Experimental and model based investigation of the links between snow bidirectional reflectance and snow microstructure

Science.gov (United States)

Dumont, M.; Flin, F.; Malinka, A.; Brissaud, O.; Hagenmuller, P.; Dufour, A.; Lapalus, P.; Lesaffre, B.; Calonne, N.; Rolland du Roscoat, S.; Ando, E.

2017-12-01

Snow optical properties are unique among Earth surface and crucial for a wide range of applications. The bi-directional reflectance, hereafter BRDF, of snow is sensible to snow microstructure. However the complex interplays between different parameters of snow microstructure namely size parameters and shape parameters on reflectance are challenging to disentangle both theoretically and experimentally. An accurate understanding and modelling of snow BRDF is required to correctly process satellite data. BRDF measurements might also provide means of characterizing snow morphology. This study presents one of the very few dataset that combined bi-directional reflectance measurements over 500-2500 nm and X-ray tomography of the snow microstructure for three different snow samples and two snow types. The dataset is used to evaluate the approach from Malinka, 2014 that relates snow optical properties to the chord length distribution in the snow microstructure. For low and medium absorption, the model accurately reproduces the measurements but tends to slightly overestimate the anisotropy of the reflectance. The model indicates that the deviation of the ice chord length distribution from an exponential distribution, that can be understood as a characterization of snow types, does not impact the reflectance for such absorptions. The simulations are also impacted by the uncertainties in the ice refractive index values. At high absorption and high viewing/incident zenith angle, the simulations and the measurements disagree indicating that some of the assumptions made in the model are not met anymore. The study also indicates that crystal habits might play a significant role for the reflectance under such geometries and wavelengths. However quantitative relationship between crystal habits and reflectance alongside with potential optical methodologies to classify snow morphology would require an extended dataset over more snow types. This extended dataset can likely be obtained

A Distributed Snow Evolution Modeling System (SnowModel)

Science.gov (United States)

Liston, G. E.; Elder, K.

2004-12-01

A spatially distributed snow-evolution modeling system (SnowModel) has been specifically designed to be applicable over a wide range of snow landscapes, climates, and conditions. To reach this goal, SnowModel is composed of four sub-models: MicroMet defines the meteorological forcing conditions, EnBal calculates surface energy exchanges, SnowMass simulates snow depth and water-equivalent evolution, and SnowTran-3D accounts for snow redistribution by wind. While other distributed snow models exist, SnowModel is unique in that it includes a well-tested blowing-snow sub-model (SnowTran-3D) for application in windy arctic, alpine, and prairie environments where snowdrifts are common. These environments comprise 68% of the seasonally snow-covered Northern Hemisphere land surface. SnowModel also accounts for snow processes occurring in forested environments (e.g., canopy interception related processes). SnowModel is designed to simulate snow-related physical processes occurring at spatial scales of 5-m and greater, and temporal scales of 1-hour and greater. These include: accumulation from precipitation; wind redistribution and sublimation; loading, unloading, and sublimation within forest canopies; snow-density evolution; and snowpack ripening and melt. To enhance its wide applicability, SnowModel includes the physical calculations required to simulate snow evolution within each of the global snow classes defined by Sturm et al. (1995), e.g., tundra, taiga, alpine, prairie, maritime, and ephemeral snow covers. The three, 25-km by 25-km, Cold Land Processes Experiment (CLPX) mesoscale study areas (MSAs: Fraser, North Park, and Rabbit Ears) are used as SnowModel simulation examples to highlight model strengths, weaknesses, and features in forested, semi-forested, alpine, and shrubland environments.

Regime shift of snow days in Switzerland

Science.gov (United States)

Marty, Christoph

2008-06-01

The number of days with a snow depth above a certain threshold is the key factor for winter tourism in an Alpine country like Switzerland. An investigation of 34 long-term stations between 200 and 1800 m asl (above sea level) going back for at least the last 60 years (1948-2007) shows an unprecedented series of low snow winters in the last 20 years. The signal is uniform despite high regional differences. A shift detection analysis revealed a significant step-like decrease in snow days at the end of the 1980's with no clear trend since then. This abrupt change resulted in a loss of 20% to 60% of the total snow days. The stepwise increase of the mean winter temperature at the end of the 1980's and its close correlation with the snow day anomalies corroborate the sensitivity of the mid-latitude winter to the climate change induced temperature increase.

Platinum nanoparticles decorated dendrite-like gold nanostructure on glassy carbon electrodes for enhancing electrocatalysis performance to glucose oxidation

Energy Technology Data Exchange (ETDEWEB)

Jia, Hongmei [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, School of Materials Science and Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang, Wuhan 430062 (China); Chang, Gang, E-mail: changgang@hubu.edu.cn [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, School of Materials Science and Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang, Wuhan 430062 (China); Lei, Ming [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China); He, Hanping [College of Chemistry and Chemical Engineer, Hubei University, Youyi Road 368, Wuchang, Wuhan, Hubei 430062 (China); Liu, Xiong; Shu, Honghui; Xia, Tiantian; Su, Jie [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, School of Materials Science and Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang, Wuhan 430062 (China); He, Yunbin, E-mail: ybhe@hubu.edu.cn [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, School of Materials Science and Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang, Wuhan 430062 (China)

2016-10-30

Highlights: • Pt/DGNs/GC composites were obtained via a clean and facile method without any templates, surfactants, or stabilizers. • Controlling chemical reduction deposition time, the amount of platinum nanoparticles on Au surface could be regulated, which further tuned electrocatalytic properties toward glucose oxidation. • The obtained Pt/DGNs/GC composites with high electrochemical active surface area (ECSA) show superior electrocatalytic activity to glucose. • The sensor based on Pt/DGNs/GC exhibited excellent sensitivity, selectivity and stability for nonenzymatic glucose detection. - Abstract: Platinum nanoparticles decorated dendrite-like gold nanostructure, bimetal composite materials on glassy carbon electrode (Pt/DGNs/GC) for enhancing electrocatalysis to glucose oxidation was designed and successfully fabricated by a facile two-step deposition method without any templates, surfactants, or stabilizers. Dendrite-like gold nanostructure was firstly deposited on the GC electrode via the potentiostatic method, and then platinum nanoparticles were decorated on the surface of gold substrate through chemical reduction deposition. X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDS) were applied to characterize the evolution of morphology and structure of the as-prepared Pt/DGNs/GC. Based on electrochemical measurements such as cyclic voltammetry, linear voltammetry and chronoamperometry, Pt/DGNs/GC exhibited significantly enhanced electrocatalytic performance to glucose oxidation compared those of pure dendrite-like Au nanoparticles in our previous report. Controlling chemical reduction deposition time, the amount of platinum nanoparticles on Au surface could be regulated, which further tuned electrocatalytic properties toward glucose oxidation. The dendrite-like gold surface partially covered by platinum nanoparticles dramatically enhanced the electrocatalytic performance for the

Low dose prenatal ethanol exposure induces anxiety-like behaviour and alters dendritic morphology in the basolateral amygdala of rat offspring.

Directory of Open Access Journals (Sweden)

Carlie L Cullen

Full Text Available Prenatal exposure to high levels of alcohol is strongly associated with poor cognitive outcomes particularly in relation to learning and memory. It is also becoming more evident that anxiety disorders and anxiety-like behaviour can be associated with prenatal alcohol exposure. This study used a rat model to determine if prenatal exposure to a relatively small amount of alcohol would result in anxiety-like behaviour and to determine if this was associated with morphological changes in the basolateral amygdala. Pregnant Sprague Dawley rats were fed a liquid diet containing either no alcohol (Control or 6% (vol/vol ethanol (EtOH throughout gestation. Male and Female offspring underwent behavioural testing at 8 months (Adult or 15 months (Aged of age. Rats were perfusion fixed and brains were collected at the end of behavioural testing for morphological analysis of pyramidal neuron number and dendritic morphology within the basolateral amygdala. EtOH exposed offspring displayed anxiety-like behaviour in the elevated plus maze, holeboard and emergence tests. Although sexually dimorphic behaviour was apparent, sex did not impact anxiety-like behaviour induced by prenatal alcohol exposure. This increase in anxiety - like behaviour could not be attributed to a change in pyramidal cell number within the BLA but rather was associated with an increase in dendritic spines along the apical dendrite which is indicative of an increase in synaptic connectivity and activity within these neurons. This study is the first to link increases in anxiety like behaviour to structural changes within the basolateral amygdala in a model of prenatal ethanol exposure. In addition, this study has shown that exposure to even a relatively small amount of alcohol during development leads to long term alterations in anxiety-like behaviour.

ESA GlobSnow Snow Water Equivalent (SWE)

Data.gov (United States)

National Aeronautics and Space Administration — The European Space Agency (ESA) Global Snow Monitoring for Climate Research (GlobSnow) snow water equivalent (SWE) v2.0 data record contains snow information derived...

New nitrogen uptake strategy: specialized snow roots.

Science.gov (United States)

Onipchenko, Vladimir G; Makarov, Mikhail I; van Logtestijn, Richard S P; Ivanov, Viktor B; Akhmetzhanova, Assem A; Tekeev, Dzhamal K; Ermak, Anton A; Salpagarova, Fatima S; Kozhevnikova, Anna D; Cornelissen, Johannes H C

2009-08-01

The evolution of plants has yielded a wealth of adaptations for the acquisition of key mineral nutrients. These include the structure, physiology and positioning of root systems. We report the discovery of specialized snow roots as a plant strategy to cope with the very short season for nutrient uptake and growth in alpine snow-beds, i.e. patches in the landscape that remain snow-covered well into the summer. We provide anatomical, chemical and experimental (15)N isotope tracking evidence that the Caucasian snow-bed plant Corydalis conorhiza forms extensive networks of specialized above-ground roots, which grow against gravity to acquire nitrogen directly from within snow packs. Snow roots capture nitrogen that would otherwise partly run off down-slope over a frozen surface, thereby helping to nourish these alpine ecosystems. Climate warming is changing and will change mountain snow regimes, while large-scale anthropogenic N deposition has increased snow N contents. These global changes are likely to impact on the distribution, abundance and functional significance of snow roots.

A distributed snow-evolution modeling system (SnowModel)

Science.gov (United States)

Glen E. Liston; Kelly. Elder

2006-01-01

SnowModel is a spatially distributed snow-evolution modeling system designed for application in landscapes, climates, and conditions where snow occurs. It is an aggregation of four submodels: MicroMet defines meteorological forcing conditions, EnBal calculates surface energy exchanges, SnowPack simulates snow depth and water-equivalent evolution, and SnowTran-3D...

Synthesis of Plate-Like Nanoalumina and Its Effect on Gas Permeability of Carbon Fiber Epoxy Composite

Directory of Open Access Journals (Sweden)

Ghadamali Karimi Khozani

2017-03-01

Full Text Available In recent years considerable efforts have been made to develop gas impermeable polymer systems. Compared with metal system counterparts they have advantages such as low density and production costs. The most important challenge in development of impermeable polymer systems is to reduce their gas permeability by proper selection of system composition and process conditions. In this work, nanoparticles were initially synthesized using Al (NO33•9H2O and sodium dodecyl sulfate as a structure-directing agent via hydrothermal method and a plate-like structure was characterized by FESEM and EDAX analyses. In the second step, epoxy/plate-like nanoalumina nanocomposites and epoxy-carbon fiber composites containing 1, 2.5, and 5 wt% nanoalumina were prepared. The effect of nanoparticle loading level on permeability of nitrogen, argon, and carbon dioxide in epoxy/plate-like nanoalumina nanocomposites was investigated. It was observed that the permeability of epoxy/plate-like nanoalumina nanocomposites toward nitrogen, argon, and carbon dioxide gases reduced 83%, 74%, and 50%, respectively. It was deduced that the permeability reduction was clearly associated with the diameter of gas molecules. Generally speaking, the results showed that the incorporation of plate-like nanoalumina particles significantly reduced the gas permeability. Also, carbon dioxide gas permeability of carbon fiber epoxy composites containing plate-like nanoalumina was investigated to show the effect of ingredients on the gas permeability of the system. The results indicated that carbon dioxide gas permeability of epoxy carbon fiber composite containing 5 wt% of plate-like nanoalumina was totally reduced 84%.

Snow and ice: Chapter 3

Science.gov (United States)

Littell, Jeremy; McAfee, Stephanie A.; O'Neel, Shad; Sass, Louis; Burgess, Evan; Colt, Steve; Clark, Paul; Hayward, Gregory D.; Colt, Steve; McTeague, Monica L.; Hollingsworth, Teresa N.

2017-01-01

Temperature and precipitation are key determinants of snowpack levels. Therefore, climate change is likely to affect the role of snow and ice in the landscapes and hydrology of the Chugach National Forest region.Downscaled climate projections developed by Scenarios Network for Alaska and Arctic Planning (SNAP) are useful for examining projected changes in snow at relatively fine resolution using a variable called “snowday fraction (SDF),” the percentage of days with precipitation falling as snow.We summarized SNAP monthly SDF from five different global climate models for the Chugach region by 500 m elevation bands, and compared historical (1971–2000) and future (2030–2059) SDF. We found that:Snow-day fraction and snow-water equivalent (SWE) are projected to decline most in late autumn (October to November) and at lower elevations.Snow-day fraction is projected to decrease 23 percent (averaged across five climate models) from October to March, between sea level and 500 m. Between sea level and 1000 m, SDF is projected to decrease by 17 percent between October and March.Snow-water equivalent is projected to decrease most in autumn (October and November) and at lower elevations (below 1500 m), an average of -26 percent for the 2030–2059 period compared to 1971– 2000. Averaged across the cool season and the entire domain, SWE is projected to decrease at elevations below 1000 m because of increased temperature, but increase at higher elevations because of increased precipitation.Compared to 1971–2000, the percentage of the landscape that is snowdominant in 2030–2059 is projected to decrease, and the percentage in which rain and snow are co-dominant (transient hydrology) is projected to increase from 27 to 37 percent. Most of this change is at lower elevations.Glaciers on the Chugach National Forest are currently losing about 6 km3 of ice per year; half of this loss comes from Columbia Glacier (Berthier et al. 2010).Over the past decade, almost all

Peri-Elastodynamic Simulations of Guided Ultrasonic Waves in Plate-Like Structure with Surface Mounted PZT

Directory of Open Access Journals (Sweden)

Subir Patra

2018-01-01

Full Text Available Peridynamic based elastodynamic computation tool named Peri-elastodynamics is proposed herein to simulate the three-dimensional (3D Lamb wave modes in materials for the first time. Peri-elastodynamics is a nonlocal meshless approach which is a scale-independent generalized technique to visualize the acoustic and ultrasonic waves in plate-like structure, micro-electro-mechanical systems (MEMS and nanodevices for their respective characterization. In this article, the characteristics of the fundamental Lamb wave modes are simulated in a sample plate-like structure. Lamb wave modes are generated using a surface mounted piezoelectric (PZT transducer which is actuated from the top surface. The proposed generalized Peri-elastodynamics method is not only capable of simulating two dimensional (2D in plane wave under plane strain condition formulated previously but also capable of accurately simulating the out of plane Symmetric and Antisymmetric Lamb wave modes in plate like structures in 3D. For structural health monitoring (SHM of plate-like structures and nondestructive evaluation (NDE of MEMS devices, it is necessary to simulate the 3D wave-damage interaction scenarios and visualize the different wave features due to damages. Hence, in addition, to simulating the guided ultrasonic wave modes in pristine material, Lamb waves were also simulated in a damaged plate. The accuracy of the proposed technique is verified by comparing the modes generated in the plate and the mode shapes across the thickness of the plate with theoretical wave analysis.

Peri-Elastodynamic Simulations of Guided Ultrasonic Waves in Plate-Like Structure with Surface Mounted PZT.

Science.gov (United States)

Patra, Subir; Ahmed, Hossain; Banerjee, Sourav

2018-01-18

Peridynamic based elastodynamic computation tool named Peri-elastodynamics is proposed herein to simulate the three-dimensional (3D) Lamb wave modes in materials for the first time. Peri-elastodynamics is a nonlocal meshless approach which is a scale-independent generalized technique to visualize the acoustic and ultrasonic waves in plate-like structure, micro-electro-mechanical systems (MEMS) and nanodevices for their respective characterization. In this article, the characteristics of the fundamental Lamb wave modes are simulated in a sample plate-like structure. Lamb wave modes are generated using a surface mounted piezoelectric (PZT) transducer which is actuated from the top surface. The proposed generalized Peri-elastodynamics method is not only capable of simulating two dimensional (2D) in plane wave under plane strain condition formulated previously but also capable of accurately simulating the out of plane Symmetric and Antisymmetric Lamb wave modes in plate like structures in 3D. For structural health monitoring (SHM) of plate-like structures and nondestructive evaluation (NDE) of MEMS devices, it is necessary to simulate the 3D wave-damage interaction scenarios and visualize the different wave features due to damages. Hence, in addition, to simulating the guided ultrasonic wave modes in pristine material, Lamb waves were also simulated in a damaged plate. The accuracy of the proposed technique is verified by comparing the modes generated in the plate and the mode shapes across the thickness of the plate with theoretical wave analysis.

Geophysical investigations of underplating at the Middle American Trench, weathering in the critical zone, and snow water equivalent in seasonal snow

Science.gov (United States)

St. Clair, James

indicate that to a first order, the permeability structure of the CZ can be predicted with knowledge of the regional tectonic stress field and local topography. In landscapes characterized by strongly compressive tectonic stresses or closely space ridges and valleys, deep zones of permeable bedrock are found beneath ridges, while the depth to impermeable bedrock beneath drainages is comparatively shallow. In landscapes characterized by weakly compressive tectonic stresses or widely spaced ridges and valleys, the depth to impermeable bedrock is approximately uniform throughout the landscape. In Chapter 3, a semi-automated method of estimating snow water equivalent (SWE) in seasonal snow packs from common offset Ground Penetrating Radar (GPR) data is presented. Many mountainous regions of the world depend on seasonal snow for fresh water resources. Water forecasting relies principally on historical records that relate SWE observations at a limited number of locations to stream discharge. As climate change contributes to a wider range of variability in seasonal snow fall, water forecasts are likely to become less reliable, thus there is a need to find new methods of estimating how much water is stored in seasonal snow. GPR has been shown to be an effective tool for measuring SWE if the radar velocity can be measured. In this chapter, a method that was originally developed to measure seismic velocities from zero-offset seismic reflection data is applied to common-offset GPR data collected over seasonal snow. The method involves suppressing continuous reflections in the image so that the velocity information contained in diffracted energy can be exploited. The filtered images are migrated through a suite of velocities and the velocity that best focus the diffracted energy is chosen on the basis of the varimax norm, which measures how peaked the energy distribution is. GPR derived SWE estimates agree with manual measurements within the uncertainty bounds of both methods. In

Calcium spikes and calcium plateaux evoked by differential polarization in dendrites of turtle motoneurones in vitro

DEFF Research Database (Denmark)

Hounsgaard, J; Kiehn, O

1993-01-01

The ability of dendrites in turtle motoneurones to support calcium spikes and calcium plateaux was investigated using differential polarization by applied electric fields. 2. Electric fields were generated by passing current through transverse slices of the turtle spinal cord between two plate......+ spikes and Ca2+ plateaux are present in dendrites of spinal motoneurones of the turtle....

Absence of Toll-Like Receptor 4 Signaling Results in Delayed Yersinia enterocolitica YopP-Induced Cell Death of Dendritic Cells

Czech Academy of Sciences Publication Activity Database

Gröbner, S.; Schulz, S.; Adkins, Irena; Gunst, D. S. J.; Waibel, M.; Wesselborg, S.; Borgmann, S.; Autenrieth, I. B.

2007-01-01

Roč. 75, č. 1 (2007), s. 512-517 ISSN 0019-9567 Institutional research plan: CEZ:AV0Z50200510 Keywords : yersinia enterocolitica * toll-like receptor 4 * dendritic cell s Subject RIV: EC - Immunology Impact factor: 3.996, year: 2007

Synthesis and ultrastructure of plate-like apatite single crystals as a model for tooth enamel

International Nuclear Information System (INIS)

Zhuang, Zhi; Yoshimura, Hideyuki; Aizawa, Mamoru

2013-01-01

Hydroxyapatite (HAp) is an inorganic constituent compound of human bones and teeth, with superior biocompatibility and bioactivity characteristics. Its crystal structure is hexagonal, characterized by a(b)- and c-planes. In vertebrate long bones, HAp crystals have a c-axis orientation, while in tooth enamel, they have an a(b)-axis orientation. Many methods can be used to synthesize c-axis oriented HAp single crystals; however, to the best of our knowledge, there have been no reports on a synthesis method for a(b)-axis oriented HAp single crystals. In this study, we successfully synthesized plate-like HAp crystals at the air–liquid interface of a starting solution via an enzyme reaction of urea with urease. Crystal phase analysis and ultrastructure observations were carried out, and the results indicated that the particles were single crystals, with almost the same a(b)-axis orientation as tooth enamel. It is hoped that by utilizing their unique surface charge and atomic arrangement, the resulting particles can be used as a high-performance biomaterial, capable of adsorbing bio-related substances and a model for tooth enamel. - Highlights: ► Synthesis of plate-like hydroxyapatite crystals at air–liquid interface ► Ultrastructural analysis of plate-like hydroxyapatite crystals ► Plate-like hydroxyapatite single crystals with a high a(b)-axis orientation ► Plate-like hydroxyapatite single crystals as a model for tooth enamel

Synthesis and ultrastructure of plate-like apatite single crystals as a model for tooth enamel

Energy Technology Data Exchange (ETDEWEB)

Zhuang, Zhi, E-mail: zhuang@meiji.ac.jp [Department of Applied Chemistry, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa 214-8571 (Japan); Yoshimura, Hideyuki, E-mail: hyoshi@isc.meiji.ac.jp [Department of Physics, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa 214-8571 (Japan); Aizawa, Mamoru, E-mail: mamorua@isc.meiji.ac.jp [Department of Applied Chemistry, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa 214-8571 (Japan)

2013-07-01

Hydroxyapatite (HAp) is an inorganic constituent compound of human bones and teeth, with superior biocompatibility and bioactivity characteristics. Its crystal structure is hexagonal, characterized by a(b)- and c-planes. In vertebrate long bones, HAp crystals have a c-axis orientation, while in tooth enamel, they have an a(b)-axis orientation. Many methods can be used to synthesize c-axis oriented HAp single crystals; however, to the best of our knowledge, there have been no reports on a synthesis method for a(b)-axis oriented HAp single crystals. In this study, we successfully synthesized plate-like HAp crystals at the air–liquid interface of a starting solution via an enzyme reaction of urea with urease. Crystal phase analysis and ultrastructure observations were carried out, and the results indicated that the particles were single crystals, with almost the same a(b)-axis orientation as tooth enamel. It is hoped that by utilizing their unique surface charge and atomic arrangement, the resulting particles can be used as a high-performance biomaterial, capable of adsorbing bio-related substances and a model for tooth enamel. - Highlights: ► Synthesis of plate-like hydroxyapatite crystals at air–liquid interface ► Ultrastructural analysis of plate-like hydroxyapatite crystals ► Plate-like hydroxyapatite single crystals with a high a(b)-axis orientation ► Plate-like hydroxyapatite single crystals as a model for tooth enamel.

Microstructure and Properties of Low Cost TC4 Titanium Alloy Plate

Directory of Open Access Journals (Sweden)

Feng Qiuyuan

2016-01-01

Full Text Available The changing law of microstructure and mechanical properties of low cost TC4 titanium alloy during deformation and annealing was investigated. The results show that the coarse cast dendritic structure of slab is broken to form rod-like or equiaxial α+β transformed microstructure by rolling deformation. After annealing, the microstructure of plate becomes uniform, moreover, the flake secondary α separates out and the amount of primary α phase decreases with the increase of annealing temperature and gradually tends to equiaxization. The tensile strength and ductility of plate show an increased tendency with deforming. When annealing temperature increases, the tensile strength firstly increases, and then reaches the maximum value at 820 °C, after that, it gradually decreases. The yield strength and reduction of area show decreasing trend as a whole, but the elongation has a little change. The plate has preferable matching of strength and ductile after annealing treatment at 750~820 °C for 1h in air.

Plate Like Convection with Viscous Strain Weakening and Corresponding Surface Deformation Pattern

Science.gov (United States)

Fuchs, L.; Becker, T. W.

2017-12-01

How plate tectonic surface motions are generated by mantle convection on Earth and possibly other terrestrial type planets has recently become more readily accessible with fully dynamic convection computations. However, it remains debated how plate-like the behavior in such models truly is, and in particular how the well plate boundary dynamics are captured in models which typically exclude the effects of deformation history and memory. Here, we analyze some of the effects of viscous strain weakening on plate behavior and the interactions between interior convection dynamics and surface deformation patterns. We use the finite element code CitcomCU to model convection in a 3D Cartesian model setup. The models are internally heated, with an Arrhenius-type temperature dependent viscosity including plastic yielding and viscous strain weakening (VSW) and healing (VSWH). VSW can mimic first order features of more complex damage mechanisms such as grain-size dependent rheology. Besides plate diagnostic parameters (Plateness, Mobility, and Toroidal: Poloidal ratio) to analyze the tectonic behavior our models, we also explore how "plate boundaries" link to convective patterns. In a first model series, we analyze general surface deformation patterns without VSW. In the early stages, deformation patterns are clearly co-located with up- and downwelling limbs of convection. Along downwellings strain-rates are high and localized, whereas upwellings tend to lead to broad zones of high deformation. At a more advanced stage, however, the plates' interior is highly deformed due to continuous strain accumulation and resurfaced inherited strain. Including only VSW leads to more localized deformation along downwellings. However, at a more advanced stage plate-like convection fails due an overall weakening of the material. This is prevented including strain healing. Deformation pattern at the surface more closely coincide with the internal convection patterns. The average surface

The value of snow cover

Science.gov (United States)

Sokratov, S. A.

2009-04-01

Snow is the natural resource, like soil and water. It has specific properties which allow its use not just for skiing but also for houses cooling in summer (Swedish experience), for air fields construction (Arctic and Antarctic), for dams (north of Russia), for buildings (not only snow-houses of some Polar peoples but artistic hotel attracting tourists in Sweden), and as art material (Sapporo snow festival, Finnish events), etc. "Adjustment" of snow distribution and amount is not only rather common practice (avalanche-protection constructions keeping snow on slopes) but also the practice with long history. So-called "snow irrigation" was used in Russia since XIX century to protect winter crop. What is now named "artificial snow production", is part of much larger pattern. What makes it special—it is unavoidable in present climate and economy situation. 5% of national income in Austria is winter tourism. 50% of the economy in Savoy relay on winter tourism. In terms of money this can be less, but in terms of jobs and income involved this would be even more considerable in Switzerland. As an example—the population of Davos is 14000 in Summer and 50000 in Winter. Skiing is growing business. In present time you can find ski slopes in Turkey and Lebanon. To keep a cite suitable for attracting tourists you need certain amount of sunny days and certain amount of snow. The snow cannons are often the only way to keep a place running. On the other hand, more artificial snow does not necessary attract more tourists, while heavy natural snowfall does attract them. Artificial snow making is costly and requires infrastructure (ponds and electric lines) with very narrow range of weather conditions. Related companies are searching for alternatives and one of them can be "weather regulation" by distribution of some chemical components in clouds. It did not happen yet, but can happen soon. The consequences of such interference in Nature is hardly known. The ski tourism is not the

Transition metal sensing by Toll-like receptor-4: next to nickel, cobalt and palladium are potent human dendritic cell stimulators

NARCIS (Netherlands)

Rachmawati, D.; Bontkes, H.J.; Verstege, M.I.; Muris, J.; von Blomberg, B.M.E.; Scheper, R.J.; van Hoogstraten, I.M.W.

2013-01-01

Background Nickel was recently identified as a potent activator of dendritic cells through ligating with human Toll-like receptor (TLR)-4. Objectives Here, we studied an extended panel of transition metals neighbouring nickel in the periodic table of elements, for their capacity to activate human

Dendritic Spine Instability in a Mouse Model of CDKL5 Disorder Is Rescued by Insulin-like Growth Factor 1.

Science.gov (United States)

Della Sala, Grazia; Putignano, Elena; Chelini, Gabriele; Melani, Riccardo; Calcagno, Eleonora; Michele Ratto, Gian; Amendola, Elena; Gross, Cornelius T; Giustetto, Maurizio; Pizzorusso, Tommaso

2016-08-15

CDKL5 (cyclin-dependent kinase-like 5) is mutated in many severe neurodevelopmental disorders, including atypical Rett syndrome. CDKL5 was shown to interact with synaptic proteins, but an in vivo analysis of the role of CDKL5 in dendritic spine dynamics and synaptic molecular organization is still lacking. In vivo two-photon microscopy of the somatosensory cortex of Cdkl5(-/y) mice was applied to monitor structural dynamics of dendritic spines. Synaptic function and plasticity were measured using electrophysiological recordings of excitatory postsynaptic currents and long-term potentiation in brain slices and assessing the expression of synaptic postsynaptic density protein 95 (PSD-95). Finally, we studied the impact of insulin-like growth factor 1 (IGF-1) treatment on CDKL5 null mice to restore the synaptic deficits. Adult mutant mice showed a significant reduction in spine density and PSD-95-positive synaptic puncta, a reduction of persistent spines, and impaired long-term potentiation. In juvenile mutants, short-term spine elimination, but not formation, was dramatically increased. Exogenous administration of IGF-1 rescued defective rpS6 phosphorylation, spine density, and PSD-95 expression. Endogenous cortical IGF-1 levels were unaffected by CDKL5 deletion. These data demonstrate that dendritic spine stabilization is strongly regulated by CDKL5. Moreover, our data suggest that IGF-1 treatment could be a promising candidate for clinical trials in CDKL5 patients. Copyright © 2016 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Rotavirus activates lymphocytes from non-obese diabetic mice by triggering toll-like receptor 7 signaling and interferon production in plasmacytoid dendritic cells.

Directory of Open Access Journals (Sweden)

Jessica A Pane

2014-03-01

Full Text Available It has been proposed that rotavirus infection promotes the progression of genetically-predisposed children to type 1 diabetes, a chronic autoimmune disease marked by infiltration of activated lymphocytes into pancreatic islets. Non-obese diabetic (NOD mice provide a model for the human disease. Infection of adult NOD mice with rhesus monkey rotavirus (RRV accelerates diabetes onset, without evidence of pancreatic infection. Rather, RRV spreads to the pancreatic and mesenteric lymph nodes where its association with antigen-presenting cells, including dendritic cells, induces cellular maturation. RRV infection increases levels of the class I major histocompatibility complex on B cells and proinflammatory cytokine expression by T cells at these sites. In autoimmunity-resistant mice and human mononuclear cells from blood, rotavirus-exposed plasmacytoid dendritic cells contribute to bystander polyclonal B cell activation through type I interferon expression. Here we tested the hypothesis that rotavirus induces bystander activation of lymphocytes from NOD mice by provoking dendritic cell activation and proinflammatory cytokine secretion. NOD mouse splenocytes were stimulated with rotavirus and assessed for activation by flow cytometry. This stimulation activated antigen-presenting cells and B cells independently of virus strain and replicative ability. Instead, activation depended on virus dose and was prevented by blockade of virus decapsidation, inhibition of endosomal acidification and interference with signaling through Toll-like receptor 7 and the type I interferon receptor. Plasmacytoid dendritic cells were more efficiently activated than conventional dendritic cells by RRV, and contributed to the activation of B and T cells, including islet-autoreactive CD8+ T cells. Thus, a double-stranded RNA virus can induce Toll-like receptor 7 signaling, resulting in lymphocyte activation. Our findings suggest that bystander activation mediated by type I

Rotavirus Activates Lymphocytes from Non-Obese Diabetic Mice by Triggering Toll-Like Receptor 7 Signaling and Interferon Production in Plasmacytoid Dendritic Cells

Science.gov (United States)

Pane, Jessica A.; Webster, Nicole L.; Coulson, Barbara S.

2014-01-01

It has been proposed that rotavirus infection promotes the progression of genetically-predisposed children to type 1 diabetes, a chronic autoimmune disease marked by infiltration of activated lymphocytes into pancreatic islets. Non-obese diabetic (NOD) mice provide a model for the human disease. Infection of adult NOD mice with rhesus monkey rotavirus (RRV) accelerates diabetes onset, without evidence of pancreatic infection. Rather, RRV spreads to the pancreatic and mesenteric lymph nodes where its association with antigen-presenting cells, including dendritic cells, induces cellular maturation. RRV infection increases levels of the class I major histocompatibility complex on B cells and proinflammatory cytokine expression by T cells at these sites. In autoimmunity-resistant mice and human mononuclear cells from blood, rotavirus-exposed plasmacytoid dendritic cells contribute to bystander polyclonal B cell activation through type I interferon expression. Here we tested the hypothesis that rotavirus induces bystander activation of lymphocytes from NOD mice by provoking dendritic cell activation and proinflammatory cytokine secretion. NOD mouse splenocytes were stimulated with rotavirus and assessed for activation by flow cytometry. This stimulation activated antigen-presenting cells and B cells independently of virus strain and replicative ability. Instead, activation depended on virus dose and was prevented by blockade of virus decapsidation, inhibition of endosomal acidification and interference with signaling through Toll-like receptor 7 and the type I interferon receptor. Plasmacytoid dendritic cells were more efficiently activated than conventional dendritic cells by RRV, and contributed to the activation of B and T cells, including islet-autoreactive CD8+ T cells. Thus, a double-stranded RNA virus can induce Toll-like receptor 7 signaling, resulting in lymphocyte activation. Our findings suggest that bystander activation mediated by type I interferon

MODIS Snow Cover Mapping Decision Tree Technique: Snow and Cloud Discrimination

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Riggs, George A.; Hall, Dorothy K.

2010-01-01

Accurate mapping of snow cover continues to challenge cryospheric scientists and modelers. The Moderate-Resolution Imaging Spectroradiometer (MODIS) snow data products have been used since 2000 by many investigators to map and monitor snow cover extent for various applications. Users have reported on the utility of the products and also on problems encountered. Three problems or hindrances in the use of the MODIS snow data products that have been reported in the literature are: cloud obscuration, snow/cloud confusion, and snow omission errors in thin or sparse snow cover conditions. Implementation of the MODIS snow algorithm in a decision tree technique using surface reflectance input to mitigate those problems is being investigated. The objective of this work is to use a decision tree structure for the snow algorithm. This should alleviate snow/cloud confusion and omission errors and provide a snow map with classes that convey information on how snow was detected, e.g. snow under clear sky, snow tinder cloud, to enable users' flexibility in interpreting and deriving a snow map. Results of a snow cover decision tree algorithm are compared to the standard MODIS snow map and found to exhibit improved ability to alleviate snow/cloud confusion in some situations allowing up to about 5% increase in mapped snow cover extent, thus accuracy, in some scenes.

Sentinels for snow science

Science.gov (United States)

Gascoin, S.; Grizonnet, M.; Baba, W. M.; Hagolle, O.; Fayad, A.; Mermoz, S.; Kinnard, C.; Fatima, K.; Jarlan, L.; Hanich, L.

2017-12-01

Current spaceborne sensors do not allow retrieving the snow water equivalent in mountain regions, "the most important unsolved problem in snow hydrology" (Dozier, 2016). While the NASA is operating an airborne mission to survey the SWE in the western USA, elsewhere, however, snow scientists and water managers do not have access to routine SWE measurements at the scale of a mountain range. In this presentation we suggest that the advent of the Copernicus Earth Observation programme opens new perspectives to address this issue in mountain regions worldwide. The Sentinel-2 mission will provide global-scale multispectral observations at 20 m resolution every 5-days (cloud permitting). The Sentinel-1 mission is already imaging the global land surface with a C-band radar at 10 m resolution every 6 days. These observations are unprecedented in terms of spatial and temporal resolution. However, the nature of the observation (radiometry, wavelength) is in the continuity of previous and ongoing missions. As a result, it is relatively straightforward to re-use algorithms that were developed by the remote sensing community over the last decades. For instance, Sentinel-2 data can be used to derive maps of the snow cover extent from the normalized difference snow index, which was initially proposed for Landsat. In addition, the 5-days repeat cycle allows the application of gap-filling algorithms, which were developed for MODIS based on the temporal dimension. The Sentinel-1 data can be used to detect the wet snow cover and track melting areas as proposed for ERS in the early 1990's. Eventually, we show an example where Sentinel-2-like data improved the simulation of the SWE in the data-scarce region of the High Atlas in Morocco through assimilation in a distributed snowpack model. We encourage snow scientists to embrace Sentinel-1 and Sentinel-2 data to enhance our knowledge on the snow cover dynamics in mountain regions.

Assimilation of snow cover and snow depth into a snow model to estimate snow water equivalent and snowmelt runoff in a Himalayan catchment

Directory of Open Access Journals (Sweden)

E. E. Stigter

2017-07-01

Full Text Available Snow is an important component of water storage in the Himalayas. Previous snowmelt studies in the Himalayas have predominantly relied on remotely sensed snow cover. However, snow cover data provide no direct information on the actual amount of water stored in a snowpack, i.e., the snow water equivalent (SWE. Therefore, in this study remotely sensed snow cover was combined with in situ observations and a modified version of the seNorge snow model to estimate (climate sensitivity of SWE and snowmelt runoff in the Langtang catchment in Nepal. Snow cover data from Landsat 8 and the MOD10A2 snow cover product were validated with in situ snow cover observations provided by surface temperature and snow depth measurements resulting in classification accuracies of 85.7 and 83.1 % respectively. Optimal model parameter values were obtained through data assimilation of MOD10A2 snow maps and snow depth measurements using an ensemble Kalman filter (EnKF. Independent validations of simulated snow depth and snow cover with observations show improvement after data assimilation compared to simulations without data assimilation. The approach of modeling snow depth in a Kalman filter framework allows for data-constrained estimation of snow depth rather than snow cover alone, and this has great potential for future studies in complex terrain, especially in the Himalayas. Climate sensitivity tests with the optimized snow model revealed that snowmelt runoff increases in winter and the early melt season (December to May and decreases during the late melt season (June to September as a result of the earlier onset of snowmelt due to increasing temperature. At high elevation a decrease in SWE due to higher air temperature is (partly compensated by an increase in precipitation, which emphasizes the need for accurate predictions on the changes in the spatial distribution of precipitation along with changes in temperature.

Snow farming: conserving snow over the summer season

Science.gov (United States)

Grünewald, Thomas; Wolfsperger, Fabian; Lehning, Michael

2018-01-01

Summer storage of snow for tourism has seen an increasing interest in the last years. Covering large snow piles with materials such as sawdust enables more than two-thirds of the initial snow volume to be conserved. We present detailed mass balance measurements of two sawdust-covered snow piles obtained by terrestrial laser scanning during summer 2015. Results indicate that 74 and 63 % of the snow volume remained over the summer for piles in Davos, Switzerland and Martell, Italy. If snow mass is considered instead of volume, the values increase to 83 and 72 %. The difference is attributed to settling and densification of the snow. Additionally, we adapted the one-dimensional, physically based snow cover model SNOWPACK to perform simulations of the sawdust-covered snow piles. Model results and measurements agreed extremely well at the point scale. Moreover, we analysed the contribution of the different terms of the surface energy balance to snow ablation for a pile covered with a 40 cm thick sawdust layer and a pile without insulation. Short-wave radiation was the dominant source of energy for both scenarios, but the moist sawdust caused strong cooling by long-wave emission and negative sensible and latent heat fluxes. This cooling effect reduces the energy available for melt by up to a factor of 12. As a result only 9 % of the net short-wave energy remained available for melt. Finally, sensitivity studies of the parameters thickness of the sawdust layer, air temperature, precipitation and wind speed were performed. We show that sawdust thickness has a tremendous effect on snow loss. Higher air temperatures and wind speeds increase snow ablation but less significantly. No significant effect of additional precipitation could be found as the sawdust remained wet during the entire summer with the measured quantity of rain. Setting precipitation amounts to zero, however, strongly increased melt. Overall, the 40 cm sawdust provides sufficient protection for mid

Measles Virus Suppresses RIG-I-like Receptor Activation in Dendritic Cells via DC-SIGN-Mediated Inhibition of PP1 Phosphatases

NARCIS (Netherlands)

Mesman, Annelies W.; Zijlstra-Willems, Esther M.; Kaptein, Tanja M.; de Swart, Rik L.; Davis, Meredith E.; Ludlow, Martin; Duprex, W. Paul; Gack, Michaela U.; Gringhuis, Sonja I.; Geijtenbeek, Teunis B. H.

2014-01-01

Dendritic cells (DCs) are targets of measles virus (MV) and play central roles in viral dissemination. However, DCs express the RIG-I-like receptors (RLRs) RIG-I and Mda5 that sense MV and induce type I interferon (IFN) production. Given the potency of this antiviral response, RLRs are tightly

Measles virus suppresses RIG-I-like receptor activation in dendritic cells via DC-SIGN-mediated inhibition of PP1 phosphatases

NARCIS (Netherlands)

A.W. Mesman (Annelies ); E.M. Zijlstra-Willems (Esther); T.M. Kaptein (Tanja); R.L. de Swart (Rik); M.E. Davis (Meredith); M. Ludlow (Martin); W.P. Duprex (Paul); M.U. Gack (Michaela); S.I. Gringhuis (Sonja); T.B.H. Geijtenbeek (Teunis)

2014-01-01

textabstractDendritic cells (DCs) are targets of measles virus (MV) and play central roles in viral dissemination. However, DCs express the RIG-I-like receptors (RLRs) RIG-I and Mda5 that sense MV and induce type I interferon (IFN) production. Given the potency of this antiviral response, RLRs are

SNOW CLEARING SERVICE WINTER 2001-2002

CERN Multimedia

ST-HM Group; Tel. 72202

2001-01-01

As usual at this time of the year, the snowing clearing service, which comes under the control of the Transport Group (ST-HM), is preparing for the start of snow-clearing operations (timetable, stand-by service, personnel responsible for driving vehicles and machines, preparation of useful and necessary equipment, work instructions, etc.) in collaboration with the Cleaning Service (ST-TFM) and the Fire Brigade (TIS-FB). The main difficulty for the snow-clearing service is the car parks, which cannot be properly cleared because of the presence of CERN and private vehicles parked there overnight in different parts of the parking areas. The ST-HM Transport Group would therefore like to invite you to park vehicles together in order to facilitate the access of the snow ploughs, thus allowing the car parks to be cleared more efficiently before the personnel arrives for work in the mornings.

Prophylactic effects of sulforaphane on depression-like behavior and dendritic changes in mice after inflammation.

Science.gov (United States)

Zhang, Ji-Chun; Yao, Wei; Dong, Chao; Yang, Chun; Ren, Qian; Ma, Min; Han, Mei; Wu, Jin; Ushida, Yusuke; Suganuma, Hiroyuki; Hashimoto, Kenji

2017-01-01

Inflammation plays a role in the pathophysiology of depression. Sulforaphane (SFN), an isothiocyanate compound derived from broccoli, is a potent activator of the NF-E2-related factor-2 (Nrf2), which plays a role in inflammation. In this study, we examined whether the prevention effects of SFN in lipopolysaccharide (LPS) induced depression-like behavior in mice. Pretreatment with SFN significantly blocked an increase in the serum tumor necrosis factor-α (TNF-α) level and an increase in microglial activation of brain regions after a single administration of LPS (0.5 mg/kg). Furthermore, SFN significantly potentiated increased serum levels of IL-10 after LPS administration. In the tail-suspension test and forced swimming test, SFN significantly attenuated an increase of the immobility time after LPS administration. In addition, SFN significantly recovered to control levels for LPS-induced alterations in the proteins such as brain-derived neurotrophic factor, postsynaptic density protein 95 and AMPA receptor 1 (GluA1) and dendritic spine density in the brain regions. Finally, dietary intake of 0.1% glucoraphanin (a glucosinolate precursor of SFN) food during the juvenile and adolescence could prevent the onset of LPS-induced depression-like behaviors and dendritic spine changes in the brain regions at adulthood. In conclusion, these findings suggest that dietary intake of SFN-rich broccoli sprout has prophylactic effects on inflammation-related depressive symptoms. Therefore, supplementation of SFN-rich broccoli sprout could be prophylactic vegetable to prevent or minimize the relapse by inflammation in the remission state of depressed patients. Copyright © 2016 Elsevier Inc. All rights reserved.

Assimilation of snow cover and snow depth into a snow model to estimate snow water equivalent and snowmelt runoff in a Himalayan catchment

NARCIS (Netherlands)

Stigter, Emmy E.; Wanders, Niko; Saloranta, Tuomo M.; Shea, Joseph M.; Bierkens, M.F.P.; Immerzeel, W.W.

2017-01-01

Snow is an important component of water storage in the Himalayas. Previous snowmelt studies in the Himalayas have predominantly relied on remotely sensed snow cover. However, snow cover data provide no direct information on the actual amount of water stored in a snowpack, i.e., the snow water

Changes in Snow Albedo Resulting from Snow Darkening Caused by Black Carbon

Science.gov (United States)

Engels, J.; Kloster, S.; Bourgeois, Q.

2014-12-01

We investigate the potential impact of snow darkening caused by pre-industrial and present-day black carbon (BC) emissions on snow albedo and subsequently climate. To assess this impact, we implemented the effect of snow darkening caused by BC emitted from natural as well as anthropogenic sources into the Max Planck Institute for Meteorology Earth System Model (MPI-M ESM). Considerable amounts of BC are emitted e.g. from fires and are transported through the atmosphere for several days before being removed by rain or snow precipitation in snow covered regions. Already very small quantities of BC reduce the snow reflectance significantly, with consequences for snow melting and snow spatial coverage. We implemented the snow albedo reduction caused by BC contamination and snow aging in the one layer land surface component (JSBACH) of the atmospheric general circulation model ECHAM6, developed at MPI-M. For this we used the single-layer simulator of the SNow, Ice, and Aerosol Radiation (SNICAR-Online (Flanner et al., 2007); http://snow.engin.umich.edu) model to derive snow albedo values for BC in snow concentrations ranging between 0 and 1500 ng(BC)/g(snow) for different snow grain sizes for the visible (0.3 - 0.7 μm) and near infrared range (0.7 - 1.5 μm). As snow grains grow over time, we assign different snow ages to different snow grain sizes (50, 150, 500, and 1000 μm). Here, a radius of 50 μm corresponds to new snow, whereas a radius of 1000 μm corresponds to old snow. The deposition rates of BC on snow are prescribed from previous ECHAM6-HAM simulations for two time periods, pre-industrial (1880-1889) and present-day (2000-2009), respectively. We perform a sensitivity study regarding the scavenging of BC by snow melt. To evaluate the newly implemented albedo scheme we will compare the modeled black carbon in snow concentrations to observed ones. Moreover, we will show the impact of the BC contamination and snow aging on the simulated snow albedo. The

RAB-10 Regulates Dendritic Branching by Balancing Dendritic Transport

Science.gov (United States)

Taylor, Caitlin A.; Yan, Jing; Howell, Audrey S.; Dong, Xintong; Shen, Kang

2015-01-01

The construction of a large dendritic arbor requires robust growth and the precise delivery of membrane and protein cargoes to specific subcellular regions of the developing dendrite. How the microtubule-based vesicular trafficking and sorting systems are regulated to distribute these dendritic development factors throughout the dendrite is not well understood. Here we identify the small GTPase RAB-10 and the exocyst complex as critical regulators of dendrite morphogenesis and patterning in the C. elegans sensory neuron PVD. In rab-10 mutants, PVD dendritic branches are reduced in the posterior region of the cell but are excessive in the distal anterior region of the cell. We also demonstrate that the dendritic branch distribution within PVD depends on the balance between the molecular motors kinesin-1/UNC-116 and dynein, and we propose that RAB-10 regulates dendrite morphology by balancing the activity of these motors to appropriately distribute branching factors, including the transmembrane receptor DMA-1. PMID:26633194

Dendritic development of Drosophila high order visual system neurons is independent of sensory experience

Directory of Open Access Journals (Sweden)

Reuter John E

2003-06-01

Full Text Available Abstract Background The complex and characteristic structures of dendrites are a crucial part of the neuronal architecture that underlies brain function, and as such, their development has been a focal point of recent research. It is generally believed that dendritic development is controlled by a combination of endogenous genetic mechanisms and activity-dependent mechanisms. Therefore, it is of interest to test the relative contributions of these two types of mechanisms towards the construction of specific dendritic trees. In this study, we make use of the highly complex Vertical System (VS of motion sensing neurons in the lobula plate of the Drosophila visual system to gauge the importance of visual input and synaptic activity to dendritic development. Results We find that the dendrites of VS1 neurons are unchanged in dark-reared flies as compared to control flies raised on a 12 hour light, 12 hour dark cycle. The dendrites of these flies show no differences from control in dendrite complexity, spine number, spine density, or axon complexity. Flies with genetically ablated eyes show a slight but significant reduction in the complexity and overall length of VS1 dendrites, although this effect may be due to a reduction in the overall size of the dendritic field in these flies. Conclusions Overall, our results indicate no role for visual experience in the development of VS dendrites, while spontaneous activity from photoreceptors may play at most a subtle role in the formation of fully complex dendrites in these high-order visual processing neurons.

Isolation of dendritic-cell-like S100β-positive cells in rat anterior pituitary gland.

Science.gov (United States)

Horiguchi, Kotaro; Fujiwara, Ken; Yoshida, Saishu; Higuchi, Masashi; Tsukada, Takehiro; Kanno, Naoko; Yashiro, Takashi; Tateno, Kozue; Osako, Shunji; Kato, Takako; Kato, Yukio

2014-07-01

S100β-protein-positive cells in the anterior pituitary gland appear to possess multifunctional properties. Because of their pleiotropic features, S100β-positive cells are assumed to be of a heterogeneous or even a non-pituitary origin. The observation of various markers has allowed these cells to be classified into populations such as stem/progenitor cells, epithelial cells, astrocytes and dendritic cells. The isolation and characterization of each heterogeneous population is a prerequisite for clarifying the functional character and origin of the cells. We attempt to isolate two of the subpopulations of S100β-positive cells from the anterior lobe. First, from transgenic rats that express green fluorescent protein (GFP) driven by the S100β protein promoter, we fractionate GFP-positive cells with a cell sorter and culture them so that they can interact with laminin, a component of the extracellular matrix. We observe that one morphological type of GFP-positive cells possesses extended cytoplasmic processes and shows high adhesiveness to laminin (process type), whereas the other is round in shape and exhibits low adherence to laminin (round type). We successfully isolate cells of the round type from the cultured GFP-positive cells by taking advantage of their low affinity to laminin and then measure mRNA levels of the two cell types by real-time polymerase chain reaction. The resultant data show that the process type expresses vimentin (mesenchymal cell marker) and glial fibrillary acidic protein (astrocyte marker). The round type expresses dendritic cell markers, CD11b and interleukin-6. Thus, we found a method for isolating dendritic-cell-like S100β-positive cells by means of their property of adhering to laminin.

Dendritic Zinc Growth in Acid Electrolyte: Effect of the pH

Science.gov (United States)

Bengoa, Leandro N.; Pary, Paola; Seré, Pablo R.; Conconi, M. Susana; Egli, Walter A.

2018-03-01

In this paper, dendritic growth at the edges of electrogalvanized steel strip has been studied using a specially designed rotating washer electrode which simulates the fluid dynamic conditions and the current density distribution at the steel strip edge found in a production line. The effect of electrolyte pH and current density on dendritic growth in an acidic zinc plating bath (ZnSO4 and H2SO4) was addressed. The temperature was kept constant at 60 °C. Solution pH was adjusted to 1, 2 or 3 using different amounts of H2SO4. In addition, the influence of temperature on the pH of the solution was determined. The current density was set at 40 or 60 A/dm2, similar to that used in the industry. Deposits were characterized using SEM and XRD. The results showed that pH strongly affects dendrites shape, length and texture. Furthermore, the morphology of dendrites at the washer edge and of deposits on the flat portion of the washer changed considerably as solution pH was increased from 1 to 3. It was found that the morphology of dendrites at the washer edge stems from the morphology of the deposit on its flat portion, which in turn determines their shape.

Snow reliability in ski resorts considering artificial snowmaking

Science.gov (United States)

Hofstätter, M.; Formayer, H.; Haas, P.

2009-04-01

Snow reliability is the key factor to make skiing on slopes possible and to ensure added value in winter tourism. In this context snow reliability is defined by the duration of a snowpack on the ski runs of at least 50 mm snow water equivalent (SWE), within the main season (Dec-Mar). Furthermore the snowpack should form every winter and be existent early enough in season. In our work we investigate the snow reliability of six Austrian ski resorts. Because nearly all Austrian resorts rely on artificial snowmaking it is of big importance to consider man made snow in the snowpack accumulation and ablation in addition to natural snow. For each study region observed weather data including temperature, precipitation and snow height are used. In addition we differentiate up to three elevations on each site (valley, intermediate, mountain top), being aware of the typical local winter inversion height. Time periods suitable for artificial snow production, for several temperature threshold (-6,-4 or -1 degree Celsius) are calculated on an hourly base. Depending on the actual snowpack height, man made snow can be added in the model with different defined capacities, considering different technologies or the usage of additives. To simulate natural snowpack accumulation and ablation we a simple snow model, based on daily precipitation and temperature. This snow model is optimized at each site separately through certain parameterization factors. Based on the local observations and the monthly climate change signals from the climate model REMO-UBA, we generate long term time series of temperature and precipitation, using the weather generator LARS. Thereby we are not only able to simulate the snow reliability under current, but also under future climate conditions. Our results show significant changes in snow reliability, like an increase of days with insufficient snow heights, especially at mid and low altitudes under natural snow conditions. Artificial snowmaking can partly

Snow as a habitat for microorganisms

Science.gov (United States)

Hoham, Ronald W.

1989-01-01

There are three major habitats involving ice and snow, and the microorganisms studied from these habitats are most eukaryotic. Sea ice is inhabited by algae called diatoms, glacial ice has sparse populations of green algai cal desmids, and the temporary and permanent snows in mountainous regions and high latitudes are inhabited mostly by green algal flagellates. The life cycle of green algal flagellates is summarized by discussing the effects of light, temperature, nutrients, and snow melts. Specific examples of optimal conditions and environmental effects for various snow algae are given. It is not likely that the eukaryotic snow algae presented are candidated for life on the planet Mars. Evolutionally, eukaryotic cells as know on Earth may not have had the opportunity to develop on Mars (if life evolved at all on Mars) since eukaryotes did not appear on Earth until almost two billion years after the first prokaryotic organisms. However, the snow/ice ecosystems on Earth present themselves as extreme habitats were there is evidence of prokaryotic life (eubacteria and cyanbacteria) of which literally nothing is known. Any future surveillances of extant and/or extinct life on Mars should include probes (if not landing sites) to investigate sites of concentrations of ice water. The possibility of signs of life in Martian polar regions should not be overlooked.

Calculation of new snow densities from sub-daily automated snow measurements

Science.gov (United States)

Helfricht, Kay; Hartl, Lea; Koch, Roland; Marty, Christoph; Lehning, Michael; Olefs, Marc

2017-04-01

In mountain regions there is an increasing demand for high-quality analysis, nowcasting and short-range forecasts of the spatial distribution of snowfall. Operational services, such as for avalanche warning, road maintenance and hydrology, as well as hydropower companies and ski resorts need reliable information on the depth of new snow (HN) and the corresponding water equivalent (HNW). However, the ratio of HNW to HN can vary from 1:3 to 1:30 because of the high variability of new snow density with respect to meteorological conditions. In the past, attempts were made to calculate new snow densities from meteorological parameters mainly using daily values of temperature and wind. Further complex statistical relationships have been used to calculate new snow densities on hourly to sub-hourly time intervals to drive multi-layer snow cover models. However, only a few long-term in-situ measurements of new snow density exist for sub-daily time intervals. Settling processes within the new snow due to loading and metamorphism need to be considered when computing new snow density. As the effect of these processes is more pronounced for long time intervals, a high temporal resolution of measurements is desirable. Within the pluSnow project data of several automatic weather stations with simultaneous measurements of precipitation (pluviometers), snow water equivalent (SWE) using snow pillows and snow depth (HS) measurements using ultrasonic rangers were analysed. New snow densities were calculated for a set of data filtered on the basis of meteorological thresholds. The calculated new snow densities were compared to results from existing new snow density parameterizations. To account for effects of settling of the snow cover, a case study based on a multi-year data set using the snow cover model SNOWPACK at Weissfluhjoch was performed. Measured median values of hourly new snow densities at the different stations range from 54 to 83 kgm-3. This is considerably lower than a 1

Snow loads in a changing climate: new risks?

Directory of Open Access Journals (Sweden)

U. Strasser

2008-01-01

Full Text Available In January/February 2006, heavy snowfalls in Bavaria (Germany lead to a series of infrastructural damage of catastrophic nature. Since on many collapsed roofs the total snow load was not exceptional, serious engineering deficiencies in roof construction and a sudden rise in the total snow load were considered to be the trigger of the events. An analysis of the then meteorological conditions reveals, that the early winter of 2005/2006 was characterised by an exceptional continuous snow cover, temperatures remained around the freezing point and no significant snowmelt was evident. The frequent freezing/thawing cycles were followed by a general compaction of the snow load. This resulted in a re-distribution and a new concentration of the snow load on specific locations on roofs. With respect to climate change, the question arises as to whether the risks relating to snow loads will increase. The future probability of a continuous snow cover occurrence with frequent freezing/thawing cycles will probably decline due to predicted higher temperatures. However, where temperatures remain low, an increase in winter precipitation will result in increased snow loads. Furthermore, the variability of extremes is predicted to increase. If heavy snowfall events are more frequent, the risk of a trigger event will likely increase. Finally, an attempt will be made here in this paper to outline a concept for an operational warning system for the Bavarian region. This system envisages to predict the development and risk of critical snow loads for a 3-day time period, utilising a combination of climate and snow modelling data and using this together with a snow pillow device (located on roofs and the results of which.

Influence of radiation on initial attachment of osteoblast-like cells on titanium plate

International Nuclear Information System (INIS)

Kakuta, Saburo; Hamazaki, Miki; Mitsumoto, Kazuyo; Itabashi, Yuto; Fujimori, Shinya; Miyazaki, Takashi; Nagumo, Masao

1996-01-01

Radiotherapy is a useful and convenient therapy for oral cancer. However, there are many side effects such as stomatitis and radionecrosis of jaws. Radionecrosis may cause loosing or infection of biomaterials used for reconstruction of jaws. In this experiment, in vitro investigation was performed to clarify the influence of radiation on initial attachment of osteoblast-like cells to the titanium plate. UMR-106 and MC3T3-E1 cells were used as osteoblast-like cells. Cell attachment was evaluated by alkaline phosphatase activity and staining attached cells with crystal violet. The results revealed that initial attachment of osteoblast-like cells to the titanium plate was dose-dependently decreased by radiation and that radiosensitivity of each cell was different respectively. Furthermore, the participation of active oxygen was suggested because of partial recovery of cell attachment by addition of superoxide dismutase and/or an antioxidant such as ascorbic acid. (author)

Statistical Physics of Neural Systems with Nonadditive Dendritic Coupling

Directory of Open Access Journals (Sweden)

David Breuer

2014-03-01

Full Text Available How neurons process their inputs crucially determines the dynamics of biological and artificial neural networks. In such neural and neural-like systems, synaptic input is typically considered to be merely transmitted linearly or sublinearly by the dendritic compartments. Yet, single-neuron experiments report pronounced supralinear dendritic summation of sufficiently synchronous and spatially close-by inputs. Here, we provide a statistical physics approach to study the impact of such nonadditive dendritic processing on single-neuron responses and the performance of associative-memory tasks in artificial neural networks. First, we compute the effect of random input to a neuron incorporating nonlinear dendrites. This approach is independent of the details of the neuronal dynamics. Second, we use those results to study the impact of dendritic nonlinearities on the network dynamics in a paradigmatic model for associative memory, both numerically and analytically. We find that dendritic nonlinearities maintain network convergence and increase the robustness of memory performance against noise. Interestingly, an intermediate number of dendritic branches is optimal for memory functionality.

Lithium dendrite and solid electrolyte interphase investigation using OsO4

Science.gov (United States)

Zier, Martin; Scheiba, Frieder; Oswald, Steffen; Thomas, Jürgen; Goers, Dietrich; Scherer, Torsten; Klose, Markus; Ehrenberg, Helmut; Eckert, Jürgen

2014-11-01

Osmium tetroxide (OsO4) staining, commonly used to enhance scattering contrast in electron microscopy of biologic tissue and polymer blends, has been adopted for studies of graphite anodes in lithium-ion batteries. OsO4 shows a coordinated reaction with components of the solid electrolyte interphase (SEI) and lithium dendrites, thereby increasing material contrast for scanning electron microscopy investigations. Utilizing the high affinity of lithium metal to react with osmium tetroxide it was possible to localize even small lithium deposits on graphite electrodes. In spite of their reaction with the OsO4 fume, the lithium dendrite morphology remains almost untouched by the staining procedure, offering information on the dendrite growth process. Correlating the quantity of osmium detected with the amount of residual ("dead") lithium of a discharged electrode, it was possible to obtain a practical measure for lithium plating and stripping efficiencies. EDX mappings allowed for a localization of electrochemically stripped lithium dendrites by their residual stained SEI shells. Cross sections, prepared by focused ion beam (FIB) of cycled graphite electrodes treated with OsO4, revealed important information about deposition and distribution of metallic lithium and the electrolyte reduction layer across the electrode.

