8,939 research outputs found
Birth, survival and death of languages by Monte Carlo simulation
Simulations of physicists for the competition between adult languages since
2003 are reviewed. How many languages are spoken by how many people? How many
languages are contained in various language families? How do language
similarities decay with geographical distance, and what effects do natural
boundaries have? New simulations of bilinguality are given in an appendix.Comment: 24 pages review, draft for Comm.Comput.Phys., plus appendix on
bilingualit
Spectroscopic test of Bose-Einstein statistics for photons
Using Bose-Einstein-statistics-forbidden two-photon excitation in atomic
barium, we have limited the rate of statistics-violating transitions, as a
fraction of an equivalent statistics-allowed transition rate, to
at the 90% confidence level. This is an improvement of
more than three orders of magnitude over the best previous result.
Additionally, hyperfine-interaction enabling of the forbidden transition has
been observed, to our knowledge, for the first time
Congener specific analysis of polychlorinated terphenyls
In order to identify and to quantify polychlorinated terphenyls (PCT) in environmental matrices, the chro-
matographic behavior of coplanar and non-coplanar congeners was evaluated. A mixture of 16 single PCT
congeners was used for method development. Four of these compounds were synthesized for the first
time by SUZUKI-coupling reaction. These were p-PCT (2,200
,6,600
-tetrachloro-, 20
,3,300
,4,400
,50
,-hexachloro-,
20
,3,300
,5,50
,500
-hexachloro-) and m-PCT (2,200
,3,300
,5,500
-hexachloro-). They were characterized by NMR
(
1
H,
13
C) spectroscopy. By means of the new column chromatographic clean-up reported here, a good
matrix removal and the separation of the coplanar PCT congeners from the non-coplanar ones was
obtained. The recovery rates for all congeners were good for the PCT in different test matrices like fat,
charcoal, and soil. The quality of the clean-up, the separation and the recovery rates were determined
by GC/MS analysis. The method was applied for the first time to a real sample from a fire accident, where
different PCT, obviously formed during the combustion process, were found. The conclusion is drawn that
this method is suitable for the analysis of PCT in different environmental samples
Computer-Simulation des Wettbewerbs zwischen Sprachen
Recent computer simulations of the competition between thousands of languages
are reviewed, and some new results on language families and language
similarities are presented.Comment: 16 pages including all figures; in GERMAN language, more results than
first versio
Potential Role of Ultrafine Particles in Associations between Airborne Particle Mass and Cardiovascular Health
Numerous epidemiologic time-series studies have shown generally consistent associations of cardiovascular hospital admissions and mortality with outdoor air pollution, particularly mass concentrations of particulate matter (PM) ≤2.5 or ≤10 μm in diameter (PM(2.5), PM(10)). Panel studies with repeated measures have supported the time-series results showing associations between PM and risk of cardiac ischemia and arrhythmias, increased blood pressure, decreased heart rate variability, and increased circulating markers of inflammation and thrombosis. The causal components driving the PM associations remain to be identified. Epidemiologic data using pollutant gases and particle characteristics such as particle number concentration and elemental carbon have provided indirect evidence that products of fossil fuel combustion are important. Ultrafine particles < 0.1 μm (UFPs) dominate particle number concentrations and surface area and are therefore capable of carrying large concentrations of adsorbed or condensed toxic air pollutants. It is likely that redox-active components in UFPs from fossil fuel combustion reach cardiovascular target sites. High UFP exposures may lead to systemic inflammation through oxidative stress responses to reactive oxygen species and thereby promote the progression of atherosclerosis and precipitate acute cardiovascular responses ranging from increased blood pressure to myocardial infarction. The next steps in epidemiologic research are to identify more clearly the putative PM casual components and size fractions linked to their sources. To advance this, we discuss in a companion article (Sioutas C, Delfino RJ, Singh M. 2005. Environ Health Perspect 113:947–955) the need for and methods of UFP exposure assessment
Near-Infrared Studies of V1280 Sco (Nova Scorpii 2007)
We present spectroscopic and photometric results of Nova V1280 Sco which was
discovered in outburst in early 2007 February. The large number of spectra
obtained of the object leads to one of the most extensive, near-infrared
spectral studies of a classical nova. The spectra evolve from a P-Cygni phase
to an emission-line phase and at a later stage is dominated by emission from
the dust that formed in this nova. A detailed model is computed to identify and
study characteristics of the spectral lines. Inferences from the model address
the vexing question of which novae have the ability to form dust. It is
demonstrated, and strikingly corroborated with observations, that the presence
of lines in the early spectra of low-ionization species like Na and Mg -
indicative of low temperature conditions - appear to be reliable indicators
that dust will form in the ejecta. It is theoretically expected that mass loss
during a nova outburst is a sustained process. Spectroscopic evidence for such
a sustained mass loss, obtained by tracing the evolution of a P-Cygni feature
in the Brackett gamma line, is presented here allowing a lower limit of 25-27
days to be set for the mass-loss duration. Photometric data recording the
nova's extended 12 day climb to peak brightness after discovery is used to
establish an early fireball expansion and also show that the ejection began
well before maximum brightness. The JHK light curves indicate the nova had a
fairly strong second outburst around 100 days after the first.Comment: Accepted in MNRAS. The paper contains 8 figures and 4 tables. Few
typographical errors were correcte
Multi-Instantons and Exact Results II: Specific Cases, Higher-Order Effects, and Numerical Calculations
In this second part of the treatment of instantons in quantum mechanics, the
focus is on specific calculations related to a number of quantum mechanical
potentials with degenerate minima. We calculate the leading multi-instanton
constributions to the partition function, using the formalism introduced in the
first part of the treatise [J. Zinn-Justin and U. D. Jentschura, e-print
quant-ph/0501136]. The following potentials are considered: (i) asymmetric
potentials with degenerate minima, (ii) the periodic cosine potential, (iii)
anharmonic oscillators with radial symmetry, and (iv) a specific potential
which bears an analogy with the Fokker-Planck equation. The latter potential
has the peculiar property that the perturbation series for the ground-state
energy vanishes to all orders and is thus formally convergent (the ground-state
energy, however, is nonzero and positive). For the potentials (ii), (iii), and
(iv), we calculate the perturbative B-function as well as the instanton
A-function to fourth order in g. We also consider the double-well potential in
detail, and present some higher-order analytic as well as numerical
calculations to verify explicitly the related conjectures up to the order of
three instantons. Strategies analogous to those outlined here could result in
new conjectures for problems where our present understanding is more limited.Comment: 55 pages, LaTeX; refs. to part I preprint update
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