Coherent Population Trapping with Controlled Interparticle Interactions

We investigate Coherent Population Trapping in a strongly interacting ultracold Rydberg gas. Despite the strong van der Waals interactions and interparticle correlations, we observe the persistence of a resonance with subnatural linewidth at the single-particle resonance frequency as we tune the interaction strength. This narrow resonance cannot be understood within a meanfield description of the strong Rydberg--Rydberg interactions. Instead, a many-body density matrix approach, accounting for the dynamics of interparticle correlations, is shown to reproduce the observed spectral features

Coverage-dependent adsorption sites in the K/Ru(0001) system: a low-energy electron-diffraction analysis

The two ordered phases p(2 × 2) at a coverage θ = 0.25 and (√3 × √3)R30° at θ = 0.33 of potassium adsorbed on Ru(0001) were analyzed by use of low-energy electron-diffraction (LEED). In the (√3 × √3)R30° phase, the K atoms occupy threefold hcp sites, while in the p(2 × 2) phase the fcc site is favoured. In both phases, the K hard-sphere radii are nearly the same and close to the covalent Pauling radius

GEANT4 : a simulation toolkit

Abstract Geant4 is a toolkit for simulating the passage of particles through matter. It includes a complete range of functionality including tracking, geometry, physics models and hits. The physics processes offered cover a comprehensive range, including electromagnetic, hadronic and optical processes, a large set of long-lived particles, materials and elements, over a wide energy range starting, in some cases, from 250 eV and extending in others to the TeV energy range. It has been designed and constructed to expose the physics models utilised, to handle complex geometries, and to enable its easy adaptation for optimal use in different sets of applications. The toolkit is the result of a worldwide collaboration of physicists and software engineers. It has been created exploiting software engineering and object-oriented technology and implemented in the C++ programming language. It has been used in applications in particle physics, nuclear physics, accelerator design, space engineering and medical physics. PACS: 07.05.Tp; 13; 2

Impacts of Hurricanes Katrina and Rita on the microbial landscape of the New Orleans area

Author Posting. © The Author(s), 2007. This is the author's version of the work. It is posted here by permission of National Academy of Sciences of the USA for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences 104 (2007): 9029-9034, doi:10.1073/pnas.0610552104.Floodwaters in New Orleans from Hurricanes Katrina and Rita were observed to contain high levels of fecal indicator bacteria and microbial pathogens, generating concern about long-term impacts of these floodwaters on the sediment and water quality of the New Orleans area and Lake Pontchartrain. We show here that fecal indicator microbe concentrations in offshore waters from Lake Pontchartrain returned to prehurricane concentrations within 2 months of the flooding induced by these hurricanes. Vibrio and Legionella species within the lake were more abundant in samples collected shortly after the floodwaters had receded compared with samples taken within the subsequent 3 months; no evidence of a long-term hurricane-induced algal bloom was observed. Giardia and Cryptosporidium were detected in canal waters. Elevated levels of fecal indicator bacteria observed in sediment could not be solely attributed to impacts from floodwaters, as both flooded and nonflooded areas exhibited elevated levels of fecal indicator bacteria. Evidence from measurements of Bifidobacterium and bacterial diversity analysis suggest that the fecal indicator bacteria observed in the sediment were from human fecal sources. Epidemiologic studies are highly recommended to evaluate the human health effects of the sediments deposited by the floodwaters.This work was funded by NSF-NIEHS Oceans and Human Health Program (NSF OCE0432368, OCE0432479, OCE0430724 and NIEHS P50 ES12736, ES012740, ES012742), the NSF-SGER Program (OCE 0554402, OCE 0554674, OCE 0554850, OCE0600130), the NSF-REU Program, and by the Georgia Sea Grant College Program (NA04OAR170033)

Axial stent strut angle influences wall shear stress after stent implantation: analysis using 3D computational fluid dynamics models of stent foreshortening

