Disorder control in crystalline GeSb2Te4 and its impact on characteristic length scales

Crystalline GeSb2Te4 (GST) is remarkable material, as it allows to continuously tune the electrical resistance by orders of magnitude without involving a phase transition or stoichiometric changes, just by altering the short-range order. While well-ordered specimen are metallic, increasing amounts of disorder can eventually lead to an insulating state with vanishing conductivity in the 0K limit, but a similar number of charge carriers. These observations make disordered GST one of the most promising candidates for the realization of a true Anderson insulator. While so far the low-temperature properties have mostly been studied in films of small grain size, here a sputter-deposition process is employed that enables preparation of a large variety of these GST states including metallic and truly insulating ones. By growing films of GST on mica substrates, biaxially textured samples with huge grain sizes are obtained. A series of these samples is employed for transport measurements, as their electron mean free path can be altered by a factor of 20. Yet, the mean free path always remains more than an order of magnitude smaller than the lateral grain size. This proves unequivocally that grain boundaries play a negligible role for electron scattering, while intragrain scattering, presumably by disordered vacancies, dominates. Most importantly, these findings underline that the Anderson insulating state as well as the system's evolution towards metallic conductivity are indeed intrinsic properties of the material

Melt pond fractions on Arctic summer sea ice retrieved from Sentinel-3 satellite data with a constrained physical forward model

Abstract. The presence of melt ponds on Arctic summer sea ice significantly alters its albedo and thereby the surface energy budget and mass balance. Large-scale observations of melt pond coverage and sea ice albedo are crucial to investigate the role of sea ice for Arctic amplification and its representation in global climate models. We present the new Melt Pond Detection 2 (MPD2) algorithm, which retrieves melt pond, sea ice, and open-ocean fractions as well as surface albedo from Sentinel-3 visible and near-infrared reflectances. In contrast to most other algorithms, our method uses neither fixed values for the spectral albedo of the surface constituents nor an artificial neural network. Instead, it aims for a fully physical representation of the reflective properties of the surface constituents based on their optical characteristics. The state vector X, containing the optical properties of melt ponds and sea ice along with the area fractions of melt ponds and open ocean, is optimized in an iterative procedure to match the measured reflectances and describe the surface state. A major problem in unmixing a compound pixel is that a mixture of half open water and half bright ice cannot be distinguished from a homogeneous pixel of darker ice. In order to overcome this, we suggest constraining the retrieval with a priori information. Initial values and constraint of the surface fractions are derived with an empirical retrieval which uses the same spectral reflectances as implemented in the physical retrieval. The snow grain size and optical thickness change with time, and thus the ice surface albedo changes throughout the season. Therefore, field observations of spectral albedo are used to develop a parameterization of the sea ice optical properties as a function of the temperature history of the sea ice. With these a priori data, the iterative optimization is initialized and constrained, resulting in a retrieval uncertainty of below 8 % for melt pond and 9 % for open-ocean fractions compared to the reference dataset. As reference data for evaluation, a 10 m resolution product of melt pond and open-ocean fraction from Sentinel-2 optical imagery is used. </jats:p

Culture and carelessness: Constituting disability in South India

This is the author's accepted manuscript. The final published article is available from the link below.Professional and lay explanations of disability, collected via interviews and participant-observation during fieldwork in Hyderabad, South India, identify “carelessness” and “superstition” as major impediments to good health among the general population, and education as the key solution. In that such findings suggest a valorization of personal responsibility for self-care, the Foucauldian concept of biopower appeared a salient framework for analysis. Although illuminating, however, biopower was ultimately inadequate for explaining what emerged, on closer analysis, as significant discrepancies between assumptions about how disabled people engaged with healthcare services and their actual beliefs and practices; and between the moral interpretations different stakeholders made of “carelessness” in describing perceived causes of disability. My data also suggested that education was not in itself a key determinant in people's healthcare decisions. This article explores these differences between official and demotic discourses concerning the causes of disability and attempts to account for them ethnographically.The British Academ

Contrasting disease patterns in seropositive and seronegative neuromyelitis optica: A multicentre study of 175 patients

BACKGROUND: The diagnostic and pathophysiological relevance of antibodies to aquaporin-4 (AQP4-Ab) in patients with neuromyelitis optica spectrum disorders (NMOSD) has been intensively studied. However, little is known so far about the clinical impact of AQP4-Ab seropositivity. OBJECTIVE: To analyse systematically the clinical and paraclinical features associated with NMO spectrum disorders in Caucasians in a stratified fashion according to the patients' AQP4-Ab serostatus. METHODS: Retrospective study of 175 Caucasian patients (AQP4-Ab positive in 78.3%). RESULTS: Seropositive patients were found to be predominantly female (p 1 myelitis attacks in the first year were identified as possible predictors of a worse outcome. CONCLUSION: This study provides an overview of the clinical and paraclinical features of NMOSD in Caucasians and demonstrates a number of distinct disease characteristics in seropositive and seronegative patients

Melt pond fraction on Arctic sea-ice from Sentinel-2 satellite optical imagery (2017-2021)

