453 research outputs found

    Coherence creation in an optically thick medium by matched propagation of a chirped laser pulse pair

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    We consider the simultaneous propagation of a pair of Raman-resonant, frequency-modulated (chirped) laser pulses in an optically thick medium, modeled by an ensemble of Λ\Lambda-atoms. A self-organization ('matching`) effect is shown for the chirped pulse pair, which leads to a quasi-lossless propagation. Furthermore, we demonstrate that a well-defined coherent superposition of the atomic ground states and, correspondingly, a coherence is robustly created in the medium that can be controlled by amplitudes of the laser pulses. The proposed scheme can be applied to substantially increase the efficiency of the optical wave mixing processes, as well as in other nonlinear processes where the initial preparation of a spatially extended medium in a coherent superposition state is required

    Strain induced pressure effect in pulsed laser deposited thin films of the strongly correlated oxide V2O3

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    V2O3 thin films about 10 nm thick were grown on Al2O3 (0001) by pulsed laser deposition. The XRD analysis is in agreement with R-3c space group. Some of them exhibit the metal / insulator transition characteristic of V2O3 bulk material and others samples exhibit a metallic behavior. For the latter, the XPS analysis indicates an oxidation state of +III for vanadium. There is no metal / insulator transition around 150 K in this sample and a strongly correlated Fermi liquid rho = AT2 behavior of the resistivity at low temperature is observed, with a value of A of 1.2 10-4 ohm cm, 3 times larger than the bulk value at 25 kbar

    The need for a more dynamic and ecological assessment of children experiencing barriers to learning to move towards inclusive education: a summary of results of the Daffodil project.

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    Although governments have recognized the need to make education more accessible to children with developmental disabilities and/or learning difficulties, many children remain excluded from participation in regular school settings, let alone receive adequate education. Though every country which ratified the United Nations (UN) 2006 Convention on the Rights of People with Disability has committed itself to inclusive education, there are many obstacles. One of them is the currently preferred way of assessing children with standardized, psychometric diagnostic tests, with a comparative and classifying purpose. This type of assessment, based on a medical impairment model and a static model of intelligence, results in reports which are sometimes not very useful for educational advice. This paper reports an overview of the results of the DAFFODIL project (Dynamic Assessment of Functioning and Oriented at Development and Inclusive Learning), created by a consortium of eight European partners in order to research more inclusive alternatives and suggest reforms to assessment and coaching procedures. It starts with a critical review of current assessment practices; then it presents criteria for good practices for assessing children with additional educational needs in a more dynamic, inclusion-oriented and contextual way. A Delphi procedure was used by 150 professionals and parents to develop a consensus for guidelines for assessment procedures oriented at mapping functional difficulties, context, interaction and possibilities for learning, with the objective to understanding learning processes, to develop more inclusive, challenging and suitable educational programmes and more useful recommendations for teachers, parents and rehabilitation staff

    Shape analysis of the nasal complex among South African groups from CBCT scans

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    Three-dimensional (3D) anatomical extraction techniques could help the forensic anthropologist in a precise and inclusive assessment of biological phenotypes for the development of facial reconstruction methods. In this research, the nose morphology and the underlying hard tissue of two South African populations were studied. To this end, a 3D computer-assisted approach based on an automated landmarking workflow was used to generate relevant 3D anatomical components, and shape discrepancies were investigated using a data set of 200 cone-beam computer tomography (CBCT) scans. The anatomical landmarks were placed on the external nose and the mid-facial skeleton (the nasal bones, the anterior nasal aperture, the zygoma, and the maxilla). Shape differences related to population affinity, sex, age, and size were statistically evaluated and visualised using geometric morphometric methods. Population affinity, sexual dimorphism, age, and size affect the nasal complex morphology. Shape variation in the mid-facial region was significantly influenced by population affinity, emphasising that shape variability was specific to the two population groups, along with the expression of sexual dimorphism and the effect of ageing. In addition, nasal complex shape and correlations vary greatly between white and black South Africans, highlighting a need for reliable population-specific 3D statistical nose prediction algorithms. Significance: ‱ 3D anatomical structures were acquired and extracted from 200 CBCT scans of modern South Africans. ‱ Geometric morphometric methods were applied. ‱ Soft- and hard-tissue nasal complex morphology vary across South African groups

    Modulated structures in electroconvection in nematic liquid crystals

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    Motivated by experiments in electroconvection in nematic liquid crystals with homeotropic alignment we study the coupled amplitude equations describing the formation of a stationary roll pattern in the presence of a weakly-damped mode that breaks isotropy. The equations can be generalized to describe the planarly aligned case if the orienting effect of the boundaries is small, which can be achieved by a destabilizing magnetic field. The slow mode represents the in-plane director at the center of the cell. The simplest uniform states are normal rolls which may undergo a pitchfork bifurcation to abnormal rolls with a misaligned in-plane director.We present a new class of defect-free solutions with spatial modulations perpendicular to the rolls. In a parameter range where the zig-zag instability is not relevant these solutions are stable attractors, as observed in experiments. We also present two-dimensionally modulated states with and without defects which result from the destabilization of the one-dimensionally modulated structures. Finally, for no (or very small) damping, and away from the rotationally symmetric case, we find static chevrons made up of a periodic arrangement of defect chains (or bands of defects) separating homogeneous regions of oblique rolls with very small amplitude. These states may provide a model for a class of poorly understood stationary structures observed in various highly-conducting materials ("prechevrons" or "broad domains").Comment: 13 pages, 13 figure

