A Second Large Subglacial Impact Crater in Northwest Greenland?

Following the discovery of the Hiawatha impact crater beneath the northwest margin of the Greenland Ice Sheet, we explored satellite and aerogeophysical data in search of additional such craters. Here we report the discovery of a possible second subglacial impact crater that is 36.5 km wide and 183 km southeast of the Hiawatha impact crater. Although buried by 2 km of ice, the structure's rim induces a conspicuously circular surface expression, it possesses a central uplift and it causes a negative gravity anomaly. The existence of two closely-spaced and similarlysized complex craters raises the possibility that they formed during related impact events. However, the second structure's morphology is shallower, its overlying ice is conformal and older, and such an event can be explained by chance. We conclude that the identified structure is very likely an impact crater, but it is unlikely to be a twin of the Hiawatha impact crater

Minimal-change renal disease and Graves’ disease: a case report and literature review

Objective: To describe a possible association between Graves' disease and nephrotic syndrome secondary to minimal change renal disease and to review the literature related to renal diseases in patients with Graves' disease. Methods: The clinical, laboratory, and renal biopsy findings in a patient with Graves' disease and minimal change renal disease are discussed. In addition, the pertinent English-language literature published from 1966 to 2009, determined by means of a MEDLINE search, is reviewed. Results: A 63-year-old man who was admitted to the hospital with nephrotic syndrome. Patient had a history of Graves' disease for last 2 years with associated ophthalmopathy. He had been treated with methimazole and low low-dose steroids (prednisone 5 mg daily). Examination revealed generalized oedemaedema and exophthalmoses. Laboratory tests showed 6.62 g/day of proteinuria. Antinuclear antibodies, anti-glomerular basement membrane antibodies, antineutrophil cytoplasmic antibody (ANCA), serum complement levels, cryoglobulin, hepatitis screen and serum and urine protein electrophoreses were normal. A kidney biopsy revealed features consistent with minimal change disease on light, immunofluorescence, and electron microscopy. The patient had an excellent clinical and laboratory response after treatment with steroids and near total thyroidectomy. Conclusions: To the best of our knowledge, this is the fourth report of the occurrence of minimal change disease in a patient with Graves' disease in the absence of any other immunologic disorder known to be associated with minimal change renal disease

Excess noise in GaAs and AlGaAs avalanche photodiodes with GaSb absorption regions—composite structures grown using interfacial misfit arrays

Interfacial misfit arrays were embedded within two avalanche photodiode (APD) structures. This allowed GaSb absorption layers to be combined with wide-bandgap multiplication regions, consisting of GaAs and Al0.8Ga0.2As, respectively. The GaAs APD represents the simplest case. The Al0.8Ga0.2As APD shows reduced dark currents of 5.07 μAcm−2 at 90% of the breakdown voltage, and values for effective below 0.2. Random-path-length modeled excess noise is compared with experimental data, for both samples. The designs could be developed further, allowing operation to be extended to longer wavelengths, using other established absorber materials which are lattice matched to GaSb

