Magnetotransport in Two-Dimensional Electron Systems with Spin-Orbit Interaction

We present magnetotransport calculations for homogeneous two-dimensional electron systems including the Rashba spin-orbit interaction, which mixes the spin-eigenstates and leads to a modified fan-chart with crossing Landau levels. The quantum mechanical Kubo formula is evaluated by taking into account spin-conserving scatterers in an extension of the self-consistent Born approximation that considers the spin degree of freedom. The calculated conductivity exhibits besides the well-known beating in the Shubnikov-de Haas (SdH) oscillations a modulation which is due to a suppression of scattering away from the crossing points of Landau levels and does not show up in the density of states. This modulation, surviving even at elevated temperatures when the SdH oscillations are damped out, could serve to identify spin-orbit coupling in magnetotransport experiments. Our magnetotransport calculations are extended also to lateral superlattices and predictions are made with respect to 1/B periodic oscillations in dependence on carrier density and strength of the spin-orbit coupling.Comment: 8 pages including 8 figures; submitted to PR

Spin Orientation and Spin Precession in Inversion-Asymmetric Quasi Two-Dimensional Electron Systems

Inversion asymmetry induced spin splitting of the electron states in quasi two-dimensional (2D) systems can be attributed to an effective magnetic field B which varies in magnitude and orientation as a function of the in-plane wave vector k||. Using a realistic 8x8 Kane model that fully takes into account spin splitting because of both bulk inversion asymmetry and structure inversion asymmetry we investigate the spin orientation and the effective field B for different configurations of a quasi 2D electron system. It is shown that these quantities depend sensitively on the crystallographic direction in which the quasi 2D system was grown as well as on the magnitude and orientation of the in-plane wave vector k||. These results are used to discuss how spin-polarized electrons can precess in the field B(k||). As a specific example we consider GaInAs-InP quantum wells.Comment: 10 pages, 6 figure

Novel C8orf37 mutations cause retinitis pigmentosa in consanguineous families of Pakistani origin

Purpose: To investigate the molecular basis of retinitis pigmentosa in two consanguineous families of Pakistani origin with multiple affected members. Methods: Homozygosity mapping and Sanger sequencing of candidate genes were performed in one family while the other was analyzed with whole exome next-generation sequencing. A minigene splicing assay was used to confirm the splicing defects. Results: In family MA48, a novel homozygous nucleotide substitution in C8orf37, c.244–2A>C, that disrupted the consensus splice acceptor site of exon 3 was found. The minigene splicing assay revealed that this mutation activated a cryptic splice site within exon 3, causing a 22 bp deletion in the transcript that is predicted to lead to a frameshift followed by premature protein truncation. In family MA13, a novel homozygous null mutation in C8orf37, c.555G>A, p.W185*, was identified. Both mutations segregated with the disease phenotype as expected in a recessive manner and were absent in 8,244 unrelated individuals of South Asian origin. Conclusions: In this report, we describe C8orf37 mutations that cause retinal dystrophy in two families of Pakistani origin, contributing further data on the phenotype and the spectrum of mutations in this form of retinitis pigmentosa

Biallelic Loss-of-Function NDUFA12 Variants Cause a Wide Phenotypic Spectrum from Leigh/Leigh-Like Syndrome to Isolated Optic Atrophy

BACKGROUND: Biallelic loss-of-function NDUFA12 variants have hitherto been linked to mitochondrial complex I deficiency presenting with heterogeneous clinical and radiological features in nine cases only. OBJECTIVES: To fully characterize, both phenotypically and genotypically, NDUFA12-related mitochondrial disease. METHODS: We collected data from cases identified by screening genetic databases of several laboratories worldwide and systematically reviewed the literature. RESULTS: Nine unreported NDUFA12 cases from six pedigrees were identified, with presentation ranging from movement disorder phenotypes (dystonia and/or spasticity) to isolated optic atrophy. MRI showed basal ganglia abnormalities (n = 6), optic atrophy (n = 2), or was unremarkable (n = 1). All carried homozygous truncating NDUFA12 variants, three of which are novel. CONCLUSIONS: Our case series expands phenotype–genotype correlations in NDUFA12-associated mitochondrial disease, providing evidence of intra- and inter-familial clinical heterogeneity for the same variant. It confirms NDUFA12 variants should be included in the diagnostic workup of Leigh/Leigh-like syndromes – particularly with dystonia – as well as isolated optic atrophy

