285 research outputs found
Melt-preferred orientation, anisotropic permeability, and melt-band formation in a deforming, partially molten aggregate
Shear deformation of partially molten rock in laboratory experiments causes
the emergence of melt-enriched sheets (bands in cross-section) that are aligned
at about 15-20 degrees to the shear plane. Deformation and deviatoric stress
also cause the coherent alignment of pores at the grain scale. This leads to a
melt-preferred orientation that may, in turn, give rise to an anisotropic
permeability. Here we develop a simple, general model of anisotropic
permeability in partially molten rocks. We use linearised analysis and
nonlinear numerical solutions to investigate its behaviour under simple-shear
deformation. In particular, we consider implications of the model for the
emergence and angle of melt-rich bands. Anisotropic permeability affects the
angle of bands and, in a certain parameter regime, it can give rise to low
angles consistent with experiments. However, the conditions required for this
regime have a narrow range and seem unlikely to be entirely met by experiments.
Anisotropic permeability may nonetheless affect melt transport and the
behaviour of partially molten rocks in Earth's mantle.Comment: 19 pages, 7 figures, accepted for publication in Geophysical Journal
International on 3 September 201
Prospects for Mirage Mediation
Mirage mediation reduces the fine-tuning in the minimal supersymmetric
standard model by dynamically arranging a cancellation between anomaly-mediated
and modulus-mediated supersymmetry breaking. We explore the conditions under
which a mirage "messenger scale" is generated near the weak scale and the
little hierarchy problem is solved. We do this by explicitly including the
dynamics of the SUSY-breaking sector needed to cancel the cosmological
constant. The most plausible scenario for generating a low mirage scale does
not readily admit an extra-dimensional interpretation. We also review the
possibilities for solving the mu/Bmu problem in such theories, a potential
hidden source of fine-tuning.Comment: 14 page
Report of the FAO/CRFM/MALMR Regional Workshop on the Collection of Demographic Information on Coastal Fishing Communities and its Use in Community-Based Fisheries and Integrated Coastal Zone Management in the Caribbean
One part of the two-part Science-to-Action Guidebook. The other part was intended for scientists, and this part is for decision-makers. Recognizing the importance of informed decisions and the differences between the scientific and decision-making processes, this guidebook provides practical tips on how to best bring these worlds together. In doing so, this guidebook emphasizes the roles of facilitating, synthesizing, translating, and communicating science to inform conservation action. It is geared toward the perspective of decision-makers working in tropical developing nations and focusing on marine resource management issues. However, the concepts are applicable to a broad range of scientists and decision-makers worldwide
Barriers to Implementation of a Technology-Based Mental Health Intervention in a Rural Setting
This study utilized qualitative focus groups with rural health providers and patients to explore barriers to implementation of a technology-based mental health intervention for the treatment of depression in a primary care setting. A randomized controlled trial (RCT) was implemented in both urban and rural primary care practices to test the feasibility and effectiveness of computerized cognitive behavioral therapy (CCBT) for depression. Early implementation identified lower rates of willingness to participate in the intervention by rural patients. Subsequently, focus groups were conducted with rural providers and patients to explore barriers to participation and strategies to overcome these barriers in future implementation efforts. Two focus groups of five to seven participants each were conducted to understand patient experiences. Groups lasted approximately one hour and were recorded and transcribed for coding purposes. Key themes identified about barriers to use of CCBT by rural patients emerged included: 1) technical barriers, 2) stigma, 3) distrust of outsiders, 4) effort/motivational barriers, and 5) staff resistance/frustration. Conversely, several positive themes related to supports for CCBT also emerged, including: 1) readiness to change/symptom severity, 2) program supports and incentives, 3) clinician support, 4) components of the intervention, and 5) individual patient characteristics
Little Technicolor
Inspired by the AdS/CFT correspondence, we show that any G/H symmetry
breaking pattern can be described by a simple two-site moose diagram. This
construction trivially reproduces the CCWZ prescription in the context of
Hidden Local Symmetry. We interpret this moose in a novel way to show that many
little Higgs theories can emerge from ordinary chiral symmetry breaking in
scaled-up QCD. We apply this reasoning to the simple group little Higgs to see
that the same low energy degrees of freedom can arise from a variety of UV
complete theories. We also show how models of holographic composite Higgs
bosons can turn into brane-localized little technicolor theories by
"integrating in" the IR brane.Comment: 26 pages, 2 figures; v2: references added; v3: added section on
vacuum alignment to match JHEP versio
The Littlest Higgs in Anti-de Sitter Space
We implement the SU(5)/SO(5) littlest Higgs theory in a slice of 5D Anti-de
Sitter space bounded by a UV brane and an IR brane. In this model, there is a
bulk SU(5) gauge symmetry that is broken to SO(5) on the IR brane, and the
Higgs boson is contained in the Goldstones from this breaking. All of the
interactions on the IR brane preserve the global symmetries that protect the
Higgs mass, but a radiative potential is generated through loops that stretch
to the UV brane where there are explicit SU(5) violating boundary conditions.
