Photoresponse of epitaxial YBa2Cu3O7-x ultrathin films

The voltage photoresponse of YBa2CH307_ x/SrTiO3 10 nm-tlfick films\ud on laser irradiation is studied using the low temperature scanning laser\ud microscopy (LTSLM) teclmique. The irradiation wavelength is 633 run.\ud The spatial response dependencies via temperature (4-100 K), beam\ud intensity modulation frequency (0-150 kHz) and bias current are\ud examined. The bolometric and non-bolometric components are\ud separated. The amplitude of the non-bolometric component at 4.2 K is\ud about 10 times higher than that of bolometric one measured near the\ud midpoint of the superconducting transition. The non-bolometric\ud component is presumably associated with weak links in the film due to\ud interdiffusion of SrTiO3 into YBCO layer. The spatial irregularity in\ud superconducting parameters is not resolved by the LTSLM method\ud since the spacing between weak links is appeared to be less than 1 um

Electric-field effect devices made of YBa2Cu3O7-x/SrTiO3 epitaxial multilayers

Three terminal superconducting electric-field effect devices, consisting of a bufferlayer of PrBa2Cu3O7-x, an ultrathin layer of YBa2Cu3O7-x and a SrTiO3 gate isolation layer were fabricated and successfully operated. Transmission electron microscopy and laser scanning microscopy showed that all layers are highly epitaxial and uniform over the device area. This is essentially important in the analysis of the mechanism of the electric field effect and for the reproducible fabrication of devices. With a 5 nm thick YBa2Cu3O7-x layer and an applied electric field of 0.85 MV/cm the critical current was decreased by 5% at low temperatures and up to 36% close to Tc. Also enhancement was obtained

A HREM study of the atomic structure and the growth mechanism of the YBa2Cu3O7/YSZ interface

The interface between yttria-stabilized zirconia (YSZ) substrate and YBa2Cu3O7 (YBCO) film was studied by high-resolution electron microscopy. In all specimens we have observed an intermediate layer of BaZrO3 located between the substrate YSZ and YBCO. The BaZrO3 layer is composed of almost equally aligned domains being 4¿8 nm in the lateral directions. Reaction products such as Y and Cu oxides were never observed in or close to the BaZrO3 reaction layer but they do occur in the YBCO film. The stacking sequence of BaZrO3/YBCO is predominantly (BaZrO3)-ZrO2-BaO/CuO-BaO-(YBCO) with CuO layer as the beginning YBCO layer. Sometimes a stacking sequence (BaZrO3)-ZrO2-BaO/BaO-CuO2-(YBCO) with a BaO layer as the beginning YBCO layer was observed. This stacking is related to a dislocation with Burgers vector a'/2 [111], where a' = 0.42 nm is the lattice constant of the cubic BaZrO3. Three main epitaxial relations (0°, 45°, 9°) between YSZ and YBCO were observed. These can be explained by near-coincidence site lattices ¿ = 25, ¿ = 49 and ¿ = 13 (for a YSZ substrate). Usually the (001) plane of the YBCO film is parallel to the (001) plane of the BaZrO3 layer and parallel to the substrate surface. In case YBCO is grown on an inclined YSZ substrate, the (001) plane of the YBCO film is parallel to the substrate surface and thus not parallel to the (001) plane of the YSZ substrate

Quasiparticle-injection effect in YBa2Cu3Ox-based planar structures

The supercurrent IS of a YBCO bridge can be modulated by the quasiparticle-injection current IG from YBCO/Au or YBCO/PBCO/Au junctions. The behavior of these structures is determined by two effects: 1) summation of the currents IS and IG in the YBCO bridge; 2) nonequilibrium suppression of the supercurrent IS by the quasiparticle-injection. The current gain coefficient ¿IS/¿IG increases linearly with decreasing temperature, reaching a value of 1.5 for YBCO/Au structures at 65 K. The nature of the nonequilibrium state and the effectiveness of the PBCO barrier layer for the formation of the quasiparticles are analyze

Multilayers for high-Tc superconducting electric field effect devices

Epitaxial multilayers, consisting of a PrBa2Cu3O7-x buffer layer, ultrathin YBa2Cu3O7-x and SrTiO3, have been grown for application in electric field effect devices. Different analytical techniques indicate a sharp interface between the layers and good dielectric properties of the SrTiO3-layer. First measurements show clear modification of the superconductor's current-voltage characteristics upon applying electric fields of 0.1-1 MV/cm

Quasiparticle injection effects in YBa2Cu3Ox-based planar structures at high operating temperatures

