Polymerization of ionic monomers in polar solvents: kinetics and mechanism of the free radical copolymerization of acrylamide/acrylic acid

A precise data set describing the kinetics of the free radical copolymerization of acrylamide/acrylic acid (AM/AA) in the range of low total monomer concentration as a function of the pH, total monomer concentration, initiator concentration, and comonomer ratio is presented. Strong impact on the reactivity ratios has been identified for the pH and total monomer concentration. Specifically, at constant total monomer concentration of 0.4 mol/l and T=313 K the reactivity ratio of AM increases from 0.54 at pH 1.8 to 3.04 at pH 12. Contrarily, the reactivity ratio of AA decreases from 1.48 to 0.32. The crossover occurs at pH≈4.2. Electrostatic effects due to the variation of the degree of ionization of AA are primarily suggested to influence the kinetics. When the total monomer concentration increases from 0.2 to 0.6 mol/l at constant pH=12, the reactivity ratios of AM and AA decrease from 4.01 to 2.13 and increase from 0.25 to 0.47, respectively. Reduction of electrostatic repulsion between the ionized monomer AA and partially charged growing polymer chain ends due to higher ionic strength at higher total monomer concentration serves as explanation of the effect. The precise data set is the prerequisite for a novel approach to calculate copolymer compositions in case of variable monomer reactivity.     

Are max-specified infant facial expressions during face-to-face interaction consistent with differential emotions theory?

Differential emotions theory (DET) proposes that infant facial expressions of emotions are differentiated. To test this hypothesis, the authors examined infant facial expressions longitudinally at 2, 4, and 6 mo of age during face-to-face play and a "still-face" interaction with their mothers. Infant expressions were coded using the Maximally Discriminative Facial Movement Coding System (Max). Consistent with DET, discrete positive expressions occurred more of the time and were of longer duration than blended expressions of positive affect. Contrary to DET, at no age did the proportions or durations of discrete and blended negative expressions differ, and they showed different patterns of developmental change. One is led to either reject or revise DET or else question the adequacy of the Max system. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrochemical study of 7α,12,20-O-trimethyl-conacytone in acetonitrile

An electrochemical study of the electroreduction in anhydrous acetonitrile of 7α,12,20-O-trimethyl-conacytone, an abietane quinoid diterpene derivative from the natural product 7α-O-methyl-conacytone, showed two reduction signals. At the first reduction step, fast chemical reactions involving the loss of the methoxyl group located at C-7 with simultaneous regeneration of the quinoid moiety were observed. This electrogenerated quinone is reduced again, at the same potential used with the former quinone, resulting in a two-electron peak. These results were obtained by cyclic voltammetry and double-step chronoamperometry experiments. The electrolysis under methylating conditions of 7α-O-methyl-conacytone, at potential values of the second electron transfer, generates as major products, methoxy-hydroquinone, where the methoxy group at C-7 is lost, which is in agreement with the proposed mechanism. Therefore, the second reduction signal was attributed to the reduction of semiquinone intermediates by a mechanism not elucidated.     

Degradation of lincomycin in aqueous medium: Coupling of solar photocatalysis and membrane separation

The photocatalytic oxidation of a common antibiotic, the lincomycin was carried out in aqueous suspensions of polycrystalline TiO₂ Degussa P25 irradiated by sunlight. In order to improve the performance of the lincomycin degradation a hybrid system consisting of a solar photoreactor with the photocatalyst in suspension coupled with a membrane module, used to confine both photocatalyst and pollutants in the reaction environment, was tested.A preliminary study was carried out in order to determine some kinetics parameters of the drug photodegradation. The influence of initial substrate concentration on the lincomycin photooxidation rate was investigated. The photooxidation rate follows a pseudo-first order kinetics with respect to the lincomycin concentration under the used experimental conditions. The presence of the membrane reactor allows the catalyst separation and to operate in continuous mode as the membranes rejection for lincomycin and its oxidation products was quite high.     

Randomized range-maxima in nearly-constant parallel time

Given an array ofn input numbers, therange-maxima problem is that of preprocessing the data so that queries of the type what is the maximum value in subarray [i..j] can be answered quickly using one processor. We present a randomized preprocessing algorithm that runs inO(log^* n) time with high probability, using an optimal number of processors on a CRCW PRAM; each query can be processed in constant time by one processor. We also present a randomized algorithm for a parallel comparison model. Using an optimal number of processors, the preprocessing algorithm runs inO( (n)) time with high probability; each query can be processed inO ( (n)) time by one processor. (As is standard, (n) is the inverse of Ackermann function.) A constant time query can be achieved by some slowdown in the performance of the preprocessing stage.     

