共查询到20条相似文献,搜索用时 31 毫秒
1.
ABSTRACTWe explored a novel doubly labelled water (DLW) method based on breath water (BW-DLW) in mice to determine whole body CO 2 production and energy expenditure noninvasively. The BW-DLW method was compared to the DLW based on blood plasma. Mice ( n?=?11, 43.5?±?4.6?g body mass (BM)) were administered orally a single bolus of doubly labelled water (1.2?g H 218O kg BM ?1 and 0.4?g 2H 2O kg BM ?1, 99 atom% (AP) 18O or 2H). To sample breath water, the mice were placed into a respiration vessel. The exhaled water vapour was condensed in a cold-trap. The isotope enrichments of breath water were compared with plasma samples. The 2H/ 1H and 18O/ 16O isotope ratios were measured by means of isotope ratio mass spectrometry. The CO 2 production (RCO 2) was calculated from the 2H and 18O enrichments in breath water and plasma over 5 days. The isotope enrichments of breath water vs. plasma were correlated (R 2?=?0.89 for 2H and 0.95 for 18O) linearly. The RCO 2 determined based on breath water and plasma was not different (113.2?±?12.7 vs. 111.4?±?11.0?mmol?d –1), respectively. In conclusion, the novel BW-DLW method is appropriate to obtain reliable estimates of RCO 2 avoiding blood sampling. 相似文献
2.
CCSD(T) and MP2 results using the aug-cc-pV5Z basis set are reported for chain, cyclic and other structures of the clusters (H 2) n, n?=?2-8, (CO 2) n, n?=?2-6 and (HF) n, n?=?2-8. In chain-like structures of (H 2) n and (CO 2) n, with the bonding type of the dimer maintained, the dissociation energy D e of the dimer doubles for the trimer, triples for the tetramer, and so on. Due to these systems being dominated by short-range forces, interactions are essentially restricted to neighbouring monomers. For other types of (H 2) n and (CO 2) n structures, the multipliers relative to the dimerisation energy can be much higher. Dissociation energies for the hexamers in S 6 symmetry of both H 2 (379?cm ?1) and CO 2 (4925?cm ?1) are over ten times the respective dimerisation energies. For the chain-like trimer of HF, however, D e is in excess of double the dimer value. Mainly due to longer-range dipolar forces, the interactions reach beyond the neighbouring monomers. The interaction energy between HF monomers in chains follows an approximate R ?2 (R being the F–F distance) relationship, The calculated dissociation energies of the HF octamer are 15,985?cm ?1 (factor of 10.4) for the chain, and 21,003?cm ?1 (factor of 13.7) for the C 6h cyclic structure. 相似文献
3.
ESR studies were conducted on Cu 2+-doped bis-(5,5′-diethylbarbiturato)bis picoline Zn(II). Two Cu 2+ lattice sites, Cu 2+(I) and Cu 2+(II), were identified. These sites exhibit two sets of four hyperfine lines in all directions. The g factor and hyperfine splitting were calculated from ESR absorption spectra: gx ?=?2.0201?±?0.002, gy ?=?2.0900?±?0.002, gz ?=?2.1634?±?0.002, Ax ?=?(30?±?2)?×?10 ?4?cm ?1, Ay ?=?(40?±?2)?×?10 ?4?cm ?1 and Az ?=?(154?±?2)?×?10 ?4?cm ?1. It was found that Cu 2+ enters the lattice substitutionally. The ground-state wavefunction of the Cu 2+ ion in this lattice was determined from the spin Hamiltonian constants obtained from the ESR studies. With the help of an optical absorption study, the nature of the bonding in the complex is also discussed. 相似文献
4.
A high pressure X-ray diffraction study of RhOOH was carried out up to 17.44?GPa to investigate the compression behavior of an oxyhydroxide with an InOOH-related structure. A fit to the third-order Birch–Murnaghan equation of state gave K0?=?208?±?6?GPa, and K′?=?9.4?±?1.3. The temperature derivative of the bulk modulus was found to be ? K/? T?=??0.06?±?0.02?GPa K ?1. The refined parameters for volume thermal expansion were α0?=?2.7?±?0.3?×?10 ?5 K ?1; α1?=?1.7?±?1.1?×?10 ?8 K ?2 in the polynomial form ( α( T)?=? α0?+? α1( T?300)). Our results show that RhOOH is very incompressible, and has a higher bulk modulus than other InOOH-structured oxyhydroxides ( e.g. δ-AlOOH, ε-FeOOH, and γ-MnOOH). 相似文献
5.
