Chiral switching by spontaneous conformational change in adsorbed organic molecules

Self-assembly of adsorbed organic molecules is a promising route towards functional surface nano-architectures, and our understanding of associated dynamic processes has been significantly advanced by several scanning tunnelling microscopy (STM) investigations. Intramolecular degrees of freedom are widely accepted to influence ordering of complex adsorbates, but although molecular conformation has been identified and even manipulated by STM, the detailed dynamics of spontaneous conformational change in adsorbed molecules has hitherto not been addressed. Molecular surface structures often show important stereochemical effects as, aside from truly chiral molecules, a large class of so-called prochiral molecules become chiral once confined on a surface with an associated loss of symmetry. Here, we investigate a model system in which adsorbed molecules surprisingly switch between enantiomeric forms as they undergo thermally induced conformational changes. The associated kinetic parameters are quantified from time-resolved STM data whereas mechanistic insight is obtained from theoretical modelling. The chiral switching is demonstrated to enable an efficient channel towards formation of extended homochiral surface domains. Our results imply that appropriate prochiral molecules may be induced (for example, by seeding) to assume only one enantiomeric form in surface assemblies, which is of relevance for chiral amplification and asymmetric heterogenous catalysis.     

Photon beam audits for radiation therapy clinics: a pilot mailed dosemeter study in Turkey

A thermoluminescent dosemeter (TLD) mailed dose audit programme was performed at five radiotherapy clinics in Turkey. The intercomparison was organised by the University of Wisconsin Radiation Calibration Laboratory (UWRCL), which was responsible for the technical aspects of the study including reference irradiations, distribution, collection and evaluation. The purpose of these audits was to perform an independent dosimetry check of the radiation beams using TLDs sent by mail. Acrylic holders, each with five TLD chips inside and instructions for their irradiation to specified absorbed dose to water of 2 Gy, were mailed to all participating clinics. TLD irradiations were performed with a 6 MV linear accelerator and (60)Co photon beams. The deviations from the TL readings of UWRCL were calculated. Discrepancies inside the limits of ±5 % between the participant-stated dose, and the TLD-measured dose were considered acceptable. One out of 10 beams checked was outside this limit, with a difference of 5.8 %.     

Fate of Listeria innocua during production and ripening of smeared hard cheese made from raw milk

The fate of 2 different Listeria innocua strains was analyzed during the production and ripening of smeared raw milk Greyerzer cheese (Gruyère). These strains were used as surrogates for the pathogenic Listeria monocytogenes, as they are physiologically very similar. Bacterial cells were added to the cheese milk at levels of 10⁵ cfu/mL. During the first 24 h of cheese making, the number of the test strains decreased to a level of below 10² cfu/g. Obviously, the cooking temperature of 56°C and the subsequent slight temperature decrease to 50°C within 70 min contributed to a distinct reduction of Listeria counts. The counts in the cheese cores did not exceed 10³ cfu/g within 12 wk of cheese ripening and Listeria was not detectable after 24 wk. In contrast to the cores of the cheeses of the 4 batches in this study, their rinds always contained a high listerial load of approximately 10⁶ to 10⁸ cfu/g throughout the entire ripening period. The smeared surface showed an increase of pH to alkaline values, corresponding to smear microbiota development. Coryneforms and Staphylococcus counts were stable at >10⁷ cfu/cm² over 175 d, whereas yeast counts decreased to about 10⁵ cfu/cm² at the end of ripening. The study shows that the smear culture had no noticeable anti-listerial potential. When removing the rind or portioning such smeared cheese loaves with a cutting device, a postprocess contamination of the core might occur, thus presenting a major hygienic risk.     

Frictional mortar contact for finite deformation problems with synthetic contact kinematics

In this paper we present a mortar based method, for frictional two dimensional contact problems. It is based on the work by Tur et al. (Comput Methods Appl Mech Eng 198(37–40):2860–2873, 2009) and uses the same concentrated integration scheme as well as a non regularized tangential contact formulation based on Lagrange multipliers only. We abstract the contact kinematics to a rather synthetic formulation. Therefore we are able to use two different methods of defining the normal field on the discretized surface normal: The popular method of averaged non-mortar side normal and the rather simple non continuous mortar side normal field. The problem is solved with a fixed point Newton–Raphson procedure and for both normal fields the full linearizations are derived. With numerical examples we show the performance of the more concise formulation of the non averaged non continuous mortar side normal field.     

Evidence for Contributions of Interactions of Constituents to the Anti-Inflammatory Activity of Hypericum Perforatum

Hypericum perforatum (Hp) extracts contain many different classes of constituents including flavonoids and biflavonoids, phloroglucinols, naphthodianthrones, caffeic acid derivatives, and unknown and/or unidentified compounds. Many constituents may be responsible for the anti-inflammatory activity of Hp including quercetin and derivatives, hyperforin, pseudohypericin, and amentoflavone. In line with antidepressant data, it appears that the interactions of constituents may be important for the anti-inflammatory activity of Hp. Interactions of constituents, tested in bioavailability models, may explain why synergistic mechanisms have been found to be important for antidepressant and antiproliferative bioactivities. This review highlights the relationship among individual constituents and the anti-inflammatory activity of Hp extracts and proposes that interactions of constituents may be important for the anti-inflammatory activity of botanical extracts, although the exact mechanisms of the interactions are still unclear.     

