Gadolinium pyrosilicate single crystals for gamma ray and thermal neutron monitoring

Bulk Gd₂Si₂O₇:Ce (GPS:Ce) single crystals obtained by Czochralski method demonstrate a high light output at γ-irradiation (3.8 times higher in comparison with Bi₄Ge₃O₁₂ (BGO)), energy resolution 13% (137Cs, 662 KeV), fast decay time (41.7 ns), and good thermal stability of light output (up to 425 K). This combination of characteristics makes this scintillator very attractive for medical imaging and high-temperature applications. Light output at thermal neutron monitoring is evaluated as twice higher in comparison with Gd₂SiO₅:Ce (GSO). The observed rather high afterglow level (0.2% after 20 ms) and moderate energy resolution (13%) certifies a room for improvement of these parameters by further optimization of crystal quality.     

Remarkable enantioselectivity of molecularly imprinted TiO2 nano-thin films

TiO(2) nano-thin films with imprinted (R)- and (S)-enantiomers of propranolol, 1,1'-bi-naphthol, and 2-(4-isobutylphenyl)-propionic acid were fabricated on quartz plates by spin-coating their solutions with Ti(O-(n)Bu)(4) in a toluene-ethanol mixture (1:1, v/v). After template removal, the imprinted films showed better binding for original templates than to the corresponding enantiomers. The assessment of template incorporation, template removal, and re-binding was conducted through UV-vis measurements. Significant enhancement of enantioselectivity was achieved by optimization of the film thickness and by heat-treatment of the imprinted films. After subtraction of non-specific binding, the optimized films provided chiral recognition with the enantioselectivity of almost 100% for (R)-propranolol and 95% for (S)-propranolol.     

Time of flight mass spectrometry for quantitative data analysis in fast transient studies using a Temporal Analysis of Products (TAP) reactor

A Time of flight (ToF) mass spectrometer suitable in terms of sensitivity, detector response and time resolution, for application in fast transient Temporal Analysis of Products (TAP) kinetic catalyst characterization is reported. Technical difficulties associated with such application as well as the solutions implemented in terms of adaptations of the ToF apparatus are discussed. The performance of the ToF was validated and the full linearity of the specific detector over the full dynamic range was explored in order to ensure its applicability for the TAP application. The reported TAP-ToF setup is the first system that achieves the high level of sensitivity allowing monitoring of the full 0-200 AMU range simultaneously with sub-millisecond time resolution. In this new setup, the high sensitivity allows the use of low intensity pulses ensuring that transport through the reactor occurs in the Knudsen diffusion regime and that the data can, therefore, be fully analysed using the reported theoretical TAP models and data processing.     

A coarse-grained model for β-<Emphasis Type="SmallCaps">d</Emphasis>-glucose based on force matching

Cellulosic ethanol production is a two-stage process that involves the hydrolysis of cellulose to form simple sugars and the fermentation of these sugars to ethanol. Hydrolysis of cellulose is the rate-limiting step, and there is a great need to characterize the process with numerical simulations to better understand the complex mechanisms involved. The ultimate goal is to generate accurate coarse-grained molecular models that are capable of predicting the structure of lignocellulose before and after pretreatment so that subsequent ab initio calculations can be performed to probe the degradation pathways. As a first step toward that goal, the force-matching method is used to derive coarse-grained models for β-d-glucose molecules in aqueous solution. Using the same reference, an all-atom molecular dynamics simulation trajectory, two sets of three- and six-site coarse-grained models of β-d-glucose are developed using two definitions of the coarse-grained center site location: center of mass (CG-CM) and geometric center (CG-GC). The performance of these coarse-grained models is evaluated by comparing the coarse-grained predictions for bond-length distributions and radial distribution functions to those obtained from the all-atom reference simulation. The six-site coarse-grained models retain more structural details than the three-site coarse-grained models. Comparison between center site definitions shows that CG-CM models generally predict local ordering better, while CG-GC models predict long-range structure better.