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Characteristic Response (characteristic + response)
Selected AbstractsDisposable Gold Electrode Array for Simultaneous Electrochemical StudiesELECTROANALYSIS, Issue 1 2008Graciela Priano Abstract An efficient and inexpensive eight gold electrode array has been manufactured by a combination of screen printing and gold electrodeposition techniques. Gold electrodeposition was performed in potentiostatic and galvanostatic conditions. Different treatments, involving temperature and polishing control, led to electrodes with different roughness. The electrochemical behavior of the generated gold surface was studied by cyclic voltammetry showing the characteristic response of polycrystalline gold, in contrast with disposable gold electrodes fabricated by screen printing from gold inks. The electrodes were chemically modified through the adsorption of alkanethiols self-assembled monolayers and the coupling of a model protein. Both reactions were followed by cyclic voltammetry and Electrochemical Impedance Spectroscopy (EIS). The electrodes have shown high reproducibility in their electrochemical behavior as well as in their modifications. [source] Electroactive Films of Multicomponent Building Blocks,ADVANCED FUNCTIONAL MATERIALS, Issue 5 2007I. Yildiz Abstract A ligand consisting of a 2,2,-bipyridine core and two 4,4,-bipyridinium arms terminated by a thiol group is prepared following a multistep synthetic procedure. Two of these ligands assemble around a single CuI center as a result of the tetrahedral coordination of their 2,2,-bipyridine cores by the metal. Both the ligand and the complex adsorb spontaneously on the surface of polycrystalline-gold electrodes. The surface coverage of the films prepared by immersing a gold substrate into a solution of the ligand increases from monolayer to multilayer values with immersion time. Instead, the complex can only form monolayers. The cyclic voltammograms of the resulting films show the characteristic response for the reversible reduction of the 4,4,-bipyridinium dications to their radical cations. In the case of the complex, a wave for the monoelectronic oxidation of the metal center can also be observed. The back reduction wave, however, is markedly broader and appears at significantly lower potentials. Model studies in solution indicate that this response is a result of the presence of free thiol groups and is consistent with a change in the coordination geometry of the metal. Specifically, the oxidation of the CuI center to a CuII ion is, presumably, accompanied by the folding of one of the thiol groups back to interact with the metal. Thus, oxidation/reduction cycles of the metal center can, in principle, be exploited to control reversibly large amplitude molecular motions at the electrode/solution interface in the shape of the folding/unfolding of oligomethylene chains. [source] Hypoxia is an inducer of vasodilator agents in peritoneal macrophages of cirrhotic patientsHEPATOLOGY, Issue 5 2002Pilar Cejudo-Martín The aim of the investigation was to assess whether hypoxia induces the production of endogenous vasoactive peptides in macrophages of cirrhotic patients with ascites because low tissue oxygenation is a relatively frequent event in these patients. Peritoneal macrophages were isolated from ascites, seeded on well plates, and cultured at different times under hypoxic (5% O2) or normoxic conditions (21% O2). Then, accumulation of vasoactive peptides sensitive to hypoxia including endothelin-1 (ET-1), vascular endothelial growth factor (VEGF), and adrenomedullin (ADM) was measured. Only VEGF and ADM were constitutively secreted, and hypoxia further stimulated the release of these vasodilator peptides. In concordance, increased messenger RNA (mRNA) levels of VEGF and ADM were found at culturing macrophages in hypoxia. This characteristic response was not observed in circulating monocytes of either cirrhotic patients or healthy subjects. Next the expression of the transcription factor, hypoxia inducible factor 1 (HIF-1), was analyzed. Expression of HIF-1, and HIF-1, messengers and HIF-1, protein subunit remained unchanged regardless of O2 tension, whereas HIF-1, protein subunit was overexpressed under hypoxic conditions. Moreover, conditioned medium from macrophages cultured under hypoxic conditions promoted a larger nitric oxide (NO) release in endothelial cells than that of normoxic macrophages. In conclusion, these data indicate that hypoxia induces the synthesis of VEGF and ADM in macrophages of cirrhotic patients, likely through HIF-1,enhanced transcriptional activity. These data suggest that a local reduction in O2 tension could enhance the synthesis of macrophage-derived vasodilators, thus aggravating the circulatory disturbance of these patients. [source] Hertzian Ring Crack Initiation in Hot-Pressed Silicon CarbidesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009Andrew A. Wereszczak The use of Hertzian indentation to measure ring crack initiation force (RCIF) distributions in four hot-pressed silicon carbide (SiC) ceramics is described. Three diamond indenter diameters were used with each SiC; the RCIF in each test was identified with the aid of an acoustic emission system; and two-parameter Weibull RCIF distributions were determined for all 12 combinations. RCIF testing was found to be an effective discriminator of contact damage initiation and response. It consistently produced the same ranking of RCIF between the four SiCs, with all three different indenter diameters, which is noteworthy because Knoop hardness and fracture toughness measurements were only subtly different or equivalent for the four SiCs. However, because RCIF, like hardness, is a characteristic response of a target material to an applied indentation condition (e.g., a function of indenter diameter) and