Seroprevalence of Trypanosoma cruzi in Eight Blood Banks in Mexico.

BACKGROUND: The true prevalence of Chagas disease in Mexico is unknown. However, it has been estimated that 1.1-4 million people are infected with Trypanosoma cruzi, which represents a potential risk for transmission of the disease via contaminated blood. AIM OF THE STUDY: To determine the Chagas disease seroprevalence in donors from eight blood banks in the north of Mexico City, and the northeast of the State of Mexico. STUDY DESIGN AND METHODS: Serum samples from blood donors (n = 515,038) were tested to detect the presence of anti-Trypanosoma cruzi antibodies in eight blood banks. The serologic screening test was performed in each of the blood banks. To confirm the seropositive blood donors, only two out of the eight blood banks used a test with a different principle with the aim of identifying anti-Trypanosoma cruzi antibodies. All tests were validated by the Mexican Institute for Epidemiological Diagnosis and Reference. RESULTS: One thousand two hundred and ten blood donors were seropositive for Trypanosoma cruzi, which represents a 0.23% seroprevalence (95% CI 0.22-0.25%). Of the seropositive blood donors, 97.03 % resided in the northeast area of the State of Mexico, Mexico City, and southern part of the State of Hidalgo. CONCLUSIONS: Active transmission of Chagas disease may be occurring in non-endemic regions in the northeast of the State of Mexico.

Recent Progress of Nanogenerators for Green Energy Harvesting: Performance, Applications, and Challenges.

Natural sources of green energy include sunshine, water, biomass, geothermal heat, and wind. These energies are alternate forms of electrical energy that do not rely on fossil fuels. Green energy is environmentally benign, as it avoids the generation of greenhouse gases and pollutants. Various systems and equipment have been utilized to gather natural energy. However, most technologies need a huge amount of infrastructure and expensive equipment in order to power electronic gadgets, smart sensors, and wearable devices. Nanogenerators have recently emerged as an alternative technique for collecting energy from both natural and artificial sources, with significant benefits such as light weight, low-cost production, simple operation, easy signal processing, and low-cost materials. These nanogenerators might power electronic components and wearable devices used in a variety of applications such as telecommunications, the medical sector, the military and automotive industries, and internet of things (IoT) devices. We describe new research on the performance of nanogenerators employing several green energy acquisition processes such as piezoelectric, electromagnetic, thermoelectric, and triboelectric. Furthermore, the materials, applications, challenges, and future prospects of several nanogenerators are discussed.

Respiratory magnetogram detected with a MEMS device.

Magnetic fields generated by the brain or the heart are very useful in clinical diagnostics. Therefore, magnetic signals produced by other organs are also of considerable interest. Here we show first evidence that thoracic muscles can produce a strong magnetic flux density during respiratory activity, that we name respiratory magnetogram. We used a small magnetometer based on microelectromechanical systems (MEMS), which was positioned inside the open thoracic cage of anaesthetized and ventilated rats. With this new MEMS sensor of about 20 nT resolution, we recorded a strong and rhythmic respiratory magnetogram of about 600 nT.

Sensing magnetic flux density of artificial neurons with a MEMS device.

We describe a simple procedure to characterize a magnetic field sensor based on microelectromechanical systems (MEMS) technology, which exploits the Lorentz force principle. This sensor is designed to detect, in future applications, the spiking activity of neurons or muscle cells. This procedure is based on the well-known capability that a magnetic MEMS device can be used to sense a small magnetic flux density. In this work, an electronic neuron (FitzHugh-Nagumo) is used to generate controlled spike-like magnetic fields. We show that the magnetic flux density generated by the hardware of this neuron can be detected with a new MEMS magnetic field sensor. This microdevice has a compact resonant structure (700 × 600 × 5 µm) integrated by an array of silicon beams and p-type piezoresistive sensing elements, which need an easy fabrication process. The proposed microsensor has a resolution of 80 nT, a sensitivity of 1.2 V.T(-1), a resonant frequency of 13.87 kHz, low power consumption (2.05 mW), quality factor of 93 at atmospheric pressure, and requires a simple signal processing circuit. The importance of our study is twofold. First, because the artificial neuron can generate well-controlled magnetic flux density, we suggest it could be used to analyze the resolution and performance of different magnetic field sensors intended for neurobiological applications. Second, the introduced MEMS magnetic field sensor may be used as a prototype to develop new high-resolution biomedical microdevices to sense magnetic fields from cardiac tissue, nerves, spinal cord, or the brain.

