White-Light Phase-Conjugate Mirrors as Distortion Correctors

White-light phase-conjugate mirrors would be incorporated into some optical systems, according to a proposal, as means of correcting for wavefront distortions caused by imperfections in large optical components. The proposal was given impetus by a recent demonstration that white, incoherent light can be made to undergo phase conjugation, whereas previously, only coherent light was known to undergo phase conjugation. This proposal, which is potentially applicable to almost any optical system, was motivated by a need to correct optical aberrations of the primary mirror of the Hubble Space telescope. It is difficult to fabricate large optical components like the Hubble primary mirror and to ensure the high precision typically required of such components. In most cases, despite best efforts, the components as fabricated have small imperfections that introduce optical aberrations that adversely affect imaging quality. Correcting for such aberrations is difficult and costly. The proposed use of white-light phase conjugate mirrors offers a relatively simple and inexpensive solution of the aberration-correction problem. Indeed, it should be possible to simplify the entire approach to making large optical components because there would be no need to fabricate those components with extremely high precision in the first place: A white-light phase-conjugate mirror could correct for all the distortions and aberrations in an optical system. The use of white-light phase-conjugate mirrors would be essential for ensuring high performance in optical systems containing lightweight membrane mirrors, which are highly deformable. As used here, "phase-conjugate mirror" signifies, more specifically, an optical component in which incident light undergoes time-reversal phase conjugation. In practice, a phase-conjugate mirror would typically be implemented by use of a suitably positioned and oriented photorefractive crystal. In the case of a telescope comprising a primary and secondary mirror (see figure) white light from a distant source would not be brought to initial focus on one or more imaging scientific instrument(s) as in customary practice. Instead, the light would be brought to initial focus on a phase-conjugate mirror. The phase-conjugate mirror would send a phase-conjugate image back, along the path of the incoming light, to the primary mirror. A transparent, highly efficient diffractive thin film deposited on the primary mirror would direct the phase-conjugate image to the imaging instrument(s)

Spatial Variation of Surface Water Quality at Gebeng Industrial Estate, Pahang, Malaysia

Gebeng is the main industrial area of Pahang, where, Tunggak is a strategic river. The anthropogenic impact on the river is as a result of rapid industrialization in Gebeng. This river is of particular importance in the study of surface water quality status because effluents from industries of Gebeng discharge into it thereby deteriorating the quality. Water quality parameters were analyzed across the river with the objective to disclose the spatial variation of the river water quality. To conduct the study, water samples were collected monthly from 10 sampling station across the river basin. The physicochemical parameters were analyzed using APHA & HACH standard methods as well as the trace elements were determined using ICP-MS (Inductively Coupled Plasma Mass Spectrometry). Data analyses were done using SPSS statistical software. The study revealed that, pollution from non-point source was associated with runoff from construction sites of newly developed industrial areas and the point source contributing the major pollutants especially from industrial wastes. According to Interim National Water Quality Standard (INWQS) based on DO, COD, ammoniacal nitrogen and some selected trace elements, major part of the river specially the mid-region was categorized as class V (very highly polluted) while some part was found in class IV (highly polluted) and rest of class III (polluted) as well. Furthermore, classification of the river based on DOE-WQI showed that seven (7) stations (2-8) were in class IV (highly polluted); station 1, 9 & 10 were found to be polluted. So, from the study it is concluded that pollution is higher in the middle stations of the river compared to the upper and lower stream. This was due to less industry at upper stream and the tidal interference was present in lower stream and obviously the industrial wastes were mixing in the middle stations most

Photoinduced Optical and Electrical High-Voltage Pulsations and Pattern Formation in Photorefractive Crystals

We review our results on conversion of CW laser Ar-ion beam power into pulsating multi-channel outputs: optical, electric and piezoelectric with simultaneous dynamic pattern formation. We show, that electrical pulsations generate high-voltage signals that may be used as a driving voltage for the conventional electro-optical modulator. We have also demonstrated the possibility of synchronization of two optical pulsators, through regulated optical coupling in a photorefractive LiNbO3 crystal. Spatial distribution of scattered light is self-organized in different patterns (hexagonal and cross-type)

Is It Possible to Predict Cardiac Death?

Cardiovascular diseases are the leading cause of death in all the world; despite having the knowledge of the main risk factors, they keep on being complicated pathologies to deal with. Cardiovascular management has introduced a lot of parameters as regards patients’ state of health; particularly, nuclear cardiology with Stress single-photon emission computed tomography myocardial perfusion imaging can carry out interesting parameters that have encouraged researchers to apply machine learning techniques to predict whether patients will die due to a cardiac event or not. The dataset consisted of 661 patients that were evaluated for suspected of known coronary artery disease at the Department of Advanced Biomedical Sciences of the University Hospital “Federico II” in Naples. Knime analytics platform was employed to implement a decision tree and Random forests. After a procedure of features reduction, 29 features were included, and the overall accuracy was 91.0%, while recall, precision, sensitivity and specificity overcame the value of 90.0%. This implementation shows the feasibility of machine learning combined with data coming from nuclear cardiology. Moreover, the possibility to predict cardiac death exploiting clinical data and parameters carried out from instrumental exams would help clinicians to provide patients with the best treatments and interventions