Snow hydrology in Mediterranean mountain regions: A review

Science.gov (United States)

Fayad, Abbas; Gascoin, Simon; Faour, Ghaleb; López-Moreno, Juan Ignacio; Drapeau, Laurent; Page, Michel Le; Escadafal, Richard

2017-08-01

Water resources in Mediterranean regions are under increasing pressure due to climate change, economic development, and population growth. Many Mediterranean rivers have their headwaters in mountainous regions where hydrological processes are driven by snowpack dynamics and the specific variability of the Mediterranean climate. A good knowledge of the snow processes in the Mediterranean mountains is therefore a key element of water management strategies in such regions. The objective of this paper is to review the literature on snow hydrology in Mediterranean mountains to identify the existing knowledge, key research questions, and promising technologies. We collected 620 peer-reviewed papers, published between 1913 and 2016, that deal with the Mediterranean-like mountain regions in the western United States, the central Chilean Andes, and the Mediterranean basin. A large amount of studies in the western United States form a strong scientific basis for other Mediterranean mountain regions. We found that: (1) the persistence of snow cover is highly variable in space and time but mainly controlled by elevation and precipitation; (2) the snowmelt is driven by radiative fluxes, but the contribution of heat fluxes is stronger at the end of the snow season and during heat waves and rain-on-snow events; (3) the snow densification rates are higher in these regions when compared to other climate regions; and (4) the snow sublimation is an important component of snow ablation, especially in high-elevation regions. Among the pressing issues is the lack of continuous ground observation in high-elevation regions. However, a few years of snow depth (HS) and snow water equivalent (SWE) data can provide realistic information on snowpack variability. A better spatial characterization of snow cover can be achieved by combining ground observations with remotely sensed snow data. SWE reconstruction using satellite snow cover area and a melt model provides reasonable information that

Snow Matters

DEFF Research Database (Denmark)

Gyimóthy, Szilvia; Jensen, Martin Trandberg

2018-01-01

attribute of high altitude mountain destinations. Hitherto, researchers mostly engaged with snowclad landscapes as a backstage; trying to deconstruct the complex symbolism and representational qualities of this elusive substance. Despite snow being a strategically crucial condition for tourism in the Alps......This chapter explores the performative potential of snow for Alpine tourism, by drawing attention to its material and nonrepresentational significance for tourism practices. European imagination has been preoccupied with snow since medieval times and even today, snow features as the sine que non...

Occurrences of dendritic gold at the McLaughlin Mine hot-spring gold deposit

Science.gov (United States)

Sherlock, R. L.; Lehrman, N. J.

1995-06-01

Two styles of gold dendrites are variably developed at the McLaughlin Mine. The most abundant occurrence is hosted by amber-coloured hydrocarbon-rich opal. Silica likely precipitated from a boiling hydrothermal fluid and complexed with immiscible hydrocarbons forming an amorphous hydrocarbon-silica phase. This phase likely scavenged particulate gold by electrostatic attraction to the hydrocarbon-silica phase. The dendritic nature of the gold is secondary and is the result of dewatering of the amorphous hydrocarbon-silica phase and crystallization of gold into syneresis fractures. The second style of dendritic gold is hosted within vein swarms that focused large volumes of fluid flow. The dendrites occur along with hydrocarbon-rich silica at the upper contact of the vein margins which isolated the dendrites allowing sufficient time for them to grow. In a manner similar to the amber-coloured opal, the dendrites may have formed by scavenging particulate gold by electrostatic attraction to the hydrocarbon-silica phase.

Recent advances in seismic non-destructive testing of concrete plate like structures

International Nuclear Information System (INIS)

Ryden, N.; Kristensen, A.; Jovall, O.

2009-01-01

This paper describes recent advances in seismic/acoustic non-destructive testing of concrete containment walls. The presented technique is focused on the characterization of the mean stiffness (seismic velocities) and thickness of the containment wall. The Impact Echo (IE) method is a well-established technique to measure the thickness of concrete plates or to locate defects in concrete plate like structures. The method relies on a good estimate of the mean velocity through the thickness of the plate and a precisely measured thickness resonant frequency. Recently the underlying theory of the IE method has been redefined and improved based on Lamb waves in a free plate. Based on this theory we have developed a new data processing technique where both propagating and standing Lamb waves are analysed in a combined manner using multichannel data. With this approach the mean velocity through the plate thickness is evaluated by using the fundamental mode Lamb wave dispersion curves. The accuracy and detection ability of the measured resonant frequency is improved by utilizing both amplitude and phase information from the multichannel record. The method has been tested on several nuclear power plants in Sweden and Finland and proved to be more robust compared to conventional IE and surface wave measurements

Mac OS X Snow Leopard Server For Dummies

CERN Document Server

Rizzo, John

2009-01-01

Making Everything Easier!. Mac OS® X Snow Leopard Server for Dummies. Learn to::;. Set up and configure a Mac network with Snow Leopard Server;. Administer, secure, and troubleshoot the network;. Incorporate a Mac subnet into a Windows Active Directory® domain;. Take advantage of Unix® power and security. John Rizzo. Want to set up and administer a network even if you don't have an IT department? Read on!. Like everything Mac, Snow Leopard Server was designed to be easy to set up and use. Still, there are so many options and features that this book will save you heaps of time and effort. It wa

The Impact Of Snow Melt On Surface Runoff Of Sava River In Slovenia

Science.gov (United States)

Horvat, A.; Brilly, M.; Vidmar, A.; Kobold, M.

2009-04-01

Snow is a type of precipitation in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Snow remains on the ground until it melts or sublimates. Spring snow melt is a major source of water supply to areas in temperate zones near mountains that catch and hold winter snow, especially those with a prolonged dry summer. In such places, water equivalent is of great interest to water managers wishing to predict spring runoff and the water supply of cities downstream. In temperate zone like in Slovenia the snow melts in the spring and contributes certain amount of water to surface flow. This amount of water can be great and can cause serious floods in case of fast snow melt. For this reason we tried to determine the influence of snow melt on the largest river basin in Slovenia - Sava River basin, on surface runoff. We would like to find out if snow melt in Slovenian Alps can cause spring floods and how serious it can be. First of all we studied the caracteristics of Sava River basin - geology, hydrology, clima, relief and snow conditions in details for each subbasin. Furtermore we focused on snow and described the snow phenomenom in Slovenia, detailed on Sava River basin. We collected all available data on snow - snow water equivalent and snow depth. Snow water equivalent is a much more useful measurement to hydrologists than snow depth, as the density of cool freshly fallen snow widely varies. New snow commonly has a density of between 5% and 15% of water. But unfortunately there is not a lot of available data of SWE available for Slovenia. Later on we compared the data of snow depth and river runoff for some of the 40 winter seasons. Finally we analyzed the use of satellite images for Slovenia to determine the snow cover for hydrology reason. We concluded that snow melt in Slovenia does not have a greater influence on Sava River flow. The snow cover in Alps can melt fast due to higher temperatures but the water distributes

Simulating Snow in Canadian Boreal Environments with CLASS for ESM-SnowMIP

Science.gov (United States)

Wang, L.; Bartlett, P. A.; Derksen, C.; Ireson, A. M.; Essery, R.

2017-12-01

The ability of land surface schemes to provide realistic simulations of snow cover is necessary for accurate representation of energy and water balances in climate models. Historically, this has been particularly challenging in boreal forests, where poor treatment of both snow masking by forests and vegetation-snow interaction has resulted in biases in simulated albedo and snowpack properties, with subsequent effects on both regional temperatures and the snow albedo feedback in coupled simulations. The SnowMIP (Snow Model Intercomparison Project) series of experiments or `MIPs' was initiated in order to provide assessments of the performance of various snow- and land-surface-models at selected locations, in order to understand the primary factors affecting model performance. Here we present preliminary results of simulations conducted for the third such MIP, ESM-SnowMIP (Earth System Model - Snow Model Intercomparison Project), using the Canadian Land Surface Scheme (CLASS) at boreal forest sites in central Saskatchewan. We assess the ability of our latest model version (CLASS 3.6.2) to simulate observed snowpack properties (snow water equivalent, density and depth) and above-canopy albedo over 13 winters. We also examine the sensitivity of these simulations to climate forcing at local and regional scales.

Equine dendritic cells generated with horse serum have enhanced functionality in comparison to dendritic cells generated with fetal bovine serum

OpenAIRE

Ziegler, Anja; Everett, Helen; Hamza, Eman; Garbani, Mattia; Gerber, Vinzenz; Marti, Eliane; Steinbach, Falko

2016-01-01

BACKGROUND: Dendritic cells are professional antigen-presenting cells that play an essential role in the initiation and modulation of T cell responses. They have been studied widely for their potential clinical applications, but for clinical use to be successful, alternatives to xenogeneic substances like fetal bovine serum (FBS) in cell culture need to be found. Protocols for the generation of dendritic cells ex vivo from monocytes are well established for several species, including hor...

A Vision for an International Multi-Sensor Snow Observing Mission

Science.gov (United States)

Kim, Edward

2015-01-01

Discussions within the international snow remote sensing community over the past two years have led to encouraging consensus regarding the broad outlines of a dedicated snow observing mission. The primary consensus - that since no single sensor type is satisfactory across all snow types and across all confounding factors, a multi-sensor approach is required - naturally leads to questions about the exact mix of sensors, required accuracies, and so on. In short, the natural next step is to collect such multi-sensor snow observations (with detailed ground truth) to enable trade studies of various possible mission concepts. Such trade studies must assess the strengths and limitations of heritage as well as newer measurement techniques with an eye toward natural sensitivity to desired parameters such as snow depth and/or snow water equivalent (SWE) in spite of confounding factors like clouds, lack of solar illumination, forest cover, and topography, measurement accuracy, temporal and spatial coverage, technological maturity, and cost.

Gender and snow crab occupational asthma in Newfoundland and Labrador, Canada

International Nuclear Information System (INIS)

Howse, Dana; Gautrin, Denyse; Neis, Barbara; Cartier, Andre; Horth-Susin, Lise; Jong, Michael; Swanson, Mark C.

2006-01-01

Fish and shellfish processing employs many thousands of people globally, with shellfish processing becoming more important in recent years. Shellfish processing is associated with multiple occupational health and safety (OHS) risks. Snow crab occupational asthma (OA) is work-related asthma associated with processing snow crab. We present a gender analysis of findings from a 3-year multifaceted study of snow crab OA in Newfoundland and Labrador, Canada. The study was carried out in four snow crab processing communities between 2001 and 2004. An anonymous survey questionnaire on knowledge, beliefs, and concerns related to processing snow crab administered to 158 workers attending community meetings at the start of the research found that women were significantly more likely than men to associate certain health problems, especially chest tightness, difficulty breathing, and cough, with crab processing (P<0.001). Worker health assessments carried out with 215 processing workers (187 current/28 former; 120 female/95 male) found that female participants were more likely to be diagnosed as almost certain/highly probable snow crab OA and allergy (P=0.001) and to be sensitized to snow crab (P=0.01) than male participants. Work histories from the health assessments were used to classify processing jobs as male or female. Allergen sampling (211 allergen samples: 115 area, 96 personal breathing zone) indicated that the plant areas where these male jobs were concentrated were associated with lower levels of aerosolized crab allergens (the agents responsible for OA to snow crab) than areas associated with female jobs. This difference was statistically significant in the two plants with poor ventilation (p<0.001 and P=0.017 for these plants). A gender analysis of work history data showed that female health assessment participants were likely to have worked longer processing snow crab than males (5 years versus 3.5 years, respectively). Cross-referencing of work history results

Improvement of a snow albedo parameterization in the Snow-Atmosphere-Soil Transfer model: evaluation of impacts of aerosol on seasonal snow cover

Science.gov (United States)

Zhong, Efang; Li, Qian; Sun, Shufen; Chen, Wen; Chen, Shangfeng; Nath, Debashis

2017-11-01

The presence of light-absorbing aerosols (LAA) in snow profoundly influence the surface energy balance and water budget. However, most snow-process schemes in land-surface and climate models currently do not take this into consideration. To better represent the snow process and to evaluate the impacts of LAA on snow, this study presents an improved snow albedo parameterization in the Snow-Atmosphere-Soil Transfer (SAST) model, which includes the impacts of LAA on snow. Specifically, the Snow, Ice and Aerosol Radiation (SNICAR) model is incorporated into the SAST model with an LAA mass stratigraphy scheme. The new coupled model is validated against in-situ measurements at the Swamp Angel Study Plot (SASP), Colorado, USA. Results show that the snow albedo and snow depth are better reproduced than those in the original SAST, particularly during the period of snow ablation. Furthermore, the impacts of LAA on snow are estimated in the coupled model through case comparisons of the snowpack, with or without LAA. The LAA particles directly absorb extra solar radiation, which accelerates the growth rate of the snow grain size. Meanwhile, these larger snow particles favor more radiative absorption. The average total radiative forcing of the LAA at the SASP is 47.5 W m-2. This extra radiative absorption enhances the snowmelt rate. As a result, the peak runoff time and "snow all gone" day have shifted 18 and 19.5 days earlier, respectively, which could further impose substantial impacts on the hydrologic cycle and atmospheric processes.

Dendritic cells in Barrett's esophagus and esophageal adenocarcinoma.

Science.gov (United States)

Bobryshev, Yuri V; Tran, Dinh; Killingsworth, Murray C; Buckland, Michael; Lord, Reginald V N

2009-01-01

Like other premalignant conditions that develop in the presence of chronic inflammation, the development and progression of Barrett's esophagus is associated with the development of an immune response, but how this immune response is regulated is poorly understood. A comprehensive literature search failed to find any report of the presence of dendritic cells in Barrett's intestinal metaplasia and esophageal adenocarcinoma and this prompted our study. We used immunohistochemical staining and electron microscopy to examine whether dendritic cells are present in Barrett's esophagus and esophageal adenocarcinoma. Immunohistochemical staining with CD83, a specific marker for dendritic cells, was performed on paraffin-embedded sections of Barrett's intestinal metaplasia (IM, n = 12), dysplasia (n = 11) and adenocarcinoma (n = 14). CD83+ cells were identified in the lamina propria surrounding intestinal type glands in Barrett's IM, dysplasia, and cancer tissues. Computerized quantitative analysis showed that the numbers of dendritic cells were significantly higher in cancer tissues. Double immunostaining with CD83, CD20, and CD3, and electron microscopy demonstrated that dendritic cells are present in Barrett's esophagus and form clusters with T cells and B cells directly within the lamina propria. These findings demonstrate that dendritic cells are present in Barrett's tissues, with a significant increase in density in adenocarcinoma compared to benign Barrett's esophagus. Dendritic cells may have a role in the pathogenesis and immunotherapy treatment of Barrett's esophagus and adenocarcinoma.

Dendritic cell vaccines.

Science.gov (United States)

Mosca, Paul J; Lyerly, H Kim; Clay, Timothy M; Morse, Michael A; Lyerly, H Kim

2007-05-01

Dendritic cells are antigen-presenting cells that have been shown to stimulate tumor antigen-specific T cell responses in preclinical studies. Consequently, there has been intense interest in developing dendritic cell based cancer vaccines. A variety of methods for generating dendritic cells, loading them with tumor antigens, and administering them to patients have been described. In recent years, a number of early phase clinical trials have been performed and have demonstrated the safety and feasibility of dendritic cell immunotherapies. A number of these trials have generated valuable preliminary data regarding the clinical and immunologic response to DC-based immunotherapy. The emphasis of dendritic cell immunotherapy research is increasingly shifting toward the development of strategies to increase the potency of dendritic cell vaccine preparations.

A probabilistic framework for acoustic emission source localization in plate-like structures

International Nuclear Information System (INIS)

Dehghan Niri, E; Salamone, S

2012-01-01

This paper proposes a probabilistic approach for acoustic emission (AE) source localization in isotropic plate-like structures based on an extended Kalman filter (EKF). The proposed approach consists of two main stages. During the first stage, time-of-flight (TOF) measurements of Lamb waves are carried out by a continuous wavelet transform (CWT), accounting for systematic errors due to the Heisenberg uncertainty; the second stage uses an EKF to iteratively estimate the AE source location and the wave velocity. The advantages of the proposed algorithm over the traditional methods include the capability of: (1) taking into account uncertainties in TOF measurements and wave velocity and (2) efficiently fusing multi-sensor data to perform AE source localization. The performance of the proposed approach is validated through pencil-lead breaks performed on an aluminum plate at systematic grid locations. The plate was instrumented with an array of four piezoelectric transducers in two different configurations. (paper)

Integration of snow management practices into a detailed snow pack model

Science.gov (United States)

Spandre, Pierre; Morin, Samuel; Lafaysse, Matthieu; Lejeune, Yves; François, Hugues; George-Marcelpoil, Emmanuelle

2016-04-01

The management of snow on ski slopes is a key socio-economic and environmental issue in mountain regions. Indeed the winter sports industry has become a very competitive global market although this economy remains particularly sensitive to weather and snow conditions. The understanding and implementation of snow management in detailed snowpack models is a major step towards a more realistic assessment of the evolution of snow conditions in ski resorts concerning past, present and future climate conditions. Here we describe in a detailed manner the integration of snow management processes (grooming, snowmaking) into the snowpack model Crocus (Spandre et al., Cold Reg. Sci. Technol., in press). The effect of the tiller is explicitly taken into account and its effects on snow properties (density, snow microstructure) are simulated in addition to the compaction induced by the weight of the grooming machine. The production of snow in Crocus is carried out with respect to specific rules and current meteorological conditions. Model configurations and results are described in detail through sensitivity tests of the model of all parameters related to snow management processes. In-situ observations were carried out in four resorts in the French Alps during the 2014-2015 winter season considering for each resort natural, groomed only and groomed plus snowmaking conditions. The model provides realistic simulations of the snowpack properties with respect to these observations. The main uncertainty pertains to the efficiency of the snowmaking process. The observed ratio between the mass of machine-made snow on ski slopes and the water mass used for production was found to be lower than was expected from the literature, in every resort. The model now referred to as "Crocus-Resort" has been proven to provide realistic simulations of snow conditions on ski slopes and may be used for further investigations. Spandre, P., S. Morin, M. Lafaysse, Y. Lejeune, H. François and E. George

Toll-like receptor triggered dendritic cell maturation and IL-12 secretion are necessary to overcome T-cell inhibition by glioma-associated TGF-beta2.

NARCIS (Netherlands)

Grauer, O.M.; Poschl, P.; Lohmeier, A.; Adema, G.J.; Bogdahn, U.

2007-01-01

Malignant gliomas are able to secrete large amounts of immunosuppressive cytokines like transforming growth factor beta 2 (TGF-beta2) and regularly escape from immune surveillance. Many strategies have been developed to induce potent anti-glioma responses, among those the use of dendritic cells (DC)

NOAA's National Snow Analyses

Science.gov (United States)

Carroll, T. R.; Cline, D. W.; Olheiser, C. M.; Rost, A. A.; Nilsson, A. O.; Fall, G. M.; Li, L.; Bovitz, C. T.

2005-12-01

NOAA's National Operational Hydrologic Remote Sensing Center (NOHRSC) routinely ingests all of the electronically available, real-time, ground-based, snow data; airborne snow water equivalent data; satellite areal extent of snow cover information; and numerical weather prediction (NWP) model forcings for the coterminous U.S. The NWP model forcings are physically downscaled from their native 13 km2 spatial resolution to a 1 km2 resolution for the CONUS. The downscaled NWP forcings drive an energy-and-mass-balance snow accumulation and ablation model at a 1 km2 spatial resolution and at a 1 hour temporal resolution for the country. The ground-based, airborne, and satellite snow observations are assimilated into the snow model's simulated state variables using a Newtonian nudging technique. The principle advantages of the assimilation technique are: (1) approximate balance is maintained in the snow model, (2) physical processes are easily accommodated in the model, and (3) asynoptic data are incorporated at the appropriate times. The snow model is reinitialized with the assimilated snow observations to generate a variety of snow products that combine to form NOAA's NOHRSC National Snow Analyses (NSA). The NOHRSC NSA incorporate all of the available information necessary and available to produce a "best estimate" of real-time snow cover conditions at 1 km2 spatial resolution and 1 hour temporal resolution for the country. The NOHRSC NSA consist of a variety of daily, operational, products that characterize real-time snowpack conditions including: snow water equivalent, snow depth, surface and internal snowpack temperatures, surface and blowing snow sublimation, and snowmelt for the CONUS. The products are generated and distributed in a variety of formats including: interactive maps, time-series, alphanumeric products (e.g., mean areal snow water equivalent on a hydrologic basin-by-basin basis), text and map discussions, map animations, and quantitative gridded products

Dendritic Spines in Depression: What We Learned from Animal Models

Directory of Open Access Journals (Sweden)

Hui Qiao

2016-01-01

Full Text Available Depression, a severe psychiatric disorder, has been studied for decades, but the underlying mechanisms still remain largely unknown. Depression is closely associated with alterations in dendritic spine morphology and spine density. Therefore, understanding dendritic spines is vital for uncovering the mechanisms underlying depression. Several chronic stress models, including chronic restraint stress (CRS, chronic unpredictable mild stress (CUMS, and chronic social defeat stress (CSDS, have been used to recapitulate depression-like behaviors in rodents and study the underlying mechanisms. In comparison with CRS, CUMS overcomes the stress habituation and has been widely used to model depression-like behaviors. CSDS is one of the most frequently used models for depression, but it is limited to the study of male mice. Generally, chronic stress causes dendritic atrophy and spine loss in the neurons of the hippocampus and prefrontal cortex. Meanwhile, neurons of the amygdala and nucleus accumbens exhibit an increase in spine density. These alterations induced by chronic stress are often accompanied by depression-like behaviors. However, the underlying mechanisms are poorly understood. This review summarizes our current understanding of the chronic stress-induced remodeling of dendritic spines in the hippocampus, prefrontal cortex, orbitofrontal cortex, amygdala, and nucleus accumbens and also discusses the putative underlying mechanisms.

Response of snow-dependent hydrologic extremes to continued global warming

Energy Technology Data Exchange (ETDEWEB)

Diffenbaugh, Noah [Stanford University; Scherer, Martin [Stanford University; Ashfaq, Moetasim [ORNL

2012-01-01

Snow accumulation is critical for water availability in the Northern Hemisphere1,2, raising concern that global warming could have important impacts on natural and human systems in snow-dependent regions1,3. Although regional hydrologic changes have been observed (for example, refs 1,3 5), the time of emergence of extreme changes in snow accumulation and melt remains a key unknown for assessing climate- change impacts3,6,7. We find that the CMIP5 global climate model ensemble exhibits an imminent shift towards low snow years in the Northern Hemisphere, with areas of western North America, northeastern Europe and the Greater Himalaya showing the strongest emergence during the near- termdecadesandat2 Cglobalwarming.Theoccurrenceof extremely low snow years becomes widespread by the late twenty-first century, as do the occurrences of extremely high early-season snowmelt and runoff (implying increasing flood risk), and extremely low late-season snowmelt and runoff (implying increasing water stress). Our results suggest that many snow-dependent regions of the Northern Hemisphere are likely to experience increasing stress from low snow years within the next three decades, and from extreme changes in snow-dominated water resources if global warming exceeds 2 C above the pre-industrial baseline.

Impact of climate change in Switzerland on socioeconomic snow indices

Science.gov (United States)

Schmucki, Edgar; Marty, Christoph; Fierz, Charles; Weingartner, Rolf; Lehning, Michael

2017-02-01

Snow is a key element for many socioeconomic activities in mountainous regions. Due to the sensitivity of the snow cover to variations of temperature and precipitation, major changes caused by climate change are expected to happen. We analyze the evolution of some key snow indices under future climatic conditions. Ten downscaled and postprocessed climate scenarios from the ENSEMBLES database have been used to feed the physics-based snow model SNOWPACK. The projected snow cover has been calculated for 11 stations representing the diverse climates found in Switzerland. For the first time, such a setup is used to reveal changes in frequently applied snow indices and their implications on various socioeconomic sectors. Toward the end of the twenty-first century, a continuous snow cover is likely only guaranteed at high elevations above 2000 m a.s.l., whereas at mid elevations (1000-1700 m a.s.l.), roughly 50 % of all winters might be characterized by an ephemeral snow cover. Low elevations (below 500 m a.s.l.) are projected to experience only 2 days with snowfall per year and show the strongest relative reductions in mean winter snow depth of around 90 %. The range of the mean relative reductions of the snow indices is dominated by uncertainties from different GCM-RCM projections and amounts to approximately 30 %. Despite these uncertainties, all snow indices show a clear decrease in all scenario periods and the relative reductions increase toward lower elevations. These strong reductions can serve as a basis for policy makers in the fields of tourism, ecology, and hydropower.

Activity-dependent trafficking of lysosomes in dendrites and dendritic spines.

Science.gov (United States)

Goo, Marisa S; Sancho, Laura; Slepak, Natalia; Boassa, Daniela; Deerinck, Thomas J; Ellisman, Mark H; Bloodgood, Brenda L; Patrick, Gentry N

2017-08-07

In neurons, lysosomes, which degrade membrane and cytoplasmic components, are thought to primarily reside in somatic and axonal compartments, but there is little understanding of their distribution and function in dendrites. Here, we used conventional and two-photon imaging and electron microscopy to show that lysosomes traffic bidirectionally in dendrites and are present in dendritic spines. We find that lysosome inhibition alters their mobility and also decreases dendritic spine number. Furthermore, perturbing microtubule and actin cytoskeletal dynamics has an inverse relationship on the distribution and motility of lysosomes in dendrites. We also find trafficking of lysosomes is correlated with synaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptors. Strikingly, lysosomes traffic to dendritic spines in an activity-dependent manner and can be recruited to individual spines in response to local activation. These data indicate the position of lysosomes is regulated by synaptic activity and thus plays an instructive role in the turnover of synaptic membrane proteins. © 2017 Goo et al.

A snow cover climatology for the Pyrenees from MODIS snow products

Science.gov (United States)

Gascoin, S.; Hagolle, O.; Huc, M.; Jarlan, L.; Dejoux, J.-F.; Szczypta, C.; Marti, R.; Sanchez, R.

2015-05-01

The seasonal snow in the Pyrenees is critical for hydropower production, crop irrigation and tourism in France, Spain and Andorra. Complementary to in situ observations, satellite remote sensing is useful to monitor the effect of climate on the snow dynamics. The MODIS daily snow products (Terra/MOD10A1 and Aqua/MYD10A1) are widely used to generate snow cover climatologies, yet it is preferable to assess their accuracies prior to their use. Here, we use both in situ snow observations and remote sensing data to evaluate the MODIS snow products in the Pyrenees. First, we compare the MODIS products to in situ snow depth (SD) and snow water equivalent (SWE) measurements. We estimate the values of the SWE and SD best detection thresholds to 40 mm water equivalent (w.e.) and 150 mm, respectively, for both MOD10A1 and MYD10A1. κ coefficients are within 0.74 and 0.92 depending on the product and the variable for these thresholds. However, we also find a seasonal trend in the optimal SWE and SD thresholds, reflecting the hysteresis in the relationship between the depth of the snowpack (or SWE) and its extent within a MODIS pixel. Then, a set of Landsat images is used to validate MOD10A1 and MYD10A1 for 157 dates between 2002 and 2010. The resulting accuracies are 97% (κ = 0.85) for MOD10A1 and 96% (κ = 0.81) for MYD10A1, which indicates a good agreement between both data sets. The effect of vegetation on the results is analyzed by filtering the forested areas using a land cover map. As expected, the accuracies decrease over the forests but the agreement remains acceptable (MOD10A1: 96%, κ = 0.77; MYD10A1: 95%, κ = 0.67). We conclude that MODIS snow products have a sufficient accuracy for hydroclimate studies at the scale of the Pyrenees range. Using a gap-filling algorithm we generate a consistent snow cover climatology, which allows us to compute the mean monthly snow cover duration per elevation band and aspect classes. There is snow on the ground at least 50% of the

Surface energy balance of seasonal snow cover for snow-melt ...

Indian Academy of Sciences (India)

This study describes time series analysis of snow-melt, radiation data and energy balance for a seasonal snow cover at Dhundi field station of SASE, which lies in Pir Panjal range of the. N–W Himalaya, for a winter season from 13 January to 12 April 2005. The analysis shows that mean snow surface temperature remains ...

Constraining snowmelt in a temperature-index model using simulated snow densities

KAUST Repository

Bormann, Kathryn J.

2014-09-01

Current snowmelt parameterisation schemes are largely untested in warmer maritime snowfields, where physical snow properties can differ substantially from the more common colder snow environments. Physical properties such as snow density influence the thermal properties of snow layers and are likely to be important for snowmelt rates. Existing methods for incorporating physical snow properties into temperature-index models (TIMs) require frequent snow density observations. These observations are often unavailable in less monitored snow environments. In this study, previous techniques for end-of-season snow density estimation (Bormann et al., 2013) were enhanced and used as a basis for generating daily snow density data from climate inputs. When evaluated against 2970 observations, the snow density model outperforms a regionalised density-time curve reducing biases from -0.027gcm-3 to -0.004gcm-3 (7%). The simulated daily densities were used at 13 sites in the warmer maritime snowfields of Australia to parameterise snowmelt estimation. With absolute snow water equivalent (SWE) errors between 100 and 136mm, the snow model performance was generally lower in the study region than that reported for colder snow environments, which may be attributed to high annual variability. Model performance was strongly dependent on both calibration and the adjustment for precipitation undercatch errors, which influenced model calibration parameters by 150-200%. Comparison of the density-based snowmelt algorithm against a typical temperature-index model revealed only minor differences between the two snowmelt schemes for estimation of SWE. However, when the model was evaluated against snow depths, the new scheme reduced errors by up to 50%, largely due to improved SWE to depth conversions. While this study demonstrates the use of simulated snow density in snowmelt parameterisation, the snow density model may also be of broad interest for snow depth to SWE conversion. Overall, the

Constraining snowmelt in a temperature-index model using simulated snow densities

KAUST Repository

Bormann, Kathryn J.; Evans, Jason P.; McCabe, Matthew

2014-01-01

Current snowmelt parameterisation schemes are largely untested in warmer maritime snowfields, where physical snow properties can differ substantially from the more common colder snow environments. Physical properties such as snow density influence the thermal properties of snow layers and are likely to be important for snowmelt rates. Existing methods for incorporating physical snow properties into temperature-index models (TIMs) require frequent snow density observations. These observations are often unavailable in less monitored snow environments. In this study, previous techniques for end-of-season snow density estimation (Bormann et al., 2013) were enhanced and used as a basis for generating daily snow density data from climate inputs. When evaluated against 2970 observations, the snow density model outperforms a regionalised density-time curve reducing biases from -0.027gcm-3 to -0.004gcm-3 (7%). The simulated daily densities were used at 13 sites in the warmer maritime snowfields of Australia to parameterise snowmelt estimation. With absolute snow water equivalent (SWE) errors between 100 and 136mm, the snow model performance was generally lower in the study region than that reported for colder snow environments, which may be attributed to high annual variability. Model performance was strongly dependent on both calibration and the adjustment for precipitation undercatch errors, which influenced model calibration parameters by 150-200%. Comparison of the density-based snowmelt algorithm against a typical temperature-index model revealed only minor differences between the two snowmelt schemes for estimation of SWE. However, when the model was evaluated against snow depths, the new scheme reduced errors by up to 50%, largely due to improved SWE to depth conversions. While this study demonstrates the use of simulated snow density in snowmelt parameterisation, the snow density model may also be of broad interest for snow depth to SWE conversion. Overall, the

Neutrophils, dendritic cells and Toxoplasma.

Science.gov (United States)

Denkers, Eric Y; Butcher, Barbara A; Del Rio, Laura; Bennouna, Soumaya

2004-03-09

Toxoplasma gondii rapidly elicits strong Type 1 cytokine-based immunity. The necessity for this response is well illustrated by the example of IFN-gamma and IL-12 gene knockout mice that rapidly succumb to the effects of acute infection. The parasite itself is skilled at sparking complex interactions in the innate immune system that lead to protective immunity. Neutrophils are one of the first cell types to arrive at the site of infection, and the cells release several proinflammatory cytokines and chemokines in response to Toxoplasma. Dendritic cells are an important source of IL-12 during infection with T. gondii and other microbial pathogens, and they are also specialized for high-level antigen presentation to T lymphocytes. Tachyzoites express at least two types of molecules that trigger innate immune cell cytokine production. One of these involves Toll-like receptor/MyD88 pathways common to many microbial pathogens. The second pathway is less conventional and involves molecular mimicry between a parasite cyclophilin and host CC chemokine receptor 5-binding ligands. Neutrophils, dendritic cells and Toxoplasma work together to elicit the immune response required for host survival. Cytokine and chemokine cross-talk between parasite-triggered neutrophils and dendritic cells results in recruitment, maturation and activation of the latter. Neutrophil-empowered dendritic cells possess properties expected of highly potent antigen presenting cells that drive T helper 1 generation.

The AMSR2 Satellite-based Microwave Snow Algorithm (SMSA) to estimate regional to global snow depth and snow water equivalent

Science.gov (United States)

Kelly, R. E. J.; Saberi, N.; Li, Q.

2017-12-01

With moderate to high spatial resolution (observation approaches yet to be fully scoped and developed, the long-term satellite passive microwave record remains an important tool for cryosphere-climate diagnostics. A new satellite microwave remote sensing approach is described for estimating snow depth (SD) and snow water equivalent (SWE). The algorithm, called the Satellite-based Microwave Snow Algorithm (SMSA), uses Advanced Microwave Scanning Radiometer - 2 (AMSR2) observations aboard the Global Change Observation Mission - Water mission launched by the Japan Aerospace Exploration Agency in 2012. The approach is unique since it leverages observed brightness temperatures (Tb) with static ancillary data to parameterize a physically-based retrieval without requiring parameter constraints from in situ snow depth observations or historical snow depth climatology. After screening snow from non-snow surface targets (water bodies [including freeze/thaw state], rainfall, high altitude plateau regions [e.g. Tibetan plateau]), moderate and shallow snow depths are estimated by minimizing the difference between Dense Media Radiative Transfer model estimates (Tsang et al., 2000; Picard et al., 2011) and AMSR2 Tb observations to retrieve SWE and SD. Parameterization of the model combines a parsimonious snow grain size and density approach originally developed by Kelly et al. (2003). Evaluation of the SMSA performance is achieved using in situ snow depth data from a variety of standard and experiment data sources. Results presented from winter seasons 2012-13 to 2016-17 illustrate the improved performance of the new approach in comparison with the baseline AMSR2 algorithm estimates and approach the performance of the model assimilation-based approach of GlobSnow. Given the variation in estimation power of SWE by different land surface/climate models and selected satellite-derived passive microwave approaches, SMSA provides SWE estimates that are independent of real or near real

Functional Identification of Dendritic Cells in the Teleost Model, Rainbow Trout (Oncorhynchus mykiss)

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Bassity, Elizabeth; Clark, Theodore G.

2012-01-01

Dendritic cells are specialized antigen presenting cells that bridge innate and adaptive immunity in mammals. This link between the ancient innate immune system and the more evolutionarily recent adaptive immune system is of particular interest in fish, the oldest vertebrates to have both innate and adaptive immunity. It is unknown whether dendritic cells co-evolved with the adaptive response, or if the connection between innate and adaptive immunity relied on a fundamentally different cell type early in evolution. We approached this question using the teleost model organism, rainbow trout (Oncorhynchus mykiss), with the aim of identifying dendritic cells based on their ability to stimulate naïve T cells. Adapting mammalian protocols for the generation of dendritic cells, we established a method of culturing highly motile, non-adherent cells from trout hematopoietic tissue that had irregular membrane processes and expressed surface MHCII. When side-by-side mixed leukocyte reactions were performed, these cells stimulated greater proliferation than B cells or macrophages, demonstrating their specialized ability to present antigen and therefore their functional homology to mammalian dendritic cells. Trout dendritic cells were then further analyzed to determine if they exhibited other features of mammalian dendritic cells. Trout dendritic cells were found to have many of the hallmarks of mammalian DCs including tree-like morphology, the expression of dendritic cell markers, the ability to phagocytose small particles, activation by toll-like receptor-ligands, and the ability to migrate in vivo. As in mammals, trout dendritic cells could be isolated directly from the spleen, or larger numbers could be derived from hematopoietic tissue and peripheral blood mononuclear cells in vitro. PMID:22427987

Snow Monitoring Using Remote Sensing Data: Modification of Normalized Difference Snow Index

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Kaplan, G.; Avdan, U.

2016-12-01

Snow cover is an important part of the Earth`s climate system so its continuous monitoring is necessary to map snow cover in high resolution. Satellite remote sensing can successfully fetch land cover and land cover changes. Although normalized difference snow index NDSI has quite good accuracy, topography shadow, water bodies and clouds can be easily misplaced as snow. Using Landsat TM, +ETM and TIRS/OLI satellite images, the NDSI was modified for more accurate snow mapping. In this paper, elimination of the misplaced water bodies was made using the high reflectance of the snow in the blue band. Afterwards, the modified NDSI (MNDSI) was used for estimating snow cover through the years on the highest mountains in Republic of Macedonia. The results from this study show that the MNDSI accuracy is bigger than the NDSI`s, totally eliminating the misplaced water bodies, and partly the one caused from topography and clouds. Also, it was noticed that the snow cover in the study area has been lowered through the years. For future studies, the MNDSI should be validated on different study areas with different characteristics.

Iron snow in the Martian core?

Science.gov (United States)

Davies, Christopher J.; Pommier, Anne

2018-01-01

The decline of Mars' global magnetic field some 3.8-4.1 billion years ago is thought to reflect the demise of the dynamo that operated in its liquid core. The dynamo was probably powered by planetary cooling and so its termination is intimately tied to the thermochemical evolution and present-day physical state of the Martian core. Bottom-up growth of a solid inner core, the crystallization regime for Earth's core, has been found to produce a long-lived dynamo leading to the suggestion that the Martian core remains entirely liquid to this day. Motivated by the experimentally-determined increase in the Fe-S liquidus temperature with decreasing pressure at Martian core conditions, we investigate whether Mars' core could crystallize from the top down. We focus on the "iron snow" regime, where newly-formed solid consists of pure Fe and is therefore heavier than the liquid. We derive global energy and entropy equations that describe the long-timescale thermal and magnetic history of the core from a general theory for two-phase, two-component liquid mixtures, assuming that the snow zone is in phase equilibrium and that all solid falls out of the layer and remelts at each timestep. Formation of snow zones occurs for a wide range of interior and thermal properties and depends critically on the initial sulfur concentration, ξ0. Release of gravitational energy and latent heat during growth of the snow zone do not generate sufficient entropy to restart the dynamo unless the snow zone occupies at least 400 km of the core. Snow zones can be 1.5-2 Gyrs old, though thermal stratification of the uppermost core, not included in our model, likely delays onset. Models that match the available magnetic and geodetic constraints have ξ0 ≈ 10% and snow zones that occupy approximately the top 100 km of the present-day Martian core.

Role of nitrite in the photochemical formation of radicals in the snow.

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Jacobi, Hans-Werner; Kleffmann, Jörg; Villena, Guillermo; Wiesen, Peter; King, Martin; France, James; Anastasio, Cort; Staebler, Ralf

2014-01-01

Photochemical reactions in snow can have an important impact on the composition of the atmosphere over snow-covered areas as well as on the composition of the snow itself. One of the major photochemical processes is the photolysis of nitrate leading to the formation of volatile nitrogen compounds. We report nitrite concentrations determined together with nitrate and hydrogen peroxide in surface snow collected at the coastal site of Barrow, Alaska. The results demonstrate that nitrite likely plays a significant role as a precursor for reactive hydroxyl radicals as well as volatile nitrogen oxides in the snow. Pollution events leading to high concentrations of nitrous acid in the atmosphere contributed to an observed increase in nitrite in the surface snow layer during nighttime. Observed daytime nitrite concentrations are much higher than values predicted from steady-state concentrations based on photolysis of nitrate and nitrite indicating that we do not fully understand the production of nitrite and nitrous acid in snow. The discrepancy between observed and expected nitrite concentrations is probably due to a combination of factors, including an incomplete understanding of the reactive environment and chemical processes in snow, and a lack of consideration of the vertical structure of snow.

Improving snow density estimation for mapping SWE with Lidar snow depth: assessment of uncertainty in modeled density and field sampling strategies in NASA SnowEx

Science.gov (United States)

Raleigh, M. S.; Smyth, E.; Small, E. E.

2017-12-01

The spatial distribution of snow water equivalent (SWE) is not sufficiently monitored with either remotely sensed or ground-based observations for water resources management. Recent applications of airborne Lidar have yielded basin-wide mapping of SWE when combined with a snow density model. However, in the absence of snow density observations, the uncertainty in these SWE maps is dominated by uncertainty in modeled snow density rather than in Lidar measurement of snow depth. Available observations tend to have a bias in physiographic regime (e.g., flat open areas) and are often insufficient in number to support testing of models across a range of conditions. Thus, there is a need for targeted sampling strategies and controlled model experiments to understand where and why different snow density models diverge. This will enable identification of robust model structures that represent dominant processes controlling snow densification, in support of basin-scale estimation of SWE with remotely-sensed snow depth datasets. The NASA SnowEx mission is a unique opportunity to evaluate sampling strategies of snow density and to quantify and reduce uncertainty in modeled snow density. In this presentation, we present initial field data analyses and modeling results over the Colorado SnowEx domain in the 2016-2017 winter campaign. We detail a framework for spatially mapping the uncertainty in snowpack density, as represented across multiple models. Leveraging the modular SUMMA model, we construct a series of physically-based models to assess systematically the importance of specific process representations to snow density estimates. We will show how models and snow pit observations characterize snow density variations with forest cover in the SnowEx domains. Finally, we will use the spatial maps of density uncertainty to evaluate the selected locations of snow pits, thereby assessing the adequacy of the sampling strategy for targeting uncertainty in modeled snow density.

Separate transcriptionally regulated pathways specify distinct classes of sister dendrites in a nociceptive neuron.

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O'Brien, Barbara M J; Palumbos, Sierra D; Novakovic, Michaela; Shang, Xueying; Sundararajan, Lakshmi; Miller, David M

2017-12-15

The dendritic processes of nociceptive neurons transduce external signals into neurochemical cues that alert the organism to potentially damaging stimuli. The receptive field for each sensory neuron is defined by its dendritic arbor, but the mechanisms that shape dendritic architecture are incompletely understood. Using the model nociceptor, the PVD neuron in C. elegans, we determined that two types of PVD lateral branches project along the dorsal/ventral axis to generate the PVD dendritic arbor: (1) Pioneer dendrites that adhere to the epidermis, and (2) Commissural dendrites that fasciculate with circumferential motor neuron processes. Previous reports have shown that the LIM homeodomain transcription factor MEC-3 is required for all higher order PVD branching and that one of its targets, the claudin-like membrane protein HPO-30, preferentially promotes outgrowth of pioneer branches. Here, we show that another MEC-3 target, the conserved TFIIA-like zinc finger transcription factor EGL-46, adopts the alternative role of specifying commissural dendrites. The known EGL-46 binding partner, the TEAD transcription factor EGL-44, is also required for PVD commissural branch outgrowth. Double mutants of hpo-30 and egl-44 show strong enhancement of the lateral branching defect with decreased numbers of both pioneer and commissural dendrites. Thus, HPO-30/Claudin and EGL-46/EGL-44 function downstream of MEC-3 and in parallel acting pathways to direct outgrowth of two distinct classes of PVD dendritic branches. Copyright © 2017 Elsevier Inc. All rights reserved.

Active action potential propagation but not initiation in thalamic interneuron dendrites

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Casale, Amanda E.; McCormick, David A.

2012-01-01

Inhibitory interneurons of the dorsal lateral geniculate nucleus of the thalamus modulate the activity of thalamocortical cells in response to excitatory input through the release of inhibitory neurotransmitter from both axons and dendrites. The exact mechanisms by which release can occur from dendrites are, however, not well understood. Recent experiments using calcium imaging have suggested that Na/K based action potentials can evoke calcium transients in dendrites via local active conductances, making the back-propagating action potential a candidate for dendritic neurotransmitter release. In this study, we employed high temporal and spatial resolution voltage-sensitive dye imaging to assess the characteristics of dendritic voltage deflections in response to Na/K action potentials in interneurons of the mouse dorsal lateral geniculate nucleus. We found that trains or single action potentials elicited by somatic current injection or local synaptic stimulation led to action potentials that rapidly and actively back-propagated throughout the entire dendritic arbor and into the fine filiform dendritic appendages known to release GABAergic vesicles. Action potentials always appeared first in the soma or proximal dendrite in response to somatic current injection or local synaptic stimulation, and the rapid back-propagation into the dendritic arbor depended upon voltage-gated sodium and TEA-sensitive potassium channels. Our results indicate that thalamic interneuron dendrites integrate synaptic inputs that initiate action potentials, most likely in the axon initial segment, that then back-propagate with high-fidelity into the dendrites, resulting in a nearly synchronous release of GABA from both axonal and dendritic compartments. PMID:22171033

Snow multivariable data assimilation for hydrological predictions in mountain areas

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Piazzi, Gaia; Campo, Lorenzo; Gabellani, Simone; Rudari, Roberto; Castelli, Fabio; Cremonese, Edoardo; Morra di Cella, Umberto; Stevenin, Hervé; Ratto, Sara Maria

2016-04-01

The seasonal presence of snow on alpine catchments strongly impacts both surface energy balance and water resource. Thus, the knowledge of the snowpack dynamics is of critical importance for several applications, such as water resource management, floods prediction and hydroelectric power production. Several independent data sources provide information about snowpack state: ground-based measurements, satellite data and physical models. Although all these data types are reliable, each of them is affected by specific flaws and errors (respectively dependency on local conditions, sensor biases and limitations, initialization and poor quality forcing data). Moreover, there are physical factors that make an exhaustive reconstruction of snow dynamics complicated: snow intermittence in space and time, stratification and slow phenomena like metamorphism processes, uncertainty in snowfall evaluation, wind transportation, etc. Data Assimilation (DA) techniques provide an objective methodology to combine observational and modeled information to obtain the most likely estimate of snowpack state. Indeed, by combining all the available sources of information, the implementation of DA schemes can quantify and reduce the uncertainties of the estimations. This study presents SMASH (Snow Multidata Assimilation System for Hydrology), a multi-layer snow dynamic model, strengthened by a robust multivariable data assimilation algorithm. The model is physically based on mass and energy balances and can be used to reproduce the main physical processes occurring within the snowpack: accumulation, density dynamics, melting, sublimation, radiative balance, heat and mass exchanges. The model is driven by observed forcing meteorological data (air temperature, wind velocity, relative air humidity, precipitation and incident solar radiation) to provide a complete estimate of snowpack state. The implementation of an Ensemble Kalman Filter (EnKF) scheme enables to assimilate simultaneously ground

Evaluating the Effects of Cytomegalovirus Glycoprotein B on the Maturation and Function of Monocyte-derived dendritic cells

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Afsson shariat

2015-11-01

Full Text Available Background & Objectives: Interaction of cytomegalovirus glycoprotein B with toll-like receptors of dendritic cells leads to early signaling and innate immune responses. The aim of this study is to evaluate the effects of cytomegalovirus glycoprotein B on the maturation and function of monocyte-derived dendritic cells in treated groups in comparison with control groups. Materials & Methods: Blood samples were taken from 5 healthy volunteers. Following the generation of monocyte-derived dendritic cells on the fifth day of cell culture, half of the immature dendritic cells were treated with cytomegalovirus glycoprotein B, and the rest of them were induced to mature dendritic untreated cells and were used as the control group. The maturation and function of dendritic cells were evaluated in these two groups. Results: The gene expression level of toll-like receptor-4 significantly increased in the group treated with glycoprotein B (p < 0.05, whereas there were no significant differences in the expression rates of CD83, CD86, CD1a, and HLA-DR and the secretion of IL-23 from monocyte-derived dendritic cells between the treated groups and the controls. Conclusion: The increase in the gene expression of toll-like receptor-4 in monocyte-derived dendritic cells treated with cytomegalovirus glycoprotein B showed that cell contact is required to elicit cellular antiviral response and toll-like receptor activation. Thus, it is critical to recognize the viral and cellular determinants of the immune system in order to develop new therapeutic strategies against cytomegalovirus.

Energy expenditure and clearing snow: a comparison of shovel and snow pusher.

Science.gov (United States)

Smolander, J; Louhevaara, V; Ahonen, E; Polari, J; Klen, T

1995-04-01

In order to assess the energy demands of manual clearing of snow, nine men did snow clearing work for 15 min with a shovel and a snow pusher. The depth of the snowcover was 400-600 mm representing a very heavy snowfall. Heart rate (HR), oxygen consumption (VO2), pulmonary ventilation (VE), respiratory exchange ratio (R), and rating of perceived exertion (RPE) were determined during the work tasks. HR, VE, R, and RPE were not significantly different between the shovel and snow pusher. HR averaged (+/- SD) 141 +/- 20 b min-1 with the shovel, and 142 +/- 19 beats.min-1 with the snow pusher. VO2 was 2.1 +/- 0.41.min-1 (63 +/- 12%VO2 max) in shovelling and 2.6 +/- 0.51.min-1 (75 +/- 14%VO2max) in snow pushing (p < 0.001). In conclusion manual clearing of snow in conditions representing heavy snowfalls was found to be strenuous physical work, not suitable for persons with cardiac risk factors, but which may serve as a mode of physical training in healthy adults.

Springtime warming and reduced snow cover from carbonaceous particles

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M. G. Flanner

2009-04-01

Full Text Available Boreal spring climate is uniquely susceptible to solar warming mechanisms because it has expansive snow cover and receives relatively strong insolation. Carbonaceous particles can influence snow coverage by warming the atmosphere, reducing surface-incident solar energy (dimming, and reducing snow reflectance after deposition (darkening. We apply a range of models and observations to explore impacts of these processes on springtime climate, drawing several conclusions: 1 Nearly all atmospheric particles (those with visible-band single-scatter albedo less than 0.999, including all mixtures of black carbon (BC and organic matter (OM, increase net solar heating of the atmosphere-snow column. 2 Darkening caused by small concentrations of particles within snow exceeds the loss of absorbed energy from concurrent dimming, thus increasing solar heating of snowpack as well (positive net surface forcing. Over global snow, we estimate 6-fold greater surface forcing from darkening than dimming, caused by BC+OM. 3 Equilibrium climate experiments suggest that fossil fuel and biofuel emissions of BC+OM induce 95% as much springtime snow cover loss over Eurasia as anthropogenic carbon dioxide, a consequence of strong snow-albedo feedback and large BC+OM emissions from Asia. 4 Of 22 climate models contributing to the IPCC Fourth Assessment Report, 21 underpredict the rapid warming (0.64°C decade⁻¹ observed over springtime Eurasia since 1979. Darkening from natural and anthropogenic sources of BC and mineral dust exerts 3-fold greater forcing on springtime snow over Eurasia (3.9 W m⁻² than North America (1.2 W m⁻². Inclusion of this forcing significantly improves simulated continental warming trends, but does not reconcile the low bias in rate of Eurasian spring snow cover decline exhibited by all models, likely because BC deposition trends are negative or near-neutral over much of Eurasia. Improved Eurasian

Enhanced solar energy absorption by internally-mixed black carbon in snow grains

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M. G. Flanner

2012-05-01

Full Text Available Here we explore light absorption by snowpack containing black carbon (BC particles residing within ice grains. Basic considerations of particle volumes and BC/snow mass concentrations show that there are generally 0.05–10⁹ BC particles for each ice grain. This suggests that internal BC is likely distributed as multiple inclusions within ice grains, and thus the dynamic effective medium approximation (DEMA (Chýlek and Srivastava, 1983 is a more appropriate optical representation for BC/ice composites than coated-sphere or standard mixing approximations. DEMA calculations show that the 460 nm absorption cross-section of BC/ice composites, normalized to the mass of BC, is typically enhanced by factors of 1.8–2.1 relative to interstitial BC. BC effective radius is the dominant cause of variation in this enhancement, compared with ice grain size and BC volume fraction. We apply two atmospheric aerosol models that simulate interstitial and within-hydrometeor BC lifecycles. Although only ~2% of the atmospheric BC burden is cloud-borne, 71–83% of the BC deposited to global snow and sea-ice surfaces occurs within hydrometeors. Key processes responsible for within-snow BC deposition are development of hydrophilic coatings on BC, activation of liquid droplets, and subsequent snow formation through riming or ice nucleation by other species and aggregation/accretion of ice particles. Applying deposition fields from these aerosol models in offline snow and sea-ice simulations, we calculate that 32–73% of BC in global surface snow resides within ice grains. This fraction is smaller than the within-hydrometeor deposition fraction because meltwater flux preferentially removes internal BC, while sublimation and freezing within snowpack expose internal BC. Incorporating the DEMA into a global climate model, we simulate increases in BC/snow radiative forcing of 43–86%, relative to scenarios that apply external optical properties to all BC. We

Enhanced Solar Energy Absorption by Internally-mixed Black Carbon in Snow Grains

Energy Technology Data Exchange (ETDEWEB)

Flanner, M. G.; Liu, Xiaohong; Zhou, Cheng; Penner, Joyce E.; Jiao, C.

2012-05-30

Here we explore light absorption by snowpack containing black carbon (BC) particles residing within ice grains. Basic considerations of particle volumes and BC/snow mass concentrations show that there are generally 0:05-109 BC particles for each ice grain. This suggests that internal BC is likely distributed as multiple inclusions within ice grains, and thus the dynamic effective medium approximation (DEMA) (Chylek and Srivastava, 1983) is a more appropriate optical representation for BC/ice composites than coated-sphere or standard mixing approximations. DEMA calculations show that the 460 nm absorption cross-section of BC/ice composites, normalized to the mass of BC, is typically enhanced by factors of 1.8-2.1 relative to interstitial BC. BC effective radius is the dominant cause of variation in this enhancement, compared with ice grain size and BC volume fraction. We apply two atmospheric aerosol models that simulate interstitial and within-hydrometeor BC lifecycles. Although only {approx}2% of the atmospheric BC burden is cloud-borne, 71-83% of the BC deposited to global snow and sea-ice surfaces occurs within hydrometeors. Key processes responsible for within-snow BC deposition are development of hydrophilic coatings on BC, activation of liquid droplets, and subsequent snow formation through riming or ice nucleation by other species and aggregation/accretion of ice particles. Applying deposition fields from these aerosol models in offline snow and sea-ice simulations, we calculate that 32-73% of BC in global surface snow resides within ice grains. This fraction is smaller than the within-hydrometeor deposition fraction because meltwater flux preferentially removes internal BC, while sublimation and freezing within snowpack expose internal BC. Incorporating the DEMA into a global climate model, we simulate increases in BC/snow radiative forcing of 43-86%, relative to scenarios that apply external optical properties to all BC. We show that snow metamorphism

Proton receptor GPR68 expression in dendritic-cell-like S100β-positive cells of rat anterior pituitary gland: GPR68 induces interleukin-6 gene expression in extracellular acidification.

Science.gov (United States)

Horiguchi, Kotaro; Higuchi, Masashi; Yoshida, Saishu; Nakakura, Takashi; Tateno, Kozue; Hasegawa, Rumi; Takigami, Shu; Ohsako, Shunji; Kato, Takako; Kato, Yukio

2014-11-01

S100β-positive cells, which do not express the classical pituitary hormones, appear to possess multifunctional properties and are assumed to be heterogeneous in the anterior pituitary gland. The presence of several protein markers has shown that S100β-positive cells are composed of populations such as stem/progenitor cells, epithelial cells, astrocytes and dendritic cells. Recently, we succeeded in separating S100β-positive cells into round-cell (dendritic-cell-like) and process-cell types. We also found the characteristic expression of anti-inflammatory factors (interleukin-6, Il-6) and membrane receptors (integrin β-6) in the round type. Here, we further investigate the function of the subpopulation of S100β-positive cells. Since IL-6 is also a paracrine factor that regulates hormone producing-cells, we examine whether a correlation exists among extracellular acid stress, IL-6 and hormone production by using primary cultures of anterior pituitary cells. Dendritic-cell-like S100β-positive cells notably expressed Gpr68 (proton receptor) and Il-6. Furthermore, the expression of Il-6 and proopiomelanocortin (Pomc) was up-regulated by extracellular acidification. The functional role of IL-6 and GPR68 in the gene expression of Pomc during extracellular acidification was also examined. Small interfering RNA for Il-6 up-regulated Pomc expression and that for Gpr68 reversed the down-regulation of Il-6 and up-regulated Pomc expression by extracellular acidification. Thus, S100β-positive dendritic-like cells can sense an increase in extracellular protons via GPR68 and respond by the production of IL-6 in order to suppress the up-regulation of Pomc expression.

Pulse reverse plating for integrated magnetics on Si

International Nuclear Information System (INIS)

Roy, S.; Connell, A.; Ludwig, M.; Wang, N.; O'Donnell, T.; Brunet, M.; McCloskey, P.; OMathuna, C.; Barman, A.; Hicken, R.J.

2005-01-01

Thin film microtransformers have been fabricated on silicon with Ni 45 Fe 55 as a core material. Fractal/dendritic growths are observed in the patterned cores in DC electroplating due to the enhancement of localized current density at defect/nucleation sites. A 'pulser' device was made in house to produce forward and reverse current of the required amplitude for a particular duration. The combination of a low amplitude long (millisecond) forward pulse and a short (microsecond) high-amplitude reverse pulse gave dendrite-free plated cores with a uniform thickness and alloy composition over a 3D topology of a microrough substrate surface. Finally, we characterized the material in situ by small signal electrical measurements, and with MOKE hysteresis loops measured on a complete device

Membrane-associated IL 1-like activity on rat dendritic cells

International Nuclear Information System (INIS)

Nagelkerken, L.M.; van Breda Vriesman, P.J.C.

1986-01-01

The secretion of interleukin 1 (IL 1) by rat dendritic cells (DC) was studied in relation to their ability to induce the production interleukin 2 (IL 2 ) and to induce IL 2 responsiveness. IL 1 (or IL 1-like activity) was measured by its capacity to enhance IL 2 production by EL4 cells. In contrast to peritoneal exudate cells (PEC) or splenic adherent cells, DC from thoracic duct lymph (TD-DC) or from spleen did not secrete detectable amounts of IL 1 on stimulation with LPS/Silica. However, TD-DC and splenic DC were able to enhance IL 2 production by EL4 cells directly, and were only two times less effective than PEC. By preventing cell-to-cell contact between stimulator cells and EL4 cells, it was demonstrated that most of the IL 2-inducing activity of TD-DC and PEC was associated with the cell membrane. Treatment with 1% paraformaldehyde (PFA) to abolish metabolic activity resulted in a 50% decrease (or inactivation) of IL 2-inducing activity of TD-DC in the EL4 assay. Moreover, UVB-irradiation (300 mJ/cm 2 ) of TD-DC, which has been described to inhibit the release of IL 1 by macrophages, caused a 70% decrease in IL 2-inducing activity. These results suggest that membrane-associated structures, that are identical to or mimic Il 1, are involved in the activation of T cells by DC

The SKINT1-like gene is inactivated in hominoids but not in all primate species: implications for the origin of dendritic epidermal T cells.

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Rania Hassan Mohamed

Full Text Available Dendritic epidermal T cells, which express an invariant Vγ5Vδ1 T-cell receptor and account for 95% of all resident T cells in the mouse epidermis, play a critical role in skin immune surveillance. These γδ T cells are generated by positive selection in the fetal thymus, after which they migrate to the skin. The development of dendritic epidermal T cells is critically dependent on the Skint1 gene expressed specifically in keratinocytes and thymic epithelial cells, suggesting an indispensable role for Skint1 in the selection machinery for specific intraepithelial lymphocytes. Phylogenetically, rodents have functional SKINT1 molecules, but humans and chimpanzees have a SKINT1-like (SKINT1L gene with multiple inactivating mutations. In the present study, we analyzed SKINT1L sequences in representative primate species and found that all hominoid species have a common inactivating mutation, but that Old World monkeys such as olive baboons, green monkeys, cynomolgus macaques and rhesus macaques have apparently functional SKINT1L sequences, indicating that SKINT1L was inactivated in a common ancestor of hominoids. Interestingly, the epidermis of cynomolgus macaques contained a population of dendritic-shaped γδ T cells expressing a semi-invariant Vγ10/Vδ1 T-cell receptor. However, this population of macaque T cells differed from rodent dendritic epidermal T cells in that their Vγ10/Vδ1 T-cell receptors displayed junctional diversity and expression of Vγ10 was not epidermis-specific. Therefore, macaques do not appear to have rodent-type dendritic epidermal T cells despite having apparently functional SKINT1L. Comprehensive bioinformatics analysis indicates that SKINT1L emerged in an ancestor of placental mammals but was inactivated or lost multiple times in mammalian evolution and that Skint1 arose by gene duplication in a rodent lineage, suggesting that authentic dendritic epidermal T cells are presumably unique to rodents.

Storing snow for the next winter: Two case studies on the application of snow farming.

