Energy distribution around 175 MeV Ar ion path in argon at the density of water

The ionization distribution in Ar gas by 175 MeV Ar ion was measured, and reduced to the energy density as a function of the radial distance in water. The energy density within the radial distance smaller than 294 nm decreased proportionally to the inverse of the square of the distance. Beyond this distance, however, the energy density decreased more steeply. The deposited energy except in the core region of the track amounts to 89% of linear energy transfer (LET).     

Simulation of NEXAFS spectra of a photo-reactive copolymer with considerably large monomer units: An ab initio molecular orbital study

We performed the simulation of near edge X-ray absorption fine structure (NEXAFS) spectra of a photo-reactive copolymer with considerably large monomer units by ab initio molecular orbital calculation, in order to explain the spectral change induced by irradiation of the linearly polarized near ultra-violet (LPNUV) light. The “building block approach” is applied for the theoretical calculation to calculate the core-excited states of the polymer with such large monomer units; the monomer unit is divided into subunits, whose core-excited states are calculated individually, and the results are summed up to simulate the spectra of the polymer. With the result of the simulation, the peaks in the observed spectra were assigned. The spectral change after the LPNUV-irradiation is attributed to the change in the electronic structure caused by the breakdown of the π-conjugation system of chalconyl group after photo-dimerization.     

Analysis of sound attenuation in a duct with a solid or porous splitter

The equivalent singularity method is developed for the analysis of sound propagation in a duct with a thin solid or point-reacting porous splitter of a finite streamwise length. The method consists in representing the splitter by a singular plane of pressure dipoles and mass sources, distributions of which are determined so that the boundary condition at the splitter surfaces is satisfied. The boundary condition is expressed in terms of two admittance parameters giving relations between pressures and normal displacements of fluid particles at the upper and lower surfaces of the splitter. Computed results are presented to illustrate the dependence of the sound power transmitted through the splitter section on the acoustic properties, length and location of the splitter and the flow Mach number. A principal cause of the sound attenuation due to a splitter is found to be the conversion of the acoustic energy into the wake vortex energy convected downstream. A solid splitter or a porous splitter of small admittance shows tuning effects—with a peak or multiple peaks in the attenuation spectrum. The tuning frequencies can be controlled by the splitter location.     

Time delay in CdS laser pumped by an electron beam

Time delays of up to 500 nsec were observed in the stimulated emission of Cd-rich CdS crystals at 80° K pumped by an electron beam. The delay decreased with increase of excitation and the memory effect of the first pulse was observed for lasing during the second pulse when two separated electron-beam pulses (double pulse) were applied to the sample.The results were compared with the trapping model proposed by Fenner in which traps provide a large amount of optical absorption and the expression for the delay in the case of electron-beam pumping was derived. The experimental results were well explained by this model.     

Chemoselectivity Control in the Asymmetric Hydrogenation of γ‐ and δ‐Keto Esters into Hydroxy Esters or Diols

The asymmetric hydrogenation of aromatic γ‐ and δ‐keto esters into optically active hydroxy esters or diols under the catalysis of a novel DIPSkewphos/3‐AMIQ–Ru^II complex was studied. Under the optimized conditions (8 atm H₂ , Ru complex/t‐C₄H₉OK=1:3.5, 25 °C) the γ‐ and δ‐hydroxy esters (including γ‐lactones) were obtained quantitatively with 97–99 % ee. When the reaction was conducted under somewhat harsh conditions (20 atm H₂ , [t‐C₄H₉OK]=50 mm , 40 °C), the 1,4‐ and 1,5‐diols were obtained predominantly with 95–99 % ee. The reactivity of the ester group was notably dependent on the length of the carbon spacer between the two carbonyl moieties of the substrate. The reaction of β‐ and ?‐keto esters selectively afforded the hydroxy esters regardless of the reaction conditions. This catalyst system was applied to the enantioselective and regioselective (for one of the two ester groups) hydrogenation of a γ‐?‐diketo diester into a trihydroxy ester.     

Simultaneous determination of five aristolochic acids and two aristololactams in Aristolochia plants by high-performance liquid chromatography

An HPLC method was developed for the simultaneous determination of five aristolochic acids (AAs) and two aristololactams (ALs) in the following six Chinese drugs derived from Aristolochia species. Samples were analyzed on a C(18) column with acetonitrile and 3.7 mm phosphoric acid buffer gradient elution, detected at 260 nm. Assay was linear over the range (microg/mL) 0.386-38.6 for aristolochic acid Va, 0.632-63.2 for aristolochic acid IVa, 0.200-20.0 for 9-hydroxy aristolochic acid I, 0.352-35.2 for aristololactam II, 0.296-29.6 for aristolochic acid II, 0.274-27.4 for aristololactam I and 3.12-312 for aristolochic acid I. Average recoveries (%) of samples were 102.0, 95.9, 99.2, 102.2, 97.2, 97.1 and 97.8 for these seven constituents, respectively. The detection limit and retention time for the seven constituents ranged from 10.0 to 15.8 ng/mL and from 12 to 21 min. As a result of drug determination, contents (in mg/g) were as follows: AA-I, 0.69-1.77; AA-II, 0.02-0.18; 9-OH AA-I, 0.04-0.12; AA-IVa, 0.76-3.36; AA-Va, 0.04-0.31; AL-I, 0.07-0.36; and AL-II, 0.01-0.09 in Madouling; AA-I, 0.03-0.41; AA-II, 0.01-0.11; 9-OH AA-I, 0.00-0.60; AA-IVa, 0.00-0.77; AA-Va, 0.00-0.14; and AL-I, 0.00-0.04 in Tianxianteng; AA-I, 1.19-4.71; and AA-II, 0.24-1.69 in Qingmuxiang; AA-I, 2.79-5.48; AA-II, 1.06-1.86; 9-OH AA-I, 0.01-0.09; AA-IVa, 0.38-0.69; AA-Va, 0.00-0.61; AL-I, 0.00-0.02; and AL-II, 0.00-0.02 in Bei-madouling-gen; AA-I, 0.64-4.23; AA-II, 0.06-0.40; and AA-IVa, 0.08-0.25; in Guangfangji; and AA-I, 1.88-9.72; AA-II, 0.26-1.88; and AA-IVa, 0.09-0.52 in Guanmutong. The other constituents were not detected in Tianxianteng, Qingmuxiang, Guangfangji and Guanmutong.     

Fluorescence properties of amido-substituted 2,3-naphthalimides: Excited-state intramolecular proton transfer (ESIPT) fluorescence and responses to Ca2+ ions

2,3-Naphthalimide derivatives incorporating trifluoroacetamido (3a) and methansulfonamido (3b) functionalities at the 1-position were prepared and their intramolecular excited state proton transfer (ESIPT) fluorescence and responses to metal ions were investigated. Compound 3a displayed normal fluorescence in the amide form in toluene and MeCN and no response to metal cations in the corresponding amidate ion form. In contrast, compound 3b gave off dual emission assignable to normal and ESIPT fluorescence. Additionally, the amidate form of compound 3b displayed off-on fluorescence response to Ca²⁺.     

Isotope-selective infrared multiphoton dissociation of CF3Br in a supersonic free jet

The carbon-isotope selectivity in the multiphoton dissociation of CF₃Br is studied in the collisional region of supersonic free jet. The isotopic abundance of¹²C and¹³C in C₂F₆ formed by recombination of the dissociation products is measured with a quadrupole mass spectrometer. An enrichmet factor of 9.4 is obtained for¹²C with the 9R(30)CO₂ laser line while the factor of 6.9 is obtained for¹³C with the 9P(16) line.