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31.
The possibility to detect and prospectively to characterize deposited organic layers directly on Spreeta sensors by Fourier transform Raman spectroscopy was studied. A special holder of sensors that enabled measurement of FT Raman spectra was developed. The effects of various angles of incidence of the laser beam on the sensor surface were studied with respect to the intensity of Raman spectra and to the risks of artifacts. No effect of measurement of FT Raman spectra on SPR functionality of sensors was proven. The key role of the surface morphology of the sensing gold layer on repeatability of SPR curves and the possibility to check the surface by optical microscopy was demonstrated. 相似文献
32.
Matías Germán dell’Erba 《Journal of statistical physics》2012,146(6):1263-1273
We perform an analytical study of a simplified bipartite matching problem in which there exists a constant matching energy,
and both heterosexual and homosexual pairings are allowed. We obtain the partition function in a closed analytical form and
we calculate the corresponding thermodynamic functions of this model. We conclude that the model is favored at high temperatures,
for which the probabilities of heterosexual and homosexual pairs tend to become equal. In the limits of low and high temperatures,
the system is extensive, however this property is lost in the general case. There exists a relation between the matching energies
for which the system becomes more stable under external (thermal) perturbations. As the difference of energies between the
two possible matches increases the system becomes more ordered, while the maximum of entropy is achieved when these energies
are equal. In this limit, there is a first order phase transition between two phases with constant entropy. 相似文献
33.
34.
Zañartu M Mehta DD Ho JC Wodicka GR Hillman RE 《The Journal of the Acoustical Society of America》2011,129(1):326-339
Different source-related factors can lead to vocal fold instabilities and bifurcations referred to as voice breaks. Nonlinear coupling in phonation suggests that changes in acoustic loading can also be responsible for this unstable behavior. However, no in vivo visualization of tissue motion during these acoustically induced instabilities has been reported. Simultaneous recordings of laryngeal high-speed videoendoscopy, acoustics, aerodynamics, electroglottography, and neck skin acceleration are obtained from a participant consistently exhibiting voice breaks during pitch glide maneuvers. Results suggest that acoustically induced and source-induced instabilities can be distinguished at the tissue level. Differences in vibratory patterns are described through kymography and phonovibrography; measures of glottal area, open/speed quotient, and amplitude/phase asymmetry; and empirical orthogonal function decomposition. Acoustically induced tissue instabilities appear abruptly and exhibit irregular vocal fold motion after the bifurcation point, whereas source-induced ones show a smoother transition. These observations are also reflected in the acoustic and acceleration signals. Added aperiodicity is observed after the acoustically induced break, and harmonic changes appear prior to the bifurcation for the source-induced break. Both types of breaks appear to be subcritical bifurcations due to the presence of hysteresis and amplitude changes after the frequency jumps. These results are consistent with previous studies and the nonlinear source-filter coupling theory. 相似文献
35.
The generation of aerodynamic sound by the interaction of flow at a Reynolds number of 150 and a Mach number of 0.2 with a rigid square cylinder attached to a rigid thin flat plate is numerically investigated. When the length of the plate is varied from L=0.5D to 6D, where D is the side length of the square cylinder, the results can be grouped into three distinct regimes. For the first regime (L?D), the sound levels decrease with increasing plate length. A 3 dB sound reduction is obtained when the length of the plate is D. For the second regime (1.25D?L?4.75D), the sound levels increase with increasing plate length. For the third regime (5D?L?6D), the sound levels decrease as the length of the plate increases but the levels are higher than for the other regimes. Results also show that the lift fluctuation is the dominant sound source. These acoustic results can be explained in terms of the fluid mechanics occurring in the near wake of the cylinder. 相似文献
36.
Pavel Řezanka Klára Navrátilová Pavel Žvátora David Sýkora Pavel Matějka Ivan Mikšík Václav Kašička Vladimír Král 《Journal of nanoparticle research》2011,13(11):5947-5957
In this study, spherical gold nanoparticles (GNPs) of 14.7 nm diameter, prepared by citrate reduction of a gold(III) salt
and characterized by UV–Vis absorption spectrometry and transmission electron microscopy, were modified by a covalent attachment
of 6I-O-(3-mercaptopropyl)β-cyclodextrin (β-CD-SH) or per-6-deoxy-per-6-mercapto-β-cyclodextrin (β-CD-SH7). Subsequently, via three
alternative approaches, β-CD-modified GNPs were immobilized onto the inner wall of the fused-silica (FS) capillaries and applied
as special stationary phases for open-tubular capillary electrochromatography (OT-CEC). The first immobilization procedure
was based on pre-derivatization of a FS capillary with (3-mercaptopropyl)trimethoxysilane (MPTMS) followed by subsequent reactions
with GNPs and β-CD-SH or β-CD-SH7. The other two preparation protocols took advantage of sol–gel approach gaining a significant
increase in the interaction surface for solutes. In both instances, the sol–gel created 3D structure was further covalently
modified with GNPs. Serving that purpose, either β-CD-SH7 modified GNPs were used for the immobilization into the sol–gel
matrix (“one-step sol–gel technique”) or native GNPs were immobilized first into the sol–gel matrix and subsequently modified
with β-CD-SH7 (“two-step sol–gel technique”). The separation performance of CD-GNPs modified FS capillaries was tested by
OT-CEC in reversed-phase mode applied to separation of a model mixture of five polyaromatic hydrocarbons. The highest separation
efficiencies were obtained with the capillaries prepared by two-step sol–gel technique. However, with respect to the relatively
low reproducibility of this method, the first of the above preparation procedures, i.e., a simple pre-derivatization of the
FS capillary with MPTMS ensued with β-CD-SH7-GNPs immobilization seems to be more feasible approach providing decent separation
efficiency. 相似文献
37.
