585 research outputs found
F-theory, GUTs, and the Weak Scale
In this paper we study a deformation of gauge mediated supersymmetry breaking
in a class of local F-theory GUT models where the scale of supersymmetry
breaking determines the value of the mu term. Geometrically correlating these
two scales constrains the soft SUSY breaking parameters of the MSSM. In this
scenario, the hidden SUSY breaking sector involves an anomalous U(1)
Peccei-Quinn symmetry which forbids bare mu and B mu terms. This sector
typically breaks supersymmetry at the desired range of energy scales through a
simple stringy hybrid of a Fayet and Polonyi model. A variant of the
Giudice-Masiero mechanism generates the value mu ~ 10^2 - 10^3 GeV when the
hidden sector scale of supersymmetry breaking is F^(1/2) ~ 10^(8.5) GeV.
Further, the B mu problem is solved due to the mild hierarchy between the GUT
scale and Planck scale. These models relate SUSY breaking with the QCD axion,
and solve the strong CP problem through an axion with decay constant f_a ~
M_(GUT) * mu / L, where L ~ 10^5 GeV is the characteristic scale of gaugino
mass unification in gauge mediated models, and the ratio \mu / L ~
M_(GUT)/M_(pl) ~ 10^(-3). We find f_a ~ 10^12 GeV, which is near the high end
of the phenomenologically viable window. Here, the axino is the goldstino mode
which is eaten by the gravitino. The gravitino is the LSP with a mass of about
10^1 - 10^2 MeV, and a bino-like neutralino is (typically) the NLSP with mass
of about 10^2 - 10^3 GeV. Compatibility with electroweak symmetry breaking also
determines the value of tan(beta) ~ 30 +/- 7.Comment: v3: 94 pages, 9 figures, clarification of Fayet-Polonyi model and
instanton corrections to axion potentia
The relationship between fetal growth and retinal nerve fiber layer thickness in a cohort of young adults
Purpose: To explore relationships between patterns of fetal anthropometric growth, as reflective of fetal wellbeing, and global retinal nerve fiber layer (RNFL) thickness measured in young adulthood.
Methods: Participants (n = 481) from within a Western Australian pregnancy cohort study underwent five serial ultrasound scans during gestation, with fetal biometry measured at each scan. Optic disc parameters were measured via spectral-domain optical coherence tomography imaging at a 20-year follow-up eye examination. Generalized estimating equations were used to evaluate differences in global RNFL thickness between groups of participants who had undergone similar growth trajectories based on fetal head circumference (FHC), abdominal circumference (FAC), femur length (FFL), and estimated fetal weight (EFW).
Results: Participants with consistently large FHCs throughout gestation had significantly thicker global RNFLs than those with any other pattern of FHC growth (P = 0.023), even after adjustment for potential confounders (P = 0.037). Based on model fit statistics, FHC growth trajectory was a better predictor of global RNFL thickness than birth weight or head circumference at birth. RNFL thickness did not vary significantly between groups of participants with different growth trajectories based on FAC, FFL, or EFW.
Conclusions: FHC growth is associated with RNFL thickness in young adulthood and, moreover, is a better predictor than either birth weight or head circumference at birth.
