Computational scheme for solving nonlinear fractional stochastic differential equations with delay

Abstract

This paper studies the numerical solution of fractional stochastic delay differential equations driven by Brownian motion. The proposed algorithm is based on linear B-spline interpolation. The convergence and the numerical performance of the method are analyzed. The technique is adopted for determining the statistical indicators of stochastic responses of fractional Langevin and Mackey-Glass models with stochastic excitations.     

Poisson-Vlasov: stochastic representation and numerical codes

In this paper, we examine the effects of the gravitational field on the dynamical evolution of the cavity-field entropy and the creation of the Schr?dinger-cat state in the Jaynes-Cummings model. We consider a moving two-level atom interacting with a single mode quantized cavity-field in the presence of a classical homogeneous gravitational field. Based on an su(2) algebra, as the dynamical symmetry group of the model, we derive the reduced density operator of the cavity-field which includes the effects of the atomic motion and the gravitational field. Also, we obtain the exact solution and the approximate solution for the system-state vector, and examine the atomic dynamics. By considering the temporal evolution of the cavity-field entropy as well as the dynamics of the Q-function of the cavity-field we study the effects of the gravitational field on the generation of the Schr?dinger-cat states of the cavity-field by using the Q-function, field entropy and approximate solution for the system-state vector. The results show that the gravitational field destroys the generation of the Schr?dinger-cat state of the cavity-field.     

Identification of a set of genes showing regionally enriched expression in the mouse brain

Background

We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods.

Results

Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner.

Conclusion

Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex.     

Constraints on the infrared behavior of the gluon propagator in Yang-Mills theories

We present rigorous upper and lower bounds for the zero-momentum gluon propagator D(0) of Yang-Mills theories in terms of the average value of the gluon field. This allows us to perform a controlled extrapolation of lattice data to infinite volume, showing that the infrared limit of the Landau-gauge gluon propagator in SU(2) gauge theory is finite and nonzero in three and in four space-time dimensions. In the two-dimensional case, we find D(0)=0, in agreement with Maas. We suggest an explanation for these results. We note that our discussion is general, although we apply our analysis only to pure gauge theory in the Landau gauge. Simulations have been performed on the IBM supercomputer at the University of S?o Paulo.     

Vibrational properties of Cs4W11O35 and Rb4W11O35 systems: high pressure and polarized Raman spectra

Cs₄ W₁₁O₃₅ (CW) and Rb₄ W₁₁O₃₅ (RW) belong to the class of hexagonal bronzes whose structure originates from the K_xWO₃ superconductor hexatungstate. Charge‐imbalanced tungsten bronzes are dielectric materials with rich polymorphism, ferroelectric properties and second‐harmonic generation. In this work, we report the polarized Raman spectra results for both CW and RW, as well as results of high‐pressure Raman scattering experiments (0.0–11.0 GPa) for the Cs₄ W₁₁O₃₅ system, in which we have observed two structural phase transitions at ∼4 and 7.5 GPa. We discuss these transformations and polarized Raman spectra on the basis of lattice dynamics calculation in the related system KNbW₂O₉. Polarized Raman spectra provide strong indication that the highest wavenumber modes observed in these systems originate from tungsten or oxygen vacancies. The observation of a soft‐like mode indicates that the observed phase transitions exhibit a displacive‐type behavior, thus further indicating that these transformations are likely related to reorientations of the octahedral units. The soft mode nature is discussed as well. PACS: 77.80.Bh; 78.30.Hv; 78.30.‐j. Copyright © 2010 John Wiley & Sons, Ltd.     

