A modular self-assembled sensing system for heavy metal ions with tunable sensitivity and selectivity

Here we describe a self-assembled sensing system composed of three separate modules: gold nano particles, a reporter element, and a recognition element. The gold nanoparticles serve as a multivalent platform for the interaction with both the reporter and recognition element and the gold nucleus serves to affect the fluorescent properties of the reporter. The reporter element serves for generation of the output signal. The recognition element serves to make the assay selective. The working principle is that the interaction of the analyte with the recognition element leads to an increased affinity for the gold nanoparticle, which causes a displacement of the reporter and a turn-ON of fluorescence. It is shown that the modular nature of the system permits straightforward tuning of the dynamic detection range, the sensitivity, and the selectivity, simply by changing the recognition module. The system can detect Hg2+ and Ag+ metal ions at nanomolar concentrations in aqueous buffer

Intercropping cereals and grain legumes: a farmer’s perspective

Intercropping cereals and grain legumes show potential for organic agriculture in many ways. However, the use of land equivalent ratio (LER) as a measure for calculating the cropping advantage of intercrops over sole crops is too simple: neglecting weed suppression, yield reliability, grain quality, and minimum profitable yield, which are all relevant fac-tors from a farmer’s perspective. Only when the crop selection for the mixtures is carefully done, and crops are grown on the right soil in the right rotation, can intercropping be made to profit

Reversible electrowetting and trapping of charge: model and experiments

We derive a model for voltage-induced wetting, so-called electrowetting, from the principle of virtual displacement. Our model includes the possibility that charge is trapped in or on the wetted surface. Experimentally, we show reversible electrowetting for an aqueous droplet on an insulating layer of 10 micrometer thickness. The insulator is coated with a highly fluorinated layer impregnated with oil, providing a contact-angle hysteresis lower than 2 degrees. Analyzing the data with our model, we find that until a threshold voltage of 240 V, the induced charge remains in the liquid and is not trapped. For potentials beyond the threshold, the wetting force and the contact angle saturate, in line with the occurrence of trapping of charge in or on the insulating layer. The data are independent of the polarity of the applied electric field, and of the ion type and molarity. We suggest possible microscopic origins for charge trapping.Comment: 13 pages & 5 figures; the paper has been accepted for publication in Langmui

The experiences and morale of Metropolitan Special Constables. an analysis of the factors associated with volunteer officer job motivation and retention

Special constables have a long established history within British policing. Today, they hold full police powers and are an important part of the police workforce across all areas in England and Wales. The Metropolitan Special Constabulary (MSC) is the largest in the country. One in four special constables nationally belong to the MSC and in 2015 they provided London with over half a million policing hours. Since 2012, the number of special constables in the MSC has fallen by 40 per cent. Despite their longevity, special constabularies are under researched and the factors associated with volunteer officer motivation and retention are pooly understood. In spite of the high levels of attrition, successive governments have promoted the benefits of special constabularies in terms of increasing legitimacy, fostering responsibilisation, and reducing costs, and encouraged forces to run regular recruitment campaigns to boost the size and capability of their special constabularies. This study uses qualitative interviewing to explore the experiences and motivations of current and former MSC officers and to understand the factors that impact upon retention. The thesis uses Clary et al.‘s (1998) functional multifactor model of volunteer motivation, widely accepted in the volunteer field, as a lens through which to analyse the results. The study highlights varying degrees of satisfaction with being a special constable and suggests that training, deployment, integration and recognition are all important factors in the morale of special constables and their commitment to further service. The study suggests that functional motivational principles are not being applied to the special constabulary. The thesis concludes by making a number of recommendations to the Metropolitan Police Service to assist in improving the morale and retention of MSC officers

Sustainable Soesterkwartier

The municipality of Amersfoort wants to construct an endurable and sustainable eco-town in the Soesterkwartier neighbourhood, by taking future climate change into account. The impact of climate change at the location of the proposed eco-town was studied by a literature review

