Two tone response of radiofrequency signals using the voltage output of a Superconducting Quantum Interference Filter

In the presence of weak time harmonic electromagnetic fields, Superconducting Quantum Interference Filters (SQIFs) show the typical behavior of non linear mixers. The SQIFs are manufactured from high-T_c grain boundary Josephson junctions and operated in active microcooler. The dependence of dc voltage output V_dc vs. static external magnetic field B is non-periodic and consists of a well pronounced unique dip at zero field, with marginal side modulations at higher fields. We have successfully exploited the parabolic shape of the voltage dip around B=0 to mix quadratically two external time harmonic rf-signals, at frequencies f_1 and f_2 below the Josephson frequency f_J, and detect the corresponding mixing signal at f_1-f_2. When the mixing takes place on the SQIF current-voltage characteristics the component at 2f_2 - f_1 is present. The experiments suggest potential applications of a SQIF as a non-linear mixing device, capable to operate at frequencies from dc to few GHz with a large dynamic range.Comment: 10 pages, 3 Figures, submitted to J. Supercond. (as proceeding of the HTSHFF Symposium, June 2006, Cardiff

Measuring rhizosphere hydraulic properties: impact of root mucilage on soil hydraulic conductivity and water retention curve

Roots are hypothesized to alter rhizosphere hydraulic properties by release of mucilage. This mechanism is expected to have strong implications for root water uptake under drought conditions. Direct measurement of rhizosphere hydraulic properties is hindered by the dynamic nature of the components involved; root hydraulics change with ontology; mucilage production, composition and diffusion are not constant; soil water content changes. An experimental approach was developed which enables to simultaneously measure hydraulic conductivity and apparent water retention curve in a radial flow setup, mimicking the flow geometry around roots. The method consists of extracting water at constant suction via a suction cup, which is centrally placed in a soil filled cylinder and recording water outflow and soil matric potential. In the past, the setup was tested for homogeneous distribution of a model substance (calcium-polygalacturonic acid) frequently used to mimic the properties of root mucilage. Now the system has been applied to investigate the impact of plant root mucilage collected from white lupine. As the system allows a local placement of mucilage treated soil around the suction cup to simulate a ‘rhizosphere’ between bulk soil and suction cup, it can be set up with the limited quantity of natural plant root mucilage available from direct collection. Quartz sand has been treated with lupine root mucilage by mixing liquid mucilage with dry sand at a concentration of 2 mg mucilage per gram soil. Treated sand has been placed as a circular layer with 3.75 mm thickness around the suction cup, which has a radius of 1.25 mm. All around this layer, the device has been filled up with untreated sand. The radius of the whole device was 25 mm. To determine soil hydraulic conductivity we inversely fitted the outflow curves and soil matric potential by solving the Richards’ equation in radial coordinates. Water outflow curves show a significant impact of lupine mucilage on water flow rate – it slows water flow from bulk soil to suction cup. Currently modelling is in process to determine soil hydraulic conductivity and water retention curves. Decreasing hydraulic conductivities and increasing water retention due to lupine mucilage treatment are expected

\u3cem\u3eDesmodium velutinum\u3c/em\u3e: A High-Quality Shrub Legume for Acid Soils in the Tropics

Drought tolerant legume shrubs can enhance the sustainability of smallholder production systems in the tropics through the provision, year-round, of high-quality feed and through their positive effect on soil. Desmodium velutinum (Willd.) DC. is one of the few shrub species that have been identified as (1) well adapted to acid tropical soils and (2) of good nutritive value (Schultze-Kraft, 1996). It is a perennial native to SE Asia and tropical Africa growing up to 3 m high, the velutinous (velvety) surfaces of its 1-foliolate leaves being a characteristic feature. It grows well on soils ranging from pH 4.0 to alkaline, prefers high rainfall (1000 to \u3e 3000 mm/year) but tolerates up to five dry months. Though previous work in West Africa (e.g., Mzamane & Agishi, 1986) and South America (e.g., Thomas & Schultze-Kraft, 1990) has indicated the potential of the species, there are only few studies and these are restricted to only one or a few accessions. It is important to assess the genetic diversity and agronomic variability in the germplasm collection of about 140 accessions that is now available in order to identify a core collection and accessions with promising agronomic performance and nutritive value. Possible relationships between accession origins, morphological-agronomic characteristics, and genetic diversity need to be assessed. The first-year results from a field experiment on forage yield and quality are presented here. The project is financially supported by the Volkswagen Stiftung, Hannover, Germany