We report on the ac dielectric permittivity (ε) and the electric conductivity (σ ω), as function of the temperature 300?K? T400?K and frequency 0.5–100?kHz for polycrystalline samples of hydrogen-bonded ferroelectric ammonium iodate, NH 4IO 3. The main feature of our measured parameters is that, the compound undergoes a ferroelectric phase transition of an improper character, at (368?±?1)K from a high temperature paraelectric phase I ( Pm2 1 b) to a low temperature ferroelectric phase II (P c21 n). The electric conduction seems to be protonic. The frequency dependent conductivity has a linear response following the universal power law (σ ( ω )?=? A( T)ω s (T)). The temperature dependence of the frequency exponent s suggests the existence of two types of conduction mechanisms. 相似文献
6.
Carbon isotopes of breath CO 2 vary depending on diet and fuel substrate used. This study examined if exercise-induced δ13C-CO 2 changes in substrate utilization were distinguishable from baseline δ13C-CO 2 variations in a population with uncontrolled diet, and compared hair isotope values and food logs to develop an isotope model of diet. Study participants included nine women with diverse Body Mass Index (BMI), age, ancestry, exercise history, and diet. Breath samples were collected prior to and up to 12?h after a 5- or 10?K walk/run. Indirect calorimetry was measured with a smartphone-enabled mobile colorimetric device, and a field-deployable isotope analyzer measured breath δ13C-CO 2 values. Diet was assessed by food logs and δ13C, δ15N of hair samples. Post-exercise δ13C-CO 2 values increased by 0.54?±?1.09‰ (1 sd, n?=?9), implying enhanced carbohydrate burning, while early morning δ13C-CO 2 values were lower than daily averages ( p?=?0.0043), indicating lipid burning during overnight fasting. Although diurnal δ13C-CO 2 variation (1.90?±?0.77‰) and participant baseline range (3.06‰) exceeded exercise-induced variation, temporal patterns distinguished exercise from dietary isotope effects. Hair δ13C and δ15N values were consistent with a new dietary isotope model. Notwithstanding the small number of participants, this study introduces a novel combination of techniques to directly monitor energy balance in free-living individuals. 相似文献
7.
It was suggested that Na–Mg carbonates might play a substantial role in mantle metasomatic processes through lowering melting temperatures of mantle peridotites. Taking into account that natrite, Na 2CO 3, eitelite, Na 2Mg(CO 3) 2, and magnesite, MgCO 3, have been recently reported from xenoliths of shallow mantle (110–115?km) origin, we performed experiments on phase relations in the system Na 2CO 3–MgCO 3 at 3?GPa and 800–1250°C. We found that the subsolidus assemblages comprise the stability fields of Na-carbonate?+?eitelite and eitelite?+?magnesite with the transition boundary at 50?mol% Na 2CO 3. The Na-carbonate–eitelite eutectic was established at 900°C and 69?mol% Na 2CO 3. Eitelite melts incongruently to magnesite and a liquid containing about 55?mol% Na 2CO 3 at 925?±?25 °C. At 1050 °C, the liquid, coexisting with Na-carbonate, contains 86–88?mol% Na 2CO 3. Melting point of Na 2CO 3 was established at 1175?±?25 °C. The Na 2CO 3 content in the liquid coexisting with magnesite decreases to 31?mol% as temperature increases to 1250°C. According to our data, the Na- and Mg-rich carbonate melt, which is more alkaline than eitelite, can be stable at the P–T conditions of the shallow lithospheric mantle with thermal gradient of 45?mW/m 2 corresponding to temperature of 900 °C at 3?GPa. 相似文献
8.
In an effort to discover potential cytotoxic agents, a series of novel (Z)-5-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)-3-((1-substituted phenyl-1H-1,2,3-triazol-4-yl)methyl)thiazolidine-2,4-dione derivatives (8a–n) were designed and synthesized in various steps with acceptable reaction procedures with quantitative yields and characterized by 1H NMR, 13C NMR, IR, HRMS and ESI–MS spectra. These newly synthesized novel derivatives were screened for their in vitro cell viability/cytotoxic studies against human breast cancer cell line (MCF-7) with various concentrations of 0.625 µM, 1.25 µM, 2.5 µM, 5 µM and 10 µM, respectively. The biological interpretation assay outcome was demonstrated in terms of cell viability percentage reduction and IC50 values against standard reference drug cisplatin. Based on these results, most of the derivatives exhibited promising cytotoxic activity. Among them, particularly compounds 8j (R1?=?OMe and R3?=?NO2) and 8e (R3?=?CF3) demonstrate remarkable cytotoxic activity with IC50 values 0.426 µM?±?0.455 and 0.608 µM?±?0.408, which are even better than the standard drug cisplatin 0.636 µM?±?0.458 and compounds 8m (R2?=?OMe and R3?=?OMe) and 8c (R3?=?OMe) exhibited closely equivalent IC50 values to the standard drug with IC50 values 0.95 µM?±?0.32 and 0.976 µM?±?0.313 and rest of the compounds exhibits moderate cytotoxic activity. Moreover, molecular modeling studies and ADME calculations of the novel synthesized derivatives are in adequate consent with the pharmacological screening results. 相似文献
9.