CO Oxidation over Au/TiO2–Carbon Catalysts: The Effect of Thermal Treatment, Stability and TiO2 Support Structure

The effect of thermal treatment on the catalyst structure and the CO oxidation performance of a Au/TiO₂ catalyst supported on a carbon composite material has been studied. X-ray absorption spectroscopy shows that the carbon composite stabilises the TiO₂ and prevent agglomeration of the particles. The activity measurements show that both Au and TiO₂ need to be present in order to obtain catalytic activity. The catalytic performance was found to be strongly affected by thermal treatments of the active phase prior to the reaction. The thermal treatments have an effect on the ordering of the TiO₂ structure, and on the CO oxidation activity. Heat treatment after Au deposition has a positive effect on the CO oxidation performance. This is attributed to the introduction of a stronger interaction between the oxide and Au which improves the catalytic activity. This also indicates that the TiO₂ support and the Au–TiO₂ interface play important roles in the CO oxidation reaction.     

Free electron laser ablation of urinary calculi: an experimentalstudy

Infrared laser ablation of urinary calculi was investigated as a function of wavelength to determine the relation of ablation threshold fluences, ablation depths, and optical absorption. A simple photothermal ablation model was employed to examine this relationship. Human urinary calculi composed of >95% uric acid, >95% cystine, >95% calcium oxalate monohydrate (COM), and >90% magnesium ammonium phosphate hexahydrate (MAPH) were used. Various wavelengths between 2.1 and 6.5 μm were selected to perform threshold fluence and ablation depth measurements. The laser source for this study was the tunable pulsed infrared free electron laser (FEL) at Vanderbilt University. Experimental results indicated a correlation of threshold fluence and ablation depth to the optical absorption properties of the calculi. When calculus optical absorption increased, the threshold fluences decreased. Although the ablation depths increased with calculus optical absorption, results indicated that in certain calculi the ablation depth was affected by optical attenuation through the ablation plume. These observations were in agreement with the photothermal ablation model, but fractures in striated calculi at higher optical absorptions indicated the contribution of a photomechanical mechanism     

Effect of silica fume on the plastic shrinkage and pore water pressure of high-strength concretes

High-strength concrete is more sensitive to cracking before and during setting than normal concrete is. The intention with the present investigation was to provide more information about the parameters responsible for this, and which can contribute to the fundamental understanding, of the problem, and in particular of the influence of silica fume. Four concretes were tested, all with water to binder ratio of 0.40, and with 0, 5, 10 and 15% silica fume. The settlement, shrinkage and pore water pressure were measured for all concretes when exposed to moisture sealed condition or 50% RH. The results indicate that the silica fume content does not significantly influence plastic shrinkage and settlement at these conditions. Another important observation was an immediate respond on external drying, which involves a low tensile strain capacity. The strain capacity seems to depend on the measured pore water pressure, which reflects the tensile stress in the pore, water. The pore water pressure close to the exposed surface became negative less than half an hour of exposure at 50% RH. The effect of silica fume content was not pronounced except for the one with 15% which showed a significantly higher rate of pressure decrease than the other concretes.     

希林格利奥酒庄 奥地利布尔根兰

正总体上,希林格利奥酒庄设计将风景、葡萄种植和建筑三种元素融为一体。希林格利奥酒庄位于乔伊斯葡萄园中央,地下空间十分深邃,四周植被茂盛,其特殊的位置显得敏感又有些困难,建筑师需要考虑如何让希林格利奥酒庄风光迷人。在旧有地窖里的走道的基础上,我们特别地利用了地下环境,将展示区的悬挑梁设计成可见的小标记,夜晚月光透过大窗户便会照亮这些小印记。生产大厅上端有8个椎体,这些椎体面朝北,呈对角线排     

Immunoreactivity of PMP-22, P0, and other 19 to 28 kDa glycoproteins in peripheral nerve myelin of mammals and fish with HNK1 and related antibodies

Mammalian peripheral nervous system (PNS) myelin contains several glycoproteins with molecular weights of 19 to 28 kDa, including the major 28 kDa P0 glycoprotein and a recently cloned protein called PMP-22. Some glycoproteins in this M(r) range in humans, cats and some other mammals react with HNK1, a mouse monoclonal antibody that identifies a carbohydrate epitope shared between the immune system and a number of adhesion proteins in the nervous system. A variety of antibodies to P0, PMP-22, and the carbohydrate determinants reacting with HNK1 were used to characterize immunochemically these 19 to 28 kDa glycoproteins of cat PNS myelin. The HNK1-reactive components include P0 and two slightly smaller 23 to 26 kDa proteins that are immunologically related to P0. However, HNK1 reacts most strongly with a lower molecular weight glycoprotein that does not react with the antibodies to P0 and was identified as PMP-22. Since the carbohydrate structure reacting with HNK1 is generally expressed on adhesion molecules, this result suggests that PMP-22 may function in cell-cell or membrane-membrane interactions. Furthermore, the related human anti-MAG monoclonal IgM antibodies from patients with neuropathy also react strongly with PMP-22, suggesting that it may be a target antigen in the pathogenesis of this disease. Purified PNS and CNS myelin from bony fish (toadfish and trout) were also shown to contain major glycoproteins, in the same 19 to 28 kDa M(r) range, that react very strongly with HNK1. It is shown that fish myelin has major proteins of this size that are immunologically and structurally related to mammalian P0, and it is demonstrated here that one of the strongly HNK1-positive proteins reacted well with an antiserum raised to bovine P0. The presence of high levels of the adhesion-related HNK1 epitope on these major myelin proteins of fish suggests that this carbohydrate structure may have played a role in the molecular evolution of myelin.