7,430 research outputs found
Formation of the Galactic globular clusters with He-rich stars in low-mass halos virialized at high redshift
Recent observations have reported that the Galactic globular clusters (GCs)
with unusually extended horizontal-branch (EHB) morphologies show a
significantly lower velocity dispersion compared with that of the entire
Galactic GC system. We consider that the observed distinctive kinematics of GCs
with EHB has valuable information on the formation epochs of GCs and
accordingly discuss this observational result based on cosmological N-body
simulations with a model of GC formation. We assume that GCs in galaxies were
initially formed in low-mass halos at high redshifts and we investigate final
kinematics of GCs in their host halos at . We find that GCs formed in
halos virialized at z>10 show lower velocity dispersions on average than those
formed at z>6 for halos with GCs at z=0. We thus suggest that the origin of the
observed lower velocity dispersion for the Galactic GCs with EHBs is closely
associated with earlier formation epochs (z>10) of halos initially hosting the
GCs in the course of the Galaxy formation. Considering that the origin of EHBs
can be due to the presence of helium-enhanced second-generation stars in GCs,
we discuss the longstanding second parameter problem of GCs in the context of
different degrees of chemical pollution in GC-forming gas clouds within
low-mass halos virialized at different redshifts.Comment: 5 pages, 3 figures, accepted by MNRAS Letter
Structural parameters for globular clusters in M31 and generalizations for the fundamental plane
The structures of globular clusters (GCs) reflect their dynamical states and
past histories. High-resolution imaging allows the exploration of morphologies
of clusters in other galaxies. Surface brightness profiles from new Hubble
Space Telescope observations of 34 globular clusters in M31 are presented,
together with fits of several different structural models to each cluster. M31
clusters appear to be adequately fit by standard King models, and do not
obviously require alternate descriptions with relatively stronger halos, such
as are needed to fit many GCs in other nearby galaxies. The derived structural
parameters are combined with corrected versions of those measured in an earlier
survey to construct a comprehensive catalog of structural and dynamical
parameters for M31 GCs with a sample size similar to that for the Milky Way.
Clusters in M31, the Milky Way, Magellanic Clouds, Fornax dwarf spheroidal and
NGC 5128 define a very tight fundamental plane with identical slopes. The
combined evidence for these widely different galaxies strongly reinforces the
view that old globular clusters have near-universal structural properties
regardless of host environment.Comment: AJ in press; 59 pages including 16 figure
USING CROWDFUNDING AS PART OF THE PRODUCT DEVELOPMENT PROCESS
AbstractCrowdfunding is the process of taking a project in need of investment and asking a large group of people to supply the investment. It allows organisations to sell their product before production, reducing the risk of new product development. Organisations such as Tesla and General Electric have used crowdfunding successfully but crowdfunding is yet to be explored as part of a formalised product development framework. This paper includes the business case for commercialising new products with crowdfunding and presents crowdfunding as part of a product development and commercialisation framework.</jats:p
Quantum diffusion on a cyclic one dimensional lattice
The quantum diffusion of a particle in an initially localized state on a
cyclic lattice with N sites is studied. Diffusion and reconstruction time are
calculated. Strong differences are found for even or odd number of sites and
the limit N->infinit is studied. The predictions of the model could be tested
with micro - and nanotechnology devices.Comment: 17 pages, 5 figure
Design for Health 4.0: Exploration of a New Area
Driven by networked Electronic Health Record systems, Artificial Intelligence, real-time data from wearable devices with an overlay of invisible user interfaces and improved analytics, Health 4.0 is changing the healthcare industry. The focus on collaboration, coherence, and convergence that will make healthcare more predictive and personalised. Furthermore, Health 4.0 realises the value of data more consistently and effectively. It can pinpoint areas of improvement and enable more informed decisions. What it also does is help move the entire healthcare industry from a system that is reactive and focused on fee-for-service to a system that is value-based, which measures outcomes and ensures proactive prevention.