The dielectric and piezoelectric properties of pyrochlore-free lead zirconate titanate-lead zinc niobate ceramics were investigated systematically as a function of Sr doping. The powders of Pb (1? x )Sr x [0.7(Zr 1 / 2Ti 1 / 2)–0.3(Zn 1 / 3Nb 2 / 3)]O 3, where x?=?0–0.06 were prepared using the columbite-(wolframite) precursor method. The ceramic materials were characterized using X-ray diffraction, dielectric spectra, hysteresis and electromechanical measurements. The phase-pure perovskite phase of Sr-doped PZN--PZT ceramics was obtained over a wide compositional range. The results showed that the optimized electrical properties were also achieved at composition x?=?0.0, which were K P?=?0.69, d 33?=?670?pC?N ?1, P r?=?31.9?µC?cm ?2 and ε rmax?=?18600. Maximum dielectric constant values of the systems decreased rapidly with increasing Sr concentration. Moreover, with increasing Sr concentration dielectric constant versus temperature curves become gradually broader. The diffuseness parameter increased significantly with Sr doping. Furthermore, Sr doping has been shown to produce a linear reduction in the transition temperature ( T m)?=?294.1–12.7 x°C with concentration ( x). Sr shifts the transition temperature of this system at a rate of 12.7°C?mol ?1%. 相似文献
10.
Using a theoretical model and mass isotopic balance, biogas (methane and CO 2) released from buried products at their microbial degradation was analysed in the landfill of municipal and non-toxic industrial solid organic waste near Kaluga city, Russia. The landfill contains about 1.34×10 6 tons of waste buried using a ‘sandwich technique’ (successive application of sand–clay and waste layers). The δ 13C values of biogenic methane with respect to CO 2 were?56.8 (±2.5) ‰, whereas the δ 13C of CO 2 peaked at+9.12‰ (+1.4±2.3‰ on average), reflecting a virtual fractionation of carbon isotopes in the course of bacterial CO 2 reduction at the landfill body. After passing through the aerated soil layers, methane was partially oxidised and characterised by δ 13C in the range of?50.6 to?38.2‰, evidencing enrichment in 13C, while the released carbon dioxide had δ 13C of?23.3 to?4.04‰, respectively. On the mass isotopic balance for the δ 13C values, the methane production in the landfill anaerobic zone and the methane emitted through the aerated landfill surface to the atmosphere, the portion of methane oxidised by methanotrophic bacteria was calculated to be from 10 to 40% (averaged about 25%). According to the theoretical estimation and field measurements, the annual rate of methane production in the landfill reached about 2.9(±1.4)×10 9 g C CH 4 yr ?1 or 5.3(±2.6)×10 6 m 3 CH 4 yr ?1. The average rates of methane production in the landfill and methane emission from landfill to the atmosphere are estimated as about 53 (±26) g C CH 4 m ?2 d ?1 (or 4 (±2) mol CH 4 m ?2 d ?1) and 33 (±12) g C CH 4 m ?2 d ?1 (or 2.7 (±1) mol CH 4 m ?2 d ?1), respectively. The calculated part of methane consumed by methanotrophic bacteria in the aerated part of the landfill was 13(±7) g C CH 4 m ?2 d ?1 (or 1.1(±0.6) mol CH 4 m ?2 d ?1) on average. 相似文献
11.
In this study, Pb 1? x (Yb 1/2Nb 1/2) 0.515Ti 0.485O 3? x{(2SrO?+?BaO)/3} [PYNT–SB x] compositions with x?=?0.00–0.05 at the rhombohedral side near the morphotropic phase boundary were investigated. The SB substitution for Pb 2+ in PYNT was found to increase the tetragonality, but greatly reduce the Curie temperature ( Tc ) and broaden the dielectric permittivity maximum. The temperature dependence of the relative permittivity follows a Curie–Weiss law above the deviation temperature ( TD ) at high temperatures for the SB-doped PYNT. The optimized properties with a piezoelectric coefficient of 610?pm?V ?1, maximum dielectric constant ( ε max) of 25,000 (at the Tc ?=?315°C and 1?kHz), and a remnant polarization ( Pr ) of 33?µC?cm ?2 were obtained in PYNT–SB0.04 ceramics. 相似文献
12.
