Chaos in Quantum Dots: Dynamical Modulation of Coulomb Blockade Peak Heights

The electrostatic energy of an additional electron on a conducting grain blocks the flow of current through the grain, an effect known as the Coulomb blockade. Current can flow only if two charge states of the grain have the same energy; in this case the conductance has a peak. In a small grain with quantized electron states, referred to as a quantum dot, the magnitude of the conductance peak is directly related to the magnitude of the wavefunction near the contacts to the dot. Since dots are generally irregular in shape, the dynamics of the electrons is chaotic, and the characteristics of Coulomb blockade peaks reflects those of wavefunctions in chaotic systems. Previously, a statistical theory for the peaks was derived by assuming these wavefunctions to be completely random. Here we show that the specific internal dynamics of the dot, even though it is chaotic, modulates the peaks: because all systems have short-time features, chaos is not equivalent to randomness. Semiclassical results are derived for both chaotic and integrable dots, which are surprisingly similar, and compared to numerical calculations. We argue that this modulation, though unappreciated, has already been seen in experiments.Comment: 4 pages, 3 postscript figs included (2 color), uses epsf.st

Semiclassical Theory of Coulomb Blockade Peak Heights in Chaotic Quantum Dots

We develop a semiclassical theory of Coulomb blockade peak heights in chaotic quantum dots. Using Berry's conjecture, we calculate the peak height distributions and the correlation functions. We demonstrate that the corrections to the corresponding results of the standard statistical theory are non-universal and can be expressed in terms of the classical periodic orbits of the dot that are well coupled to the leads. The main effect is an oscillatory dependence of the peak heights on any parameter which is varied; it is substantial for both symmetric and asymmetric lead placement. Surprisingly, these dynamical effects do not influence the full distribution of peak heights, but are clearly seen in the correlation function or power spectrum. For non-zero temperature, the correlation function obtained theoretically is in good agreement with that measured experimentally.Comment: 5 color eps figure

Hispanics/Latinos With Type 2 Diabetes Have Functional and Symptomatic Pulmonary Impairment Mirroring Kidney Microangiopathy: Findings From the Hispanic Community Health Study/Study of Latinos (HCHS/SOL)

Type 2 diabetes mellitus (DM) has been associated with lung dysfunction, but this association has not been explored in Hispanics/Latinos. The relation between diabetic nephropathy and lung function and symptoms has not been explored

The Deglaciation of Maine, USA

The glacial geology of Maine records the northward recession of the Late Wisconsinan Laurentide Ice Sheet, followed by development of a residual ice cap in the Maine-Québec border region due to marine transgression of the St. Lawrence Lowland in Canada. The pattern of deglaciation across southern Maine has been reconstructed from numerous end moraines, deltas and submarine fans deposited during marine transgression of the coastal lowland. Inland from the marine limit, a less-detailed sequence of deglaciation is recorded by striation patterns, meltwater channels, scattered moraines and waterlain deposits that constrain the trend of the ice margin. There is no evidence that the northern Maine ice cap extended as far south-west as the Boundary Mountains and New Hampshire border. Newly-obtained radiocarbon ages from marine and terrestrial ice-proximal environments have improved the chronology of glacial recession in Maine. Many of these ages were obtained by coring late-glacial sediments beneath ponds and lakes. Data from this study show that the state was deglaciated between about 14.5 and 11.0 ka BP (14C years). The coastal moraine belt in southern Maine was deposited by oscillatory ice-margin retreat during the cold pre-Bølling time. Rapid ice recession to northern Maine then occurred between 13 and 11 ka BP, during the warmer Bølling/Allerød chronozones. Radiocarbon-dated pond sediments in western and northern Maine show lithologic evidence of Younger Dryas climatic cooling and persistence of the northern ice cap into Younger Dryas time. A large discrepancy still exists between radiocarbon ages of deglaciation in coastal south-western Maine and the timing of ice retreat indicated by New England varve records in areas to the west. Part of this problem may stem from the uncertainty of reservoir corrections applied to the radiocarbon ages of marine organics

Spin and e-e interactions in quantum dots: Leading order corrections to universality and temperature effects

We study the statistics of the spacing between Coulomb blockade conductance peaks in quantum dots with large dimensionless conductance g. Our starting point is the ``universal Hamiltonian''--valid in the g->oo limit--which includes the charging energy, the single-electron energies (described by random matrix theory), and the average exchange interaction. We then calculate the magnitude of the most relevant finite g corrections, namely, the effect of surface charge, the ``gate'' effect, and the fluctuation of the residual e-e interaction. The resulting zero-temperature peak spacing distribution has corrections of order Delta/sqrt(g). For typical values of the e-e interaction (r_s ~ 1) and simple geometries, theory does indeed predict an asymmetric distribution with a significant even/odd effect. The width of the distribution is of order 0.3 Delta, and its dominant feature is a large peak for the odd case, reminiscent of the delta-function in the g->oo limit. We consider finite temperature effects next. Only after their inclusion is good agreement with the experimental results obtained. Even relatively low temperature causes large modifications in the peak spacing distribution: (a) its peak is dominated by the even distribution at kT ~ 0.3 Delta (at lower T a double peak appears); (b) it becomes more symmetric; (c) the even/odd effect is considerably weaker; (d) the delta-function is completely washed-out; and (e) fluctuation of the coupling to the leads becomes relevant. Experiments aimed at observing the T=0 peak spacing distribution should therefore be done at kT<0.1 Delta for typical values of the e-e interaction.Comment: 15 pages, 4 figure

