Tangible nanocomposites with diverse properties for heart valve application

Cardiovascular disease claims millions of lives every year throughout the world. Biomaterials are used widely for the treatment of this fatal disease. With the advent of nanotechnology, the use of nanocomposites has become almost inevitable in the field of biomaterials. The versatile properties of nanocomposites, such as improved durability and biocompatibility, make them an ideal choice for various biomedical applications. Among the various nanocomposites, polyhedral oligomeric silsesquioxane-poly(carbonate-urea)urethane, bacterial cellulose with polyvinyl alcohol, carbon nanotubes, graphene oxide and nano-hydroxyapatite nanocomposites have gained popularity as putative choices for biomaterials in cardiovascular applications owing to their superior properties. In this review, various studies performed utilizing these nanocomposites for improving the mechanical strength, anti-calcification potential and hemocompatibility of heart valves are reviewed and summarized. The primary motive of this work is to shed light on the emerging nanocomposites for heart valve applications. Furthermore, we aim to promote the prospects of these nanocomposites in the campaign against cardiovascular diseases.     

The effect of vibrational relaxation on the discharge coefficient of critical flow venturis

This paper identifies a new mechanism that can affect the discharge coefficient of critical nozzle flows. Specifically, vibrational relaxation effects are demonstrated to significantly influence the discharge coefficient of selected gases in critical venturi flows. This phenomenon explains why certain gases — like carbon dioxide — exhibit calibration characteristics that differ significantly from other gases (e.g., N₂, O₂, Ar, He, and H₂). A mathematical model is developed which predicts this behavior, and vibrational non-equilibrium effects are further substantiated by two independent experiments.     

Modeling nitrous oxide emissions from tile-drained winter wheat fields in Central France

Modeling nitrous oxide (N₂O) emissions from agricultural soils is still a challenge due to influences of artificial management practices on the complex interactions between soil factors and microbial activities. The aims of this study were to evaluate the process-based DeNitrification-DeComposition (DNDC, version 9.5) model and modified non-linear empirical Nitrous Oxide Emission (NOE_V2) model with weekly N₂O flux measurements at eight sites cropped with winter wheat across a tile-drained landscape (around 30-km²) in Central France. Adjustments of the model default field capacity and wilting point and the optimum crop production were necessary for DNDC95 to better match soil water content and crop biomass yields, respectively. Multiple effects of varying soil water and nitrate contents on the fraction of N₂O emitted through denitrification were added in NOE_V2. DNDC95 and NOE_V2 successfully predicted background N₂O emissions and fertilizer-induced emission peaks at all sites during the experimental period but overestimated the daily fluxes on the sampling dates by 54 and 25 % on average, respectively. Cumulative emissions were slightly overestimated by DNDC95 (4 %) and underestimated by NOE_V2 (15 %). The differences between evaluations of both models for daily and cumulative emissions indicate that low frequency measurements induced uncertainty in model validation. Nonetheless, our validations for soil water content with daily resolution suggest that DNDC95 well represented the effect of tile drainage on soil hydrology. The model overestimated soil ammonium and nitrate contents mostly due to incorrect nitrogen partitioning when urea ammonium nitrate solution was applied. The performance of the model would be improved if DNDC included the canopy interception and foliar nitrogen uptake when liquid fertilizer was sprayed over the crops.     

In situ TEM studies of tribo-induced bonding modifications in near-frictionless carbon films

Direct in situ TEM evidence is presented for a mechanically-induced increase in sp² bond content in the tribolayers formed on near-frictionless carbon (NFC) films. An in situ TEM nanomanipulation holder is used to perform sliding experiments between a nano-sized tungsten probe and electron transparent NFC samples. Electron energy loss spectra (EELS) were acquired between sliding events to show an incremental increase in the 1s-π peak, suggesting that a graphitization-like process occurs which can lead to a change in the tribological performance of a variety of hard carbon films. Presently, this behavior is only observed for one of the two varieties of NFC, while supporting TEM imaging evidence is in qualitative agreement with macroscopic friction and wear behavior.     

