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81.
Bittencourt MF Dong KE Caetano AL Viel TA Andrada e Silva MA Buck HS 《The Journal of the Acoustical Society of America》2010,128(5):2949-2954
Unlike humans, who communicate in frequency bands between 250 Hz and 6 kHz, rats can communicate in frequencies above 18 kHz. Their vocalization types depend on the context and are normally associated to subjective or emotional states. It was reported significant vocal changes due to administration of replacement testosterone in a trained tenor singer with hypogonadism. Speech-Language Pathology clinical practices are being sought by singers who sporadically use anabolic steroids associated with physical exercise. They report difficulties in reaching and keeping high notes, "breakage" in the passage of musical notes and post singing vocal fatigue. Those abnormalities could be raised by the association of anabolic steroids and physical exercise. Thus, in order to verify if this association could promote vocal changes, maximum, minimum and fundamental frequencies and call duration in rats treated with anabolic steroids and physically trained (10 weeks duration) were evaluated. The vocalizations were obtained by handling the animals. At the end of that period, rats treated and trained showed significant decrease in call duration, but not in other parameters. The decrease in call duration could be associated to functional alterations in the vocal folds of treated and trained animals due to a synergism between anabolic steroids and physical training. 相似文献
82.
Andrea Rodriguez Loriett Cartaya Alexis Maldonado Edgar Marquez José R. Mora Tania Cordova 《Molecular physics》2017,115(14):1624-1632
The study on the mechanism of the gas-phase elimination or thermal decomposition kinetics of 2, 2-dimethyl-3-butenal has been carried out by using theoretical calculation at MP2, combined ab initio CBSQB3 and DFT (B3LYP, B3PW91, MPW1PW91, PBEPBE, PBE1PBE, CAMB3LYP, M06, B97d) levels of theory. A good reasonable agreement between experimental and calculated parameters was obtained by using CAMB3LYP/6-311G(d,pd) calculations. The contrasted calculated parameters against experimental values suggested decarbonylation reaction to proceed through a concerted five-membered cyclic transition state type of mechanism, involving the hydrogen transfer from the carbonyl carbon to the gamma carbon, consistent with observed kinetic isotope effect. The breaking of alpha carbon–carbonyl carbon bond to produce carbon monoxide is 50% advanced in the transition state. The reaction mechanism may be described as a concerted moderately non-synchronous process. Examination of the Atoms in Molecules (AIM) analysis of electron density supports the suggested mechanism. 相似文献
83.
A. J. Saleh Ahammad Abdullah Al Mamun Tania Akter M. A. Mamun S. Faraezi F. Z. Monira 《Journal of Solid State Electrochemistry》2016,20(7):1933-1939
A non-enzymatic impedimetric glucose sensor was fabricated based on the adsorption of gold nanoparticles (GNPs) onto conductive polyaniline (PANI)-modified glassy carbon electrode (GCE). The modified electrode (GCE/PANI/GNPs) was characterized by using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). The determination of glucose concentration was based on the measurement of EIS with the mediation of electron transfer by ferricyanide ([Fe(CN)6]3?). The [Fe(CN)6]3? is reduced to ferrocyanide ([Fe(CN)6]4?), which in turn is oxidized at GCE/PANI/GNPs. An increase in the glucose concentration results in an increase in the diffusion current density of the [Fe(CN)6]4? oxidation, which corresponds to a decrease in the faradaic charge transfer resistance (R ct). A wide linear concentration range from 0.3 to 10 mM with a lower detection limit of 0.1 mM for glucose was obtained. The proposed sensor shows high sensitivity, good reproducibility, and stability. In addition, the sensor exhibits no interference from common interfering substances such as ascorbic acid, acetaminophen, and uric acid. 相似文献
84.