Translational Relevance: This research demonstrates an association between intrauterine growth and long-term optic nerve health, providing a basis for further exploring the extent of the influence of fetal wellbeing on clinical conditions linked to RNFL thinning
Stress-Activity Mapping: Physiological Responses During General Duty Police Encounters
Policing is a highly stressful and dangerous profession that involves a complex set of environmental, psychosocial, and health risks. The current study examined autonomic stress responses experienced by 64 police officers, during general duty calls for service (CFS) and interactions with the public. Advancing previous research, this study utilized GPS and detailed operational police records as objective evidence of specific activities throughout a CFS. These data were then used to map officersâ heart rate to both the phase of a call (e.g., dispatch, enroute) and incident factors (e.g., call priority, use-of-force). Furthermore, physical movement (i.e., location and inertia) was tracked and assisted in differentiating whether cardiovascular reactivity was due to physical or psychological stress. Officer characteristics, including years of service and training profiles, were examined to conduct a preliminary exploration of whether experience and relevant operational skills training impacted cardiovascular reactivity. Study results provide foundational evidence that CFS factors, specifically the phase of the call (i.e., arrival on scene, encountering a subject) and incident factors (i.e., call priority, weapons, arrest, use-of-force), influence physiologica
A novel computational approach to combine the optical and thermal modelling of Linear Fresnel Collectors using the finite volume method
A computational approach is presented, which uses the finite volume (FV) method in the Computational Fluid Dynamics (CFD) solver ANSYS Fluent to conduct the ray tracing required to quantify the optical performance of a line concentration Concentrated Solar Power (CSP) receiver, as well as the conjugate heat transfer modelling required to estimate the thermal efficiency of such a receiver. A Linear Fresnel Collector (LFC) implementation is used to illustrate the approach. It is shown that the Discrete Ordinates method can provide an accurate solution to the Radiative Transfer Equation (RTE) if the shortcomings of its solution are resolved appropriately in the FV CFD solver. The shortcomings are due to false scattering and the so-called ray effect inherent in the FV solution. The approach is first evaluated for a 2-D test case involving oblique collimated radiation and then for a more complex 2-D LFC optical domain based on the FRESDEMO project. For the latter, results are compared with and validated against those obtained with the Monte Carlo ray tracer, SolTrace. The outcome of the FV ray tracing in the LFC optical domain is mapped as a non-uniform heat flux distribution in the 3-D cavity receiver domain and this distribution is included in the FV conjugate heat transfer CFD model as a volumetric source. The result of this latter model is the determination of the heat transferred to the heat transfer fluid running in the collector tubes, thereby providing an estimation of the overall thermal efficiency. To evaluate the effectiveness of the phased approach in terms of accuracy and computational cost, the novel 2-D:3-D phased approach is compared with results of a fully integrated, but expensive 3-D optical and thermal model. It is shown that the less expensive model provides similar results and hence a large cost saving. The novel approach also provides the benefit of working in one simulation environment, i.e. ANSYS Workbench, where optimisation studies can be carried out to maximise the performance of linear CSP reflector layout and receiver configurations
An insight into the yielding and normal compression of sand with irregularly-shaped particles using DEM
The micro mechanics of one-dimensional and isotropic normal compression of granular soil have recently been revealed using the discrete element method. By modelling soil grains as spheres and implementing a new crushing model, the authors have previously investigated the influence of fracture mechanism, particle strengths (and distributions), and the size-hardening law on both the normal compression line and resultant particle size distribution; this resulted in a new compression law. In this work, irregular particle shape is introduced, using âclumpsâ (groups of spherical particles), allowing different relative densities of the same material to be subjected to normal compression. An investigation into the mechanics of yielding is presented, in which the onset of crushing is related to the average particle octahedral shear stress and âyieldâ is seen to be a function of the available void space. Beyond yield, the normal compression lines for the clumps at different initial densities are examined and compared to that for spheres. The effect of coordination number and particle shape on the normal compression are studied, and in particular the micro mechanics behind the evolution of a fractal particle size distribution are revealed
The epidemiology of dry eye disease in the UK: The Aston dry eye study
Purpose: Cross-sectional studies on dry eye disease (DED) have relied on different diagnoses hindering conclusions about the disease epidemiology. This study offers an insight into DED epidemiology in the UK using prior and recent diagnostic recommendations. Methods: Study participants comprised 282 volunteers from Birmingham, UK (median 40 years, range 18â88 years, 56% females). DED was defined by the Tear Film Ocular Surface Dry Eye Workshop II (TFOS DEWS II) criteria, based on a positive symptom score with the Dry Eye Questionnaire (DEQ-5) and Ocular Surface Disease Index (OSDI), and one of the following homeostasis markers: non-invasive tear break-up time of 8 mOsm/L (TearLab Osmolarity System); or > 5 corneal spots, >9 conjunctival spots or lower/upper lid-wiper-epitheliopathy staining of â„ 2 mm length and â„ 25% width (Oculus Keratograph 5 M). In addition, the Women's Health Study (WHS) criteria, based on symptoms or a prior dry eye diagnosis, was assessed. DED risk factors were gathered using a self-administered questionnaire. Results: DED prevalence by the TFOS DEWS II criteria was 32.1% (95% confidence interval 25.5â37.7% and 29.5% (95% confidence interval 24.4â35.1% by the WHS criteria. Female sex, systemic and/or ocular health conditions, short sleep duration and prolonged outdoor leisure time spent were significant DED risk factors (p †0.05). Conclusions: Approximately one-third of the adult UK population have DED, aligning with the prevalence reported in multiple counties globally. Female sex, systemic/ocular health conditions, short sleep duration and prolonged outdoor leisure time are positive predictors of DED
On the thermal sunset diagram for scalar field theories
We study the so-called `` sunset diagram'', which is one of two-loop
self-energy diagrams, for scalar field theories at finite temperature.
