Solvent fluctuations around solvophobic, solvophilic and patchy nanostructures and the accompanying solvent mediated interactions

Using classical density functional theory (DFT) we calculate the density profile $\rho({\mathbf r})$ and local compressibility $\chi({\mathbf r})$ of a simple liquid solvent in which a pair of blocks with (microscopic) rectangular cross-section are immersed. We consider blocks that are solvophobic, solvophilic and also ones that have both solvophobic and solvophilic patches. Large values of $\chi({\mathbf r})$ correspond to regions in space where the liquid density is fluctuating most strongly. We seek to elucidate how enhanced density fluctuations correlate with the solvent mediated force between the blocks, as the distance between the blocks and the chemical potential of the liquid reservoir vary. For sufficiently solvophobic blocks, at small block separations and small deviations from bulk gas-liquid coexistence, we observe a strongly attractive (near constant) force, stemming from capillary evaporation to form a low density gas-like intrusion between the blocks. The accompanying $\chi({\mathbf r})$ exhibits structure which reflects the incipient gas-liquid interfaces that develop. We argue that our model system provides a means to understanding the basic physics of solvent mediated interactions between nanostructures, and between objects such as proteins in water, that possess hydrophobic and hydrophilic patches.Comment: 19 pages, 21 figure

The standard mean-field treatment of inter-particle attraction in classical DFT is better than one might expect

In classical density functional theory (DFT) the part of the Helmholtz free energy functional arising from attractive inter-particle interactions is often treated in a mean-field or van der Waals approximation. On the face of it, this is a somewhat crude treatment as the resulting functional generates the simple random phase approximation (RPA) for the bulk fluid pair direct correlation function. We explain why using standard mean-field DFT to describe inhomogeneous fluid structure and thermodynamics is more accurate than one might expect based on this observation. By considering the pair correlation function $g(x)$ and structure factor $S(k)$ of a one-dimensional model fluid, for which exact results are available, we show that the mean-field DFT, employed within the test-particle procedure, yields results much superior to those from the RPA closure of the bulk Ornstein-Zernike equation. We argue that one should not judge the quality of a DFT based solely on the approximation it generates for the bulk pair direct correlation function.Comment: 9 pages, 3 figure

Heart Rate Monitoring During Different Lung Volume Phases Using Seismocardiography

Seismocardiography (SCG) is a non-invasive method that can be used for cardiac activity monitoring. This paper presents a new electrocardiogram (ECG) independent approach for estimating heart rate (HR) during low and high lung volume (LLV and HLV, respectively) phases using SCG signals. In this study, SCG, ECG, and respiratory flow rate (RFR) signals were measured simultaneously in 7 healthy subjects. The lung volume information was calculated from the RFR and was used to group the SCG events into low and high lung-volume groups. LLV and HLV SCG events were then used to estimate the subjects HR as well as the HR during LLV and HLV in 3 different postural positions, namely supine, 45 degree heads-up, and sitting. The performance of the proposed algorithm was tested against the standard ECG measurements. Results showed that the HR estimations from the SCG and ECG signals were in a good agreement (bias of 0.08 bpm). All subjects were found to have a higher HR during HLV (HR$_\text{HLV}$) compared to LLV (HR$_\text{LLV}$) at all postural positions. The HR$_\text{HLV}$/HR$_\text{LLV}$ ratio was 1.11$\pm$0.07, 1.08$\pm$0.05, 1.09$\pm$0.04, and 1.09$\pm$0.04 (mean$\pm$SD) for supine, 45 degree-first trial, 45 degree-second trial, and sitting positions, respectively. This heart rate variability may be due, at least in part, to the well-known respiratory sinus arrhythmia. HR monitoring from SCG signals might be used in different clinical applications including wearable cardiac monitoring systems

Warm Ice Giant GJ 3470b. I. A Flat Transmission Spectrum Indicates a Hazy, Low-methane, and/or Metal-rich Atmosphere