Tania Córdova-Sintjago Nancy Villa Lijuan Fang Raymond G. Booth 《Molecular physics》2014,112(3-4):398-407
The serotonin (5-hydroxytryptamine, 5-HT) 5-HT2 G protein-coupled receptor (GPCR) family consists of types 2A, 2B, and 2C that share ~75% transmembrane (TM) sequence identity. Agonists for 5-HT2C receptors are under development for psychoses; whereas, at 5-HT2A receptors, antipsychotic effects are associated with antagonists – in fact, 5-HT2A agonists can cause hallucinations and 5-HT2B agonists cause cardiotoxicity. It is known that 5-HT2A TM6 residues W6.48, F6.51, and F6.52 impact ligand binding and function; however, ligand interactions with these residues at the 5-HT2C receptor have not been reported. To predict and validate molecular determinants for 5-HT2C-specific activation, results from receptor homology modelling, ligand docking, and molecular dynamics simulation studies were compared with experimental results for ligand binding and function at wild type and W6.48A, F6.51A, and F6.52A point-mutated 5-HT2C receptors. 相似文献
85.
For cleanup of animal fat before GC analysis of organochlorine pesticides and polychlorinated biphenyls, freezing-lipid filtration with solid-phase extraction and matrix solid-phase dispersion were evaluated to replace the official Brazilian methodology that uses preparative alumina column chromatography. General drawbacks associated with this last technique, such as the use of large amounts of solvent, laborious and time-consuming procedure could be avoided by using these alternative approaches. Experiments were carried out to study the performance by using different combinations of sorbents and elution solvents. Efficiency of alternative extraction methods in terms of fat removal and recovery capability was monitored by gravimetry, TLC, and GC with electron capture detection. Freezing-lipid filtration with solid-phase extraction afforded better clean up efficiency with recoveries in a range of 54.5 to 103.6% with the relative standard deviation of less than 10% for all compounds under investigation. 相似文献
86.
Cherta L Beltran J Portolés T Hernández F 《Analytical and bioanalytical chemistry》2012,402(7):2301-2314
A multiresidue method has been developed for quantification and identification of 66 multiclass priority organic pollutants
in water by fast gas chromatography (GC) coupled to mass spectrometry (MS). Capabilities and limitations of single quadrupole
mass spectrometer as detector in fast GC were studied evaluating the chromatographic responses in terms of sensitivity and
chromatographic peak shapes, as they were influenced by scan time. The number of monitored ions in a selected ion monitoring
(SIM) group strongly conditioned the scan time and subsequently the number of data points per peak. A compromise between peak
shape and scan time was adopted in order to reach the proper conditions for quantitative analysis. An average of 10–15 points
per peak was attained for most compounds, involving scan times between 0.1 and 0.22 s. The method was validated for mineral,
surface, and groundwater. A solid-phase extraction pre-concentration step using C18 cartridges was applied. Four isotopically labeled standards were added to the samples before extraction and used as surrogates
to ensure a reliable quantification. Analyses were performed by GC–MS in electron ionization mode, monitoring the three most
abundant and/or specific ions for each compound and using the intensity ratios as a confirmatory parameter. With a chromatographic
run of less than 10 min, SIM mode provided excellent sensitivity and identification capability due to the monitoring of three
ions and the evaluation of their intensity ratio. Limits of detection below 10 ng/L were reached for most of the 66 compounds
in the three matrices studied. Accuracy and precision of the method were evaluated by means of recovery experiments at two
fortification levels (10 and 100 ng/L), obtaining recoveries between 70% and 120% in most cases and relative standard deviations
below 20%. The possibilities of a simultaneous SIM scan method have also been explored for non-target qualitative analysis.
The developed method has been applied to the analysis of surface water samples collected from the Mediterranean region of
Spain. 相似文献
87.
Silva PR Almeida VO Machado GB Benvenutti EV Costa TM Gallas MR 《Langmuir : the ACS journal of surfaces and colloids》2012,28(2):1447-1452
A dispersant for multiwall carbon nanotubes (MWCNTs) is proposed that fulfils the requirements of creating a uniform dispersion in the matrix and obtaining a good interface between CNTs and the matrix, and is soluble in generic nonpolar solvents. This dispersant is based on a long chain surfactant, called in this work dabcosil stearate, containing a stearate-based 18-carbon alkyl chain as an anion, and a silsesquioxane containing a bridged, positively charged 1,4-diazoniabicyclo[2.2.2]octane group. It provides not only a very good dispersion medium for the MWCNTs, but also a very good interface between MWCNTs and ceramic matrices, such as alumina and zirconia, prepared by the sol-gel method. 相似文献
88.
