Priorities in post harvest research support for sorghum and millet in eastern Africa

Meeting: Regional Sorghum and Millet Workshop, 6th, 20-27 July 1988, S

Analysis of progress and achievements in regional dehulling projects

Meeting: International Workshop on Policy, Practice and Potential Relating to Uses of Sorghum and Millets, 8-12 Feb. 1988, Bulawayo, Z

Priorities for applied research in the post harvest sector of rootcrops

Meeting: Eastern and Southern Africa Regional Root Crops Workshop, 3d, 7-11 Dec. 1987, Mzuzu, M

Priorities in post harvest research support for sorghum and millet in eastern Africa

Meeting: Regional Sorghum and Millet Workshop, 6th, 20-27 July 1988, S

Topological transitions in superconductor nanomembranes under a strong transport current

The topological defects, vortices in bulk superconductors (SCs) and phase slips in low-dimensional SCs are known to lead to the occurrence of a finite resistance. We report on a topological transition between the both types of topological defects under a strong transport current in an open SC nanotube with a submicron-scale inhomogeneity of the normal-to-the-surface component of the applied magnetic field. When the magnetic field is orthogonal to the axis of the nanotube, which carries the transport current in the azimuthal direction, the phase-slip regime is characterized by the vortex/antivortex lifetime ∼ 10−14 s versus the vortex lifetime ∼ 10−11 s for vortex chains in the half-tubes, and the induced voltage shows a pulse as a function of the magnetic field. The topological transition between the vortex-chain and phase-slip regimes determines the magnetic-field–voltage and current–voltage characteristics of curved SC nanomembranes to pursue high-performance applications in advanced electronics and quantum computing

Poisoning of bubble propelled catalytic micromotors: The chemical environment matters

Self-propelled catalytic microjets have attracted considerable attention in recent years and these devices have exhibited the ability to move in complex media. The mechanism of propulsion is via the Pt catalysed decomposition of H2O2 and it is understood that the Pt surface is highly susceptible to poisoning by sulphur-containing molecules. Here, we show that important extracellular thiols as well as basic organic molecules can significantly hamper the motion of catalytic microjet engines. This is due to two different mechanisms: (i) molecules such as dimethyl sulfoxide can quench the hydroxyl radicals produced at Pt surfaces and reduce the amount of oxygen gas generated and (ii) molecules containing -SH, -SSR, and -SCH3 moieties can poison the catalytically active platinum surface, inhibiting the motion of the jet engines. It is essential that the presence of such molecules in the environment be taken into consideration for future design and operation of catalytic microjet engines. We show this effect on catalytic micromotors prepared by both rolled-up and electrodeposition approaches, demonstrating that such poisoning is universal for Pt catalyzed micromotors. We believe that our findings will contribute significantly to this field to develop alternative systems or catalysts for self-propulsion when practical applications in the real environment are considered

Experimental methods of post-growth tuning of the excitonic fine structure splitting in semiconductor quantum dots

Deterministic sources of polarization entangled photon pairs on demand are considered as important building blocks for quantum communication technology. It has been demonstrated that semiconductor quantum dots (QDs), which exhibit a sufficiently small excitonic fine structure splitting (FSS) can be used as triggered, on-chip sources of polarization entangled photon pairs. As-grown QDs usually do not have the required values of the FSS, making the availability of post-growth tuning techniques highly desired. This article reviews the effect of different post-growth treatments and external fields on the FSS such as thermal annealing, magnetic fields, the optical Stark effect, electric fields, and anisotropic stress. As a consequence of the tuning of the FSS, for some tuning techniques a rotation of the polarization of the emitted light is observed. The joint modification of polarization orientation and FSS can be described by an anticrossing of the bright excitonic states

Transport in ZnCoO thin films with stable bound magnetic polarons

Diluted magnetic ZnCoO films with 5 at.% Co have been fabricated by pulsed laser deposition on c-plane sapphire substrates and Schottky and Ohmic contacts have been prepared in top-top configuration. The diode current is significantly reduced after the diode has been subjected to an external magnetic field. In the reverse bias range the corresponding positive magnetoresistance is persistent and amounts to more than 1800% (50 K), 240% (30 K), and 50% (5 K). This huge magnetoresistance can be attributed to the large internal magnetic field in depleted ZnCoO with ferromagnetic exchange between stable bound magnetic polarons

Ultracompact three-dimensional tubular conductivity microsensors for ionic and biosensing applications

We present ultracompact three-dimensional tubular structures integrating Au-based electrodes as impedimetric microsensors for the in-flow determination of mono- and divalent ionic species and HeLa cells. The microsensors show an improved performance of 2 orders of magnitude (limit of detection = 0.1 nM for KCl) compared to conventional planar conductivity detection systems integrated in microfluidic platforms and the capability to detect single HeLa cells in flowing phosphate buffered saline. These highly integrated conductivity tubular sensors thus open new possibilities for lab-in-a-tube devices for bioapplications such as biosensing and bioelectronics