18,246 research outputs found
Smectic-Nematic Phase Transition as Wrinkling Transition in a Stack of Membranes
We point out that the smectic-nematic phase transition may considered as a
transition of a stack of membranes in dimensions, in which the
layers become so wrinkled that they interpenetrate each other are no longer
distinguishable.Comment: Author Information under
http://www.physik.fu-berlin.de/~kleinert/institution.html . Latest update of
paper also at http://www.physik.fu-berlin.de/~kleinert/137
Master of Science
thesisOne in four women in the U.S. will contract a pelvic floor disorder (PFD) in her lifetime. High intra-abdominal pressure (IAP) may be a factor influencing the development of PFDs, causing women at risk for PFDs to receive physical activity restrictions. However, there is limited research as to what daily activities and exercises cause high IAPs. Our lab developed an intravaginal pressure transducer to measure IAP in women during exercise and daily activities, but utilizing the transducer as a long-term measurement device may present compliance issues. Waist-worn accelerometers, which measure acceleration and physical activity, are more commonly utilized devices and may prove to be reliable replacements for the transducer. We hypothesized that there is a positive correlation between the mean maximal vector magnitude for acceleration and the mean maximal IAP and mean area under the curve (AUC) for IAP. After measuring 25 women's IAP and acceleration during specific exercises, we found an R2 of 0.7405 for the relationship between mean maximal accelerometer vector magnitude and mean maximal intra-abdominal pressure and of 0.5255 for the relationship between mean maximal accelerometer vector magnitude and mean area under the curve for intra-abdominal pressure. Analysis of different walking stages presented even higher R2 values, demonstrating that waist-worn accelerometers may present a viable method for predicting IAP
Pump-probe differencing technique for cavity-enhanced, noise-canceling saturation laser spectroscopy
We present an experimental technique enabling mechanical-noise free,
cavity-enhanced frequency measurements of an atomic transition and its
hyperfine structure. We employ the 532nm frequency doubled output from a Nd:YAG
laser and an iodine vapour cell. The cell is placed in a traveling-wave
Fabry-Perot interferometer (FPI) with counter-propagating pump and probe beams.
The FPI is locked using the Pound-Drever-Hall (PDH) technique. Mechanical noise
is rejected by differencing pump and probe signals. In addition, this
differenced error signal gives a sensitive measure of differential
non-linearity within the FPI.Comment: 3 pages, 5 figures, submitted to Optics Letter
Transmission of PhC coupled-resonator waveguide (PhCCRW) structure enhanced via mode matching
A method for increasing the coupling efficiency between ridge optical waveguides and PhCCRWs is described. This increase is achieved via W1 channel waveguide sections, formed within a two-dimensional triangular lattice photonic crystal using mode-matching. The mode-matching is achieved by low quality-factor modified cavities added to both the input and output ports of the PhCCRW. A three dimensional finite-difference time-domain method has been used to simulate light propagation through the modified PhCCRW. We have fabricated PhCCRWs working at 1.5”m in silicon-on-insulator material. Measurements and simulations show that the overall transmission is improved by a factor of two
Stress-induced nuclear accumulation is dispensable for Hog1-dependent gene expression and virulence in a fungal pathogen
The authors thank E. Veal for intellectual input. This work was funded by the UK Biotechnology and Biological Research Council [J.Q. BB/K016393/1; A.J.P.B. BB/K017365/1], the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) [D.M.M. NC/N002482/1] and the Wellcome Trust Strategic Award in Medical Mycology and Fungal Immunology [097377]). D.M.M. and A.J.P.B. are also supported by the MRC Centre for Medical Mycology at the University of Aberdeen (MR/N006364/1).Peer reviewedPublisher PD
Action functional and quasi-potential for the Burgers equation in a bounded interval
Consider the viscous Burgers equation on
the interval with the inhomogeneous Dirichlet boundary conditions
, . The flux is the function , is the viscosity, and the boundary data satisfy
. We examine the quasi-potential corresponding to an action
functional, arising from non-equilibrium statistical mechanical models,
associated to the above equation. We provide a static variational formula for
the quasi-potential and characterize the optimal paths for the dynamical
problem. In contrast with previous cases, for small enough viscosity, the
variational problem defining the quasi potential admits more than one
minimizer. This phenomenon is interpreted as a non-equilibrium phase transition
and corresponds to points where the super-differential of the quasi-potential
is not a singleton
Small excitonic complexes in a disk-shaped quantum dot
Confined excitonic complexes in two dimensions, consisting of N_e electrons
and N_h holes, are studied by means of Bethe-Goldstone equations. Systems with
up to twelve pairs, and asymmetric configurations with N_e \ne N_h are
considered. The weak confinement regime gives indication of weak binding or
even unbinding in the triexciton and the four-exciton system, and binding in
the higher complexes.Comment: 13 pages, 4 figures, submitted to Physica
Final state interactions in the electroweak nuclear response
I review the description of the electroweak nuclear response at large
momentum transfer within nonrelativistic many-body theory. Special
consideration is given to the effects of final state interactions, which are
known to be large in both inclusive and semi-inclusive processes. The results
of theoretical calculations of electron-nucleus scattering observables are
compared to the data, and the generalization to charged current
neutrino-nucleus interactions is discussed.Comment: Invited talk at NUINT05. To be published in Nucl. Phys. B Proceedings
Supplemen
Experimental and modeling studies on the synthesis and properties of higher fatty esters of corn starch
This paper describes a systematic study on the synthesis of higher fatty esters of corn starch (starch laurate and starch stĂ©arate) by using the corresponding vinyl esters. The reactions were carried out in DMSO using basic catalysts (Na2HPO4, K2CO3, and Naacetate). The effect of the process variables (vinyl ester to starch ratio, catalyst intake, reaction temperature and type of the catalyst) on the degree of substitution (DS) of the starch laurate and starch stearate esters was determined by performing a total of 54 experiments. The results were adequately modeled using a non-linear multivariable regression model (R2Ăąâ°Â„0. 96). The basicity of the catalyst and the reaction temperature have the highest impact on the product DS. The thermal and mechanical properties of some representative product samples were determined. High-DS products (DS = 2.26-2.39) are totally amorphous whereas the low-DS ones (DS = 1.45-1.75) are still partially crystalline. The thermal stability of the esterlfied products is higher than that of native starch. Mechanical tests show that the products have a tensile strength (stress at break) between 2.7-3.5 MPa, elongation at break of 3-26%, and modulus of elasticity of 46-113 MPa.
Occurrence of preterm calving in Great Britain and associations with milk production and reproductive performance in dairy cattle
This study describes the occurrence of preterm calving in Great Britain and evaluates its associations with subsequent milk production and reproductive performances and survival on farm of dairy cows. A total of 53 British dairy farms and 5759 animals with detailed breeding and milk recording data available were used to form two study groups: preterm calving (calving occurring between days 266 and 277 of gestation) and full-term calving (calving occurring at 278 days of gestation and over). Mixed effects models were implemented to compare milk production, clinical cases of mastitis and number of services per conception between groups. Kaplan-Meier curves and Cox regression analyses compared time from calving to conception, calving interval and survival on farm between groups. Preterm calving cows showed significantly lower milk yield (P<0.01) and butter fat per cent (P=0.02), increased milk protein per cent (P=0.01), longer survival on farm (P<0.01), and a tendency for shorter calving to conception intervals and fewer services per conception, although other factors were involved in the reproduction outcomes. Experiencing a preterm calving is associated with lower milk production and longer survival times on farm. Potential risk factors for preterm calving, such as infectious diseases, diet and husbandry practices, should be further investigated
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