Comparación de cambios clínicos y hemodinámicos en pacientes con insuficiencia venosa mixta según tipo de manejo.

Existen varias causas de la insuficiencia venosa profunda, la insuficiencia venosa superficial es una de ellas; por tal motivo, una intervención activa de la insuficiencia superficial ya sea cirugía convencional, esclerosis o radiofrecuencia mejora el reflujo del sistema venoso profundo. En nuestro medio no se acostumbra a intervenir los pacientes con insuficiencia venosa mixta bajo la creencia de exacerbar la enfermedad o generar complicaciones. Se pretende documentar los cambios clínicos y hemodinámicos en pacientes con insuficiencia venosa mixta según tipo de manejo, médico vs quirúrgico

Solid-state NMR characterization of a series of copolymers containing fluorene, phenylene and thiophene units

Fluorene and thiophene units are commonly used in polymeric materials for electro-optical applications. Due to differences in reactivity, the final composition of polymers containing these components often differs from that used in their preparation. This contribution describes the synthesis of PPV type terpolymers built by fluorene, phenylene and thiophene units and their quantification by CPMAS NMR. The similarity of the three aromatic co-monomers makes it difficult to separate the analytical responses that would allow quantification of each copolymer unit in the chain. In this sense, we show that the combination of dipolar dephased CPMAS with radiofrequency ramp and proper spectral treatment allows a good estimation and quantification of the copolymer constitution. (C) 2011 Elsevier Ltd. All rights reserved.

Effects of Crossing Saddle Coil Conductors: Electric Length X Mutual Inductance

In magnetic resonance imaging (MRI), either on human or animal studies, the main requirements for radiofrequency (RF) coils are to produce a homogeneous RF field while used as a transmitter coil and to have the best signal-to-noise ratio (SNR) while used as a receiver. Besides, they need to be easily frequency adjustable and have input impedance matching 50 Omega to several different load conditions. New theoretical and practical concepts are presented here for considerable enhancing of RF coil homogeneity for MRI experiments on small animals. To optimize field homogeneity, we have performed simulations using Blot and Savart law varying the coil`s window angle, achieving the optimum one. However, when the coil`s dimensions are the same order of the wave length and according to transmission line theory, differences in electrical length and effects of mutual inductances between adjacent strip conductors decrease both field homogeneity and SNR. The problematic interactions between strip conductors by means of mutual inductance were eliminated by inserting crossings at half electrical length, avoiding distortion on current density, thus eliminating sources of field inhomogeneity. Experimental results show that measured field maps and simulations are in good agreement. The new coil design, dubbed double-crossed saddle described here have field homogeneity and SNR superior than the linearly driven 8-rung birdcage coil. One of our major findings was that the effects of mutual inductance are more significant than differences in electrical length for this frequency and coil dimensions. In vitro images of a primate Cebus paela brain were acquired, confirming double-crossed saddle superiority. (C) 2010 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 37B: 193-201, 2010

Localization with orientation using RSSI measurements: RF map based approach

Localization of RFIDs in the indoor environment will entail determining both the position and the orientation of the user. This paper develops estimator using RSSI measurements to predict the position and orientation of a transmitter in an indoor environment. The best estimator tried was an K-nearest neighbours model that gave an accuracy of approximately 83% for position prediction and 93% for orientation prediction. It was also found that the RSSI values change throughout the day, meaning that an adaptive estimator is necessary for localization.

Faster CRT-RSA Decryption towards RFID applications

In this paper we present a strategy to design the RSA parameters in such a manner so that the CRT-RSA decryption becomes more efficient than the existing methods. We achieve around 21% improvement in speed over the currently best known implementation strategy for CRT-RSA decryption with our properly chosen parameters that also helps in terms of less memory requirement. Moreover, we argue in detail the cryptographic security regarding our choice of the secret parameters.

