Modelling hourly rates of evaporation from small lakes

The paper presents the results of a field study of open water evaporation carried out on three small lakes in Western and Northern Canada. In this case small lakes are defined as those for which the temperature above the water surface is governed by the upwind land surface conditions; that is, a continuous boundary layer exists over the lake, and large-scale atmospheric effects such as entrainment do not come into play. Lake evaporation was measured directly using eddy covariance equipment; profiles of wind speed, air temperature and humidity were also obtained over the water surfaces. Observations were made as well over the upwind land surface. <br><br> The major factors controlling open water evaporation were examined. The study showed that for time periods shorter than daily, the open water evaporation bears no relationship to the net radiation; the wind speed is the most significant factor governing the evaporation rates, followed by the land-water temperature contrast and the land-water vapour pressure contrast. The effect of the stability on the wind field was demonstrated; relationships were developed relating the land-water wind speed contrast to the land-water temperature contrast. The open water period can be separated into two distinct evaporative regimes: the warming period in the Spring, when the land is warmer than the water, the turbulent fluxes over water are suppressed; and the cooling period, when the water is warmer than the land, the turbulent fluxes over water are enhanced. <br><br> Relationships were developed between the hourly rates of lake evaporation and the following significant variables and parameters (wind speed, land-lake temperature and humidity contrasts, and the downwind distance from shore). The result is a relatively simple versatile model for estimating the hourly lake evaporation rates. The model was tested using two independent data sets. Results show that the modelled evaporation follows the observed values very well; the model follows the diurnal trends and responds to changes in environmental conditions

Quantitative Evaluation of Spinodal Decomposition in Fe-Cr by Atom Probe Tomography and Radial Distribution Function Analysis

Nanostructure evolution during low temperature aging of three binary Fe-Cr alloys has been investigated by atom probe tomography. A new method based on radial distribution function (RDF) analysis to quantify the composition wavelength and amplitude of spinodal decomposition is proposed. Wavelengths estimated from RDF have a power-law type evolution and are in reasonable agreement with wavelengths estimated using other more conventional methods. The main advantages of the proposed method are the following: (1) Selecting a box size to generate the frequency diagram, which is known to generate bias in the evaluation of amplitude, is avoided. (2) The determination of amplitude is systematic and utilizes the wavelength evaluated first to subsequently evaluate the amplitude. (3) The RDF is capable of representing very subtle decomposition, which is not possible using frequency diagrams, and thus a proposed theoretical treatment of the experimental RDF creates the possibility to determine amplitude at very early stages of spinodal decomposition

TB98: Oxygen Diffusion Rate Relationships under Three Soil Conditions

The objective of this study was to determine the oxygen diffusion rate (ODR)—soil moisture relationship for three sieved, root-free soils to determine if there are basic ODR-soil characteristic differences that might influence data at different soil water contents in the presence of plant roots. Advanced knowledge of ODR-soil moisture relationships would also help scientists to evaluate the effect of variation in the water table on plant growth.https://digitalcommons.library.umaine.edu/aes_techbulletin/1105/thumbnail.jp

Primary and secondary electrical space power based on advanced PEM systems

For new space ventures, power continues to be a pacing function for mission planning and experiment endurance. Although electrochemical power is a well demonstrated space power technology, current hardware limitations impact future mission viability. In order to document and augment electrochemical technology, a series of experiments for the National Aeronautics and Space Administration Lewis Research Center (NASA LeRC) are underway at the Los Alamos National Laboratory that define operational parameters on contemporary proton exchange membrane (PEM) hardware operating with hydrogen and oxygen reactants. Because of the high efficiency possible for water electrolysis, this hardware is also thought part of a secondary battery design built around stored reactants - the so-called regenerative fuel cell. An overview of stack testing at Los Alamos and of analyses related to regenerative fuel cell systems are provided in this paper. Finally, this paper describes work looking at innovative concepts that remove complexity from stack hardware with the specific intent of higher system reliability. This new concept offers the potential for unprecedented electrochemical power system energy densities

Estimates in Beurling--Helson type theorems. Multidimensional case

We consider the spaces $A_p(\mathbb T^m)$ of functions $f$ on the $m$ -dimensional torus $\mathbb T^m$ such that the sequence of the Fourier coefficients $\hat{f}=\{\hat{f}(k), ~k \in \mathbb Z^m\}$ belongs to $l^p(\mathbb Z^m), ~1\leq p<2$. The norm on $A_p(\mathbb T^m)$ is defined by $\|f\|_{A_p(\mathbb T^m)}=\|\hat{f}\|_{l^p(\mathbb Z^m)}$. We study the rate of growth of the norms $\|e^{i\lambda\varphi}\|_{A_p(\mathbb T^m)}$ as $|\lambda|\rightarrow \infty, ~\lambda\in\mathbb R,$ for $C^1$ -smooth real functions $\varphi$ on $\mathbb T^m$ (the one-dimensional case was investigated by the author earlier). The lower estimates that we obtain have direct analogues for the spaces $A_p(\mathbb R^m)$

Coupled wind-forced controls of the Bering–Chukchi shelf circulation and the Bering Strait throughflow: Ekman transport, continental shelf waves, and variations of the Pacific–Arctic sea surface height gradient

