87 research outputs found
Enhanced roughness of lipid membranes caused by external electric fields
The behavior of lipid membranes in the presence of an external electric field
is studied and used to examine the influence of such fields on membrane
parameters such as roughness and show that for a micro sized membrane,
roughness grows as the field increases. The dependence of bending rigidity on
the electric field is also studied and an estimation of thickness of the
accumulated charges around lipid membranes in a free-salt solution is
presented.Comment: 9 pages, 6 figures, to appear in Computational Materials Scienc
Big bang simulation in superfluid 3He-B -- Vortex nucleation in neutron-irradiated superflow
We report the observation of vortex formation upon the absorption of a
thermal neutron in a rotating container of superfluid He-B. The nuclear
reaction n + He = p + H + 0.76MeV heats a cigar shaped region of the
superfluid into the normal phase. The subsequent cooling of this region back
through the superfluid transition results in the nucleation of quantized
vortices. Depending on the superflow velocity, sufficiently large vortex rings
grow under the influence of the Magnus force and escape into the container
volume where they are detected individually with nuclear magnetic resonance.
The larger the superflow velocity the smaller the rings which can expand. Thus
it is possible to obtain information about the morphology of the initial defect
network. We suggest that the nucleation of vortices during the rapid cool-down
into the superfluid phase is similar to the formation of defects during
cosmological phase transitions in the early universe.Comment: 4 pages, LaTeX file, 4 figures are available at
ftp://boojum.hut.fi/pub/publications/lowtemp/LTL-95009.p
B-L Cosmic Strings in Heterotic Standard Models
E_{8} X E_{8} heterotic string and M-theory, when compactified on smooth
Calabi-Yau manifolds with SU(4) vector bundles, can give rise to softly broken
N=1 supersymmetric theories with the exact matter spectrum of the MSSM,
including three right-handed neutrinos and one Higgs-Higgs conjugate pair of
supermultiplets. These vacua have the SU(3)_{C} X SU(2)_{L} X U(1)_{Y} gauge
group of the standard model augmented by an additional gauged U(1)_{B-L}. Their
minimal content requires that the B-L symmetry be spontaneously broken by a
vacuum expectation value of at least one right-handed sneutrino. The soft
supersymmetry breaking operators can induce radiative breaking of the B-L gauge
symmetry with an acceptable B-L/electroweak hierarchy. In this paper, it is
shown that U(1)_{B-L} cosmic strings occur in this context, potentially with
both bosonic and fermionic superconductivity. We present a numerical analysis
that demonstrates that boson condensates can, in principle, form for theories
of this type. However, the weak Yukawa and gauge couplings of the right-handed
sneutrino suggests that bosonic superconductivity will not occur in the
simplest vacua in this context. The electroweak phase transition also disallows
fermion superconductivity, although substantial bound state fermion currents
can exist.Comment: 41 pages, 5 figure
Anomaly Mediation and Cosmology
We consider an extension of the MSSM wherein anomaly mediation is the source
of supersymmetry breaking, and the tachyonic slepton problem is solved by a
gauged U(1) symmetry, which is broken at high energies in a manner preserving
supersymmetry, thereby also facilitating the see-saw mechanism for neutrino
masses and a natural source for the Higgs mu-term. We show that these
favourable outcomes can occur both in the presence and the absence of a large
Fayet-Iliopoulos (FI) D-term associated with the new U(1). We explore the
cosmological consequences of the model, showing that it naturally produces a
period of hybrid inflation, terminating in the production of cosmic strings. In
spite of the presence of a U(1) (even with an FI term), inflation is effected
by the F-term, with a D-flat tree potential (the FI term, if present, being
cancelled by non-zero squark and slepton fields). Calculating the 1-loop
corrections to the inflaton potential, we estimate the constraints on the
parameters of the model from Cosmic Microwave Background data. We will see that
a consequence of these constraints is that the Higgs mu-term necessarily small.
