1,443 research outputs found
Abundances of Baade's Window Giants from Keck/HIRES Spectra: II. The Alpha- and Light Odd Elements
We report detailed chemical abundance analysis of 27 RGB stars towards the
Galactic bulge in Baade's Window for elements produced by massive stars: O, Na,
Mg, Al, Si, Ca and Ti. All of these elements are overabundant in the bulge
relative to the disk, especially Mg, indicating that the bulge is enhanced in
Type~II supernova ejecta and most likely formed more rapidly than the disk. We
attribute a rapid decline of [O/Fe] to metallicity-dependent yields of oxygen
in massive stars, perhaps connected to the Wolf-Reyet phenomenon. he explosive
nucleosynthesis alphas, Si, Ca and Ti, possess identical trends with [Fe/H],
consistent with their putative common origin. We note that different behaviors
of hydrostatic and explosive alpha elements can be seen in the stellar
abundances of stars in Local Group dwarf galaxies. We also attribute the
decline of Si,Ca and Ti relative to Mg, to metallicity- dependent yields for
the explosive alpha elements from Type~II supernovae. The starkly smaller
scatter of [/Fe] with [Fe/H] in the bulge, as compared to the halo, is
consistent with expected efficient mixing for the bulge. The metal-poor bulge
[/Fe] ratios are higher than ~80% of the halo. If the bulge formed from
halo gas, the event occured before ~80% of the present-day halo was formed. The
lack of overlap between the thick and thin disk composition with the bulge does
not support the idea that the bulge was built by a thickening of the disk
driven by the bar. The trend of [Al/Fe] is very sensitive to the chemical
evolution environment. A comparison of the bulge, disk and Sgr dSph galaxy
shows a range of ~0.7 dex in [Al/Fe] at a given [Fe/H], presumably due to a
range of Type~II/Type~Ia supernova ratios in these systems.Comment: 51 pages, 6 tables, 27 figures, submitte
Measurement of the neutral axis in avian eggshells reveals which species conform to the golden ratio
Avian eggs represent a striking evolutionary adaptation for which shell thickness is crucial. An understudied eggshell property includes the neutral axis, a line that is drawn through any bent structure and whose precise location is characterized by the kâfactor. Previous studies have established that, for chicken eggs, mean k corresponds to the golden ratio (Ί = 1.618, or 0.618 in its reciprocal form). We hypothesized whether such an arrangement of the neutral axis conforms to the eggshell of any bird or only to eggshells with a certain set of geometric parameters. Implementing a suite of innovative methodological approaches, we investigated variations in k of 435 avian species, exploring which correspond to Ί. We found that mean k is highly variable among birds and does not always conform to Ί, being much lower in spherical and ellipsoid eggs and higher in pyriform eggs. While 21 species had k values within 0.618 ± 0.02 (including four falcon species) and the Falconinae subfamily (six species) revealed a mean of 0.618, it is predominantly domesticated species (chicken, ducks, and geese) that lay eggs whose neutral axis corresponds to the golden ratio. Thus, the study of the mathematical secrets of the eggshell related to the golden ratio of its neutral axis suggests its speciesâspecific signatures in birds
Observing Nearby Nuclei on Paramagnetic Trityls and MOFs via DNP and Electron Decoupling
Dynamic nuclear polarization (DNP) is an NMR sensitivity enhancement
technique that mediates polarization transfer from unpaired electrons to
NMR-active nuclei. Despite its success in elucidating important structural
information on biological and inorganic materials, the detailed
polarization-transfer pathway-from the electrons to the nearby and then the
bulk solvent nuclei, and finally to the molecules of interest-remains unclear.
In particular, the nuclei in the paramagnetic polarizing agent play significant
roles in relaying the enhanced NMR polarizations to more remote nuclei. Despite
their importance, the direct NMR observation of these nuclei is challenging
because of poor sensitivity. Here, we show that a combined DNP and electron
decoupling approach can facilitate direct NMR detection of these nuclei. We
achieved an ~80 % improvement in NMR intensity via electron decoupling at 0.35
T and 80 K on trityl radicals. Moreover, we recorded a DNP enhancement factor
of ~ 90 and ~11 % higher NMR intensity using electron decoupling on
a paramagnetic metal-organic framework, magnesium hexaoxytriphenylene (MgHOTP
MOF)
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Query Health: standards-based, cross-platform population health surveillance
Objective: Understanding population-level health trends is essential to effectively monitor and improve public health. The Office of the National Coordinator for Health Information Technology (ONC) Query Health initiative is a collaboration to develop a national architecture for distributed, population-level health queries across diverse clinical systems with disparate data models. Here we review Query Health activities, including a standards-based methodology, an open-source reference implementation, and three pilot projects. Materials and methods Query Health defined a standards-based approach for distributed population health queries, using an ontology based on the Quality Data Model and Consolidated Clinical Document Architecture, Health Quality Measures Format (HQMF) as the query language, the Query Envelope as the secure transport layer, and the Quality Reporting Document Architecture as the result language. Results: We implemented this approach using Informatics for Integrating Biology and the Bedside (i2b2) and hQuery for data analytics and PopMedNet for access control, secure query distribution, and response. We deployed the reference implementation at three pilot sites: two public health departments (New York City and Massachusetts) and one pilot designed to support Food and Drug Administration post-market safety surveillance activities. The pilots were successful, although improved cross-platform data normalization is needed. Discussions This initiative resulted in a standards-based methodology for population health queries, a reference implementation, and revision of the HQMF standard. It also informed future directions regarding interoperability and data access for ONC's Data Access Framework initiative. Conclusions: Query Health was a test of the learning health system that supplied a functional methodology and reference implementation for distributed population health queries that has been validated at three sites
Bayesian Analysis for Risk Assessment of Selected Medical Events in Support of the Integrated Medical Model Effort
