3,203 research outputs found
Photodefinition of channel waveguide in electro-optic polymer
Polymers with optically active nonlinear chromophores have been shown to have a promising future in low cost and high speed electro–optic device applications. However, a main question of concern is the photochemical stability of the chromophores for long term application. The chromophore TCVDPA with a benzene bridge between a tricyanovinyl acceptor and an amino donor has been reported to have high photochemical stability combined with high electro-optic activity. In the current work direct waveguide definition of the host polymer SU-8, a negative photoresist, containing this chromophore by masked UV exposure followed by development, has been demonstrated. This was possible by utilizing the chromophore low absorption window in the UV region that allows crosslinking of the host polymer by exposing to UV light followed by thermal curing
Analysis of Y(4660) and related bound states with QCD sum rules
In this article, we take the vector charmonium-like state Y(4660) as a
bound state (irrespective of the hadro-charmonium and the
molecular state) tentatively, study its mass using the QCD sum rules, the
numerical value is consistent with the experimental
data. Considering the SU(3) symmetry of the light flavor quarks and the heavy
quark symmetry, we also study the bound states ,
and with the QCD sum rules,
and make reasonable predictions for their masses.Comment: 18 pages, 32 figures, revised versio
TRANSIENT MODELLING OF A NATURAL CIRCULATION LOOP UNDER VARIABLE PRESSURE
The objective of the present work is to model the transient operation of a natural circulation loop, which is one-tenth scale in height to a typical Passive Residual Heat Removal system (PRHR) of an Advanced Pressurized Water Nuclear Reactor and was designed to meet the single and two-phase ow similarity criteria to it. The loop consists of a core barrel with electrically heated rods, upper and lower plena inter- connected by hot and cold pipe legs to a seven-tube shell heat exchanger of countercurrent design, and an expansion tank with a descending tube. A long transient characterized the loop operation, during which a phenomenon of self-pressurization, without self-regulation of the pressure, was experimentally observed. This represented a unique situation, named natural circulation under variable pressure (NCVP). The self-pressurization was originated in the air trapped in the expansion tank and compressed by the loop
water dilatation, as it heated up during each experiment. The mathematical model, initially oriented to the single-phase ow, included the heat capacity of the structure and employed a cubic polynomial approximation for the density, in the buoyancy term calculation. The heater was modelled taking into account the di erent heat capacities of the heating elements and the heater walls. The heat exchanger was
modelled considering the coolant heating, during the heat exchanging process. The self-pressurization was modelled as an isentropic compression of a perfect gas. The whole model was computationally im-plemented via a set of nite di erence equations. The corresponding computational algorithm of solution was of the explicit, marching type, as for the time discretization, in an upwind scheme, regarding the space discretization. The computational program was implemented in MATLAB. Several experiments
were carried out in the natural circulation loop, having the coolant ow rate and the heating power as control parameters. The variables used in the comparison between experimental and calculated data were some relevant loop temperatures and pressures. The results obtained from the computational model agree qualitatively well with the experimental NCVP data
Sarna sarcóptica dos suínos: estratégia de ação no controle e avaliação econômica.
bitstream/item/58756/1/CUsersPiazzonDocuments172.pd
The contribution of faint AGNs to the ionizing background at z~4
Finding the sources responsible for the hydrogen reionization is one of the
most pressing issues in cosmology. Bright QSOs are known to ionize their
surrounding neighborhood, but they are too few to ensure the required HI
ionizing background. A significant contribution by faint AGNs, however, could
solve the problem, as recently advocated on the basis of a relatively large
space density of faint active nuclei at z>4. We have carried out an exploratory
spectroscopic program to measure the HI ionizing emission of 16 faint AGNs
spanning a broad U-I color interval, with I~21-23 and 3.6<z<4.2. These AGNs are
three magnitudes fainter than the typical SDSS QSOs (M1450<~-26) which are
known to ionize their surrounding IGM at z>~4. The LyC escape fraction has been
detected with S/N ratio of ~10-120 and is between 44 and 100% for all the
observed faint AGNs, with a mean value of 74% at 3.6<z<4.2 and
-25.1<M1450<-23.3, in agreement with the value found in the literature for much
brighter QSOs (M1450<~-26) at the same redshifts. The LyC escape fraction of
our faint AGNs does not show any dependence on the absolute luminosities or on
the observed U-I colors. Assuming that the LyC escape fraction remains close to
~75% down to M1450~-18, we find that the AGN population can provide between 16
and 73% (depending on the adopted luminosity function) of the whole ionizing UV
background at z~4, measured through the Lyman forest. This contribution
increases to 25-100% if other determinations of the ionizing UV background are
adopted. Extrapolating these results to z~5-7, there are possible indications
that bright QSOs and faint AGNs can provide a significant contribution to the
reionization of the Universe, if their space density is high at M1450~-23.Comment: Accepted for publication on A&A, 16 pages, 22 figure
First Ex-Vivo Validation of a Radioguided Surgery Technique with beta- Radiation
Purpose: A radio-guided surgery technique with beta- -emitting radio-tracers
was suggested to overcome the effect of the large penetration of gamma
radiation. The feasibility studies in the case of brain tumors and abdominal
neuro-endocrine tumors were based on simulations starting from PET images with
several underlying assumptions. This paper reports, as proof-of-principle of
this technique, an ex-vivo test on a meningioma patient. This test allowed to
validate the whole chain, from the evaluation of the SUV of the tumor, to the
assumptions on the bio-distribution and the signal detection.
