933 research outputs found
Behaviour change techniques for telephone-delivered and supported health coaching interventions
This Evidence Check review examined the effectiveness of specific behaviour change techniques (BCTs) delivered by telephone in two areas: promoting healthy weight; and supporting parents. The review found that telephone-delivered interventions to promote healthy weight can be effectively used to change physical activity levels and improve diet. Interventions designed to support parents have been shown to improve both children’s behaviour and parents’ wellbeing. None of the included studies identified specific tools to determine which BCTs should be employed and when. The authors recommend the systematic use of theory to identify behavioural determinants and select the most effective BCT
Generalized Kahler manifolds and off-shell supersymmetry
We solve the long standing problem of finding an off-shell supersymmetric
formulation for a general N = (2, 2) nonlinear two dimensional sigma model.
Geometrically the problem is equivalent to proving the existence of special
coordinates; these correspond to particular superfields that allow for a
superspace description. We construct and explain the geometric significance of
the generalized Kahler potential for any generalized Kahler manifold; this
potential is the superspace Lagrangian.Comment: 21 pages; references clarified and added; theorem generalized; typos
correcte
Investigation of a hydraulic impact: a technology in rock breaking
The finite element method and dimensional analysis have been applied in the
present paper to study a hydraulic impact, which is utilized in a non-explosive
rock breaking technology in mining industry. The impact process of a high speed
piston on liquid water, previously introduced in a borehole drilled in rock, is
numerically simulated. The research is focused on the influences of all the
parameters involved in the technology on the largest principal stress in the
rock, which is considered as one of the key factors to break the rock. Our
detailed parametric investigation reveals that the variation of the isotropic
rock material properties, especially its density, has no significant influence
on the largest principal stress. The influences of the depth of the hole and
the depth of the water column are also very small. On the other hand,
increasing the initial kinetic energy of the piston can dramatically increase
the largest principal stress and the best way to increase the initial kinetic
energy of the piston is to increase its initial velocity. Results from the
current dimensional analysis can be applied to optimize this non-explosive rock
breaking technology
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Analysis of the distribution of the number of bidders in construction contract auctions
The number of bidders, N, involved in a construction procurement auction is known to have an important effect on the value of the lowest bid and the mark-up applied by bidders. In practice, for example, it is important for a bidder to have a good estimate of N when bidding for a current contract. One approach, instigated by Friedman in 1956, is to make such an estimate by statistical analysis and modelling. Since then, however, finding a suitable model for N has been an enduring problem for researchers and, despite intensive research activity in the subsequent 30 years, little progress has been made, due principally to the absence of new ideas and perspectives. The debate is resumed by checking old assumptions, providing new evidence relating to concomitant variables and proposing a new model. In doing this and in order to ensure universality, a novel approach is developed and tested by using a unique set of 12 construction tender databases from four continents. This shows the new model provides a significant advancement on previous versions. Several new research questions are also posed and other approaches identified for future study
Coherent matter wave inertial sensors for precision measurements in space
We analyze the advantages of using ultra-cold coherent sources of atoms for
matter-wave interferometry in space. We present a proof-of-principle experiment
that is based on an analysis of the results previously published in [Richard et
al., Phys. Rev. Lett., 91, 010405 (2003)] from which we extract the ratio h/m
for 87Rb. This measurement shows that a limitation in accuracy arises due to
atomic interactions within the Bose-Einstein condensate
BAs and boride III-V alloys
Boron arsenide, the typically-ignored member of the III-V arsenide series
BAs-AlAs-GaAs-InAs is found to resemble silicon electronically: its Gamma
conduction band minimum is p-like (Gamma_15), not s-like (Gamma_1c), it has an
X_1c-like indirect band gap, and its bond charge is distributed almost equally
