Orbital photogalvanic effects in quantum-confined structures

We report on the circular and linear photogalvanic effects caused by free-carrier absorption of terahertz radiation in electron channels on (001)-oriented and miscut silicon surfaces. The photocurrent behavior upon variation of the radiation polarization state, wavelength, gate voltage and temperature is studied. We present the microscopical and phenomenological theory of the photogalvanic effects, which describes well the experimental results. In particular, it is demonstrated that the circular (photon-helicity sensitive) photocurrent in silicon-based structures is of pure orbital nature originating from the quantum interference of different pathways contributing to the absorption of monochromatic radiation.Comment: 8 pages, 5 figures, two culumne

Cognitive rehabilitation in multiple sclerosis: A systematic review

Abstract Background Cognitive impairment is a common clinical feature of multiple sclerosis (MS) at both the earlier and later stages of the disease, and has a significant impact on patients' functional status and quality of life. The need to address this deficit should be taken into account in clinical practice and research studies. Objective To conduct an updated systematic review of all published studies of cognitive rehabilitation interventions in people with MS, including studies with methodological shortcomings, to highlight major strengths and weaknesses in the field and to provide directions for future research. Search methods We searched electronic databases (PubMed and Web of Science) for articles published in English up until January 2014. The reference lists of all identified articles were also searched to complete the initial list of references. Data extraction Articles were categorized into outcome measures: cognition, imaging, mood, fatigue, quality of life and self-perceived cognitive deficits. All articles were reviewed independently and assessed according to predetermined criteria. Results A total of 33 studies met the inclusion criteria of which 4 were of Level II-1 and none was Level I. Although the majority of these studies reported some improvements in cognitive abilities (N = 31), the evidence which has been reported in the literature remains inconclusive and no definite conclusions can be drawn about the effect of different types of interventions on cognitive rehabilitation outcomes (recommendation C). Conclusions This review identified conflicting findings in the published literature about the effectiveness of various forms of cognitive rehabilitation techniques used in patients with MS. Studies with more rigorous methodology are therefore needed to clarify which form of cognitive rehabilitation may lead to greater clinical improvement

Extending The Sleuth Kit and its underlying model for pooled storage file system forensic analysis

Carrier's book File System Forensic Analysis is one of the most comprehensive sources when it comes to the forensic analysis of file systems. Published in 2005, it provides details about the most commonly used file systems of that time as well as a process model to analyze file systems in general. The Sleuth Kit is the implementation of Carrier's model and it is still widely used during forensic analyses today—standalone or as a basis for forensic suites such as Autopsy. While The Sleuth Kit is still actively maintained, the model has not seen any updates since then. Moreover, there is no support for modern file systems implementing new paradigms such as pooled storage. In this paper, we present an update to Carrier's model which enables the analysis of pooled storage file systems. To demonstrate that our model is suitable, we implemented it for ZFS—a file system for large scale storage, cloud, and virtualization environments—and show how to perform an analysis of this file system using our model and extended toolkit

Observation of orbital circular photogalvanic effect

We report on the observation of the circular photogalvanic effect in Si-metal-oxide-semiconductor fieldeffect transistors with inversion channel excited by terahertz radiation. We demonstrate that in spite of the fact that the photocurrent is caused by transfer of the photon angular momentum to free carriers, it is not due to spin orientation but has a pure orbital origin. It results from the quantum interference of different pathways contributing to the free-carrier absorption of monochromatic radiation

Remobilization of Phytol from Chlorophyll Degradation Is Essential for Tocopherol Synthesis and Growth of Arabidopsis

vom Dorp K, Hölzl G, Plohmann C, et al. Remobilization of Phytol from Chlorophyll Degradation Is Essential for Tocopherol Synthesis and Growth of Arabidopsis. The Plant Cell. 2015;27(10): 2846–2859.Phytol from chlorophyll degradation can be phosphorylated to phytyl-phosphate and phytyl-diphosphate, the substrate for tocopherol (vitamin E) synthesis. A candidate for the phytyl-phosphate kinase from Arabidopsis thaliana (At1g78620) was identified via a phylogeny-based approach. This gene was designated VITAMIN E DEFICIENT6 (VTE6) because the leaves of the Arabidopsis vte6 mutants are tocopherol deficient. The vte6 mutant plants are incapable of photoautotrophic growth. Phytol and phytyl-phosphate accumulate, and the phytyl-diphosphate content is strongly decreased in vte6 leaves. Phytol feeding and enzyme assays with Arabidopsis and recombinant Escherichia coli cells demonstrated that VTE6 has phytyl-P kinase activity. Overexpression of VTE6 resulted in increased phytyl-diphosphate and tocopherol contents in seeds, indicating that VTE6 encodes phytyl-phosphate kinase. The severe growth retardation of vte6 mutants was partially rescued by introducing the phytol kinase mutation vte5. Double mutant plants (vte5 vte6) are tocopherol deficient and contain more chlorophyll, but reduced amounts of phytol and phytyl-phosphate compared with vte6 mutants, suggesting that phytol or phytyl-phosphate are detrimental to plant growth. Therefore, VTE6 represents the missing phytyl-phosphate kinase, linking phytol release from chlorophyll with tocopherol synthesis. Moreover, tocopherol synthesis in leaves depends on phytol derived from chlorophyll, not on de novo synthesis of phytyl-diphosphate from geranylgeranyl-diphosphate

Remobilization of Phytol from Chlorophyll Degradation Is Essential for Tocopherol Synthesis and Growth of Arabidopsis

Phytol from chlorophyll degradation can be phosphorylated to phytyl-phosphate and phytyl-diphosphate, the substrate for tocopherol (vitamin E) synthesis. A candidate for the phytyl-phosphate kinase from Arabidopsis thaliana (At1g78620) was identified via a phylogeny-based approach. This gene was designated VITAMIN E DEFICIENT6 (VTE6) because the leaves of the Arabidopsis vte6 mutants are tocopherol deficient. The vte6 mutant plants are incapable of photoautotrophic growth. Phytol and phytyl-phosphate accumulate, and the phytyl-diphosphate content is strongly decreased in vte6 leaves. Phytol feeding and enzyme assays with Arabidopsis and recombinant Escherichia coli cells demonstrated that VTE6 has phytyl-P kinase activity. Overexpression of VTE6 resulted in increased phytyl-diphosphate and tocopherol contents in seeds, indicating that VTE6 encodes phytyl-phosphate kinase. The severe growth retardation of vte6 mutants was partially rescued by introducing the phytol kinase mutation vte5. Double mutant plants (vte5 vte6) are tocopherol deficient and contain more chlorophyll, but reduced amounts of phytol and phytyl-phosphate compared with vte6 mutants, suggesting that phytol or phytyl-phosphate are detrimental to plant growth. Therefore, VTE6 represents the missing phytyl-phosphate kinase, linking phytol release from chlorophyll with tocopherol synthesis. Moreover, tocopherol synthesis in leaves depends on phytol derived from chlorophyll, not on de novo synthesis of phytyl-diphosphate from geranylgeranyl-diphosphate