We briefly discuss the mechanisms for baryogenesis via conventional
leptogenesis, the out-of-equilibrium production of neutrinos from the cosmic
strings, or the Affleck-Dine mechanism. Cosmic string decays also boost the
relic density of dark matter above the low value normally obtained in AMSB
scenarios.Comment: 34 pages. Revised to incorporate discussion of the case when the
Fayet-Ilipoulos term is absen
Lessons learned from implementation of a demonstration program to reduce the burden of anemia and hookworm in women in Yen Bai Province, Viet Nam
Background Iron deficiency, anemia and hookworm disease are important public health problems for women of reproductive age living in developing countries and affect the health of newborns and infants. Iron supplementation and deworming treatment are effective in addressing these problems in both pregnant and non-pregnant women. Daily iron supplementation and deworming after the first trimester is recommended for pregnant women although these programs usually do not operate efficiently or effectively. Weekly iron-folic acid supplementation and regular deworming for non-pregnant women may be a viable approach for improving iron status and preventing anemia during the reproductive years. Addressing these diseases at a population level before women become pregnant could significantly improve women's health before and during pregnancy, as well as their infants' growth and development. Methods and Results This paper describes the major processes undertaken in a demonstration intervention of preventive weekly iron-folic acid supplementation with regular deworming for all 52,000 women aged 15–45 years in two districts of Yen Bai province, in northern Viet Nam. The intervention strategy included extensive consultation with community leaders and village, commune, district and provincial health staff, and training for village health workers. Distribution of the drugs was integrated with the existing health service infrastructure and the village health workers were the direct point of contact with women. Iron-folic acid tablets and deworming treatment were provided free of charge from May 2006. An independent Vietnamese NGO was commissioned to evaluate compliance and identify potential problems. The program resulted in effective distribution of iron-folic acid tablets and deworming treatment to all villages in the target districts, with full or partial compliance of 85%. Conclusion Training for health staff, the strong commitment of all partners and the use of appropriate educational materials led to broad support for weekly iron-folic acid supplementation and high participation in the regular deworming days. In March 2008 the program was expanded to all districts in the province, a target population of approximately 250,000 WRA, and management was handed over to provincial authorities
Balance training program is highly effective in improving functional status and reducing the risk of falls in elderly women with osteoporosis: a randomized controlled trial
INTRODUCTION: The purpose of this study was to investigate the effect of a 12-month Balance Training Program on balance, mobility and falling frequency in women with osteoporosis. METHODS: Sixty-six consecutive elderly women were selected from the Osteometabolic Disease Outpatient Clinic and randomized into 2 groups: the ‘Intervention’, submitted for balance training; and the ‘Control’, without intervention. Balance, mobility and falling frequency were evaluated before and at the end of the trial, using the Berg Balance Scale (BBS), the Clinical Test Sensory Interaction Balance (CTSIB) and the Timed “Up & Go” Test (TUGT). Intervention used techniques to improve balance consisting of a 1-hour session each week and a home-based exercise program. RESULTS: Sixty women completed the study and were analyzed. The BBS difference was significant higher in the Intervention group compared to Control (5.5 ± 5.67 vs −0.5 ± 4.88 score, p < 0.001). Similarly, the number of patients in the Intervention group presented improvement in two conditions of CTSIB compared to Control (eyes closed and unstable surface condition: 13 vs one patient, p < 0.001 and eyes open, visual conflict and unstable surface condition: 12 vs one patient, p < 0.001). Additionally, the differences between the TUGT were reduced in the Intervention group compared to Control (−3.65 ± 3.61 vs 2.27 ± 7.18 seconds, p< 0.001). Notably, this improvement was paralleled by a reduction in the number of falls/patient in the Intervention group compared to Control (−0.77 ± 1.76 vs 0.33 ± 0.96, p = 0.018). CONCLUSION: This longitudinal prospective study demonstrated that an intervention using balance training is effective in improving functional and static balance, mobility and falling frequency in elderly women with osteoporosis
Vacuum Topology of the Two Higgs Doublet Model
We perform a systematic study of generic accidental Higgs-family and CP
symmetries that could occur in the two-Higgs-doublet-model potential, based on
a Majorana scalar-field formalism which realizes a subgroup of GL(8,C). We
derive the general conditions of convexity and stability of the scalar
potential and present analytical solutions for two non-zero neutral vacuum
expectation values of the Higgs doublets for a typical set of six symmetries,
in terms of the gauge-invariant parameters of the theory. By means of a
homotopy-group analysis, we identify the topological defects associated with
the spontaneous symmetry breaking of each symmetry, as well as the massless
Goldstone bosons emerging from the breaking of the continuous symmetries. We
find the existence of domain walls from the breaking of Z_2, CP1 and CP2
discrete symmetries, vortices in models with broken U(1)_PQ and CP3 symmetries
and a global monopole in the SO(3)_HF-broken model. The spatial profile of the
topological defect solutions is studied in detail, as functions of the
potential parameters of the two-Higgs doublet model. The application of our
Majorana scalar-field formalism in studying more general scalar potentials that
are not constrained by the U(1)_Y hypercharge symmetry is discussed. In
particular, the same formalism may be used to properly identify seven
additional symmetries that may take place in a U(1)_Y-invariant scalar
potential.Comment: 89 pages, 13 tables and 12 figures (version as to appear in JHEP
Entry of Human Papillomavirus Type 16 by Actin-Dependent, Clathrin- and Lipid Raft-Independent Endocytosis
Infectious endocytosis of incoming human papillomavirus type 16 (HPV-16), the main etiological agent of cervical cancer, is poorly characterized in terms of cellular requirements and pathways. Conflicting reports attribute HPV-16 entry to clathrin-dependent and -independent mechanisms. To comprehensively describe the cell biological features of HPV-16 entry into human epithelial cells, we compared HPV-16 pseudovirion (PsV) infection in the context of cell perturbations (drug inhibition, siRNA silencing, overexpression of dominant mutants) to five other viruses (influenza A virus, Semliki Forest virus, simian virus 40, vesicular stomatitis virus, and vaccinia virus) with defined endocytic requirements. Our analysis included infection data, i.e. GFP expression after plasmid delivery by HPV-16 PsV, and endocytosis assays in combination with electron, immunofluorescence, and video microscopy. The results indicated that HPV-16 entry into HeLa and HaCaT cells was clathrin-, caveolin-, cholesterol- and dynamin-independent. The virus made use of a potentially novel ligand-induced endocytic pathway related to macropinocytosis. This pathway was distinct from classical macropinocytosis in regards to vesicle size, cholesterol-sensitivity, and GTPase requirements, but similar in respect to the need for tyrosine kinase signaling, actin dynamics, Na+/H+ exchangers, PAK-1 and PKC. After internalization the virus was transported to late endosomes and/or endolysosomes, and activated through exposure to low pH
QCD and strongly coupled gauge theories : challenges and perspectives
We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.Peer reviewe
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