Science.gov (United States)

Grünewald, Thomas; Wolfsperger, Fabian

2016-04-01

Snow farming is the conservation of snow during the warm half-year. This means that large piles of snow are formed in spring in order to be conserved over the summer season. Well-insulating materials such as chipped wood are added as surface cover to reduce melting. The aim of snow farming is to provide a "snow guaranty" for autumn or early winter - this means that a specific amount of snow will definitively be available, independent of the weather conditions. The conserved snow can then be used as basis for the preparation of winter sports grounds such as cross-country tracks or ski runs. This helps in the organization of early winter season sport events such as World Cup races or to provide appropriate training conditions for athletes. We present a study on two snow farming projects, one in Davos (Switzerland) and one in the Martell valley of South Tyrol. At both places snow farming has been used for several years. For the summer season 2015, we monitored both snow piles in order to assess the amount of snow conserved. High resolution terrestrial laser scanning was performed to measure snow volumes of the piles at the beginning and at the end of the summer period. Results showed that only 20% to 30 % of the snow mass was lost due to ablation. This mass loss was surprisingly low considering the extremely warm and dry summer. In order to identify the most relevant drivers of snow melt we also present simulations with the sophisticated snow cover models SNOWPACK and Alpine3D. The simulations are driven by meteorological input data recorded in the vicinity of the piles and enable a detailed analysis of the relevant processes controlling the energy balance. The models can be applied to optimize settings for snow farming and to examine the suitability of new locations, configurations or cover material for future snow farming projects.

Dendritic cell neoplasms: an overview.

Science.gov (United States)

Kairouz, Sebastien; Hashash, Jana; Kabbara, Wadih; McHayleh, Wassim; Tabbara, Imad A

2007-10-01

Dendritic cell neoplasms are rare tumors that are being recognized with increasing frequency. They were previously classified as lymphomas, sarcomas, or histiocytic neoplasms. The World Health Organization (WHO) classifies dendritic cell neoplasms into five groups: Langerhans' cell histiocytosis, Langerhans' cell sarcoma, Interdigitating dendritic cell sarcoma/tumor, Follicular dendritic cell sarcoma/tumor, and Dendritic cell sarcoma, not specified otherwise (Jaffe, World Health Organization classification of tumors 2001; 273-289). Recently, Pileri et al. provided a comprehensive immunohistochemical classification of histiocytic and dendritic cell tumors (Pileri et al., Histopathology 2002;59:161-167). In this article, a concise overview regarding the pathological, clinical, and therapeutic aspects of follicular dendritic, interdigitating dendritic, and Langerhans' cell tumors is presented.

A Rapid Culture Technique Produces Functional Dendritic-Like Cells from Human Acute Myeloid Leukemia Cell Lines

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Jian Ning

2011-01-01

Full Text Available Most anti-cancer immunotherapeutic strategies involving dendritic cells (DC as vaccines rely upon the adoptive transfer of DC loaded with exogenous tumour-peptides. This study utilized human acute myeloid leukemia (AML cells as progenitors from which functional dendritic-like antigen presenting cells (DLC were generated, that constitutively express tumour antigens for recognition by CD8+ T cells. DLC were generated from AML cell lines KG-1 and MUTZ-3 using rapid culture techniques and appropriate cytokines. DLC were evaluated for their cell-surface phenotype, antigen uptake and ability to stimulate allogeneic responder cell proliferation, and production of IFN-γ; compared with DC derived from normal human PBMC donors. KG-1 and MUTZ-3 DLC increased expression of CD80, CD83, CD86, and HLA-DR, and MUTZ-3 DLC downregulated CD14 and expressed CD1a. Importantly, both KG-1 and MUTZ-3-derived DLC promoted proliferation of allogeneic responder cells more efficiently than unmodified cells; neither cells incorporated FITC-labeled dextran, but both stimulated IFN-γ production from responding allogeneic CD8+ T cells. Control DC produced from PBMC using the FastDC culture also expressed high levels of critical cell surface ligands and demonstrated good APC function. This paper indicates that functional DLC can be cultured from the AML cell lines KG-1 and MUTZ-3, and FastDC culture generates functional KG-1 DLC.

Past and future of the Austrian snow cover - results from the CC-Snow project

Science.gov (United States)

Strasser, Ulrich; Marke, Thomas; Hanzer, Florian; Ragg, Hansjörg; Kleindienst, Hannes; Wilcke, Renate; Gobiet, Andreas

2013-04-01

This study has the goal to simulate the evolution of the Austrian snow cover from 1971 to 2050 by means of a coupled modelling scheme, and to estimate the effect of climate change on the evolution of the natural snow cover. The model outcomes are interepreted with focus on both the future natural snow conditions, and the effects on winter skiing tourism. Therefore the regional temperature-index snow model SNOWREG is applied, providing snow maps with a spatial resolution of 250 m. The model is trained by means of assimilating local measurements and observed natural snow cover patterns. Meteorological forcing consists of the output of four realizations of the ENSEMBLES project for the A1B emission scenario. The meteorological variables are downscaled and error corrected with a quantile based empirical-statistical method on a daily time basis. The control simulation is 1971-2000, and the scenario simulation 2021-2050. Spatial interpolation is performed on the basis of parameter-elevation relations. We compare the four different global/regional climate model combinations and their effect on the snow modelling, and we explain the patterns of the resulting snow cover by means of regional climatological characteristics. The provinces Tirol and Styria serve as test regions, being typical examples for the two climatic subregions of Austria. To support the interpretation of the simulation results we apply indicators which enable to define meaningful measures for the comparison of the different periods and regions. Results show that the mean duration of the snow cover will decrease by 15 to 30 days per winter season, mostly in elevations between 2000 and 2500 m. Above 3000 m the higher winter precipitation can compensate this effect, and mean snow cover duration may even slightly increase. We also investigate the local scale by application of the physically based mountain snow model AMUNDSEN. This model is capable of producing 50 m resolution output maps for indicators

Snow mechanics and avalanche formation: field experiments on the dynamic response of the snow cover

Science.gov (United States)

Schweizer, Jürg; Schneebeli, Martin; Fierz, Charles; Föhn, Paul M. B.

1995-11-01

Knowledge about snow mechanics and snow avalanche formation forms the basis of any hazard mitigation measures. The crucial point is the snow stability. The most relevant mechanical properties - the compressive, tensile and shear strength of the individual snow layers within the snow cover - vary substantially in space and time. Among other things the strength of the snow layers depends strongly on the state of stress and the strain rate. The evaluation of the stability of the snow cover is hence a difficult task involving many extrapolations. To gain insight in the release mechanism of slab avalanches triggered by skiers, the skier's impact is measured with a load cell at different depths within the snow cover and for different snow conditions. The study focused on the effects of the dynamic loading and of the damping by snow compaction. In accordance with earlier finite-element (FE) calculations the results show the importance of the depth of the weak layer or interface and the snow conditions, especially the sublayering. In order to directly measure the impact force and to study the snow properties in more detail, a new instrument, called rammrutsch was developed. It combines the properties of the rutschblock with the defined impact properties of the rammsonde. The mechanical properties are determined using (i) the impact energy of the rammrutsch and (ii) the deformations of the snow cover measured with accelerometers and digital image processing of video sequences. The new method is well suited to detect and to measure the mechanical processes and properties of the fracturing layers. The duration of one test is around 10 minutes and the method seems appropriate for determining the spatial variability of the snow cover. A series of experiments in a forest opening showed a clear difference in the snow stability between sites below trees and ones in the free field of the opening.

Snow cover dynamics and water balance in complex high alpine terrain

Science.gov (United States)

Warscher, Michael; Kraller, Gabriele; Kunstmann, Harald; Strasser, Ulrich; Franz, Helmut

2010-05-01

The water balance in high alpine regions in its full complexity is so far insufficiently understood. High altitudinal gradients, a strong variability of meteorological variables in time and space, complex hydrogeological situations, unquantified lateral snow transport processes and heterogenous snow cover dynamics result in high uncertainties in the quantification of the water balance. To achieve interpretable modeling results we have complemented the deterministic hydrological model WaSiM-ETH with the high-alpine specific snow model AMUNDSEN. The integration of the new snow module was done to improve the modeling of water fluxes influenced by the dynamics of the snow cover, which greatly affect the water cycle in high alpine regions. To enhance the reproduction of snow deposition and ablation processes, the new approach calculates the energy balance of the snow cover considering the terrain-dependent radiation fluxes, the interaction between tree canopy and snow cover as well as lateral snow transport processes. The test site for our study is the Berchtesgaden National Park which is characterized by an extreme topography with mountain ranges covering an altitude from 607 to 2713 m.a.s.l. About one quarter of the investigated catchment area, which comprises 433 km² in total, is terrain steeper than 35°. Due to water soluble limestone being predominant in the region, a high number of subsurface water pathways (karst) exist. The results of several tracer experiments and extensive data of spring observations provide additional information to meet the challenge of modeling the unknown subsurface pathways and the complex groundwater system of the region. The validation of the new snow module is based on a dense network of meteorological stations which have been adapted to measure physical properties of the snow cover like snow water equivalent and liquid water content. We will present first results which show that the integration of the new snow module generates a

Dendrite-Free Sodium-Metal Anodes for High-Energy Sodium-Metal Batteries.

Science.gov (United States)

Sun, Bing; Li, Peng; Zhang, Jinqiang; Wang, Dan; Munroe, Paul; Wang, Chengyin; Notten, Peter H L; Wang, Guoxiu

2018-05-31

Sodium (Na) metal is one of the most promising electrode materials for next-generation low-cost rechargeable batteries. However, the challenges caused by dendrite growth on Na metal anodes restrict practical applications of rechargeable Na metal batteries. Herein, a nitrogen and sulfur co-doped carbon nanotube (NSCNT) paper is used as the interlayer to control Na nucleation behavior and suppress the Na dendrite growth. The N- and S-containing functional groups on the carbon nanotubes induce the NSCNTs to be highly "sodiophilic," which can guide the initial Na nucleation and direct Na to distribute uniformly on the NSCNT paper. As a result, the Na-metal-based anode (Na/NSCNT anode) exhibits a dendrite-free morphology during repeated Na plating and striping and excellent cycling stability. As a proof of concept, it is also demonstrated that the electrochemical performance of sodium-oxygen (Na-O 2 ) batteries using the Na/NSCNT anodes show significantly improved cycling performances compared with Na-O 2 batteries with bare Na metal anodes. This work opens a new avenue for the development of next-generation high-energy-density sodium-metal batteries. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-resolution LIDAR and ground observations of snow cover in a complex forested terrain in the Sierra Nevada - implications for optical remote sensing of seasonal snow.

Science.gov (United States)

Kostadinov, T. S.; Harpold, A.; Hill, R.; McGwire, K.

2017-12-01

retrievals from hyperspectral imaging spectroradiometer (AVIRIS) data. Initial evidence suggest fSCA was generally lower under canopy and that overall snow cover estimates were overestimated as a result. Implications for a canopy correction applicable to coarser-resolution sensors like MODIS are discussed, as are topography and view angle effects.

Modelling snow accumulation and snow melt in a continuous hydrological model for real-time flood forecasting

International Nuclear Information System (INIS)

Stanzel, Ph; Haberl, U; Nachtnebel, H P

2008-01-01

Hydrological models for flood forecasting in Alpine basins need accurate representation of snow accumulation and snow melt processes. A continuous, semi-distributed rainfall-runoff model with snow modelling procedures using only precipitation and temperature as input is presented. Simulation results from an application in an Alpine Danube tributary watershed are shown and evaluated with snow depth measurements and MODIS remote sensing snow cover information. Seasonal variations of runoff due to snow melt were simulated accurately. Evaluation of simulated snow depth and snow covered area showed strengths and limitations of the model and allowed an assessment of input data quality. MODIS snow cover images were found to be valuable sources of information for hydrological modelling in alpine areas, where ground observations are scarce.

Modelling snow accumulation and snow melt in a continuous hydrological model for real-time flood forecasting

Energy Technology Data Exchange (ETDEWEB)

Stanzel, Ph; Haberl, U; Nachtnebel, H P [Institute of Water Management, Hydrology and Hydraulic Engineering, University of Natural Resources and Applied Life Sciences, Muthgasse 18, 1190 Vienna (Austria)], E-mail: philipp.stanzel@boku.ac.at

2008-11-01

Hydrological models for flood forecasting in Alpine basins need accurate representation of snow accumulation and snow melt processes. A continuous, semi-distributed rainfall-runoff model with snow modelling procedures using only precipitation and temperature as input is presented. Simulation results from an application in an Alpine Danube tributary watershed are shown and evaluated with snow depth measurements and MODIS remote sensing snow cover information. Seasonal variations of runoff due to snow melt were simulated accurately. Evaluation of simulated snow depth and snow covered area showed strengths and limitations of the model and allowed an assessment of input data quality. MODIS snow cover images were found to be valuable sources of information for hydrological modelling in alpine areas, where ground observations are scarce.

What color should snow algae be and what does it mean for glacier melt?

Science.gov (United States)

Dial, R. J.; Ganey, G. Q.; Loso, M.; Burgess, A. B.; Skiles, M.

2017-12-01

Specialized microbes colonize glaciers and ice sheets worldwide and, like all organisms, they are unable to metabolize water in its solid form. It is well understood that net solar radiation controls melt in almost all snow and ice covered environments, and theoretical and empirical studies have documented the substantial reduction of albedo by these microbes both on ice and on snow, implicating a microbial role in glacier melt. If glacial microbiomes are limited by liquid water, and the albedo-reducing properties of individual cells enhance melt rates, then natural selection should favor those microbes that melt ice and snow crystals most efficiently. Here we: (1) argue that natural selection favors a red color on snow and a near-black color on ice based on instantaneous radiative forcing. (2) Review results of the first replicated, controlled field experiment to both quantify the impact of microbes on snowmelt in "red-snow" communities and demonstrate their water-limitation and (3) show the extent of snow-algae's spatial distribution and estimate their contribution to snowmelt across a large Alaskan icefield using remote sensing. On the 700 km2 of a 2,000 km2 maritime icefield in Alaska where red-snow was present, microbes increased snowmelt over 20% by volume, a percentage likely to increase as the climate warms and particulate pollution intensifies with important implications for models of sea level rise.

Snow snake performance monitoring.

Science.gov (United States)

2008-12-01

A recent study, Three-Dimensional Roughness Elements for Snow Retention (FHWA-WY-06/04F) (Tabler 2006), demonstrated : positive evidence for the effectiveness of Snow Snakes, a new type of snow fence suitable for use within the highway right-of...

Scaling and Numerical Model Evaluation of Snow-Cover Effects on the Generation and Modification of Daytime Mesoscale Circulations.

Science.gov (United States)

Segal, M.; Garratt, J. R.; Pielke, R. A.; Ye, Z.

1991-04-01

Consideration of the sensible heat flux characteristics over a snow surface suggests a significant diminution in the magnitude of the flux, compared to that over a snow-free surface under the same environmental conditions. Consequently, the existence of snow-covered mesoscale areas adjacent to snow-free areas produces horizontal thermal gradients in the lower atmosphere during the daytime, possibly resulting in a `snow breeze.' In addition, suppression of the daytime thermally induced upslope flow over snow-covered slopes is likely to occur. The present paper provides scaling and modeling evaluations of these situations, with quantification of the generated and modified circulations. These evaluations suggest that under ideal situations involved with uniform snow cover over large areas, particularly in late winter and early spring, a noticeable `snow breeze' is likely to develop. Additionally: suppression of the daytime thermally induced upslope flow is significant and may even result in a daytime drainage flow. The effects of bare ground patchiness in the snow cover on these circulations are also explored, both for flat terrain and slope-flow situations. A patchiness fraction greater than 0.5 is found to result in a noticeably reduced snow-breeze circulation, while a patchiness fraction of only 0.1 caused the simulated daytime drainage flow over slopes to he reversed.

Simulating snow maps for Norway: description and statistical evaluation of the seNorge snow model

Directory of Open Access Journals (Sweden)

T. M. Saloranta

2012-11-01

Full Text Available Daily maps of snow conditions have been produced in Norway with the seNorge snow model since 2004. The seNorge snow model operates with 1 × 1 km resolution, uses gridded observations of daily temperature and precipitation as its input forcing, and simulates, among others, snow water equivalent (SWE, snow depth (SD, and the snow bulk density (ρ. In this paper the set of equations contained in the seNorge model code is described and a thorough spatiotemporal statistical evaluation of the model performance from 1957–2011 is made using the two major sets of extensive in situ snow measurements that exist for Norway. The evaluation results show that the seNorge model generally overestimates both SWE and ρ, and that the overestimation of SWE increases with elevation throughout the snow season. However, the R²-values for model fit are 0.60 for (log-transformed SWE and 0.45 for ρ, indicating that after removal of the detected systematic model biases (e.g. by recalibrating the model or expressing snow conditions in relative units the model performs rather well. The seNorge model provides a relatively simple, not very data-demanding, yet nonetheless process-based method to construct snow maps of high spatiotemporal resolution. It is an especially well suited alternative for operational snow mapping in regions with rugged topography and large spatiotemporal variability in snow conditions, as is the case in the mountainous Norway.

Dim light at night provokes depression-like behaviors and reduces CA1 dendritic spine density in female hamsters.

Science.gov (United States)

Bedrosian, Tracy A; Fonken, Laura K; Walton, James C; Haim, Abraham; Nelson, Randy J

2011-08-01

The prevalence of major depression has increased in recent decades; however, the underlying causes of this phenomenon remain unspecified. One environmental change that has coincided with elevated rates of depression is increased exposure to artificial light at night. Shift workers and others chronically exposed to light at night are at increased risk of mood disorders, suggesting that nighttime illumination may influence brain mechanisms mediating affect. We tested the hypothesis that exposure to dim light at night may impact affective responses and alter morphology of hippocampal neurons. Ovariectomized adult female Siberian hamsters (Phodopus sungorus) were housed for 8 weeks in either a light/dark cycle (LD) or a light/dim light cycle (DM), and then behavior was assayed. DM-hamsters displayed more depression-like responses in the forced swim and the sucrose anhedonia tests compared with LD-hamsters. Conversely, in the elevated plus maze DM-hamsters reduced anxiety-like behaviors. Brains from the same animals were processed using the Golgi-Cox method and hippocampal neurons within CA1, CA3, and the dentate gyrus were analyzed for morphological characteristics. In CA1, DM-hamsters significantly reduced dendritic spine density on both apical and basilar dendrites, an effect which was not mediated by baseline cortisol, as concentrations were equivalent between groups. These results demonstrate dim light at night is sufficient to reduce synaptic spine connections to CA1. Importantly, the present results suggest that night-time low level illumination, comparable to levels that are pervasive in North America and Europe, may contribute to the increasing prevalence of mood disorders. Copyright © 2011 Elsevier Ltd. All rights reserved.

A Particle Batch Smoother Approach to Snow Water Equivalent Estimation

Science.gov (United States)

Margulis, Steven A.; Girotto, Manuela; Cortes, Gonzalo; Durand, Michael

2015-01-01

This paper presents a newly proposed data assimilation method for historical snow water equivalent SWE estimation using remotely sensed fractional snow-covered area fSCA. The newly proposed approach consists of a particle batch smoother (PBS), which is compared to a previously applied Kalman-based ensemble batch smoother (EnBS) approach. The methods were applied over the 27-yr Landsat 5 record at snow pillow and snow course in situ verification sites in the American River basin in the Sierra Nevada (United States). This basin is more densely vegetated and thus more challenging for SWE estimation than the previous applications of the EnBS. Both data assimilation methods provided significant improvement over the prior (modeling only) estimates, with both able to significantly reduce prior SWE biases. The prior RMSE values at the snow pillow and snow course sites were reduced by 68%-82% and 60%-68%, respectively, when applying the data assimilation methods. This result is encouraging for a basin like the American where the moderate to high forest cover will necessarily obscure more of the snow-covered ground surface than in previously examined, less-vegetated basins. The PBS generally outperformed the EnBS: for snow pillows the PBSRMSE was approx.54%of that seen in the EnBS, while for snow courses the PBSRMSE was approx.79%of the EnBS. Sensitivity tests show relative insensitivity for both the PBS and EnBS results to ensemble size and fSCA measurement error, but a higher sensitivity for the EnBS to the mean prior precipitation input, especially in the case where significant prior biases exist.

Snow Precipitation and Snow Cover Climatic Variability for the Period 1971–2009 in the Southwestern Italian Alps: The 2008–2009 Snow Season Case Study

Directory of Open Access Journals (Sweden)

Simona Fratianni

2010-10-01

Full Text Available Snow cover greatly influences the climate in the Alpine region and is one of the most relevant parameters for the climate change analysis. Nevertheless, snow precipitation variability is a relatively underexplored field of research because of the lack of long-term, continuous and homogeneous time series. After a historical research aiming to recover continuous records, three high quality time series of snow precipitation and snow depth recorded in the southwestern Italian Alps were analyzed. The comparison between the climatological indices over the 30 years reference period 1971–2000 and the decade 2000–2009 outlined a general decrease in the amount of snow precipitation, and a shift in the seasonal distribution of the snow precipitation in the most recent period. In the analysis of the last decade snow seasons characteristics, the attention was focused on the heavy snowfalls that occurred in Piedmont during the 2008–2009 snow season: MODerate resolution Imager Spectroradiometer (MODIS snow cover products were used to evaluate snow cover extension at different times during the snow season, and the results were set in relation to the temperatures.

Canadian snow and sea ice: historical trends and projections

Science.gov (United States)

Mudryk, Lawrence R.; Derksen, Chris; Howell, Stephen; Laliberté, Fred; Thackeray, Chad; Sospedra-Alfonso, Reinel; Vionnet, Vincent; Kushner, Paul J.; Brown, Ross

2018-04-01

The Canadian Sea Ice and Snow Evolution (CanSISE) Network is a climate research network focused on developing and applying state of the art observational data to advance dynamical prediction, projections, and understanding of seasonal snow cover and sea ice in Canada and the circumpolar Arctic. Here, we present an assessment from the CanSISE Network on trends in the historical record of snow cover (fraction, water equivalent) and sea ice (area, concentration, type, and thickness) across Canada. We also assess projected changes in snow cover and sea ice likely to occur by mid-century, as simulated by the Coupled Model Intercomparison Project Phase 5 (CMIP5) suite of Earth system models. The historical datasets show that the fraction of Canadian land and marine areas covered by snow and ice is decreasing over time, with seasonal and regional variability in the trends consistent with regional differences in surface temperature trends. In particular, summer sea ice cover has decreased significantly across nearly all Canadian marine regions, and the rate of multi-year ice loss in the Beaufort Sea and Canadian Arctic Archipelago has nearly doubled over the last 8 years. The multi-model consensus over the 2020-2050 period shows reductions in fall and spring snow cover fraction and sea ice concentration of 5-10 % per decade (or 15-30 % in total), with similar reductions in winter sea ice concentration in both Hudson Bay and eastern Canadian waters. Peak pre-melt terrestrial snow water equivalent reductions of up to 10 % per decade (30 % in total) are projected across southern Canada.

Snow accretion on overhead wires

Energy Technology Data Exchange (ETDEWEB)

Sakamoto, Y. [Meteorological Research Inst. for Technology Co. Ltd., Tokyo (Japan); Tachizaki, S.; Sudo, N. [Tohoku Electric Power Co. Ltd., Miyagi (Japan)

2005-07-01

Wet snow accretion can cause extensive damage to transmission systems. This paper reviewed some of the difficulties faced by researchers in the study of wet snow accretion on overhead lines in Japan. The study of snow accretion phenomena is complicated by the range of phase changes in water. Snowflakes produced in an upper atmospheric layer with a temperature below freezing do not melt when they go through a lower atmospheric layer with a temperature above freezing, but are in a mixed state of solid and liquid due to the latent heat of melting. The complicated properties of water make studies of snow accretion difficult, as well as the fact that snow changes its physical properties rapidly, due to the effects of ambient temperature, rainfall, and solar radiation. The adhesive forces that cause snow accretion include freezing; bonding through freezing; sintering; condensation and freezing of vapor in the air; mechanical intertwining of snowflakes; capillary action due to liquids; coherent forces between ice particles and water formed through the metamorphosis of snowflakes. In addition to these complexities, differences in laboratory room environments and natural snow environments can also pose difficulties for researchers. Equations describing the relationship between the density of accreted snow and the meteorological parameters involved were presented, as well as empirical equations which suggested that snow accretion efficiency has a dependency on air temperature. An empirical model for estimating snow loads in Japan was outlined, as well as various experiments observing show shedding. Correlations for wet snow accretion included precipitation intensity; duration of precipitation; air temperature; wind speed and wind direction in relation to the overhead line. Issues concerning topography and wet snow accretion were reviewed. It was concluded that studies of snow accretion will benefit by the collection of data in each matrix of the relevant parameters. 12 refs

Estimation of Snow Particle Model Suitable for a Complex and Forested Terrain: Lessons from SnowEx

Science.gov (United States)

Gatebe, C. K.; Li, W.; Stamnes, K. H.; Poudyal, R.; Fan, Y.; Chen, N.

2017-12-01

SnowEx 2017 obtained consistent and coordinated ground and airborne remote sensing measurements over Grand Mesa in Colorado, which feature sufficient forested stands to have a range of density and height (and other forest conditions); a range of snow depth/snow water equivalent (SWE) conditions; sufficiently flat snow-covered terrain of a size comparable to airborne instrument swath widths. The Cloud Absorption Radiometer (CAR) data from SnowEx are unique and can be used to assess the accuracy of Bidirectional Reflectance-Distribution Functions (BRDFs) calculated by different snow models. These measurements provide multiple angle and multiple wavelength data needed for accurate surface BRDF characterization. Such data cannot easily be obtained by current satellite remote sensors. Compared to ground-based snow field measurements, CAR measurements minimize the effect of self-shading, and are adaptable to a wide variety of field conditions. We plan to use the CAR measurements as the validation data source for our snow modeling effort. By comparing calculated BRDF results from different snow models to CAR measurements, we can determine which model best explains the snow BRDFs, and is therefore most suitable for application to satellite remote sensing of snow parameters and surface energy budget calculations.

An electrostatic charge measurement of blowing snow particles focusing on collision frequency to the snow surface

Science.gov (United States)

Omiya, S.; Sato, A.

2010-12-01

Blowing snow particles are known to have an electrostatic charge. This charge may be a contributing factor in the formation of snow drifts and snow cornices and changing of the trajectory of blowing snow particles. These formations and phenomena can cause natural disaster such as an avalanche and a visibility deterioration, and obstruct transportation during winter season. Therefore, charging phenomenon of the blowing snow particles is an important issue in terms of not only precise understanding of the particle motion but disaster prevention. The primary factor of charge accumulation to the blowing snow particles is thought to be due to “saltation” of them. The “saltation” is one of movement forms of blowing snow: when the snow particles are transported by the wind, they repeat frictional collisions with the snow surface. In previous studies, charge-to-mass ratios measured in the field were approximately -50 to -10 μC/kg, and in the wind tunnel were approximately -0.8 to -0.1 μC/kg. While there were qualitatively consistent in sign, negative, there were huge gaps quantitatively between them. One reason of those gaps is speculated to be due to differences in fetch. In other words, the difference of the collision frequency of snow particles to the snow surface has caused the gaps. But it is merely a suggestion and that has not been confirmed. The purpose of this experiment is to measure the charge of blowing snow particles focusing on the collision frequency and clarify the relationship between them. Experiments were carried out in the cryogenic wind tunnel of Snow and Ice Research Center (NIED, JAPAN). A Faraday cage and an electrometer were used to measure the charge of snow particles. These experiments were conducted over the hard snow surface condition to prevent the erosion of the snow surface and the generation of new snow particles from the surface. The collision frequency of particle was controlled by changing the wind velocity (4.5 to 7 m/s) under

Retention and radiative forcing of black carbon in eastern Sierra Nevada snow

Directory of Open Access Journals (Sweden)

K. M. Sterle

2013-02-01

Full Text Available When contaminated by absorbing particles, such as refractory black carbon (rBC and continental dust, snow's albedo decreases and thus its absorption of solar radiation increases, thereby hastening snowmelt. For this reason, an understanding of rBC's affect on snow albedo, melt processes, and radiation balance is critical for water management, especially in a changing climate. Measurements of rBC in a sequence of snow pits and surface snow samples in the eastern Sierra Nevada of California during the snow accumulation and ablation seasons of 2009 show that concentrations of rBC were enhanced sevenfold in surface snow (~25 ng g^–1 compared to bulk values in the snowpack (~3 ng g^–1. Unlike major ions, which were preferentially released during the initial melt, rBC and continental dust were retained in the snow, enhancing concentrations well into late spring, until a final flush occurred during the ablation period. We estimate a combined rBC and continental dust surface radiative forcing of 20 to 40 W m⁻² during April and May, with dust likely contributing a greater share of the forcing.

Deriving Snow-Cover Depletion Curves for Different Spatial Scales from Remote Sensing and Snow Telemetry Data

Science.gov (United States)

Fassnacht, Steven R.; Sexstone, Graham A.; Kashipazha, Amir H.; Lopez-Moreno, Juan Ignacio; Jasinski, Michael F.; Kampf, Stephanie K.; Von Thaden, Benjamin C.

2015-01-01

During the melting of a snowpack, snow water equivalent (SWE) can be correlated to snow-covered area (SCA) once snow-free areas appear, which is when SCA begins to decrease below 100%. This amount of SWE is called the threshold SWE. Daily SWE data from snow telemetry stations were related to SCA derived from moderate-resolution imaging spectro radiometer images to produce snow-cover depletion curves. The snow depletion curves were created for an 80,000 sq km domain across southern Wyoming and northern Colorado encompassing 54 snow telemetry stations. Eight yearly snow depletion curves were compared, and it is shown that the slope of each is a function of the amount of snow received. Snow-cover depletion curves were also derived for all the individual stations, for which the threshold SWE could be estimated from peak SWE and the topography around each station. A stations peak SWE was much more important than the main topographic variables that included location, elevation, slope, and modelled clear sky solar radiation. The threshold SWE mostly illustrated inter-annual consistency.

Facile One-Pot Synthesis of Flower Like Cobalt Oxide Nanostructures on Nickel Plate and Its Supercapacitance Properties.

Science.gov (United States)

Kandasamy, N; Venugopal, T; Kannan, K

2018-06-01

A flower like cobalt oxide nanostructured thin film (Co2O3) on Nickel (Ni) plate as have been successfully developed via alcoholic Seed Layer assisted chemical bath Deposition (SLD) process. Through the controlled alkaline electrolytes, the flower and paddles like Co2O3 nanoarchitectures were formed. The prepared thin film was characterized by X-ray diffraction (XRD), scanning electron microscope with energy dispersive X-ray (SEM and EDX), Atomic Force Microscope (AFM), Raman spectroscopy techniques. Electron micrograph reveals the flower and paddles like nanostructured Co2O3 thin film deposited on Ni plates. The electrochemical characteristics were investigated using cyclic voltammetry (CV), charge-discharge and AC impedance spectroscopy in different aqueous electrolytes such as NaOH, KOH, and LiOH. The maximum specific capacitance of 856 Fg-1 was attained with 2 M KOH electrolyte with 2 mVs-1 of the Co2O3 thin film coated Ni plate at 80 °C using SLD method. The capacitance values obtained with various electrolytes are in the order of KOH > NaOH > LiOH. The results indicate that the present method is economical and the material is ecofriendly with enhanced capacitance property.

Dendrite Injury Triggers DLK-Independent Regeneration

Directory of Open Access Journals (Sweden)

Michelle C. Stone

2014-01-01

Full Text Available Axon injury triggers regeneration through activation of a conserved kinase cascade, which includes the dual leucine zipper kinase (DLK. Although dendrites are damaged during stroke, traumatic brain injury, and seizure, it is not known whether mature neurons monitor dendrite injury and initiate regeneration. We probed the response to dendrite damage using model Drosophila neurons. Two larval neuron types regrew dendrites in distinct ways after all dendrites were removed. Dendrite regeneration was also triggered by injury in adults. Next, we tested whether dendrite injury was initiated with the same machinery as axon injury. Surprisingly, DLK, JNK, and fos were dispensable for dendrite regeneration. Moreover, this MAP kinase pathway was not activated by injury to dendrites. Thus, neurons respond to dendrite damage and initiate regeneration without using the conserved DLK cascade that triggers axon regeneration.

Optical and acoustic sensing using Fano-like resonances in dual phononic and photonic crystal plate

Energy Technology Data Exchange (ETDEWEB)

Amoudache, Samira [Institut d' Electronique, de Microélectronique et de Nanotechnologie, Université de Lille 1, 59655 Villeneuve d' Ascq (France); Laboratoire de Physique et Chimie Quantique, Université Mouloud Mammeri, B.P. 17 RP, 15000 Tizi-Ouzou (Algeria); Moiseyenko, Rayisa [Department of Physics, Technical University of Denmark, DTU Physics, Building 309, DK-2800 Kongens Lyngby (Denmark); Pennec, Yan, E-mail: yan.pennec@univ-lille1.fr; Rouhani, Bahram Djafari [Institut d' Electronique, de Microélectronique et de Nanotechnologie, Université de Lille 1, 59655 Villeneuve d' Ascq (France); Khater, Antoine [Institut des Molécules et Matériaux du Mans (IMMM), UMR CNRS 6283, l' UNAM, Université du Maine, 72085 Le Mans (France); Lucklum, Ralf [Institute of Micro and Sensor Systems (IMOS), Otto-von-Guericke-University, P.O. Box 4120, D-39016 Magdeburg (Germany); Tigrine, Rachid [Laboratoire de Physique et Chimie Quantique, Université Mouloud Mammeri, B.P. 17 RP, 15000 Tizi-Ouzou (Algeria)

2016-03-21

We perform a theoretical study based on the transmissions of optical and acoustic waves normally impinging to a periodic perforated silicon plate when the embedded medium is a liquid and show the existence of Fano-like resonances in both cases. The signature of the resonances appears as well-defined asymmetric peaks in the phononic and photonic transmission spectra. We show that the origin of the Fano-like resonances is different with respect to the nature of the wave. In photonic, the origin comes from guided modes in the photonic plate while in phononic we show that it comes from the excitation of standing waves confined inside the cavity coming from the deformation of the water/silicon edges of the cylindrical inclusion. We finally use these features for sensing and show ultra-sensitivity to the light and sound velocities for different concentrations of analytes.

Dendrite-like Co3O4 nanostructure and its applications in sensors, supercapacitors and catalysis.

Science.gov (United States)

Pang, Huan; Gao, Feng; Chen, Qun; Liu, Rongmei; Lu, Qingyi

2012-05-21

Dendrite-like Co(3)O(4) nanostructure, made up of many nanorods with diameters of 15-20 nm and lengths of 2-3 μm, has been successfully prepared by calcining the corresponding nanostructured Co-8-hydroxyquinoline coordination precursor in air. The Co(3)O(4) nanostructure was evaluated as an electrochemical sensor for H(2)O(2) detection and the results reveal that it has good linear dependence and high sensitivity to H(2)O(2) concentration changes. As an electrode material of a supercapacitor, it was found that the nanostructured Co(3)O(4) electrode exhibits high specific capacitance and long cycle life. The Co(3)O(4) nanostructure also has good catalytic properties and is steadily active for CO oxidation, giving 100% CO conversion at low temperatures. The multifunctional Co(3)O(4) nanostructure would be a promising functional nanomaterial applied in multi industrialized fields.

Dendro-dendritic interactions between motion-sensitive large-field neurons in the fly.

Science.gov (United States)

Haag, Juergen; Borst, Alexander

2002-04-15

For visual course control, flies rely on a set of motion-sensitive neurons called lobula plate tangential cells (LPTCs). Among these cells, the so-called CH (centrifugal horizontal) cells shape by their inhibitory action the receptive field properties of other LPTCs called FD (figure detection) cells specialized for figure-ground discrimination based on relative motion. Studying the ipsilateral input circuitry of CH cells by means of dual-electrode and combined electrical-optical recordings, we find that CH cells receive graded input from HS (large-field horizontal system) cells via dendro-dendritic electrical synapses. This particular wiring scheme leads to a spatial blur of the motion image on the CH cell dendrite, and, after inhibiting FD cells, to an enhancement of motion contrast. This could be crucial for enabling FD cells to discriminate object from self motion.

SNOW THICKNESS ON AUSTRE GRØNFJORDBREEN, SVALBARD, FROM RADAR MEASUREMENTS AND STANDARD SNOW SURVEYS

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I. I. Lavrentiev

2018-01-01

Full Text Available Summary Comparison of two methods of measurements of snow cover thickness on the glacier Austre Grønfjordbreen, Svalbard was performed in the spring of 2014. These methods were the radar (500 MHz observations and standard snow surveys. Measurements were conducted in 77 different points on the surface of the glacier. A good correlation (R2 = 0.98 was revealed. In comparison with the data of snow surveys, the radar measurements show a similar but more detailed pattern of the distribution of the snow cover depth. The discrepancy between the depths of snow cover on maps plotted from data of both methods did not exceed 30 cm in most parts of the glacier. The standard error of interpolation of the radar data onto the entire glacier surface amounts, on average, to 18 cm. This corresponds to the error of radar measurements of 18.8% when an average snow depth is about 160 cm and 9.4% at its maximum thickness of 320 cm. The distance between the measurement points at which the spatial covariance of the snow depth disappears falls between 236 and 283 m along the glacier, and between 117 and 165 m across its position. We compared the results of radar measurements of the pulse-delay time of reflections from the base of the snow cover with the data of manual probe measurements at 10 points and direct measurements of snow depth and average density in 12 snow pits. The average speed of radio waves propagation in the snow was determined as Vcr = 23.4±0.2 cm ns−1. This magnitude and the Looyenga and Kovacs formulas allowed estimating the average density of snow cover ρL = 353.1±13.1 kg m−3 and ρK = 337.4±12.9 kg m−3. The difference from average density measured in 12 pits ρav.meas = 387.4±12.9 kg m−3 amounts to −10.8% and −14.8%. In 2014, according to snow and radar measurements, altitudinal gradient of snow accumulation on the glacier Austre Grønfjordbreen was equal to 0.21 m/100 m, which is smaller than the

Dendritic excitability modulates dendritic information processing in a purkinje cell model.

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Coop, Allan D; Cornelis, Hugo; Santamaria, Fidel

2010-01-01

Using an electrophysiological compartmental model of a Purkinje cell we quantified the contribution of individual active dendritic currents to processing of synaptic activity from granule cells. We used mutual information as a measure to quantify the information from the total excitatory input current (I(Glu)) encoded in each dendritic current. In this context, each active current was considered an information channel. Our analyses showed that most of the information was encoded by the calcium (I(CaP)) and calcium activated potassium (I(Kc)) currents. Mutual information between I(Glu) and I(CaP) and I(Kc) was sensitive to different levels of excitatory and inhibitory synaptic activity that, at the same time, resulted in the same firing rate at the soma. Since dendritic excitability could be a mechanism to regulate information processing in neurons we quantified the changes in mutual information between I(Glu) and all Purkinje cell currents as a function of the density of dendritic Ca (g(CaP)) and Kca (g(Kc)) conductances. We extended our analysis to determine the window of temporal integration of I(Glu) by I(CaP) and I(Kc) as a function of channel density and synaptic activity. The window of information integration has a stronger dependence on increasing values of g(Kc) than on g(CaP), but at high levels of synaptic stimulation information integration is reduced to a few milliseconds. Overall, our results show that different dendritic conductances differentially encode synaptic activity and that dendritic excitability and the level of synaptic activity regulate the flow of information in dendrites.

Estimating Snow Water Storage in North America Using CLM4, DART, and Snow Radiance Data Assimilation

Science.gov (United States)

Kwon, Yonghwan; Yang, Zong-Liang; Zhao, Long; Hoar, Timothy J.; Toure, Ally M.; Rodell, Matthew

2016-01-01

This paper addresses continental-scale snow estimates in North America using a recently developed snow radiance assimilation (RA) system. A series of RA experiments with the ensemble adjustment Kalman filter are conducted by assimilating the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) brightness temperature T(sub B) at 18.7- and 36.5-GHz vertical polarization channels. The overall RA performance in estimating snow depth for North America is improved by simultaneously updating the Community Land Model, version 4 (CLM4), snow/soil states and radiative transfer model (RTM) parameters involved in predicting T(sub B) based on their correlations with the prior T(sub B) (i.e., rule-based RA), although degradations are also observed. The RA system exhibits a more mixed performance for snow cover fraction estimates. Compared to the open-loop run (0.171m RMSE), the overall snow depth estimates are improved by 1.6% (0.168m RMSE) in the rule-based RA whereas the default RA (without a rule) results in a degradation of 3.6% (0.177mRMSE). Significant improvement of the snow depth estimates in the rule-based RA as observed for tundra snow class (11.5%, p < 0.05) and bare soil land-cover type (13.5%, p < 0.05). However, the overall improvement is not significant (p = 0.135) because snow estimates are degraded or marginally improved for other snow classes and land covers, especially the taiga snow class and forest land cover (7.1% and 7.3% degradations, respectively). The current RA system needs to be further refined to enhance snow estimates for various snow types and forested regions.

Unexpected Patterns in Snow and Dirt

Science.gov (United States)

Ackerson, Bruce J.

2018-01-01

For more than 30 years, Albert A. Bartlett published "Thermal patterns in the snow" in this journal. These are patterns produced by heat sources underneath the snow. Bartlett's articles encouraged me to pay attention to patterns in snow and to understanding them. At winter's end the last snow becomes dirty and is heaped into piles. This snow comes from the final clearing of sidewalks and driveways. The patterns observed in these piles defied my intuition. This melting snow develops edges where dirt accumulates, in contrast to ice cubes, which lose sharp edges and become more spherical upon melting. Furthermore, dirt absorbs more radiation than snow and yet doesn't melt and round the sharp edges of snow, where dirt accumulates.

Impact of the snow cover scheme on snow distribution and energy budget modeling over the Tibetan Plateau

Science.gov (United States)

Xie, Zhipeng; Hu, Zeyong; Xie, Zhenghui; Jia, Binghao; Sun, Genhou; Du, Yizhen; Song, Haiqing

2018-02-01

This paper presents the impact of two snow cover schemes (NY07 and SL12) in the Community Land Model version 4.5 (CLM4.5) on the snow distribution and surface energy budget over the Tibetan Plateau. The simulated snow cover fraction (SCF), snow depth, and snow cover days were evaluated against in situ snow depth observations and a satellite-based snow cover product and snow depth dataset. The results show that the SL12 scheme, which considers snow accumulation and snowmelt processes separately, has a higher overall accuracy (81.8%) than the NY07 (75.8%). The newer scheme performs better in the prediction of overall accuracy compared with the NY07; however, SL12 yields a 15.1% underestimation rate while NY07 overestimated the SCF with a 15.2% overestimation rate. Both two schemes capture the distribution of the maximum snow depth well but show large positive biases in the average value through all periods (3.37, 3.15, and 1.48 cm for NY07; 3.91, 3.52, and 1.17 cm for SL12) and overestimate snow cover days compared with the satellite-based product and in situ observations. Higher altitudes show larger root-mean-square errors (RMSEs) in the simulations of snow depth and snow cover days during the snow-free period. Moreover, the surface energy flux estimations from the SL12 scheme are generally superior to the simulation from NY07 when evaluated against ground-based observations, in particular for net radiation and sensible heat flux. This study has great implications for further improvement of the subgrid-scale snow variations over the Tibetan Plateau.

Modeling the influence of snow cover temperature and water content on wet-snow avalanche runout

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C. Vera Valero

2018-03-01

Full Text Available Snow avalanche motion is strongly dependent on the temperature and water content of the snow cover. In this paper we use a snow cover model, driven by measured meteorological data, to set the initial and boundary conditions for wet-snow avalanche calculations. The snow cover model provides estimates of snow height, density, temperature and liquid water content. This information is used to prescribe fracture heights and erosion heights for an avalanche dynamics model. We compare simulated runout distances with observed avalanche deposition fields using a contingency table analysis. Our analysis of the simulations reveals a large variability in predicted runout for tracks with flat terraces and gradual slope transitions to the runout zone. Reliable estimates of avalanche mass (height and density in the release and erosion zones are identified to be more important than an exact specification of temperature and water content. For wet-snow avalanches, this implies that the layers where meltwater accumulates in the release zone must be identified accurately as this defines the height of the fracture slab and therefore the release mass. Advanced thermomechanical models appear to be better suited to simulate wet-snow avalanche inundation areas than existing guideline procedures if and only if accurate snow cover information is available.

Mechanical coupling between transsynaptic N-cadherin adhesions and actin flow stabilizes dendritic spines

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Chazeau, Anaël; Garcia, Mikael; Czöndör, Katalin; Perrais, David; Tessier, Béatrice; Giannone, Grégory; Thoumine, Olivier

2015-01-01

The morphology of neuronal dendritic spines is a critical indicator of synaptic function. It is regulated by several factors, including the intracellular actin/myosin cytoskeleton and transcellular N-cadherin adhesions. To examine the mechanical relationship between these molecular components, we performed quantitative live-imaging experiments in primary hippocampal neurons. We found that actin turnover and structural motility were lower in dendritic spines than in immature filopodia and increased upon expression of a nonadhesive N-cadherin mutant, resulting in an inverse relationship between spine motility and actin enrichment. Furthermore, the pharmacological stimulation of myosin II induced the rearward motion of actin structures in spines, showing that myosin II exerts tension on the actin network. Strikingly, the formation of stable, spine-like structures enriched in actin was induced at contacts between dendritic filopodia and N-cadherin–coated beads or micropatterns. Finally, computer simulations of actin dynamics mimicked various experimental conditions, pointing to the actin flow rate as an important parameter controlling actin enrichment in dendritic spines. Together these data demonstrate that a clutch-like mechanism between N-cadherin adhesions and the actin flow underlies the stabilization of dendritic filopodia into mature spines, a mechanism that may have important implications in synapse initiation, maturation, and plasticity in the developing brain. PMID:25568337

The Goddard Snow Radiance Assimilation Project: An Integrated Snow Radiance and Snow Physics Modeling Framework for Snow/cold Land Surface Modeling

Science.gov (United States)

Kim, E.; Tedesco, M.; Reichle, R.; Choudhury, B.; Peters-Lidard C.; Foster, J.; Hall, D.; Riggs, G.

2006-01-01

Microwave-based retrievals of snow parameters from satellite observations have a long heritage and have so far been generated primarily by regression-based empirical "inversion" methods based on snapshots in time. Direct assimilation of microwave radiance into physical land surface models can be used to avoid errors associated with such retrieval/inversion methods, instead utilizing more straightforward forward models and temporal information. This approach has been used for years for atmospheric parameters by the operational weather forecasting community with great success. Recent developments in forward radiative transfer modeling, physical land surface modeling, and land data assimilation are converging to allow the assembly of an integrated framework for snow/cold lands modeling and radiance assimilation. The objective of the Goddard snow radiance assimilation project is to develop such a framework and explore its capabilities. The key elements of this framework include: a forward radiative transfer model (FRTM) for snow, a snowpack physical model, a land surface water/energy cycle model, and a data assimilation scheme. In fact, multiple models are available for each element enabling optimization to match the needs of a particular study. Together these form a modular and flexible framework for self-consistent, physically-based remote sensing and water/energy cycle studies. In this paper we will describe the elements and the integration plan. All modules will operate within the framework of the Land Information System (LIS), a land surface modeling framework with data assimilation capabilities running on a parallel-node computing cluster. Capabilities for assimilation of snow retrieval products are already under development for LIS. We will describe plans to add radiance-based assimilation capabilities. Plans for validation activities using field measurements will also be discussed.

Optical and acoustic sensing using Fano-like resonances in dual phononic and photonic crystal plate

DEFF Research Database (Denmark)

Amoudache, Samira; Moiseyenko, Rayisa; Pennec, Yan

2016-01-01

We perform a theoretical study based on the transmissions of optical and acoustic waves normally impinging to a periodic perforated silicon plate when the embedded medium is a liquid and show the existence of Fano-like resonances in both cases. The signature of the resonances appears as well-defi...... of standing waves confined inside the cavity coming from the deformation of the water/silicon edges of the cylindrical inclusion. We finally use these features for sensing and show ultra-sensitivity to the light and sound velocities for different concentrations of analytes.......-defined asymmetric peaks in the phononic and photonic transmission spectra. We show that the origin of the Fano-like resonances is different with respect to the nature of the wave. In photonic, the origin comes from guided modes in the photonic plate while in phononic we show that it comes from the excitation...

A dendrite-autonomous mechanism for direction selectivity in retinal starburst amacrine cells.

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Hausselt, Susanne E; Euler, Thomas; Detwiler, Peter B; Denk, Winfried

2007-07-01

Detection of image motion direction begins in the retina, with starburst amacrine cells (SACs) playing a major role. SACs generate larger dendritic Ca(2+) signals when motion is from their somata towards their dendritic tips than for motion in the opposite direction. To study the mechanisms underlying the computation of direction selectivity (DS) in SAC dendrites, electrical responses to expanding and contracting circular wave visual stimuli were measured via somatic whole-cell recordings and quantified using Fourier analysis. Fundamental and, especially, harmonic frequency components were larger for expanding stimuli. This DS persists in the presence of GABA and glycine receptor antagonists, suggesting that inhibitory network interactions are not essential. The presence of harmonics indicates nonlinearity, which, as the relationship between harmonic amplitudes and holding potential indicates, is likely due to the activation of voltage-gated channels. [Ca(2+)] changes in SAC dendrites evoked by voltage steps and monitored by two-photon microscopy suggest that the distal dendrite is tonically depolarized relative to the soma, due in part to resting currents mediated by tonic glutamatergic synaptic input, and that high-voltage-activated Ca(2+) channels are active at rest. Supported by compartmental modeling, we conclude that dendritic DS in SACs can be computed by the dendrites themselves, relying on voltage-gated channels and a dendritic voltage gradient, which provides the spatial asymmetry necessary for direction discrimination.

A dendrite-autonomous mechanism for direction selectivity in retinal starburst amacrine cells.

Directory of Open Access Journals (Sweden)

Susanne E Hausselt

2007-07-01

Full Text Available Detection of image motion direction begins in the retina, with starburst amacrine cells (SACs playing a major role. SACs generate larger dendritic Ca(2+ signals when motion is from their somata towards their dendritic tips than for motion in the opposite direction. To study the mechanisms underlying the computation of direction selectivity (DS in SAC dendrites, electrical responses to expanding and contracting circular wave visual stimuli were measured via somatic whole-cell recordings and quantified using Fourier analysis. Fundamental and, especially, harmonic frequency components were larger for expanding stimuli. This DS persists in the presence of GABA and glycine receptor antagonists, suggesting that inhibitory network interactions are not essential. The presence of harmonics indicates nonlinearity, which, as the relationship between harmonic amplitudes and holding potential indicates, is likely due to the activation of voltage-gated channels. [Ca(2+] changes in SAC dendrites evoked by voltage steps and monitored by two-photon microscopy suggest that the distal dendrite is tonically depolarized relative to the soma, due in part to resting currents mediated by tonic glutamatergic synaptic input, and that high-voltage-activated Ca(2+ channels are active at rest. Supported by compartmental modeling, we conclude that dendritic DS in SACs can be computed by the dendrites themselves, relying on voltage-gated channels and a dendritic voltage gradient, which provides the spatial asymmetry necessary for direction discrimination.

Remote defect imaging for plate-like structures based on the scanning laser source technique

Science.gov (United States)

Hayashi, Takahiro; Maeda, Atsuya; Nakao, Shogo

2018-04-01

In defect imaging with a scanning laser source technique, the use of a fixed receiver realizes stable measurements of flexural waves generated by laser at multiple rastering points. This study discussed the defect imaging by remote measurements using a laser Doppler vibrometer as a receiver. Narrow-band burst waves were generated by modulating laser pulse trains of a fiber laser to enhance signal to noise ratio in frequency domain. Averaging three images obtained at three different frequencies suppressed spurious distributions due to resonance. The experimental system equipped with these newly-devised means enabled us to visualize defects and adhesive objects in plate-like structures such as a plate with complex geometries and a branch pipe.

Establishing Winter Origins of Migrating Lesser Snow Geese Using Stable Isotopes

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Viviane Hénaux

2012-06-01

Full Text Available Increases in Snow Goose (Chen caerulescens populations and large-scale habitat changes in North America have contributed to the concentration of migratory waterfowl on fewer wetlands, reducing resource availability, and enhancing risks of disease transmission. Predicting wintering locations of migratory individuals is critical to guide wildlife population management and habitat restoration. We used stable carbon (δ13C, nitrogen (δ15N, and hydrogen (δ2H isotope ratios in muscle tissue of wintering Snow Geese to discriminate four major wintering areas, the Playa Lake Region, Texas Gulf Coast, Louisiana Gulf Coast, and Arkansas, and infer the wintering locations of individuals collected later during the 2007 and 2008 spring migrations in the Rainwater Basin (RWB of Nebraska. We predicted the wintering ground derivation of migrating Snow Geese using a likelihood-based approach. Our three-isotope analysis provided an efficient discrimination of the four wintering areas. The assignment model predicted that 53% [95% CI: 37-69] of our sample of Snow Geese from the RWB in 2007 had most likely originated in Louisiana, 38% [23-54] had wintered on Texas Gulf Coast, and 9% [0-20] in Arkansas; the assessment suggested that 89% [73-100] of our 2008 sample had most likely come from Texas Gulf Coast, 9% [0-27] from Louisiana Gulf Coast, and 2% [0-9] from Arkansas. Further segregation of wintering grounds and additional sampling of spring migrating Snow Geese would refine overall assignment and help explain interannual variations in migratory connectivity. The ability to distinguish origins of northbound geese can support the development of spatially-adaptive management strategies for the midcontinent Snow Goose population. Establishing migratory connectivity using isotope assignment techniques can be extended to other waterfowl species to determine critical habitat, evaluate population energy requirements, and inform waterfowl conservation and management

Modelling of snow exceedances

Science.gov (United States)

Jordanova, Pavlina K.; Sadovský, Zoltán; Stehlík, Milan

2017-07-01

Modelling of snow exceedances is of great importance and interest for ecology, civil engineering and general public. We suggest the favorable fit for exceedances related to the exceptional snow loads from Slovakia, assuming that the data is driven by Generalised Pareto Distribution or Generalized Extreme Value Distribution. Further, the statistical dependence between the maximal snow loads and the corresponding altitudes is studied.

Hydrological Implications of Covering Wind-Blown Snow Accumulations with Geotextiles on Mount Aragats, Armenia

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Alexander Nestler

2014-07-01

Full Text Available Snow is an excellent water reservoir, naturally storing large quantities of water at time scales from a few days to several months. In summer-dry countries, like Armenia, runoff due to snow melt from mountain regions is highly important for a sustained water supply (irrigation, hydropower. Snow fields on Mount Aragats, Armenia’s highest peak, often persist until July, providing vital amounts of melt water. Artificially managing these wind-driven snow accumulations as a natural water reservoir might have considerable potential. In the context of the Swiss-Armenian joint venture, Freezwater, snow fields are covered with geotextiles in order to delay snow melt long enough to provide additional melt water in the dry season of the year. In this study, we analyze the hydrological effectiveness of the artificial management of the natural snow cover on Mount Aragats based on various field measurements acquired over a three-year period and numerical modeling. Over the winter season, partly more than five meter-thick snow deposits are formed supported by snow redistribution by strong wind. Repeated mappings of snow fields indicate that snow cover patterns remain highly consistent over time. Measurements of ablation below manually applied geotextiles show a considerable reduction of melt rates by more than 50%. Simulations with an energy-balance model and a distributed temperature-index model allow assessing the hydrological effect of artificial snow management for different initial snow depths and elevations and suggest that coverage is needed at a large scale in order to generate a significant impact on discharge.

Land Surface Model Biases and their Impacts on the Assimilation of Snow-related Observations

Science.gov (United States)

Arsenault, K. R.; Kumar, S.; Hunter, S. M.; Aman, R.; Houser, P. R.; Toll, D.; Engman, T.; Nigro, J.

2007-12-01

Some recent snow modeling studies have employed a wide range of assimilation methods to incorporate snow cover or other snow-related observations into different hydrological or land surface models. These methods often include taking both model and observation biases into account throughout the model integration. This study focuses more on diagnosing the model biases and presenting their subsequent impacts on assimilating snow observations and modeled snowmelt processes. In this study, the land surface model, the Community Land Model (CLM), is used within the Land Information System (LIS) modeling framework to show how such biases impact the assimilation of MODIS snow cover observations. Alternative in-situ and satellite-based observations are used to help guide the CLM LSM in better predicting snowpack conditions and more realistic timing of snowmelt for a western US mountainous region. Also, MODIS snow cover observation biases will be discussed, and validation results will be provided. The issues faced with inserting or assimilating MODIS snow cover at moderate spatial resolutions (like 1km or less) will be addressed, and the impacts on CLM will be presented.

The shaping of two distinct dendritic spikes by A-type voltage-gated K+ channels

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Sungchil eYang

2015-12-01

Full Text Available Dendritic ion channels have been a subject of intense research in neuroscience because active ion channels in dendrites shape input signals. Ca2+-permeable channels including NMDA receptors (NMDARs have been implicated in supralinear dendritic integration, and the IA conductance in sublinear integration. Despite their essential roles in dendritic integration, it has remained uncertain whether these conductances coordinate with, or counteract, each other in the process of dendritic integration. To address this question, experiments were designed in hippocampal CA1 neurons with a recent 3D digital holography system that has shown excellent performance for spatial photoactivation. The results demonstrated a role of IA as a key contributor to two distinct dendritic spikes, low- and high-threshold Ca2+ spikes, through a preferential action of IA on Ca2+-permeable channel-mediated currents, over fast AMPAR-mediated currents. It is likely that the rapid kinetics of IA provides feed-forward inhibition to counteract the delayed Ca2+ channel-mediated dendritic excitability. This research reveals one dynamic ionic mechanism of dendritic integration, and may contribute to a new understanding of neuronal hyperexcitability embedded in several neural diseases such as epilepsy, fragile X syndrome and Alzheimer's disease.

Antarctic snow and global climate

International Nuclear Information System (INIS)

Granberg, H.B.

2001-01-01

Global circulation models (GCM) indicate that global warming will be most pronounced at polar regions and high latitudes, causing concern about the stability of the Antarctic ice cap. A project entitled the Seasonal Snow in Antarctica examined the properties of the near surface snow to determine the current conditions that influence snow cover development. The goal was to assess the response of the snow cover in Queen Maud Land (QML) to an increased atmospheric carbon dioxide content. The Antarctic snow cover in QML was examined as part of the FINNARP expeditions in 1999 and 2000 which examined the processes that influence the snow cover. Its energy and mass balance were also assessed by examining the near surface snow strata in shallow (1-2 m) pits and by taking measurements of environmental variables. This made it possible to determine if the glacier is in danger of melting at this northerly location in the Antarctic. The study also made it possible to determine which variables need to change and by how much, for significant melting to occur. It was shown that the Antarctic anticyclone creates particular conditions that protect the snow cover from melting. The anticyclone brings dry air from the stratosphere during most of the year and is exempt from the water vapour feedback. It was concluded that even a doubling of atmospheric carbon dioxide will not produce major snow melt runoff. 8 refs

Evaluation of snow cover and snow depth on the Qinghai–Tibetan Plateau derived from passive microwave remote sensing

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L. Dai

2017-08-01

Full Text Available Snow cover on the Qinghai–Tibetan Plateau (QTP plays a significant role in the global climate system and is an important water resource for rivers in the high-elevation region of Asia. At present, passive microwave (PMW remote sensing data are the only efficient way to monitor temporal and spatial variations in snow depth at large scale. However, existing snow depth products show the largest uncertainties across the QTP. In this study, MODIS fractional snow cover product, point, line and intense sampling data are synthesized to evaluate the accuracy of snow cover and snow depth derived from PMW remote sensing data and to analyze the possible causes of uncertainties. The results show that the accuracy of snow cover extents varies spatially and depends on the fraction of snow cover. Based on the assumption that grids with MODIS snow cover fraction > 10 % are regarded as snow cover, the overall accuracy in snow cover is 66.7 %, overestimation error is 56.1 %, underestimation error is 21.1 %, commission error is 27.6 % and omission error is 47.4 %. The commission and overestimation errors of snow cover primarily occur in the northwest and southeast areas with low ground temperature. Omission error primarily occurs in cold desert areas with shallow snow, and underestimation error mainly occurs in glacier and lake areas. With the increase of snow cover fraction, the overestimation error decreases and the omission error increases. A comparison between snow depths measured in field experiments, measured at meteorological stations and estimated across the QTP shows that agreement between observation and retrieval improves with an increasing number of observation points in a PMW grid. The misclassification and errors between observed and retrieved snow depth are associated with the relatively coarse resolution of PMW remote sensing, ground temperature, snow characteristics and topography. To accurately understand the variation in snow

MODIS Snow and Sea Ice Products

Science.gov (United States)

Hall, Dorothy K.; Riggs, George A.; Salomonson, Vincent V.

2004-01-01

In this chapter, we describe the suite of Earth Observing System (EOS) Moderate-Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua snow and sea ice products. Global, daily products, developed at Goddard Space Flight Center, are archived and distributed through the National Snow and Ice Data Center at various resolutions and on different grids useful for different communities Snow products include binary snow cover, snow albedo, and in the near future, fraction of snow in a 5OO-m pixel. Sea ice products include ice extent determined with two different algorithms, and sea ice surface temperature. The algorithms used to develop these products are described. Both the snow and sea ice products, available since February 24,2000, are useful for modelers. Validation of the products is also discussed.

