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Transcranial alternating current stimulation (TACS) of the brain is widely used in neuroscience, but the electric fields produced when multiple stimulation electrodes are used are not well understood. Here, the authors directly record electric fields in primate brains during multi-electrode TACS.

Vitrimers are polymer networks with dynamic covalent bonds that allow the network to reconfigure its connectivity while maintaining a constant number of chemical bonds at all temperatures. The melt viscosity of vitrimers thus gradually decreases with temperature. This behavior makes vitrimers more difficult to process than typical thermoplastics using conventional processing techniques, such as extrusion. Although many strategies have been reported to address this issue, it remains challenging to overcome a key tradeoff between improving the processability or the mechanical performance. Herein, this work presents a new strategy for overcoming this tradeoff in the context of elastomeric vitrimers. The approach entails the cross‐linking of a functionalized low‐glass transition (Tg) polymer matrix with an incompatible high‐Tg polymer featuring pendant groups with complementary reactivity. When compared to a conventional homogeneous vitrimer, the microphase‐separated materials prepared by reactive extrusion present improved tensile properties and creep resistance at room temperature while also exhibiting enhanced processability at high temperature. These enhanced properties are a consequence of the combination of the phase separation between the soft and hard phases, the restriction of dynamic cross‐linking reactions within the interfacial zones, and the judicious selection of the Tg of the hard phase to be in between the use and processing temperatures. [ABSTRACT FROM AUTHOR]

This study investigates spatial patterns in glacier characteristics and area changes at decadal scales in the eastern Himalaya - Nepal (Arun and Tamor basins), India (Teesta basin in Sikkim) and parts of China and Bhutan - based on various satellite imagery: Corona KH4 imagery, Landsat 7 Enhanced Thematic Mapper Plus (ETM+) and Advanced Spaceborne Thermal Emission Radiometer (ASTER), QuickBird (QB) and WorldView-2 (WV2). We compare and contrast glacier surface area changes over the period of 1962-2000/2006 and their dependency on glacier topography (elevation, slope, aspect, percent debris cover) and climate (solar radiation, precipitation) on the eastern side of the topographic barrier (Sikkim) versus the western side (Nepal). Glacier mapping from 2000 Landsat ASTER yielded 1463±88 km2 total glacierized area, of which 569±34 km2 was located in Sikkim and 488±29 km2 in eastern Nepal. Supraglacial debris covered 11% of the total glacierized area, and supraglacial lakes covered about 5.8% of the debris-covered glacier area alone. Glacier area loss (1962 to 2000) was 0:50±0:2%yr-1, with little difference between Nepal (0:53±0:2%yr -1) and Sikkim (0:44±0:2%yr-1). Glacier area change was controlled mostly by glacier area, elevation, altitudinal range and, to a smaller extent, slope and aspect. In the Kanchenjunga–Sikkim area, we estimated a glacier area loss of 0:23±0:08%yr-1 from 1962 to 2006 based on high-resolution imagery. On a glacier-by-glacier basis, clean glaciers exhibit more area loss on average from 1962 to 2006 (34 %) compared to debris-covered glaciers (22 %). Glaciers in this region of the Himalaya are shrinking at similar rates to those reported for the last decades in other parts of the Himalaya, but individual glacier rates of change vary across the study area with respect to local topography, percent debris cover or glacier elevations. [ABSTRACT FROM AUTHOR]

