A new view of the spin echo diffusive diffraction on porous structures

Analysis with the characteristic functional of stochastic motion is used for the gradient spin echo measurement of restricted motion to clarify details of the diffraction-like effect in a porous structure. It gives the diffusive diffraction as an interference of spin phase shifts due to the back-flow of spins bouncing at the boundaries, when mean displacement of scattered spins is equal to the spin phase grating prepared by applied magnetic field gradients. The diffraction patterns convey information about morphology of the surrounding media at times long enough that opposite boundaries are restricting displacements. The method explains the dependence of diffraction on the time and width of gradient pulses, as observed at the experiments and the simulations. It also enlightens the analysis of transport properties by the spin echo, particularly in systems, where the motion is restricted by structure or configuration

Penetration of Air Jets Issuing from Circular, Square, and Elliptical Orifices Directed Perpendicularly to an Air Stream

An experimental investigation was conducted to determine the penetration of air jets d.irected perpendicularlY to an air stream. Jets Issuing from circular, square, and. elliptical orifices were investigated. and. the jet penetration at a position downstream of the orifice was determined- as a function of jet density, jet velocity, air-stream d.enaity, air-stream velocity, effective jet diameter, and. orifice flow coeffIcient. The jet penetrations were determined for nearly constant values of air-stream density at three tunnel-air velocities arid for a large range of Jet velocities and. densities. The results were correlated in terms of dimensionless parameters and the penetrations of the various shapes were compared. Greater penetration was obtained. with the square orifices and the elliptical orifices having an axis ratio of 4:1 at low tunnel-air velocities and low jet pressures than for the other orifices investigated. The square orifices gave the best penetrations at the higher values of tunnel-air velocity and jet total pressure

Morphology of coastal lagoon entrances: waves versus tides

Lagoon inlets and river entrances on sandy coasts are shaped by waves, tides and freshwater outflows interacting subject to geological constraints. In dimensionless terms the relative importance of fresh water discharge Q versus peak tidal discharge Q is quantified simply by Q/Q, where the tidal peak discharge may be taken either as the actual Q = ωaA corresponding to the actual bay tidal amplitude aB or the potential Q = ωaA, which is based on the ocean tide amplitude aO. ω is the tidal angular frequency and A is the bay surface area at mid tide. The quantification of the relative strength of waves versus tides is less obvious and has not previously been clearly resolved. The case is made here for it being quantified by (Equation presented), where tidal dominance resulting in the canonical funnel shaped estuary occurs for (Equation presented) and, at the other end of the spectrum, intermittently open/closed systems (ICOLLS) occur for (Equation presented) denotes the average offshore significant wave height and g is acceleration due to gravity. More comprehensive data may lead to the inclusion of the wave period as well as the wave height in future formulations

Inlet morpho-dynamics during a storm event inferred from tidal records: a case study of the Brunswick River, NSW, Australia

A 24.5h moving window is used to analyse storm effects on the tidal dynamics. Compared to earlier studies using window lengths varying between 2h (for tsunami analysis) to 14 days for tidal inlet analysis, the present method provides good resolution of variations of hydraulic efficiency during storms or floods. The importance of de-trending before carrying out the harmonics analysis has been studied and it was found to be highly important. De-trending involved removing the 24.5h mean before harmonic analysis. The main results are the morphodynamic timescale Tmorph and the varying response functions F1 and F2 of the diurnal and semi-diurnal tidal constituents through a storm event at the Brunswick River, Australia. Tmorph is inferred from time series of primary semi-diurnal gain G2(t) = |F2 | with an exp(-t/Tmorph) curve fit. The results show only insignificant morphological change. Thus, the changes in tidal response for this medium sized catchment are mainly due to hydraulic effects. These include the influence of river flow Qf via the non-linear friction term and increased estuary surface area during the flood. The traces of both F1(t) and F2(t) in the complex plane show an equilibrium before the storm, dynamic change during the storm and relaxation mimicked by exp(-t/Tmorph) after the storm

