Globally, cardiac arrest (CA) is a leading cause of death and disability. Asphyxial CA (ACA)-induced kidney damage is a crucial factor in reducing the survival rate. The purpose of this study was to investigate the role of antioxidant enzymes in histopathological renal damage in an ACA rat model at different time points. A total of 88 rats were divided into five groups and exposed to ACA except for the sham group. To evaluate glomerular function and oxidative stress, serum levels of blood urea nitrogen (BUN) and creatinine (Crtn) and malondialdehyde (MDA) levels in renal tissues were measured. To determine histopathological damage, hematoxylin and eosin staining, periodic acid-Schiff staining, and Masson's trichrome staining were performed. Expression levels of antioxidant enzymes including superoxide dismutase-1 (SOD-1), superoxide dismutase-2 (SOD-2), catalase (CAT), and glutathione peroxidase (GPx) were measured by immunohistochemistry (IHC). Survival rate of the experimental rats was reduced to 80% at 6 h, 55% at 12 h, 42.9% at 1 day, and 33% at 2 days after return of spontaneous circulation. Levels of BUN, Crtn, and MDA started to increase significantly in the early period of CA induction. Renal histopathological damage increased markedly from 6 h until two days post-CA. Additionally, expression levels of antioxidant enzymes were significantly decreased at 6 h, 12 h, 1 day, and 2 days after CA. CA-induced oxidative stress and decreased levels of antioxidant enzymes (SOD-1, SOD-2, CAT, GPx) from 6 h to two days could be possible mediators of severe renal tissue damage and increased mortality rate.

Abstract This paper presents an analysis of the impact of various dielectric properties material’s effects on broadband pyramidal microwave absorbers (PMA). The Computer Simulation Technology (CST) studio software simulates and analyzes the PMA over 0.7 GHz to 30 GHz frequency range. To achieve the best reflectivity performance of the PMA, different types of dielectric materials and the thickness of the base layers were analyzed and investigated. The average of four types of sample materials studied, the reflectivity level is between -50 dB and -27 dB for the desired range of frequency, 0.7 GHz to 30 GHz. The sample-4 material has a dielectric constant of 3.83, and a loss tangent of 1.52 has the best microwave absorption, absorbing microwaves above -48 dB over the frequency range of 0.7 GHz to 30 GHz. Because of its microwave absorption capability, sample-4 could be used in a microwave pyramidal absorber.

The recent researches on the tracking of binary offset carrier (BOC) modulated signals have been studied focusing on resolving the ambiguity problem caused by the multiple side-peaks in BOC autocorrelation. In this paper, we propose a novel unambiguous BOC tracking scheme with an improved tracking performance by using partial-pulses of BOC signals. Firstly, we observe that a sub-carrier consists of two partial rectangular pulses referred to as partial-pulses, and then, generate multiple partial-correlations composing the BOC autocorrelation. Finally, a correlation function with no side-peak is constructed by combining the partial-correlations, and then, a delay lock loop employing the proposed unambiguous correlation function adjusts the phase of the local BOC signals. From numerical results, it is confirmed that the proposed scheme provides a better tracking performance than the conventional schemes in terms of the tracking error standard deviation.

In orthogonal frequency division multiplexing (OFDM) systems, an integer part of a frequency offset (IFO) that causes ambiguity in data demodulation is estimated generally by comparing correlations between the received and local signals for IFO candidates. In this paper, we propose an IFO estimation scheme that provides a tradeoff between the estimation performance and the computational complexity including a conventional scheme as a special case. In the proposed scheme, template signals are formed by combining frequency-shifted training symbols, allowing the receiver to reduce the number of IFO candidates in the estimation process. Numerical results illustrate the tradeoff of the proposed scheme: The proposed scheme exhibits a tradeoff between the correct estimation probability and the computational complexity taking the number of the training symbols used to construct the template signal as a parameter.

This paper addresses the problem of detection of randomly arriving or departing primary user (PU) signals in cognitive radio systems. The detection problem of the dynamic PU signal is modeled as a binary hypothesis testing problem where the PU signal might randomly depart or arrive during the sensing period. Then, we detect the cyclostationarity of the PU signal using a test statistic derived from the spectral autocoherence function in dynamic PU signal environments. Numerical results show that the proposed scheme offers an improved spectrum sensing performance than the conventional energy detector for dynamic PU environments.

