973 resultados para Ion-selective electrodes


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The aqueous alkaline reaction of 1,3-bis(4-cyanopyridinium)propane dibromide, a reactant constituted of two pyridinium rings linked by a three-methylene bridge, generates a novel compound,1 -(4-cyano-2-oxo-1,2-dihydro-1-pyridyl)-3-(4-cyano-1,2-dihydro-1-pyridyl)propane. The reaction pathway is attributed to the proximity of the OH- ion inserted between two pyridinium moieties, which occurs only in bis(pyridinium) derivatives connected by short methylene spacers, where charge-conformational effects are important.

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Three comparative assays were performed seeking to improve the sensitivity of the diagnosis of Bordetella bronchiseptica infection analyzing swine nasal swabs. An initial assay compared the recovery of B. bronchiseptica from swabs simultaneously inoculated with B. bronchiseptica and some interfering bacteria, immersed into three transport formulations (Amies with charcoal, trypticase soy broth and phosphate buffer according to Soerensen supplemented with 5% of bovine fetal serum) and submitted to different temperatures (10ºC and 27ºC) and periods of incubation (24, 72 and 120 hours). A subsequent assay compared three selective media (MacConkey agar, modified selective medium G20G and a ceftiofur medium) for their recovery capabilities from clinical specimens. One last assay compared the polymerase chain reaction to the three selective media. In the first assay, the recovery of B. bronchiseptica from transport systems was better at 27ºC and the three formulations had good performances at this temperature, but the collection of qualitative and quantitative analysis indicated the advantage of Amies medium for nasal swabs transportation. The second assay indicated that MacConkey agar and modified G20G had similar results and were superior to the ceftiofur medium. In the final assay, polymerase chain reaction presented superior capability of B. bronchiseptica detection to culture procedures.

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Bloodsucking parasites such as ticks have evolved a wide variety of immunomodulatory proteins that are secreted in their saliva, allowing them to feed for long periods of time without being detected by the host immune system. One possible strategy used by ticks to evade the host immune response is to produce proteins that selectively bind and neutralize the chemokines that normally recruit cells of the innate immune system that protect the host from parasites. We have identified distinct cDNAs encoding novel chemokine binding proteins (CHPBs), which we have termed Evasins, using an expression cloning approach. These CHBPs have unusually stringent chemokine selectivity, differentiating them from broader spectrum viral CHBPs. Evasin-1 binds to CCL3, CCL4, and CCL18; Evasin-3 binds to CXCL8 and CXCL1; and Evasin-4 binds to CCL5 and CCL11. We report the characterization of Evasin-1 and -3, which are unrelated in primary sequence and tertiary structure, and reveal novel folds. Administration of recombinant Evasin-1 and - 3 in animal models of disease demonstrates that they have potent antiinflammatory properties. These novel CHBPs designed by nature are even smaller than the recently described single-domain antibodies (Hollinger, P., and P. J. Hudson. 2005. Nat. Biotechnol. 23: 1126-1136), and may be therapeutically useful as novel antiinflammatory agents in the future.

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In order to understand the potential selective activation of the rectus abdominis muscle, we conducted two experiments. In the first, subjects performed two controlled isometric exercises: the curl up (supine trunk raise) and the leg raise (supine bent leg raise) at low intensity (in which only a few motor units are recruited). In the second experiment, subjects performed the same exercises, but they were required to maintain a certain force level in order to induce fatigue. We recorded the electromyographic (EMG) activities of the lower and upper portions of the rectus abdominis muscle during the exercises and used spatial-temporal and frequency analyses to describe muscle activation patterns. At low-intensity contractions, the ratio between the EMG intensities of the upper and lower portions during the curl up exercise was significantly larger than during the leg raise exercise (p = 0.02). A cross-correlation analysis indicated that the signals of the abdominal portions were related to each other and this relation did not differ between the tasks (p = 0.12). In the fatiguing condition, fatigue for the upper portion was higher than for the lower portion during the curl up exercise (p = 0.008). We conclude that different exercises evoked, to a certain degree, individualized activation of each part of the rectus abdominis muscle, but different portions of the rectus abdominis muscle contributed to the same task, acting like a functional unit. These results corroborate the relevance of varying exercise to modify activation patterns of the rectus abdominis muscle.

