Development and operation of fiber-based radiation protection beam-loss monitor for PAL-XFEL

Journal of Radioanalytical and Nuclear Chemistry - Beam loss monitor using a long optical fiber has been developed and operated for radiation protection in PAL-XFEL, which is an X-ray free electron...     

Simultaneous Detection of Single Attoliter Droplet Collisions by Electrochemical and Electrogenerated Chemiluminescent Responses

We provide evidence of single attoliter oil droplet collisions at the surface of an ultra‐microelectrode (UME) by the observation of simultaneous electrochemical current transients (i–t curves) and electrogenerated chemiluminescent (ECL) transients in an oil/water emulsion. An emulsion system based on droplets of toluene and tri‐n‐propylamine (2:1 v/v) emulsified with an ionic liquid and suspended in an aqueous continuous phase was formed by ultrasonification. When an ECL luminophore, such as rubrene, is added to the emulsion droplet, stochastic events can be tracked by observing both the current blips from oxidation at the electrode surface and the ECL blips from the follow‐up ECL reaction, which produces light. This report provides a means of studying fundamental aspects of electrochemistry using the attoliter oil droplet and offers complementary analytical techniques for analyzing discrete collision events, size distribution of emulsion systems, and individual droplet electroactivity.     

Identification of Novel Rab27a/Melanophilin Blockers by Pharmacophore-Based Virtual Screening

Melanocytes are unique cells that produce specific melanin-containing intracellular organelles called melanosomes. Melanosomes are transported from the perinuclear area of melanocytes toward the plasma membrane as they become more melanized in order to increase skin pigmentation. In this vesicular trafficking of melanosomes, Rab27a, melanophilin, and myosin Va play crucial roles in linking melanosomes to actin-based motors. To identify novel compounds to inhibit binding interface between Rab27a and melanophilin, a pharmacophore model was built based on a modeled 3D structure of the protein complex that describes the essential binding residues in the intermolecular interaction. A pharmacophore model was employed to screen a chemical library database. Finally, 25 virtual hits were selected for biological evaluations. The biological activities of 11 analogues were evaluated in a second assay. Two compounds were identified as having concentration-dependent inhibitory activity. By analyzing structure–activity relationships of derivatives of BMD-20, two hydroxyl functional groups were found to be critical for blocking the intermolecular binding between Rab27a and melanophilin.     

Synthesis and surface properties of self-crosslinking core–shell acrylic copolymer emulsions containing fluorine/silicone in the shell

Stable emulsions of a core–shell acrylic copolymer (non-crosslinkable V0, and crosslinkable V2, V4, V6, and V8, where the numbers indicate the wt% of crosslinking agent based on the total acrylate monomer content) containing butyl acrylate (BA, 45 wt%), glycidyl methacrylate (GMA, 45 wt%), heptadecafluorodecyl methacrylate (PFA, 10 wt%), and various contents of crosslinking agent (vinyltriethoxysilane, VTES) were synthesized using a three-stage seeded emulsion polymerization process with a small amount of surfactant. The average particle size and viscosity of emulsions increased significantly with increasing VTES content. This study examined the effects of the VTES content on the surface/mechanical properties of self-crosslinked copolymer film samples containing a fixed acrylate monomer content to find the optimum VTES content. XPS showed that the film–air surface of the copolymer samples had a higher fluorine/silicone content than the film–dish interface. The tensile strength/modulus, thermal stability, and two Tgs (α and β Tgs) of the film samples increased significantly with increasing VTES content. The contact angle of the film samples increased with increasing VTES content up to approximately 6 wt%, and then decreased slightly. The optimum VTES content was approximately 6 wt% based on the total acrylate monomer content to obtain a high water/oil repellent coating material (V6) with the highest water/methylene iodide-contact angles (118.2°/81.8°) and lowest surface energy (18.4 mN/m).     

A Dynamic Model for Cellulosic Biomass Hydrolysis: a Comprehensive Analysis and Validation of Hydrolysis and Product Inhibition Mechanisms

The objective of this study is to perform a comprehensive enzyme kinetics analysis in view of validating and consolidating a semimechanistic kinetic model consisting of homogeneous and heterogeneous reactions for enzymatic hydrolysis of lignocellulosic biomass proposed by the U.S. National Renewable Energy Laboratory (Kadam et al., Biotechnol Prog 20(3):698–705, 2004) and its variations proposed in this work. A number of dedicated experiments were carried out under a range of initial conditions (Avicel® versus pretreated barley straw as substrate, different enzyme loadings and different product inhibitors such as glucose, cellobiose and xylose) to test the hydrolysis and product inhibition mechanisms of the model. A nonlinear least squares method was used to identify the model and estimate kinetic parameters based on the experimental data. The suitable mathematical model for industrial application was selected among the proposed models based on statistical information (weighted sum of square errors). The analysis showed that transglycosylation plays a key role at high glucose levels. It also showed that the values of parameters depend on the selected experimental data used for parameter estimation. Therefore, the parameter values are not universal and should be used with caution. The model proposed by Kadam et al. (Biotechnol Prog 20(3):698–705, 2004) failed to predict the hydrolysis phenomena at high glucose levels, but when combined with transglycosylation reaction(s), the prediction of cellulose hydrolysis behaviour over a broad range of substrate concentrations (50–150 g/L) and enzyme loadings (15.8–31.6 and 1–5.9 mg protein/g cellulose for Celluclast and Novozyme 188, respectively) was possible. This is the first study introducing transglycosylation into the semimechanistic model. As long as these type of models are used within the boundary of their validity (substrate type, enzyme source and substrate concentration), they can support process design and technology improvement efforts at pilot and full-scale studies.     

