Control of spin current by a magnetic YIG substrate in NiFe/Al nonlocal spin valves

We study the effect of a magnetic insulator [yttrium iron garnet (YIG)] substrate on the spin-transport properties of Ni80Fe20/Al nonlocal spin valve (NLSV) devices. The NLSV signal on the YIG substrate is about two to three times lower than that on a nonmagnetic SiO2 substrate, indicating that a significant fraction of the spin current is absorbed at the Al/YIG interface. By measuring the NLSV signal for varying injector-to-detector distances and using a three-dimensional spin-transport model that takes spin-current absorption at the Al/YIG interface into account, we obtain an effective spin-mixing conductance G(up arrow down arrow) similar or equal to 5-8 x 10(13) Omega(-1) m(-2). We also observe a small, but clear, modulation of the NLSV signal when rotating the YIG magnetization direction with respect to the fixed spin polarization of the spin accumulation in the Al. Spin relaxation due to thermal magnons or roughness of the YIG surface may be responsible for the observed small modulation of the NLSV signal.</p

The Suaineadh Project : a stepping stone towards the deployment of large flexible structures in space

The Suaineadh project aims at testing the controlled deployment and stabilization of space web. The deployment system is based on a simple yet ingenious control of the centrifugal force that will pull each of the four daughters sections apart. The four daughters are attached onto the four corners of a square web, and will be released from their initial stowed configuration attached to a central hub. Enclosed in the central hub is a specifically designed spinning reaction wheel that controls the rotational speed with a closed loop control fed by measurements from an onboard inertial measurement sensor. Five other such sensors located within the web and central hub provide information on the surface curvature of the web, and progression of the deployment. Suaineadh is currently at an advanced stage of development: all the components are manufactured with the subsystems integrated and are presently awaiting full integration and testing. This paper will present the current status of the Suaineadh project and the results of the most recent set of tests. In particular, the paper will cover the overall mechanical design of the system, the electrical and sensor assemblies, the communication and power systems and the spinning wheel with its control system

Effect of Retrapping on Thermoluminescence Peak Intensities of Small Amorphous Silicon Quantum Dots

The effect of retrapping on thermoluminescence intensity peak corresponding to each trap of small amorphous silicon quantum dots in three traps -one recombination center model is investigated. For first order kinetics, where there is no effect of retrapping, the thermoluminescence intensity clearly depends on the level of the trap beneath the edge of the conduction band. This energy difference between the edge of the conduction band and the level of the trap is called trap depth (activation energy). The shallowest trap gives the highest thermoluminescence intensity peak for first order kinetics. However, it was clearly observed that for second order and a case beyond second order kinetics, the thermoluminescence intensity peak corresponding to each trap does not depend on the trap depth. In this case, the retrapping probability coefficients are taken into account and most electrons which are detrapped from the shallow trap(s) will be retrapped to the deeper trap(s) resulting in fewer electrons taking part in the recombination process. This significantly reduces the thermoluminescence intensity peaks of the shallower trap(s). It was observed that the deepest trap, with very high concentration of electrons due to the retrapping phenomenon, gives the highest thermoluminescence intensity. In addition, the variation of concentration of electrons in each trap and the intensity of the thermoluminescence are presented. Though we considered the model of three traps and one recombination center, this phenomenon is true for any multiple traps

Thermoelectric spin voltage in graphene

In recent years, new spin-dependent thermal effects have been discovered in ferromagnets, stimulating a growing interest in spin caloritronics, a field that exploits the interaction between spin and heat currents. Amongst the most intriguing phenomena is the spin Seebeck effect, in which a thermal gradient gives rise to spin currents that are detected through the inverse spin Hall effect. Non-magnetic materials such as graphene are also relevant for spin caloritronics, thanks to efficient spin transport, energy-dependent carrier mobility and unique density of states. Here, we propose and demonstrate that a carrier thermal gradient in a graphene lateral spin valve can lead to a large increase of the spin voltage near to the graphene charge neutrality point. Such an increase results from a thermoelectric spin voltage, which is analogous to the voltage in a thermocouple and that can be enhanced by the presence of hot carriers generated by an applied current. These results could prove crucial to drive graphene spintronic devices and, in particular, to sustain pure spin signals with thermal gradients and to tune the remote spin accumulation by varying the spin-injection bias

