549 research outputs found
Evaluation of the risk of contamination by pesticides
Pesticides have the particularity of accumulating mainly in aquatic ecosystems. The concentration of pesticides in such contaminated ecosystems appears to be a potential health risk resulting from the human consumption of fish from these ecosystems. The aim of this study is to determine the pesticide residue levels of Chrysichthys nigrodigitatus and Tilapia zilli Ă Tilapia guinensis. 120 samples of each species, distributed from 96 samples for sector IV and 24 samples for sector V, were collected from February 2014 to January 2015. These were analyzed by gas chromatography coupled to a spectrometer of mass (GC / MS), after extraction and purification respectively by accelerated solvent extraction (ASE) and by adsorption chromatography on Oasis HLB Plus cartridges. Pesticide concentrations detected in fish muscle ranged from 0 to 40.66 ĂŹg / kg in the study area. All values found for the health risk index (HI) in Chrysichthys nigrodigitatus and Tilapia hybrid muscles are well below 1 (HI < 1). Pesticide residues detected in both fish species do not pose a potential risk to human health.Keywords: Contamination, pesticides, Chrysichthys nigrodigitatus, Tilapia, risk. French Title: Evaluation du risque de contamination par les pesticidesLes pesticides ont la particularitĂ© de sâaccumuler principalement dans les Ă©cosystĂšmes aquatiques. La concentration de pesticides dans de tels Ă©cosystĂšmes contaminĂ©s apparaĂźt comme un risque potentiel pour la santĂ© rĂ©sultant de la consommation humaine de poissons de ces Ă©cosystĂšmes. Cette Ă©tude a pour objectif de dĂ©terminer la concentration de rĂ©sidus de pesticides chez Chrysichthys nigrodigitatus et Tilapia zilli Ă Tilapia guinensis. 120 Ă©chantillons de chaque espĂšce, repartis en raison de 96 Ă©chantillons pour le secteur IV et 24 Ă©chantillons pour le secteur V, ont Ă©tĂ© collectĂ©s de fĂ©vrier 2014 Ă janvier 2015. Ceux-ci ont Ă©tĂ© analysĂ©s par chromatographie en phase gazeuse couplĂ©e Ă un spectromĂštre de masse (GC / MS), aprĂšs Extraction et purification respectivement par ExtractionAccĂ©lĂ©rĂ©e par Solvant (ASE) et par chromatographie dâadsorption sur cartouches Oasis HLB Plus. Les concentrations de pesticides quantifiĂ©s et non dĂ©tectĂ©s dans les muscles des poissons variaient entre 0 et 40,66 ĂŹg/kg dans la zone dâĂ©tude. Toutes les valeurs trouvĂ©es pour lâindice de risque pour la santĂ© (HI) dans les muscles de Chrysichthys nigrodigitatus et de Tilapia hybride sont nettement infĂ©rieures Ă 1 (HI <1). Les rĂ©sidus de pesticides dĂ©tectĂ©s chez les deux espĂšces de poisson ne prĂ©sentent pasde risque potentiel pour la santĂ© humaine.Mots-clĂ©s : Contaminations, pesticides, Chrysichthys nigrodigitatus, Tilapia, risque
Malfunction of a ventriculoperitoneal shunt during pregnancy: Two clinical cases and literature review
Bringing a pregnancy to term is possible for a woman carrying a ventriculoperitoneal bypass valve, however, pregnancy can be a source of malfunction of the bypass system. We report two cases of malfunction of a VPS during the pregnancy's 3rd trimester in two patients aged 25 and 30 years respectively. The valve was examined in both cases and the persistence of the neurological signs required a cesarean section. The diagnostic aspects and management strategies were discussed as regards these two cases and throughout the literature review
The Non-Consensus 1992 Consensus
The 1992 Consensus is perhaps the most crucial political term for cross-strait relations. Surveys show that the public consistently supports it in Taiwan. Despite the alleged broad support, there has not been an academic study examining if Taiwanese people understand the content of the 1992 Consensus. Such an inquiry is important as the administration in Taiwan has yet accepted the Consensus in its interactions with Beijing. A nearly representative online survey was conducted in July 2018, and 1001 Taiwanese respondents were recruited to choose among different âdefinitionsâ of the 1992 Consensus. Results show that only one-third of the respondents chose the version that Kuomintang agreed on, while another one-third misperceived the 1992 Consensus as a country-to-country agreement. Taiwanese people might have supported the Consensus for content that it is not. We then discuss the policy implications of our study for both China and Taiwan and provide future research orientations
Signatures of black holes at the LHC
Signatures of black hole events at CERN's Large Hadron Collider are
discussed. Event simulations are carried out with the Fortran Monte Carlo
generator CATFISH. Inelasticity effects, exact field emissivities, color and
charge conservation, corrections to semiclassical black hole evaporation,
gravitational energy loss at formation and possibility of a black hole remnant
are included in the analysis.Comment: 13 pages, 7 figure
Analysis of Various Polarization Asymmetries In The Inclusive Decay In The Fourth-Generation Standard Model
In this study a systematical analysis of various polarization asymmetries in
inclusive b \rar s \ell^+ \ell^- decay in the standard model (SM) with four
generation of quarks is carried out. We found that the various asymmetries are
sensitive to the new mixing and quark masses for both of the and
channels. Sizeable deviations from the SM values are obtained. Hence, b \rar s
\ell^+ \ell^- decay is a valuable tool for searching physics beyond the SM,
especially in the indirect searches for the fourth-generation of quarks (.Comment: 19 Pages, 10 Figures, 3 Table
A renormalizable SO(10) GUT scenario with spontaneous CP violation
We consider fermion masses and mixings in a renormalizable SUSY SO(10) GUT
with Yukawa couplings of scalar fields in the representation 10 + 120 + 126
bar. We investigate a scenario defined by the following assumptions: i) A
single large scale in the theory, the GUT scale. ii) Small neutrino masses
generated by the type I seesaw mechanism with negligible type II contributions.
