2,732 research outputs found

    Vascular regeneration in a basal chordate is due to the presence of immobile, bi-functional cells.

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    The source of tissue turnover during homeostasis or following injury is usually due to proliferation of a small number of resident, lineage-restricted stem cells that have the ability to amplify and differentiate into mature cell types. We are studying vascular regeneration in a chordate model organism, Botryllus schlosseri, and have previously found that following surgical ablation of the extracorporeal vasculature, new tissue will regenerate in a VEGF-dependent process within 48 hrs. Here we use a novel vascular cell lineage tracing methodology to assess regeneration in parabiosed individuals and demonstrate that the source of regenerated vasculature is due to the proliferation of pre-existing vascular resident cells and not a mobile progenitor. We also show that these cells are bi-potential, and can reversibly adopt two fates, that of the newly forming vessels or the differentiated vascular tissue at the terminus of the vasculature, known as ampullae. In addition, we show that pre-existing vascular resident cells differentially express progenitor and differentiated cell markers including the Botryllus homologs of CD133, VEGFR-2, and Cadherin during the regenerative process

    Self-Assembly in the Growth of Precious Opal

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    It is proposed that primary nucleation of amorphous microspherulites of hydrated silica in natural proto-precious-opal can be followed by a long range superlattice ordering process by means of electrostatic self-assembly. Necessary conditions in the thermodynamics are a high surface charge density on microspherulite surfaces, a long Debye length and an appropriate number density of nucleation centres. A further chemical requirement is a high alkaline environmental pH from 9 to 10. It is also proposed that the characteristic concentric spherical shell-like structure of spherulites, centred on primary nuclei, are due to sequential deposition of intrinsic salts which precipitate out when the corresponding solubility limits in the liquid are successively exceeded. It can be that the better-known sedimentation of microspherulites under gravity only plays part in the final stabilization period of overall growth.Comment: 12 pages pdf http://dx.doi.org/10.1016/j.jcrysgro.2009.09.04

    Boundary-Layer-Ingesting Inlet Flow Control

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    An experimental study was conducted to provide the first demonstration of an active flow control system for a flush-mounted inlet with significant boundary-layer-ingestion in transonic flow conditions. The effectiveness of the flow control in reducing the circumferential distortion at the engine fan-face location was assessed using a 2.5%-scale model of a boundary-layer-ingesting offset diffusing inlet. The inlet was flush mounted to the tunnel wall and ingested a large boundary layer with a boundary-layer-to-inlet height ratio of 35%. Different jet distribution patterns and jet mass flow rates were used in the inlet to control distortion. A vane configuration was also tested. Finally a hybrid vane/jet configuration was tested leveraging strengths of both types of devices. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass flow rates through the duct and the flow control actuators. The distortion and pressure recovery were measured at the aerodynamic interface plane. The data show that control jets and vanes reduce circumferential distortion to acceptable levels. The point-design vane configuration produced higher distortion levels at off-design settings. The hybrid vane/jet flow control configuration reduced the off-design distortion levels to acceptable ones and used less than 0.5% of the inlet mass flow to supply the jets

    The space physics environment data analysis system (SPEDAS)

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    With the advent of the Heliophysics/Geospace System Observatory (H/GSO), a complement of multi-spacecraft missions and ground-based observatories to study the space environment, data retrieval, analysis, and visualization of space physics data can be daunting. The Space Physics Environment Data Analysis System (SPEDAS), a grass-roots software development platform (www.spedas.org), is now officially supported by NASA Heliophysics as part of its data environment infrastructure. It serves more than a dozen space missions and ground observatories and can integrate the full complement of past and upcoming space physics missions with minimal resources, following clear, simple, and well-proven guidelines. Free, modular and configurable to the needs of individual missions, it works in both command-line (ideal for experienced users) and Graphical User Interface (GUI) mode (reducing the learning curve for first-time users). Both options have “crib-sheets,” user-command sequences in ASCII format that can facilitate record-and-repeat actions, especially for complex operations and plotting. Crib-sheets enhance scientific interactions, as users can move rapidly and accurately from exchanges of technical information on data processing to efficient discussions regarding data interpretation and science. SPEDAS can readily query and ingest all International Solar Terrestrial Physics (ISTP)-compatible products from the Space Physics Data Facility (SPDF), enabling access to a vast collection of historic and current mission data. The planned incorporation of Heliophysics Application Programmer’s Interface (HAPI) standards will facilitate data ingestion from distributed datasets that adhere to these standards. Although SPEDAS is currently Interactive Data Language (IDL)-based (and interfaces to Java-based tools such as Autoplot), efforts are under-way to expand it further to work with python (first as an interface tool and potentially even receiving an under-the-hood replacement). We review the SPEDAS development history, goals, and current implementation. We explain its “modes of use” with examples geared for users and outline its technical implementation and requirements with software developers in mind. We also describe SPEDAS personnel and software management, interfaces with other organizations, resources and support structure available to the community, and future development plans.Published versio

    The impact of computed high b-value images on the diagnostic accuracy of DWI for prostate cancer: A receiver operating characteristics analysis.

