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41.
M. A. A. O’Neill S. Gaisford A. E. Beezer C. V. Skaria P. Sears 《Journal of Thermal Analysis and Calorimetry》2006,84(2):301-306
Isothermal
calorimetry is finding extensive application in a number of research areas.
This popularity is reflected in the number of commercially available instruments
which are capable of yielding a variety of thermodynamic and kinetic parameters.
Whilst there has been much discussion of ways in which to validate any values
returned from these instruments very little has been done quantitatively to
compare the relative performances of different instruments. This paper highlights
the use of a test and reference reaction quantitatively to compare the performance
of three instruments (Thermometric TAM, THT μRC and a Setaram HSDSC
III); the specifications of these instruments provide a range from high-sensitivity,
long equilibration time to lower-sensitivity, short equilibration time. The
comparison is made through a statistical analysis of values returned for the
rate constant, enthalpy of reaction and activation energy for the base catalysed
hydrolysis of methyl paraben. The statistical analysis from the data set discussed
here indicates that there is no significant difference between the returned
thermodynamic and kinetic parameters from the TAM and μRC. The analysis
revealed however that the HSDSC returns values for the rate constant which
are significantly different from both the TAM and μRC, although it is
noted that this instrument was not specifically designed to operate in a step-isothermal
mode and that it was possible to apply a correction to the data. In all cases
the enthalpy data returned from all instruments were statistically similar
although the μRC and HSDSC returned values which were, for the rate
constant and activation energy, less precise than those obtained from the
TAM. As well as highlighting the importance of using test and reference reactions,
this study also shows that proper instrument selection is an important factor
when designing a calorimetric experimental series. 相似文献
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46.
The spin-rotational Hamiltonian for an asymmetric-top molecule in a given vibrational level of an open-shell electronic state may contain more parameters than can be determined from the observed energy levels. This paper describes the reduction of the Hamiltonian by means of a unitary transformation to a form suitable for fitting to observed energies. It is shown that, for molecules of lower than orthorhombic symmetry, there are fewer determinable quadratic spin-rotation parameters than have been used previously. For example, for a molecule belonging to the group C8, there are four, not five, determinable spin-rotation constants, ?αβ. Similar indeterminacies exist among the quartic terms of the spin-rotation Hamiltonian. The case of a molecule of orthorhombic symmetry, for which there are six determinable quartic parameters, is considered in detail. The results are applied to the experimental data available on the spin-rotation splittings of the HO2 and NH2 radicals in their ground vibrational and electronic states. 相似文献
47.
Dimeric aminoglycosides as antibiotics 总被引:4,自引:0,他引:4
Agnelli F Sucheck SJ Marby KA Rabuka D Yao SL Sears PS Liang FS Wong CH 《Angewandte Chemie (International ed. in English)》2004,43(12):1562-1566
48.
Paik H Schuster DI Bishop LS Kirchmair G Catelani G Sears AP Johnson BR Reagor MJ Frunzio L Glazman LI Girvin SM Devoret MH Schoelkopf RJ 《Physical review letters》2011,107(24):240501
Superconducting quantum circuits based on Josephson junctions have made rapid progress in demonstrating quantum behavior and scalability. However, the future prospects ultimately depend upon the intrinsic coherence of Josephson junctions, and whether superconducting qubits can be adequately isolated from their environment. We introduce a new architecture for superconducting quantum circuits employing a three-dimensional resonator that suppresses qubit decoherence while maintaining sufficient coupling to the control signal. With the new architecture, we demonstrate that Josephson junction qubits are highly coherent, with T2 ~ 10 to 20 μs without the use of spin echo, and highly stable, showing no evidence for 1/f critical current noise. These results suggest that the overall quality of Josephson junctions in these qubits will allow error rates of a few 10(-4), approaching the error correction threshold. 相似文献
49.
Mikhailova JM Buck A Borot A Schmid K Sears C Tsakiris GD Krausz F Veisz L 《Optics letters》2011,36(16):3145-3147
We report the generation of few-cycle multiterawatt light pulses with a temporal contrast of 10(10), when measured as close as 2 ps to the pulse's peak. Tens of picoseconds before the main pulse, the contrast value is expected to spread much beyond the measurement limit. Separate measurements of contrast improvement factors at different stages of the laser system indicate that real contrast values may reach 10(19) and 10(14), when measured 50 and 25 ps before the pulse's peak, respectively. The combination of the shortest pulse duration and the highest contrast renders our system a promising front-end architecture for future multipetawatt laser facilities. 相似文献
50.
Kaori KobayashiGregory E. Hall James T. MuckermanTrevor J. Sears Anthony J. Merer 《Journal of Molecular Spectroscopy》2002,212(2):133-141
The (0,0) and (1,0) bands of the E3Π-X3Δ transition of TiO in the near-infrared have been recorded by frequency modulated laser absorption spectroscopy in a laser ablation/free jet expansion source. The observed linewidths (FWHM) varied from 300 to 500 MHz according to the expansion conditions and are dominated by residual Doppler broadening in the unskimmed source. Data for the (0,0) band have been obtained for TiO molecules containing all the naturally occurring Ti isotopes but, for the weaker (1,0) band, only for 48TiO. Rotational constants for the two upper state vibrational levels were derived by fitting the data to an effective Hamiltonian; equilibrium parameters have been calculated. The experimental results are compared to the results of ab initio calculations on the E-X system. Ab initio results for the b-a system and for the lowest 3Σ− state are also presented. They indicate that the D3Σ− state is not a very low-lying state. 相似文献