ABSTRACT
In this work we analyze the energy efficiency constraints on drivers for Visible light communication (VLC) emitters. This is the main reason why LED is becoming the main source of illumination. We study the effect of the waveform shape and the modulation techniques on the overall energy efficiency of an LED lamp. For a similar level of illumination, we calculate the emitter energy efficiency ratio η (PLED/PTOTAL) for different signals. We compare switched and sinusoidal signals and analyze the effect of both OOK and OFDM modulation techniques depending on the power supply adjustment, level of illumination and signal amplitude distortion. Switched and OOK signals present higher energy efficiency behaviors (0.86≤η≤0.95) than sinusoidal and OFDM signals (0.53≤η≤0.79).
ABSTRACT
As in the case of other heavy metals, a considerable body of evidence suggests that overexposure to uranium may cause pathological alterations to the kidneys in both humans and animals. In the present work, our aim was to analyze the available data from a critical perspective that should provide a view of the real danger of the nephrotoxicity of this metal for human beings. A further aim was to elaborate a comparative compilation of the renal pathophysiological data obtained in humans and experimental animals with a view to gaining more insight into our knowledge of the mechanisms of action and renal damage. Finally, we address the existing perspectives for the improvement of diagnostic methods and the treatment of intoxications by uranium, performing an integrated analysis of all these aspects.