Indicators of Fatigue in Collegiate Women Tennis Players

To date very few research studies are available describing a detailed sports science profile of collegiate women tennis players, as many other existing studies only provide data on Junior tennis players or middle-aged subjects. The purpose of this investigation was to examine seasonal changes in training and competition on physiological and psychological measures in 13 NCAA Division I collegiate women tennis players (mean ± SD: age, 19.69 ± 1.32 years; height, 168.82 ± 4.59 cm; and weight, 64.75 ± 2.89 kg). All testing was conducted during the fall season. All subjects signed a University IRB approved informed consent form. Every two weeks (T1 - T6) subjects performed a maximal serve velocity test and an athlete burnout questionnaire (ABQ) from which the global burnout index (the mean score of the 3 ABQ subscales) was used. Subjects also completed a spider agility test and the Australian Sports Commission 20m shuttle run test at T1, T4, and T6. Lastly, the team indicated their ratings of perceived exertion (RPE) after every practice and conditioning session, which was later used to calculate training load (RPE x min). One Way ANOVA with repeated measures testing revealed no differences (p \u3e .05) in maximal serve velocity, spider agility test times, and global burnout index scores throughout the fall season. However 20m shuttle run test values revealed that aerobic capacity increased significantly (p \u3c0.05) from T1 to T4 (mean ± SD, 34.12 ± 4.50 ml/kg/min to 39.05 ± 4.55 ml/kg/min) with no differences between T4 and T6 (39.05 ± 4.55 ml/kg/min to 40.15 ± 3.62 ml/kg/min). The RPE results revealed that there was an fluctuating pattern in the teams training load, which decreased significantly (p \u3c 0.05) from T1 to T6 (mean ± SD, 3020.00 +/- 695.85 to 1933.33 ± 959.89). Dependent t-tests revealed significant differences (p \u3c 0.05) when comparing T1 (as baseline) to T6 in the athletes\u27 maximal (and average) serve velocity (mean ± SD, 146.45 ± 7.16 km/hr to 140.66 ± 7.96 km/hr), and global burnout scores (mean ± SD, 2.35 ± 0.50 to 2.54 ± 0.56). Therefore, fatigue as indicated by an increased global burnout index and decreased maximal serve velocity increased in women tennis players across their fall season even as workload decreased. In conclusion, it is vital for a conditioning program to be implemented during the three month summer break to which collegiate tennis teams can adhere. This would decrease the potential for detraining and ensure more time could be spent on other important determinants of tennis performance. Collegiate tennis coaches and strength and conditioning specialists should train tennis players in an anaerobic, tennis-specific manner that works the correct energy systems in order to accomplish the major goal of tennis training, which is to avoid the onset of fatigue during competition and practice

Distribution Iteration: A Robust Alternative to Source Iteration for Solving the Discrete Ordinates Radiation Transport Equations in Slab and XY- Geometries

The discrete ordinates method is widely used to solve the Boltzmann transport equation for neutral particle transport for many engineering applications. Source iteration is used to solve the discrete ordinates system of equations, but can be slow to converge in highly scattering problems. Synthetic acceleration techniques have been developed to address this shortcoming; however, recent research has shown synthetic acceleration to lose effectiveness or diverge for certain problems. LTC Wager introduced an alternative to source iteration and demonstrated it in slab geometry. Here the method is further developed, enhancing efficiency in various ways, and demonstrated in XY-geometry as well as slab geometry. It is shown to be efficient even for those problems for which diffusion-synthetic and transport-synthetic accelerations fail or are ineffective. The method has significant advantages for massively-parallel implementations

Spin-dependent transport in metal/semiconductor tunnel junctions

This paper describes a model as well as experiments on spin-polarized tunnelling with the aid of optical spin orientation. This involves tunnel junctions between a magnetic material and gallium arsenide (GaAs), where the latter is optically excited with circularly polarized light in order to generate spin-polarized carriers. A transport model is presented that takes account of carrier capture in the semiconductor surface states, and describes the semiconductor surface in terms of a spin-dependent energy distribution function. The so-called surface spin-splitting can be calculated from the balance of the polarized electron and hole flow in the semiconductor subsurface region, the polarized tunnelling current across the tunnel barrier between the magnetic material and the semiconductor surface, and the spin relaxation at the semiconductor surface. Measurements are presented of the circular-polarization-dependent photocurrent (the so-called helicity asymmetry) in thin-film tunnel junctions of Co/Al2O3/GaAs. In the absence of a tunnel barrier, the helicity asymmetry is caused by magneto-optical effects (magnetic circular dichroism). In the case where a tunnel barrier is present, the data cannot be explained by magneto-optical effects alone; the deviations provide evidence that spin-polarized tunnelling due to optical spin orientation occurs. In Co/τ-MnAl/AlAs/GaAs junctions no deviations from the magneto-optical effects are observed, most probably due to the weak spin polarization of τ-MnAl along the tunnelling direction; the latter is corroborated by bandstructure calculations. Finally, the application of photoexcited GaAs for spin-polarized tunnelling in a scanning tunnelling microscope is discussed.