iii) A suitable form of spontaneous CP breaking which induces hermitian mass
matrices for all fermion mass terms of the Dirac type. Our assumptions define
an 18-parameter scenario for the fermion mass matrices for 18 experimentally
known observables. Performing a numerical analysis, we find excellent fits to
all observables in the case of both the normal and inverted neutrino mass
spectrum.Comment: 16 pages, two eps figure
SUSY GUT Model Building
I discuss an evolution of SUSY GUT model building, starting with the
construction of 4d GUTs, to orbifold GUTs and finally to orbifold GUTs within
the heterotic string. This evolution is an attempt to obtain realistic string
models, perhaps relevant for the LHC. This review is in memory of the sudden
loss of Julius Wess, a leader in the field, who will be sorely missed.Comment: 24 pages, 14 figures, lectures given at PiTP 2008, Institute for
Advanced Study, Princeton, to be published in the European Physical Journal
To wet or not to wet: that is the question
Wetting transitions have been predicted and observed to occur for various
combinations of fluids and surfaces. This paper describes the origin of such
transitions, for liquid films on solid surfaces, in terms of the gas-surface
interaction potentials V(r), which depend on the specific adsorption system.
The transitions of light inert gases and H2 molecules on alkali metal surfaces
have been explored extensively and are relatively well understood in terms of
the least attractive adsorption interactions in nature. Much less thoroughly
investigated are wetting transitions of Hg, water, heavy inert gases and other
molecular films. The basic idea is that nonwetting occurs, for energetic
reasons, if the adsorption potential's well-depth D is smaller than, or
comparable to, the well-depth of the adsorbate-adsorbate mutual interaction. At
the wetting temperature, Tw, the transition to wetting occurs, for entropic
reasons, when the liquid's surface tension is sufficiently small that the free
energy cost in forming a thick film is sufficiently compensated by the fluid-
surface interaction energy. Guidelines useful for exploring wetting transitions
of other systems are analyzed, in terms of generic criteria involving the
"simple model", which yields results in terms of gas-surface interaction
parameters and thermodynamic properties of the bulk adsorbate.Comment: Article accepted for publication in J. Low Temp. Phy
Cosmic acceleration from second order gauge gravity
We construct a phenomenological theory of gravitation based on a second order
gauge formulation for the Lorentz group. The model presents a long-range
modification for the gravitational field leading to a cosmological model
provided with an accelerated expansion at recent times. We estimate the model
parameters using observational data and verify that our estimative for the age
of the Universe is of the same magnitude than the one predicted by the standard
model. The transition from the decelerated expansion regime to the accelerated
one occurs recently (at ).Comment: RevTex4 15 pages, 1 figure. Accepted for publication in Astrophysics
& Space Scienc
Tomonaga-Luttinger parameters for quantum wires
The low-energy properties of a homogeneous one-dimensional electron system
are completely specified by two Tomonaga-Luttinger parameters and
. In this paper we discuss microscopic estimates of the values of
these parameters in semiconductor quantum wires that exploit their relationship
to thermodynamic properties. Motivated by the recognized similarity between
correlations in the ground state of a one-dimensional electron liquid and
correlations in a Wigner crystal, we evaluate these thermodynamic quantities in
a self-consistent Hartree-Fock approximation. According to our calculations,
the Hartree-Fock approximation ground state is a Wigner crystal at all electron
densities and has antiferromagnetic order that gradually evolves from
spin-density-wave to localized in character as the density is lowered. Our
results for are in good agreement with weak-coupling perturbative
estimates at high densities, but deviate strongly at low
densities, especially when the electron-electron interaction is screened at
long distances. vanishes at small carrier density
whereas we conjecture that when , implying that
should pass through a minimum at an intermediate density.
Observation of such a non-monotonic dependence on particle density would allow
to measure the range of the microscopic interaction. In the spin sector we find
that the spin velocity decreases with increasing interaction strength or
decreasing . Strong correlation effects make it difficult to obtain fully
consistent estimates of from Hartree-Fock calculations. We
conjecture that v_{\sigma}/\vf\propto n/V_0 in the limit where
is the interaction strength.Comment: RevTeX, 23 pages, 8 figures include
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