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The synthesis of [Ru(NO(2)) L(bpy)(2)](+) (bpy = 2,2'-bipyridine and L = pyridine (py) and pyrazine (pz)) can be accomplished by addition of [Ru(NO) L(bpy) 2](PF(6))(3) to aqueous solutions of physiological pH. The electrochemical processes of [Ru(NO2) L(bpy) 2]+ in aqueous solution were studied by cyclic voltammetry and differential pulse voltammetry. The anodic scan shows a peak around 1.00 V vs. Ag/AgCl attributed to the oxidation process centered on the metal ion. However, in the cathodic scan a second peak around-0.60 V vs. Ag/AgCl was observed and attributed to the reduction process centered on the nitrite ligand. The controlled reduction potential electrolysis at-0.80 V vs. Ag/AgCl shows NO release characteristics as judged by NO measurement with a NO-sensor. This assumption was confirmed by ESI/MS(+) and spectroelectrochemical experiment where cis-[Ru(bpy)(2)L(H(2)O)](2+) was obtained as a product of the reduction of cis-[Ru(II)(NO(2)) L(bpy)(2)](+). The vasorelaxation observed in denuded aortic rings pre-contracted with 0.1 mu mol L(-1) phenylephrine responded with relaxation in the presence of cis-[RuII(NO2) L(bpy) 2]+. The potential of rat aorta cells to metabolize cis-[RuII(NO(2)) L(bpy)(2)](+) was also followed by confocal analysis. The obtained results suggest that NO release happens by reduction of cis-[RuII(NO(2)) L(bpy)(2)](+) inside the cell. The maximum vasorelaxation was achieved with 1 x 10(-5) mol L(-1) of cis-[RuII(NO(2)) L(bpy)(2)](+) complex.

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Three-particle azimuthal correlation measurements with a high transverse momentum trigger particle are reported for pp, d + Au, and Au + Au collisions at root(S)NN = 200 GeV by the STAR experiment. Dijet structures are observed in pp, d + Au and peripheral Au + Au collisions. An additional structure is observed in central Au + Au data, signaling conical emission of correlated charged hadrons. The conical emission angle is found to be theta = 1.37 +/- 0.02(stat)(-0.07)(+0.06)(syst), independent of p perpendicular to.

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We measure directed flow (v(1)) for charged particles in Au + Au and Cu + Cu collisions at root s(NN) = 200 and 62.4 GeV, as a function of pseudorapidity (eta), transverse momentum (p(t)), and collision centrality, based on data from the STAR experiment. We find that the directed flow depends on the incident energy but, contrary to all available model implementations, not on the size of the colliding system at a given centrality. We extend the validity of the limiting fragmentation concept to v(1) in different collision systems, and investigate possible explanations for the observed sign change in v(1)(p(t)).

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We present the first spin alignment measurements for the K*(0)(892) and phi(1020) vector mesons produced at midrapidity with transverse momenta up to 5 GeV/c at root s(NN) = 200 GeV at RHIC. The diagonal spin-density matrix elements with respect to the reaction plane in Au+Au collisions are rho(00) = 0.32 +/- 0.04 (stat) +/- 0.09 (syst) for the K*(0) (0.8 < p(T) < 5.0 GeV/c) and rho(00) = 0.34 +/- 0.02 (stat) +/- 0.03 (syst) for the phi (0.4 < p(T) < 5.0 GeV/c) and are constant with transverse momentum and collision centrality. The data are consistent with the unpolarized expectation of 1/3 and thus no evidence is found for the transfer of the orbital angular momentum of the colliding system to the vector-meson spins. Spin alignments for K(*0) and phi in Au+Au collisions were also measured with respect to the particle's production plane. The phi result, rho(00) = 0.41 +/- 0.02 (stat) +/- 0.04 (syst), is consistent with that in p+p collisions, rho(00) = 0.39 +/- 0.03 (stat) +/- 0.06 (syst), also measured in this work. The measurements thus constrain the possible size of polarization phenomena in the production dynamics of vector mesons.

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Photoproduction reactions occur when the electromagnetic field of a relativistic heavy ion interacts with another heavy ion. The STAR Collaboration presents a measurement of rho(0) and direct pi(+)pi(-) photoproduction in ultraperipheral relativistic heavy ion collisions at root s(NN) = 200 GeV. We observe both exclusive photoproduction and photoproduction accompanied by mutual Coulomb excitation. We find a coherent cross section of sigma(AuAu -> Au*Au*rho(0)) = 530 +/- 19(stat.) +/- 57(syst.) mb, in accord with theoretical calculations based on a Glauber approach, but considerably below the predictions of a color dipole model. The rho 0 transverse momentum spectrum (p(T)(2)) is fit by a double exponential curve including both coherent and incoherent coupling to the target nucleus; we find sigma(inc)/sigma(coh) = 0.29 +/- 0.03 (stat.) +/- 0.08 (syst.). The ratio of direct pi(+)pi(-) to rho(0) production is comparable to that observed in gamma(p) collisions at HERA and appears to be independent of photon energy. Finally, the measured rho(0) spin helicity matrix elements agree within errors with the expected s-channel helicity conservation.