Reliability Consequences of Liberalization in the Electricity Sector: Existing Research and Remaining Questions

The generation, transmission and distribution of energy are among the most vital prerequisites for the functioning of modern societies. Since the early 1990s, the energy sectors of Western societies have been through a process of institutional restructuring, where large state‐owned monopolies have been divided into several independent organizations. Also, the organizations responsible for providing energy, like most other industrial organizations today, have made increasing use of outsourcing strategies. Taken together, these developments represent a significant change in the framework conditions for the energy sector. How this development affects the reliability of energy supply and the capacity for effective crisis management is an important question from both a research perspective as well as from a societal point of view. This article reviews the current literature on these issues, aiming to identify research gaps in the existing literature. Several research gaps are identified.     

Monolithic precolumns as efficient tools for guiding the design of nanoparticulate drug-delivery formulations

The development of nanomedicines for improved diagnosis and treatment of diseases is pushing current analytical methods to their limits. More efficient, quantitative high-throughput screening methods are needed to guide the optimization of promising nanoparticulate drug delivery formulations. In response to this need, we present herein a novel approach using monolithic separation media. The unique porosity of our capillary monolithic precolumns allows the direct injection and online removal of protamine-oligonucleotide nanoparticles ("proticles") without column clogging, thus avoiding the need for time-consuming off-line sample workup. Furthermore, ring-opening metathesis polymerization (ROMP)-derived monoliths show equivalent preconcentration efficiency for the target drug vasoactive intestinal peptide (VIP) as conventional particle-packed precolumns. The performance of the ROMP-derived monolithic precolumns was constant over at least 100 injections of crude proticle-containing and 300 injections of highly acidic samples. Applying a validated LC-MS/MS capillary monolithic column switching method, we demonstrate the rapid determination of both drug load and in vitro drug release kinetics of proticles within the critical first 2 h and investigate the stability of VIP-loaded proticles in aqueous storage medium intended for inhalation therapy.     

On the mode of action of N-phenyl-2-naphthylamine in plants

N-phenyl-2-naphthylamine, a sediment contaminant previously identified as a major toxicant of site-specific importance was investigated for its mode of toxic action. From short-term bioassays with daphnids, fish eggs, bacteria, and algae it appears that this compound has specific phytotoxic properties at concentrations below 100 microg/L, which cannot be explained assuming an unspecific narcosis type of action in plants. Also, hydroxy-, nitro-, and methylderivatives show clear excess toxicity as compared to baseline toxic effects. Of several plant-specific growth and development processes investigated, only photosynthesis could be demonstrated to be affected at short exposure times and low concentrations. Disturbance of primary photosynthetic reactions such as oxygen evolution and fluorescence quenching, however, becomes only apparent after 2-3 h of exposure, which is in sharp contrast to known specific inhibitors targeting processes such as electron transport or ATP production. This, and concentration-time-effect modeling lead to the suggestion that N-phenyl-2-naphthylamine acts intracellular as a reactive compound in cell membranes producing irreversible, and thus cumulative, damage over time in algae. The effects may become first apparent in membrane-rich compartments such as the algal chloroplast.     

分散剂净化处理泄漏石油重新受到重视

在工业上，很少有化学品的用途比表面活性剂更广泛，化学分散剂是表面活性剂中的一类多作用品种，正日益广泛地应用于泄漏石油净化到工业处理乃至油漆，涂料和个人用品中固体的稳定化应用等。     

Effect of recycled polypropylene on polypropylene/high‐density polyethylene blends

The effect of recycled PP on incompatible blends of virgin polypropylene (PP) and high‐density polyethylene (HDPE) was studied. Recycled PP from urban solid waste was extracted with methyl ethyl ketone and the compatibilizing action of the product before and after extraction was examined. The characterization of the recycled PP was performed by FTIR, NMR, and DSC analyses. Mechanical properties of the blends were evaluated. The results showed partial compatibility of the blend components, reflected in the improvement of the tensile strength and elongation. Best results were achieved by the addition of extracted recycled PP on the 50/50 PP/HDPE blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1305–1311, 2001