1,443 research outputs found
Analysis of measured stress data in a solid rocket motor
A sinusoidal regression model is fitted to stress and temperature response data in a solid rocket motor under various thermal loading conditions. Using the model statistics and measured failure data, failure probability and reliability calculations are performed for each loading condition via two different approaches
Synthesis and pinning properties of the infinite-layer superconductor Sr0.9La0.1CuO
We report the high-pressure synthesis of the electron-doped infinite-layer
superconductor Sr0.9La0.1CuO2 and its superconducting properties. A Rietveld
analysis of X-ray powder diffraction data showed that, within the resolution of
the measurement, the sample had purely an infinite-layer structure without any
discernible impurities. The superconducting volume fraction and the transition
width were greatly improved compared to those in previous reports. The
irreversibility field line and the intragranular critical current density were
much higher than those of La1.85Sr0.15CuO4 and Nd1.85Ce0.15CuO4. The stronger
pinning behaviors are consistent with the strong interlayer coupling due to the
short distance between CuO2 planes.Comment: Physica C (in press) 5 pages, 4 figur
Resistance training enhances delayed memory in healthy middle-aged and older adults: A randomised controlled trial
Objectives
High-intensity exercise is a potential therapeutic tool to postpone or prevent the onset of cognitive decline. However, there is a lack of sufficient evidence regarding the longitudinal effects of structured resistance training on cognitive function in healthy adults. The purpose of this study was to investigate the effect of two ecologically valid, intense 12-week resistance training programs on cognitive function in late middle-aged adults.
Design
Single-site parallel randomised controlled trial at the Department of Exercise Science strength and conditioning laboratory. Groups allocated by minimisation randomisation.
Methods
Forty-five healthy adults (age range = 41-69 years) were enrolled and randomised into A.) high-load, long rest resistance training (n = 14), or B.) moderate-load, short rest resistance training (n = 15) twice per week for 12 weeks, or a non-exercising control (n = 16). Follow-up within 7 days. Data were collected September 2016-December 2017. Cognitive function assessed using the CogState computerised battery. Assessors were blinded to participant group allocation. Secondary outcomes were maximal muscle strength and body composition.
Results
Forty-four participants were analysed in 2018. Delayed verbal memory performance was improved (p = 0.02) in resistance training groups (g = 0.67-0.79) when compared to the control group, with no differences between training groups. Likewise, increases in maximal muscle strength were observed (p < 0.01) in resistance training groups when compared to the control group, with no differences between training groups. No differences in body composition were observed. There were no adverse events or side-effects of the intervention.
Conclusions
12 weeks of intense resistance training improves delayed verbal memory irrespective of training design (i.e., high-load vs. moderate-load)
Force-Extension Relations for Polymers with Sliding Links
Topological entanglements in polymers are mimicked by sliding rings
(slip-links) which enforce pair contacts between monomers. We study the
force-extension curve for linear polymers in which slip-links create additional
loops of variable size. For a single loop in a phantom chain, we obtain exact
expressions for the average end-to-end separation: The linear response to a
small force is related to the properties of the unstressed chain, while for a
large force the polymer backbone can be treated as a sequence of Pincus--de
Gennes blobs, the constraint effecting only a single blob. Generalizing this
picture, scaling arguments are used to include self-avoiding effects.Comment: 4 pages, 5 figures; accepted to Phys. Rev. E (Brief Report
Exciton swapping in a twisted graphene bilayer as a solid-state realization of a two-brane model
It is shown that exciton swapping between two graphene sheets may occur under
specific conditions. A magnetically tunable optical filter is described to
demonstrate this new effect. Mathematically, it is shown that two turbostratic
graphene layers can be described as a "noncommutative" two-sheeted
(2+1)-spacetime thanks to a formalism previously introduced for the study of
braneworlds in high energy physics. The Hamiltonian of the model contains a
coupling term connecting the two layers which is similar to the coupling
existing between two braneworlds at a quantum level. In the present case, this
term is related to a K-K' intervalley coupling. In addition, the experimental
observation of this effect could be a way to assess the relevance of some
