Thermoelectric cross-plane properties on p- and n-Ge/SixGe1-x superlattices

Silicon and germanium materials have demonstrated an increasing attraction for energy harvesting, due to their sustainability and integrability with complementary metal oxide semiconductor and micro-electro-mechanical-system technology. The thermoelectric efficiencies for these materials, however, are very poor at room temperature and so it is necessary to engineer them in order to compete with telluride based materials, which have demonstrated at room temperature the highest performances in literature [1]. Micro-fabricated devices consisting of mesa structures with integrated heaters, thermometers and Ohmic contacts were used to extract the cross-plane values of the Seebeck coefficient and the thermal conductivity from p- and n-Ge/SixGe1-x superlattices. A second device consisting in a modified circular transfer line method structure was used to extract the electrical conductivity of the materials. A range of p-Ge/Si0.5Ge0.5 superlattices with different doping levels was investigated in detail to determine the role of the doping density in dictating the thermoelectric properties. A second set of n-Ge/Si0.3Ge0.7 superlattices was fabricated to study the impact that quantum well thickness might have on the two thermoelectric figures of merit, and also to demonstrate a further reduction of the thermal conductivity by scattering phonons at different wavelengths. This technique has demonstrated to lower the thermal conductivity by a 25% by adding different barrier thicknesses per period

Ultra-high critical current densities of superconducting YBa2_2Cu3_3O7−δ_{7-\delta} thin films in the overdoped state

Doping is one of the most relevant paths to tune the functionality of cuprates, it determines carrier density and the overall physical properties of these impressive superconducting materials. We present an oxygen doping study of YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO) thin films from underdoped to overdoped state, correlating the measured charge carrier density, $n_\textrm{H}$, the hole doping, $p$, and the critical current density, $J_\textrm{c}$. Our results show a continuous increase of $J_\textrm{c}$ with charge carrier density, reaching 90 MA/cm$^2$ at 5 K for $p$-doping at the Quantum Critical Point (QCP), linked to an increase of the superconducting condensation energy. The ultra-high $J_\textrm{c}$ achived corresponds to a third of the depairing current, i.e. a value 60 % higher than ever reported in YBCO films. The overdoped regime is characterized by a sudden increase of $n_\textrm{H}$, associated to the reconstruction of the Fermi-surface at the QCP. Overdoping YBCO opens a promising route to extend the current carrying capabilities of REBCO coated conductors for applications

Oblique roughness replication in strained SiGe/Si multilayers

The replication of the interface roughness in SiGe/Si multilayers grown on miscut Si(001) substrates has been studied by means of x-ray reflectivity reciprocal space mapping. The interface profiles were found to be highly correlated and the direction of the maximal replication was inclined with respect to the growth direction. This oblique replication is explained by the influence of the inhomogeneous strain distribution around step bunches. The formation of step bunches is described by a kinetic step-flow model based on the work by Tersoff et al. [Phys. Rev. Lett. 75, 2730 (1995)]. We have generalized this model by taking into account local variations of the in-plane strain. The angle of obliqueness deduced from these calculations agrees very well with the experimental findings

Immunotherapeutic targeting of membrane Hsp70-expressing tumors using recombinant human granzyme B

Background: We have previously reported that human recombinant granzyme B (grB) mediates apoptosis in membrane heat shock protein 70 (Hsp70)-positive tumor cells in a perforin-independent manner

Metatranscriptomics captures dynamic shifts in mycorrhizal coordination in boreal forests

Carbon storage and cycling in boreal forests—the largest terrestrial carbon store—ismoderated by complex interactions between trees and soil microorganisms. However,existing methods limit our ability to predict how changes in environmental conditionswill alter these associations and the essential ecosystem services they provide. To addressthis, we developed a metatranscriptomic approach to analyze the impact of nutrientenrichment on Norway sprucefine roots and the community structure, function, andtree–microbe coordination of over 350 root-associated fungal species. In response toaltered nutrient status, host trees redefined their relationship with the fungal commu-nity by reducing sugar efflux carriers and enhancing defense processes. This resulted ina profound restructuring of the fungal community and a collapse in functional coordi-nation between the tree and the dominant Basidiomycete species, and an increase infunctional coordination with versatile Ascomycete species. As such, there was a func-tional  shift  in  community  dominance  from  Basidiomycetes  species,  with  importantroles in enzymatically cycling recalcitrant carbon, to Ascomycete species that have mela-nized cell walls that are highly resistant to degradation. These changes were accompa-nied  by  prominent  shifts  in  transcriptional  coordination  between  over  60  predictedfungal effectors, with more than 5,000 Norway spruce transcripts, providing mechanis-tic insight into the complex molecular dialogue coordinating host trees and their fungalpartners. The host–microbe dynamics captured by this study functionally inform howthese complex and  sensitive biological  relationships may mediate  the carbon  storagepotential of boreal soils under changing nutrient conditions

A New Combined European Permanent Network Station Coordinates Solution

The EUREF (International Association of Geodesy (IAG) Reference Frame Sub-Commission for Europe) network of continuously operating GPS stations (EPN) was primarily established for reference frame maintenance, and also plays an important role for geodynamical research in Europe. The main goal of this paper is to obtain an independent homogeneous time-series of the EPN station coordinates, which is also available in SINEX format. A new combined solution of the EPN station coordinates was computed. The combination was performed independently for every week, in three steps: 1. the stated constraints on the coordinates were removed from the individual solutions of the Analysis Centers; 2. the de-constrained solutions were aligned to ITRF2000; 3. the resulting solutions were combined using the Helmert block-ing technique. All the data from GPS week 900 to week 1302 (April 1997 - December 2004) were used. We investigated in detail the behavior of the transformation parameters aligning the new combined solution to ITRF2000. In general, the time-series of the transformation parameters show a good stability in time although small systematic effects can be seen, most likely caused by station instabilities. A comparison of the new combined solution to the official EUREF weekly combined solution is also presented