not a material property, the implications and possible limitations should be acknowledged when using RCIF to discriminate the target material response. [source] Direction sensitive sensor probe for the evaluation of voluntary and reflex pelvic floor contractions,NEUROUROLOGY AND URODYNAMICS, Issue 3 2007Christos E. Constantinou Abstract Aims The development of a vaginal probe for the evaluation of the dynamics of pelvic floor function is described. Fundamental criteria in the design of this probe involves the incorporation of a means of assessing whether the isotonic forces closing the vagina are equally distributed or whether they are greater in some directions than others. The aim of this study is to present the design of directionally sensitive multi-sensor probe, having circumferential spatial resolution, constructed to identify the distribution of anisotropic forces acting on the vagina following voluntary and reflex pelvic floor contractions. Materials and Methods Probe system consists of four pairs of force/displacement sensors mounted on leaf springs enabling isotonic measurements of voluntary and reflex contractions. Assembly is retractable to 23 mm for insertion, and expandable to 60 mm for measurement. Simultaneous measurements were made of force and displacement with the sensors oriented in the anterior/posterior and left/right orientation of the vagina. Using this probe, measurements were carried out to identify the temporal and spatial characteristic response of the vaginal wall. Data were analyzed with respect to voluntary pelvic floor and cough-induced contractions of nine subjects having a mean age of 64 years. Results A robust probe system was developed and measurements were successfully made. Initial results show that the maximum force and displacement occurs during reflex contractions in the anterior aspect of the vagina validating the anisotropic nature of the forces acting on the vaginal wall. The data also show that both the force and displacement produced by the cough-induced has a higher magnitude than voluntary pelvic floor contraction. Conclusions A directional multi-sensor vaginal probe has been developed to evaluate the force and displacement produced during isotonic pelvic floor contractions. Analysis of the results provided new biomechanical data demonstrating the anisotropic nature of vaginal closure as a consequence of pelvic floor contractions. Neurourol. Urodynam. 26:386,391, 2007. © 2007 Wiley-Liss, Inc. [source] Not All Injury-induced Muscle Proteolysis Is Due to Increased Activity of the Ubiquitin/Proteasome System: Evidence for Up-Regulation of Macrophage-associated Lysosomal Proteolysis in a Model of Local TraumaNUTRITION REVIEWS, Issue 1 2003Article first published online: 16 SEP 200 A characteristic response to injury is a dramatic loss of skeletal muscle protein owing to increased muscle protein breakdown. Over the past decade, numerous studies have indicated that up-regulaton of the ubiquitin-proteasome system is a common mechanism underlying such injury-induced muscle proteolysis. However, a recent study using a single-impact trauma to the gastrocnemius muscle found that, although the rate of muscle proteolysis was dramatically increased, the ubiquitin-proteasome system was not involved. Rather, an increase in lysosomal activity, through infiltration of the damaged tissue by mononuclear macrophages, is responsible for the high rates of protein breakdown. [source] Relationship between grain-boundary capacitance and bulk shallow donors in SnO2 polycrystalline semiconductorPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2008P. R. Bueno Abstract The relationship between grain-boundary capacitance and extrinsic shallow donors caused by Nb addition to SnO2·CoO binary polycrystalline system has been investigated by means of combined techniques such as I ,V characteristic response, complex impedance and capacitance analysis and electrostatic force microscopy. The estimated role of the Nb doping is to increase the concentration of shallow donors that are capable of enhancing the electronic donation to grain-boundary acceptors. This effect leads to the formation of potential barriers at grain boundaries with a simultaneous increase of grain-boundary capacitance and non-Ohmic features of the polycrystalline device doped with Nb atoms. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Spectroscopic Properties of Various Quinolone Antibiotics in Aqueous,organic Solvent Mixtures¶PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2004Hyoung-Ryun Park The spectroscopic properties of enoxacin (ENO), oxolinic acid (OXO) and nalidixic acid (NAL) were studied in various H2O-CH3OH and H2O-CH3CN mixed solvents because these solvents were thought to behave as a biological mimetic system. ENO has piperazinyl group, but OXO and NAL do not have this substituent. The fluorescence emission spectra of ENO were very sensitive to the composition of the solvents. In the Lippert-Mataga analysis of the steady-state fluorescence data, clear reverse solvatochromism was exhibited for ENO in both mixed solvents. This observation can be explained using the excited state twisted intramolecular charge transfer (TICT) from the nitrogen of the piperazinyl group to the keto oxygen. Theoretical calculations further support this observation. The nonradiative and radiative rate constants of these molecules were analyzed as a function of dipolarity,polarizability (,*) and hydrogen bond donor acidity (,) of the mixed solvents. These results for ENO were consistent with the suggested mechanism of the TICT very well. The influence of bulk dielectric effect was more significant relative to the specific hydrogen bonding interactions. The emission spectra of OXO and NAL do not exhibit any characteristic responses to the properties of the solvent. [source] | |||||||||||||