Several long series of up to 40 equally spaced lines are observed in the radio-frequency range 15–90?MHz that are attributed to stimulated emission from the electronically excited condensed matter called Rydberg Matter (RM). These frequencies are more than a factor of 1000 smaller than for most ordinary molecules, and if they did not agree with RM clusters they would indicate extremely large and heavy molecules that are unlikely to exist in the gas phase at room temperature. Theoretical predictions for RM clusters agree within 2% with the observed frequencies. Such clusters are planar, six-fold symmetric oblate rotors. The most prominent series with B?=?0.9292?±?0.0001?MHz (3.067?×?10 ?5?cm ?1) agrees accurately with the theoretically predicted B value for the cluster K 19 in excitation level n?=?4, thus with a K–K bond length of 2.4074?nm. Two other prominent long series agree accurately with K 19 at n?=?5 and 6, with bond lengths of 3.804 and 5.518?nm, respectively. The ratio between the interatomic distance and the electron orbit radius for n?=?4 is found to be 2.8433?±?0.0003, a considerable improvement in precision over the theoretical value of 2.9. 相似文献
13.
ABSTRACTThe high-resolution infrared spectrum of CHD 279Br has been investigated by Fourier transform spectroscopy in the range 700–900?cm ?1 at an unapodized resolution of 0.0035?cm ?1. This spectral region is characterised by the absorptions of the ν 5 (814.5185?cm ?1) and ν 9 (716.9649?cm ?1) fundamental bands, corresponding to H–C–Br deformation and CD 2 rocking modes, respectively. The ν 5 vibration of symmetry species A′ gives rise to an a-/ c-hybrid band with a predominant a-type component, while the ν 9 mode of A′′ symmetry produces a b-type envelope. The spectral analysis resulted in the identification of 5290 ( J′?≤?63 and Ka′?≤?13) and 1657 ( J′?≤?53 and Ka′?≤?12) transitions for ν 5 and ν 9 bands, respectively. The assigned data were fitted using the Watson’s S-reduced Hamiltonian in the I r representation and the v5?=?1 and v9?=?1 state parameters up to the quartic centrifugal distortion terms have been obtained. From spectral simulations the dipole moment ratio |Δμ a/Δμ c| of the ν 5 band has been determined to be 1.4?±?0.1 while the intensity ratio between ν 5 and ν 9 fundamentals has been estimated to have a value of 4.3?±?0.5. 相似文献
14.
Rate constants for the reactions of Cl atoms with CH 3OCHCl 2 and CH 3OCH 2CH 2Cl were determined at (296 ± 2) K and atmospheric pressure using synthetic air as bath gas. Decay rates of these organic compounds were measured relative to the following reference compounds: CH 2ClCH 2Cl and n‐C 5H 12. Using rate constants of 1.33 × 10 ?12 and 2.52 × 10 ?10 cm 3 molecule ?1 sec ?1 for the reaction of Cl atoms with CH 2ClCH 2Cl and n‐C 5H 12, respectively, the following rate coefficients were derived: k(Cl + CH 3OCHCl 2) = (1.05 ± 0.11) × 10 ?12 and k(Cl + CH 3OCH 2CH 2Cl) = (1.14 ± 0.10) × 10 ?10, in units of cm 3 molecule ?1 s ?1. The rate constants obtained were compared with previous literature data and a correlation was found between the rate coefficients of some CH 3OCHR 1R 2 + Cl reactions and ΔElectronegativity of ? CHR 1R 2. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
15.
We report on some electrical properties and solid–solid phase transitions of organic–inorganic hybrid layered halide perovskite and intercalated compound ( n-C 12H 25NH 3) 2ZnCl 4 which is one member of the long-chain compounds of the series ( n-C nH 2n+1NH 3) 2,( n = 8–18). The complex dielectric permittivity ?*(ω, T) and the ac conductivity σ (ω, T) were measured as functions of temperature 100 K < T < 390 K and frequency 5 kHz < f < 100 kHz. Moreover, the differential scanning calorimetery and the differential thermal analysis thermograms were performed. The analysis of our data confirms the existence of a structural phase transition at T ≈ (362?±?2) K, where the compound changes its state from intercalation to non-intercalation with a drastic increase in the c-axis by about 16.4%.The behavior of the frequency-dependent conductivity follows the Jonscher universal power law: σ (ω, T) α?s(?,T). The mechanism of electrical conduction in the low-temperature phase (phase II) can be described as quantum mechanical tunneling model. 相似文献
16.
