Sub two-cycle soliton-effect pulse compression at 800 nm in Photonic Crystal Fibers

The possibility of soliton self-compression of ultrashort laser pulses down to the few-cycle regime in photonic crystal fibers is numerically investigated. We show that efficient sub-two-cycle temporal compression of nanojoule-level 800 nm pulses can be achieved by employing short (typically 5-mm-long) commercially available photonic crystal fibers and pulse durations of around 100 fs, regardless of initial linear chirp, and without the need of additional dispersion compensation techniques. We envisage applications in a new generation of compact and efficient sub-two cycle laser pulse sources.Comment: 16 pages, 6 figure

Quantum non-demolition measurements of single donor spins in semiconductors

We propose a technique for measuring the state of a single donor electron spin using a field-effect transistor induced two-dimensional electron gas and electrically detected magnetic resonance techniques. The scheme is facilitated by hyperfine coupling to the donor nucleus. We analyze the potential sensitivity and outline experimental requirements. Our measurement provides a single-shot, projective, and quantum non-demolition measurement of an electron-encoded qubit state.Comment: 8+ pages. 4 figures. Published versio

Awakening the Entrepreneurial Spirit: Exploring the Relationship Between Organizational Factors and Perceptions of Entrepreneurial Self-Efficacy and Desirability in a Corporate Setting

While efforts at understanding how the entrepreneurial spirit is awakened (e.g., unwrapping the cognitive “black box”) have been productive in the new venture context, it remains largely unexplored in a corporate setting.This study extends previous research by investigating the relationship between organizational antecedents and perceptions of entrepreneurial self-efficacy and desirability of entrepreneurial activity. In a field study of organizations consistent with a corporate entrepreneurial archetype typology, we found that (1) individual work discretion and time availability impacted entrepreneurial self-efficacy, and (2) individual interest in work innovation influenced perceived desirability of innovative behaviors

Accuracy of genomic selection in simulated populations mimicking the extent of linkage disequilibrium in beef cattle

<p>Abstract</p> <p>Background</p> <p>The success of genomic selection depends mainly on the extent of linkage disequilibrium (LD) between markers and quantitative trait loci (QTL), the number of animals in the training set (TS) and the heritability (h²) of the trait. The extent of LD depends on the genetic structure of the population and the density of markers. The aim of this study was to calculate accuracy of direct genomic estimated breeding values (DGEBV) using best linear unbiased genomic prediction (GBLUP) for different marker densities, heritabilities and sizes of the TS in simulated populations that mimicked previously reported extent and pattern of LD in beef cattle.</p> <p>Results</p> <p>The accuracy of DGEBV increased significantly (p < 0.05) with the increase in the number of bulls in the TS (480, 960 or 1920), trait h²(0.10, 0.25 or 0.40) and marker densities (40 k or 800 k). Increasing the number of animals in the TS by 4-fold and using their phenotypes to estimate marker effects was not sufficient to maintain or increase the accuracy of DGEBV obtained using estimated breeding values (EBVs) when the trait h²was lower than 0.40 for both marker densities. Comparing to expected accuracies of parent average (PA), the gains by using DGEBV would be of 27%, 13% and 10% for trait h²equal to 0.10, 0.25 and 0.40, respectively, considering the scenario with 40 k markers and 1920 bulls in TS.</p> <p>Conclusions</p> <p>As reported in dairy cattle, the size of the TS and the extent of LD have major impact on the accuracy of DGEBV. Based on the findings of this simulation study, large TS, as well as dense marker panels, aiming to increase the level of LD between markers and QTL, will likely be needed in beef cattle for successful implementation of genomic selection.</p

Symbolic stochastic dynamical systems viewed as binary N-step Markov chains

A theory of systems with long-range correlations based on the consideration of binary N-step Markov chains is developed. In the model, the conditional probability that the i-th symbol in the chain equals zero (or unity) is a linear function of the number of unities among the preceding N symbols. The correlation and distribution functions as well as the variance of number of symbols in the words of arbitrary length L are obtained analytically and numerically. A self-similarity of the studied stochastic process is revealed and the similarity group transformation of the chain parameters is presented. The diffusion Fokker-Planck equation governing the distribution function of the L-words is explored. If the persistent correlations are not extremely strong, the distribution function is shown to be the Gaussian with the variance being nonlinearly dependent on L. The applicability of the developed theory to the coarse-grained written and DNA texts is discussed.Comment: 14 pages, 13 figure

Electrical activation and electron spin resonance measurements of implanted bismuth in isotopically enriched silicon-28

We have performed continuous wave and pulsed electron spin resonance measurements of implanted bismuth donors in isotopically enriched silicon-28. Donors are electrically activated via thermal annealing with minimal diffusion. Damage from bismuth ion implantation is repaired during thermal annealing as evidenced by narrow spin resonance linewidths (B_pp=12uT and long spin coherence times T_2=0.7ms, at temperature T=8K). The results qualify ion implanted bismuth as a promising candidate for spin qubit integration in silicon.Comment: 4 pages, 4 figure