A novel mutual authentication scheme with minimum disclosure for rfid systems

In this paper we present a novel approach to authentication and privacy in RFID systems based on the minimum disclosure property and in conformance to EPC Class-1 Gen-2 specifications. We take into account the computational constraints of EPC Class-1 Gen-2 passive RFID tags and only the cyclic redundancy check (CRC) and pseudo random number generator (PRNG) functions that passive RFID tags are capable of are employed. Detailed security analysis of our scheme shows that it can offer robust security properties in terms of tag anonymity and tag untraceability while at the same time being robust to replay, tag impersonation and desynchronisation attacks. Simulations results are also presented to study the scalability of the proposed scheme and its impact on authentication delay.

Management of advanced neuroendocrine tumors with hepatic metastasis

Neuroendocrine tumors (NETs) in general and specifically these gastroenteropancreatic-neuroendocrine tumors often present a considerable diagnostic and therapeutic challenge, especially those that behave in an aggressive fashion. The majority of tumors are diagnosed at a stage that the only curative treatment, radical surgical intervention, is no longer an option and thus long-term therapy with somatostatin analogs is focused on symptom amelioration and in the improvement of quality of life. Although biotherapy is currently the most efficient treatment to achieve palliation, conventional chemotherapy may have some utility in undifferentiated or highly proliferating neuroendocrine carcinomas and pancreatic NETs. Hepatic metastases, depending on size, location, and number may be amenable to surgical resection or radiofrequency ablation. If surgery is not feasible, embolization either alone (bland), in combination with chemotherapeutic agents, or using radioactive microspheres can be used. Peptide receptor targeted radiotherapy using radiolabeled octapeptide analogs (⁹⁰Yttrium or ¹⁷⁷Lutetium-octreotide) may lead to reduction in tumor size, but in most circumstances has a tumor stabilizing effect. A variety of antiangiogenesis and growth factor-targeted agents have been evaluated, but to date, the results have failed to meet our expectations.

A secure tag ownership transfer scheme in a closed loop RFID system

In this paper we propose a novel secure tag ownership transfer scheme for closed loop RFID systems. An important property of our method is that the ownership transfer is guaranteed to be atomic and the scheme is protected against desynchronisation leading to permanent DoS. Further, it is suited to the computational constraints of EPC Class-1 Gen-2 passive RFID tags as they only use the CRC and PRNG functions that passive RFID tags are capable of. We provide a detailed security analysis to show that our scheme satisfies the required security properties of tag anonymity, tag location privacy, forward secrecy, forward untraceability while being resistant to replay, desynchronisation and server impersonation attacks. Performance comparisons show that our scheme is practical and can be implemented on passive low-cost RFID tags.

A secure search protocol based on Quadratic Residues for EPC Class-1 Gen-2 UHF RFID tags

Radio Frequency Identification (RFID) is a technological revolution that is expected to soon replace barcode systems. One of the important features of an RFID system is its ability to search for a particular tag among a group of tags. This task is quite common where RFID systems play a vital role. To our knowledge not much work has been done in this secure search area of RFID. Also, most of the existing work do not comply with the C1G2 standards. Our work aims to fill that gap by proposing a protocol based on Quadratic Residues property that does not use the expensive hash functions or any complex encryption schemes but achieves total compliance with industry standards while meeting the security requirements.

Radio frequency energy harvesting from a feeding source in a passive deep brain stimulation device for murine preclinical research

This paper presents the development of an energy harvesting circuit for use with a head-mountable deep brain stimulation (DBS) device. It consists of a circular planar inverted-F antenna (PIFA) and a Schottky diode-based Cockcroft-Walton 4-voltage rectifier. The PIFA has the volume of π × 10(2) × 1.5 mm(3), resonance frequency of 915 MHz, and bandwidth of 16 MHz (909-925 MHz) at a return loss of -10 dB. The rectifier offers maximum efficiency of 78% for the input power of -5 dBm at a 5 kΩ load resistance. The developed rectenna operates efficiently at 915 MHz for the input power within -15 dBm to +5 dBm. For operating a DBS device, the DC voltage of 2 V is recorded from the rectenna terminal at a distance of 55 cm away from a 26.77 dBm transmitter in free space. An in-vitro test of the DBS device is presented.