    SignaFish: A zebrafish-specific signaling pathway resource

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    Understanding living systems requires an in-depth knowledge of the signaling networks that drive cellular homeostasis, regulate intercellular communication, and contribute to cell fates during development. Several resources exist to provide high-throughput data sets or manually curated interaction information from human or invertebrate model organisms. We previously developed SignaLink, a uniformly curated, multi-layered signaling resource containing information for human and for the model organisms nematode Caenorhabditis elegans and fruit fly Drosophila melanogaster. Until now, the use of the SignaLink database for zebrafish pathway analysis was limited. To overcome this limitation, we created SignaFish ( http://signafish.org ), a fish-specific signaling resource, built using the concept of SignaLink. SignaFish contains more than 200 curation-based signaling interactions, 132 further interactions listed in other resources, and it also lists potential miRNA-based regulatory connections for seven major signaling pathways. From the SignaFish website, users can reach other web resources, such as ZFIN. SignaFish provides signaling or signaling-related interactions that can be examined for each gene or downloaded for each signaling pathway. We believe that the SignaFish resource will serve as a novel navigating point for experimental design and evaluation for the zebrafish community and for researchers focusing on nonmodel fish species, such as cyclids

    Electronic structure of MgB2_2: X-ray emission and absorption studies

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    Measurements of x-ray emission and absorption spectra of the constituents of MgB2_2 are presented. The results obtained are in good agreement with calculated x-ray spectra, with dipole matrix elements taken into account. The comparison of x-ray emission spectra of graphite, AlB2_2, and MgB2_2 in the binding energy scale supports the idea of charge transfer from σ\sigma to π\pi bands, which creates holes at the top of the bonding σ\sigma bands and drives the high-Tc_cComment: final version as published in PR

    Factors Influencing Mental Health Service Utilization by Children with Serious Emotional and Behavioral Disturbance: Results from the LAMS Study

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    The official published article is available online at http://doi.org/10.1176/appi.ps.62.6.650.OBJECTIVE: To describe service utilization of a cohort of children with emotional and behavioral disorders who visited outpatient mental health clinics in four Midwest cities. METHOD: Data come from the Longitudinal Assessment of Manic Symptoms (LAMS) Study. 707 youth (ages 6–12 years) and their parents completed diagnostic assessments, demographic information and an assessment of mental health service utilization. Analyses examined the relationship of demographics, diagnoses, impairment, and comorbidity to the type and level of services utilized. RESULTS: Service utilization is multimodal with half of the youth receiving both outpatient and school services during their lifetime. Non-need factors including age, sex, race, and insurance, were related to types of services used. Youth diagnosed with a bipolar spectrum disorder had higher utilization of inpatient services and two or more services at one time compared to youth diagnosed with depressive or disruptive disorders. More than half of youth diagnosed with bipolar or depressive disorders had received both medication and therapy during their lifetime whereas for youth diagnosed with a disruptive disorder therapy only was more common. Impairment and comorbidity were not related to service utilization. CONCLUSIONS: Use of mental health services for children begins at a very young age and occurs in multiple service sectors. Type of service use is related to insurance and race/ethnicity, underscoring the need for research on treatment disparities. Contrary to findings from results based on administrative data, medication alone was infrequent. However, the reasonably low use of combination therapy suggests that clinicians and families need to be educated on the effectiveness of multimodal treatment

    A multi-proxy approach to exploring Homo sapiens’ arrival, environments and adaptations in Southeast Asia

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    The capability of Pleistocene hominins to successfully adapt to different types of tropical forested environments has long been debated. In order to investigate environmental changes in Southeast Asia during a critical period for the turnover of hominin species, we analysed palaeoenvironmental proxies from five late Middle to Late Pleistocene faunas. Human teeth discoveries have been reported at Duoi U’Oi, Vietnam (70–60 ka) and Nam Lot, Laos (86–72 ka). However, the use of palaeoproteomics allowed us to discard the latter, and, to date, no human remains older than ~ 70 ka are documented in the area. Our findings indicate that tropical rainforests were highly sensitive to climatic changes over that period, with significant fluctuations of the canopy forests. Locally, large-bodied faunas were resilient to these fluctuations until the cooling period of the Marine Isotope Stage 4 (MIS 4; 74–59 ka) that transformed the overall biotope. Then, under strong selective pressures, populations with new phenotypic characteristics emerged while some other species disappeared. We argue that this climate-driven shift offered new foraging opportunities for hominins in a novel rainforest environment and was most likely a key factor in the settlement and dispersal of our species during MIS 4 in SE Asia
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