Changes in Imja Tsho in the Mount Everest Region of Nepal

Imja Tsho, located in the Sagarmatha ( Everest) National Park of Nepal, is one of the most studied and rapidly growing lakes in the Himalayan range. Compared with previous studies, the results of our sonar bathymetric survey conducted in September of 2012 suggest that its maximum depth has increased from 90.5 to 116.3 +/- 5.2 m since 2002, and that its estimated volume has grown from 35.8 +/- 0.7 to 61.7 +/- 3.7 million m(3). Most of the expansion of the lake in recent years has taken place in the glacier terminus-lake interface on the eastern end of the lake, with the glacier receding at about 52 m yr(-1) and the lake expanding in area by 0.04 km(2) yr(-1). A ground penetrating radar survey of the Imja-Lhotse Shar glacier just behind the glacier terminus shows that the ice is over 200 m thick in the center of the glacier. The volume of water that could be released from the lake in the event of a breach in the damming moraine on the western end of the lake has increased to 34.1 +/- 1.08 million m(3) from the 21 million m(3) estimated in 2002.USAID Climate Change Resilient Development (CCRD) projectFulbright FoundationNational Geographic SocietyCenter for Research in Water Resource

Stem cells and fluid flow drive cyst formation in an invertebrate excretory organ.

Cystic kidney diseases (CKDs) affect millions of people worldwide. The defining pathological features are fluid-filled cysts developing from nephric tubules due to defective flow sensing, cell proliferation and differentiation. The underlying molecular mechanisms, however, remain poorly understood, and the derived excretory systems of established invertebrate models (Caenorhabditis elegans and Drosophila melanogaster) are unsuitable to model CKDs. Systematic structure/function comparisons revealed that the combination of ultrafiltration and flow-associated filtrate modification that is central to CKD etiology is remarkably conserved between the planarian excretory system and the vertebrate nephron. Consistently, both RNA-mediated genetic interference (RNAi) of planarian orthologues of human CKD genes and inhibition of tubule flow led to tubular cystogenesis that share many features with vertebrate CKDs, suggesting deep mechanistic conservation. Our results demonstrate a common evolutionary origin of animal excretory systems and establish planarians as a novel and experimentally accessible invertebrate model for the study of human kidney pathologies

Six Degrees of Epistasis: Statistical Network Models for GWAS

There is growing evidence that much more of the genome than previously thought is required to explain the heritability of complex phenotypes. Recent studies have demonstrated that numerous common variants from across the genome explain portions of genetic variability, spawning various avenues of research directed at explaining the remaining heritability. This polygenic structure is also the motivation for the growing application of pathway and gene set enrichment techniques, which have yielded promising results. These findings suggest that the coordination of genes in pathways that are known to occur at the gene regulatory level also can be detected at the population level. Although genes in these networks interact in complex ways, most population studies have focused on the additive contribution of common variants and the potential of rare variants to explain additional variation. In this brief review, we discuss the potential to explain additional genetic variation through the agglomeration of multiple gene–gene interactions as well as main effects of common variants in terms of a network paradigm. Just as is the case for single-locus contributions, we expect each gene–gene interaction edge in the network to have a small effect, but these effects may be reinforced through hubs and other connectivity structures in the network. We discuss some of the opportunities and challenges of network methods for analyzing genome-wide association studies (GWAS) such as the study of hubs and motifs, and integrating other types of variation and environmental interactions. Such network approaches may unveil hidden variation in GWAS, improve understanding of mechanisms of disease, and possibly fit into a network paradigm of evolutionary genetics

Modeling water resources management at the basin level: review and future directions

Water quality / Water resources development / Agricultural production / River basin development / Mathematical models / Simulation models / Water allocation / Policy / Economic aspects / Hydrology / Reservoir operation / Groundwater management / Drainage / Conjunctive use / Surface water / GIS / Decision support systems / Optimization methods / Water supply

