Twonniers: Interaction-induced effects on Bose-Hubbard parameters

We study the effects of the repulsive on-site interactions on the broadening of the localized Wannier functions used for calculating the parameters to describe ultracold atoms in optical lattices. For this, we replace the common single-particle Wannier functions, which do not contain any information about the interactions, by two-particle Wannier functions ("Twonniers") obtained from an exact solution which takes the interactions into account. We then use these interaction-dependent basis functions to calculate the Bose--Hubbard model parameters, showing that they are substantially different both at low and high lattice depths, from the ones calculated using single-particle Wannier functions. Our results suggest that density effects are not negligible for many parameter ranges and need to be taken into account in metrology experiments.Comment: 6 pages, 3 figure

Hydraulic Transport Across Hydrophilic and Hydrophobic Nanopores: Flow Experiments with Water and n-Hexane

We experimentally explore pressure-driven flow of water and n-hexane across nanoporous silica (Vycor glass monoliths with 7 or 10 nm pore diameters, respectively) as a function of temperature and surface functionalization (native and silanized glass surfaces). Hydraulic flow rates are measured by applying hydrostatic pressures via inert gases (argon and helium, pressurized up to 70 bar) on the upstream side in a capacitor-based membrane permeability setup. For the native, hydrophilic silica walls, the measured hydraulic permeabilities can be quantitatively accounted for by bulk fluidity provided we assume a sticking boundary layer, i.e. a negative velocity slip length of molecular dimensions. The thickness of this boundary layer is discussed with regard to previous capillarity-driven flow experiments (spontaneous imbibition) and with regard to velocity slippage at the pore walls resulting from dissolved gas. Water flow across the silanized, hydrophobic nanopores is blocked up to a hydrostatic pressure of at least 70 bar. The absence of a sticking boundary layer quantitatively accounts for an enhanced n-hexane permeability in the hydrophobic compared to the hydrophilic nanopores.Comment: 15 pages, 7 figures, in press, Physical Review E 201

Inclusive Curriculum: Making STEM Accessible for ALL Students

Historically, women and people from marginalized community groups have accounted for a small portion of those pursuing STEM careers. In this session, participants will reflect on their current curriculum and consider new practices for making STEM coursework accessible to at-risk students and other students from underrepresented populations. This will be a conversation based session where participants will share about their experiences and reflect on their classrooms

Unscented Kalman Filter for State and Parameter Estimation in Vehicle Dynamics

Automotive research and development passed through a vast evolution during past decades. Many passive and active driver assistance systems were developed, increasing the passengers’ safety and comfort. This ongoing process is a main focus in current research and offers great potential for further systems, especially focusing on the task of autonomous and cooperative driving in the future. For that reason, information about the current stability in terms of dynamic behavior and vehicle environment are necessary for the systems to perform properly. Thus, model-based online state and parameter estimation have become important throughout the last years using a detailed vehicle model and standard sensors, gathering this information. In this chapter, state and parameter estimation in vehicle dynamics utilizing the unscented Kalman filter is presented. The estimation runs in real time based on a detailed vehicle model and standard measurements taken within the car. The results are validated using a Volkswagen Golf GTE Plug-In Hybrid for various dynamic test maneuvers and a Genesys Automotive Dynamic Motion Analyzer (ADMA) measurement unit for high-precision measurements of the vehicle’s states. Online parameter estimation is shown for friction coefficient estimation performing maneuvers on different road surfaces

Thermotropic nematic order upon nano-capillary filling

Optical birefringence and light absorption measurements reveal four regimes for the thermotropic behavior of a nematogen liquid (7CB) upon sequential filling of parallel-aligned capillaries of 12 nm diameter in a monolithic, mesoporous silica membrane. No molecular reorientation is observed for the first adsorbed monolayer. In the film-condensed state (up to 1 nm thickness) a weak, continuous paranematic-to-nematic (P-N) transition is found, which is shifted by 10 K below the discontinuous bulk transition at T_IN=305K. The capillary-condensed state exhibits a more pronounced, albeit still continuous P-N reordering, located 4 K below T_IN. This shift vanishes abruptly on complete filling of the capillaries, which we tentatively trace to a 10 MPa tensile pressure release associated with the disappearance of concave menisci in the confined liquid.Comment: 6 pages, 3 figure

