2,892 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 suÃnos: estratégia de ação no controle e avaliação econômica.
bitstream/item/58756/1/CUsersPiazzonDocuments172.pd
Metasomatism induced by alkaline magma in the upper mantle of northern Victoria Land (Antarctica): an experimental approach
Magma generation in the Ross Sea system is related to partial melting of strongly
metasomatised mantle sources where amphibole most probably plays a crucial role. In this
context, metasomatism induced by a mela-nephelinite melt in lithospheric mantle of the Mt.
Melbourne Volcanic Province (northern Victoria Land – NVL, Antarctica) was investigated
experimentally studying the effects of melt interaction with lherzolite at 1.5-2.0 GPa and
T=975-1300°C, and wehrlite at 1.0 GPa and T=1050-1250°C. The experiments were
designed to induce melt infiltration into the ultramafic rocks. The observed modifications in
minerals are compared with those found in mantle xenoliths from NVL. The effects of
metasomatic modifications are evaluated on the basis of run temperature, distance from the
infiltrating melt and on the diffusion rates of chemical components. Both in lherzolite and
wehrlite, clinopyroxene exhibits large compositional variations ranging from primary
diopside to high Mg-Cr-(Na) augitic and omphacitic clinopyroxenes in lherzolite, and to
low Mg and high Ti-Al-Fe-Na augites in wehrlite. Olivine (in wehrlite) and spinel (in
lherzolite) also result compositionally modified, the former shows enrichments in Fe, the
latter displays a higher Cr/(Cr+Al) ratio. The systematic variations in mineral compositions
imply modifications of the chemistry of the infiltrating melt as recorded by the glass
veinlets and patches observed in some charges. In experiments involving wehrlite
paragenesis, the glass composition approaches that of melt patches associated to both
amphibole-free and amphibole-bearing natural samples, and is related to
olivine+clinopyroxene crystallisation coupled with primary clinopyroxene dissolution at the
contact between the metasomatising melt and the solid matrix. Even if amphibole
crystallisation was not attained in the experiments, we were able to explain the occurrence
of amphibole in the natural system considering that in this case a hot metasomatising melt
infiltrates a cooler matrix
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
Porotaxia em larva de carrapatos do gênero Amblyomma como caracterÃsiticas morfológicas adicionais para a identificação dos estágios imaturos.
Variabilidade intraespecÃfica e interespecÃfica das estruturas tegumentares sobre o idiossoma.bitstream/CPAF-RO-2009-09/12171/1/bpd45_porotaxia-em-larvas-de-carrapatos.pd
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
Metodologia para o estudo da porotaxia em larvas de carrapatos Ixodidae.
A determinação especÃfica do estágio larval dos ixodÃdeos tem sido um imenso problema para a sistemática nos últimos anos. Este trabalho visa a elaboração de uma metodologia de descrição de nomenclatura para as larvas de Ixodidae.bitstream/item/24724/1/cot321-carrapato.pd
Breast cancer treatment de-escalation: breaking the SOUND barrier
Breast Cancer (BC) is the leading oncological diagnosis, with the annual incidence expected to exceed 3 million new cases by 2040 due to population growth and ageing. Despite the increasing number of BC patients, recent advancements in multidisciplinary treatment have enabled surgical de-escalation, maintaining equivalent oncological outcomes. Areas of surgical de-escalation include avoidance of axillary lymph node dissection in patients with low disease burden, re-excision in close margins after breast conserving surgery, and even complete avoidance of surgery in selected cases. Despite the evidence supporting these de-escalation protocols, their implementation is inconsistent. The article discusses how these strategies can be further integrated into BC treatment plans to improve patients' quality of life and optimize health care resources. The future of BC management may be shaped by genomic tests, offering more tailored and potentially less invasive treatment strategies. A comprehensive understanding of tumor biology has facilitated the development of strategies such as neoadjuvant chemotherapy, with the potential to further de-escalate surgery. The need for a multidisciplinary approach to BC care, incorporating emerging diagnostic tools and understanding of individual patient's disease trajectory, is paramount. It is essential to challenge the perception of more aggressive treatments as inherently better and ensure decisions are based on high-quality evidence, preserving the principle of 'do no harm'. The focus of future BC research should be on identifying markers capable of predicting the risk of distant recurrence and implementing a true multidisciplinary de-escalation approach
- …