Mechanism of structure formation of microbial cellulose during nascent stage

The structure of microbial cellulose (MC) produced by Acetobacter xylinum was studied in presence of Fluorescent Brightener, Direct Blue 1, 14, 15, 53, Direct Red 28, 75 and 79, as probe. X-ray diffraction pattern of the product showed that it was a crystalline complex of dye and cellulose. The product has the structure in which the monomolecular layer of the dye molecule is included between the cellulose sheets corresponding to the ( $ 1\bar{1}0 $ ) planes of microbial cellulose. As a result of dye inclusion, d-spacing of lower angle plane (100) of products becomes 8.0–8.8 Å instead of 6.1 Å of MC. The d-spacing for the higher angle plane must be (010) plane due to stronger van der Waals forces between the pyranose rings which reduced 5.3 Å space of (110) plane of MC to 3.9–4.5 Å in the product. However, cellulose regenerated from FB, DR28 products was cellulose I and IV, respectively, and that from each DB1, 14, 15, 53, DR75 and 79 products was cellulose II. Solid state ¹³C NMR and deuteration-IR showed the product was non-crystalline which was contrasted to X-ray results. The regenerated celluloses were cellulose I_β, IV_I and II, respectively. Thus the structure of the product depends on the characteristics of dye which affects the conformation of cellulose at the nascent stage by the direct interaction with cellulose chains. The different regenerated celluloses as well as different fine structure in the same cellulose allomorph were produced depending mainly on number and position of the sulfonate groups in the dye.     

Improved methods for the synthesis and isolation of imidazolium based ionic salts

Solvent-free reactions were used for the synthesis of a series of imidazolium-based ionic salts: 3,3′-[pyridine-2,6-diylbis(methylene)]bis(1-R-1H-imidazol-3-ium)chloride; (R = methyl, ethyl, butyl, isobutyl, hexyl, and benzyl). A simple and effective filtration process was used to isolate all the products in high purity and with yields ?93% within a 24 h period. The highly pure ionic compounds which are precursors to N-heterocyclic carbene ligands used in catalysis were fully characterized as gray-white hygroscopic salts.     

Investigate the capability of INAA absolute method to determine the concentrations of 238U and 232Th in rock samples

This work aimed to study the capability of INAA absolute method in determining the elemental concentration of ²³⁸U and ²³²Th in the rock samples. The INAA absolute method was implemented in PUSPATI TRIGA Mark II research reactor, Malaysian Nuclear Agency (NM). The accuracy of INAA absolute method was performed by analyzing the IAEA certified reference material (CRM) Soil-7. The analytical results showed the deviations between experimental and certified values were mostly less than 10 % with Z-score in most cases less than 1. In general, the results of analysed CRM Soil-7 show a good agreement between certified and experimental results which mean that the INAA absolute method can be used accurately for elemental analysis of uranium and thorium in various types of samples. The concentration of ²³⁸U and ²³²Th ranged from 1.77 to 24.25 and 0.88 to 95.50 ppm respectively. The highest value of ²³⁸U and ²³²Th was recorded for granite rock sample G17 of ²³⁸U and sample G9 of ²³²Th, whereas the lower value was 1.77 ppm of ²³⁸U recorded in sandstone rock and 0.88 ppm of ²³²Th for gabbro. Moreover, a comparison of the ²³⁸U and ²³²Th results obtained by the INAA absolute method shows an acceptable level of consistency with those obtained by the INAA relative method.     

