751 research outputs found

    Observing cosmic string loops with gravitational lensing surveys

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    We show that the existence of cosmic strings can be strongly constrained by the next generation of gravitational lensing surveys at radio frequencies. We focus on cosmic string loops, which simulations suggest would be far more numerous than long (horizon-sized) strings. Using simple models of the loop population and minimal assumptions about the lensing cross section per loop, we estimate the optical depth to lensing and show that extant radio surveys such as CLASS have already ruled out a portion of the cosmic string model parameter space. Future radio interferometers, such as LOFAR and especially SKA, may constrain GÎŒ/c2<10−9G\mu/c^2 < 10^{-9} in some regions of parameter space, outperforming current constraints from pulsar timing and the CMB by up to two orders of magnitude. This method relies on direct detections of cosmic strings, and so is less sensitive to the theoretical uncertainties in string network evolution that weaken other constraints.Comment: 20 pages, 3 figures. v3: Some clarification of text, revised figure, appendix added. Submitted to Phys. Rev.

    An Economic Impact Analysis of the Proposed Yakima/Klickitat Fishery Enhancement Project; Preliminary Design Report, Appendix D.

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    The objective of this study is to estimate the economic impact of the proposed Yakima/Klickitat Production Project on the local economies of the Yakima and Klickitat subbasins. The project, when operating at planned maximum production, will augment the total number of salmon and steelhead returning to the subbasins by 77,600 and will increase the sustainable terminal harvest by 55,160. These estimates do not include fish harvested in the ocean or in the mainstem Columbia. In addition to evaluating the impacts of the construction, operations and maintenance, experimentation and monitoring, and harvest activities described in the Draft Environmental Assessment (Bonneville Power Administration, 1989), our analysis also evaluates some passageway improvements and Phase II screening of irrigation structures. Both of these augmentations are required In order for the project to reach maximum planned harvest levels. The study area includes the Yakima Subbasin economy (Yakima and Kittitas counties), the mid-Columbia Basin/Klickitat Subbasin economies (Klickitat, Hood River, and Wasco counties), and the Tri-Cities economy (Benton and Franklin counties). The study period extends from 1990 through 2015: from preconstruction planning activities through reaching maximum production

    An Economic Impact Analysis of the Proposed Yakima/Klickitat Fishery Enhancement Project; Preliminary Design Report, Appendix D.

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    The objective of this study is to estimate the economic impact of the proposed Yakima/Klickitat Production Project on the local economies of the Yakima and Klickitat subbasins. The project, when operating at planned maximum production, will augment the total number of salmon and steelhead returning to the subbasins by 77,600 and will increase the sustainable terminal harvest by 55,160. These estimates do not include fish harvested in the ocean or in the mainstem Columbia. In addition to evaluating the impacts of the construction, operations and maintenance, experimentation and monitoring, and harvest activities described in the Draft Environmental Assessment (Bonneville Power Administration, 1989), our analysis also evaluates some passageway improvements and Phase II screening of irrigation structures. Both of these augmentations are required In order for the project to reach maximum planned harvest levels. The study area includes the Yakima Subbasin economy (Yakima and Kittitas counties), the mid-Columbia Basin/Klickitat Subbasin economies (Klickitat, Hood River, and Wasco counties), and the Tri-Cities economy (Benton and Franklin counties). The study period extends from 1990 through 2015: from preconstruction planning activities through reaching maximum production

    Macrophages inhibit and enhance endometriosis depending on their origin

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    Macrophages are intimately involved in the pathophysiology of endometriosis, a chronic inflammatory disorder characterized by the growth of endometrial-like tissue (lesions) outside the uterus. By combining genetic and pharmacological monocyte and macrophage depletion strategies we determined the ontogeny and function of macrophages in a mouse model of induced endometriosis. We demonstrate that lesion-resident macrophages are derived from eutopic endometrial tissue, infiltrating large peritoneal macrophages (LpM) and monocytes. Furthermore, we found endometriosis to trigger continuous recruitment of monocytes and expansion of CCR2+ LpM. Depletion of eutopic endometrial macrophages results in smaller endometriosis lesions, whereas constitutive inhibition of monocyte recruitment significantly reduces peritoneal macrophage populations and increases the number of lesions. Reprogramming the ontogeny of peritoneal macrophages such that embryo-derived LpM are replaced by monocyte-derived LpM decreases the number of lesions that develop. We propose a putative model whereby endometrial macrophages are “proendometriosis” while newly recruited monocyte-derived macrophages, possibly in LpM form, are “antiendometriosis.” These observations highlight the importance of monocyte-derived macrophages in limiting disease progression

    The baboon (Papio anubis) extracranial carotid artery: An anatomical guide for endovascular experimentation

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    BACKGROUND: As novel endovascular strategies are developed for treating neurological disease, there is an increasing need to evaluate these techniques in relevant preclinical models. The use of non-human primates is especially critical given their structural and physiological homology with humans. In order to conduct primate endovascular studies, a comprehensive understanding of the carotid anatomy is necessary. We therefore performed a detailed examination of the vessel lengths, lumen diameters and angles of origin of the baboon extracranial carotid system. METHODS: We characterized the extracranial carotid system often male baboons (Papio anubis, range 15.1–28.4 kg) by early post-mortem dissection. Photographic documentation of vessel lengths, lumen diameters, and angles of origin were measured for each segment of the carotid bilaterally. RESULTS: The common carotid arteries averaged 94.7 ± 1.7 mm (left) and 87.1 ± 1.6 mm (right) in length. The average minimal common carotid lumen diameters were 3.0 ± 0.3 mm (left) and 2.9 ± 0.2 mm (right). Each animal had a common brachiocephalic artery arising from the aorta which bifurcated into the left common carotid artery and right braciocephalic artery after 21.5 ± 1.6 mm. The vascular anatomy was found to be consistent among animals despite a wide range of animal weights. CONCLUSIONS: The consistency in the Papio anubis extracranial carotid system may promote the use of this species in the preclinical investigation of neuro-interventional therapies