The Exploration Medical Capability project is creating a catalog of risk assessments using the Integrated Medical Model (IMM). The IMM is a software-based system intended to assist mission planners in preparing for spaceflight missions by helping them to make informed decisions about medical preparations and supplies needed for combating and treating various medical events using Probabilistic Risk Assessment. The objective is to use statistical analyses to inform the IMM decision tool with estimated probabilities of medical events occurring during an exploration mission. Because data regarding astronaut health are limited, Bayesian statistical analysis is used. Bayesian inference combines prior knowledge, such as data from the general U.S. population, the U.S. Submarine Force, or the analog astronaut population located at the NASA Johnson Space Center, with observed data for the medical condition of interest. The posterior results reflect the best evidence for specific medical events occurring in flight. Bayes theorem provides a formal mechanism for combining available observed data with data from similar studies to support the quantification process. The IMM team performed Bayesian updates on the following medical events: angina, appendicitis, atrial fibrillation, atrial flutter, dental abscess, dental caries, dental periodontal disease, gallstone disease, herpes zoster, renal stones, seizure, and stroke
Egg-inspired engineering in the design of thin-walled shelled vessels: a theoretical approach for shell strength
A novel subdiscipline of bionics is emerging in the form of âegg-inspired engineeringâ through the use of egg-shaped ovoids as thin-walled tanks and building structures. HuÌgelschĂ€fferâs and Narushinâs models of egg geometry are highly applicable within this proposed subdiscipline. Here we conducted a comparative analysis between the two models with respect to some of the most important egg parameters. These included contents volume, shell volume, and the location of the neutral axis along the shell thickness. As a first step, theoretical studies using the Narushinâs model were carried out due to the lack (or limited amount) of data on the geometric relationships of parameters and available calculation formulae. Considering experimental data accumulated in the engineering and construction industries, we postulate a hypothesis that there is a correlation between location of the neutral axis and the strength of the walls in the egg-shaped structure. We suggest that the use of Narushinâs model is preferable to HuÌgelschĂ€fferâs model for designing thin-walled shelled vessels and egg-shaped building structures. This is due to its relative simplicity (because of the requirement for only two initial parameters in the basic equation), optimal geometry in terms of material costs per unit of internal capacity, and effective prerequisites for shell strength characteristics
A novel Egg Quality Index as an alternative to Haugh unit score
An unusually popular index reflecting the quality of the egg contents and known as the Haugh unit (HU) score is empirical in nature. Because of that, a number of studies appeared that contradict or try to improve this index. In this regard, we set a study that pursued several goals: (i) to trace the rationale for developing the HU index and give it a theoretical reassessment; and (ii) based on the assumptions of previous studies in this field, to revisit and refine the index by increasing such its components as the mathematical adequacy and information value. As a result, an alternative index was inferred that we called the Egg Quality Index (EQI) and described using the appropriate mathematical dependencies. This novel index, in addition to the egg weight (W), takes into account the physical properties of the thick albumen (by measuring its height, H) and yolk (by identifying its diameter, d, or height, h). We, then, compared the two indices, HU and EQI, using the simulation modelling approach. The results of comparison of the two indices as applied to a various set of parameters characteristic of chicken eggs suggested a wider potential for using EQI due to the inclusion of an additional parameter reflecting the yolk condition as well as a more accurate distribution of the studied eggs in quality grade groups with various gradations of consumer attractiveness
Sequence-Dependent Dynamics of Synthetic and Endogenous RSSs in V(D)J Recombination
Developing lymphocytes of jawed vertebrates cleave and combine distinct gene segments to assemble antigenâreceptor genes. This process called V(D)J recombination that involves the RAG recombinase binding and cutting recombination signal sequences (RSSs) composed of conserved heptamer and nonamer sequences flanking less well-conserved 12- or 23-bp spacers. Little quantitative information is known about the contributions of individual RSS positions over the course of the RAGâRSS interaction. We employ a single-molecule method known as tethered particle motion to track the formation, lifetime and cleavage of individual RAGâ12RSSâ23RSS paired complexes (PCs) for numerous synthetic and endogenous 12RSSs. We reveal that single-bp changes, including in the 12RSS spacer, can significantly and selectively alter PC formation or the probability of RAG-mediated cleavage in the PC. We find that some rarely used endogenous gene segments can be mapped directly to poor RAG binding on their adjacent 12RSSs. Finally, we find that while abrogating RSS nicking with CaÂČâș leads to substantially shorter PC lifetimes, analysis of the complete lifetime distributions of any 12RSS even on this reduced system reveals that the process of exiting the PC involves unidentified molecular details whose involvement in RAGâRSS dynamics are crucial to quantitatively capture kinetics in V(D)J recombination
A universal formula for avian egg shape
The birdâs oomorphology has far escaped mathematical formulation universally applicable. All bird egg shapes can be laid in four basic geometric figures: sphere, ellipsoid, ovoid, and pyriform (conical/pear-shaped). The first three have a clear mathematical definition, each derived from expression of the previous, but a formula for the pyriform profile has yet to be inferred. To rectify this, we introduced an additional function into the ovoid formula. The subsequent mathematical model fits a completely novel geometric shape that can be characterized as the last stage in the evolution of the sphereâellipsoidâHĂŒgelschĂ€fferâs ovoid transformation applicable to any avian egg shape geometry. Required measurements are the egg length, maximum breadth, and diameter at the terminus from the pointed end. This mathematical description is invariably a significant step in understanding not only the egg shape itself, but how and why it evolved, thus making widespread biological and technological applications theoretically possible
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