共查询到20条相似文献,搜索用时 46 毫秒
1.
M. Hampl J. Leitner K. Růžička M. Straka P. Svoboda 《Journal of Thermal Analysis and Calorimetry》2007,87(2):553-556
The heat capacity and the heat content of
bismuth niobate BiNb5O14 were
measured by the relaxation time method, DSC and drop method, respectively.
The temperature dependence of heat capacity in the form C
pm=455.84+0.06016T–7.7342·106/T
2 (J K–1
mol–1) was derived by the least squares method
from the experimental data. Furthermore, the standard molar entropy at 298.15
K S
m=397.17 J K–1
mol–1 was derived from the low temperature
heat capacity measurement. 相似文献
2.
I. M. Chung H. Y. Park S. C. Chun J. J. Kim A. Ahmad 《Chemistry of Natural Compounds》2007,43(4):417-421
Three new compounds, 4-hydroxymethylene-7-(9,9,13-trimethylcyclohexyl)-heptanyl-3′,7′,7′-trimethylcyclohexa-2′,4′-dien-1′-oate
(1), 1-(n-hexadec-7-enoxy)-6-(n-octadecanoxy)-β-D-glucopyranoside (2), and (Z)-12-hydroxy-9-octadecenoic acid-12-β-D-glucopyranoside (3), along with the known compound hexacosanoic acid (4), were isolated and identified from the rice hulls of Oryza sativa. Their structures were elucidated by 1D and 2D NMR spectroscopic techniques (1H-1H COSY, 1H-13C HETCOR, DEPT) aided by EIMS, FABMS, HRFABMS, and IR spectra.
Published in Khimiya Prirodnykh Soedinenii, No. 4, pp. 344–347, July–August, 2007. 相似文献
3.
I. M. Chung Mohd Ali A. Ahmad C. Y. Yu K. H. Ma J. G. Gwag Y. J. Park 《Chemistry of Natural Compounds》2005,41(6):650-653
One new compound 3,7,11,15,19-pentamethyl-9α,10α,11α,17α,18α-pentahydroxy-n-tetracosan-1-oxy-p-hydroxycaffeoate (oryzaterpenyl
caffeoate) (1), together with three known fatty acids linoleic acid, stearic acid and myristic acid were isolated and identified from the
rice grain of Oryza sativa. The structure of the new compound was elucidated by 1D and 2D NMR spectroscopic techniques (1H-1HCOSY, 1H-13C HETCOR) aided by EI-MS, and IR spectra.
__________
Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 535–537, November–December, 2005. 相似文献
4.
V. Kharton A. Kovalevsky E. Tsipis A. Viskup E. Naumovich J. Jurado J. Frade 《Journal of Solid State Electrochemistry》2002,7(1):30-36
Deficiency in the A sublattice of perovskite-type Sr1–
y
Fe0.8Ti0.2O3–δ (y=0–0.06) leads to suppression of oxygen-vacancy ordering and to increasing oxygen ionic conductivity, unit cell volume, thermal
expansion, and stability in CO2-containing atmospheres. The total electrical conductivity, predominantly p-type electronic in air, decreases with increasing
A-site deficiency at 300–700 K and is essentially independent of the cation vacancy concentration at higher temperatures.
Oxygen ion transference numbers for Sr1–
y
Fe0.8Ti0.2O3–δ in air, estimated from the faradaic efficiency and oxygen permeation data, vary in the range from 0.002 to 0.015 at 1073–1223 K,
increasing with temperature. The maximum ionic conductivity was observed for Sr0.97Fe0.8Ti0.2O3–δ ceramics. In the system Sr0.97Fe1–
x
Ti
x
O3–δ (x=0.1–0.6), thermal expansion and electron-hole conductivity both decrease with x. Moderate additions of titanium (up to 20%) in Sr0.97(Fe,Ti)O3–δ result in higher ionic conductivity and lower activation energy for ionic transport, owing to disordering in the oxygen sublattice;
further doping decreases the ionic conduction. It was shown that time degradation of the oxygen permeability, characteristic
of Sr(Fe,Ti)O3–δ membranes and resulting from partial ordering processes, can be reduced by cycling of the oxygen pressure at the membrane
permeate side. Thermal expansion coefficients of Sr1–
y
Ti1–
x
Fe
x
O3–δ (x=0.10–0.60, y=0–0.06) in air are in the range (11.7–16.5)×10–6 K–1 at 350–750 K and (16.6–31.1)×10–6 K–1 at 750–1050 K.