Resonant Magnetic Field Sensors Based On MEMS Technology.

Microelectromechanical systems (MEMS) technology allows the integration of magnetic field sensors with electronic components, which presents important advantages such as small size, light weight, minimum power consumption, low cost, better sensitivity and high resolution. We present a discussion and review of resonant magnetic field sensors based on MEMS technology. In practice, these sensors exploit the Lorentz force in order to detect external magnetic fields through the displacement of resonant structures, which are measured with optical, capacitive, and piezoresistive sensing techniques. From these, the optical sensing presents immunity to electromagnetic interference (EMI) and reduces the read-out electronic complexity. Moreover, piezoresistive sensing requires an easy fabrication process as well as a standard packaging. A description of the operation mechanisms, advantages and drawbacks of each sensor is considered. MEMS magnetic field sensors are a potential alternative for numerous applications, including the automotive industry, military, medical, telecommunications, oceanographic, spatial, and environment science. In addition, future markets will need the development of several sensors on a single chip for measuring different parameters such as the magnetic field, pressure, temperature and acceleration.

Seroprevalencia de brucelosis en disponentes de sangre del Hospital General de México / Seroprevalence of brucellosis among blood-donors at the Hospital General de Mexico

De mayo de 1994 a mayo de 1995 se atendieron en el Banco de Sangres del Hospital General de México a 18,491 hemodisponentes; de éstos, 317 (1.71 por ciento) fueron positivos a brucela confirmados por la prueba de rosa de Bengala. El estudio se realizó debido a la alta detección de disponentes asintomáticos positivos a brucela. Objetivo: Conocer la prevalencia de brucela positiva por serología en disponentes de sangre. Conocer el medio por el cual se infectaron. Material y métodos: Muestra de 228 hemodisponentes que cumplieron con los criterios de la Norma Oficial Mexicana (NOM-003-SSA2 1993), positivos a brucela, a los cuales se les realizó encuesta y valoración clínica. Resultados: De 9,590 disponentes, 228 fueron positivos, con una prevalencia de 2.8 por ciento; sólo uno presentó manifestaciones clínicas, el cual se perdió durante el seguimiento. La brucelosis resultó ser más frecuente en hombres en edad productiva; predominó en el estado de México; en el Distrito Federal, la delegación más afectada es Iztapalapa. El medio contaminante en general es leche y sus derivados, a pesar de ser comercial. El caso clínicamente positivos, consumió leche bronca y derivados de cabra. Conclusiones: Se requiere la confirmación adicional con 2 mercapto-etanol para definir brucelosis activa, llevar una conducta más conservadora en la eliminación de sangre de donadores serologicamente positivos a brucela y clínicamente senos. Se debe considerar al Distrito Federal y al estado de México como zonas endémicas de brucela debido a la migración

Fracción excretada de sodio en el recién nacido de pretérmino con creatinina sérica normal / Fractional sodium excretion in preterm neonates with normal plasma creatinine

El propósito de este trabajo prospectivo fue determinar el valor normal de la fracción excretada de sodio (FENa) en el recién nacido (RN) de pretérmino, debido a que en la literatura existen controversias en sus resultados, lo que la ha hecho poco útil en este tipo de pacientes. Por ello se estudiaron 110 RN de pretérmino de enero a noviembre de 1993; 70 fueron masculinos y 40 femeninos, sin datos clínicos de insuficiencia renal y con creatinina sérica normal. La FENa varió de 0.01 a 4 por ciento (este último dato se dio únicamente en un sólo paciente, en los restantes no pasó de 2.98 por ciento), con un promedio de 0.5ñ0.62 por ciento, una mediana de 0.28 por ciento y una moda de 0.12 por ciento. La edad gestacional varió de 28 a 36 semanas con un promedio de 34ñ1.8 semanas. El peso varió de 725 a 2,475 g con un promedio de 1,834ñ370 g, con una moda de 1,750 g. No hubo diferencia estadísticamente significativa de la FENa, sodio urinario, sodio sérico, creatinina urinaria, cratinina sérica entre los pacientes con edades comprendidas entre la primera, segunda, tercera y cuarta semanas de vida extrauterina. Tampoco hubo diferencia significativa entre la FENa de pacientes de 30 semanas o menos y la FENa de los mayores de esa edad gestacional. Se concluye que la FENa es un parámetro útil para evaluar la función renal en el RN de pretérmino de 28 a 36 semanas de edad gestacional pudiéndose tomar como valores hasta 3 por ciento