Flux-pinning mediated superconducting diode effect in NbSe2/CrGeTe3 heterostructure

In ferromagnet/superconductor bilayer systems, dipolar fields from the ferromagnet can create asymmetric energy barriers for the formation and dynamics of vortices through flux pinning. Conversely, the flux emanating from vortices can pin the domain walls of the ferromagnet, thereby creating asymmetric critical currents. Here, we report the observation of a superconducting diode effect (SDE) in a NbSe2/CrGeTe3 van der Waals heterostructure in which the magnetic domains of CrGeTe3 control the Abrikosov vortex dynamics in NbSe2. In addition to extrinsic vortex pinning mechanisms at the edges of NbSe2, flux-pinning-induced bulk pinning of vortices can alter the critical current. This asymmetry can thus be explained by considering the combined effect of this bulk pinning mechanism along with the vortex tilting induced by the Lorentz force from the transport current in the NbSe2/CrGeTe3 heterostructure. We also provide evidence of critical current modulation by flux pinning depending on the history of the field setting procedure. Our results suggest a method of controlling the efficiency of the SDE in magnetically coupled van der Waals superconductors, where dipolar fields generated by the magnetic layer can be used to modulate the dynamics of the superconducting vortices in the superconductors

The synergy between TB and HIV co-infection on perceived stigma in Ethiopia

<p>Abstract</p> <p>Background</p> <p>The synergy between tuberculosis (TB) and human immunodeficiency virus (HIV) co-infection on perceived stigma is not well studied. The objective of this study was to assess the effect of TB/HIV co-infection on perceived stigma in selected hospitals of Oromiya region, Ethiopia. A cross sectional study was conducted from February to April, 2009 in Adama, Nekemet and Jimma Specialized hospitals. Data were collected by trained HIV counselors. A structured questionnaire which consisted of socio-demographic variables, clinical information, perceived stigma, and depression was used to collect the data</p> <p>Findings</p> <p>A total of 591 participants were included in the study of whom 124 (20.9%) were co-infected with TB/HIV. The stigma items were highly reliable (Cronbach's alpha = 0.93) and had strong inter dimension correlation. Respondents who were co-infected with TB and HIV were more likely to have perceived stigma compared to non-co-infected HIV patients, [OR = 1.4, (95% CI: 1.2, 2.0)]. Non-literate individuals [OR = 1.9, (95% CI: 1.2, 3.0)] and females [OR = 1.6, (95% CI: 1.2, 2.3)] had also more perceived stigma.</p> <p>Conclusions</p> <p>TB/HIV co-infected patients, non-literate individuals and females were more likely to have high perceived stigma. Behavioral Change Communication should focus on these segments of the population to rectify the high perceived stigma.</p

Cooling and heating with electron spins: Observation of the spin Peltier effect

The Peltier coefficient describes the amount of heat that is carried by an electrical current when it passes through a material. Connecting two materials with different Peltier coefficients causes a net heat flow towards or away from the interface, resulting in cooling or heating at the interface - the Peltier effect. Spintronics describes the transport of charge and angular momentum by making use of separate spin-up and spin-down channels. Recently, the merger of thermoelectricity with spintronics has given rise to a novel and rich research field named spin caloritronics. Here, we report the first direct experimental observation of refrigeration/heating driven by a spin current, a new spin thermoelectric effect which we call the spin Peltier effect. The heat flow is generated by the spin dependency of the Peltier coefficient inside the ferromagnetic material. We explored the effect in a specifically designed spin valve pillar structure by measuring the temperature using an electrically isolated thermocouple. The difference in heat flow between the two magnetic configurations leads to a change in temperature. With the help of 3-D finite element modeling, we extracted permalloy spin Peltier coefficients in the range of -0.9 to -1.3 mV. These results enable magnetic control of heat flow and provide new functionality for future spintronic devices

