2,185 research outputs found
Corrections to the Central Limit Theorem for Heavy-Tailed Probability Densities
Classical Edgeworth expansions provide asymptotic correction terms to the
Central Limit Theorem (CLT) up to an order that depends on the number of
moments available. In this paper, we provide subsequent correction terms beyond
those given by a standard Edgeworth expansion in the general case of regularly
varying distributions with diverging moments (beyond the second). The
subsequent terms can be expressed in a simple closed form in terms of certain
special functions (Dawson's integral and parabolic cylinder functions), and
there are qualitative differences depending on whether the number of moments
available is even, odd or not an integer, and whether the distributions are
symmetric or not. If the increments have an even number of moments, then
additional logarithmic corrections must also be incorporated in the expansion
parameter. An interesting feature of our correction terms for the CLT is that
they become dominant outside the central region and blend naturally with known
large-deviation asymptotics when these are applied formally to the spatial
scales of the CLT
A near-infrared spectroscopic screening of the red giant populations in omega Centauri
Near-infrared spectra of 21 giants in omega Centauri, spanning the whole
range of metallicities observed in this cluster, are presented. This work is
part of a coordinated photometric and spectroscopic campaign in the optical and
in the infrared, aimed at studying the complex stellar population of omega
Centauri and understanding its formation and chemical evolution. By analyzing
the several CO and OH molecular bands and atomic lines in the spectra of the
selected giants, metal abundances and abundance ratios have been obtained. The
existence of three major metallicity regimes at [Fe/H]=-1.6, -1.2 and
[Fe/H]<-0.5 has been confirmed. The most metal-rich stars in our sample show a
lower (if any) alpha-enhancement when compared to the more metal-poor
components, suggesting that they should have formed in a medium significantly
polluted by type Ia supernova ejecta. Isotopic carbon abundances have been also
inferred, providing an average 13C/12C=4, which clearly indicates that
extra-mixing processes occurred in the stellar interiors during the ascent on
the Red Giant Branch.Comment: 22 pages, 7 .ps figures. aastex. Accepted for pubilcation in the
Astrophysical Journa
Reversible and Irreversible Interactions of Poly(3-hexylthiophene) with Oxygen Studied by Spin-Sensitive Methods
Understanding of degradation mechanisms in polymer:fullerene
bulk-heterojunctions on the microscopic level aimed at improving their
intrinsic stability is crucial for the breakthrough of organic photovoltaics.
These materials are vulnerable to exposure to light and/or oxygen, hence they
involve electronic excitations. To unambiguously probe the excited states of
various multiplicities and their reactions with oxygen, we applied combined
magneto-optical methods based on multifrequency (9 and 275 GHz) electron
paramagnetic resonance (EPR), photoluminescence (PL), and PL-detected magnetic
resonance (PLDMR) to the conjugated polymer poly(3-hexylthiophene) (P3HT) and
polymer:fullerene bulk heterojunctions (P3HT:PCBM; PCBM =
[6,6]-phenyl-C61-butyric acid methyl ester). We identified two distinct
photochemical reaction routes, one being fully reversible and related to the
formation of polymer:oxygen charge transfer complexes, the other one,
irreversible, being related to the formation of singlet oxygen under
participation of bound triplet excitons on the polymer chain. With respect to
the blends, we discuss the protective effect of the methanofullerenes on the
conjugated polymer bypassing the triplet exciton generation
Mechanism of Formation of Monodispersed Colloids by Aggregation of Nanosize Precursors
It has been experimentally established in numerous cases that precipitation
of monodispersed colloids from homogeneous solutions is a complex process.
Specifically, it was found that in many systems nuclei, produced rapidly in a
supersaturated solution, grow to nanosize primary particles (singlets), which
then coagulate to form much larger final colloids in a process dominated by
irreversible capture of these singlets. This paper describes a kinetic model
that explains the formation of dispersions of narrow size distribution in such
systems. Numerical simulations of the kinetic equations, with experimental
model parameter values, are reported. The model was tested for a system
involving formation of uniform spherical gold particles by reduction of auric
chloride in aqueous solutions. The calculated average size, the width of the
particle size distribution, and the time scale of the process, agreed
reasonably well with the experimental values.Comment: 38 pages in plain TeX and 7 JPG figure
Properties of the molecular gas in a starbursting QSO at z=1.83 in the COSMOS field
Using the IRAM 30m telescope, we have detected the CO J=2-1, 4-3, 5-4, and
6-5 emission lines in the millimeter-bright, blank-field selected AGN COSMOS
J100038+020822 at redshift z=1.8275. The sub-local thermodynamic equilibrium
(LTE) excitation of the J=4 level implies that the gas is less excited than
that in typical nearby starburst galaxies such as NGC253, and in the
high-redshift quasars studied to date, such as J1148+5251 or BR1202-0725. Large
velocity gradient (LVG) modeling of the CO line spectral energy distribution
(CO SED; flux density vs. rotational quantum number) yields H2 densities in the
range 10^{3.5}--10^{4.0} cm-3, and kinetic temperatures between 50 K and 200 K.