Electronic Publication 相似文献
5.
T. V. Kharlamova 《Chemistry of Natural Compounds》2007,43(4):391-394
The alkylation of 1,6,8-trihydroxy-3-methylanthraquinone (frangula-emodin) by α-bromoalkylmethylketones was investigated. Hydroxyls in the 1-and 8-positions of the β-derivatives were O-acylated. The compositions and structures of the prepared compounds were confirmed by elemental analysis and UV, IR, PMR,
and 13C NMR spectroscopy.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 324–326, July–August, 2007. 相似文献
6.
The present work deals with the composite system (CuI)
x
–(Ag2O–TeO2)100–
x
, where x=30, 35, 40, 45, 50, 55, 60, 65, 70 and 75 mol%, respectively, synthesized by a solid-state reaction route. Powder specimens
were analysed using differential scanning calorimetry, X-ray diffraction and Fourier transform infrared techniques. These
studies have revealed the formation of Cu3TeO6, AgI and/or other phases. The ambient temperature electrical conductivities obtained for the samples using a complex impedance
method were found to lie in the range 10–6–10–4 Scm–1, with low activation energies, thus indicating their superionic nature. The typical composition 35CuI–32.5Ag2O–32.5TeO2 was identified as the best conducting one, having an electrical conductivity of 6×10–4 Scm–1 at 296 K and an activation energy of 0.23 eV. Ion transport number measurements carried out using Wagner's polarization technique
as well as by an electromotive force method suggested that silver ions were responsible for the observed transport features
of the composite system.
Electronic Publication 相似文献
7.
D. Desideri M. A. Meli C. Roselli L. Feduzi 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(2):591-600
In various samples of Mytilus galloprovincialis, 210Po was determined by alpha-spectrometry while Mn, Fe, Ni, Cu, Zn, Cd, Sn, Hg and Pb by energy dispersive, polarised X-ray
fluorescence spectrometry (EDPXRF). The mussels of different sizes were taken from 7 sites in the central Adriatic Sea along
the Marche coastal region during the four seasons of the year. 210Po activity concentration ranged between 57 and 343 Bq·kg−1 dry weight. The concentration ranges of heavy metals (μg·g−1 dry weight) were as follows: Mn: 72.9–83.1; Fe: 45.1–754; Ni: 1.3–7.6; Cu: 17.9–156; Zn: 60.9–189; Cd: 0.6–1.0; Sn: 0.6–3.9;
Hg always <0.5; Pb: 2.0–9.0. The data obtained depend upon the site and the period of the sampling and they are also compared
with those obtained by other authors for the same organism in the Mediterranean and other Italian seas. 相似文献
8.
L. Lugo M. J. P. Comuñas E. R. López J. Fernández 《Journal of Thermal Analysis and Calorimetry》2007,87(1):179-187
New densities are reported over the whole composition range for 1-iodoperfluorohexane+n-octane system at temperatures from 288.15 to 308.15
K at atmospheric pressure. These data have been used to compute the excess
molar volumes, V
m
E.
Large positive V
m
E
values have been obtained over the entire range of composition, which increases
when the temperature rises. The experimental data were used to calculate the
isobaric thermal expansivity, and the quantities (∂V
m
E/∂T)p and (∂H
m
E/∂p)T. Furthermore,
the results have been used to investigate the volumetric prediction ability
of the equations of state Soave–Redlich–Kwong, Peng–Robinson,
Patel–Teja and Soave–Redlich–Kwong with volume translation. 相似文献
9.
S. F. Santos M. C. de Andrade J. A. Sampaio A. B. da Luz T. Ogasawara 《Journal of Thermal Analysis and Calorimetry》2007,87(3):743-746
TiO2–CeO2 oxides
for application as ceramic pigments were synthesized by the Pechini method.
In the present work the polymeric network of the pigment precursor was studied
using thermal analysis. Results obtained using TG and DTA showed the occurrence
of three main mass loss stages and profiles associated to the decomposition
of the organic matter and crystallization. The kinetics of the degradation
was evaluated by means of TG applying different heating rates. The activation
energies (E
a) and
reaction order (n) for each stage were
determined using Horowitz–Metzger, Coats–Redfern, Kissinger and
Broido methods. Values of E
a
varying between 257–267 kJ mol–1 and n=0–1 were found. According to the kinetic
analysis the decomposition reactions were diffusion controlled. 相似文献
10.
