Dark matter halo's and self similarity

This papers explores the self similar solutions of the Vlasov-Poisson system and their relation to the gravitational collapse of dynamically cold systems. Analytic solutions are derived for power law potential in one dimension, and extensions of these solutions in three dimensions are proposed. Next the self similarity of the collapse of cold dynamical systems is investigated numerically. The fold system in phase space is consistent with analytic self similar solutions, the solutions present all the proper self-similar scalings. An additional point is the appearance of an $x^{-(1/2)}$ law at the center of the system for initial conditions with power law index larger than $-(1/2)$. It is found that the first appearance of the $x^{-(1/2)}$ law corresponds to the formation of a singularity very close to the center. Finally the general properties of self similar multi dimensional solutions near equilibrium are investigated. Smooth and continuous self similar solutions have power law behavior at equilibrium. However cold initial conditions result in discontinuous phase space solutions, and the smoothed phase space density looses its auto similar properties. This problem is easily solved by observing that the probability distribution of the phase space density $P$ is identical except for scaling parameters to the probability distribution of the smoothed phase space density $P_S$. As a consequence $P_S$ inherit the self similar properties of $P$. This particular property is at the origin of the universal power law observed in numerical simulation for ${\rho}/{\sigma^3}$. The self similar properties of $P_S$ implies that other quantities should have also an universal power law behavior with predictable exponents. This hypothesis is tested using a numerical model of the phase space density of cold dark matter halo's, an excellent agreement is obtained.Comment: Final versio

Role of the Internet in Teacher Reflexive Practitioners Research

Suvremeno društvo dovelo je do mijenjanja odnosa prema nastavniku, koji od propagatora nastavnog procesa postaje pokretač kritičkog mijenjanja preuzimajući ulogu kritičkog refleksivnog praktičara. Za refleksivnog praktičara važna je refleksija u akciji koju možemo definirati kao spremnost za inovacije i djelovanja na novi način. Predmet istraživanja refleksivnog praktičara može biti raznolik, ali su istraživanja nastavnika refleksivnih praktičara vezana uvijek za njihovu vlastitu praksu. Istraživanja nastaju kao odgovor na konkretna pitanja, probleme i dileme odgojno-obrazovne prakse i predstavljaju pokušaje neposrednog rješavanja tih problema, odnosno mijenjanja i usavršavanja te prakse. Od nastavnika refleksivnog praktičara očekuje se stalno povećanje medijske i informatičke pismenosti za koje se smatra da adekvatno upotrijebljene doprinose podizanju kvalitete istraživanja. U radu se diskutira o ulozi interneta u istraživačkom radu nastavnika refleksivnog praktičara, kao i o prednostima i nedostacima interneta.Modern society has led to a changing attitude towards the teacher, propagator of the teaching process becomes a critical driver of changing taking on the role of critical reflective practitioners. For a reflective practitioner is an important reflection of the action can be defined as the willingness to innovate and act in new ways. Case study of a reflective practitioner can be varied, but research reflective teacher practitioners still tied to their own practice. Surveys made ​​in response to specific questions, problems and dilemmas of educational practice and an immediate attempt to solve these problems and make changes, and training and practice. The teacher reflective practitioner is expected to steadily increase in media and information literacy that are believed to contribute adequately used to improving the quality of research. This paper discusses the role of the internet in research reflective teacher practitioners, as well as the advantages and disadvantages of the internet

Functional electrical stimulation for foot drop in multiple sclerosis: a systematic review and meta-analysis of the effect on gait speed

