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With an optically active langasite (LGS) crystal as the electro-optic Q-switch, we demonstrate an efficient Q-switched laser with a repetition rate of 200 kHz. Based on the theoretical analysis of the interaction between optical activity and electro-optic property, the optical activity of the crystal has no influence on the birefringence during Q-switching if the quarter wave plate used was rotated to align with the polarization direction. With a Nd:LuVO4 crystal possessing a large emission cross-section and a short fluorescence lifetime as the gain medium, a stable LGS Q-switched laser was designed with average output power of 4.39 W, corresponding to a slope efficiency of 29.4% and with a minimum pulse width of 5.1 ns. This work represents the highest repetition rate achieved so far in a LGS Q-switched laser and it can provide a practical Q-switched laser with a tunable high repetition rates for many applications, such as materials processing, laser ranging, medicine, military applications, biomacromolecule materials, remote sensing, etc.

A monolithically integrated mode-locked semiconductor laser is proposed. The compound ring cavity is composed of a colliding pulse mode-locking (ML) subcavity and a passive Fabry-Perot feedback subcavity. These two 1.6 mm long subcavities are coupled by using on-chip reflectors at both ends, enabling harmonic mode locking. By changing DC-bias conditions, optical mode spacing from 50 to 450 GHz is experimentally demonstrated. Ultrafast pulses shorter than 0.3 ps emitted from this laser diode are shown in autocorrelation traces. ; European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 642355 FiWiN5G, Spanish Ministerio de Economia y Competitividad DiDACTIC project (TEC2013-47753-C3-3-R), and Consejería de Educación, Juventud y Deporte of Comunidad de Madrid DIFRAGEOS project (P2013/ICE-3004).

We report on the direct low-repetition rate femtosecond pulse laser microfabrication of optical waveguides in KTP crystals and the characterization of refractive index changes after the thermal annealing of the sample, with the focus on studying the potential for direct laser fabricating Mach-Zehnder optical modulators. We have fabricated square cladding waveguides by means of stacking damage tracks, and found that the refractive index decrease is large for vertically polarized light (c-axis; TM polarized) but rather weak for horizontally polarized light (a-axis; TE polarized), this leading to good near-infrared light confinement for TM modes but poor for TE modes. However, after performing a sample thermal annealing we have found that the thermal process enables a refractive index increment of around 1.5x10−3 for TE polarized light, while maintaining the negative index change of around −1x10−2 for TM polarized light. In order to evaluate the local refractive index changes we have followed a multistep procedure: We have first characterized the waveguide cross-sections by means of Raman micro-mapping to access the lattice micro-modifications and their spatial extent. Secondly we have modeled the waveguides following the modified region sizes obtained by micro-Raman with finite element method software to obtain a best match between the experimental propagation modes and the simulated ones. Furthermore we also report the fabrication of Mach-Zehnder structures and the evaluation of propagation losses. ; This work was partially supported by the Ministerio de Economía y Competitividad, under Project FIS2013-44174-P, by the Spanish Government under project MAT2013-47395-C4-4-R and TEC2014-55948-R and by the Generalitat de Catalunya under project 2014SGR1358. F.D. acknowledges additional support through the ICREA academia award 2010ICREA-02 for excellence in research.

