1,204 research outputs found
Solving variational inequalities defined on a domain with infinitely many linear constraints
We study a variational inequality problem whose domain is defined by infinitely many linear inequalities. A discretization method and an analytic center based inexact cutting plane method are proposed. Under proper assumptions, the convergence results for both methods are given. We also provide numerical examples to illustrate the proposed method
The long-time dynamics of two hydrodynamically-coupled swimming cells
Swimming micro-organisms such as bacteria or spermatozoa are typically found
in dense suspensions, and exhibit collective modes of locomotion qualitatively
different from that displayed by isolated cells. In the dilute limit where
fluid-mediated interactions can be treated rigorously, the long-time
hydrodynamics of a collection of cells result from interactions with many other
cells, and as such typically eludes an analytical approach. Here we consider
the only case where such problem can be treated rigorously analytically, namely
when the cells have spatially confined trajectories, such as the spermatozoa of
some marine invertebrates. We consider two spherical cells swimming, when
isolated, with arbitrary circular trajectories, and derive the long-time
kinematics of their relative locomotion. We show that in the dilute limit where
the cells are much further away than their size, and the size of their circular
motion, a separation of time scale occurs between a fast (intrinsic) swimming
time, and a slow time where hydrodynamic interactions lead to change in the
relative position and orientation of the swimmers. We perform a multiple-scale
analysis and derive the effective dynamical system - of dimension two -
describing the long-time behavior of the pair of cells. We show that the system
displays one type of equilibrium, and two types of rotational equilibrium, all
of which are found to be unstable. A detailed mathematical analysis of the
dynamical systems further allows us to show that only two cell-cell behaviors
are possible in the limit of , either the cells are attracted to
each other (possibly monotonically), or they are repelled (possibly
monotonically as well), which we confirm with numerical computations
Observational constraint on generalized Chaplygin gas model
We investigate observational constraints on the generalized Chaplygin gas
(GCG) model as the unification of dark matter and dark energy from the latest
observational data: the Union SNe Ia data, the observational Hubble data, the
SDSS baryon acoustic peak and the five-year WMAP shift parameter. It is
obtained that the best fit values of the GCG model parameters with their
confidence level are ()
, ()
. Furthermore in this model, we can see that the
evolution of equation of state (EOS) for dark energy is similar to quiessence,
and its current best-fit value is with the confidence
level .Comment: 9 pages, 5 figure
Two-domains bulklike Fermi surface of Ag films deposited onto Si(111)-(7x7)
Thick metallic silver films have been deposited onto Si(111)-(7x7) substrates
at room temperature. Their electronic properties have been studied by using
angle resolved photoelectron spectroscopy (ARPES). In addition to the
electronic band dispersion along the high-symmetry directions, the Fermi
surface topology of the grown films has been investigated. Using ARPES, the
spectral weight distribution at the Fermi level throughout large portions of
the reciprocal space has been determined at particular perpendicular
electron-momentum values. Systematically, the contours of the Fermi surface of
these films reflected a sixfold symmetry instead of the threefold symmetry of
Ag single crystal. This loss of symmetry has been attributed to the fact that
these films appear to be composed by two sets of domains rotated 60 from
each other. Extra, photoemission features at the Fermi level were also
detected, which have been attributed to the presence of surface states and
\textit{sp}-quantum states. The dimensionality of the Fermi surface of these
films has been analyzed studying the dependence of the Fermi surface contours
with the incident photon energy. The behavior of these contours measured at
particular points along the Ag L high-symmetry direction puts forward
the three-dimensional character of the electronic structure of the films
investigated.Comment: 10 pages, 12 figures, submitted to Physical Review
Combined constraints on modified Chaplygin gas model from cosmological observed data: Markov Chain Monte Carlo approach
We use the Markov Chain Monte Carlo method to investigate a global
constraints on the modified Chaplygin gas (MCG) model as the unification of
dark matter and dark energy from the latest observational data: the Union2
dataset of type supernovae Ia (SNIa), the observational Hubble data (OHD), the
cluster X-ray gas mass fraction, the baryon acoustic oscillation (BAO), and the
cosmic microwave background (CMB) data. In a flat universe, the constraint
results for MCG model are,
()
,
()
,
()
,
()
, and ()
.Comment: 12 pages, 1figur
The effect of temperature on adhesion forces between surfaces and model foods containing whey protein and sugar
The formation of fouling deposit from foods and food components is a severe problem in food processing and leads to frequent cleaning. The design of surfaces that resist fouling may decrease the need for cleaning and thus increase efficiency. Atomic force microscopy has been used to measure adhesion forces between stainless steel (SS) and fluoro-coated glass (FCG) microparticles and the model food deposits (i) whey protein (WPC), (ii) sweetened condensed milk, and (iii) caramel. Measurements were performed over a range of processing temperatures between 30 and 90 oC and at contact times up to 60 s. There is a significant increase in adhesion force of both types of microparticle to WPC at 90 oC for all contact times. For confectionary deposits adhesion to SS was similar. Adhesion of confectionary deposits to FCG at 30 oC revealed a decrease in adhesion compared to SS; at higher temperatures the adhesion forces were similar
How does Inflation Depend Upon the Nature of Fluids Filling Up the Universe in Brane World Scenario
