A methodological approach to fully automated highly accelerated life tests

Microsystem Technologies - Highly accelerated life test (HALT) is a test methodology to evaluate reliability of mechanical and electromechanical devices. HALT is often used on devices that must be...     

Analysis of the particle swarm algorithm in the optimization of a three-phase slurry catalytic reactor

The Particle Swarm Optimization (PSO) method was employed to optimize an industrial chemical process characterized by being difficult to be optimized by conventional deterministic methods. The chemical process is a three phase catalytic slurry reactor (tubular geometry) in which the reaction of the hydrogenation of o-cresol producing 2-methyl-cyclohexanol is carried out. The optimization problem was formulated considering as input variables the operating conditions of the reactor and as objective function the maximization of productivity, subject to the environmental constraint of conversion. The process was represented by a multivariable non-linear rigorous mathematical model and in order to solve the optimization problem, the performance of the PSO algorithm was evaluated considering four sets of parameters values suggested by the literature. PSO demonstrated to be efficient and robust to solve the constrained optimization problem, independently of the values of the PSO parameters. The solution of the rigorous mathematical model of the reactor was associated with a high computational burden, and although the PSO algorithm presented high rate of convergence, the attempt to make possible the optimization in a timeframe suitable to real time applications failed because the algorithm lost robustness (fraction of the number of runs the algorithm reached the optimization goal) when run with a reduced number of function evaluations. Therefore, if this type of application is desired, simplified mathematical models with fast and simple numerical methods must be preferred.     

Neuroprotective Role of Liver Growth Factor “LGF” in an Experimental Model of Cerebellar Ataxia

Cerebellar ataxias (CA) comprise a heterogeneous group of neurodegenerative diseases characterized by a lack of motor coordination. They are caused by disturbances in the cerebellum and its associated circuitries, so the major therapeutic goal is to correct cerebellar dysfunction. Neurotrophic factors enhance the survival and differentiation of selected types of neurons. Liver growth factor (LGF) is a hepatic mitogen that shows biological activity in neuroregenerative therapies. We investigate the potential therapeutic activity of LGF in the 3-acetylpiridine (3-AP) rat model of CA. This model of CA consists in the lesion of the inferior olive-induced by 3-AP (40 mg/kg). Ataxic rats were treated with 5 µg/rat LGF or vehicle during 3 weeks, analyzing: (a) motor coordination by using the rota-rod test; and (b) the immunohistochemical and biochemical evolution of several parameters related with the olivo-cerebellar function. Motor coordination improved in 3-AP-lesioned rats that received LGF treatment. LGF up-regulated NeuN and Bcl-2 protein levels in the brainstem, and increased calbindin expression and the number of neurons receiving calbindin-positive projections in the cerebellum. LGF also reduced extracellular glutamate and GABA concentrations and microglia activation in the cerebellum. In view of these results, we propose LGF as a potential therapeutic agent in cerebellar ataxias.     

Ascorbate Peroxidase and Catalase Activities and Their Genetic Regulation in Plants Subjected to Drought and Salinity Stresses

Hydrogen peroxide (H₂O₂), an important relatively stable non-radical reactive oxygen species (ROS) is produced by normal aerobic metabolism in plants. At low concentrations, H₂O₂ acts as a signal molecule involved in the regulation of specific biological/physiological processes (photosynthetic functions, cell cycle, growth and development, plant responses to biotic and abiotic stresses). Oxidative stress and eventual cell death in plants can be caused by excess H₂O₂ accumulation. Since stress factors provoke enhanced production of H₂O₂ in plants, severe damage to biomolecules can be possible due to elevated and non-metabolized cellular H₂O₂. Plants are endowed with H₂O₂-metabolizing enzymes such as catalases (CAT), ascorbate peroxidases (APX), some peroxiredoxins, glutathione/thioredoxin peroxidases, and glutathione sulfo-transferases. However, the most notably distinguished enzymes are CAT and APX since the former mainly occurs in peroxisomes and does not require a reductant for catalyzing a dismutation reaction. In particular, APX has a higher affinity for H₂O₂ and reduces it to H₂O in chloroplasts, cytosol, mitochondria and peroxisomes, as well as in the apoplastic space, utilizing ascorbate as specific electron donor. Based on recent reports, this review highlights the role of H₂O₂ in plants experiencing water deficit and salinity and synthesizes major outcomes of studies on CAT and APX activity and genetic regulation in drought- and salt-stressed plants.     

Hydrothermal syntheses of ETS-10 like vanadosilicates using chiral organic molecules. Part I

Vanadosilicates with the structures of ETS-10 and AM-6 microporous materials have been hydrothermally synthesized using organic directing structures agent (SDAs) derivatives of decahydroquinoline, 3,5-dimethyl-piperidine, 2,6-dimethyl-piperidine and (S)-Sparteine. Derivatives of these chiral amines have not been explored before in the sol gel chemistry of vanadosilicates. Physicochemical characterization of the obtained vanadosilicate materials with these different chiral templates was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman and infrared (IR) spectroscopy, solid-state NMR spectroscopy, and differential thermogravimetric analysis (DTA)/thermogravimetric analysis (TGA). The results suggest that the presence of the chiral organic templates have different effects in terms of the final phase of the synthesized materials and their morphology. The products obtained using chiral template derivatives of decahydroquinoline reveal that certain products might be very enriched with chiral polymorph A while others present structures which are similar to other large-porous vanadosilicate such as AM-6 and AM-13. Derivatives of 2,6-dimethyl-piperidine and 3,5-dimethyl-piperidine have not favored any structure that resembles a chiral polymorph A, but only known vanadosilicates such as AM-6, AM-13. Derivatives of (S)-Sparteine, on the other hand, have not only favored the formation of structures enriched with a large amount of chiral polymorph A, but also their use has resulted in other unknown vanadosilicate structures whose physicochemical characterizations are in progress.     

