Study of a high spatial resolution 10B-based thermal neutron detector for application in neutron reflectometry: the Multi-Blade prototype

Although for large area detectors it is crucial to find an alternative to detect thermal neutrons because of the 3He shortage, this is not the case for small area detectors. Neutron scattering science is still growing its instruments' power and the neutron flux a detector must tolerate is increasing. For small area detectors the main effort is to expand the detectors' performances. At Institut Laue-Langevin (ILL) we developed the Multi-Blade detector which wants to increase the spatial resolution of 3He-based detectors for high flux applications. We developed a high spatial resolution prototype suitable for neutron reflectometry instruments. It exploits solid 10B-films employed in a proportional gas chamber. Two prototypes have been constructed at ILL and the results obtained on our monochromatic test beam line are presented here

Quantitative Study of Magnetotransport through a (Ga,Mn)As Single Ferromagnetic Domain

We have performed a systematic investigation of the longitudinal and transverse magnetoresistance of a single ferromagnetic domain in (Ga,Mn)As. We find that, by taking into account the intrinsic dependence of the resistivity on the magnetic induction, an excellent agreement between experimental results and theoretical expectations is obtained. Our findings provide a detailed and fully quantitative validation of the theoretical description of magnetotransport through a single ferromagnetic domain. Our analysis furthermore indicates the relevance of magneto-impurity scattering as a mechanism for magnetoresistance in (Ga,Mn)As.Comment: 5 pages, 4 figures; v2: missing references included, figures recompressed to improve readabilit

Potential of model predictive control of a polder water system including pumps, weirs and gates

This work presents an assessment of the potential of model predictive control (MPC) of a Dutch polder system. The system drains to the Linge river and includes 13 weirs, 4 hydraulic gates and 4 large pumping stations each equipped with multiple pumps, managed by the Water Board Rivierenland. The management of the system must comply with several goals: keep the water levels within the bounds of safety, pump out the excess water at minimum cost or CO2 emission, but always have enough water for irrigation and shipping. To achieve these goals there are weirs regulating the water level in different pools, pumping stations to pump water in and out and gates to let water in and out by free flow when possible. These pumping stations consume large amounts of energy. We propose multi-objective mixed-integer optimization by using goal programming to prioritize different operational objectives. For the control of the pumps mixed-integer optimization is used, which makes it possible to not only model the energy consumption of the pumps while in operation, but also to model if the pumps are turned on or off. The control system is implemented using RTC-Tools, an open-source software tool to implement MPC. It is demonstrated that the proposed control system implementation can comply with the operational goals of the water board: keeping the water levels within the bounds while reducing the operational costs. The proposed control system has been tested numerically on data from the year 2013, and it is shown that it highly outperforms the current operation.</p

Theory of Diluted Magnetic Semiconductor Ferromagnetism

We present a theory of carrier-induced ferromagnetism in diluted magnetic semiconductors (III_{1-x} Mn_x V) which allows for arbitrary itinerant-carrier spin polarization and dynamic correlations. Both ingredients are essential in identifying the system's elementary excitations and describing their properties. We find a branch of collective modes, in addition to the spin waves and Stoner continuum which occur in metallic ferromagnets, and predict that the low-temperature spin stiffness is independent of the strength of the exchange coupling between magnetic ions and itinerant carriers. We discuss the temperature dependence of the magnetization and the heat capacity

Monitoramento da multidisciplinaridade no processo de transferência de tecnologia em uma universidade: proposta de análise de cluster

ABSTRACTThis paper discusses the management of the technology transfer process conducted by a Technology Transfer Office (TTO) of a federal public university. Patent co-authorship and multidisciplinarity were used as concepts to evaluate and monitor the quality of academic and practical contribution and their potential for commercial application, using descriptive statistics and cluster analysis. Considering only multidisciplinary patents, binary cluster analysis was conducted, using Jaccard similarity measurement and single linkage method to determine proximity among academic units. Apart from the analysis of the number of patents, the approach enabled discussions and questions regarding the differences between patent generation patterns, resultant from the specific organizational culture and structures. The discussions are relevant to improve the identification of opportunities in technology transfer processes by the TTO

Theory of Magnetic Properties and Spin-Wave Dispersion for Ferromagnetic (Ga,Mn)As

