Electrochemical behavior of the Ti–6Al–4V alloy coated with a-C:H films

In this work diamond-like carbon films were deposited on the Ti–6Al–4V alloy, which has been used in aeronautics and biomedical fields, by electrical discharges using a magnetron cathode and a 99.999% graphite target in two different atmospheres, the first one constituted by argon and hydrogen and the second one by argon and methane. Films deposited using the argon/hydrogen mixture were called a-C:H, while films deposited using the argon/methane mixture were called DLC. Raman spectroscopy was used to study the structure of the films. The Raman spectra profile of the a-C:H films is quite different from that of the DLC films. The disorder degree of the graphite crystalline phase in a-C:H films is higher than in DLC films (a-C:H films present small values for the the I_D/I_G ratio). Potentiodynamic corrosion tests in 0.5 mol l⁻¹ NaCl aqueous solution, pH 5.8, at room temperature (≈25 °C) were carried out as for the a-C:H as for the DLC coated surfaces. Comparison between the corrosion parameters of a-C:H and DLC coated surfaces under similar deposition time, showed that DLC coated surfaces present bigger corrosion potential (E_corr) and polarization resistance than those coated with a-C:H films. Electrochemical impedance spectroscopy (EIS) was also used to study the electrochemical behavior of a-C:H and DLC coated surfaces exposed to 0.5 mol l⁻¹ aqueous solution. The EIS results were simulated with equivalent electrical circuit models for porous films. The results of these simulations showed similar tendency to the one observed in the potentiodynamic corrosion tests. The DLC film resistance and the charge transfer resistance (R_ct) for the DLC coated surface/electrolyte interface were bigger than the ones determined for the a-C:H coated surfaces.     

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...     

Clear-cell smooth muscle tumor of the skin

We report a case of a previously undescribed benign neoplasm characterized by a poorly circumscribed proliferation of clear cells, arranged both singly and in elongated fascicles oriented in haphazard fashion within the middle and lower reticular dermis. The fascicles consisted of spindle-shaped cells that were periodic acid-Schiff positive and diastase labile. These cells were characterized by oval, hyperchromatic, cigar-shaped nuclei and clear cytoplasm. Immunohistochemically, neoplastic cells were diffusely positive for smooth muscle actin (1A4), common muscle actin (HHF-35), and vimentin. Immunoreactivity for fibronectin was also focally noted. The neoplasm, which we designated clear-cell smooth muscle tumor of the skin, should be distinguished from smooth muscle hamartoma and other smooth muscle proliferations at cutaneous level. We highlight in this case report the histopathologic differential diagnosis among other tumors with myofibroblastic, melanocytic, and neural differentiation.     

Stimulation of tachykinin NK-3 receptors in the nucleus basalis magnocellularis reduces alcohol intake in rats

Injections in the nucleus basalis magnocellularis (NBM) of the tachykinin (TK) NK-3 receptor agonist [Asp5,6,MePhe8]substance P(5-11), also referred to as amino-senktide (NH2-SENK), markedly reduced alcohol intake in genetically selected alcohol-preferring rats, offered 10% ethanol 2 h/day. The threshold dose in the NBM was 0.5 ng/site, while neither 1 nor 10 ng/rat of NH2-SENK inhibited alcohol intake following administration into the lateral ventricle. Injection of NH2-SENK, 25 ng/site, in the NBM did not modify water or food intake in water deprived rats, providing evidence for the behavioral selectivity of the effect on ethanol intake. The selective TK NK-3 receptor antagonist, R-820, injected in the NBM at the dose of 1000 ng/site 5 min before NH2-SENK 5 ng/site, significantly reduced the effect of NH2-SENK. The selective TK NK-1 receptor agonist [Sar9,Met(O2)11]substance P inhibited alcohol intake following injection in the NBM only at 25 ng/site; but the same dose induced marked grooming and inhibited also water intake in water deprived rats. The present results confirm that TK NK-3, but not NK-1, receptor agonists selectively inhibit ethanol intake in alcohol-preferring rats and suggest that the NBM is a site of action for their effect.     

