with the neighboring Cd in the former Cu positions. Substantial electronic differences in partial densities-of-states (PDOS) and COHP data for all atoms emphasize these. Strong contributions of nearby Au 5d(10) to bonding states without altering the formal vec are the likely origin of these effects.     

Thermal,vibrational, and dielectric studies on PVP/LiBF4+ionic liquid [EMIM][BF4]-based polymer electrolyte films

Free-standing polymer electrolyte membranes based on poly(vinyl) pyrrolidone (PVP)/salt(LiBF₄) having different amounts of ionic liquid (IL) [EMIM][BF₄] were prepared and characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, and alternating current (AC) impedance spectroscopic techniques. The DSC results show a shift in T_m of PVP with salt/or IL content. TGA and DTGA (first derivative of TGA) results give evidence of the presence of uncomplexed PVP, PVP/salt, and PVP/IL complexes. Signatures of these entities are also present in the dielectric spectra. Complexation of PVP with salt and IL has been confirmed by FT-IR analysis. Electrical conductivity as a function of temperature has been studied for PVP/LiBF₄/IL [EMIM][BF₄]. Role of IL in changing phase transition, conductivity, and dielectric relaxation frequency has been discussed.     

Stabilization of betatron tune in Indus-2 storage ring

Indus-2 is a synchrotron radiation source that is operational at RRCAT, Indore, India. It is essentially pertinent in any synchrotron radiation facility to store the electron beam without beam loss. During the day to day operation of Indus-2 storage ring, difficulty was being faced in accumulating higher beam current. After examination, it was found that the working point was shifting from its desired value during accumulation. For smooth beam accumulation, a fixed desired tune in both horizontal and vertical plane plays a significant role in avoiding beam loss via the resonance process. This required a betatron tune feedback system to be put in the storage ring. After putting ON this feedback, the beam accumulation was smooth. The details of this feedback and its working principle are described in this paper.     

Atomic electronegativity based on hardness and floating spherical gaussian orbital approach

Journal of Mathematical Chemistry - Electronegativity (χ) is an important property of any chemical species as it helps to predict the pattern of physico-chemical interactions. In the present...     

Supramolecular Association in the Structure of 2,9-<Emphasis Type="Italic">C</Emphasis>-<Emphasis Type="Italic">meso</Emphasis>-2,5,5,7,9,12,12,14-Octamethyl-1,8-diaza-4,11-diazoniacyclotetradecane as its Bis(nitrate) and Bis(acetate) Trihydrate

Abstract In the crystal structure of the nitrate salt, columns of di-cationic macrocycles, each disposed about a center of inversion, are interspersed by pairs of nitrate anions that form charged-assisted N–H···O hydrogen-bonding interactions, reinforced by C–H···O contacts. The topology of the resulting supramolecular architecture is that of a linear chain and these associate via further weak C–H···O contacts. In the structure of the acetate trihydrate, di-cationic macrocycles are circumscribed by 32-membered rings defined by O–H···O interactions, involving the acetate anions and solvent water molecules. Systematic variations in the geometric parameters in the molecular structures are correlated with the influence of intermolecular interactions. The nitrate crystallizes in the monoclinic space group P2₁/n with a = 8.3524(11) ?, b = 12.5497(16) ?, c = 11.1208(16) ?, β = 103.180(3)°, and Z = 2. The acetate trihydrate also crystallizes in the monoclinic space group P2₁/n with a = 9.6679(15) ?, b = 15.278(2) ?, c = 9.8376(18) ?, β = 106.068(5)°, and Z = 2. Index Abstract Supramolecular Association in the Structure of 2,9- C-meso -2,5,5,7,9,12,12,14-Octamethyl-1,8-diaza-4,11- diazoniacyclotetradecane as its Bis(nitrate) and Bis(acetate) Trihydrate Saroj K. S. Hazari, ⁽¹⁾ Tapashi G. Roy, ^(1)* Kanak K. Barua ⁽¹⁾ and Edward R. T. Tiekink ^(2)* A linear supramolecular chain stabilized by charge-assisted N–H···O hydrogen-bonding interactions is found in the nitrate salt. In the acetate trihydrate, di-cationic macrocycles are circumscribed by 32-membered rings constructed by O–H···O hydrogen-bonds. Supramolecular Association in the Structure of 2,9- C-meso -2,5,5,7,9,12,12,14-Octamethyl-1,8-diaza-4,11- diazoniacyclotetradecane as its Bis(nitrate) and Bis(acetate) Trihydrate Saroj K. S. Hazari, ⁽¹⁾ Tapashi G. Roy, ^(1)* Kanak K. Barua ⁽¹⁾ and Edward R. T. Tiekink ^{(2)* (1)}Department of Chemistry, University of Chittagong, Chittagong-4331, Bangladesh ⁽²⁾Department of Chemistry, The University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-0698 Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

Effects of seasonal growth on ratio dependent delayed prey predator system

The Beddington–DeAngelis ratio dependent prey predator model with time delay has been discussed. The existence of Hopf bifurcation has been established. The numerical simulations have shown that seasonal growth and delay can give rise to variety of attractors including periodic, quasi-periodic as well as chaotic oscillations. The degree of complexity in the system increases with increase in magnitude of delay, or frequency of seasonal variation. The model parameters involved in functional response can also affect the complexity of the system.     

