Transport in the 3-dimensional Anderson model: an analysis of the dynamics on scales below the localization length

Single-particle transport in disordered potentials is investigated on scales below the localization length. The dynamics on those scales is concretely analyzed for the 3-dimensional Anderson model with Gaussian on-site disorder. This analysis particularly includes the dependence of characteristic transport quantities on the amount of disorder and the energy interval, e.g., the mean free path which separates ballistic and diffusive transport regimes. For these regimes mean velocities, respectively diffusion constants are quantitatively given. By the use of the Boltzmann equation in the limit of weak disorder we reveal the known energy-dependencies of transport quantities. By an application of the time-convolutionless (TCL) projection operator technique in the limit of strong disorder we find evidence for much less pronounced energy dependencies. All our results are partially confirmed by the numerically exact solution of the time-dependent Schroedinger equation or by approximative numerical integrators. A comparison with other findings in the literature is additionally provided.Comment: 23 pages, 10 figure

Analytic computation of the Instantaneous Normal Modes spectrum in low density liquids

We analytically compute the spectrum of the Hessian of the Hamiltonian for a system of N particles interacting via a purely repulsive potential in one dimension. Our approach is valid in the low density regime, where we compute the exact spectrum also in the localized sector. We finally perform a numerical analysis of the localization properties of the eigenfunctions.Comment: 4 RevTeX pages, 4 EPS figures. Revised version to appear on Phys. Rev. Let

Physicochemical, in vitro and in vivo evaluation of flurbiprofen microemulsion

Flurbiprofen, a potent nonsteroidal anti-inflammatory drug, is widely used for relief of pain in patients suffering from rheumatic diseases, migraine, sore throat and primary dysmenorrheal. However, this drug has many gastrointestinal side effects produced by its oral administration, such as gastric bleeding and peptic ulcer. These effects were responsible for non-compliance among patients, which ultimately results in treatment failure. The physicochemical properties of flurbiprofen, make it a suitable candidate for transdermal drug delivery, which can overcome the drawbacks of oral administration. In this sense, microemulsions have been proved to increase the cutaneous absorption of lipophilic drugs when compared to conventional drug delivery systems. The purpose of this study was to formulate and characterize gel based microemulsions, for topical delivery of flurbiprofen. Different gel bases, containing microemulsion and hydro-alcoholic solution of flurbiprofen, were developed and compared. In vitro study showed that gels containing microemulsion had a higher permeation rate than those containing hydro-alcoholic solutions. Additionally, formulation of Carbopol-I (microemulsion) showed higher percent of inhibition of inflammation than others bases. Further, skin irritation study demonstrated that Carbopol-I was none irritating. Flurbiprofen microemulsion incorporated on Carbopol-I showed physicochemical, in vitro and in vivo characteristics suitable for the development of alternative transdermal delivery formulation87

The development of a new blood substitute

Trattasi di un sommario pubblicato online nel sito dell'Agenzia di divulgazione scientifica Atlas of Science, AoS Nordic AB, Moscow, Russia, riguardante l'impiego di nuovi sostituti del sangu

Localization Properties of the Periodic Random Anderson Model

We consider diagonal disordered one-dimensional Anderson models with an underlying periodicity. We assume the simplest periodicity, i.e., we have essentially two lattices, one that is composed of the random potentials and the other of non-random potentials. Due to the periodicity special resonance energies appear, which are related to the lattice constant of the non-random lattice. Further on two different types of behaviors are observed at the resonance energies. When a random site is surrounded by non-random sites, this model exhibits extended states at the resonance energies, whereas otherwise all states are localized with, however, an increase of the localization length at these resonance energies. We study these resonance energies and evaluate the localization length and the density of states around these energies.Comment: 4 page

Anderson Localization, Non-linearity and Stable Genetic Diversity

In many models of genotypic evolution, the vector of genotype populations satisfies a system of linear ordinary differential equations. This system of equations models a competition between differential replication rates (fitness) and mutation. Mutation operates as a generalized diffusion process on genotype space. In the large time asymptotics, the replication term tends to produce a single dominant quasispecies, unless the mutation rate is too high, in which case the populations of different genotypes becomes de-localized. We introduce a more macroscopic picture of genotypic evolution wherein a random replication term in the linear model displays features analogous to Anderson localization. When coupled with non-linearities that limit the population of any given genotype, we obtain a model whose large time asymptotics display stable genotypic diversityComment: 25 pages, 8 Figure

Localization and fluctuations of local spectral density on tree-like structures with large connectivity: Application to the quasiparticle line shape in quantum dots

We study fluctuations of the local density of states (LDOS) on a tree-like lattice with large branching number $m$. The average form of the local spectral function (at given value of the random potential in the observation point) shows a crossover from the Lorentzian to semicircular form at $\alpha\sim 1/m$, where $\alpha= (V/W)^2$, $V$ is the typical value of the hopping matrix element, and $W$ is the width of the distribution of random site energies. For $\alpha>1/m^2$ the LDOS fluctuations (with respect to this average form) are weak. In the opposite case, $\alpha<1/m^2$, the fluctuations get strong and the average LDOS ceases to be representative, which is related to the existence of the Anderson transition at $\alpha_c\sim 1/(m^2\log^2m)$. On the localized side of the transition the spectrum is discrete, and LDOS is given by a set of $\delta$-like peaks. The effective number of components in this regime is given by $1/P$, with $P$ being the inverse participation ratio. It is shown that $P$ has in the transition point a limiting value $P_c$ close to unity, $1-P_c\sim 1/\log m$, so that the system undergoes a transition directly from the deeply localized to extended phase. On the side of delocalized states, the peaks in LDOS get broadened, with a width $\sim\exp\{-{const}\log m[(\alpha-\alpha_c)/\alpha_c]^{-1/2}\}$ being exponentially small near the transition point. We discuss application of our results to the problem of the quasiparticle line shape in a finite Fermi system, as suggested recently by Altshuler, Gefen, Kamenev, and Levitov.Comment: 12 pages, 1 figure. Misprints in eqs.(21) and (28) corrected, section VII added. Accepted for publication in Phys. Rev.

