1,250 research outputs found
Simulation Studies of Nanomagnet-Based Architecture
We report a simulation study on interacting ensembles of Co nanomagnets that
can perform basic logic operations and propagate logic signals, where the state
variable is the magnetization direction. Dipole field coupling between
individual nanomagnets drives the logic functionality of the ensemble and
coordinated arrangements of the nanomagnets allow for the logic signal to
propagate in a predictable way. Problems with the integrity of the logic signal
arising from instabilities in the constituent magnetizations are solved by
introducing a biaxial anisotropy term to the Gibbs magnetic free energy of each
nanomagnet. The enhanced stability allows for more complex components of a
logic architecture capable of random combinatorial logic, including horizontal
wires, vertical wires, junctions, fanout nodes, and a novel universal logic
gate. Our simulations define the focus of scaling trends in nanomagnet-based
logic and provide estimates of the energy dissipation and time per nanomagnet
reversal
Entropy and Hausdorff Dimension in Random Growing Trees
We investigate the limiting behavior of random tree growth in preferential
attachment models. The tree stems from a root, and we add vertices to the
system one-by-one at random, according to a rule which depends on the degree
distribution of the already existing tree. The so-called weight function, in
terms of which the rule of attachment is formulated, is such that each vertex
in the tree can have at most K children. We define the concept of a certain
random measure mu on the leaves of the limiting tree, which captures a global
property of the tree growth in a natural way. We prove that the Hausdorff and
the packing dimension of this limiting measure is equal and constant with
probability one. Moreover, the local dimension of mu equals the Hausdorff
dimension at mu-almost every point. We give an explicit formula for the
dimension, given the rule of attachment
Solid-state thermal degradation behaviour of 1-D coordination polymers of Ni(II) and Cu(II) bridged by conjugated ligand
Monometallic complexes [Cudadb·yH2O]n (2) and [Nidadb·yH2O]n (3) and heterobimetallic complex [Cu0.5Ni0.5dadb·yH2O]n (4) {where dadbH2 = 2,5-Diamino-3,6-dichloro-1,4-benzoquinone (1); y = 2-4; n = degree of polymerization} were characterized by elemental analysis, atomic absorption spectroscopy, infrared spectroscopy (FTIR) and powder X-ray diffraction. The thermal behaviour of the complexes was studied by thermal analysis (TG/DTA) under air as well as under helium atmospheres. The released gaseous products were investigated by evolved gas analysis performed by an online coupled mass spectrometer (TG/DTA-MS). Thermal degradation of 2 under helium atmosphere is distributed over five steps, whereas 3 and 4 exhibited only four degradation steps due to overlap of second and third degradation steps of into one major step. All the complexes exhibit three steps degradation under air. The complex 2 loses NH group in the second and HCl/Cl2, CO groups simultaneously in third steps of decomposition under helium, whereas it loses NH and CO groups simultaneously in low temperature region of second step of degradation under air atmosphere as the loss of CO group is facilitated by air. EGA-MS under air and helium atmospheres shows that HCl, CO/CO2 and (CN)2 fragments are lost simultaneously at multiple steps, and not successively as predicted earlier. Rate of evolution of most evolved gases exhibits several maxima as a consequence of degradation followed by recombination reactions. Final residues under air and helium atmospheres correspond to the metal oxides and metals along with some carbonaceous matter. © 2013 Akadémiai Kiadó, Budapest, Hungary
Black Male Collegiate Athletes’ Perceptions of Their Career and Academic Preparation: A Mixed Methods Study
We employed a mixed methods approach with sequential explanatory design (Creswell & Plano Clark, 2017) and a Social Capital Theory framework (Bourdieu, 1977) to investigate three research questions: (1) In what ways were participants’ career and college readiness capital developed during high school? (2) How do participants view their academic and career growth and development prior to and after coming to college? (3) Who provided career and college development to participants in this study prior to their college entrance? Results revealed potential reasons why disparities existed between Black and White participants beginning in K-12 and continuing through college. Implications for anti-racist school counseling are given
Cooperative Transport of Brownian Particles
We consider the collective motion of finite-sized, overdamped Brownian
particles (e.g., motor proteins) in a periodic potential. Simulations of our
model have revealed a number of novel cooperative transport phenomena,
including (i) the reversal of direction of the net current as the particle
density is increased and (ii) a very strong and complex dependence of the
average velocity on both the size and the average distance of the particles.Comment: 4 pages, 5 figure
The generalized localization lengths in one dimensional systems with correlated disorder
The scale invariant properties of wave functions in finite samples of one
dimensional random systems with correlated disorder are analyzed. The random
dimer model and its generalizations are considered and the wave functions are
compared. Generalized entropic localization lengths are introduced in order to
characterize the states and compared with their behavior for exponential
localization. An acceptable agreement is obtained, however, the exponential
form seems to be an oversimplification in the presence of correlated disorder.
