Two-photon spin injection in semiconductors

A comparison is made between the degree of spin polarization of electrons excited by one- and two-photon absorption of circularly polarized light in bulk zincblende semiconductors. Time- and polarization-resolved experiments in (001)-oriented GaAs reveal an initial degree of spin polarization of 49% for both one- and two-photon spin injection at wavelengths of 775 and 1550 nm, in agreement with theory. The macroscopic symmetry and microscopic theory for two-photon spin injection are reviewed, and the latter is generalized to account for spin-splitting of the bands. The degree of spin polarization of one- and two-photon optical orientation need not be equal, as shown by calculations of spectra for GaAs, InP, GaSb, InSb, and ZnSe using a 14x14 k.p Hamiltonian including remote band effects. By including the higher conduction bands in the calculation, cubic anisotropy and the role of allowed-allowed transitions can be investigated. The allowed-allowed transitions do not conserve angular momentum and can cause a high degree of spin polarization close to the band edge; a value of 78% is calculated in GaSb, but by varying the material parameters it could be as high as 100%. The selection rules for spin injection from allowed-allowed transitions are presented, and interband spin-orbit coupling is found to play an important role.Comment: 12 pages including 7 figure

Extracting surface representations from rim curves

LNCS v. 3852 is the conference proceedings of ACCV 2006In this paper, we design and implement a novel method for constructing a mixed triangle/quadrangle mesh from the 3D space curves (rims) estimated from the profiles of an object in an image sequence without knowing the original 3D topology of the object. To this aim, a contour data structure for representing visual hull, which is different from that for CT/MRI, is introduced. In this paper, we (1) solve the "branching structure" problem by introducing some additional "directed edge", and (2) extract a triangle/ quadrangle closed mesh from the contour structure with an algorithm based on dynamic programming. Both theoretical demonstration and real world results show that our proposed method has sufficient robustness with respect to the complex topology of the object, and the extracted mesh is of high quality. © Springer-Verlag Berlin Heidelberg 2006.postprintThe 7th Asian Conference on Computer Vision (ACCV 2006), Hyderabad, India, 13-16 January 2006. In Lecture Notes in Computer Science, 2006, v. 3852, p. 732-74

Safe and complete contig assembly via omnitigs

Contig assembly is the first stage that most assemblers solve when reconstructing a genome from a set of reads. Its output consists of contigs -- a set of strings that are promised to appear in any genome that could have generated the reads. From the introduction of contigs 20 years ago, assemblers have tried to obtain longer and longer contigs, but the following question was never solved: given a genome graph $G$ (e.g. a de Bruijn, or a string graph), what are all the strings that can be safely reported from $G$ as contigs? In this paper we finally answer this question, and also give a polynomial time algorithm to find them. Our experiments show that these strings, which we call omnitigs, are 66% to 82% longer on average than the popular unitigs, and 29% of dbSNP locations have more neighbors in omnitigs than in unitigs.Comment: Full version of the paper in the proceedings of RECOMB 201

Improving teaching: Enhancing ways of being university teachers

My aim in this paper is to theorize my teaching in a course for experienced university teachers, in a context of increased attention to such courses. My focus in the course is transforming and enhancing ways of being university teachers, through integrating knowing, acting and being. In other words, epistemology is not seen as an end in itself, but rather it is in the service of ontology. In the paper, I explore and illustrate how this focus on ontology is enacted in the course

Massive multiplication of genome and ribosomes in dormant cells (akinetes) of Aphanizomenon ovalisporum (Cyanobacteria)

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in The ISME Journal 6 (2012): 670–679, doi:10.1038/ismej.2011.128.Akinetes are dormancy cells commonly found among filamentous cyanobacteria, many of which are toxic and/or nuisance, bloom-forming species. Development of akinetes from vegetative cells is a process that involves morphological and biochemical modifications. Here we applied a single cell approach to quantify genome and ribosome content of akinetes and vegetative cells in Aphanizomenon ovalisporum (Cyanobacteria). Vegetative cells of A. ovalisporum were naturally polyploid and contained on average 8 genome copies per cell. However, the chromosomal content of akinetes increased up to 450 copies, with an average value of 119 genome copies per akinete, 15 fold higher that in vegetative cells. Based on fluorescence in situ hybridization with a probe targeting 16S rRNA and detection with confocal laser scanning microscopy we conclude that ribosomes accumulated in akinetes to a higher level than that found in vegetative cells. We further present evidence that this massive accumulation of nucleic acids in akinetes is likely supported by phosphate supplied from inorganic polyphosphate bodies that were abundantly present in vegetative cells, but notably absent from akinetes. These results are interpreted in the context of cellular investments for proliferation following long term dormancy, as the high nucleic acid content would provide the basis for extended survival, rapid resumption of metabolic activity and cell division upon germination.Supported by the Gruss Lipper Foundation research award (AS). This study was part of the Joint German-Israeli-Project (FKZ 02WT0985, WR803) funded by the German Ministry of Research and Technology (BMBF) and Israel Ministry of Science and Technology (MOST)

Role of Antiplatelet Therapy in Patients Managed for Complex Aortic Aneurysms using Fenestrated or Branched Endovascular Repair

Abstract Objective Despite the increasing number of fenestrated and branched endovascular aortic repair (F/B-EVAR) procedures, evidence on post-operative antiplatelet therapy is very limited. This study aimed to investigate the role of single antiplatelet therapy (SAPT) vs. double antiplatelet therapy (DAPT) after F/B-EVAR in 30 day and follow up outcomes. Methods A multicentre retrospective analysis was conducted, including F/B-EVAR patients managed from 1 January 2018 to 31 December 2022. Comparative outcomes were assessed according to post-operative antiplatelet therapy. The cohort was divided into the SAPT group (acetylsalicylic acid [ASA] or clopidogrel) and DAPT group (ASA and clopidogrel). The duration of SAPT or DAPT was one to six months. Primary outcomes were 30 day death, and cardiovascular ischaemic and major haemorrhagic events. Secondary outcomes were survival and target vessel (TV) patency during follow up. Results A total of 1 430 patients were included: 955 under SAPT and 475 under DAPT. The 30 day mortality rate was similar (SAPT 2.1% vs. DAPT 1.5%; p = .42). Cardiovascular ischaemic events were lower in the DAPT group (SAPT 11.9% vs. DAPT 8.2%; p = .040), with DAPT being an independent protector for acute mesenteric (p = .009) and lower limb ischaemia (p = .020). No difference was found in 30 day major haemorrhagic events (SAPT 7.5% vs. DAPT 6.3%; p = .40). The mean follow up was 21.8 ± 2.9 months. Cox regression showed no survival confounders, with similar rates between groups (log rank p = .71). DAPT patients enjoyed higher TV patency (SAPT 93.4%, standard error [SE] 0.7% vs. DAPT 97.0%, SE 0.6%; log rank p = .007) at thirty six months. Cox regression revealed B-EVAR as a predictor of worse TV patency (hazard ratio 2.03, 95% confidence interval 1.36 – 3.03; p < .001). DAPT was related to higher patency within B-EVAR patients (SAPT 87.2%, SE 2.1% vs. DAPT 94.9%, SE 1.9%; p < .001). Conclusion DAPT after F/B-EVAR was associated with lower risk of cardiovascular ischaemic events and higher TV patency, especially in B-EVAR cases. No difference in major haemorrhagic events was observed at 30 day