GaMnAs: layers, wires and dots

Thin layers of GaMnAs ferromagnetic semiconductor grown by molecular beam epitaxy on GaAs(001) substrates were studied. To improve their magnetic properties the post-growth annealing procedures were applied, using the surface passivation layers of amorphous arsenic. This post growth treatment effectively increases the ferromagnetic-to-paramagnetic phase transition temperature in GaMnAs, and provides surface-rich MnAs layer which can be used for formation of low dimensional structures such as superlattices. If the surface rich MnAs layer consists of MnAs dots, then it is possible to grow Mn-doped GaAs nanowiresComment: 15 pages, 14 figures. To be published in Proc. XXXVII International School on the Physics of Semiconducting Compounds "Jaszowiec 2008", June 2008, Polan

Semiconductor quantum ring as a solid-state spin qubit

The implementation of a spin qubit in a quantum ring occupied by one or a few electrons is proposed. Quantum bit involves the Zeeman sublevels of the highest occupied orbital. Such a qubit can be initialized, addressed, manipulated, read out and coherently coupled to other quantum rings. An extensive discussion of relaxation and decoherence is presented. By analogy with quantum dots, the spin relaxation times due to spin-orbit interaction for experimentally accessible quantum ring architectures are calculated. The conditions are formulated under which qubits build on quantum rings can have long relaxation times of the order of seconds. Rapidly improving nanofabrication technology have made such ring devices experimentally feasible and thus promising for quantum state engineering.Comment: 16 pages, 3 figure 3 table

Dynamic evaluation of renal electrolyte gradient by in situ tissue impedance studies

The combined operations of the loops of Henle (countercurrent multiplier) and the vasa recta (countercurrent exchanger) establish hypertonicity of the renal medulla with respect to the cortex. The extent of this hypertonicity or the magnitude of the cortico-papillary solute concentration gradient is of obvious physiological interest: The hypertonic milieu provides a driving force for water reabsorption in the collecting system and reflects the rate of solute delivery from the tubules to the interstitium as opposed to solute “washout” from the interstitium by the vasa recta blood

All-electrical measurement of spin injection in a magnetic pp-nn junction diode

Magnetic $p$-$n$ junction diodes are fabricated to investigate spin-polarized electron transport. The injection of spin-polarized electrons in a semiconductor is achieved by driving a current from a ferromagnetic injector (Fe), into a bulk semiconductor ($n$-GaAs) via schottky contact. For detection, a diluted magnetic semiconductor ($p$-GaMnAs) layer is used. Clear magnetoresistance was observed only when a high forward bias was applied across the $p$-$n$ junction.Comment: 4 pages, 4 figure

Information system purchase and integration contingencies when companies merge

This study grounds empirically the purchasing and further integration of an implemented information system set in the frenzied context of a corporate merger. A single longitudinal case study from the Norwegian pelagic seafood industry provides a detailed long-term account of developing the information system prior to, during and after a merger in the seafood industry that relies on wild catch. It is characterised by high dependence on features of nature and society to secure sustainable production. Contingency theory together with a process view of production reveals how interactions unfold over time to develop the new unified information system. Features of integration, interaction and interdependency represent different facets of information system purchase and development. The merger process represents an abnormality for the organisation as a continuous entity. Information system development in the case, therefore, takes place in a weakly integrated network of merging firms with severe time constraints. Given high uncertainty, solutions emerge through interaction. Deterministic optimisation is, in this context, a fluffy managerial dream. Normally, information system purchase and information system development involve reciprocal interdependencies involving mutual adjustments through intensive technologies and tight interaction among all parties involved. The coercive behaviour of management seeking efficiencies overrules these planning ideals. This indicates that purchasing, in a corporate merger context, is complex and approached as a complex system in a network. Solutions used in this approach originate because of emergent-networked interaction.publishedVersio

Qualitative and quantitative differences in the motor and somatosensory cortical projections of the rat claustrum — combined retrograde transport and stereological studies

Using axonal retrograde tracing, combined with morphometric analysis, we compared the distribution and number of claustral neurons projecting to the motor and somatosensory cortical areas in the Wistar rat. Comparable volumes of the retrograde tracer Fluoro-Gold, were injected into the motor or somatosensory cortices. Injections into these areas resulted in labeling of neurons along the entire length of the claustrum. Neurons retrogradely labeled after injection into the motor cortex prevailed in the anterior part of the claustrum, whereas those projecting to the somatosensory cortex predominated in the central part. The mean number of claustral neurons retrogradely labeled after tracer injections into the motor cortex significantly outnumbered that from the somatosensory cortical area (

Identification of clinical risk factors of atrial fibrillation in congestive heart failure

Background: Factors associated with the development of atrial fibrillation (AF) in generalpopulation have been described, but it is still unknown whether the same risk factors applyto heart failure (HF) patients. The aim of this study was to identify clinical factors related tovarious forms of AF in HF patients.Methods: The clinical and echocardiographic characteristics were assessed in 155 HF patients:50 with sinus rhythm, 52 with non-permanent AF, and 53 with permanent AF.Results: Multivariate logistic regression analysis showed that the increase in the NYHAclass was an independent risk factor for both forms of AF. The occurrence of permanent AF incomparison to sinus rhythm group was independently associated with hs-C-reactive protein(CRP) elevation above 1 mg/dL (OR 1.87, 95% CI 1.05–3.35), left atrial dimension above4 cm (OR 3.78, 95% CI 1.29–11.06) and tricuspid maximal pressure gradient elevation above35 mm Hg (OR 5.01, 95% CI 1.38–18.27). The presence of coronary disease was independentlyassociated with less frequent occurrence of permanent AF in comparison to sinus rhythm group(OR 0.21, 95% CI 0.06–0.67).Conclusions: More advanced congestive HF was associated with presence of both types of AF.Non-ischemic etiology of HF and elevated CRP are independently associated with permanentAF compared to sinus rhythm. Left ventricular diastolic dysfunction indicators (increasedtricuspid maximal pressure gradient and left artial dimension) are independently associatedwith permanent AF