4,056 research outputs found
Range Extensions for Four Sea Basses (Pisces: Serranidae) from the Eastern Gulf of Mexico with a Color Note on Hemanthias leptus (Ginsburg)
Polarization of lepton from scalar tau decay as a probe of neutralino mixing
The lepton arising from the scalar tau (\st) decay is naturally
polarized. \ptau depends on the left--right mixing of the \st and the
gaugino--higgsino mixing of the neutralino. The polarization \ptau could be
measured from the energy distribution of the decay products of at future
\epem colliders. A measurement of \ptauand of the \st production cross
section allows to determine both these mixing angles.Comment: 20 pages Latex, 5 figures(not included). compressed ps file of the
figures available at ftp://ftp.kek.jp/kek/preprints/TH/TH-425/fig.ps.g
Physics Prospects at the Hadron Colliders
I start with a brief introduction to the elementary particles and their
interactions, Higgs mechanism and supersymmetry. The major physics objectives
of the Tevatron and LHC colliders are identified. The status and prospects of
the top quark, charged Higgs boson and superparticle searches are discussed in
detail, while those of the neutral Higgs boson(s) are covered in a parallel
talk by R.J.N. Phillips at this workshop.Comment: 16 pages Latex + 15 figures (available on request
Concentrations of Dark Halos from their Assembly Histories
(abridged) We study the relation between the density profiles of dark matter
halos and their mass assembly histories, using a statistical sample of halos in
a high-resolution N-body simulation of the LCDM cosmology. For each halo at
z=0, we identify its merger-history tree, and determine concentration
parameters c_vir for all progenitors, thus providing a structural merger tree
for each halo. We fit the mass accretion histories by a universal function with
one parameter, the formation epoch a_c, defined when the log mass accretion
rate dlogM/dloga falls below a critical value S. We find that late forming
galaxies tend to be less concentrated, such that c_vir ``observed'' at any
epoch a_o is strongly correlated with a_c via c_vir=c_1*a_o/a_c. Scatter about
this relation is mostly due to measurement errors in c_v and a_c, implying that
the actual spread in c_vir for halos of a given mass can be mostly attributed
to scatter in a_c. We demonstrate that this relation can also be used to
predict the mass and redshift dependence of c_v, and the scatter about the
median c_vir(M,z), using accretion histories derived from the Extended
Press-Schechter (EPS) formalism, after adjusting for a constant offset between
the formation times as predicted by EPS and as measured in the simulations;this
new ingredient can thus be easily incorporated into semi-analytic models of
galaxy formation. The correlation found between halo concentration and mass
accretion rate suggests a physical interpretation: for high mass infall rates
the central density is related to the background density; when the mass infall
rate slows, the central density stays approximately constant and the halo
concentration just grows as R_vir. The tight correlation demonstrated here
provides an essential new ingredient for galaxy formation modeling.Comment: 19 pages, 18 figures, uses emulateapj5.tex. ApJ, in press; revised to
match accepted versio
SIDM on FIRE: Hydrodynamical Self-Interacting Dark Matter simulations of low-mass dwarf galaxies
We compare a suite of four simulated dwarf galaxies formed in 10 haloes of collisionless Cold Dark Matter (CDM) with galaxies
simulated in the same haloes with an identical galaxy formation model but a
non-zero cross-section for dark matter self-interactions. These cosmological
zoom-in simulations are part of the Feedback In Realistic Environments (FIRE)
project and utilize the FIRE-2 model for hydrodynamics and galaxy formation
physics. We find the stellar masses of the galaxies formed in Self-Interacting
Dark Matter (SIDM) with are very similar to those in CDM
(spanning ) and all runs lie on a
similar stellar mass -- size relation. The logarithmic dark matter density
slope () in the central pc remains
steeper than for the CDM-Hydro simulations with stellar mass
and core-like in the most massive galaxy.