Like the original littlest Higgs, this model exhibits collective breaking in
that two interactions must be turned on in order to generate a Higgs potential.
In AdS space, however, collective breaking does not appear in coupling
constants directly but rather in the choice of UV brane boundary conditions. We
match this AdS construction to the known low energy structure of the littlest
Higgs and comment on some of the tensions inherent in the AdS construction. We
calculate the 5D Coleman-Weinberg effective potential for the Higgs and find
that collective breaking is manifest. In a simplified model with only the SU(2)
gauge structure and the top quark, the physical Higgs mass can be of order 200
GeV with no considerable fine tuning (25%). We sketch a more realistic model
involving the entire gauge and fermion structure that also implements T-parity,
and we comment on the tension between T-parity and flavor structure.Comment: 42 pages, 7 figures, 3 tables; v2: minor rewording, JHEP format; v3:
to match JHEP versio
Clinicopathological evaluation of chronic traumatic encephalopathy in players of American football
IMPORTANCE: Players of American football may be at increased risk of long-term neurological conditions, particularly chronic traumatic encephalopathy (CTE).
OBJECTIVE: To determine the neuropathological and clinical features of deceased football players with CTE.
DESIGN, SETTING, AND PARTICIPANTS: Case series of 202 football players whose brains were donated for research. Neuropathological evaluations and retrospective telephone clinical assessments (including head trauma history) with informants were performed blinded. Online questionnaires ascertained athletic and military history.
EXPOSURES: Participation in American football at any level of play.
MAIN OUTCOMES AND MEASURES: Neuropathological diagnoses of neurodegenerative diseases, including CTE, based on defined diagnostic criteria; CTE neuropathological severity (stages I to IV or dichotomized into mild [stages I and II] and severe [stages III and IV]); informant-reported athletic history and, for players who died in 2014 or later, clinical presentation, including behavior, mood, and cognitive symptoms and dementia.
RESULTS: Among 202 deceased former football players (median age at death, 66 years [interquartile range, 47-76 years]), CTE was neuropathologically diagnosed in 177 players (87%; median age at death, 67 years [interquartile range, 52-77 years]; mean years of football participation, 15.1 [SD, 5.2]), including 0 of 2 pre–high school, 3 of 14 high school (21%), 48 of 53 college (91%), 9 of 14 semiprofessional (64%), 7 of 8 Canadian Football League (88%), and 110 of 111 National Football League (99%) players. Neuropathological severity of CTE was distributed across the highest level of play, with all 3 former high school players having mild pathology and the majority of former college (27 [56%]), semiprofessional (5 [56%]), and professional (101 [86%]) players having severe pathology. Among 27 participants with mild CTE pathology, 26 (96%) had behavioral or mood symptoms or both, 23 (85%) had cognitive symptoms, and 9 (33%) had signs of dementia. Among 84 participants with severe CTE pathology, 75 (89%) had behavioral or mood symptoms or both, 80 (95%) had cognitive symptoms, and 71 (85%) had signs of dementia.
CONCLUSIONS AND RELEVANCE: In a convenience sample of deceased football players who donated their brains for research, a high proportion had neuropathological evidence of CTE, suggesting that CTE may be related to prior participation in football.This study received support from NINDS (grants U01 NS086659, R01 NS078337, R56 NS078337, U01 NS093334, and F32 NS096803), the National Institute on Aging (grants K23 AG046377, P30AG13846 and supplement 0572063345-5, R01 AG1649), the US Department of Defense (grant W81XWH-13-2-0064), the US Department of Veterans Affairs (I01 CX001038), the Veterans Affairs Biorepository (CSP 501), the Veterans Affairs Rehabilitation Research and Development Traumatic Brain Injury Center of Excellence (grant B6796-C), the Department of Defense Peer Reviewed Alzheimer’s Research Program (grant 13267017), the National Operating Committee on Standards for Athletic Equipment, the Alzheimer’s Association (grants NIRG-15-362697 and NIRG-305779), the Concussion Legacy Foundation, the Andlinger Family Foundation, the WWE, and the NFL
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