126 research outputs found
Growth and structure of polycrystalline Cr/Au multilayered thin films
BrĂĽckl H, Vancea J, Lecheler R, Reiss G, Hoffmann H. Growth and structure of polycrystalline Cr/Au multilayered thin films. Thin solid films. 1994;250(1-2):56-60.Metallic multilayered thin films have recently been investigated due to their new magnetic and transport properties. The interest here is focussed on the characterization of the interfaces between the layers. The analysis of growth and structure of polycrystalline Cr/Au multilayers is accomplished by two complementary techniques: in situ ultrahigh vacuum scanning tunnelling microscopy and ex situ transmission electron microscopy. The combination of these powerful methods provides detailed information about structural characteristics such as crystallite size, surface roughness and crystallographic orientation. Moreover, conclusions can be drawn on the atomic arrangement and growth mechanism at the Cr-Au interface. The results are supported by semiempirical and theoretical expectations
Noncommutative fluid dynamics in the Snyder space-time
In this paper, we construct for the first time the non-commutative fluid with
the deformed Poincare invariance. To this end, the realization formalism of the
noncommutative spaces is employed and the results are particularized to the
Snyder space. The non-commutative fluid generalizes the fluid model in the
action functional formulation to the noncommutative space. The fluid equations
of motion and the conserved energy-momentum tensor are obtained.Comment: 12 pages. Version published by Phys. Rev.
Time varying gravitational constant G via the entropic force
If the uncertainty principle applies to the Verlinde entropic idea, it leads
to a new term in the Newton's second law of mechanics in the Planck's scale.
This curious velocity dependence term inspires a frictional feature of the
gravity. In this short letter we address that this new term modifies the
effective mass and the Newtonian constant as the time dependence quantities.
Thus we must have a running on the value of the effective mass on the particle
mass near the holographic screen and the . This result has a nigh
relation with the Dirac hypothesis about the large numbers hypothesis (L.N.H.)
[1]. We propose that the corrected entropic terms via Verlinde idea can be
brought as a holographic evidence for the authenticity of the Dirac idea.Comment: Accepted for publication in "Communications in Theoretical Physics
(CTP)",Major revisio
Entropic corrections to Newton's law
In this short letter we calculate separately the generalized uncertainty
principle (GUP) and self gravitational corrections to the Newton's
gravitational formula. We show that for a complete description of the GUP and
self-gravity effects, both temperature and the entropy must be modified.Comment: 4 pages, Accepted for publication in "Physica Scripta",Title changed,
Major revisio
On the Dirac Eigenvalues as Observables of the on-shell N=2 D=4 Euclidean Supergravity
We generalize previous works on the Dirac eigenvalues as dynamical variables
of the Euclidean gravity and N=1 D=4 supergravity to on-shell N=2 D=4 Euclidean
supergravity. The covariant phase space of the theory is defined as as the
space of the solutions of the equations of motion modulo the on-shell gauge
transformations. In this space we define the Poisson brackets and compute their
value for the Dirac eigenvalues.Comment: 10 pages, LATeX fil
Development and Validation of a Predictive Model of Acute Glucose Response to Exercise in Individuals With Type 2 Diabetes
Background: Our purpose was to develop and test a predictive model of the acute glucose response to exercise in individuals with type 2 diabetes.
Design and methods: Data from three previous exercise studies (56 subjects, 488 exercise sessions) were combined and used as a development dataset. A mixed-effects Least Absolute Shrinkage Selection Operator (LASSO) was used to select predictors among 12 potential predictors. Tests of the relative importance of each predictor were conducted using the Lindemann Merenda and Gold (LMG) algorithm. Model structure was tested using likelihood ratio tests. Model accuracy in the development dataset was assessed by leave-one-out cross-validation.
Prospectively captured data (47 individuals, 436 sessions) was used as a test dataset. Model accuracy was calculated as the percentage of predictions within measurement error. Overall model utility was assessed as the number of subjects with ≤ 1 model error after the third exercise session. Model accuracy across individuals was assessed graphically. In a post-hoc analysis, a mixed-effects logistic regression tested the association of individuals\u27 attributes with model error.
