Cholesteryl acetate as a stationary phase for the gas chromatography of some volatile oil constituents

Cholesteryl acetate provides a useful low-polarity stationary phase in packed columns for the gas chromatography of some volatile oil constituents like terpene hydrocarbons, certain terpenoids and some aromatics. With a high mobile phase flow-rate, it is best used above its melting point as a normal liquid (115°C and more) although it has a narrow mesomeric temperature range below this as a chiral nematic liquid crystal. It can be used to resolve racemic linalol, but not carvone.     

Partonic Flow and phi-Meson production in Au+Au collisions at sqrt radical sNN = 200 GeV

We present first measurements of the phi-meson elliptic flow (v2(pT)) and high-statistics pT distributions for different centralities from radical sNN=200 GeV Au+Au collisions at RHIC. In minimum bias collisions the v2 of the phi meson is consistent with the trend observed for mesons. The ratio of the yields of the Omega to those of the phi as a function of transverse momentum is consistent with a model based on the recombination of thermal s quarks up to pT approximately 4 GeV/c, but disagrees at higher momenta. The nuclear modification factor (R CP) of phi follows the trend observed in the K S 0 mesons rather than in Lambda baryons, supporting baryon-meson scaling. These data are consistent with phi mesons in central Au+Au collisions being created via coalescence of thermalized s quarks and the formation of a hot and dense matter with partonic collectivity at RHIC.     

Centrality dependence of charged-hadron transverse-momentum spectra in d+Au collisions at sqrt[s(NN)]=200 GeV

We have measured transverse momentum distributions of charged hadrons produced in d+Au collisions at sqrt[s(NN)]=200 GeV. The spectra were obtained for transverse momenta 0.25相似文献   

Correlation coefficients of solute relative retentions for pairs of modified cyclodextrins: evaluation of selectivity by differently responding gas chromatographic stationary phases

Relative retention times versus the n-undecane for ten diverse probe solutes from volatile oils are scatterplotted between pairs of modified cyclodextrin (CD) phases. If the resulting line of best fit has a very high correlation coefficient (r), then the two CDs are behaving similarly and will not give different results. A low value of r between two CD phases indicates they behave contrastingly enough to give different analyses. Presuming a laboratory wants three differently behaving commercial CDs, twelve are considered in this way to find the optimum three pairings (each showing r to be less than 0.800 with an average of less than 0.700). These requirements are met by Chiraldex G-DA (gamma-dipentyl) and A-PH (alpha-hydroxypropyl, dimethyl) with Beta-Dex 225 (beta-diacetyl, butyldimethylsilyl) capillaries. Solutes that fall close to the line of fit between two of the phases are undergoing "normal" transient CD molecular interaction with both. They may then show extra retention with the third phase on the other two plots, which suggests close solute-guest/CD-host molecular fit. Another possibility is that this third modified CD may behave merely as a normal non-CD phase to such a solute (shown by the rejection of it) with a lower retention than is normal. Hierarchical cluster analysis seems unreliable to indicate CD-phase relationships.     

Baryon rapidity loss in relativistic Au + Au collisions

An excitation function of proton rapidity distributions for different centralities is reported from AGS Experiment E917 for Au+Au collisions at 6, 8, and 10.8 GeV/nucleon. The rapidity distributions from peripheral collisions have a valley at midrapidity which smoothly change to distributions that display a broad peak at midrapidity for central collisions. The mean rapidity loss increases with increasing beam energy, whereas the fraction of protons consistent with isotropic emission from a stationary source at midrapidity decreases with increasing beam energy. The data suggest that the stopping is substantially less than complete at these energies.     

Interphotoreceptor Retinoid‐Binding Protein Protects Retinoids from Photodegradation

Retinol degrades rapidly in light into a variety of photoproducts. It is remarkable that visual cycle retinoids can evade photodegradation as they are exchanged between the photoreceptors, retinal pigment epithelium and Müller glia. Within the interphotoreceptor matrix, all‐trans retinol, 11‐cis retinol and retinal are bound by interphotoreceptor retinoid‐binding protein (IRBP). Apart from its role in retinoid trafficking and targeting, could IRBP have a photoprotective function? HPLC was used to evaluate the ability of IRBP to protect all‐trans and 11‐cis retinols from photodegradation when exposed to incandescent light (0 to 8842 μW cm^?2); time periods of 0–60 min, and bIRBP: retinol molar ratios of 1:1 to 1:5. bIRBP afforded a significant prevention of both all‐trans and 11‐cis retinol to rapid photodegradation. The effect was significant over the entire light intensity range tested, and extended to the bIRBP: retinol ratio 1:5. In view of the continual exposure of the retina to light, and the high oxidative stress in the outer retina, our results suggest IRBP may have an important protective role in the visual cycle by reducing photodegradation of all‐trans and 11‐cis retinols. This role of IRBP is particularly relevant in the high flux conditions of the cone visual cycle.     

High-temperature specific heat and susceptibility of the quadratic S = 12 XY model. Comparison with data on CoCl2.6H2O and CoBr2.6H2O

This susceptibility of the quadratic, $\text{S =}\text{1}\text{2}$, XY model as determined by the high-temperature series expansion is presented and compared with experimental data on CoCl₂.6H₂O and CoBr₂.6H₂O. For the specific heat of CoCl₂.6H₂O a similar comparison is made. For kT/|J| > 1.5 a good agreement between theory and experiment is found, yielding J/k = ?2.05 ± 0.1 and ?2.45 ± 0.1 K for the intralayer exchange of the Cl and the Br salt, respectively. These values compare favourably with those available from other sources.     

Determination of submicromolar amounts of uranium(VI) by compleximetric titration with pyridine-2,6-dicarboxylic acid

Uranium(VI) is selectively determined by a compleximetric titration with pyridine-2,6-dicarboxylic acid, using arsenazo-I indicator and hexamethylenetetramine buffer at pH 4.9. Cyclohexanediaminetetraacetic acid and diethylenetriaminepentaacetic acid provide masking of interfering metal ions. A probe colorimeter apparatus is recommended for end-point detection. The relative standard deviation is 0.6% for 0.17–0.76 μmol of uranium.