3,756 research outputs found
Notification of pesticide poisoning in the western Cape, 1987 - 1991
There is a paucity of data on pesticide-related morbidity and mortality in South Africa. A review of notifications to the western Cape office of the Department of National Health and Population Development from 1987 to 1991 was undertaken to describe the epidemiological profile of pesticide poisoning in the region. Two hundred and twenty five cases of pesticide poisoning were identified, of which the majority were from rural areas. Farmers, farm workers and their families were most frequently involved in poisoning events, which included accidents arising outside of workplace production (44%), self-inflicted injury (35%) and direct occupational contamination (11%). Farm pesticide stores were the most frequent source of pesticide and a seasonal variation in the trend of poisoning events could be discerned; this corresponded to agricultural spraying practices in the region. The mortality rate was significantly higher among those with self-inflicted injury, particularly farm workers. A concurrent review of hospital admissions for 1991 found that 78% of cases had not been notified. In view of the key role of surveillance in reducing pesticide-related morbidity and mortality, a call is made to improve notification of pesticide poisoning so as to facilitate control of an important potential public health problem
Two-photon absorption and broadband optical limiting with bis-donor stilbenes
Large two-photon absorptivities are reported for symmetrical bis-donor stilbene derivatives with dialkylamino or diphenylamino groups. These molecules exhibit strong optical limiting of nanosecond pulses over a broad spectral range in the visible. Relative to bis(di-n-butylamino)stilbene, bis(diphenylamino)stilbene exhibits a 90-nm red shift of its optical limiting band but only a minimal shift of ~13 nm of its lowest one-photon electronic absorption band. Mixtures of these compounds offer an unprecedented combination of broad optical limiting bandwidth and high linear transparency
Lattice Effects in Crystal Evaporation
We study the dynamics of a stepped crystal surface during evaporation, using
the classical model of Burton, Cabrera and Frank, in which the dynamics of the
surface is represented as a motion of parallel, monoatomic steps. The validity
of the continuum approximation treated by Frank is checked against numerical
calculations and simple, qualitative arguments. The continuum approximation is
found to suffer from limitations related, in particular, to the existence of
angular points. These limitations are often related to an adatom detachment
rate of adatoms which is higher on the lower side of each step than on the
upper side ("Schwoebel effect").Comment: DRFMC/SPSMS/MDN, Centre d'Etudes Nucleaires de Grenoble, 25 pages,
LaTex, revtex style. 8 Figures, available upon request, report# UBFF30119
Spiral surface growth without desorption
Spiral surface growth is well understood in the limit where the step motion
is controlled by the local supersaturation of adatoms near the spiral ridge. In
epitaxial thin-film growth, however, spirals can form in a step-flow regime
where desorption of adatoms is negligible and the ridge dynamics is governed by
the non-local diffusion field of adatoms on the whole surface. We investigate
this limit numerically using a phase-field formulation of the
Burton-Cabrera-Frank model, as well as analytically. Quantitative predictions,
which differ strikingly from those of the local limit, are made for the
selected step spacing as a function of the deposition flux, as well as for the
dependence of the relaxation time to steady-state growth on the screw
dislocation density.Comment: 9 pages, 3 figures, RevTe
Ten Misconceptions from the History of Analysis and Their Debunking
The widespread idea that infinitesimals were "eliminated" by the "great
triumvirate" of Cantor, Dedekind, and Weierstrass is refuted by an
uninterrupted chain of work on infinitesimal-enriched number systems. The
elimination claim is an oversimplification created by triumvirate followers,
who tend to view the history of analysis as a pre-ordained march toward the
radiant future of Weierstrassian epsilontics. In the present text, we document
distortions of the history of analysis stemming from the triumvirate ideology
of ontological minimalism, which identified the continuum with a single number
system. Such anachronistic distortions characterize the received interpretation
of Stevin, Leibniz, d'Alembert, Cauchy, and others.Comment: 46 pages, 4 figures; Foundations of Science (2012). arXiv admin note:
text overlap with arXiv:1108.2885 and arXiv:1110.545
Impurity-induced diffusion bias in epitaxial growth
We introduce two models for the action of impurities in epitaxial growth. In
the first, the interaction between the diffusing adatoms and the impurities is
``barrier''-like and, in the second, it is ``trap''-like. For the barrier
model, we find a symmetry breaking effect that leads to an overall down-hill
current. As expected, such a current produces Edwards-Wilkinson scaling. For
the trap model, no symmetry breaking occurs and the scaling behavior appears to