We report our spectroscopic investigation of the transiting ice giant GJ 3470b's atmospheric transmission, and the first results of extrasolar planet observations from the new Keck/MOSFIRE spectrograph. We measure a planet/star radius ratio of Rp/Rs = 0.0789 +/- 0.0020 in a bandpass from 2.09-2.36 micron and in six narrower bands across this wavelength range. When combined with existing broadband photometry, these measurements rule out cloud-free atmospheres in chemical equilibrium assuming either solar abundances (5.4 sigma confidence) or a moderate level of metal enrichment (50x solar abundances, 3.8 sigma), confirming previous results that such models are not representative for cool, low-mass, externally irradiated extrasolar planets. Current measurements are consistent with a flat transmission spectrum, which suggests that the atmosphere is explained by high-altitude clouds and haze, disequilibrium chemistry, unexpected abundance patterns, or the atmosphere is extremely metal-rich (>200x solar). Because GJ 3470b's low bulk density sets an upper limit on the planet's atmospheric enrichment of <300x solar, the atmospheric mean molecular weight must be <9. Thus, if the atmosphere is cloud-free its spectral features should be detectable with future observations. Transit observations at shorter wavelengths will provide the best opportunity to discriminate between plausible scenarios. We obtained optical spectroscopy with the GMOS spectrograph, but these observations exhibit large systematic uncertainties owing to thin, persistent cirrus conditions. Finally, we also provide the first detailed look at the steps necessary for well-calibrated MOSFIRE observations, and provide advice for future observations with this instrument.Comment: Accepted to A&A. Light curves will be available at CDS (or download arXiv tarball

Land‐Use Change in Rural America: Rates, Drivers, and Consequences1

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117239/1/eap20051561849.pd

The determination of organic phosphorus in sea water with perchloric acid oxidation

A method is proposed for the determination of organic phosphorus in sea water; in this procedure the organic material is oxidized with perchloric acid and the organic phosphorus is converted to phosphate. Oxidation in a perchloric acid medium ia superior to sulfuric acid: (a) The perchlorate salts formed upon digestion of sea water are readily water-soluble in contrast to certain sulfates; (b) A small blank correction for impurities must be applied...

Factors Influencing the Distribution of Riparian Breeding Birds along the Yellowstone River

Riparian zones provide some of the most diverse and productive habitats for native birds in the western U.S. However, most riparian zones have been significantly modified by human activities. It is important to identify relationships between riparian birds and characteristics of the environment to understand the potential influences of floodplain management on birds. We examined the factors affecting riparian bird species distribution within cottonwood forests along the middle and lower sections of the Yellowstone River in Montana. We investigated the influences of local habitat, forest cover, and land use on the occurrence or abundance of 14 bird species. Furthermore, we considered whether geographical location along the river affected bird species distribution. There was strong evidence that these factors were important to birds, and the relative influences of each factor depended upon life history characteristics of each species. The effect of river location on the occurrence or abundance of species suggests that broad-scale influences may be important predictors of bird distribution along rivers. The Yellowstone River is one of the few remaining free-flowing rivers in the lower 48 states, and may serve as a reference for understanding the factors influencing the distribution of birds along a river, and provide valuable information for the management of riparian species

How Well Can We Predict Wildlife Corridors? Tests of Alternative Modeling Approaches in Migratory Elk and Dispersing Wolverines

Landscape connectivity has become a key focus of conservation biology as natural habitat is increasingly fragmented by human land use. Several landscape modeling approaches are now relied upon to identify likely dispersal and migration corridors and guide conservation planning. However, the predictive accuracy of these methods has seen limited testing against empirical movement data, which limits confidence in their utility and confuses selection of appropriate methods for a given application. To address these issues, we used GPS collar data from migrating elk and dispersing wolverines to evaluate the ability of common modeling approaches (cost-distance/least-cost path models and circuit theory models) to predict observed movement routes. While both methods made generally similar predictions, cost-distance models consistently outperformed circuit theory models, and predictive success was much higher for elk than for wolverine movements. Furthermore, the form and complexity of underlying landscape resistance maps influenced model performance and revealed unforeseen differences between models. These findings illustrate that corridor model performance depends greatly on focal species and landscape characteristics as well as selection of appropriate methods for the application at hand

Two-dimensional colloidal fluids exhibiting pattern formation

Fluids with competing short range attraction and long range repulsive interactions between the particles can exhibit a variety of microphase separated structures. We develop a lattice-gas (generalised Ising) model and analyse the phase diagram using Monte Carlo computer simulations and also with density functional theory (DFT). The DFT predictions for the structures formed are in good agreement with the results from the simulations, which occur in the portion of the phase diagram where the theory predicts the uniform fluid to be linearly unstable. However, the mean-field DFT does not correctly describe the transitions between the different morphologies, which the simulations show to be analogous to micelle formation. We determine how the heat capacity varies as the model parameters are changed. There are peaks in the heat capacity at state points where the morphology changes occur. We also map the lattice model onto a continuum DFT that facilitates a simplification of the stability analysis of the uniform fluid.Comment: 13 pages, 15 figure