Establishing Foundation Archives: A Reader and Guide to First Steps

This publication is an anthology of papers presented at a conference held at the Rockefeller Archive Center in January 1990, and sponsored by the Council on Foundations. This collaboration of the Archive Center and the Council provided a rare opponunity for foundations to learn both why preserving documents is imponant and how several foundations have approached finding a repository or setting up and managing an archives. Participants in the conference had the added privilege of conferring with experts and seeing an operating archive as they toured the Rockefeller Archive Center.Foundations are institutions that are shaping private initiatives for the public good, so documenting this aspect of American society falls uniquely under the stewardship of the organizations themselves. Foundation documents often provide the only surviving records of the important contributions of nonprofits and foundations to civic life. These records will help to inform future judgments and ensure that the history of the field is not lost. The publication of this volume was intended to make the information shared at the conference more widely available and to provide an entry point and a primer for foundations as they begin their records and archives journey

Bodyweight Perceptions among Texas Women: The Effects of Religion, Race/Ethnicity, and Citizenship Status

Despite previous work exploring linkages between religious participation and health, little research has looked at the role of religion in affecting bodyweight perceptions. Using the theoretical model developed by Levin et al. (Sociol Q 36(1):157–173, 1995) on the multidimensionality of religious participation, we develop several hypotheses and test them by using data from the 2004 Survey of Texas Adults. We estimate multinomial logistic regression models to determine the relative risk of women perceiving themselves as overweight. Results indicate that religious attendance lowers risk of women perceiving themselves as very overweight. Citizenship status was an important factor for Latinas, with noncitizens being less likely to see themselves as overweight. We also test interaction effects between religion and race. Religious attendance and prayer have a moderating effect among Latina non-citizens so that among these women, attendance and prayer intensify perceptions of feeling less overweight when compared to their white counterparts. Among African American women, the effect of increased church attendance leads to perceptions of being overweight. Prayer is also a correlate of overweight perceptions but only among African American women. We close with a discussion that highlights key implications from our findings, note study limitations, and several promising avenues for future research

Status of Muon Collider Research and Development and Future Plans

The status of the research on muon colliders is discussed and plans are outlined for future theoretical and experimental studies. Besides continued work on the parameters of a 3-4 and 0.5 TeV center-of-mass (CoM) energy collider, many studies are now concentrating on a machine near 0.1 TeV (CoM) that could be a factory for the s-channel production of Higgs particles. We discuss the research on the various components in such muon colliders, starting from the proton accelerator needed to generate pions from a heavy-Z target and proceeding through the phase rotation and decay ($\pi \to \mu \nu_{\mu}$) channel, muon cooling, acceleration, storage in a collider ring and the collider detector. We also present theoretical and experimental R & D plans for the next several years that should lead to a better understanding of the design and feasibility issues for all of the components. This report is an update of the progress on the R & D since the Feasibility Study of Muon Colliders presented at the Snowmass'96 Workshop [R. B. Palmer, A. Sessler and A. Tollestrup, Proceedings of the 1996 DPF/DPB Summer Study on High-Energy Physics (Stanford Linear Accelerator Center, Menlo Park, CA, 1997)].Comment: 95 pages, 75 figures. Submitted to Physical Review Special Topics, Accelerators and Beam

Skin prick testing in patients using beta-blockers: a retrospective analysis

<p>Abstract</p> <p>Rationale</p> <p>The use of beta-blockers is a relative contraindication in allergen skin testing yet there is a paucity of literature on adverse events in this circumstance. We examined a population of skin tested patients on beta-blockers to look for any adverse effects.</p> <p>Methods</p> <p>Charts from 2004-2008 in a single allergy clinic were reviewed for any patients taking a beta-blocker when skin tested. Data was examined for skin test reactivity, type of skin test, concomitant asthma diagnosis, allergens tested, and adverse events.</p> <p>Results</p> <p>One hundred and ninety-one patients were taking beta-blockers when skin testing occurred. Seventy-two patients had positive skin tests. No tests resulted in an adverse event.</p> <p>Conclusions</p> <p>This data demonstrates the relative safety of administrating of skin prick tests to patients on beta-blocker treatment. Larger prospective studies are needed to substantiate the findings of this study.</p