be of the conserved-KPZ type.Comment: 5 pages(with the 5 figures), latex, revtex3.0, epsf, rotate, multico
Leibniz's Infinitesimals: Their Fictionality, Their Modern Implementations, And Their Foes From Berkeley To Russell And Beyond
Many historians of the calculus deny significant continuity between
infinitesimal calculus of the 17th century and 20th century developments such
as Robinson's theory. Robinson's hyperreals, while providing a consistent
theory of infinitesimals, require the resources of modern logic; thus many
commentators are comfortable denying a historical continuity. A notable
exception is Robinson himself, whose identification with the Leibnizian
tradition inspired Lakatos, Laugwitz, and others to consider the history of the
infinitesimal in a more favorable light. Inspite of his Leibnizian sympathies,
Robinson regards Berkeley's criticisms of the infinitesimal calculus as aptly
demonstrating the inconsistency of reasoning with historical infinitesimal
magnitudes. We argue that Robinson, among others, overestimates the force of
Berkeley's criticisms, by underestimating the mathematical and philosophical
resources available to Leibniz. Leibniz's infinitesimals are fictions, not
logical fictions, as Ishiguro proposed, but rather pure fictions, like
imaginaries, which are not eliminable by some syncategorematic paraphrase. We
argue that Leibniz's defense of infinitesimals is more firmly grounded than
Berkeley's criticism thereof. We show, moreover, that Leibniz's system for
differential calculus was free of logical fallacies. Our argument strengthens
the conception of modern infinitesimals as a development of Leibniz's strategy
of relating inassignable to assignable quantities by means of his
transcendental law of homogeneity.Comment: 69 pages, 3 figure
Seasonal Variations of the 7Be Solar Neutrino Flux
Measuring the 7Be solar neutrino flux is crucial towards solving the solar
neutrino puzzle. The Borexino experiment, and possibly the KamLAND experiment,
will be capable of studying the 7Be neutrinos in the near future. We discuss
(1) how the seasonal variation of the Borexino and KamLAND data can be used to
measure the 7Be solar neutrino flux in a background independent way and (2) how
anomalous seasonal variations might be used to discover vacuum neutrino
oscillations, independent of the solar model and the measurement of the
background. In particular, we find that, after three years of Borexino or
KamLAND running, vacuum neutrino oscillations can be either established or
excluded for almost all values of (sin^2 2 theta, Delta m^2) preferred by the
Homestake, GALLEX, SAGE, and Super-Kamiokande data. We also discuss how well
seasonal variations of the data can be used to measure (sin^2 2 theta, Delta
m^2) in the case of vacuum oscillations.Comment: 39 pages, 13 figures, uses psfig. Now the impact of the MSW effect on
vacuum oscillations taken into account. Conclusions unchanged. References
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Search for Light CP-odd Higgs in Radiative Decays of Upsilon(1S)
We search for a non-SM-like CP-odd Higgs boson (a0_1) with m(a0_1)< 2m(b) in
radiative decays of the Upsilon(1S), using 21.5M Upsilon(1S) mesons directly
produced in e+e- annihilation. We investigate a0_1 --> tau+tau- and a0_1 -->
mu+mu- decay channels. No significant signal is found. We obtain upper limits
on the product of B(Upsilon(1S)-->gamma a0_1) and B(a0_1-->tau+tau-) or
B(a0_1-->mu+mu-). Our tau+tau- results are almost two orders of magnitude more
stringent than previous upper limits. Our data provide no evidence for a Higgs
state with a mass of 214 MeV decaying to mu+mu-. Existence of such a state was
previously proposed as an explanation for 3 Sigma+ --> p mu+mu- events, having
mu+mu- masses just above the kinematic threshold, observed by the HyperCP
experiment. Our results constrain NMSSM models.Comment: 12 pages, available through http://www.lns.cornell.edu/public/CLNS/,
submitted to PR
Determination of the D0 -> K+pi- Relative Strong Phase Using Quantum-Correlated Measurements in e+e- -> D0 D0bar at CLEO
We exploit the quantum coherence between pair-produced D0 and D0bar in
psi(3770) decays to study charm mixing, which is characterized by the
parameters x and y, and to make a first determination of the relative strong
phase \delta between doubly Cabibbo-suppressed D0 -> K+pi- and Cabibbo-favored
D0bar -> K+pi-. We analyze a sample of 1.0 million D0D0bar pairs from 281 pb^-1
of e+e- collision data collected with the CLEO-c detector at E_cm = 3.77 GeV.
By combining CLEO-c measurements with branching fraction input and
time-integrated measurements of R_M = (x^2+y^2)/2 and R_{WS} = Gamma(D0 ->
K+pi-)/Gamma(D0bar -> K+pi-) from other experiments, we find \cos\delta = 1.03
+0.31-0.17 +- 0.06, where the uncertainties are statistical and systematic,
respectively. In addition, by further including external measurements of charm
mixing parameters, we obtain an alternate measurement of \cos\delta = 1.10 +-
0.35 +- 0.07, as well as x\sin\delta = (4.4 +2.7-1.8 +- 2.9) x 10^-3 and \delta
= 22 +11-12 +9-11 degrees.Comment: 37 pages, also available through
http://www.lns.cornell.edu/public/CLNS/2007/. Incorporated referee's comment
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