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    To evaluate the performance of computed high b value diffusion-weighted images (DWI) in prostate cancer detection. 97 consecutive patients who had undergone multiparametric MRI of the prostate followed by biopsy were reviewed. Five radiologists independently scored 138 lesions on native high b-value images (b = 1200 s/mm2), apparent diffusion coefficient (ADC) maps, and computed high b-value images (contrast equivalent to b = 2000 s/mm2) to compare their diagnostic accuracy. Receiver operating characteristic (ROC) analysis and McNemar's test were performed to assess the relative performance of computed high b value DWI, native high b-value DWI and ADC maps. No significant difference existed in the area under the curve (AUC) for ROCs comparing B1200 (b = 1200 s/mm2) to computed B2000 (c-B2000) in 5 readers. In 4 of 5 readers c-B2000 had significantly increased sensitivity and/or decreased specificity compared to B1200 (McNemar's p < 0.05), at selected thresholds of interpretation. ADC maps were less accurate than B1200 or c-B2000 for 2 of 5 readers (P < 0.05). This study detected no consistent improvement in overall diagnostic accuracy using c-B2000, compared with B1200 images. Readers detected more cancer with c-B2000 images (increased sensitivity) but also more false positive findings (decreased specificity)

    Discerning population connectivity and natal origins of Pacific herring (Clupea pallasi): inferences on population structure from otolith chemistry

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    Pacific herring, Clupea pallasi, undertake annual migrations between feeding and spawning grounds that link life stages, habitats, populations, communities, and ecosystems. However, movement patterns of these highly mobile fish are poorly understood. Declines in Pacific herring abundance and slow population recoveries in the absence of fishing pressure have elevated concerns over the status of this ecologically, economically, and culturally important species. Pacific herring spawn on substrate in nearshore habitats where eggs and larvae develop for approximately two weeks before hatching. Early development within discrete spawning grounds could facilitate the incorporation of distinctive chemical signatures within otoliths that could be used as intrinsic markers to trace movements and mixing among groups or regions. Identifying the direction and strength of connectivity among groups can reveal source populations and promote the development of population- and ecosystem-based management strategies that reflect ecologically relevant spatial scales. We applied otolith microchemistry data to: 1) test the utility of elemental signatures to distinguish the natal origins of larval herring; 2) evaluate inter-annual variation in natal signatures within spawning sites; and 3) assess the similarity of edge and natal signatures of adult herring within and among spawning sites. In 2015 and 2016, we sampled actively spawning adult herring and their offspring in the northern Salish Sea and across British Columbia, Canada. Otoliths were extracted, aged, and their elemental composition analyzed using laser ablation inductively coupled plasma mass spectrometry. Cohort-specific analyses were applied to assess consistency among elemental signatures and broader, age-specific movement patterns. Our analyses show that otolith elemental signatures of Pacific herring can provide insight into complex population structure at scales of 10s – 1000 kms to inform and enhance spatially-explicit approaches to conservation and management

    The Membership and Distance of the Open Cluster Collinder 419

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    The young open cluster Collinder 419 surrounds the massive O star, HD 193322, that is itself a remarkable multiple star system containing at least four components. Here we present a discussion of the cluster distance based upon new spectral classifications of the brighter members, UBV photometry, and an analysis of astrometric and photometric data from the UCAC3 and 2MASS catalogs. We determine an average cluster reddening of E(B-V)=0.37 +- 0.05 mag and a cluster distance of 741 +- 36 pc. The cluster probably contains some very young stars that may include a reddened M3 III star, IRAS~20161+4035

    Alterations in Redox Homeostasis During Recovery From Unexplained Underperformance Syndrome in an Elite International Rower.

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    This case study of an international rower examines a diagnosis of Unexplained Under Performance Syndrome (UUPS or Overtraining Syndrome) describing a full recovery and return to elite competition the same year. On diagnosis and 4 and 14 months post-diagnosis, detailed assessments including physiological, nutritional, and biomarkers were made. Clinical examination and laboratory results for haematology, biochemistry, thyroid function, immunology, vitamins and minerals were unremarkable and did not explain the presentation and diagnosis. Redox biomarkers including hydroperoxides, plasma antioxidant capacity, red blood cell glutathione, superoxide dismutase, co-enzyme Q10, vitamin E (α and γ-tocopherol), and carotenoids (lutein, α-carotene, β-carotene) provided evidence of altered redox homeostasis. The recovery strategy began with 12 days of training abstinence and nutritional interventions, followed by 6-weeks of modified training. Four months post-intervention performance had recovered strongly, resulting in the athlete becoming European champion that same year. Further improvements in physiological and performance indices were observed at 14 months post-intervention. Physiologically relevant increases in concentrations of carotenoids were achieved at each post-intervention time point, exceeding the reported critical difference values. We conclude that increasing athlete phytonutrient intake may enhance recovery and tolerance to training and environmental stressors, reducing the risk of unexplained under performance syndrome. Alterations in redox homeostasis should be considered as part of the medical management in unexplained under performance syndrome. This is the first reported case study of an elite athlete with alterations in redox homeostasis in conjunction with a diagnosis of unexplained under performance syndrome
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