Objective: To review the efficacy of functional electrical stimulation (FES) used for foot drop in people with multiple sclerosis (pwMS) on gait speed in short and long walking performance tests. Data sources: Five databases (Cochrane Library, CINAHL, Embase, MEDLINE, Pubmed) and reference lists were searched. Study selection: Studies of both observational and experimental design where gait speed data in pwMS could be extracted were included. Data extraction: Data were independently extracted and recorded. Methodological quality was assessed using the Effective Public Health Practice Project (EPHPP) tool. Data synthesis: Nineteen studies (described in 20 articles) recruiting 490 pwMS were identified and rated moderate or weak, with none gaining a strong rating. All studies rated weak for blinding. Initial and ongoing orthotic and therapeutic effects were assessed with regards to the impact of FES on gait speed in short and long walking tests. Meta-analyses of the short walk tests revealed a significant initial orthotic effect (t = 2.14, p = 0.016) with a mean increase in gait speed of 0.05 meters per second (m/s) and ongoing orthotic effect (t = 2.81, p = 0.003) with a mean increase of 0.08m/s. There were no initial or ongoing effect on gait speed in long walk tests and no therapeutic effect on gait speed in either short or long walk tests. Conclusions: FES used for foot drop has a positive initial and ongoing effect on gait speed in short walking tests. Further fully-powered randomized controlled trials comparing FES with alternative treatments are required

STIS Longslit Spectroscopy Of The Narrow Line Region Of NGC 4151. I. Kinematics and Emission Line Ratios

Longslit spectra of the Seyfert galaxy NGC 4151 from the UV to near infrared have been obtained with STIS to study the kinematics and physical conditions in the NLR. The kinematics show evidence for three components, a low velocity system in normal disk rotation, a high velocity system in radial outflow at a few hundred km/s relative to the systemic velocity and an additional high velocity system also in outflow with velocities up to 1400 km/s, in agreement with results from STIS slitless spectroscopy (Hutchings et al., 1998, Kaiser et al., 1999, Hutchings et al., 1999) We have explored two simple kinematic models and suggest that radial outflow in the form of a wind is the most likely explanation. We also present evidence indicating that the wind may be decelerating with distance from the nucleus. We find that the emission line ratios along our slits are all entirely consistent with photoionization from the nuclear continuum source. A decrease in the [OIII]5007/H-beta and [OIII]5007/[OII]3727 ratios suggests that the density decreases with distance from the nucleus. This trend is borne out by the [SII] ratios as well. We find no strong evidence for interaction between the radio jet and the NLR gas in either the kinematics or the emission line ratios in agreement with the results of Kaiser et al. (1999) who find no spatial coincidence of NLR clouds and knots in the radio jet. These results are in contrast to other recent studies of nearby AGN which find evidence for significant interaction between the radio source and the NLR gas.Comment: 32 pages, 13 figures, accepted for publication in The Astrophysical Journa

Nitisinone Arrests but Does Not Reverse Ochronosis in Alkaptonuric Mice.

Alkaptonuria (AKU) is an ultrarare autosomal recessive disorder resulting from a deficiency of homogentisate 1,2 dioxygenase (HGD), an enzyme involved in the catabolism of phenylalanine and tyrosine. Loss of HGD function prevents metabolism of homogentisic acid (HGA), leading to increased levels of plasma HGA and urinary excretion. Excess HGA becomes deposited in collagenous tissues and subsequently undergoes polymerisation, principally in the cartilages of loaded joints, in a process known as ochronosis. This results in an early-onset, devastating osteoarthropathy for which there is currently no effective treatment. We recently described the natural history of ochronosis in a murine model of AKU, demonstrating that deposition of ochronotic pigment begins very early in life and accumulates with age. Using this model, we were able to show that lifetime treatment with nitisinone, a potential therapy for AKU, was able to completely prevent deposition of ochronotic pigment. However, although nitisinone has been shown to inhibit ochronotic deposition, whether it can also facilitate removal of existing pigment has not yet been examined. We describe here that midlife administration of nitisinone to AKU mice arrests further deposition of ochronotic pigment in the tibiofemoral joint, but does not result in the clearance of existing pigment. We also demonstrate the dose-dependent response of plasma HGA to nitisinone, highlighting its efficacy for personalised medicine, where dosage can be tailored to the individual AKU patient