18 pags, 11 figs, 5 tabs ; Here, we illustrate what happens inside the catalytic cleft of an enzyme when substrate or ligand binds on single-millisecond timescales. The initial phase of the enzymatic cycle is observed with near-atomic resolution using the most advanced X-ray source currently available: the European XFEL (EuXFEL). The high repetition rate of the EuXFEL combined with our mix-and-inject technology enables the initial phase of ceftriaxone binding to the Mycobacterium tuberculosis β-lactamase to be followed using time-resolved crystallography in real time. It is shown how a diffusion coefficient in enzyme crystals can be derived directly from the X-ray data, enabling the determination of ligand and enzyme-ligand concentrations at any position in the crystal volume as a function of time. In addition, the structure of the irreversible inhibitor sulbactam bound to the enzyme at a 66 ms time delay after mixing is described. This demonstrates that the EuXFEL can be used as an important tool for biomedically relevant research. ; This work was supported by the National Science Foundation Science and Technology Center 'BioXFEL' through award STC-1231306, and in part by the US Department of Energy, Office of Science, Basic Energy Sciences under contract DESC0002164 (AO, algorithm design and development) and by the National Science Foundation under contract Nos. 1551489 (AO, underlying analytical models) and DBI-2029533 (AO, functional conformations). This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. 1450681 to JLO. The work was also supported by funds from the National Institutes of Health grant R01 GM117342-0404. Funding and support are also acknowledged from the National Institutes of Health grant R01 GM095583, from the Biodesign Center for Applied Structural Discovery at ASU, from National Science Foundation award No. 1565180 and the US Department of Energy through Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. KAZ was supported by the Cornell Molecular Biophysics Training Program (NIH T32-GM008267). This work was also supported by the Cluster of Excellence 'CUI: Advanced Imaging of Matter' of the Deutsche Forschungsgemeinschaft (DFG), EXC 2056, project ID 390715994. CFEL is supported by the Gottfried Wilhelm Leibniz Program of the DFG, the 'X-probe' project funded by the European Union 2020 Research and Innovation Program under Marie Sklodowska-Curie grant agreement 637295, the European Research Council, 'Frontiers in Attosecond X-ray Science: Imaging and Spectroscopy (AXSIS)', ERC-2013-SyG 609920, and the Human Frontiers Science Program grant RGP0010 2017. This work is also supported by the AXSIS project funded by the European Research Council under the European Union Seventh Framework Program (FP/2007-2013)/ERC Grant Agreement No. 609920. ; Peer reviewed

Die Lasertechnologie bietet Vorteile im Vergleich zu konventionellen, mechanischen Verfahren zur Mikromaterialbearbeitung. Eine Vielzahl von praxisrelevanten Werkstoffen lässt sich flexibel und ohne Werkzeugverschleiß strukturieren. Dieser Beitrag betrachtet die Senkung der Prozesszeit mittels angepasster Laser- und Prozessparameter. Die Bewertung der Arbeitsergebnisse erfolgte anhand der Abtragseffizienz sowie der Oberflächen- und Randzoneneigenschaften nach der Laserbearbeitung.
 
Laser technology offers advantages over conventional mechanical methods for micro machining. A large number of relevant materials can be structured flexibly without tool wear. This article considers the reduction of process time by means of adapted laser and process parameters. The results were evaluated based on the ablation efficiency as well as the surface topography and subsurface properties after laser processing.

The current study considers grade repetition rates in the early years of school, Prep to Year 3, in Queensland state schools, of which there is a significant gap in the Australian research literature. Data accessed from the Queensland Government's Department of Education and Training (DET), shows that particular groups of students are more at risk of being repeated in the Preschool/Prep year. These groups include boys and until recently, Non-Indigenous students. However, the most recent data collected in 2009 shows that Indigenous students are more at risk of being repeated in all early years of schooling. As grade repetition has been shown to have limited value, it remains a concern that this intervention practice continues to be offered to students, and in particular Indigenous students, who may already be educationally disadvantaged. While grade repetition rates are low in Queensland state schools, the possible negative academic, social and emotional consequences for students who are repeated warrants serious re-evaluation of this long-term, early intervention practice in Australian schools.

Despite the Indian government's continuing efforts to encourage children to attend school, levels of educational wellbeing among some groups of children during their elementary schooling remain low. High school dropout and grade repetition rates are among the negative and deleterious outcomes of poor educational wellbeing in children that are rarely discussed as policy issues. Using the panel dataset of the India Human Development Survey (IHDS) conducted in 2005 and 2012, this study explores the effects of educational wellbeing on children's later educational outcomes, as measured by their school dropout and grade repetition rates. Variation in the educational outcomes of children across states was also examined. The results show that the children whose educational wellbeing index was below average during their elementary schooling were more likely to drop out of school or repeat a grade in early adolescence. For policymakers, this study highlights that the experiences of children during their elementary schooling merit more attention.

