7,427 research outputs found

    Taylor's Theorem for Functionals on BMO with Application to BMO Local Minimizers

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    In this note two results are established for energy functionals that are given by the integral of W(x,u(x)) W(\mathbf x,\nabla \mathbf u(\mathbf x)) over ΩRn\Omega \subset\mathbb{R}^n with uBMO(Ω;RN×n)\nabla \mathbf u \in BMO(\Omega;{\mathbb R}^{N\times n}), the space of functions of Bounded Mean Oscillation of John & Nirenberg. A version of Taylor's theorem is first shown to be valid provided the integrand WW has polynomial growth. This result is then used to demonstrate that, for the Dirichlet, Neumann, and mixed problems, every Lipschitz-continuous solution of the corresponding Euler-Lagrange equations at which the second variation of the energy is uniformly positive is a strict local minimizer of the energy in W1,BMO(Ω;RN)W^{1,BMO}(\Omega;\mathbb{R}^N), the subspace of the Sobolev space W1,1(Ω;RN)W^{1,1}(\Omega;\mathbb{R}^N) for which the weak derivative uBMO(Ω;RN×n)\nabla\mathbf u \in BMO(\Omega;{\mathbb R}^{N\times n}).Comment: 8 page

    Applications of Partial Supersymmetry

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    I examine quantum mechanical Hamiltonians with partial supersymmetry, and explore two main applications. First, I analyze a theory with a logarithmic spectrum, and show how to use partial supersymmetry to reveal the underlying structure of this theory. This method reveals an intriguing equivalence between two formulations of this theory, one of which is one-dimensional, and the other of which is infinite-dimensional. Second, I demonstrate the use of partial supersymmetry as a tool to obtain the asymptotic energy levels in non-relativistic quantum mechanics in an exceptionally easy way. In the end, I discuss possible extensions of this work, including the possible connections between partial supersymmetry and renormalization group arguments.Comment: 11 pages, harvmac, no figures; typo corrected in identifying info on title pag

    ImpRess: an Implementation Readiness checklist developed using a systematic review of randomised controlled trials assessing cognitive stimulation for dementia

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    Background Research reporting results of clinical trials, psychosocial or technological interventions frequently omit critical details needed to inform implementation in practice. The aim of this article is to develop an Implementation Readiness (ImpRess) checklist, that includes criteria deemed useful in measuring readiness for implementation and apply it to trials of cognitive stimulation in dementia, providing a systematic review of their readiness for widespread implementation. Methods Five electronic databases were searched. After initial screening of papers, two reviewers assessed quality and scored the included studies based on the ImpRess checklist specifically developed for this review. Results Twenty studies met the inclusion criteria. As determined by the ImpRess checklist, scores ranged from 11 to 29 out of 52. According to the checklist the most comprehensive and ready to implement version of cognitive stimulation was Cognitive Stimulation Therapy. Conclusions Reports of interventions rarely include consideration of implementation in practice. Contrary to the growing number of reporting guidelines, crucial items within the ImpRess checklist have been frequently overlooked. This study was able to show that the ImpRess checklist was feasible in practice and reliable. The checklist may be useful in evaluating readiness for implementation for other manualised interventions

    Stable periodic waves in coupled Kuramoto-Sivashinsky - Korteweg-de Vries equations

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    Periodic waves are investigated in a system composed of a Kuramoto-Sivashinsky - Korteweg-de Vries (KS-KdV) equation, which is linearly coupled to an extra linear dissipative equation. The model describes, e.g., a two-layer liquid film flowing down an inclined plane. It has been recently shown that the system supports stable solitary pulses. We demonstrate that a perturbation analysis, based on the balance equation for the field momentum, predicts the existence of stable cnoidal waves (CnWs) in the same system. It is found that the mean value U of the wave field u in the main subsystem, but not the mean value of the extra field, affects the stability of the periodic waves. Three different areas can be distinguished inside the stability region in the parameter plane (L,U), where L is the wave's period. In these areas, stable are, respectively, CnWs with positive velocity, constant solutions, and CnWs with negative velocity. Multistability, i.e., the coexistence of several attractors, including the waves with several maxima per period, appears at large value of L. The analytical predictions are completely confirmed by direct simulations. Stable waves are also found numerically in the limit of vanishing dispersion, when the KS-KdV equation goes over into the KS one.Comment: a latex text file and 16 eps files with figures. Journal of the Physical Society of Japan, in pres

    Scaling of Selfavoiding Tethered Membranes: 2-Loop Renormalization Group Results

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    The scaling properties of selfavoiding polymerized membranes are studied using renormalization group methods. The scaling exponent \nu is calculated for the first time at two loop order. \nu is found to agree with the Gaussian variational estimate for large space dimension d and to be close to the Flory estimate for d=3.Comment: 4 pages, RevTeX + 20 .eps file

    Expanding the Description of Spaceflight Effects beyond Bone Mineral Density [BMD]: Trabecular Bone Score [TBS] in ISS Astronauts