Ethyl formate undergoes spontaneous hydrolysis through two parallel mechanistic pathways: water catalysis and specific hydrogen-ion catalysis. The proton inventory of the water reaction at 37.0 °C was determined from the overall conversion curves, in H 2O/D 2O mixtures of deuterium atom fraction n, resulting in k 1( n)=(2.1±0.1)×10 ?5 s ?1 (1? n+0.42 n) (1? n+0.83 n) 2, in agreement with the results of six other cases of carboxylic acid derivatives. This result contributes to the validation of the accuracy of the proton inventory technique. 相似文献
17.
Measurements of the line strengths of the (11 10,03 10) II-00 00 band of CO 2 (1932.466 cm ?1) have been made with high resolution. They exhibit a strong Coriolis interaction which enhances the P-branch intensity while reducing that of the R branch. The rotationless dipole moment of the transition and the ξ-constant representing this interaction have been determined as: R(0) = (6.57 ± 0.03) × 10 ?4D, ξ = ?0.0598 ± 0.0002. 相似文献
18.
The structure of Na 6.69Ca 3.355(SO 4) 6Cl 0.77F 0.63, isostructural with fluorapatite, was determined by X-ray powder diffraction methods. The results of Rietveld refinement revealed a space group P6 3/m with lattice parameters of a?=?9.477 (2) Å, c?=?6.865 (5) Å. Final refinement led to R F?=?1.83 % and R B?=?7.64 %. The location of Na + ions in the M (2) sites surrounding the channels was related particularly to the high polarizability of the Ca 2+. The ionic conductivity over a wide range of temperature was investigated according to the complex impedance method. The highest overall conductivity values were found at σ 500 °C?=?1.03?×?10 ?5?S?cm ?1 and E a?=?0.70 eV. 相似文献
19.
The gas‐phase elimination kinetics of selected ethyl esters of 2‐oxo‐carboxylic acid have been studied over the temperature range of 270–415 °C and pressures of 37–114 Torr. The reactions are homogeneous, unimolecular, and follow a first‐order rate law in a seasoned static reaction vessel, with an added free radical suppressor toluene. The observed overall and partial rate coefficients are expressed by the following Arrhenius equations: - Ethyl oxalyl chloride
- log koverall (s?1) = (13.22 ± 0.45) ? (179.4 ± 4.9) kJ mol?1 (2.303 RT)?1
- Ethyl piperidineglyoxylate
- log k(CO2) (s?1) = (12.00 ± 0.30) ? (191.2 ± 3.9) kJ mol?1 (2.303 RT)?1
- log k(CO) (s?1) = (12.60 ± 0.09) ? (210.7 ± 1.2) kJ mol?1 (2.303 RT)?1
- log kt(overall) (s?1) = (12.22 ± 0.26) ? (193.4 ± 3.4) kJ mol?1 (2.303 RT)?1
- Ethyl benzoyl formate
- log k(CO2) (s?1) = (12.89 ± 0.72) ? (203.8 ± 9.0) kJ mol?1 (2.303 RT)?1
- log k(CO) (s?1) = (13.39 ± 0.31) ? (213.3 ± 3.9) kJ mol?1 (2.303 RT)?1
- log kt(overall) (s?1) = (13.24 ± 0.60) ? (205.8 ± 7.6) kJ mol?1 (2.303 RT)?1
The kinetic and thermodynamic parameters of these reactions, together with those reported in the literature, lead to consider three different mechanistic pathways of elimination. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
20.
Abstract Catabolism of the natural branched-chain L-amino acids in overnight fasted healthy volunteers was comparatively studied by performing oral loading tests with 1- 13C-labelled L-leucine, L-valine, and L-isoleucine (38 μmol x kg (body weight) ?1), respectively. On the basis of the 13CO 2 exhalation and the 13C-isotope enrichment in the plasma branched-chain compounds, whole body branched-chain L-amino acid oxidation rates were estimated applying a seven compartment model and non-linear regression analysis. Mean computed in vivo oxidation rates were in the order L-leucine ? L-valine > L-isoleucine and amounted to 0.32 ± 0.06, 0.22 ± 0.04, and 0.17 ± 0.05 μmol x (kg body wt.) ?1 x min ?1 ( n = 5), respectively. The data are discussed with respect to current estimates of human branched-chain L-amino acid requirements. 相似文献
|