Efeitos biológicos in vitro de agentes físicos utilizados em fisioterapia

The uses of radiobiocomplexes labeled with technetium-99m contributed to health science advances. Stannous chloride (SnCl2) has been used as a reducing agent for the labeling process. Cytotoxic and genotoxic effect of the SnCl2 have been described in several studies and with this experimental models alterations in molecular and cellular level can be evaluated. In the last years the physicals therapists acquired new devices which emits electromagnetic radiation such us Extremely Low Frequency Pulsated Electromagnetic Fields (E.L.F. P.E.M.F.), radiofrequency, Intense Pulsed Light (I.P.L.) and others which emits sonic waves such us Biorresonance. Scientific evidence of the effects and dosage is important to protect public health and to reach exposition levels that result in significant biological effects. The aim of this project is to verify the effects of these physical agents in plasmid DNA and E. coli AB1157 cultures in presence or absence of SnCl2 and the effects in blood constituents labeled with technetium-99m. Wistar rats blood was exposed to the cited sources and the labelling of blood constituents with 99mTc was carried through. Cultures of E. coli AB1157 and plasmidial samples DNA had been also exposed the physical agents. The results suggest that these agents are capable of altering neither the survival of E. coli cells or plasmid DNA electrophoresis mobility. The multidiscipline character was clearly in this study due the interaction between Nuclear Medicine department of the UERJ and the Laboratory of Physical Agents of the Maimonides University in Argentina until the union between the teacher (biomedical and physiotherapist) and student (physiotherapist), besides collaborators of the area of Physics and Biology, promoting new ideas and perspectives and also adding the knowledge of different areas and origins

Laparoscopy hepatic biopsy through cauterization

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise e otimização de superfícies seletivas de Frequência utilizando redes neurais artificiais e algoritmos de otimização natural

The bidimensional periodic structures called frequency selective surfaces have been well investigated because of their filtering properties. Similar to the filters that work at the traditional radiofrequency band, such structures can behave as band-stop or pass-band filters, depending on the elements of the array (patch or aperture, respectively) and can be used for a variety of applications, such as: radomes, dichroic reflectors, waveguide filters, artificial magnetic conductors, microwave absorbers etc. To provide high-performance filtering properties at microwave bands, electromagnetic engineers have investigated various types of periodic structures: reconfigurable frequency selective screens, multilayered selective filters, as well as periodic arrays printed on anisotropic dielectric substrates and composed by fractal elements. In general, there is no closed form solution directly from a given desired frequency response to a corresponding device; thus, the analysis of its scattering characteristics requires the application of rigorous full-wave techniques. Besides that, due to the computational complexity of using a full-wave simulator to evaluate the frequency selective surface scattering variables, many electromagnetic engineers still use trial-and-error process until to achieve a given design criterion. As this procedure is very laborious and human dependent, optimization techniques are required to design practical periodic structures with desired filter specifications. Some authors have been employed neural networks and natural optimization algorithms, such as the genetic algorithms and the particle swarm optimization for the frequency selective surface design and optimization. This work has as objective the accomplishment of a rigorous study about the electromagnetic behavior of the periodic structures, enabling the design of efficient devices applied to microwave band. For this, artificial neural networks are used together with natural optimization techniques, allowing the accurate and efficient investigation of various types of frequency selective surfaces, in a simple and fast manner, becoming a powerful tool for the design and optimization of such structures

Análise de Handover inter e intra-célula em um sistema de telefonia celular através de método de medição simplificado

This dissertation has the purpose to present a portable device named PlugData MG100G, equipped with a cellular module, to analyze the radiofrequency coverage in a GSM network situated in João Pessoa city, state of Paraíba, at four distinct regions. The equipment, originally, was developed to be used in fixed environments, so it was adapted so that it could be used in conditions of mobility. From the Mobile Measurement Reports (MMRs) RF coverage and the handover process are analyzed. The MMRs enable the identification of the serving cell and the list of the closest neighboring cells monitored by the mobile. This work analyses only data referent to the serving cell and the two closest neighboring cells. Inter-cell and intra-cell handovers are identified. The frequency planning and quality of service offered by the network related to the regions are discussed as well