Active-sterile neutrino oscillations in the early Universe: asymmetry generation at low |delta m^2| and the Landau-Zener approximation

It is well established that active-sterile neutrino oscillations generate large neutrino asymmetries for very small mixing angles ($\sin^2 2\theta_0\lesssim 10^{-4}$), negative values of $\delta m^2$ and provided that $|\delta m^2|\gtrsim 10^{-4} {\rm eV^2}$. By numerically solving the quantum kinetic equations, we show that the generation still occurs at much lower values of $|\delta m^2|$. We also describe the borders of the generation at small mixing angles and show how our numerical results can be analytically understood within the framework of the Landau-Zener approximation thereby extending previous work based on the adiabatic limit. This approximate approach leads to a fair description of the MSW dominated regime of the neutrino asymmetry evolution and is also able to correctly reproduce its final value. We also briefly discuss the impact that neutrino asymmetry generation could have on big bang nucleosynthesis, CMBR and relic neutrinos.Comment: 29 pages, 8 figures; to appear on Phys. ReV. D; figure 7 added, new curves in figure 5a, new figure

A conceptual model of daily water balance following partial clearing from forest to pasture

A simple conceptual water balance model representing the streamflow generation processes on a daily time step following land use change is presented. The model consists of five stores: (i) Dry, Wet and Subsurface Stores for vertical and lateral water flow, (ii) a transient Stream zone Store (iii) a saturated Goundwater Store. The soil moisture balance in the top soil Dry and Wet Stores are the most important components of the model and characterize the dynamically varying saturated areas responsible for surface runoff, interflow and deep percolation. The Subsurface Store describes the unsaturated soil moisture balance, extraction of percolated water by vegetation and groundwater recharge. The Groundwater Store controls the baseflow to stream (if any) and the groundwater contribution to the stream zone saturated areas. The daily model was developed following a <I>downward approach</I> by analysing data from Ernies (control) and Lemon (53% cleared) catchments in Western Australia and elaborating a monthly model. The daily model performed very well in simulating daily flow generation processes for both catchments. Most of the model parameters were incorporated a priori from catchment attributes such as surface slope, soil depth, porosity, stream length and initial groundwater depth, and some were calibrated by matching the observed and predicted hydrographs. The predicted groundwater depth, and streamflow volumes across all time steps from daily to monthly to annual were in close agreement with observations for both catchments

A daily salt balance model for stream salinity generation processes following partial clearing from forest to pasture

We developed a coupled salt and water balance model to represent the stream salinity generation process following land use changes. The conceptual model consists of three main components with five stores: (i) Dry, Wet and Subsurface Stores, (ii) a saturated Groundwater Store and (iii) a transient Stream zone Store. The Dry and Wet Stores represent the salt and water movement in the unsaturated zone and also the near-stream dynamic saturated areas, responsible for the generation of salt flux associated with surface runoff and interflow. The unsaturated Subsurface Store represents the salt bulge and the salt fluxes. The Groundwater Store comes into play when the groundwater level is at or above the stream invert and quantifies the salt fluxes to the Stream zone Store. In the stream zone module, we consider a 'free mixing' between the salt brought about by surface runoff, interflow and groundwater flow. Salt accumulation on the surface due to evaporation and its flushing by initial winter flow is also incorporated in the Stream zone Store. The salt balance model was calibrated sequentially following successful application of the water balance model. Initial salt stores were estimated from measured salt profile data. We incorporated two lumped parameters to represent the complex chemical processes like diffusion-dilution-dispersion and salt fluxes due to preferential flow. The model has performed very well in simulating stream salinity generation processes observed at Ernies and Lemon experimental catchments in south west of Western Australia. The simulated and observed stream salinity and salt loads compare very well throughout the study period with NSE of 0.7 and 0.4 for Ernies and Lemon catchment respectively. The model slightly over predicted annual stream salt load by 6.2% and 6.8%

Rooftop and indoor reception with transmit diversity applied to DVB-T networks: A long term measurement campaign

Although transmit Delay Diversity (DD) can provide a gain in indoor and other Non Line of Sight situations (NLOS), it can introduce degradation in rooftop reception. In fact, when the Ricean K factor of the channel is significantly high (e.g. Line of Sight reception), the channel performs similar to an AWGN channel where the performance degrades due to DD that artificially increase the fading. This paper investigates through practical evaluation the impacts of Transmit DD on LOS and NLOS stationary reception. Then, it studies 2 techniques to reduce the degradation performance in LOS while aiming to keep the same diversity gain in NLOS receptio

A daily salt balance model for stream salinity generation processes following partial clearing from forest to pasture

