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131.
The temporal evolution of a perturbation of the equilibrium distribution of a condensed Bose gas is investigated using the kinetic equation which describes collision between condensate and noncondensate atoms. The dynamics is studied in the low momentum limit where an analytical treatment is feasible. Explicit results are given for the behavior at large times in different temperature regimes. 相似文献
132.
In this study, performances of the profilometry method based on structured-light projection are analyzed in the case of a large dimension object and a short distance from the acquisition system. This work is based on the calibration procedure introduced by Brèque et al. After the evaluation of Brèque's pinhole model, a new calibration procedure based on polynomial transformations is proposed. The proposed work is founded on a systematic study of different degrees of a polynomial form. Random and systematic errors are calculated to show accuracies for polynomial degrees equal to 1, 2, 3 and 4. Different sources of errors are presented and discussed. The developed calibration is applied to a human body and a human-size dummy. 相似文献
133.
Summary: A rapid preparation of the title compound in essentially pure form upon solvent removal and its reaction with Grignard reagents in the presence of copper (I) is reported. 相似文献
134.
Juan C. del Valle Enrique Camarillo Julio A. Gonzalo Carmen Aragó Manuel Marqués 《哲学杂志》2015,95(7):683-690
Recently, the paraelectric response of water was investigated in the range 0–100 °C. It showed an almost perfect Curie–Weiss behaviour up to 60 °C, but a slight change in slope of 1/εd versus T at 60 °C was overlooked. In this work, we report optical extinction measurements on metallic (gold and silver) nanoparticles dispersed in water, annealed at various temperatures in the range from 20 to 90 °C. An anomalous response at 60 °C is clearly detectable, which we associate to a subtle structural transformation in the water molecules at that temperature. This water anomaly is also manifested by means of a blue shift in the longitudinal surface plasmon resonance of the metallic nanoparticles for the solutions annealed at temperatures higher than about 60 °C. A reanalysis of 1/εd (T) for water in the whole temperature range leads us to conclude that the water molecule undergoes a subtle transformation from a low temperature (0–60 °C) configuration with a dipole moment μ1 = 2.18 D (close to the molecular dipole moment of ice) to a high temperature (60–100 °C) configuration with μ2 = 1.87 D (identical to the molecular dipole moment in water vapour). 相似文献
135.
Summary In this paper we have used Wittrick's theory on the propagation of deformation waves in a coiled wire — taking only into account the coupling between the displacements of the wire cross-section along the tangent and along the binormal of the average helix — in oder to show how the natural frequencies of the axial and rotational modes of a cylindrical helical spring vary according to a non-linear function of the wave number. Moreover it is here demonstrated that the natural frequencies resulting from the proposed theory for the natural modes to which correspond wave lengths greater than two coils do not differ much from those which can be calculated by considering the spring as a periodic discrete system. Theoretical results are finally tested by an appropriate experimental investigation.
Research supported by the Ministero della Pubblica Istruzione, Italy. 相似文献
Sommario Viene utilizzata la teoria proposta dal Wittrick sulla propagazione delle onde di deformazione in un filo avvolto ad elica, tenendo conto del solo accoppiamento tra gli spostamenti delle sezioni del filo lungo la tangente e lungo la binormale all'elica media, per mettere in evidenza come le pulsazioni naturali dei modi assiali e rotazionali di una molla ad elica cilindrica varino secondo una funzione non lineare del numero d'onda. Si dimostra che le pulsazioni naturali che si ottengono dalla teoria proposta, per modi di vibrare cui corrispondono lunghezze d'onda maggiori di due spire, sono poco discoste da quelle prevedibili considerando la molla come sistema discreto periodico. I risultati della teoria surriportata vengono infine controllati a mezzo di una opportuna indagine sperimentale.
