126 research outputs found
Region-wide glacier mass balances over the Pamir-Karakoram-Himalaya during 1999-2011 (vol 7, pg 1263, 2013)
ISI Document Delivery No.: 273OY Times Cited: 0 Cited Reference Count: 1 Cited References: Gardelle J, 2013, CRYOSPHERE, V7, P1263, DOI 10.5194/tc-7-1263-2013 Gardelle, J. Berthier, E. Arnaud, Y. Kaab, A. 0 COPERNICUS GESELLSCHAFT MBH GOTTINGEN CRYOSPHEREThe 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 regionwide 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 (â0.22±0.12mw.e. yrâ1 to â0.33±0.14mw.e. yrâ1) and larger losses in the western Himalaya (â0.45±0.13mw.e. yrâ1). 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. yrâ1) and also observed for glaciers in the western Pamir (+0.14±0.13mw.e. yrâ1). Thus, the "Karakoram anomaly" should be renamed the "Pamir- Karakoram anomaly", at least for the last decade. The overall mass balance of PKH glaciers, â0.14±0.08mw.e. yrâ1, 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
Homeostasis of the astrocytic glutamate transporter GLT-1 is altered in mouse models of Lafora disease
10 pĂĄginas, 6 figurasLafora disease (LD, OMIM 254780) is a fatal rare disorder characterized by epilepsy and neurodegeneration. Although in recent years a lot of information has been gained on the molecular basis of the neurodegeneration that accompanies LD, the molecular basis of epilepsy is poorly understood. Here, we present evidence indicating that the homeostasis of glutamate transporter GLT-1 (EAAT2) is compromised in mouse models of LD. Our results indicate that primary astrocytes from LD mice have reduced capacity of glutamate transport, probably because they present a reduction in the levels of the glutamate transporter at the plasma membrane. On the other hand, the overexpression in cellular models of laforin and malin, the two proteins related to LD, results in an accumulation of GLT-1 (EAAT2) at the plasma membrane and in a severe reduction of the ubiquitination of the transporter. All these results suggest that the laforin/malin complex slows down the endocytic recycling of the GLT-1 (EAAT2) transporter. Since, defects in the function of this transporter lead to excitotoxicity and epilepsy, we suggest that the epilepsy that accompanies LD could be due, at least in part, to deficiencies in the function of the GLT-1 (EAAT2) transporter.This work was supported by grants from the Spanish Ministry of Education and Science SAF2014-54604-C3-1-R, an ACCI2012 action from CIBERER, a grant from the Alicia Koplowitz Foundation (2015) and a grant from Generalitat Valenciana (PrometeoII/2014/029). A.B. held a postdoctoral fellowship from the Program âJunta para la AmpliaciĂłn de Estudiosâ (JAE-Doc) co-funded by the European Social Fund (ESF). C.M-B holds a FPU fellowship from the Spanish Ministry of Education, Culture and Sports.Peer reviewe
Pharmacological Interventions to Ameliorate Neuropathological Symptoms in a Mouse Model of Lafora Disease
14 pĂĄginas; 9 figuras.Lafora disease (LD, OMIM 254780) is a rare fatal neurodegenerative disorder that usually occurs during childhood with generalized tonic-clonic seizures, myoclonus, absences, drop attacks or visual seizures. Unfortunately, at present, available treatments are only palliatives and no curative drugs are available yet. The hallmark of the disease is the accumulation of insoluble polyglucosan inclusions, called Lafora bodies (LBs), within the neurons but also in heart, muscle and liver cells. Mouse models lacking functional EPM2A or EPM2B genes (the two major loci related to the disease) recapitulate the Lafora disease phenotype: they accumulate polyglucosan inclusions, show signs of neurodegeneration and have a dysregulation of protein clearance and endoplasmic reticulum stress response. In this study, we have subjected a mouse model of LD (Epm2b-/-) to different pharmacological interventions aimed to alleviate protein clearance and endoplasmic reticulum stress. We have used two chemical chaperones, trehalose and 4-phenylbutyric acid. In addition, we have used metformin, an activator of AMP-activated protein kinase (AMPK), as it has a recognized neuroprotective role in other neurodegenerative diseases. Here, we show that treatment with 4-phenylbutyric acid or metformin decreases the accumulation of Lafora bodies and polyubiquitin protein aggregates in the brain of treated animals. 4-Phenylbutyric acid and metformin also diminish neurodegeneration (measured in terms of neuronal loss and reactive gliosis) and ameliorate neuropsychological tests of Epm2b-/- mice. As these compounds have good safety records and are already approved for clinical uses on different neurological pathologies, we think that the translation of our results to the clinical practice could be straightforward.This work was supported by grants from the Spanish Ministry of Education and Science SAF2011-27442, FundaciĂł La Marato de TV3 (ref. 100130) and an ACCI2012 action from CIBERER. A.B. holds a postdoctoral fellowship from the Program âJunta para la AmpliaciĂłn de Estudiosâ (JAE-Doc) co-funded by the European Social Fund (ESF).Peer reviewe
Reduced melt on debris-covered glaciers: investigations from Changri Nup Glacier, Nepal