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    Dual-energy x-ray absorptiometry [DXA] is the widely-applied bone densitometry method used to diagnose osteoporosis in a terrestrial population known to be at risk for age-related bone loss. This medical test, which measures areal bone mineral density [aBMD] of clinically-relevant skeletal sites (e.g., hip and spine), helps the clinician to identify which persons, among postmenopausal women and men older than 50 years, are at high risk for low trauma or fragility fractures and might require an intervention. The most recognized osteoporotic fragility fracture is the vertebral compression fracture which can lead to kyphosis or hunched backs typically seen in the elderly. DXA measurement of BMD however is recognized to be insufficient as a sole index for assessing fracture risk. DXA's limitation may be related to its inability to monitor changes in structural parameters, such as trabecular vs. cortical bone volumes, bone geometry or trabecular microarchitecture. Hence, in order to understand risks to human health and performance due to space exposure, NASA needs to expand its measurements of bone to include other contributors to skeletal integrity. To this aim, the Bone and Mineral Lab conducted a pilot study for a novel measurement of bone microarchitecture that can be obtained by retrospective analysis of DXA scans. Trabecular Bone Score (TBS) assesses changes to trabecular microarchitecture by measuring the grey color "texture" information extracted from DXA images of the lumbar spine. An analysis of TBS in 51 ISS astronauts was conducted to assess if TBS could detect 1) an effect of spaceflight and 2) a response to countermeasures independent of DXA BMD. In addition, changes in trunk body lean tissue mass and in trunk body fat tissue mass were also evaluated to explore an association between body composition, as impacted by ARED exercise, and bone microarchitecture. The pilot analysis of 51 astronaut scans of the lumbar spine suggests that, following an ISS mission, DXA BMD and TBS are detecting different effects of ARED exercise and of ARED + Bisphosphonate on the lumbar spine of astronauts. There is emerging evidence associating reduced TBS with terrestrial metabolic bone disorders where a TBS 1.350 is associated with "normal." However, it is not possible to conclude how the spaceflight-induced changes in TBS increase risk for vertebral fractures in the astronaut or if changes in body composition of the trunk region could be an indirect method of assessing exercise effect on bone microarchitecture. More importantly, this pilot analysis demonstrates a new, minimal risk approach for monitoring changes to vertebral bone microarchitecture. This method could help assess the combined skeletal effects of spaceflight with the effects of aging in the astronaut after return to Earth

    Asexuality: Classification and characterization

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    This is a post-print version of the article. The official published version can be obtaineed at the link below.The term “asexual” has been defined in many different ways and asexuality has received very little research attention. In a small qualitative study (N = 4), individuals who self-identified as asexual were interviewed to help formulate hypotheses for a larger study. The second larger study was an online survey drawn from a convenience sample designed to better characterize asexuality and to test predictors of asexual identity. A convenience sample of 1,146 individuals (N = 41 self-identified asexual) completed online questionnaires assessing sexual history, sexual inhibition and excitation, sexual desire, and an open-response questionnaire concerning asexual identity. Asexuals reported significantly less desire for sex with a partner, lower sexual arousability, and lower sexual excitation but did not differ consistently from non-asexuals in their sexual inhibition scores or their desire to masturbate. Content analyses supported the idea that low sexual desire is the primary feature predicting asexual identity

    Birth characteristics and childhood carcinomas

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    BACKGROUND: Carcinomas in children are rare and have not been well studied. METHODS: We conducted a population-based case–control study and examined associations between birth characteristics and childhood carcinomas diagnosed from 28 days to 14 years during 1980–2004 using pooled data from five states (NY, WA, MN, TX, and CA) that linked their birth and cancer registries. The pooled data set contained 57 966 controls and 475 carcinoma cases, including 159 thyroid and 126 malignant melanoma cases. We used unconditional logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: White compared with ‘other' race was positively associated with melanoma (OR=3.22, 95% CI 1.33–8.33). Older maternal age increased the risk for melanoma (OR(per 5-year age increase)=1.20, 95% CI 1.00–1.44), whereas paternal age increased the risk for any carcinoma (OR=1.10(per 5-year age increase), 95% CI 1.01–1.20) and thyroid carcinoma (OR(per 5-year age increase)=1.16, 95% CI 1.01–1.33). Gestational age <37 vs 37–42 weeks increased the risk for thyroid carcinoma (OR=1.87, 95% CI 1.07–3.27). Plurality, birth weight, and birth order were not significantly associated with childhood carcinomas. CONCLUSION: This exploratory study indicates that some birth characteristics including older parental age and low gestational age may be related to childhood carcinoma aetiology

    Universal Negative Poisson Ratio of Self Avoiding Fixed Connectivity Membranes

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    We determine the Poisson ratio of self-avoiding fixed-connectivity membranes, modeled as impenetrable plaquettes, to be sigma=-0.37(6), in statistical agreement with the Poisson ratio of phantom fixed-connectivity membranes sigma=-0.32(4). Together with the equality of critical exponents, this result implies a unique universality class for fixed-connectivity membranes. Our findings thus establish that physical fixed-connectivity membranes provide a wide class of auxetic (negative Poisson ratio) materials with significant potential applications in materials science.Comment: 4 pages, 3 figures, LaTeX (revtex) Published version - title changed, one figure improved and one reference change
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