Improving the combination of cellulose and lignin using xylan as a compatibilizer

Cellulose - Both cellulose and lignin are rich natural resources; however, recombining them to...     

Hydrogen bonds and protonation of carbonyl-containing polynuclear rhodium complexes

According to IR spectroscopy data, the interaction of bi-, tri-, and tetranuclear cyclopentadienylcarbonyl rhodium complexes with rather weak protic acids (phenols, fluoroalcohols) in low-polarity media results in the formation of hydrogen bonds of the OH...O=C type with bridged carbonyl groups. According to¹H NMR data, protonation of these complexes with strong acids (CF₃COOH and HBF₄) occurs at the the Rh-Rh bond to give the symmetrical bridge.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 386–388, February, 1995.This work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 93-03-0461).     

Quantum-chemical study on the tautomerism of primary nitramines: the mechanism of N-nitro-anion protonation excludingaci-form formation

The values of the energy barriers to intramolecular 1,3-H shift reactions, in whichaci-forms of N- and C-nitro-compounds: 1 and are capable of transforming into 2 and , respectively, have been calculated by the semi-empirical AM1 method. The barrier heights (39 and 59.4 kcal/mol) reflect the kinetic stability of both tautomeric forms of the N- and C-nitro-compounds.Ab initio calculations in the 3–21G basis set of the structure and energies of stationary points on the potential energy surface of the system MeN=NO₂ H₃O demonstrated that there exists the principal possibility of the formation of only tautomer 2 (which is more stable than1).Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No 1, pp. 100–104, January, 1993.     

Investigation on standard molar enthalpy of combustion,specific heat capacity and thermal behavior of methionine

Journal of Thermal Analysis and Calorimetry - The standard molar enthalpy of combustion of methionine was determined to be ? 6661.03 kJ mol?1 by XRY-1C...     

Thermal behavior of the heart of SHR and wistar rats

Summary Hypertension is a major and growing public health problem. It is responsible for the mortality of millions of people around world, and is increasing each year. Nevertheless, the understanding of the relationship between the composition of the heart's cells, hypertension and health diseases is still very incomplete. The present study focuses on the evaluation of the attributes of some hearts of Spontaneous Hypertension Rats (SHR), comparing with SHR which received additional amounts of polysaccharide (SHR+P) and with wistar rats (normal blood pressure) by Thermal Analysis. Some differences could be seen between groups, as the residue content after 800°C was different for rats from different groups, and of wistar rats hearts samples showed 5.3±0.3% of residues vs. 8.3±1.5% of the SHR. DSC profiles for wistar rats showed one intense endothermic event at 160°C, with enthalpy transition of 450 J g^-1 and more three small events. Thermal analyses curves also showed some differences between freezing and no freezing samples, probably associated to the denaturation of proteins and degradation of organic materials.     

Coordination compounds of heterocyclic bases: synthesis,characterization, computational and biological studies

Research on Chemical Intermediates - In this study, the geometry, spectroscopic characteristics and coordination patterns of three biologically active ligands and their...     

Ab Initio Chemical Kinetics for the Thermal Decomposition of SiH4 + Ion and Related Reverse Ion–Molecule Reactions of Interest to PECVD of a-Si:H Films

Plasma Chemistry and Plasma Processing - The thermal unimolecular decomposition of SiH4 + ion and its related reverse reactions, SiH3 + + H and SiH2 + + H2, have...     

Effects of La-doping on structural,electrical and multiferroic properties of Bi6Fe2Ti3O18 thin films

Journal of Sol-Gel Science and Technology - Bi6Fe2Ti3O18 (BFTO) and La-doped Bi6?xLaxFe2Ti3O18 (BLFT) (x = 0.03; BLFT3, x = 0.06; BLFT6 and 0.09; BLFT9)...     

