832 research outputs found
Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
In diffuse interstellar clouds the chemistry that leads to the formation of
the oxygen bearing ions OH+, H2O+, and H3O+ begins with the ionization of
atomic hydrogen by cosmic rays, and continues through subsequent hydrogen
abstraction reactions involving H2. Given these reaction pathways, the observed
abundances of these molecules are useful in constraining both the total
cosmic-ray ionization rate of atomic hydrogen (zeta_H) and molecular hydrogen
fraction, f(H2). We present observations targeting transitions of OH+, H2O+,
and H3O+ made with the Herschel Space Observatory along 20 Galactic sight lines
toward bright submillimeter continuum sources. Both OH+ and H2O+ are detected
in absorption in multiple velocity components along every sight line, but H3O+
is only detected along 7 sight lines. From the molecular abundances we compute
f(H2) in multiple distinct components along each line of sight, and find a
Gaussian distribution with mean and standard deviation 0.042+-0.018. This
confirms previous findings that OH+ and H2O+ primarily reside in gas with low
H2 fractions. We also infer zeta_H throughout our sample, and find a log-normal
distribution with mean log(zeta_H)=-15.75, (zeta_H=1.78x10^-16 s^-1), and
standard deviation 0.29 for gas within the Galactic disk, but outside of the
Galactic center. This is in good agreement with the mean and distribution of
cosmic-ray ionization rates previously inferred from H3+ observations.
Ionization rates in the Galactic center tend to be 10--100 times larger than
found in the Galactic disk, also in accord with prior studies.Comment: 76 pages, 25 figures, 6 tables; accepted for publication in Ap
Abnormalities in brain structure and behavior in GSK-3alpha mutant mice
<p>Abstract</p> <p>Background</p> <p>Glycogen synthase kinase-3 (GSK-3) is a widely expressed and highly conserved serine/threonine protein kinase encoded by two genes that generate two related proteins: GSK-3α and GSK-3β. Mice lacking a functional GSK-3α gene were engineered in our laboratory; they are viable and display insulin sensitivity. In this study, we have characterized brain functions of GSK-3α KO mice by using a well-established battery of behavioral tests together with neurochemical and neuroanatomical analysis.</p> <p>Results</p> <p>Similar to the previously described behaviours of GSK-3β<sup>+/-</sup>mice, GSK-3α mutants display decreased exploratory activity, decreased immobility time and reduced aggressive behavior. However, genetic inactivation of the GSK-3α gene was associated with: decreased locomotion and impaired motor coordination, increased grooming activity, loss of social motivation and novelty; enhanced sensorimotor gating and impaired associated memory and coordination. GSK-3α KO mice exhibited a deficit in fear conditioning, however memory formation as assessed by a passive avoidance test was normal, suggesting that the animals are sensitized for active avoidance of a highly aversive stimulus in the fear-conditioning paradigm. Changes in cerebellar structure and function were observed in mutant mice along with a significant decrease of the number and size of Purkinje cells.</p> <p>Conclusion</p> <p>Taken together, these data support a role for the GSK-3α gene in CNS functioning and possible involvement in the development of psychiatric disorders.</p
The Pan-STARRS Moving Object Processing System
We describe the Pan-STARRS Moving Object Processing System (MOPS), a modern
software package that produces automatic asteroid discoveries and
identifications from catalogs of transient detections from next-generation
astronomical survey telescopes. MOPS achieves > 99.5% efficiency in producing
orbits from a synthetic but realistic population of asteroids whose
measurements were simulated for a Pan-STARRS4-class telescope. Additionally,
using a non-physical grid population, we demonstrate that MOPS can detect
populations of currently unknown objects such as interstellar asteroids.
MOPS has been adapted successfully to the prototype Pan-STARRS1 telescope
despite differences in expected false detection rates, fill-factor loss and
relatively sparse observing cadence compared to a hypothetical Pan-STARRS4
telescope and survey. MOPS remains >99.5% efficient at detecting objects on a
single night but drops to 80% efficiency at producing orbits for objects
detected on multiple nights. This loss is primarily due to configurable MOPS
processing limits that are not yet tuned for the Pan-STARRS1 mission.
The core MOPS software package is the product of more than 15 person-years of
software development and incorporates countless additional years of effort in
third-party software to perform lower-level functions such as spatial searching
or orbit determination. We describe the high-level design of MOPS and essential
subcomponents, the suitability of MOPS for other survey programs, and suggest a
road map for future MOPS development.Comment: 57 Pages, 26 Figures, 13 Table
23 High Redshift Supernovae from the IfA Deep Survey: Doubling the SN Sample at z>0.7
We present photometric and spectroscopic observations of 23 high redshift
supernovae spanning a range of z=0.34-1.03, 9 of which are unambiguously
classified as Type Ia. These supernovae were discovered during the IfA Deep
Survey, which began in September 2001 and observed a total of 2.5 square
degrees to a depth of approximately m=25-26 in RIZ over 9-17 visits, typically
every 1-3 weeks for nearly 5 months, with additional observations continuing
until April 2002. We give a brief description of the survey motivations,
observational strategy, and reduction process. This sample of 23 high-redshift
supernovae includes 15 at z>0.7, doubling the published number of objects at
these redshifts, and indicates that the evidence for acceleration of the
universe is not due to a systematic effect proportional to redshift. In
combination with the recent compilation of Tonry et al. (2003), we calculate
cosmological parameter density contours which are consistent with the flat
universe indicated by the CMB (Spergel et al. 2003). Adopting the constraint
that Omega_total = 1.0, we obtain best-fit values of (Omega_m,
Omega_Lambda)=(0.33, 0.67) using 22 SNe from this survey augmented by the
literature compilation. We show that using the empty-beam model for
gravitational lensing does not eliminate the need for Omega_Lambda > 0.