According to our analysis in the case of the random dimer model and the two new
models the presence of power-law localization cannot be ruled out.Comment: 7 pages, LaTeX (IOP style), 2 figure
Stability limits of n-nonane calculated from molecular dynamics interface simulations
Based on molecular dynamics simulation of the vapor-liquid interface the classical thermodynamic spinodal for n-nonane is estimated using an earlier developed method. The choice of n-nonane as investigated molecule originates from the question whether a deviation from the spherical symmetry of a molecule affects the prediction of the stability limit data. As a result we find that the estimated stability limit data for n-nonane are consistent within the experimental data available for the homologous series of the n-alkanes. It turns out that the slight alignment of the molecules parallel to the interface reported in the literature does not affect the method of transferring interface properties to the bulk phase stability limit
Sleep Disturbances and Glucose Metabolism in Older Adults: The Cardiovascular Health Study.
ObjectiveWe examined the associations of symptoms of sleep-disordered breathing (SDB), which was defined as loud snoring, stopping breathing for a while during sleep, and daytime sleepiness, and insomnia with glucose metabolism and incident type 2 diabetes in older adults.Research design and methodsBetween 1989 and 1993, the Cardiovascular Health Study recruited 5,888 participants ≥65 years of age from four U.S. communities. Participants reported SDB and insomnia symptoms yearly through 1989-1994. In 1989-1990, participants underwent an oral glucose tolerance test, from which insulin secretion and insulin sensitivity were estimated. Fasting glucose levels were measured in 1989-1990 and again in 1992-1993, 1994-1995, 1996-1997, and 1998-1999, and medication use was ascertained yearly. We determined the cross-sectional associations of sleep symptoms with fasting glucose levels, 2-h glucose levels, insulin sensitivity, and insulin secretion using generalized estimated equations and linear regression models. We determined the associations of updated and averaged sleep symptoms with incident diabetes in Cox proportional hazards models. We adjusted for sociodemographics, lifestyle factors, and medical history.ResultsObserved apnea, snoring, and daytime sleepiness were associated with higher fasting glucose levels, higher 2-h glucose levels, lower insulin sensitivity, and higher insulin secretion. The risk of the development of type 2 diabetes was positively associated with observed apnea (hazard ratio [HR] 1.84 [95% CI 1.19-2.86]), snoring (HR 1.27 [95% CI 0.95-1.71]), and daytime sleepiness (HR 1.54 [95% CI 1.13-2.12]). In contrast, we did not find consistent associations between insomnia symptoms and glucose metabolism or incident type 2 diabetes.ConclusionsEasily collected symptoms of SDB are strongly associated with insulin resistance and the incidence of type 2 diabetes in older adults. Monitoring glucose metabolism in such patients may prove useful in identifying candidates for lifestyle or pharmacological therapy. Further studies are needed to determine whether insomnia symptoms affect the risk of diabetes in younger adults
Ratchet Effect in Surface Electromigration: Smoothing Surfaces by an ac Field
We demonstrate that for surfaces that have a nonzero Schwoebel barrier the
application of an ac field parallel to the surface induces a net electro-
migration current that points in the descending step direction. The magnitude
of the current is calculated analytically and compared with Monte Carlo
simulations. Since a downhill current smoothes the surface, our results imply
that the application of ac fields can aid the smoothing process during
annealing and can slow or eliminate the Schwoebel-barrier-induced mound
formation during growth.Comment: 4 pages, LaTeX, 4 ps figure
Improvement of a Fixed Point Transformations and SVD-based Adaptive Controller
In this paper some refinement of a novel control approach is reported that fits to the “traditional line of thinking” according to which in the most practical cases neither very precise, nor even complete system model is needed for obtaining precise control for dynamical systems. The validity of this statement is briefly pointed out in the most popular approaches as the main idea of the “Robust Sliding Mode / Variable Structure Controllers”, in the Adaptive Inverse Dynamics and in the Slotine-Li Adaptive Controllers based on Lyapunov's 2nd Method, and in a recently published problem tackling using the simple geometric interpretation of the Singular Value Decomposition (SVD). In the present approach the originally proposed convergent, iterative Cauchy sequences are nonlinearly moderated to adaptively control a coupled nonlinear system, the cart plus double pendulum serving as popular paradigm of dynamicall not very well conditioned systems. It is shown that the proposed moderation removes the small sharp fluctuation in the control torque that inherently belonged to the original solution without significantly degrading the control quality. This statement is substantiated by simulation results.N/
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