7,861 research outputs found

    D-brane Inspired Fermion Mass Textures

    Get PDF
    In this paper, the issues of the quark mass hierarchies and the Cabbibo Kobayashi Maskawa mixing are analyzed in a class of intersecting D-brane configurations with Standard Model gauge symmetry. The relevant mass matrices are constructed taking into account the constraints imposed by extra abelian symmetries and anomaly cancelation conditions. Possible mass generating mechanisms including perturbative as well as non-perturbative effects are discussed and specific patterns of mass textures are found characterized by the hierarchies of the scales where the various sources contribute. It is argued that the Cholesky decomposition of the mass matrices is the most appropriate way to determine the properties of these fermion mass patterns, while the associated triangular mass matrix form provides a unified description of all phenomenologically equivalent symmetric and non-symmetric mass matrices. An elegant analytic formula is derived for the Cholesky triangular form of the mass matrices where the entries are given as simple functions of the mass eigenstates and the diagonalizing transformation entries. Finally, motivated by the possibility of vanishing zero Yukawa mass entries in several D-brane and F-theory constructions due to the geometry of the internal space, we analyse in detail all possible texture-zeroes mass matrices within the proposed new context. These new texture-zeroes are compared to those existing in the literature while D-brane inspired cases are worked out in detail.Comment: 58 pages, 7 figure

    The transcriptome of the novel dinoflagellate Oxyrrhis marina (Alveolata: Dinophyceae): response to salinity examined by 454 sequencing

    Get PDF
    This is the final version of the article. Available from [BioMed Central via the DOI in this record.BACKGROUND: The heterotrophic dinoflagellate Oxyrrhis marina is increasingly studied in experimental, ecological and evolutionary contexts. Its basal phylogenetic position within the dinoflagellates make O. marina useful for understanding the origin of numerous unusual features of the dinoflagellate lineage; its broad distribution has lent O. marina to the study of protist biogeography; and nutritive flexibility and eurytopy have made it a common lab rat for the investigation of physiological responses of marine heterotrophic flagellates. Nevertheless, genome-scale resources for O. marina are scarce. Here we present a 454-based transcriptome survey for this organism. In addition, we assess sequence read abundance, as a proxy for gene expression, in response to salinity, an environmental factor potentially important in determining O. marina spatial distributions. RESULTS: Sequencing generated ~57 Mbp of data which assembled into 7, 398 contigs. Approximately 24% of contigs were nominally identified by BLAST. A further clustering of contigs (at ≥ 90% identity) revealed 164 transcript variant clusters, the largest of which (Phosphoribosylaminoimidazole-succinocarboxamide synthase) was composed of 28 variants displaying predominately synonymous variation. In a genomic context, a sample of 5 different genes were demonstrated to occur as tandem repeats, separated by short (~200-340 bp) inter-genic regions. For HSP90 several intergenic variants were detected suggesting a potentially complex genomic arrangement. In response to salinity, analysis of 454 read abundance highlighted 9 and 20 genes over or under expressed at 50 PSU, respectively. However, 454 read abundance and subsequent qPCR validation did not correlate well - suggesting that measures of gene expression via ad hoc analysis of sequence read abundance require careful interpretation. CONCLUSION: Here we indicate that tandem gene arrangements and the occurrence of multiple transcribed gene variants are common and indicate potentially complex genomic arrangements in O. marina. Comparison of the reported data set with existing O. marina and other dinoflagellates ESTs indicates little sequence overlap likely as a result of the relatively limited extent of genome scale sequence data currently available for the dinoflagellates. This is one of the first 454-based transcriptome surveys of an ancestral dinoflagellate taxon and will undoubtedly prove useful for future comparative studies aimed at reconstructing the origin of novel features of the dinoflagellates.This work was supported by a NERC grant (NE/F005237/1) awarded to PCW, DJSM, and CDL. We would like to thank Dr Margret Hughes of the Liverpool CGR for conducting 454 sequencing, and Dr Kevin Ashelford for invaluable scripting and bioinformatics support

    Vitamin D Supplementation and Pain-Related Emergency Department Visits in Children with Sickle Cell Disease

