447 research outputs found
Modified Fowler-Nordheim Field-Emission Formulae from a Nonplanar-Emitter Model
Field emission formulae, current-voltage characteristics and energy
distribution of emitted electrons, are derived analytically for a nonplanar
(hyperboloidal) metallic emitter model. The traditional Fowler-Nordheim
formulae, which are derived from a planar emitter model, are modified, and the
assumption of the planar emitter in the F-N model is reconsidered. Our
analytical calculation also reveals the backgrounds of the previous numerical
discussion by He et al. on the effect of the geometry of emitter on field
emission. The new formulae contain a parameter which characterizes the
sharpness of the hyperboloidal emitter, and experimental data of field
emissions from clean tungsten emitters and nanotip emitters are analyzed by
making use of this feature.Comment: 9 pages, 8 figure
Feasibility study and pilot cluster randomised controlled trial of the GoActive Intervention aiming to promote physical activity among adolescents: outcomes and lessons learnt
Assess the feasibility of implementing the GoActive intervention in secondary schools, to identify improvements, test study procedures, determine preliminary effectiveness to increase moderate-to-vigorous physical activity (MVPA), and inform power calculations to establish programme effectiveness.
Feasibility study (1 school) and pilot CRCT (2 intervention;1 control school(s))
460 participants (46.6% female; 13.2(0.4) years-old).
8-week intervention (2013) involved: classes choosing weekly activities encouraged by Mentors (older adolescents) and in-class peer-leaders. Students gain points for trying activities which are entered into an intra-mural competition.
Planned quantitative (questionnaire) and qualitative (focus groups) process evaluation addressed enjoyment, confidence, participation, suggested improvements. Outcomes were assessed at baseline and follow-up (week 8) in pilot CRCT and included: accelerometer-assessed MVPA; adolescent-reported activity type, wellbeing, peer-support, shyness, sociability. ANCOVA was used to assess preliminary effectiveness as change in MVPA adjusted for baseline.
All Year 9 students in intervention schools were exposed to the intervention; over all schools 77% of eligible students were measured. 71% boys and 74% girls found GoActive âfunâ; 38% boys and 32% girls said it increased confidence and 64% boys and 59% girls said they would continue with a GoActive activity. Suggested improvements included more Mentorship; improved training; streamlined points recording. Pilot results indicated potential effectiveness ((adjusted mean difference (95%CI)p-value) (MVPA mins) 5.1(1.1,9.2)p=0.014)) and suggest recruitment of 16 schools (2400 adolescents) for a full trial. Compared to control, intervention students reported greater peer support 0.5(0.1,0.9)p=0.03, wellbeing 1.8(0.1, 3.4)p=0.04 but no difference in shyness/sociability. Participation in activity types approached significance (intervention group 2.3(-0.2,4.7)p=0.07 more activity types).
Results suggest feasibility and indicate potential effectiveness of GoActive to increase MVPA and support a fully-powered evaluation of effectiveness and cost-effectiveness. Process evaluation data was used to refine GoActive prior to a full trial.
ISRCTN registry ISRCTN31583496.Funding for this study and the work of all authors was supported, wholly or in part, by the Centre for Diet and Activity Research (CEDAR), a UKCRC Public Health Research Centre of Excellence (RES-590-28-0002). Funding from the British Heart Foundation, Department of Health, Economic and Social Research Council, Medical Research Council, and the Wellcome Trust, under the auspices of the UK Clinical Research Collaboration, is gratefully acknowledged. The work of Kirsten Corder, Helen Brown and Esther M F van Sluijs was supported by the Medical Research Council (MC_UU_12015/7)
An epigenomic approach to therapy for tamoxifen-resistant breast cancer
Tamoxifen has been a frontline treatment for estrogen receptor alpha (ERα)-positive breast tumors in premenopausal women. However, resistance to tamoxifen occurs in many patients. ER still plays a critical role in the growth of breast cancer cells with acquired tamoxifen resistance, suggesting that ERα remains a valid target for treatment of tamoxifen-resistant (Tam-R) breast cancer. In an effort to identify novel regulators of ERα signaling, through a small-scale siRNA screen against histone methyl modifiers, we found WHSC1, a histone H3K36 methyltransferase, as a positive regulator of ERα signaling in breast cancer cells. We demonstrated that WHSC1 is recruited to the ERα gene by the BET protein BRD3/4, and facilitates ERα gene expression. The small-molecule BET protein inhibitor JQ1 potently suppressed the classic ERα signaling pathway and the growth of Tam-R breast cancer cells in culture. Using a Tam-R breast cancer xenograft mouse model, we demonstrated in vivo anti-breast cancer activity by JQ1 and a strong long-lasting effect of combination therapy with JQ1 and the ER degrader fulvestrant. Taken together, we provide evidence that the epigenomic proteins BRD3/4 and WHSC1 are essential regulators of estrogen receptor signaling and are novel therapeutic targets for treatment of Tam-R breast cancer
Nuclear Electric Dipole Moment of 3He
A permanent electric dipole moment (EDM) of a physical system requires
time-reversal (T) and parity (P) violation. Experimental programs are currently
pushing the limits on EDMs in atoms, nuclei, and the neutron to regimes of
fundamental theoretical interest. Here we calculate the magnitude of the
PT-violating EDM of 3He and the expected sensitivity of such a measurement to
the underlying PT-violating interactions. Assuming that the coupling constants
are of comparable magnitude for pi-, rho-, and omega-exchanges, we find that
the pion-exchange contribution dominates. Our results suggest that a
measurement of the 3He EDM is complementary to the planned neutron and deuteron
experiments, and could provide a powerful constraint for the theoretical models
of the pion-nucleon PT-violating interaction.Comment: 6 pages, 1 figur