Microtubule nucleation and organization in dendrites

Science.gov (United States)

Delandre, Caroline; Amikura, Reiko; Moore, Adrian W.

2016-01-01

ABSTRACT Dendrite branching is an essential process for building complex nervous systems. It determines the number, distribution and integration of inputs into a neuron, and is regulated to create the diverse dendrite arbor branching patterns characteristic of different neuron types. The microtubule cytoskeleton is critical to provide structure and exert force during dendrite branching. It also supports the functional requirements of dendrites, reflected by differential microtubule architectural organization between neuron types, illustrated here for sensory neurons. Both anterograde and retrograde microtubule polymerization occur within growing dendrites, and recent studies indicate that branching is enhanced by anterograde microtubule polymerization events in nascent branches. The polarities of microtubule polymerization events are regulated by the position and orientation of microtubule nucleation events in the dendrite arbor. Golgi outposts are a primary microtubule nucleation center in dendrites and share common nucleation machinery with the centrosome. In addition, pre-existing dendrite microtubules may act as nucleation sites. We discuss how balancing the activities of distinct nucleation machineries within the growing dendrite can alter microtubule polymerization polarity and dendrite branching, and how regulating this balance can generate neuron type-specific morphologies. PMID:27097122

Observations of distributed snow depth and snow duration within diverse forest structures in a maritime mountain watershed

Science.gov (United States)

Dickerson-Lange, Susan E.; Lutz, James A.; Gersonde, Rolf; Martin, Kael A.; Forsyth, Jenna E.; Lundquist, Jessica D.

2015-11-01

Spatially distributed snow depth and snow duration data were collected over two to four snow seasons during water years 2011-2014 in experimental forest plots within the Cedar River Municipal Watershed, 50 km east of Seattle, Washington, USA. These 40 × 40 m forest plots, situated on the western slope of the Cascade Range, include unthinned second-growth coniferous forests, variable density thinned forests, forest gaps in which a 20 m diameter (approximately equivalent to one tree height) gap was cut in the middle of each plot, and old-growth forest. Together, this publicly available data set includes snow depth and density observations from manual snow surveys, distributed snow duration observations from ground temperature sensors and time-lapse cameras, meteorological data collected at two open locations and three forested locations, and forest canopy data from airborne light detection and ranging (LiDAR) data and hemispherical photographs. These colocated snow, meteorological, and forest data have the potential to improve understanding of forest influences on snow processes, and provide a unique model-testing data set for hydrological analyses in a forested, maritime watershed. We present empirical snow depletion curves within forests to illustrate an application of these data to improve subgrid representation of snow cover in distributed modeling.

Combining snow depth and innovative skier flow measurements in order to improve snow grooming techniques

Science.gov (United States)

Carmagnola, Carlo Maria; Albrecht, Stéphane; Hargoaa, Olivier

2017-04-01

In the last decades, ski resort managers have massively improved their snow management practices, in order to adapt their strategies to the inter-annual variability in snow conditions and to the effects of climate change. New real-time informations, such as snow depth measurements carried out on the ski slopes by grooming machines during their daily operations, have become available, allowing high saving, efficiency and optimization gains (reducing for instance the groomer fuel consumption and operation time and the need for machine-made snow production). In order to take a step forward in improving the grooming techniques, it would be necessary to keep into account also the snow erosion by skiers, which depends mostly on the snow surface properties and on the skier attendance. Today, however, most ski resort managers have only a vague idea of the evolution of the skier flows on each slope during the winter season. In this context, we have developed a new sensor (named Skiflux) able to measure the skier attendance using an infrared beam crossing the slopes. Ten Skiflux sensors have been deployed during the 2016/17 winter season at Val Thorens ski area (French Alps), covering a whole sector of the resort. A dedicated software showing the number of skier passages in real time as been developed as well. Combining this new Skiflux dataset with the snow depth measurements from grooming machines (Snowsat System) and the snow and meteorological conditions measured in-situ (Liberty System from Technoalpin), we were able to create a "real-time skiability index" accounting for the quality of the surface snow and its evolution during the day. Moreover, this new framework allowed us to improve the preparation of ski slopes, suggesting new strategies for adapting the grooming working schedule to the snow quality and the skier attendance. In the near future, this work will benefit from the advances made within the H2020 PROSNOW project ("Provision of a prediction system allowing

Changes in dendritic architecture: not your "usual suspect" in control of the onset of puberty in male rats.

Science.gov (United States)

Hemond, Peter J; O'Boyle, Michael P; Hemond, Zoe; Gay, Vernon L; Suter, Kelly

2013-01-01

Until the recent past, the search for the underlying drive for the pubertal increase in gonadotropin-releasing hormone (GnRH) hormone from the GnRH-containing neurons in the hypothalamus was largely focused on extrinsic factors. The most recent evidence however indicates changes in the structure of GnRH neurons themselves may contribute to this fundamental event in development. Based on our studies in males, dendritic architecture is not static from birth until adulthood. Instead, dendrites undergo a dramatic remodeling during the postnatal period which is independent of testosterone and occurs before the pubertal increase in GnRH release. First, the number of dendrites emanating from somata is reduced between infancy and adulthood. Moreover, a dendrite of adult GnRH neurons invariability arises at angle of 180°from the axon as opposed to the extraordinary variability in location during infancy. In fact, in some neurons from infants, no dendrite even resides in the adult location. Thus, there is a spatially selective remodeling of primary dendrites. Secondly, dendrites of GnRH neurons from infants were highly branched prior to assuming the compact morphology of adults. Finally, other morphological aspects of GnRH neurons such as total dendritic length, the numbers of dendrite branches and the lengths of higher order branches were significantly greater in infants than adults, indicating a consolidation of dendritic arbors. Activity in multi-compartment models of GnRH neurons, suggest the impact of structure on neuronal activity is exerted with both active and passive dendrites. Thus, passive properties make a defining contribution to function. Accordingly, changes in morphology alone are likely to have functional consequences for the pattern of activity in GnRH neurons. Our findings suggest structural remodeling of dendrites during the postnatal period likely facilitates repetitive action potentials and thus, GnRH release at the time of puberty.

Combining low-cost GPS receivers with upGPR to derive continuously liquid water content, snow height and snow water equivalent in Alpine snow covers

Science.gov (United States)

Koch, Franziska; Schmid, Lino; Prasch, Monika; Heilig, Achim; Eisen, Olaf; Schweizer, Jürg; Mauser, Wolfram

2015-04-01

The temporal evolution of Alpine snowpacks is important for assessing water supply, hydropower generation, flood predictions and avalanche forecasts. Especially in high mountain regions with an extremely varying topography, it is until now often difficult to derive continuous and non-destructive information on snow parameters. Since autumn 2012, we are running a new low-cost GPS (Global Positioning System) snow measurement experiment at the high alpine study site Weissfluhjoch (2450 m a.s.l.) in Switzerland. The globally and freely broadcasted GPS L1-band (1.57542 GHz) was continuously recorded with GPS antennas, which are installed at the ground surface underneath the snowpack. GPS raw data, containing carrier-to-noise power density ratio (C/N0) as well as elevation and azimuth angle information for each time step of 1 s, was stored and analyzed for all 32 GPS satellites. Since the dielectric permittivity of an overlying wet snowpack influences microwave radiation, the bulk volumetric liquid water content as well as daily melt-freeze cycles can be derived non-destructively from GPS signal strength losses and external snow height information. This liquid water content information is qualitatively in good accordance with meteorological and snow-hydrological data and quantitatively highly agrees with continuous data derived from an upward-looking ground-penetrating radar (upGPR) working in a similar frequency range. As a promising novelty, we combined the GPS signal strength data with upGPR travel-time information of active impulse radar rays to the snow surface and back from underneath the snow cover. This combination allows determining liquid water content, snow height and snow water equivalent from beneath the snow cover without using any other external information. The snow parameters derived by combining upGPR and GPS data are in good agreement with conventional sensors as e.g. laser distance gauges or snow pillows. As the GPS sensors are cheap, they can easily

Everywhere and nowhere: snow and its linkages

Science.gov (United States)

Hiemstra, C. A.

2017-12-01

Interest has grown in quantifying higher latitude precipitation change and snow-related ecosystem and economic impacts. There is a high demand for creating and using snow-related datasets, yet available datasets contain limitations, aren't scale appropriate, or lack thorough validation. Much of the uncertainty in snow estimates relates to ongoing snow measurement problems that are chronic and pervasive in windy, Arctic environments. This, coupled with diminishing support for long-term snow field observations, creates formidable hydrologic gaps in snow dominated landscapes. Snow touches most aspects of high latitude landscapes and spans albedo, ecosystems, soils, permafrost, and sea ice. In turn, snow can be impacted by disturbances, landscape change, ecosystem, structure, and later arrival of sea or lake ice. Snow, and its changes touch infrastructure, housing, and transportation. Advances in snow measurements, modeling, and data assimilation are under way, but more attention and a concerted effort is needed in a time of dwindling resources to make required advances during a time of rapid change.

[Characteristics of mercury exchange flux between soil and atmosphere under the snow retention and snow melting control].

Science.gov (United States)

Zhang, Gang; Wang, Ning; Ai, Jian-Chao; Zhang, Lei; Yang, Jing; Liu, Zi-Qi

2013-02-01

Jiapigou gold mine, located in the upper Songhua River, was once the largest mine in China due to gold output, where gold extraction with algamation was widely applied to extract gold resulting in severe mercury pollution to ambient environmental medium. In order to study the characteristics of mercury exchange flux between soil (snow) and atmosphere under the snow retention and snow melting control, sampling sites were selected in equal distances along the slope which is situated in the typical hill-valley terrain unit. Mercury exchange flux between soil (snow) and atmosphere was determined with the method of dynamic flux chamber and in all sampling sites the atmosphere concentration from 0 to 150 cm near to the earth in the vertical direction was measured. Furthermore, the impact factors including synchronous meteorology, the surface characteristics under the snow retention and snow melting control and the mercury concentration in vertical direction were also investigated. The results are as follows: During the period of snow retention and melting the air mercury tends to gather towards valley bottom along the slope and an obvious deposit tendency process was found from air to the earth's surface under the control of thermal inversion due to the underlying surface of cold source (snow surface). However, during the period of snow melting, mercury exchange flux between the soil and atmosphere on the surface of the earth with the snow being melted demonstrates alternative deposit and release processes. As for the earth with snow covered, the deposit level of mercury exchange flux between soil and atmosphere is lower than that during the period of snow retention. The relationship between mercury exchange flux and impact factors shows that in snow retention there is a remarkable negative linear correlation between mercury exchange flux and air mercury concentration as well as between the former and the air temperature. In addition, in snow melting mercury exchange

Measured Black Carbon Deposition on the Sierra Nevada Snow Pack and Implication for Snow Pack Retreat

Energy Technology Data Exchange (ETDEWEB)

Hadley, O.L.; Corrigan, C.E.; Kirchstetter, T.W.; Cliff, S.S.; Ramanathan, V.

2010-01-12

Modeling studies show that the darkening of snow and ice by black carbon deposition is a major factor for the rapid disappearance of arctic sea ice, mountain glaciers and snow packs. This study provides one of the first direct measurements for the efficient removal of black carbon from the atmosphere by snow and its subsequent deposition to the snow packs of California. The early melting of the snow packs in the Sierras is one of the contributing factors to the severe water problems in California. BC concentrations in falling snow were measured at two mountain locations and in rain at a coastal site. All three stations reveal large BC concentrations in precipitation, ranging from 1.7 ng/g to 12.9 ng/g. The BC concentrations in the air after the snow fall were negligible suggesting an extremely efficient removal of BC by snow. The data suggest that below cloud scavenging, rather than ice nuclei, was the dominant source of BC in the snow. A five-year comparison of BC, dust, and total fine aerosol mass concentrations at multiple sites reveals that the measurements made at the sampling sites were representative of large scale deposition in the Sierra Nevada. The relative concentration of iron and calcium in the mountain aerosol indicates that one-quarter to one-third of the BC may have been transported from Asia.

Sierra Nevada, California, U.S.A., Snow Algae: Snow albedo changes, algal-bacterial interrelationships and ultraviolet radiation effects

International Nuclear Information System (INIS)

Thomas, W.H.; Duval, B.

1995-01-01

In the Tioga Pass area (upper LeeVining Creek watershed) of the Sierra Nevada (California), snow algae were prevalent in the early summers of 1993 and 1994. Significant negative correlations were found between snow water content. However, red snow caused by algal blooms did not decrease mean albedos in representative snowfields. This was due to algal patchiness; mean albedos would not decrease over the whole water catchment basin; and water supplies would not be affected by the presence of algae. Albedo was also reduced by dirt on the snow, and wind-blown dirt may provide a source of allochthonous organic matter for snow bacteria. However, several observations emphasize the importance of an autochthonous source for bacterial nutrition. Bacterial abundances and production rates were higher in red snow containing algae than in noncolored snow. Bacterial production was about two orders-of-magnitude lower than photosynthetic algal production. Bacteria were also sometimes attached to algal cells. In experiments where snow algae were contained in UV-transmitting quartz tubes, ultraviolet radiation inhibited red snow (collected form open, sunlit areas) photosynthesis about 25%, while green snow (collected from forested, shady locations) photosynthesis was inhibited by 85%. Methanol extracts of red snow algae had greater absorbances in blue and UV spectral regions than did algae from green snow. These differences in UV responses and spectra may be due to habitat (sun vs shade) differences, or may be genetic, since different species were found in the two snow types. However, both habitat and genetic mechanisms may be operating together to cause these differences. 53 refs., 5 figs., 5 tabs

MODIS Snow Cover Recovery Using Variational Interpolation

Science.gov (United States)

Tran, H.; Nguyen, P.; Hsu, K. L.; Sorooshian, S.

2017-12-01

Cloud obscuration is one of the major problems that limit the usages of satellite images in general and in NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) global Snow-Covered Area (SCA) products in particular. Among the approaches to resolve the problem, the Variational Interpolation (VI) algorithm method, proposed by Xia et al., 2012, obtains cloud-free dynamic SCA images from MODIS. This method is automatic and robust. However, computational deficiency is a main drawback that degrades applying the method for larger scales (i.e., spatial and temporal scales). To overcome this difficulty, this study introduces an improved version of the original VI. The modified VI algorithm integrates the MINimum RESidual (MINRES) iteration (Paige and Saunders., 1975) to prevent the system from breaking up when applied to much broader scales. An experiment was done to demonstrate the crash-proof ability of the new algorithm in comparison with the original VI method, an ability that is obtained when maintaining the distribution of the weights set after solving the linear system. After that, the new VI algorithm was applied to the whole Contiguous United States (CONUS) over four winter months of 2016 and 2017, and validated using the snow station network (SNOTEL). The resulting cloud free images have high accuracy in capturing the dynamical changes of snow in contrast with the MODIS snow cover maps. Lastly, the algorithm was applied to create a Cloud free images dataset from March 10, 2000 to February 28, 2017, which is able to provide an overview of snow trends over CONUS for nearly two decades. ACKNOWLEDGMENTSWe would like to acknowledge NASA, NOAA Office of Hydrologic Development (OHD) National Weather Service (NWS), Cooperative Institute for Climate and Satellites (CICS), Army Research Office (ARO), ICIWaRM, and UNESCO for supporting this research.

Evaluation of SNODAS snow depth and snow water equivalent estimates for the Colorado Rocky Mountains, USA

Science.gov (United States)

Clow, David W.; Nanus, Leora; Verdin, Kristine L.; Schmidt, Jeffrey

2012-01-01

The National Weather Service's Snow Data Assimilation (SNODAS) program provides daily, gridded estimates of snow depth, snow water equivalent (SWE), and related snow parameters at a 1-km2 resolution for the conterminous USA. In this study, SNODAS snow depth and SWE estimates were compared with independent, ground-based snow survey data in the Colorado Rocky Mountains to assess SNODAS accuracy at the 1-km2 scale. Accuracy also was evaluated at the basin scale by comparing SNODAS model output to snowmelt runoff in 31 headwater basins with US Geological Survey stream gauges. Results from the snow surveys indicated that SNODAS performed well in forested areas, explaining 72% of the variance in snow depths and 77% of the variance in SWE. However, SNODAS showed poor agreement with measurements in alpine areas, explaining 16% of the variance in snow depth and 30% of the variance in SWE. At the basin scale, snowmelt runoff was moderately correlated (R2 = 0.52) with SNODAS model estimates. A simple method for adjusting SNODAS SWE estimates in alpine areas was developed that uses relations between prevailing wind direction, terrain, and vegetation to account for wind redistribution of snow in alpine terrain. The adjustments substantially improved agreement between measurements and SNODAS estimates, with the R2 of measured SWE values against SNODAS SWE estimates increasing from 0.42 to 0.63 and the root mean square error decreasing from 12 to 6 cm. Results from this study indicate that SNODAS can provide reliable data for input to moderate-scale to large-scale hydrologic models, which are essential for creating accurate runoff forecasts. Refinement of SNODAS SWE estimates for alpine areas to account for wind redistribution of snow could further improve model performance. Published 2011. This article is a US Government work and is in the public domain in the USA.

Spatiotemporal variability of snow cover and snow water equivalent in the last three decades over Eurasia

Science.gov (United States)

Zhang, Yinsheng; Ma, Ning

2018-04-01

Changes in the extent and amount of snow cover in Eurasia are of great interest because of their vital impacts on the global climate system and regional water resource management. This study investigated the spatial and temporal variability of the snow cover extent (SCE) and snow water equivalent (SWE) of the continental Eurasia using the Northern Hemisphere Equal-Area Scalable Earth Grid (EASE-Grid) Weekly SCE data for 1972-2006 and the Global Monthly EASE-Grid SWE data for 1979-2004. The results indicated that, in general, the spatial extent of snow cover significantly decreased during spring and summer, but varied little during autumn and winter over Eurasia in the study period. The date at which snow cover began to disappear in spring has significantly advanced, whereas the timing of snow cover onset in autumn did not vary significantly during 1972-2006. The snow cover persistence period declined significantly in the western Tibetan Plateau as well as partial area of Central Asia and northwestern Russia, but varied little in other parts of Eurasia. "Snow-free breaks" (SFBs) with intermittent snow cover in the cold season were principally observed in the Tibetan Plateau and Central Asia, causing a low sensitivity of snow cover persistence period to the timings of snow cover onset and disappearance over the areas with shallow snow. The averaged SFBs were 1-14 weeks during the study period and the maximum intermittence could even reach 25 weeks in certain years. At a seasonal scale, SWE usually peaked in February or March, but fell gradually since April across Eurasia. Both annual mean and annual maximum SWE decreased significantly during 1979-2004 in most parts of Eurasia except for eastern Siberia as well as northwestern and northeastern China. The possible cross-platform inconsistencies between two passive microwave radiometers may cause uncertainties in the detected trends of SWE here, suggesting an urgent need of producing a long-term, more homogeneous SWE

Insulin-like growth factor I (IGF-1) Ec/Mechano Growth factor--a splice variant of IGF-1 within the growth plate.

Science.gov (United States)

Schlegel, Werner; Raimann, Adalbert; Halbauer, Daniel; Scharmer, Daniela; Sagmeister, Susanne; Wessner, Barbara; Helmreich, Magdalena; Haeusler, Gabriele; Egerbacher, Monika

2013-01-01

Human insulin-like growth factor 1 Ec (IGF-1Ec), also called mechano growth factor (MGF), is a splice variant of insulin-like growth factor 1 (IGF-1), which has been shown in vitro as well as in vivo to induce growth and hypertrophy in mechanically stimulated or damaged muscle. Growth, hypertrophy and responses to mechanical stimulation are important reactions of cartilaginous tissues, especially those in growth plates. Therefore, we wanted to ascertain if MGF is expressed in growth plate cartilage and if it influences proliferation of chondrocytes, as it does in musculoskeletal tissues. MGF expression was analyzed in growth plate and control tissue samples from piglets aged 3 to 6 weeks. Furthermore, growth plate chondrocyte cell culture was used to evaluate the effects of the MGF peptide on proliferation. We showed that MGF is expressed in considerable amounts in the tissues evaluated. We found the MGF peptide to be primarily located in the cytoplasm, and in some instances, it was also found in the nucleus of the cells. Addition of MGF peptides was not associated with growth plate chondrocyte proliferation.

Snow observations in Mount Lebanon (2011-2016)

Science.gov (United States)

Fayad, Abbas; Gascoin, Simon; Faour, Ghaleb; Fanise, Pascal; Drapeau, Laurent; Somma, Janine; Fadel, Ali; Bitar, Ahmad Al; Escadafal, Richard

2017-08-01

We present a unique meteorological and snow observational dataset in Mount Lebanon, a mountainous region with a Mediterranean climate, where snowmelt is an essential water resource. The study region covers the recharge area of three karstic river basins (total area of 1092 km2 and an elevation up to 3088 m). The dataset consists of (1) continuous meteorological and snow height observations, (2) snowpack field measurements, and (3) medium-resolution satellite snow cover data. The continuous meteorological measurements at three automatic weather stations (MZA, 2296 m; LAQ, 1840 m; and CED, 2834 m a.s.l.) include surface air temperature and humidity, precipitation, wind speed and direction, incoming and reflected shortwave irradiance, and snow height, at 30 min intervals for the snow seasons (November-June) between 2011 and 2016 for MZA and between 2014 and 2016 for CED and LAQ. Precipitation data were filtered and corrected for Geonor undercatch. Observations of snow height (HS), snow water equivalent, and snow density were collected at 30 snow courses located at elevations between 1300 and 2900 m a.s.l. during the two snow seasons of 2014-2016 with an average revisit time of 11 days. Daily gap-free snow cover extent (SCA) and snow cover duration (SCD) maps derived from MODIS snow products are provided for the same period (2011-2016). We used the dataset to characterize mean snow height, snow water equivalent (SWE), and density for the first time in Mount Lebanon. Snow seasonal variability was characterized with high HS and SWE variance and a relatively high snow density mean equal to 467 kg m-3. We find that the relationship between snow depth and snow density is specific to the Mediterranean climate. The current model explained 34 % of the variability in the entire dataset (all regions between 1300 and 2900 m a.s.l.) and 62 % for high mountain regions (elevation 2200-2900 m a.s.l.). The dataset is suitable for the investigation of snow dynamics and for the forcing

Snow, ice and solar radiation

NARCIS (Netherlands)

Kuipers Munneke, P.

2009-01-01

The snow-covered ice sheets of Antarctica and Greenland reflect most of the incoming solar radiation. The reflectivity, commonly called the albedo, of snow on these ice sheets has been observed to vary in space and time. In this thesis, temporal and spatial changes in snow albedo is found to depend

Spatial and temporal variability in seasonal snow density

KAUST Repository

Bormann, Kathryn J.

2013-03-01

Snow density is a fundamental physical property of snowpacks used in many aspects of snow research. As an integral component in the remote sensing of snow water equivalent and parameterisation of snow models, snow density may be used to describe many important features of snowpack behaviour. The present study draws on a significant dataset of snow density and climate observations from the United States, Australia and the former Soviet Union and uses regression-based techniques to identify the dominant climatological drivers for snow densification rates, characterise densification rate variability and estimate spring snow densities from more readily available climate data. Total winter precipitation was shown to be the most prominent driver of snow densification rates, with mean air temperature and melt-refreeze events also found to be locally significant. Densification rate variance is very high at Australian sites, very low throughout the former Soviet Union and between these extremes throughout much of the US. Spring snow densities were estimated using a statistical model with climate variable inputs and best results were achieved when snow types were treated differently. Given the importance of snow density information in many snow-related research disciplines, this work has implications for current methods of converting snow depths to snow water equivalent, the representation of snow dynamics in snow models and remote sensing applications globally. © 2013 Elsevier B.V.

Spatial and temporal variability in seasonal snow density

KAUST Repository

Bormann, Kathryn J.; Westra, Seth; Evans, Jason P.; McCabe, Matthew

2013-01-01

Snow density is a fundamental physical property of snowpacks used in many aspects of snow research. As an integral component in the remote sensing of snow water equivalent and parameterisation of snow models, snow density may be used to describe many important features of snowpack behaviour. The present study draws on a significant dataset of snow density and climate observations from the United States, Australia and the former Soviet Union and uses regression-based techniques to identify the dominant climatological drivers for snow densification rates, characterise densification rate variability and estimate spring snow densities from more readily available climate data. Total winter precipitation was shown to be the most prominent driver of snow densification rates, with mean air temperature and melt-refreeze events also found to be locally significant. Densification rate variance is very high at Australian sites, very low throughout the former Soviet Union and between these extremes throughout much of the US. Spring snow densities were estimated using a statistical model with climate variable inputs and best results were achieved when snow types were treated differently. Given the importance of snow density information in many snow-related research disciplines, this work has implications for current methods of converting snow depths to snow water equivalent, the representation of snow dynamics in snow models and remote sensing applications globally. © 2013 Elsevier B.V.

Moving sidewalk for snow board gelande; Snow board gerendemuke ugoku hodo

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-04-20

This is a moving sidewalk installed on the indoor type artificial snow board gelande at Shigenobu-cho, Ehime prefecture, constructed for the first time in Shikoku. It carries snow boarders in gelande. The main specifications are as follows. Type: 800 type. Sidewalk width: 600mm. Length: 76.0m. Speed: 30m/min. Inclination angle: 13 degrees (inclination type). The features are as follows. (1) The tread is rubber-belt made and skid-resistant if it gets wet. (2) It is equipped with the each-part antifreezer, considering the snow quality and the environment where it is used at low temperature. (translated by NEDO)

Unexpected Patterns in Snow and Dirt

Science.gov (United States)

Ackerson, Bruce J.

2018-01-01

For more than 30 years, Albert A. Bartlett published "Thermal patterns in the snow" in this journal. These are patterns produced by heat sources underneath the snow. Bartlett's articles encouraged me to pay attention to patterns in snow and to understanding them. At winter's end the last snow becomes dirty and is heaped into piles. This…

Testing a blowing snow model against distributed snow measurements at Upper Sheep Creek, Idaho, United States of America

Science.gov (United States)

Rajiv Prasad; David G. Tarboton; Glen E. Liston; Charles H. Luce; Mark S. Seyfried

2001-01-01

In this paper a physically based snow transport model (SnowTran-3D) was used to simulate snow drifting over a 30 m grid and was compared to detailed snow water equivalence (SWE) surveys on three dates within a small 0.25 km2 subwatershed, Upper Sheep Creek. Two precipitation scenarios and two vegetation scenarios were used to carry out four snow transport model runs in...

Water losses during technical snow production

Science.gov (United States)

Grünewald, Thomas; Wolfsperger, Fabian

2017-04-01

These days, the production of technical snow can be seen as a prerequisite for winter tourism. Huge amounts of water are used for technical snow production by ski resorts, especially in the beginning of the winter season. The aim is to guarantee an appropriate amount of snow to reliably provide optimal ski runs until the date of season opening in early December. Technical snow is generated by pumping pressurized water through the nozzles of a snow machine and dispersing the resulting spray of small water droplets which freeze during their travel to the ground. Cooling and freezing of the droplets can only happen if energy is emitted to the air mass surrounding the droplets. This heat transfer is happening through convective cooling and though evaporation and sublimation of water droplets and ice particles. This means that also mass is lost from the droplets and added in form of vapor to the air. It is important to note that not all water that is pumped through the snow machine is converted to snow distributed on the ground. Significant amounts of water are lost due to wind drift, sublimation and evaporation while droplets are traveling through the air or to draining of water which is not fully frozen when arriving at the ground. Studies addressing this question are sparse and the quantity of the water losses is still unclear. In order to assess this question in more detail, we obtained several systematic field observations at a test site near Davos, Switzerland. About a dozen of snow making tests had been performed during the last winter seasons. We compare the amount of water measured at the intake of the snow machine with the amount of snow accumulating at the ground during a night of snow production. The snow mass was calculated from highly detailed repeated terrestrial laser scanning measurements in combination with manually gathered snow densities. In addition a meteorological station had been set up in the vicinity observing all relevant meteorological

Monitoring Forsmark. Snow depth, snow water content and ice cover during the winter 2010/2011

Energy Technology Data Exchange (ETDEWEB)

Wass, Eva (Geosigma AB (Sweden))

2011-07-15

Snow depth and ice cover have been measured and observed during the winter 2010/2011. This type of measurements started in the winter 2002/2003 and has been ongoing since then. In addition to these parameters, the water content of the snow was calculated at each measurement occasion from the weight of a snow sample. Measurements and observations were conducted on a regular basis from the beginning of November 2010 until the middle of April 2011. A persistent snow cover was established in the end of November 2010 and remained until the beginning of April 2011 at the station with longest snow cover duration. The period of ice cover was 160 days in Lake Eckarfjaerden, whereas the sea bay at SFR was ice covered for 135 days

Monitoring Forsmark. Snow depth, snow water content and ice cover during the winter 2010/2011

International Nuclear Information System (INIS)

Wass, Eva

2011-07-01

Snow depth and ice cover have been measured and observed during the winter 2010/2011. This type of measurements started in the winter 2002/2003 and has been ongoing since then. In addition to these parameters, the water content of the snow was calculated at each measurement occasion from the weight of a snow sample. Measurements and observations were conducted on a regular basis from the beginning of November 2010 until the middle of April 2011. A persistent snow cover was established in the end of November 2010 and remained until the beginning of April 2011 at the station with longest snow cover duration. The period of ice cover was 160 days in Lake Eckarfjaerden, whereas the sea bay at SFR was ice covered for 135 days

An inverse approach for elucidating dendritic function

Directory of Open Access Journals (Sweden)

Benjamin Torben-Nielsen

2010-09-01

Full Text Available We outline an inverse approach for investigating dendritic function-structure relationships by optimizing dendritic trees for a-priori chosen computational functions. The inverse approach can be applied in two different ways. First, we can use it as a `hypothesis generator' in which we optimize dendrites for a function of general interest. The optimization yields an artificial dendrite that is subsequently compared to real neurons. This comparison potentially allows us to propose hypotheses about the function of real neurons. In this way, we investigated dendrites that optimally perform input-order detection. Second, we can use it as a `function confirmation' by optimizing dendrites for functions hypothesized to be performed by classes of neurons. If the optimized, artificial, dendrites resemble the dendrites of real neurons the artificial dendrites corroborate the hypothesized function of the real neuron. Moreover, properties of the artificial dendrites can lead to predictions about yet unmeasured properties. In this way, we investigated wide-field motion integration performed by the VS cells of the fly visual system. In outlining the inverse approach and two applications, we also elaborate on the nature of dendritic function. We furthermore discuss the role of optimality in assigning functions to dendrites and point out interesting future directions.

Improving snow water equivalent simulations in an alpine basin using blended gage precipitation and snow pillow measurements

Science.gov (United States)

Sohrabi, M.; Safeeq, M.; Conklin, M. H.

2017-12-01

Snowpack is a critical freshwater reservoir that sustains ecosystem, natural habitat, hydropower, agriculture, and urban water supply in many areas around the world. Accurate estimation of basin scale snow water equivalent (SWE), through both measurement and modeling, has been significantly recognized to improve regional water resource management. Recent advances in remote data acquisition techniques have improved snow measurements but our ability to model snowpack evolution is largely hampered by poor knowledge of inherently variable high-elevation precipitation patterns. For a variety of reasons, majority of the precipitation gages are located in low and mid-elevation range and function as drivers for basin scale hydrologic modeling. Here, we blend observed gage precipitation from low and mid-elevation with point observations of SWE from high-elevation snow pillow into a physically based snow evolution model (SnowModel) to better represent the basin-scale precipitation field and improve snow simulations. To do this, we constructed two scenarios that differed in only precipitation. In WTH scenario, we forced the SnowModel using spatially distributed gage precipitation data. In WTH+SP scenario, the model was forced with spatially distributed precipitation data derived from gage precipitation along with observed precipitation from snow pillows. Since snow pillows do not directly measure precipitation, we uses positive change in SWE as a proxy for precipitation. The SnowModel was implemented at daily time step and 100 m resolution for the Kings River Basin, USA over 2000-2014. Our results show an improvement in snow simulation under WTH+SP as compared to WTH scenario, which can be attributed to better representation in high-elevation precipitation patterns under WTH+SP. The average Nash Sutcliffe efficiency over all snow pillow and course sites was substantially higher for WTH+SP (0.77) than for WTH scenario (0.47). The maximum difference in observed and simulated

Phase field modeling of dendritic coarsening during isothermal

Directory of Open Access Journals (Sweden)

Zhang Yutuo

2011-08-01

Full Text Available Dendritic coarsening in Al-2mol%Si alloy during isothermal solidification at 880K was investigated by phase field modeling. Three coarsening mechanisms operate in the alloy: (a melting of small dendrite arms; (b coalescence of dendrites near the tips leading to the entrapment of liquid droplets; (c smoothing of dendrites. Dendrite melting is found to be dominant in the stage of dendritic growth, whereas coalescence of dendrites and smoothing of dendrites are dominant during isothermal holding. The simulated results provide a better understanding of dendrite coarsening during isothermal solidification.

Climate change impacts on snow water availability in the Euphrates-Tigris basin

Directory of Open Access Journals (Sweden)

M. Özdoğan

2011-09-01

changes in snow water availability presented here are likely to be indicative of climate change impacts on the water resources of the Euphrates-Tigris basin.

Equine dendritic cells generated with horse serum have enhanced functionality in comparison to dendritic cells generated with fetal bovine serum.

Science.gov (United States)

Ziegler, Anja; Everett, Helen; Hamza, Eman; Garbani, Mattia; Gerber, Vinzenz; Marti, Eliane; Steinbach, Falko

2016-11-15

Dendritic cells are professional antigen-presenting cells that play an essential role in the initiation and modulation of T cell responses. They have been studied widely for their potential clinical applications, but for clinical use to be successful, alternatives to xenogeneic substances like fetal bovine serum (FBS) in cell culture need to be found. Protocols for the generation of dendritic cells ex vivo from monocytes are well established for several species, including horses. Currently, the gold standard protocol for generating dendritic cells from monocytes across various species relies upon a combination of GM-CSF and IL-4 added to cell culture medium which is supplemented with FBS. The aim of this study was to substitute FBS with heterologous horse serum. For this purpose, equine monocyte-derived dendritic cells (eqMoDC) were generated in the presence of horse serum or FBS and analysed for the effect on morphology, phenotype and immunological properties. Changes in the expression of phenotypic markers (CD14, CD86, CD206) were assessed during dendritic cell maturation by flow cytometry. To obtain a more complete picture of the eqMoDC differentiation and assess possible differences between FBS- and horse serum-driven cultures, a transcriptomic microarray analysis was performed. Lastly, immature eqMoDC were primed with a primary antigen (ovalbumin) or a recall antigen (tetanus toxoid) and, after maturation, were co-cultured with freshly isolated autologous CD5 + T lymphocytes to assess their T cell stimulatory capacity. The microarray analysis demonstrated that eqMoDC generated with horse serum were indistinguishable from those generated with FBS. However, eqMoDC incubated with horse serum-supplemented medium exhibited a more characteristic dendritic cell morphology during differentiation from monocytes. A significant increase in cell viability was also observed in eqMoDC cultured with horse serum. Furthermore, eqMoDC generated in the presence of horse serum

Orientations of dendritic growth during solidification

Science.gov (United States)

Lee, Dong Nyung

2017-03-01

Dendrites are crystalline forms which grow far from the limit of stability of the plane front and adopt an orientation which is as close as possible to the heat flux direction. Dendritic growth orientations for cubic metals, bct Sn, and hcp Zn, can be controlled by thermal conductivity, Young's modulus, and surface energy. The control factors have been elaborated. Since the dendrite is a single crystal, its properties such as thermal conductivity that influences the heat flux direction, the minimum Young's modulus direction that influences the strain energy minimization, and the minimum surface energy plane that influences the crystal/liquid interface energy minimization have been proved to control the dendritic growth direction. The dendritic growth directions of cubic metals are determined by the minimum Young's modulus direction and/or axis direction of symmetry of the minimum crystal surface energy plane. The dendritic growth direction of bct Sn is determined by its maximum thermal conductivity direction and the minimum surface energy plane normal direction. The primary dendritic growth direction of hcp Zn is determined by its maximum thermal conductivity direction and the minimum surface energy plane normal direction and the secondary dendrite arm direction of hcp Zn is normal to the primary dendritic growth direction.

Long-term analyses of snow dynamics within the french Alps on the 1900-2100 period. Analyses of historical snow water equivalent observations, modelisations and projections of a hundred of snow courses.

Science.gov (United States)

Mathevet, T.; Joel, G.; Gottardi, F.; Nemoz, B.

2017-12-01

The aim of this communication is to present analyses of climate variability and change on snow water equivalent (SWE) observations, reconstructions (1900-2016) and scenarii (2020-2100) of a hundred of snow courses dissiminated within the french Alps. This issue became particularly important since a decade, in regions where snow variability had a large impact on water resources availability, poor snow conditions in ski resorts and artificial snow production. As a water resources manager in french mountainuous regions, EDF (french hydropower company) has developed and managed a hydrometeorological network since 1950. A recent data rescue research allowed to digitize long term SWE manual measurments of a hundred of snow courses within the french Alps. EDF have been operating an automatic SWE sensors network, complementary to the snow course network. Based on numerous SWE observations time-series and snow accumulation and melt model (Garavaglia et al., 2017), continuous daily historical SWE time-series have been reconstructed within the 1950-2016 period. These reconstructions have been extented to 1900 using 20 CR reanalyses (ANATEM method, Kuentz et al., 2015) and up to 2100 using GIEC Climate Change scenarii. Considering various mountainous areas within the french Alps, this communication focuses on : (1) long term (1900-2016) analyses of variability and trend of total precipitation, air temperature, snow water equivalent, snow line altitude, snow season length , (2) long term variability of hydrological regime of snow dominated watersheds and (3) future trends (2020 -2100) using GIEC Climate Change scenarii. Comparing historical period (1950-1984) to recent period (1984-2016), quantitative results within a region in the north Alps (Maurienne) shows an increase of air temperature by 1.2 °C, an increase of snow line height by 200m, a reduction of SWE by 200 mm/year and a reduction of snow season length by 15 days. These analyses will be extended from north to south

Sublimation From Snow in Northern Environments

Science.gov (United States)

Pomeroy, J. W.

2002-12-01

Sublimation from snow is an often neglected component of water and energy balances. Research under the Mackenzie GEWEX Study has attempted to understand the snow and atmospheric processes controlling sublimation and to estimate the magnitude of sublimation in high latitude catchments. Eddy correlation units were used to measure vertical water vapour fluxes from a high latitude boreal forest, snow-covered tundra and shrub-covered tundra in Wolf Creek Research Basin, near Whitehorse Yukon, Territory Canada. Over Jan-Apr. water vapour fluxes from the forest canopy amounted to 18.3 mm, a significant loss from winter snowfall of 54 mm. Most of this loss occurred when the canopy was snow-covered. The weight of snow measured on a suspended, weighed tree indicates that this flux is dominated by sublimation of intercepted snow. In the melt period (April), water vapour fluxes were uniformly small ranging from 0.21 mm/day on the tundra slope, 0.23 mm/day for the forest and 0.27 mm/day for the shrub-tundra. During the melt period the forest and shrub canopies was snow-free and roots were frozen, so the primary source of water vapour from all sites was the surface snow.

[Snow cover pollution monitoring in Ufa].

Science.gov (United States)

Daukaev, R A; Suleĭmanov, R A

2008-01-01

The paper presents the results of examining the snow cover polluted with heavy metals in the large industrial town of Ufa. The level of man-caused burden on the snow cover of the conventional parts of the town was estimated and compared upon exposure to a wide range of snow cover pollutants. The priority snow cover pollutants were identified among the test heavy metals.

Effects of multilayer snow scheme on the simulation of snow: Offline Noah and coupled with NCEP CFSv2

Science.gov (United States)

Saha, Subodh Kumar; Sujith, K.; Pokhrel, Samir; Chaudhari, Hemantkumar S.; Hazra, Anupam

2017-03-01

The Noah version 2.7.1 is a moderately complex land surface model (LSM), with a single layer snowpack, combined with vegetation and underlying soil layer. Many previous studies have pointed out biases in the simulation of snow, which may hinder the skill of a forecasting system coupled with the Noah. In order to improve the simulation of snow by the Noah, a multilayer snow scheme (up to a maximum of six layers) is introduced. As Noah is the land surface component of the Climate Forecast System version 2 (CFSv2) of the National Centers for Environmental Prediction (NCEP), the modified Noah is also coupled with the CFSv2. The offline LSM shows large improvements in the simulation of snow depth, snow water equivalent (SWE), and snow cover area during snow season (October to June). CFSv2 with the modified Noah reveals a dramatic improvements in the simulation of snow depth and 2 m air temperature and moderate improvements in SWE. As suggested in the previous diagnostic and sensitivity study, improvements in the simulation of snow by CFSv2 have lead to the reduction in dry bias over the Indian subcontinent (by a maximum of 2 mm d-1). The multilayer snow scheme shows promising results in the simulation of snow as well as Indian summer monsoon rainfall and hence this development may be the part of the future version of the CFS.

Hardness properties and microscopic investigation of crack- crystal interaction in SiO(2)-MgO-Al(2)O(3)-K(2)O-B(2)O(3)-F glass ceramic system.

Science.gov (United States)

Roy, Shibayan; Basu, Bikramjit

2010-01-01

In view of the potential engineering applications requiring machinability and wear resistance, the present work focuses to evaluate hardness property and to understand the damage behavior of some selected glass-ceramics having different crystal morphologies with SiO(2)-MgO-Al(2)O(3)-K(2)O-B(2)O(3)-F composition, using static micro-indentation tests as well as dynamic scratch tests, respectively. Vickers hardness of up to 5.5 GPa has been measured in glass-ceramics containing plate like mica crystals. Scratch tests at a high load of 50 Nin artificial saliva were carried out in order to simulate the crack-microstructure interaction during real-time abrasion wear and machining operation. The experimental observations indicate that the novel "spherulitic-dendritic shaped "crystals, similar to the plate like crystals, have the potential to hinder the scratching induced crack propagation. In particular, such potential of the 'spherulitic-dendritic' crystals become more effective due to the larger interfacial area with the glass matrix as well as the dendritic structure of each mica plate, which helps in crack deflection and crack blunting, to a larger extent.While modest damage tolerant behavior is observed in case of 'spherulitic-dendritic' crystal containing material, severe brittle fracture of plate like crystals were noted, when both were scratched at 50 N load.

Simulating the Dependence of Sagebrush Steppe Vegetation on Redistributed Snow in a Semi-Arid Watershed.

Science.gov (United States)

Soderquist, B.; Kavanagh, K.; Link, T. E.; Strand, E. K.; Seyfried, M. S.

2014-12-01

In mountainous regions across the western USA, the composition of aspen (Populus tremuloides) and sagebrush steppe plant communities is often closely related to heterogeneous soil moisture subsidies resulting from redistributed snow. With decades of climate and precipitation data across elevational and precipitation gradients, the Reynolds Creek Experimental Watershed (RCEW) and critical zone observatory (CZO) in southwest Idaho provides a unique opportunity to study the relationship between vegetation types and redistributed snow. Within the RCEW, the total amount of precipitation has remained unchanged over the past 50 years, however the percentage of the precipitation falling as snow has declined by approximately 4% per decade at mid-elevation sites. As shifts in precipitation phase continue, future trends in vegetation composition and net primary productivity (NPP) of different plant functional types remains a critical question. We hypothesize that redistribution of snow may supplement drought sensitive species like aspen more so than drought tolerant species like mountain big sagebrush (Artemisia tridentata spp. vaseyana). To assess the importance of snowdrift subsidies on sagebrush steppe vegetation, NPP of aspen, shrub, and grass species was simulated at three sites using the biogeochemical process model BIOME-BGC. Each site is located directly downslope from snowdrifts providing soil moisture inputs to aspen stands and neighboring vegetation. Drifts vary in size with the largest containing up to four times the snow water equivalent (SWE) of a uniform precipitation layer. Precipitation inputs used by BIOME-BGC were modified to represent the redistribution of snow and simulations were run using daily climate data from 1985-2013. Simulated NPP of annual grasses at each site was not responsive to subsidies from drifting snow. However, at the driest site, aspen and shrub annual NPP was increased by as much as 44 and 30%, respectively, with the redistribution of

Rice Bran Feruloylated Oligosaccharides Activate Dendritic Cells via Toll-Like Receptor 2 and 4 Signaling

Directory of Open Access Journals (Sweden)

Chi Chen Lin

2014-04-01

Full Text Available This work presents the effects of feruloylated oligosaccharides (FOs of rice bran on murine bone marrow-derived dendritic cells (BMDCs and the potential pathway through which the effects are mediated. We found that FOs induced phenotypic maturation of DCs, as shown by the increased expression of CD40, CD80/CD86 and MHC-I/II molecules. FOs efficiently induced maturation of DCs generated from C3H/HeN or C57BL/6 mice with normal toll-like receptor 4 (TLR-4 or TLR-2 but not DCs from mice with mutated TLR4 or TLR2. The mechanism of action of FOs may be mediated by increased phosphorylation of ERK, p38 and JNK mitogen-activated protein kinase (MAPKs and increased NF-kB activity, which are important signaling molecules downstream of TLR-4 and TLR-2. These data suggest that FOs induce DCs maturation through TLR-4 and/or TLR-2 and that FOs might have potential efficacy against tumor or virus infection or represent a candidate-adjuvant approach for application in immunotherapy and vaccination.

Regulation of dendrite growth and maintenance by exocytosis

Science.gov (United States)

Peng, Yun; Lee, Jiae; Rowland, Kimberly; Wen, Yuhui; Hua, Hope; Carlson, Nicole; Lavania, Shweta; Parrish, Jay Z.; Kim, Michael D.

2015-01-01

ABSTRACT Dendrites lengthen by several orders of magnitude during neuronal development, but how membrane is allocated in dendrites to facilitate this growth remains unclear. Here, we report that Ras opposite (Rop), the Drosophila ortholog of the key exocytosis regulator Munc18-1 (also known as STXBP1), is an essential factor mediating dendrite growth. Neurons with depleted Rop function exhibit reduced terminal dendrite outgrowth followed by primary dendrite degeneration, suggestive of differential requirements for exocytosis in the growth and maintenance of different dendritic compartments. Rop promotes dendrite growth together with the exocyst, an octameric protein complex involved in tethering vesicles to the plasma membrane, with Rop–exocyst complexes and exocytosis predominating in primary dendrites over terminal dendrites. By contrast, membrane-associated proteins readily diffuse from primary dendrites into terminals, but not in the reverse direction, suggesting that diffusion, rather than targeted exocytosis, supplies membranous material for terminal dendritic growth, revealing key differences in the distribution of materials to these expanding dendritic compartments. PMID:26483382

Breeding snow: an instrumented sample holder for simultaneous tomographic and thermal studies

International Nuclear Information System (INIS)

Pinzer, B; Schneebeli, M

2009-01-01

To study the recrystallization processes during temperature gradient metamorphism of snow, we developed a sample holder that allows applying well-defined and stable thermal gradients to a snow sample while it is scanned in an x-ray micro-tomograph. To this end, both the thermal insulation of the sample as well as image contrast and resolution of the tomography had to be optimized. We solved this conflict by using thin aluminum cylinders in combination with highly insulating foam. This design is light, does not corrupt image quality and provides very good thermal decoupling from the environment. The sample holder was instrumented to measure the effective conductivity of the snow sample and calibrated using five materials of known conductivity. Finite element simulations were consistent with the calibration measurements and gave insight into the internal temperature and heat flux fields. With this setup, geometric and thermal evolution of snow under realistic thermal boundary conditions like alternating temperature gradients can be measured

Parameterizations for narrowband and broadband albedo of pure snow and snow containing mineral dust and black carbon

Science.gov (United States)

Dang, Cheng; Brandt, Richard E.; Warren, Stephen G.

2015-06-01

The reduction of snow spectral albedo by black carbon (BC) and mineral dust, both alone and in combination, is computed using radiative transfer modeling. Broadband albedo is shown for mass fractions covering the full range from pure snow to pure BC and pure dust, and for snow grain radii from 5 µm to 2500 µm, to cover the range of possible grain sizes on planetary surfaces. Parameterizations are developed for opaque homogeneous snowpacks for three broad bands used in general circulation models and several narrower bands. They are functions of snow grain radius and the mass fraction of BC and/or dust and are valid up to BC content of 10 ppm, needed for highly polluted snow. A change of solar zenith angle can be mimicked by changing grain radius. A given mass fraction of BC causes greater albedo reduction in coarse-grained snow; BC and grain radius can be combined into a single variable to compute the reduction of albedo relative to pure snow. The albedo reduction by BC is less if the snow contains dust, a common situation on mountain glaciers and in agricultural and grazing lands. Measured absorption spectra of mineral dust are critically reviewed as a basis for specifying dust properties for modeling. The effect of dust on snow albedo at visible wavelengths can be represented by an "equivalent BC" amount, scaled down by a factor of about 200. Dust has little effect on the near-IR albedo because the near-IR albedo of pure dust is similar to that of pure snow.

Review of ice and snow runway pavements

Directory of Open Access Journals (Sweden)

Greg White

2018-05-01

Full Text Available Antarctica is the highest, driest, coldest, windiest, most remote and most pristine place on Earth. Polar operations depend heavily on air transportation and support for personnel and equipment. It follows that improvement in snow and ice runway design, construction and maintenance will directly benefit polar exploration and research. Current technologies and design methods for snow and ice runways remain largely reliant on work performed in the 1950s and 1960s. This paper reviews the design and construction of polar runways using snow and ice as geomaterials. The inability to change existing snow and ice thickness or temperature creates a challenge for polar runway design and construction, as does the highly complex mechanical behaviour of snow, including the phenomena known as sintering. It is recommended that a modern approach be developed for ice and snow runway design, based on conventional rigid and flexible pavement design principles. This requires the development on an analytical model for the prediction of snow strength, based on snow age, temperature history and density. It is also recommended that the feasibility of constructing a snow runway at the South Pole be revisited, in light of contemporary snow sintering methods. Such a runway would represent a revolutionary advance for the logistical support of Antarctic research efforts. Keywords: Runway, Pavement, Snow, Ice, Antarctic

Pavement Snow Melting

Energy Technology Data Exchange (ETDEWEB)

Lund, John W.

2005-01-01

The design of pavement snow melting systems is presented based on criteria established by ASHRAE. The heating requirements depends on rate of snow fall, air temperature, relative humidity and wind velocity. Piping materials are either metal or plastic, however, due to corrosion problems, cross-linked polyethylene pipe is now generally used instead of iron. Geothermal energy is supplied to systems through the use of heat pipes, directly from circulating pipes, through a heat exchanger or by allowing water to flow directly over the pavement, by using solar thermal storage. Examples of systems in New Jersey, Wyoming, Virginia, Japan, Argentina, Switzerland and Oregon are presented. Key words: pavement snow melting, geothermal heating, heat pipes, solar storage, Wyoming, Virginia, Japan, Argentina, Klamath Falls.

Snow cover as a source of technogenic pollution of surface water during the snow melting period

OpenAIRE

Labuzova Olga; Noskova Tatyana; Lysenko Maria; Ovcharenko Elena; Papina Tatyana

2016-01-01

The study of pollutants in melt water of snow cover and snow disposal sites in the city of Barnaul showed that during the snow melting period the surface water is not subjected to significant technogenic impact according to a number of studied indices. The oils content is an exception: it can exceed MAC more than 20 times in river- water due to the melting of city disposal sites. Environmental damage due to an oils input into water resources during the snow melting period...

Canadian snow and sea ice: assessment of snow, sea ice, and related climate processes in Canada's Earth system model and climate-prediction system

Science.gov (United States)

Kushner, Paul J.; Mudryk, Lawrence R.; Merryfield, William; Ambadan, Jaison T.; Berg, Aaron; Bichet, Adéline; Brown, Ross; Derksen, Chris; Déry, Stephen J.; Dirkson, Arlan; Flato, Greg; Fletcher, Christopher G.; Fyfe, John C.; Gillett, Nathan; Haas, Christian; Howell, Stephen; Laliberté, Frédéric; McCusker, Kelly; Sigmond, Michael; Sospedra-Alfonso, Reinel; Tandon, Neil F.; Thackeray, Chad; Tremblay, Bruno; Zwiers, Francis W.

2018-04-01

use in operational seasonal prediction and for generating large ensembles of multidecadal simulations. Improvements in climate-prediction systems like CanSIPS rely not just on simulation quality but also on using novel observational constraints and the ready transfer of research to an operational setting. Improvements in seasonal forecasting practice arising from recent research include accurate initialization of snow and frozen soil, accounting for observational uncertainty in forecast verification, and sea ice thickness initialization using statistical predictors available in real time.

The Snow Must Go On: Ground Ice Encasement, Snow Compaction and Absence of Snow Differently Cause Soil Hypoxia, CO2 Accumulation and Tree Seedling Damage in Boreal Forest.

Science.gov (United States)

Martz, Françoise; Vuosku, Jaana; Ovaskainen, Anu; Stark, Sari; Rautio, Pasi

2016-01-01

At high latitudes, the climate has warmed at twice the rate of the global average with most changes observed in autumn, winter and spring. Increasing winter temperatures and wide temperature fluctuations are leading to more frequent rain-on-snow events and freeze-thaw cycles causing snow compaction and formation of ice layers in the snowpack, thus creating ice encasement (IE). By decreasing the snowpack insulation capacity and restricting soil-atmosphere gas exchange, modification of the snow properties may lead to colder soil but also to hypoxia and accumulation of trace gases in the subnivean environment. To test the effects of these overwintering conditions changes on plant winter survival and growth, we established a snow manipulation experiment in a coniferous forest in Northern Finland with Norway spruce and Scots pine seedlings. In addition to ambient conditions and prevention of IE, we applied three snow manipulation levels: IE created by artificial rain-on-snow events, snow compaction and complete snow removal. Snow removal led to deeper soil frost during winter, but no clear effect of IE or snow compaction done in early winter was observed on soil temperature. Hypoxia and accumulation of CO2 were highest in the IE plots but, more importantly, the duration of CO2 concentration above 5% was 17 days in IE plots compared to 0 days in ambient plots. IE was the most damaging winter condition for both species, decreasing the proportion of healthy seedlings by 47% for spruce and 76% for pine compared to ambient conditions. Seedlings in all three treatments tended to grow less than seedlings in ambient conditions but only IE had a significant effect on spruce growth. Our results demonstrate a negative impact of winter climate change on boreal forest regeneration and productivity. Changing snow conditions may thus partially mitigate the positive effect of increasing growing season temperatures on boreal forest productivity.

High fidelity remote sensing of snow properties from MODIS and the Airborne Snow Observatory: Snowflakes to Terabytes

Science.gov (United States)

Painter, T.; Mattmann, C. A.; Brodzik, M.; Bryant, A. C.; Goodale, C. E.; Hart, A. F.; Ramirez, P.; Rittger, K. E.; Seidel, F. C.; Zimdars, P. A.

2012-12-01

The response of the cryosphere to climate forcings largely determines Earth's climate sensitivity. However, our understanding of the strength of the simulated snow albedo feedback varies by a factor of three in the GCMs used in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, mainly caused by uncertainties in snow extent and the albedo of snow-covered areas from imprecise remote sensing retrievals. Additionally, the Western US and other regions of the globe depend predominantly on snowmelt for their water supply to agriculture, industry and cities, hydroelectric power, and recreation, against rising demand from increasing population. In the mountains of the Upper Colorado River Basin, dust radiative forcing in snow shortens snow cover duration by 3-7 weeks. Extended to the entire upper basin, the 5-fold increase in dust load since the late-1800s results in a 3-week earlier peak runoff and a 5% annual loss of total runoff. The remotely sensed dynamics of snow cover duration and melt however have not been factored into hydrological modeling, operational forecasting, and policymaking. To address these deficiencies in our understanding of snow properties, we have developed and validated a suite of MODIS snow products that provide accurate fractional snow covered area and radiative forcing of dust and carbonaceous aerosols in snow. The MODIS Snow Covered Area and Grain size (MODSCAG) and MODIS Dust Radiative Forcing in Snow (MODDRFS) algorithms, developed and transferred from imaging spectroscopy techniques, leverage the complete MODIS surface reflectance spectrum. The two most critical properties for understanding snowmelt runoff and timing are the spatial and temporal distributions of snow water equivalent (SWE) and snow albedo. We have created the Airborne Snow Observatory (ASO), an imaging spectrometer and scanning LiDAR system, to quantify SWE and snow albedo, generate unprecedented knowledge of snow properties, and provide complete

Insulin-like growth factor I (IGF-1 Ec/Mechano Growth factor--a splice variant of IGF-1 within the growth plate.

Directory of Open Access Journals (Sweden)

Werner Schlegel

Full Text Available Human insulin-like growth factor 1 Ec (IGF-1Ec, also called mechano growth factor (MGF, is a splice variant of insulin-like growth factor 1 (IGF-1, which has been shown in vitro as well as in vivo to induce growth and hypertrophy in mechanically stimulated or damaged muscle. Growth, hypertrophy and responses to mechanical stimulation are important reactions of cartilaginous tissues, especially those in growth plates. Therefore, we wanted to ascertain if MGF is expressed in growth plate cartilage and if it influences proliferation of chondrocytes, as it does in musculoskeletal tissues. MGF expression was analyzed in growth plate and control tissue samples from piglets aged 3 to 6 weeks. Furthermore, growth plate chondrocyte cell culture was used to evaluate the effects of the MGF peptide on proliferation. We showed that MGF is expressed in considerable amounts in the tissues evaluated. We found the MGF peptide to be primarily located in the cytoplasm, and in some instances, it was also found in the nucleus of the cells. Addition of MGF peptides was not associated with growth plate chondrocyte proliferation.

Distribution of Snow and Maximum Snow Water Equivalent Obtained by LANDSAT Data and Degree Day Method

Science.gov (United States)

Takeda, K.; Ochiai, H.; Takeuchi, S.

1985-01-01

Maximum snow water equivalence and snowcover distribution are estimated using several LANDSAT data taken in snowmelting season over a four year period. The test site is Okutadami-gawa Basin located in the central position of Tohoku-Kanto-Chubu District. The year to year normalization for snowmelt volume computation on the snow line is conducted by year to year correction of degree days using the snowcover percentage within the test basin obtained from LANDSAT data. The maximum snow water equivalent map in the test basin is generated based on the normalized snowmelt volume on the snow line extracted from four LANDSAT data taken in a different year. The snowcover distribution on an arbitrary day in snowmelting of 1982 is estimated from the maximum snow water equivalent map. The estimated snowcover is compared with the snowcover area extracted from NOAA-AVHRR data taken on the same day. The applicability of the snow estimation using LANDSAT data is discussed.

Laser-filamentation-induced condensation and snow formation in a cloud chamber.

Science.gov (United States)

Ju, Jingjing; Liu, Jiansheng; Wang, Cheng; Sun, Haiyi; Wang, Wentao; Ge, Xiaochun; Li, Chuang; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

2012-04-01

Using 1 kHz, 9 mJ femtosecond laser pulses, we demonstrate laser-filamentation-induced spectacular snow formation in a cloud chamber. An intense updraft of warm moist air is generated owing to the continuous heating by the high-repetition filamentation. As it encounters the cold air above, water condensation and large-sized particles spread unevenly across the whole cloud chamber via convection and cyclone like action on a macroscopic scale. This indicates that high-repetition filamentation plays a significant role in macroscopic laser-induced water condensation and snow formation.

Deriving Snow Cover Metrics for Alaska from MODIS

Directory of Open Access Journals (Sweden)

Chuck Lindsay

2015-09-01

Full Text Available Moderate Resolution Imaging Spectroradiometer (MODIS daily snow cover products provide an opportunity for determining snow onset and melt dates across broad geographic regions; however, cloud cover and polar darkness are limiting factors at higher latitudes. This study presents snow onset and melt dates for Alaska, portions of western Canada and the Russian Far East derived from Terra MODIS snow cover daily 500 m grid data (MOD10A1 and evaluates our method for filling data gaps caused by clouds or polar darkness. Pixels classified as cloud or no data were reclassified by: spatial filtering using neighboring pixel values; temporal filtering using pixel values for days before/after cloud cover; and snow-cycle filtering based on a time series assessment of a pixel’s position within snow accumulation, cover or melt periods. During the 2012 snow year, these gap-filling methods reduced cloud pixels from 27.7% to 3.1%. A total of 12 metrics (e.g., date of first and last snow, date of persistent snow cover and periods of intermittence for each pixel were calculated by snow year. A comparison of MODIS-derived snow onset and melt dates with in situ observations from 244 weather stations generally showed an early bias in MODIS-derived dates and an effect of increasing cloudiness exacerbating bias. Our results show that mean regional duration of seasonal snow cover is 179–311 days/year and that snow cover is often intermittent, with 41% of the area experiencing ≥2 snow-covered periods during a snow season. Other regional-scale patterns in the timing of snow onset and melt are evident in the yearly 500 m gridded products publically available at http://static.gina.alaska.edu/NPS_products/MODIS_snow/.

