Collapse arrest and soliton stabilization in nonlocal nonlinear media

We investigate the properties of localized waves in systems governed by nonlocal nonlinear Schrodinger type equations. We prove rigorously by bounding the Hamiltonian that nonlocality of the nonlinearity prevents collapse in, e.g., Bose-Einstein condensates and optical Kerr media in all physical dimensions. The nonlocal nonlinear response must be symmetric, but can be of completely arbitrary shape. We use variational techniques to find the soliton solutions and illustrate the stabilizing effect of nonlocality.Comment: 4 pages with 3 figure

Chalcogenide-glass polarization-maintaining photonic crystal fiber for mid-infrared supercontinuum generation

In this paper, we report the design and fabrication of a highly birefringent polarization-maintaining photonic crystal fiber (PM-PCF) made from chalcogenide glass, and its application to linearly-polarized supercontinuum (SC) generation in the mid-infrared region. The PM fiber was drawn using the casting method from As38Se62 glass which features a transmission window from 2 to 10 $\mu m$ and a high nonlinear index of 1.13.10$^{-17}$m$^{2}$W$^{-1}$. It has a zero-dispersion wavelength around 4.5 $\mu m$ and, at this wavelength, a large birefringence of 6.10$^{-4}$ and consequently strong polarization maintaining properties are expected. Using this fiber, we experimentally demonstrate supercontinuum generation spanning from 3.1-6.02 $\mu m$ and 3.33-5.78 $\mu m$ using femtosecond pumping at 4 $\mu m$ and 4.53 $\mu m$, respectively. We further investigate the supercontinuum bandwidth versus the input pump polarization angle and we show very good agreement with numerical simulations of the two-polarization model based on two coupled generalized nonlinear Schr\"odinger equations.Comment: 13 pages, 8 figure

Coherent spin control by electromagnetic vacuum fluctuations

In coherent control, electromagnetic vacuum fluctuations usually cause coherence loss through irreversible spontaneous emission. However, since the dissipation via emission is essentially due to correlation of the fluctuations, when emission ends in a superposition of multiple final states, correlation between different pathways may build up if the "which-way" information is not fully resolved (i.e., the emission spectrum is broader than the transition energy range). Such correlation can be exploited for spin-flip control in a $\Lambda$-type three-level system, which manifests itself as an all-optical spin echo in nonlinear optics with two orders of optical fields saved as compared with stimulated Raman processes. This finding represents a new class of optical nonlinearity induced by electromagnetic vacuum fluctuations.Comment: 7 pages including 5 figure

Quadratic solitons as nonlocal solitons

We show that quadratic solitons are equivalent to solitons of a nonlocal Kerr medium. This provides new physical insight into the properties of quadratic solitons, often believed to be equivalent to solitons of an effective saturable Kerr medium. The nonlocal analogy also allows for novel analytical solutions and the prediction of novel bound states of quadratic solitons.Comment: 4 pages, 3 figure

Efficient gene disruption in diverse strains of Toxoplasma gondii using CRISPR/CAS9

ABSTRACT Toxoplasma gondii has become a model for studying the phylum Apicomplexa, in part due to the availability of excel-lent genetic tools. Although reverse genetic tools are available in a few widely utilized laboratory strains, they rely on special ge-netic backgrounds that are not easily implemented in natural isolates. Recent progress in modifying CRISPR (clustered regularly interspaced short palindromic repeats), a system of DNA recognition used as a defense mechanism in bacteria and archaea, has led to extremely efficient gene disruption in a variety of organisms. Here we utilized a CRISPR/CAS9-based system with single guide RNAs to disrupt genes in T. gondii. CRISPR/CAS9 provided an extremely efficient system for targeted gene disruption and for site-specific insertion of selectable markers through homologous recombination. CRISPR/CAS9 also facilitated site-specific insertion in the absence of homology, thus increasing the utility of this approach over existing technology. We then tested whether CRISPR/CAS9 would enable efficient transformation of a natural isolate. Using CRISPR/CAS9, we were able to rapidly generate both rop18 knockouts and complemented lines in the type I GT1 strain, which has been used for forward genetic crosses but which remains refractory to reverse genetic approaches. Assessment of their phenotypes in vivo revealed that ROP18 con-tributed a greater proportion to acute pathogenesis in GT1 than in the laboratory type I RH strain. Thus, CRISPR/CAS9 extends reverse genetic techniques to diverse isolates of T. gondii, allowing exploration of a much wider spectrum of biological diversity. IMPORTANCE Genetic approaches have proven very powerful for studying the biology of organisms, including microbes. How-ever, ease of genetic manipulation varies widely among isolates, with common lab isolates often being the most amenable to suc

