Anomalous Electron Transport in Field-Effect Transistors with Titanium Ditelluride Semimetal Thin-Film Channels

We report on "graphene-like" mechanical exfoliation of thin films of titanium ditelluride and investigation of their electronic properties. The exfoliated crystalline TiTe2 films were used as the channel layers in the back-gated field-effect transistors fabricated with Ti/Al/Au metal contacts on SiO2/Si substrates. The room-temperature current-voltage characteristics revealed strongly non-linear behavior with signatures of the source-drain threshold voltage similar to those observed in the charge-density-wave devices. The drain-current showed an unusual non-monotonic dependence on the gate bias characterized by the presence of multiple peaks. The obtained results can be potentially used for implementation of the non-Boolean logic gates.Comment: 11 pages, 4 figure

A Variational Principle Based Study of KPP Minimal Front Speeds in Random Shears

Variational principle for Kolmogorov-Petrovsky-Piskunov (KPP) minimal front speeds provides an efficient tool for statistical speed analysis, as well as a fast and accurate method for speed computation. A variational principle based analysis is carried out on the ensemble of KPP speeds through spatially stationary random shear flows inside infinite channel domains. In the regime of small root mean square (rms) shear amplitude, the enhancement of the ensemble averaged KPP front speeds is proved to obey the quadratic law under certain shear moment conditions. Similarly, in the large rms amplitude regime, the enhancement follows the linear law. In particular, both laws hold for the Ornstein-Uhlenbeck process in case of two dimensional channels. An asymptotic ensemble averaged speed formula is derived in the small rms regime and is explicit in case of the Ornstein-Uhlenbeck process of the shear. Variational principle based computation agrees with these analytical findings, and allows further study on the speed enhancement distributions as well as the dependence of enhancement on the shear covariance. Direct simulations in the small rms regime suggest quadratic speed enhancement law for non-KPP nonlinearities.Comment: 28 pages, 14 figures update: fixed typos, refined estimates in section

Isobaric multiplet yrast energies and isospin non-conserving forces

The isovector and isotensor energy differences between yrast states of isobaric multiplets in the lower half of the $pf$ region are quantitatively reproduced in a shell model context. The isospin non-conserving nuclear interactions are found to be at least as important as the Coulomb potential. Their isovector and isotensor channels are dominated by J=2 and J=0 pairing terms, respectively. The results are sensitive to the radii of the states, whose evolution along the yrast band can be accurately followed.Comment: 4 pages, 4 figures. Superseeds second part of nucl-th/010404

MC++: A parallel, portable, Monte Carlo neutron transport code in C++

MC++ is an implicit multi-group Monte Carlo neutron transport code written in C++ and based on the Parallel Object-Oriented Methods and Applications (POOMA) class library. MC++ runs in parallel on and is portable to a wide variety of platforms, including MPPs, SMPs, and clusters of UNIX workstations. MC++ is being developed to provide transport capabilities to the Accelerated Strategic Computing Initiative (ASCI). It is also intended to form the basis of the first transport physics framework (TPF), which is a C++ class library containing appropriate abstractions, objects, and methods for the particle transport problem. The transport problem is briefly described, as well as the current status and algorithms in MC++ for solving the transport equation. The alpha version of the POOMA class library is also discussed, along with the implementation of the transport solution algorithms using POOMA. Finally, a simple test problem is defined and performance and physics results from this problem are discussed on a variety of platforms

The effects of cognitive-behavioural therapy on mood-related ruminative response style in depressed adolescents