Modeling particulate removal in plate-plate and wire-plate electrostatic precipitators

Directory of Open Access Journals (Sweden)

S Ramechecandane

2016-09-01

Full Text Available The present study is concerned with the modeling of electrically charged particles in a model plate-plate and a single wire-plate electrostatic precipitator (ESP. The particle concentration distributions for both a plate-plate and a wire-plate ESP are calculated using a modified drift flux model. Numerical investigations are performed using the modified drift flux model for particle number concentration, in addition to the RNG k - ε model for the mean turbulent flow field and the Poisson equation for the electric field. The proposed model and the outlined methodology for coupling the flow field, electric field, charging kinetics and particle concentration is applied to two model precipitators that are truly representative of a wide class of commercialized ESPs. The present investigation is quite different from the earlier studies as it does not make assumptions like a homogeneous electric field or an infinite turbulent diffusivity. The electric field calculated is a strong function of position and controls the migration velocity of particles. Hence, the proposed model can be implemented in a flow solver to obtain a full-fledged solution for any kind of ESP with no limitations on the particle number concentration, as encountered in a Lagrangian approach. The effect of turbulent diffusivity on particle number concentration in a plate-plate ESP is investigated in detail and the results obtained are compared with available experimental data. Similarly, the effect of particle size/diameter and applied electric potential on the accumulative collection performance in the case of a wire-plate ESP is studied and the results obtained are compared with available numerical data. The numerical results obtained using the modified drift flux model for both the plate-plate and wire-plate ESP are in close agreement with available experimental and numerical data.

Snow darkening caused by black carbon emitted from fires

Science.gov (United States)

Engels, Jessica; Kloster, Silvia; Bourgeois, Quentin

2014-05-01

We implemented the effect of snow darkening caused by black carbon (BC) emitted from forest fires into the Max Planck Institute for Meteorology Earth System Model (MPI-M ESM) to estimate its potential climate impact of present day fire occurrence. Considerable amounts of black carbon emitted from fires are transported into snow covered regions. Already very small quantities of black carbon reduce the snow reflectance, with consequences for snow melting and snow spatial coverage. Therefore, the SNICAR (SNow And Ice Radiation) model (Flanner and Zender (2005)) is implemented in the land surface component (JSBACH) of the atmospheric general circulation model ECHAM6, developed at the MPI-M. The SNICAR model includes amongst other processes a complex calculation of the snow albedo depending on black carbon in snow and snow grain growth depending on water vapor fluxes for a five layer snow scheme. For the implementation of the SNICAR model into the one layer scheme of ECHAM6-JSBACH, we used the SNICAR-online version (http://snow.engin.umich.edu). This single-layer simulator provides the albedo of snow for selectable combinations of impurity content (e.g. black carbon), snow grain size, and incident solar flux characteristics. From this scheme we derived snow albedo values for black carbon in snow concentrations ranging between 0 and 1500 ng(BC)/g(snow) and for different snow grain sizes for the visible (0.3 - 0.7 µm) and near infrared range (0.7 - 1.5 µm). As snow grains grow over time, we assign different snow ages to different snow grain sizes (50, 150, 500, and 1000 µm). Here, a radius of 50 µm corresponds to new snow, whereas a radius of 1000 µm corresponds to old snow. The required snow age is taken from the BATS (Biosphere Atmosphere Transfer Scheme, Dickinson et al. (1986)) snow albedo implementation in ECHAM6-JSBACH. Here, we will present an extended evaluation of the model including a comparison of modeled black carbon in snow concentrations to observed

Early results from NASA's SnowEx campaign

Science.gov (United States)

Kim, Edward; Gatebe, Charles; Hall, Dorothy; Misakonis, Amy; Elder, Kelly; Marshall, Hans Peter; Hiemstra, Chris; Brucker, Ludovic; Crawford, Chris; Kang, Do Hyuk; De Marco, Eugenia; Beckley, Matt; Entin, Jared

2017-04-01

SnowEx is a multi-year airborne snow campaign with the primary goal of addressing the question: How much water is stored in Earth's terrestrial snow-covered regions? Year 1 (2016-17) focuses on the distribution of snow-water equivalent (SWE) and the snow energy balance in a forested environment. The year 1 primary site is Grand Mesa and the secondary site is the Senator Beck Basin, both in western, Colorado, USA. Ten core sensors on four core aircraft will make observations using a broad suite of airborne sensors including active and passive microwave, and active and passive optical/infrared sensing techniques to determine the sensitivity and accuracy of these potential satellite remote sensing techniques, along with models, to measure snow under a range of forest conditions. SnowEx also includes an extensive range of ground truth measurements—in-situ samples, snow pits, ground based remote sensing measurements, and sophisticated new techniques. A detailed description of the data collected will be given and some early results will be presented. Seasonal snow cover is the largest single component of the cryosphere in areal extent (covering an average of 46M km2 of Earth's surface (31 % of land areas) each year). This seasonal snow has major societal impacts in the areas of water resources, natural hazards (floods and droughts), water security, and weather and climate. The only practical way to estimate the quantity of snow on a consistent global basis is through satellites. Yet, current space-based techniques underestimate storage of snow water equivalent (SWE) by as much as 50%, and model-based estimates can differ greatly vs. estimates based on remotely-sensed observations. At peak coverage, as much as half of snow-covered terrestrial areas involve forested areas, so quantifying the challenge represented by forests is important to plan any future snow mission. Single-sensor approaches may work for certain snow types and certain conditions, but not for others

Long-term variability in Northern Hemisphere snow cover and associations with warmer winters

Science.gov (United States)

McCabe, Gregory J.; Wolock, David M.

2010-01-01

A monthly snow accumulation and melt model is used with gridded monthly temperature and precipitation data for the Northern Hemisphere to generate time series of March snow-covered area (SCA) for the period 1905 through 2002. The time series of estimated SCA for March is verified by comparison with previously published time series of SCA for the Northern Hemisphere. The time series of estimated Northern Hemisphere March SCA shows a substantial decrease since about 1970, and this decrease corresponds to an increase in mean winter Northern Hemisphere temperature. The increase in winter temperature has caused a decrease in the fraction of precipitation that occurs as snow and an increase in snowmelt for some parts of the Northern Hemisphere, particularly the mid-latitudes, thus reducing snow packs and March SCA. In addition, the increase in winter temperature and the decreases in SCA appear to be associated with a contraction of the circumpolar vortex and a poleward movement of storm tracks, resulting in decreased precipitation (and snow) in the low- to mid-latitudes and an increase in precipitation (and snow) in high latitudes. If Northern Hemisphere winter temperatures continue to warm as they have since the 1970s, then March SCA will likely continue to decrease.

An Assessment of Existing Methodologies to Retrieve Snow Cover Fraction from MODIS Data

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Théo Masson

2018-04-01

Full Text Available The characterization of snow extent is critical for a wide range of applications. Since 1966, snow maps at different spatial resolutions have been produced using various satellite sensor images. Nowadays, the most widely used products are likely those derived from Moderate-Resolution Imaging Spectroradiometer (MODIS data, which cover the whole Earth at a near-daily frequency. There are a variety of snow mapping methods for MODIS data, based on different methodologies and applied at different spatial resolutions. Up to now, all these products have been tested and evaluated separately. This study aims to compare the methods currently available for retrieving snow from MODIS data. The focus is on fractional snow cover, which represents the snow cover area at the subpixel level. We examine the two main approaches available for generating such products from MODIS data; namely, linear regression of the Normalized Difference Snow Index (NDSI and spectral unmixing (SU. These two approaches have resulted in several methods, such as MOD10A1 (the NSIDC MODIS snow product for NDSI regression, and MODImLAB for SU. The assessment of these approaches was carried out using higher resolution binary snow maps (i.e., showing the presence or absence of snow at spatial resolutions of 10, 20, and 30 m, produced by SPOT 4, SPOT 5, and LANDSAT-8, respectively. Three areas were selected in order to provide landscape diversity: the French Alps (117 dates, the Pyrenees (30 dates, and the Moroccan Atlas (24 dates. This study investigates the impact of reference maps on accuracy assessments, and it is suggested that NDSI-based high spatial resolution reference maps advantage NDSI medium-resolution snow maps. For MODIS snow maps, the results show that applying an NDSI approach to accurate surface reflectance corrected for topographic and atmospheric effects generally outperforms other methods for the global retrieval of snow cover area. The improvements to the newer version

Snow cover as a source of technogenic pollution of surface water during the snow melting period

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Labuzova Olga

2016-10-01

Full Text Available The study of pollutants in melt water of snow cover and snow disposal sites in the city of Barnaul showed that during the snow melting period the surface water is not subjected to significant technogenic impact according to a number of studied indices. The oils content is an exception: it can exceed MAC more than 20 times in river- water due to the melting of city disposal sites. Environmental damage due to an oils input into water resources during the snow melting period can be more than 300000 thousand rubles.

Hydrologic response across a snow persistence gradient on the west and east slopes of the Rocky Mountains in Colorado

Science.gov (United States)

Richard, G. A.; Hammond, J. C.; Kampf, S. K.; Moore, C. D.; Eurich, A.

2017-12-01

Snowpack trend analyses and modeling studies suggest that lower elevation snowpacks in mountain regions are most sensitive to drought and warming temperatures, however, in Colorado, most snow monitoring occurs in the high elevations where snow lasts throughout the winter and most streamflow monitoring occurs at lower elevations. The lack of combined snow and streamflow monitoring in watersheds along the transition from intermittent to persistent snow creates a gap in our understanding of snowmelt and runoff within the intermittent-persistent snow transition. Expanded hydrologic monitoring that spans the gradient of snow conditions in Colorado can help improve streamflow prediction and inform land and water managers. This study established hydrologic monitoring watersheds in intermittent, transitional, and persistent snow zones on the east slope and west slope of the Rocky Mountains in Colorado, and uses this monitoring network to improve understanding of how snow accumulation and melt affect soil moisture and streamflow generation under different snow conditions. We monitored six small watersheds (three west slope, three east slope) (0.8 to 3.9 km2) that drain intermittent, transitional, and persistent snow zones. At each site, we measured: streamflow, snow depth, soil moisture, precipitation, air temperature, and snow water equivalent (SWE). In our first season of monitoring, the west slope persistent and transitional sites had more mid-winter melt and infiltration, shorter snowpack duration, and lower peak SWE than the east slope sites. Snow cover remained at the east slope persistent site into June, whereas much of the snow at the persistent site on the west slope had already melted by early June. The difference in soil water input likely has consequences for streamflow response that we will continue to examine in future years. At the west slope intermittent site, the stream did not flow during the entire first year of monitoring, while at the east slope

Seasonal variation in the input of atmospheric selenium to northwestern Greenland snow

Energy Technology Data Exchange (ETDEWEB)

Lee, Khanghyun; Hong, Sang-Bum [Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon 406–840 (Korea, Republic of); Lee, Jeonghoon [Department of Science Education, Ewha womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul 120-750 (Korea, Republic of); Chung, Jiwoong; Hur, Soon-Do [Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon 406–840 (Korea, Republic of); Hong, Sungmin, E-mail: smhong@inha.ac.kr [Department of Ocean Sciences, Inha University, 100 Inharo, Nam-gu, Incheon 402-751 (Korea, Republic of)

2015-09-01

Oxygen isotope ratio (δ{sup 18}O) and concentrations of Al, Na{sup +}, methanesulfonic acid (MSA), SO{sub 4}{sup 2−}, and selenium (Se) in a continuous series of 70 snow samples from a 3.2-m snow pit at a site in northwestern Greenland were determined using ultraclean procedures. Well-defined depth profiles of δ{sup 18}O, Al, and sea-salt-Na{sup +} allowed the determination of chronology of the snow pit that spanned approximately 6 years from spring 2003 to summer 2009. Se concentrations were at a low pg/g level, ranging from 7.2 to 45 pg/g, and exhibited high variability with generally higher values during winter and spring and lower values during summer and fall. Very high crustal enrichment factors (EF{sub c}) of Se averaging approximately 26,600 for the entire time period indicate a small contribution from crust dust. High Se/MSA ratios are generally observed in the winter and spring snow layers, in which the Se concentrations were relatively high (> 20 pg/g). This suggests that a significant component of the Se present in the snow layers is of anthropogenic origin. During the summer season, however, high EF{sub c} values are accompanied with low Se/MSA, indicating an increased contribution of marine biogenic sources. Significant correlations between Se, Al, and non-sea-salt SO{sub 4}{sup 2−} highlight that significant inputs of Se to the snow are likely controlled by the seasonality in the transport efficiency of anthropogenic Se from the source regions to the site. Based on the seasonal changes in Se concentrations, Se/MSA, and Se/S ratios observed in the samples, the input of anthropogenic Se to the site appears to be governed by the long-range transportation of Se emitted from coal combustion in East Asian countries, especially in China. - Highlights: • The first comprehensive seasonal variation of Se in Greenland snow is presented. • Data exhibit pronounced seasonality in the fallout of Se to Greenland. • High Se/MSA ratios indicate a

Seasonal variation in the input of atmospheric selenium to northwestern Greenland snow

International Nuclear Information System (INIS)

Lee, Khanghyun; Hong, Sang-Bum; Lee, Jeonghoon; Chung, Jiwoong; Hur, Soon-Do; Hong, Sungmin

2015-01-01

Oxygen isotope ratio (δ 18 O) and concentrations of Al, Na + , methanesulfonic acid (MSA), SO 4 2− , and selenium (Se) in a continuous series of 70 snow samples from a 3.2-m snow pit at a site in northwestern Greenland were determined using ultraclean procedures. Well-defined depth profiles of δ 18 O, Al, and sea-salt-Na + allowed the determination of chronology of the snow pit that spanned approximately 6 years from spring 2003 to summer 2009. Se concentrations were at a low pg/g level, ranging from 7.2 to 45 pg/g, and exhibited high variability with generally higher values during winter and spring and lower values during summer and fall. Very high crustal enrichment factors (EF c ) of Se averaging approximately 26,600 for the entire time period indicate a small contribution from crust dust. High Se/MSA ratios are generally observed in the winter and spring snow layers, in which the Se concentrations were relatively high (> 20 pg/g). This suggests that a significant component of the Se present in the snow layers is of anthropogenic origin. During the summer season, however, high EF c values are accompanied with low Se/MSA, indicating an increased contribution of marine biogenic sources. Significant correlations between Se, Al, and non-sea-salt SO 4 2− highlight that significant inputs of Se to the snow are likely controlled by the seasonality in the transport efficiency of anthropogenic Se from the source regions to the site. Based on the seasonal changes in Se concentrations, Se/MSA, and Se/S ratios observed in the samples, the input of anthropogenic Se to the site appears to be governed by the long-range transportation of Se emitted from coal combustion in East Asian countries, especially in China. - Highlights: • The first comprehensive seasonal variation of Se in Greenland snow is presented. • Data exhibit pronounced seasonality in the fallout of Se to Greenland. • High Se/MSA ratios indicate a significant contribution from anthropogenic sources. �

Dendritic Kv3.3 potassium channels in cerebellar purkinje cells regulate generation and spatial dynamics of dendritic Ca2+ spikes.

Science.gov (United States)

Zagha, Edward; Manita, Satoshi; Ross, William N; Rudy, Bernardo

2010-06-01

Purkinje cell dendrites are excitable structures with intrinsic and synaptic conductances contributing to the generation and propagation of electrical activity. Voltage-gated potassium channel subunit Kv3.3 is expressed in the distal dendrites of Purkinje cells. However, the functional relevance of this dendritic distribution is not understood. Moreover, mutations in Kv3.3 cause movement disorders in mice and cerebellar atrophy and ataxia in humans, emphasizing the importance of understanding the role of these channels. In this study, we explore functional implications of this dendritic channel expression and compare Purkinje cell dendritic excitability in wild-type and Kv3.3 knockout mice. We demonstrate enhanced excitability of Purkinje cell dendrites in Kv3.3 knockout mice, despite normal resting membrane properties. Combined data from local application pharmacology, voltage clamp analysis of ionic currents, and assessment of dendritic Ca(2+) spike threshold in Purkinje cells suggest a role for Kv3.3 channels in opposing Ca(2+) spike initiation. To study the physiological relevance of altered dendritic excitability, we measured [Ca(2+)](i) changes throughout the dendritic tree in response to climbing fiber activation. Ca(2+) signals were specifically enhanced in distal dendrites of Kv3.3 knockout Purkinje cells, suggesting a role for dendritic Kv3.3 channels in regulating propagation of electrical activity and Ca(2+) influx in distal dendrites. These findings characterize unique roles of Kv3.3 channels in dendrites, with implications for synaptic integration, plasticity, and human disease.

Radiation shielding plate

International Nuclear Information System (INIS)

Kobayashi, Torakichi; Sugawara, Takeo.

1983-01-01

Purpose: To reduce the weight and stabilize the configuration of a radiation shielding plate which is used in close contact with an object to be irradiated with radiation rays. Constitution: The radiation shielding plate comprises a substrate made of lead glass and a metallic lead coating on the surface of the substrate by means of plating, vapor deposition or the like. Apertures for permeating radiation rays are formed to the radiation shielding plate. Since the shielding plate is based on a lead glass plate, a sufficient mechanical strength can be obtained with a thinner structure as compared with the conventional plate made of metallic lead. Accordingly, if the shielding plate is disposed on a soft object to be irradiated with radiation rays, the object and the plate itself less deform to obtain a radiation irradiation pattern with distinct edges. (Moriyama, K.)

Analysis of the snow-atmosphere energy balance during wet-snow instabilities and implications for avalanche prediction

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C. Mitterer

2013-02-01

Full Text Available Wet-snow avalanches are notoriously difficult to predict; their formation mechanism is poorly understood since in situ measurements representing the thermal and mechanical evolution are difficult to perform. Instead, air temperature is commonly used as a predictor variable for days with high wet-snow avalanche danger – often with limited success. As melt water is a major driver of wet-snow instability and snow melt depends on the energy input into the snow cover, we computed the energy balance for predicting periods with high wet-snow avalanche activity. The energy balance was partly measured and partly modelled for virtual slopes at different elevations for the aspects south and north using the 1-D snow cover model SNOWPACK. We used measured meteorological variables and computed energy balance and its components to compare wet-snow avalanche days to non-avalanche days for four consecutive winter seasons in the surroundings of Davos, Switzerland. Air temperature, the net shortwave radiation and the energy input integrated over 3 or 5 days showed best results in discriminating event from non-event days. Multivariate statistics, however, revealed that for better predicting avalanche days, information on the cold content of the snowpack is necessary. Wet-snow avalanche activity was closely related to periods when large parts of the snowpack reached an isothermal state (0 °C and energy input exceeded a maximum value of 200 kJ m⁻² in one day, or the 3-day sum of positive energy input was larger than 1.2 MJ m⁻². Prediction accuracy with measured meteorological variables was as good as with computed energy balance parameters, but simulated energy balance variables accounted better for different aspects, slopes and elevations than meteorological data.

A Bayesian spatial assimilation scheme for snow coverage observations in a gridded snow model

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S. Kolberg

2006-01-01

Full Text Available A method for assimilating remotely sensed snow covered area (SCA into the snow subroutine of a grid distributed precipitation-runoff model (PRM is presented. The PRM is assumed to simulate the snow state in each grid cell by a snow depletion curve (SDC, which relates that cell's SCA to its snow cover mass balance. The assimilation is based on Bayes' theorem, which requires a joint prior distribution of the SDC variables in all the grid cells. In this paper we propose a spatial model for this prior distribution, and include similarities and dependencies among the grid cells. Used to represent the PRM simulated snow cover state, our joint prior model regards two elevation gradients and a degree-day factor as global variables, rather than describing their effect separately for each cell. This transformation results in smooth normalised surfaces for the two related mass balance variables, supporting a strong inter-cell dependency in their joint prior model. The global features and spatial interdependency in the prior model cause each SCA observation to provide information for many grid cells. The spatial approach similarly facilitates the utilisation of observed discharge. Assimilation of SCA data using the proposed spatial model is evaluated in a 2400 km2 mountainous region in central Norway (61° N, 9° E, based on two Landsat 7 ETM+ images generalized to 1 km2 resolution. An image acquired on 11 May, a week before the peak flood, removes 78% of the variance in the remaining snow storage. Even an image from 4 May, less than a week after the melt onset, reduces this variance by 53%. These results are largely improved compared to a cell-by-cell independent assimilation routine previously reported. Including observed discharge in the updating information improves the 4 May results, but has weak effect on 11 May. Estimated elevation gradients are shown to be sensitive to informational deficits occurring at high altitude, where snowmelt has not started

Modelling technical snow production for skiing areas in the Austrian Alps with the physically based snow model AMUNDSEN

Science.gov (United States)

Hanzer, F.; Marke, T.; Steiger, R.; Strasser, U.

2012-04-01

Tourism and particularly winter tourism is a key factor for the Austrian economy. Judging from currently available climate simulations, the Austrian Alps show a particularly high vulnerability to climatic changes. To reduce the exposure of ski areas towards changes in natural snow conditions as well as to generally enhance snow conditions at skiing sites, technical snowmaking is widely utilized across Austrian ski areas. While such measures result in better snow conditions at the skiing sites and are important for the local skiing industry, its economic efficiency has also to be taken into account. The current work emerges from the project CC-Snow II, where improved future climate scenario simulations are used to determine future natural and artificial snow conditions and their effects on tourism and economy in the Austrian Alps. In a first step, a simple technical snowmaking approach is incorporated into the process based snow model AMUNDSEN, which operates at a spatial resolution of 10-50 m and a temporal resolution of 1-3 hours. Locations of skiing slopes within a ski area in Styria, Austria, were digitized and imported into the model environment. During a predefined time frame in the beginning of the ski season, the model produces a maximum possible amount of technical snow and distributes the associated snow on the slopes, whereas afterwards, until to the end of the ski season, the model tries to maintain a certain snow depth threshold value on the slopes. Due to only few required input parameters, this approach is easily transferable to other ski areas. In our poster contribution, we present first results of this snowmaking approach and give an overview of the data and methodology applied. In a further step in CC-Snow, this simple bulk approach will be extended to consider actual snow cannon locations and technical specifications, which will allow a more detailed description of technical snow production as well as cannon-based recordings of water and energy

Environmental impacts of urban snow management - The alpine case study of Innsbruck

International Nuclear Information System (INIS)

Engelhard, C.; De Toffol, S.; Lek, I.; Rauch, W.; Dallinger, R.

2007-01-01

In regions with colder climate, snow at roads can accumulate significant amounts of pollutant chemicals. In northern countries various efforts have been made to face this problem, but for the alpine region little is known about the pollution of urban snow. The present case study was carried out in the city of Innsbruck (Austria). It aimed at measuring pollution of roadside snow and estimating the impact of snow management practises on environmental quality. Concentrations of copper, zinc, lead, cadmium, suspended solids and chloride were determined during a series of sampling events. Various locations with low and high traffic densities and in different distances from a highway have been investigated. The concentrations of copper were generally higher at sites with high traffic density compared to locations with low traffic impact. In contrast to this, the concentrations of zinc and lead remained almost unvaried irrespective of traffic density at the different sampling sites. For cadmium, the picture was more diverse, showing moderately elevated concentrations of this metal also at the urban reference site not polluted by traffic. This indicates that there may be also other important sources for cadmium besides traffic. Suspended solids accumulated in the roadside snow, the highest concentrations were found at the sites with high traffic density. The chloride concentrations were considerable in the snow, especially at the highway. Based on the results of the present measurement campaign, the environmental impact of snow disposal in rivers was also estimated. A negative impact on rivers from snow disposal seems likely to occur, although the discharged loads could only be calculated with substantial uncertainty, considering the high variability of the measured pollutant concentrations. For a more accurate evaluation of this management practise on rivers, further investigations would be necessary

A novel linear physical model for remote sensing of snow wetness and snow density using the visible and infrared bands

Science.gov (United States)

Varade, D. M.; Dikshit, O.

2017-12-01

Modeling and forecasting of snowmelt runoff are significant for understanding the hydrological processes in the cryosphere which requires timely information regarding snow physical properties such as liquid water content and density of snow in the topmost layer of the snowpack. Both the seasonal runoffs and avalanche forecasting are vastly dependent on the inherent physical characteristics of the snowpack which are conventionally measured by field surveys in difficult terrains at larger impending costs and manpower. With advances in remote sensing technology and the increase in the availability of satellite data, the frequency and extent of these surveys could see a declining trend in future. In this study, we present a novel approach for estimating snow wetness and snow density using visible and infrared bands that are available with most multi-spectral sensors. We define a trapezoidal feature space based on the spectral reflectance in the near infrared band and the Normalized Differenced Snow Index (NDSI), referred to as NIR-NDSI space, where dry snow and wet snow are observed in the left diagonal upper and lower right corners, respectively. The corresponding pixels are extracted by approximating the dry and wet edges which are used to develop a linear physical model to estimate snow wetness. Snow density is then estimated using the modeled snow wetness. Although the proposed approach has used Sentinel-2 data, it can be extended to incorporate data from other multi-spectral sensors. The estimated values for snow wetness and snow density show a high correlation with respect to in-situ measurements. The proposed model opens a new avenue for remote sensing of snow physical properties using multi-spectral data, which were limited in the literature.

Plate-fin array cooling using a finger-like piezoelectric fan

International Nuclear Information System (INIS)

Shyu, Jin-Cherng; Syu, Jhih-Zong

2014-01-01

In this study, the heat transfer of a plate-fin array cooled by a vibrating finger-like piezoelectric fan comprising four flexible rectangular blades was investigated. The results indicated that the heat transfer enhancement of the fin array cooled by a vibrating piezoelectric fan at x/L = 0.5 and H = 5 mm ranged between 1.5 and 3.3, regardless of the fin array orientation. However, the heat transfer enhancement caused by a fan being placed at either edge of the fin array yielded a dissimilar result between both of the fin array orientations because of the superimposed effects of the boundary layer development and the air flow induced by the fan. This dissimilarity was especially noticeable when the piezoelectric fan was composed of aluminum blades to accommodate the moderate Reynolds number. In addition to the Reynolds number, the ratio of the fan blade vibration envelope to the source area determined the Nu number of the piezoelectric fan-cooled fin array. This design enhanced the fin array heat transfer and reduced cooler volume by embedding multiple vibrating beams into the fin array. -- Highlights: • Heat transfer of a piezoelectric fan-cooled plate-fin array was investigated. • Effects of fan position, fan height and fan material on heat transfer were examined. • Similar heat transfer enhancement range was shown for both fin array orientations. • Fin heat transfer with a running Al fan at x = 0 was higher than that at x = 0.25L. • Besides fan Reynolds number, the area ratio also determined Nu of the fin array

Blowing snow sublimation and transport over Antarctica from 11 years of CALIPSO observations

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S. P. Palm

2017-11-01

Full Text Available Blowing snow processes commonly occur over the earth's ice sheets when the 10 m wind speed exceeds a threshold value. These processes play a key role in the sublimation and redistribution of snow thereby influencing the surface mass balance. Prior field studies and modeling results have shown the importance of blowing snow sublimation and transport on the surface mass budget and hydrological cycle of high-latitude regions. For the first time, we present continent-wide estimates of blowing snow sublimation and transport over Antarctica for the period 2006–2016 based on direct observation of blowing snow events. We use an improved version of the blowing snow detection algorithm developed for previous work that uses atmospheric backscatter measurements obtained from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization lidar aboard the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation satellite. The blowing snow events identified by CALIPSO and meteorological fields from MERRA-2 are used to compute the blowing snow sublimation and transport rates. Our results show that maximum sublimation occurs along and slightly inland of the coastline. This is contrary to the observed maximum blowing snow frequency which occurs over the interior. The associated temperature and moisture reanalysis fields likely contribute to the spatial distribution of the maximum sublimation values. However, the spatial pattern of the sublimation rate over Antarctica is consistent with modeling studies and precipitation estimates. Overall, our results show that the 2006–2016 Antarctica average integrated blowing snow sublimation is about 393 ± 196 Gt yr−1, which is considerably larger than previous model-derived estimates. We find maximum blowing snow transport amount of 5 Mt km−1 yr−1 over parts of East Antarctica and estimate that the average snow transport from continent to ocean is about 3.7 Gt yr−1. These

Evaluation of North Eurasian snow-off dates in the ECHAM5.4 atmospheric general circulation model

Directory of Open Access Journals (Sweden)

P. Räisänen

2014-12-01

Full Text Available The timing of springtime end of snowmelt (snow-off date in northern Eurasia in version 5.4 of the ECHAM5 atmospheric general circulation model (GCM is evaluated through comparison with a snow-off date data set based on space-borne microwave radiometer measurements and with Russian snow course data. ECHAM5 reproduces well the observed gross geographical pattern of snow-off dates, with earliest snow-off (in March in the Baltic region and latest snow-off (in June in the Taymyr Peninsula and in northeastern parts of the Russian Far East. The primary biases are (1 a delayed snow-off in southeastern Siberia (associated with too low springtime temperature and too high surface albedo, in part due to insufficient shielding by canopy; and (2 an early bias in the western and northern parts of northern Eurasia. Several sensitivity experiments were conducted, where biases in simulated atmospheric circulation were corrected through nudging and/or the treatment of surface albedo was modified. While this alleviated some of the model biases in snow-off dates, 2 m temperature and surface albedo, especially the early bias in snow-off in the western parts of northern Eurasia proved very robust and was actually larger in the nudged runs. A key issue underlying the snow-off biases in ECHAM5 is that snowmelt occurs at too low temperatures. Very likely, this is related to the treatment of the surface energy budget. On one hand, the surface temperature Ts is not computed separately for the snow-covered and snow-free parts of the grid cells, which prevents Ts from rising above 0 °C before all snow has vanished. Consequently, too much of the surface net radiation is consumed in melting snow and too little in heating the air. On the other hand, ECHAM5 does not include a canopy layer. Thus, while the albedo reduction due to canopy is accounted for, the shielding of snow on ground by the overlying canopy is not considered, which leaves too much solar radiation available for

Photochemical degradation of PCBs in snow.

Science.gov (United States)

Matykiewiczová, Nina; Klánová, Jana; Klán, Petr

2007-12-15

This work represents the first laboratory study known to the authors describing photochemical behavior of persistent organic pollutants in snow at environmentally relevant concentrations. The snow samples were prepared by shock freezing of the corresponding aqueous solutions in liquid nitrogen and were UV-irradiated in a photochemical cold chamber reactor at -25 degrees C, in which simultaneous monitoring of snow-air exchange processeswas also possible. The main photodegradation pathway of two model snow contaminants, PCB-7 and PCB-153 (c approximately 100 ng kg(-1)), was found to be reductive dehalogenation. Possible involvement of the water molecules of snow in this reaction has been excluded by performing the photolyses in D2O snow. Instead, trace amounts of volatile organic compounds have been proposed to be the major source of hydrogen atom in the reduction, and this hypothesis was confirmed by the experiments with deuterated organic cocontaminants, such as d6-ethanol or d8-tetrahydrofuran. It is argued that bimolecular photoreduction of PCBs was more efficient or feasible than any other phototransformations under the experimental conditions used, including the coupling reactions. The photodegradation of PCBs, however, competed with a desorption process responsible for the pollutant loss from the snow samples, especially in case of lower molecular-mass congeners. Organic compounds, apparently largely located or photoproduced on the surface of snow crystals, had a predisposition to be released to the air but, at the same time, to react with other species in the gas phase. It is concluded that physicochemical properties of the contaminants and trace co-contaminants, their location and local concentrations in the matrix, and the wavelength and intensity of radiation are the most important factors in the evaluation of organic contaminants' lifetime in snow. Based on the results, it has been estimated that the average lifetime of PCBs in surface snow, connected

Loropetalum chinense 'Snow Panda'

Science.gov (United States)

A new Loropetalum chinense, ‘Snow Panda’, developed at the U.S. National Arboretum is described. ‘Snow Panda’ (NA75507, PI660659) originated from seeds collected near Yan Chi He, Hubei, China in 1994 by the North America-China Plant Exploration Consortium (NACPEC). Several seedlings from this trip w...

Missing (in-situ) snow cover data hampers climate change and runoff studies in the Greater Himalayas

International Nuclear Information System (INIS)

Rohrer, Mario; Salzmann, Nadine; Stoffel, Markus; Kulkarni, Anil V.

2013-01-01

The Himalayas are presently holding the largest ice masses outside the polar regions and thus (temporarily) store important freshwater resources. In contrast to the contemplation of glaciers, the role of runoff from snow cover has received comparably little attention in the past, although (i) its contribution is thought to be at least equally or even more important than that of ice melt in many Himalayan catchments and (ii) climate change is expected to have widespread and significant consequences on snowmelt runoff. Here, we show that change assessment of snowmelt runoff and its timing is not as straightforward as often postulated, mainly as larger partial pressure of H 2 O, CO 2 , CH 4 , and other greenhouse gases might increase net long-wave input for snowmelt quite significantly in a future atmosphere. In addition, changes in the short-wave energy balance – such as the pollution of the snow cover through black carbon – or the sensible or latent heat contribution to snowmelt are likely to alter future snowmelt and runoff characteristics as well. For the assessment of snow cover extent and depletion, but also for its monitoring over the extremely large areas of the Himalayas, remote sensing has been used in the past and is likely to become even more important in the future. However, for the calibration and validation of remotely-sensed data, and even more so in light of possible changes in snow-cover energy balance, we strongly call for more in-situ measurements across the Himalayas, in particular for daily data on new snow and snow cover water equivalent, or the respective energy balance components. Moreover, data should be made accessible to the scientific community, so that the latter can more accurately estimate climate change impacts on Himalayan snow cover and possible consequences thereof on runoff. - Highlights: • Remotely sensed snow-cover data need to be validated by in-situ measurements. • More in-situ snow measurement programs are needed along

Missing (in-situ) snow cover data hampers climate change and runoff studies in the Greater Himalayas

Energy Technology Data Exchange (ETDEWEB)

Rohrer, Mario [Meteodat GmbH, Technoparkstrasse 1, CH-8005 Zurich (Switzerland); Salzmann, Nadine [Department of Geosciences, Geography, University of Fribourg, Chemin du Musée 4, CH-1700 Fribourg (Switzerland); Stoffel, Markus, E-mail: markus.stoffel@unige.ch [Institute for Environmental Sciences, University of Geneva, Chemin de Drize 7, CH-1227 Carouge, Geneva (Switzerland); Dendrolab.ch, Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, CH-3012 Bern (Switzerland); Kulkarni, Anil V. [Divecha Center for Climate Change, Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore 560 012 (India)

2013-12-01

The Himalayas are presently holding the largest ice masses outside the polar regions and thus (temporarily) store important freshwater resources. In contrast to the contemplation of glaciers, the role of runoff from snow cover has received comparably little attention in the past, although (i) its contribution is thought to be at least equally or even more important than that of ice melt in many Himalayan catchments and (ii) climate change is expected to have widespread and significant consequences on snowmelt runoff. Here, we show that change assessment of snowmelt runoff and its timing is not as straightforward as often postulated, mainly as larger partial pressure of H{sub 2}O, CO{sub 2}, CH{sub 4}, and other greenhouse gases might increase net long-wave input for snowmelt quite significantly in a future atmosphere. In addition, changes in the short-wave energy balance – such as the pollution of the snow cover through black carbon – or the sensible or latent heat contribution to snowmelt are likely to alter future snowmelt and runoff characteristics as well. For the assessment of snow cover extent and depletion, but also for its monitoring over the extremely large areas of the Himalayas, remote sensing has been used in the past and is likely to become even more important in the future. However, for the calibration and validation of remotely-sensed data, and even more so in light of possible changes in snow-cover energy balance, we strongly call for more in-situ measurements across the Himalayas, in particular for daily data on new snow and snow cover water equivalent, or the respective energy balance components. Moreover, data should be made accessible to the scientific community, so that the latter can more accurately estimate climate change impacts on Himalayan snow cover and possible consequences thereof on runoff. - Highlights: • Remotely sensed snow-cover data need to be validated by in-situ measurements. • More in-situ snow measurement programs are

Merging datasets from NASA SnowEx to better understand how snow falls and moves.

Science.gov (United States)

Gongora, J. A.; Marshall, H. P.; Glenn, N. F.

2017-12-01

A modelers ability to estimated snow depth and snow water equivalent (SWE) for mountain snow depends strongly on their understanding of snowpack spatial distribution and the soundness of the models initial conditions. This work focuses on the application of data science and efficient algorithms to find optimal locations in mountainous terrain to act as initital conditions for machine driven interpolation methods. By using graphs, collections of pairwise relationships between objects, to describe our data we were able to efficiently search, partition, and understand snowpack from the persepetive of this data structure.

The Airborne Snow Observatory: fusion of scanning lidar, imaging spectrometer, and physically-based modeling for mapping snow water equivalent and snow albedo

Science.gov (United States)

Snow cover and its melt dominate regional climate and water resources in many of the world’s mountainous regions. Snowmelt timing and magnitude in mountains tend to be controlled by absorption of solar radiation and snow water equivalent, respectively, and yet both of these are very poorly known ev...

[Analysis of influencing factors of snow hyperspectral polarized reflections].

Science.gov (United States)

Sun, Zhong-Qiu; Zhao, Yun-Sheng; Yan, Guo-Qian; Ning, Yan-Ling; Zhong, Gui-Xin

2010-02-01

Due to the need of snow monitoring and the impact of the global change on the snow, on the basis of the traditional research on snow, starting from the perspective of multi-angle polarized reflectance, we analyzed the influencing factors of snow from the incidence zenith angles, the detection zenith angles, the detection azimuth angles, polarized angles, the density of snow, the degree of pollution, and the background of the undersurface. It was found that these factors affected the spectral reflectance values of the snow, and the effect of some factors on the polarization hyperspectral reflectance observation is more evident than in the vertical observation. Among these influencing factors, the pollution of snow leads to an obvious change in the snow reflectance spectrum curve, while other factors have little effect on the shape of the snow reflectance spectrum curve and mainly impact the reflection ratio of the snow. Snow reflectance polarization information has not only important theoretical significance, but also wide application prospect, and provides new ideas and methods for the quantitative research on snow using the remote sensing technology.

Cold, Ice, and Snow Safety (For Parents)

Science.gov (United States)

... to mention a few. Plus, someone has to shovel the snow, right? Once outdoors, however, take precautions ... re going to get the family outside to shovel the snow? Fine, but take care. Snow shoveling ...

Daily gridded datasets of snow depth and snow water equivalent for the Iberian Peninsula from 1980 to 2014

Science.gov (United States)

Alonso-González, Esteban; López-Moreno, J. Ignacio; Gascoin, Simon; García-Valdecasas Ojeda, Matilde; Sanmiguel-Vallelado, Alba; Navarro-Serrano, Francisco; Revuelto, Jesús; Ceballos, Antonio; Jesús Esteban-Parra, María; Essery, Richard

2018-02-01

We present snow observations and a validated daily gridded snowpack dataset that was simulated from downscaled reanalysis of data for the Iberian Peninsula. The Iberian Peninsula has long-lasting seasonal snowpacks in its different mountain ranges, and winter snowfall occurs in most of its area. However, there are only limited direct observations of snow depth (SD) and snow water equivalent (SWE), making it difficult to analyze snow dynamics and the spatiotemporal patterns of snowfall. We used meteorological data from downscaled reanalyses as input of a physically based snow energy balance model to simulate SWE and SD over the Iberian Peninsula from 1980 to 2014. More specifically, the ERA-Interim reanalysis was downscaled to 10 km × 10 km resolution using the Weather Research and Forecasting (WRF) model. The WRF outputs were used directly, or as input to other submodels, to obtain data needed to drive the Factorial Snow Model (FSM). We used lapse rate coefficients and hygrobarometric adjustments to simulate snow series at 100 m elevations bands for each 10 km × 10 km grid cell in the Iberian Peninsula. The snow series were validated using data from MODIS satellite sensor and ground observations. The overall simulated snow series accurately reproduced the interannual variability of snowpack and the spatial variability of snow accumulation and melting, even in very complex topographic terrains. Thus, the presented dataset may be useful for many applications, including land management, hydrometeorological studies, phenology of flora and fauna, winter tourism, and risk management. The data presented here are freely available for download from Zenodo (https://doi.org/10.5281/zenodo.854618). This paper fully describes the work flow, data validation, uncertainty assessment, and possible applications and limitations of the database.

Optimizing placements of ground-based snow sensors for areal snow cover estimation using a machine-learning algorithm and melt-season snow-LiDAR data

Science.gov (United States)

Oroza, C.; Zheng, Z.; Glaser, S. D.; Bales, R. C.; Conklin, M. H.

2016-12-01

We present a structured, analytical approach to optimize ground-sensor placements based on time-series remotely sensed (LiDAR) data and machine-learning algorithms. We focused on catchments within the Merced and Tuolumne river basins, covered by the JPL Airborne Snow Observatory LiDAR program. First, we used a Gaussian mixture model to identify representative sensor locations in the space of independent variables for each catchment. Multiple independent variables that govern the distribution of snow depth were used, including elevation, slope, and aspect. Second, we used a Gaussian process to estimate the areal distribution of snow depth from the initial set of measurements. This is a covariance-based model that also estimates the areal distribution of model uncertainty based on the independent variable weights and autocorrelation. The uncertainty raster was used to strategically add sensors to minimize model uncertainty. We assessed the temporal accuracy of the method using LiDAR-derived snow-depth rasters collected in water-year 2014. In each area, optimal sensor placements were determined using the first available snow raster for the year. The accuracy in the remaining LiDAR surveys was compared to 100 configurations of sensors selected at random. We found the accuracy of the model from the proposed placements to be higher and more consistent in each remaining survey than the average random configuration. We found that a relatively small number of sensors can be used to accurately reproduce the spatial patterns of snow depth across the basins, when placed using spatial snow data. Our approach also simplifies sensor placement. At present, field surveys are required to identify representative locations for such networks, a process that is labor intensive and provides limited guarantees on the networks' representation of catchment independent variables.

Influence of snow shovel shaft configuration on lumbosacral biomechanics during a load-lifting task.

Science.gov (United States)

Lewinson, Ryan T; Rouhi, Gholamreza; Robertson, D Gordon E

2014-03-01

Lower-back injury from snow shovelling may be related to excessive joint loading. Bent-shaft snow shovels are commonly available for purchase; however, their influence on lower back-joint loading is currently not known. Therefore, the purpose of this study was to compare L5/S1 extension angular impulses between a bent-shaft and a standard straight-shaft snow shovel. Eight healthy subjects participated in this study. Each completed a simulated snow-lifting task in a biomechanics laboratory with each shovel design. A standard motion analysis procedure was used to determine L5/S1 angular impulses during each trial, as well as peak L5/S1 extension moments and peak upper body flexion angle. Paired-samples t-tests (α = 0.05) were used to compare variables between shovel designs. Correlation was used to determine the relationship between peak flexion and peak moments. Results of this study show that the bent-shaft snow shovel reduced L5/S1 extension angular impulses by 16.5% (p = 0.022), decreased peak moments by 11.8% (p = 0.044), and peak flexion by 13.0% (p = 0.002) compared to the straight-shaft shovel. Peak L5/S1 extension moment magnitude was correlated with peak upper body flexion angle (r = 0.70). Based on these results, it is concluded that the bent-shaft snow shovel can likely reduce lower-back joint loading during snow shovelling, and thus may have a role in snow shovelling injury prevention. Copyright © 2013 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Missing (in-situ) snow cover data hampers climate change and runoff studies in the Greater Himalayas.

Science.gov (United States)

Rohrer, Mario; Salzmann, Nadine; Stoffel, Markus; Kulkarni, Anil V

2013-12-01

The Himalayas are presently holding the largest ice masses outside the polar regions and thus (temporarily) store important freshwater resources. In contrast to the contemplation of glaciers, the role of runoff from snow cover has received comparably little attention in the past, although (i) its contribution is thought to be at least equally or even more important than that of ice melt in many Himalayan catchments and (ii) climate change is expected to have widespread and significant consequences on snowmelt runoff. Here, we show that change assessment of snowmelt runoff and its timing is not as straightforward as often postulated, mainly as larger partial pressure of H2O, CO2, CH4, and other greenhouse gases might increase net long-wave input for snowmelt quite significantly in a future atmosphere. In addition, changes in the short-wave energy balance - such as the pollution of the snow cover through black carbon - or the sensible or latent heat contribution to snowmelt are likely to alter future snowmelt and runoff characteristics as well. For the assessment of snow cover extent and depletion, but also for its monitoring over the extremely large areas of the Himalayas, remote sensing has been used in the past and is likely to become even more important in the future. However, for the calibration and validation of remotely-sensed data, and even more so in light of possible changes in snow-cover energy balance, we strongly call for more in-situ measurements across the Himalayas, in particular for daily data on new snow and snow cover water equivalent, or the respective energy balance components. Moreover, data should be made accessible to the scientific community, so that the latter can more accurately estimate climate change impacts on Himalayan snow cover and possible consequences thereof on runoff. © 2013 Elsevier B.V. All rights reserved.

Extraordinary blowing snow transport events in East Antarctica

Energy Technology Data Exchange (ETDEWEB)

Scarchilli, Claudio; Agnoletto, Lucia [ENEA, Rome (Italy); Universita di Siena, Dipartimento di Scienze della Terra, Siena (Italy); Frezzotti, Massimo; Grigioni, Paolo; Silvestri, Lorenzo de [ENEA, Rome (Italy); Dolci, Stefano [CNR, Rome (Italy); Consorzio P.N.R.A. S.C.r.l., Rome (Italy)

2010-06-15

In the convergence slope/coastal areas of Antarctica, a large fraction of snow is continuously eroded and exported by wind to the atmosphere and into the ocean. Snow transport observations from instruments and satellite images were acquired at the wind convergence zone of Terra Nova Bay (East Antarctica) throughout 2006 and 2007. Snow transport features are well-distinguished in satellite images and can extend vertically up to 200 m as first-order quantitatively estimated by driftometer sensor FlowCapt trademark. Maximum snow transportation occurs in the fall and winter seasons. Snow transportation (drift/blowing) was recorded for {proportional_to}80% of the time, and 20% of time recorded, the flux is >10{sup -2} kg m{sup -2} s{sup -1} with particle density increasing with height. Cumulative snow transportation is {proportional_to}4 orders of magnitude higher than snow precipitation at the site. An increase in wind speed and transportation ({proportional_to}30%) was observed in 2007, which is in agreement with a reduction in observed snow accumulation. Extensive presence of ablation surface (blue ice and wind crust) upwind and downwind of the measurement site suggest that the combine processes of blowing snow sublimation and snow transport remove up to 50% of the precipitation in the coastal and slope convergence area. These phenomena represent a major negative effect on the snow accumulation, and they are not sufficiently taken into account in studies of surface mass balance. The observed wind-driven ablation explains the inconsistency between atmospheric model precipitation and measured snow accumulation value. (orig.)

Application of the MODIS “snow cover” product for identification of the snow cover pattern in Gis-Baikal region

Directory of Open Access Journals (Sweden)

E. A. Istomina

2014-01-01

Full Text Available Validation of remote sensing data MODIS «snow cover» in the period from September to May 2000/01, 2007/08, 2008/09 is realized on the base of weather stations data. Good repeatability of weather stations data and snow cover data is shown (more than 80% when snow depth is exceeds 2 cm. The minimum accuracy is in May and October for the variety of snowfall winters. Remote sensing data give possibility to extend the dot information of hydrometeorological stations network on the spatial snow distribution to the mountainous area of Predbajkalje where ground-based observations are absent. According to remote sensing earlier appearance and later melting of snow in mountain areas were identified. The plains and basins areas are characterized by later appearance and earlier melting of snow.

Ground Snow Measurements: Comparisons of the Hotplate, Weighing and Manual Methods

Science.gov (United States)

Wettlaufer, A.; Snider, J.; Campbell, L. S.; Steenburgh, W. J.; Burkhart, M.

2015-12-01

The Yankee Environmental Systems (YES) Hotplate was developed to avoid some of the problems associated with weighing snowfall sensors. This work compares Hotplate, weighing sensor (ETI NOAH-II) and manual measurements of liquid-equivalent depth. The main field site was at low altitude in western New York; Hotplate and ETI comparisons were also made at two forested subalpine sites in southeastern Wyoming. The manual measurement (only conducted at the New York site) was derived by weighing snow cores sampled from a snow board. The two recording gauges (Hotplate and ETI) were located within 5 m of the snow board. Hotplate-derived accumulations were corrected using a wind-speed dependent catch efficiency and the ETI orifice was heated and alter shielded. Three important findings are evident from the comparisons: 1) The Yes-derived accumulations, recorded in a user-accessible file, were compared to accumulations derived using an in-house calibration and fundamental measurements (plate power, long and shortwave radiances, wind speed, and temperature). These accumulations are highly correlated (N=24; r2=0.99), but the YES-derived values are larger by 20%. 2) The in-house Hotplate accumulations are in good agreement with ETI-based accumulations but with larger variability (N=24; r2=0.88). 3) The comparison of in-house Hotplate accumulation versus manual accumulation, expressed as mm of liquid, exhibits a fitted linear relationship Y (in-house) versus X (manual) given by Y = -0.2 (±1.4) + 0.9 (±0.1) · X (N= 20; r2=0.89). Thus, these two methods agree within statistical uncertainty.

Divergent Effects of Dendritic Cells on Pancreatitis

Science.gov (United States)

2015-09-01

role of dendritic cells in pancreatitis. Dendritic cells are professional antigen presenting cells which initiate innate and adaptive immune... Lymphoid -tissue-specific homing of bone- marrow-derived dendritic cells . Blood. 113:6638–6647. http://dx.doi .org/10.1182/blood-2009-02-204321 Dapito...Award Number: W81XWH-12-1-0313 TITLE: Divergent Effects of Dendritic Cells on Pancreatitis PRINCIPAL INVESTIGATOR: Dr. George Miller

Silver Flakes and Silver Dendrites for Hybrid Electrically Conductive Adhesives with Enhanced Conductivity

Science.gov (United States)

Ma, Hongru; Li, Zhuo; Tian, Xun; Yan, Shaocun; Li, Zhe; Guo, Xuhong; Ma, Yanqing; Ma, Lei

2018-03-01

Silver dendrites were prepared by a facile replacement reaction between silver nitrate and zinc microparticles of 20 μm in size. The influence of reactant molar ratio, reaction solution volume, silver nitrate concentration, and reaction time on the morphology of dendrites was investigated systematically. It was found that uniform tree-like silver structures are synthesized under the optimal conditions. Their structure can be described as a trunk, symmetrical branches, and leaves, which length scales of 5-10, 1-2 μm, and 100-300 nm, respectively. All features were systematically characterized by scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and x-ray powder diffraction. A hybrid fillers system using silver flakes and dendrites as electrically conductive adhesives (ECAs) exhibited excellent overall performance. This good conductivity can be attributed mainly to the synergy between the silver microflakes (5-20 μm sized irregular sheet structures) and dendrites, allowing more conductive pathways to be formed between the fillers. In order to further optimize the overall electrical conductivity, various mixtures of silver microflakes and silver dendrites were tested in ECAs, with results indicating that the highest conductivity was shown when the amounts of silver microflakes, silver dendrites and the polymer matrix were 69.4 wt.% (20.82 vol.%), 0.6 wt.% (0.18 vol.%), and 30.0 wt.% (79.00 vol.%), respectively. The corresponding mass ratio of silver flakes to silver dendrites was 347:3. The resistivity of ECAs reached as low as 1.7 × 10-4 Ω cm.

acquisition of antigens by airway dendritic cells. do we know enough?

African Journals Online (AJOL)

kiama

These responses are thought to be mediated via dendritic cells, which are located in the basal ... delivery to the DC in the airways. Are the ... feature of inflammatory airway disease, like asthma .... drug delivery and as vectors in delivery of.

REMOD: a computational tool for remodeling neuronal dendrites

Directory of Open Access Journals (Sweden)

Panagiotis Bozelos

2014-05-01

Full Text Available In recent years, several modeling studies have indicated that dendritic morphology is a key determinant of how individual neurons acquire a unique signal processing profile. The highly branched dendritic structure that originates from the cell body, explores the surrounding 3D space in a fractal-like manner, until it reaches a certain amount of complexity. Its shape undergoes significant alterations not only in various neuropathological conditions, but in physiological, too. Yet, despite the profound effect that these alterations can have on neuronal function, the causal relationship between structure and function remains largely elusive. The lack of a systematic approach for remodeling neuronal cells and their dendritic trees is a key limitation that contributes to this problem. In this context, we developed a computational tool that allows the remodeling of any type of neurons, given a set of exemplar morphologies. The tool is written in Python and provides a simple GUI that guides the user through various options to manipulate selected neuronal morphologies. It provides the ability to load one or more morphology files (.swc or .hoc and choose specific dendrites to operate one of the following actions: shrink, remove, extend or branch (as shown in Figure 1. The user retains complete control over the extent of each alteration and if a chosen action is not possible due to pre-existing structural constraints, appropriate warnings are produced. Importantly, the tool can also be used to extract morphology statistics for one or multiple morphologies, including features such as the total dendritic length, path length to the root, branch order, diameter tapering, etc. Finally, an experimental utility enables the user to remodel entire dendritic trees based on preloaded statistics from a database of cell-type specific neuronal morphologies. To our knowledge, this is the first tool that allows (a the remodeling of existing –as opposed to the de novo

Signaling network of dendritic cells in response to pathogens: a community-input supported knowledgebase.

Science.gov (United States)

Patil, Sonali; Pincas, Hanna; Seto, Jeremy; Nudelman, German; Nudelman, Irina; Sealfon, Stuart C

2010-10-07

Dendritic cells are antigen-presenting cells that play an essential role in linking the innate and adaptive immune systems. Much research has focused on the signaling pathways triggered upon infection of dendritic cells by various pathogens. The high level of activity in the field makes it desirable to have a pathway-based resource to access the information in the literature. Current pathway diagrams lack either comprehensiveness, or an open-access editorial interface. Hence, there is a need for a dependable, expertly curated knowledgebase that integrates this information into a map of signaling networks. We have built a detailed diagram of the dendritic cell signaling network, with the goal of providing researchers with a valuable resource and a facile method for community input. Network construction has relied on comprehensive review of the literature and regular updates. The diagram includes detailed depictions of pathways activated downstream of different pathogen recognition receptors such as Toll-like receptors, retinoic acid-inducible gene-I-like receptors, C-type lectin receptors and nucleotide-binding oligomerization domain-like receptors. Initially assembled using CellDesigner software, it provides an annotated graphical representation of interactions stored in Systems Biology Mark-up Language. The network, which comprises 249 nodes and 213 edges, has been web-published through the Biological Pathway Publisher software suite. Nodes are annotated with PubMed references and gene-related information, and linked to a public wiki, providing a discussion forum for updates and corrections. To gain more insight into regulatory patterns of dendritic cell signaling, we analyzed the network using graph-theory methods: bifan, feedforward and multi-input convergence motifs were enriched. This emphasis on activating control mechanisms is consonant with a network that subserves persistent and coordinated responses to pathogen detection. This map represents a navigable

Application of snow models to snow removal operations on the Going-to-the-Sun Road, Glacier National Park

Science.gov (United States)

Fagre, Daniel B.; Klasner, Frederick L.

2000-01-01

Snow removal, and the attendant avalanche risk for road crews, is a major issue on mountain highways worldwide. The Going-to-the-Sun Road is the only road that crosses Glacier National Park, Montana. This 80-km highway ascends over 1200m along the wall of a glaciated basin and crosses the continental divide. The annual opening of the road is critical to the regional economy and there is public pressure to open the road as early as possible. Despite the 67-year history of snow removal activities, few stat on snow conditions at upper elevations were available to guide annual planning for the raod opening. We examined statistical relationships between the opening date and nearby SNOTEL data on snow water equivalence (WE) for 30 years. Early spring SWE (first Monday in April) accounted for only 33% of the variance in road opening dates. Because avalanche spotters, used to warn heavy equipment operators of danger, are ineffective during spring storms or low-visibility conditions, we incorporated the percentage of days with precipitation during plowing as a proxy for visibility. This improved the model's predictive power to 69%/ A mountain snow simulator (MTSNOW) was used to calculate the depth and density of snow at various points along the road and field data were collected for comparison. MTSNOW underestimated the observed snow conditions, in part because it does not yet account for wind redistribution of snow. The severe topography of the upper reaches of the road are subjected to extensive wind redistribution of snow as evidence by the formation of "The Big Drift" on the lee side of Logan Pass.

Effect of snow cover on soil frost penetration

Science.gov (United States)

Rožnovský, Jaroslav; Brzezina, Jáchym

2017-12-01

Snow cover occurrence affects wintering and lives of organisms because it has a significant effect on soil frost penetration. An analysis of the dependence of soil frost penetration and snow depth between November and March was performed using data from 12 automated climatological stations located in Southern Moravia, with a minimum period of measurement of 5 years since 2001, which belong to the Czech Hydrometeorological institute. The soil temperatures at 5 cm depth fluctuate much less in the presence of snow cover. In contrast, the effect of snow cover on the air temperature at 2 m height is only very small. During clear sky conditions and no snow cover, soil can warm up substantially and the soil temperature range can be even higher than the range of air temperature at 2 m height. The actual height of snow is also important - increased snow depth means lower soil temperature range. However, even just 1 cm snow depth substantially lowers the soil temperature range and it can therefore be clearly seen that snow acts as an insulator and has a major effect on soil frost penetration and soil temperature range.

Regional pattern of snow characteristics around Antarctic Lake Vostok

Science.gov (United States)

Vladimirova, Diana; Ekaykin, Alexey; Popov, Sergey; Shibaev, Yuriy; Kozachek, Anna; Lipenkov, Vladimir

2015-04-01

Since 1998 Russian Antarctic Expedition has organized several scientific traverses in the region of subglacial Lake Vostok mainly devoted to the radar echo and seismic sounding of the glacier and water (the results have been published elsewhere). Along with the geophysical studies, a number of glaciological investigations have been carried out: snow pit digging, installation of accumulation stakes, snow sampling to study the stable water isotope content. Here we for the first time present a synthesis of these works and demonstrate a series of maps that characterize the snow density, isotope content and accumulation rate the studied region. A general tendency of the snow accumulation rate and isotope content is a significant increase from south (south-west) to north (north-east) from 35 to 23 mm w.e. per year and from -53,3 ‰ to -57,3 ‰ for delta oxygen-18 respectively, which likely reflects the continental-scale pattern, i.e., increase from inland to the coast. Deuterium excess varies from 11,7 ‰ to 16,3 ‰ is negatively correlated with the isotope content, which is typical for central Antarctica. The snow density demonstrate different pattern: higher values offshore the lake (up to 0,356 g/cm^3), and lower values within the lake's shoreline (lower limit is 0,328 g/cm^3). We suggest that this is related to the katabatic wind activity: very flat nearly horizontal surface of the glacier above the lake is not favorable for the strong winds, which leads to lower surface snow density. Superimposed on the main trend is the regional pattern, namely, curved contour lines in the middle part of the lake. We suggest that it may be related to the local anomalies of the snow drift by wind. Indeed, on the satellite images of the lake one can easily see a snowdrift stretching from the lake's western shore downwind in the middle part of the lake. The isolines of delta oxygen-18 and deuterium excess become perpendicular to each other in the north part of the lake which also

Regulation of dendrite growth and maintenance by exocytosis

OpenAIRE

Peng, Yun; Lee, Jiae; Rowland, Kimberly; Wen, Yuhui; Hua, Hope; Carlson, Nicole; Lavania, Shweta; Parrish, Jay Z.; Kim, Michael D.

2015-01-01

Dendrites lengthen by several orders of magnitude during neuronal development, but how membrane is allocated in dendrites to facilitate this growth remains unclear. Here, we report that Ras opposite (Rop), the Drosophila ortholog of the key exocytosis regulator Munc18-1 (also known as STXBP1), is an essential factor mediating dendrite growth. Neurons with depleted Rop function exhibit reduced terminal dendrite outgrowth followed by primary dendrite degeneration, suggestive of differential req...

SWEAT: Snow Water Equivalent with AlTimetry

Science.gov (United States)

Agten, Dries; Benninga, Harm-Jan; Diaz Schümmer, Carlos; Donnerer, Julia; Fischer, Georg; Henriksen, Marie; Hippert Ferrer, Alexandre; Jamali, Maryam; Marinaci, Stefano; Mould, Toby JD; Phelan, Liam; Rosker, Stephanie; Schrenker, Caroline; Schulze, Kerstin; Emanuel Telo Bordalo Monteiro, Jorge

2017-04-01

To study how the water cycle changes over time, satellite and airborne remote sensing missions are typically employed. Over the last 40 years of satellite missions, the measurement of true water inventories stored in sea and land ice within the cryosphere have been significantly hindered by uncertainties introduced by snow cover. Being able to determine the thickness of this snow cover would act to reduce such error, improving current estimations of hydrological and climate models, Earth's energy balance (albedo) calculations and flood predictions. Therefore, the target of the SWEAT (Snow Water Equivalent with AlTimetry) mission is to directly measure the surface Snow Water Equivalent (SWE) on sea and land ice within the polar regions above 60°and below -60° latitude. There are no other satellite missions currently capable of directly measuring SWE. In order to achieve this, the proposed mission will implement a novel combination of Ka- and Ku-band radioaltimeters (active microwave sensors), capable of penetrating into the snow microstructure. The Ka-band altimeter (λ ≈ 0.8 cm) provides a low maximum snow pack penetration depth of up to 20 cm for dry snow at 37 GHz, since the volume scattering of snow dominates over the scattering caused by the underlying ice surface. In contrast, the Ku-band altimeter (λ ≈ 2 cm) provides a high maximum snowpack penetration depth of up to 15 m in high latitudes regions with dry snow, as volume scattering is decreased by a factor of 55. The combined difference in Ka- and Ku-band signal penetration results will provide more accurate and direct determination of SWE. Therefore, the SWEAT mission aims to improve estimations of global SWE interpreted from passive microwave products, and improve the reliability of numerical snow and climate models.

