264 research outputs found
Constraints on Scalar Asymmetric Dark Matter from Black Hole Formation in Neutron Stars
We consider possibly observable effects of asymmetric dark matter (ADM) in
neutron stars. Since dark matter does not self-annihilate in the ADM scenario,
dark matter accumulates in neutron stars, eventually reaching the Chandrasekhar
limit and forming a black hole. We focus on the case of scalar ADM, where the
constraints from Bose-Einstein condensation and subsequent black hole formation
are most severe due to the absence of Fermi degeneracy pressure. We also note
that in some portions of this constrained parameter space, non-trivial effects
from Hawking radiation can modify our limits. We find that for scalar ADM with
mass between 100 keV and 10^5 GeV, the constraint from pulsars in globular
clusters on the scattering cross-section with neutrons ranges from \sigma_n <
10^{-45} cm^2 to 10^{-52} cm}^2. In particular, for scalar ADM with mass
between 1 GeV and 1 TeV (in the case where black hole evaporation due to
Hawking radiation is unimportant), the constraint on the scattering
cross-section is below what is reachable with ton scale direct detection
experiments.Comment: 24 pages, 5 figures; updated to match published versio
An investigation into the possible effects New Performance Management may have on academic identity and culture within Business Schools in Post 1992 Universities
The purpose of this scoping study is to consider New Performance Management (NPM) in relation to academic identity, culture within business schools taking into consideration job satisfaction and stress and its possible impact upon academic identity. To this end, this paper focuses on one aspect of that study, NPM compared against gender and age range. A critical realism approach is adopted where we can look at how different mechanisms (for example policies and power influences via the UK Government), may impact upon academic identity and the culture the individual works within. The study found that participants identified that their school was driven by targets, and as such had an audit culture. Nevertheless, we found this was not always the case among those who were inexperienced at teaching in HE, and/or were relatively new to the school
The Multidimensional Mortality Awareness Measure & Model (MMAMM): Development and validation of a new self-report questionnaire & psychological framework
For each of eight literature-identified conceptual dimensions of mortality awareness, questionnaire items were generated, producing 89 in all. 359 participants responded to these items and to questionnaires measuring health attitudes, risk-taking, rebelliousness and demographic variables. Multivariate correlational analyses investigated the underlying structure of the item pool and the construct validity as well as the reliability of the emergent empirically derived subscales. Five components, rather than eight, were identified. Given the item content of each, the associated mortality awareness subscales were labelled as: legacy, fearfulness, acceptance, disempowerment, and disengagement. Each attained an acceptable level of internal reliability. Relationships with other variables supported the construct validity of these empirically derived subscales and more generally of this five-factor model. In conclusion, this new multidimensional measure and model of mortality awareness extends our understanding of this important aspect of human existence and supports a more integrative and optimistic approach to mortality awareness than previously available
Neutrino Phenomenology in a 3+1+1 Framework
Evidence continues to grow in the MiniBooNE (MB) antineutrino mode supporting
a low-energy excess compatible with the MB neutrino mode and possibly also
confirming the results of the LSND experiment. At least one sterile neutrino is
required to explain the anomalies consistent with the observations of other
experiments. At the same time, there is a strong tension between the positive
signals of LSND and MB and the null results of nu_e and nu_mu disappearance
experiments. We explore a scenario, first proposed in \cite{Nelson:2010hz},
where the presence of an additional heavy sterile neutrino (with mass well
above an eV) can alleviate tension between LSND, MB and the null results of
disappearance experiments. We compare and contrast this 3+1+1 scenario with the
more standard 3+1 scenario and carry out global fits to all oscillation data
including new 2011 MB anti-nu data. We find that the tension can be somewhat
alleviated and that a phenomenologically viable window for the heavy neutrino,
consistent with rare decays and BBN constraints, can be found if the fifth
neutrino has a mass of order 0.3 - 10 GeV. We also find, however, that the 2011
MB anti-nu data exacerbates the tension with null experiments in both the 3+1
and 3+1+1 models when the lowest energy bins are included, resulting in little
improvement in the global fit. We also discuss the implications of an
additional neutrino for the reactor and gallium anomalies, and show that an
oscillation explanation of the anomalies is disfavored by cosmological
considerations, direct searches, and precision electroweak tests.Comment: 22 pages, 5 figures; replaced to reflect journal versio
Turning off the Lights: How Dark is Dark Matter?