Relative Humidity on Mars: New Results From the Phoenix TECP Sensor

In situ measurements of relative humidity (RH) on Mars have only been performed by the Phoenix (PHX) and Mars Science Laboratory (MSL) missions. Here we present results of our recalibration of the PHX thermal and electrical conductivity probe (TECP) RH sensor. This recalibration was conducted using a TECP engineering model subjected to the full range of environmental conditions at the PHX landing site in the Michigan Mars Environmental Chamber. The experiments focused on the warmest and driest conditions (daytime) because they were not covered in the original calibration (Zent et al., 2010, https://doi.org/10.1029/2009JE003420) and previous recalibration (Zent et al., 2016, https://doi.org/10.1002/2015JE004933). In nighttime conditions, our results are in excellent agreement with the previous 2016 recalibration, while in daytime conditions, our results show larger water vapor pressure values. We obtain vapor pressure values in the range ~0.005–1.4 Pa, while Zent et al. (2016, https://doi.org/10.1002/2015JE004933) obtain values in the range ~0.004–0.4 Pa. Our higher daytime values are in better agreement with independent estimates from the ground by the PHX Surface Stereo Imager instrument and from orbit by Compact Reconnaissance Imaging Spectrometer for Mars. Our results imply larger day‐to‐night ratios of water vapor pressure at PHX compared to MSL, suggesting a stronger atmosphere‐regolith interchange in the Martian arctic than at lower latitudes. Further, they indicate that brine formation at the PHX landing site via deliquescence can be achieved only temporarily between midnight and 6 a.m. on a few sols. The results from our recalibration are important because they shed light on the near‐surface humidity environment on Mars.Key PointsWe have recalibrated the relative humidity sensor of the Mars Phoenix landerWe obtain water vapor pressure values in the range ~0.005–1.4 Pa, while in previous recalibrations, values in the range ~0.004–0.4 PaOur results show a two‐order‐of‐magnitude diurnal variation of water vapor pressure, suggesting a strong atmosphere‐regolith interchangePlain Language SummaryWe present our recalibration of Phoenix’s humidity sensor. This recalibration was conducted with a copy of the sensor subjected to the environmental conditions at the Phoenix landing site. Our experiments focus on the warmest and driest conditions because they were not covered in previous calibrations. Our recalibration shows daytime water content values one order of magnitude larger than those in the previous calibration. At nighttime conditions, our results are in excellent agreement with the previous calibration. Our higher daytime values are in better agreement with independent estimates from the ground, and from orbit. Our results imply larger diurnal variations of water content at Phoenix compared to Curiosity, suggesting a stronger atmosphere‐soil interchange in the Martian arctic than at lower latitudes. Further, they indicate that environmental conditions favorable for the formation of saline solutions (brine) are only achieved temporarily between midnight and 6 a.m. on a few Martian days. The results from our recalibration are important because measurements of humidity on the Martian surface are needed to shed light on the local and global water cycle of Mars, and so far, only the Phoenix mission in the arctic region and the Curiosity rover at equatorial latitudes have performed such measurements.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153252/1/jgre21230.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153252/2/jgre21230_am.pd

Reversible suppression of an essential gene in adult mice using transgenic RNA interference

RNAi has revolutionized loss-of-function genetics by enabling sequence-specific suppression of virtually any gene. Furthermore, tetracycline response elements (TRE) can drive expression of short hairpin RNAs (shRNAs) for inducible and reversible target gene suppression. Here, we demonstrate the feasibility of transgenic inducible RNAi for suppression of essential genes. We set out to directly target cell proliferation by screening an RNAi library against DNA replication factors and identified multiple shRNAs against Replication Protein A, subunit 3 (RPA3). We generated transgenic mice with TRE-driven Rpa3 shRNAs whose expression enforced a reversible cell cycle arrest. In adult mice, the block in cell proliferation caused rapid atrophy of the intestinal epithelium which led to weight loss and lethality within 8-11 d of shRNA induction. Upon shRNA withdrawal, villus atrophy and weight loss were fully reversible. Thus, shRpa3 transgenic mice provide an interesting tool to study tissue maintenance and regeneration. Overall, we have established a robust system that serves the purpose of temperature-sensitive alleles in other model organisms, enabling inducible and reversible suppression of essential genes in a mammalian system

Statistical Modeling of the Default Mode Brain Network Reveals a Segregated Highway Structure