Results: Minutes since eating, a non-linear transformation of minutes since eating, post-prandial state, hemoglobin A1c, sulfonylurea status, age, and exercise session number were identified as novel predictors. Minutes since eating, its transformations, and hemoglobin A1c combined to account for 19.6% of the variance in glucose response. Sulfonylurea status, age, and exercise session each accounted for \u3c1.0% of the variance. In the development dataset, a model with random slopes for pre-exercise glucose improved fit over a model with random intercepts only (likelihood ratio 34.5, p \u3c 0.001). Cross-validated model accuracy was 83.3%. In the test dataset, overall accuracy was 80.2%. The model was more accurate in pre-prandial than postprandial exercise (83.6% vs. 74.5% accuracy respectively). 31/47 subjects had ≤1 model error after the third exercise session. Model error varied across individuals and was weakly associated with within-subject variability in pre-exercise glucose (Odds ratio 1.49, 95% Confidence interval 1.23-1.75).
Conclusions: The preliminary development and test of a predictive model of acute glucose response to exercise is presented. Further work to improve this model is discussed
Nonequilibrium dynamics of strings in time-dependent plane wave backgrounds
We formulate and study the nonequilibrium dynamics of strings near the
singularity of the time-dependent plane wave background in the framework of the
Nonequilibrium Thermo Field Dynamics (NETFD). In particular, we construct the
Hilbert space of the thermal string oscillators at nonequilibrium and
generalize the NETFD to describe the coordinates of the center of mass of the
thermal string. The equations of motion of the thermal fields and the
Hamiltonian are derived. Due to the time-dependence of the oscillator
frequencies, a counterterm is present in the Hamiltonian. This counterterm
determines the correlation functions in a perturbative fashion. We compute the
two point correlation function of the thermal string at zero order in the power
expansion.Comment: 21 page
An MRI evaluation of grey matter damage in African Americans with MS
Objective: Multiple sclerosis (MS) is less prevalent in African Americans (AAs) than Caucasians (CAs) but in the former the disease course tends to be more severe. In order to clarify the MRI correlates of disease severity in AAs, we performed a multimodal brain MRI study to comprehensively assess the extent of grey matter (GM) damage and the degree of functional adaptation to structural damage in AAs with MS. Methods: In this cross-sectional study, we characterized GM damage in terms of focal lesions and volume loss and functional adaptation during the execution of a simple motor task on a sample of 20 AAs and 20 CAs with MS and 20 healthy controls (CTRLs). Results: In AAs, we observed a wider range of EDSS scores than CAs, with multisystem involvement being more likely in AAs (p < 0.01). While no significant differences were detected in lesion loads and global brain volumes, AAs showed regional atrophy in the posterior lobules of cerebellum, temporo-occipital and frontal regions in comparison with CAs (p < 0.01), with cerebellar atrophy being the best metric in differentiating AAs from CAs (p = 0.007, AUC = 0.96 and p = 0.005, AUC = 0.96, respectively for right and left cerebellar clusters). In AAs, the functional analysis of cortical activations showed an increase in task-related activation of areas involved in high level processing and a decreased activation in the medial prefrontal cortex compared to CAs. Interpretation: In our study, the direct comparison of AAs and CAs points to cerebellar atrophy as the main difference between subgroups
Higher Dimensional Recombination of Intersecting D-branes
We study recombinations of D-brane systems intersecting at more than one
angle using super Yang-Mills theory. We find the condensation of an
off-diagonal tachyon mode relates to the recombination, as was clarified for
branes at one angle in hep-th/0303204. For branes at two angles, after the
tachyon mode between two D2-branes condensed, D2-brane charge is distributed in
the bulk near the intersection point. We also find that, when two intersection
angles are equal, the off-diagonal lowest mode is massless, and a new stable
non-abelian configuration, which is supersymmetric up to a quadratic order in
the fluctuations, is obtained by the deformation by this mode.Comment: 18 pages, 2 figures, JHEP style. v3:references added, minor
corrections, English improve
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