Effects of dirty snow in nuclear winter simulations

International Nuclear Information System (INIS)

Vogelmann, A.M.; Robock, A.; Ellingson, R.G.

1988-01-01

A large-scale nuclear war would inject smoke into the atmosphere from burning forests, cities, and industries in targeted areas. This smoke could fall out onto snow and ice and would lower cryospheric albedos by as much as 50%. A global energy balance climate model is used to investigate the maximum effect these ''dirty snow'' albedos have on the surface temperature in nuclear winter simulations which span several years. These effects are investigated for different nuclear winter scenarios, snow precipitation rates, latitudinal distributions of smoke, and seasonal timings. We find that dirty snow, in general, would have a small temperature effect at mid- and low latitudes but could have a large temperature effect at polar latitudes, particularly if the soot is able to reappear significantly in later summers. Factors which limit the climatic importance of the dirty snow are (1) the dirty snow albedo is lowest when the atmosphere still contains a large amount of light-absorbing smoke; (2) even with dirty snow, sea ice areas can still increase, which helps maintain colder temperatures through the sea ice thermal inertial feedback; (3) the snow and ice areas affected by the dirty snow albedos are largest when there is little seasonal solar insolation; and (4) the area affected by the dirty snow is relatively small under all circumstances. copyright American Geophysical Union 1988

A spatially distributed isotope sampling network in a snow-dominated catchment for the quantification of snow meltwater

Science.gov (United States)

Rücker, Andrea; Boss, Stefan; Von Freyberg, Jana; Zappa, Massimiliano; Kirchner, James

2017-04-01

In mountainous catchments with seasonal snowpacks, river discharge in downstream valleys is largely sustained by snowmelt in spring and summer. Future climate warming will likely reduce snow volumes and lead to earlier and faster snowmelt in such catchments. This, in turn, may increase the risk of summer low flows and hydrological droughts. Improved runoff predictions are thus required in order to adapt water management to future climatic conditions and to assure the availability of fresh water throughout the year. However, a detailed understanding of the hydrological processes is crucial to obtain robust predictions of river streamflow. This in turn requires fingerprinting source areas of streamflow, tracing water flow pathways, and measuring timescales of catchment storage, using tracers such as stable water isotopes (18O, 2H). For this reason, we have established an isotope sampling network in the Alptal, a snowmelt-dominated catchment (46.4 km2) in Central-Switzerland, as part of the SREP-Drought project (Snow Resources and the Early Prediction of hydrological DROUGHT in mountainous streams). Precipitation and snow cores are analyzed for their isotopic signature at daily or weekly intervals. Three-week bulk samples of precipitation are also collected on a transect along the Alptal valley bottom, and along an elevational transect perpendicular to the Alptal valley axis. Streamwater samples are taken at the catchment outlet as well as in two small nested sub-catchments (automatic snow lysimeter system was developed, which also facilitates real-time monitoring of snowmelt events, system status and environmental conditions (air and soil temperature). Three lysimeter systems were installed within the catchment, in one forested site and two open field sites at different elevations, and have been operational since November 2016. We will present the isotope time series from our regular sampling network, as well as initial results from our snowmelt lysimeter sites. Our

Performance evaluation of snow and ice plows.

Science.gov (United States)

2015-11-01

Removal of ice and snow from road surfaces is a critical task in the northern tier of the United States, : including Illinois. Highways with high levels of traffic are expected to be cleared of snow and ice quickly : after each snow storm. This is ne...

Krüppel-like Factor 4 modulates interleukin-6 release in human dendritic cells after in vitro stimulation with Aspergillus fumigatus and Candida albicans

Science.gov (United States)

Czakai, Kristin; Leonhardt, Ines; Dix, Andreas; Bonin, Michael; Linde, Joerg; Einsele, Hermann; Kurzai, Oliver; Loeffler, Jürgen

2016-01-01

Invasive fungal infections are associated with high mortality rates and are mostly caused by the opportunistic fungi Aspergillus fumigatus and Candida albicans. Immune responses against these fungi are still not fully understood. Dendritic cells (DCs) are crucial players in initiating innate and adaptive immune responses against fungal infections. The immunomodulatory effects of fungi were compared to the bacterial stimulus LPS to determine key players in the immune response to fungal infections. A genome wide study of the gene regulation of human monocyte-derived dendritic cells (DCs) confronted with A. fumigatus, C. albicans or LPS was performed and Krüppel-like factor 4 (KLF4) was identified as the only transcription factor that was down-regulated in DCs by both fungi but induced by stimulation with LPS. Downstream analysis demonstrated the influence of KLF4 on the interleukine-6 expression in human DCs. Furthermore, KLF4 regulation was shown to be dependent on pattern recognition receptor ligation. Therefore KLF4 was identified as a controlling element in the IL-6 immune response with a unique expression pattern comparing fungal and LPS stimulation. PMID:27346433

Studies of diffuse and direct solar radiation over snow

International Nuclear Information System (INIS)

Wesely, M.L.; Everett, R.G.

1976-01-01

Two interesting questions can be addressed by examination of solar radiation records obtained while the surface is covered with snow. One concerns the extent to which airborne particulate matter affects solar radiation received at the surface during winter conditions that are typical of those in the northeastern quarter of the United States. The other relates to the importance of complicated light scatterng in the earth-atmosphere system when the surface albedo is large. With the snow surface reflecting 50% or more of the incident radiation, it is likely that a significant addition to diffuse radiation would result from light that is reflected from the surface and then scattered back to the earth by the atmosphere. Preliminary data from measurements made during the winter of 1975 to 1976 are reported

A Genome-Wide Screen for Dendritically Localized RNAs Identifies Genes Required for Dendrite Morphogenesis

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Mala Misra

2016-08-01

Full Text Available Localizing messenger RNAs at specific subcellular sites is a conserved mechanism for targeting the synthesis of cytoplasmic proteins to distinct subcellular domains, thereby generating the asymmetric protein distributions necessary for cellular and developmental polarity. However, the full range of transcripts that are asymmetrically distributed in specialized cell types, and the significance of their localization, especially in the nervous system, are not known. We used the EP-MS2 method, which combines EP transposon insertion with the MS2/MCP in vivo fluorescent labeling system, to screen for novel localized transcripts in polarized cells, focusing on the highly branched Drosophila class IV dendritic arborization neurons. Of a total of 541 lines screened, we identified 55 EP-MS2 insertions producing transcripts that were enriched in neuronal processes, particularly in dendrites. The 47 genes identified by these insertions encode molecularly diverse proteins, and are enriched for genes that function in neuronal development and physiology. RNAi-mediated knockdown confirmed roles for many of the candidate genes in dendrite morphogenesis. We propose that the transport of mRNAs encoded by these genes into the dendrites allows their expression to be regulated on a local scale during the dynamic developmental processes of dendrite outgrowth, branching, and/or remodeling.

Evaluating Local Primary Dendrite Arm Spacing Characterization Techniques Using Synthetic Directionally Solidified Dendritic Microstructures

Science.gov (United States)

Tschopp, Mark A.; Miller, Jonathan D.; Oppedal, Andrew L.; Solanki, Kiran N.

2015-10-01

Microstructure characterization continues to play an important bridge to understanding why particular processing routes or parameters affect the properties of materials. This statement certainly holds true in the case of directionally solidified dendritic microstructures, where characterizing the primary dendrite arm spacing is vital to developing the process-structure-property relationships that can lead to the design and optimization of processing routes for defined properties. In this work, four series of simulations were used to examine the capability of a few Voronoi-based techniques to capture local microstructure statistics (primary dendrite arm spacing and coordination number) in controlled (synthetically generated) microstructures. These simulations used both cubic and hexagonal microstructures with varying degrees of disorder (noise) to study the effects of length scale, base microstructure, microstructure variability, and technique parameters on the local PDAS distribution, local coordination number distribution, bulk PDAS, and bulk coordination number. The Voronoi tesselation technique with a polygon-side-length criterion correctly characterized the known synthetic microstructures. By systematically studying the different techniques for quantifying local primary dendrite arm spacings, we have evaluated their capability to capture this important microstructure feature in different dendritic microstructures, which can be an important step for experimentally correlating with both processing and properties in single crystal nickel-based superalloys.

Lactobacillus acidophilus induces virus immune defence genes in murine dendritic cells by a Toll-like receptor-2-dependent mechanism

DEFF Research Database (Denmark)

Weiss, Gudrun Margarethe; Rasmussen, Simon; Hjerrild Zeuthen, L.

2010-01-01

Lactobacilli are probiotics that, among other health-promoting effects, have been ascribed immunostimulating and virus-preventive properties. Certain Lactobacillus spp. have been shown to possess strong interleukin-12 (IL-12) -inducing properties. As IL-12 production depends on the up......-regulation of type I interferons (IFNs), we hypothesized that the strong IL-12-inducing capacity of Lactobacillus acidophilus NCFM in murine bone-marrow-derived dendritic cells (DCs) is caused by an up-regulation of IFN-beta, which subsequently induces IL-12 and the double-stranded RNA binding Toll-like receptor-3...... detected in another L. acidophilus strain (X37), but was not a property of other probiotic strains tested, i.e. Bifidobacterium bifidum Z9 and Escherichia coli Nissle 1917. The IFN-beta expression was markedly reduced in TLR-2(-/-) DCs, dependent on endocytosis, and the major cause of the induction of Il...

Collaborative Research: Snow Accumulation and Snow Melt in a Mixed Northern Hardwood-Conifer Forest, Version 1

Data.gov (United States)

National Aeronautics and Space Administration — This data set contains snow depth, Snow Water Equivalent (SWE), and forest cover characteristics for sites at the Hubbard Brook Experimental Forest in northern New...

Anti tumor vaccination with hybrid dendritic-tumour cells

International Nuclear Information System (INIS)

Barbuto, Jose Alexandre M.; Neves, Andreia R.; Ensina, Luis Felipe C.; Anselmo, Luciene B.

2005-01-01

Dendritic cells are the most potent antigen-presenting cells, and the possibility of their use for cancer vaccination has renewed the interest in this therapeutic modality. Nevertheless, the ideal immunization protocol with these cells has not been described yet. In this paper we describe the preliminary results of a protocol using autologous tumor and allogeneic dendritic hybrid cell vaccination every 6 weeks, for metastatic melanoma and renal cell carcinoma (RCC) patients. Thirty-five patients were enrolled between March 2001 and March 2003. Though all patients included presented with large tumor burdens and progressive diseases, 71% of them experienced stability after vaccination, with durations up to 19 months. Among RCC patients 3/22 (14%) presented objective responses. The median time to progression was 4 months for melanoma and 5.7 months for RCC patients; no significant untoward effects were noted. Furthermore, immune function, as evaluated by cutaneous delayed-type hypersensitivity reactions to recall antigens and by peripheral blood proliferative responses to tumor-specific and nonspecific stimuli, presented a clear tendency to recover in vaccinated patients. These data indicate that dendritic cell-tumor cell hybrid vaccination affects the natural history of advanced cancer and provide support for its study in less advanced patients, who should, more likely, benefit even more from this approach. (author)

Validation of MODIS snow cover images over Austria

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J. Parajka

2006-01-01

Full Text Available This study evaluates the Moderate Resolution Imaging Spectroradiometer (MODIS snow cover product over the territory of Austria. The aims are (a to analyse the spatial and temporal variability of the MODIS snow product classes, (b to examine the accuracy of the MODIS snow product against in situ snow depth data, and (c to identify the main factors that may influence the MODIS classification accuracy. We use daily MODIS grid maps (version 4 and daily snow depth measurements at 754 climate stations in the period from February 2000 to December 2005. The results indicate that, on average, clouds obscured 63% of Austria, which may significantly restrict the applicability of the MODIS snow cover images to hydrological modelling. On cloud-free days, however, the classification accuracy is very good with an average of 95%. There is no consistent relationship between the classification errors and dominant land cover type and local topographical variability but there are clear seasonal patterns to the errors. In December and January the errors are around 15% while in summer they are less than 1%. This seasonal pattern is related to the overall percentage of snow cover in Austria, although in spring, when there is a well developed snow pack, errors tend to be smaller than they are in early winter for the same overall percent snow cover. Overestimation and underestimation errors balance during most of the year which indicates little bias. In November and December, however, there appears to exist a tendency for overestimation. Part of the errors may be related to the temporal shift between the in situ snow depth measurements (07:00 a.m. and the MODIS acquisition time (early afternoon. The comparison of daily air temperature maps with MODIS snow cover images indicates that almost all MODIS overestimation errors are caused by the misclassification of cirrus clouds as snow.

Vertical solidification of dendritic binary alloys

Science.gov (United States)

Heinrich, J. C.; Felicelli, S.; Poirier, D. R.

1991-01-01

Three numerical techniques are employed to analyze the influence of thermosolutal convection on defect formation in directionally solidified (DS) alloys. The finite-element models are based on the Boussinesq approximation and include the plane-front model and two plane-front models incorporating special dendritic regions. In the second model the dendritic region has a time-independent volume fraction of liquid, and in the last model the dendritic region evolves as local conditions dictate. The finite-element models permit the description of nonlinear thermosolutal convection by treating the dendritic regions as porous media with variable porosities. The models are applied to lead-tin alloys including DS alloys, and severe segregation phenomena such as freckles and channels are found to develop in the DS alloys. The present calculations and the permeability functions selected are shown to predict behavior in the dendritic regions that qualitatively matches that observed experimentally.

Monitoring Areal Snow Cover Using NASA Satellite Imagery

Science.gov (United States)

Harshburger, Brian J.; Blandford, Troy; Moore, Brandon

2011-01-01

The objective of this project is to develop products and tools to assist in the hydrologic modeling process, including tools to help prepare inputs for hydrologic models and improved methods for the visualization of streamflow forecasts. In addition, this project will facilitate the use of NASA satellite imagery (primarily snow cover imagery) by other federal and state agencies with operational streamflow forecasting responsibilities. A GIS software toolkit for monitoring areal snow cover extent and producing streamflow forecasts is being developed. This toolkit will be packaged as multiple extensions for ArcGIS 9.x and an opensource GIS software package. The toolkit will provide users with a means for ingesting NASA EOS satellite imagery (snow cover analysis), preparing hydrologic model inputs, and visualizing streamflow forecasts. Primary products include a software tool for predicting the presence of snow under clouds in satellite images; a software tool for producing gridded temperature and precipitation forecasts; and a suite of tools for visualizing hydrologic model forecasting results. The toolkit will be an expert system designed for operational users that need to generate accurate streamflow forecasts in a timely manner. The Remote Sensing of Snow Cover Toolbar will ingest snow cover imagery from multiple sources, including the MODIS Operational Snowcover Data and convert them to gridded datasets that can be readily used. Statistical techniques will then be applied to the gridded snow cover data to predict the presence of snow under cloud cover. The toolbar has the ability to ingest both binary and fractional snow cover data. Binary mapping techniques use a set of thresholds to determine whether a pixel contains snow or no snow. Fractional mapping techniques provide information regarding the percentage of each pixel that is covered with snow. After the imagery has been ingested, physiographic data is attached to each cell in the snow cover image. This data

Use of AMSR-E microwave satellite data for land surface characteristics and snow cover variation

Directory of Open Access Journals (Sweden)

Mukesh Singh Boori

2016-12-01

Full Text Available This data article contains data related to the research article entitled “Global land cover classification based on microwave polarization and gradient ratio (MPGR” [1] and “Microwave polarization and gradient ratio (MPGR for global land surface phenology” [2]. This data article presents land surface characteristics and snow cover variation information from sensors like EOS Advanced Microwave Scanning Radiometer (AMSR-E. This data article use the HDF Explorer, Matlab, and ArcGIS software to process the pixel latitude, longitude, snow water equivalent (SWE, digital elevation model (DEM and Brightness Temperature (BT information from AMSR-E satellite data to provide land surface characteristics and snow cover variation data in all-weather condition at any time. This data information is useful to discriminate different land surface cover types and snow cover variation, which is turn, will help to improve monitoring of weather, climate and natural disasters.

Air–snow exchange of nitrate: a modelling approach to investigate physicochemical processes in surface snow at Dome C, Antarctica

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J. Bock

2016-10-01

Full Text Available Snowpack is a multiphase (photochemical reactor that strongly influences the air composition in polar and snow-covered regions. Snowpack plays a special role in the nitrogen cycle, as it has been shown that nitrate undergoes numerous recycling stages (including photolysis in the snow before being permanently buried in the ice. However, the current understanding of these physicochemical processes remains very poor. Several modelling studies have attempted to reproduce (photochemical reactions inside snow grains, but these have relied on strong assumptions to characterise snow reactive properties, which are not well defined. Air–snow exchange processes such as adsorption, solid-state diffusion, or co-condensation also affect snow chemical composition. Here, we present a physically based model of these processes for nitrate. Using as input a 1-year-long time series of atmospheric nitrate concentration measured at Dome C, Antarctica, our model reproduces with good agreement the nitrate measurements in the surface snow. By investigating the relative importance of the main exchange processes, this study shows that, on the one hand, the combination of bulk diffusion and co-condensation allows a good reproduction of the measurements (correlation coefficient r = 0.95, with a correct amplitude and timing of summer peak concentration of nitrate in snow. During winter, nitrate concentration in surface snow is mainly driven by thermodynamic equilibrium, whilst the peak observed in summer is explained by the kinetic process of co-condensation. On the other hand, the adsorption of nitric acid on the surface of the snow grains, constrained by an already existing parameterisation for the isotherm, fails to fit the observed variations. During winter and spring, the modelled concentration of adsorbed nitrate is respectively 2.5 and 8.3-fold higher than the measured one. A strong diurnal variation driven by the temperature cycle and a peak occurring in early

Merging a Terrain-Based Parameter and Snow Particle Counter Data for the Assessment of Snow Redistribution in the Col du Lac Blanc Area

Science.gov (United States)

Schön, Peter; Prokop, Alexander; Naaim-Bouvet, Florence; Vionnet, Vincent; Guyomarc'h, Gilbert; Heiser, Micha; Nishimura, Kouichi

2015-04-01

Wind and the associated snow drift are dominating factors determining the snow distribution and accumulation in alpine areas, resulting in a high spatial variability of snow depth that is difficult to evaluate and quantify. The terrain-based parameter Sx characterizes the degree of shelter or exposure of a grid point provided by the upwind terrain, without the computational complexity of numerical wind field models. The parameter has shown to qualitatively predict snow redistribution with good reproduction of spatial patterns. It does not, however, provide a quantitative estimate of changes in snow depths. The objective of our research was to introduce a new parameter to quantify changes in snow depths in our research area, the Col du Lac Blanc in the French Alps. The area is at an elevation of 2700 m and particularly suited for our study due to its consistently bi-modal wind directions. Our work focused on two pronounced, approximately 10 m high terrain breaks, and we worked with 1 m resolution digital snow surface models (DSM). The DSM and measured changes in snow depths were obtained with high-accuracy terrestrial laser scan (TLS) measurements. First we calculated the terrain-based parameter Sx on a digital snow surface model and correlated Sx with measured changes in snow-depths (Δ SH). Results showed that Δ SH can be approximated by Δ SHestimated = α * Sx, where α is a newly introduced parameter. The parameter α has shown to be linked to the amount of snow deposited influenced by blowing snow flux. At the Col du Lac Blanc test side, blowing snow flux is recorded with snow particle counters (SPC). Snow flux is the number of drifting snow particles per time and area. Hence, the SPC provide data about the duration and intensity of drifting snow events, two important factors not accounted for by the terrain parameter Sx. We analyse how the SPC snow flux data can be used to estimate the magnitude of the new variable parameter α . To simulate the development

Bioavailability of mineral-bound iron to a snow algae-bacteria co-culture and implications for albedo-altering snow algae blooms.

Science.gov (United States)

Harrold, Z R; Hausrath, E M; Garcia, A H; Murray, A E; Tschauner, O; Raymond, J; Huang, S

2018-01-26

Snow algae can form large-scale blooms across the snowpack surface and near-surface environments. These pigmented blooms can decrease snow albedo, increase local melt rates, and may impact the global heat budget and water cycle. Yet, underlying causes for the geospatial occurrence of these blooms remain unconstrained. One possible factor contributing to snow algae blooms is the presence of mineral dust as a micronutrient source. We investigated the bioavailability of iron (Fe) -bearing minerals, including forsterite (Fo 90 , Mg 1.8 Fe 0.2 SiO 4 ), goethite, smectite and pyrite as Fe sources for a Chloromonas brevispina - bacteria co-culture through laboratory-based experimentation. Fo 90 was capable of stimulating snow algal growth and increased the algal growth rate in otherwise Fe-depleted co-cultures. Fo 90 -bearing systems also exhibited a decrease in bacteria:algae ratios compared to Fe-depleted conditions, suggesting a shift in microbial community structure. The C. brevispina co-culture also increased the rate of Fo 90 dissolution relative to an abiotic control. Analysis of 16S rRNA genes in the co-culture identified Gammaproteobacteria , Betaprotoeobacteria and Sphingobacteria , all of which are commonly found in snow and ice environments. Archaea were not detected. Collimonas and Pseudomonas , which are known to enhance mineral weathering rates, comprised two of the top eight (> 1 %) OTUs. These data provide unequivocal evidence that mineral dust can support elevated snow algae growth under otherwise Fe-depleted growth conditions, and that snow algae can enhance mineral dissolution under these conditions. IMPORTANCE Fe, a key micronutrient for photosynthetic growth, is necessary to support the formation of high-density snow algae blooms. The laboratory experiments described herein allow for a systematic investigation of snow algae-bacteria-mineral interactions and their ability to mobilize and uptake mineral-bound Fe. Results provide unequivocal and

Next Generation Snow Cover Mapping: Can Future Hyperspectral Satellite Spectrometer Systems Improve Subpixel Snow-covered Area and Grain Size in the Sierra Nevada?

Science.gov (United States)

Hill, R.; Calvin, W. M.; Harpold, A.

2017-12-01

Mountain snow storage is the dominant source of water for humans and ecosystems in western North America. Consequently, the spatial distribution of snow-covered area is fundamental to both hydrological, ecological, and climate models. Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data were collected along the entire Sierra Nevada mountain range extending from north of Lake Tahoe to south of Mt. Whitney during the 2015 and 2016 snow-covered season. The AVIRIS dataset used in this experiment consists of 224 contiguous spectral channels with wavelengths ranging 400-2500 nanometers at a 15-meter spatial pixel size. Data from the Sierras were acquired on four days: 2/24/15 during a very low snow year, 3/24/16 near maximum snow accumulation, and 5/12/16 and 5/18/16 during snow ablation and snow loss. Building on previous retrieval of subpixel snow-covered area algorithms that take into account varying grain size we present a model that analyzes multiple endmembers of varying snow grain size, vegetation, rock, and soil in segmented regions along the Sierra Nevada to determine snow-cover spatial extent, snow sub-pixel fraction, and approximate grain size. In addition, varying simulated models of the data will compare and contrast the retrieval of current snow products such as MODIS Snow-Covered Area and Grain Size (MODSCAG) and the Airborne Space Observatory (ASO). Specifically, does lower spatial resolution (MODIS), broader resolution bandwidth (MODIS), and limited spectral resolution (ASO) affect snow-cover area and grain size approximations? The implications of our findings will help refine snow mapping products for planned hyperspectral satellite spectrometer systems such as EnMAP (slated to launch in 2019), HISUI (planned for inclusion on the International Space Station in 2018), and HyspIRI (currently under consideration).

Adrenergic Modulation Regulates the Dendritic Excitability of Layer 5 Pyramidal Neurons In Vivo

Directory of Open Access Journals (Sweden)

Christina Labarrera

2018-04-01

Full Text Available Summary: The excitability of the apical tuft of layer 5 pyramidal neurons is thought to play a crucial role in behavioral performance and synaptic plasticity. We show that the excitability of the apical tuft is sensitive to adrenergic neuromodulation. Using two-photon dendritic Ca2+ imaging and in vivo whole-cell and extracellular recordings in awake mice, we show that application of the α2A-adrenoceptor agonist guanfacine increases the probability of dendritic Ca2+ events in the tuft and lowers the threshold for dendritic Ca2+ spikes. We further show that these effects are likely to be mediated by the dendritic current Ih. Modulation of Ih in a realistic compartmental model controlled both the generation and magnitude of dendritic calcium spikes in the apical tuft. These findings suggest that adrenergic neuromodulation may affect cognitive processes such as sensory integration, attention, and working memory by regulating the sensitivity of layer 5 pyramidal neurons to top-down inputs. : Labarrera et al. show that noradrenergic neuromodulation can be an effective way to regulate the interaction between different input streams of information processed by an individual neuron. These findings may have important implications for our understanding of how adrenergic neuromodulation affects sensory integration, attention, and working memory. Keywords: cortical layer 5 pyramidal neuron, dendrites, norepinephrine, HCN, Ih, Ca2+ spike, apical tuft, guanfacine, ADHD, somatosensory cortex

Esterified dendritic TAM radicals with very high stability and enhanced oxygen sensitivity.

Science.gov (United States)

Song, Yuguang; Liu, Yangping; Hemann, Craig; Villamena, Frederick A; Zweier, Jay L

2013-02-15

In this work, we have developed a new class of dendritic TAM radicals (TG, TdG, and dTdG) through a convergent method based on the TAM core CT-03 or its deuterated analogue dCT-03 and trifurcated Newkome-type monomer. Among these radicals, dTdG exhibits the best EPR properties with sharpest EPR singlet and highest O(2) sensitivity due to deuteration of both the ester linker groups and the TAM core CT-03. Like the previous dendritic TAM radicals, these new compounds also show extremely high stability toward various reactive species owing to the dendritic encapsulation. The highly charged nature of these molecules resulting from nine carboxylate groups prevents concentration-dependent EPR line broadening at physiological pH. Furthermore, we demonstrate that these TAM radicals can be easily derivatized (e.g., PEGylation) at the nine carboxylate groups and the resulting PEGylated analogue dTdG-PEG completely inhibits the albumin binding, thereby enhancing suitability for in vivo applications. These new dendritic TAM radicals show great potential for in vivo EPR oximetric applications and provide insights on approaches to develop improved and targeted EPR oximetric probes for biomedical applications.

Isoflurane reversibly destabilizes hippocampal dendritic spines by an actin-dependent mechanism.

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Jimcy Platholi

Full Text Available General anesthetics produce a reversible coma-like state through modulation of excitatory and inhibitory synaptic transmission. Recent evidence suggests that anesthetic exposure can also lead to sustained cognitive dysfunction. However, the subcellular effects of anesthetics on the structure of established synapses are not known. We investigated effects of the widely used volatile anesthetic isoflurane on the structural stability of hippocampal dendritic spines, a postsynaptic structure critical to excitatory synaptic transmission in learning and memory. Exposure to clinical concentrations of isoflurane induced rapid and non-uniform shrinkage and loss of dendritic spines in mature cultured rat hippocampal neurons. Spine shrinkage was associated with a reduction in spine F-actin concentration. Spine loss was prevented by either jasplakinolide or cytochalasin D, drugs that prevent F-actin disassembly. Isoflurane-induced spine shrinkage and loss were reversible upon isoflurane elimination. Thus, isoflurane destabilizes spine F-actin, resulting in changes to dendritic spine morphology and number. These findings support an actin-based mechanism for isoflurane-induced alterations of synaptic structure in the hippocampus. These reversible alterations in dendritic spine structure have important implications for acute anesthetic effects on excitatory synaptic transmission and synaptic stability in the hippocampus, a locus for anesthetic-induced amnesia, and have important implications for anesthetic effects on synaptic plasticity.

Standard practice for acoustic emission examination of plate-like and flat panel composite structures used in aerospace applications

CERN Document Server

American Society for Testing and Materials. Philadelphia

2010-01-01

1.1 This practice covers acoustic emission (AE) examination or monitoring of panel and plate-like composite structures made entirely of fiber/polymer composites. 1.2 The AE examination detects emission sources and locates the region(s) within the composite structure where the emission originated. When properly developed AE-based criteria for the composite item are in place, the AE data can be used for nondestructive examination (NDE), characterization of proof testing, documentation of quality control or for decisions relative to structural-test termination prior to completion of a planned test. Other NDE methods may be used to provide additional information about located damage regions. For additional information see Appendix X1. 1.3 This practice can be applied to aerospace composite panels and plate-like elements as a part of incoming inspection, during manufacturing, after assembly, continuously (during structural health monitoring) and at periodic intervals during the life of a structure. 1.4 This pra...

Synaptic Control of Secretory Trafficking in Dendrites

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Cyril Hanus

2014-06-01

Full Text Available Localized signaling in neuronal dendrites requires tight spatial control of membrane composition. Upon initial synthesis, nascent secretory cargo in dendrites exits the endoplasmic reticulum (ER from local zones of ER complexity that are spatially coupled to post-ER compartments. Although newly synthesized membrane proteins can be processed locally, the mechanisms that control the spatial range of secretory cargo transport in dendritic segments are unknown. Here, we monitored the dynamics of nascent membrane proteins in dendritic post-ER compartments under regimes of low or increased neuronal activity. In response to activity blockade, post-ER carriers are highly mobile and are transported over long distances. Conversely, increasing synaptic activity dramatically restricts the spatial scale of post-ER trafficking along dendrites. This activity-induced confinement of secretory cargo requires site-specific phosphorylation of the kinesin motor KIF17 by Ca2+/calmodulin-dependent protein kinases (CaMK. Thus, the length scales of early secretory trafficking in dendrites are tuned by activity-dependent regulation of microtubule-dependent transport.

Synthesis and silica coating of calcia-doped ceria/plate-like titanate (K0.8Li0.27Ti1.73O4) nanocomposite by seeded polymerization technique

International Nuclear Information System (INIS)

El-Toni, Ahmed Mohamed; Yin, Shu; Sato, Tsugio

2007-01-01

Calcia-doped ceria is of potential interest as an ultraviolet (UV) radiation blocking material in personal care products because of the excellent UV light absorption property and low catalytic ability for the oxidation of organic materials superior to undoped ceria. In order to reduce the oxidation catalytic activity further, calcia-doped ceria was coated with amorphous silica by means of seeded polymerization technique. Generally, nanoparticles of inorganic materials do not provide a good coverage for human skin because of the agglomeration of the particles. The plate-like particles are required to enhance the coverage ability of inorganic materials. This can be accomplished by synthesis of calcia-doped ceria/plate-like potassium lithium titanate (K 0.8 Li 0.27 Ti 1.73 O 4 ) nanocomposite with subsequent silica coating to control catalytic activity of calcia-doped ceria. Calcia-doped ceria/plate-like potassium lithium titanate nanocomposite was prepared by soft chemical method followed by silica coating via seeded polymerization technique. Silica coated calcia-doped ceria/plate-like potassium lithium titanate nanocomposite was characterized by X-ray diffraction, SEM, TEM, XPS and FT-IR

Role of Tibetan Buddhist monasteries in snow leopard conservation.

Science.gov (United States)

Li, Juan; Wang, Dajun; Yin, Hang; Zhaxi, Duojie; Jiagong, Zhala; Schaller, George B; Mishra, Charudutt; McCarthy, Thomas M; Wang, Hao; Wu, Lan; Xiao, Lingyun; Basang, Lamao; Zhang, Yuguang; Zhou, Yunyun; Lu, Zhi

2014-02-01

The snow leopard (Panthera uncia) inhabits the rugged mountains in 12 countries of Central Asia, including the Tibetan Plateau. Due to poaching, decreased abundance of prey, and habitat degradation, it was listed as endangered by the International Union for Conservation of Nature in 1972. Current conservation strategies, including nature reserves and incentive programs, have limited capacities to protect snow leopards. We investigated the role of Tibetan Buddhist monasteries in snow leopard conservation in the Sanjiangyuan region in China's Qinghai Province on the Tibetan Plateau. From 2009 to 2011, we systematically surveyed snow leopards in the Sanjiangyuan region. We used the MaxEnt model to determine the relation of their presence to environmental variables (e.g., elevation, ruggedness) and to predict snow leopard distribution. Model results showed 89,602 km(2) of snow leopard habitat in the Sanjiangyuan region, of which 7674 km(2) lay within Sanjiangyuan Nature Reserve's core zones. We analyzed the spatial relation between snow leopard habitat and Buddhist monasteries and found that 46% of monasteries were located in snow leopard habitat and 90% were within 5 km of snow leopard habitat. The 336 monasteries in the Sanjiangyuan region could protect more snow leopard habitat (8342 km(2) ) through social norms and active patrols than the nature reserve's core zones. We conducted 144 household interviews to identify local herders' attitudes and behavior toward snow leopards and other wildlife. Most local herders claimed that they did not kill wildlife, and 42% said they did not kill wildlife because it was a sin in Buddhism. Our results indicate monasteries play an important role in snow leopard conservation. Monastery-based snow leopard conservation could be extended to other Tibetan Buddhist regions that in total would encompass about 80% of the global range of snow leopards. © 2013 Society for Conservation Biology.

Intrinsic versus extrinsic controls on the development of calcite dendrite bushes, Shuzhishi Spring, Rehai geothermal area, Tengchong, Yunnan Province, China

Science.gov (United States)

Jones, Brian; Peng, Xiaotong

2012-04-01

In the Rehai geothermal area, located near Tengchong, there is an old succession of crystalline calcite that formed from a spring that is no longer active. The thin-bedded succession, exposed on the south bank of Zaotang River, is formed of three-dimensional dendrite bushes that are up to 6 cm high and 3 cm in diameter with multiple levels of branching. Bedding is defined by color, which ranges from white to gray to almost black and locally accentuated by differential weathering that highlights the branching motif of the dendrites. The succession developed through repeated tripartite growth cycles that involved: Phase I that was characterized by rapid vertical growth of the dendrite bushes with ever-increasing branching; Phase II that developed once growth of the dendrites had almost or totally ceased, and involved an initial phase of etching that was followed by the precipitation of various secondary minerals (sheet calcite, trigonal calcite crystals, hexagonal calcite crystals, hexagonal plates formed of Ca and P, Mn precipitates, Si-Mg reticulate coatings, opal-CT lepispheres) on the branches of the calcite dendrites, and Phase III that involved deposition of detrital quartz, feldspar, clay, and calcite on top of the dendrite bushes. The tripartite growth cycle is attributed primarily to aperiodic cycles in the CO2 content of the spring water that was controlled by subsurface igneous activity rather than climatic controls. High CO2 coupled with rapid CO2 degassing triggered growth of the dendrite bushes. As CO2 levels waned, saturation levels in the spring water decreased and calcite dendrite growth ceased and precipitation of the secondary minerals took place, possibly in the microcosms of microbial mats. Deposition of the detrital sediment was probably related to surface runoff that was triggered by periods of high rainfall. Critically, this study shows that intrinsic factors rather than extrinsic factors (e.g., climate) were the prime control on the

Loss of Dendritic Complexity Precedes Neurodegeneration in a Mouse Model with Disrupted Mitochondrial Distribution in Mature Dendrites

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Guillermo López-Doménech

2016-10-01

Full Text Available Correct mitochondrial distribution is critical for satisfying local energy demands and calcium buffering requirements and supporting key cellular processes. The mitochondrially targeted proteins Miro1 and Miro2 are important components of the mitochondrial transport machinery, but their specific roles in neuronal development, maintenance, and survival remain poorly understood. Using mouse knockout strategies, we demonstrate that Miro1, as opposed to Miro2, is the primary regulator of mitochondrial transport in both axons and dendrites. Miro1 deletion leads to depletion of mitochondria from distal dendrites but not axons, accompanied by a marked reduction in dendritic complexity. Disrupting postnatal mitochondrial distribution in vivo by deleting Miro1 in mature neurons causes a progressive loss of distal dendrites and compromises neuronal survival. Thus, the local availability of mitochondrial mass is critical for generating and sustaining dendritic arbors, and disruption of mitochondrial distribution in mature neurons is associated with neurodegeneration.

Coding and decoding with dendrites.

Science.gov (United States)

Papoutsi, Athanasia; Kastellakis, George; Psarrou, Maria; Anastasakis, Stelios; Poirazi, Panayiota

2014-02-01

Since the discovery of complex, voltage dependent mechanisms in the dendrites of multiple neuron types, great effort has been devoted in search of a direct link between dendritic properties and specific neuronal functions. Over the last few years, new experimental techniques have allowed the visualization and probing of dendritic anatomy, plasticity and integrative schemes with unprecedented detail. This vast amount of information has caused a paradigm shift in the study of memory, one of the most important pursuits in Neuroscience, and calls for the development of novel theories and models that will unify the available data according to some basic principles. Traditional models of memory considered neural cells as the fundamental processing units in the brain. Recent studies however are proposing new theories in which memory is not only formed by modifying the synaptic connections between neurons, but also by modifications of intrinsic and anatomical dendritic properties as well as fine tuning of the wiring diagram. In this review paper we present previous studies along with recent findings from our group that support a key role of dendrites in information processing, including the encoding and decoding of new memories, both at the single cell and the network level. Copyright © 2013 Elsevier Ltd. All rights reserved.

Insights on nitrate sources at Dome C (East Antarctic Plateau from multi-year aerosol and snow records

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Rita Traversi

2014-06-01

Full Text Available Here we present the first multi-year record of nitrate in the atmospheric aerosol (2005–2008 and surface snow (2006–08 from central Antarctica. PM10 and size-segregated aerosol, together with superficial snow, have been collected all year-round at high resolution (daily for all the snow samples and for most of aerosol samples at Dome C since the 2004/05 field season and analysed for main and trace ionic markers. The suitability of the sampling location in terms of possible contamination from the base is shown in detail. In spite of the relevance of nitrate in Antarctic atmosphere, both for better understanding the chemistry of N cycle in the plateau boundary layer and for improving the interpretation of long-term nitrate records from deep ice core records, nitrate sources in Antarctica are not well constrained yet, neither in extent nor in timing. A recurring seasonal pattern was pointed out in both aerosol and snow records, showing summer maxima and winter minima, although aerosol maxima lead the snow ones of 1–2 months, possibly due to a higher acidity in the atmosphere in mid-summer, favouring the repartition of nitrate as nitric acid and thus its uptake by the surface snow layers. On the basis of a meteorological analysis of one major nitrate event, of data related to PSC I extent and of irradiance values, we propose that the high nitrate summer levels in aerosol and snow are likely due to a synergy of enhanced source of nitrate and/or its precursors (such as the stratospheric inputs, higher solar irradiance and higher oxidation rates in this season. Moreover, we show here a further evidence of the substantial contribution of HNO3/NOx re-emission from the snowpack, already shown in previous works, and which can explain a significant fraction of atmospheric nitrate, maintaining the same seasonal pattern in the snow. As concerning snow specifically, the presented data suggest that nitrate is likely to be controlled mainly by atmospheric

Development of effective tumor immunotherapy using a novel dendritic cell-targeting Toll-like receptor ligand.

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Nadeeka H De Silva

Full Text Available Although dendritic cell (DC-based immunotherapy shows little toxicity, improvements should be necessary to obtain satisfactory clinical outcome. Using interferon-gamma injection along with DCs, we previously obtained significant clinical responses against small or early stage malignant tumors in dogs. However, improvement was necessary to be effective to largely developed or metastatic tumors. To obtain effective methods applicable to those tumors, we herein used a DC-targeting Toll-like receptor ligand, h11c, and examined the therapeutic effects in murine subcutaneous and visceral tumor models and also in the clinical treatment of canine cancers. In murine experiments, most and significant inhibition of tumor growth and extended survival was observed in the group treated with the combination of h11c-activated DCs in combination with interferon-gamma and a cyclooxygenase2 inhibitor. Both monocytic and granulocytic myeloid-derived suppressor cells were significantly reduced by the combined treatment. Following the successful results in mice, the combined treatment was examined against canine cancers, which spontaneously generated like as those in human. The combined treatment elicited significant clinical responses against a nonepithelial malignant tumor and a malignant fibrous histiocytoma. The treatment was also successful against a bone-metastasis of squamous cell carcinoma. In the successful cases, the marked increase of tumor-responding T cells and decrease of myeloid-derived suppressor cells and regulatory T cells was observed in their peripheral blood. Although the combined treatment permitted the growth of lung cancer of renal carcinoma-metastasis, the marked elevated and long-term maintaining of the tumor-responding T cells was observed in the patient dog. Overall, the combined treatment gave rise to emphatic amelioration in DC-based cancer therapy.

Research of Snow-Melt Process on a Heated Platform

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Vasilyev Gregory P.

2016-01-01

Full Text Available The article has shown the results of experimental researches of the snow-melt on a heated platform-near building heat-pump snow-melt platform. The near-building (yard heat pump platforms for snow melt with the area up to 10-15 m2 are a basis of the new ideology of organization of the street cleaning of Moscow from snow in the winter period which supposes the creation in the megalopolis of the «distributed snow-melt system» (DSMS using non-traditional energy sources. The results of natural experimental researches are presented for the estimation of efficiency of application in the climatic conditions of Moscow of heat pumps in the snow-melt systems. The researches were conducted on a model sample of the near-building heat-pump platform which uses the low-potential thermal energy of atmospheric air. The conducted researches have confirmed experimentally in the natural conditions the possibility and efficiency of using of atmospheric air as a source of low-potential thermal energy for evaporation of the snow-melt heat pump systems in the climatic conditions of Moscow. The results of laboratory researches of snow-melt process on a heated horizontal platform are presented. The researches have revealed a considerable dependence of efficiency of the snow-melt process on its piling mode (form-building and the organization of the process of its piling mode (form-building and the organization of the process of its (snow mass heat exchange with the surface of the heated platform. In the process of researches the effect of formation of an «ice dome» under the melting snow mass called by the fact that in case of the thickness of snow loaded on the platform more than 10 cm the water formed from the melting snow while the contact with the heating surface don’t spread on it, but soaks into the snow, wets it due to capillary effect and freezes. The formation of «ice dome» leads to a sharp increase of snow-melt period and decreases the operating

Microbial Community Analysis of Colored Snow from an Alpine Snowfield in Northern Japan Reveals the Prevalence of Betaproteobacteria with Snow Algae.

Science.gov (United States)

Terashima, Mia; Umezawa, Kazuhiro; Mori, Shoichi; Kojima, Hisaya; Fukui, Manabu

2017-01-01

Psychrophilic algae blooms can be observed coloring the snow during the melt season in alpine snowfields. These algae are important primary producers on the snow surface environment, supporting the microbial community that coexists with algae, which includes heterotrophic bacteria and fungi. In this study, we analyzed the microbial community of green and red-colored snow containing algae from Mount Asahi, Japan. We found that Chloromonas spp. are the dominant algae in all samples analyzed, and Chlamydomonas is the second-most abundant genus in the red snow. For the bacterial community profile, species belonging to the subphylum Betaproteobacteria were frequently detected in both green and red snow, while members of the phylum Bacteroidetes were also prominent in red snow. Furthermore, multiple independently obtained strains of Chloromonas sp. from inoculates of red snow resulted in the growth of Betaproteobacteria with the alga and the presence of bacteria appears to support growth of the xenic algal cultures under laboratory conditions. The dominance of Betaproteobacteria in algae-containing snow in combination with the detection of Chloromonas sp. with Betaproteobacteria strains suggest that these bacteria can utilize the available carbon source in algae-rich environments and may in turn promote algal growth.

Snow model design for operational purposes

Science.gov (United States)

Kolberg, Sjur

2017-04-01

A parsimonious distributed energy balance snow model intended for operational use is evaluated using discharge, snow covered area and grain size; the latter two as observed from the MODIS sensor. The snow model is an improvement of the existing GamSnow model, which is a part of the Enki modelling framework. Core requirements for the new version have been: 1. Reduction of calibration freedom, motivated by previous experience of non-identifiable parameters in the existing version 2. Improvement of process representation based on recent advances in physically based snow modelling 3. Limiting the sensitivity to forcing data which are poorly known over the spatial domain of interest (often in mountainous areas) 4. Preference for observable states, and the ability to improve from updates. The albedo calculation is completely revised, now based on grain size through an emulation of the SNICAR model (Flanner and Zender, 2006; Gardener and Sharp, 2010). The number of calibration parameters in the albedo model is reduced from 6 to 2. The wind function governing turbulent energy fluxes has been reduced from 2 to 1 parameter. Following Raleigh et al (2011), snow surface radiant temperature is split from the top layer thermodynamic temperature, using bias-corrected wet-bulb temperature to model the former. Analyses are ongoing, and the poster will bring evaluation results from 16 years of MODIS observations and more than 25 catchments in southern Norway.

Zinc and Copper Effects on Stability of Tubulin and Actin Networks in Dendrites and Spines of Hippocampal Neurons.

Science.gov (United States)

Perrin, Laura; Roudeau, Stéphane; Carmona, Asuncion; Domart, Florelle; Petersen, Jennifer D; Bohic, Sylvain; Yang, Yang; Cloetens, Peter; Ortega, Richard

2017-07-19

Zinc and copper ions can modulate the activity of glutamate receptors. However, labile zinc and copper ions likely represent only the tip of the iceberg and other neuronal functions are suspected for these metals in their bound state. We performed synchrotron X-ray fluorescence imaging with 30 nm resolution to image total biometals in dendrites and spines from hippocampal neurons. We found that zinc is distributed all along the dendrites while copper is mainly pinpointed within the spines. In spines, zinc content is higher within the spine head while copper is higher within the spine neck. Such specific distributions suggested metal interactions with cytoskeleton proteins. Zinc supplementation induced the increase of β-tubulin content in dendrites. Copper supplementation impaired the β-tubulin and F-actin networks. Copper chelation resulted in the decrease of F-actin content in dendrites, drastically reducing the number of F-actin protrusions. These results indicate that zinc is involved in microtubule stability whereas copper is essential for actin-dependent stability of dendritic spines, although copper excess can impair the dendritic cytoskeleton.

Sleeping dendrites: fiber-optic measurements of dendritic calcium activity in freely moving and sleeping animals

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Julie Seibt

2014-03-01

Full Text Available Dendrites are the post-synaptic sites of most excitatory and inhibitory synapses in the brain, making them the main location of cortical information processing and synaptic plasticity. Although current hypotheses suggest a central role for sleep in proper cognitive function and brain plasticity, virtually nothing is known about changes in dendritic activity across the sleep-wake cycle and how waking experience modifies this activity. To start addressing these questions, we developed a method that allows long-term recordings of EEGs/EMG combined with in vivo cortical calcium (Ca2+ activity in freely moving and sleeping rats. We measured Ca2+ activity from populations of dendrites of layer (L 5 pyramidal neurons (n = 13 rats that we compared with Ca2+ activity from populations of neurons in L2/3 (n = 11 rats. L5 and L2/3 neurons were labelled using bolus injection of OGB1-AM or GCaMP6 (1. Ca2+ signals were detected using a fiber-optic system (cannula diameter = 400µm, transmitting the changes in fluorescence to a photodiode. Ca2+ fluctuations could then be correlated with ongoing changes in brain oscillatory activity during 5 major brain states: active wake [AW], quiet wake [QW], NREM, REM and NREM-REM transition (or intermediate state, [IS]. Our Ca2+ recordings show large transients in L5 dendrites and L2/3 neurons that oscillate predominantly at frequencies In summary, we show that this technique is successful in monitoring fluctuations in ongoing dendritic Ca2+ activity during natural brain states and allows, in principle, to combine behavioral measurement with imaging from various brain regions (e.g. deep structures in freely behaving animals. Using this method, we show that Ca2+ transients from populations of L2/3 neurons and L5 dendrites are deferentially regulated across the sleep/wake cycle, with dendritic activity being the highest during the IS sleep. Our correlation analysis suggests that specific sleep EEG activity during NREM and IS

Modelling the snowmelt and the snow water equivalent by creating a simplified energy balance conceptual snow model

Science.gov (United States)

Riboust, Philippe; Thirel, Guillaume; Le Moine, Nicolas; Ribstein, Pierre

2016-04-01

A better knowledge of the accumulated snow on the watersheds will help flood forecasting centres and hydro-power companies to predict the amount of water released during spring snowmelt. Since precipitations gauges are sparse at high elevations and integrative measurements of the snow accumulated on watershed surface are hard to obtain, using snow models is an adequate way to estimate snow water equivalent (SWE) on watersheds. In addition to short term prediction, simulating accurately SWE with snow models should have many advantages. Validating the snow module on both SWE and snowmelt should give a more reliable model for climate change studies or regionalization for ungauged watersheds. The aim of this study is to create a new snow module, which has a structure that allows the use of measured snow data for calibration or assimilation. Energy balance modelling seems to be the logical choice for designing a model in which internal variables, such as SWE, could be compared to observations. Physical models are complex, needing high computational resources and many different types of inputs that are not widely measured at meteorological stations. At the opposite, simple conceptual degree-day models offer to simulate snowmelt using only temperature and precipitation as inputs with fast computing. Its major drawback is to be empirical, i.e. not taking into account all of the processes of the energy balance, which makes this kind of model more difficult to use when willing to compare SWE to observed measurements. In order to reach our objectives, we created a snow model structured by a simplified energy balance where each of the processes is empirically parameterized in order to be calculated using only temperature, precipitation and cloud cover variables. This model's structure is similar to the one created by M.T. Walter (2005), where parameterizations from the literature were used to compute all of the processes of the energy balance. The conductive fluxes into the

New technology of lead-tin plating of superconducting RF resonators for the ANU LINAC

International Nuclear Information System (INIS)

Lobanov, N.R.; Weisser, D.C.

2003-01-01

The RF accelerating resonators for the ANU superconducting LINAC have been re-plated with lead-tin and their performance substantially improved. The re-plating was at first derailed by the appearance of dendrites on the surface. This problem was overcome by a new combination of two techniques. Rather than the standard process of chemically stripping the old Pb and hand polishing the Cu substrate the unsatisfactory Pb surface was mechanically polished and then re-plated. This is enormously easier, faster and doesn't put at risk the thin cosmetic electron beam welds or the repaired ones. Reverse pulse plating was then used to re-establish an excellent superconducting surface. Average acceleration fields of 3.5 to 3.9 MV/m have been achieved. The re-plated resonators will double the energy gain of the accelerator significantly extending capability of the facility research. Lead-tin plating provides fast adequate results with modest equipment and at relatively low cost. SUNY re-plated six high-beta SLRs with 2 microns of Pb-Sn using a modern, commercial, methane-sulfonate process (Lea Ronal Solderon MHS-L) and a simple open-air procedure. This proven success motivated ANU to adopt MSA chemistry and to re-plate the first SLR in November 1998 followed by re-plating all twelve SLRs by November 2002. This increased the booster energy gain by almost 100%

Forced copulation results in few extrapair fertilizations in Ross's and lesser snow geese

Science.gov (United States)

Dunn, P.O.; Afton, A.D.; Gloutney, M.L.; Alisauskas, R.T.

1999-01-01

Extrapair paternity varies from 0 to over 70% of young among various populations of birds. Comparative studies have suggested that this variation is related to nesting density, breeding synchrony and the proportion of extrapair copulations. We used minisatellite DNA fingerprinting to examine levels of extrapair paternity in Ross's geese, Chen rossi, and lesser snow geese, C. caerulescens c. (hereafter snow geese) nesting in the largest known goose colony in the world. These geese have one of the highest known percentages of extrapair copulation (46-56% of all attempted copulations), and all of these appeared to be forced. Among all successful copulations, 33 and 38% were extrapair in Ross's and snow geese, respectively. Despite the high percentage of extrapair copulations, extrapair paternity was low in both Ross's and snow geese (2-5% of young). Extrapair paternity was not related to nest density in either species. However, in snow geese, extrapair paternity was more likely to occur in nests of females that nested asynchronously, either early or late in the season. This is one of a few reported examples of a negative relationship between extrapair paternity and breeding synchrony. Extrapair young also tended to come from eggs laid later in the clutch. Although forced extrapair copulations appear to be a relatively inefficient reproductive tactic for males, they may provide a reproductive advantage for some males.

Randomly oriented twin domains in electrodeposited silver dendrites

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Ivanović Evica R.

2015-01-01

Full Text Available Silver dendrites were prepared by electrochemical deposition. The structures of Ag dendrites, the type of twins and their distribution were investigated by scanning electron microscopy (SEM, Z-contrast high angle annular dark field transmission electron microscopy (HAADF, and crystallografically sensitive orientation imaging microscopy (OIM. The results revealed that silver dendrites are characterized by the presence of randomly distributed 180° rotational twin domains. The broad surface of dendrites was of the {111} type. Growth directions of the main dendrite stem and all branches were of type. [Projekat Ministarstva nauke Republike Srbije, br. 172054

Estimation of the condition of snow cover in Voronezh according to the chemical analysis of water from melted snow

OpenAIRE

Prozhorina Tatyana Ivanovna; Bespalova Elena Vladimirovna; Yakunina Nadezhda

2014-01-01

Snow cover possesses high sorption ability and represents informative object to identify technogenic pollution of an urban environment. In this article the investigation data of a chemical composition of snow fallen in Voronezh during the winter period of 2014 are given. Relationships between existence of pollutants in snow and the level of technogenic effect are analyzed.

Physiochemical characterization of insoluble residues in California Sierra Nevada snow

Science.gov (United States)

Creamean, Jessie; Axson, Jessica; Bondy, Amy; Craig, Rebecca; May, Nathaniel; Shen, Hongru; Weber, Michael; Warner, Katy; Pratt, Kerri; Ault, Andrew

2015-04-01

The effects atmospheric aerosols have on cloud particle formation are dependent on both the aerosol physical and chemical characteristics. For instance, larger, irregular-shaped mineral dusts efficiently form cloud ice crystals, enhancing precipitation, whereas small, spherical pollution aerosols have the potential to form small cloud droplets that delay the autoconversion of cloudwater to precipitation. Thus, it is important to understand the physiochemical properties and sources of aerosols that influence cloud and precipitation formation. We present an in-depth analysis of the size, chemistry, and sources of soluble and insoluble residues found in snow collected at three locations in the California Sierra Nevada Mountains during the 2012/2013 winter season. For all sites, February snow samples contained high concentrations of regional pollutants such as ammonium nitrate and biomass burning species, while March snow samples were influenced by mineral dust. The snow at the lower elevation sites in closer proximity to the Central Valley of California were heavily influenced by agricultural and industrial emissions, whereas the highest elevation site was exposed to a mixture of Central Valley pollutants in addition to long-range transported dust from Asia and Africa. Further, air masses likely containing transported dust typically traveled over cloud top heights at the low elevation sites, but were incorporated into the cold (-28°C, on average) cloud tops more often at the highest elevation site, particularly in March, which we hypothesize led to enhanced ice crystal formation and thus the observation of dust in the snow collected at the ground. Overall, understanding the spatial and temporal dependence of aerosol sources is important for remote mountainous regions such as the Sierra Nevada where snowpack provides a steady, vital supply of water.

Signaling network of dendritic cells in response to pathogens: a community-input supported knowledgebase

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Nudelman Irina

2010-10-01

Full Text Available Abstract Background Dendritic cells are antigen-presenting cells that play an essential role in linking the innate and adaptive immune systems. Much research has focused on the signaling pathways triggered upon infection of dendritic cells by various pathogens. The high level of activity in the field makes it desirable to have a pathway-based resource to access the information in the literature. Current pathway diagrams lack either comprehensiveness, or an open-access editorial interface. Hence, there is a need for a dependable, expertly curated knowledgebase that integrates this information into a map of signaling networks. Description We have built a detailed diagram of the dendritic cell signaling network, with the goal of providing researchers with a valuable resource and a facile method for community input. Network construction has relied on comprehensive review of the literature and regular updates. The diagram includes detailed depictions of pathways activated downstream of different pathogen recognition receptors such as Toll-like receptors, retinoic acid-inducible gene-I-like receptors, C-type lectin receptors and nucleotide-binding oligomerization domain-like receptors. Initially assembled using CellDesigner software, it provides an annotated graphical representation of interactions stored in Systems Biology Mark-up Language. The network, which comprises 249 nodes and 213 edges, has been web-published through the Biological Pathway Publisher software suite. Nodes are annotated with PubMed references and gene-related information, and linked to a public wiki, providing a discussion forum for updates and corrections. To gain more insight into regulatory patterns of dendritic cell signaling, we analyzed the network using graph-theory methods: bifan, feedforward and multi-input convergence motifs were enriched. This emphasis on activating control mechanisms is consonant with a network that subserves persistent and coordinated responses to

Orchestration of transplantation tolerance by regulatory dendritic cell therapy or in-situ targeting of dendritic cells.

Science.gov (United States)

Morelli, Adrian E; Thomson, Angus W

2014-08-01

Extensive research in murine transplant models over the past two decades has convincingly demonstrated the ability of regulatory dendritic cells (DCregs) to promote long-term allograft survival. We review important considerations regarding the source of therapeutic DCregs (donor or recipient) and their mode of action, in-situ targeting of DCregs, and optimal therapeutic regimens to promote DCreg function. Recent studies have defined protocols and mechanisms whereby ex-vivo-generated DCregs of donor or recipient origin subvert allogeneic T-cell responses and promote long-term organ transplant survival. Particular interest has focused on how donor antigen is acquired, processed and presented by autologous dendritic cells, on the stability of DCregs, and on in-situ targeting of dendritic cells to promote their tolerogenic function. New evidence of the therapeutic efficacy of DCregs in a clinically relevant nonhuman primate organ transplant model and production of clinical grade DCregs support early evaluation of DCreg therapy in human graft recipients. We discuss strategies currently used to promote dendritic cell tolerogenicity, including DCreg therapy and in-situ targeting of dendritic cells, with a view to improved understanding of underlying mechanisms and identification of the most promising strategies for therapeutic application.

Low-Dose Cyclophosphamide Synergizes with Dendritic Cell-Based Immunotherapy in Antitumor Activity

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Joris D. Veltman

2010-01-01

Full Text Available Clinical immunotherapy trials like dendritic cell-based vaccinations are hampered by the tumor's offensive repertoire that suppresses the incoming effector cells. Regulatory T cells are instrumental in suppressing the function of cytotoxic T cells. We studied the effect of low-dose cyclophosphamide on the suppressive function of regulatory T cells and investigated if the success rate of dendritic cell immunotherapy could be improved. For this, mesothelioma tumor-bearing mice were treated with dendritic cell-based immunotherapy alone or in combination with low-dose of cyclophosphamide. Proportions of regulatory T cells and the cytotoxic T cell functions at different stages of disease were analyzed. We found that low-dose cyclophosphamide induced beneficial immunomodulatory effects by preventing the induction of Tregs, and as a consequence, cytotoxic T cell function was no longer affected. Addition of cyclophosphamide improved immunotherapy leading to an increased median and overall survival. Future studies are needed to address the usefulness of this combination treatment for mesothelioma patients.

(NDSI) and Normalised Difference Principal Component Snow Index

African Journals Online (AJOL)

Phila Sibandze

According to Bonan (2002), snow plays a significant role in influencing heat regimes and local, regional ... sensitive indicator to climate change. In South Africa, snow is .... This image was captured on the earliest cloud free day after a snow fall.

Photopolarimetric Retrievals of Snow Properties

Science.gov (United States)

Ottaviani, M.; van Diedenhoven, B.; Cairns, B.

2015-01-01

Polarimetric observations of snow surfaces, obtained in the 410-2264 nm range with the Research Scanning Polarimeter onboard the NASA ER-2 high-altitude aircraft, are analyzed and presented. These novel measurements are of interest to the remote sensing community because the overwhelming brightness of snow plagues aerosol and cloud retrievals based on airborne and spaceborne total reflection measurements. The spectral signatures of the polarized reflectance of snow are therefore worthwhile investigating in order to provide guidance for the adaptation of algorithms currently employed for the retrieval of aerosol properties over soil and vegetated surfaces. At the same time, the increased information content of polarimetric measurements allows for a meaningful characterization of the snow medium. In our case, the grains are modeled as hexagonal prisms of variable aspect ratios and microscale roughness, yielding retrievals of the grains' scattering asymmetry parameter, shape and size. The results agree with our previous findings based on a more limited data set, with the majority of retrievals leading to moderately rough crystals of extreme aspect ratios, for each scene corresponding to a single value of the asymmetry parameter.

