2,798 research outputs found
[O II] line ratios
Based on new calculations we reconfirm the low and high density limits on the
forbidden fine structure line ratio [O II] I(3729)/I(3726): lim_{N_ e} --> 0} =
1.5 and lim_{N_ e} --> \infty} = 0.35. Employing [O II] collision strengths
calculated using the Breit-Pauli R-matrix method we rule out any significant
deviation due to relativistic effects from these canonical values. The present
results are in substantial agreement with older calculations by Pradhan (1976)
and validate the extensive observational analysis of gaseous nebulae by Copetti
and Writzel (2002) and Wang et al (2004) that reach the same conclusions. The
present theoretical results and the recent observational analyses differ
significantly from the calculations by MacLaughlin and Bell (1998) and Keenan
et al (1999). The new maxwellian averaged effective collision strengths are
presented for the 10 transitions among the first 5 levels to enable
computations of [O II] line ratios.Comment: Submitted to MNRAS (Letters), 4 pages, 2 figures, 1 tabl
Respuesta eléctrica de películas gruesas del sistema SnO2-TiO2,conformadas con polvos cerámicos obtenidosa través del método pechini
El óxido de estaño, SnO2, es el compuesto más utilizado en la fabricación de sensores de gas, principalmente para gases
reductores como el CO y H2. Dado que la respuesta de estos sensores depende fuertemente de su superficie, es de gran interés
desarrollar métodos de síntesis que permitan obtener nanopartículas de estos compuestos para utilizarlas posteriormente en
la conformación de películas. En el presente trabajo se describe adecuadamente el método del precursor polimérico utilizado
para obtener nanopartículas de SnO2-TiO2. Los polvos cerámicos obtenidos se caracterizaron mediante ATD/TG, DRX,
FTIR, y MEB. Además, se analizó el comportamiento eléctrico de las películas gruesas obtenidas, cuando son expuestas a
atmósferas de O2 y CO.Peer reviewe
d=3 random field behavior near percolation
The highly diluted antiferromagnet Mn(0.35)Zn(0.65)F2 has been investigated
by neutron scattering for H>0. A low-temperature (T<11K), low-field (H<1T)
pseudophase transition boundary separates a partially antiferromagnetically
ordered phase from the paramagnetic one. For 1<H<7T at low temperatures, a
region of antiferromagnetic order is field induced but is not enclosed within a
transition boundary.Comment: 9 pages, 4 figure
Ordering in the dilute weakly-anisotropic antiferromagnet Mn(0.35)Zn(0.65)F2
The highly diluted antiferromagnet Mn(0.35)Zn(0.65)F2 has been investigated
by neutron scattering in zero field. The Bragg peaks observed below the Neel
temperature TN (approximately 10.9 K) indicate stable antiferromagnetic
long-range ordering at low temperature. The critical behavior is governed by
random-exchange Ising model critical exponents (nu approximately 0.69 and gamma
approximately 1.31), as reported for Mn(x)Zn(1-x)F2 with higher x and for the
isostructural compound Fe(x)Zn(1-x)F2. However, in addition to the Bragg peaks,
unusual scattering behavior appears for |q|>0 below a glassy temperature Tg
approximately 7.0 K. The glassy region T<Tg corresponds to that of noticeable
frequency dependence in earlier zero-field ac susceptibility measurements on
this sample. These results indicate that long-range order coexists with
short-range nonequilibrium clusters in this highly diluted magnet.Comment: 7 pages, 5 figure
Ductus venosus agenesis and fetal malformations: what can we expect? - a systematic review of the literature
Background: The ductus venosus agenesis (DVA) is a rare condition with a variable prognosis that relies partly on the presence of associated conditions. The purpose of our study was to analyze the literature regarding the postnatal outcome of fetuses with DVA associated with fetal malformations, in order to discuss the best management options for couples. Methods: We performed a systematic review of the literature of MEDLINE and SCOPUS electronic databases in a 25-year period from 1992 to September 2017. Results: We found 340 cases of DVA associated with fetal abnormalities. The most common chromosomal abnormalities were: monosomy X (12/48, 25%), trisomy 21 (11/48, 22.9%) and trisomy 18 (6/48, 12.5%). From the 340 cases with DVA, in 31 cases the umbilical venous shunt type was not reported. Of the fetuses, 60.8% (188/309) had an extrahepatic umbilical venous drainage while 39.2% (121/309) presented an intrahepatic connection. The DVA was associated in 71 cases (23.0%) with cardiac abnormalities, in 82 cases (26.5%) with extracardiac abnormalities and in 85 cases (27.5%) with both cardiac and extracardiac abnormalities. Conclusion: DVA associated with both cardiac and extracardiac malformations may confer a poorer fetal outcome, a clinically relevant fact that should clarify what can be expected from this entity and help prenatal counseling
Medical Termination of Delayed Miscarriage: Four-Year Experience with an Outpatient Protocol
Purpose: To evaluate the efficacy of an outpatient protocol with vaginal misoprostol to treat delayed miscarriage.
