RESUMO
Electromagnetic noise absorber sheets have become a solution for solving complex electromagnetic interference (EMI) problems due to their high magnetic losses. This contribution is focused on characterizing a novel structure that is based on an absorber film with a metal layer attached on its top side. Two different absorber compositions were combined with Al and Cu metal layers in order to study the improvement on the performance of these structures, depending on the complex permeability, absorber film thickness, and type of metal. The transmission attenuation power ratio of the absorber films is analyzed and compared to the performance of absorber and metal structures. The measurement procedure is carried out attaching the films into a microstrip line that has been designed based on IEC standard (IEC 62333-2). This test fixture is employed as a transmission line to simulate a general noise path. The performance of absorber composites to filter electromagnetic noise is evaluated through analyzing S21 and S11 parameters. This is carried out with the aim of finding out in which conditions the absorption loss is improved when a metal layer is attached. In addition, the possible re-radiation effect, due to the magnetic field that is generated by the eddy currents induced in the metal layer, is examined.
RESUMO
The gap of standardization for conducted and field coupled electromagnetic interferences (EMI) in the 2-150 kHz frequency range can lead to Electromagnetic Compatibility (EMC) problems. This is caused by power systems such as Pulse Width Modulation (PWM) controlled rectifiers, photovoltaic inverters or charging battery units in electric vehicles. This is a very important frequency spectral due to interferences generated in a wide range of devices and, specifically, communication problems in the new technologies and devices incorporated to the traditional grid to convert it into a Smart Grid. Consequently, it is necessary to provide new solutions to attenuate this kind of interference, which involves finding new materials that are able to filter the electromagnetic noise. This contribution is focused on characterizing the performance of a novel material based on nanocrystalline and comparing it to most common material compositions such as MnZn and NiZn. This research is carried out from the point of view of the manufacturing process, magnetic properties and EMI suppression ability. This last item is carried out through two analysis procedures: a theoretical method by determining the attenuation ratio by measuring impedance parameter and proposing a new empirical technique based on measuring directly the insertion loss parameter. Therefore, the main aim of this characterization process is to determine the performance of nanocrystalline compared to traditional cable ferrite compositions to reduce the interferences in this controversial frequency range. From the results obtained, it is possible to deduce that nanocrystalline cable ferrite provides the best performance to filter the electromagnetic noise in the 2-150 kHz frequency range.
RESUMO
Los microorganismos del género Shigella causan habitualmente infecciones en el tracto gastrointestinal y solo en muy raras ocasiones pueden ser responsables de infecciones extraintestinales, como la vulvovaginitis. En la infancia, la vulvovaginitis por Shigella es muy inusual, aunque debe ser tenida en cuenta ya que puede ser responsable de hasta un 2-4% de los casos pediátricos. Se presenta el caso de una niña de ocho años, de origen boliviano, que acude a nuestra consulta por presentar desde hace dos meses un sangrado vaginal intermitente junto a flujo vaginal mucopurulento y maloliente. Ante la cronicidad y características del cuadro clínico, se derivó al hospital para descartar cuerpo extraño vaginal o indicios de abuso sexual y se recogió un cultivo del exudado vaginal que resultó positivo a Shigella sonnei; se realizaron también coprocultivo, cultivo de exudado perianal y urocultivo, que resultaron negativos. Se estableció tratamiento antibiótico dirigido según antibiograma, consiguiendo la resolución completa del cuadro tras dos tandas del mismo. La mayoría de las vulvovaginitis en niñas en edad prepuberal son inespecíficas y secundarias a malos hábitos higiénicos o irritantes locales y el resultado del cultivo del exudado muestra las más de las veces flora mixta bacteriana, pero en casos de vulvovaginitis crónica de evolución tórpida debemos recordar estudiar otras causas específicas, como cuerpo extraño vaginal, abuso sexual si existen indicios o buscar bacterias patógenas específicas que precisen tratamiento (AU)
Shigella´s group of microorganisms are pathogens that usually cause infections in the gastrointestinal tract and only in rare occasions may be responsible for extraintestinal infections such as vulvovaginitis. In childhood, vulvovaginitis caused by Shigella is very inusual, although it must be taken into account as it can be responsible for up to 2-4% of the pediatric cases. In a particular case an eight-year-old Bolivian girl came to our center as she showed intermittent vaginal bleeding as well as mucopurulent and fetid vaginal discharge. Given the chronicity and the characteristics of the clinical profile, the girl was transferred to the hospital in order to rule out a possible intravaginal foreign body or signs of sexual abuse. Furthermore, a culture of vaginal exudates was obtained which tested positive for Shigella sonnei. Stool, perianal exudate and urine cultures were done and the results were negative. Antibiotic treatment was provided, conducted according to the results obtained by an antibiogram, getting the complete resolution of the case after two series of it. The vast majority of vulvovaginitis in prepubertal girls are unspecific and caused by bad hygienic habits, local irritants or mixed bacteria flora, however, in cases of chronic vulvovaginitis with torpid evolution, we must remember to study other specific causes such as intravaginal foreign body, sexual abuse in the event that there were signs or isolate specific pathogen bacterias which may require treatment (AU)
