Electromagnetic freezing: Effects of weak oscillating magnetic fields on crab sticks

Since the earlier 2000s, electromagnetic freezers have been sold all over the world. According to the manufacturers, the oscillating magnetic fields (OMFs) applied by these devices are capable of avoiding ice damage in frozen foods. To assess the effectiveness of OMFs in preserving food quality, we froze crab sticks in a commercial electromagnetic freezer, both with (<2 mT, 6-59 Hz) and without OMF application. Crab sticks were also frozen in a conventional freezer, both with static- and forced-air conditions, to compare electromagnetic freezing with conventional methods. After 24 h and 1, 3, 6, 9, and 12 months of storage, we did not find any effect of the OMFs on the drip loss, water-holding capacity, toughness, and whiteness of the crab sticks frozen in the electromagnetic device. Moreover, no advantage of electromagnetic freezing over air-blast freezing was detected at the conditions tested. More experiments at larger magnetic field strength and wider frequency ranges are needed to have a complete view of the potential effects of OMFs on food freezing.This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project AGL2012-39756-C02-01. Antonio C. Rodríguez acknowledges the predoctoral contract BES-2013-065942 from MINECO, jointly financed by the European Social Fund, in the framework of the National Program for the Promotion of Talent and its Employability (National Sub-Program for Doctors Training).Peer reviewe

Effects of magnetic fields on freezing: Application to biological products

Magnetic freezing is nowadays established as a commercial reality mainly oriented towards the food market. According to advertisements, magnetic freezing is able to generate tiny ice crystals throughout the frozen product, prevent cell destruction, and preserve the quality of fresh food intact after thawing. If all these advantages were true, magnetic freezing would represent a significant advance in freezing technology, not only for food preservation but also for cryopreservation of biological specimens, such as cells, tissues, and organs. Magnetic fields (MFs) are supposed to act directly on water by orientating, vibrating and/or spinning molecules to prevent them from clustering and, thus, promote supercooling. However, many doubts exist about the real effects of MFs on freezing and the science behind the potential mechanisms involved. To provide a basis for extending the understanding of magnetic freezing, this paper presents a critical review of the materials published in the literature up to now, including both patents and experimental results. After examining the information available, it was not possible to discern whether MFs have an appreciable effect on supercooling, freezing kinetics, ice crystals, quality, and/or viability of the frozen products. Experiments in the literature frequently fail to identify and/or control all the factors that can play a role in magnetic freezing. Moreover, many of the comparisons between magnetic and conventional freezing are not correctly designed to draw valid conclusions and wide ranges of MF intensities and frequencies are unexplored. Therefore, more rigorous experimentation and further evidence are needed to confirm or reject the efficacy of MFs in improving the quality of frozen products.This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project AGL2012-39756-C02-01. A. C. Rodríguez acknowledges a predoctoral contract from MINECO, jointly financed by the European Social Fund, in the framework of the National Program for the Promotion of Talent and its Employability (National Sub-Program for Doctors Training).Peer reviewe

Approaching Ideal Polyphase Filter Response in 65-nm CMOS

This work analyzes the effect of the most critical non-idealities on a passive polyphase filter implemented in a 65-nm CMOS technology, to attain single-sideband transmission in a 5 GHz Wi-Fi alike communication system. Non-idealities impact on this kind of passive complex filter have not been thoroughly analyzed in literature

Study of Passive CMOS Mixers Effects on Image Rejection Ratio

In this brief, modeling and simulation of quadrature passive mixers are analyzed, focusing on the impact they have on the image rejection ratio (IRR). For this purpose, a 65-nm CMOS technology is used

Estrategia de Diseño de Amplificadores de Bajo Ruido Integrados en Tecnología CMOS nanométrica

Las topologías empleadas en los amplificadores de bajo ruido (LNA) han ido haciéndose cada vez más complejas, con las desventajas que ello implica en coste y tiempo de diseño. Este trabajo propone lo contrario, volver a topologías más sencillas y aprovechar dicha sencillez para optimizarlas logrando resultados altamente competitivos

