Spectrum of acetylene: 1650–1950 Å

A discontinuity in ¹³C-isotope shifts is used to fix the location of a diffuse 00 of gaseous ¹²C₂H₂ at 54 116 cm^?1. The shifts and analogy with a known band system of HCN suggest the assignment B? ¹B_u - X? ¹ Σ⁺_g for the new electronic transition.     

A hybrid Monte Carlo approach to molecular aggregation in a porous medium

A Monte Carlo simulation is used to study the segregation of liquid crystal molecules (short chains) in a heterogeneous matrix (of barrier concentration ) in an ordering field (E). Aggregation of molecules, pinned by the matrix barriers, is enhanced at lower temperature (T) and higher barrier concentrations via clusters of clustering growth. Variation of the radial distribution function with T and , rms displacement of molecules, and visual analysis of their distribution reveal that the size of the molecular aggregates is relatively larger and less dispersed at higher than that at a lower at T=0.2. The orientational molecular ordering is found to be lower at low temperature at higher . Molecules remain segregated at higher temperatures unless the porosity is reduced and the ordering field is increased considerably. Received 29 October 1999 and Received in final form 19 January 2000     

Multidimensional optimization of structural changes of molecules upon lonization in Franck-Condon factor calculations

Two different iterative methods, namely, the conjugate gradients method and the pattern search method, are applied to Franck-Condon factor calculations using the Coon et al. method (J. B. Coon, R. E. DeWames, and C. M. Loyd, J. Mol. Spectrosc.8, 235–299 (1962)) and the generating function method (T. E. Sharp and H. M. Rosenstock, J. Chem. Phys.41, 3453–3463 (1964); R. Botter, V. H. Dibeler, J. A. Walker, and H. M. Rosenstock, J. Chem. Phys.44, 1271–1278 (1966)). In such treatment, either the changes in normal coordinates or the changes in internal symmetry displacement coordinates are refined automatically until the weighted sum of square deviation between the calculated and the observed Franck-Condon factors is minimized. Some properties of the methods used are given and their applications to several cases are discussed in detail.     

Mesomorphic behaviour of new azomethine liquid crystals having terminal bromo substituent

A homologous series of azomethine esters,4-n-alkanoyloxybenzylidene-4’-bromoanilines possessing even number of carbon atoms at the terminal alkanoyloxy chain(C_n-1H_2n-1COO- n = 8,10,12,14,16,18) was synthesized and characterized.Whilst n-octanoyloxy to n-dodecanoyloxy derivatives exhibited enantiotropic smectic A and smectic B phases,n-tetradecanoyloxy to n-octadecanoyloxy derivatives possessed enantiotropic smectic A and monotropic smectic B properties.n-Decanoyloxy derivatives demonstrated the optimum exhibition for both smectic A and smectic B phases.It was found that the length of terminal alkanoyloxy chain has an influence on mesomorphic properties.     

Potential use of deep eutectic solvents to facilitate lignocellulosic biomass utilization and conversion

High reliance on crude oil for energy consumption results in the urgent need to explore and develop alternative renewable sources. One of the most promising routes is the transformation of biomass into biofuels and chemicals. The introduction of deep eutectic solvents in 2004 received a considerable amount of attention across different research fields, particularly in biomass processing. The effectiveness of deep eutectic solvents in breaking down the recalcitrant structure in biomass highlights its impact on the transformation of biomass into various value-added products. In addition, deep eutectic solvents are widely regarded as promising “green” solvents due to their low cost, low toxicity, and biodegradable properties. In this paper, some background information on lignocellulosic biomass and deep eutectic solvents is given. Furthermore, the roles of deep eutectic solvents in biomass processing are discussed, focusing on the impacts of deep eutectic solvents on the selectivity of chemical processes and dissolution of biomass. This review also highlights the advantages and limitations of deep eutectic solvents associated with their usage in biomass valorization.     

Energy bands of sp-hybrid crystals in the many-neighbor approximation

The many-neighbor approximation (MNA) is a molecular orbital approach in which the nth nearest-neighbor interaction is written in terms of the nth power of the next-nearest-neighbor (NNN) interaction parameter ρ(<1). By adopting such an approach, an examination is made of the effect of the MN interactions on the crossed-band structure of sp-hybrid crystals. The results obtained show that the MN interactions cause the two allowed bands to expand, with increasing ρ, at the expense of the band gap. The significance of this gap reduction for Shockley surface states is briefly discussed.     

Mesomorphic behavior of new benzothiazole liquid crystals having Schiff base linker and terminal methyl group

正A homologous series of heterocycles,6-methyl-2-(4-alkoxybenzylidenamino)benzothiazoles,were synthesized and characterized using FT-IR,~1H and ~(13)C NMR and mass spectrometric analysis.Enantiotropic nematic phase was observed for shorter members.Smectic A phase only emerged from octyloxy derivative onwards.The terminal methyl group at the benzothiazole fragment and the Schiff base linkage influenced the mesomorphic behavior of the present series.     

Rapid determination of vitamin B12 concentration with a chemiluminescence lab on a chip

This paper reports a novel method for the rapid determination of vitamin B(12) concentration in a continuous-flow lab-on-a-chip system. This new method is based on luminol-peroxide chemiluminescence (CL) assays for the detection of cobalt(II) ions in vitamin B(12) molecules. The lab-on-a-chip device consisted of two passive micromixers acting as microreactors and a double spiral microchannel network serving as an optical detection region. This system could operate in two modes. In the first mode, samples are acidified and evaluated directly in the microchip. In the second mode, samples are treated externally by acidification prior to detection in the microchip. In the first mode, the linear range obtained was between 1.00 ng ml(-1) to 10 μg ml(-1), R(2) = 0.996, with a relative standard deviation (RSD) of 1.23 to 2.31% (n = 5) and a limit of detection (lod) of 0.368 pg ml(-1). The minimum sample volume required and the analytical time were 30 μl and 3.6 s, respectively. In the second mode, the linear range obtained was between 0.10 ng ml(-1) to 10 μg ml(-1), R(2) = 0.994, with the RSD of 0.90 to 2.32% (n = 6) and a lod of 0.576 pg ml(-1). The minimum sample and the analytical time required were 50 μl and 6 s, respectively. The lab on a chip working in mode II was successfully used for the determination of vitamin B(12) concentrations in nutritional supplemental tablets and hen egg yolks.