1,704 research outputs found
Facing the wind of the pre-FUor V1331 Cyg
The mass outflows in T Tauri stars (TTS) are thought to be an effective
mechanism to remove angular momentum during the pre-main-sequence contraction
of a low-mass star. The most powerful winds are observed at the FUor stage of
stellar evolution. V1331 Cyg has been considered as a TTS at the pre-FUor
stage. We analyse high-resolution spectra of V1331 Cyg collected in 1998-2007
and 20-d series of spectra taken in 2012. For the first time the photospheric
spectrum of the star is detected and stellar parameters are derived: spectral
type G7-K0 IV, mass 2.8 Msun, radius 5 Rsun, vsini < 6 km/s. The photospheric
spectrum is highly veiled, but the amount of veiling is not the same in
different spectral lines, being lower in weak transitions and much higher in
strong transitions. The Fe II 5018, Mg I 5183, K I 7699 and some other lines of
metals are accompanied by a `shell' absorption at radial velocity of about -240
km/s. We show that these absorptions form in the post-shock gas in the jet,
i.e. the star is seen though its jet. The P Cyg profiles of H-alpha and H-beta
indicate the terminal wind velocity of about 500 km/s, which vary on
time-scales from several days to years. A model of the stellar wind is
developed to interpret the observations. The model is based on calculation of
hydrogen spectral lines using the radiative transfer code TORUS. The observed
H-alpha and H-beta line profiles and their variability can be well reproduced
with a stellar wind model, where the mass-loss rate and collimation (opening
angle) of the wind are variable. The changes of the opening angle may be
induced by small variability in magetization of the inner disc wind. The
mass-loss rate is found to vary within (6-11)x10^{-8} Msun/yr, with the
accretion rate of 2.0x10^{-6} Msun/yr.Comment: 11 pages, 12 figures; accepted for publication in MNRAS.
Typographical errors have been corrected after the proof stag
Childhood hypopigmented mycosis fungoides: a commonly delayed diagnosis
Primary cutaneous lymphomas (PCLs) are exceedingly rare in children and adolescents, with mycosis fungoides (MF) being the most frequent PCL diagnosed in childhood. There are numerous unusual clinical variants of MF, including the hypopigmented type form (HMF). HMF is exceptional overall, but comparatively common among children. We present an 8-year-old boy with a 3-year history of progressive, generalised, scaly, hypopigmented round patches and few erythematous papules. He was first diagnosed with pityriasis alba (PA), and moisturisers were prescribed with no improvement. Skin biopsy showed typical features of MF, and the patient was successfully treated with narrowband ultraviolet B. HMF may simulate atopic dermatitis, PA, pityriasis lichenoides, tinea versicolour, vitiligo, postinflammatory hypopigmentation or leprosy. Therefore, persistent and unusual hypopigmented lesions should be biopsied to rule out this rare variant of MF
BAHA in children: Indications, results and complications
O BAHA (Bone Anchored Hearing Aid - prótese auditiva ancorada no osso) é utilizado em malformações do ouvido externo e médio, otorreia crónica, doença ossicular inoperável e como alternativa à prótese auditiva convencional por inadaptação/ impossibilidade. Este artigo descreve a experiência de colocação de BAHA no Hospital Maria Pia – Centro Hospitalar do Porto na última década, por estudo retrospectivo de 47 pacientes. O ganho audiométrico médio foi de 33,9 dB em relação aos valores base e de 14,4 dB em relação ao uso de próteses auditivas convencionais, com limiar auditivo médio com BAHA de 17,8 dB. Não houve qualquer complicação intra-operatória. No pós-operatório, quatro casos exigiram cirurgia para revisão da pele, em dois casos não houve integração óssea do implante e em três casos houve extrusão do implante por traumatismo directo. Este estudo conclui que os BAHA são um método eficaz e seguro de aparelhamento auditivo em crianças.info:eu-repo/semantics/publishedVersio
Novel precoded relay-assisted algorithm for cellular systems