Thermally reduced graphenes exhibiting a close relationship to amorphous carbon

Graphene is an important material for sensing and energy storage applications. Since the vast majority of sensing and energy storage chemical and electrochemical systems require bulk quantities of graphene, thermally reduced graphene oxide (TRGO) is commonly employed instead of pristine graphene. The sp(2) planar structure of TRGO is heavily damaged, consisting of a very short sp(2) crystallite size of nanometre length and with areas of sp(3) hybridized carbon. Such a structure of TRGO is reminiscent of the key characteristic of the structure of amorphous carbon, which is defined as a material without long-range crystalline order consisting of both sp(2) and sp(3) hybridized carbons. Herein, we describe the characterization of TRGO, its parent graphite material and carbon black (a form of amorphous carbon) via transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry experiments. We used the data obtained as well as consideration of practical factors to perform a comparative assessment of the relative electrochemical performances of TRGO against amorphous carbon. We found out that TRGO and amorphous carbon exhibit almost identical characteristics in terms of density of defects in the sp(2) lattice and a similar crystallite size as determined by Raman spectroscopy. These two materials also exhibit similar amounts of oxygen containing groups as determined by XPS and nearly indistinguishable cyclic voltammetric response providing almost identical heterogeneous electron transfer constants. This leads us to conclude that for some sensing and energy storage electrochemical applications, the use of amorphous carbon might be a much more economical solution than the one requiring digestion of highly crystalline graphite with strong oxidants to graphite oxide and then thermally exfoliating it to thermally reduced graphene oxide.     

Role of Draw Rate and Molecular Weight when Electrospun Nanofibers are Post-Drawn with Residual Solvent

The postdrawing process is poorly understood for polymer nanofibers due to the difficulty of manipulating nanofiber structures. Here, an angled track system facilitates postdrawing of individual nanofibers with control of parameters including molecular weight, draw rate, draw ratio, and solvent evaporation time. In this study, the effects of molecular weight, draw rate, and relative residual solvent content on final nanofiber properties are investigated. Molecular weight is first investigated to clarify any influence polymer chain length can have on drawing in facilitating or hindering chain extensibility. Polyacrylonitrile nanofibers with 50 and 150 kDa molecular weights behave similarly with postdrawing resulting in reduced diameters and enhanced mechanics. Since solvent quantity during drawing is a time sensitive component it is meaningful to assess the impact of draw rate on the chemical and structural makeup of postdrawn fibers. Chemical bond vibrations and chain orientation are sensitive to draw rate when polycaprolactone nanofibers are dried for 3 minutes prior to postdrawing, but this dependency to draw rate is not observed when fibers are postdrawn immediately upon collection. These findings demonstrate that the amount of retained solvent at collection is relevant to this postprocessing approach, and highlights the dynamics of solvent evaporation during postdrawing.     

Well defined CuI(NO), CuI(NO)2 and CuII(NO)X (X = O− and/or NO 2 − ) complexes in CuI-ZSMS prepared by interaction of H-ZSM5 with gaseous CuCl

In this note an exchange procedure of the acidic protons of H-ZSM5 by Cu^I ions through reaction with CuCl in the gas phase is described. In the so obtained Cu^I-ZSM5 exchanged zeolite the Cu^I ions are in well defined configuration and form with NO mono and di-nitrosyl complexes of high structural and spectroscopic quality. The Cu^I(NO)₂ species are transformed at RT into Cu^II(NO)X (X=O^– and/or NO ₂ ^– ) species which could represent an intermediate in NO decomposition.     

Identification of Aminoimidazole and Aminothiazole Derivatives as Src Family Kinase Inhibitors

Src family kinases (SFKs) are a family of non‐receptor tyrosine kinases (TKs) implicated in the regulation of many cellular processes. The aberrant activity of these TKs has been associated with the growth and progression of cancer. In particular, c‐Src is overexpressed or hyperactivated in a variety of solid tumors and is most likely a strong promoting factor for the development of metastasis. Herein, the synthesis of new 4‐aminoimidazole and 2‐aminothiazole derivatives and their in vitro biological evaluation are described for their potential use as SFK inhibitors. Initially, 2‐aminothiazole analogues of dasatinib and 4‐aminoimidazole derivatives were synthesized and tested against the SFKs Src, Fyn, Lyn, and Yes. Five hits were identified as the most promising compounds, with K_i values in the range of 90–480 nm . A combination of molecular docking, homology modeling, and molecular dynamics were then used to investigate the possible binding mode of such compounds within the ATP binding site of the SFKs. Finally, the antiproliferative activities of the best candidates were evaluated against SH‐SY5Y and K562 cell lines. Compound 3 b [2‐(4‐{2‐methyl‐6‐[(5‐phenylthiazol‐2‐yl)amino]pyrimidin‐4‐yl}piperazin‐1‐yl)ethanol] was found to be the most active inhibitor.