Temperature‐induced phase transformations in Na2WO4 and Na2MoO4 crystals

Temperature‐dependent Raman studies on Na₂WO₄and Na₂MoO₄ crystals were performed in order to obtain information on structural changes induced by temperature evolution. The stability of the cubic phase of Na₂WO₄and Na₂MoO₄crystals was assessed and our results indicate that this phase is stable in the 8–823 K and 15–773 K ranges for Na₂WO₄ and Na₂MoO₄, respectively. The crystal of Na₂WO₄ shows a phase transition occurring at 833 K. Na₂MoO₄undergoes a sequence of three phase transitions, which were observed at 783–803, 823–913 and 943–950 K. In both crystals, a strong first‐order phase transition occurs as indicated by the behavior of the Raman modes: the Raman bands split and new bands appear below 100 cm⁻¹. These transitions are connected with tilting and/or rotations of the WO₄and MoO₄ tetrahedra, which leads to a disorder at the WO₄and MoO₄ sites. Copyright © 2010 John Wiley & Sons, Ltd.     

Comparative bioavailability of two zolpidem hemitartrate formulations in healthy human Brazilian volunteers using high-performance liquid chromatography coupled to tandem mass spectrometry

To assess the bioequivalence of two zolpidem hemitartrate formulations in 30 healthy volunteers. Plasma samples were obtained over a 24 h period. Plasma concentrations of zolpidem were analyzed by liquid chromatography coupled to tandem mass spectrometry with positive ion electrospray ionization using multiple reaction monitoring. Values of peak concentration (C_max), area under curve (AUC), half-life, elimination constant, volume of distribution and clearance showed statistically significant differences when comparing women (604.34 ng h/ml, 127.36 ng/ml, 4.4 h, 0.18 1/h, 50.56 L and 8.55 L/h, respectively) and men (276.1 ng h/ml, 70.9 ng/ml, 3.3 h, 0.26 1/h, 91.42 L and 24.34 L/h, respectively), receiving the same dose (5 mg), respectively. The geometric means with corresponding 90% confidence interval for Test/Reference percentage ratios were 99.73% (CI 93.69–106.16) for C_max, 97.44% (90% CI = 91.85–103.37%) for area under curve of plasma concentration until the last concentration observed (AUC_last) and 98.30% (90% CI = 92.48–104.49) for the area under curve between the first sample (pre-dosage) and infinity (AUC_0–inf). Since the 90% CI for AUC_last, AUC_0–inf and C_max ratios were within the 80–125% interval proposed by the US Food and Drug Administration, it was concluded that zolpidem hemitartrate formulation (5 mg orodispersible tablet) is bioequivalent to the zolpidem hemitartrate formulation (Patz SL 5 mg sublingual tablet) with regard to both the rate and the extent of absorption. A new formulation of zolpidem 2.5 mg may be useful in women for the same clinical benefits as the 5 mg formulation in men.     

Elucidating the Influence of Electrical Potentials on the Formation of Charged Oligopeptide Self-Assembled Monolayers on Gold

Self-assembled monolayers (SAMs) based on oligopeptides have garnered immense interest for a wide variety of innovative biomedical and electronic applications. However, to exploit their full potential, it is necessary to understand and control the surface chemistry of oligopeptides. Herein, we report on how different electrical potentials affect the adsorption kinetics, stability and surface coverage of charged oligopeptide SAMs on gold surfaces. Kinetic analysis using electrochemical surface plasmon resonance (e-SPR) reveals a slower oligopeptide adsorption rate at more positive or negative electrical potentials. Additional analysis of the potential-assisted formed SAMs by X-ray photoelectron spectroscopy demonstrates that an applied electrical potential has minimal effect on the packing density. These findings not only reveal that charged oligopeptides exhibit a distinct potential-assisted assembly behaviour but that an electrical potential offers another degree of freedom in controlling their adsorption rate.     

Segmental order parameters in a nonionic surfactant lamellar phase studied with 1H-13C solid-state NMR

A lyotropic nonionic lamellar system composed of pentaethyleneglycol mono n-dodecyl ether and D(2)O was studied using natural abundance (13)C NMR under magic-angle spinning. Applying a two-dimensional recoupling method proposed by Dvinskikh (R-PDLF), (1)H-(13)C dipolar couplings were estimated over a range of temperatures (300-335 K), thus enabling analysis of structural changes in the liquid crystalline system. The results obtained are used to correlate the conformation and mobility of local sites in the surfactant molecule with overall changes in the lamellar structure.