2,266 research outputs found

    Convective Fingering of an Autocatalytic Reaction Front

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    We report experimental observations of the convection-driven fingering instability of an iodate-arsenous acid chemical reaction front. The front propagated upward in a vertical slab; the thickness of the slab was varied to control the degree of instability. We observed the onset and subsequent nonlinear evolution of the fingers, which were made visible by a {\it p}H indicator. We measured the spacing of the fingers during their initial stages and compared this to the wavelength of the fastest growing linear mode predicted by the stability analysis of Huang {\it et. al.} [{\it Phys. Rev. E}, {\bf 48}, 4378 (1993), and unpublished]. We find agreement with the thickness dependence predicted by the theory.Comment: 11 pages, RevTex with 3 eps figures. To be published in Phys Rev E, [email protected], [email protected], [email protected]

    Refractory Thrombocytopenia During Liver Transplantation Requiring Splenectomy

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    Although thrombocytopenia is common in end-stage liver disease, severe, refractory thrombocytopenia during liver transplantation is rare, and if immune based, usually presents months or years later. This case describes an adult woman in whom preoperative evaluation had not determined an immune-related cause of thrombocytopenia. Clot strength was dramatically impaired as measured by thrombelastography during the transplant. Following a lack of response to repeat platelet transfusions, splenectomy was performed after graft reperfusion with rapid temporal restoration of clot strength. This case shows a severe manifestation of perioperative thrombocytopenia during liver transplantation and clinically guided management when measured clot strength is too low for accurate determination

    Aerodynamic flight evaluation analysis and data base update

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    Research was conducted to determine the feasibility of replacing the Solid Rocket Boosters on the existing Space Shuttle Launch Vehicle (SSLV) with Liquid Rocket Boosters (LRB). As a part of the LRB selection process, a series of wind tunnel tests were conducted along with aero studies to determine the effects of different LRB configurations on the SSLV. Final results were tabulated into increments and added to the existing SSLV data base. The research conducted in this study was taken from a series of wind tunnel tests conducted at Marshall's 14-inch Trisonic Wind Tunnel. The effects on the axial force (CAF), normal force (CNF), pitching moment (CMF), side force (CY), wing shear force (CSR), wing torque moment (CTR), and wing bending moment (CBR) coefficients were investigated for a number of candidate LRB configurations. The aero effects due to LRB protuberances, ET/LRB separation distance, and aft skirts were also gathered from the tests. Analysis was also conducted to investigate the base pressure and plume effects due to the new booster geometries. The test results found in Phases 1 and 2 of wind tunnel testing are discussed and compared. Preliminary LRB lateral/directional data results and trends are given. The protuberance and gap/skirt effects are discussed. The base pressure/plume effects study is discussed and results are given

    Computing the zeros of the partial sums of the Riemann zeta function

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    In this paper, we introduce a formula for the exact number of zeros of every partial sum of the Riemann zeta function inside infinitely many rectangles of the critical strips where they are situated

    A Prototype Front-End Readout Chip for Silicon Microstrip Detectors Using an Advanced SiGe Technology

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    The upgrade of the ATLAS detector for the high luminosity upgrade of the LHC will require a rebuild of the Inner Detector as well as replacement of the readout electronics of the Liquid Argon Calorimeter and other detector components. We proposed some time ago to study silicon germanium (SiGe) BiCMOS technologies as a possible choice for the required silicon microstrip and calorimeter front-end chips given that they showed promise to provide necessary low noise at low power. Evaluation of the radiation hardness of these technologies has been under study. To validate the expected performance of these technologies, we designed and fabricated an 8-channel front-end readout chip for a silicon microstrip detector using the IBM 8WL technology, a likely choice for the ATLAS upgrade. Preliminary electrical characteristics of this chip will be presented

    Magnitude and frequency variations of vector-borne infection outbreaks using the Ross–Macdonald model : explaining and predicting outbreaks of dengue fever