Mean field theory of the Mott-Anderson transition

We present a theory for disordered interacting electrons that can describe both the Mott and the Anderson transition in the respective limits of zero disorder and zero interaction. We use it to investigate the T=0 Mott-Anderson transition at a fixed electron density, as a the disorder strength is increased. Surprisingly, we find two critical values of disorder W_{nfl} and W_c. For W > W_{nfl}, the system enters a ``Griffiths'' phase, displaying metallic non-Fermi liquid behavior. At even stronger disorder, W=W_c > W_{nfl} the system undergoes a metal insulator transition, characterized by the linear vanishing of both the typical density of states and the typical quasiparticle weight.Comment: 4 pages, 2 figures, REVTEX, eps

Menor incidência de hipoglicemia noturna com o uso de insulina lispro comparada à insulina humana regular no tratamento de pacientes com diabetes do tipo 1

Insulin lispro is a human insulin analog of rapid onset of action and duration, which mimics the physiological insulin profile after a meal. We have evaluated the safety and efficacy of lispro insulin in comparison with human regular insulin in a crossover, multicenter, randomized trial in 25 type 1 diabetic patients in use of human NPH and regular insulin (median age = 16 years). After administration of lispro or regular insulin for 2 months, the patients were transferred for the other insulin for two more months, maintaining the basal NPH insulin regimen. There was no difference in the postprandial glucose excursion and glycated hemoglobin A1c comparing the 2 groups (lispro and regular). The relative percentage decrease in glycemia was significantly greater with lispro insulin after lunch, in the first phase of the study (p<0.02). The total number of hypo-glycemic episodes was not different comparing both groups. However, there was a significant difference in the nocturnal hypoglycemia incidence with initial administration of lispro (p<0.05). With initial administration of regular insulin, there was an increase in the incidence of nocturnal hypoglycemia (p=0.038), with a subsequent reduction of hypoglycemia with insulin lispro (p=0.04). In the end of the study, 68% of the patients referred preference and better feeling with lispro, compared to regular insulin. Insulin lispro was a safe and efficacious option, with lower incidence of nocturnal hypoglycemia in type 1 diabetics. An optimization of the basal insulin regimen is necessary to improve glucose control with the use of rapid-action insulin.Insulina lispro é um análogo da insulina humana de ação e duração rápida, que mimeíiza o perfil fisiológico da insulina após uma refeição. Avaliamos a segurança e eficácia da insulina lispro em comparação com a insulina humana regular em um estudo multicêntrico, randomizado e cruzado em 27 diabéticos tipo 1 em uso de insulina humana NPH e regular (idade mediana = 16 anos). Após uso de insulina lispro ou regular por 2 meses, fez-se a transferência para a outra insulina por mais 2 meses mantendo-se a insulina NPH basal. Não houve diferença em relação à excursão prandial da glicemia da hemoglobina glicosilada A1C, comparando-se os 2 grupos (lispro e regular). O decréscimo percentual relativo da glicemia foi significantemente maior com insulina lispro no período do almoço, na primeira fase do estudo (p<0,02). O número total de episódios hipoglicêmicos não foi diferente, comparando os 2 grupos. Houve, porém, uma redução significante na incidência de hipoglicemia noturna e na madrugada com o uso inicial de lispro (p<0,05). Com o uso inicial de insulina regular, houve incremento na incidência de hipoglicemia noturna (p=0,038), com redução posterior na incidência da hipoglicemia com insulina lispro (p=0,04). Ao final do estudo, 68% dos pacientes referiram preferência e maior comodidade com insulina lispro em relação à insulina regular. A insulina lispro se mostrou uma opção segura e eficaz, com menor incidência de hipoglicemia noturna em diabéticos tipo 1. Uma otimização do regime de insulina basal é necessária para melhora do controle glicêmico, quando em uso de uma insulina de ação rápida.Universidade Federal do CearáUniversidade de São Paulo Faculdade de MedicinaUniversidade Federal de São Paulo (UNIFESP)Laboratório Eli Lilly do BrasilUNIFESPSciEL

Phase diagram of localization in a magnetic field

The phase diagram of localization is numerically calculated for a three-dimensional disordered system in the presence of a magnetic field using the Peierls substitution. The mobility edge trajectory shifts in the energy-disorder space when increasing the field. In the band center, localized states near the phase boundary become delocalized. The obtained field dependence of the critical disorder is in agreement with a power law behavior expected from scaling theory. Close to the tail of the band the magnetic field causes localization of extended states.Comment: 4 pages, RevTeX, 3 PS-figures (4 extra references are included, minor additions), to appear in Phys. Rev. B as a Brief Repor