5,060 research outputs found

    A diatom assessment of borehole sediments from the Jubilee Line Extension

    Get PDF
    The diatom assessment was carried out in conjunction with pollen and lithostratigraphical assessments. At this assessment stage the primary aim of the diatom evaluation was to determine, for selected samples: whether or not diatoms are present or absent; the quality of preservation of diatoms and; and to list the main species present and their ecological, particularly salinity, optima. An additional aim was to evaluate the potential use of diatom analysis in further investigations of these sediments and in particular the usefulness of diatom analysis in, qualitatively or quantitatively, reconstructing the salinity conditions under which the sediments formed. Using the preliminary conclusions of this investigation it is hoped that the diatom assessment will assist in focusing on key questions within the site stratigraphy re. salinity and sea-level during different periods of the location's development

    Comprehensive Evaluation of Peripheral Nerve Regeneration in the Acute Healing Phase Using Tissue Clearing and Optical Microscopy in a Rodent Model

    Get PDF
    Peripheral nerve injury (PNI), a common injury in both the civilian and military arenas, is usually associated with high healthcare costs and with patients enduring slow recovery times, diminished quality of life, and potential long-term disability. Patients with PNI typically undergo complex interventions but the factors that govern optimal response are not fully characterized. A fundamental understanding of the cellular and tissue-level events in the immediate postoperative period is essential for improving treatment and optimizing repair. Here, we demonstrate a comprehensive imaging approach to evaluate peripheral nerve axonal regeneration in a rodent PNI model using a tissue clearing method to improve depth penetration while preserving neural architecture. Sciatic nerve transaction and end-to-end repair were performed in both wild type and thy-1 GFP rats. The nerves were harvested at time points after repair before undergoing whole mount immunofluorescence staining and tissue clearing. By increasing the optic depth penetration, tissue clearing allowed the visualization and evaluation of Wallerian degeneration and nerve regrowth throughout entire sciatic nerves with subcellular resolution. The tissue clearing protocol did not affect immunofluorescence labeling and no observable decrease in the fluorescence signal was observed. Large-area, high-resolution tissue volumes could be quantified to provide structural and connectivity information not available from current gold-standard approaches for evaluating axonal regeneration following PNI. The results are suggestive of observed behavioral recovery in vivo after neurorrhaphy, providing a method of evaluating axonal regeneration following repair that can serve as an adjunct to current standard outcomes measurements. This study demonstrates that tissue clearing following whole mount immunofluorescence staining enables the complete visualization and quantitative evaluation of axons throughout nerves in a PNI model. The methods developed in this study could advance PNI research allowing both researchers and clinicians to further understand the individual events of axonal degeneration and regeneration on a multifaceted level

    Refined system parameters and TTV study of transiting exoplanetary system HAT-P-20

    Get PDF
    This work is supported by National Natural Science Foundation of China through grants No. U1531121, No. 10873031 and No. 11473066.We report new photometric observations of the transiting exoplanetary system HAT-P-20, obtained using CCD cameras at Yunnan Observatories and Ho Koon Nature Education cum Astronomical Centre, China, from 2010 to 2013, and Observatori Ca l'Ou, Sant Marti Sesgueioles, Spain, from 2013 to 2015. The observed data are corrected for systematic errors according to the coarse de-correlation and SYSREM algorithms, so as to enhance the signal of the transit events. In order to consistently model the star spots and transits of this exoplanetary system, we develop a highly efficient tool STMT based on the analytic models of Mandel & Agol and Montalto et al. The physical parameters of HAT-P-20 are refined by homogeneously analyzing our new data, the radial velocity data, and the earlier photometric data in the literature with the Markov chain Monte Carlo technique. New radii and masses of both host star and planet are larger than those in the discovery paper due to the discrepancy of the radius among K-dwarfs between predicted values by standard stellar models and empirical calibration from observations. Through the analysis of all available mid-transit times calculated with the normal model and spotted model, we conclude that the periodic transit timing variations in these transit events revealed by employing the normal model are probably induced by spot crossing events. From the analysis of the distribution of occulted spots by HAT-P-20b, we constrain the misaligned architecture between the planetary orbit and the spin of the host star.Publisher PDFPeer reviewe

