Two-Well System under Large Amplitude Periodic Forcing: Stochastic Synchronization, Stochastic Resonance and Stability

We study the residence time distributions and explore the possibility of observing stochastic resonance and synchonization of passages in a two-well system driven by a periodic forcing of amplitude larger than a marginal value beyond which one of the two wells become unstable and diasppear. We define and calculate hysteresis loop in the system, the area of which measures the degree of synchronization between the residence time statistics and the input signal, as a function of input noise strength. We analyse the noise induced stability obtained in such a deterministically overall unstable system and within this context discuss the above two phenomena.Comment: Mod. Phys. Lett. B 1997, in print, figures available on reques

AC driven thermal ratchets

We consider the motion of a overdamped Brownian particle in periodic asymmetric potential with space dependent friction coefficient. In the presence of external time periodic forcing, the system shows multiple current reversals on varying the amplitude of the external forcing and the temperature of the thermal bath. In the adiabatic regime we find a single reversal of current as a function of noise strength which can only be accounted due to the presence of space dependent friction coefficient. For very large forcing term, the current does not go to zero, instead it asymptotically tends to a limiting value depending on the phase shift between the potential and the friction. This fact plays an important role in obtaining multiple current reversals.Comment: 4 pages, latex/revtex, 4 eps figures. Proceedings of CMDAYS2K, held at Guru Ghasidas University, Bilaspur, Chattisgarh, India, Aug 29-31, 2

Stochastic resonance and nonlinear response in a dissipative quantum two-state system

We study the dynamics of a dissipative two-level, system driven by a monochromatic ac field, starting from the usual spin-boson Hamiltonian. The quantum Langevin equations for the spin variables are obtained. The amplitude of the coherent oscillations in the average position of the particle is studied in the high temperature limit. The system exhibits quantum stochastic resonance in qualitative agreement with earlier numerical results.Comment: PRB April 1997, figures available on reques

Eenhancement of solubility and dissolution rate of Furosemide by ternary solid dispersion technique

Purpose: This investigation was carried out to determine if a solid dispersion of furosemide in different carrier such as poloxamer 407P, PEG 6000, and PVPK30 would enhance the dissolution properties of the drug. Method: Solid dispersion of drug Furosemide, PEG 6000 and Poloxamer 407 and PVP K30 were prepared with a view to study the influence of polymer on solubility and dissolution of this poorly soluble drug furosemide. Solid dispersions of furosemide were prepared using different ratios of furosemide, PEG 6000, Poloxamer 407, pvpk30 as carrier by, solvent evaporation method. They were evaluated for percentage yield, drug content, FTIR spectral studies, DSC, XRD, solubility, and in-vitro dissolution. The dissolution studies were performed at 37 0.5oC and 50 rpm in simulated gastric fluid (0.1 N HCl). Result: The solubility profile indicated that there is increase in solubility of furosemide when polymer concentration is increased. The solid dispersion complex of drug (1:4:4 ratios) of drug: poloxamer 407: pvpk30 was giving better dissolution profile as compared to pure drug and other solid dispersions. This in turn can improve the bioavailability. FT-IR, DSC shows the compatibility of drug and carrier. Conclusion: Solid dispersion technique can be used to improve the dissolution of furosemide

ANALYSIS OF JOB STRESS AFFECTING PERFORMANCE OF TECHNICAL TEACHERS

In this modern society job stress is a much talked complex phenomena leading to many disastrous consequences. Moderate level of stress that motivates a teacher is good. But as per the review of literature at international and national levels scenarios; some of the findings of the study reveals that majority of teachers faces serious problems of job stress due to various reasons such as work overload, lack of resources, role ambiguity, fair/less compensation, inadequate work environment etc. Also poor relations with colleagues, students’ indiscipline, lack of support from higher authorities, negative community attitude, farrago of thoughts related to profession and improper trainings contributes greatly in enhancing the problem. The quality of Technical education is serious concern of current situation which poses many issues to the future of technical youth. In this research it is tried to analyses the causes of stress and impact on quality because of stress. This will be done by designing the questionnaire depicting various reasons of stress in the educational Institutions as mentioned above. After that analysis will be done before coming the conclusion by applying various statistical methods on the data collected.  The results will help us in identifying the key factors impacting quality of Technical Teachers. Hence this research is expected to contribute towards increase in the productivity of teachers in technical education. In future this research can be applied to the teacher community as a whole.&nbsp

Noise assisted directed motion at the molecular level - 2

The term noise is used to describe fluctuations about the mean deterministic stationary value of a physical quantity. It is now being increasingly realised that noise is an important ingredient to bring order in dynamical processes. Though it appears counterintuitive, noise seems to help in directing transport processes in biological systems at the molecular level. In Part 2 of the article, we discuss some more examples of noise assisted directed motion

Efficiency and current reversals in spatially inhomogeneous ratchets

Efficiency of generation of net unidirectional current in an adiabatically driven symmetric periodic potential system is studied. The efficiency shows a maximum, in the case of an inhomogeneous system with spatially varying periodic friction coefficient, as a function of temperature. The ratchet is not most efficient when it gives maximum current. The direction of current may also be reversed as a function of noise strength when, instead, an asymmetric periodic potential is considered

Supersymmetry and Fokker-Planck dynamics in periodic potentials

Recently, the Fokker-Planck dynamics of particles in periodic potentials ±V, have been investigated by using the matrix continued fraction method. It was found that the two periodic potentials, one being bistable and the other metastable give the same diffusion coefficient in the overdamped limit. We show that this result naturally follows from the fact that the considered potentials in the corresponding Schrodinger equation form supersymmetric partners. We show that these differing potentials ±V also exhibit symmetry in current and diffusion coefficients: J+(F)=−J−(−F) and D+(F)=D−(−F) in the presence of a constant applied force F. Moreover, we show numerically that the transport properties in these potentials are related even in the presence of oscillating drive