The effect of household heads training about the use of treated bed nets on the burden of malaria and anaemia in under-five children: a cluster randomized trial in Ethiopia

<p>Abstract</p> <p>Background</p> <p>Long-lasting insecticide-treated bed nets (LLITN) have demonstrated a significant effect in reducing malaria-related morbidity and mortality. However, barriers on the utilization of LLITN have hampered the desired outcomes. The aim of this study was to assess the effect of community empowerment on the burden of malaria and anaemia in under-five children in Ethiopia.</p> <p>Methods</p> <p>A cluster randomized trial was done in 22 (11 intervention and 11 control) villages in south-west Ethiopia. The intervention consisted of tailored training of household heads about the proper use of LLITN and community network system. The burden of malaria and anaemia in under-five children was determined through mass blood investigation at baseline, six and 12 months of the project period. Cases of malaria and anaemia were treated based on the national protocol. The burden of malaria and anaemia between the intervention and control villages was compared using the complex logistic regression model by taking into account the clustering effect. Eight Focus group discussions were conducted to complement the quantitative findings.</p> <p>Results</p> <p>A total of 2,105 household heads received the intervention and the prevalence of malaria and anaemia was assessed among 2410, 2037 and 2612 under-five children at baseline, six and 12 months of the project period respectively. During the high transmission/epidemic season, children in the intervention arm were less likely to have malaria as compared to children in the control arm (OR = 0.42; 95%CI: 0.32, 0.57). Symptomatic malaria also steadily declined in the intervention villages compared to the control villages in the follow up periods. Children in the intervention arm were less likely to be anaemic compared to those in the control arm both at the high (OR = 0.84; 95%CI: 0.71, 0.99)) and low (OR = 0.73; 95%CI: 0.60, 0.89) transmission seasons.</p> <p>Conclusion</p> <p>Training of household heads on the utilization of LLITN significantly reduces the burden of malaria in under-five children. The Ministry of Health of Ethiopia in collaboration with other partners should design similar strategies in high-risk areas to control malaria in Ethiopia.</p> <p>Trial registration</p> <p>Australia and New Zealand Clinical Trials Register (ANZCTR): <a href="http://www.anzctr.org.au/ACTRN12610000035022.aspx">ACTRN12610000035022</a></p

Glucose intolerance and gestational diabetes risk in relation to sleep duration and snoring during pregnancy: a pilot study

<p>Abstract</p> <p>Background</p> <p>Insufficient sleep and poor sleep quality, considered endemic in modern society, are associated with obesity, impaired glucose tolerance and diabetes. Little, however, is known about the consequences of insufficient sleep and poor sleep quality during pregnancy on glucose tolerance and gestational diabetes.</p> <p>Methods</p> <p>A cohort of 1,290 women was interviewed during early pregnancy. We collected information about sleep duration and snoring during early pregnancy. Results from screening and diagnostic testing for gestational diabetes mellitus (GDM) were abstracted from medical records. Generalized linear models were fitted to derive relative risk (RR) and 95% confidence intervals (95% CIs) of GDM associated with sleep duration and snoring, respectively.</p> <p>Results</p> <p>After adjusting for maternal age and race/ethnicity, GDM risk was increased among women sleeping ≤ 4 hours compared with those sleeping 9 hours per night (RR = 5.56; 95% CI 1.31-23.69). The corresponding RR for lean women (<25 kg/m²) was 3.23 (95% CI 0.34-30.41) and 9.83 (95% CI 1.12-86.32) for overweight women (≥ 25 kg/m²). Overall, snoring was associated with a 1.86-fold increased risk of GDM (RR = 1.86; 95% CI 0.88-3.94). The risk of GDM was particularly elevated among overweight women who snored. Compared with lean women who did not snore, those who were overweight and snored had a 6.9-fold increased risk of GDM (95% CI 2.87-16.6).</p> <p>Conclusions</p> <p>These preliminary findings suggest associations of short sleep duration and snoring with glucose intolerance and GDM. Though consistent with studies of men and non-pregnant women, larger studies that include objective measures of sleep duration, quality and apnea are needed to obtain more precise estimates of observed associations.</p