A semi-schematic model for the center of mass dynamics in supercooled molecular liquids

We introduce a semi-schematic mode-coupling model to describe the slow dynamics in molecular liquids, retaining explicitly only the description of the center of mass degrees of freedom. Angular degrees of freedom are condensed in a q-vector independent coupling parameter. We compare the time and q-dependence of the density fluctuation correlators with numerical data from a 250 ns long molecular dynamics simulation. Notwithstanding the choice of a network-forming liquid as a model for comparing theory and simulation, the model describes the main static and dynamic features of the relaxation in a broad q-vector range.Comment: Revtex, 2 figure

X-ray Based Visualization of the Electrolyte Filling Process of Lithium Ion Batteries

The electrolyte filling process constitutes the interface between cell assembly and formation of lithium ion batteries. Electrolyte filling is known as a quality critical and also time consuming process step. To avoid limitations in battery quality a homogeneous electrolyte distribution is necessary. Therefore, especially large sized cells are stored for hours. To accelerate filling and wetting processes the effect of materials- and process parameters on electrolyte distribution needs to be investigated. Unfortunately, in situ methods to characterize the filling and wetting state are still rare, limited in availability or even time-consuming in preparation. To overcome these drawbacks this paper introduces X-ray as an innovative method to visualize the electrolyte filling process in large scaled lithium ion batteries. Therefore, an experimental setup was developed to enable in situ X-ray measurements during the filling process of large scaled cells. Additionally, an evaluation process for the optical data was proposed. Based on these images the suitability of X-ray as visualization method is shown considering three exemplary filling parameters.BMBF, 03XP0069A, Cell-Fi - Beschleunigung der Elektrolytaufnahme durch optimierte Befüllungs- und Wettingprozess

Impairment of LTD and cerebellar learning by Purkinje cell–specific ablation of cGMP-dependent protein kinase I

The molecular basis for cerebellar plasticity and motor learning remains controversial. Cerebellar Purkinje cells (PCs) contain a high concentration of cGMP-dependent protein kinase type I (cGKI). To investigate the function of cGKI in long-term depression (LTD) and cerebellar learning, we have generated conditional knockout mice lacking cGKI selectively in PCs. These cGKI mutants had a normal cerebellar morphology and intact synaptic calcium signaling, but strongly reduced LTD. Interestingly, no defects in general behavior and motor performance could be detected in the LTD-deficient mice, but the mutants exhibited an impaired adaptation of the vestibulo-ocular reflex (VOR). These results indicate that cGKI in PCs is dispensable for general motor coordination, but that it is required for cerebellar LTD and specific forms of motor learning, namely the adaptation of the VOR

Competitive Equilibrium in the Random Assignment Problem

This paper studies the problem of random assignment with fractional endowments. In the random assignment problem, a number of objects has to be assigned to a number of agents. Though the objects are indivisible, an assignment can be probabilistic: it can give an agent some probability of getting an object. Fractional endowments complicate the matter because the assignment has to make an agent weakly better off than his endowment. I first formulate an exchange economy that resembles the random assignment problem and prove the existence of competitive equilibrium in this economy. I then propose a pseudo-market mechanism for the random assignment problem that is based on the competitive equilibrium. This mechanism is individually rational, Pareto Optimal and justified envy-free but not incentive compatible

I-BEAT: New ultrasonic method for single bunch measurement of ion energy distribution

The shape of a wave carries all information about the spatial and temporal structure of its source, given that the medium and its properties are known. Most modern imaging methods seek to utilize this nature of waves originating from Huygens' principle. We discuss the retrieval of the complete kinetic energy distribution from the acoustic trace that is recorded when a short ion bunch deposits its energy in water. This novel method, which we refer to as Ion-Bunch Energy Acoustic Tracing (I-BEAT), is a generalization of the ionoacoustic approach. Featuring compactness, simple operation, indestructibility and high dynamic ranges in energy and intensity, I-BEAT is a promising approach to meet the needs of petawatt-class laser-based ion accelerators. With its capability of completely monitoring a single, focused proton bunch with prompt readout it, is expected to have particular impact for experiments and applications using ultrashort ion bunches in high flux regimes. We demonstrate its functionality using it with two laser-driven ion sources for quantitative determination of the kinetic energy distribution of single, focused proton bunches.Comment: Paper: 17 Pages, 3 figures Supplementary Material 16 pages, 7 figure

Onsager Loop-Transition and First Order Flux-Line Lattice Melting in High-TcT_c Superconductors