Quantification of dendritic and axonal growth after injury to the auditory system of the adult cricket Gryllus bimaculatus

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Alexandra ePfister

2013-08-01

Full Text Available Dendrite and axon growth and branching during development are regulated by a complex set of intracellular and external signals. However, the cues that maintain or influence adult neuronal morphology are less well understood. Injury and deafferentation tend to have negative effects on adult nervous systems. An interesting example of injury-induced compensatory growth is seen in the cricket, Gryllus bimaculatus. After unilateral loss of an ear in the adult cricket, auditory neurons within the central nervous system sprout to compensate for the injury. Specifically, after being deafferented, ascending neurons (AN-1 and AN-2 send dendrites across the midline of the prothoracic ganglion where they receive input from auditory afferents that project through the contralateral auditory nerve (N5. Deafferentation also triggers contralateral N5 axonal growth. In this study, we quantified AN dendritic and N5 axonal growth at 30 hours, as well as at 3, 5, 7, 14 and 20 days after deafferentation in adult crickets. Significant differences in the rates of dendritic growth between males and females were noted. In females, dendritic growth rates were non-linear; a rapid burst of dendritic extension in the first few days was followed by a plateau reached at 3 days after deafferentation. In males, however, dendritic growth rates were linear, with dendrites growing steadily over time and reaching lengths, on average, twice as long as in females. On the other hand, rates of N5 axonal growth showed no significant sexual dimorphism and were linear. Within each animal, the growth rates of dendrites and axons were not correlated, indicating that independent factors likely influence dendritic and axonal growth in response to injury in this system. Our findings provide a basis for future study of the cellular features that allow differing dendrite and axon growth patterns as well as sexually dimorphic dendritic growth in response to deafferentation.

Snow Leopard

Indian Academy of Sciences (India)

adult females (dimorphic); a male on average weighing between. 45–55 kg, while a .... performance of wild prey, eventually leading to a decline in their population. Research .... working towards enhancing knowledge on snow leopard ecology.

Measurement of snow interception and canopy effects on snow accumulation and melt in a mountainous maritime climate, Oregon, United States

Science.gov (United States)

Storck, Pascal; Lettenmaier, Dennis P.; Bolton, Susan M.

2002-11-01

The results of a 3 year field study to observe the processes controlling snow interception by forest canopies and under canopy snow accumulation and ablation in mountain maritime climates are reported. The field study was further intended to provide data to develop and test models of forest canopy effects on beneath-canopy snowpack accumulation and melt and the plot and stand scales. Weighing lysimeters, cut-tree experiments, and manual snow surveys were deployed at a site in the Umpqua National Forest, Oregon (elevation 1200 m). A unique design for a weighing lysimeter was employed that allowed continuous measurements of snowpack evolution beneath a forest canopy to be taken at a scale unaffected by variability in canopy throughfall. Continuous observations of snowpack evolution in large clearings were made coincidentally with the canopy measurements. Large differences in snow accumulation and ablation were observed at sites beneath the forest canopy and in large clearings. These differences were not well described by simple relationships between the sites. Over the study period, approximately 60% of snowfall was intercepted by the canopy (up to a maximum of about 40 mm water equivalent). Instantaneous sublimation rates exceeded 0.5 mm per hour for short periods. However, apparent average sublimation from the intercepted snow was less than 1 mm per day and totaled approximately 100 mm per winter season. Approximately 72 and 28% of the remaining intercepted snow was removed as meltwater drip and large snow masses, respectively. Observed differences in snow interception rate and maximum snow interception capacity between Douglas fir (Pseudotsuga menziesii), white fir (Abies concolor), ponderosa pine (Pinus ponderosa), and lodgepole pine (Pinus contorta) were minimal.

Molecular identity of dendritic voltage-gated sodium channels.

Science.gov (United States)

Lorincz, Andrea; Nusser, Zoltan

2010-05-14

Active invasion of the dendritic tree by action potentials (APs) generated in the axon is essential for associative synaptic plasticity and neuronal ensemble formation. In cortical pyramidal cells (PCs), this AP back-propagation is supported by dendritic voltage-gated Na+ (Nav) channels, whose molecular identity is unknown. Using a highly sensitive electron microscopic immunogold technique, we revealed the presence of the Nav1.6 subunit in hippocampal CA1 PC proximal and distal dendrites. Here, the subunit density is lower by a factor of 35 to 80 than that found in axon initial segments. A gradual decrease in Nav1.6 density along the proximodistal axis of the dendritic tree was also detected without any labeling in dendritic spines. Our results reveal the characteristic subcellular distribution of the Nav1.6 subunit, identifying this molecule as a key substrate enabling dendritic excitability.

Toll-like receptor 7/8 agonists stimulate plasmacytoid dendritic cells to initiate TH17-deviated acute contact dermatitis in human subjects.

Science.gov (United States)

Garzorz-Stark, Natalie; Lauffer, Felix; Krause, Linda; Thomas, Jenny; Atenhan, Anne; Franz, Regina; Roenneberg, Sophie; Boehner, Alexander; Jargosch, Manja; Batra, Richa; Mueller, Nikola S; Haak, Stefan; Groß, Christina; Groß, Olaf; Traidl-Hoffmann, Claudia; Theis, Fabian J; Schmidt-Weber, Carsten B; Biedermann, Tilo; Eyerich, Stefanie; Eyerich, Kilian

2018-04-01

A standardized human model to study early pathogenic events in patients with psoriasis is missing. Activation of Toll-like receptor 7/8 by means of topical application of imiquimod is the most commonly used mouse model of psoriasis. We sought to investigate the potential of a human imiquimod patch test model to resemble human psoriasis. Imiquimod (Aldara 5% cream; 3M Pharmaceuticals, St Paul, Minn) was applied twice a week to the backs of volunteers (n = 18), and development of skin lesions was monitored over a period of 4 weeks. Consecutive biopsy specimens were taken for whole-genome expression analysis, histology, and T-cell isolation. Plasmacytoid dendritic cells (pDCs) were isolated from whole blood, stimulated with Toll-like receptor 7 agonist, and analyzed by means of extracellular flux analysis and real-time PCR. We demonstrate that imiquimod induces a monomorphic and self-limited inflammatory response in healthy subjects, as well as patients with psoriasis or eczema. The clinical and histologic phenotype, as well as the transcriptome, of imiquimod-induced inflammation in human skin resembles acute contact dermatitis rather than psoriasis. Nevertheless, the imiquimod model mimics the hallmarks of psoriasis. In contrast to classical contact dermatitis, in which myeloid dendritic cells sense haptens, pDCs are primary sensors of imiquimod. They respond with production of proinflammatory and T H 17-skewing cytokines, resulting in a T H 17 immune response with IL-23 as a key driver. In a proof-of-concept setting systemic treatment with ustekinumab diminished imiquimod-induced inflammation. In human subjects imiquimod induces contact dermatitis with the distinctive feature that pDCs are the primary sensors, leading to an IL-23/T H 17 deviation. Despite these shortcomings, the human imiquimod model might be useful to investigate early pathogenic events and prove molecular concepts in patients with psoriasis. Copyright © 2017 The Authors. Published by Elsevier

Improving the Terrain-Based Parameter for the Assessment of Snow Redistribution in the Col du Lac Blanc Area and Comparisons with TLS Snow Depth Data

Science.gov (United States)

Schön, Peter; Prokop, Alexander; Naaim-Bouvet, Florence; Nishimura, Kouichi; Vionnet, Vincent; Guyomarc'h, Gilbert

2014-05-01

Wind and the associated snow drift are dominating factors determining the snow distribution and accumulation in alpine areas, resulting in a high spatial variability of snow depth that is difficult to evaluate and quantify. The terrain-based parameter Sx characterizes the degree of shelter or exposure of a grid point provided by the upwind terrain, without the computational complexity of numerical wind field models. The parameter has shown to qualitatively predict snow redistribution with good reproduction of spatial patterns, but has failed to quantitatively describe the snow redistribution, and correlations with measured snow heights were poor. The objective of our research was to a) identify the sources of poor correlations between predicted and measured snow re-distribution and b) improve the parameters ability to qualitatively and quantitatively describe snow redistribution in our research area, the Col du Lac Blanc in the French Alps. The area is at an elevation of 2700 m and particularly suited for our study due to its constant wind direction and the availability of data from a meteorological station. Our work focused on areas with terrain edges of approximately 10 m height, and we worked with 1-2 m resolution digital terrain and snow surface data. We first compared the results of the terrain-based parameter calculations to measured snow-depths, obtained by high-accuracy terrestrial laser scan measurements. The results were similar to previous studies: The parameter was able to reproduce observed patterns in snow distribution, but regression analyses showed poor correlations between terrain-based parameter and measured snow-depths. We demonstrate how the correlations between measured and calculated snow heights improve if the parameter is calculated based on a snow surface model instead of a digital terrain model. We show how changing the parameter's search distance and how raster re-sampling and raster smoothing improve the results. To improve the parameter

Gain stabilized microchannel plates and a treatment method for microchannel plates

International Nuclear Information System (INIS)

1979-01-01

Microchannel plates having increased gain and significantly improved aging characteristics are provided by forming a thin film of a cesium compound on the channel walls. In an exemplary embodiment, a suface film of cesium hydroxide is applied to the interior wall surfaces of an MCP by saturating the plate with a solution of the compound, then allowing the solvent to evaporate. The cesium hydroxide residue on the walls subsequently is converted to cesium oxide by a high temperature bake. Microchannel plates are used in image amplifiers, radiation detectors and such like equipment. (Auth.)

Sequence learning in differentially activated dendrites

DEFF Research Database (Denmark)

Nielsen, Bjørn Gilbert

2003-01-01

. It is proposed that the neural machinery required in such a learning/retrieval mechanism could involve the NMDA receptor, in conjunction with the ability of dendrites to maintain differentially activated regions. In particular, it is suggested that such a parcellation of the dendrite allows the neuron......Differentially activated areas of a dendrite permit the existence of zones with distinct rates of synaptic modification, and such areas can be individually accessed using a reference signal which localizes synaptic plasticity and memory trace retrieval to certain subregions of the dendrite...... to participate in multiple sequences, which can be learned without suffering from the 'wash-out' of synaptic efficacy associated with superimposition of training patterns. This is a biologically plausible solution to the stability-plasticity dilemma of learning in neural networks....

Dendritic Actin Cytoskeleton: Structure, Functions, and Regulations

Directory of Open Access Journals (Sweden)

Anja Konietzny

2017-05-01

Full Text Available Actin is a versatile and ubiquitous cytoskeletal protein that plays a major role in both the establishment and the maintenance of neuronal polarity. For a long time, the most prominent roles that were attributed to actin in neurons were the movement of growth cones, polarized cargo sorting at the axon initial segment, and the dynamic plasticity of dendritic spines, since those compartments contain large accumulations of actin filaments (F-actin that can be readily visualized using electron- and fluorescence microscopy. With the development of super-resolution microscopy in the past few years, previously unknown structures of the actin cytoskeleton have been uncovered: a periodic lattice consisting of actin and spectrin seems to pervade not only the whole axon, but also dendrites and even the necks of dendritic spines. Apart from that striking feature, patches of F-actin and deep actin filament bundles have been described along the lengths of neurites. So far, research has been focused on the specific roles of actin in the axon, while it is becoming more and more apparent that in the dendrite, actin is not only confined to dendritic spines, but serves many additional and important functions. In this review, we focus on recent developments regarding the role of actin in dendrite morphology, the regulation of actin dynamics by internal and external factors, and the role of F-actin in dendritic protein trafficking.

Distinct uptake mechanisms but similar intracellular processing of two different toll-like receptor ligand-peptide conjugates in dendritic cells.

Science.gov (United States)

Khan, Selina; Bijker, Martijn S; Weterings, Jimmy J; Tanke, Hans J; Adema, Gosse J; van Hall, Thorbald; Drijfhout, Jan W; Melief, Cornelis J M; Overkleeft, Hermen S; van der Marel, Gijsbert A; Filippov, Dmitri V; van der Burg, Sjoerd H; Ossendorp, Ferry

2007-07-20

Covalent conjugation of Toll-like receptor ligands (TLR-L) to synthetic antigenic peptides strongly improves antigen presentation in vitro and T lymphocyte priming in vivo. These molecularly well defined TLR-L-peptide conjugates, constitute an attractive vaccination modality, sharing the peptide antigen and a defined adjuvant in one single molecule. We have analyzed the intracellular trafficking and processing of two TLR-L conjugates in dendritic cells (DCs). Long synthetic peptides containing an ovalbumin cytotoxic T-cell epitope were chemically conjugated to two different TLR-Ls the TLR2 ligand, Pam(3)CysSK(4) (Pam) or the TLR9 ligand CpG. Rapid and enhanced uptake of both types of TLR-L-conjugated peptide occurred in DCs. Moreover, TLR-L conjugation greatly enhanced antigen presentation, a process that was dependent on endosomal acidification, proteasomal cleavage, and TAP translocation. The uptake of the CpG approximately conjugate was independent of endosomally-expressed TLR9 as reported previously. Unexpectedly, we found that Pam approximately conjugated peptides were likewise internalized independently of the expression of cell surface-expressed TLR2. Further characterization of the uptake mechanisms revealed that TLR2-L employed a different uptake route than TLR9-L. Inhibition of clathrin- or caveolin-dependent endocytosis greatly reduced uptake and antigen presentation of the Pam-conjugate. In contrast, internalization and antigen presentation of CpG approximately conjugates was independent of clathrin-coated pits but partly dependent on caveolae formation. Importantly, in contrast to the TLR-independent uptake of the conjugates, TLR expression and downstream TLR signaling was required for dendritic cell maturation and for priming of naïve CD8(+) T-cells. Together, our data show that targeting to two distinct TLRs requires distinct uptake mechanism but follows similar trafficking and intracellular processing pathways leading to optimal antigen

Pathogenic TH17 inflammation is sustained in the lungs by conventional dendritic cells and Toll-like receptor 4 signaling.

Science.gov (United States)

Shalaby, Karim H; Lyons-Cohen, Miranda R; Whitehead, Gregory S; Thomas, Seddon Y; Prinz, Immo; Nakano, Hideki; Cook, Donald N

2017-11-14

Mechanisms that elicit mucosal T H 17 cell responses have been described, yet how these cells are sustained in chronically inflamed tissues remains unclear. We sought to understand whether maintenance of lung T H 17 inflammation requires environmental agents in addition to antigen and to identify the lung antigen-presenting cell (APC) types that sustain the self-renewal of T H 17 cells. Animals were exposed repeatedly to aspiration of ovalbumin alone or together with environmental adjuvants, including common house dust extract (HDE), to test their role in maintaining lung inflammation. Alternatively, antigen-specific effector/memory T H 17 cells, generated in culture with CD4 + T cells from Il17a fate-mapping mice, were adoptively transferred to assess their persistence in genetically modified animals lacking distinct lung APC subsets or cell-specific Toll-like receptor (TLR) 4 signaling. T H 17 cells were also cocultured with lung APC subsets to determine which of these could revive their expansion and activation. T H 17 cells and the consequent neutrophilic inflammation were poorly sustained by inhaled antigen alone but were augmented by inhalation of antigen together with HDE. This was associated with weight loss and changes in lung physiology consistent with interstitial lung disease. The effect of HDE required TLR4 signaling predominantly in lung hematopoietic cells, including CD11c + cells. CD103 + and CD11b + conventional dendritic cells interacted directly with T H 17 cells in situ and revived the clonal expansion of T H 17 cells both ex vivo and in vivo, whereas lung macrophages and B cells could not. T H 17-dependent inflammation in the lungs can be sustained by persistent TLR4-mediated activation of lung conventional dendritic cells. Published by Elsevier Inc.

Airborne Surveys of Snow Depth over Arctic Sea Ice

Science.gov (United States)

Kwok, R.; Panzer, B.; Leuschen, C.; Pang, S.; Markus, T.; Holt, B.; Gogineni, S.

2011-01-01

During the spring of 2009, an ultrawideband microwave radar was deployed as part of Operation IceBridge to provide the first cross-basin surveys of snow thickness over Arctic sea ice. In this paper, we analyze data from three approx 2000 km transects to examine detection issues, the limitations of the current instrument, and the regional variability of the retrieved snow depth. Snow depth is the vertical distance between the air \\snow and snow-ice interfaces detected in the radar echograms. Under ideal conditions, the per echogram uncertainty in snow depth retrieval is approx 4 - 5 cm. The finite range resolution of the radar (approx 5 cm) and the relative amplitude of backscatter from the two interfaces limit the direct retrieval of snow depths much below approx 8 cm. Well-defined interfaces are observed over only relatively smooth surfaces within the radar footprint of approx 6.5 m. Sampling is thus restricted to undeformed, level ice. In early April, mean snow depths are 28.5 +/- 16.6 cm and 41.0 +/- 22.2 cm over first-year and multiyear sea ice (MYI), respectively. Regionally, snow thickness is thinner and quite uniform over the large expanse of seasonal ice in the Beaufort Sea, and gets progressively thicker toward the MYI cover north of Ellesmere Island, Greenland, and the Fram Strait. Snow depth over MYI is comparable to that reported in the climatology by Warren et al. Ongoing improvements to the radar system and the utility of these snow depth measurements are discussed.

Snowscape Ecology: Linking Snow Properties to Wildlife Movements and Demography

Science.gov (United States)

Prugh, L.; Verbyla, D.; van de Kerk, M.; Mahoney, P.; Sivy, K. J.; Liston, G. E.; Nolin, A. W.

2017-12-01

Snow enshrouds up to one third of the global land mass annually and exerts a major influence on animals that reside in these "snowscapes," (landscapes covered in snow). Dynamic snowscapes may have especially strong effects in arctic and boreal regions where dry snow persists for much of the year. Changes in temperature and hydrology are transforming northern regions, with profound implications for wildlife that are not well understood. We report initial findings from a NASA ABoVE project examining effects of snow properties on Dall sheep (Ovis dalli dalli). We used the MODSCAG snow fraction product to map spring snowline elevations and snow-off dates from 2000-2015 throughout the global range of Dall sheep in Alaska and northwestern Canada. We found a negative effect of spring snow cover on Dall sheep recruitment that increased with latitude. Using meteorological data and a daily freeze/thaw status product derived from passive microwave remote sensing from 1983-2012, we found that sheep survival rates increased in years with higher temperatures, less winter precipitation, fewer spring freeze-thaw events, and more winter freeze-thaw events. To examine the effects of snow depth and density on sheep movements, we used location data from GPS-collared sheep and a snowpack evolution model (SnowModel). We found that sheep selected for shallow, fluffy snow at high elevations, but they selected for denser snow as depth increased. Our field measurements identified a critical snow density threshold of 329 (± 18 SE) kg/m3 to support the weight of Dall sheep. Thus, sheep may require areas of shallow, fluffy snow for foraging, while relying on hard-packed snow for winter travel. These findings highlight the importance of multiple snowscape properties on wildlife movements and demography. The integrated study of snow properties and ecological processes, which we call snowscape ecology, will greatly improve global change forecasting.

De Novo Transcriptome Analysis Shows That SAV-3 Infection Upregulates Pattern Recognition Receptors of the Endosomal Toll-Like and RIG-I-Like Receptor Signaling Pathways in Macrophage/Dendritic Like TO-Cells

Directory of Open Access Journals (Sweden)

Cheng Xu

2016-04-01

Full Text Available A fundamental step in cellular defense mechanisms is the recognition of “danger signals” made of conserved pathogen associated molecular patterns (PAMPs expressed by invading pathogens, by host cell germ line coded pattern recognition receptors (PRRs. In this study, we used RNA-seq and the Kyoto encyclopedia of genes and genomes (KEGG to identify PRRs together with the network pathway of differentially expressed genes (DEGs that recognize salmonid alphavirus subtype 3 (SAV-3 infection in macrophage/dendritic like TO-cells derived from Atlantic salmon (Salmo salar L headkidney leukocytes. Our findings show that recognition of SAV-3 in TO-cells was restricted to endosomal Toll-like receptors (TLRs 3 and 8 together with RIG-I-like receptors (RLRs and not the nucleotide-binding oligomerization domain-like receptors NOD-like receptor (NLRs genes. Among the RLRs, upregulated genes included the retinoic acid inducible gene I (RIG-I, melanoma differentiation association 5 (MDA5 and laboratory of genetics and physiology 2 (LGP2. The study points to possible involvement of the tripartite motif containing 25 (TRIM25 and mitochondrial antiviral signaling protein (MAVS in modulating RIG-I signaling being the first report that links these genes to the RLR pathway in SAV-3 infection in TO-cells. Downstream signaling suggests that both the TLR and RLR pathways use interferon (IFN regulatory factors (IRFs 3 and 7 to produce IFN-a2. The validity of RNA-seq data generated in this study was confirmed by quantitative real time qRT-PCR showing that genes up- or downregulated by RNA-seq were also up- or downregulated by RT-PCR. Overall, this study shows that de novo transcriptome assembly identify key receptors of the TLR and RLR sensors engaged in host pathogen interaction at cellular level. We envisage that data presented here can open a road map for future intervention strategies in SAV infection of salmon.

Snow effects on alpine vegetation in the Qinghai-Tibetan Plateau

Science.gov (United States)

Wang, Kun; Zhang, Li; Qiu, Yubao; Ji, Lei; Tian, Feng; Wang, Cuizhen; Wang, Zhiyong

2013-01-01

Understanding the relationships between snow and vegetation is important for interpretation of the responses of alpine ecosystems to climate changes. The Qinghai-Tibetan Plateau is regarded as an ideal area due to its undisturbed features with low population and relatively high snow cover. We used 500 m Moderate Resolution Imaging Spectroradiometer (MODIS) datasets during 2001–2010 to examine the snow–vegetation relationships, specifically, (1) the influence of snow melting date on vegetation green-up date and (2) the effects of snow cover duration on vegetation greenness. The results showed that the alpine vegetation responded strongly to snow phenology (i.e., snow melting date and snow cover duration) over large areas of the Qinghai-Tibetan Plateau. Snow melting date and vegetation green-up date were significantly correlated (p growth was influenced by different seasonal snow cover durations (SCDs) in different regions. Generally, the December–February and March–May SCDs played a significantly role in vegetation growth, both positively and negatively, depending on different water source regions. Snow's positive impact on vegetation was larger than the negative impact.

Soot in the atmosphere and snow surface of Antarctica

International Nuclear Information System (INIS)

Warren, S.G.; Clarke, A.D.

1990-01-01

Samples of snow collected near the south pole during January and February 1986 were analyzed for the presence of light-absorbing particles by passing the melted snow through a nuclepore filter. Transmission of light through the filter showed that snow far from the station contains the equivalent of 0.1-0.3 ng of carbon per gram of snow (ng/g). Samples of ambient air were filtered and found to contain about 1-2 ng of carbon per kilogram of air, giving a scavenging ratio of about 150. The snow downwind of the station exhibited a well-defined plume of soot due to the burning of diesel fuel, but even in the center of the plume 1 km downwind, the soot concentration was only 3 ng/g, too small to affect snow albedo significantly. Measurements of snow albedo near large inland stations are therefore probably representative of their surrounding regions

Objective Characterization of Snow Microstructure for Microwave Emission Modeling

Science.gov (United States)

Durand, Michael; Kim, Edward J.; Molotch, Noah P.; Margulis, Steven A.; Courville, Zoe; Malzler, Christian

2012-01-01

Passive microwave (PM) measurements are sensitive to the presence and quantity of snow, a fact that has long been used to monitor snowcover from space. In order to estimate total snow water equivalent (SWE) within PM footprints (on the order of approx 100 sq km), it is prerequisite to understand snow microwave emission at the point scale and how microwave radiation integrates spatially; the former is the topic of this paper. Snow microstructure is one of the fundamental controls on the propagation of microwave radiation through snow. Our goal in this study is to evaluate the prospects for driving the Microwave Emission Model of Layered Snowpacks with objective measurements of snow specific surface area to reproduce measured brightness temperatures when forced with objective measurements of snow specific surface area (S). This eliminates the need to treat the grain size as a free-fit parameter.

Analyzing dendritic growth in a population of immature neurons in the adult dentate gyrus using laminar quantification of disjointed dendrites

Directory of Open Access Journals (Sweden)

Shira eRosenzweig

2011-03-01

Full Text Available In the dentate gyrus of the hippocampus, new granule neurons are continuously produced throughout adult life. A prerequisite for the successful synaptic integration of these neurons is the sprouting and extension of dendrites into the molecular layer of the dentate gyrus. Thus, studies aimed at investigating the developmental stages of adult neurogenesis often use dendritic growth as an important indicator of neuronal health and maturity. Based on the known topography of the dentate gyrus, characterized by distinct laminar arrangement of granule neurons and their extensions, we have developed a new method for analysis of dendritic growth in immature adult-born granule neurons. The method is comprised of laminar quantification of cell bodies, primary, secondary and tertiary dendrites separately and independently from each other. In contrast to most existing methods, laminar quantification of dendrites does not require the use of exogenous markers and does not involve arbitrary selection of individual neurons. The new method relies on immonuhistochemical detection of endogenous markers such as doublecortin to perform a comprehensive analysis of a sub-population of immature neurons. Disjointed, orphan dendrites that often appear in the thin histological sections are taken into account. Using several experimental groups of rats and mice, we demonstrate here the suitable techniques for quantifying neurons and dendrites, and explain how the ratios between the quantified values can be used in a comparative analysis to indicate variations in dendritic growth and complexity.

The tiger genome and comparative analysis with lion and snow leopard genomes.

Science.gov (United States)

Cho, Yun Sung; Hu, Li; Hou, Haolong; Lee, Hang; Xu, Jiaohui; Kwon, Soowhan; Oh, Sukhun; Kim, Hak-Min; Jho, Sungwoong; Kim, Sangsoo; Shin, Young-Ah; Kim, Byung Chul; Kim, Hyunmin; Kim, Chang-Uk; Luo, Shu-Jin; Johnson, Warren E; Koepfli, Klaus-Peter; Schmidt-Küntzel, Anne; Turner, Jason A; Marker, Laurie; Harper, Cindy; Miller, Susan M; Jacobs, Wilhelm; Bertola, Laura D; Kim, Tae Hyung; Lee, Sunghoon; Zhou, Qian; Jung, Hyun-Ju; Xu, Xiao; Gadhvi, Priyvrat; Xu, Pengwei; Xiong, Yingqi; Luo, Yadan; Pan, Shengkai; Gou, Caiyun; Chu, Xiuhui; Zhang, Jilin; Liu, Sanyang; He, Jing; Chen, Ying; Yang, Linfeng; Yang, Yulan; He, Jiaju; Liu, Sha; Wang, Junyi; Kim, Chul Hong; Kwak, Hwanjong; Kim, Jong-Soo; Hwang, Seungwoo; Ko, Junsu; Kim, Chang-Bae; Kim, Sangtae; Bayarlkhagva, Damdin; Paek, Woon Kee; Kim, Seong-Jin; O'Brien, Stephen J; Wang, Jun; Bhak, Jong

2013-01-01

Tigers and their close relatives (Panthera) are some of the world's most endangered species. Here we report the de novo assembly of an Amur tiger whole-genome sequence as well as the genomic sequences of a white Bengal tiger, African lion, white African lion and snow leopard. Through comparative genetic analyses of these genomes, we find genetic signatures that may reflect molecular adaptations consistent with the big cats' hypercarnivorous diet and muscle strength. We report a snow leopard-specific genetic determinant in EGLN1 (Met39>Lys39), which is likely to be associated with adaptation to high altitude. We also detect a TYR260G>A mutation likely responsible for the white lion coat colour. Tiger and cat genomes show similar repeat composition and an appreciably conserved synteny. Genomic data from the five big cats provide an invaluable resource for resolving easily identifiable phenotypes evident in very close, but distinct, species.

The tiger genome and comparative analysis with lion and snow leopard genomes

Science.gov (United States)

Cho, Yun Sung; Hu, Li; Hou, Haolong; Lee, Hang; Xu, Jiaohui; Kwon, Soowhan; Oh, Sukhun; Kim, Hak-Min; Jho, Sungwoong; Kim, Sangsoo; Shin, Young-Ah; Kim, Byung Chul; Kim, Hyunmin; Kim, Chang-uk; Luo, Shu-Jin; Johnson, Warren E.; Koepfli, Klaus-Peter; Schmidt-Küntzel, Anne; Turner, Jason A.; Marker, Laurie; Harper, Cindy; Miller, Susan M.; Jacobs, Wilhelm; Bertola, Laura D.; Kim, Tae Hyung; Lee, Sunghoon; Zhou, Qian; Jung, Hyun-Ju; Xu, Xiao; Gadhvi, Priyvrat; Xu, Pengwei; Xiong, Yingqi; Luo, Yadan; Pan, Shengkai; Gou, Caiyun; Chu, Xiuhui; Zhang, Jilin; Liu, Sanyang; He, Jing; Chen, Ying; Yang, Linfeng; Yang, Yulan; He, Jiaju; Liu, Sha; Wang, Junyi; Kim, Chul Hong; Kwak, Hwanjong; Kim, Jong-Soo; Hwang, Seungwoo; Ko, Junsu; Kim, Chang-Bae; Kim, Sangtae; Bayarlkhagva, Damdin; Paek, Woon Kee; Kim, Seong-Jin; O’Brien, Stephen J.; Wang, Jun; Bhak, Jong

2013-01-01

Tigers and their close relatives (Panthera) are some of the world’s most endangered species. Here we report the de novo assembly of an Amur tiger whole-genome sequence as well as the genomic sequences of a white Bengal tiger, African lion, white African lion and snow leopard. Through comparative genetic analyses of these genomes, we find genetic signatures that may reflect molecular adaptations consistent with the big cats’ hypercarnivorous diet and muscle strength. We report a snow leopard-specific genetic determinant in EGLN1 (Met39>Lys39), which is likely to be associated with adaptation to high altitude. We also detect a TYR260G>A mutation likely responsible for the white lion coat colour. Tiger and cat genomes show similar repeat composition and an appreciably conserved synteny. Genomic data from the five big cats provide an invaluable resource for resolving easily identifiable phenotypes evident in very close, but distinct, species. PMID:24045858

Activation of nucleotide-binding domain-like receptor containing protein 3 inflammasome in dendritic cells and macrophages by Streptococcus sanguinis.

Science.gov (United States)

Saeki, Ayumi; Suzuki, Toshihiko; Hasebe, Akira; Kamezaki, Ryousuke; Fujita, Mari; Nakazawa, Futoshi; Shibata, Ken-Ichiro

2017-03-01

Streptococcus sanguinis is frequently isolated from the blood of patients with infective endocarditis and contributes to the pathology of this disease through induction of interleukin (IL)-1β responsible for the development of the disease. However, the mechanism of IL-1β induction remains unknown. In this study, S. sanguinis activated a murine dendritic cell (DC) to induce IL-1β and this activity was attenuated by silencing the mRNAs of nucleotide-binding domain-like receptor containing protein 3 (NLRP3) and caspase-1. S. sanguinis induced IL-1β production in murine bone marrow-derived macrophage, but this activity was significantly reduced in bone marrow-derived macrophages from NLRP3-, apoptosis-associated speck-like protein containing a caspase-recruitment domain-, and caspase-1-deficient mice. DC phagocytosed S. sanguinis cells, followed by the release of adenosine triphosphate (ATP). The ATP-degradating enzyme attenuated the release of ATP and IL-1β. The inhibitors for ATP receptor reduced IL-1β release in DC. These results strongly suggest that S. sanguinis has the activity to induce IL-1β through the NLRP3 inflammasome in macrophage and DC and interaction of purinergic receptors with ATP released is involved in expression of the activity. © 2016 John Wiley & Sons Ltd.

Snow management practices in French ski resorts

Science.gov (United States)

Spandre, Pierre; Francois, Hugues; George-Marcelpoil, Emmanuelle; Morin, Samuel

2016-04-01

Winter tourism plays a fundamental role in the economy of French mountain regions but also in other countries such as Austria, USA or Canada. Ski operators originally developed grooming methods to provide comfortable and safe skiing conditions. The interannual variability of snow conditions and the competition with international destinations and alternative tourism activities encouraged ski resorts to mitigate their dependency to weather conditions through snowmaking facilities. However some regions may not be able to produce machine made snow due to inadequate conditions and low altitude resorts are still negatively impacted by low snow seasons. In the meantime, even though the operations of high altitude resorts do not show any dependency to the snow conditions they invest in snowmaking facilities. Such developments of snowmaking facilities may be related to a confused and contradictory perception of climate change resulting in individualistic evolutions of snowmaking facilities, also depending on ski resorts main features such as their altitude and size. Concurrently with the expansion of snowmaking facilities, a large range of indicators have been used to discuss the vulnerability of ski resorts such as the so-called "100 days rule" which was widely used with specific thresholds (i.e. minimum snow depth, dates) and constraints (i.e. snowmaking capacity). The present study aims to provide a detailed description of snow management practices and major priorities in French ski resorts with respect to their characteristics. We set up a survey in autumn 2014, collecting data from 56 French ski operators. We identify the priorities of ski operators and describe their snowmaking and grooming practices and facilities. The operators also provided their perception of the ski resort vulnerability to snow and economic challenges which we could compare with the actual snow conditions and ski lift tickets sales during the period from 2001 to 2012.

The Complete Reconfiguration of Dendritic Gold

Science.gov (United States)

Paneru, Govind; Flanders, Bret

2014-03-01

Reconfigurability-by-design is an important strategy in modern materials science, as materials with this capability could potentially be used to confer hydrophobic, lipophobic, or anti-corrosive character to substrates in a regenerative manner. The present work extends the directed electrochemical nanowire assembly (DENA) methodology, which is a technique that employs alternating voltages to grow single crystalline metallic nanowires and nano-dendrites from simple salt solutions, to enable the complete dissolution of macroscopic arrays of metallic dendrites following their growth. Our main finding is that structural reconfiguration of dendritic gold is induced by changes in the MHz-level frequencies of voltages that are applied to the dendrites. Cyclic voltammetry and micro-Raman spectroscopy have been used to show that dendritic gold grows and dissolves by the same chemical mechanisms as bulk gold. Hence, the redox chemistry that occurs at the crystal-solution interface is no different than the established electrochemistry of gold. What differs in this process and allows for reconfiguration to occur is the diffusive behavior of the gold chloride molecules in the solution adjacent to the interface. We will present a simple model that captures the physics of this behavior.

Winter survival of Scots pine seedlings under different snow conditions.

Science.gov (United States)

Domisch, Timo; Martz, Françoise; Repo, Tapani; Rautio, Pasi

2018-04-01

Future climate scenarios predict increased air temperatures and precipitation, particularly at high latitudes, and especially so during winter. Soil temperatures, however, are more difficult to predict, since they depend strongly on the fate of the insulating snow cover. 'Rain-on-snow' events and warm spells during winter can lead to thaw-freeze cycles, compacted snow and ice encasement, as well as local flooding. These adverse conditions could counteract the otherwise positive effects of climatic changes on forest seedling growth. In order to study the effects of different winter and snow conditions on young Scots pine (Pinus sylvestris L.) seedlings, we conducted a laboratory experiment in which 80 1-year-old Scots pine seedlings were distributed between four winter treatments in dasotrons: ambient snow cover (SNOW), compressed snow and ice encasement (ICE), flooded and frozen soil (FLOOD) and no snow (NO SNOW). During the winter treatment period and a 1.5-month simulated spring/early summer phase, we monitored the needle, stem and root biomass of the seedlings, and determined their starch and soluble sugar concentrations. In addition, we assessed the stress experienced by the seedlings by measuring chlorophyll fluorescence, electric impedance and photosynthesis of the previous-year needles. Compared with the SNOW treatment, carbohydrate concentrations were lower in the FLOOD and NO SNOW treatments where the seedlings had almost died before the end of the experiment, presumably due to frost desiccation of aboveground parts during the winter treatments. The seedlings of the ICE treatment showed dead needles and stems only above the snow and ice cover. The results emphasize the importance of an insulating and protecting snow cover for small forest tree seedlings, and that future winters with changed snow patterns might affect the survival of tree seedlings and thus forest productivity.

Subpixel Snow Cover Mapping from MODIS Data by Nonparametric Regression Splines

Science.gov (United States)

Akyurek, Z.; Kuter, S.; Weber, G. W.

2016-12-01

Spatial extent of snow cover is often considered as one of the key parameters in climatological, hydrological and ecological modeling due to its energy storage, high reflectance in the visible and NIR regions of the electromagnetic spectrum, significant heat capacity and insulating properties. A significant challenge in snow mapping by remote sensing (RS) is the trade-off between the temporal and spatial resolution of satellite imageries. In order to tackle this issue, machine learning-based subpixel snow mapping methods, like Artificial Neural Networks (ANNs), from low or moderate resolution images have been proposed. Multivariate Adaptive Regression Splines (MARS) is a nonparametric regression tool that can build flexible models for high dimensional and complex nonlinear data. Although MARS is not often employed in RS, it has various successful implementations such as estimation of vertical total electron content in ionosphere, atmospheric correction and classification of satellite images. This study is the first attempt in RS to evaluate the applicability of MARS for subpixel snow cover mapping from MODIS data. Total 16 MODIS-Landsat ETM+ image pairs taken over European Alps between March 2000 and April 2003 were used in the study. MODIS top-of-atmospheric reflectance, NDSI, NDVI and land cover classes were used as predictor variables. Cloud-covered, cloud shadow, water and bad-quality pixels were excluded from further analysis by a spatial mask. MARS models were trained and validated by using reference fractional snow cover (FSC) maps generated from higher spatial resolution Landsat ETM+ binary snow cover maps. A multilayer feed-forward ANN with one hidden layer trained with backpropagation was also developed. The mutual comparison of obtained MARS and ANN models was accomplished on independent test areas. The MARS model performed better than the ANN model with an average RMSE of 0.1288 over the independent test areas; whereas the average RMSE of the ANN model

Velocity distribution in snow avalanches

Science.gov (United States)

Nishimura, K.; Ito, Y.

1997-12-01

In order to investigate the detailed structure of snow avalanches, we have made snow flow experiments at the Miyanomori ski jump in Sapporo and systematic observations in the Shiai-dani, Kurobe Canyon. In the winter of 1995-1996, a new device to measure static pressures was used to estimate velocities in the snow cloud that develops above the flowing layer of avalanches. Measurements during a large avalanche in the Shiai-dani which damaged and destroyed some instruments indicate velocities increased rapidly to more than 50 m/s soon after the front. Velocities decreased gradually in the following 10 s. Velocities of the lower flowing layer were also calculated by differencing measurement of impact pressure. Both recordings in the snow cloud and in the flowing layer changed with a similar trend and suggest a close interaction between the two layers. In addition, the velocity showed a periodic change. Power spectrum analysis of the impact pressure and the static pressure depression showed a strong peak at a frequency between 4 and 6 Hz, which might imply the existence of either ordered structure or a series of surges in the flow.

Why on the snow? Winter emergence strategies of snow-active Chironomidae (Diptera) in Poland.

Science.gov (United States)

Soszyńska-Maj, Agnieszka; Paasivirta, Lauri; Giłka, Wojciech

2016-10-01

A long-term study of adult non-biting midges (Chironomidae) active in winter on the snow in mountain areas and lowlands in Poland yielded 35 species. The lowland and mountain communities differed significantly in their specific composition. The mountain assemblage was found to be more diverse and abundant, with a substantial contribution from the subfamily Diamesinae, whereas Orthocladiinae predominated in the lowlands. Orthocladius wetterensis Brundin was the most characteristic and superdominant species in the winter-active chironomid communities in both areas. Only a few specimens and species of snow-active chironomids were recorded in late autumn and early winter. The abundance of chironomids peaked in late February in the mountain and lowland areas with an additional peak in the mountain areas in early April. However, this second peak of activity consisted mainly of Orthocladiinae, as Diamesinae emerged earliest in the season. Most snow-active species emerged in mid- and late winter, but their seasonal patterns differed between the 2 regions as a result of the different species composition and the duration of snow cover in these regions. Spearman's rank correlation coefficient tests yielded positive results between each season and the number of chironomid individuals recorded in the mountain area. A positive correlation between air temperature, rising to +3.5 °C, and the number of specimens recorded on the snow in the mountain community was statistically significant. The winter emergence and mate-searching strategies of chironomids are discussed in the light of global warming, and a brief compilation of most important published data on the phenomena studied is provided. © 2015 Institute of Zoology, Chinese Academy of Sciences.

The Potential for Snow to Supply Human Water Demand in the Present and Future

Science.gov (United States)

Mankin, Justin S.; Viviroli, Daniel; Singh, Deepti; Hoekstra, Arjen Y.; Diffenbaugh, Noah S.

2015-01-01

Runoff from snowmelt is regarded as a vital water source for people and ecosystems throughout the Northern Hemisphere (NH). Numerous studies point to the threat global warming poses to the timing and magnitude of snow accumulation and melt. But analyses focused on snow supply do not show where changes to snowmelt runoff are likely to present the most pressing adaptation challenges, given sub-annual patterns of human water consumption and water availability from rainfall. We identify the NH basins where present spring and summer snowmelt has the greatest potential to supply the human water demand that would otherwise be unmet by instantaneous rainfall runoff. Using a multi-model ensemble of climate change projections, we find that these basins - which together have a present population of approx. 2 billion people - are exposed to a 67% risk of decreased snow supply this coming century. Further, in the multi-model mean, 68 basins (with a present population of more than 300 million people) transition from having sufficient rainfall runoff to meet all present human water demand to having insufficient rainfall runoff. However, internal climate variability creates irreducible uncertainty in the projected future trends in snow resource potential, with about 90% of snow-sensitive basins showing potential for either increases or decreases over the near-term decades. Our results emphasize the importance of snow for fulfilling human water demand in many NH basins, and highlight the need to account for the full range of internal climate variability in developing robust climate risk management decisions.

Prevent Snow from Blocking your Tailpipe

Centers for Disease Control (CDC) Podcasts

2014-12-11

If it's snowing, make sure your vehicle’s tailpipe is clear of snow before starting the engine to prevent carbon monoxide poisoning.  Created: 12/11/2014 by National Center for Environmental Health (NCEH).   Date Released: 12/11/2014.

Livestock Husbandry and Snow Leopard Conservation

NARCIS (Netherlands)

Mohammad, Ghulam; Mostafawi, Sayed Naqibullah; Dadul, Jigmet; Rosen, Tatjana; Mishra, Charudutt; Bhatnagar, Yash Veer; Trivedi, Pranav; Timbadia, Radhika; Bijoor, Ajay; Murali, Ranjini; Sonam, Karma; Thinley, Tanzin; Namgail, Tsewang; Prins, Herbert H.T.; Nawaz, Muhammad Ali; Ud Din, Jaffar; Buzdar, Hafeez

2016-01-01

Livestock depredation is a key source of snow leopard mortality across much of the species' range. Snow leopards break into livestock corrals, killing many domestic animals and thereby inflicting substantial economic damage. Locals may retaliate by killing the cat and selling its parts.

High resolution micro-XRF maps of iron oxides inside sensory dendrites of putative avian magnetoreceptors

International Nuclear Information System (INIS)

Falkenberg, G; Fleissner, G E; Fleissner, G U E; Schuchardt, K; Kuehbacher, M; Chalmin, E; Janssens, K

2009-01-01

Iron mineral containing sensory dendrites in the inner lining of the upper beak of homing pigeons and various bird species are the first candidate structures for an avian magnetic field receptor. A new concept of magnetoreception is based on detailed ultra-structural optical and electron microscopy analyses in combination with synchrotron radiation microscopic X-ray fluorescence analysis (micro-XRF) and microscopic X-ray absorption near edge structures (micro-XANES). Several behavioral experiments and first mathematical simulations affirm our avian magnetoreceptor model. The iron minerals inside the dendrites are housed in three different subcellular compartments (bullets, platelets, vesicles), which could be clearly resolved and identified by electron microscopy on ultrathin sections. Micro-XRF and micro-XANES data obtained at HASYLAB beamline L added information about the elemental distribution and Fe speciation, but are averaged over the complete dendrite due to limited spatial resolution. Here we present recently performed micro-XRF maps with sub-micrometer resolution (ESRF ID21), which reveal for the first time subcellular structural information from almost bulk-like dendrite sample material. Due to the thickness of 30 μm the microarchitecture of the dendrites can be considered as undisturbed and artefacts introduced by sectioning might be widely reduced.

J-SEx : The Jollie Snow Experiment, New Zealand

Science.gov (United States)

Kerr, T.; Singh, S.; Kees, L.; Webster, C.; Clark, M.; Hendrikx, J.; Woods, R.

2012-04-01

Intensive snow observations have been collected in a steep alpine catchment (the Jollie Valley) in the Southern Alps of New Zealand for four years at the time of maximum snow storage. The campaign, called the Jollie Snow Experiment (J-SEx), was undertaken to improve understanding of snow variability in a steep alpine landscape. Observation methods included manual depth-probing at hundreds of locations with associated snowpit-digging, and surface and air-borne ground penetrating radar. In addition, repeat (daily) oblique photography was carried out on a subcatchment for two of the years. Analysis of the observations, in conjunction with similar observations from around the world has enabled direction to be given for selecting optimal modelling scales, and an indication of what processes need to be resolved at the different scales. For instance, if models are to operate at sub-100 m horizontal scales, they need to resolve drifting, sloughing and avalanching processes. Binary regression tree methods have been applied to identify terrain variables which explain the observed snow mass variability. This has enabled an assessment of total catchment snow storage to be established for each year. This assessment showed that the controlling variables change from year to year, so that no single terrain-based interpolation method may be generally applied. The change in the terrain relationships each year has been taken as an indication that the different frequencies of snowfall-related climate types from one year to the next affects which terrain characteristics have the greatest impact on snow variability. Assessment of terrain effects at the slope scale indicates that slope angle has the potential to be a strong influence on snow variability in that steep slopes do not build up large accumulations, and that low-angled regions below steep areas become areas of large snow build-up. This "slope" effect is clearly evident from the repeat photography, with the last areas to melt

Variability of snow line elevation, snow cover area and depletion in the main Slovak basins in winters 2001–2014

Directory of Open Access Journals (Sweden)

Krajčí Pavel

2016-03-01

Full Text Available Spatial and temporal variability of snow line (SL elevation, snow cover area (SCA and depletion (SCD in winters 2001–2014 is investigated in ten main Slovak river basins (the Western Carpathians. Daily satellite snow cover maps from MODIS Terra (MOD10A1, V005 and Aqua (MYD10A1, V005 with resolution 500 m are used.

Toll-like receptor activation enhances cell-mediated immunity induced by an antibody vaccine targeting human dendritic cells

Directory of Open Access Journals (Sweden)

Berger Marc A

2007-01-01

Full Text Available Abstract Previously, we have successfully targeted the mannose receptor (MR expressed on monocyte-derived dendritic cells (DCs using a fully human MR-specific antibody, B11, as a vehicle to deliver whole protein tumor antigens such as the human chorionic gonadotropin hormone (hCGβ. Since MRs play a role in bridging innate immunity with adaptive immunity we have explored several toll-like receptor (TLR-specific ligands that may synergize with MR targeting and be applicable as adjuvants in the clinic. We demonstrate that antigen-specific helper and cytolytic T cells from both healthy donors and cancer patients were effectively primed with B11-hCGβ-treated autologous DCs when a combination of one or several TLR ligands is used. Specifically, concomitant signaling of DCs via TLR3 with dsRNA (poly I:C and DC TLR 7/8 with Resiquimod (R-848, respectively, elicited efficient antigen presentation-mediated by MR-targeting. We demonstrate that MR and TLRs contribute towards maturation and activation of DCs by a mechanism that may be driven by a combination of adjuvant and antibody vaccines that specifically deliver antigenic targets to DCs.

What controls the isotopic composition of Greenland surface snow?

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H. C. Steen-Larsen

2014-02-01

Full Text Available Water stable isotopes in Greenland ice core data provide key paleoclimatic information, and have been compared with precipitation isotopic composition simulated by isotopically enabled atmospheric models. However, post-depositional processes linked with snow metamorphism remain poorly documented. For this purpose, monitoring of the isotopic composition (δ18O, δD of near-surface water vapor, precipitation and samples of the top (0.5 cm snow surface has been conducted during two summers (2011–2012 at NEEM, NW Greenland. The samples also include a subset of 17O-excess measurements over 4 days, and the measurements span the 2012 Greenland heat wave. Our observations are consistent with calculations assuming isotopic equilibrium between surface snow and water vapor. We observe a strong correlation between near-surface vapor δ18O and air temperature (0.85 ± 0.11‰ °C−1 (R = 0.76 for 2012. The correlation with air temperature is not observed in precipitation data or surface snow data. Deuterium excess (d-excess is strongly anti-correlated with δ18O with a stronger slope for vapor than for precipitation and snow surface data. During nine 1–5-day periods between precipitation events, our data demonstrate parallel changes of δ18O and d-excess in surface snow and near-surface vapor. The changes in δ18O of the vapor are similar or larger than those of the snow δ18O. It is estimated using the CROCUS snow model that 6 to 20% of the surface snow mass is exchanged with the atmosphere. In our data, the sign of surface snow isotopic changes is not related to the sign or magnitude of sublimation or deposition. Comparisons with atmospheric models show that day-to-day variations in near-surface vapor isotopic composition are driven by synoptic variations and changes in air mass trajectories and distillation histories. We suggest that, in between precipitation events, changes in the surface snow isotopic composition are driven by these changes in near

Small scale variability of snow density on Antarctic sea ice

Science.gov (United States)

Wever, N.; Leonard, K. C.; Paul, S.; Jacobi, H. W.; Proksch, M.; Lehning, M.

2016-12-01

Snow on sea ice plays an important role in air-ice-sea interactions. For example, snow may smooth the ice surface when snow drift is occurring, while at the same time it may also generate roughness elements by interactions with the wind. Snow density is a key property in many processes, for example by influencing the thermal conductivity of the snow layer, radiative transfer inside the snow as well as the effects of aerodynamic forcing on the snowpack. We present data from an in-situ measurement campaign in the Weddell Sea during two subsequent cruises of RV Polarstern. By comparing snow density from snow pits and snow micro penetrometer (SMP) measurements, augmented by terrestrial laser scanning (TLS) on an area of 50x50 m2, highly resolved density profiles and surface topology were acquired at a horizontal resolution of approximately 30 cm. Average snow densities are about 280 kg/m3, but the analysis also reveals a high spatial variability in snow density on sea ice in both horizontal and vertical direction, ranging from roughly 170 to 360 kg/m3. This variability is expressed by coherent snow structures over several meters, which disappear over larger distances. A comparison with TLS data indicates that the spatial variability is related to deviations in surface topology. This suggests a strong influence from surface processes, for example wind, on the temporal development of density profiles. The fundamental relationship between density variations, surface roughness and changes therein as investigated in this study are interpreted with respect to larger-scale ice-movement and the ice mass balance.

Analysis of small biomolecules and xenobiotic metabolism using converted graphene-like monolayer plates and laser desorption/ionization time-of-flight mass spectrometry.

Science.gov (United States)

Kang, Hyunook; Yun, Hoyeol; Lee, Sang Wook; Yeo, Woon-Seok

2017-06-01

We report a method of small molecule analysis using a converted graphene-like monolayer (CGM) plate and laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF MS) without organic matrices. The CGM plate was prepared from self-assembled monolayers of biphenyl-4-thiol on gold using electron beam irradiation followed by an annealing step. The above plate was utilized for the LDI-TOF MS analyses of various small molecules and their mixtures, e.g., amino acids, sugars, fatty acids, oligoethylene glycols, and flavonoids. The CGM plate afforded high signal-to-noise ratios, good limits of detection (1pmol to 10fmol), and reusability for up to 30 cycles. As a practical application, the enzymatic activity of the cytochrome P450 2A6 (CYP2A6) enzyme in human liver microsomes was assessed in the 7-hydroxylation of coumarin using the CGM plate without other purification steps. We believe that the prepared CGM plate can be practically used with the advantages of simplicity, sensitivity, and reusability for the matrix-free analysis of small biomolecules. Copyright © 2017 Elsevier B.V. All rights reserved.

Embryonic origins of a motor system: motor dendrites form a myotopic map in Drosophila.

Directory of Open Access Journals (Sweden)

Matthias Landgraf

2003-11-01

Full Text Available The organisational principles of locomotor networks are less well understood than those of many sensory systems, where in-growing axon terminals form a central map of peripheral characteristics. Using the neuromuscular system of the Drosophila embryo as a model and retrograde tracing and genetic methods, we have uncovered principles underlying the organisation of the motor system. We find that dendritic arbors of motor neurons, rather than their cell bodies, are partitioned into domains to form a myotopic map, which represents centrally the distribution of body wall muscles peripherally. While muscles are segmental, the myotopic map is parasegmental in organisation. It forms by an active process of dendritic growth independent of the presence of target muscles, proper differentiation of glial cells, or (in its initial partitioning competitive interactions between adjacent dendritic domains. The arrangement of motor neuron dendrites into a myotopic map represents a first layer of organisation in the motor system. This is likely to be mirrored, at least in part, by endings of higher-order neurons from central pattern-generating circuits, which converge onto the motor neuron dendrites. These findings will greatly simplify the task of understanding how a locomotor system is assembled. Our results suggest that the cues that organise the myotopic map may be laid down early in development as the embryo subdivides into parasegmental units.

Phospholipid Homeostasis Regulates Dendrite Morphogenesis in Drosophila Sensory Neurons

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Shan Meltzer

2017-10-01

Full Text Available Disruptions in lipid homeostasis have been observed in many neurodevelopmental disorders that are associated with dendrite morphogenesis defects. However, the molecular mechanisms of how lipid homeostasis affects dendrite morphogenesis are unclear. We find that easily shocked (eas, which encodes a kinase with a critical role in phospholipid phosphatidylethanolamine (PE synthesis, and two other enzymes in this synthesis pathway are required cell autonomously in sensory neurons for dendrite growth and stability. Furthermore, we show that the level of Sterol Regulatory Element-Binding Protein (SREBP activity is important for dendrite development. SREBP activity increases in eas mutants, and decreasing the level of SREBP and its transcriptional targets in eas mutants largely suppresses the dendrite growth defects. Furthermore, reducing Ca2+ influx in neurons of eas mutants ameliorates the dendrite morphogenesis defects. Our study uncovers a role for EAS kinase and reveals the in vivo function of phospholipid homeostasis in dendrite morphogenesis.

Dendritic ion channelopathy in acquired epilepsy

Science.gov (United States)

Poolos, Nicholas P.; Johnston, Daniel

2012-01-01

Summary Ion channel dysfunction or “channelopathy” is a proven cause of epilepsy in the relatively uncommon genetic epilepsies with Mendelian inheritance. But numerous examples of acquired channelopathy in experimental animal models of epilepsy following brain injury have also been demonstrated. Our understanding of channelopathy has grown due to advances in electrophysiology techniques that have allowed the study of ion channels in the dendrites of pyramidal neurons in cortex and hippocampus. The apical dendrites of pyramidal neurons comprise the vast majority of neuronal surface membrane area, and thus the majority of the neuronal ion channel population. Investigation of dendritic ion channels has demonstrated remarkable plasticity in ion channel localization and biophysical properties in epilepsy, many of which produce hyperexcitability and may contribute to the development and maintenance of the epileptic state. Here we review recent advances in dendritic physiology and cell biology, and their relevance to epilepsy. PMID:23216577

Snow noise disturbance in Antarctic radio communications and development of mobile antenna for snow vehicle in Antarctica

Directory of Open Access Journals (Sweden)

Isao Fukushima

1997-07-01

Full Text Available Radio operators of the Japanese Antarctic Research Expedition (JARE have encountered critical radio noise disturbances caused by blizzards during oversnow travel. This noise appears to be caused by corona discharge at the edges of the vertical whip antenna. This paper describes several examples of snow noise experienced in Antarctica by JARE, the mechanism of generation of the noise, and a method of reducing the intensity of the noise. It also describes a High Effeciency Transmission Line Antenna which is small enough to mount on a snow vehicle and reduces the intensity of the snow noise.

Color Image of Snow White Trenches and Scraping

Science.gov (United States)

2008-01-01

This image was acquired by NASA's Phoenix Mars Lander's Surface Stereo Imager on the 31st Martian day of the mission, or Sol 31 (June 26, 2008), after the May 25, 2008 landing. This image shows the trenches informally called 'Snow White 1' (left), 'Snow White 2' (right), and within the Snow White 2 trench, the smaller scraping area called 'Snow White 3.' The Snow White 3 scraped area is about 5 centimeters (2 inches) deep. The dug and scraped areas are within the diggiing site called 'Wonderland.' The Snow White trenches and scraping prove that scientists can take surface soil samples, subsurface soil samples, and icy samples all from one unit. Scientists want to test samples to determine if some ice in the soil may have been liquid in the past during warmer climate cycles. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is led by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver

Coupling the snow thermodynamic model SNOWPACK with the microwave emission model of layered snowpacks for subarctic and arctic snow water equivalent retrievals

Science.gov (United States)

Langlois, A.; Royer, A.; Derksen, C.; Montpetit, B.; Dupont, F.; GoïTa, K.

2012-12-01

Satellite-passive microwave remote sensing has been extensively used to estimate snow water equivalent (SWE) in northern regions. Although passive microwave sensors operate independent of solar illumination and the lower frequencies are independent of atmospheric conditions, the coarse spatial resolution introduces uncertainties to SWE retrievals due to the surface heterogeneity within individual pixels. In this article, we investigate the coupling of a thermodynamic multilayered snow model with a passive microwave emission model. Results show that the snow model itself provides poor SWE simulations when compared to field measurements from two major field campaigns. Coupling the snow and microwave emission models with successive iterations to correct the influence of snow grain size and density significantly improves SWE simulations. This method was further validated using an additional independent data set, which also showed significant improvement using the two-step iteration method compared to standalone simulations with the snow model.

Snow cover distribution over elevation zones in a mountainous catchment

Science.gov (United States)

Panagoulia, D.; Panagopoulos, Y.

2009-04-01

A good understanding of the elevetional distribution of snow cover is necessary to predict the timing and volume of runoff. In a complex mountainous terrain the snow cover distribution within a watershed is highly variable in time and space and is dependent on elevation, slope, aspect, vegetation type, surface roughness, radiation load, and energy exchange at the snow-air interface. Decreases in snowpack due to climate change could disrupt the downstream urban and agricultural water supplies, while increases could lead to seasonal flooding. Solar and longwave radiation are dominant energy inputs driving the ablation process. Turbulent energy exchange at the snow cover surface is important during the snow season. The evaporation of blowing and drifting snow is strongly dependent upon wind speed. Much of the spatial heterogeneity of snow cover is the result of snow redistribution by wind. Elevation is important in determining temperature and precipitation gradients along hillslopes, while the temperature gradients determine where precipitation falls as rain and snow and contribute to variable melt rates within the hillslope. Under these premises, the snow accumulation and ablation (SAA) model of the US National Weather Service (US NWS) was applied to implement the snow cover extent over elevation zones of a mountainous catchment (the Mesochora catchment in Western-Central Greece), taking also into account the indirectly included processes of sublimation, interception, and snow redistribution. The catchment hydrology is controlled by snowfall and snowmelt and the simulated discharge was computed from the soil moisture accounting (SMA) model of the US NWS and compared to the measured discharge. The elevationally distributed snow cover extent presented different patterns with different time of maximization, extinction and return during the year, producing different timing of discharge that is a crucial factor for the control and management of water resources systems.

COSMO-SkyMed Image Investigation of Snow Features in Alpine Environment

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Simonetta Paloscia

2017-01-01

Full Text Available In this work, X band images acquired by COSMO-SkyMed (CSK on alpine environment have been analyzed for investigating snow characteristics and their effect on backscattering variations. Preliminary results confirmed the capability of simultaneous optical and Synthetic Aperture Radar (SAR images (Landsat-8 and CSK in separating snow/no-snow areas and in detecting wet snow. The sensitivity of backscattering to snow depth has not always been confirmed, depending on snow characteristics related to the season. A model based on Dense Media Radiative Transfer theory (DMRT-QMS was applied for simulating the backscattering response on the X band from snow cover in different conditions of grain size, snow density and depth. By using DMRT-QMS and snow in-situ data collected on Cordevole basin in Italian Alps, the effect of grain size and snow density, beside snow depth and snow water equivalent, was pointed out, showing that the snow features affect the backscatter in different and sometimes opposite ways. Experimental values of backscattering were correctly simulated by using this model and selected intervals of ground parameters. The relationship between simulated and measured backscattering for the entire dataset shows slope >0.9, determination coefficient, R2 = 0.77, and root mean square error, RMSE = 1.1 dB, with p-value <0.05.

Wet Snow Mapping in Southern Ontario with Sentinel-1A Observations

Science.gov (United States)

Chen, H.; Kelly, R. E. J.

2017-12-01

Wet snow is defined as snow with liquid water present in an ice-water mix. It is can be an indicator for the onset of the snowmelt period. Knowledge about the extent of wet snow area can be of great importance for the monitoring of seasonal snowmelt runoff with climate-induced changes in snowmelt duration having implications for operational hydrological and ecological applications. Spaceborne microwave remote sensing has been used to observe seasonal snow under all-weather conditions. Active microwave observations of snow at C-band are sensitive to wet snow due to the high dielectric contrast with non-wet snow surfaces and synthetic aperture radar (SAR) is now openly available to identify and map the wet snow areas globally at relatively fine spatial resolutions ( 100m). In this study, a semi-automated workflow is developed from the change detection method of Nagler et al. (2016) using multi-temporal Sentinel-1A (S1A) dual-polarization observations of Southern Ontario. Weather station data and visible-infrared satellite observations are used to refine the wet snow area estimates. Wet snow information from National Operational Hydrologic Remote Sensing Center (NOHRSC) is used to compare with the S1A estimates. A time series of wet snow maps shows the variations in backscatter from wet snow on a pixel basis. Different land cover types in Southern Ontario are assessed with respect to their impacts on wet snow estimates. While forests and complex land surfaces can impact the ability to map wet snow, the approach taken is robust and illustrates the strong sensitivity of the approach to wet snow backscattering characteristics. The results indicate the feasibility of the change detection method on non-mountainous large areas and address the usefulness of Sentinel-1A data for wet snow mapping.

