Measurement of the electron–hole pair creation energy in Al0.52In0.48P using X-ray radiation

The average energy consumed in the generation of an electron–hole pair (ε AlInP ) in Al 0.52 In 0.48 P was experimentally measured across the temperature range −20 °C to 100 ∘ C, using a custom AlInP X-ray-photodiode, an 55 Fe radioisotope X-ray source, and custom low-noise charge-sensitive preamplifier electronics. ε AlInP was found to linearly decrease with increasing temperature according to the equation ε AlInP = (-0.0033 eV/K ± 0.0003 eV/K)T + (6.31 eV ± 0.10 eV). At room temperature (20 °C), ε AlInP = 5.34 eV ± 0.07 eV

Prototype GaAs X‐ray detector and preamplifier electronics for a deep seabed mineral XRF spectrometer

Work towards developing a prototype GaAs based X-ray fluorescence spectrometer focusing on the detector-preamplifier system for in situ characterisation of deep seabed minerals is presented. Such an instrument could be useful for marine geology and provide insight into hydrothermal processes. It would also be beneficial for deep sea mining applications. The GaAs photodiode was electrically characterised at 4 °C (ambient seawater temperature) and 33 °C. A system energy resolution (full width at half maximum) at 5.9 keV of 580 eV at 4°C, limited by the dielectric noise, broadening to 680 eV at 33°C, was recorded. The spectral performance of the system was characterised across the energy range 4.95 keV to 21.17 keV, at 33°C, using high-purity X-ray fluorescence calibration samples excited by a Mo target X-ray tube. The charge output from the system was found to be linear with incident photon energy. The energy resolution was found to broaden from 695 eV at 4.95 keV to 735 eV at 21.17 keV, attributed to the increasing Fano noise with energy. The same X-ray tube was used to fluoresce an unprepared manganese nodule (revealing the presence of Mn, Fe, Ni, Cu, Zn, Pb, Sr, and Mo) and a black smoker hydrothermal vent sample (containing Fe, Co, Ni, Cu, Zn, Pb, and Mo). Such a spectrometer may also find use in future space missions to study the hydrothermal vents that are believed to exist in the oceans of Jupiter's moon Europa

Dynamin- and Rab5-Dependent Endocytosis of a Ca²⁺-Activated K⁺ Channel, KCa2.3

Regulation of the number of ion channels at the plasma membrane is a critical component of the physiological response. We recently demonstrated that the Ca2+-activated K+ channel, KCa2.3 is rapidly endocytosed and enters a Rab35- and EPI64C-dependent recycling compartment. Herein, we addressed the early endocytic steps of KCa2.3 using a combination of fluorescence and biotinylation techniques. We demonstrate that KCa2.3 is localized to caveolin-rich domains of the plasma membrane using fluorescence co-localization, transmission electron microscopy and co-immunoprecipitation (co-IP). Further, in cells lacking caveolin-1, we observed an accumulation of KCa2.3 at the plasma membrane as well as a decreased rate of endocytosis, as assessed by biotinylation. We also demonstrate that KCa2.3 and dynamin II are co-localized following endocytosis as well as demonstrating they are associated by co-IP. Further, expression of K44A dynamin II resulted in a 2-fold increase in plasma membrane KCa2.3 as well as a 3-fold inhibition of endocytosis. Finally, we evaluated the role of Rab5 in the endocytosis of KCa2.3. We demonstrate that expression of a dominant active Rab5 (Q79L) results in the accumulation of newly endocytosed KCa2.3 on to the membrane of the Rab5-induced vacuoles. We confirmed this co-localization by co-IP; demonstrating that KCa2.3 and Rab5 are associated. As expected, if Rab5 is required for the endocytosis of KCa2.3, expression of a dominant negative Rab5 (S34N) resulted in an approximate 2-fold accumulation of KCa2.3 at the plasma membrane. This was confirmed by siRNA-mediated knockdown of Rab5. Expression of the dominant negative Rab5 also resulted in a decreased rate of KCa2.3 endocytosis. These results demonstrate that KCa2.3 is localized to a caveolin-rich domain within the plasma membrane and is endocytosed in a dynamin- and Rab5-dependent manner prior to entering the Rab35/EPI64C recycling compartment and returning to the plasma membrane. © 2012 Gao et al

Light Ions Response of Silicon Carbide Detectors

Silicon carbide (SiC) Schottky diodes 21 mum thick with small surfaces and high N-dopant concentration have been used to detect alpha particles and low energy light ions. In particular 12C and 16O beams at incident energies between 5 and 18 MeV were used. The diode active-region depletion-thickness, the linearity of the response, energy resolution and signal rise-time were measured for different values of the applied reverse bias. Moreover the radiation damage on SiC diodes irradiated with 53 MeV 16O beam has been explored. The data show that SiC material is radiation harder than silicon but at least one order of magnitude less hard than epitaxial silicon diodes. An inversion in the signal was found at a fluence of 10^15 ions/cm^2.Comment: 20 pages, 16 figures, submitted for publication to Nuclear Instruments and Methods in Physics Research