Cooperative schemes are promising solutions for cellular wireless systems to improve system fairness, extend coverage and increase capacity. The use of relays is of significant interest to allow radio access in situations where a direct path is not available or has poor quality. A data precoded relay-assisted scheme is proposed for a system cooperating with 2 relays, each equipped with either a single antenna or 2-antenna array. However, because of the half-duplex constraint at the relays, relaying-assisted transmission would require the use of a higher order constellation than in the case when a continuous link is available from the BS to the UT. This would imply a penalty in the power efficiency. The simple precoding scheme proposed exploits the relation between QPSK and 16-QAM, by alternately transmitting through the 2 relays, achieving full diversity, while significantly reducing power penalty. Analysis of the pairwise error probability of the proposed algorithm with a single antenna in each relay is derived and confirmed with numerical results. We show the performance improvements of the precoded scheme, relatively to equivalent distributed SFBC scheme employing 16-QAM, for several channel quality scenarios. Copyright © 2010 Sara Teodoro, et al.European project CODIVPortuguese project CADWINPortuguese project AGILEFC
Structural study of the interaction of vanadate with the ligand 1,2-dimethyl-3-hydroxy-4-pyridinone (Hdmpp) in aqueous solution
The interaction of vanadate with the ligand 1,2-dimethyl-3-hydroxy-4-pyridinone (Hdmpp) was studied in aqueous solution using a combination of multinuclear NMR and EPR spectroscopies, as well as potentiometry and cyclic voltammetry. The different species in solution were identified and characterized, and their pKa values and stability constants determined. The vanadium complexes formed in solution are strongly dependent on media composition (ionic strength, presence of buffer), pH and metal-to-ligand ratio (M:L). Two major species -- V(V)/dmpp and V(V)/(dmpp)2 -- are formed in a 140 mM NaCl solution within the pH range 4.5 to 9.0, when M:L=1:2. In the presence of excess ligand (M:L<=1:5), only the 1:2 complex is present, and at pH<4 paramagnetic species are detected by EPR in solution, thus indicating a reducing capacity of the ligand. Cyclic voltammetry shows that redox processes in solution are not just electron transfer, but are accompanied by chemical reactions. The pKa values and stability constants were determined both by 51V NMR spectroscopy and potentiometry. The present results have a particular interest in the understanding of the aqueous solution chemistry in aerobic conditions of bis(1,2-dimethyl-3-hydroxy-4-pyridinonato) oxovanadium(IV) complex, VO(dmpp)2, a vanadium compound with potential insulin-mimetic properties.http://www.sciencedirect.com/science/article/B6TGG-40X8DKT-3C/1/3226f220763b348a4f3d74ae0fcd0e2
The indirect effect of contextual factors on the emotional distress of infertile couples
Few studies were dedicated to study the role of contextual factors, such as the socioeconomic status and urban rural residence in emotional distress of infertile couples. This study aimed to explore the impact of contextual factors on emotional distress, either directly or by affecting the importance of parenthood in one’s life which in turn affects emotional distress. In this cross-sectional study, 70 couples recruited during hormonal stimulation phase prior to IVF completed clinical and sociodemographic forms and self-report questionnaires assessing representations about the importance of parenthood and emotional distress. Path analysis using structural equation modelling was used to examine direct and indirect effects among variables. Results indicated that social economic status and Urban-Rural residence had an impact in emotional distress by affecting the representations about the importance of parenthood in one’s life. Gender differences were found regarding model paths, suggesting that the social context may contribute more to women’s emotional distress than to their partners’ distress. When delineating psychological interventions, health care providers should consider that cultural values about children and parenthood contribute to shape the infertility experienc
Leiomioma da Uretra Feminina - Revisão da Literatura a Propósito de Caso Clínico
Oleiomioma da uretra é uma patologia rara, estando descritos cerca de uma centena de
casos na literatura. São tumores benignos, constituídos por músculo liso e surgem mais
frequentemente na idade fértil.Otratamento é cirúrgico com excisão da massa, existindo
contudo possibilidade de recidiva local.