theoretical concepts of the braneworld hypothesis.Comment: 15 pages, 3 figures, final version published in European Physical
Journal
Sustainable cooling method for machining titanium alloy
Hard to machine materials such as Titanium Alloy TI-6AI-4V Grade 5 are notoriously known to generate high temperatures and adverse reactions between the workpiece and the tool tip materials. These conditions all contribute to an increase in the wear mechanisms, reducing tool life. Titanium Alloy, for example always requires coolant to be used during machining. However, traditional flood cooling needs to be replaced due to environmental issues, and an alternative cooling method found that has minimum impact on the environment. For true sustainable cooling of the tool it is necessary to account for all energy used in the cooling process, including the energy involved in producing the coolant. Previous research has established that efficient cooling of the tool interface improves the tool life and cutting action. The objective of this research is to determine the most appropriate sustainable cooling method that can also reduce the rate of wear at the tool interface
Implementation fidelity of a voluntary sector-led diabetes education programme
© 2018, © Michele S.Y. Kok, Mat Jones, Emma Solomon-Moore and Jane R. Smith. Purpose: The quality of voluntary sector-led community health programmes is an important concern for service users, providers and commissioners. Research on the fidelity of programme implementation offers a basis for assessing and further enhancing practice. The purpose of this paper is to report on the fidelity assessment of Living Well Taking Control (LWTC) – a voluntary sector-led, community-based education programme in England focussing on the prevention and management of type 2 diabetes. Design/methodology/approach: This fidelity of implementation (FoI) study was conducted with the Devon-based LWTC programme. A fidelity checklist was developed to analyse audio records of group-based lifestyle education sessions – implementation was rated in terms of adherence to protocol and competence in delivery; the influence of wider contextual factors was also assessed. Kappa statistics (κ) were used to test for inter-rater agreement. Course satisfaction data were used as a supplementary indicator of facilitator competence. Findings: Analysis of 28 sessions, from five diabetes prevention and two diabetes management groups (total participants, n=49), yielded an overall implementation fidelity score of 77.3 per cent for adherence (moderate inter-rater agreement, κ=0.60) and 95.1 per cent for competence (good inter-rater agreement, κ=0.71). The diabetes prevention groups consistently achieved higher adherence scores than the diabetes management groups. Facilitator competence was supported by high participant satisfaction ratings. Originality/value: An appropriate level of implementation fidelity was delivered for the LWTC group-based education programme, which provides some confidence that outcomes from the programme reflected intervention effectiveness. This study demonstrates the viability of assessing the FoI in a voluntary sector-led public health initiative and the potential of this method for assuring quality and informing service development
Bloch bundles, Marzari-Vanderbilt functional and maximally localized Wannier functions
We consider a periodic Schroedinger operator and the composite Wannier
functions corresponding to a relevant family of its Bloch bands, separated by a
gap from the rest of the spectrum. We study the associated localization
functional introduced by Marzari and Vanderbilt, and we prove some results
about the existence and exponential localization of its minimizers, in
dimension d < 4. The proof exploits ideas and methods from the theory of
harmonic maps between Riemannian manifolds.Comment: 37 pages, no figures. V2: the appendix has been completely rewritten.
V3: final version, to appear in Commun. Math. Physic
A Simultaneous Forbush Decrease Associated with an Earthward Coronal Mass Ejection Observed by STEREO
Application of Pulsed Field Gel Electrophoresis to Determine Îł-ray-induced Double-strand Breaks in Yeast Chromosomal Molecules
The frequency of DNA double-strand breaks (dsb) was determined in yeast cells exposed to Îł-rays under anoxic conditions. Genomic DNA of treated cells was separated by pulsed field gel electrophoresis, and two different approaches for the evaluation of the gels were employed: (1) The DNA mass distribution profile obtained by electrophoresis was compared to computed profiles, and the number of DSB per unit length was then derived in terms of a fitting procedure; (2) hybridization of selected chromosomes was performed, and a comparison of the hybridization signals in treated and untreated samples was then used to derive the frequency of dsb
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