The Lockman Hole is well known as the region with the lowest neutral atomic hydrogen column density on the entire sky. We present an analysis of the soft X-ray background radiation towards the Lockman Hole using ROSAT all-sky survey data. This data is correlated with the Leiden/Dwingeloo survey (Galactic H i 21 cm-line emission) in order to model the soft X-ray background by using radiative tra...

The standard expressions for the noise that is due to photon fluctuations in thermal background radiation typically apply only for a single detector and are often strictly valid only for single-mode illumination. I describe a technique for rigorously calculating thermal photon noise, which allows for arbitrary numbers of optical inputs and detectors, multiple-mode illumination, and both interna...

Radon, a source of natural background radiation, has been a subject of extensive studies as a major causative agent of lung cancer at the domestic and international levels. This study investigated and compared domestic and international methods of radon measurement. In the United States, radon is measured through primary and secondary testing, and a similar method is used in Canada. In the Unit...

A soft X-ray excess has been claimed to exist in and around a number of galaxy clusters and this emission has been attributed to the warm-hot intergalactic medium that may constitute most of the baryons in the local universe. We have re-examined a study of the XMM-Newton observations on this topic by Kaastra et al. (2003) and find that the X-ray excess (or deficit) depends upon Galactic latitud...

A 60 kV neutral Li beam is injected into the edge plasma of JET to measure the electron density. The beam observation system has been improved by replacing a Czerny-Turner spectrometer with a high-resolution transmission-grating spectrometer and a fast back-illuminated frame-transfer camera. The larger throughput of the spectrometer, the increased sensitivity, and the faster readout of the new ...

This is the second of four articles on the medical aspects of nuclear explosions. Last week described the blast and heat effects and explained that with modern large bombs significant radiation injury was likely to be due to fallout rather than to the radiation emitted by the explosion itself because most people subjected to the extremely short-lived initial radiation would be killed or fatally...

The carcinogenic risks of exposure to low-level ionising radiation used by the ICRP have been challenged as being, at the same time, both too high and too low. This paper explains that the epidemiological evidence will always be limited at low doses, so that understanding the cellular mechanisms of carcinogenesis is increasingly important to assess the biological risks. An analysis is then give...

The effects on health by mobile radiations have been subject of debate for a long time. Mobile phones emit electromagnetic radiations in the microwave range (300 MHz [0.3 GHz] and 300 GHz). According to International Agency for Research on Cancer, the mobile radiations are classified as Group-2B possibly carcinogenic radiations i.e. there “could be some risk” of carcinogenicity.1 At the same ti...

We report clear experimental evidence for second harmonic generation at hard x-ray wavelengths. Using a 1.7 Å pumping beam generated by a free electron laser, we observe second harmonic generation in diamond. The generated second harmonic is of order 10 times the background radiation, scales quadratically with pump pulse energy, and is generated over a narrow phase-matching condition. Of import...