IMMUNIOMODULATIONG EFFECTS OF THE FUCOIDAN—GALACTOSAN SULFATE（F12） ON MACROPHAGES IN MICE

The immunomodulating effects of F12 on mouse peritoneal macroplhages was intended to be studied with different doses of 20,40,80,and 120mg/Kg.F12 increased peroxidase activity in dexc dependent mammer from 0.02±0.001,to 0.175±0.038,0.211±0.041,0.137±0.045and 0.078±0.036,respectively,increased cytotoxicity from 127.33±22.96 to 162.74±19.53,237.30±25.15,178.62±36.22and 158.66±42.75dpm,respectively,promoted phagocytic activity from 0.03±0.01 to 0.21±0.016,0.43±0.041,0.40±0.032 and 0.30±0.160^b,Furthermore,F12 in a concentration of 15,30,60,120ug/ml enhanced IL-1 production from 0.15±0.02 to 0.20±0.005^b 0.21±0.02,0.22±0.005,0.24±0.002and 0.22±0.02,respectively,Thus F12 can be considered as an effective stimulator of macrophages.     

Effect of temperature,humidity and pressure on electric properties of the cells based on PTB7-Th,PC61BM and graphene composite

Journal of Thermal Analysis and Calorimetry - In this paper, fabrication and characterization of Cu/PTB7-Th (35 mass%)/PC $$_{61}$$ BM (35 mass%)/graphene (30 mass%)/Ag...     

Influence of measurement parameters of laser flash analysis on the observed thermal diffusivity and the choice of parameters to get repeatable measurements

Journal of Thermal Analysis and Calorimetry - This work is a continuation of our researches on the study of thermodynamic properties of organic compound mixtures and made...     

Controlled nanosheet morphology of titanium carbide Ti3C2Tx MXene via drying methods and its electrochemical analysis

Journal of Solid State Electrochemistry - The different temperature drying processes were carried out at −60 °C, 15 °C, and 60 °C to control the...     

Crystal structure,chemical stability and electrical properties of Sr2MnNbO6 − δ, Sr2Cr0.5Mn0.5NbO6 − δ and Sr2CuNbO6 − δ perovskites

Journal of Solid State Electrochemistry - The 3d-cation-substituted perovskites Sr2MnNbO6 − δ, Sr2Cr0.5Mn0.5NbO6 − δ and...     

Thermal characterization of natural and modified cyclodextrins using TG-MS combined technique

Summary Thermoanalytical techniques (TG, DSC) are frequently used in the investigation of the thermal properties of cyclodextrins and their inclusion complexes. However, the above techniques do not provide information on the chemical composition of the evolved fragments upon the thermal decomposition. In this study &agr;-, &bgr;- and &ggr;-cyclodextrins and 4 methylated and 3 ethylated &bgr;-CD derivatives were investigated with a TG-MS combined thermoanalytical technique in order to get information about their fragmentation behaviour. By comparison of the TG/DTA curves, a different thermal behaviour was found for each of the native and the chemically modified cyclodextrins. Except for the water loss profiles and the solid-solid phase transformations, the thermal behaviour of the (investigated) native CDs do not show remarkable differences. However, the chemical modification of the native &bgr;-CD resulting in a new compound may change the strength of interactions between host and guest causing differences in the thermal stabilities of the derivatives. The mass spectrometry results supported the observed thermal differences and showed significant alterations in the fragmentation of ethylated and methylated compounds. The investigated natural CDs possess a very similar fragmentation profile, due to the common &agr;-D-glucopyranose building units. In the case of modified CDs characteristic signals of the substituents are present.     

Excess heat capacities and excess molar enthalpies of the mixtures containing tetrahydropyran,piperidine and cyclic alkanones

Journal of Thermal Analysis and Calorimetry - In the present study, molar heat capacities, $$\left( {C_{\text{P}}^{{}} } \right)_{123}$$ , at T/K = 293.15–308.15 K...     

Phase behaviour of polymer-grafted DPPC membranes for drug delivery systems design

Summary DPPC dispersions containing DPPE with attached PEG of molecular masses 350, 2000 and 5000 were investigated by DSC in order to determine their phase behaviour and potential use as drug delivery systems. In comparison with previously obtained ESR data, DSC provided a definition of the lipid composition and temperature at which the vesicles are in a liquid crystalline phase. For DPPC DPPE-PEG 350 the composition range is at molar fractions 0<_&khgr;PEG350<0.5.For DPPC DPPE-PEG 2000 the range of applicability is 0<_{&khgr;PEG2000}<0.07 and for DPPC/DPPE-PEG 5000 system it is 0<_{&khgr;PEG5000}<0.05.     