The modulation of the supercurrent Is of a YBCO bridge by the quasiparticle-injection current IG from the YBCO/Au or YBCO/PBCO/Au junctions at temperatures of 60¿85 K is determined by two effects: (1) summation of the currents IS and IG in the YBCO bridge, and (2) nonequilibrium suppression of IS by the quasiparticle injection. At a thickness of the PBCO barrier of 40 nm the modulation of IS can be described by the current-summation effect only. For YBCO/Au structures the current gain ¿IS/¿IG increases linearly with decreasing temperature, reaching the value of 2 at 60 K. Numerical simulations of the current- voltage characteristics show an increase of the effective temperature T* of the YBCO bridge under injection only at small thicknesses of the PBCO barrier. Visualization of the voltage drop over the junction area by laser scanning microscopy shows a qualitative agreement with the electrical measurements with respect to the current summation and nonequilibrium effects

Narratives and Counternarratives: Somali-Canadians on Recruitment as Foreign Fighters to Al-Shabaab

© 2015 The Author. Recently, the Somali diaspora has found itself at the centre of heightened security concerns surrounding the proliferation of international terrorist networks and their recruitment strategies. These concerns have reached new levels since the absorption of al-Shabaab into al-Qaeda in 2012. Based on a qualitative analysis of interviews with 118 members of Canada's largest Somali community, this article draws upon narrative criminology to reverse the 'why they joined' question that serves as the predicate for much recent radicalization scholarship, and instead explores, 'why they would never join'. We encounter Somali-Canadians equipping themselves with sophisticated counternarratives that vitiate the enticements of al-Shabaab. Particularly, notions of 'coolness', 'trickery' and 'religious perversion' mediate participants' perceptions of al-Shabaab and enable a self-empowering rejection of its recruitment narratives. In particular, we find resonances between the narratives of non-recruitsand 'bogeyman' narratives that exist commonly in many cultures. Theefficacy of these narratives for resilience is three-fold, positioning the recruiters as odious agents, recruits as weak-minded dupes and our participants as knowledgeable storytellers who can forewarnothers against recruitment to al-Shabaab.published_or_final_versio

Electric field effect on epitaxial YBa₂Cu₃O_7−x thin films

By applying a strong electric field perpendicular to the surface of an ultrathin, highly uniform epitaxial YBa2Cu3O7¿x film, the critical current was depressed and enhanced over 20% at temperatures close to Tc, and 5% at lower temperatures. Careful analysis of the electric field dependent I-V characteristics and Arrhenius plots indicate that the electric field effect can be interpreted as a change in the pinning potential and/or the vortex-antivortex interaction potential in the Kosterlitz-Thouless regime, as a result of a change in the carrier density in the superconductor

Epidemiology of orbital fractures in a large hospital in the Netherlands: results of implementation of a multidisciplinary orbital trauma team

Introduction:This study aims to describe the epidemiology, aetiology and therapy of orbital fractures in a large municipal hospital in The Hague, Netherlands, and to demonstrate the effectiveness of an integrated approach of orbital trauma care with a team consisting of an ophthalmologist, an orthoptist and an oral and maxillofacial (OMF) surgeon.Methods:We obtained data from patients with an orbital fracture between June 2015 until July 2018. Primary outcomes were the classification of orbital fractures and treatment (conservative or surgical).Results:182 patients were included in this study. The most common type of orbital fracture was an isolated orbital floor fracture (n=56, 30.8%). In most cases, therapy was conservative (69.2%). When surgical repair was indicated, a polydioxanone (PDS) plate was most commonly used (11.5%). The main cause of an orbital fracture was a fall accident (38.5%), followed by assault (32.4%). 32.4% of the patients were intoxicated with alcohol.Conclusion:In our study population, almost 70% (69.2%) of the patients were treated conservatively in our study. Compared to the international literature, this percentage is considerably higher than in other studies. In our opinion, our integrated approach to orbital trauma has led to a justifiable reduction of the proportion of cases receiving surgical intervention in orbital fractures. We would like to advocate the implementation of a similar team in other hospitals to improve the quality and cost-effectiveness of treatment in patients with orbital fractures.Imaging- and therapeutic targets in neoplastic and musculoskeletal inflammatory diseas

The caregiver’s experience of childhood cancer treatment in South Africa

Background: This study explored the treatment-related, financial and psychological experiences of caregivers during cancer treatment of their children in South Africa’s (SA) public and private sectors. Methods: In this exploratory study, three focus groups were conducted with caregivers of children undergoing cancer treatment in SA’s public healthcare sector. A fourth small focus group with two parents in the private sector was conducted online. A mixed-methods approach was employed using a combination of thematic analysis and grounded theory. Results: Of the 20 public sector caregivers, many expressed frustration at the number of visits to primary healthcare clinics before being referred. Caregivers had difficulties coping with and accepting the diagnosis, alongside managing continued care for the child and other children at home. Support received by family and community members was varied. Financial strain was an important concern. The two private sector parents indicated greater levels of support and no financial hardship, but expressed similar levels of emotional stress. Conclusion: These caregiver experiences indicate that improvements are urgently needed in the recognition of childhood cancer symptoms at primary healthcare level in SA. They also highlight a need for increased financial support from government through social grants, travel allowances and nutritional support