Neutrino Masses in Supersymmetry: R-Parity and Leptogenesis

In the supersymmetric standard model of particle interactions, R-parity nonconservation is often invoked to obtain nonzero neutrino masses. We point out here that such interactions of the supersymmetric particles would erase any pre-existing lepton or baryon asymmetry of the universe before the electroweak phase transition through the $B + L$ violating sphaleron processes. We then show how neutrino masses may be obtained in supersymmetry (assuming R-parity conservation) together with successful leptogenesis and predict the possible existence of new observable particles.Comment: LATEX, 12 page

Integrated Design and Implementation of Embedded Control Systems with Scilab

Embedded systems are playing an increasingly important role in control engineering. Despite their popularity, embedded systems are generally subject to resource constraints and it is therefore difficult to build complex control systems on embedded platforms. Traditionally, the design and implementation of control systems are often separated, which causes the development of embedded control systems to be highly time-consuming and costly. To address these problems, this paper presents a low-cost, reusable, reconfigurable platform that enables integrated design and implementation of embedded control systems. To minimize the cost, free and open source software packages such as Linux and Scilab are used. Scilab is ported to the embedded ARM-Linux system. The drivers for interfacing Scilab with several communication protocols including serial, Ethernet, and Modbus are developed. Experiments are conducted to test the developed embedded platform. The use of Scilab enables implementation of complex control algorithms on embedded platforms. With the developed platform, it is possible to perform all phases of the development cycle of embedded control systems in a unified environment, thus facilitating the reduction of development time and cost.Comment: 15 pages, 14 figures; Open Access at http://www.mdpi.org/sensors/papers/s8095501.pd

Allowable Low-Energy E_6 Subgroups from Leptogenesis

There are only two viable low-energy $E_6$ subgroups: $SU(3)_C \times SU(2)_L \times U(1)_Y \times U(1)_N$ or $SU(3)_C \times SU(2)_L \times SU(2)'_R \times U(1)_{Y_L + Y'_R}$, which would not erase any preexisting lepton asymmetry of the Universe that may have been created by the decay of heavy singlet (right-handed) neutrinos or any other mechanism. They are also the two most favored $E_6$ subgroups from a recent analysis of present neutral-current data. We study details of the leptogenesis, as well as some salient experimental signatures of the two models.Comment: 12 page

Shot Noise Suppression in Avalanche Photodiodes

We identify a new shot noise suppression mechanism in a thin (~100 nm) heterostructure avalanche photodiode. In the low-gain regime the shot noise is suppressed due to temporal correlations within amplified current pulses. We demonstrate in a Monte Carlo simulation that the effective excess noise factors can be <1, and reconcile the apparent conflict between theory and experiments. This shot noise suppression mechanism is independent of known mechanisms such as Coulomb interaction, or reflection at heterojunction interfaces.Comment: Phys. Rev. Lett., accepted for publicatio

ZnO nanorod arrays as electron injection layers for efficient organic light emitting diodes

Nanostructured oxide arrays have received significant attention as charge injection and collection electrodes in numerous optoelectronic devices. Zinc oxide (ZnO) nanorods have received particular interest owing to the ease of fabrication using scalable, solution processes with a high degree of control of rod dimension and density. Here, vertical ZnO nanorods as electron injection layers in organic light emitting diodes are implemented for display and lighting purposes. Implementing nanorods into devices with an emissive polymer, poly(9,9-dioctyluorene-alt-benzothiadiazole) (F8BT) and poly(9,9-di-n-octylfluorene-alt-N-(4-butylphenyl)dipheny-lamine) (TFB) as an electron blocking layer, brightness and efficiencies up to 8602 cd m−2 and 1.66 cd A−1 are achieved. Simple solution processing methodologies combined with postdeposition thermal processing are highlighted to achieve complete wetting of the nanorod arrays with the emissive polymer. The introduction of TFB to minimize charge leakage and nonradiative exciton decay results in dramatic increases to device yields and provides an insight into the operating mechanism of these devices. It is demonstrated that the detected emission originates from within the polymer layers with no evidence of ZnO band edge or defect emission. The work represents a significant development for the ongoing implementation of ZnO nanorod arrays into efficient light emitting devices

Fluorene copolymer bilayers for emission colour tuning in inverted hybrid light emitting diodes

© The Royal Society of Chemistry 2015.We present a robust, entirely solution-based processing route for the deposition of planar F8BT/TFB poly(9,9-dioctylfluorene-alt-benzothiadiazole)/poly(9,9-dioctylfluorene-alt-N-(4-butylphenyl)-diphenylamine) emissive/hole transport bilayers for emission colour tuning in inverted organic-inorganic hybrid light emitting diodes (HyLEDs). Our method allows the facile exploration of TFB thickness for the first time within inverted devices; here we describe the influence of TFB thickness on the device performance. In particular, we demonstrate significant variations in device electroluminescence with highly controlled tunability between green and orange (550 to 610 nm) emission; correlating directly with the thickness of the TFB layer. These changes are in parallel with a 20-fold increase in current efficiency with respect to F8BT-only devices, with our bilayer devices exhibiting luminance values exceeding 11 000 cd m-2. Additionally, through reflectance and angle-dependent electroluminescence measurements we explore the presence of microcavity effects and their impact on device behaviour. We introduce TFB not only as a charge blocking/transporting layer but also as an optical emission-tuning layer

Geothermal Energy from the Main Karoo Basin (South Africa): An Outcrop Analogue Study of Permian Sandstone Reservoir Formations

The geothermal potential of the Main Karoo Basin has not been addressed in the past. A first assessment of Permian sandstone formations in the Eastern Cape Province, including down-hole temperature data from deep boreholes, and evaluation of groundwater temperature and heat flow values from literature leads to 3130 TWh (11.3 EJ) of power generation potential within the central and southern parts of the basin. The low permeability lithotypes may be operated as enhanced geothermal systems (EGS), depending on the fracture porosity in the deeper subsurface. In some areas auto-convective thermal water circulation might be expected and direct heat use becomes reasonable

alpha - HgS Nanocrystals: Synthesis, Structure and Optical Properties

Well-separated mercury sulfide (HgS) nanocrystals are synthesized by a wet chemical route. Transmission electron microscopy studies show that nanocrystals are nearly spherical in shape with average size of 9 nm. Grazing angle X-ray diffraction confirms that HgS nanocrystals are in cinnabar phase. Particle induced X-ray emission and Rutherford back scattering spectrometry analysis reveal HgS nanocrystals are stoichiometric and free from foreign impurities. The optical absorption measurements show two excitonic peaks corresponding to electron-heavy hole and electron-light hole transitions, which are blue shifted by 0.1 and 0.2 eV, respectively, from its bulk value, due to quantum size effect. The experimental data obtained by optical absorption measurement is simulated with a theoretical model considering the particle size distribution as Gaussian