    Magnetogenesis from Cosmic String Loops

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    Large-scale coherent magnetic fields are observed in galaxies and clusters, but their ultimate origin remains a mystery. We reconsider the prospects for primordial magnetogenesis by a cosmic string network. We show that the magnetic flux produced by long strings has been overestimated in the past, and give improved estimates. We also compute the fields created by the loop population, and find that it gives the dominant contribution to the total magnetic field strength on present-day galactic scales. We present numerical results obtained by evolving semi-analytic models of string networks (including both one-scale and velocity-dependent one-scale models) in a Lambda-CDM cosmology, including the forces and torques on loops from Hubble redshifting, dynamical friction, and gravitational wave emission. Our predictions include the magnetic field strength as a function of correlation length, as well as the volume covered by magnetic fields. We conclude that string networks could account for magnetic fields on galactic scales, but only if coupled with an efficient dynamo amplification mechanism.Comment: 10 figures; v3: small typos corrected to match published version. MagnetiCS, the code described in paper, is available at http://markcwyman.com/ and http://www.damtp.cam.ac.uk/user/dhw22/code/index.htm

    The ACS Nearby Galaxy Survey Treasury IX. Constraining asymptotic giant branch evolution with old metal-poor galaxies

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    In an attempt to constrain evolutionary models of the asymptotic giant branch (AGB) phase at the limit of low masses and low metallicities, we have examined the luminosity functions and number ratio between AGB and red giant branch (RGB) stars from a sample of resolved galaxies from the ACS Nearby Galaxy Survey Treasury (ANGST). This database provides HST optical photometry together with maps of completeness, photometric errors, and star formation histories for dozens of galaxies within 4 Mpc. We select 12 galaxies characterized by predominantly metal-poor populations as indicated by a very steep and blue RGB, and which do not present any indication of recent star formation in their color--magnitude diagrams. Thousands of AGB stars brighter than the tip of the RGB (TRGB) are present in the sample (between 60 and 400 per galaxy), hence the Poisson noise has little impact in our measurements of the AGB/RGB ratio. We model the photometric data with a few sets of thermally pulsing AGB (TP-AGB) evolutionary models with different prescriptions for the mass loss. This technique allows us to set stringent constraints to the TP-AGB models of low-mass metal-poor stars (with M<1.5 Msun, [Fe/H]<~-1.0). Indeed, those which satisfactorily reproduce the observed AGB/RGB ratios have TP-AGB lifetimes between 1.2 and 1.8 Myr, and finish their nuclear burning lives with masses between 0.51 and 0.55 Msun. This is also in good agreement with recent observations of white dwarf masses in the M4 old globular cluster. These constraints can be added to those already derived from Magellanic Cloud star clusters as important mileposts in the arduous process of calibrating AGB evolutionary models.Comment: To appear in ApJ, a version with better resolution is in http://stev.oapd.inaf.it/~lgirardi/rgbagb.pd

    Diagnostic and Prognostic Significance of Complement in Patients with Alcohol-associated Hepatitis

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    BACKGROUND and AIMS: Given the lack of effective therapies and high mortality in acute alcohol-associated hepatitis (AH), it is important to develop rationally-designed biomarkers for effective disease management. Complement, a critical component of the innate immune system, contributes to uncontrolled inflammatory responses leading to liver injury, but is also involved in hepatic regeneration. Here we investigated if a panel of complement proteins and activation products would provide useful biomarkers for severity of AH and aid in predicting 90 days mortality. APPROACH and RESULTS: Plasma samples collected at time of diagnosis from 254 patients with moderate and severe AH recruited from four medical centers and 31 healthy individuals were used to quantify complement proteins by ELISA and Luminex arrays. Components of the classical and lectin pathways, including complement factors C2, C4b and C4d, as well as complement factor I (CFI) and C5, were reduced in AH patients compared to healthy individuals. In contrast, components of the alternative pathway, including complement factor Ba (CFBa) and factor D (CFD), were increased. Markers of complement activation were also differentially evident, with C5a increased and the soluble terminal complement complex (sC5b9) decreased in AH. Mannose binding lectin (MBL), C4b, CFI, C5 and sC5b9 were negatively correlated with model for end-stage liver disease (MELD) score, while CFBa and CFD were positively associated with disease severity. Lower CFI and sC5b9 were associated with increased 90-day mortality in AH. CONCLUSIONS: Taken together, these data indicate that AH is associated with a profound disruption of complement. Inclusion of complement, especially CFI and sC5b9, along with other laboratory indicators, could improve diagnostic and prognostic indications of disease severity and risk of mortality for AH patients

    Quasi-Quantum Groups, Knots, Three-Manifolds, and Topological Field Theory

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    We show how to construct, starting from a quasi-Hopf algebra, or quasi-quantum group, invariants of knots and links. In some cases, these invariants give rise to invariants of the three-manifolds obtained by surgery along these links. This happens for a finite-dimensional quasi-quantum group, whose definition involves a finite group GG, and a 3-cocycle \om, which was first studied by Dijkgraaf, Pasquier and Roche. We treat this example in more detail, and argue that in this case the invariants agree with the partition function of the topological field theory of Dijkgraaf and Witten depending on the same data G, \,\om.Comment: 30 page
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