We present maps of melt pond fraction on Arctic sea-ice produced from a classification of Sentinel-2 optical imagery. The maps have a spatial resolution of 10 m. The classification was performed pixelwise, obtaining values between 0 and 1, corresponding to 0 % and 100 % of melt ponds detected within the pixel. Additionally, a mask of open water pixels is given. The dataset consists of 31 cloud-free scenes spanning the Arctic up to latitudes of 82.3 ° and covering areas of 1000 km² up to 10000 km², each. The dates of the scenes range from 2017 to 2021, limited to the summer months June, July and August. A special focus is on the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC), all scenes for summer 2020 cover the Central observatory of the MOSAiC expedition. Each .nc file contains arrays of melt pond fraction and open water mask as well as the georeferencing data in the CF standard format. As additional global variables, the date (YYYYMMDD), time (HHMMSS) and epsg code are given

Sea ice density and salinity profiles measured during RV POLARSTERN cruise PS131

During the Polarstern cruise PS131 in July and August 2022 in the marginal ice zone in the Fram Strait and at two ice stations on fast ice (Greenland), ice core samples were obtained with a 9 cm Kovacs corer on ice stations. This dataset contains vertical density and salinity profiles obtained by cutting the core in 4 cm intervals (for the upper 40cm) and 10 cm intervals for the remaining part. The samples were weighted on the ice. Together with the known volume densities can be calculated for each sample. They were then taken to the ship for later salinity measurements (Greisinger G1410 salinometer). For most of the samples, the whole ice layer was sampled, but for some, only the upper 40 cm were measured. However, the measured total ice thickness is included in the dataset. For more information of these measurements the user is referred to Chapter 8 of the cruise report

Silencing of the Rac1 GTPase MtROP9 in Medicago truncatula Stimulates Early Mycorrhizal and Oomycete Root Colonizations But Negatively Affects Rhizobial Infection[C][W][OA]

RAC/ROP proteins (ρ-related GTPases of plants) are plant-specific small G proteins that function as molecular switches within elementary signal transduction pathways, including the regulation of reactive oxygen species (ROS) generation during early microbial infection via the activation of NADPH oxidase homologs of plants termed RBOH (for respiratory burst oxidase homolog). We investigated the role of Medicago truncatula Jemalong A17 small GTPase MtROP9, orthologous to Medicago sativa Rac1, via an RNA interference silencing approach. Composite M. truncatula plants (MtROP9i) whose roots have been transformed by Agrobacterium rhizogenes carrying the RNA interference vector were generated and infected with the symbiotic arbuscular mycorrhiza fungus Glomus intraradices and the rhizobial bacterium Sinorhizobium meliloti as well as with the pathogenic oomycete Aphanomyces euteiches. MtROP9i transgenic lines showed a clear growth-reduced phenotype and revealed neither ROS generation nor MtROP9 and MtRBOH gene expression after microbial infection. Coincidently, antioxidative compounds were not induced in infected MtROP9i roots, as documented by differential proteomics (two-dimensional differential gel electrophoresis). Furthermore, MtROP9 knockdown clearly promoted mycorrhizal and A. euteiches early hyphal root colonization, while rhizobial infection was clearly impaired. Infected MtROP9i roots showed, in part, extremely swollen noninfected root hairs and reduced numbers of deformed nodules. S. meliloti nodulation factor treatments of MtROP9i led to deformed root hairs showing progressed swelling of its upper regions or even of the entire root hair and spontaneous constrictions but reduced branching effects occurring only at swollen root hairs. These results suggest a key role of Rac1 GTPase MtROP9 in ROS-mediated early infection signaling

Transmission of spectral solar irradiance through sea ice measured at different water depths during Polarstern expedition PS131

Measurements of transmitted irradiance under sea ice and corresponding incident solar radiation at the surface have been performed during the Polarstern expedition PS131, ATWAICE. During this expedition, three major ice floes were revisited to repeat measurements with a time gap of approximately one week and thereby analyze temporal development. Additionally, measurements on another ice floe were repeated 8 times within one day to observe the daily cycle of incoming and transmitted irradiance. All observations took place in the Fram Strait, north of Svalbard, between July 13 and August 6, 2022. The radiation measurements have been performed with Ramses spectral radiometers (TriOS, Rastede, Germany) in the wavelength range 316 to 952 nm. The incoming irradiance sensor was installed at approximately 1 m above the sea ice surface. The transmittance sensor was lowered through a hole (diameter about 10 cm) into the water down to 40 to 50 m depth. There are three datasets, two of them contain the raw data of the incoming and transmittance sensors. The third file contains temporally interpolated data (to 1s) of integrated intensity of both sensors and an estimation of the transmittance which is the ratio of the incoming and the transmitted irradiance. All times are given in UTC. The "incoming" dataset contains the date and time as index, the integration time of the sensor in ms and the measured intensity per channel in mW/m²/nm. The "transmitted" dataset contains the same information for the sensor in the water complemented with the sensor depth in meters and its inclination in two directions in degree (°). The "interpolated" dataset contains again the date and time, sensor depth and inclination information, and the integration times of the two sensors complemented with the integrated intensity measured by the two sensors in W/m² and their ratio which is the transmittance in percent (%). Additionally included, are plots of the sensor depth-transmittance relation for all 19 observations and the ice thickness and ice draft measured at the measurement site. Two figures show the measurement setup