Stability of periodic waves of 1D cubic nonlinear Schrödinger equations

International audienceWe study the stability of the cnoidal, dnoidal and snoidal elliptic functions as spatially-periodic standing wave solutions of the 1D cubic nonlinear Schrödinger equations. First, we give global variational characterizations of each of these periodic waves, which in particular provide alternate proofs of their orbital stability with respect to same-period perturbations, restricted to certain subspaces. Second, we prove the spectral stability of the cnoidal waves against same-period perturbations (in a certain parameter range), and provide an alternate proof of this (known) fact for the snoidal waves, which does not rely on complete integrability. Third, we give a rigorous version of a formal asymptotic calculation of Rowlands to establish the instability of a class of real-valued periodic waves in 1D, which includes the cnoidal waves of the 1D cubic focusing nonlinear Schrödinger equation, against perturbations with period a large multiple of their fundamental period. Finally, we develop a numerical method to compute the minimizers of the energy with fixed mass and momentum constraints. Numerical experiments support and complete our analytical results

Collider events on a quantum computer

An intuitive definition of the partonic flavor of a jet in quantum chromodynamics is often only well-defined in the deep ultraviolet, where the strong force becomes a free theory and a jet consists of a single parton. However, measurements are performed in the infrared, where a jet consists of numerous particles and requires an algorithmic procedure to define their phase space boundaries. To connect these two regimes, we introduce a novel and simple partonic jet flavor definition in the infrared. We define the jet flavor to be the net flavor of the partons that lie exactly along the direction of the Winner-Take-All recombination scheme axis of the jet, which is safe to all orders under emissions of soft particles, but is not collinear safe. Collinear divergences can be absorbed into a perturbative fragmentation function that describes the evolution of the jet flavor from the ultraviolet to the infrared. The evolution equations are linear and a small modification to traditional DGLAP and we solve them to leading-logarithmic accuracy. The evolution equations exhibit fixed points in the deep infrared, we demonstrate quantitative agreement with parton shower simulations, and we present various infrared and collinear safe observables that are sensitive to this flavor definition

Self-concepts and psychological health in children and adolescents with reading difficulties and the impact of assistive technology to compensate and facilitate reading ability

This study investigated self-image, psychological health, and the impact of Assistive Technology (AT) on self-concept and psychological health in 137 children and adolescents with reading difficulties during a systematic intervention program and in a one-year follow-up. Participants were randomly assigned to a control or an intervention group. The interventions aimed to teach participants how to understand texts using AT. The control group received no intervention. To investigate self-esteem, self-image, anxiety, and depression, all participants were assessed with the Cultural Free Self-Esteem Inventory, 3rd edition (CFSEI-3) before intervention and one year post-interventions. Forty-one participants were also assessed on the Beck Youth Inventory (BYI). The AT was found to have no impact on participants\u27 self-esteem. The CFSEI-3 showed similar values for self-esteem in a norm group and the study groups at pre-intervention, which made an increase from using AT less expected. The results are discussed in terms of contextual explanatory factors, such as educators\u27 increased knowledge of reading difficulties and dyslexia. The results on the BYI were somewhat inconclusive since the younger group of participants showed more anxiety than the norm group, but the adolescent group did not. This may be due to small sample size, so further research is recommended

Nitrogen restricts future sub-Arctic treeline advance in an individual-based dynamic vegetation model

Arctic environmental change induces shifts in high-latitude plant community composition and stature with implications for Arctic carbon cycling and energy exchange. Two major components of change in high-latitude ecosystems are the advancement of trees into tundra and the increased abundance and size of shrubs. How future changes in key climatic and environmental drivers will affect distributions of major ecosystem types is an active area of research. Dynamic vegetation models (DVMs) offer a way to investigate multiple and interacting drivers of vegetation distribution and ecosystem function. We employed the LPJ-GUESS tree-individual-based DVM over the Torneträsk area, a sub-Arctic landscape in northern Sweden. Using a highly resolved climate dataset to downscale CMIP5 climate data from three global climate models and two 21st-century future scenarios (RCP2.6 and RCP8.5), we investigated future impacts of climate change on these ecosystems. We also performed model experiments where we factorially varied drivers (climate, nitrogen deposition and [CO2]) to disentangle the effects of each on ecosystem properties and functions. Our model predicted that treelines could advance by between 45 and 195 elevational metres by 2100, depending on the scenario. Temperature was a strong driver of vegetation change, with nitrogen availability identified as an important modulator of treeline advance. While increased CO2 fertilisation drove productivity increases, it did not result in range shifts of trees. Treeline advance was realistically simulated without any temperature dependence on growth, but biomass was overestimated. Our finding that nitrogen cycling could modulate treeline advance underlines the importance of representing plant-soil interactions in models to project future Arctic vegetation change