International audienceApproximately 25âŻ% of the glacierized area in the Everest region is covered by debris, yet the surface mass balance of debris-covered portions of these glaciers has not been measured directly. In this study, ground-based measurements of surface elevation and ice depth are combined with terrestrial photogrammetry, unmanned aerial vehicle (UAV) and satellite elevation models to derive the surface mass balance of the debris-covered tongue of Changri Nup Glacier, located in the Everest region. Over the debris-covered tongue, the mean elevation change between 2011 and 2015 is â0.93âŻmâŻyearâ1 or â0.84âŻm water equivalent per year (w.e.âŻaâ1). The mean emergence velocity over this region, estimated from the total ice flux through a cross section immediately above the debris-covered zone, is +0.37âŻmâŻw.e.âŻaâ1. The debris-covered portion of the glacier thus has an area-averaged mass balance of â1.21âŻÂ±âŻ0.2âŻmâŻw.e.âŻaâ1 between 5240 and 5525âŻmâŻaboveâŻseaâŻlevel (mâŻa.s.l.). Surface mass balances observed on nearby debris-free glaciers suggest that the ablation is strongly reduced (by ca. 1.8âŻmâŻw.e.âŻaâ1) by the debris cover. The insulating effect of the debris cover has a larger effect on total mass loss than the enhanced ice ablation due to supraglacial ponds and exposed ice cliffs. This finding contradicts earlier geodetic studies and should be considered for modelling the future evolution of debris-covered glaciers
Kovacs effect and fluctuation-dissipation relations in 1D kinetically constrained models
Strong and fragile glass relaxation behaviours are obtained simply changing
the constraints of the kinetically constrained Ising chain from symmetric to
purely asymmetric. We study the out-of-equilibrium dynamics of those two models
focusing on the Kovacs effect and the fluctuation--dissipation relations. The
Kovacs or memory effect, commonly observed in structural glasses, is present
for both constraints but enhanced with the asymmetric ones. Most surprisingly,
the related fluctuation-dissipation (FD) relations satisfy the FD theorem in
both cases. This result strongly differs from the simple quenching procedure
where the asymmetric model presents strong deviations from the FD theorem.Comment: 13 pages and 7 figures. To be published in J. Phys.
Four years of mass balance on Chhota Shigri Glacier, Himachal Pradesh, India, a new benchmark glacier in the western Himalaya
ABSTRACT. Little is known about th
Transpressional tectonics and Carboniferous magmatism in the Limousin, Massif Central, France: Structural and <sup>40</sup>Ar/<sup>39</sup>Ar investigations
New structural, microstructural, and 40Ar/39 Ar data from the NW Massif Central (France) provide additional constraints on the timing and tectonic setting of late Variscan granite magmatism. Previous studies had emphasized the role of late orogenic extension in the emplacement of granite plutons in the Limousin region. In contrast, the new data set is consistent with syntectonic emplacement of magma in a dextral simple shear active from 350 to 300 Ma in a transpressional regime. As an alternative hypothesis to late orogenic extension, we propose that magmas migrated into tensional bridges between active P shears associated with a lithospheric shear zone comparable to a pop-up structure. The Galician region, in the western end of the Ibero-Armorican tectonic arc, exhibits major left-lateral ductile shear zones which can be interpreted as conjugate structures to the Limousin and Armorican shear zones. Copyright 2007 by the American Geophysical Union
Ice cliff contribution to the tongue-wide ablation of Changri Nup Glacier, Nepal, central Himalaya
Ice cliff backwasting on debris-covered glaciers is recognized
as an important mass-loss process that is potentially responsible for the
debris-cover anomaly, i.e. the fact that debris-covered and
debris-free glacier tongues appear to have similar thinning rates in the
Himalaya. In this study, we quantify the total contribution of ice cliff
backwasting to the net ablation of the tongue of Changri Nup Glacier, Nepal,
between 2015 and 2017. Detailed backwasting and surface thinning rates were
obtained from terrestrial photogrammetry collected in November 2015 and 2016,
unmanned air vehicle (UAV) surveys conducted in November 2015, 2016 and 2017,
and Pléiades tri-stereo imagery obtained in November 2015, 2016 and 2017.
UAV- and Pléiades-derived ice cliff volume loss estimates were
3 % and 7 % less than the value calculated from the
reference terrestrial photogrammetry. Ice cliffs cover between 7 % and
8 % of the total map view area of the Changri Nup tongue. Yet from
November 2015 to November 2016 (November 2016 to November 2017), ice cliffs
contributed to 23±5 % (24±5 %) of the total ablation observed
on the tongue. Ice cliffs therefore have a net ablation rate 3.1±0.6
(3.0±0.6) times higher than the average glacier tongue surface.
However, on Changri Nup Glacier, ice cliffs still cannot compensate for the
reduction in ablation due to debris-cover. In addition to cliff enhancement,
a combination of reduced ablation and lower emergence velocities could be
responsible for the debris-cover anomaly on debris-covered tongues.</p
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