Quantum physics in inertial and gravitational fields
Covariant generalizations of well-known wave equations predict the existence
of inertial-gravitational effects for a variety of quantum systems that range
from Bose-Einstein condensates to particles in accelerators. Additional effects
arise in models that incorporate Born reciprocity principle and the notion of a
maximal acceleration. Some specific examples are discussed in detail.Comment: 25 pages,1 figure,to appear in "Relativity in Rotating Frame
Mouse Studies to Shape Clinical Trials for Mitochondrial Diseases: High Fat Diet in Harlequin Mice
BACKGROUND: Therapeutic options in human mitochondrial oxidative phosphorylation (OXPHOS) diseases have been poorly evaluated mostly because of the scarcity of cohorts and the inter-individual variability of disease progression. Thus, while a high fat diet (HFD) is often recommended, data regarding efficacy are limited. Our objectives were 1) to determine our ability to evaluate therapeutic options in the Harlequin OXPHOS complex I (CI)-deficient mice, in the context of a mitochondrial disease with human hallmarks and 2) to assess the effects of a HFD. METHODS AND FINDINGS: Before launching long and expensive animal studies, we showed that palmitate afforded long-term death-protection in 3 CI-mutant human fibroblasts cell lines. We next demonstrated that using the Harlequin mouse, it was possible to draw solid conclusions on the efficacy of a 5-month-HFD on neurodegenerative symptoms. Moreover, we could identify a group of highly responsive animals, echoing the high variability of the disease progression in Harlequin mice. CONCLUSIONS: These results suggest that a reduced number of patients with identical genetic disease should be sufficient to reach firm conclusions as far as the potential existence of responders and non responders is recognized. They also positively prefigure HFD-trials in OXPHOS-deficient patients
Electric Dipole Moments in the MSSM at Large tan(beta)
Within the minimal supersymmetric standard model (MSSM), the large tan(beta)
regime can lead to important modifications in the pattern of CP-violating
sources contributing to low energy electric dipole moments (EDMs). In
particular, four-fermion CP-violating interactions induced by Higgs exchange
should be accounted for alongside the constituent EDMs of quarks and electrons.
To this end, we present a comprehensive analysis of three low energy EDM
observables - namely the EDMs of thallium, mercury and the neutron - at large
tan(beta), in terms of one- and two-loop contributions to the constituent EDMs
and four-fermion interactions. We concentrate on the constrained MSSM as well
as the MSSM with non-universal Higgs masses, and include the CP-violating
phases of mu and A. Our results indicate that the atomic EDMs receive
significant corrections from four-fermion operators, especially when Im(A) is
the only CP-violating source, whereas the neutron EDM remains relatively
insensitive to these effects. As a consequence, in a large portion of the
parameter space, one cannot infer a separate bound on the electron EDM via the
experimental constraint on the thallium EDM. Furthermore, we find that the
electron EDM can be greatly reduced due to the destructive interference of one-
and two-loop contributions with the latter being dominated by virtual staus.Comment: 39 pages, 17 figure
Three randomised studies of dentine hypersensitivity reduction after short-term SnF2 toothpaste use
Probing exotic phenomena at the interface of nuclear and particle physics with the electric dipole moments of diamagnetic atoms: A unique window to hadronic and semi-leptonic CP violation
The current status of electric dipole moments of diamagnetic atoms which
involves the synergy between atomic experiments and three different theoretical
areas -- particle, nuclear and atomic is reviewed. Various models of particle
physics that predict CP violation, which is necessary for the existence of such
electric dipole moments, are presented. These include the standard model of
particle physics and various extensions of it. Effective hadron level combined
charge conjugation (C) and parity (P) symmetry violating interactions are
derived taking into consideration different ways in which a nucleon interacts
with other nucleons as well as with electrons. Nuclear structure calculations
of the CP-odd nuclear Schiff moment are discussed using the shell model and
other theoretical approaches. Results of the calculations of atomic electric
dipole moments due to the interaction of the nuclear Schiff moment with the
electrons and the P and time-reversal (T) symmetry violating
tensor-pseudotensor electron-nucleus are elucidated using different
relativistic many-body theories. The principles of the measurement of the
electric dipole moments of diamagnetic atoms are outlined. Upper limits for the
nuclear Schiff moment and tensor-pseudotensor coupling constant are obtained
combining the results of atomic experiments and relativistic many-body
theories. The coefficients for the different sources of CP violation have been
estimated at the elementary particle level for all the diamagnetic atoms of
current experimental interest and their implications for physics beyond the
standard model is discussed. Possible improvements of the current results of
the measurements as well as quantum chromodynamics, nuclear and atomic
calculations are suggested.Comment: 46 pages, 19 tables and 16 figures. A review article accepted for
EPJ
Violations of fundamental symmetries in atoms and tests of unification theories of elementary particles
High-precision measurements of violations of fundamental symmetries in atoms
are a very effective means of testing the standard model of elementary
particles and searching for new physics beyond it. Such studies complement
measurements at high energies. We review the recent progress in atomic parity
nonconservation and atomic electric dipole moments (time reversal symmetry
violation), with a particular focus on the atomic theory required to interpret
the measurements.Comment: 103 pages, 23 figures; submitted to Physics Reports; comments welcom
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