The effect of the alternative prey, Paramecium caudatum (Peniculida: Parameciidae), on the predation of Culex pipiens (Diptera: Culicidae) by the copepods Macrocyclops albidus and Megacyclops viridis (Cyclopoida: Cyclopidae)

Biological control can be an effective tool to combat public health risks associated with mosquito-borne disease. However, target impacts of biological control agents may be reduced by biotic contexts such as the presence of alternative prey. In turn, this can impede our ability to realistically assess biocontrol agent efficacy. Here, we examine the effects of alternative ciliate prey on the predation potential of two cyclopoid copepods, Macrocyclops albidus Jurine (Cyclopoida: Cyclopidae) and Megacyclops viridis Jurine (Cyclopoida: Cyclopidae), towards larvae of the West Nile virus vector mosquito Culex pipiens Linnaeus (Diptera: Culicidae). Using functional responses (FRs; resource use under different resource densities), we demonstrate that both copepods exhibit potentially destabilising Type II FRs towards mosquito prey. However, where the alternative prey was present, we observed species-specific modulations to FR form and magnitude. For M. albidus, FRs remained Type II where ciliate prey were present, however, maximum feeding rates on mosquito larvae were reduced. Conversely, for M. viridis, FRs moved towards more stabilising Type III, whilst maximum feeding rates on mosquito larvae were not significantly reduced. Whilst both species of cyclopoid copepod were able to effectively target and consume larval mosquitoes in the presence of alternative prey, we demonstrate that overall efficacies may be reduced in aquatic habitats which contain multiple prey types. We thus advocate that biotic contexts such as prey selectivity should be integrated into predatory biocontrol agent examinations for mosquitoes which vector pathogens and parasites, to more holistically assess their efficacy

An exploration of predictors of children's nurses' attitudes, knowledge, confidence and clinical behavioural intentions towards children and young people who self-harm

Aims and objectives: To explore the potential predictors of children's nurses? attitudes, knowledge and confidence towards caring for children and young people admitted to hospital with self-harm. Background Admissions to paediatric inpatient settings for individuals who have self-harmed are growing. Limited previous research suggests that nurses have mixed attitudes towards people who have self-harmed and potentially lack the confidence to provide effective care. There is a specific paucity of research in this area for children's nurses. Design: A cross-sectional descriptive survey was used to gather data for exploration of variables associated with attitudes, confidence, knowledge and clinical behavioural intentions of 98 registered children's nurses in a single tertiary children's hospital, colocated in a large acute NHS Trust in the UK. Methods: Data were collected over a 4 weeks in 2015, using an online survey tool. The predictive effect of several demographic variables was tested on the outcomes of attitudes, knowledge, confidence and behavioural intentions, which were collected using relevant, previously used outcome measures. Results: Increased experience was found to be associated with improved attitudes relating to negativity. Previous training in caring for children who had self-harmed was found to be associated with improved attitudes around perceived effectiveness of their care. Higher academic qualifications and having undertaken previous training on self-harm were each found to be associated with increased knowledge of self-harm, and increased age was associated with reduced knowledge of self-harm. Conclusions: This study provides an initial exploration of variables associated with attitudes, knowledge, confidence and behaviour intentions of registered children's nurses in relation to caring for CYP who have self-harmed. Relevance to clinical practice: Targeted training on caring for CYP who have self-harmed should be considered as a component of continuing education for registered children's nurses in the UK to improve the experience and outcomes for this patient group

Dynamic decoherence control of a solid-state nuclear quadrupole qubit

We report on the application of a dynamic decoherence control pulse sequence on a nuclear quadrupole transition in $Pr^{3+}:Y_2SiO_5$ . Process tomography is used to analyse the effect of the pulse sequence. The pulse sequence was found to increase the decoherence time of the transition to over 30 seconds. Although the decoherence time was significantly increased, the population terms were found to rapidly decay on the application of the pulse sequence. The increase of this decay rate is attributed to inhomogeneity in the ensemble. Methods to circumvent this limit are discussed.Comment: 4 pages, 6 figure