IEEE 802.11e standard has been specified to support differentiated quality of service (QoS), one of the critical issues on the conventional IEEE 802.11 wireless local area networks (WLANs). Enhanced Distributed Channel Access (EDCA) is the fundamental and mandatory contention-based channel access method of IEEE 802.11e, and delivers traffic based on differentiated Access Categories (ACs). A general three dimensional Markov chain model of IEEE 802.11e EDCA for performance analysis is proposed in this paper. The analytical model considers multiple stations with an arbitrary number of different ACs. It also differentiates the contention window (CW) sizes and the arbitration interframe spaces (AIFSs), and considers virtual collision mechanism. Based on the model, the saturation throughput of EDCA is derived, and the accuracy of the proposed model is validated via simulations.

Due to the open environment, all network systems suffer from various security threats. The remote user authentication scheme is a secure mechanism to allow users obtaining a variety of information services through insecure channels. For efficiency and security, many remote user authentication schemes identify users with smart cards. However, many smart card based schemes are vulnerable to lots of attacks. Recently, Hsiang et al. proposed a smart card based remote authentication scheme. In this article, we show that their scheme is vulnerable to the smart-card-loss-attack. That is, if an unauthorized person obtains the smart card, he/she can guess the correct password to masquerade as a legitimate user to login the system. The attack is caused by the smart card outputs fixed message for the same inputs. We propose an improved scheme to fix the flaw. The improved scheme withstands the off-line password guessing attack, parallel session attack and smart-card-loss-attack. Moreover, it also has the merits of providing mutual authentication, no verification table and users can freely update their passwords.

In this paper, we propose a carrier frequency offset (CFO) estimation scheme which is robust to the fractional CFO variation for orthogonal frequency division multiplexing (OFDM) systems. The proposed scheme first performs the envelope equalization process to convert the offset estimation problem to a carrier estimation problem, and then, estimates the integer and fractional parts of CFO by using periodogram of the received signal. Especially, in the estimation stage for fraction CFO, the ratio of the square-roots of periodograms is employed enlarging the estimation range of the stage than that of the conventional scheme. Numerical results demonstrate that the proposed scheme has better estimation performance than the conventional scheme for wider fractional CFO range in various channel conditions.

In this paper, we propose a hybrid maximum likelihood (ML) decoding scheme for multiple-input multiple-output (MIMO) systems. After partitioning the searching tree into several stages, the proposed scheme adopts the combination of depth- and breadth-first search methods in an organized way. Taking the number of stages, the size of signal constellation, and the number of antennas as the parameter of the scheme, we provide extensive simulation results for various MIMO communication conditions. Numerical results indicate that, when the depth- and breadth-first search methods are employed appropriately, the proposed scheme exhibits substantially lower computational complexity than conventional ML decoders while maintaining the ML bit error performance.

Resumen El fenómeno de oscilación en llamas: variación cíclica de la velocidad de propagación durante el desarrollo de la llama, ha sido estudiado en el pasado en nubes de polvo o gotas e incluso en mezclas gaseosas. A pesar de que el fenomeno ha sido estudiado desde diferentes perspectivas aún no hay una explicación única aceptada. En el presente trabajo, los efectos de la inercia de los gotas fueron investigados, comparando los datos experimentales con predicciones de modelos de oscilacion de velocidad de llama causada por la interaccion aerodinamica del movimiento del gas cercano al frente de llama con las gotas. Los estudios de combustión del presente trabajo, en nubes con tamaño de gota casi único, pusieron de manifiesto la diferencia entre la velocidad de las gotas y la velocidad cerca del frente de llama. Esta diferencia produjo variación en la relación de equivalencia local que a su vez se manifestó en oscilaciones de la velocidad de propagación. Por simplicidad se ha utilizado para las pruebas, un equipo que permite estudios fundamentales de la combustión en nubes de gotas, bajo condiciones estrictamente controladas (establecidas en forma precisa) de presión, temperatura y relación de equivalencia. La distribución de las gotas dentro de la mezcla sin combustión se caracterizó en otro estudio

