Exploring the origin of ice-filled craters in the north polar region of Mars

We investigate the origins of enigmatic ice-filled craters in the north polar region of Mars. We test several explanations for their origin, namely: (1) as polar cap remnants (2) accumulation independently of the polar cap, and (3) upwelling of subsurface water, analogous to either aufice or pingo formation on Earth. Each of these hypotheses has a significant impact on our understanding of Mars’ recent geological and climatic history and the behaviour of water and water ice at high latitudes. We used several lines of evidence to assess the most likely formation mechanism. We first performed a crater survey based on THEMIS visual data and MOLA elevation data to identify any craters that had domal central lumps which were different from normal central peaks. From this survey we identified 17 craters for further study. These include Louth, Korolev, Dokka and other unnamed craters. Using data from orbiting spectrometers; OMEGA on ESA’s Mars Express and CRISM on NASA’s Mars Reconnaissance Orbiter; we verified that the composition of the exposed central domes was predominantly water ice. We found the domes fell into three groups: (1) those completely covered by dunes, (2) those partially covered by dunes and (3) those with no dunes. We investigated the morphology and the relative position of the domes using MOLA elevation data. We found that the domes are always asymmetrically placed within the craters. However, this asymmetry could not easily be linked to wind directions as revealed by dune slip-faces [2]. The domes often have a moat-like structure and in some cases do not cover the entire crater floor, e.g. Louth Crater. From image data, we identified six craters which possessed internal stratigraphy, in the form of regularly spaced layers, and of these we have inspected three in detail. We found that the layers possess both strong sinuosity and high angle unconformities. We interpret the internal stratigraphy as representing a sequence of regular cyclic accumulations, which produced the layers, followed by asymmetric ablation and subsequent resumption of accumulation, to produce the unconformities. Hence, the present-day shape of the domes indicates that they are in a phase of ablation.We attribute the colour contrasts between layers to different levels of dust, or particulate content. This could form a source for the dunes, which are often located on the summits of these domes. We find that this sequence is best explained by a model of atmospheric condensation. Our measurements of internal layer spacing and observations of layer stratigraphy argues that these deposits are not linked directly to a former, more extensive polar cap

Evolution of the rates of mass wasting and fluvial sediment transfer from the epicentral area of the 1999, Mw 7.6 earthquake

The 1999 Chichi earthquake (Mw=7.6) triggered more than 20,000 landslides in the epicentral area in central west Taiwan, and subsequent typhoons have caused an even larger number of slope failures. As a result, the suspended sediment load of the epi- central Choshui River has increased dramatically. Measurements of suspended sedi- ment at a downstream gauging station indicate that the unit sediment concentration increased about six times due to the earthquake, and decreased exponentially due to flushing by subsequent typhoons. The e-folding time scale of the seismic perturbation of sediment transfer in the Choshui River is 3-5 years. Based on this estimate of the de- cay of the erosional response to the earthquake, a mass balance can be calculated for the earthquake, including co-seismic uplift and subsidence, post-seismic relaxation, and erosion. This mass balance shows that the Chi-Chi earthquake has acted to build ridge topography in the hanging wall of the fault, but in the far field, some destruc- tion of topography has occurred. However, our estimate of seismically-driven erosion may be incomplete. A detailed analysis of landsliding in the Chenyoulan tributary of the Choshui River indicates that most co-and post seismic landslide debris remains on hillslopes within the catchment. Recent typhoons have continued to cause high rates of landsliding high in the landscape, but rates of mass wasting near the stream net- work have decreased. The full geomorphic response to the Chi-Chi earthquake may be much larger, and more protracted than indicated by river gauging data

Functional asymmetry of transmembrane segments in nicotinic acetylcholine receptors

Nicotinic acetylcholine receptors are heteropentameric ion channels that open upon activation to a single conducting state. The second transmembrane segments of each subunit were identified as channel-forming elements, but their respective contribution in the gating process remains unclear. Moreover, the detailed impact of variations of the membrane potential, such as occurring during an action potential, on the transmembrane domains, is unknown. Residues at the 12′ position, close to the center of each second transmembrane segment, play a key role in channel gating. We examined their functional symmetry by substituting a lysine to that position of each subunit and measuring the electrical activity of single channels. For 12′ lysines in the α, γ and δ subunits rapid transitions between an intermediate and large conductance appeared, which are interpreted as single lysine protonation events. From the kinetics of these transitions we calculated the pK a values of respective lysines and showed that they vary differently with membrane hyperpolarization. Respective mutations in β or ε subunits gave receptors with openings of either intermediate or large conductance, suggesting extreme pK a values in two open state conformations. The results demonstrate that these parts of the highly homologous transmembrane domains, as probed by the 12′ lysines, sense unequal microenvironments and are differently affected by physiologically relevant voltage changes. Moreover, observation of various gating events for mutants of α subunits suggests that the open channel pore exists in multiple conformations, which in turn supports the notion of functional asymmetry of the channe

A lifelong study of a pack Rhodesian ridgeback dogs reveals subclinical and clinical tick-borne Anaplasma phagocytophilum infections with possible reinfection or persistence.