The current investigation was an examination of the repetition-to-repetition magnitudes and changes in kinetic and kinematic characteristics of the back squat using accentuated eccentric loading (AEL) and cluster sets. Trained male subjects (age = 26.1 ± 4.1 years, height = 183.5 ± 4.3 cm, body mass = 92.5 ± 10.5 kg, back squat to body mass ratio = 1.8 ± 0.3) completed four load condition sessions, each consisting of three sets of five repetitions of either traditionally loaded straight sets (TL), traditionally loaded cluster sets (TLC), AEL cluster sets (AEC), and AEL straight sets where only the initial repetition had eccentric overload (AEL1). Eccentric overload was applied using weight releasers, creating a total eccentric load equivalent to 105% of concentric one repetition maximum (1RM). Concentric load was 80% 1RM for all load conditions. Using straight sets (TL and AEL1) tended to decrease peak power (PP) (d = −1.90 to −0.76), concentric rate of force development (RFDCON) (d = −1.59 to −0.27), and average velocity (MV) (d = −3.91 to −1.29), with moderate decreases in MV using cluster sets (d = −0.81 to −0.62). Greater magnitude eccentric rate of force development (RFDECC) was observed using AEC at repetition three (R3) and five (R5) compared to all load conditions (d = 0.21–0.65). Large within-condition changes in RFDECC from repetition one to repetition three (∆REP1–3) were present using AEL1 (d = 1.51), demonstrating that RFDECC remained elevated for at least three repetitions despite overload only present on the initial repetition. Overall, cluster sets appear to permit higher magnitude and improved maintenance of concentric outputs throughout a set. Eccentric overload with the loading protocol used in the current study does not appear to potentiate concentric output regardless of set configuration but may cause greater RFDECC compared to traditional loading.

We consider Incremental Redundancy Hybrid Automatic Repeat reQuest (IR-HARQ) in which the code rate and modulation of the initial transmission and all retransmissions are adjusted based on average channel statistics. In the absence of instantaneous channel state information at the transmitter (CSIT), we present a method which computes, prior to transmission, the optimum code rates and modulations and explicitly considers a given maximum number of retransmissions. For the case that additional feedback on CSI of previous transmission attempts is available, we present two heuristic schemes which exploit this knowledge and offer increased throughput at the cost of higher computational complexity. We employ a rate-adaptive non-binary LDPC coding scheme which makes use of non-binary repetitions. While this coding scheme is particularly well-suited for adaptive IR-HARQ, we note that the presented analysis can be applied to any other channel code which employs soft decoding. ; Grant number : This work was supported by the Catalan and Spanish Governments under SGR-RC (2009SGR1046). © 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

Inclusive education is described as an 'apprenticeship in democracy' as it is concerned with the identification and dismantling of exclusionary practices in schools. One such practice is grade repetition, which is known to result in school disaffection and early school leaving. In South Africa, grade repetition is disproportionately experienced by black and poor learners, resulting in the unequal realization of the democratic right to education. The rate of grade repetition in this country is high, but little is known about teachers' beliefs about the practice. This article presents the results of a self-administered questionnaire in which Johannesburg teachers described what they regarded as the benefits and drawbacks of grade repetition. The data showed that teachers believe that the additional time spent in a repeated year compensates for immaturity, allows learners to 'catch up', and be better prepared for the subsequent grade. Teachers do acknowledge negative emotional and behavioural consequences of grade repetition, but many see no drawbacks to the practice. These beliefs are discussed with reference to the context in which they are engendered, with particular focus on the strong teacher and curriculum control over the pace at which knowledge acquisition is expected. It is argued that addressing the high levels of grade repetition will need critical examination of both the teacher beliefs that sustain the practice, and the habits of schools that make failure inevitable for some learners.