Experience from this survey indicates great potential for similar large-scale
surveys while also revealing the limitations of performing surveys for z>1 SNe
from the ground.Comment: 67 pages, 12 figures, 12 tables, accepted for publication in the
Astrophysical Journa
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Computerized Ultrasound Risk Evaluation (CURE) System: Development of Combined Transmission and Reflection Ultrasound with New Reconstruction Algorithms for Breast Imaging
Our Computerized Ultrasound Risk Evaluation (CURE) system has been developed to the engineering prototype stage and generated unique data sets of both transmission and reflection ultrasound (US). This paper will help define the clinical underpinnings of the developmental process and interpret the imaging results from a similar perspective. The CURE project was designed to incorporate numerous diagnostic parameters to improve upon two major areas of early breast cancer detection. CURE may provide improved tissue characterization of breast masses and reliable detection of abnormal microcalcifications found in some breast cancers and ductal carcinoma in situ (DCIS). Current breast US is limited to mass evaluation, whereas mammography also detects and guides biopsy of malignant calcifications. Screening with CURE remains a distant goal, but improved follow-up of mammographic abnormalities may represent a feasible breakthrough. Improved tissue characterization could result in reduction of the estimated one million benign biopsies each year in the United States, costing up to several billion dollars. Most breast calcifications are benign and comprise-80% of stereotactic biopsies guided by mammography. Ultrasound has the capability of finding some groups of calcifications, but further improvements in resolution should also address tissue characterization to define the soft tissue filling of ducts by DCIS. In this manner, CURE may be able to more accurately identify the malignant calcifications associated with progression of DCIS or early cancers. Currently, high-resolution US images of the breast are performed in the reflection mode at higher frequencies, which also limits depth of penetration. Reconstruction of reflection ultrasound images relies upon acoustic impedance differences in the tissue and includes only direct backscatter of the ultrasound signal. Resolution and tissue contrast of current US continues to improve with denser transducer arrays and image processing, but the operator dependent nature of using a moveable transducer head remains a significant problem for thorough coverage of the entire breast. We have therefore undertaken the development of a whole breast (i.e., including auxiliary tail) system, with improved resolution and tissue characterization abilities. The extensive ultrasound physics considerations, engineering, materials process development and subsequent algorithm reconstruction are beyond the scope of this initial paper. The proprietary nature of these processes will be forthcoming as the intellectual property is fully secured. We will focus here on the imaging outcomes as they apply to eventual expansion into clinical use
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The influence of landscape composition and configuration on crop yield resilience
1. Sustainable agriculture aims to produce sufficient food while minimizing environmental damage. To achieve this, we need to understand the role of agricultural landscapes in providing diverse ecosystem services and how these affect crop production and resilience, that is, maintaining yields despite environmental perturbation.
We used 10 years of English wheat yield data to derive three metrics of resilience (relative yield across the time series, yield stability around a moving average and resistance to an extreme weather event) at 10 km × 10 km resolution. We used remotely sensed maps to calculate measures of landscape structure, including composition (proportions of different land cover types) and configuration (metrics of connectivity and proximity), known to affect ecosystem service delivery (e.g. control of pests by beneficial invertebrates). We then used an information‐theoretic approach to identify the best‐fitting combination of landscape structure predictors for each resilience metric, using a potential yield model to account for the effects of climate and soils.
Relative yield showed a strongly positive relationship with the area of arable land. For yield stability, this relationship was evident but alongside other landscape structure variables in the best‐fitting model. No relationship with arable land was evident for resistance.
Yield stability showed a strongly positive effect of proximity to semi‐natural habitats. For resistance, the best‐fitting model included positive relationships with the cover of semi‐natural habitats and proximity to semi‐natural grasslands.
Synthesis and applications. Landscapes with the highest relative wheat yields did not show the highest yield stability or resistance to extreme events. As resilience metrics were derived from shorter portions of the time series, the importance of semi‐natural habitats compared to arable land increased. This is probably driven by the complex interplay between landscape structure, agricultural management and ecosystem services. These results demonstrate that measuring relative yield over time may be insufficient to capture the full effect that non‐arable components of the landscape, and the ecosystem services they deliver, have on other aspects of resilience, and that there are clear trade‐offs in managing agricultural landscapes to maximize different aspects of crop yield resilience
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Biological, clinical and population relevance of 95 loci for blood lipids.
Plasma concentrations of total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol and triglycerides are among the most important risk factors for coronary artery disease (CAD) and are targets for therapeutic intervention. We screened the genome for common variants associated with plasma lipids in >100,000 individuals of European ancestry. Here we report 95 significantly associated loci (P < 5 x 10(-8)), with 59 showing genome-wide significant association with lipid traits for the first time. The newly reported associations include single nucleotide polymorphisms (SNPs) near known lipid regulators (for example, CYP7A1, NPC1L1 and SCARB1) as well as in scores of loci not previously implicated in lipoprotein metabolism. The 95 loci contribute not only to normal variation in lipid traits but also to extreme lipid phenotypes and have an impact on lipid traits in three non-European populations (East Asians, South Asians and African Americans). Our results identify several novel loci associated with plasma lipids that are also associated with CAD. Finally, we validated three of the novel genes-GALNT2, PPP1R3B and TTC39B-with experiments in mouse models. Taken together, our findings provide the foundation to develop a broader biological understanding of lipoprotein metabolism and to identify new therapeutic opportunities for the prevention of CAD
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