INTRODUCTION: The success of vascular stents in the restoration of blood flow is limited by restenosis. Recent data generated from computational fluid dynamics (CFD) models suggest that the vascular geometry created by an implanted stent causes local alterations in wall shear stress (WSS) that are associated with neointimal hyperplasia (NH). Foreshortening is a potential limitation of stent design that may affect stent performance and the rate of restenosis. The angle created between axially aligned stent struts and the principal direction of blood flow varies with the degree to which the stent foreshortens after implantation. METHODS: In the current investigation, we tested the hypothesis that stent foreshortening adversely influences the distribution of WSS and WSS gradients using time-dependent 3D CFD simulations of normal arteries based on canine coronary artery measurements of diameter and blood flow. WSS and WSS gradients were calculated using conventional techniques in ideal (16 mm) and progressively foreshortened (14 and 12 mm) stented computational vessels. RESULTS: Stent foreshortening increased the intrastrut area of the luminal surface exposed to low WSS and elevated spatial WSS gradients. Progressive degrees of stent foreshortening were also associated with strut misalignment relative to the direction of blood flow as indicated by analysis of near-wall velocity vectors. CONCLUSION: The current results suggest that foreshortening may predispose the stented vessel to a higher risk of neointimal hyperplasia

Alterations in regional vascular geometry produced by theoretical stent implantation influence distributions of wall shear stress: analysis of a curved coronary artery using 3D computational fluid dynamics modeling

BACKGROUND: The success of stent implantation in the restoration of blood flow through areas of vascular narrowing is limited by restenosis. Several recent studies have suggested that the local geometric environment created by a deployed stent may influence regional blood flow characteristics and alter distributions of wall shear stress (WSS) after implantation, thereby rendering specific areas of the vessel wall more susceptible to neointimal hyperplasia and restenosis. Stents are most frequently implanted in curved vessels such as the coronary arteries, but most computational studies examining blood flow patterns through stented vessels conducted to date use linear, cylindrical geometric models. It appears highly probable that restenosis occurring after stent implantation in curved arteries also occurs as a consequence of changes in fluid dynamics that are established immediately after stent implantation. METHODS: In the current investigation, we tested the hypothesis that acute changes in stent-induced regional geometry influence distributions of WSS using 3D coronary artery CFD models implanted with stents that either conformed to or caused straightening of the primary curvature of the left anterior descending coronary artery. WSS obtained at several intervals during the cardiac cycle, time averaged WSS, and WSS gradients were calculated using conventional techniques. RESULTS: Implantation of a stent that causes straightening, rather than conforms to the natural curvature of the artery causes a reduction in the radius of curvature and subsequent increase in the Dean number within the stented region. This straightening leads to modest skewing of the velocity profile at the inlet and outlet of the stented region where alterations in indices of WSS are most pronounced. For example, time-averaged WSS in the proximal portion of the stent ranged from 8.91 to 11.7 dynes/cm(2 )along the pericardial luminal surface and 4.26 to 4.88 dynes/cm(2 )along the myocardial luminal surface of curved coronary arteries as compared to 8.31 dynes/cm(2 )observed throughout the stented region of a straight vessel implanted with an equivalent stent. CONCLUSION: The current results predicting large spatial and temporal variations in WSS at specific locations in curved arterial 3D CFD simulations are consistent with clinically observed sites of restenosis. If the findings of this idealized study translate to the clinical situation, the regional geometry established immediately after stent implantation may predispose portions of the stented vessel to a higher risk of neointimal hyperplasia and subsequent restenosis

Efficacy of essential oil mouthwash with and without alcohol: a 3-Day plaque accumulation model