In the Everest region, Nepal, ground-based monitoring programmes were started on the debris-free Mera Glacier (27.7° N, 86.9° E; 5.1 km2, 6420 to 4940m a.s.l.) in 2007 and on the small Pokalde Glacier (27.9° N, 86.8° E; 0.1 km2, 5690 to 5430ma.s.l., ~25 km north of Mera Glacier) in 2009. These glaciers lie on the southern flank of the central Himalaya under the direct influence of the Indian monsoon and receive more than 80% of their annual precipitation in summer (June to September). Despite a large interannual variability with glacier-wide mass balances ranging from -0.67±0.28m w.e. in 2011-2012 (Equilibriumline altitude (ELA) at -5800ma.s.l.) to ∔0.46±0.28m w.e. in 2010-2011 (ELA at ~5340ma.s.l.), Mera Glacier has been shrinking at a moderate mass balance rate of -0.08±0.28m w.e. yr-1 since 2007. Ice fluxes measured at two distinct transverse cross sections at -5350ma.s.l. and -5520m a.s.l. confirm that the mean state of this glacier over the last one or two decades corresponds to a limited mass loss, in agreement with remotely-sensed regionwide mass balances of the Everest area. Seasonal mass balance measurements show that ablation and accumulation are concomitant in summer which in turn is the key season controlling the annual glacier-wide mass balance. Unexpectedly, ablation occurs at all elevations in winter due to wind erosion and sublimation, with remobilised snow potentially being sublimated in the atmosphere. Between 2009 and 2012, the small Pokalde Glacier lost mass more rapidly than Mera Glacier with respective mean glacier-wide mass balances of -0.72 and -0.23±0.28m w.e. yr-1. Low-elevation glaciers, such as Pokalde Glacier, have been usually preferred for in-situ observations in Nepal and more generally in the Himalayas, which may explain why compilations of ground-based mass balances are biased toward negative values compared with the regional mean under the present-day climate. [ABSTRACT FROM AUTHOR]

The recent evolution of Pamir-Karakoram- Himalaya (PKH) glaciers, widely acknowledged as valuable high-altitude as well as mid-latitude climatic indicators, remains poorly known. To estimate the region-wide glacier mass balance for 9 study sites spread from the Pamir to the Hengduan Shan (eastern Himalaya), we compared the 2000 Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) to recent (2008- 2011) DEMs derived from SPOT5 stereo imagery. During the last decade, the region-wide glacier mass balances were contrasted with moderate mass losses in the eastern and central Himalaya (-0.22±0.12mw.e. yr-1 to -0.33±0.14mw.e. yr-1) and larger losses in the western Himalaya (-0.45±0.13mw.e. yr-1). Recently reported slight mass gain or balanced mass budget of glaciers in the central Karakoram is confirmed for a larger area (+0.10±0.16mw.e. yr-1) and also observed for glaciers in the western Pamir (+0.14±0.13mw.e. yr-1). Thus, the "Karakoram anomaly" should be renamed the "Pamir- Karakoram anomaly", at least for the last decade. The overall mass balance of PKH glaciers, -0.14±0.08mw.e. yr-1, is two to three times less negative than the global average for glaciers distinct from the Greenland and Antarctic ice sheets. Together with recent studies using ICESat and GRACE data, DEM differencing confirms a contrasted pattern of glacier mass change in the PKH during the first decade of the 21st century. [ABSTRACT FROM AUTHOR]

The volume change of the Chhota Shigri Glacier (India, 32° 20 N, 77° 300 E) between 1988 and 2010 has been determined using in situ geodetic measurements. This glacier has experienced only a slight mass loss between 1988 and 2010 (-3.8±2.0mw.e. (water equivalent) corresponding to -0.17 pm 0.09mw.e. yr-1). Using satellite digital elevation models (DEM) differencing and field measurements, we measure a negative mass balance (MB) between 1999 and 2010 (-4.8±1.8mw.e. corresponding to -0.44±0.16mw.e. yr-1). Thus, we deduce a slightly positive or near-zero MB between 1988 and 1999 (+1.0±2.7mw.e. corresponding to +0.09±0.24mw.e. yr-1). Furthermore, satellite DEM differencing reveals that the MB of the Chhota Shigri Glacier (-0.39 pm 0.15mw.e. yr-1) has been only slightly less negative than the MB of a 2110 km2 glaciarized area in the Lahaul and Spiti region (-0.44±0.09mw.e. yr-1) during 1999-2011. Hence, we conclude that the ice wastage is probably moderate in this region over the last 22 yr, with near equilibrium conditions during the nineties, and an ice mass loss after. The turning point from balanced to negative mass budget is not known but lies probably in the late nineties and at the latest in 1999. This positive or near-zero MB for Chhota Shigri Glacier (and probably for the surrounding glaciers of the Lahaul and Spiti region) during at least part of the 1990s contrasts with a recent compilation of MB data in the Himalayan range that indicated ice wastage since 1975. However, in agreement with this compilation, we confirm more negative balances since the beginning of the 21st century. [ABSTRACT FROM AUTHOR]