Various tick-borne infections often occur without specific clinical signs and are therefore notoriously hard to diagnose separately in veterinary practice. Longitudinal studies over multiple tick seasons performing clinical, serological and molecular investigations in parallel, may elucidate the relationship between infection and disease. In this regard, six related Rhodesian Ridgeback dogs living as a pack became subject of lifetime studies due to ongoing tick infestations and recurring clinical problems. Blood samples for diagnostic tests were obtained throughout the years 2000 to 2009

Axillary plexus blockade in microvascular surgery, a steal phenomenon?

A case report is presented of an axillary plexus blockade following a second toe-to-hand transfer. After completion of the microvascular anastomoses and restoration of blood flow to the transplanted toe, the axillary plexus blockade was started. Together with the vasodilation of the hand and forearm there was a marked drop in blood flow in the transplanted toe. Possible explanations for this phenomenon are considered. We suggest starting axillary plexus blockade before completion of microvascular anastomoses and maintaining a continuous postoperative blockade

Redistribution of multi-phase particulate organic carbon in a marine shelf and canyon system during an exceptional river flood: Effects of Typhoon Morakot on the Gaoping River-Canyon system

This is the final published version of the article. It was originally published in Marine Geology (Sparkes RB, Lin I-T, Hovius N, Galy A, Liu JT, Xu X, Yang R, Marine Geology 2015, 363, 191–201, doi:10.1016/j.margeo.2015.02.013) http://dx.doi.org/10.1016/j.margeo.2015.02.013Volumetrically, turbidity currents are the prime suppliers of sediment to the deep sea, and conveyors of organic carbon from the terrestrial biosphere and submarine shelf into marine depositional basins. They result from complex processes of erosion, transport and deposition that can be difficult to study in detail. Here we present data from the Gaoping submarine canyon system, off SW Taiwan, which was perturbed in 2009 by the addition of flood deposits following Typhoon Morakot and sampled by gravity coring less than 2 months after the event. We use the different origins of organic carbon, distinguished by their carbon and nitrogen concentrations and δ13C and δ15N isotopic composition, to compare and contrast standard and extreme sedimentological conditions. Using well-constrained end-members, the results were de-convolved into inputs of metamorphic and sedimentary fossil organic carbon eroded within the Gaoping River basin, terrestrial non-fossil carbon and marine organic matter. In the upper Gaoping Canyon, sedimentation is dominated by the highly-localised hyperpycnal input of river washload and submarine sediment slumps, each associated with extensive flooding following Typhoon Morakot, whilst the shelf experienced deposition and reworking of hemi-pelagic marine sediments. A terrestrial signal is also found in the core-top of a fine-grained shelf sample over 20 km from the Gaoping Canyon, in a region normally dominated by marine carbon deposition, showing that Morakot was an unusually large flood event. Conversely, sediment from just above the canyon thalweg contains 0.23 wt.% depth-averaged marine organic carbon (37% of the TOC content) implying that terrestrial OC-dominated turbidites are tightly constrained within the canyon. Hyperpycnal processes can lead to the rapid and efficient transport of both terrestrial and submarine sediments to more permanent burial locations.RS was supported by an Engineering and Physical Sciences Research Council (EP/P502365/1 and EP/P504120/1) studentship. JTL was supported by grant number NSC95-2745-M-110-001 for the Fate of Terrestrial–Nonterrestrial Sediments in High Yield Particle–Export River–Sea Systems Program, which provided the cores in this study. We thank Peter Talling for his insightful and constructive comments on the manuscript and a further, anonymous reviewer for generous endorsement

Preaxial polydactyly of the foot: Clinical and genetic implications for the orthopedic practice based on a literature review and 76 patients

Background and purpose — Preaxial polydactyly of the foot is a rare malformation and clinicians are often unfamiliar with the associated malformations and syndromes. In order to give guidelines for diagnostics and referral to a clinical geneticist, we provide an overview of the presentation using a literature review and our own patient population. Patients and methods — The literature review was based on the Human Phenotype Ontology (HPO) project. From the HPO dataset, all phenotypes describing preaxial polydactyly were obtained and related diseases were identified and selected. An overview was generated in a heatmap, in which the phenotypic contribution of 12 anatomical groups to each disease is displayed. Clinical cases were obtained from our hospital database a