    Get PDF
    Objectives: Sickle cell disease (SCD) is the most prevalent inherited hematological disorder and affects 100,000 individuals in the United States. Pain is the most common cause of emergency department (ED) visits in the SCD population, which profoundly affects quality of life. Vitamin D supplementation is a potential target for reducing pain. Thus, the goal of the present study was to identify the prevalence of vitamin D deficiency and explore the relationship between vitamin D supplementation and ED visits in pediatric patients with SCD. / Design: We conducted a retrospective chart review of 110 patients with SCD aged 8 to 16 years who had at least one ED visit for SCD pain during the 6-year study period. Patients were categorized into three vitamin D supplementation groups: patients who did not receive supplementation, patients supplemented with 25-hydroxyvitamin D levels (< 30 ng/mL), and patients supplemented with at least one sufficient 25-hydroxyvitamin D level (≥ 30 ng/mL). / Results: Overall, 45% of patients were vitamin D deficient. Only 20% of patients had sufficient vitamin D levels. This number increased to 55% when examining only patients who did not receive vitamin D supplementation. For patients supplemented with vitamin D, the number of ED visits was significantly lower after they reached the sufficient range (≥ 30 ng/mL), p = .03. / Conclusions: Our findings indicate that reductions in the number of pain-related ED visits may be achieved by normalizing 25-hydroxyvitamin D levels with supplementation. In addition, findings highlight the need for screening and vitamin D supplementation being incorporated into routine care for pediatric patients with SCD

    Unifying CP violations of quark and lepton sectors

    Full text link
    A preliminary determination of the Dirac phase in the PMNS matrix is \dell\approx -\frac{\pi}{2}. A rather accurately determined Jarlskog invariant JJ in the CKM matrix is close to the maximum. Since the phases in the CKM and PMNS matrices will be accurately determined in the future, it is an interesting problem to relate these two phases. This can be achieved in a families-unified grand unification if the weak CP violation is introduced spontaneously {\it \`a la} Froggatt and Nielsen at a high energy scale, where only one meaningful Dirac CP phase appears.Comment: 10 pages with 3 figure

    Computer simulation of syringomyelia in dogs

    Get PDF
    Syringomyelia is a pathological condition in which fluid-filled cavities (syringes) form and expand in the spinal cord. Syringomyelia is often linked with obstruction of the craniocervical junction and a Chiari malformation, which is similar in both humans and animals. Some brachycephalic toy breed dogs such as Cavalier King Charles Spaniels (CKCS) are particularly predisposed. The exact mechanism of the formation of syringomyelia is undetermined and consequently with the lack of clinical explanation, engineers and mathematicians have resorted to computer models to identify possible physical mechanisms that can lead to syringes. We developed a computer model of the spinal cavity of a CKCS suffering from a large syrinx. The model was excited at the cranial end to simulate the movement of the cerebrospinal fluid (CSF) and the spinal cord due to the shift of blood volume in the cranium related to the cardiac cycle. To simulate the normal condition, the movement was prescribed to the CSF. To simulate the pathological condition, the movement of CSF was blocked

    In-memory computing on a photonic platform

    Get PDF
    This is the final version. Available from the publisher via the DOI in this record.All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from the authors or Oxford Research Archive for Data (https://ora.ox.ac.uk).Collocated data processing and storage are the norm in biological computing systems such as the mammalian brain. As our ability to create better hardware improves, new computational paradigms are being explored beyond von Neumann architectures. Integrated photonic circuits are an attractive solution for on-chip computing which can leverage the increased speed and bandwidth potential of the optical domain, and importantly, remove the need for electro-optical conversions. Here we show that we can combine integrated optics with collocated data storage and processing to enable all-photonic in-memory computations. By employing nonvolatile photonic elements based on the phase-change material, Ge2Sb2Te5, we achieve direct scalar and matrix-vector multiplication, featuring a novel single-shot Write/Erase and a drift-free process. The output pulse, carrying the information of the light-matter interaction, is the result of the computation. Our all-optical approach is novel, easy to fabricate and operate, and sets the stage for development of entirely photonic computers.Engineering and Physical Sciences Research Council (EPSRC)Deutsche Forschungsgemeinschaft (DFG)European Research Council (ERC

    Mine closure of pit lakes as terminal sinks: best available practice when options are limited?