The aim of this paper is to provide the community with a comprehensive overview of the studies of glaciers in the tropical Andes conducted in recent decades leading to the current status of the glaciers in the context of climate change. In terms of changes in surface area and length, we show that the glacier retreat in the tropical Andes over the last three decades is unprecedented since the maximum extension of the Little Ice Age (LIA, mid-17th-early 18th century). In terms of changes in mass balance, although there have been some sporadic gains on several glaciers, we show that the trend has been quite negative over the past 50 yr, with a mean mass balance deficit for glaciers in the tropical Andes that is slightly more negative than the one computed on a global scale. A break point in the trend appeared in the late 1970s with mean annual mass balance per year decreasing from ?0.2mw.e. in the period 1964- 1975 to ?0.76mw.e. in the period 1976-2010. In addition, even if glaciers are currently retreating everywhere in the tropical Andes, it should be noted that this is much more pronounced on small glaciers at low altitudes that do not have a permanent accumulation zone, and which could disappear in the coming years/decades. Monthly mass balance measurements performed in Bolivia, Ecuador and Colombia show that variability of the surface temperature of the Pacific Ocean is the main factor governing variability of the mass balance at the decadal timescale. Precipitation did not display a significant trend in the tropical Andes in the 20th century, and consequently cannot explain the glacier recession On the other hand, temperature increased at a significant rate of 0.10 °C decade-1 in the last 70 yr. The higher frequency of El Niño events and changes in its spatial and temporal occurrence since the late 1970s together with a warming troposphere over the tropical Andes may thus explain much of the recent dramatic shrinkage of glaciers in this part of the world. [ABSTRACT FROM AUTHOR]

The article offers information on the study conducted by the authors related to the association of glacier annual mass balance and glacier albedo retrieved from Moderate Imaging Spectroradiometer (MODIS) data. It states that the accuracy of the retrieved albedo is estimated using both field measurements, at two automatic weather stations located on the glacier, and albedo values derived from terrestrial photographs.

The article presents a study which examines the temporal and spatial variations of surface albedo on Saint Sorlin Glacier in French Alps, France. The study develops a method of retrieving the albedo of frozen surfaces using terrestrial photography during the summers 2008 and 2009. The results of the study reveal the factors contributing to the variability of the albedo of glaciers including size and shape of the ice grains, surface roughness and content of impurities.

A major proportion of flow in the Indus River is contributed by its snow- and glacier-fed river catchments situated in the Himalaya, Karakoram and Hindukush ranges. It is therefore essential to understand the cryosphere dynamics in this area for water resource management. The MODIS MOD10A2 remote-sensing database of snow cover products from March 2000 to December 2009 was selected to analyse the snow cover changes in the Hunza River basin (the snow- and glacier-fed sub-catchment of the Indus River). A database of daily flows for the Hunza River at Dainyor Bridge over a period of 40 yr and climate data (precipitation and temperature) for 10 yr from three meteorological stations within the catchment was made available to investigate the hydrological regime in the area. Analysis of remotely sensed cryosphere (snow and ice cover) data during the last decade (2000-2009) suggest a rather slight expansion of cryosphere in the area in contrast to most of the regions in the world where glaciers are melting rapidly. This increase in snow cover may be the result of an increase in winter precipitation caused by westerly circulation. The impact of global warm- ing is not effective because a large part of the basin area lies under high altitudes where the temperature remains negative throughout most of the year. [ABSTRACT FROM AUTHOR]

