The fate of NOx emissions due to nocturnal oxidation at high latitudes: 1-D simulations and sensitivity experiments

The fate of nitrogen oxide pollution during high-latitude winter is controlled by reactions of dinitrogen pentoxide (N2O5) and is highly affected by the competition between heterogeneous atmospheric reactions and deposition to the snowpack. MISTRA (MIcrophysical STRAtus), a 1-D photochemical model, simulated an urban pollution plume from Fairbanks, Alaska to investigate this competition of N2O5 reactions and explore sensitivity to model parameters. It was found that dry deposition of N2O5 made up a significant fraction of N2O5 loss near the snowpack, but reactions on aerosol particles dominated loss of N2O5 over the integrated atmospheric column. Sensitivity experiments found the fate of NOx emissions were most sensitive to NO emission flux, photolysis rates, and ambient temperature. The results indicate a strong sensitivity to urban area density, season and clouds, and temperature, implying a strong sensitivity of the results to urban planning and climate change. Results suggest that secondary formation of particulate (PM2.5) nitrate in the Fairbanks downtown area does not contribute significant mass to the total PM2.5 concentration, but appreciable amounts are formed downwind of downtown due to nocturnal NOx oxidation and subsequent reaction with ammonia on aerosol particles

Description and evaluation of the Acoustic Profiling of Ocean Currents (APOC) system used on R. V. Oceanus cruise 96 on 11-22 May 1981

The underway current profiling system which consists of a microprocessor controlled data logger that collects and formats data from a four beam Ametek-Straza 300 kHz acoustic Doppler current profiler, heading from the ship's gyrocompass, and navigation information from a Loran-C receiver and a satellite navigation unit is discussed. Data are recorded on magnetic tape and real time is calculated. Time averaging is required to remove effects of ship motion. An intercomparison is made with a moored vector measuring current meter (VMCM). The mean difference in hourly averaged APOC and VMCM currents over the four hour intercomparison is a few mm s minus including: two Gulf Stream crossings, a warm core ring survey, and shallow water in a frontal zone to the east of Nantucket Shoals

The effectiveness of low power co-channel lamppost mounted 3G/WCDMA microcells

This paper considers the effectiveness of low power lamppost mounted 3G/WCDMA microcells to capture traffic when deployed on a common carrier frequency with an overlaying 3G/WCDMA macrocell layer. The paper assesses the potential offload achieved through the deployment of thirteen low power (+24dBm maximum output power) lamppost mounted 3G/WCDMA microcells along a busy street in central London through both simulation and field trials. The paper concludes that low power +24dBm 3G/WCDMA microcells have the potential to significantly offload a co-channel macrocell layer, provided that the microcells are placed in areas of high traffic and are spaced close enough together (<100m) to provide contiguous microcell dominance

Hydrographic data from R/V endeavor cruise #90

The final cruise of the NSF sponsored Warm Core Rings Program studied a Warm Core Ring (WCR) in the Fall of 1982 as it formed from a large northward meander of the Gulf Stream. This ring, known as 82-H or the eighth ring identified in 1982, formed over the New England Seamounts near 39.5 deg N, 65 deg W. Surveys using Expendable Bathythermographs, Conductivity-Temperature-Depth-Oxygen stations and Doppler Current Profiling provide a look at the genesis of a WCR. These measurements reveal that WCR 82-H separated from the Gulf Stream sometime between October 2-5. This ring was a typical WCR with a diameter of about 200 km and speeds in the high velocity core of the 175 cm/sec. Satellite imagery of 82-H following the cruise showed that it drifted WSW in the Slope Water region at almost 9 km/day, had at least one interaction with the Gulf Stream and was last observed on February 8, 1983 at 39 deg N, 72 deg W

Does the galaxy correlation length increase with the sample depth?

We have analyzed the behavior of the correlation length, $r_0$, as a function of the sample depth by extracting from the CfA2 redshift survey volume--limited samples out to increasing distances. For a fractal distribution, the value of $r_0$ would increase with the volume occupied by the sample. We find no linear increase for the CfA2 samples of the sort that would be expected if the Universe preserved its small scale fractal character out to the distances considered (60--100\hmpc). The results instead show a roughly constant value for $r_0$ as a function of the size of the sample, with small fluctuations due to local inhomogeneities and luminosity segregation. Thus the fractal picture can safely be discarded.Comment: Accepted for publication in ApJ

Local amplification of glucocorticoids in the aging brain and impaired spatial memory

The hippocampus is a prime target for glucocorticoids (GCs) and a brain structure particularly vulnerable to ageing. Prolonged exposure to excess GCs compromises hippocampal electrophysiology, structure and function. Blood GC levels tend to increase with ageing and correlate with impaired spatial memory in ageing rodents and humans. The magnitude of GC action within tissues depends not only on levels of steroid hormone that enter the cells from the periphery and the density of intracellular receptors but also on the local metabolism of GCs by 11&#223;-hydroxysteroid dehydrogenases (11&#223;-HSD). The predominant isozyme in the adult brain, 11&#223;-HSD1, locally regenerates active GCs from inert 11-keto forms thus amplifying GC levels within specific target cells including in the hippocampus and cortex. Ageing associates with elevated hippocampal and neocortical 11&#223;-HSD1 and impaired spatial learning while deficiency of 11&#223;-HSD1 in knockout mice prevents the emergence of cognitive decline with age. Furthermore, short-term pharmacological inhibition of 11&#223;-HSD1 in already aged mice reverses spatial memory impairments. Here, we review research findings that support a key role for GCs with special emphasis on their intracellular regulation by 11&#223;-HSD1 in the emergence of spatial memory deficits with ageing, and discuss the use of 11&#223;-HSD1 inhibitors as a promising novel treatment in ameliorating/improving age-related memory impairments