We present a microscopic theory of the long-wavelength magnetic properties of the ferromagnetic diluted magnetic semiconductor (Ga,Mn)As. Details of the host semiconductor band structure, described by a six-band Kohn-Luttinger Hamiltonian, are taken into account. We relate our quantum-mechanical calculation to the classical micromagnetic energy functional and determine anisotropy energies and exchange constants. We find that the exchange constant is substantially enhanced compared to the case of a parabolic heavy-hole-band model.Comment: 9 pages, 4 figure

Some Restrictions Abroad Affecting Corporations

A neutron detector concept based on solid layers of boron carbide enriched in 1 B has been in development for the last few years as an alternative for He-3 by collaboration between the ILL, ESS and Linkoping University. This Multi-Grid detector uses layers of aluminum substrates coated with (B4C)-B-10 on both sides that are traversed by the incoming neutrons. Detection is achieved using a gas counter readout principle. By segmenting the substrate and using multiple anode wires, the detector is made inherently position sensitive. This development is aimed primarily at neutron scattering instruments with large detector areas, such as time-of-flight chopper spectrometers. The most recent prototype has been built to be interchangeable with the He-3 detectors of IN6 at ILL. The 1 B detector has an active area of 32 x 48 cm(2). It was installed at the IN6 instrument and operated for several weeks, collecting data in parallel with the regularly scheduled experiments, thus providing the first side-by-side comparison with the conventional He-3 detectors. Results include an efficiency comparison, assessment of the in-detector scattering contribution, sensitivity to gamma-rays and the signal-to-noise ratio in time-of-flight spectra. The good expected performance has been confirmed with the exception of an unexpected background count rate. This has been identified as natural alpha activity in aluminum. New convertor substrates are under study to eliminate this source of background

Betahistine in Meniere's disease or syndrome: a systematic review

Background: Meniere's disease is characterized by recurrent episodes of vertigo, hearing loss, and tinnitus, often with a feeling of fullness in the ear. Although betahistine is thought to be specifically effective for Meniere's disease, no evidence for a benefit from the use of betahistine exists, despite its widespread use. Reassessment of the effect of betahistine for Meniere's disease is now warranted. Search Methods: We searched for randomized controlled trials (RCTs) in the Central Register of Controlled Trials (CENTRAL), Ovid Medline, Ovid Embase, CINAHL, Web of Science, Clinicaltrials.gov, ICTRP, and additional sources for published and unpublished trials, in which betahistine was compared to placebo. Data Collection and Analysis: Our outcomes involved vertigo, significant adverse effect (upper gastrointestinal discomfort), hearing loss, tinnitus, aural fullness, other adverse effects, and disease-specific health-related quality of life. We used GRADE to assess the quality of the evidence. Main Results: We included 10 studies: 5 studies used a crossover design and the remaining 5 were parallel-group RCTs. One study with a low risk of bias found no significant difference between the betahistine groups and placebo with respect to vertigo after a long-term follow-up period. No significant difference in the incidence of upper gastrointestinal discomfort was found in 2 studies (low-certainty evidence). No differences in hearing loss, tinnitus, or well-being and disease-specific health-related quality of life were found (low- to very low-certainty of evidence). Data on aural fullness could not be extracted. No significant difference between the betahistine and the placebo groups (low-certainty evidence) could be demonstrated in the other adverse effect outcome with respect to dull headache. The pooled risk ratio for other adverse effect in the long term demonstrated a lower risk in favor of placebo over betahistine. Conclusions: High-quality studies evaluating the effect of betahistine on patients with Meniere's disease are lacking. However, one study with low risk of bias found no evidence of a difference in the effect of betahistine on the primary outcome, vertigo, in patients with Meniere's disease when compared to placebo. The main focus of future research should be on the use of comparable outcome measures by means of patient-reported outcome measures.Disorders of the head and nec

Indirect exchange in GaMnAs bilayers via spin-polarized inhomogeneous hole gas: Monte Carlo simulation

The magnetic order resulting from an indirect exchange between magnetic moments provided by spin-polarized hole gas in the metallic phase of a GaMnAs double layer structure is studied via Monte Carlo simulation. The coupling mechanism involves a perturbative calculation in second order of the interaction between the magnetic moments and carriers (holes). We take into account a possible polarization of the hole gas due to the existence of an average magnetization in the magnetic layers, establishing, in this way, a self-consistency between the magnetic order and the electronic structure. That interaction leads to an internal ferromagnetic order inside each layer, and a parallel arrangement between their magnetizations, even in the case of thin layers. This fact is analyzed in terms of the inter- and intra-layer interactions.Comment: 17 pages and 14 figure