The H2 mass of (3.6 - 5.4) x 10^{10} M_sun implied by the line intensities
compares well with our estimate of the dynamical mass within the inner 1.5 kpc
of the object. Fitting a two-component gray body spectrum, we find a dust mass
of 1.2 x 10^{9} M_sun, and cold and hot dust temperatures of 42+/-5 K and
160+/-25 K, respectively. The broad MgII line allows us to estimate the mass of
the central black hole as 1.7 x 10^{9} M_sun. Although the optical spectrum and
multi-wavelength SED matches those of an average QSO, the molecular gas content
and dust properties resemble those of known submillimeter galaxies (SMGs). The
optical morphology of this source shows tidal tails that suggest a recent
interaction or merger. Since it shares properties of both starburst and AGN,
this object appears to be in a transition from a strongly starforming
submillimeter galaxy to a QSO.Comment: Accepted for publication in Astronomy & Astrophysics (A&A
Correlation of cutaneous tension distribution and tissue oxygenation with acute external tissue expansion
Today, the biomechanical fundamentals of skin expansion are based on viscoelastic models of the skin. Although many studies have been conducted in vitro, analyses performed in vivo are rare. Here, we present in vivo measurements of the expansion at the skin surface as well as measurement of the corresponding intracutaneous oxygen partial pressure. In our study the average skin stretching was 24%, with a standard deviation of 11%, excluding age or gender dependency. The measurement of intracutaneous oxygen partial pressure produced strong inter-individual fluctuations, including initial values at the beginning of the measurement, as well as varying individual patient reactions to expansion of the skin. Taken together, we propose that even large defect wounds can be closed successfully using the mass displacement caused by expansion especially in areas where soft, voluminous tissue layers are present
Male breast cancer
Male breast cancer (MBC) is a rare disease representing less than 1% of all breast cancers (BC) and less than 1% of cancers in men. Age at presentation is mostly in the late 60s. MBC is recognized as an estrogen-driven disease, specifically related to hyperestrogenism. About 20% of MBC patients have family history for BC. Mutations in BRCA1 and, predominantly, BRCA2, account for approximately 10% of MBC cases.
Because of its rarity, MBC is often compared with female BC (FBC). Based on age-frequency distribution, age-specific incidence rate patterns and prognostic factors profiles, MBC is considered similar to late-onset, postmenopausal estrogen/progesterone receptor positive (ER+/PR+) FBC. However, clinical and pathological characteristics of MBC do not exactly overlap FBC. Compared with FBC, MBC has been reported to occur later in life, present at a higher stage, and display lower histologic grade, with a higher proportion of ER+ and PR+ tumors.
Although rare, MBC remains a substantial cause for morbidity and mortality in men, probably because of its occurrence in advanced age and delayed diagnosis. Diagnosis and treatment of MBC generally is similar to that of FBC. Men tend to be treated with mastectomy rather than breast-conserving surgery. The backbone of adjuvant therapy or palliative treatment for advanced disease is endocrine, mostly tamoxifen.
Use of FBC-based therapy led to the observation that treatment outcomes for MBC are worse and that survival rates for MBC do not improve like FBC. These different outcomes may suggest a non-appropriate utilization of treatments and that different underlying pathogenetic mechanisms may exist between male and female BC
Brownian force noise from molecular collisions and the sensitivity of advanced gravitational wave observatories
We present an analysis of Brownian force noise from residual gas damping of
reference test masses as a fundamental sensitivity limit in small force
experiments. The resulting acceleration noise increases significantly when the
distance of the test mass to the surrounding experimental apparatus is smaller
than the dimension of the test mass itself. For the Advanced LIGO
interferometric gravitational wave observatory, where the relevant test mass is
a suspended 340 mm diameter cylindrical end mirror, the force noise power is
increased by roughly a factor 40 by the presence of a similarly shaped reaction
mass at a nominal separation of 5 mm. The force noise, of order 20 fN\rthz\ for
Pa of residual H gas, rivals quantum optical
fluctuations as the dominant noise source between 10 and 30 Hz. We present here
a numerical and analytical analysis for the gas damping force noise for
Advanced LIGO, backed up by experimental evidence from several recent
measurements. Finally, we discuss the impact of residual gas damping on the
gravitational wave sensitivity and possible mitigation strategies.Comment: 13 pages with 9 figures (fixed typos found in proofs
Bringing Habits and Emotions into Food Waste Behaviour
This study examined consumer food waste behaviour using a comprehensive model integrating the theory of planned behaviour (TPB), the theory of interpersonal behaviour, and the comprehensive model of environmental behaviour. Using a temporally lagged design, one hundred and seventy-two respondents answered four questionnaires over a period of 14 months. Questionnaires measured emotions in relation to food waste, habits, the TPB variables, intention to reduce food waste, and self-reported food waste behaviour. Results showed that the less well-studied variables of habits and emotions were important determinants of participants’ intentions to reduce food waste and their current food waste behaviour. As expected, we found that negative emotions were associated with greater intentions to reduce food waste, but contrary to our predictions they were also associated with higher levels of food waste behaviour. In other words, participants who experienced more negative emotion when thinking about food waste intended to reduce their waste but actually ended up wasting more food. Results also show that participants with a greater sense of control, and more normative support for reducing food waste also had stronger intentions to engage in the behaviour. Our findings extend existing understanding and underscore the importance of the non-cognitive determinants of behaviour, namely emotions and habits. The implications for research and practice are discussed
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