Ivabradine Induces Cardiac Protection against Myocardial Infarction by Preventing Cyclophilin-A Secretion in Pigs under Coronary Ischemia/Reperfusion

In response to cardiac ischemia/reperfusion, proteolysis mediated by extracellular matrix metalloproteinase inducer (EMMPRIN) and its secreted ligand cyclophilin-A (CyPA) significantly contributes to cardiac injury and necrosis. Here, we aimed to investigate if, in addition to the effect on the funny current (I(f)), Ivabradine may also play a role against cardiac necrosis by reducing EMMPRIN/CyPA-mediated cardiac inflammation. In a porcine model of cardiac ischemia/reperfusion (IR), we found that administration of 0.3 mg/kg Ivabradine significantly improved cardiac function and reduced cardiac necrosis by day 7 after IR, detecting a significant increase in cardiac CyPA in the necrotic compared to the risk areas, which was inversely correlated with the levels of circulating CyPA detected in plasma samples from the same subjects. In testing whether Ivabradine may regulate the levels of CyPA, no changes in tissue CyPA were found in healthy pigs treated with 0.3 mg/kg Ivabradine, but interestingly, when analyzing the complex EMMPRIN/CyPA, rather high glycosylated EMMPRIN, which is required for EMMPRIN-mediated matrix metalloproteinase (MMP) activation and increased CyPA bonding to low-glycosylated forms of EMMPRIN were detected by day 7 after IR in pigs treated with Ivabradine. To study the mechanism by which Ivabradine may prevent secretion of CyPA, we first found that Ivabradine was time-dependent in inhibiting co-localization of CyPA with the granule exocytosis marker vesicle-associated membrane protein 1 (VAMP1). However, Ivabradine had no effect on mRNA expression nor in the proteasome and lysosome degradation of CyPA. In conclusion, our results point toward CyPA, its ligand EMMPRIN, and the complex CyPA/EMMPRIN as important targets of Ivabradine in cardiac protection against IR.     

Insoluble Vascular Amyloid Deposits Trigger Disruption of the Neurovascular Unit in Alzheimer’s Disease Brains

Alzheimer’s disease (AD) is a neurodegenerative disease, characterized histopathologically by intra-neuronal tau-related lesions and by the accumulation of amyloid β-peptide (Aβ) in the brain parenchyma and around cerebral blood vessels. According to the vascular hypothesis of AD, an alteration in the neurovascular unit (NVU) could lead to Aβ vascular accumulation and promote neuronal dysfunction, accelerating neurodegeneration and dementia. To date, the effects of insoluble vascular Aβ deposits on the NVU and the blood–brain barrier (BBB) are unknown. In this study, we analyze different Aβ species and their association with the cells that make up the NVU. We evaluated post-mortem AD brain tissue. Multiple immunofluorescence assays were performed against different species of Aβ and the main elements that constitute the NVU. Our results showed that there are insoluble vascular deposits of both full-length and truncated Aβ species. Besides, insoluble aggregates are associated with a decrease in the phenotype of the cellular components that constitute the NVU and with BBB disruption. This approach could help identify new therapeutic targets against key molecules and receptors in the NVU that can prevent the accumulation of vascular fibrillar Aβ in AD.     

Numerical characterization and experimental verification of an in-plane MEMS-actuator with thin-film aluminum heater

In this paper, a novel concept of a thermo-mechanical MEMS actuator using aluminum thin-film heaters on a thermal oxide for electrical insulation is presented. The actuator is part of an universal tensile testing platform for thermo-mechanical material characterization of one dimensional materials on a micro- and nano-scopic scale under different environmental conditions, as varying temperatures, pressure, moisture or even vacuum and is realised in BDRIE technology. It is shown, that the actuator concept fulfills the requirements for the use in a tensile loading stage along with heterogeneously integrated nanofunctional elements, following a specimen centered approach in line with bottom-up self-assembly processes. Simulation and experiment agree very well in the thermal and mechanical domain and allow subsequent optimisation of the actuator performance.     

Effect of cold environment on hepatic microsomal Δ6 and Δ9 desaturase activity of male rats

Male rats maintained at 24 C and then shifted to 5 C for 5 days increased food intake and decreased in growth rate and food conversion. No modification was observed in Δ6 desaturase activity, while Δ9 desaturase activity decreased after this period of time. These results were confirmed by liver microsomal and mitochondrial fatty acid composition. The phospholipid composition of liver microsomes was unaltered, whereas in mitochondria, phosphatidylcholine and sphingomyelin decreased and phosphatidylethanolamine increased due to the cold environment. The influence of food intake and weight changes on fatty acid metabolism was studied using (i) rats maintained at 5 C with restricted food intake to match the food intake of those kept at 24 C with food ad libitum and (ii) rats maintained at 24 C whose food intake was also restricted so that their growth rate would be the same as that of rats maintained at 5 C with food ad libitum, respectively. These results indicate that the negative metabolic balance state of these cold conditions is not an active factor modifier of Δ6 desaturase activity, whereas it decreases Δ9 desaturase activity, reflecting the lipogenic characteristics of the latter enzyme.