Understanding energetic disorder in electron-deficient-core-based non-fullerene solar cells

Recent advances in material design for organic solar cells(OSCs) are primarily focused on developing near-infrared nonfullerene acceptors, typically A-DA′D-A type acceptors(where A abbreviates an electron-withdrawing moiety and D, an electron-donor moiety), to achieve high external quantum efficiency while maintaining low voltage loss. However, the charge transport is still constrained by unfavorable molecular conformations, resulting in high energetic disorder and limiting the device performance. Here, a facile design strategy is reported by introducing the "wing"(alkyl chains) at the terminal of the DA′D central core of the A-DA′D-A type acceptor to achieve a favorable and ordered molecular orientation and therefore facilitate charge carrier transport. Benefitting from the reduced disorder, the electron mobilities could be significantly enhanced for the"wing"-containing molecules. By carefully changing the length of alkyl chains, the mobility of acceptor has been tuned to match with that of donor, leading to a minimized charge imbalance factor and a high fill factor(FF). We further provide useful design strategies for highly efficient OSCs with high FF.     

Miscibility of poly(ethylene terephthalate)/poly(ethylene 2,6-naphthalate) blends by transesterification

The effects of transesterification on the miscibility of poly(ethylene terephthalate)/poly(ethylene 2,6-naphthalate) were studied. Blends were obtained by solution precipitation at room temperature to avoid transesterification during blend preparation. The physical blends and transesterified products were analyzed by wide-angle x-ray scattering, differential scanning calorimetry, and nuclear magnetic resonance spectroscopy. It was found that the physical blends are immiscible and when the extent of transesterification reaches 50% of the completely randomized state, independent of blend composition, the blends are not crystallizable and show a single glass transition temperature between those of starting polymers. The interchange reactions were significantly influenced by annealing temperature and time but negligibly by blend composition. © 1996 John Wiley & Sons, Inc.     

On the Onsager Variation Principle and its Generalization for Nonlinear Irreversible Thermodynamics

The Onsager variation principle is examined from the viewpoint of the thermodynamic analogue of the D'Alembert principle in mechanics when the irreversible processes are linear and thus the system is near equilibrium. The thermodynamic D'Alembert principle is shown to be a precursor to the Onsager variation principle. The thermodynamic D'Alembert principle is then generalised to the cases of nonlinear irreversible processes occurring removed from equilibrium and a generalised form of the Onsager variation principle is obtained under some restricting conditions. The restricted variation principle so deduced has an accompanying exact differential form generalising the Clausius entropy differential (equilibrium Gibbs relations) and contains in it the essence of the thermodynamics of irreversible processes in systems where non-linear transport processes occur. An example is given for the nonlinear dissipation function in the variation functional. The evolution equations for fluxes are shown to yield those known in the literature.     

Analysis of phantom centering positioning on image noise and radiation dose in axial scan type of brain CT

ABSTRACT

This study examined the dose and image quality according to the position change of a human phantom in a CT scan. This study used an MDCT 128 Slice CT Scanner instrument. An axial scan was performed with a 16 cm CTDI phantom of a human phantom, and the dose was measured using a pencil chamber meter. The phantom was scanned 10 cm above and below the isocenter and 15 cm above the right and left. The position of the phantom is indicated by C-0 in the isocenter position, S-10 in the upper 10 cm, I-10 in the lower 10 cm, R-15 in the right 15 cm, and L-15 in the left 15 cm. The test was performed 30 times using the brain CT protocol to calculate the dose and the dose width product (DWP). The acquired images were analyzed using the ImageJ program. Statistical analysis was performed using SPSS with one-way ANOVA (p < .05). The mean DWP values of the CT scanner were C-0 31.97 mGy·cm, S-10 24.52 mGy·cm, I-10 24.28 mGy· cm, R-15 17.95 mGy·cm, and L15 17.6 mGy·cm. Compared to the isocenter (C-0), the DLP values measured at each site were 23.3% for S-10, 24% for I-10, 43.8% for R-15, and 44.9% for L15. A significant difference in the one-way ANOVA statistical process was observed (p>0.05). C-0 was measured to be 7.42 HU, S-10 7.87 HU, I-10 8.4 HU, R-15 117 HU, and L-15 13.6 HU for evaluating the image quality. Compared to C-0, S-10 was 5.39%, I-10 was 13.2%, R-15 was 57.6%, and L-15 was 83.2%. The PSNR for S-10, I-10, R-15, and L-15 was 17.37, 17.5, 16.62, and 16.37 dB, respectively. A good quality image can be obtained by positioning the subject precisely in the isocenter in the axial scan, if possible, because the irradiated dose to the subject is low, which can lead to an increase in noise in image reconstruction.