Integrated impedance bridge for absolute capacitance measurements at cryogenic temperatures and finite magnetic fields

We developed an impedance bridge that operates at cryogenic temperatures (down to 60 mK) and in perpendicular magnetic fields up to at least 12 T. This is achieved by mounting a GaAs HEMT amplifier perpendicular to a printed circuit board containing the device under test and thereby parallel to the magnetic field. The measured amplitude and phase of the output signal allows for the separation of the total impedance into an absolute capacitance and a resistance. Through a detailed noise characterization, we find that the best resolution is obtained when operating the HEMT amplifier at the highest gain. We obtained a resolution in the absolute capacitance of 6.4~aF$/\sqrt{\textrm{Hz}}$ at 77 K on a comb-drive actuator, while maintaining a small excitation amplitude of 15~$k_\text{B} T/e$. We show the magnetic field functionality of our impedance bridge by measuring the quantum Hall plateaus of a top-gated hBN/graphene/hBN heterostructure at 60~mK with a probe signal of 12.8~$k_\text{B} T/e$.Comment: 7 pages, 5 figure

GeSn lasers for CMOS integration

In search of a suitable CMOS compatible light source many routes and materials are under investigation. Si-based group IV (Si)GeSn alloys offer a tunable bandgap from indirect to direct, making them ideal candidates for on-chip photonics and nano-electronics. An overview of recent achievements in material growth and device developments will be given. Optically pumped waveguide and microdisk structures with different strain and various Sn concentrations provide direct evidence of gain in these alloys and the width of the emission wavelength range that can be covered. Towards the aim of electrically pumped lasers, a set of different homojunction light emitting diodes and more complex heterostructure SiGeSn/GeSn LEDs is presented. Detailed investigation of electroluminescence spectra indicate that GeSn/SiGeSn heterostructures will be advantageous for future laser fabrication

Direct bandgap GeSn microdisk lasers at 2.5 μm for monolithic integration on Si-platform

We report on the first experimental demonstration of direct bandgap group IV GeSn microdisk (MD) lasers (λem=2.5 μm) grown on Si(001). The evidence of lasing is supported by a detailed analysis of strain-dependent emission characteristics of GeSn alloys with xSn ≥ 12 at.%. Residual compressive strain within the layer is relieved via under-etching of the MD enabling increased energy offsets up to EL-EΓ=80 meV. The lasing threshold and max. temperature amount to 220 kW/cm2 and 135 K, respectively

A Novel Reading Scheme for Assessing the Extent of Radiographic Abnormalities and Its Association with Disease Severity in Sputum Smear-Positive Tuberculosis: An Observational Study in Hyderabad/India.

Existing reading schemes for chest X-ray (CXR) used to grade the extent of disease severity at diagnosis in patients with pulmonary tuberculosis (PTB) are often based on numerical scores that summate specific radiographic features. However, since PTB is known to exhibit a wide heterogeneity in pathology, certain features might be differentially associated with clinical parameters of disease severity.We aimed to grade disease severity in PTB patients at diagnosis and after completion of DOTS treatment by developing a reading scheme based on five different radiographic manifestations and analyze their association with the clinical parameters of systemic involvement and infectivity.141 HIV-negative adults with newly diagnosed sputum smear-positive PTB were enrolled in a prospective observational study in Hyderabad, India. The presence and extent on CXRs of five radiographic manifestations, i.e., lung involvement, alveolar infiltration, cavitation, lymphadenopathy and pleural effusion, were classified using the new reading scheme by using a four-quadrant approach. We evaluated the inter-reader reliability of each manifestation, and its association with BMI and sputum smear positivity at diagnosis. The presence and extent of these radiographic manifestations were further compared with CXRs on completion of DOTS treatment.At diagnosis, an average lung area of 51.7% +/- 23.3% was affected by radiographic abnormalities. 94% of the patients had alveolar infiltrates, with 89.4% located in the upper quadrants, suggesting post primary PTB and in 34.8% of patients cavities were found. We further showed that the extent of affected lung area was a negative predictor of BMI (β value -0.035, p 0.019). No significant association of BMI with any of the other CXR features was found. The extent of alveolar infiltrates, along with the presence of cavitation, were strongly associated with sputum smear positivity. The microbiological cure rate in our cohort after 6 months of DOTS treatment was 95%. The extent of the affected lung area in these patients decreased from 56.0% +/- 21.5% to 31.0 +/- 20% and a decrease was also observed in the extent of alveolar infiltrates from 98.4% to 25.8% in at least one quadrant, presence of cavities from 34.8% to 1.6%, lymphadenopathy from 46.8% to 16.1%, and pleural effusion from 19.4% to 6.5%.We established a new assessment scheme for grading disease severity in PTB by specifically considering five radiographic manifestations which were differently associated with the BMI and sputum smear positivity, changed to a different extent after 6 months of treatment and exhibited an excellent agreement between radiologists. Our results suggest that this reading scheme might contribute to the estimation of disease severity with respect to differences in disease pathology. Further studies are needed to determine a correlation with short and long-term pulmonary function impairment and whether there would be any benefit in lengthening or modulating therapy based on this CXR severity assessment

