Flexible multibody impact simulations based on the isogeometric analysis approach

Multibody System Dynamics - Usually detailed impact simulations are based on isoparametric finite element models. For the inclusion in multibody dynamics simulation, e.g., in the framework of the...     

Photopinking of white PVC products: A kind of magic

Short‐term photoeffects like photograying, photobluing, and photopinking are well‐known in the polyvinyl chloride (PVC) industry. While photobluing and photograying are well understood regarding their mechanisms of occurrences there are still some missing facts. Furthermore, there are three different types of pinking effects with three different mechanisms and consequently three different ways to avoid this discoloration of mainly white PVC products. The recent paper is focusing on one hand of the photopinking of PVC products, which are stabilized with nitrogen‐containing, organic stabilizer whose mechanism was not explained until today. In the past there was neither a method to analyze nor to simulate this type of photopinking. However, the discovery of a charge transfer complex between the nitrogen‐containing substance and nitric acid gave the basic idea to investigate this phenomenon by photo‐electromotive force investigations of titanium dioxide and the nitrogen‐containing substance and by cyclo voltammetry. On the other hand, the authors are attempting to supplement the findings regarding the mechanism of the photopinking of white window profiles which are lead stabilized and which were installed north‐facing in cooler areas with high humidity. Again, a simulation and the analysis of the color‐giving substance of the north‐faced photopinking were impossible in the past. The authors assumed that antioxidants might play an important rule for this type of discoloration. They supported their hypothesis by synthesis of quinoid structures based on antioxidants, spectroscopic investigations, artificial weathering, and electrochemical calculations. J. VINYL ADDIT. TECHNOL., 24:195–207, 2018. © 2016 Society of Plastics Engineers     

Probing Human Telomeric DNA and RNA Topology and Ligand Binding in a Cellular Model by Using Responsive Fluorescent Nucleoside Probes

The development of biophysical systems that enable an understanding of the structure and ligand‐binding properties of G‐quadruplex (GQ)‐forming nucleic acid sequences in cells or models that mimic the cellular environment would be highly beneficial in advancing GQ‐directed therapeutic strategies. Herein, the establishment of a biophysical platform to investigate the structure and recognition properties of human telomeric (H‐Telo) DNA and RNA repeats in a cell‐like confined environment by using conformation‐sensitive fluorescent nucleoside probes and a widely used cellular model, bis(2‐ethylhexyl) sodium sulfosuccinate reverse micelles (RMs), is described. The 2′‐deoxy and ribonucleoside probes, composed of a 5‐benzofuran uracil base analogue, faithfully report the aqueous micellar core through changes in their fluorescence properties. The nucleoside probes incorporated into different loops of H‐Telo DNA and RNA oligonucleotide repeats are minimally perturbing and photophysically signal the formation of respective GQ structures in both aqueous buffer and RMs. Furthermore, these sensors enable a direct comparison of the binding affinity of a ligand to H‐Telo DNA and RNA GQ structures in the bulk and confined environment of RMs. These results demonstrate that this combination of a GQ nucleoside probe and easy‐to‐handle RMs could provide new opportunities to study and devise screening‐compatible assays in a cell‐like environment to discover GQ binders of clinical potential.     

Native Chemical Ligation Directed by Photocleavable Peptide Nucleic Acid (PNA) Templates

A novel peptide–peptide ligation strategy is introduced that has the potential to provide peptide libraries of linearly or branched coupled fragments and will be suited to introduce simultaneous protein modifications at different ligation sites. Ligation is assisted by templating peptide nucleic acid (PNA) strands, and therefore, ligation specificity is solely encoded by the PNA sequence. PNA templating, in general, allows for various kinds of covalent ligation reactions. As a proof of principle, a native chemical ligation strategy was elaborated. This PNA‐templated ligation includes easy on‐resin procedures to couple linkers and PNA to the respective peptides, and a traceless photocleavage of the linker/PNA oligomer after the ligation step. A 4,5‐dimethoxy‐2‐nitrobenzaldehyde‐based linker that allowed the photocleavable linkage of two bio‐oligomers was developed.     