GaAs spectrometer for planetary electron spectroscopy

Work towards producing a radiation-hard and high temperature tolerant direct detection electron spectrometer is reported. The motivation is to develop a low-mass, low-volume, low-power, multi-mission capable instrument for future space science missions. The resultant prototype electron spectrometer employed a GaAs p+-i-n+ mesa photodiode (10 µm i layer thickness; β00 μm diameter) and a custom-made charge-sensitive preamplifier. The GaAs detector was initially electrically characterized as a function of temperature. The detector-preamplifier assembly was then investigated for its utility in electron spectroscopy across the temperature range 100 °C to 20 °C using a laboratory 63Ni radioisotope - particle source (end point energy = 66 keV). Monte Carlo simulations using the computer program CASINO were conducted and showed that the spectrometer had a quantum detection efficiency which increased with increasing electron energy up to 70 keV; a quantum detection efficiency of 73 % was calculated. The accumulated 63Ni - particle spectra together with CASINO simulations of the detected spectra showed that the GaAs based spectrometer could be used for counting electrons and measuring the energy deposited per electron in the detector’s active region (i layer). The development of a GaAs electron spectrometer of this type may find use in future space missions to environments of intense radiation (such as at the surface of Europa for investigation of electron-driven radiolysis of ice) and high temperature (such as at Mercury, and comets passing close to the Sun)

European cancer mortality predictions for the year 2012

Background: Estimating current cancer mortality figures is important for defining priorities for prevention and treatment. Materials and methods: Using logarithmic Poisson count data joinpoint models on mortality and population data from the World Health Organization database, we estimated numbers of deaths and age-standardized rates in 2012 from all cancers and selected cancer sites for the whole European Union (EU) and its six more populated countries. Results: Cancer deaths in the EU in 2012 are estimated to be 1 283 101 (717 398 men and 565 703 women) corresponding to standardized overall cancer death rates of 139/100 000 men and 85/100 000 women. The fall from 2007 was 10% in men and 7% in women. In men, declines are predicted for stomach (−20%), leukemias (−11%), lung and prostate (−10%) and colorectal (−7%) cancers, and for stomach (−23%), leukemias (−12%), uterus and colorectum (−11%) and breast (−9%) in women. Almost stable rates are expected for pancreatic cancer (+2-3%) and increases for female lung cancer (+7%). Younger women show the greatest falls in breast cancer mortality rates in the EU (−17%), and declines are expected in all individual countries, except Poland. Conclusion: Apart for lung cancer in women and pancreatic cancer, continuing falls are expected in mortality from major cancers in the E

Electrical and ultraviolet characterization of 4H-SiC Schottky photodiodes

Fabrication and electrical and optical characterization of 4H-SiC Schottky UV photodetectors with nickel silicide interdigitated contacts is reported. Dark capacitance and current measurements as a function of applied voltage over the temperature range 20 °C – 120 °C are presented. The results show consistent performance among devices. Their leakage current density, at the highest investigated temperature (120 °C), is in the range of nA/cm2 at high internal electric field. Properties such as barrier height and ideality factor are also computed as a function of temperature. The responsivities of the diodes as functions of applied voltage were measured using a UV spectrophotometer in the wavelength range 200 nm - 380 nm and compared with theoretically calculated values. The devices had a mean peak responsivity of 0.093 A/W at 270 nm and −15 V reverse bias

A comparison of trends in mortality from primary liver cancer and intrahepatic cholangiocarcinoma in Europe

Background To update and compare mortality from primary liver cancer (PLC) and intrahepatic cholangiocarcinoma (ICC) in Europe in 1990-2010. Materials and methods We used data from the World Health Organization (WHO) to compute age-standardized (world population) mortality rates, and used joinpoint analysis to identify substantial changes. Results Between 2002 and 2007, PLC rates in the European Union (EU) declined from 3.9 to 3.6/100 000 men. Around 2007, the highest male rates were in France (6.2/100 000), Spain (4.9), and Italy (4.0), while the lowest ones were in Sweden (1.1), the Netherlands (1.2), and the UK (1.8). In women, mortality was lower (0.8/100 000 in 2007 in the EU), and showed more favourable trends, with a decline of over 2% per year over the last two decades as compared with 0.4% in men, in the EU. In contrast, the EU mortality from ICC increased by around 9% in both sexes from 1990 to 2008, reaching rates of 1.1/100 000 men and 0.75/100 000 women. The highest rates were in UK, Germany, and France (1.2-1.5/100 000 men, 0.8-1.1/100 000 women). Conclusions PLC mortality has become more uniform across Europe over recent years, with an overall decline; in contrast, ICC mortality has substantially increased in most Europ

Shot Noise in Linear Macroscopic Resistors

We report on a direct experimental evidence of shot noise in a linear macroscopic resistor. The origin of the shot noise comes from the fluctuation of the total number of charge carriers inside the resistor associated with their diffusive motion under the condition that the dielectric relaxation time becomes longer than the dynamic transit time. Present results show that neither potential barriers nor the absence of inelastic scattering are necessary to observe shot noise in electronic devices.Comment: 10 pages, 5 figure