Methods: Retrospective analysis of prospectively collected data on women medically treated for missed abortion with an outpatient protocol. The inclusion criteria were: ultrasound-based diagnosis of missed abortion with less than 10 weeks; no heavy bleeding, infection, inflammatory bowel disease or misoprostol allergy; no more than 2 previous spontaneous abortions; the preference of the patient regarding the medical management. The protocol consisted of: 1) a single dose of 800 µg of misoprostol administered intravaginally at the emergency department, after which the patients were discharged home; 2) clinical and ultrasonographic evaluation 48 hours later – if the intrauterine gestational sac was still present, the application of 800 µg of vaginal misoprostol was repeated, and the patients were discharged home; 3) clinical and ultrasonography evaluation 7 days after the initiation of the protocol – if the intrauterine gestational sac was still present, surgical management was proposed. The protocol was introduced in January 2012. Every woman received oral analgesia and written general recommendations. We also gave them a paper form to be presented and filled out at each evaluation.
Results: Complete miscarriage with misoprostol occurred in 340 women (90.2%). Surgery was performed in 37 (9.8%) patients, representing the global failure rate of the protocol. Miscarriage was completed after the first misoprostol administration in 208 (55.2%) women, with a success rate after the second administration of 78.1% (132/169). The average age of the women with complete resolution using misoprostol was superior to the average age of those who required surgery (33.99 years versus 31.74 years; p = 0.031). Based on the ultrasonographic findings in the first evaluation, the women diagnosed with fetal loss achieved greater success rates compared with those diagnosed with empty sac (p = 0.049).
Conclusions: We conclude this is an effective and safe option in the majority of delayed miscarriage cases during the first trimester, reducing surgical procedures and their consequences
Tratamiento de las complicaciones vasculares tras aplicación del método de Ilizarov: Aportación de tres casos
Entre 1987 y 1991 fueron intervenidos 209 pacientes mediante el método de
Ilizarov en nuestra institución. Tres de los pacientes presentaron complicaciones vasculares durante
el tratamiento. Todos ellos eran adultos y habían sido tratados por pseudoartrosis de un
hueso largo. La lesión vascular ocurrió en la arteria femoral superficial en un caso, la arteria
poplítea en otro y la arteria tibial posterior en el último de ellos. El signo clínico del problema
vascular fue la presencia de la hemorragia en el punto de salida cutánea de las agujas de
Kirschner de transfixión. Se realizó exploración arteriográfica en todos los casos, pero su interpretación
fue difícil debido a la presencia del fijador externo. El tratamiento de la complicación
vascular fue: en el caso de la lesión de la arteria femoral fue retirado el fijador y realizado
un by-pass con un injerto invertido obtenido de la vena safena; en el caso de lesión de la arteria
poplítea, se realizó la misma técnica pero sin retirar el fijador. En el último caso la lesión
de la arteria tibial posterior se trató mediante ligadura de la misma. En todos los casos, la evolución
del tratamiento vascular fue excelente, siendo posible finalizar el tratamiento ortopédico.From 1987 to 1991, 209 patients were operated on by the Ilizarov method in
our institution. Among them, 3 patients presented vascular complications during the treatment.