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    The classical Ross–Macdonald model is often utilized to model vector-borne infections; however, this model fails on several fronts. First, using measured (or estimated) parameters, which values are accepted from the literature, the model predicts a much greater number of cases than what is usually observed. Second, the model predicts a single large outbreak that is followed by decades of much smaller outbreaks, which is not consistent with what is observed. Usually towns or cities report a number of recurrences for many years, even when environmental changes cannot explain the disappearance of the infection between the peaks. In this paper, we continue to examine the pitfalls in modelling this class of infections, and explain that, if properly used, the Ross–Macdonald model works and can be used to understand the patterns of epidemics and even, to some extent, be used to make predictions.We model several outbreaks of dengue fever and show that the variable pattern of yearly recurrence (or its absence) can be understood and explained by a simple Ross–Macdonald model modified to take into account human movement across a range of neighbourhoods within a city. In addition, we analyse the effect of seasonal variations in the parameters that determine the number, longevity and biting behaviour of mosquitoes. Based on the size of the first outbreak, we show that it is possible to estimate the proportion of the remaining susceptible individuals and to predict the likelihood and magnitude of the eventual subsequent outbreaks. This approach is described based on actual dengue outbreaks with different recurrence patterns from some Brazilian regions

    The lncRNA landscape of breast cancer reveals a role for DSCAM-AS1 in breast cancer progression.

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    Molecular classification of cancers into subtypes has resulted in an advance in our understanding of tumour biology and treatment response across multiple tumour types. However, to date, cancer profiling has largely focused on protein-coding genes, which comprise <1% of the genome. Here we leverage a compendium of 58,648 long noncoding RNAs (lncRNAs) to subtype 947 breast cancer samples. We show that lncRNA-based profiling categorizes breast tumours by their known molecular subtypes in breast cancer. We identify a cohort of breast cancer-associated and oestrogen-regulated lncRNAs, and investigate the role of the top prioritized oestrogen receptor (ER)-regulated lncRNA, DSCAM-AS1. We demonstrate that DSCAM-AS1 mediates tumour progression and tamoxifen resistance and identify hnRNPL as an interacting protein involved in the mechanism of DSCAM-AS1 action. By highlighting the role of DSCAM-AS1 in breast cancer biology and treatment resistance, this study provides insight into the potential clinical implications of lncRNAs in breast cancer

    A Chromosome-Length Reference Genome for the Endangered Pacific Pocket Mouse Reveals Recent Inbreeding in a Historically Large Population

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    High-quality reference genomes are fundamental tools for understanding population history, and can provide estimates of genetic and demographic parameters relevant to the conservation of biodiversity. The federally endangered Pacific pocket mouse (PPM), which persists in three small, isolated populations in southern California, is a promising model for studying how demographic history shapes genetic diversity, and how diversity in turn may influence extinction risk. To facilitate these studies in PPM, we combined PacBio HiFi long reads with Omni-C and Hi-C data to generate a de novo genome assembly, and annotated the genome using RNAseq. The assembly comprised 28 chromosome-length scaffolds (N50 = 72.6 MB) and the complete mitochondrial genome, and included a long heterochromatic region on chromosome 18 not represented in the previously available short-read assembly. Heterozygosity was highly variable across the genome of the reference individual, with 18% of windows falling in runs of homozygosity (ROH) >1 MB, and nearly 9% in tracts spanning >5 MB. Yet outside of ROH, heterozygosity was relatively high (0.0027), and historical Ne estimates were large. These patterns of genetic variation suggest recent inbreeding in a formerly large population. Currently the most contiguous assembly for a heteromyid rodent, this reference genome provides insight into the past and recent demographic history of the population, and will be a critical tool for management and future studies of outbreeding depression, inbreeding depression, and genetic load

    Lobster Attack Induces Sensitization In the Sea Hare, Aplysia Californica

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    Studies of the neural mechanisms of learning, especially of sensitization, have benefitted from extensive research on the model species, Aplysia californica (hereafter Aplysia). Considering this volume of literature on mechanisms, it is surprising that our understanding of the ecological context of sensitization in Aplysia is completely lacking. Indeed, the widespread use of strong electric shock to induce sensitization (an enhancement of withdrawal reflexes following noxious stimulation) is completely unnatural and leaves unanswered the question of whether this simple form of learning has any ecological relevance. We hypothesized that sublethal attack by a co-occurring predator, the spiny lobster, Panulirus interruptus, might be a natural sensitizing stimulus. We tested reflex withdrawal of the tail-mantle and head of individual Aplysia before and after attack by lobsters. Lobster attack significantly increased the amplitude of both reflexes, with a temporal onset that closely matched that observed with electric shock. This result suggests that electric shock may indeed mimic at least one naturally occurring sensitizing stimulus, suggesting, for the first time, an ecological context for this well studied form of learning
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