Numerical Simulation of Groundwater Flow with Gradually Increasing Heterogeneity due to Clogging

Well injection replenishes depleting water levels in a well field. Observation well water levels some distance away from the injection well are the indicators of the success of a well injection program. Simulation of the observation well response, located a few tens of meters from the injection well, is likely to be affected by the effects of nonhomogeneous medium, inclined initial water table, and aquifer clogging. Existing algorithms, such as the U.S. Geological Survey groundwater flow software MODFLOW, are capable of handling the first two conditions, whereas time-dependent clogging effects are yet to be introduced in the groundwater flow models. Elsewhere, aquifer clogging is extensively researched in theory of filtration; scope for its application in a well field is a potential research problem. In the present paper, coupling of one such filtration theory to MODFLOW is introduced. Simulation of clogging effects during “Hansol” well recharge in the parts of western India is found to be encouraging.

Rolling tachyons, random matrices, and Coulomb gas thermodynamics

Time-dependent backgrounds in string theory provide a natural testing ground for physics concerning dynamical phenomena which cannot be reliably addressed in usual quantum field theories and cosmology. A good, tractable example to study is the rolling tachyon background, which describes the decay of an unstable brane in bosonic and supersymmetric Type II string theories. In this thesis I use boundary conformal field theory along with random matrix theory and Coulomb gas thermodynamics techniques to study open and closed string scattering amplitudes off the decaying brane. The calculation of the simplest example, the tree-level amplitude of n open strings, would give us the emission rate of the open strings. However, even this has been unknown. I will organize the open string scattering computations in a more coherent manner and will argue how to make further progress.

Nickel(II) meso-hydroxyporphyrin complexes revisited: Palladium-catalysed synthesis, electronic structures of derived oxy radicals, and oxidative coupling to a dioxoporphodimethene dyad

We report the synthesis and characterisation of new examples of meso-hydroxynickel(II) porphyrins with 5,15-diphenyl and 10-phenyl-5,15-diphenyl/diaryl substitu- tion. The OH group was introduced by using carbonate or hydroxide as nucleophile by using palladium/phosphine cat- alysis. The NiPor OHs exist in solution in equilibrium with the corresponding oxy radicals NiPor OC. The 15-phenyl group stabilises the radicals, so that the 1H NMR spectra of {NiPor OH} are extremely broad due to chemical exchange with the paramagnetic species. The radical concentration for the diphenylporphyrin analogue is only 1%, and its NMR line-broadening was able to be studied by variable-tempera- ture NMR spectroscopy. The EPR signals of NiPor OC are con- sistent with somewhat delocalised porphyrinyloxy radicals, and the spin distributions calculated by using density func- tional theory match the EPR and NMR spectroscopic obser- vations. Nickel(II) meso-hydroxy-10,20-diphenylporphyrin was oxidatively coupled to a dioxo-terminated porphodimethene dyad, the strongly red-shifted electronic spectrum of which was successfully modelled by using time-dependent DFT calculations.

Manifestation of conical intersections in resonance Raman intensities

This paper deals with the manifestations of conical intersections (CIs), unequivocal spectroscopic signatures of which are still elusive, in the resonance Raman intensities. In particular, the results of our calculations on the `two state-two vibrational mode' and the `two state-three vibrational mode' models are presented. The models comprise two excited states of different spatial symmetry, one bright and one dark, which are coupled by a nontotally symmetric mode while the energy gap between them is tuned by one/two totally symmetric modes. Time dependent theory for vibronically coupled states is employed for the calculation and analysis of Raman excitation profiles (REPs). The manifestation of intersections in REPs is studied by extensive modelm calculations and the results of two specific models are presented. Themfeasibility of using REPs to probe the role of CIs in polyatomic systems is ascertained by multimode calculations on two polyatomic systems viz., pyrazine and trans-azobenzene. The study also notes the importance of the pump excitation wavelength dependence in a femtosecond time-resolved experiment probing the intersection-induced nonadiabatic dynamics. Copyright (C) 2009 John Wiley & Sons, Ltd.

Climatic potential of delta O-18 of Abies spectabilis from the Nepal Himalaya

A 50-year tree-ring delta O-18 chronology of Abies spectabilis growing close to the tree line (3850 m asl) in the Nepal Himalaya is established to explore its dendroclimatic potential. Response function analysis with ambient climatic records revealed that tree-ring delta O-18 is primarily governed by rainfall during the monsoon season (June September), and the regression model accounts for 35% of the variance in rainfall. Extreme dry years identified in instrumental weather data are detected in the delta O-18 chronology. Further, tree-ring delta O-18 is much more sensitive to rainfall fluctuations than other tree-ring parameters such as width and density typically used in dendroclimatology. Correlation analyses with Nino 3.4 SST reveal time-dependent behavior of ENSO-monsoon relationships. (C) 2009 Elsevier GmbH. All rights reserved.

