Reactions of Ar+, Ne+, and He+ with SiF4 from thermal energy to 50 eV c.m.

Journal ArticleGuided ion-beam techniques are used to measure the cross sections for reaction of SiF4 with Ar+, Ne+, and He+ from thermal to 50 eV. Charge transfer followed by loss of F atoms are the sole processes observed. All SiFx + (x = 0-4) products are observed, except for SiF4 + from reaction with Ne+ and He+, and Si+ from reaction with Ar+

Energetics and dynamics in the reaction of Si+ with SiF4. Thermochemistry of SiFx and SiFx+ (x=1,2,3)

Journal ArticleThe title reaction is studied using guided ion beam mass spectrometry. Absolute reaction cross sections are measured as a function of kinetic energy from thermal to 40 eV, and three endothermic product channels are observed. The dominant SiF+ + SiF3 channel is only slightly endothermic, while the SiF3+ + SiF and SiF2+ + SiF2 channels have much higher thresholds. The SiF3 + cross section magnitude is about half that of SiF+, while the SiF2+ cross section is an order of magnitude smaller than that of SiF+

Wavefunction extended Lagrangian Born-Oppenheimer molecular dynamics

Extended Lagrangian Born-Oppenheimer molecular dynamics [Niklasson, Phys. Rev. Lett. 100 123004 (2008)] has been generalized to the propagation of the electronic wavefunctions. The technique allows highly efficient first principles molecular dynamics simulations using plane wave pseudopotential electronic structure methods that are stable and energy conserving also under incomplete and approximate self-consistency convergence. An implementation of the method within the planewave basis set is presented and the accuracy and efficiency is demonstrated both for semi-conductor and metallic materials.Comment: 6 pages, 3 figure

School Milk Consumption in Germany - What are Important Product Attributes for Children and Parents?

Food Consumption/Nutrition/Food Safety,

Driving factors for school milk demand in Germany

School milk consumption has declined steadily in Germany. A research project was set up to retrieve quantifiable information on the different factors of influence and to develop solutions to improve the school milk consumption.. The main goal is to evaluate the impact of price, product range, distribution form, information campaigns, regional situation, county based social index, socially-funded school milk distribution, and gender shares, as well as the immigration background share within a class. A total of 400 primary schools were selected by stratified random sampling. Surveys for principals and school milk managers were used to gain information on distribution problems throughout the milk chain, on the handling, and their attitudes towards school milk and milk in general. The price of school milk is being reduced stepwise in the 2008/09 school year. The quantity of consumption is reported per class. A multilevel analysis is applied to determine the factors driving consumption at the class level. First results will be validated. The paper comprises an extended introduction, followed by the research approach. A descriptive analysis is given following a detailed description of the experiment.. The estimation procedure is discussed before the results are presented. Finally, a qualification of outcomes and conclusions concerning further research are found.School Milk, Demand Subsidy, Food Demand, Multilevel Analysis., Agricultural and Food Policy, Food Consumption/Nutrition/Food Safety,

Hydropower production and river rehabilitation: A case study on an alpine river

Despite the numerous benefits of hydropower production, this renewable energy source can have serious negative consequences on the environment. For example, dams act as barriers for the longitudinal migration of organisms and transport of particulate matter. Accelerated siltation processes in the receiving river reduce the vertical connectivity between river and groundwater. Hydropeaks, caused by short-term changes in hydropower operation, result in a negative impact on both habitat and organisms, especially during winter months when natural discharge is low and almost constant. In this study, we report the current deficits present in the River Rhone from two different scientific perspectives - fish ecology and hydrology. Potential rehabilitation solutions in synergy with flood protection measures are discussed. We focus on the effects of hydropeaking in relation to longitudinal and vertical dimensions and discuss local river widening as a potential rehabilitation tool. The fish fauna in the Rhone is characterized by a highly unnatural structure (low diversity, impaired age distribution). A high correlation between fish biomass and monotonous morphology (poor cover availability) was established. Tracer hydrology provided further details about the reduced permeability of the riverbank, revealing a high degree of siltation with K values of about 4.7 × 10−6m s−1. Improving the hydrologic situation is therefore essential for the successful rehabilitation of the Rhone River. To this end, hydropeaks in the river reaches must be attenuated. This can be realized by a combination of different hard technical and soft operational measures such as retention reservoirs or slower up and down ramping of turbine

Vanadium dioxide : A Peierls-Mott insulator stable against disorder

Vanadium dioxide undergoes a first order metal-insulator transition at 340 K. In this work, we develop and carry out state of the art linear scaling DFT calculations refined with non-local dynamical mean-field theory. We identify a complex mechanism, a Peierls-assisted orbital selection Mott instability, which is responsible for the insulating M$_1$ phase, and furthermore survives a moderate degree of disorder.Comment: 5 pages, 4 figures. Supplementary material 8 pages, 4 figures. This version (v2) matches that accepted for Physical Review Letters on 16th May 201