The mechanism of glutamine-dependent amidotransferases

Glutamine-dependent amidotransferases have been known for more than 30 years. The mechanism by which these enzymes generate ammonia from the glutamine amide nitrogen and transfer it to seven different chemical classes of acceptors has been the subject of intense scrutiny for the last 5 years. The increasing number of biochemical and structural studies dealing with amidotransferases and with mechanistically related enzymes has disclosed the dichotomy of the mechanisms within these enzymes for achieving the glutamine amide bond cleavage. Some of them use a catalytic Cys/His/Glu triad similar to serine protease, whereas the aminoterminal cysteine of the others is believed to play the same function. The transfer of ammonia from the glutamine site to the acceptor site which must operate in a concerted manner has been demonstrated in two cases to involve channelling but is still matter of investigation.     

Adsorption equilibria of benzodiazepines on a hybrid polymeric chiral stationary phase

The chromatographic behavior of a series of racemic benzodiazepines was evaluated under linear and nonlinear conditions on a new hybrid polymeric (DACH-ACR) chiral stationary phase (CSP). Differently substituted benzodiazepines were employed as probes to make hypotheses concerning possible molecular interaction mechanisms originating between target compounds and active sites on the CSP. Hydrogen bonds were found to be pivotal for chromatographic retention and chiral selectivity. The competitive effect from a mobile-phase (MP) modifier able to interact with the CSP through H-bonds was investigated. The performance of the polymeric DACH-ACR CSP for preparative purposes was also evaluated. The competitive adsorption isotherms of two benzodiazepines, lorazepam and temazepam, were measured at different MP compositions through the so-called inverse method. The adsorption data were fitted with a competitive bi-Langmuir adsorption isotherm. Enantiomeric separations under nonlinear conditions were modeled by using the equilibrium dispersive (ED) model of chromatography. Theoretical overloaded band profiles (obtained by solving the system of partial differential equations described by the ED model) matched, in a significantly accurate way, the profiles experimentally measured.     

Design and synthesis of new classes of heterocyclic C-glycoconjugates and carbon-linked sugar and heterocyclic amino acids by asymmetric multicomponent reactions (AMCRs)

While chemical efficiency relies on several factors, the multicomponent reaction (MCR) approach was considered as a powerful synthetic tool for preparing target molecules of biological relevance in an efficient manner. Four classes of new bioactive molecules were designed and synthesized by asymmetric MCRs, in some cases with the cooperation of polymer-assisted solution-phase (PASP) technique. These include (a) C-glycosyl dihydropyrimidines and dihydropyridines via Biginelli and Hantzsch cyclocondensations, (b) C-glycosyl beta-amino acids via Mannich- and Reformatsky-type reactions, (c) C-glycosyl beta-lactams via Staudinger reaction, and (d) heterocyclic alpha-amino acids (glycine and alanine) via the Biginelli and Hantzsch reactions.     

Hydraulic/partitioning tracer tomography for DNAPL source zone characterization: small-scale sandbox experiments

Dense nonaqueous phase liquids (DNAPL) are prevalent at a large number of sites throughout the world. The variable release history, unstable flow, and geologic heterogeneity make the spatial distribution of DNAPLs complex. This causes difficulties in site remediation contributing to long-term groundwater contamination for decades to centuries. We present laboratory experiments to demonstrate the efficacy of Sequential Successive Linear Estimator (SSLE) algorithm that images DNAPL source zones. The algorithm relies on the fusion of hydraulic and partitioning tracer tomography (HPTT) to derive the best estimate of the K heterogeneity, DNAPL saturation (S(N)) distribution, and their uncertainty. The approach is nondestructive and can be applied repeatedly. Results from our laboratory experiments show that S(N) distributions compare favorably with DNAPL distributions observed in the sandbox but not so with local saturation estimates from core samples. We also found that the delineation of K heterogeneity can have a large impact on computed S(N) distributions emphasizing the importance of accurate delineation of hydraulic heterogeneity.     

Disc brake squeal characterization through simplified test rigs

This paper presents a review of recent investigations on brake squeal noise carried out on simplified experimental rigs. The common theme of these works is that of approaching the study of squeal noise on experimental set-ups that are much simpler than commercial disc brakes, providing the possibility of repeatable measurements of squeal occurrence. As a consequence, it is possible to build consistent and robust models of the experimental apparatus to simulate the squeal events and to understand the physics behind squeal instabilities.