Stationary-phase focusing in capillary gas-liquid chromatography: Enhancement of the maximum permissible sample size

Equations have been derived to predict the extent to which the sample size may be increased, without decreasing the column performance, by stationary-phase focusing at sub-ambient temperatures. Under favorable circumstances the sample size may be enhanced several hundredfold.     

Power efficiency of a semiconductor laser with an external cavity

Optical feedback modifies the power vs. current diagram of a laser diode as well as its spectrum. Though optimization of the spectral characteristics is usually the main goal in the design of an external cavity source, power efficiency is also important, especially with relatively high power devices, where temperature variations due to dissipation can have an impact on the wavelength stability and on the laser lifetime. A useful parameter to describe the total power efficiency of the stabilized laser, relative to that of the solitary laser, is proposed in this paper. The dependence of this parameter on the characteristics of the active device, and of the external cavity, is investigated.     

Anti-plane elastodynamic analysis of planes with multiple defects

The solution of a screw dislocation under time-harmonic condition is obtained in an infinite isotropic plane by means of the Fourier transform method. The stress components reveal the familiar Cauchy singularity at the location of dislocation. The solution is employed to derive integral equations for a plane weakened by cracks and cavities. Cavities are considered as closed curved cracks without singularity. Several examples are solved and the stress intensity factor of cracks and hoop stress on cavities are obtained.     

Determination of the configuration of histrelin,and LHRH analog,by chiral capillary gas chromatography

Summary Summary The assigned chirality at each center of the synthetic nonapeptide histrelin (L-pyroglutamyl-L-histidyl-L-tryptophyl-L-seryl-L-tyrosyl-D-N^im-benzyl-histidyl-L-leucyl-L-arginyl-L-proline-ethylamide) was verified using chiral gas chromatography. The procedure involved acid hydrolysis of histrelin to the constituent amino acids, derivatization as the N-pentafluoropropionyl/isopropyl esters and the analysis of the mixture using a commercially available 25m chiral capillary column (Chirasil-L-Val). There was no significant difference in the retention time of the amino acids obtained from the hydrolysate mixture when compared to the appropriate standards. Additionally, the hydrolysate was spiked with the D and L amino acids to prove the identity of closely eluting peaks. Luteinizing hormone-releasing hormone     

General Mechanism for Chiral Recognition by Native and Modified Cyclodextrins

A general mechanism for chiral recognition by native and modified cyclodextrins hasbeen proposed by reconsidering the data reported so far. Cyclodextrins in aqueoussolution adopt asymmetrically twisted structures, which seems to be the origin of chiralrecognition.     

Scheme for implementing quantum secret sharing via cavity QED

An experimentally feasible scheme for implementing quantum secret sharing via cavity quantum electrodynamics （QED） is proposed. The scheme requires the large detuning of the cavity field from the atomic transition, the cavity is only virtually excited, thus the requirement on the quality factor of the cavity is greatly loosened.     

Rotational spectra, nuclear quadrupole hyperfine tensors, and conformational structures of the mustard gas simulent 2-chloroethyl ethyl sulfide

Rotational spectra have been recorded for both the ³⁵Cl and ³⁷Cl isotopic forms of two structural conformations of 2-chloroethyl ethyl sulfide (CEES). The rotational constants of the ³⁵Cl and ³⁷Cl isotopomers were used to identify the conformational isomers. A total of 236 hyperfine transitions have been assigned for 47 rotational transitions of the ³⁵Cl isotope of a GGT conformer, and 146 hyperfine have been assigned for 37 rotational transitions of the ³⁷Cl isotopomer. For the second conformer, a total of 128 (110) hyperfine and 30 (28) rotational transitions have also been assigned to the ³⁵Cl (³⁷Cl) isotopes of a TGT conformation. The extensive hyperfine splitting data, measured to high resolution with a compact Fourier transform microwave spectrometer, were used to determine both the diagonal and off-diagonal elements of the ³⁵Cl and ³⁷Cl nuclear quadrupole coupling tensors in the inertial tensor principal axis system. The experimental rotational constant data, as well as the ³⁵Cl and ³⁷Cl nuclear quadrupole coupling tensors, were compared to the results from 27 optimized ab initio (HF/6-311++G^∗∗ and MP2/6-311++G^∗∗) model structures.     

The role of adsorption phenomena in capillary gas-liquid-solid chromatography

The method of invariant relative retention value determination using commerciallly produced fused silica open-tubular columns with different contents of stationary liquid phase has been tested. Invariant retention values are determined only by interaction of analyzed compound with stationary liquid phase and are independent of the adsorptive interactions in the studied system.     

Implications of the solvent effect in quantitative capillary gas chromatography of minor constituents in mixtures—a study using deuterium labeled and unlabeled benzofluoranthenes

Perdeuterated benzofluoranthenes have slightly shorter retention times than their equivalent unlabeled forms in a DB-5 capillary column. Under column overload conditions, perdeuterated benzofluoranthenes in moderate multifold excesses, which might be encountered in their use as internal standards and carriers for quantitative analysis, are seen to exhibit both normal and reverse solvent effects on their close eluting congeners. In some cases the effects may be used to advantage by knowledgeable analysts, but for the ignorant and unwary the effects can lead to serious errors in identification and quantification.