Research supported by the Ministero della Pubblica Istruzione, Italy. 相似文献
136.
del Valle JC 《The Journal of chemical physics》2006,124(10):104506
The photophysics of the 5-hydroxyflavone (5HF) molecule has been revised. Conversely to what has been hitherto reported, the proton-transfer fluorescence of 5HF has been recorded under xenon lamp excitation in cyclohexane, hexane, ethanol, ethyl ether, 2-methyl-2-propanol, and dimethylsulfoxide at room temperature. The 5HF fluorescence spectra only exhibit one emission band centered at ca. 700 nm. A small photoreaction quantum yield of 10(-5)-10(-6) denotes the great photostability exemplified by 5HF in hydrocarbon solvent, ethanol, and dimethylsulfoxide. This great photostability is predominantly explained owing to an internal conversion process from the first excited singlet state 1(pi,pi*)1 (S1), which has a repulsive (proton-transfer) potential energy curve with respect to the stretching of the OH bond and only one energy minimum for the proton-transfer tautomer. The S1'-S0' energy gap proves to be small because of important modifications found in the molecular geometry of 5HF upon photoexcitation. A computational strategy, based upon theoretical calculations at the B3LYP density functional theory (DFT) and time-dependent DFT levels, supports the experimental spectroscopic evidence. Also an abnormal singlet-triplet splitting for a pi,pi* configuration has been found in 5HF. 相似文献
137.
Cortina M Duran A Alegret S del Valle M 《Analytical and bioanalytical chemistry》2006,385(7):1186-1194
Intelligent and automatic systems based on arrays of non-specific-response chemical sensors were recently developed in our
laboratory. For multidetermination applications, the normal choice is an array of potentiometric sensors to generate the signal,
and an artificial neural network (ANN) correctly trained to obtain the calibration model. As a great amount of information
is required for the proper modelling, we proposed its automated generation by using the sequential injection analysis (SIA)
technique. First signals used were steady-state: the equilibrium signal after a step-change in concentration. We have now
adapted our procedures to record the transient response corresponding to a sample step. The novelty in this approach is therefore
the use of the dynamic components of the signal in order to better discriminate or differentiate a sample. In the developed
electronic tongue systems, detection is carried out by using a sensor array formed by five potentiometric sensors based on
PVC membranes. For the developed application we employed two different chloride-selective sensors, two nitrate-selective sensors
and one generic response sensor. As the amount of raw data (fivefold recordings corresponding to the five sensors) is excessive
for an ANN, some feature extraction step prior to the modelling was needed. In order to attain substantial data reduction
and noise filtering, the data obtained were fitted with orthonormal Legendre polynomials. In this case, a third-degree Legendre
polynomial was shown to be sufficient to fit the data. The coefficients of these polynomials were the input information fed
into the ANN used to model the concentrations of the determined species (Cl−, and ). Best results were obtained by using a backpropagation neural network trained with the Bayesian regularisation algorithm;
the net had a single hidden layer containing three neurons with the tansig transfer function. The results obtained from the time-dependent response were compared with those obtained from steady-state
conditions, showing the former superior performance. Finally, the method was applied for determining anions in synthetic samples
and real water samples, where a satisfactory comparison was also achieved.
相似文献
138.
Bonanni A Esplandiu MJ Pividori MI Alegret S del Valle M 《Analytical and bioanalytical chemistry》2006,385(7):1195-1201
Impedance spectroscopy is proposed as the transduction principle for detecting the hybridization of DNA complementary strands.
In our experiments, different DNA oligonucleotides were used as model gene substances. The gene probe is first immobilized
on a graphite-epoxy composite working electrode based genosensor. Detection principle is based on changes of impedance spectra
of a redox marker, the ferro/ferricyanide couple, after hybridization with target DNA. Resistance offered to the electrochemical
reaction serves as the working signal, allowing for an unlabelled gene assay.
相似文献
139.
Nicolas G. Martinelli Yoann Olivier Dr. Stavros Athanasopoulos Dr. Mari‐Carmen Ruiz Delgado Dr. Kathryn R. Pigg Demétrio A. da Silva Filho Dr. Roel S. Sánchez‐Carrera Dr. Elisabetta Venuti Raffaele G. Della Valle Prof. Jean‐Luc Brédas Prof. David Beljonne Dr. Jérôme Cornil Dr. 《Chemphyschem》2009,10(13):2158-2158
140.