We investigate the functional organization of the Default Mode Network (DMN) – an important subnetwork within the brain associated with a wide range of higher-order cognitive functions. While past work has shown the whole-brain network of functional connectivity follows small-world organizational principles, subnetwork structure is less well understood. Current statistical tools, however, are not suited to quantifying the operating characteristics of functional networks as they often require threshold censoring of information and do not allow for inferential testing of the role that local processes play in determining network structure. Here, we develop the correlation Generalized Exponential Random Graph Model (cGERGM) – a statistical network model that uses local processes to capture the emergent structural properties of correlation networks without loss of information. Examining the DMN with the cGERGM, we show that, rather than demonstrating small-world properties, the DMN appears to be organized according to principles of a segregated highway – suggesting it is optimized for function-specific coordination between brain regions as opposed to information integration across the DMN. We further validate our findings through assessing the power and accuracy of the cGERGM on a testbed of simulated networks representing various commonly observed brain architectures

Clinical Blood Flow Quantification with Segmented k-Space Magnetic Resonance Phase Velocity Mapping

To evaluate the accuracy of segmented k-space magnetic resonance phase velocity mapping (PVM) in quantifying aortic blood flow from through-plane velocity measurements. Two segmented PVM schemes were evaluated, one with seven lines per segment (seg-7) and one with nine lines per segment (seg-9), in twenty patients with cardiovascular disease. A non-segmented (non-seg) PVM acquisition was also performed to provide the reference data. There was agreement between the aortic flow curves acquired with segmented and non-segmented PVM. The calculated systolic and total flow volume per cycle from the seg-7 and the seg-9 scans correlated and agreed with the flow volumes from the non-seg scans (differences \u3c 5%). Sign tests showed that there were no statistically significant differences (P-values \u3c 0.05) between the segmented and the non-segmented PVM measurements. Seg-9, which was the fastest among the three sequences, provided adequate spatial and temporal resolution (\u3e 10 phases per cycle)

Planar Procrustes analysis of tooth shape

Abstract Accurate quantification of variation in tooth shape is important in studies of dental development, which typically have involved measuring distances between subjectively identified landmarks, key points of correspondence on teeth. An established statistical framework now exists for the analysis of shape when objects are represented as configurations of landmark coordinates; allowing work with the full geometry of objects, which is otherwise lost. This approach was introduced here to the study of tooth morphology, demonstrating how after optimally matching shapes to account for the unwanted effects of location, scale and rotation, most standard descriptive and inferential statistical techniques can be adapted and applied successfully. The techniques are illustrated using a sample of buccal-surface images of central incisors from patients with hypodontia; a significant difference is found in mean buccal-surface shape (Hotelling's two-sample T 2 -test; P=0.004) when compared to a corresponding control group. Successful implementation of these methods depends on the accuracy and reliability with which the landmarks are collected; issues and problems to be addressed are discussed

Development and Pilot Feasibility Study of a Health Information Technology Tool to Calculate Mortality Risk for Patients with Asymptomatic Carotid Stenosis: The Carotid Risk Assessment Tool (CARAT)

Patients with no history of stroke but with stenosis of the carotid arteries can reduce the risk of future stroke with surgery or stenting. At present, a physicians’ ability to recommend optimal treatments based on an individual’s risk profile requires estimating the likelihood that a patient will have a poor peri-operative outcomes and the likelihood that the patient will survive long enough to gain benefit from the procedure. We describe the development of the CArotid Risk Assessment Tool (CARAT) into a 2-year mortality risk calculator within the electronic medical record, integrating the tool into the clinical workflow, training the clinical team to use the tool, and assessing the feasibility and acceptability of the tool in one clinic setting

Curricular orientations to real-world contexts in mathematics

A common claim about mathematics education is that it should equip students to use mathematics in the ‘real world’. In this paper, we examine how relationships between mathematics education and the real world are materialised in the curriculum across a sample of eleven jurisdictions. In particular, we address the orientation of the curriculum towards application of mathematics, the ways that real-world contexts are positioned within the curriculum content, the ways in which different groups of students are expected to engage with real-world contexts, and the extent to which high-stakes assessments include real-world problem solving. The analysis reveals variation across jurisdictions and some lack of coherence between official orientations towards use of mathematics in the real world and the ways that this is materialised in the organisation of the content for students