Solvation dynamics in dipolar liquids

The time dependent response of a polar solvent to a changing charge distribution is studied in solvation dynamics. The change in the energy of the solute is measured by a time domain Stokes shift in the fluorescence spectrum of the solute. Alternatively, one can use sophisticated non-linear optical spectroscopic techniques to measure the energy fluctuation of the solute at equilibrium. In both methods, the measured dynamic response is expressed by the normalized solvation time correlation function, S(t). The latter is found to exhibit uniquefeatures reflecting both the static and dynamic characteristics of each solvent. For water, S(t) consists of a dominant sub-50 fs ultrafast component, followed by a multi-exponential decay. Acetonitrile exhibitsa sub-100 fs ultrafast component, followed by an exponential decay. Alcohols and amides show features unique to each solvent and solvent series. However, understanding and interpretation of these results have proven to be difficult, and often controversial. Theoretical studiesand computer simulations have greatly facilitated the understanding ofS(t) in simple systems. Recently solvation dynamics has been used extensively to explore dynamics of complex systems, like micelles and reverse micelles, protein and DNA hydration layers, sol-gel mixtures and polymers. In each case one observes rich dynamical features, characterized again by multi-exponential decays but the initial and final time constants are now widely separated. In this tutorial review, we discuss the difficulties in interpreting the origin of the observed behaviour in complex systems.

Analysis of Dynamic Heterogeneity in a Glass Former from the Spatial Correlations of Mobility

The growth of characteristic length scales associated with dynamic heterogeneity in glass-forming liquids is investigated in an extensive computational study of a four-point, time-dependent structure factor defined from spatial correlations of mobility, for a model liquid for system sizes extending up to 351 232 particles, in constant-energy and constant-temperature ensembles. Our estimates for dynamic correlation lengths and susceptibilities are consistent with previous results from finite size scaling. We find scaling exponents that are inconsistent with predictions from inhomogeneous mode coupling theory and a recent simulation confirmation of these predictions.

Polarization relaxation, dielectric dispersion, and solvation dynamics in dense dipolar liquid

A unified treatment of polarization relaxation, dielectric dispersion and solvation dynamics in a dense, dipolar liquid is presented. It is shown that the information of solvent polarization relaxation that is obtained by macroscopic dielectric dispersion experiments is not sufficient to understand dynamics of solvation of a newly created ion or dipole. In solvation, a significant contribution comes from intermediate wave vector processes which depend critically on the short range (nearest‐neighbor) spatial and orientational order that are present in a dense, dipolar liquid. An analytic expression is obtained for the time dependent solvation energy that depends, in addition to the translational and rotational diffusion coefficients of the liquid, on the ratio of solute–solvent molecular sizes and on the microscopic structure of the polar liquid. Mean spherical approximation (MSA) theory is used to obtain numerical results for polarization relaxation, for wave vector and frequency dependent dielectric function and for time dependent solvation energy. We find that in the absence of translational contribution, the solvation of an ion is, in general, nonexponential. In this case, the short time decay is dominated by the longitudinal relaxation time but the long time decay is dominated by much slower large wave vector processes involving nearest‐neighbor molecules. The presence of a significant translational contribution drastically alters the decay behavior. Now, the long‐time behavior is given by the longitudinal relaxation time constant and the short time dynamics is controlled by the large wave vector processes. Thus, although the continuum model itself is conceptually wrong, a continuum model like result is recovered in the presence of a sizeable translational contribution. The continuum model result is also recovered in the limit of large solute to solvent size ratio. In the opposite limit of small solute size, the decay is markedly nonexponential (if the translational contribution is not very large) and a complete breakdown of the continuum model takes place. The significance of these results is discussed.

Undamped oscillations of homogeneous collisionless stellar systems

The Lewis (1968) invariant of the time-dependent harmonic oscillator is used to construct exact time-dependent, uniform density solutions of the collisionless Boltzmann equation. The spatially bound solutions are time-periodic.

Hepatotoxicity of pulegone in rats: Its effects on microsomal enzymes, in vivo

Oral administration of pulegone (400 mg/kg) to rats once daily for five days caused significant decreases in the levels of liver microsomal cytochrome P-450 and heme. Cytochrome b5 and NAD(P)H-cytochrome c-reductase activities were not affected. Massive hepatotoxicy accompanied by an increase in serum glutamate pyruvate transaminase (SGPT) and a decrease in glucose-6-phosphatase were observed upon treatment with pulegone. A significant decrease in aminopyrine N-demethylase was also noticed after pulegone administration. Menthone or carvone (600 mg/kg), compounds related to pulegone, when administered orally did not cause any decrease in cytochrome P-450 levels. The hepatotoxic effects of pulegone were both dose and time dependent. Pretreatment of rats with phenobarbital (PB) or diethylmaleate (DEM) potentiated the hepatotoxicity caused by pulegone, whereas, pretreatment with 3-methylcholanthrene (3-MC) or piperonyl butoxide protected from it. It appears that a PB induced cytochrome P-450 catalysed reactive metabolite(s) may be responsible for the hepatotoxicity caused by pulegone.