Encoding difficulty promotes postlearning changes in sleep spindle activity during napping

Learning-dependent increases in sleep spindle density have been reported during nocturnal sleep immediately after the learning session. Here, we investigated experience-dependent changes in daytime sleep EEG activity after declarative learning of unrelated word pairs. At weekly intervals, 13 young male volunteers spent three 24 h sessions in the laboratory under carefully controlled homeostatic and circadian conditions. At approximately midday, subjects performed either one of two word-pair learning tasks or a matched nonlearning control task, in a counterbalanced order. The two learning lists differed in the level of concreteness of the words used, resulting in an easier and a more difficult associative encoding condition, as confirmed by performance at immediate cued recall. Subjects were then allowed to sleep for 4 h; afterward, delayed cued recall was tested. Compared with the control condition, sleep EEG spectral activity in the low spindle frequency range and the density of low-frequency sleep spindles (11.25-13.75 Hz) were both significantly increased in the left frontal cortex after the difficult but not after the easy encoding condition. Furthermore, we found positive correlations between these EEG changes during sleep and changes in memory performance between pre-nap and post-nap recall sessions. These results indicate that, like during nocturnal sleep, daytime sleep EEG oscillations including spindle activity are modified after declarative learning of word pairs. Furthermore, we demonstrate here that the nature of the learning material is a determinant factor for sleep-related alterations after declarative learning

Excited-state spectroscopy using single-spin manipulation in diamond

We use single-spin resonant spectroscopy to study the spin structure in the orbital excited-state of a diamond nitrogen-vacancy center at room temperature. We find that the excited state spin levels have a zero-field splitting that is approximately half of the value of the ground state levels, a g-factor similar to the ground state value, and a hyperfine splitting ~20x larger than in the ground state. In addition, the width of the resonances reflects the electronic lifetime in the excited state. We also show that the spin-splitting can significantly differ between NV centers, likely due to the effects of local strain, which provides a pathway to control over the spin Hamiltonian and may be useful for quantum information processing.Comment: 15 pages, 3 figure

Estudo de associações genômicas para idade ao primeiro e segundo parto em bovinos da raça Canchim.

Recentemente, programas de melhoramento genético de bovinos de corte têm dado maior ênfase para características reprodutivas de fêmeas devido à sua importância econômica para o sistema de produção. O objetivo deste trabalho foi estudar a associação entre polimorfismos de base única (SNP) com os valores genéticos das características idade ao primeiro (IPP) e segundo (ISP) parto em bovinos de corte de raça sintética. Neste estudo foram utilizados 285 animais da raça Canchim e 114 animais do grupo genético MA (utilizados na formação da raça Canchim), genotipados com o painel de alta densidade (786.799 SNPs). Após o controle de qualidade de informações (genótipos e fenótipos) restaram 672.778 SNPs e 392 animais. Foram observadas associações para IPP nos cromossomos 4 e 27, e para ISP nos cromossomos 10, 11 e 15. Após a correção para múltiplos testes (?false discovery rate?) ao nível de 10%, seis e quatro SNPs foram significativamente associados, ao longo do cromossomo, com IPP e ISP. Novos e promissores genes associados com características reprodutivas foram identificados, como os genes SLC8A1 e UBQLN3. Com base nas análises de associação entre SNPs e as características estudadas, verificou-se que os SNPs observados como significativos poderiam ser utilizados na seleção genômica da raça Canchim. As regiões polimórficas identificadas apresentaram funções moleculares e processos biológicos que podem estar envolvidos na manutenção do organismo e no desempenho reprodutivo. Os genes associados à IPP e ISP poderiam ser utilizados como genes candidatos para a melhoria do desempenho de fêmeas e, indiretamente, de machos. A validação destes resultados em outra população de bovinos Canchim deve ser conduzida futuramente para confirmação das associações genômicas

A genetic algorithm based approach to fiber design for high coherence and large bandwidth supercontinuum generation

We present a new approach to the design of optical microstructured fibers that have group velocity dispersion (GVD) and effective nonlinear coefficient (gamma ) tailored for supercontinuum (SC) generation. This hybrid approach combines a genetic algorithm (GA) with pulse propagation modeling, but without include it into the GA loop, to allow the efficient design of fibers that are capable of generating highly coherent and large bandwidth SC in the mid-infrared (Mid-IR) spectrum. To the best of our knowledge, this is the first use of a GA to design fiber for SC generation. We investigate the robustness of these fiber designs to variation in the fiber's structural parameters. The optimized fiber structure based on a type of tellurite glass (70TeO(2) - 10 Na(2)O - 20 ZnF(2)) is predicted to have near-zero group velocity dispersion (< +/-2 ps/nm/km) from 2 to 3 microm, and a effective nonlinear coefficient of gamma approximately 174 W(-1)km(-1) at 2 microm. The SC output of this fiber shows a significant bandwidth and coherence increase compare to a fiber with a single zero group velocity dispersion wavelength at 2 microm.Wen Qi Zhang, Shahraam Afshar V. and Tanya M. Monr