on the two atoms in the unit cell, exhibiting nearly perfect covalency. The
reasons for these are tracked down to the anomalously low atomic p orbital
energy in the boron and to the unusually strong s-s repulsion in BAs relative
to most other III-V compounds. We find unexpected valence band offsets of BAs
with respect to GaAs and AlAs. The valence band maximum (VBM) of BAs is
significantly higher than that of AlAs, despite the much smaller bond length of
BAs, and the VBM of GaAs is only slightly higher than in BAs. These effects
result from the unusually strong mixing of the cation and anion states at the
VBM. For the BAs-GaAs alloys, we find (i) a relatively small (~3.5 eV) and
composition-independent band gap bowing. This means that while addition of
small amounts of nitrogen to GaAs lowers the gap, addition of small amounts of
boron to GaAs raises the gap (ii) boron ``semi-localized'' states in the
conduction band (similar to those in GaN-GaAs alloys), and (iii) bulk mixing
enthalpies which are smaller than in GaN-GaAs alloys. The unique features of
boride III-V alloys offer new opportunities in band gap engineering.Comment: 18 pages, 14 figures, 6 tables, 61 references. Accepted for
publication in Phys. Rev. B. Scheduled to appear Oct. 15 200
Melting behavior of ultrathin titanium nanowires
The thermal stability and melting behavior of ultrathin titanium nanowires
with multi-shell cylindrical structures are studied using molecular dynamic
simulation. The melting temperatures of titanium nanowires show remarkable
dependence on wire sizes and structures. For the nanowire thinner than 1.2 nm,
there is no clear characteristic of first-order phase transition during the
melting, implying a coexistence of solid and liquid phases due to finite size
effect. An interesting structural transformation from helical multi-shell
cylindrical to bulk-like rectangular is observed in the melting process of a
thicker hexagonal nanowire with 1.7 nm diameter.Comment: 4 pages, 4 figure
Methods for detecting PER2::LUCIFERASE bioluminescence rhythms in freely moving mice [preprint]
Circadian rhythms are driven by daily oscillations of gene expression. An important tool for studying cellular and tissue rhythms is the use of a gene reporter, such as bioluminescence from the reporter gene luciferase controlled by a rhythmically expressed gene of interest. Here we describe methods that allow measurement of bioluminescence from a freely-moving mouse housed in a standard cage. Using a LumiCycle In Vivo (Actimetrics), we determined conditions that allow detection of circadian rhythms of bioluminescence from the PER2 reporter, PER2::LUC, in freely behaving mice. We tested delivery of D-luciferin via a subcutaneous minipump and in the drinking water. Further, we demonstrate that a synthetic luciferase substrate, CycLuc1, can support circadian rhythms of bioluminescence, even when delivered at a lower concentration than D-luciferin. We share our analysis scripts and suggestions for further improvements in this method. This approach will be straightforward to apply to mice with tissue-specific reporters, allowing insights into responses of specific peripheral clocks to perturbations such as environmental or pharmacological manipulations
Seesaw mechanism in the sneutrino sector and its consequences
The seesaw-extended MSSM provides a framework in which the observed light
neutrino masses and mixing angles can be generated in the context of a natural
theory for the TeV-scale. Sneutrino-mixing phenomena provide valuable tools for
connecting the physics of neutrinos and supersymmetry. We examine the
theoretical structure of the seesaw-extended MSSM, retaining the full
complexity of three generations of neutrinos and sneutrinos. In this general
framework, new flavor-changing and CP-violating sneutrino processes are
allowed, and are parameterized in terms of two matrices that
respectively preserve and violate lepton number. The elements of these matrices
can be bounded by analyzing the rate for rare flavor-changing decays of charged
leptons and the one-loop contribution to neutrino masses. In the former case,
new contributions arise in the seesaw extended model which are not present in
the ordinary MSSM. In the latter case, sneutrino--antisneutrino mixing
generates the leading correction at one-loop to neutrino masses, and could
provide the origin of the observed texture of the light neutrino mass matrix.
Finally, we derive general formulae for sneutrino--antisneutrino oscillations
and sneutrino flavor-oscillations. Unfortunately, neither oscillation phenomena
is likely to be observable at future colliders.Comment: 69 pages, 5 figures, uses axodraw.sty. Version accepted for
publication in JHEP: some comments and one more Appendix with additional
discussion added, references update
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