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Background: Chronic Chagas disease cardiomyopathy (CCC) is an inflammatory dilated cardiomyopathy with a worse prognosis than other cardiomyopathies. CCC occurs in 30 % of individuals infected with Trypanosoma cruzi, endemic in Latin America. Heart failure is associated with impaired energy metabolism, which may be correlated to contractile dysfunction. We thus analyzed the myocardial gene and protein expression, as well as activity, of key mitochondrial enzymes related to ATP production, in myocardial samples of end-stage CCC, idiopathic dilated (IDC) and ischemic (IC) cardiomyopathies. Methodology/Principal Findings: Myocardium homogenates from CCC (N = 5), IC (N = 5) and IDC (N = 5) patients, as well as from heart donors (N = 5) were analyzed for protein and mRNA expression of mitochondrial creatine kinase (CKMit) and muscular creatine kinase (CKM) and ATP synthase subunits aplha and beta by immunoblotting and by real-time RT-PCR. Total myocardial CK activity was also assessed. Protein levels of CKM and CK activity were reduced in all three cardiomyopathy groups. However, total CK activity, as well as ATP synthase alpha chain protein levels, were significantly lower in CCC samples than IC and IDC samples. CCC myocardium displayed selective reduction of protein levels and activity of enzymes crucial for maintaining cytoplasmic ATP levels. Conclusions/Significance: The selective impairment of the CK system may be associated to the loss of inotropic reserve observed in CCC. Reduction of ATP synthase alpha levels is consistent with a decrease in myocardial ATP generation through oxidative phosphorylation. Together, these results suggest that the energetic deficit is more intense in the myocardium of CCC patients than in the other tested dilated cardiomyopathies.

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We describe the design and implementation of a high voltage pulse power supply (pulser) that supports the operation of a repetitively pulsed filtered vacuum arc plasma deposition facility in plasma immersion ion implantation and deposition (Mepiiid) mode. Negative pulses (micropulses) of up to 20 kV in magnitude and 20 A peak current are provided in gated pulse packets (macropulses) over a broad range of possible pulse width and duty cycle. Application of the system consisting of filtered vacuum arc and high voltage pulser is demonstrated by forming diamond-like carbon (DLC) thin films with and without substrate bias provided by the pulser. Significantly enhanced film/substrate adhesion is observed when the pulser is used to induce interface mixing between the DLC film and the underlying Si substrate. (C) 2010 American Institute of Physics. [doi:10.1063/1.3518969]

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Shallow subsurface layers of gold nanoclusters were formed in polymethylmethacrylate (PMMA) polymer by very low energy (49 eV) gold ion implantation. The ion implantation process was modeled by computer simulation and accurately predicted the layer depth and width. Transmission electron microscopy (TEM) was used to image the buried layer and individual nanoclusters; the layer width was similar to 6-8 nm and the cluster diameter was similar to 5-6 nm. Surface plasmon resonance (SPR) absorption effects were observed by UV-visible spectroscopy. The TEM and SPR results were related to prior measurements of electrical conductivity of Au-doped PMMA, and excellent consistency was found with a model of electrical conductivity in which either at low implantation dose the individual nanoclusters are separated and do not physically touch each other, or at higher implantation dose the nanoclusters touch each other to form a random resistor network (percolation model). (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3231449]

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We have investigated the fundamental structural properties of conducting thin films formed by implanting gold ions into polymethylmethacrylate (PMMA) polymer at 49 eV using a repetitively pulsed cathodic arc plasma gun. Transmission electron microscopy images of these composites show that the implanted ions form gold clusters of diameter similar to 2-12 nm distributed throughout a shallow, buried layer of average thickness 7 nm, and small angle x-ray scattering (SAXS) reveals the structural properties of the PMMA-gold buried layer. The SAXS data have been interpreted using a theoretical model that accounts for peculiarities of disordered systems.

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Using a quasitoroidal set of coordinates with coaxial circular magnetic surfaces, the Vlasov equation is solved for collisionless plasmas, and the dielectric tensor is found for large aspect ratio tokamaks in a low frequency band. Taking into account q-profile and charge separation parallel electric field, it is found that the Alfven wave continuum is deformed by ion geodesic effects producing continuum minimum at the rational magnetic surfaces. Low frequency geodesic ion induced Alfven waves are found below the continuum minimum where collisionless damping has a gap for Maxwell distribution. In kinetic approach, the ion thermal motion defines the geodesic effect but the mode frequency is strongly corrected due to parallel motion of electrons.

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A buried conducting layer of metal/polymer nanocomposite was formed by very low energy gold ion implantation into polymethylmethacrylate. The conducting layer is similar to 3 nm deep and of width similar to 1 nm. In situ resistivity measurements were performed as the implantation proceeded, and the conductivity thus obtained as a function of buried gold concentration. The measured conductivity obeys the behavior well established for composites in the percolation regime. The critical concentration, below which the polymer remains an insulator, is attained at a dose similar to 1.0 x 10(16) atoms/cm(2) of implanted gold ions. (C) 2008 American Institute of Physics.