Porous ceramic bone scaffolds for vascularized bone tissue regeneration

Hydroxyapatite scaffolds with a multi modal porosity designed for use in tissue engineering of vascularized bone graft substitutes were prepared by three dimensional printing. Depending on the ratio of coarse (mean particle size 50 microm) to fine powder (mean particle size 4 microm) in the powder granulate and the sintering temperature total porosity was varied from 30% to 64%. While macroscopic pore channels with a diameter of 1 mm were created by CAD design, porosity structure in the sintered solid phase was governed by the granulate structure of the printing powder. Scaffolds sintered at 1,250 degrees C were characterized by a bimodal pore structure with intragranular pores of 0.3-0.4 microm and intergranular pores of 20 microm whereas scaffolds sintered at 1,400 degrees C exhibit a monomodal porosity with a maximum of pore size distribution at 10-20 microm. For in-vivo testing, matrices were implanted subcutaneously in four male Lewis rats. Scaffolds with 50% porosity and an average pore size of approximately 18 microm were successfully transferred to rats and vascularized within 4 weeks.     

Ozone Differentially Affects Perception of Plant Volatiles in Western Honey Bees

Floral scents play a key role in mediating plant-pollinator interactions. Volatile organic compounds (VOCs) emitted by flowers are used by flower visitors as olfactory cues to locate flowers, both from a distance and at close range. More recently it has been demonstrated that reactive molecules such as ozone can modify or degrade VOCs, and this may impair the communication between plants and their pollinators. However, it is not known whether such reactive molecules also may affect the olfactory system of pollinators, and thus not only influence signal transmission but perception of the signal. In this study, we used electroantennographic measurements to determine the effect of increased levels of ozone on antennal responses in western honey bees (Apis mellifera L.). Linalool and 2-phenylethanol, both known to be involved in location of flowers by the bees, and (Z)-3-hexenyl acetate, a widespread green leaf volatile also detected by bees, were used. The results showed that ozone affected antennal responses to the different substances differently. Ozone decreased antennal responses to (Z)-3-hexenyl acetate, whereas responses to linalool and 2-phenylethanol were not influenced by ozone. Overall, the study does not provide evidence that pollination by honey bees is impaired by damage in the olfactory system of the bees caused by increased levels of ozone, at least when linalool and 2-phenylethanol are the attractive signals. However, the results also suggest that ozone can change the overall perception of an odor blend. This might have negative effects in pollination systems and other organismic interactions mediated by specific ratios of compounds.     

Spectral characterization of eucalyptus wood

The main difficulties in wood and pulp analyses arise principally from their numerous components with different chemical structures. Therefore, the basic problem in a specific analytical procedure may be the selective separation of the main carbohydrate-derived components from lignin due to their chemical association and structural coexistence. The processing of the wood determines some structural modification in its components depending on the type of wood and the applied procedure. Fourier transform infrared (FT-IR) spectrometry and X-ray diffraction have been applied to analyze Eucalyptus g. wood chips and unbleached and chlorite-bleached pulp. The differences between samples have been established by examination of the spectra of the fractions obtained by successive extraction (acetone extractives, acetone free extractive samples, hemicelluloses, and lignins) by evaluating the derivative spectra, band deconvolution, etc. The energy and the hydrogen bonding distance have been evaluated. The relationship between spectral characteristics and sample composition has been established, as well as the variation of the degree of crystallinity after pulping and bleaching. The integral absorption and lignin/carbohydrate ratios calculated from FT-IR spectra of the IR bands assigned to different bending or stretching in lignin groups are stronger in the spectrum of eucalyptus chips than those from brown stock (BS) pulp spectra because of the smaller total amount of lignin in the latter. FT-IR spectra clearly show that after chlorite bleaching the structure of the wood components is partially modified or removed. Along with FT-IR data, the X-ray results confirmed the low content of lignin in the pulp samples by increasing the calculated values of the crystalline parameters. It was concluded that FT-IR spectroscopy can be used as a quick method to differentiate Eucalyptus globulus samples.     