Study of cold-formed steel structural members made of thick sheets and plates

INTRODUCTION In steel design, the Specification for the Design of Cold-Formed Steel Structural Members l issued by the American Iron and Steel Institute has long been used for structural members cold-formed to shape from steel sheet or strip used for load-carrying purposes in buildings and other thin walled steel structures. Even though no thickness limitation was included in previous editions of the Specification, 2,3, the thickness of material used in the cold-formed steel construction was often limited to about 1/4 inch because the maximum thickness of steels used under all ASTM Specifications listed in Section 1.2 of the AISI Specification 2,3 is 0.2449 inch. During recent years, carbon steel sheets and plates in coils up to 1/2 inch thick have been successfully used for cold-formed steel structural members in building construction (schools, shopping centers, and apartments), industrial plants, farm equipment, railway cars, ship and barge construction, truck trailers, earthmoving equipment, highway median barriers, bridge construc-tion, conveyors, machinery frames, and others. 4,5 Cold-formed steel plate sections up to about 3/4 inch in thickness have been used for steel plate structures and transmission poles. Consequently, the scope of the AISI Specification was extended in 1968 to include the use of steel sheets, strip, and plates up to 1/2 inch in thickness provided that such steel conforms to the chemical and mechanical requirements of one of the listed material specifications. 1 In view of the fact that the AISI design provisions have been mainly based upon the research work conducted on specimens made from relatively thin steel sheets and strip in the thicknesses ranging from 0.03 to 0.19 inch,6 some building code organizations have limited the application of the AISI Specification only to steels under 1/4 inch thick, due to the fact that the validity of some design provisions presently included in the AISI Specification has not been demonstrated fully for cold-formed steel sections thicker than 1/4 inch in thickness. In order to study the structural behavior of steel members cold-formed from thick steel plates (up to about 1 inch in thickness) for the purpose of verification of some AISI design provisions, a research project entitled Study of Cold-Formed Steel Structural Members Made of Thick Sheets and Plates was initiated in September, 1971, at the University of Missouri-Rolla (UMR) under the sponsorship of the American Iron and Steel Institute. The research work reported herein was directed by Dr. Wei-Wen Yu, Professor of Civil Engineering, under the supervision of Dr. J. H. Senne, Chairman and Professor of the University of Missouri-Rolla Department of Civil Engineering. Research Assistants for the project were Victor A. S. Liu and William M. McKinney, graduate students of the Department of Civil Engineering. This report summarizes the research work on the study of thick, coldformed, steel sections conducted at the University of Missouri-Rolla during the academic year 1971-72 (September 1971 to December 1972). The objectives of the project and the planned program are described in Section 2. The findings obtained from a preliminary investigation are discussed in Section 3. Section 4 contains a discussion of the buckling strength and the effective design width of stiffened compression elements; emphasis is placed on the use of thick sheets and plates. The buckling strength of an initially curved unstiffened plate is discussed in Section S. Section 6 describes the effect of cold-work on mechanical properties of thick sheets and plates. Finally, a summary is presented in Section 7. Future work on the project for the academic year 1972-73 is outlined in Section 8. It should be noted that some of the findings reported herein have been discussed in the First and Second Progress Reports 7,8 and in a paper orally presented at the Research Session of the 1972 ASCE National Structural Engineering Meeting held in Cleveland, Ohio.9 This investigation was sponsored by American Iron and Steel Institute. The financial assistance given by the Institute and the technical guidance provided by the AISI Staff and the Institute\u27s Task Group on Thicker Sheets and Plates are gratefully acknowledged. The AISI Staff responsible for this project included Dr. A.L. Johnson and Mr. D.J. Clark. The Task Group was constituted as follows: Mr. A.J. Oudheusden, Chairman, Messrs. H.R. Fink, T.J. Jones, R.W. Haussler, and D.S. Wolford, members

Using Mussel Isotope Ratios to Assess Anthropogenic Nitrogen Inputs to Freshwater Ecosystems