Gásir in Eyjafjörđur: International Exchange and Local Economy in Medieval Iceland

The site of Gásir in Eyjafjörður in northeast Iceland was excavated from 2001–2006, revealing details of one of the larger seasonal trading centers of medieval Iceland. Interdisciplinary investigations of the site have shed light upon the organization of the site and provided confirmation of documentary accounts of both prestige items (gyrfalcons, walrus ivory) and bulk goods (sulphur) concentrated for export. Gásir was a major point of cultural contact as well as economic exchange between Icelanders and the world of medieval Europe, and the zooarchaeological analyses indicated a mix of foodways and the presence of exotic animals and a well-developed provisioning system, which supplied high-quality meat and fresh fish to the traders. The excavations demonstrated an unexpected regional-level economic impact of the seasonally occupied site on the surrounding rural countryside, and contribute to ongoing investigations of the extent and impact of overseas trade in medieval Iceland

GeSn lasers for monolithic integration on Si

Lasing under optical pumping is shown in suspended GeSn microdisks fabricated on a Ge virtual substrate with a lasing threshold below 1 mW at 20K

Early and Middle Holocene Hunter-Gatherer Occupations in Western Amazonia: The Hidden Shell Middens

We report on previously unknown early archaeological sites in the Bolivian lowlands, demonstrating for the first time early and middle Holocene human presence in western Amazonia. Multidisciplinary research in forest islands situated in seasonally-inundated savannahs has revealed stratified shell middens produced by human foragers as early as 10,000 years ago, making them the oldest archaeological sites in the region. The absence of stone resources and partial burial by recent alluvial sediments has meant that these kinds of deposits have, until now, remained unidentified. We conducted core sampling, archaeological excavations and an interdisciplinary study of the stratigraphy and recovered materials from three shell midden mounds. Based on multiple lines of evidence, including radiocarbon dating, sedimentary proxies (elements, steroids and black carbon), micromorphology and faunal analysis, we demonstrate the anthropogenic origin and antiquity of these sites. In a tropical and geomorphologically active landscape often considered challenging both for early human occupation and for the preservation of hunter-gatherer sites, the newly discovered shell middens provide evidence for early to middle Holocene occupation and illustrate the potential for identifying and interpreting early open-air archaeological sites in western Amazonia. The existence of early hunter-gatherer sites in the Bolivian lowlands sheds new light on the region's past and offers a new context within which the late Holocene "Earthmovers" of the Llanos de Moxos could have emerged. © 2013 Lombardo et al

Gluten sensitivity enteropathy in patients with recurrent aphthous stomatitis

<p>Abstract</p> <p>Background</p> <p>Gluten sensitive enteropathy (GSE) is an autoimmune enteropathy triggered by the ingestion of gluten-containing grains in susceptible individuals. Recurrent aphthous stomatitis (RAS) may be the sole manifestation of GSE. The aim of this study was to determine the prevalence of gluten sensitivity enteropathy (GSE) in a large group of patients with RAS and assess the efficacy of gluten free diet (GFD) on the improvement of aphthous lesions in those who were diagnosed with GSE.</p> <p>Methods</p> <p>Two hundred and forty seven patients with RAS were included. The patients had at least three aphthous attacks per year. Patients were screened by IgA anti-endomysial antibody (EMA), IgA anti tissue transglutaminase (TTG) and serum IgA level. Those with a positive serology underwent endoscopic biopsies of the duodenal mucosa and patients with negative serology were excluded. The diagnosis of GSE was based on a positive serological test and abnormal duodenal histology. For patients with GSE, gluten free diet was recommended.</p> <p>Results</p> <p>Six out of 247 RAS patients had positive TTG test alone, and one had positive EMA and TTG. All 7 patients with positive serologic tests underwent duodenal biopsies. Histological findings were compatible with GSE in all of them (Marsh I in four patients, Marsh II in two patients and Marsh IIIB in one another.). The mean age of GSE patients was 27.42 ± 10.56 (range, 13 to 40) years old. They were suffering from RAS for an average duration of 4.5 years. All of the 7 GSE patients had not responded to the routine anti-aphthae medications, including topical corticosteroids, tetracycline and colchicine. Four patients who adhered to a strict gluten-free diet showed noticeable improvement in their aphthous lesions over a period of 6 months.</p> <p>Conclusion</p> <p>A significant minority (e.g. 2.83%) of RAS patients have GSE. This could be compared with the 0.9% prevalence of GSE in the general population of Iran. This study suggests that evaluation for celiac disease is appropriate in patients with RAS. Additionally, the unresponsiveness to conventional anti-aphthae treatment could be an additional risk indicator.</p