Phosphorothiolate analogues of phosphatidylinositols as assay substrates for phospholipase C

Accurate measurement of phosphatidylinositol-specific phospholipase C (PI-PLC) activity is important in view of the key role of this enzyme in signal-transduction pathways. In this work we synthesized enantiomerically pure phosphorothiolate analogues of all natural PI-PLC substrates, including those of phosphatidylinositol 4,5-bisphosphate (PI-4,5-P2), 4-phosphate (PI-4-P), 5-phosphate (PI-5-P) and unphosphorylated PI, in both long- and short-chain versions. The enzymatic cleavage of these substrates produces thiol analogues of diacyl glycerol, which can be quantified by UV absorbance after treatment with dipyridyl disulfide. The monodisperse dihexanoyl derivatives are suitable substrates for PI-PLC assay: they give rise to high enzyme activity, and provide excellent linear kinetic responses. For all substrates, we found a good linear correlation between the reaction rate and the amount of enzyme; this indicated the suitability of this assay for enzyme quantification. The short-chain substrates enable the enzyme specificity with variously phosphorylated inositol head groups to be established--unobstructed by substrate aggregation, "scooting" kinetics on micelles, or surface dilution effects. The kinetic results indicated allosteric behavior of PLC for all substrates tested. We found that substrates phosphorylated at the inositol 4-position (phosphorothiolate analogues of PI-4,5-P2 and PI-4-P) displayed very similar kinetic properties, and were cleaved with approximately 20- to 30-fold higher activity than the 4-nonphosphorylated substrates (analogues of PI-5-P and PI). Hence it appears that interactions between the enzyme and the 4-phosphate group of the substrate, but not its 5-phosphate group, is important for PI-PLC catalysis. In addition, the binding affinities of all four substrate types were found to be quite similar; this indicates that the energy of enzyme interaction with the 4-phosphate group is directed almost entirely to catalysis.     

A randomized, multicenter trial of weight-adjusted intravenous heparin dose titration and point-of-care coagulation monitoring in hospitalized patients with active thromboembolic disease. Antithrombotic Therapy Consortium Investigators

BACKGROUND: Therapy with intravenous unfractionated heparin improves clinical outcome in patients with active thromboembolic disease, but achieving and maintaining a therapeutic level of anticoagulation remains a major challenge for clinicians. METHODS: A total of 113 patients requiring heparin for at least 48 hours were randomly assigned at 7 medical centers to either weight-adjusted or non-weight-adjusted dose titration. They were separately assigned to either laboratory-based or point-of-care (bedside) coagulation monitoring. RESULTS: Weight-adjusted heparin dosing yielded a higher mean activated partial thromboplastin time (aPTT) value 6 hours after treatment initiation than non-weight-adjusted dosing (99.9 vs 78.8 seconds; P =.002) and reduced the time required to exceed a minimum threshold (aPTT >45 seconds) of anticoagulation (10.5 vs 8.6 hours; P =.002). Point-of-care coagulation monitoring significantly reduced the time from blood sample acquisition to a heparin infusion adjustment (0.4 vs 1.6 hours; P <.0001) and to reach the therapeutic aPTT range (51 to 80 seconds) (16.1 vs 19.4 hours; P =.24) compared with laboratory monitoring. Although a majority of patients participating in the study surpassed the minimum threshold of anticoagulation within the first 12 hours and reached the target aPTT within 24 hours, maintaining the aPTT within the therapeutic range was relatively uncommon (on average 30% of the overall study period) and did not differ between treatment or monitoring strategies. CONCLUSIONS: Weight-adjusted heparin dosing according to a standardized titration nomogram combined with point-of-care coagulation monitoring using the BMC Coaguchek Plus System represents an effective and widely generalizable strategy for managing patients with thromboembolic disease that fosters the rapid achievement of a desired range of anticoagulation. Additional work is needed, however, to improve on existing patient-specific strategies that can more effectively sustain a therapeutic state of anticoagulation.