Monte-Carlo simulations in conjunction with finite-size scaling analysis are used to investigate the $(H,T)$-phase diagram in uniaxial anisotropic high- $T_c$ superconductors, both in zero magnetic field and in intermediate magnetic fields for various mass-anisotropies. The model we consider is the uniformly frustrated anisotropic Villain Model. In zero magnetic field, and for all anisotropies considered, we find one single second order phase transition, mediated by an Onsager vortex-loop blowout. This is the superconductor-normal metal transition.A comparison with numerical simulations and a critical scaling analysis of the zero-field loop-transition yields the same exponent of the loop distribution function at the critical point. In the intermediate magnetic field regime, we find two anomalies in the specific heat. The first anomaly at a temperature $T_m$ is associated with the melting transition of the flux-line lattice. The second anomaly at a temperature $T_z$ is one where phase coherence along the field direction is destroyed. We argue that $T_m=T_z$ in the thermodynamic and continuum limit. Hence, there is no regime where the flux line lattice melts into a disentangled flux-line liquid. The loss of phase coherence parallel to the magnetic field in the sample is argued to be due to the proliferation of closed non-field induced vortex loops on the scale of the magnetic length in the problem, resulting in flux-line cutting and recombination. In the flux-line liquid phase, therefore, flux-lines appear no longer to be well defined entities. A finite-size scaling analysis of the delta function peak specific heat anomaly at the melting transition is used to extract the discontinuity of the entropy at the melting transition.This entropy discontinuity is found to increase rapidly with mass-anisotropy.Comment: 22 pages, 11 figures included, to be published in Phys. Rev. B, 57 xxx (1998

Ground State Vortex Lattice Structures in d-wave Superconductors

We show in a realistic $d_{x^{2}-y^{2}}$ symmetry gap model for a cuprate superconductor that the clean vortex lattice has discontinuous structural transitions (at and near T=0), as a function of the magnetic field $B$ along the c-axis. The transitions arise from the singular nonlocal and anisotropic susceptibility of the $d_{x^{2}-y^{2}}$ superconductor to the perturbation caused by supercurrents associated with vortices. The susceptibility, due to virtual Dirac quasiparticle-hole excitation, is calculated carefully, and leads to a ground state transition for the triangular lattice from an orientation along one of the crystal axis to one at 45$^o$ to them, i.e, along the gap zero direction. The field scale is seen to be 5 Tesla $\sim (\Delta_{0}/ta)^{2}\Phi_{0}$, where $\Delta_{0}$ is the gap maximum, $t$ is the nearest neighbour hopping, $a$ is the lattice constant, and $\Phi_{0}$ is the flux quantum. At much higher fields ($\sim 28T$) there is a discontinuous transition to a centred square structure. The source of the differences from existing calculations, and experimental observability are discussed, the latter especially in view of the very small (a few degrees $K$ per vortex) differences in the ground state energy.Comment: To be published in Phys. Rev.

The sodium iodide symporter (NIS) as theranostic gene: its emerging role in new imaging modalities and non-viral gene therapy

Cloning of the sodium iodide symporter (NIS) in 1996 has provided an opportunity to use NIS as a powerful theranostic transgene. Novel gene therapy strategies rely on image-guided selective NIS gene transfer in non-thyroidal tumors followed by application of therapeutic radionuclides. This review highlights the remarkable progress during the last two decades in the development of the NIS gene therapy concept using selective non-viral gene delivery vehicles including synthetic polyplexes and genetically engineered mesenchymal stem cells. In addition, NIS is a sensitive reporter gene and can be monitored by high resolution PET imaging using the radiotracers sodium [ 124 I]iodide ([ 124 I]NaI) or [ 18 F]tetrafluoroborate ([ 18 F]TFB). We performed a small preclinical PET imaging study comparing sodium [ 124 I]iodide and in-house synthesized [ 18 F]TFB in an orthotopic NIS-expressing glioblastoma model. The results demonstrated an improved image quality using [ 18 F]TFB. Building upon these results, we will be able to expand the NIS gene therapy approach using non-viral gene delivery vehicles to target orthotopic tumor models with low volume disease, such as glioblastoma

Testing "microscopic" theories of glass-forming liquids

We assess the validity of "microscopic" approaches of glass-forming liquids based on the sole k nowledge of the static pair density correlations. To do so we apply them to a benchmark provided by two liquid models that share very similar static pair density correlation functions while disp laying distinct temperature evolutions of their relaxation times. We find that the approaches are unsuccessful in describing the difference in the dynamical behavior of the two models. Our study is not exhausti ve, and we have not tested the effect of adding corrections by including for instance three-body density correlations. Yet, our results appear strong enough to challenge the claim that the slowd own of relaxation in glass-forming liquids, for which it is well established that the changes of the static structure factor with temperature are small, can be explained by "microscopic" appr oaches only requiring the static pair density correlations as nontrivial input.Comment: 10 pages, 7 figs; Accepted to EPJE Special Issue on The Physics of Glasses. Arxiv version contains an addendum to the appendix which does not appear in published versio