1,1-Diethynylsilacycloalkanes and Propellanes Based Thereon

Previously unknown 1,1-diethylnylsilacycloalkanes (CH₂)4nSi(C& = CH)₂ (n = 3, 4) were prepared by the reaction of HC& = CMgBr with 1,1-dichlorosilacycloalkanes (CH₂)4nSiCl₂ (n = 3, 4). The reaction of (CH₂)₄Si(C& = CMgBr)₂ with (CH2)4SiCl2 in THF under conditions of high dilution gives cyclo(tetramethylene)- silethynes [(CH2)4SiC& = C]4 with an admixture of cyclodi(tetramethylene)silethyne [(CH2)4SiC& = C]2. The re- action of Me2Si(C& = CSiMe2C& = CMgBr)2 with (CH2)4SiCl2 was used to prepare 1,1,4,4,7,7-hexamethyl-10,10- tetramethylene-1,4,4,10-tetrasilacyclododeca-2,5,8,11-tetrayne.     

Sol hydrolysis and condensation reaction time influence the sensitivity of class II xerogel-based sensing materials

Simplicity of preparation, a wide variety of precursors, and numerous processing variables (e.g., pH, time, temperature) are often described as attractive aspects of sol–gel derived materials. In the current work we create a series of O₂-responsive xerogel-based sensor films by simultaneously co-hydrolyzing and co-condensing tetramethylorthosilane and n-octyltriethoxysilane. Tris(4,7′-diphenyl-1,10′-phenanthroline) ruthenium(II) ([Ru(dpp)₃]²⁺) is used as the O₂-responsive luminophore. We determine the effects of [Ru(dpp)₃]²⁺ addition time to the sol and the sol hydrolysis and condensation reaction time (H&C) on the xerogel film O₂ sensitivity. [Ru(dpp)₃]²⁺ addition time has no significant effect on the O₂ sensitivity; H&C effects the O₂ sensitivity. The highest O₂ sensitivity is seen at early H&C (0.5 h). This behavior arises because TMOS and C8-TMOS react at different rates to form sols. At early H&C the co-hydrolysis and co-condensation reactions are not complete and the so formed sols are rich in C8-TMOS in comparison to their composition at longer H&C. At longer H&C, the TMOS and C8-TMOS co-hydrolyze and co-condense more completely. SEM images show that xerogel films formed at early H&C is more porous in comparison to those formed a longer H&C. The results of these experiments: (a) highlight the importance of documenting how sols are processed and xerogels formed and (b) demonstrate the use of a single sol formulation and H&C to create suites of sensor materials with different responses.     

DSC study of glycerol-extracted muscle fibers in intermediate states of ATP hydrolysis

Summary The heat capacity of contractile proteins actin and myosin was studied in psoas muscle of rabbit in strongly and weakly binding state of myosin to actin as a function of temperature by DSC. Deconvolution of the unfolding scans makes possible to characterize the structural domains of the macromolecules. We tried to approach the unfolding process in different intermediate state of ATP hydrolysis. The thermal transitions were calorimetrically irreversible, therefore the two-state irreversible model that describes fairly well the denaturation of different proteins was used for evaluation of the denaturation processes in muscle fibers in strongly (rigor, ADP) and weakly binding states (ATP·V_i, ADP·AlF₄) of myosin to actin. Deconvolution resulted in four transitions, the first three transition temperatures were almost independent of the intermediate states of muscle, the last transition temperature was shifted to higher temperature, when the buffer solution was manipulated. The mean values in strongly binding states were T_m1=52.9±0.7°C, T_m2=57.9±0.7°C, T_m3=63.7±1.0°C and T_m4=67.8±0.7°C, but the last transition increased to higher temperature depending on the P_i analogue.