Galactomannans with galactose:mannose ratios 1:1.48 and 1:1.33, [α]D +67.9 and +76.4°, [η] 870.3 and 1337.1 mL/g, and molecular weights 999 and 1549 kDa, respectively, were isolated in 0.59
and 4.65% yields (of seed mass) from seeds of Astragalus alpinus and A. tibetanus (Fabaceae). Physicochemical methods (CrO3 oxidation; methylation–GC/MS; IR, NMR, and 13C spectroscopy) found that the main polysaccharide chain consisted of 1,4-β-D-mannopyranose units substituted 67.5% (A. alpinus) and 75.2% (A. tibetanus) at the C-6 position by single α -D-galactopyranose units. The contents of mannobiose blocks Man–Man, (Gal)Man–Man/Man–Man(Gal), and (Gal)Man–Man(Gal) variously
substituted with galactose were according to 13C NMR spectroscopy 15.9, 55.5, and 28.6% in A. alpinus galactomannan and 9.9, 42.3, and 47.8% in A. tibetanus galactomannan. 相似文献
11.
M. A. V. Ribeiro da Silva Cláudia P. F. Santos 《Journal of Thermal Analysis and Calorimetry》2007,87(1):21-25
The standard (p
0=0.1
MPa) molar enthalpy of formation, Δf
H
0
m, for crystalline N-phenylphthalimide
was derived from its standard molar enthalpy of combustion, in oxygen, at
the temperature 298.15 K, measured by static bomb-combustion calorimetry,
as –206.0±3.4 kJ mol–1. The
standard molar enthalpy of sublimation, Δg
cr
H
0
m
, at T=298.15 K, was derived, from high
temperature Calvet microcalorimetry, as 121.3±1.0 kJ mol–1.
The derived standard molar enthalpy of formation, in the gaseous state,
is analysed in terms of enthalpic increments and interpreted in terms of molecular
structure. 相似文献
12.
Evaluation of <Superscript>137</Superscript>Cs soil-to-plant transfer: Natural and model experiments
D. Butkus B. Lukšienė M. Konstantinova 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(2):411-416
Soil and meadow grass were sampled in the whole territory of Lithuania in 1992–2000. For the laboratory experiment, spring
wheat Triticum aestivum L. “Nandu” was used because its root system type is similar to that of perennial meadow grass. The 137Cs soil-to-plant transfer factor of spring wheat was determined and the results were compared with the predicted values using
a compartment model of soil-to-plant transfer and with the results of the field experiment. The results of comparing the measured
and calculated transfer factor using the model show rather good coincidence, however, the calculated values were overestimated.
The reason for overestimation can be that the uptake rate is not influenced only by the soil-to-plant transfer. The results
of the model experiment (from 0.005 m2·kg−1 to 0.053 m2·kg−1) are close to those of the field measurements for grass (from 0.013 m2·kg−1 in 1992–1995 to 0.10 m2·kg−1 in 1999–2000). 相似文献
13.
Wei Zhao Aisheng Xiong Xiaoyan Fu Feng Gao Yongsheng Tian Rihe Peng 《Applied biochemistry and biotechnology》2010,162(8):2157-2165
To obtain a high level expression of phytase with favorable characteristics, a codon-optimized phytase gene from Citrobacter freundii was synthesized and transferred into Pichia pastoris. Small-scale expression experiments and activity assays were used to screen positive colonies. After purified by Ni2+–NTA agarose affinity column, the characterizations of the recombinant phytase were determined. The recombinant phytase (r-phyC)
had two distinct pH optima at 2.5 and 4.5 and an optimal temperature at 50 °C. It retained more than 80% activity after being
incubated under various buffer (pH 1.5–8.0) at 37 °C for 1 h. The specific activity, Km, and Vmax values of r-phyC for sodium phytate were 2,072 ± 18 U mg−1, 0.52 ± 0.04 mM, and 2,380 ± 84 U mg−1 min−1, respectively. The enzyme activity was significantly improved by 1 mM of K+, Ca2+, and Mg2+. These characteristics contribute to its potential application in feed industry. 相似文献
14.
P. V. Verdes M. M. Mato J. L. Legido E. Jiménez M. I. Paz Andrade 《Journal of Thermal Analysis and Calorimetry》2007,88(2):583-586
Excess molar enthalpies, H
E,
for the binary mixtures {p-xylene+(1–x) octane}, {x
p-xylene+(1–x)
diethyl carbonate}, {x octane+(1–x) diethyl carbonate} and the corresponding ternary
system {x
1
p-xylene+x
2
octane+(1–x
1–x
2) diethyl carbonate} have
been measured by using a Calvet microcalorimeter at 298.15 K under atmospheric
pressure. The experimental H
E
values are all positive for the binary and ternary mixtures over the entire
composition range. 相似文献
15.