By constructing different parameters which are able to give us the
information about our universe during inflation,(specially at the start and the
end of the inflationary universe) a brief idea of brane world inflation is
given in this work. What will be the size of the universe at the end of
inflation,i.e.,how many times will it grow than today's size is been speculated
and analysed thereafter. Different kinds of fluids are taken to be the matter
inside the brane. It is observed that in the case of highly positive pressure
grower gas like polytropic,the size of the universe at the end of inflation is
comparitively smaller. Whereas for negative pressure creators (like chaplygin
gas) this size is much bigger. Except thse two cases, inflation has been
studied for barotropic fluid and linear redshift parametrization too. For them the size of the universe after
inflation is much more high. We also have seen that this size does not depend
upon the potential energy at the end of the inflation. On the contrary, there
is a high impact of the initial potential energy upon the size of inflation.Comment: 20 page
A pooled analysis of dietary sugar/carbohydrate intake and esophageal and gastric cardia adenocarcinoma incidence and survival in the USA
Background: During the past 40 years, esophageal/gastric cardia adenocarcinoma (EA/ GCA) incidence increased in Westernized countries, but survival remained low. A parallel increase in sugar intake, which may facilitate carcinogenesis by promoting hyperglycaemia, led us to examine sugar/carbohydrate intake in association with EA/GCA incidence and survival. Methods: We pooled 500 EA cases, 529 GCA cases and 2027 controls from two US population-based case-control studies with cases followed for vital status. Dietary intake, assessed by study-specific food frequency questionnaires, was harmonized and pooled to estimate 12 measures of sugar/carbohydrate intake. Multivariable-adjusted odds ratios (ORs) and hazard ratios [95% confidence intervals (CIs)] were calculated using multinomial logistic regression and Cox proportional hazards regression, respectively. Results: EA incidence was increased by 51-58% in association with sucrose (ORQ5vs.Q1=1.51, 95% CI=1.01-2.27), sweetened desserts/beverages (ORQ5vs.Q1=1.55, 95% CI=1.06-2.27) and the dietary glycaemic index (ORQ5vs.Q1=1.58, 95% CI=1.13-2.21). Bodymass index (BMI) and gastro-esophageal reflux disease (GERD) modified these associations (Pmultiplicative-interaction ≤ 0.05). For associations with sucrose and sweetened desserts/beverages, respectively, the OR was elevated for BMI < 25 (ORQ4-5vs.Q1-3=1.79, 95% CI=1.26-2.56 and ORQ4-5vs.Q1-3=1.45, 95% CI=1.03-2.06), but not BMI≥25 (ORQ4-5vs.Q1-3=1.05, 95% CI=0.76-1.44 and ORQ4-5vs.Q1-3=0.85, 95% CI=0.62-1.16). The EA-glycaemic index association was elevated for BMI≥25 (ORQ4-5vs.Q1-3=1.38, 95% CI=1.03-1.85), but not BMI < 25 (ORQ4-5vs.Q1-3=0.88, 95% CI=0.62-1.24). The sucrose-EA association OR for GERD < weekly was 1.58 (95% CI=1.16-2.14), but for GERD≥weekly was 1.01 (95% CI=0.70-1.47). Sugar/carbohydrate measures were not associated with GCA incidence or EA/GCA survival. Conclusions: If confirmed, limiting intake of sucrose (e.g. table sugar), sweetened desserts/ beverages, and foods that contribute to a high glycaemic index, may be plausible EA risk reduction strategies
On the Nature and Genesis of EUV Waves: A Synthesis of Observations from SOHO, STEREO, SDO, and Hinode
A major, albeit serendipitous, discovery of the SOlar and Heliospheric
Observatory mission was the observation by the Extreme Ultraviolet Telescope
(EIT) of large-scale Extreme Ultraviolet (EUV) intensity fronts propagating
over a significant fraction of the Sun's surface. These so-called EIT or EUV
waves are associated with eruptive phenomena and have been studied intensely.
However, their wave nature has been challenged by non-wave (or pseudo-wave)
interpretations and the subject remains under debate. A string of recent solar
missions has provided a wealth of detailed EUV observations of these waves
bringing us closer to resolving their nature. With this review, we gather the
current state-of-art knowledge in the field and synthesize it into a picture of
an EUV wave driven by the lateral expansion of the CME. This picture can
account for both wave and pseudo-wave interpretations of the observations, thus
resolving the controversy over the nature of EUV waves to a large degree but
not completely. We close with a discussion of several remaining open questions
in the field of EUV waves research.Comment: Solar Physics, Special Issue "The Sun in 360",2012, accepted for
publicatio
17-beta-Estradiol in relation to age at menarche and adult obesity in premenopausal women
BACKGROUND: We hypothesize that premenopausal endogenous estradiol may be associated with age at menarche and adult overweight and obesity, potentially contributing to breast cancer risk. METHODS: We assessed age at menarche by questionnaire among 204 healthy Norwegian women, aged 25 – 35 years. Measures of body composition included body mass index (BMI, kg/m2), waist circumference (WC, cm), waist-to-hip ratio (WHR) and fat percentage dual energy X-ray absorptiometry, (DEXA). Daily salivary 17-b-estradiol (E2) concentrations were collected throughout one entire menstrual cycle and assessed by radioimmunoassay (RIA). Linear regression analyses and linear mixed models for repeated measures were used and potential confounding factors and effect modifiers were tested.
RESULTS: Among women with an early age at menarche (12 years), the overall mean salivary E2 concentration increased by 3.7 pmol/l (95% confidence interval, 1.8 – 5.7 pmol/l) with each 9.8 cm (1 SD) increase in WC, which represents a 20.7% change in the mean for the total group. Among the same early maturers, a 1 SD (0.06) change in WHR was directly associated with a 24.0% change in mean E2 concentration for the total group.
CONCLUSIONS: Our findings support the hypothesis that early age at menarche, together with adult overweight and obesity, result in high levels of 17-b-estradiol throughout the menstrual cycle.AnthropologyHuman Evolutionary Biolog
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