International audienceWe developed a coupled salt and water balance model to represent the stream salinity generation process following land use changes. The conceptual model consists of three main components with five stores: (i) Dry, Wet and Subsurface Stores, (ii) a saturated Groundwater Store and (iii) a transient Stream zone Store. The Dry and Wet Stores represent the salt and water movement in the unsaturated zone and also the near-stream dynamic saturated areas, responsible for the generation of salt flux associated with surface runoff and interflow. The unsaturated Subsurface Store represents the salt bulge and the salt fluxes. The Groundwater Store comes into play when the groundwater level is at or above the stream invert and quantifies the salt fluxes to the Stream zone Store. In the stream zone module, we consider a "free mixing" between the salt brought about by surface runoff, interflow and groundwater flow. Salt accumulation on the surface due to evaporation and its flushing by initial winter flow is also incorporated in the Stream zone Store. The salt balance model was calibrated sequentially following successful application of the water balance model. Initial salt stores were estimated from measured salt profile data. We incorporated two lumped parameters to represent the complex chemical processes like diffusion-dilution-dispersion and salt fluxes due to preferential flow. The model has performed very well in simulating stream salinity generation processes observed at Ernies and Lemon experimental catchments in south west of Western Australia. The simulated and observed stream salinity and salt loads compare very well throughout the study period with NSE of 0.7 and 0.4 for Ernies and Lemon catchment respectively. The model slightly over predicted annual stream salt load by 6.2% and 6.8%

Parameter sensitivity to climate and landscape variability of a simple, lumped salt and water balance model

International audienceA salt and water balance model is developed to represent salinity generation following land use changes in Western Australia. The model consists of five interconnecting stores: (i) Dry, Wet and Subsurface unsaturated Stores, (ii) a transient Stream zone Store and (iii) a saturated Groundwater Store. The salinity generation process in Western Australia is highly dependent on annual rainfall, potential energy for evaporation, salt fall and land use history of a catchment. We selected six experimental catchments with different land use histories across a climatic gradient to test the model and assess parameter sensitivity. The model was successful in representing the streamflow and salinity generation processes of all catchments. In the process of application, we classified the model parameters into three sets: (i) "known", (ii) "fixed" and (iii) "variable". The "known" parameter set is calculated a priori from catchment attributes. The "fixed" set comprises regionalised parameters that remain unchanged across all catchments once calibrated in one catchment. The "variable" set of seven physically meaningful parameters were calibrated at one catchment, estimated a priori for other catchments and then subsequently adjusted for best fit. The "variable" set represents: (i) the depth (d), spatial distribution (b, c), relationship of the lateral hydraulic conductivity with moisture content (ia) and vertical conductivity (Kuv) of the top soil, (ii) lateral conductivity (Kll) of the groundwater system, and (iii) salt release (Cu) from top soil. Sensitivity analyses of key model parameters show that the relationship of the top soil lateral hydraulic conductivity with soil moisture content (ia) is the most sensitive parameter. Other sensitive parameters include the depth of the top soil and its spatial distribution (d, b, c)

Focus on the origin of matter

The origin of matter in the Universe is a fascinating cosmological puzzle that has triggered a formidable intellectual enterprise, started in 1967 with the prescient paper by Andrej Sakharov (1967 Pisma Zh. Eksp. Teor. Fiz. 5 32; 1967 JETP Lett. 52 4; 1991 Sov. Phys.—Usp. 34 392; 1991 Usp. Fiz. Nauk 161 61) aimed at relating a cosmological observation to the fundamental laws of physics, the goal of baryogenesis. A successful model of baryogenesis should ultimately identify the required source of charge parity violation and the origin of the cosmological matter–antimatter asymmetry. This focus issue is not only a review of the main ideas that have been proposed in baryogenesis but should also bear witness to the great vitality of the field and to show how future experimental results could bring a breakthrough in baryogenesis during the coming years. For this reason we selected, out of the multitude of proposed baryogenesis models, those that will more likely experience a significant experimental test during the coming years

Early postoperative outcome after curative colorectal cancer surgery

Introduction:Colorectal cancer is uncommon in the Indian subcontinent, so there is a paucity of outcome data from this region. The aim of our study was to identify risk factors for early postoperative morbidity and mortality following curative colorectal cancer surgery in our set-up. Methods: The data on Patients with pathologically confirmed colorectal cancer who underwent curative surgery at Aga Khan University Hospital, Karachi, Pakistan, between January 1999 and December 2008 were recorded. Patients who developed early postoperative morbidity or mortality were compared with those who followed a healthy course after surgery. Results: A total of 250 consecutive Patients underwent colorectal cancer surgery during the study period. Postoperative complications were found in 34.8 percent of the Patients, out of which four deaths occurred. Serum albumin level less than 3.5 g/dl (odds ratio [OR] 3.75, 95 percent confidence interval [CI] 1.37-10.23) and tumours involving the left colon (OR 2.60, 95 percent CI 1.02-6.64) were identified as independent risk factors for early postoperative complications on multivariate analysis. Conclusions: A low serum albumin level and the presence of a left-sided colonic tumour were significant risk factors for early postoperative complications. Information on these complications and the risk factors for early postoperative outcome is an important consideration for Patients and surgeons

Behaviour in Magnetic Fields of Fast Conventional and Fine-Mesh Photomultipliers

The performance of both conventional and fine-mesh Hamamatsu photomultipliers has been measured inside moderate magnetic fields. This has allowed the test of effective shielding solutions for photomultipliers, to be used in time-of-flight detectors based on scintillation counters. Both signal amplitude reduction or deterioration of the timing properties inside magnetic fields have been investigated

Applicability of Trends in Nuclear Safety Analysis to Space Nuclear Power Systems

A survey is presented of some current trends in nuclear safety analysis that may be relevant to space nuclear power systems. This includes: lessons learned from operating power reactor safety and licensing; approaches to the safety design of advanced and novel reactors and facilities; the roles of risk assessment, extremely unlikely accidents, safety goals/targets; and risk-benefit analysis and communication