    Get PDF
    In an arid climate, pit lake evaporation rates can exceed influx rates, causing the lake to function as a hydraulic terminal sink, with water levels in the pit remaining below surrounding groundwater levels. We present case studies from Western Australia for two mines nearing closure. At the first site, modelling indicates that waste dump covers for the potentially acid forming (PAF) material would not be successful over the long term (1,000 years or more). The second site is a case study where PAF management is limited by the current waste rock dump location and suitable cover materials. Pit lake water balance modelling using Goldsim software indicated that both pit lakes would function as hydraulic terminal sinks if not backfilled above long-term equilibrium water levels. Poor water quality will likely develop as evapoconcentration increases contaminant concentrations, providing a potential threat to local wildlife. Even so, the best current opportunity to limit the risk of contaminant migration and protect regional groundwater environments may be to limit backfill and intentionally produce a terminal sink pit lake

    Multisite pain and self-reported falls in older people: systematic review and meta-analysis.

    Get PDF
    BACKGROUND: Multisite pain and falls are common in older people, and isolated studies have identified multisite pain as a potential falls risk factor. This study aims to synthesise published literature to further explore the relationship between multisite pain and falls and to quantify associated risks. METHODS: Bibliographic databases were searched from inception to December 2017. Studies of community-dwelling adults aged 50 years and older with a multisite pain measurement and a falls outcome were included. Two reviewers screened articles, undertook quality assessment and extracted data. Random-effects meta-analysis was used to pool the effect estimate (odds ratio (OR) and 95% confidence interval (95%CI)). Heterogeneity was assessed by I2; sensitivity analyses used adjusted risk estimates and exclusively longitudinal studies. RESULTS: The search identified 49,577 articles, 3145 underwent abstract review, 22 articles were included in the systematic review and 18 were included in the meta-analysis. The unadjusted pooled OR of 1.82 (95%CI 1.55-2.13), demonstrating that those reporting multisite pain are at increased risk of falls, is supported by the adjusted pooled OR of 1.56 (95%CI 1.39-1.74). Multisite pain predicts future falls risk (OR = 1.74 (95%CI 1.57-1.93)). For high-quality studies, those reporting multisite pain have double the odds of a future fall compared to their pain-free counterparts. CONCLUSION: Multisite pain is associated with an increased future falls risk in community-dwelling older people. Increasing public awareness of multisite pain as a falls risk factor and advising health and social care professionals to identify older people with multisite pain to signpost accordingly will enable timely falls prevention strategies to be implemented

    Memristive Effects in Oxygenated Amorphous Carbon Nanodevices

    Get PDF
    This is the author accepted manuscript. The final version is available from IOP Publishing via the DOI in this record.Computing with resistive-switching (memristive) memory devices has shown much recent progress and offers an attractive route to circumvent the von-Neumann bottleneck, i.e. the separation of processing and memory, which limits the performance of conventional computer architectures. Due to their good scalability and nanosecond switching speeds, carbon-based resistive-switching memory devices could play an important role in this respect. However, devices based on elemental carbon, such as tetrahedral amorphous carbon or t-aC, typically suffer from a low cycling endurance. A material that has proven to be capable of combining the advantages of elemental carbon-based memories with simple fabrication methods and good endurance performance for binary memory applications is oxygenated amorphous carbon, or a-COx. Here, we examine the memristive capabilities of nanoscale a-COx devices, in particular their ability to provide the multilevel and accumulation properties that underpin computing type applications. We show the successful operation of nanoscale a-COx memory cells for both the storage of multilevel states (here 3-level) and for the provision of an arithmetic accumulator. We implement a base-16, or hexadecimal, accumulator and show how such a device can carry out hexadecimal arithmetic and simultaneously store the computed result in the self-same a-COx cell, all using fast (sub-10 ns) and low-energy (sub-pJ) input pulses.This work was funded by the EU Research & Innovation project CareRAMM, grant no. 30998
    • …
    corecore