Apresenta-seumcaso clínico de leiomioma da uretra e realizou-se revisão da literatura
Unveiling extremely veiled T Tauri stars
Photospheric absorption lines in classical T Tauri stars (CTTS) are weak
compared to normal stars. This so-called veiling is normally identified with an
excess continuous emission formed in shock-heated gas at the stellar surface
below the accretion streams. We have selected four stars (RW Aur A, RU Lup, S
CrA NW and S CrA SE) with unusually strong veiling to make a detailed
investigation of veiling versus stellar brightness and emission line strengths
for comparisons to standard accretion models. We have monitored the stars
photometrically and spectroscopically at several epochs. In standard accretion
models a variable accretion rate will lead to a variable excess emission.
Consequently, the stellar brightness should vary accordingly. We find that the
veiling of absorption lines in these stars is strongly variable and usually so
large that it would require the release of several stellar luminosities of
potential energy. At states of very large line dilution, the correspondingly
large veiling factors derived correlate only weakly with brightness. Moreover,
the emission line strengths violate the expected trend of veiling versus line
strength. The veiling can change dramatically in one night, and is not
correlated with the phase of the rotation periods found for two stars. We show
that in at least three of the stars, when the veiling becomes high, the
photospheric lines become filled-in by line emission, which produces large
veiling factors unrelated to changes in any continuous emission from shocked
regions. We also consider to what extent extinction by dust and electron
scattering in the accretion stream may affect veiling measures in CTTS. We
conclude that the degree of veiling cannot be used as a measure of accretion
rates in CTTS with rich emission line spectra.Comment: Accepted for publication in A&A Letters. New language-edited version.
(4 pages, 3 figures
Mobilidade em cidades de média dimensão: o caso da cidade de Faro
Recentemente em Portugal, finais 2013, através do projeto de investigação INLUT - “Integração dos usos do solo e transportes em cidades de média dimensão”, que está a ser desenvolvido em parceria por quatro Universidades Portuguesas (IPCB, FAUTL, UTAD e UALG) e financiado pela FCT – Fundação para a Ciência e a Tecnologia, realizaram-se inquéritos gerais à mobilidade em quatro cidades de média dimensão (Faro, Santarém, Vila Real, e Castelo Branco) com o principal objetivo de se analisar a relação entre os usos do solo e os padrões de deslocação da população residente.
Com o presente artigo pretende-se apresentar a metodologia seguida, e uma síntese dos resultados obtidos nos 1257 inquéritos à mobilidade realizados à população residente no perímetro urbano de Faro e Montenegro/Gambelas, nas seguintes variáveis: dados da amostra, identificação das áreas homogéneas da área de estudo, distribuição espacial dos inquiridos por local de residência, sexo e estrutura etária dos inquiridos, habilitações literárias, situação face ao mercado de trabalho, potencial de mobilidade, posse de veículos, número de viagens em um dia, hora de início da primeira viagem, apresentação das atitudes (perfil do inquirido), rendimento mensal liquido do aglomerado, cadeia de atividades, taxa de imobilidade, número médio de viagens, tempo médio gasto em viagens, os motivos, as cadeias de atividades realizadas,
o modo de transporte escolhido, principais razões da escolha do modo de transporte, número de transbordos efetuados, entre outras.
Dado que em Portugal, nas últimas duas décadas, têm vindo a ser realizados inquéritos à mobilidade geral em duas cidades de grandes dimensões: a cidade de Lisboa e a cidade do Porto com a finalidade de estudar os padrões de deslocação dos residentes e visitantes e melhorar a oferta de transportes públicos nas áreas metropolitanas destas duas grandes cidades, apresenta-se também uma breve análise comparativa entre os padrões de mobilidade da cidade de Faro, com os padrões de mobilidade da grande cidade de Lisboa.info:eu-repo/semantics/publishedVersio
- …