Stable nitrogen isotope ratios (δ15N) of freshwater mussels from a series of lakes and ponds were related to watershed land use characteristics to assess their utility in determining the source of nitrogen inputs to inland water bodies. Nitrogen isotope ratios measured in freshwater mussels from 19 lakes and ponds in Rhode Island, U.S.A., ranged from 4.9–12.6% and were found to significantly correlate with the fraction of residential development in 100 and 200 m buffer zones around the ponds. Mussel δ15N values in 12 of the 19 ponds also showed significant correlation with average dissolved nitrate concentrations, which ranged from 23–327 μg L-1. These observations, in light of previous studies which link elevated δ15N values of nitrogen derived from septic wastewater with those seen in biota, suggest that mussel isotope ratios may reflect nitrogen source in freshwater ecosystems. We followed an iterative approach using multiple regression analysis to assess the relationship between mussel δ15N and the land use categories fraction residential development, fraction feedlot agriculture, fraction row-crop agriculture, and fraction natural vegetation in 100 and 200 m buffer zones and pond watersheds. From this we developed a simple regression model to predict mussel δ15N from the fraction of residential development in the 200 m buffer zone around the pond. Subsequent testing with data from 16 additional sites in the same ecoregion led us to refine the model by incorporating the fraction of natural vegetation. The overall average absolute difference between measured and predicted δ15N values using the two-parameter model was 1.6%. Potential sources of error in the model include differences in the scale and categorization of land-use data used to generate and test the model, differences in physical characteristics, such as retention time and range of residential development, and exclusion of sources of enriched nitrogen such as runoff from feedlot operations or increased nitrogen loading from inefficient or failed septic systems

Accretion of low angular momentum material onto black holes: 2D magnetohydrodynamical case

We report on the second phase of our study of slightly rotating accretion flows onto black holes. We consider magnetohydrodynamical (MHD) accretion flows with a spherically symmetric density distribution at the outer boundary, but with spherical symmetry broken by the introduction of a small, latitude-dependent angular momentum and a weak radial magnetic field. We study accretion flows by means of numerical 2D, axisymmetric, MHD simulations with and without resistive heating. Our main result is that the properties of the accretion flow depend mostly on an equatorial accretion torus which is made of the material that has too much angular momentum to be accreted directly. The torus accretes, however, because of the transport of angular momentum due to the magnetorotational instability (MRI). Initially, accretion is dominated by the polar funnel, as in the hydrodynamic inviscid case, where material has zero or very low angular momentum. At the later phase of the evolution, the torus thickens towards the poles and develops a corona or an outflow or both. Consequently, the mass accretion through the funnel is stopped. The accretion of rotating gas through the torus is significantly reduced compared to the accretion of non-rotating gas (i.e., the Bondi rate). It is also much smaller than the accretion rate in the inviscid, weakly rotating case.Our results do not change if we switch on or off resistive heating. Overall our simulations are very similar to those presented by Stone, Pringle, Hawley and Balbus despite different initial and outer boundary conditions. Thus, we confirm that MRI is very robust and controls the nature of radiatively inefficient accretion flows.Comment: submitted in Ap

Allometric length-weight relationships for benthic prey of aquatic wildlife in coastal marine habitats

We developed models to estimate the soft tissue content of benthic marine invertebrates that are prey for aquatic wildlife. Allometric regression models of tissue wet weight with shell length for 10 species of benthic invertebrates had r2 values ranging from 0.29 for hermit crabs Pagurus longicarpus to 0.98 for green crabs Carcinus maenas. As a class, bivalves had the highest r2 values (0.84) and crustaceans the lowest (0.48). Energy and nutrient content of soft tissue is also presented for the 10 benthic species. The energy content was lowest in crabs, and ranged within 2.20–4.71 kcal g-1 dry weight. Fat content was highly variable (range: 3.5–16.0%), and protein content ranged within 43.1–68.1% and was highest for shrimp Palaemonetes pugio. Comparison between classes of organisms of the amount of soft tissue per unit shell length showed that crustaceans yield five times more soft tissue per unit shell length than bivalves, and four times more than gastropods. The models we present use simple measures, such as the length of shell or wet weight of the entire animal, to quantitatively estimate the amount of available soft tissue in benthic prey that are usually consumed in total (with shell and soft tissue intact) but for which only the soft tissue is used for nutritional gain. This information can be combined with energy and nutrient content data to calculate energy or nutrient based carrying capacities that can help assess available resources for shorebirds, waterfowl and marine mammals