Influence of mental health literacy on help-seeking behaviour for mental health problems in the Swiss young adult community: a cohort and longitudinal case–control study

Poor knowledge about mental health disorders and their treatment likely contributes to the large treatment gap reported for mental health problems. Therefore, we studied the association between mental health literacy (MHL) and active help-seeking in a community sample. Participants were recruited from an add-on questionnaire study to the 'Bern Epidemiological At-Risk' (BEAR) study on 16-40-year-old community subjects of the Swiss canton Bern. At baseline, data of N = 1504, and at 3-year follow-up, data of N = 535 were available. Based on an unlabelled case vignette (on depression or schizophrenia), MHL was assessed by the questionnaire of Angermeyer and colleagues. Cross-sectional and longitudinal baseline predictors of help-seeking were analysed using path analyses. Additionally, sensitivity analyses of the prospective model were computed for sex, vignette, and baseline mental health problems/disorders. Cross-sectionally, help-seeking was associated with non-endorsement of biogenetic causal explanations, presence of mental health problems/disorders, help-seeking before baseline, poorer functioning, and lower health satisfaction. The prospective model was similar; yet, help-seeking at follow-up was associated with endorsements of the causal explanation 'biogenetics' and, additionally, 'childhood trauma' but not the presence of baseline mental health problems/disorders. Sensitivity analyses revealed a significant impact on sex, vignette, and mental health problems/disorders. For example, actual functional problems were predictive in males, while health satisfaction was predictive in females. Our findings indicate that future studies on drivers of help-seeking should assess very large community samples with case vignettes on different mental disorders to examine appropriate subgroups and their likely interaction to address group-specific factors in awareness campaigns

Enzyme prodrug therapy achieves site-specific, personalized physiological responses to the locally produced nitric oxide

Nitric oxide (NO) is a highly potent but short-lived endogenous radical with a wide spectrum of physiological activities. In this work, we developed an enzymatic approach to the site-specific synthesis of NO mediated by biocatalytic surface coatings. Multilayered polyelectrolyte films were optimized as host compartments for the immobilized β-galactosidase (β-Gal) enzyme through a screen of eight polycations and eight polyanions. The lead composition was used to achieve localized production of NO through the addition of β-Gal–NONOate, a prodrug that releases NO following enzymatic bioconversion. The resulting coatings afforded physiologically relevant flux of NO matching that of the healthy human endothelium. The antiproliferative effect due to the synthesized NO in cell culture was site-specific: within a multiwell dish with freely shared media and nutrients, a 10-fold inhibition of cell growth was achieved on top of the biocatalytic coatings compared to the immediately adjacent enzyme-free microwells. The physiological effect of NO produced via the enzyme prodrug therapy was validated ex vivo in isolated arteries through the measurement of vasodilation. Biocatalytic coatings were deposited on wires produced using alloys used in clinical practice and successfully mediated a NONOate concentration-dependent vasodilation in the small arteries of rats. The results of this study present an exciting opportunity to manufacture implantable biomaterials with physiological responses controlled to the desired level for personalized treatment

Proton radiography and tomography with application to proton therapy

Proton radiography and tomography have long promised benefit for proton therapy. Their first suggestion was in the early 1960s and the first published proton radiographs and CT images appeared in the late 1960s and 1970s, respectively. More than just providing anatomical images, proton transmission imaging provides the potential for the more accurate estimation of stopping-power ratio (SPR) inside a patient and hence improved treatment planning and verification. With the recent explosion in growth of clinical proton therapy facilities, the time is perhaps ripe for the imaging modality to come to the fore. Yet many technical challenges remain to be solved before proton CT scanners become commonplace in the clinic. Research and development in this field is currently more active that at any time with several prototype designs emerging. This review introduces the principles of proton radiography and tomography, its historical developments, the raft of modern prototype systems and the primary design issues

The response of the smallholder farm to the introduction of cattle in eastern amazon: the case of the Bragantina region.

Editado por Reinhard Lieberei, Helmut Bianchi, Vera Boehm, Christoph Reisdorff