AbstractWe develop a conceptual model of the closely co-dependent Bering shelf, Bering Strait, and Chukchi shelf circulation fields by evaluating the effects of wind stress over the North Pacific and western Arctic using atmospheric reanalyses, current meter observations, satellite-based sea surface height (SSH) measurements, hydrographic profiles, and numerical model integrations. This conceptual model suggests Bering Strait transport anomalies are primarily set by the longitudinal location of the Aleutian Low, which drives oppositely signed anomalies at synoptic and annual time scales. Synoptic time scale variations in shelf currents result from local wind forcing and remotely generated continental shelf waves, whereas annual variations are driven by basin scale adjustments to wind stress that alter the magnitude of the along-strait (meridional) pressure gradient. In particular, we show that storms centered over the Bering Sea excite continental shelf waves on the eastern Bering shelf that carry northward velocity anomalies northward through Bering Strait and along the Chukchi coast. The integrated effect of these storms tends to decrease the northward Bering Strait transport at annual to decadal time scales by imposing cyclonic wind stress curl over the Aleutian Basin and the Western Subarctic Gyre. Ekman suction then increases the water column density through isopycnal uplift, thereby decreasing the dynamic height, sea surface height, and along-strait pressure gradient. Storms displaced eastward over the Gulf of Alaska generate an opposite set of Bering shelf and Aleutian Basin responses. While Ekman pumping controls Canada Basin dynamic heights (Proshutinsky et al., 2002), we do not find evidence for a strong relation between Beaufort Gyre sea surface height variations and the annually averaged Bering Strait throughflow. Over the western Chukchi and East Siberian seas easterly winds promote coastal divergence, which also increases the along-strait pressure head, as well as generates shelf waves that impinge upon Bering Strait from the northwest

Atmospheric conditions and their effect on ball-milled magnesium diboride

Magnesium diboride bulk pellets were fabricated from pre-reacted MgB2 powder ball milled with different amounts of exposure to air. Evidence of increased electron scattering including increased resistivity, depressed Tc, and enhanced Hc2 of the milled and heat treated samples were observed as a result of increased contact with air. These and other data were consistent with alloying with carbon as a result of exposure to air. A less clear trend of decreased connectivity associated with air exposure was also observed. In making the case that exposure to air should be considered a doping process, these results may explain the wide varibability of "undoped" MgB2 properties extant in the literature.Comment: Work presented at ASC 2006 in Seattl

Serum amyloid protein is associated with outcome following acute ischaemic stroke: data from the REmote ischaemic Conditioning After Stroke Trial (RECAST)

Background: Remote ischaemic per-conditioning (RIC) in experimental ischaemic stroke is neuroprotective. Several neurohumoral, vascular and inflammatory mediators are implicated. Methods: The REmote ischaemic Conditioning After Stroke Trial (RECAST) was a pilot blinded sham-controlled trial in patients with ischaemic stroke, randomised to receive four 5-minute cycles of RIC within 24 hours of ictus. Plasma taken pre-intervention, immediately post-intervention and on day 4 was analysed for nitric oxide (nitrate/nitrite) levels using chemiluminescence and other biomarkers were analysed by enzyme-linked immunosorbent assay (ELISA): alpha-2-macroglobulin (A2M), serum amyloid protein (SAP), e-selectin, vascular endothelial growth factor (VEGF). Biomarkers were correlated with outcome (Day 90 National Institutes of Health Stroke Scale [NIHSS], modified Rankin scale [mRS], Barthel index [BI]) using Pearson’s correlation coefficient. Results: In all 26 patients, an increase in SAP (pre- to post-intervention) positively correlated with worse day 90 mRS (r=0.429, p=0.029) and negatively with worse BI (r=-0.392, p=0.048), whilst an increase in SAP from day 0 to 4 positively correlated with worse day 90 NIHSS (r=0.400, p=0.043), mRS (r=0.505, p=0.008) and negatively with worse BI (r=-0.439, p=0.025). RIC reduced SAP levels from pre- to post-intervention (n=13, 2-way ANOVA, p<0.05), whilst sham did not. No significant changes over time or by treatment, or correlations with outcome were seen for A2M, e-selectin, nitric oxide or VEGF. Conclusion: Increased plasma levels of SAP are associated with worse clinical outcomes after ischaemic stroke. RIC reduced SAP levels from pre- to post-intervention. Larger studies assessing biomarkers and efficacy of RIC in acute ischaemic stroke are warranted

Azole Drugs Are Imported By Facilitated Diffusion in Candida albicans and Other Pathogenic Fungi

Despite the wealth of knowledge regarding the mechanisms of action and the mechanisms of resistance to azole antifungals, very little is known about how the azoles are imported into pathogenic fungal cells. Here the in-vitro accumulation and import of Fluconazole (FLC) was examined in the pathogenic fungus, Candida albicans. In energized cells, FLC accumulation correlates inversely with expression of ATP-dependent efflux pumps. In de-energized cells, all strains accumulate FLC, suggesting that FLC import is not ATP-dependent. The kinetics of import in de-energized cells displays saturation kinetics with a Km of 0.64 uM and Vmax of 0.0056 pmol/min/108 cells, demonstrating that FLC import proceeds via facilitated diffusion through a transporter rather than passive diffusion. Other azoles inhibit FLC import on a mole/mole basis, suggesting that all azoles utilize the same facilitated diffusion mechanism. An analysis of related compounds indicates that competition for azole import depends on an aromatic ring and an imidazole or triazole ring together in one molecule. Import of FLC by facilitated diffusion is observed in other fungi, including Cryptococcus neoformans, Saccharomyces cerevisiae, and Candida krusei, indicating that the mechanism of transport is conserved among fungal species. FLC import was shown to vary among Candida albicans resistant clinical isolates, suggesting that altered facilitated diffusion may be a previously uncharacterized mechanism of resistance to azole drugs

A note on a model for the quasilinear wave equation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46188/1/205_2004_Article_BF00281480.pd