Genetic variation in the endangered Southwestern Willow Flycatcher

The Southwestern Willow Flycatcher (Empidonax traillii extimus) is an endangered Neotropical migrant that breeds in isolated remnants of dense riparian habitat in the southwestern United States. We estimated genetic variation at 20 breeding sites of the Southwestern Willow Flycatcher (290 individuals) using 38 amplified fragment length polymorphisms (AFLPs). Our results suggest that considerable genetic diversity exists within the subspecies and within local breeding sites. Statistical analyses of genetic variation revealed only slight, although significant, differentiation among breeding sites (Mantel's r = 0.0705, P < 0.0005; theta = 0.0816, 95% CI = 0.0608 to 0.1034; Phi sub(ST) = 0.0458, P < 0.001). UPGMA cluster analysis of the AFLP markers indicates that extensive gene flow has occurred among breeding sites. No one site stood out as being genetically unique or isolated. Therefore, the small level of genetic structure that we detected may not be biologically significant. Ongoing field studies are consistent with this conclusion. Of the banded birds that were resighted or recaptured in Arizona during the 1996 to 1998 breeding seasons, one-third moved between breeding sites and two-thirds were philopatric. Low differentiation may be the result of historically high rangewide diversity followed by recent geographic isolation of breeding sites, although observational data indicate that gene flow is a current phenomenon. Our data suggest that breeding groups of E. t. extimus act as a metapopulation

Risk factors for COPD exacerbations in inhaled medication users: the COPDGene study biannual longitudinal follow-up prospective cohort.

BackgroundDespite inhaled medications that decrease exacerbation risk, some COPD patients experience frequent exacerbations. We determined prospective risk factors for exacerbations among subjects in the COPDGene Study taking inhaled medications.Methods2113 COPD subjects were categorized into four medication use patterns: triple therapy with tiotropium (TIO) plus long-acting beta-agonist/inhaled-corticosteroid (ICS ± LABA), tiotropium alone, ICS ± LABA, and short-acting bronchodilators. Self-reported exacerbations were recorded in telephone and web-based longitudinal follow-up surveys. Associations with exacerbations were determined within each medication group using four separate logistic regression models. A head-to-head analysis compared exacerbation risk among subjects using tiotropium vs. ICS ± LABA.ResultsIn separate logistic regression models, the presence of gastroesophageal reflux, female gender, and higher scores on the St. George's Respiratory Questionnaire were significant predictors of exacerbator status within multiple medication groups (reflux: OR 1.62-2.75; female gender: OR 1.53 - OR 1.90; SGRQ: OR 1.02-1.03). Subjects taking either ICS ± LABA or tiotropium had similar baseline characteristics, allowing comparison between these two groups. In the head-to-head comparison, tiotropium users showed a trend towards lower rates of exacerbations (OR = 0.69 [95 % CI 0.45, 1.06], p = 0.09) compared with ICS ± LABA users, especially in subjects without comorbid asthma (OR = 0.56 [95% CI 0.31, 1.00], p = 0.05).ConclusionsEach common COPD medication usage group showed unique risk factor patterns associated with increased risk of exacerbations, which may help clinicians identify subjects at risk. Compared to similar subjects using ICS ± LABA, those taking tiotropium showed a trend towards reduced exacerbation risk, especially in subjects without asthma.Trial registrationClinicalTrials.gov NCT00608764, first received 1/28/2008

Impact of confinement and polarizability on dynamics of ionic liquids

Polarizability is a key factor when it comes to an accurate description of different ionic systems. The general importance of including polarizability into molecular dynamics simulations was shown in various recent studies for a wide range of materials, ranging from proteins to water to complex ionic liquids and for solid–liquid interfaces. While most previous studies focused on bulk properties or static structure factors, this study investigates in more detail the importance of polarizable surfaces on the dynamics of a confined ionic liquid in graphitic slit pores, as evident in modern electrochemical capacitors or in catalytic processes. A recently developed polarizable force field using Drude oscillators is modified in order to describe a particular room temperature ionic liquid accurately and in agreement with recently published experimental results. Using the modified parameters, various confinements are investigated and differences between non-polarizable and polarizable surfaces are discussed. Upon introduction of surface polarizability, changes in the dipole orientation and in the density distribution of the anions and cations at the interface are observed and are also accompanied with a dramatic increase in the molecular diffusivity in the contact layer. Our results thus clearly underline the importance of considering not only the polarizability of the ionic liquid but also that of the surface