All were adults and have been treated for long bone pseudoarthrosis. The vascular lesion ocurred
at the femoral superficial artery in one case, at the popliteal artery in other case, and at
the posterior tibial artery in the third case. The clinical sign of vascular damage was bleeding
through the cutaneous point of the Kirschnner transfixion wires in all cases. Arteriography was
done in all cases but its interpretation was very difficult because of the presence of the external
fixator. In the case of femoral artery, injury the external fixator was removed and a vascular
by-pass was performed with an inverted graft of the saphenous vein. The same procedure was
done in the case with a popliteal artery injury but without removal of the external fixator. The
case with lesion of the posterior tibial artery was treated by arterial hgature. In all cases, outcome
was satisfactory, allowing completion of the orthopaedic treatment
A 2d Honeycomb Photonic Crystal Under Applied Magnetic Fields
The band-structure properties of a photonic two-dimensional honeycomb lattice formed by cylindrical semiconductor shell rods with dielectric permitivities ε 1 and ε 2, and embedded in a background with permitivity ε 3, is studied by using an standard plane-wave expansion. The properties of bandgaps and density of states, considering dispersive dielectric responses, are investigated together with the possibility of fabricating systems with tunable photonic bandgaps, due to the Voigt magneto-optical effect, under the influence of an external magnetic field. © 2008 SPIE.7138J. D. Joannopoulos, R. D. Meade, J. N. Winn, Photonic Crystals: Molding the Flow of Light, Princeton University Press, Princeton, 1995E. Istrate and E. H. Sargent, Rev. Mod. Phys. 78, 455 (2006)Xu, C., Hu, X., Li, Y., Liu, X., Fu, R., Zi, J., (2003) Phys. Rev. B, 68, p. 193201Kee, C.-S., Kim, J.-E., Park, H.Y., Park, I., Lim, H., (2000) Phys. Rev. B, 61, p. 15523Anderson, C.M., Giapis, K.P., (1996) Phys. Rev. Lett, 77, p. 2949Rezaei, B., Kalafi, M., (2006) Optics Commun, 266, p. 159Busch, K., John, S., (1999) Phys. Rev. Lett, 83, p. 967S. B. Cavalcanti, M. de Dios-Leyva, E. Reyes-Gómez, and L. E. Oliveira, Phys. Rev. B 74, 153102 (2006)ibid., Phys. Rev. E 75, 026607 (2007)Ho, K.M., Chan, C.T., Soukoulis, C.M., (1990) Phys. Rev. Lett, 65, p. 315
Deep LOFAR 150 MHz imaging of the Bo\"otes field: Unveiling the faint low-frequency sky
We have conducted a deep survey (with a central rms of )
with the LOw Frequency ARray (LOFAR) at 120-168 MHz of the Bo\"otes field, with
an angular resolution of , and obtained a sample of
10091 radio sources ( limit) over an area of .
The astrometry and flux scale accuracy of our source catalog is investigated.
The resolution bias, incompleteness and other systematic effects that could
affect our source counts are discussed and accounted for. The derived 150 MHz
source counts present a flattening below sub-mJy flux densities, that is in
agreement with previous results from high- and low- frequency surveys. This
flattening has been argued to be due to an increasing contribution of
star-forming galaxies and faint active galactic nuclei. Additionally, we use
our observations to evaluate the contribution of cosmic variance to the scatter
in source counts measurements. The latter is achieved by dividing our Bo\"otes
mosaic into 10 non-overlapping circular sectors, each one with an approximate
area of The counts in each sector are computed in the
same way as done for the entire mosaic. By comparing the induced scatter with
that of counts obtained from depth observations scaled to 150MHz, we find that
the scatter due to cosmic variance is larger than the Poissonian
errors of the source counts, and it may explain the dispersion from previously
reported depth source counts at flux densities . This work
demonstrates the feasibility of achieving deep radio imaging at low-frequencies
with LOFAR.Comment: A\&A in press. 15 pages, 16 figure
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