Aurélie Matéos Jean‐Michel Girardet Daniel Mollé Catherine Corbier Jean‐Luc Gaillard Laurent Miclo 《Rapid communications in mass spectrometry : RCM》2010,24(11):1533-1542
Equine β‐casein is phosphorylated at variable degrees and isoforms carrying 3 to 7 phosphate groups (3P–7P) have been found in milk, but the phosphorylated amino acid residues of each isoform are not yet identified. In the present work, the different phosphorylation variants were first isolated by ion‐exchange chromatography and then hydrolysed by trypsin to generate caseinophosphopeptides (CPPs), each containing all the potential phosphorylation sites. The equine CPPs were prepared by metal oxide affinity chromatography, a method based on the affinity of phosphate groups towards titanium dioxide immobilized onto a micro‐column. This method turned out to be an efficient tool to separate the CPPs Arg1–Lys34 and Glu4–Lys34 from non‐phosphorylated peptides. Purification was achieved by reversed‐phase high‐performance liquid chromatography (RP‐HPLC) and each CPP was hydrolyzed by endoproteinase Glu‐C. Finally, the digests were analyzed by RP‐HPLC/electrospray ionization mass spectrometry (RP‐HPLC/ESI‐MS) and identified by nano‐electrospray ionization tandem mass spectrometry (nESI‐MS/MS) to locate the phosphorylated sites of the β‐casein isoforms 4P–7P with accuracy. Thus, the isoform 4P was found to be phosphorylated on residues Ser9, Ser23, Ser24, and Ser25. Addition of phosphate groups on Ser18, Thr12, and Ser10 led to the formation of the isoforms 5P–7P, respectively. The results indicated that the in vivo phosphorylation of the equine β‐casein follows a sequential way and is not randomly performed. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
38.
We propose an SQP algorithm for mathematical programs with vanishing constraints which solves at each iteration a quadratic program with linear vanishing constraints. The algorithm is based on the newly developed concept of \({\mathcal {Q}}\)-stationarity (Benko and Gfrerer in Optimization 66(1):61–92, 2017). We demonstrate how \({\mathcal {Q}}_M\)-stationary solutions of the quadratic program can be obtained. We show that all limit points of the sequence of iterates generated by the basic SQP method are at least M-stationary and by some extension of the method we also guarantee the stronger property of \({\mathcal {Q}}_M\)-stationarity of the limit points. 相似文献
39.
Perullini Mercedes Jobbágy Matías Bilmes Sara A. Torriani Iris L. Candal Roberto 《Journal of Sol-Gel Science and Technology》2011,59(1):174-180
Silica matrices synthesized from a pre-hydrolysis step in ethanol followed by alcohol removal at low pressure distillation,
and condensation in water, are suitable for encapsulation of biomolecules and microorganisms and building bioactive materials
with optimized optical properties. Here we analyze the microstructure of these hydrogels from the dependence of I(q) data acquired from SAXS experiments over a wide range of silica concentration and pH employed in the condensation step. From
the resulting data it is shown that there is a clear correlation between the microscopic parameters—cluster fractal dimension
(D), elementary particle radius (a) and cluster gyration radius (R)—with the attenuation of visible light when the condensation step proceeds at pH < 6. At higher pHs, there is a steep dependence
of the cluster density (~R
D−3) with the condensation pH, and non-monotonous changes of attenuance are less than 20%, revealing the complexity of the system.
These results, which were obtained for a wide pH and silica concentration range, reinforce the idea that the behavior of gels
determined in a restricted interval of synthesis variables cannot be extrapolated, and comparison of gelation times is not
enough for predicting their properties. 相似文献
40.
This study deals with O2− generation in corona discharge (CD) in point to plane geometry for single flow ion mobility spectrometry (IMS) with gas outlet located behind the ionization source. We have designed CD of special geometry in order to achieve the high O2− yield. Using this ion source we have achieved in zero air conditions that up to 74% all negative ions were O2− or O2−(H2O). It has been demonstrated that the non-electronegative nitrogen positively influences the efficiency of O2− generation in O2/N2 mixtures. The reduced ion mobility of 2.27 cm2 V−1 s−1 has been measured for O2−/O2−(H2O) ions in zero air. Additional ions detected in zero air (less than 200 ppb CO2) using the mass spectrometric and IMS technique were, NO2−, N2O2− (2.37 cm2 V−1 s−1), NO3−, N2O3− and N2O3−(H2O). The CO3− and CO4− ions have been detected after the introduction of 5 ppm CO2 into zero air. 相似文献