Synthesis,spectroscopy, electrochemistry,and methylation reaction of the dithiolate-based cobalt(II) complex derived from tert-butyl N-(2-mercaptoethyl)carbamate

A dithiolate-containing a carbamate mononuclear cobalt(II) complex namely, [Co(Boc-S)₂] (1), was obtained by the reaction of a methanolic solution of cobalt(II) nitrate hexahydrate with two equimolar amounts of the deprotonated form of tert-butyl N-(2-mercaptoethyl)carbamate (Boc-SH). The cobalt(II) complex (1) was characterized in the solid state and in solution by using FT–IR, Raman, UV–visible, and EI–mass spectroscopies, as well as thermal and X-ray diffraction studies. Spectral data showed that the carbamate (Boc-SH) acts as a mono-anionic bidentate ligand coordinating the cobalt(II) ion through two imine nitrogen and two deprotonated thiolate sulfur donor atoms in a distorted tetrahedral geometry. The thermoanalytical data evidence that the complex is stable up to 165 °C and undergoes complete decomposition, resulting in CoO. TEM imaging of the oxide residue shows its nano size clusters, suggesting that the complex (1) may be used as a precursor for nano-oxides. X-ray powder diffraction patterns evidence an isomorphism among the complex. The redox behavior of the cobalt(II) complex was also investigated by cyclic voltammetry. The reaction of the dithiolate cobalt(II) complex (1) with methyl iodide appears to occur intramolecularly with the cobalt-bound dithiolate, forming the cobalt(II)-bound dithioether complex [Co(Boc–SCH₃)₂]I₂ (2), as a dication complex with a clean second-order reaction of 13.24 × 10⁻² M⁻¹·s⁻¹.     

The exploring microstructural,caloric, and corrosion behavior of NiTiNb shape-memory alloys

Journal of Thermal Analysis and Calorimetry - The influence of four different quantities of niobium (Nb) on some physical and chemical properties of Ni-Ti alloy was examined in this study....     

New Quinoxaline Derivatives as Dual Pim-1/2 Kinase Inhibitors: Design,Synthesis and Biological Evaluation

Proviral integration site for Moloney murine leukemia virus (Pim)-1/2 kinase overexpression has been identified in a variety of hematologic (e.g., multiple myeloma or acute myeloid leukemia (AML)) and solid (e.g., colorectal carcinoma) tumors, playing a key role in cancer progression, metastasis, and drug resistance, and is linked to poor prognosis. These kinases are thus considered interesting targets in oncology. We report herein the design, synthesis, structure–activity relationships (SAR) and in vitro evaluations of new quinoxaline derivatives, acting as dual Pim1/2 inhibitors. Two lead compounds (5c and 5e) were then identified, as potent submicromolar Pim-1 and Pim-2 inhibitors. These molecules were also able to inhibit the growth of the two human cell lines, MV4-11 (AML) and HCT-116 (colorectal carcinoma), expressing high endogenous levels of Pim-1/2 kinases.     

Coupling RSM with soot model for the study of soot formation in a momentum-dominated strained jet flames

Journal of Thermal Analysis and Calorimetry - This paper presents a comparison between the numerically determined soot volume fraction (SVF) in a momentum-dominated turbulent diffusion strained jet...     

Isoshamixanthone: a new pyrano xanthone from endophytic Aspergillus sp. ASCLA and absolute configuration of epiisoshamixanthone

Abstract

Isoshamixanthone (1), a new stereoisomeric pyrano xanthone together with the previously known fungal metabolites, epiisoshamixanthone (2), sterigmatocystin (3), arugosin C (4), norlichexanthone (5), diorcinol (6), ergosterol and methyllinoleate, were obtained from the endophytic fungal strain Aspergillus sp. ASCLA isolated from leaf tissues of the medicinal plant Callistemon subulatus. The chemical structure of the new xanthone (1) was elucidated by extensive 1D, 2D NMR, and ESI HR mass measurements, and by comparison with literature data. The constitutions and absolute configurations of 1 and epiisoshamixanthone (2) were additionally confirmed by X-ray crystallography. Compounds 1,2 were evaluated for their potential anticancer activity using the human cervix carcinoma cell line (KB-3-1). The antimicrobial activities of the fungal extract and compounds 1,2 were studied using a panel of pathogenic microorganisms as well.