The Crystal and Molecular Structure of the Dinuclear Mo(VI) Species: [(cis-MoO2L)(μ-O)(cis-MoOL(OH2)]?·?CHCl3 where L?=?(S-benzyl 3-(2-Hydroxyphenyl)Methylenedithiocarbazate)

Abstract  The title dinuclear complex, [(cis-MoO₂L)(μ-O)(cis-MoOL(OH₂)], was characterized as a chloroform solvate. In this structure, one Mo atom features a cis-[MoO₂]²⁺ core to which is also bonded a dinegative, tridentate S-benzyl 3-(2-hydroxyphenyl)methylenedithiocarbazate ligand (= L), via sulfur-, oxygen-, and nitrogen-donors, and a water molecule completes the distorted octahedral coordination geometry. A similar NO₄S donor set is found for the other Mo atom but in this case, the water molecule is substituted by a bridging oxo atom derived from the first Mo species. Two dimers associate via cooperative O–H⋯O hydrogen bonds to form a supramolecular dimer which, in turn, are linked into supramolecular chains via O–H⋯N hydrogen bonding. The complex crystallizes in the triclinic space group P-1 with a = 10.4714(12) ?, b = 10.7627(14) ?, c = 16.708(2) ?, α = 87.916(7)°, β = 76.249(6)°, γ = 83.610(7)°, and Z = 2. Index Abstract  Dinuclear [(cis-MoO₂L)(μ-O)(cis-MoOL(OH₂)], characterized as a chloroform solvate, with octahedral Mo centers, are connected into supramolecular dimers via O–H⋯O hydrogen bonding which are connected via O–H⋯N hydrogen bonds into chains.      

93Nb(n,2n)92mNb, 93Nb(n,α)90mY and 92Mo(n,p)92mNb reactions at 14.78 MeV and covariance analysis

Journal of Radioanalytical and Nuclear Chemistry - The cross sections for the 93Nb(n,2n)92mNb, 93Nb(n,α)90mY and the 92Mo(n,p)92mNb reactions have been measured with respect to the...     

Microsatellite instability and its correlation with clinicopathological features in a series of thyroid tumors prevalent in iodine deficient areas

Thyroid tumors display diverse spectrum of histopathological groups with geographic variation in its prevalence. Influence of iodine deficiency (a major causative factor) in its etiology, prevalence, or aggressiveness is debatable which reflects the existence of various genetic events in pathogenesis. The present study was undertaken to study the role of Microsatellite instability (MSI) or LOH (loss of heterozygosity), an indicator of defective mismatch repair system as a genetic change and to explore it as a prognostic marker in thyroid tumors. Tumor tissues from total thyroidectomy surgical specimens and blood (matched control) of 36 patients from iodine deficient areas (10 benign; 26 malignant) were obtained after their consent. Urinary iodine analysis was done by alkali ash method for which 10 ml of urine was collected from 18 patients before surgery. Genomic DNA, isolated from tumor tissue and blood was amplified by polymerase chain reaction (PCR) using mono and dinucleotide markers - BAT-26, BAT-40, TGF(RII, IGFIIR, hMSH3, BAX, D2S123, D9S283, D9S851 and D18S58. PCR products were analysed on 8% denaturing polyacrylamide gel followed by autoradiography. Of total, 66.6% of tumors [70% (7/10) benign and 65.4% malignant cases (17/26)] showed MSI/LOH. Strong association of MSI/LOH with low iodine (P = 0.01) and with AMES risk groups i.e. age (P = 0.02), tumor size (P = 0.04) and metastases (P = 0.002) in thyroid tumors was observed. This may help in predicting the biological behaviour and strengthening the hypothesis that iodine deficiency has influence on MSI in thyroid tumors. Our results further substantiate the risk group classification and help in deciding the treatment modality in particular patient.     

Prudent Practices in ex situ Durability Analysis Using Cyclic Voltammetry for Platinum-based Electrocatalysts

Platinum (Pt)-based electrocatalysts are at the vanguard of research initiatives to meet activity and durability targets for promoting large-scale adoption of fuel cell vehicles. Ex situ characterization of electrocatalyst activity and durability using cyclic voltammetry (CV) has a steep learning curve. Thus, many researchers who do not receive formal training in electrochemistry are left unsure how to proceed. Herein, we identify and compile prudent practices for reliable assessment of ECSA values with examples from our research on nanoscale catalytic films formed by the self-terminating electrodeposition of Pt. Starting with a conceptual framework to understand typical features in the CV of reversible redox couples, we present prudent practices in acquiring CV data aimed at nonelectrochemists. We then highlight specific features related to ECSA computation from Pt CV. Finally, we suggest safeguards that help avoid missteps and achieve repeatable results while conducting ex situ durability tests that extend over days.