Microstructural and corrosion resistance characterisation of NiTi shape memory alloy modified at low-temperature plasma with carbon coatings produced via RFCVD and IBAD methods

ABSTRACT

NiTi shape memory alloy, both before and after low-temperature oxynitriding under glow discharge conditions combined with the production of a nano-sized outer carbon coating, was investigated. The study compares two types of carbon coatings: produced via the RFCVD (radio frequency chemical vapour deposition) and IBAD (ion beam-assisted deposition) methods. The latter was also enriched by randomly distributed silver nanoparticles. The study showed slight changes in roughness parameters and increased corrosion resistance after surface treatment processes. The largest impedance module and corrosion potential and the smallest density of corrosion current were achieved for samples with a carbon coating produced via the RFCVD process. The presented surface modifications using hybrid processes can extend the use of NiTi alloy in medicine due to the increased biocompatibility.     

Molecular Pathways of Cellular Senescence and Placental Aging in Late Fetal Growth Restriction and Stillbirth

Abnormally accelerated, premature placental senescence plays a crucial role in the genesis of pregnancy pathologies. Abnormal growth in the third trimester can present as small for gestational age fetuses or fetal growth restriction. One differs from the other by the presence of signs of placental insufficiency and the risk of stillbirth. The majority of stillbirths occur in normally grown fetuses and are classified as “unexplained”, which often leads to conclusions that they were unpreventable. The main characteristic of aging is a gradual decline in the function of cells, tissues, and organs. These changes result in the accumulation of senescent cells in mitotic tissues. These cells begin the aging process that disrupts tissues’ normal functions by affecting neighboring cells, degrading the extracellular matrix, and reducing tissues’ regeneration capacity. Different degrees of abnormal placentation result in the severity of fetal growth restriction and its sequelae, including fetal death. This review aims to present the current knowledge and identify future research directions to understand better placental aging in late fetal growth restriction and unexplained stillbirth. We hypothesized that the final diagnosis of placental insufficiency can be made only using markers of placental senescence.     

Multi-layered graphenic structures as the effect of chemical modification of thermally treated anthracite

Graphenic materials have been produced from thermally treated highly metamorphosed carbon material – anthracite using two different methods: (1) the improved Hummers method followed by thermal reduction and (2) cycloaddition of azomethine ylide. Distinct differences were found between both anthracite-derived graphenic materials. The oxidation Hummers process resulted in a wide variety of oxygen functional groups incorporated into the carbon layers, while subsequent thermal reduction caused separation of graphene sheets but reduced the oxygen moieties. The cycloaddition of azometine ylide led to the formation of functionalized graphene sheets containing mostly 3,4-bonded N-methyl-2-(3,4-dihydroxyphenyl)pyrrolidine groups. The first attempts of application of anthracite-derived fillers to epoxy composites showed the improvement of their mechanical and viscoelastic properties, comparable to composites with graphene nanofillers.     

Energy Analysis on Use of Air and Superheated Steam as Drying Media

The physical properties of air and superheated steam were analysed in a range of temperature applied in paper and paperboard drying processes. On the basis of tests carried out on a pilot stand the values of energy indices for air and steam drying processes are compared. With the drying media temperature as T_m = 300°C, nozzle velocity v= 60m/s and using the Huang and Mujumdar model as well as relationships given by Chance a compartive analysis of the results has been carried out Variation of several indices in the range of temperatures 100-600°C and various nozzle velocities was studied.     

Psychogenic, neurogenic, and systemic stressor effects on plasma corticosterone and behavior: Mouse strain-dependent outcomes.

The effects of several stressors were assessed in inbred strains of mice, BALB/cByJ and C57BL/6ByJ, thought to be differentially reactive to stressors. Behavioral reactivity was greater in BALB/cByJ mice with respect to open-field emergence, step-down responding, response to a predator (rat) or to fox urine odor. Neurogenic insults (e.g., footshock, forced swim, restraint) and a systematic stressor (intraperitoneal interlukin-1β treatment) likewise provoked a greater rise of plasma corticisterone in the BALB/cByJ mice. Psychogenic stressors (e.g., novel open-field exposure, acoustic startle stimuli) also enhanced plasma corticosterone to a greater extent in BALB/cByJ mice, but such an outcome was not apparent following predator-related cues. In appears that whereas stressor reactivity and adrenal glucorticoid release may be exaggerated in BALB/cByJ mice, such effects may be dependent on the specific characteristic of the stressor situation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Non-structural protein 3 of hepatitis C virus inhibits phosphorylation mediated by cAMP-dependent protein kinase

Inspection of the amino acid sequence of the non-structural region of the hepatitis C virus (HCV) gene product reveals a sequence of 14 amino acids, Arg1487-Arg-Gly-Arg-Thr-Gly-Arg-Gly-Arg-Arg-Gly-Ile-Tyr-Arg1500 , located in the non-structural protein, NS3. This sequence is highly similar to the inhibitory site of the heat-stable inhibitor of cAMP-dependent protein kinase (PKA) and to the autophosphorylation site in the hinge region of the PKA type II regulatory domain. A synthetic peptide that corresponds to the HCV sequence above and a set of shorter analogues act as competitive inhibitors of PKA. A 43.5-kDa fragment of NS3 that consists of residues 1189-1525 of the HCV polyprotein inhibits PKA in a similar range to the investigated synthetic peptides. In contrast to the short peptides, which show competitive inhibition, HCV-polyprotein-(1189-1525) influences PKA in a mixed-inhibition-type manner. A possible mechanism explaining these differences is the formation of complexes that consist of the protein substrate, the enzyme and the HCV-polyprotein-(1189-1525). Binding studies with PKA and the non-hydrolysable ATP analogue [14C]fluorosulfonylbenzoyladenosine and [3H]cAMP do not reveal any influence of the short HCV-derived peptides or HCV-polyprotein-(1189-1525) upon the affinity of PKA for these nucleotides. The complex interactions of the NS3 fragments could influence one of the most important signal pathways of the cell and, therefore, could possibly provide new pathological mechanisms for HCV infections of liver.     

Modeling enzymatic reactions involving transition metals

High-accuracy quantum chemistry has now been applied for almost 10 years to biological problems involving transition metal active sites. The leading theoretical method is hybrid density functional theory (DFT), usually with the B3LYP functional. The chemical models vary in size, commonly from 30 to 100 atoms treated fully quantum mechanically. Two schools exist, one using the smallest possible adequate models and the other using as large models as possible and sometimes including the entire enzyme by combining quantum mechanics with molecular mechanics. In our group, we have found that the latter approach, which is much more time-consuming and error prone, is seldom needed. In this Account, methods and models will be described and examples of recent applications given. The examples are chosen to illustrate trends and to show cases where theory has predicted new mechanisms not suggested previously.