Genotoxic and histotoxic effects of air pollutants at a benzene station on albino rats

Background: This study was designed to explore the hazardous effects of occupational exposure to air pollutants arising from benzene stations.Methods: A total of 48 albino rats were divided into three groups each of sixteen animals. Groups-I and II were kept at a benzene station for 60 and 120 days, respectively; while group-III was kept as a control under normal laboratory conditions. At the end of the experiment, animals were sacrificed and bone marrow samples were taken to investigate the effect of air pollutants at a benzene station on chromosomal aberrations and micronuclei formation. Tissue samples were also picked out to evaluate histotoxic effects of these air pollutants.Results: Results indicated pronounced time-dependent effects because of the work place pollutants. Genetic examination revealed higher frequency of chromosomal aberrations and elevated mitotic index after exposure to air pollutants. Micronuclei formation also increased either in polychromatic or normochromatic erythrocyte due to air pollutants. Histopathological examination revealed congestion of the pulmonary blood vessels with pulmonary edema. Bronchial hyperplasia and metaplasia were also seen in late stage of exposure. The liver showed degenerative changes or even necrosis of hepatocytes, while the kidneys showed congestion of the renal blood vessels and glomerular tufts. Hyalinization of the glomeruli was also detected. The heart showed various mononuclear infiltration and the testes showed degenerative changes of seminiferous tubules. Spleen showed hemosiderosis while testes showed degenerative changes of seminiferous tubules.Conclusions: The findings of the present study indicated that benzene exposure may lead to toxic effects including, genotoxicities and histotoxicities. In order to minimize the predicted toxic effect of occupational exposure to benzene the strict protective measures should be put in consideration

Dynamic load modulation of high power amplifiers with varactor-based matching networks

In this paper, the results of dynamic load modulation on a high power amplifier is shown with experiments. A simple static nonlinear model is used as an inverse model, and by dynamically controlling both the input signal to the power amplifier and the load impedance, high efficiency operation of the power amplifier is achieved. The modulated measurements show the feasibility of dynamic load modulation for practical high power, high frequency applications

Digital Predistortion for High Efficiency Power Amplifier Architectures Using a Dual-input Modeling Approach

In this paper, a novel model is proposed for dual-input high efficiency power amplifier (PA) architectures, such as envelope tracking (ET) and varactor-based dynamic load modulation (DLM). Compared to the traditional single-input modeling approach, the proposed model incorporates the baseband supply voltage/load control as an input. This advantage makes the new approach capable to achieve maximized average power-added efficiency (PAE) and minimized output distortion simultaneously. Furthermore, the new approach has shown to be robust towards time misalignment between the RF input and baseband supply voltage/load control signals, and it can be applied with a reduced-bandwidth baseband supply voltage/load control. Experiments have been performed in a varactor-based DLM PA architecture to evaluate the new modeling approach. The results show that it can achieve 9 dB and 7 dB better performance than the traditional approaches in terms of adjacent channel leakage ratio and normalized mean square error, respectively. At the same time, the average PAE is maximized. Similar results have been achieved with the proposed model even when reduced-bandwidth baseband load control signal is used or time misalignment between the RF and baseband load control input signals exists. Although the new approach is only tested with DLM architecture in this paper, it is very general and can be applied to ET architectures as well

Fan and Ventilation Rate Monitoring of Cage-Free Layer Houses in California

Ventilation rates were continuously monitored in two cage-free layer houses located in California from March 1, 2012 to May 13, 2013. The average number of brown Lohmann laying hens in each house was 33,300. Temperature, relative humidity, static pressure, and running status of 48 ventilation fans were continuously monitored and recorded every minute. Regression models were developed to relate house temperature and ventilation rate to inlet air temperature, and to relate airflow rate to building static pressure (R2 = 0.98). Results showed that the daily mean ventilation rate per hen ranged from 1.91 to 8.72 m3 h-1 hen-1, averaging at 4.49 ±1.53 m3 h-1 hen-1. The standard uncertainty of daily mean ventilation rate was determined to be 3.7%. The 91-cm and 130-cm fans were found to perform at 82% and 63% of the manufacturer rated airflow rates, respectively. The minimum and maximum static pressure was 11.0 and 50.6 Pa, respectively, corresponding to 2 and 16 running tunnel fans. When the house temperature exceeded 30ºC, an evaporative cooling system was activated, which could reduce the inlet air temperature by 6.3ºC and concurrently increased the indoor air humidity ratio by 3.4 g per kg dry air. Cooling pad efficiency was 66%. The sidewall fans and tunnel fans were operated at 65% and 20% of the total time when layers occupied the houses. The new rational formula to calculate dry base ventilation rates was developed based upon the ratio of water vapor volume to moist air volume. The developed models and data collected in this research can be used to calculate the ventilation rates in cage-free layer houses so that it can be possible to assure healthy conditions needed for layers. They can also be used in the design of cage free houses and in the calculations of emissions of air pollutants from these houses

Valuing Public Goods More Generally: The Case of Infrastructure

We examine the relationship between local public goods, prices, wages, and population in an equilibrium inter-city model. Non-traded production, federal taxes, and imperfect mobility all affect how public goods (or “amenities” more broadly) should be valued from data. Reinterpreting the estimated effects of public infrastructure on prices and wages in Haughwout (2002), we find infrastructure over twice as valuable with our more general model. New estimates based on more years, cities, and data-sets indicate stronger wage and positive population effects of infrastructure. These imply higher values of infrastructure to firms, and also to households if moving costs are substantial

An RF Carrier Bursting System using Partial Quantization Noise Cancellation

This paper introduces a novel method for bandpass cancellation of the quantization noise occurring in high efficiency, envelope pulsed transmitter architectures - or carrier bursting. An equivalent complex baseband model of the proposed system, including the Sigma Delta-modulator and cancellation signal generation, is developed. Analysis of the baseband model is performed, leading to analytical expressions of the power amplifier drain efficiency, assuming the use of an ideal class B power amplifier. These expressions are further used to study the impact of key system parameters, i.e. the compensation signal variance and clipping probability, on the class~B power amplifier drain efficiency and signal-to-noise ratio. The paper concludes with simulations followed by practical measurements in order to validate the functionality of the method and to evaluate the performance-trend predictions made by the theoretical framework in terms of efficiency and spectral purity