Snow and ice blocking of tunnels

Energy Technology Data Exchange (ETDEWEB)

Lia, Leif

1998-12-31

Hydroelectric power development in cold regions causes much concern about operational reliability and dam safety. This thesis studies the temperature distribution in tunnels by means of air temperature measurements in six tunnel spillways and five diversion tunnels. The measurements lasted for two consecutive winters. The air through flow tunnel is used as it causes cooling of both rock and water. In open spillway tunnels, frost reaches the entire tunnel. In spillway tunnels with walls, the frost zones reach about 100 m from the downstream end. In mildly-inclined diversion tunnels, a frost free zone is located in the middle of the tunnel and snow and ice problems were only observed in the inlet and outlet. Severe aufeis is accumulation is observed in the frost zones. The heat transfer from rock to air, water and ice is calculated and used in a prediction model for the calculation of aufeis build-up together with local field observation data. The water penetration of snow plugs is also calculated, based on the heat balance. It takes 20 to 50 days for water to enter the blocked tunnel. The empirical values are 30 to 60 days, but only 1 day if the temperature of the snow pack is 0{sup o}C. Sensitivity analyses are carried out for temperature variations in rock, snow, water and ice. Systematic field observation shows that it is important for hydropower companies to know about the effects of snow and ice blocking in an area. A risk analysis of dam safety is presented for a real case. Finally, the thesis proposes solutions which can reduce the snow and ice problems. 79 refs., 63 figs., 11 tabs.

Assessment and placement of living snow fences to reduce highway maintenance costs and improve safety (living snow fences).

Science.gov (United States)

2015-05-01

Living snow fences (LSF) are designed plantings of trees and/or shrubs and native grasses along highways, roads : and ditches that create a vegetative buffer that traps and controls blowing and drifting snow. These strategically : placed fences have ...

Pyroclast/snow interactions and thermally driven slurry formation. Part 2: Experiments and theoretical extension to polydisperse tephra

Science.gov (United States)

Walder, J.S.

2000-01-01

Erosion of snow by pyroclastic flows and surges presumably involves mechanical scour, but there may be thermally driven phenomena involved as well. To investigate this possibility, layers of hot (up to 400??C), uniformly sized, fine- to medium-grained sand were emplaced vertically onto finely shaved ice ('snow'); thus there was no relative shear motion between sand and snow and no purely mechanical scour. In some cases large vapor bubbles, commonly more than 10 mm across, rose through the sand layer, burst at the surface, and caused complete convective overturn of the sand, which then scoured and mixed with snow and transformed into a slurry. In other cases no bubbling occurred and the sand passively melted its way downward into the snow as a wetting front moved upward into the sand. A continuum of behaviors between these two cases was observed. Vigorous bubbling and convection were generally favored by high temperature, small grain size, and small layer thickness. A physically based theory of heat- and mass transfer at the pyroclast/snow interface, developed in Part 1 of this paper, does a good job of explaining the observations as a manifestation of unstable vapor-driven fluidization. The theory, when extrapolated to the behavior of actual, poorly sorted pyroclastic flow sediments, leads to the prediction that the observed 'thermal-scour' phenomenon should also occur for many real pyroclastic flows passing over snow. 'Thermal scour' is therefore likely to be involved in the generation of lahars.

Resilience to Changing Snow Depth in a Shrubland Ecosystem.

Science.gov (United States)

Loik, M. E.

2008-12-01

Snowfall is the dominant hydrologic input for high elevations and latitudes of the arid- and semi-arid western United States. Sierra Nevada snowpack provides numerous important services for California, but is vulnerable to anthropogenic forcing of the coupled ocean-atmosphere system. GCM and RCM scenarios envision reduced snowpack and earlier melt under a warmer climate, but how will these changes affect soil and plant water relations and ecosystem processes? And, how resilient will this ecosystem be to short- and long-term forcing of snow depth and melt timing? To address these questions, our experiments utilize large- scale, long-term roadside snow fences to manipulate snow depth and melt timing in eastern California, USA. Interannual snow depth averages 1344 mm with a CV of 48% (April 1, 1928-2008). Snow fences altered snow melt timing by up to 18 days in high-snowfall years, and affected short-term soil moisture pulses less in low- than medium- or high-snowfall years. Sublimation in this arid location accounted for about 2 mol m- 2 of water loss from the snowpack in 2005. Plant water potential increased after the ENSO winter of 2005 and stayed relatively constant for the following three years, even after the low snowfall of winter 2007. Over the long-term, changes in snow depth and melt timing have impacted cover or biomass of Achnatherum thurberianum, Elymus elemoides, and Purshia tridentata. Growth of adult conifers (Pinus jeffreyi and Pi. contorta) was not equally sensitive to snow depth. Thus, complex interactions between snow depth, soil water inputs, physiological processes, and population patterns help drive the resilience of this ecosystem to changes in snow depth and melt timing.

Evaluating Multispectral Snowpack Reflectivity With Changing Snow Correlation Lengths

Science.gov (United States)

Kang, Do Hyuk; Barros, Ana P.; Kim, Edward J.

2016-01-01

This study investigates the sensitivity of multispectral reflectivity to changing snow correlation lengths. Matzler's ice-lamellae radiative transfer model was implemented and tested to evaluate the reflectivity of snow correlation lengths at multiple frequencies from the ultraviolet (UV) to the microwave bands. The model reveals that, in the UV to infrared (IR) frequency range, the reflectivity and correlation length are inversely related, whereas reflectivity increases with snow correlation length in the microwave frequency range. The model further shows that the reflectivity behavior can be mainly attributed to scattering rather than absorption for shallow snowpacks. The largest scattering coefficients and reflectivity occur at very small correlation lengths (approximately 10(exp -5 m) for frequencies higher than the IR band. In the microwave range, the largest scattering coefficients are found at millimeter wavelengths. For validation purposes, the ice-lamella model is coupled with a multilayer snow physics model to characterize the reflectivity response of realistic snow hydrological processes. The evolution of the coupled model simulated reflectivities in both the visible and the microwave bands is consistent with satellite-based reflectivity observations in the same frequencies. The model results are also compared with colocated in situ snow correlation length measurements (Cold Land Processes Field Experiment 2002-2003). The analysis and evaluation of model results indicate that the coupled multifrequency radiative transfer and snow hydrology modeling system can be used as a forward operator in a data-assimilation framework to predict the status of snow physical properties, including snow correlation length.

The influence of phospho-tau on dendritic spines of cortical pyramidal neurons in patients with Alzheimer’s disease

Science.gov (United States)

Merino-Serrais, Paula; Benavides-Piccione, Ruth; Blazquez-Llorca, Lidia; Kastanauskaite, Asta; Rábano, Alberto; Avila, Jesús

2013-01-01

The dendritic spines on pyramidal cells represent the main postsynaptic elements of cortical excitatory synapses and they are fundamental structures in memory, learning and cognition. In the present study, we used intracellular injections of Lucifer yellow in fixed tissue to analyse over 19 500 dendritic spines that were completely reconstructed in three dimensions along the length of the basal dendrites of pyramidal neurons in the parahippocampal cortex and CA1 of patients with Alzheimer’s disease. Following intracellular injection, sections were immunostained for anti-Lucifer yellow and with tau monoclonal antibodies AT8 and PHF-1, which recognize tau phosphorylated at Ser202/Thr205 and at Ser396/404, respectively. We observed that the diffuse accumulation of phospho-tau in a putative pre-tangle state did not induce changes in the dendrites of pyramidal neurons, whereas the presence of tau aggregates forming intraneuronal neurofibrillary tangles was associated with progressive alteration of dendritic spines (loss of dendritic spines and changes in their morphology) and dendrite atrophy, depending on the degree of tangle development. Thus, the presence of phospho-tau in neurons does not necessarily mean that they suffer severe and irreversible effects as thought previously but rather, the characteristic cognitive impairment in Alzheimer’s disease is likely to depend on the relative number of neurons that have well developed tangles. PMID:23715095

Immune monitoring using mRNA-transfected dendritic cells

DEFF Research Database (Denmark)

Borch, Troels Holz; Svane, Inge Marie; Met, Özcan

2016-01-01

Dendritic cells are known to be the most potent antigen presenting cell in the immune system and are used as cellular adjuvants in therapeutic anticancer vaccines using various tumor-associated antigens or their derivatives. One way of loading antigen into the dendritic cells is by m......RNA electroporation, ensuring presentation of antigen through major histocompatibility complex I and potentially activating T cells, enabling them to kill the tumor cells. Despite extensive research in the field, only one dendritic cell-based vaccine has been approved. There is therefore a great need to elucidate...... and understand the immunological impact of dendritic cell vaccination in order to improve clinical benefit. In this chapter, we describe a method for performing immune monitoring using peripheral blood mononuclear cells and autologous dendritic cells transfected with tumor-associated antigen-encoding mRNA....

βIII Spectrin Is Necessary for Formation of the Constricted Neck of Dendritic Spines and Regulation of Synaptic Activity in Neurons.

Science.gov (United States)

Efimova, Nadia; Korobova, Farida; Stankewich, Michael C; Moberly, Andrew H; Stolz, Donna B; Wang, Junling; Kashina, Anna; Ma, Minghong; Svitkina, Tatyana

2017-07-05

Dendritic spines are postsynaptic structures in neurons often having a mushroom-like shape. Physiological significance and cytoskeletal mechanisms that maintain this shape are poorly understood. The spectrin-based membrane skeleton maintains the biconcave shape of erythrocytes, but whether spectrins also determine the shape of nonerythroid cells is less clear. We show that βIII spectrin in hippocampal and cortical neurons from rodent embryos of both sexes is distributed throughout the somatodendritic compartment but is particularly enriched in the neck and base of dendritic spines and largely absent from spine heads. Electron microscopy revealed that βIII spectrin forms a detergent-resistant cytoskeletal network at these sites. Knockdown of βIII spectrin results in a significant decrease in the density of dendritic spines. Surprisingly, the density of presynaptic terminals is not affected by βIII spectrin knockdown. However, instead of making normal spiny synapses, the presynaptic structures in βIII spectrin-depleted neurons make shaft synapses that exhibit increased amplitudes of miniature EPSCs indicative of excessive postsynaptic excitation. Thus, βIII spectrin is necessary for formation of the constricted shape of the spine neck, which in turn controls communication between the synapse and the parent dendrite to prevent excessive excitation. Notably, mutations of SPTNB2 encoding βIII spectrin are associated with neurodegenerative syndromes, spinocerebellar ataxia Type 5, and spectrin-associated autosomal recessive cerebellar ataxia Type 1, but molecular mechanisms linking βIII spectrin functions to neuronal pathologies remain unresolved. Our data suggest that spinocerebellar ataxia Type 5 and spectrin-associated autosomal recessive cerebellar ataxia Type 1 pathology likely arises from poorly controlled synaptic activity that leads to excitotoxicity and neurodegeneration. SIGNIFICANCE STATEMENT Dendritic spines are small protrusions from neuronal

Secure matching of Dutch car license plates

NARCIS (Netherlands)

Sunil, A.B.; Erkiny, Z.; Veugenyz, T.

2016-01-01

License plate matching plays an important role in applications like law enforcement, traffic management and road pricing, where the plate is first recognized and then compared to a database of authorized vehicle registration plates. Unfortunately, there are several privacy related issues that should

Transient potentials in dendritic systems of arbitrary geometry.

Science.gov (United States)

Butz, E G; Cowan, J D

1974-09-01

A simple graphical calculus is developed that generates analytic solutions for membrane potential transforms at any point on the dendritic tree of neurons with arbitrary dendritic geometries, in response to synaptic "current" inputs. Such solutions permit the computation of transients in neurons with arbitrary geometry and may facilitate analysis of the role of dendrites in such cells.

Human immunodeficiency virus-like particles activate multiple types of immune cells

International Nuclear Information System (INIS)

Sailaja, Gangadhara; Skountzou, Ioanna; Quan, Fu-Shi; Compans, Richard W.; Kang, Sang-Moo

2007-01-01

The rapid spread of human immunodeficiency virus (HIV) worldwide makes it a high priority to develop an effective vaccine. Since live attenuated or inactivated HIV is not likely to be approved as a vaccine due to safety concerns, HIV virus like particles (VLPs) offer an attractive alternative because they are safe due to the lack of a viral genome. Although HIV VLPs have been shown to induce humoral and cellular immune responses, it is important to understand the mechanisms by which they induce such responses and to improve their immunogenicity. We generated HIV VLPs, and VLPs containing Flt3 ligand (FL), a dendritic cell growth factor, to target VLPs to dendritic cells, and investigated the roles of these VLPs in the initiation of adaptive immune responses in vitro and in vivo. We found that HIV-1 VLPs induced maturation of dendritic cells and monocyte/macrophage populations in vitro and in vivo, with enhanced expression of maturation markers and cytokines. Dendritic cells pulsed with VLPs induced activation of splenocytes resulting in increased production of cytokines. VLPs containing FL were found to increase dendritic cells and monocyte/macrophage populations in the spleen when administered to mice. Administration of VLPs induced acute activation of multiple types of cells including T and B cells as indicated by enhanced expression of the early activation marker CD69 and down-regulation of the homing receptor CD62L. VLPs containing FL were an effective form of antigen in activating immune cells via dendritic cells, and immunization with HIV VLPs containing FL resulted in enhanced T helper type 2-like immune responses

The effects of early-life seizures on hippocampal dendrite development and later-life learning and memory.

Science.gov (United States)

Casanova, J R; Nishimura, Masataka; Swann, John W

2014-04-01

Severe childhood epilepsy is commonly associated with intellectual developmental disabilities. The reasons for these cognitive deficits are likely multifactorial and will vary between epilepsy syndromes and even among children with the same syndrome. However, one factor these children have in common is the recurring seizures they experience - sometimes on a daily basis. Supporting the idea that the seizures themselves can contribute to intellectual disabilities are laboratory results demonstrating spatial learning and memory deficits in normal mice and rats that have experienced recurrent seizures in infancy. Studies reviewed here have shown that seizures in vivo and electrographic seizure activity in vitro both suppress the growth of hippocampal pyramidal cell dendrites. A simplification of dendritic arborization and a resulting decrease in the number and/or properties of the excitatory synapses on them could help explain the observed cognitive disabilities. There are a wide variety of candidate mechanisms that could be involved in seizure-induced growth suppression. The challenge is designing experiments that will help focus research on a limited number of potential molecular events. Thus far, results suggest that growth suppression is NMDA receptor-dependent and associated with a decrease in activation of the transcription factor CREB. The latter result is intriguing since CREB is known to play an important role in dendrite growth. Seizure-induced dendrite growth suppression may not occur as a single process in which pyramidal cells dendrites simply stop growing or grow slower compared to normal neurons. Instead, recent results suggest that after only a few hours of synchronized epileptiform activity in vitro dendrites appear to partially retract. This acute response is also NMDA receptor dependent and appears to be mediated by the Ca(+2)/calmodulin-dependent phosphatase, calcineurin. An understanding of the staging of seizure-induced growth suppression and the

Three-dimensional structural image analysis and mechanics of snow

OpenAIRE

Theile, Thiemo

2011-01-01

Summary This work deals with the problem of predicting the mechanical behaviour of dry snow based on the geometries and properties of its constituents. This approach is known as homogenisation. The main constituents of dry snow are ice and air. Their geometry, i.e. the microstructure, varies widely depending on the type of snow. The shape of individual, sintered snow grains varies and may take the form of stellar crystals, rounded and facetted grains or depth hoar crystals. ...

Improving Snow Modeling by Assimilating Observational Data Collected by Citizen Scientists

Science.gov (United States)

Crumley, R. L.; Hill, D. F.; Arendt, A. A.; Wikstrom Jones, K.; Wolken, G. J.; Setiawan, L.

2017-12-01

Modeling seasonal snow pack in alpine environments includes a multiplicity of challenges caused by a lack of spatially extensive and temporally continuous observational datasets. This is partially due to the difficulty of collecting measurements in harsh, remote environments where extreme gradients in topography exist, accompanied by large model domains and inclement weather. Engaging snow enthusiasts, snow professionals, and community members to participate in the process of data collection may address some of these challenges. In this study, we use SnowModel to estimate seasonal snow water equivalence (SWE) in the Thompson Pass region of Alaska while incorporating snow depth measurements collected by citizen scientists. We develop a modeling approach to assimilate hundreds of snow depth measurements from participants in the Community Snow Observations (CSO) project (www.communitysnowobs.org). The CSO project includes a mobile application where participants record and submit geo-located snow depth measurements while working and recreating in the study area. These snow depth measurements are randomly located within the model grid at irregular time intervals over the span of four months in the 2017 water year. This snow depth observation dataset is converted into a SWE dataset by employing an empirically-based, bulk density and SWE estimation method. We then assimilate this data using SnowAssim, a sub-model within SnowModel, to constrain the SWE output by the observed data. Multiple model runs are designed to represent an array of output scenarios during the assimilation process. An effort to present model output uncertainties is included, as well as quantification of the pre- and post-assimilation divergence in modeled SWE. Early results reveal pre-assimilation SWE estimations are consistently greater than the post-assimilation estimations, and the magnitude of divergence increases throughout the snow pack evolution period. This research has implications beyond the

Inorganic carbon addition stimulates snow algae primary productivity

Science.gov (United States)

Hamilton, T. L.; Havig, J. R.

2017-12-01

Earth has experienced glacial/interglacial oscillations throughout its history. Today over 15 million square kilometers (5.8 million square miles) of Earth's land surface is covered in ice including glaciers, ice caps, and the ice sheets of Greenland and Antarctica, most of which are retreating as a consequence of increased atmospheric CO2. Glaciers are teeming with life and supraglacial snow and ice surfaces are often red due to blooms of photoautotrophic algae. Recent evidence suggests the red pigmentation, secondary carotenoids produced in part to thrive under high irradiation, lowers albedo and accelerates melt. However, there are relatively few studies that report the productivity of snow algae communities and the parameters that constrain their growth on snow and ice surfaces. Here, we demonstrate that snow algae primary productivity can be stimulated by the addition of inorganic carbon. We found an increase in light-dependent carbon assimilation in snow algae microcosms amended with increasing amounts of inorganic carbon. Our snow algae communities were dominated by typical cosmopolitan snow algae species recovered from Alpine and Arctic environments. The climate feedbacks necessary to enter and exit glacial/interglacial oscillations are poorly understood. Evidence and models agree that global Snowball events are accompanied by changes in atmospheric CO2 with increasing CO2 necessary for entering periods of interglacial time. Our results demonstrate a positive feedback between increased CO2 and snow algal productivity and presumably growth. With the recent call for bio-albedo effects to be considered in climate models, our results underscore the need for robust climate models to include feedbacks between supraglacial primary productivity, albedo, and atmospheric CO2.

Modification of dendritic development.

Science.gov (United States)

Feria-Velasco, Alfredo; del Angel, Alma Rosa; Gonzalez-Burgos, Ignacio

2002-01-01

Since 1890 Ramón y Cajal strongly defended the theory that dendrites and their processes and spines had a function of not just nutrient transport to the cell body, but they had an important conductive role in neural impulse transmission. He extensively discussed and supported this theory in the Volume 1 of his extraordinary book Textura del Sistema Nervioso del Hombre y de los Vertebrados. Also, Don Santiago significantly contributed to a detailed description of the various neural components of the hippocampus and cerebral cortex during development. Extensive investigation has been done in the last Century related to the functional role of these complex brain regions, and their association with learning, memory and some limbic functions. Likewise, the organization and expression of neuropsychological qualities such as memory, exploratory behavior and spatial orientation, among others, depend on the integrity and adequate functional activity of the cerebral cortex and hippocampus. It is known that brain serotonin synthesis and release depend directly and proportionally on the availability of its precursor, tryptophan (TRY). By using a chronic TRY restriction model in rats, we studied their place learning ability in correlation with the dendritic spine density of pyramidal neurons in field CA1 of the hippocampus during postnatal development. We have also reported alterations in the maturation pattern of the ability for spontaneous alternation and task performance evaluating short-term memory, as well as adverse effects on the density of dendritic spines of hippocampal CA1 field pyramidal neurons and on the dendritic arborization and the number of dendritic spines of pyramidal neurons from the third layer of the prefrontal cortex using the same model of TRY restriction. The findings obtained in these studies employing a modified Golgi method, can be interpreted as a trans-synaptic plastic response due to understimulation of serotoninergic receptors located in the

Small scale variability of snow properties on Antarctic sea ice

Science.gov (United States)

Wever, Nander; Leonard, Katherine; Paul, Stephan; Jacobi, Hans-Werner; Proksch, Martin; Lehning, Michael

2016-04-01

Snow on sea ice plays an important role in air-ice-sea interactions, as snow accumulation may for example increase the albedo. Snow is also able to smooth the ice surface, thereby reducing the surface roughness, while at the same time it may generate new roughness elements by interactions with the wind. Snow density is a key property in many processes, for example by influencing the thermal conductivity of the snow layer, radiative transfer inside the snow as well as the effects of aerodynamic forcing on the snowpack. By comparing snow density and grain size from snow pits and snow micro penetrometer (SMP) measurements, highly resolved density and grain size profiles were acquired during two subsequent cruises of the RV Polarstern in the Weddell Sea, Antarctica, between June and October 2013. During the first cruise, SMP measurements were done along two approximately 40 m transects with a horizontal resolution of approximately 30 cm. During the second cruise, one transect was made with approximately 7.5 m resolution over a distance of 500 m. Average snow densities are about 300 kg/m3, but the analysis also reveals a high spatial variability in snow density on sea ice in both horizontal and vertical direction, ranging from roughly 180 to 360 kg/m3. This variability is expressed by coherent snow structures over several meters. On the first cruise, the measurements were accompanied by terrestrial laser scanning (TLS) on an area of 50x50 m2. The comparison with the TLS data indicates that the spatial variability is exhibiting similar spatial patterns as deviations in surface topology. This suggests a strong influence from surface processes, for example wind, on the temporal development of density or grain size profiles. The fundamental relationship between variations in snow properties, surface roughness and changes therein as investigated in this study is interpreted with respect to large-scale ice movement and the mass balance.

High Resolution Insights into Snow Distribution Provided by Drone Photogrammetry

Science.gov (United States)

Redpath, T.; Sirguey, P. J.; Cullen, N. J.; Fitzsimons, S.

2017-12-01

Dynamic in time and space, New Zealand's seasonal snow is largely confined to remote alpine areas, complicating ongoing in situ measurement and characterisation. Improved understanding and modeling of the seasonal snowpack requires fine scale resolution of snow distribution and spatial variability. The potential of remotely piloted aircraft system (RPAS) photogrammetry to resolve spatial and temporal variability of snow depth and water equivalent in a New Zealand alpine catchment is assessed in the Pisa Range, Central Otago. This approach yielded orthophotomosaics and digital surface models (DSM) at 0.05 and 0.15 m spatial resolution, respectively. An autumn reference DSM allowed mapping of winter (02/08/2016) and spring (10/09/2016) snow depth at 0.15 m spatial resolution, via DSM differencing. The consistency and accuracy of the RPAS-derived surface was assessed by comparison of snow-free regions of the spring and autumn DSMs, while accuracy of RPAS retrieved snow depth was assessed with 86 in situ snow probe measurements. Results show a mean vertical residual of 0.024 m between DSMs acquired in autumn and spring. This residual approximated a Laplace distribution, reflecting the influence of large outliers on the small overall bias. Propagation of errors associated with successive DSMs saw snow depth mapped with an accuracy of ± 0.09 m (95% c.l.). Comparing RPAS and in situ snow depth measurements revealed the influence of geo-location uncertainty and interactions between vegetation and the snowpack on snow depth uncertainty and bias. Semi-variogram analysis revealed that the RPAS outperformed systematic in situ measurements in resolving fine scale spatial variability. Despite limitations accompanying RPAS photogrammetry, this study demonstrates a repeatable means of accurately mapping snow depth for an entire, yet relatively small, hydrological basin ( 0.5 km2), at high resolution. Resolving snowpack features associated with re-distribution and preferential

The impact of the snow cover on sea-ice thickness products retrieved by Ku-band radar altimeters

Science.gov (United States)

Ricker, R.; Hendricks, S.; Helm, V.; Perovich, D. K.

2015-12-01

Snow on sea ice is a relevant polar climate parameter related to ocean-atmospheric interactions and surface albedo. It also remains an important factor for sea-ice thickness products retrieved from Ku-band satellite radar altimeters like Envisat or CryoSat-2, which is currently on its mission and the subject of many recent studies. Such satellites sense the height of the sea-ice surface above the sea level, which is called sea-ice freeboard. By assuming hydrostatic equilibrium and that the main scattering horizon is given by the snow-ice interface, the freeboard can be transformed into sea-ice thickness. Therefore, information about the snow load on hemispherical scale is crucial. Due to the lack of sufficient satellite products, only climatological values are used in current studies. Since such values do not represent the high variability of snow distribution in the Arctic, they can be a substantial contributor to the total sea-ice thickness uncertainty budget. Secondly, recent studies suggest that the snow layer cannot be considered as homogenous, but possibly rather featuring a complex stratigraphy due to wind compaction and/or ice lenses. Therefore, the Ku-band radar signal can be scattered at internal layers, causing a shift of the main scattering horizon towards the snow surface. This alters the freeboard and thickness retrieval as the assumption that the main scattering horizon is given by the snow-ice interface is no longer valid and introduces a bias. Here, we present estimates for the impact of snow depth uncertainties and snow properties on CryoSat-2 sea-ice thickness retrievals. We therefore compare CryoSat-2 freeboard measurements with field data from ice mass-balance buoys and aircraft campaigns from the CryoSat Validation Experiment. This unique validation dataset includes airborne laser scanner and radar altimeter measurements in spring coincident to CryoSat-2 overflights, and allows us to evaluate how the main scattering horizon is altered by the

UAS applications in high alpine, snow-covered terrain

Science.gov (United States)

Bühler, Y.; Stoffel, A.; Ginzler, C.

2017-12-01

Access to snow-covered, alpine terrain is often difficult and dangerous. Hence parameters such as snow depth or snow avalanche release and deposition zones are hard to map in situ with adequate spatial and temporal resolution and with spatial continuous coverage. These parameters are currently operationally measured at automated weather stations and by observer networks. However such isolated point measurements are not able to capture the information spatial continuous and to describe the high spatial variability present in complex mountain topography. Unmanned Aerial Systems (UAS) have the potential to fill this gap by frequently covering selected high alpine areas with high spatial resolution down to ground resolutions of even few millimeters. At the WSL Institute for Snow and Avalanche Research SLF we test different photogrammetric UAS with visual and near infrared bands. During the last three years we were able to gather experience in more than 100 flight missions in extreme terrain. By processing the imagery applying state-of-the-art structure from motion (SfM) software, we were able to accurately document several avalanche events and to photogrammetrically map snow depth with accuracies from 1 to 20 cm (dependent on the flight height above ground) compare to manual snow probe measurements. This was even possible on homogenous snow surfaces with very little texture. A key issue in alpine terrain is flight planning. We need to cover regions at high elevations with large altitude differences (up to 1 km) with high wind speeds (up to 20 m/s) and cold temperatures (down to - 25°C). Only a few UAS are able to cope with these environmental conditions. We will give an overview on our applications of UAS in high alpine terrain that demonstrate the big potential of such systems to acquire frequent, accurate and high spatial resolution geodata in high alpine, snow covered terrain that could be essential to answer longstanding questions in avalanche and snow hydrology

Learn Mac OS X Snow Leopard

CERN Document Server

Meyers, Scott

2009-01-01

You're smart and savvy, but also busy. This comprehensive guide to Apple's Mac OS X 10.6, Snow Leopard, gives you everything you need to know to live a happy, productive Mac life. Learn Mac OS X Snow Leopard will have you up and connected lickity split. With a minimum of overhead and a maximum of useful information, you'll cover a lot of ground in the time it takes other books to get you plugged in. If this isn't your first experience with Mac OS X, skip right to the "What's New in Snow Leopard" sections. You may also find yourself using this book as a quick refresher course or a way

The role of dendritic non-linearities in single neuron computation

Directory of Open Access Journals (Sweden)

Boris Gutkin

2014-05-01

Full Text Available Experiment has demonstrated that summation of excitatory post-synaptic protientials (EPSPs in dendrites is non-linear. The sum of multiple EPSPs can be larger than their arithmetic sum, a superlinear summation due to the opening of voltage-gated channels and similar to somatic spiking. The so-called dendritic spike. The sum of multiple of EPSPs can also be smaller than their arithmetic sum, because the synaptic current necessarily saturates at some point. While these observations are well-explained by biophysical models the impact of dendritic spikes on computation remains a matter of debate. One reason is that dendritic spikes may fail to make the neuron spike; similarly, dendritic saturations are sometime presented as a glitch which should be corrected by dendritic spikes. We will provide solid arguments against this claim and show that dendritic saturations as well as dendritic spikes enhance single neuron computation, even when they cannot directly make the neuron fire. To explore the computational impact of dendritic spikes and saturations, we are using a binary neuron model in conjunction with Boolean algebra. We demonstrate using these tools that a single dendritic non-linearity, either spiking or saturating, combined with somatic non-linearity, enables a neuron to compute linearly non-separable Boolean functions (lnBfs. These functions are impossible to compute when summation is linear and the exclusive OR is a famous example of lnBfs. Importantly, the implementation of these functions does not require the dendritic non-linearity to make the neuron spike. Next, We show that reduced and realistic biophysical models of the neuron are capable of computing lnBfs. Within these models and contrary to the binary model, the dendritic and somatic non-linearity are tightly coupled. Yet we show that these neuron models are capable of linearly non-separable computations.

Is Eurasian October snow cover extent increasing?

International Nuclear Information System (INIS)

Brown, R D; Derksen, C

2013-01-01

A number of recent studies present evidence of an increasing trend in Eurasian snow cover extent (SCE) in the October snow onset period based on analysis of the National Oceanic and Atmospheric Administration (NOAA) historical satellite record. These increases are inconsistent with fall season surface temperature warming trends across the region. Using four independent snow cover data sources (surface observations, two reanalyses, satellite passive microwave retrievals) we show that the increasing SCE is attributable to an internal trend in the NOAA CDR dataset to chart relatively more October snow cover extent over the dataset overlap period (1982–2005). Adjusting the series for this shift results in closer agreement with other independent datasets, stronger correlation with continentally-averaged air temperature anomalies, and a decrease in SCE over 1982–2011 consistent with surface air temperature warming trends over the same period. (letter)

Dendritic slow dynamics enables localized cortical activity to switch between mobile and immobile modes with noisy background input.

Directory of Open Access Journals (Sweden)

Hiroki Kurashige

Full Text Available Mounting lines of evidence suggest the significant computational ability of a single neuron empowered by active dendritic dynamics. This motivates us to study what functionality can be acquired by a network of such neurons. The present paper studies how such rich single-neuron dendritic dynamics affects the network dynamics, a question which has scarcely been specifically studied to date. We simulate neurons with active dendrites networked locally like cortical pyramidal neurons, and find that naturally arising localized activity--called a bump--can be in two distinct modes, mobile or immobile. The mode can be switched back and forth by transient input to the cortical network. Interestingly, this functionality arises only if each neuron is equipped with the observed slow dendritic dynamics and with in vivo-like noisy background input. If the bump activity is considered to indicate a point of attention in the sensory areas or to indicate a representation of memory in the storage areas of the cortex, this would imply that the flexible mode switching would be of great potential use for the brain as an information processing device. We derive these conclusions using a natural extension of the conventional field model, which is defined by combining two distinct fields, one representing the somatic population and the other representing the dendritic population. With this tool, we analyze the spatial distribution of the degree of after-spike adaptation and explain how we can understand the presence of the two distinct modes and switching between the modes. We also discuss the possible functional impact of this mode-switching ability.

Morphological Characterization of the Action Potential Initiation Segment in GnRH Neuron Dendrites and Axons of Male Mice.

Science.gov (United States)

Herde, Michel K; Herbison, Allan E

2015-11-01

GnRH neurons are the final output neurons of the hypothalamic network controlling fertility in mammals. In the present study, we used ankyrin G immunohistochemistry and neurobiotin filling of live GnRH neurons in brain slices from GnRH-green fluorescent protein transgenic male mice to examine in detail the location of action potential initiation in GnRH neurons with somata residing at different locations in the basal forebrain. We found that the vast majority of GnRH neurons are bipolar in morphology, elaborating a thick (primary) and thinner (secondary) dendrite from opposite poles of the soma. In addition, an axon-like process arising predominantly from a proximal dendrite was observed in a subpopulation of GnRH neurons. Ankyrin G immunohistochemistry revealed the presence of a single action potential initiation zone ∼27 μm in length primarily in the secondary dendrite of GnRH neurons and located 30 to 140 μm distant from the cell soma, depending on the type of process and location of the cell body. In addition to dendrites, the GnRH neurons with cell bodies located close to hypothalamic circumventricular organs often elaborated ankyrin G-positive axon-like structures. Almost all GnRH neurons (>90%) had their action potential initiation site in a process that initially, or ultimately after a hairpin loop, was coursing in the direction of the median eminence. These studies indicate that action potentials are initiated in different dendritic and axonal compartments of the GnRH neuron in a manner that is dependent partly on the neuroanatomical location of the cell body.

Snow Cover Monitoring Using MODIS Data in Liaoning Province, Northeastern China

Directory of Open Access Journals (Sweden)

Yu Lu

2010-03-01

Full Text Available This paper presents the results of snow cover monitoring studies in Liaoning Province, northeastern China, using MODIS data. Snow cover plays an important role in both the regional water balance and soil moisture properties during the early spring in northeastern China. In addition, heavy snowfalls commonly trigger hazards such as flooding, caused by rapid snow melt, or crop failure, resulting from fluctuations in soil temperature associated with changes in the snow cover. The latter is a function of both regional, or global, climatic changes, as well as fluctuations in the albedo resulting from variations in the Snow Covered Area (SCA. These impacts are crucial to human activities, especially to those living in middle-latitude areas such as Liaoning Province. Thus, SCA monitoring is currently an important tool in studies of global climate change, particularly because satellite remote sensing data provide timely and efficient snow cover information for large areas. In this study, MODIS L1B data, MODIS Daily Snow Products (MOD10A1 and MODIS 8-day Snow Products (MOD10A2 were used to monitor the SCA of Liaoning Province over the winter months of November–April, 2006–2008. The effects of cloud masking and forest masking on the snow monitoring results were also assessed. The results show that the SCA percentage derived from MODIS L1B data is relatively consistent, but slightly higher than that obtained from MODIS Snow Products. In situ data from 25 snow stations were used to assess the accuracy of snow cover monitoring from the SCA compared to the results from MODIS Snow Products. The studies found that the SCA results were more reliable than MODIS Snow Products in the study area.

Dendritic thickness: a morphometric parameter to classify mouse retinal ganglion cells

Directory of Open Access Journals (Sweden)

L.D. Loopuijt

2007-10-01

Full Text Available To study the dendritic morphology of retinal ganglion cells in wild-type mice we intracellularly injected these cells with Lucifer yellow in an in vitro preparation of the retina. Subsequently, quantified values of dendritic thickness, number of branching points and level of stratification of 73 Lucifer yellow-filled ganglion cells were analyzed by statistical methods, resulting in a classification into 9 groups. The variables dendritic thickness, number of branching points per cell and level of stratification were independent of each other. Number of branching points and level of stratification were independent of eccentricity, whereas dendritic thickness was positively dependent (r = 0.37 on it. The frequency distribution of dendritic thickness tended to be multimodal, indicating the presence of at least two cell populations composed of neurons with dendritic diameters either smaller or larger than 1.8 µm ("thin" or "thick" dendrites, respectively. Three cells (4.5% were bistratified, having thick dendrites, and the others (95.5% were monostratified. Using k-means cluster analysis, monostratified cells with either thin or thick dendrites were further subdivided according to level of stratification and number of branching points: cells with thin dendrites were divided into 2 groups with outer stratification (0-40% and 2 groups with inner (50-100% stratification, whereas cells with thick dendrites were divided into one group with outer and 3 groups with inner stratification. We postulate, that one group of cells with thin dendrites resembles cat ß-cells, whereas one group of cells with thick dendrites includes cells that resemble cat a-cells.

Major ions in spitsbergen snow samples

International Nuclear Information System (INIS)

Semb, A.; Braekkan, R.; Joranger, E.

1984-01-01

Chemical analysis of Spitsbergen snow cores sampled in spring 1983, reveals a spatial pattern consistent with orographic deposition of major anthropogenic pollutants with air movements from southeast towards northwest. The highest concentrations of pollutant species were found at an altitude of 700 metres above sea level, and are higher than for any other recorded snow samples from the Arctic

Assessment of the economic risk for the ski resorts of changes in snow cover duration

Directory of Open Access Journals (Sweden)

S. A. Sokratov

2014-01-01

Full Text Available Winter tourism that is intensively developed in the Russian Federation in recent years strongly depends on the snow availability and properties in the region. Climate changes exert significant influence on the functioning of mountain ski resorts, especially if they are located in areas with relatively high air temperatures in winter season. At the present time, a snowy cluster of mountain ski resorts is intensively progressing in vicinity of Krasnaya Polyana. This region in the West Caucasus (Russia is characterized by relatively warm climate conditions. The snow cover thickness (of 1% insurance in area of the Aibga mountain range may reach 8.1 m. But the snow cover thickness is not the only characteristic of the mountain skiing attractiveness. According to the Swiss standards a mountain ski resort can be considered reliable if during seven seasons of ten ones the snow cover with minimal thickness of 30–50 cm exists for a time not shorter than 100 days during a period from 1st December till 15th April.According to the forecast, during future decades the calculated amount of solid precipitation should reduce by 25–30% in mountain regions on the south macro-slope of the Great Caucasus. As the calculations show, by 2041–2050 the maximal decade thickness of snow cover will decrease by 29–35% while a number of days with snow – by 35–40%. If this is the case, artificial snow will be needed in addition to the natural one. But, under warm climate conditions using of plants for artificial snow production will require a certain perfecting of the nowadays technologies, and very likely, with use of chemicals. That is why a shadowing of existing mountain ski routes by means of the tree planting along them could be ecologically more promising. As for the mountain ski resorts of the West Caucasus, we should mention a possible weakening of the avalanche activity as a potential positive effect of the climate warming predicted by models.

Dendritic cells and skin sensitization: Biological roles and uses in hazard identification

International Nuclear Information System (INIS)

Ryan, Cindy A.; Kimber, Ian; Basketter, David A.; Pallardy, Marc; Gildea, Lucy A.; Gerberick, G. Frank

2007-01-01

Recent advances have been made in our understanding of the roles played by cutaneous dendritic cells (DCs) in the induction of contact allergy. A number of associated changes in epidermal Langerhans cell phenotype and function required for effective skin sensitization are providing the foundations for the development of cellular assays (using DC and DC-like cells) for skin sensitization hazard identification. These alternative approaches to the identification and characterization of skin sensitizing chemicals were the focus of a Workshop entitled 'Dendritic Cells and Skin Sensitization: Biological Roles and Uses in Hazard Identification' that was given at the annual Society of Toxicology meeting held March 6-9, 2006 in San Diego, California. This paper reports information that was presented during the Workshop

Water, ice and mud: Lahars and lahar hazards at ice- and snow-clad volcanoes

Science.gov (United States)

Waythomas, Christopher F.

2014-01-01

Large-volume lahars are significant hazards at ice and snow covered volcanoes. Hot eruptive products produced during explosive eruptions can generate a substantial volume of melt water that quickly evolves into highly mobile flows of ice, sediment and water. At present it is difficult to predict the size of lahars that can form at ice and snow covered volcanoes due to their complex flow character and behaviour. However, advances in experiments and numerical approaches are producing new conceptual models and new methods for hazard assessment. Eruption triggered lahars that are ice-dominated leave behind thin, almost unrecognizable sedimentary deposits, making them likely to be under-represented in the geological record.

Dendritic cells recognize tumor-specific glycosylation of carcinoembryonic antigen on colorectal cancer cells through dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin

NARCIS (Netherlands)

van Gisbergen, Klaas P. J. M.; Aarnoudse, Corlien A.; Meijer, Gerrit A.; Geijtenbeek, Teunis B. H.; van Kooyk, Yvette

2005-01-01

Dendritic cells play a pivotal role in the induction of antitumor immune responses. Immature dendritic cells are located intratumorally within colorectal cancer and intimately interact with tumor cells, whereas mature dendritic cells are present peripheral to the tumor. The majority of colorectal

RAB-10-Dependent Membrane Transport Is Required for Dendrite Arborization

Science.gov (United States)

Zou, Wei; Yadav, Smita; DeVault, Laura; Jan, Yuh Nung; Sherwood, David R.

2015-01-01

Formation of elaborately branched dendrites is necessary for the proper input and connectivity of many sensory neurons. Previous studies have revealed that dendritic growth relies heavily on ER-to-Golgi transport, Golgi outposts and endocytic recycling. How new membrane and associated cargo is delivered from the secretory and endosomal compartments to sites of active dendritic growth, however, remains unknown. Using a candidate-based genetic screen in C. elegans, we have identified the small GTPase RAB-10 as a key regulator of membrane trafficking during dendrite morphogenesis. Loss of rab-10 severely reduced proximal dendritic arborization in the multi-dendritic PVD neuron. RAB-10 acts cell-autonomously in the PVD neuron and localizes to the Golgi and early endosomes. Loss of function mutations of the exocyst complex components exoc-8 and sec-8, which regulate tethering, docking and fusion of transport vesicles at the plasma membrane, also caused proximal dendritic arborization defects and led to the accumulation of intracellular RAB-10 vesicles. In rab-10 and exoc-8 mutants, the trans-membrane proteins DMA-1 and HPO-30, which promote PVD dendrite stabilization and branching, no longer localized strongly to the proximal dendritic membranes and instead were sequestered within intracellular vesicles. Together these results suggest a crucial role for the Rab10 GTPase and the exocyst complex in controlling membrane transport from the secretory and/or endosomal compartments that is required for dendritic growth. PMID:26394140

Light-absorbing Particles in Snow and Ice: Measurement and Modeling of Climatic and Hydrological Impact

Energy Technology Data Exchange (ETDEWEB)

Qian, Yun; Yasunari, Teppei J.; Doherty, Sarah J.; Flanner, M. G.; Lau, William K.; Ming, J.; Wang, Hailong; Wang, Mo; Warren, Stephen G.; Zhang, Rudong

2015-01-01

Light absorbing particles (LAP, e.g., black carbon, brown carbon, and dust) influence water and energy budgets of the atmosphere and snowpack in multiple ways. In addition to their effects associated with atmospheric heating by absorption of solar radiation and interactions with clouds, LAP in snow on land and ice can reduce the surface reflectance (a.k.a., surface darkening), which is likely to accelerate the snow aging process and further reduces snow albedo and increases the speed of snowpack melt. LAP in snow and ice (LAPSI) has been identified as one of major forcings affecting climate change, e.g. in the fourth and fifth assessment reports of IPCC. However, the uncertainty level in quantifying this effect remains very high. In this review paper, we document various technical methods of measuring LAPSI and review the progress made in measuring the LAPSI in Arctic, Tibetan Plateau and other mid-latitude regions. We also report the progress in modeling the mass concentrations, albedo reduction, radiative forcing, andclimatic and hydrological impact of LAPSI at global and regional scales. Finally we identify some research needs for reducing the uncertainties in the impact of LAPSI on global and regional climate and the hydrological cycle.

A New Ka-Band Scanning Radar Facility: Polarimetric and Doppler Spectra Measurements of Snow Events

Science.gov (United States)

Oue, M.; Kollias, P.; Luke, E. P.; Mead, J.

2017-12-01

Polarimetric radar analyses offer the capability of identification of ice hydrometeor species as well as their spatial distributions. In addition to polarimetric parameter observations, Doppler spectra measurements offer unique insights into ice particle properties according to particle fall velocities. In particular, millimeter-wavelength radar Doppler spectra can reveal supercooled liquid cloud droplets embedded in ice precipitation clouds. A Ka-band scanning polarimetric radar, named KASPR, was installed in an observation facility at Stony Brook University, located 22 km west of the KOKX NEXRAD radar at Upton, NY. The KASPR can measure Doppler spectra and full polarimetric variables, including radar reflectivity, differential reflectivity (ZDR), differential phase (φDP), specific differential phase (KDP), correlation coefficient (ρhv), and linear depolarization ratio (LDR). The facility also includes a micro-rain radar and a microwave radiometer capable of measuring reflectivity profiles and integrated liquid water path, respectively. The instruments collected initial datasets during two snowstorm events and two snow shower events in March 2017. The radar scan strategy was a combination of PPI scans at 4 elevation angles (10, 20, 45, and 60°) and RHI scans in polarimetry mode, and zenith pointing with Doppler spectra collection. During the snowstorm events the radar observed relatively larger ZDR (1-1.5 dB) and enhanced KDP (1-2 ° km-1) at heights corresponding to a plate/dendrite crystal growth regime. The Doppler spectra showed that slower-falling particles ( 1 m s-1). The weakly increased ZDR could be produced by large, faster falling particles such as quasi-spherical aggregates, while the enhanced KDP could be produced by highly-oriented oblate, slowly-falling particles. Below 2 km altitude, measurements of dual wavelength ratio (DWR) based on Ka and S-band reflectivities from the KASPR and NEXRAD radars were available. Larger DWR (>10 dB) suggested

Quantifying small-scale spatio-temporal variability of snow stratigraphy in forests based on high-resolution snow penetrometry

Science.gov (United States)

Teich, M.; Hagenmuller, P.; Bebi, P.; Jenkins, M. J.; Giunta, A. D.; Schneebeli, M.

2017-12-01

Snow stratigraphy, the characteristic layering within a seasonal snowpack, has important implications for snow remote sensing, hydrology and avalanches. Forests modify snowpack properties through interception, wind speed reduction, and changes to the energy balance. The lack of snowpack observations in forests limits our ability to understand the evolution of snow stratigraphy and its spatio-temporal variability as a function of forest structure and to observe snowpack response to changes in forest cover. We examined the snowpack under canopies of a spruce forest in the central Rocky Mountains, USA, using the SnowMicroPen (SMP), a high resolution digital penetrometer. Weekly-repeated penetration force measurements were recorded along 10 m transects every 0.3 m in winter 2015 and bi-weekly along 20 m transects every 0.5 m in 2016 in three study plots beneath canopies of undisturbed, bark beetle-disturbed and harvested forest stands, and an open meadow. To disentangle information about layer hardness and depth variabilities, and to quantitatively compare the different SMP profiles, we applied a matching algorithm to our dataset, which combines several profiles by automatically adjusting their layer thicknesses. We linked spatial and temporal variabilities of penetration force and depth, and thus snow stratigraphy to forest and meteorological conditions. Throughout the season, snow stratigraphy was more heterogeneous in undisturbed but also beneath bark beetle-disturbed forests. In contrast, and despite remaining small diameter trees and woody debris, snow stratigraphy was rather homogenous at the harvested plot. As expected, layering at the non-forested plot varied only slightly over the small spatial extent sampled. At the open and harvested plots, persistent crusts and ice lenses were clearly present in the snowpack, while such hard layers barely occurred beneath undisturbed and disturbed canopies. Due to settling, hardness significantly increased with depth at

When Models and Observations Collide: Journeying towards an Integrated Snow Depth Product

Science.gov (United States)

Webster, M.; Petty, A.; Boisvert, L.; Markus, T.; Kurtz, N. T.; Kwok, R.; Perovich, D. K.

2017-12-01

Knowledge of snow depth is essential for assessing changes in sea ice mass balance due to snow's insulating and reflective properties. In remote sensing applications, the accuracy of sea ice thickness retrievals from altimetry crucially depends on snow depth. Despite the need for snow depth data, we currently lack continuous observations that capture the basin-scale snow depth distribution and its seasonal evolution. Recent in situ and remote sensing observations are sparse in space and time, and contain uncertainties, caveats, and/or biases that often require careful interpretation. Likewise, using model output for remote sensing applications is limited due to uncertainties in atmospheric forcing and different treatments of snow processes. Here, we summarize our efforts in bringing observational and model data together to develop an approach for an integrated snow depth product. We start with a snow budget model and incrementally incorporate snow processes to determine the effects on snow depth and to assess model sensitivity. We discuss lessons learned in model-observation integration and ideas for potential improvements to the treatment of snow in models.

The unfolded protein response is required for dendrite morphogenesis

Science.gov (United States)

Wei, Xing; Howell, Audrey S; Dong, Xintong; Taylor, Caitlin A; Cooper, Roshni C; Zhang, Jianqi; Zou, Wei; Sherwood, David R; Shen, Kang

2015-01-01

Precise patterning of dendritic fields is essential for the formation and function of neuronal circuits. During development, dendrites acquire their morphology by exuberant branching. How neurons cope with the increased load of protein production required for this rapid growth is poorly understood. Here we show that the physiological unfolded protein response (UPR) is induced in the highly branched Caenorhabditis elegans sensory neuron PVD during dendrite morphogenesis. Perturbation of the IRE1 arm of the UPR pathway causes loss of dendritic branches, a phenotype that can be rescued by overexpression of the ER chaperone HSP-4 (a homolog of mammalian BiP/ grp78). Surprisingly, a single transmembrane leucine-rich repeat protein, DMA-1, plays a major role in the induction of the UPR and the dendritic phenotype in the UPR mutants. These findings reveal a significant role for the physiological UPR in the maintenance of ER homeostasis during morphogenesis of large dendritic arbors. DOI: http://dx.doi.org/10.7554/eLife.06963.001 PMID:26052671

Scales of snow depth variability in high elevation rangeland sagebrush

Science.gov (United States)

Tedesche, Molly E.; Fassnacht, Steven R.; Meiman, Paul J.

2017-09-01

In high elevation semi-arid rangelands, sagebrush and other shrubs can affect transport and deposition of wind-blown snow, enabling the formation of snowdrifts. Datasets from three field experiments were used to investigate the scales of spatial variability of snow depth around big mountain sagebrush ( Artemisia tridentata Nutt.) at a high elevation plateau rangeland in North Park, Colorado, during the winters of 2002, 2003, and 2008. Data were collected at multiple resolutions (0.05 to 25 m) and extents (2 to 1000 m). Finer scale data were collected specifically for this study to examine the correlation between snow depth, sagebrush microtopography, the ground surface, and the snow surface, as well as the temporal consistency of snow depth patterns. Variograms were used to identify the spatial structure and the Moran's I statistic was used to determine the spatial correlation. Results show some temporal consistency in snow depth at several scales. Plot scale snow depth variability is partly a function of the nature of individual shrubs, as there is some correlation between the spatial structure of snow depth and sagebrush, as well as between the ground and snow depth. The optimal sampling resolution appears to be 25-cm, but over a large area, this would require a multitude of samples, and thus a random stratified approach is recommended with a fine measurement resolution of 5-cm.

Adolescent cocaine exposure simplifies orbitofrontal cortical dendritic arbors

Directory of Open Access Journals (Sweden)

Lauren M DePoy

2014-10-01

Full Text Available Cocaine and amphetamine remodel dendritic spines within discrete cortico-limbic brain structures including the orbitofrontal cortex (oPFC. Whether dendrite structure is similarly affected, and whether pre-existing cellular characteristics influence behavioral vulnerabilities to drugs of abuse, remain unclear. Animal models provide an ideal venue to address these issues because neurobehavioral phenotypes can be defined both before, and following, drug exposure. We exposed mice to cocaine from postnatal days 31-35, corresponding to early adolescence, using a dosing protocol that causes impairments in an instrumental reversal task in adulthood. We then imaged and reconstructed excitatory neurons in deep-layer oPFC. Prior cocaine exposure shortened and simplified arbors, particularly in the basal region. Next, we imaged and reconstructed orbital neurons in a developmental-genetic model of cocaine vulnerability – the p190rhogap+/- mouse. p190RhoGAP is an actin cytoskeleton regulatory protein that stabilizes dendrites and dendritic spines, and p190rhogap+/- mice develop rapid and robust locomotor activation in response to cocaine. Despite this, oPFC dendritic arbors were intact in drug-naïve p190rhogap+/- mice. Together, these findings provide evidence that adolescent cocaine exposure has long-term effects on dendrite structure in the oPFC, and they suggest that cocaine-induced modifications in dendrite structure may contribute to the behavioral effects of cocaine more so than pre-existing structural abnormalities in this cell population.

A Citizen Science Campaign to Validate Snow Remote-Sensing Products

Science.gov (United States)

Wikstrom Jones, K.; Wolken, G. J.; Arendt, A. A.; Hill, D. F.; Crumley, R. L.; Setiawan, L.; Markle, B.

2017-12-01

The ability to quantify seasonal water retention and storage in mountain snow packs has implications for an array of important topics, including ecosystem function, water resources, hazard mitigation, validation of remote sensing products, climate modeling, and the economy. Runoff simulation models, which typically rely on gridded climate data and snow remote sensing products, would be greatly improved if uncertainties in estimates of snow depth distribution in high-elevation complex terrain could be reduced. This requires an increase in the spatial and temporal coverage of observational snow data in high-elevation data-poor regions. To this end, we launched Community Snow Observations (CSO). Participating citizen scientists use Mountain Hub, a multi-platform mobile and web-based crowdsourcing application that allows users to record, submit, and instantly share geo-located snow depth, snow water equivalence (SWE) measurements, measurement location photos, and snow grain information with project scientists and other citizen scientists. The snow observations are used to validate remote sensing products and modeled snow depth distribution. The project's prototype phase focused on Thompson Pass in south-central Alaska, an important infrastructure corridor that includes avalanche terrain and the Lowe River drainage and is essential to the City of Valdez and the fisheries of Prince William Sound. This year's efforts included website development, expansion of the Mountain Hub tool, and recruitment of citizen scientists through a combination of social media outreach, community presentations, and targeted recruitment of local avalanche professionals. We also conducted two intensive field data collection campaigns that coincided with an aerial photogrammetric survey. With more than 400 snow depth observations, we have generated a new snow remote-sensing product that better matches actual SWE quantities for Thompson Pass. In the next phase of the citizen science portion of

Introduction to snow rheology

International Nuclear Information System (INIS)

Montmollin, Vincent de

1978-01-01

The tests described in the thesis are rotating shearing tests, with rotational constant speed ranging between 0.00075 rpm and 0.75 rpm. The results obtained are similar to those observed with compression tests at constant speed, except that shearing tests are carried out with densities nearly constant. So, we show three different domains when the rotation speed increases: 1) viscous (without failure) 2) brittle of first type (cycles of brittle failures) and 3) brittle of second type (only one brittle failure and solid friction). These results show clearly that the fundamental mechanism that rules the mechanisms of snow, is fast metamorphosis of bonds, binding ice grains: this metamorphosis is important when solicitation speeds are low (permanent rate of shearing in viscous domain, regeneration of the failure surfaces in the brittle domain of the first type) and this metamorphosis does not exist when speed increases (only one failure and solid friction in the brittle domain of second type). It is also included an important bibliographic analysis of the snow mechanics, and an experimental and theoretical study about shock wave propagation in natural snow covers. (author) [fr

Blowing snow detection from ground-based ceilometers : Application to East Antarctica

NARCIS (Netherlands)

Gossart, Alexandra; Souverijns, Niels; Gorodetskaya, Irina V.; Lhermitte, S.L.M.; Lenaerts, Jan T M; Schween, Jan H.; Mangold, Alexander; Laffineur, Quentin; van Lipzig, Nicole P. M.

2017-01-01

Blowing snow impacts Antarctic ice sheet surface mass balance by snow redistribution and sublimation. However, numerical models poorly represent blowing snow processes, while direct observations are limited in space and time. Satellite retrieval of blowing snow is hindered by clouds and only the

Evaluation of NVE's snow station network; Subreport in R et D project 302H15 Good snow data; Evaluering av NVE sitt snoestasjonsnettverk

Energy Technology Data Exchange (ETDEWEB)

Ree, Bjoerg Lirhus; Landroe, Hilde; Trondsen, Elise; Moeen, Knut M.

2011-03-15

NVE has measured snow water equivalent of snow pillow in forty years. Our snow station network has risen since 1997 from 6 to 25 stations. It was therefore absolutely necessary to do a review and quality assurance of NVE's snow data. This report discusses the snow data measured continuously - snow water equivalent and snow depth. Each station and the parameters it measures are described and evaluated. It is concluded in relation to whether stations should be continued or not. Stations technical solutions are well described, both of NVE's standard stations and the two test stations, Filefjell and Svarttjoernbekken. It has been o importance to bring out what problems the instruments have or may have and provide suggestions for solutions to them. Problems related to measure the water equivalent under Norwegian conditions, with the challenges and winter rain and re-freezing provides, is also reviewed. Alternatives to water equivalent measurements with a snow pillow, which is the traditional way in this country, are presented. Some of the alternative methods NVE tests out, for the others only description and our opinion is given. (Author)

Cellular Automaton Modeling of Dendritic Growth Using a Multi-grid Method

International Nuclear Information System (INIS)

Natsume, Y; Ohsasa, K

2015-01-01

A two-dimensional cellular automaton model with a multi-grid method was developed to simulate dendritic growth. In the present model, we used a triple-grid system for temperature, solute concentration and solid fraction fields as a new approach of the multi-grid method. In order to evaluate the validity of the present model, we carried out simulations of single dendritic growth, secondary dendrite arm growth, multi-columnar dendritic growth and multi-equiaxed dendritic growth. From the results of the grid dependency from the simulation of single dendritic growth, we confirmed that the larger grid can be used in the simulation and that the computational time can be reduced dramatically. In the simulation of secondary dendrite arm growth, the results from the present model were in good agreement with the experimental data and the simulated results from a phase-field model. Thus, the present model can quantitatively simulate dendritic growth. From the simulated results of multi-columnar and multi-equiaxed dendrites, we confirmed that the present model can perform simulations under practical solidification conditions. (paper)

Con-nectin axons and dendrites.

Science.gov (United States)

Beaudoin, Gerard M J

2006-07-03

Unlike adherens junctions, synapses are asymmetric connections, usually between axons and dendrites, that rely on various cell adhesion molecules for structural stability and function. Two cell types of adhesion molecules found at adherens junctions, cadherins and nectins, are thought to mediate homophilic interaction between neighboring cells. In this issue, Togashi et al. (see p. 141) demonstrate that the differential localization of two heterophilic interacting nectins mediates the selective attraction of axons and dendrites in cooperation with cadherins.

Dendrites Enable a Robust Mechanism for Neuronal Stimulus Selectivity.

Science.gov (United States)

Cazé, Romain D; Jarvis, Sarah; Foust, Amanda J; Schultz, Simon R

2017-09-01

Hearing, vision, touch: underlying all of these senses is stimulus selectivity, a robust information processing operation in which cortical neurons respond more to some stimuli than to others. Previous models assume that these neurons receive the highest weighted input from an ensemble encoding the preferred stimulus, but dendrites enable other possibilities. Nonlinear dendritic processing can produce stimulus selectivity based on the spatial distribution of synapses, even if the total preferred stimulus weight does not exceed that of nonpreferred stimuli. Using a multi-subunit nonlinear model, we demonstrate that stimulus selectivity can arise from the spatial distribution of synapses. We propose this as a general mechanism for information processing by neurons possessing dendritic trees. Moreover, we show that this implementation of stimulus selectivity increases the neuron's robustness to synaptic and dendritic failure. Importantly, our model can maintain stimulus selectivity for a larger range of loss of synapses or dendrites than an equivalent linear model. We then use a layer 2/3 biophysical neuron model to show that our implementation is consistent with two recent experimental observations: (1) one can observe a mixture of selectivities in dendrites that can differ from the somatic selectivity, and (2) hyperpolarization can broaden somatic tuning without affecting dendritic tuning. Our model predicts that an initially nonselective neuron can become selective when depolarized. In addition to motivating new experiments, the model's increased robustness to synapses and dendrites loss provides a starting point for fault-resistant neuromorphic chip development.

Bergmann glia and the recognition molecule CHL1 organize GABAergic axons and direct innervation of Purkinje cell dendrites.

Directory of Open Access Journals (Sweden)

Fabrice Ango

2008-04-01

Full Text Available The geometric and subcellular organization of axon arbors distributes and regulates electrical signaling in neurons and networks, but the underlying mechanisms have remained elusive. In rodent cerebellar cortex, stellate interneurons elaborate characteristic axon arbors that selectively innervate Purkinje cell dendrites and likely regulate dendritic integration. We used GFP BAC transgenic reporter mice to examine the cellular processes and molecular mechanisms underlying the development of stellate cell axons and their innervation pattern. We show that stellate axons are organized and guided towards Purkinje cell dendrites by an intermediate scaffold of Bergmann glial (BG fibers. The L1 family immunoglobulin protein Close Homologue of L1 (CHL1 is localized to apical BG fibers and stellate cells during the development of stellate axon arbors. In the absence of CHL1, stellate axons deviate from BG fibers and show aberrant branching and orientation. Furthermore, synapse formation between aberrant stellate axons and Purkinje dendrites is reduced and cannot be maintained, leading to progressive atrophy of axon terminals. These results establish BG fibers as a guiding scaffold and CHL1 a molecular signal in the organization of stellate axon arbors and in directing their dendritic innervation.