1,374 research outputs found
A timely call to establish an international convention on the rights of older people
Global pandemics inevitably reveal many vulnerabilities in national and global health systems, as well as society more broadly. The COVID-19 pandemic has amplified the importance of public health, the value of therapeutic medicine, and the power of vaccines. The pandemic has also made apparent stark inequities in access to testing, treatment, and vaccines
Brane World Susy Breaking from String/M Theory
String and M-theory realizations of brane world supersymmetry breaking
scenarios are considered in which visible sector Standard Model fields are
confined on a brane, with hidden sector supersymmetry breaking isolated on a
distant brane. In calculable examples with an internal manifold of any volume
the Kahler potential generically contains brane--brane non-derivative contact
interactions coupling the visible and hidden sectors and is not of the no-scale
sequestered form. This leads to non-universal scalar masses and without
additional assumptions about flavor symmetries may in general induce dangerous
sflavor violation even though the Standard Model and supersymmetry branes are
physically separated. Deviations from the sequestered form are dictated by bulk
supersymmetry and can in most cases be understood as arising from exchange of
bulk supergravity fields between branes or warping of the internal geometry.
Unacceptable visible sector tree-level tachyons arise in many models but may be
avoided in certain classes of compactifications. Anomaly mediated and gaugino
mediated contributions to scalar masses are sub-dominant except in special
circumstances such as a flat or AdS pure five--dimensional bulk geometry
without bulk vector multiplets.Comment: Latex, 83 pages, references adde
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Near-Earth asteroid sample return missions
The rate of discovery of new NEAs and the success of D-S 1 and NEAR-Shoemaker, suggest that sample return from NEAs is now technically feasible. Here we present a summary of a recent workshop on the topic
Constraining the period of the ringed secondary companion to the young star J1407 with photographic plates
Context. The 16 Myr old star 1SWASP J140747.93-394542.6 (V1400 Cen) underwent
a series of complex eclipses in May 2007, interpreted as the transit of a giant
Hill sphere filling debris ring system around a secondary companion, J1407b. No
other eclipses have since been detected, although other measurements have
constrained but not uniquely determined the orbital period of J1407b. Finding
another eclipse towards J1407 will help determine the orbital period of the
system, the geometry of the proposed ring system and enable planning of further
observations to characterize the material within these putative rings. Aims. We
carry out a search for other eclipses in photometric data of J1407 with the aim
of constraining the orbital period of J1407b. Methods. We present photometry
from archival photographic plates from the Harvard DASCH survey, and Bamberg
and Sonneberg Observatories, in order to place additional constraints on the
orbital period of J1407b by searching for other dimming and eclipse events.
Using a visual inspection of all 387 plates and a period-folding algorithm we
performed a search for other eclipses in these data sets. Results. We find no
other deep eclipses in the data spanning from 1890 to 1990, nor in recent
time-series photometry from 2012-2018. Conclusions. We rule out a large
fraction of putative orbital periods for J1407b from 5 to 20 years. These
limits are still marginally consistent with a large Hill sphere filling ring
system surrounding a brown dwarf companion in a bound elliptical orbit about
J1407. Issues with the stability of any rings combined with the lack of
detection of another eclipse, suggests that J1407b may not be bound to J1407.Comment: 8 pages, 3 tables, 4 figures, accepted for publication in A&A. LaTeX
files of the paper, scripts for the figures, and a minimal working FPA can be
found under https://github.com/robinmentel/Constraining-Period
Corporate financing decisions: UK survey evidence
Despite theoretical developments in recent years, our understanding of corporate capital structure remains incomplete. Prior empirical research has been dominated by archival regression studies which are limited in their ability to fully reflect the diversity found in practice. The present paper reports on a comprehensive survey of corporate financing decision-making in UK listed companies. A key finding is that firms are heterogeneous in their capital structure policies. About half of the firms seek to maintain a target debt level, consistent with trade-off theory, but 60 per cent claim to follow a financing hierarchy, consistent with pecking order theory. These two theories are not viewed by respondents as either mutually exclusive or exhaustive. Many of the theoretical determinants of debt levels are widely accepted by respondents, in particular the importance of interest tax shield, financial distress, agency costs and also, at least implicitly, information asymmetry. Results also indicate that cross-country institutional differences have a significant impact on financial decisions
From M-ary Query to Bit Query: a new strategy for efficient large-scale RFID identification
The tag collision avoidance has been viewed as one of the most important research problems in RFID communications and bit tracking technology has been widely embedded in query tree (QT) based algorithms to tackle such challenge. Existing solutions show further opportunity to greatly improve the reading performance because collision queries and empty queries are not fully explored. In this paper, a bit query (BQ) strategy based Mary query tree protocol (BQMT) is presented, which can not only eliminate idle queries but also separate collided tags into many small subsets and make full use of the collided bits. To further optimize the reading performance, a modified dual prefixes matching (MDPM) mechanism is presented to allow multiple tags to respond in the same slot and thus significantly reduce the number of queries. Theoretical analysis and simulations are supplemented to validate the effectiveness of the proposed BQMT and MDPM, which outperform the existing QT-based algorithms. Also, the BQMT and MDPM can be combined to BQMDPM to improve the reading performance in system efficiency, total identification time, communication complexity and average energy cost
Observations of Hunter-Schreger Bands
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66575/2/10.1177_00220345560350052201.pd
The effect of finite-range interactions in classical transport theory
The effect of scattering with non-zero impact parameters between consituents
in relativistic heavy ion collisions is investigated. In solving the
relativistic Boltzmann equation, the characteristic range of the collision
kernel is varied from approximately one fm to zero while leaving the mean-free
path unchanged. Modifying this range is shown to significantly affect spectra
and flow observables. The finite range is shown to provide effective
viscosities, shear, bulk viscosity and heat conductivity, with the viscous
coefficients being proportional to the square of the interaction range
Travelling solitons in the parametrically driven nonlinear Schroedinger equation
We show that the parametrically driven nonlinear Schroedinger equation has
wide classes of travelling soliton solutions, some of which are stable. For
small driving strengths nonpropogating and moving solitons co-exist while
strongly forced solitons can only be stably when moving sufficiently fast.Comment: The paper is available as the JINR preprint E17-2000-147(Dubna,
Russia) and the preprint of the Max-Planck Institute for the Complex Systems
mpipks/0009011, Dresden, Germany. It was submitted to Physical Review
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