Glucofructans from Saussurea lappa (Asteraceae) roots were studied. It was found that free fructose and oligomeric glucofructans (saccharose, 1-kestose, nystose,
1F-β-fructofuranosylnystose, and 1F-β-fructofuranosyl-1F-β-fructofuranosylnystose) were present. The dominant polymer Sl-GF (MW 51.4 kDa), which was a linear inulin-type glucofructan
consisting of β-(2 → 1)-bonded fructofuranose units, was isolated and characterized. The total content of glucofructans in Saussurea lappa roots was 476.97–578.27 mg/g. 相似文献
16.
The new cycloartane glycoside cyclochivinoside C, 24S-cycloartan-3β,6α,16β,24,25-pentaol 3,16-di-O-β-D-glucopyranoside, was isolated from the aerial part of Astragalus chivensis. The structures of the isolated compounds were established by chemical transformations and PMR and 13C NMR spectra.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 460–462, September–October, 2007. 相似文献
17.
P. V. Verdes M. M. Mato J. L. Legido E. Jiménez M. I. Paz Andrade 《Journal of Thermal Analysis and Calorimetry》2007,88(2):613-616
Excess molar enthalpies
of the ternary system {x
1
p-xylene+x
2decane+(1–x
1–x
2)diethyl
carbonate} and the involved binary mixtures {p-xylene+(1–x)decane}, {xp-xylene+(1–x)diethyl carbonate} and {xdecane+(1–x)diethyl carbonate} have been determined at the
temperature of 298.15 K and atmospheric pressure, over the whole composition
range, using a Calvet microcalorimeter. The experimental excess molar enthalpies H
m
E
are positive for all the binary systems studied over the whole composition
range. Excess molar enthalpy for the ternary system is positive as well, showing
maximum values at x
1=0, x
2=0.4920, x
3=0.5080, H
m,123
E=1524
J mol–1. 相似文献
18.
Jian Zhang Zhi-Qi Yin Peng Cao You-Bin Li Jin-Ao Duan 《Chemistry of Natural Compounds》2008,44(6):701-703
A new flavonol derivative 3, 8-dihydroxy-10-methoxy-5-H-isochromeno[4, 3-b]chromen-7-one (1) together with four known compounds, glutinone (2), luteolin (3), acacetin 7-O-α-L-rhamnopyranosyl- (1→6)-β-D-glucopyranoside (4), and rutin (5) were isolated from the dried roots of Fagopyrum dibotrys. Their structures were determined by UV, IR, MS, 1H, and 13C NMR spectroscopic analysis, including 2D NMR.
Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 567–568, November–December, 2008. 相似文献
19.
Lang SM Claes P Neukermans S Janssens E 《Journal of the American Society for Mass Spectrometry》2011,22(9):1508-1514
Structural information on free transition metal doped aluminum clusters, Al
n
TM
+ (TM = Ti, V, Cr), was obtained by studying their ability for argon physisorption. Systematic size (n = 5 – 35) and temperature (T = 145 – 300 K) dependent investigations reveal that bare Al
n
+ clusters are inert toward argon, while Al
n
TM
+ clusters attach one argon atom up to a critical cluster size. This size is interpreted as the geometrical transition from
surface-located dopant atoms to endohedrally doped aluminum clusters with the transition metal atom residing in an aluminum
cage. The critical size, n
crit
, is found to be surprisingly large, namely n
crit = 16 and n
crit = 19 – 21 for TM = V, Cr, and TM = Ti, respectively. Experimental cluster–argon bond dissociation energies have been derived as function of cluster size from
equilibrium mass spectra and are in the 0.1–0.3 eV range. 相似文献
20.
The enzymatic synthesis of three isotopomers of l-DOPA labeled with deuterium and tritium at α carbon atom was elaborated. These compounds were converted into [(1S)-2H]–, [(1S)-
3H]–, and doubly labeled [(1S)-2H/3H]-dopamines using enzyme tyrosine decarboxylase. Doubly labeled (1R) isotopologue, i.e., [(1R)-2H/3H]-dopamine, was afforded by enzymatic decarboxylation of authentic l-DOPA carried out in deuteriated and tritiated incubation medium. 相似文献