    A fast radio burst with a low dispersion measure

    Get PDF
    Fast radio bursts (FRBs) are millisecond pulses of radio emission of seemingly extragalactic origin. More than 50 FRBs have now been detected, with only one seen to repeat. Here we present a new FRB discovery, FRB 110214, which was detected in the high latitude portion of the High Time Resolution Universe South survey at the Parkes telescope. FRB 110214 has one of the lowest dispersion measures of any known FRB (DM = 168.9±\pm0.5 pc cm3^{-3}), and was detected in two beams of the Parkes multi-beam receiver. A triangulation of the burst origin on the sky identified three possible regions in the beam pattern where it may have originated, all in sidelobes of the primary detection beam. Depending on the true location of the burst the intrinsic fluence is estimated to fall in the range of 50 -- 2000 Jy ms, making FRB 110214 one of the highest-fluence FRBs detected with the Parkes telescope. No repeating pulses were seen in almost 100 hours of follow-up observations with the Parkes telescope down to a limiting fluence of 0.3 Jy ms for a 2-ms pulse. Similar low-DM, ultra-bright FRBs may be detected in telescope sidelobes in the future, making careful modeling of multi-beam instrument beam patterns of utmost importance for upcoming FRB surveys.Comment: 8 pages, 3 figures, accepted for publication in MNRA

    The Sun was not born in M 67

    Full text link
    Using the most recent proper-motion determination of the old, Solar-metallicity, Galactic open cluster M 67, in orbital computations in a non-axisymmetric model of the Milky Way, including a bar and 3D spiral arms, we explore the possibility that the Sun once belonged to this cluster. We have performed Monte Carlo numerical simulations to generate the present-day orbital conditions of the Sun and M 67, and all the parameters in the Galactic model. We compute 3.5 \times 10^5 pairs of orbits Sun-M 67 looking for close encounters in the past with a minimum distance approach within the tidal radius of M 67. In these encounters we find that the relative velocity between the Sun and M 67 is larger than 20 km/s. If the Sun had been ejected from M 67 with this high velocity by means of a three-body encounter, this interaction would destroy an initial circumstellar disk around the Sun, or disperse its already formed planets. We also find a very low probability, much less than 10^-7, that the Sun was ejected from M 67 by an encounter of this cluster with a giant molecular cloud. This study also excludes the possibility that the Sun and M 67 were born in the same molecular cloud. Our dynamical results convincingly demonstrate that M67 could not have been the birth cluster of our Solar System.Comment: Astronomical Journal accepted (35 pages, 9 figures

    Who Produces for Whom in the World Economy?

    No full text
    International audienceFor two decades, the share of trade in inputs, also called vertical trade, has been dramatically increasing. In reallocating trade flows to their original input-producing industries and countries, this paper suggests a new measure of international trade: "value-added trade" and makes it possible to answer the question "who produces for whom?". In 2004, 27% of international trade was vertical trade. The industrial and geographic patterns of value-added trade are very different from those of standard trade. Value-added trade is relatively less important in regional trade but the difference is not more important for Asia than for AmericaLa part du commerce en produits intermédiaires dans le commerce international, appelé aussi "commerce vertical", n'a cessé d'augmenter depuis vingt ans. Cet article propose une nouvelle mesure du commerce international "le commerce en valeur ajoutée" qui réalloue les flux commerciaux aux pays et aux secteurs produisant les intrants. Les répartitions géographique et sectorielle du commerce en valeur ajoutée sont très différentes de celles du commerce " standard ". La différence entre le commerce en valeur ajoutée et le commerce standard est plus importante dans le cas du commerce régional mais ce n'est pas plus le cas en Asie qu'en Amérique

    Incidence and predictors of new-onset constipation during acute hospitalisation after stroke

    Get PDF
    Objectives: We investigated new-onset constipation in patients with stroke compared with orthopaedic conditions and explored the predictors associated with constipation during acute hospitalisation. Methods: This was a prospective matched cohort study of 110 patients comparing stroke patients (n = 55) with orthopaedic patients (n = 55) admitted to a large tertiary acute hospital. Both cohorts were matched by age and sex. The incidence of new-onset constipation which occurred during a patient's acute hospitalisation was determined. Demographics, comorbidity, clinical factors, laboratory parameters and medications were evaluated as possible predictors of constipation. Results: The incidence of new-onset constipation was high for both stroke (33%) and orthopaedic patients (27%; p = 0.66). Seven stroke patients (39%) and four orthopaedic patients (27%) developed their first onset of constipation on day 2 of admission. Mobility gains (RR 0.741, p < 0.001) and the use of prophylactic laxatives (RR 0.331, p < 0.01) had a protective effect against constipation. Bedpan use (RR 2.058, p < 0.05) and longer length of stay (RR 1.032, p < 0.05) increased the risk of developing new-onset constipation. Conclusions: New-onset constipation is common among patients admitted for stroke and orthopaedic conditions during acute hospitalisation. The early occurrence, on day 2 of admission, calls for prompt preventive intervention for constipation
    corecore