A Akesson TK Lind R Barker A Hughes M Cárdenas 《Langmuir : the ACS journal of surfaces and colloids》2012,28(36):13025-13033
Poly(amidoamine) (PAMAM) dendrimers are promising candidates in several applications within the medical field. However, it is still to date not fully understood whether they are able to passively translocate across lipid bilayers. Recently, we used fluorescence microscopy to show that PAMAM dendrimers induced changes in the permeability of lipid membranes but the dendrimers themselves could not translocate to be released into the vesicle lumen. Because of the lack of resolution, these experiments could not assess whether the dendrimers were able to translocate but remained attached to the membrane. Using quartz crystal microbalance with dissipation monitoring and neutron reflectivity, a structural investigation was performed to determine how dendrimers interact with zwitterionic and negatively charged lipid bilayers. We hereby show that dendrimers adsorb on top of lipid bilayers without significant dendrimer translocation, regardless of the lipid membrane surface charge. Thus, most likely dendrimers are actively transported through cell membranes by protein-mediated endocytosis in agreement with previous cell studies. Finally, the higher activity of PAMAM dendrimers for phosphoglycerol-containing membranes is in line with their high antimicrobial activity against Gram-negative bacteria. 相似文献
89.
Solubility experiments of ethoxylates surfactants denoted as CiEOj (where Ci = hydrocarbon tail, EOj = oxyethylene groups, i = 6 to 8 and j = 3 to 5) in sub- and supercritical carbon dioxide were carried out at different temperatures, pressures, and concentrations in a Cailletet apparatus as a representative model for dry cleaning system. For a variety of compositions, results are reported for binary systems within temperature and pressure ranges of (260 to 310) K and (2.0 to 10) MPa respectively. In each experiment, the surfactants reach equilibrium with carbon dioxide at different concentrations. The data show that with all the surfactants upon increasing concentration, the liquid–liquid (L–L) curve shifts to lower temperatures. Therefore, the one-phase solution gap is reduced in pressure and temperature at higher concentrations. When the length of the hydrocarbon tail remains constant and the ethoxylated chain is increased from three to five groups, the L–L curve once again shifts to lower temperatures and the two phases start earlier. This effect can be attributed to the higher surfactant’s polarity due to the increase in j. On the other hand, when the number of ethoxylated groups j remains constant and the length of the hydrocarbon tail is increased from six to eight carbon atoms, no significant shift in the L–L curve is observed. That signals the fact that the appearance of two phases is directly related to the number of ethoxylated group which determine the polarity of the molecule. 相似文献
90.
The mononuclear amidinate complexes [(η6‐cymene)‐RuCl( 1a )] ( 2 ) and [(η6‐C6H6)RuCl( 1b )] ( 3 ), with the trimethylsilyl‐ethinylamidinate ligands [Me3SiC≡CC(N‐c‐C6H11)2]– ( 1a– ) and[Me3SiC≡CC(N‐i‐C3H7)2]– ( 1b– ) were synthesized in high yields by salt metathesis. In addition, the related phosphane complexes[(η5‐C5H5)Ru(PPh3)( 1b )] ( 4a ) [(η5‐C5Me5)Ru(PPh3)( 1b )] ( 4b ), and [(η6‐C6H6)Ru(PPh3)( 1b )](BF4) ( 5 ‐BF4) were prepared by ligand exchange reactions. Investigations on the removal of the trimethyl‐silyl group using [Bu4N]F resulted in the isolation of [(η6‐C6H6)Ru(PPh3){(N‐i‐C3H7)2CC≡CH}](BF4) ( 6 ‐BF4) bearing a terminal alkynyl hydrogen atom, while 2 and 3 revealed to yield intricate reaction mixtures. Compounds 1a / b to 6 ‐BF4 were characterized by multinuclear NMR (1H, 13C, 31P) and IR spectroscopy and elemental analyses, including X‐ray diffraction analysis of 1b , 2 , and 3 . 相似文献