<p>Abstract</p> <p>Background</p> <p>The aim of this study was to evaluate the antiplaque effect of a new alcohol free essential oil mouthwash with respect to a control of an essential oil with alcohol mouthwash, using an <it>in vivo </it>plaque regrowth model of 3-days.</p> <p>Methods</p> <p>The study was designed as a double-masked, randomized, crossover clinical trial, involving 30 volunteers to compare two different essential oil containing mouthwashes, during a 3-day plaque accumulation model. After receiving a thorough professional prophylaxis at the baseline, over the next 3-days each volunteer refrained from all oral hygiene measures and had two daily rinses with 20 ml of the test mouthwash (alcohol free essential oil) or the control mouthwash (essential oil with alcohol). At the end of the each experimental period, plaque was assessed and the panelists filled out a questionnaire. Each subject underwent a 14 days washout period and there was a second allocation.</p> <p>Results</p> <p>The essential oil mouthwash with ethanol shows a better inhibitory effect of plaque regrowth in 3-days than the mouthwash test with only essential oil in the whole mouth (plaque index = 2.18 against 2.46, respectively, p < 0.05); for the lower jaw (plaque index = 2.28 against 2.57, respectively, p < 0.05); for the upper jaw (plaque index = 2.08 against 2.35, respectively, p < 0.05); for the incisors (plaque index = 1.93 against 2.27, respectively, p < 0.05); and the canines (plaque index = 1.99 against 2.47, respectively, p < 0.05).</p> <p>Conclusion</p> <p>The essential oil containing mouthwash without alcohol seems to have a less inhibiting effect on the plaque regrowth than the traditional alcoholic solution.</p> <p>Trial Registration</p> <p>ClinicalTrials.gov <a href="http://www.clinicaltrials.gov/ct2/show/NCT01411618">NCT01411618</a></p

Dentifrices, mouthwashes, and remineralization/caries arrestment strategies

While our knowledge of the dental caries process and its prevention has greatly advanced over the past fifty years, it is fair to state that the management of this disease at the level of the individual patient remains largely empirical. Recommendations for fluoride use by patients at different levels of caries risk are mainly based on the adage that more is better. There is a general understanding that the fluoride compound, concentration, frequency of use, duration of exposure, and method of delivery can influence fluoride efficacy. Two important factors are (1) the initial interaction of relatively high concentrations of fluoride with the tooth surface and plaque during application and (2) the retention of fluoride in oral fluids after application

Collateral circulation: Past and present

Following an arterial occlusion outward remodeling of pre-existent inter-connecting arterioles occurs by proliferation of vascular smooth muscle and endothelial cells. This is initiated by deformation of the endothelial cells through increased pulsatile fluid shear stress (FSS) caused by the steep pressure gradient between the high pre-occlusive and the very low post-occlusive pressure regions that are interconnected by collateral vessels. Shear stress leads to the activation and expression of all NOS isoforms and NO production, followed by endothelial VEGF secretion, which induces MCP-1 synthesis in endothelium and in the smooth muscle of the media. This leads to attraction and activation of monocytes and T-cells into the adventitial space (peripheral collateral vessels) or attachment of these cells to the endothelium (coronary collaterals). Mononuclear cells produce proteases and growth factors to digest the extra-cellular scaffold and allow motility and provide space for the new cells. They also produce NO from iNOS, which is essential for arteriogenesis. The bulk of new tissue production is carried by the smooth muscles of the media, which transform their phenotype from a contractile into a synthetic and proliferative one. Important roles are played by actin binding proteins like ABRA, cofilin, and thymosin beta 4 which determine actin polymerization and maturation. Integrins and connexins are markedly up-regulated. A key role in this concerted action which leads to a 2-to-20 fold increase in vascular diameter, depending on species size (mouse versus human) are the transcription factors AP-1, egr-1, carp, ets, by the Rho pathway and by the Mitogen Activated Kinases ERK-1 and -2. In spite of the enormous increase in tissue mass (up to 50-fold) the degree of functional restoration of blood flow capacity is incomplete and ends at 30% of maximal conductance (coronary) and 40% in the vascular periphery. The process of arteriogenesis can be drastically stimulated by increases in FSS (arterio-venous fistulas) and can be completely blocked by inhibition of NO production, by pharmacological blockade of VEGF-A and by the inhibition of the Rho-pathway. Pharmacological stimulation of arteriogenesis, important for the treatment of arterial occlusive diseases, seems feasible with NO donors