Quasiquartet CEF ground state with possible quadrupolar ordering in the tetragonal compound YbRu2_{2}Ge2_{2}

e have investigated the magnetic properties of YbRu$_{2}$Ge$_{2}$ by means of magnetic susceptibility $\chi$(T), specific heat C(T) and electrical resistivity $\rho$(T) measurements performed on flux grown single crystals. The Curie-Weiss behavior of $\chi$(T) along the easy plane, the large magnetic entropy at low temperatures and the weak Kondo like increase in $\rho$(T) proves a stable trivalent Yb state. Anomalies in C(T), $\rho$(T) and $\chi$(T) at T$_{0}$ = 10.2 K, T$_{1}$ = 6.5 K and T$_{2}$ = 5.7 K evidence complex ordering phenomena, T$_{0}$ being larger than the highest Yb magnetic ordering temperature found up to now. The magnetic entropy just above T$_{0}$ amounts to almost Rln4, indicating that the crystal electric field (CEF) ground state is a quasiquartet instead of the expected doublet. The behavior at T$_{0}$ is rather unusual and suggest that this transition is related to quadrupolar ordering, being a consequence of the CEF quasiquartet ground state. The combination of a quasiquartet CEF ground state, a high ordering temperature, and the relevance of quadrupolar interactions makes YbRu$_{2}$Ge$_{2}$ a rather unique system among Yb based compounds.Comment: 11 pages, 5 figure, submitted to PRB rapi

Two-dimensional electron-gas-like charge transport at magnetic Heusler alloy-SrTiO3_3 interface

We report remarkably low residual resistivity, giant residual resistivity ratio, free-electron-like Hall resistivity and high mobility ($\approx$ 10$^4$ cm$^2$V$^{-1}$s$^{-1}$) charge transport in epitaxial films of Co$_2$MnSi and Co$_2$FeSi grown on (001) SrTiO$_3$. This unusual behavior is not observed in films deposited on other cubic oxide substrates of comparable lattice parameters. The scaling of the resistivity with thickness of the films allow extraction of interface conductance, which can be attributed to a layer of oxygen vacancies confined within 1.9 nm of the interface as revealed by atomically resolved electron microscopy and spectroscopy. The high mobility transport observed here at the interface of a fully spin polarized metal is potentially important for spintronics applications

Engagement-related process factors in services for street-connected children and young people in low and middle income countries: a thematic synthesis

A recent Cochrane/ Campbell systematic review of interventions for promoting reintegration and reducing harmful behaviour and lifestyles in street-connected children and young people, supported by the International Initiative for Impact Evaluation (3ie), identified 11 studies evaluating 12 different interventions which met the inclusion criteria (Coren et al. 2013). The research studies had to contain a comparison group and look at street-connected children and young people between the ages of 0 and 24. None of the included studies were from low- and middle-income countries (LMICs), or involved process evaluations. The current thematic synthesis focused on engagement processes and strategies in studies pertaining to LMICs but excluded from the review on methodological grounds, complemented by studies identified through a search update conducted in March 2013. We included twenty-seven qualitative or mixed methods studies, which examined broad range of interventions and services adopted in 21 LMICs. The synthesis methods were primarily qualitative. On the basis of our findings, we conceptualised engagement as consisting of outreach and sustaining phases. Three separate dimensions emerged in the sustaining phases: meeting multiple needs, relations to adult service users, and community and family engagement. Our synthesis outlines challenges and dilemmas of engagement in each of these areas. The data also highlighted some common shortcomings in the service sector in LMICs, including lack of appropriate professional training and service development, lack of funding, and lack of co-operation with other relevant agencies. Innovative approaches to engagement, such as participatory initiatives and partnerships with universities, are also discussed

Numerical solutions of the three-dimensional magnetohydrodynamic alpha-model

We present direct numerical simulations and alpha-model simulations of four familiar three-dimensional magnetohydrodynamic (MHD) turbulence effects: selective decay, dynamic alignment, inverse cascade of magnetic helicity, and the helical dynamo effect. The MHD alpha-model is shown to capture the long-wavelength spectra in all these problems, allowing for a significant reduction of computer time and memory at the same kinetic and magnetic Reynolds numbers. In the helical dynamo, not only does the alpha-model correctly reproduce the growth rate of magnetic energy during the kinematic regime, but it also captures the nonlinear saturation level and the late generation of a large scale magnetic field by the helical turbulence.Comment: 12 pages, 19 figure