Synthesis of chiral azobenzene-based compounds for use in the photochemical tuning of the helical structure of liquid crystals

We have synthesized azobenzene-based molecules containing either one or two chiral groups. A cholesteric phase can be induced by adding the chiral azobenzene compounds to a host nematic liquid crystal. We investigated the effects of the trans-cis photoisomerization of the chiral azobenzene compounds on the properties of the cholesteric phase, such as the helical pitch length. This can be increased or decreased by the photoisomerization of the chiral azobenzene compounds. We discuss the photochemically driven change in the helical pitch of the cholesteric phase with respect to structural effects involving the chiral groups.     

Neutron in-beam Mössbauer spectroscopic study of iron disulfide at room temperature

An in-beam emission Mössbauer spectrum of ⁵⁷Fe arising from the ⁵⁶Fe(n, γ) ⁵⁷Fe reaction in iron disulfide at room temperature was measured with a parallel plate avalanche counter. It was clearly observed that the nuclear reaction and the following process lead to the production of a new chemical species of iron different from the parent compound.     

Space-time evolution of bulk QCD matter at RHIC

We introduce a combined fully three-dimensional macroscopic/microscopic transport approach employing relativistic 3D-hydrodynamics for the early, dense, deconfined stage of the reaction and a microscopic non-equilibrium model for the later hadronic stage where the equilibrium assumptions are not valid anymore. Within this approach we study the dynamics of hot, bulk QCD matter, which is being created in ultra-relativistic heavy-ion collisions at RHIC. In particular, we perform a detailed analysis of the reaction dynamics, hadronic freeze-out, transverse flow and elliptic flow. PACS 25.75.-q; 24.10.Nz; 24.10.Lx     

Polymerization of methyl methacrylate by resin containing polyethylenepolyamine side chain–peroxide system

Macroreticular resins (RST) bearing polyethylenepolyamine side chain were prepared by the amination of the chloromethylated macroreticular styrene—divinylbenzene copolymer beads. The polymerization of methyl methacrylate (MMA) was carried out in a water—organic solvent mixture containing hydroperoxide and RST. The polymerization of MMA proceeded smoothly in the presence of both hydroperoxide and RST. The presence of water was indispensable for this polymerization. 1,4-Dioxane hydroperoxide showed a high activity for the polymerization of MMA. The polymerization of MMA by this system was greatly affected by the structure of the resins. It was especially accelerated by using macroreticular resins with appropriate porosities.     

Evaluating results from the Relativistic Heavy Ion Collider with perturbative QCD and hydrodynamics

We review the basic concepts of perturbative quantum chromodynamics (QCD) and relativistic hydrodynamics, and their applications to hadron production in high energy nuclear collisions. We discuss results from the Relativistic Heavy Ion Collider (RHIC) in light of these theoretical approaches. Perturbative QCD and hydrodynamics together explain a large amount of experimental data gathered during the first decade of RHIC running, although some questions remain open. We focus primarily on practical aspects of the calculations, covering basic topics like perturbation theory, initial state nuclear effects, jet quenching models, ideal hydrodynamics, dissipative corrections, freeze-out and initial conditions. We conclude by comparing key results from RHIC to calculations.     

Determination of aflatoxins in food samples by automated on-line in-tube solid-phase microextraction coupled with liquid chromatography–mass spectrometry

A simple and sensitive automated method for determination of aflatoxins (B1, B2, G1, and G2) in nuts, cereals, dried fruits, and spices was developed consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–mass spectrometry (LC–MS). Aflatoxins were separated within 8 min by high-performance liquid chromatography using a Zorbax Eclipse XDB-C8 column with methanol/acetonitrile (60/40, v/v): 5 mM ammonium formate (45:55) as the mobile phase. Electrospray ionization conditions in the positive ion mode were optimized for MS detection of aflatoxins. The pseudo-molecular ions [M+H]⁺ were used to detect aflatoxins in selected ion monitoring (SIM) mode. The optimum in-tube SPME conditions were 25 draw/eject cycles of 40 μL of sample using a Supel-Q PLOT capillary column as an extraction device. The extracted aflatoxins were readily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME LC–MS with SIM method, good linearity of the calibration curve (r > 0.9994) was obtained in the concentration range of 0.05–2.0 ng/mL using aflatoxin M1 as an internal standard, and the detection limits (S/N = 3) of aflatoxins were 2.1–2.8 pg/mL. The in-tube SPME method showed >23-fold higher sensitivity than the direct injection method (10 μL injection volume). The within-day and between-day precision (relative standard deviations) at the concentration of 1 ng/mL aflatoxin mixture were below 3.3% and 7.7% (n = 5), respectively. This method was applied successfully to analysis of food samples without interference peaks. The recoveries of aflatoxins spiked into nuts and cereals were >80%, and the relative standard deviations were <11.2%. Aflatoxins were detected at <10 ng/g in several commercial food samples.