In contrast, every SIDM hydrodynamic simulation yields a flatter profile, with
. Moreover, the central density profiles predicted in SIDM runs
without baryons are similar to the SIDM runs that include FIRE-2 baryonic
physics. Thus, SIDM appears to be much more robust to the inclusion of
(potentially uncertain) baryonic physics than CDM on this mass scale,
suggesting SIDM will be easier to falsify than CDM using low-mass galaxies. Our
FIRE simulations predict that galaxies less massive than provide potentially ideal targets for discriminating models,
with SIDM producing substantial cores in such tiny galaxies and CDM producing
cusps.Comment: 10 Pages, 7 figures, submitted to MNRA
The Importance of Commutability of Reference Materials Used as Calibrators: The Example of Ceruloplasmin
Bostonia. Volume 11
Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs
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Using scenarios to explore UK upland futures
Uplands around the world are facing significant social, economic and environmental changes, and decision-makers need to better understand what the future may hold if they are to adapt and maintain upland goods and services. This paper draws together all major research comprising eight studies that have used scenarios to describe possible futures for UK uplands. The paper evaluates which scenarios are perceived by stakeholders to be most likely and desirable, and assesses the benefits and drawbacks of the scenario methods used in UK uplands to date. Stakeholders agreed that the most desirable and likely scenario would be a continuation of hill farming (albeit at reduced levels) based on cross-compliance with environmental measures. The least desirable scenario is a withdrawal of government financial support for hill farming. Although this was deemed by stakeholders to be the least likely scenario, the loss of government support warrants close attention due to its potential implications for the local economy. Stakeholders noted that the environmental implications of this scenario are much less clear-cut. As such, there is an urgent need to understand the full implications of this scenario, so that upland stakeholders can adequately prepare, and policy-makers can better evaluate the likely implications of different policy options. The paper concludes that in future, upland scenario research needs to: (1) better integrate in-depth and representative participation from stakeholders during both scenario development and evaluation; and (2) make more effective use of visualisation techniques and simulation models
How Common are the Magellanic Clouds?
We introduce a probabilistic approach to the problem of counting dwarf
satellites around host galaxies in databases with limited redshift information.
This technique is used to investigate the occurrence of satellites with
luminosities similar to the Magellanic Clouds around hosts with properties
similar to the Milky Way in the object catalog of the Sloan Digital Sky Survey.
Our analysis uses data from SDSS Data Release 7, selecting candidate
Milky-Way-like hosts from the spectroscopic catalog and candidate analogs of
the Magellanic Clouds from the photometric catalog. Our principal result is the
probability for a Milky-Way-like galaxy to host N_{sat} close satellites with
luminosities similar to the Magellanic Clouds. We find that 81 percent of
galaxies like the Milky Way are have no such satellites within a radius of 150
kpc, 11 percent have one, and only 3.5 percent of hosts have two. The
probabilities are robust to changes in host and satellite selection criteria,
background-estimation technique, and survey depth. These results demonstrate
that the Milky Way has significantly more satellites than a typical galaxy of
its luminosity; this fact is useful for understanding the larger cosmological
context of our home galaxy.Comment: Updated to match published version. Added referenc
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Resilience and food security: rethinking an ecological concept
1. Focusing on food production, in this paper we define resilience in the food security context as maintaining production of sufficient and nutritious food in the face of chronic and acute environmental perturbations. In agri-food systems, resilience is manifest over multiple spatial scales: field, farm, regional and global. Metrics comprise production and nutritional diversity as well as socio-economic stability of food supply.
2. Approaches to enhancing resilience show a progression from more ecologically-based methods at small scales to more socially-based interventions at larger scales. At the field scale, approaches include the use of mixtures of crop varieties, livestock breeds and of forage species, polycultures, and boosting ecosystem functions. Stress-tolerant crops, or with greater plasticity, provide technological solutions.
3. At the farm scale, resilience may be conferred by diversifying crops and livestock and by farmers implementing adaptive approaches in response to perturbations. Biodiverse landscapes may enhance resilience, but the evidence is weak. At regional to global scales, resilient food systems will be achieved by coordination and implementation of resilience approaches among farms, advice to farmers and targeted research.
4. Synthesis. Threats to food production are predicted to increase under climate change and land degradation. Holistic responses are needed that integrate across spatial scales. Ecological knowledge is critical, but should be implemented alongside agronomic solutions and socio-economic transformations
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