In this paper, the authors will first explore the realm of the emerging area of Health 4.0 and identify its opportunities and challenges. This includes understanding the relevant base technologies as well as the design principles for the realization of smart healthcare product, systems and product-service-systems of the future. Following on from there, the authors focus on the role of design in the specific context of healthcare
On the Origin of Mass--Metallicity Relations, Blue Tilts, and Scaling Relations for Metal-poor Globular Cluster Systems
We investigate formation processes and physical properties of globular
cluster systems (GCSs) in galaxies based on high-resolution cosmological
simulations with globular clusters. We focus on metal-poor clusters (MPCs) and
correlations with their host galaxies by assuming that MPC formation is
truncated at a high redshift (z_trun > 6). We find that the correlation between
mean metallicities (Z_gc) of MPCs and their host galaxy luminosities (L)
flattens from z=z_trun to z=0. We also find that the observed relation (Z_gc ~
L^0.15) in MPCs can be reproduced well in the models with Z_gc ~ L^0.5 at
z=z_trun when z_trun ~ 10, if mass-to-light-ratios are assumed to be constant
at z=z_trun. However, better agreement with the observed relation is found for
models with different mass-to-light-ratios between z=z_trun and z=0. It is also
found that the observed color-magnitude relation of luminous MPCs (i.e., ``blue
tilts'') may only have a small contribution from the stripped stellar nuclei of
dwarf galaxies, which have nuclei masses that correlate with their total mass
at z=z_trun. The simulated blue tilts are found to be seen more clearly in more
massive galaxies, which reflects the fact that more massive galaxies at z=0 are
formed from a larger number of dwarfs with stellar nuclei formed at z>z_trun.
The half-number radii (R_e) of GCSs, velocity dispersions of GCSs (sigma), and
their host galaxy masses (M_h) are found to be correlated with one another such
that R_e ~ M_h^{0.57} and sigma ~ M_h^{0.32}.Comment: 15 pages, 20 figures, accepted by MNRA
Mini-batch learning of exponential family finite mixture models
Mini-batch algorithms have become increasingly popular due to the requirement
for solving optimization problems, based on large-scale data sets. Using an
existing online expectation-{}-maximization (EM) algorithm framework, we
demonstrate how mini-batch (MB) algorithms may be constructed, and propose a
scheme for the stochastic stabilization of the constructed mini-batch
algorithms. Theoretical results regarding the convergence of the mini-batch EM
algorithms are presented. We then demonstrate how the mini-batch framework may
be applied to conduct maximum likelihood (ML) estimation of mixtures of
exponential family distributions, with emphasis on ML estimation for mixtures
of normal distributions. Via a simulation study, we demonstrate that the
mini-batch algorithm for mixtures of normal distributions can outperform the
standard EM algorithm. Further evidence of the performance of the mini-batch
framework is provided via an application to the famous MNIST data set
Fostering collaborative research for rare genetic disease: The example of Niemann-Pick type C disease
Rare disease represents one of the most significant issues facing the medical community and health care providers worldwide, yet the majority of these disorders never emerge from their obscurity, drawing little attention from the medical community or the pharmaceutical industry. The challenge therefore is how best to mobilize rare disease stakeholders to enhance basic, translational and clinical research to advance understanding of pathogenesis and accelerate therapy development. Here we describe a rare, fatal brain disorder known as Niemann-Pick type C (NPC) and an innovative research collaborative known as Support of Accelerated Research for NPC (SOAR-NPC) which illustrates one pathway through which knowledge of a rare disease and its possible treatments are being successfully advanced. Use of the “SOAR” mechanism, we believe, offers a blueprint for similar advancement for many other rare disorders
Molecular Gas in Candidate Double Barred Galaxies III. A Lack of Molecular Gas?
Most models of double-barred galaxies suggest that a molecular gas component
is crucial for maintaining long-lived nuclear bars. We have undertaken a CO
survey in an attempt to determine the gas content of these systems and to
locate double barred galaxies with strong CO emission that could be candidates
for high resolution mapping. We observed 10 galaxies in CO J=2-1 and J=3-2 and
did not detect any galaxies that had not already been detected in previous CO
surveys. We preferentially detect emission from galaxies containing some form
of nuclear activity. Simulations of these galaxies require that they contain 2%
to 10% gas by mass in order to maintain long-lived nuclear bars. The fluxes for
the galaxies for which we have detections suggest that the gas mass fraction is
in agreement with these models requirements. The lack of emission in the other
galaxies suggests that they contain as little as 7 x 10^6 solar masses of
molecular material which corresponds to < 0.1% gas by mass. This result
combined with the wide variety of CO distributions observed in double barred
galaxies suggests the need for models of double-barred galaxies that do not
require a large, well ordered molecular gas component.Comment: 17 pages (3 figures embedded on pg 17). To appear in the March 10
issue of the Astrophysical Journa
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