Abstract The phenomenon of flame oscillation, the cyclic variation of flame speed during flame development, has been studied in the past in clouds of dust or droplets and even in gaseous mixtures. Although it has been addressed in the past using several approaches there is no yet a unique accepted explanation. In the present work, drop inertia effects were investigated, by comparing the experimental data with modelled predictions of oscillations in flame speed caused by the aerodynamic interaction of the gas motion ahead of the flame front with the drops. The combustion studies of nearly mono-sized droplet clouds in the present work revealed the differences between the speed of droplets and the gas velocity near the flame front. These resulted in variations in local equivalence ratio, which in turn manifested in flame speed oscillations. For simplification a combustion vessel has been used to study the combustion of droplet clouds from a fundamental point of view, under strictly controlled (accurately established) conditions of pressure, temperature and equivalence ratio. The distribution of droplets within the mixture (spatially and in time), without combustion, was characterised somewhere else

Resumen Estudiar la combustión de atomizados es difícil debido a la multiplicidad de variables interdependientes involucradas, tales como presión, temperatura, tamaño de gotas, distribución del tamaño de gotas, etc., especialmente en equipos industriales. Por ello, se ha seleccionado para el presente estudio un equipo para ensayos fundamentales de la combustión en nubes de gotas. Antes de efectuar un estudio de la combustión es indispensable caracterizar los aerosoles producidos en este equipo. La distribución de gotas dentro de la mezcla sin combustión se caracterizó usando varios diagnósticos con laser y se determinaron variables como diámetro medio Sauter, número densidad y relación de equivalencia gaseosa y de líquido. En este recipiente, se obtuvieron nubes de gotas prácticamente de tamaño único, siendo el tamaño de estas una función del tiempo muy bien definida

Abstract The study of spray combustion is difficult due to the multiplicity of inter-dependent variables, such as pressure, temperature, droplet size, droplet size distribution, etc, especially industrial cases. Therefore, a combustion vessel developed to study the combustion of droplet clouds from a fundamental point of view has been chosen for the present work. However, it was required a full characterization of the aerosols produced before any combustion study could be undertaken. The distribution of droplets within the mixture, without combustion, was characterised using several laser diagnostics, variables such as Sauter mean diameter, number density, gas and liquid equivalence ratios were determined. Nearly mono-sized droplet clouds were obtained in this vessel and the droplet diameter was a well defined function of time

El método del amonio modificado fue utilizado para preparar catalizadores del tipo filosilicatos de hierro. Los estudios de caracterización por reducción a temperatura programada (RTP) de los catalizadores, indican que en los sólidos sintetizados se encuentran presentes por lo menos dos fases. Una fase de baja temperatura correspondiente a óxidos ó hidróxidos del metal y una fase de alta temperatura (1054 °C) correspondiente a filosilicatos de hierro. La presencia de estas fases también fue observada por espectroscopia infrarroja con transformada de Fourier (IRFT) y difracción de rayos X (DRX). Estudios realizados por espectroscopia de fotoelectrones de rayos X de éstos sólidos indican que la relación O/Si entre la parte del pico O1s que no está enlazada al hierro y el pico Si2p es de 2.5 típica de los filosilicatos. La actividad y selectividad a la formación de alcoholes superiores de éstos catalizadores fue estudiada, en un sistema de reacción de alta presión, después de someter estos sólidos a un pretratamiento térmico reductivo a 450°C. Los resultados indican que los sólidos reducidos usando velocidades de calentamiento de 0.5°C/min mantienen una superficie hidroxilada estable en las condiciones de reacción y son muy selectivos a la formación de alcoholes superiores. En estas condiciones, los catalizadores presentan valores de actividad y selectividad superiores a aquella obtenida para catalizadores de mayor carga metálica.

The modified ammonia method was used to prepare iron Phyllosilicates catalyst type. The temperature programmed reduction profiles studies (TPR) show at least two phases in such catalysts. One phase at lower temperature corresponding to one metal oxide or hydroxide and an iron Phyllosilicate phase at higher temperature (1054 °C). Such phases were observed by Fourier Transformed Infrared Spectroscopy (IRFT) and X-ray Diffraction (XRD). Studies by X-ray Photoelectron Spectroscopy (XPS) indicated that the O/Si ratio between the part of the O1s peak not bonded to iron, and the Si2p peak is about 2.5 typical of Phyllosilicates. The activity and selectivity to the synthesis of higher alcohols of these catalysts was studied in a high pressure reaction system after a thermal reductive pretreatment at 450°C. The results indicated that the solids pretreated using a heating rate of 0.5°C/min kept an stable hydroxide surface under the reaction conditions and are very selective to the higher alcohols formation. In such conditions, the activity and selectivity is higher than for the high loading catalysts.