Modeling server-unreliability in closed queuing-networks

A method is presented to model server unreliability in closed queuing networks. Breakdowns and repairs of servers, assumed to be time-dependent, are modeled using virtual customers and virtual servers in the system. The problem is thus converted into a closed queue with all reliable servers and preemptive resume priority centers. Several recent preemptive priority approximations and an approximation of the one proposed are used in the analysis. This method has approximately the same computational requirements as that of mean-value analysis for a network of identical dimensions and is therefore very efficient

Study of magnetic field effect on the specific heat and entropy in DyBa2Cu3O7-x

The change in the specific heat by the application of magnetic field up to 161 for high temperature superconductor system for DyBa2Cu3O7-x by Revaz et al. [23] is examined through the phenomenological Ginzburg-Landau(G-L) theory of anisotropic Type-II superconductors. The observed specific heat anomaly near T-c with magnetic field is explained qualitatively through the expression <Delta C > = (B-a/T-c) t/(1 - t)(alpha Theta(gamma)lambda(2)(m)(0)), which is the anisotropic formulation of the G-L theory in the London limit developed by Kogan and coworkers; relating to the change in specific heat Delta C for the variation of applied magnetic field for different orientations with c-axis. The analysis of this equation explains satisfactorily the specific heat anomaly near T-c and determines the anisotropic ratio gamma as 5.608, which is close to the experimental value 5.3 +/- 0.5given in the paper of Revaz et al. for this system. (C) 2010 Elsevier B.V. All rights reserved.

Semi-similar solutions of the unsteady compressible second-order boundary layer flow at the stagnation point

Semi-similar solutions of the unsteady compressible laminar boundary layer flow over two-dimensional and axisymmetric bodies at the stagnation point with mass transfer are studied for all the second-order boundary layer effects when the free stream velocity varies arbitrarily with time. The set of partial differential equations governing the unsteady compressible second-order boundary layers representing all the effects are derived for the first time. These partial differential equations are solved numerically using an implicit finite-difference scheme. The results are obtained for two particular unsteady free stream velocity distributions: (a) an accelerating stream and (b) a fluctuating stream. It is observed that the total skin friction and heat transfer are strongly affected by the surface mass transfer and wall temperature. However, their variation with time is significant only for large times. The second-order boundary layer effects are found to be more pronounced in the case of no mass transfer or injection as compared to that for suction. Résumé Des solutions semi-similaires d'écoulement variable compressible de couche limite sur des corps bi-dimensionnels thermique, sont étudiées pour tous les effets de couche limite du second ordre, lorsque la vitesse de l'écoulement libre varie arbitrairement avec le temps. Le systéme d'équations aux dérivées partielles représentant tous les effets est écrit pour la premiére fois. On le résout numériquement á l'aide d'un schéma implicite aux différences finies. Les résultats sont obtenus pour deux cas de vitesse variable d'écoulement libre: (a) un écoulement accéléré et (b) un écoulement fluctuant. On observe que le frottement pariétal total et le transfert de chaleur sont fortement affectés par le transfert de masse et la température pariétaux. Néanmoins, leur variation avec le temps est sensible seulement pour des grandes durées. Les effets sont trouvés plus prononcés dans le cas de l'absence du transfert de masse ou de l'injection par rapport au cas de l'aspiration.

Solvation of an ion and of a dipole in a dipolar liquid: How different are the dynamics

Theoretical expressions for the time-dependent solvation energy of an ion and of a dipole in a dense dipolar liquid are derived from microscopic considerations. We show that in contradiction to the prediction of the continuum models, the dynamics of these two species are significantly different from each other. Especially, the zero wavevector contribution, which is significant for ions, is totally absent for dipoles. Dipolar solvation may be profoundly influenced by the translational modes of the host solvent.

Aggregation of calcium ionophore (A23187) in phospholipid vesicles

The circular dichroism studies on calcium ionophore, A23187, incorporated in Dipalmitoyl phosphatidyl choline (DPPC) vesicle showed interesting time dependent changes in the CD spectra. Analysis of the data indicated the possible aggregation of the observed dimeric structure of this molecule in non-polar solvents into a stacked dimeric pore in the phospholipid vesicle.