Methods: A patient affected by meningioma was administered 300 MBq of
90Y-DOTATOC. Several samples extracted from the meningioma and the nearby Dura
Mater were analyzed with a beta- probe designed specifically for this
radio-guided surgery technique. The observed signals were compared both with
the evaluation from the histology and with the Monte Carlo simulation.
Results: we obtained a large signal on the bulk tumor (105 cps) and a
significant signal on residuals of 0.2 ml (28 cps). We also show that
simulations predict correctly the observed yields and this allows us to
estimate that the healthy tissues would return negligible signals (~1 cps).
This test also demonstrated that the exposure of the medical staff is
negligible and that among the biological wastes only urine has a significant
activity.
Conclusions: This proof-of-principle test on a patient assessed that the
technique is feasible with negligible background to medical personnel and
confirmed that the expectations obtained with Monte Carlo simulations starting
from diagnostic PET images are correct.Comment: 17 pages, 4 Figs, Accepted by Physica Medic
Amblyomma cajennense (Fabricius, 1787) (Acari: Ixodidae), the Cayenne tick: phylogeography and evidence for allopatric speciation
Background: Amblyomma cajennense F. is one of the best known and studied ticks in the New World because of its very wide distribution, its economical importance as pest of domestic ungulates, and its association with a variety of animal and human pathogens. Recent observations, however, have challenged the taxonomic status of this tick and indicated that intraspecific cryptic speciation might be occurring. In the present study, we investigate the evolutionary and demographic history of this tick and examine its genetic structure based on the analyses of three mitochondrial (12SrDNA, d-loop, and COII) and one nuclear (ITS2) genes. Because A. cajennense is characterized by a typical trans-Amazonian distribution, lineage divergence dating is also performed to establish whether genetic diversity can be linked to dated vicariant events which shaped the topology of the Neotropics. Results: Total evidence analyses of the concatenated mtDNA and nuclear + mtDNA datasets resulted in well-resolved and fully congruent reconstructions of the relationships within A. cajennense. The phylogenetic analyses consistently found A. cajennense to be monophyletic and to be separated into six genetic units defined by mutually exclusive haplotype compositions and habitat associations. Also, genetic divergence values showed that these lineages are as distinct from each other as recognized separate species of the same genus. The six clades are deeply split and node dating indicates that they started diverging in the middle-late Miocene. Conclusions: Behavioral differences and the results of laboratory cross-breeding experiments had already indicated that A. cajennense might be a complex of distinct taxonomic units. The combined and congruent mitochondrial and nuclear genetic evidence from this study reveals that A. cajennense is an assembly of six distinct species which have evolved separately from each other since at least 13.2 million years ago (Mya) in the earliest and 3.3 Mya in the latest lineages. The temporal and spatial diversification modes of the six lineages overlap the phylogeographical history of other organisms with similar extant trans-Amazonian distributions and are consistent with the present prevailing hypothesis that Neotropical diversity often finds its origins in the Miocene, after the Andean uplift changed the topology and consequently the climate and ecology of the Neotropics.Fil: Beati, Lorenza. Georgia State University; Estados UnidosFil: Nava, Santiago. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria, Rafaela; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Burkman, Erica J.. Georgia State University; Estados UnidosFil: Barros Battesti, Darcy M.. Governo Do Estado de Sao Paulo. Secretaria Da Saude. Instituto Butantan; Brasil;Fil: Labruna, Marcelo B.. Universidade do Sao Paulo; Brasil;Fil: Guglielmone, Alberto Alejandro. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria, Rafaela; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Cáceres, Abraham G.. Instituto Nacional de Salud; PerúFil: Guzman Cornejo, Carmen. Universidad Nacional Autónoma de México; México;Fil: Léon, Renato. Universidad San Francisco de Quito; Ecuador;Fil: Durden, Lance A.. Georgia State University; Estados UnidosFil: Faccini, João L.H.. Universidade Federal Rural Do Rio de Janeiro; Brasi
Methods to estimate access to care and the effect of interventions on the outcomes of congenital disorders
In the absence of intervention, early-onset congenital disorders lead to pregnancy loss, early death, or disability. Currently, lack of epidemiological data from many settings limits the understanding of the burden of these conditions, thus impeding health planning, policy-making, and commensurate resource allocation. The Modell Global Database of Congenital Disorders (MGDb) seeks to meet this need by combining general biological principles with observational and demographic data, to generate estimates of the burden of congenital disorders. A range of interventions along the life course can modify adverse outcomes associated with congenital disorders. Hence, access to and quality of services available for the prevention and care of congenital disorders affects both their birth prevalence and the outcomes for affected individuals. Information on this is therefore important to enable burden estimates for settings with limited observational data, but is lacking from many settings. This paper, the third in this special issue on methods used in the MGDb for estimating the global burden of congenital disorders, describes key interventions that impact on outcomes of congenital disorders and methods used to estimate their coverage where empirical data are not available
Porotaxia em larva de carrapatos do gênero Amblyomma como caracterísiticas morfológicas adicionais para a identificação dos estágios imaturos.
Variabilidade intraespecífica e interespecífica das estruturas tegumentares sobre o idiossoma.bitstream/CPAF-RO-2009-09/12171/1/bpd45_porotaxia-em-larvas-de-carrapatos.pd
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