118,377 research outputs found
The imprint of accretion on the UV spectrum of young stellar objects: an X-Shooter view
No full textThe evolution of protoplanetary disks is regulated by its interaction with the central forming star. This interaction happens through accretion of matter from the disk onto the star, and its most significant signatures are the continuum excess in the UV part of the spectrum and the presence of various emission lines. With the VLT/X-Shooter spectrograph, the excess emission in the UV due to accretion can being studied simultaneously with the signatures in the visible and in the near-infrared, giving a simultaneous and complete view of this phenomenon. Here we present some results we obtained using observation and modeling of the UV-excess in young forming stars, which are: (1) the determination of stellar and accretion properties in candidate older accreting young stellar objects and (2) the study of the star-disk interaction in the early stages of planetary system evolution in transitional disk systems
Wernicke's syndrome during parenteral feeding: Not an unusual complication
No full textObjective
Wernicke's encephalopathy (WE) is an acute disorder due to thiamine deficiency, characterized by ophthalmoplegia, ataxia, and mental confusion, similar to that classically observed in alcoholism. Some cases of WE were reported to coincide with other conditions such as hyperemesis gravidarum, bariatric surgery, and total parenteral nutrition. In this study the objective was to retrospectively evaluate the prevalence of WE among intravenously fed patients in our hospital during the previous 2 y.
Methods
Among all cases of WE diagnosed by cranial magnetic resonance scan during a 2-y period in the Azienda Ospedaliera of Padua, we identified patients who exhibited WE during parenteral feeding. Albumin plasma levels, measured at the onset of WE symptoms, were used to estimate nutritional status.
Results
We found seven cases of WE that coincided with intravenous feeding. WE occurred, on average, 13 d after the start of glucose infusion. The five subjects with albumin plasma levels lower than 35 g/L at the onset of WE received glucose infusion for fewer days. In six cases the clinical signs disappeared the day after thiamine infusion. In one case mental function did not normalize and the patient developed Korsakoff's syndrome despite prolonged thiamine treatment.
Conclusion
During a 2-y period we observed a high prevalence of WE in intravenously fed patients due to lack of thiamine supplementation. A prophylactic treatment must be performed in at-risk patients and multivitamin infusion containing thiamine must be administered daily during the course of intravenous feeding
Spherical-multipole expansion of an inhomogeneous electromagnetic plane wave in lossless media
No full textThe spherical-multipole expansion of an inhomogeneous electromagnetic plane wave is derived by extending the spherical source coordinates v to a complex number. The analytical results are successfully validated by comparing the numerical evaluation of the multipole expansion with the corresponding closed-form results. The paper also contains a first result for an inhomogeneous plane electromagnetic wave diffracted by a perfectly conducting semiinfinite circular cone
Design of high-impedance screens by using multilayered frequency selective surfaces
No full textIn this paper, a multilayered dielectric structure backed by a perfectly electric conducting (PEC) ground plane is investigated for realizing high-impedance surfaces. These surfaces behave like a perfect magnetic conductor (PMC) at a certain frequency range. The inclusion of an FSS in the structure provides an additional degree of freedom which can be exploited to obtain the desired frequency and angular performance. All the presented solutions are derived by using a genetic algorithm-based synthesis procedure. The genetic algorithm (GA) resorts to an electromagnetic solver based on the method of moments (MoM) to describe the scattering behavior of the structure. In particular, the GA determines the permittivity and the thickness of each dielectric layer and the shape and the dimensions of the FSS screen. The synthesized structures arc discussed with particular reference to the frequency response and to the robustness of the solution with respect to the angle of illumination
Synthesis of Artificial Magnetic Conductors by Using Multilayered Frequency Selective Surfaces
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