Spectral characteristics of water megamaser galaxies II: ESO 103-G035, TXS 2226-184, and IC 1481

Long-slit optical emission-line spectra of the H2O megamaser galaxies ESO 103-G03, TXS 2226-184, and IC 1481 are evaluated in order to look for characteristics typical for water-megamaser galaxies. We present rotation curves, line ratios, electron densities, temperatures, and Hbeta luminosities. The successful line-profile decompositions rest on d-Lorentzians with an additional parameter d to adjust the wings, rather than Gaussians or Lorentzians as basic functions. No significant velocity gradient is found along the major axis in the innermost 2 kpc of TXS 2226-184. IC 1481 reveals a spectrum suggestive of a vigorous starburst in the central kiloparsec 10^8 years ago. None of the three galaxies shows any hints for outflows nor special features which could give clues to the presence of H2O megamaser emission. The galaxies are of normal Seyfert-2 (ESO 103-G035) or LINER (TXS 2226-184, IC 1481) type.Comment: 12 pages, 14 figures, accepted for publication in A&A, corrected typo

Ac hopping conduction at extreme disorder takes place on the percolating cluster

Simulations of the random barrier model show that ac currents at extreme disorder are carried almost entirely by the percolating cluster slightly above threshold; thus contradicting traditional theories contributions from isolated low-activation-energy clusters are negligible. The effective medium approximation in conjunction with the Alexander-Orbach conjecture leads to an excellent analytical fit to the universal ac conductivity with no nontrivial fitting parameters

Deterministic optical polarisation in nitride quantum dots at thermoelectrically cooled temperatures.

We report the successful realisation of intrinsic optical polarisation control by growth, in solid-state quantum dots in the thermoelectrically cooled temperature regime (≥200 K), using a non-polar InGaN system. With statistically significant experimental data from cryogenic to high temperatures, we show that the average polarisation degree of such a system remains constant at around 0.90, below 100 K, and decreases very slowly at higher temperatures until reaching 0.77 at 200 K, with an unchanged polarisation axis determined by the material crystallography. A combination of Fermi-Dirac statistics and k·p theory with consideration of quantum dot anisotropy allows us to elucidate the origin of the robust, almost temperature-insensitive polarisation properties of this system from a fundamental perspective, producing results in very good agreement with the experimental findings. This work demonstrates that optical polarisation control can be achieved in solid-state quantum dots at thermoelectrically cooled temperatures, thereby opening the possibility of polarisation-based quantum dot applications in on-chip conditions

Tight-Binding model for semiconductor nanostructures

An empirical $s_cp^3_a$ tight-binding (TB) model is applied to the investigation of electronic states in semiconductor quantum dots. A basis set of three $p$-orbitals at the anions and one $s$-orbital at the cations is chosen. Matrix elements up to the second nearest neighbors and the spin-orbit coupling are included in our TB-model. The parametrization is chosen so that the effective masses, the spin-orbit-splitting and the gap energy of the bulk CdSe and ZnSe are reproduced. Within this reduced $s_cp_a^3$ TB-basis the valence (p-) bands are excellently reproduced and the conduction (s-) band is well reproduced close to the $\Gamma$-point, i.e. near to the band gap. In terms of this model much larger systems can be described than within a (more realistic) $sp^3s^*$-basis. The quantum dot is modelled by using the (bulk) TB-parameters for the particular material at those sites occupied by atoms of this material. Within this TB-model we study pyramidal-shaped CdSe quantum dots embedded in a ZnSe matrix and free spherical CdSe quantum dots (nanocrystals). Strain-effects are included by using an appropriate model strain field. Within the TB-model, the strain-effects can be artifically switched off to investigate the infuence of strain on the bound electronic states and, in particular, their spatial orientation. The theoretical results for spherical nanocrystals are compared with data from tunneling spectroscopy and optical experiments. Furthermore the influence of the spin-orbit coupling is investigated