<p>Abstract</p> <p>Background</p> <p>A mood-related ruminative response style increases the risk of onset and persistence of depression. This preliminary study investigated whether, in depressed adolescents, cognitive-behaviour therapy reduces mood-related ruminative response style. Whether specific factors within the rumination scale were differentially affected by CBT is also reported.</p> <p>Methods</p> <p>26 depressed adolescents were randomised to receiving serotonin-specific reuptake inhibitor antidepressants (SSRI) plus psychosocial treatment as usual or SSRI and psychosocial treatment as usual plus CBT. Ruminative response style and depressive symptoms were measured at baseline and after 30 weeks of treatment, with the Responses to Depression Questionnaire and Mood and Feelings Questionnaire.</p> <p>Results</p> <p>There were significantly greater reductions in ruminations in the CBT group compared to the non-CBT group (<it>p </it>= .002). There was no significant difference in the reduction in self-reported depressive symptoms between the groups. Rumination was reduced to levels of never-depressed controls in adolescents who had recovered from depression and received CBT. There were greater falls in the CBT group in the more pathological 'brooding' factor of rumination.</p> <p>Conclusion</p> <p>These findings suggest that adding CBT to SSRI medication in the presence of active clinical care causes a greater reduction in mood-related ruminative response style in depressed adolescents. This may reduce the risk of future relapse.</p> <p>Trial registration</p> <p>Current Controlled Trials ISRCNT83809224.</p

Coulomb Energy of Nuclei

The density functional determining the Coulomb energy of nuclei is calculated to the first order in $e^2$. It is shown that the Coulomb energy includes three terms: the Hartree energy; the Fock energy; and the correlation Coulomb energy (CCE), which contributes considerably to the surface energy, the mass difference between mirror nuclei, and the single-particle spectrum. A CCE-based mechanism of a systematic shift of the single-particle spectrum is proposed. A dominant contribution to the CCE is shown to come from the surface region of nuclei. The CCE effect on the calculated proton drip line is examined, and the maximum charge $Z$ of nuclei near this line is found to decrease by 2 or 3 units. The effect of Coulomb interaction on the effective proton mass is analyzed.Comment: 10 pages, Latex. Devoted to 90-th Anniversary of A.B. Migdal's Birthda

Optical studies for the super separator spectrometer S3

International audienceS3 (Super Separator Spectrometer) [1] is a future device designed for experiments with the high intensity heavy ion stable beams of SPIRAL2 [2] at GANIL (Caen, France). It will include a target resistant to these very high intensities, a first stage momentum achromat for primary beam extraction and suppression, a second stage mass spectrometer and a dedicated detection system. This spectrometer includes large aperture quadrupole triplets with embedded multipolar corrections. To enable the primary beam extraction one triplet has to be opened on one side, which requires an appropriate design of such a multipolar magnet. The final mass separation power required for S3 needs a careful design of the optics with a high level of aberration correction. Multiple symmetric lattices were studied for this purpose. A 4-fold symmetric lattice and the achieved results are described in this paper

Semi-Parametric Drift and Diffusion Estimation for Multiscale Diffusions

We consider the problem of statistical inference for the effective dynamics of multiscale diffusion processes with (at least) two widely separated characteristic time scales. More precisely, we seek to determine parameters in the effective equation describing the dynamics on the longer diffusive time scale, i.e. in a homogenization framework. We examine the case where both the drift and the diffusion coefficients in the effective dynamics are space-dependent and depend on multiple unknown parameters. It is known that classical estimators, such as Maximum Likelihood and Quadratic Variation of the Path Estimators, fail to obtain reasonable estimates for parameters in the effective dynamics when based on observations of the underlying multiscale diffusion. We propose a novel algorithm for estimating both the drift and diffusion coefficients in the effective dynamics based on a semi-parametric framework. We demonstrate by means of extensive numerical simulations of a number of selected examples that the algorithm performs well when applied to data from a multiscale diffusion. These examples also illustrate that the algorithm can be used effectively to obtain accurate and unbiased estimates.Comment: 32 pages, 10 figure

Composite nucleons in scalar and vector mean-fields

We emphasize that the composite structure of the nucleon may play quite an important role in nuclear physics. It is shown that the momentum-dependent repulsive force of second order in the scalar field, which plays an important role in Dirac phenomenology, can be found in the quark-meson coupling (QMC) model, and that the properties of nuclear matter are well described through the quark-scalar density in a nucleon and a self-consistency condition for the scalar field. The difference between theories of point-like nucleons and composite ones may be seen in the change of the $\omega$-meson mass in nuclear matter if the composite nature of the nucleon suppresses contributions from nucleon-antinucleon pair creation.Comment: 10 page