High-accuracy measurements of snow Bidirectional Reflectance Distribution Function (BRDF) were performed for four natural snow samples with a spectrogonioradiometer in the 500-2600 nm wavelength range. These measurements are one of the first sets of direct snow BRDF values over a wide range of lighting and viewing geometry. They were compared to BRDF calculated with two optical models. Variations of the snow anisotropy factor with lighting geometry, wavelength and snow physical properties were investigated. Results show that at wavelengths with small penetration depth, scattering mainly occurs in the very top layers and the anisotropy factor is controlled by the phase function. In this condition, forward scattering peak or double scattering peak is observed. In contrast at shorter wavelengths, the penetration of the radiation is much deeper and the number of scattering events increases. The anisotropy factor is thus nearly constant and decreases at grazing observation angles. The whole dataset is available on demand from the corresponding author. [ABSTRACT FROM AUTHOR]

High-accuracy measurements of snow Bidirectional Reflectance Distribution Function (BRDF) were performed for four natural snow samples with a spectrogonio-radiometer in the 500-2600 nm wavelength range. These measurements are one of the first set of direct snow BRDF values over a wide range of lighting and viewing geometry. They were compared to BRDF calculated with two optical models. Variations of the snow anisotropy factor with lighting geometry, wavelength and snow physical properties were investigated. Results show that at wavelengths with small penetration depth, scattering mainly occurs in the very top layers and the anisotropy factor is controlled by the phase function. In this condition, forward scattering peak or double scattering peak is observed. In constrast at shorter wavelengths, the penetration of the radiation is much deeper and the number of scattering events increases. The anisotropy factor is thus nearly constant and decreases at grazing observation angles. [ABSTRACT FROM AUTHOR]

We propose to fuse the high spatial content of two 250-m spectral bands of the moderate resolution imaging spectroradiometer (MODIS) into its five 500-m bands using wavelet-based multiresolution analysis. Our objective was to test the effectiveness of this technique to increase the accuracy of snow mapping in mountainous environments. To assess the performance of this approach, we took advantage of the simultaneity between the advanced spaceborne thermal emission and reflection radiometer (ASTER) and MODIS sensors. With a 15-m spatial resolution, the ASTER sensor provided reference snow maps, which were then compared to MODIS-derived snow maps. The benefit of the method was assessed through the investigation of various metrics, which showed an improvement from 3% to 20%. Therefore, the enhanced snow map is of great benefit for environmental and hydrological applications in steep terrain. [ABSTRACT FROM PUBLISHER]

Neural oscillations play a crucial role in communication between remote brain areas. Transcranial electric stimulation with alternating currents (TACS) can manipulate these brain oscillations in a non-invasive manner. Recently, TACS using multiple electrodes with phase shifted stimulation currents were developed to alter long-range connectivity. Typically, an increase in coordination between two areas is assumed when they experience an in-phase stimulation and a disorganization through an anti-phase stimulation. However, the underlying biophysics of multi-electrode TACS has not been studied in detail. Here, we leverage direct invasive recordings from two non-human primates during multi-electrode TACS to characterize electric field magnitude and phase as a function of the phase of stimulation currents. Further, we report a novel "traveling wave" stimulation where the location of the electric field maximum changes over the stimulation cycle. Our results provide a mechanistic understanding of the biophysics of multi-electrode TACS and enable future developments of novel stimulation protocols. Transcranial alternating current stimulation (TACS) of the brain is widely used in neuroscience, but the electric fields produced when multiple stimulation electrodes are used are not well understood. Here, the authors directly record electric fields in primate brains during multi-electrode TACS. [ABSTRACT FROM AUTHOR]

The article offers information on the dissociation of broadband high-frequency activity and neuronal firing in the neocortex. It mentions that broadband high-frequency activity as a key analytic signal in human intracranial recordings. It discusses that association with local multiunit activity (MUA).