Energy funneling in a bent chain of Morse oscillators with long-range coupling

A bent chain of coupled Morse oscillators with long-range dispersive interaction is considered. Moving localized excitations may be trapped in the bending region. Thus chain geometry acts like an impurity. An energy funneling effect is observed in the case of random initial conditions.Comment: 6 pages, 12 figures. Submitted to Physical Review E, Oct. 13, 200

Efficacy, Model of delivery, Intensity and Targets of Pragmatic Interventions for Children with Developmental Language Disorder:A Systematic Review

BACKGROUND: It is widely acknowledged that children with developmental language disorder (DLD) predominantly have difficulties in the areas of grammar and vocabulary, with preserved pragmatic skills. Consequently, few studies focus on the pragmatic skills of children with DLD, and there is a distinct lack of studies examining the effectiveness of pragmatic interventions. AIMS: To carry out a systematic review of the literature on pragmatic interventions for children with DLD. METHODS & PROCEDURES: This systematic review was registered with PROSPERO (ID = CRD42017067239). A systematic search in seven databases yielded 1031 papers, of which 11 met our inclusion criteria. The included papers focused on interventions for children with DLD (mean = 3–18 years), enhancing oral language pragmatic skills, published between January 2006 and May 2020, and were based on a group‐study design such as randomized control trial or pre‐post‐testing. Study participants were monolingual speakers. The quality of papers was appraised using the Cochrane Risk of bias tool for randomized controlled trials. OUTCOMES & RESULTS: There was a high degree of variability between the included intervention studies, especially regarding intensity, intervention targets and outcomes. The evidence suggested that pragmatic intervention is feasible for all models of delivery (individual, small and large group) and that interventions for pragmatic language are mostly focused on encouragement of conversation and narrative skills observed through parent–child interaction or shared book‐reading activities. CONCLUSIONS & IMPLICATIONS: This study highlights the importance of promoting and explicitly teaching pragmatic skills to children with DLD in structured interventions. A narrative synthesis of the included studies revealed that in addition to direct intervention, indirect intervention can also contribute to improving oral pragmatic skills of children with DLD. WHAT THIS PAPER ADDS: WHAT IS ALREADY KNOWN ON THE SUBJECT? An increasing number of studies have shown that difficulties in acquiring pragmatic language is not only present in children with autism. WHAT THIS STUDY ADDS TO EXISTING KNOWLEDGE? Interventions for pragmatic language in children with DLD are mostly focused on encouragement of conversation and narrative skills, very often through parent–child interaction or shared book‐reading activities. Interventions that target language pragmatic are feasible for all models of delivery (individual, small and large group). WHAT ARE THE POTENTIAL OR ACTUAL CLINICAL IMPLICATIONS OF THIS WORK? The efficacy of the existing studies varies, and it is difficult to give recommendations regarding the intensity and duration of the specific intervention. In addition to offering pragmatic intervention directly from a specialist, pragmatic interventions can also be carried out indirectly if the intervention is under the continuous supervision of a specialist

Zornia contorta Mohlenbr.

Vic. CochabambapublishedVersio

Villamilla rivinioides Rusby

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