Spintronics: Fundamentals and applications

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes from the published versio

An organelle-specific protein landscape identifies novel diseases and molecular mechanisms

Cellular organelles provide opportunities to relate biological mechanisms to disease. Here we use affinity proteomics, genetics and cell biology to interrogate cilia: poorly understood organelles, where defects cause genetic diseases. Two hundred and seventeen tagged human ciliary proteins create a final landscape of 1,319 proteins, 4,905 interactions and 52 complexes. Reverse tagging, repetition of purifications and statistical analyses, produce a high-resolution network that reveals organelle-specific interactions and complexes not apparent in larger studies, and links vesicle transport, the cytoskeleton, signalling and ubiquitination to ciliary signalling and proteostasis. We observe sub-complexes in exocyst and intraflagellar transport complexes, which we validate biochemically, and by probing structurally predicted, disruptive, genetic variants from ciliary disease patients. The landscape suggests other genetic diseases could be ciliary including 3M syndrome. We show that 3M genes are involved in ciliogenesis, and that patient fibroblasts lack cilia. Overall, this organelle-specific targeting strategy shows considerable promise for Systems Medicine

Hormone withdrawal-associated symptoms with ethinylestradiol 20 µg/drospirenone 3 mg (24/4 regimen) versus ethinylestradiol 20 µg/desogestrel 150 µg (21/7 regimen)

Johannes Bitzer,1 Maria Jesusa Banal-Silao,2 Hans-Joachim Ahrendt,3 Jaime Restrepo,4 Marion Hardtke,5 Ulrike Wissinger-Graefenhahn,6 Dietmar Trummer7 1Department of Obstetrics and Gynecology, University Hospital of Basel, Basel, Switzerland; 2University of the Philippines College of Medicine, Manila, Philippines; 3Praxis für Frauenheilkunde, Klinische Forschung und Weiterbildung (Clinical Research and Further Education), Magdeburg, Germany; 4Centro de Investigación Clínica, Clinica Medellin Poblado, Medellin, Colombia; 5Global Clinical Development Operations, Bayer Pharma AG, Berlin, Germany; 6Global Medical Affairs Women’s Healthcare, Bayer Pharma AG, Berlin, Germany; 7Clinical Statistics Europe, Bayer Pharma AG, Berlin, Germany Objective: To assess whether the combined oral contraceptive (COC) ethinylestradiol (EE) 20 µg/drospirenone 3 mg taken in a 24/4-day regimen (ie, 4-day hormone-free interval) is more effective than an EE 20 µg/desogestrel (DSG) 150 µg COC taken in a 21/7-day regimen (ie, 7-day hormone-free interval) in reducing hormone withdrawal-associated symptoms (HWAS).Methods: This double-blind, randomized study (NLM identifier: NCT01076582) was conducted at 34 centers in 12 countries. Otherwise healthy women who experienced ≥2 HWAS of headache, pelvic pain, and/or bloating when using their current COCs in a 21/7-day regimen were recruited. Subjects rated the severity of their HWAS daily on a seven-point Likert scale during a baseline cycle and during four 28-day cycles with EE/drospirenone 24/4 (n=290) or EE/DSG 21/7 (n=304). The primary variable was the mean change from baseline to cycle 4 in the composite HWAS score (sum of scores for all three symptoms) during cycle days 22–28.Results: In the EE/drospirenone 24/4 group, the mean (standard deviation) composite HWAS score during cycle days 22–28 was reduced from 42.2 (24.8) at baseline to 12.8 (13.4) at cycle 4 (change from baseline: -30.3 [22.9]). In the EE/DSG 21/7 group, the corresponding value was reduced from 41.9 (25.8) to 14.3 (13.2) (change from baseline: -27.7 [24.8]), not significantly different versus EE/drospirenone 24/4. Bleeding pattern, treatment response, rescue medication use, compliance, quality of life, and tolerability were similar between treatments.Conclusion: Both EE/drospirenone 24/4 and EE/DSG 21/7 reduced the composite HWAS score from baseline to cycle 4 in otherwise healthy women. The differences between treatments were too small to be statistically significant.Keywords: combined oral contraceptives, ethinylestradiol, drospirenone, desogestrel, hormone withdrawa