We consider current observational constraints on the electromagnetic charge
of dark matter. The velocity dependence of the scattering cross-section through
the photon gives rise to qualitatively different constraints than standard dark
matter scattering through massive force carriers. In particular, recombination
epoch observations of dark matter density perturbations require that
, the ratio of the dark matter to electronic charge, is less than
for , rising to for .
Though naively one would expect that dark matter carrying a charge well below
this constraint could still give rise to large scattering in current direct
detection experiments, we show that charged dark matter particles that could be
detected with upcoming experiments are expected to be evacuated from the
Galactic disk by the Galactic magnetic fields and supernova shock waves, and
hence will not give rise to a signal. Thus dark matter with a small charge is
likely not a source of a signal in current or upcoming dark matter direct
detection experiments.Comment: 19 pages, 2 figures; v2 - figures fixed, references adde
Inspecting the Higgs for New Weakly Interacting Particles
We explore new physics scenarios which are optimally probed through precision Higgs measurements rather than direct collider searches. Such theories consist of additional electroweak charged or singlet states which couple directly to or mix with the Higgs boson; particles of this kind may be weakly constrained by direct limits due to their meager production rates and soft decay products. We present a simplified framework which characterizes the effects of these states on Higgs physics by way of tree level mixing (with neutral scalars) and loop level modifications (from electrically charged states), all expressed in terms of three mixing angles and three loop parameters, respectively. The theory parameters are constrained and in some cases even fixed by ratios of Higgs production and decay rates. Our setup is simpler than a general effective operator analysis, in that we discard parameters irrelevant to Higgs observables while retaining complex correlations among measurements that arise due to the underlying mixing and radiative effects. We show that certain correlated observations are forbidden, e.g. a depleted ratio of Higgs production from gluon fusion versus vector boson fusion together with a depleted ratio of Higgs decays to bb[over-bar] versus WW. Moreover, we study the strong correlation between the Higgs decay rate to γγ and WW and how it can be violated in the presence of additional electrically charged particles. Our formalism maps straightforwardly onto a variety of new physics models, such as the NMSSM. We show, for example, that with a Higgsino of mass m_(χ ± 1) ≳ 100 GeV and a singlet-Higgs coupling of λ = 0.7, the photon signal strength can deviate from the vector signal strength by up to ∼ 40 − 60% while depleting the vector signal strength by only 5 − 15% relative to the Standard Model
A compilation, classification, and comparison of lists of spontaneous speaking vocabulary of children in kindergarten, Grade I, Grade II, and Grade III
Thesis (Ed.M.)--Boston UniversityLanguage development has been studied for many years.
The beginning vocabularies are easy to count ana record.
As tne child grows and moves about, his speaking vocabulary
increases very rapidly. Some estimates suggest
that a minimum speaking vocabulary at six years would include
three thousand words.
New words have come into children's speaking vocabularies
as a result of modern technology since World War II.
Lists of spontaneous vocabulary furnish material for teachers
and text book writers. The purpose of this study is
to analyze two lists recorded in 1954 and 1955.
An attempt has been made to classify the new list.