For this purpose, we first find the complete expression of the bubble
diagram, the one-loop subdiagram of the sunset diagram, for arbitrary momentum.
We calculate the temperature independent part and dependent part of the
sunset diagram separately. For the former, we obtain the discontinuous part
first and the finite continuous part next using a twice-subtracted dispersion
relation. For the latter, we express it as a one-dimensional integral in terms
of the bubble diagram.
We also study the structure of the discontinuous part of the sunset diagram.
Physical processes, which are responsible for it, are identified. Processes due
to the scattering with particles in the heat bath exist only at finite
temperature and generate discontinuity for arbitrary momentum, which is a
remarkable feature of the two-loop diagrams at finite temperature.
As an application of our result, we study the effect of the diagram on the
spectral function of the sigma meson at finite temperature in the linear sigma
model, which was obtained at one-loop order previously. At high temperature
where the decay is forbidden, sigma acquires a finite width
of the order of while within the one-loop calculation its width
vanishes. At low temperature, the spectrum does not deviate much from that at
one-loop order. Possible consequences with including other two-loop diagrams
are discussed.Comment: 30 page
K\"{a}hler-Einstein metrics on strictly pseudoconvex domains
The metrics of S. Y. Cheng and S.-T. Yau are considered on a strictly
pseudoconvex domains in a complex manifold. Such a manifold carries a complete
K\"{a}hler-Einstein metric if and only if its canonical bundle is positive. We
consider the restricted case in which the CR structure on is
normal. In this case M must be a domain in a resolution of the Sasaki cone over
. We give a condition on a normal CR manifold which it cannot
satisfy if it is a CR infinity of a K\"{a}hler-Einstein manifold. We are able
to mostly determine those normal CR 3-manifolds which can be CR infinities.
Many examples are given of K\"{a}hler-Einstein strictly pseudoconvex manifolds
on bundles and resolutions.Comment: 30 pages, 1 figure, couple corrections, improved a couple example
Arp2/3 Complex Is Required for Macrophage Integrin Functions but Is Dispensable for FcR Phagocytosis and In Vivo Motility
The Arp2/3 complex nucleates branched actin, forming networks involved in lamellipodial protrusion, phagocytosis, and cell adhesion. We derived primary bone marrow macrophages lacking Arp2/3 complex (Arpc2â/â) and directly tested its role in macrophage functions. Despite protrusion and actin assembly defects, Arpc2â/â macrophages competently phagocytose via FcR and chemotax toward CSF and CX3CL1. However, CR3 phagocytosis and fibronectin haptotaxis, both integrin-dependent processes, are disrupted. Integrin-responsive actin assembly and αM/ÎČ2 integrin localization are compromised in Arpc2â/â cells. Using an in vivo system to observe endogenous monocytes migrating toward full-thickness ear wounds we found that Arpc2â/â monocytes maintain cell speeds and directionality similar to control. Our work reveals that the Arp2/3 complex is not a general requirement for phagocytosis or chemotaxis but is a critical driver of integrin-dependent processes. We demonstrate further that cells lacking Arp2/3 complex function in vivo remain capable of executing important physiological responses that require rapid directional motility. Using a combination of cell culture-based and in vivo mouse experiments, Rotty et al. demonstrate that the actin-nucleating Arp2/3 complex is not absolutely required for macrophage FcR phagocytosis, chemotaxis, or in vivo monocyte directional motility. Rather, the complex has a critical role in regulating integrin-dependent macrophage processes
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