Reparación de las fracturas de huesos largos en traumatismos craneoencefálicos: estudio experimental en la rata

Los pacientes con traumatismo craneoencefálico presentan una respuesta osteogénica alterada. Para estudiar si existe o no un callo de fractura más voluminoso o más prematuro en las fracturas de hueso largo se ha buscado un modelo experimental en rata Wistar con y sin lesión encefálica. El estudio no demuestra diferencias significativas. Se discute la importancia de factores terapéuticos más que el hecho del traumatismo creaneoencefálico.Osteogenic response deviates significantly in patients with traumatic brain injury. In this study, we analyze if there is an increased volume or earlier callus formation in long bones fractures in Wistar rats with and without brain injury. The results show no significant difference. The importance of some therapeutical aspects other than head injury are discussed

Metodología de diseño de LNA de banda ancha robustos frente a variaciones de proceso

Los amplificadores de bajo ruido requieren cumplir unas especificaciones de diseño muy estrictas. Esto hace delicado y tedioso su diseño, especialmente si se desea garantizar su robustez al sufrir las variaciones de proceso. Para solventarlo, este trabajo presenta una metodología de optimización

Metodología de diseño de LNA de banda ancha robustos frente a variaciones de proceso

Los amplificadores de bajo ruido requieren cumplir unas especificaciones de diseño muy estrictas. Esto hace delicado y tedioso su diseño, especialmente si se desea garantizar su robustez al sufrir las variaciones de proceso. Para solventarlo, este trabajo presenta una metodología de optimización

Dynamics of thermal ignition of spray flames in mixing layers

Conditions are identified under which analyses of laminar mixing layers can shed light on aspects of turbulent spray combustion. With this in mind, laminar spray-combustion models are formulated for both non-premixed and partially premixed systems. The laminar mixing layer separating a hot-air stream from a monodisperse spray carried by either an inert gas or air is investigated numerically and analytically in an effort to increase understanding of the ignition process leading to stabilization of high-speed spray combustion. The problem is formulated in an Eulerian framework, with the conservation equations written in the boundary-layer approximation and with a one-step Arrhenius model adopted for the chemistry description. The numerical integrations unveil two different types of ignition behaviour depending on the fuel availability in the reaction kernel, which in turn depends on the rates of droplet vaporization and fuel-vapour diffusion. When sufficient fuel is available near the hot boundary, as occurs when the thermochemical properties of heptane are employed for the fuel in the integrations, combustion is established through a precipitous temperature increase at a well-defined thermal-runaway location, a phenomenon that is amenable to a theoretical analysis based on activation-energy asymptotics, presented here, following earlier ideas developed in describing unsteady gaseous ignition in mixing layers. By way of contrast, when the amount of fuel vapour reaching the hot boundary is small, as is observed in the computations employing the thermochemical properties of methanol, the incipient chemical reaction gives rise to a slowly developing lean deflagration that consumes the available fuel as it propagates across the mixing layer towards the spray. The flame structure that develops downstream from the ignition point depends on the fuel considered and also on the spray carrier gas, with fuel sprays carried by air displaying either a lean deflagration bounding a region of distributed reaction or a distinct double-flame structure with a rich premixed flame on the spray side and a diffusion flame on the air side. Results are calculated for the distributions of mixture fraction and scalar dissipation rate across the mixing layer that reveal complexities that serve to identify differences between spray-flamelet and gaseous-flamelet problems

Generación de una tensión de polarización variable para la compensación de efectos de proceso en LNA sin inductores

This work presents and evaluates different alternatives to implement a bias circuit that compensates for variations in the manufacturing process in a low noise amplifier (LNA) based on a common gate stage with transconductance enhancement. The study covers three topologies and a comparison and verification is made through corner analysis and Monte Carlo.Este trabajo presenta y evalúa diferentes alternativas para implementar un circuito de polarización que compense las variaciones del proceso de fabricación en un amplificador de bajo ruido (LNA) basado en una etapa puerta común con realce de transconductancia. El estudio cubre tres topologías y se efectúa una comparativa y comprobación mediante análisis de corners y Monte Carlo