The lists were compared with three existing lists, Rinsland,
International Kindergarten Union and Gates
Recommended from our members
Small advances and swift retreat: Race-conscious educational policy in the Obama and Trump administrations
The three terms comprising the Obama and Trump presidencies provide an opportunity to understand the evolution of race-conscious education policy in an increasingly multiracial, unequal, and divided society. Through document review and interviews with civil rights lawyers, government officials, congressional staffers, and intermediary organization personnel, we sought to understand how Obama officials envisioned and changed the role of the federal government in fostering K-12 race-conscious educational policies and what mechanisms they used to advance priorities. We also explored changes Trump administration officials made to federal civil rights policies and through which institutional means. Our findings reveal through-lines between past and present political agendas and the methods for enactment. Obama’s interagency efforts to reinvigorate civil rights oversight and enforcement in education harkened back to the mid-1960s era of bipartisan cooperation around school desegregation. Yet the decades-long legal and policy retrenchment against civil rights advances made in the 1960s constrained further progress. Trump’s administration advocated for the privatization of public education through increased choice and opposed race-consciousness in education law and policy. The reshaping of the federal judiciary under Trump presents challenges for race-consciousness in the law for years to come. Recognizing these consistent through-lines and constraints will be essential for advocates and policymakers going forward
Recruiting participants with peripheral arterial disease for clinical trials: Experience from the Study to Improve Leg Circulation (SILC)
ObjectiveTo describe the success of diverse recruitment methods in a randomized controlled clinical trial of exercise in persons with peripheral arterial disease (PAD).MethodsAn analysis of recruitment sources conducted for the 746 men and women completing a baseline visit for the study to improve leg circulation (SILC), a randomized controlled trial of exercise for patients with PAD. For each recruitment source, we determined the number of randomized participants, the rate of randomization among those completing a baseline visit, and cost per randomized participant.ResultsOf the 746 individuals who completed a baseline visit, 156 were eligible and randomized. The most frequent sources of randomized participants were newspaper advertising (n = 67), mailed recruitment letters to patients with PAD identified at the study medical center (n = 25), and radio advertising (n = 18). Costs per randomized participant were 2167 for Life Line Screening, 3931 for mailed postcards to older community dwelling men and women, and $5691 for radio advertising. Among those completing a baseline visit, randomization rates ranged from 10% for those identified from radio advertising to 32% for those identified from the Chicago Veterans Administration and 33% for those identified from posted flyers.ConclusionMost participants in a randomized controlled trial of exercise were recruited from newspaper advertising and mailed recruitment letters to patients with known PAD. The highest randomization rates after a baseline visit occurred among participants identified from posted flyers and mailed recruitment letters to PAD patients
Recommended from our members
Durability of Benefits From Supervised Treadmill Exercise in People With Peripheral Artery Disease.
Background It is currently unknown whether 6Â months of supervised treadmill exercise has a durable benefit on 6-minute walk performance, even after exercise is completed, in people with peripheral artery disease. Methods and Results A total of 156 participants with peripheral artery disease were randomized to 1 of 3 groups: supervised treadmill exercise, supervised resistance training, or attention control. Participants received supervised sessions during months 1 to 6 and telephone contact during months 6 to 12. Primary outcomes were change in 6-minute walk distance and short physical performance battery at 6-month follow-up and have been reported previously. Secondary outcomes were change in 6-minute walk and short physical performance battery at 12-month follow-up and are reported here. A group of 134 participants (86%) completed the 12-month follow-up. At 6-month follow-up, compared with control, 6-minute walk distance improved in the treadmill exercise group (+36.1Â m, 95% CI =13.9-58.3, P=0.001). Between 6- and 12-month follow-up, 6-minute walk distance significantly declined (-28.6Â m, 95% CI=-52.6 to -4.5, P=0.020) and physical activity declined -272 activity units (95% CI =-546 to +2, P=0.052) in the treadmill exercise group compared with controls. At 12-month follow-up, 6Â months after completing supervised treadmill exercise, change in 6-minute walk distance was not different between the treadmill exercise and control groups (+7.5, 95% CI =-17.5 to +32.6, P=0.56). There were no differences in short physical performance battery change between either exercise group and control at 6-month or 12-month follow-up. Conclusions A 6-month supervised treadmill exercise intervention that improved 6-minute walk distance at 6-month follow-up did not have persistent benefit at 12-month follow-up. These results do not support a durable benefit of supervised treadmill exercise in peripheral artery disease. Clinical Trial Registration URL : https://www.clinicaltrials.gov . Identifier: NCT 00106327
- …