Calibrated Sub-Bundles in Non-Compact Manifolds of Special Holonomy

This paper is a continuation of math.DG/0408005. We first construct special Lagrangian submanifolds of the Ricci-flat Stenzel metric (of holonomy SU(n)) on the cotangent bundle of S^n by looking at the conormal bundle of appropriate submanifolds of S^n. We find that the condition for the conormal bundle to be special Lagrangian is the same as that discovered by Harvey-Lawson for submanifolds in R^n in their pioneering paper. We also construct calibrated submanifolds in complete metrics with special holonomy G_2 and Spin(7) discovered by Bryant and Salamon on the total spaces of appropriate bundles over self-dual Einstein four manifolds. The submanifolds are constructed as certain subbundles over immersed surfaces. We show that this construction requires the surface to be minimal in the associative and Cayley cases, and to be (properly oriented) real isotropic in the coassociative case. We also make some remarks about using these constructions as a possible local model for the intersection of compact calibrated submanifolds in a compact manifold with special holonomy.Comment: 20 pages; for Revised Version: Minor cosmetic changes, some paragraphs rewritten for improved clarit

Executive function in first-episode schizophrenia

BACKGROUND: We tested the hypothesis that schizophrenia is primarily a frontostriatal disorder by examining executive function in first-episode patients. Previous studies have shown either equal decrements in many cognitive domains or specific deficits in memory. Such studies have grouped test results or have used few executive measures, thus, possibly losing information. We, therefore, measured a range of executive ability with tests known to be sensitive to frontal lobe function. METHODS: Thirty first-episode schizophrenic patients and 30 normal volunteers, matched for age and NART IQ, were tested on computerized test of planning, spatial working memory and attentional set shifting from the Cambridge Automated Neuropsychological Test Battery. Computerized and traditional tests of memory were also administered for comparison. RESULTS: Patients were worse on all tests but the profile was non-uniform. A componential analysis indicated that the patients were characterized by a poor ability to think ahead and organize responses but an intact ability to switch attention and inhibit prepotent responses. Patients also demonstrated poor memory, especially for free recall of a story and associate learning of unrelated word pairs. CONCLUSIONS: In contradistinction to previous studies, schizophrenic patients do have profound executive impairments at the beginning of the illness. However, these concern planning and strategy use rather than attentional set shifting, which is generally unimpaired. Previous findings in more chronic patients, of severe attentional set shifting impairment, suggest that executive cognitive deficits are progressive during the course of schizophrenia. The finding of severe mnemonic impairment at first episode suggests that cognitive deficits are not restricted to one cognitive domain

Similar but different: Revealing the relative roles of species‐traits versus biome properties structuring genetic variation in South American marsh rats

AimWetland habitats, and the ecological restrictions imposed by them, structure patterns of genetic variation in constituent taxa. As such, genetic variation may reflect properties of the specific biomes species inhabit, or shared life history traits among species may result in similar genetic structure. We evaluated these hypotheses jointly by quantifying the similarity of genetic structure in three South American marsh rat species (Holochilus), and test how genetic variation in each species relates to biome‐specific environmental space and historical stability.LocationSouth America.TaxonRodentia.MethodsUsing complementary analyses (Mantel tests, dbRDA, Procrustes, covariance structure of allele frequencies and environmental niche models [ENMs]) with 8,000–32,000 SNPs per species, we quantified the association between genomic variation and geographic and/or environmental differences.ResultsSignificant association between genetic variation and geography was identified for all species. Similarity in the strength of the association suggests connectivity patterns dictated by shared species‐traits predominate at the biome scale. However, substantial amounts of genetic variation are not explained by geography. Focusing on this portion of the variance, we demonstrate a significant quantitative association between genetic variation and the environmental space of a biome, and a qualitative association with varying regional stability. Specifically, historically stable areas estimated from ecological niche models are correlated with local levels of geographic structuring, suggesting that local biome‐specific histories affect population isolation/connectivity.Main conclusionsThese tests show that although species exhibit similar patterns of genetic variation that are consistent with shared natural histories, irrespective of inhabiting different wetland biomes, local biome‐specific properties (i.e. varying environmental conditions and historical stability) contribute to departures from equilibrium patterns of genetic variation expected by isolation by geographic distance. The reflection of these biome‐specific properties in the genetic structure of the marsh rats provides a window into the differences among South American wetlands with evolutionary consequences for their respective constituent assemblages.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149336/1/jbi13529.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149336/2/jbi13529_am.pd

Spanning tree generating functions and Mahler measures

We define the notion of a spanning tree generating function (STGF) $\sum a_n z^n$, which gives the spanning tree constant when evaluated at $z=1,$ and gives the lattice Green function (LGF) when differentiated. By making use of known results for logarithmic Mahler measures of certain Laurent polynomials, and proving new results, we express the STGFs as hypergeometric functions for all regular two and three dimensional lattices (and one higher-dimensional lattice). This gives closed form expressions for the spanning tree constants for all such lattices, which were previously largely unknown in all but one three-dimensional case. We show for all lattices that these can also be represented as Dirichlet $L$-series. Making the connection between spanning tree generating functions and lattice Green functions produces integral identities and hypergeometric connections, some of which appear to be new.Comment: 26 pages. Dedicated to F Y Wu on the occasion of his 80th birthday. This version has additional references, additional calculations, and minor correction