Randomised controlled trials in Scandinavian educational research

Background: The Scandinavian countries have a long history of implementing social interventions, but the interventions have not been examined using randomised controlled trials until relatively recently compared with countries like the United States and the United Kingdom. Purpose: The purpose of this paper is to examine the history of randomised controlled trials in Scandinavian compulsory schools (grades 0–10; pupil ages 6–15). Specifically, we investigate drivers and barriers for randomised controlled trials in educational research and the differences between the three Scandinavian countries Denmark, Norway, and Sweden. Methods: To locate relevant trials, we performed a systematic search of four bibliographic databases and a search for grey literature. Results were combined with trials located through direct contact with researchers and government officials. A trial was included if one or more interventions were randomly assigned to groups of students and carried out in a school setting with the primary aim of improving the academic performance of children aged 6–15 in grades 0–10 in Denmark, Norway, or Sweden. We included both conducted and ongoing trials. Publications that seemed relevant were screened based on full-text versions. Data extraction included information from the included studies on grade level, study period, sample size (N), project owner, funding source, and theme. In addition, we conducted two semi-structured interviews by phone or in person with central employees in funding agencies and ministries and 25 correspondences with researchers and policymakers. Findings and conclusion: RCTs in grades 0–10 were few in all of Scandinavia until about 2011, after which there was an increase in all three countries, although at different rates. The largest number of trials has been conducted in Denmark, and the increase is more marked in Denmark and Norway compared with Sweden. International trends towards more impact evaluations and results from international comparisons such as PISA have likely affected the development in all countries, but while many trials in Denmark and Norway are the result of policy initiatives, only one such example in Sweden was identified. We believe the lack of government initiatives to promote RCTs in Sweden is the most likely explanation for the differences across the Scandinavian countries. Funding and coordination from the government are often crucial for the implementation of RCTs and are likely more important in smaller countries such as the Scandinavian ones. Supporting institutions have now been established in all three countries, and we believe that the use of RCTs in Scandinavian educational research is likely to continue.publishedVersio

Synthesis and evaluation of human phosphodiesterases (PDE) 5 inhibitor analogs as trypanosomal PDE inhibitors. 2. Tadalafil analogs

Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Bioorganic & Medicinal Chemistry Letters 22 (2012): 2582-2584, doi:10.1016/j.bmcl.2012.01.118.In this report we describe our ongoing target repurposing efforts focused on discovery of inhibitors of the essential trypanosomal phosphodiesterase TbrPDEB1. This enzyme has been implicated in virulence of Trypanosoma brucei, the causative agent of human African trypanosomiasis (HAT). We outline the synthesis and biological evaluation of analogs of tadalafil, a human PDE5 inhibitor currently utilized for treatment of erectile dysfunction, and report that these analogs are weak inhibitors of TbrPDEB1.This work was supported by the National Institutes of Health (R01AI082577), Boston University and Northeastern University

Effects of assistive technology for students with reading and writing disabilities

Background: Assistive technology has been used to mitigate reading disabilities for almost three decades, and tablets with text-to-speech and speech-to-text apps have been introduced in recent years to scaffold reading and writing. Few scientifically rigorous studies, however, have investigated the benefits of this technology. Purpose: The aim was to explore the effects of assistive technology for students with severe reading disabilities. Method: This study included 149 participants. The intervention group received 24 sessions of assistive technology training, and the control group received treatment as usual. Results: Both the intervention and control groups improved as much in 1 year as the normed population did. However, gains did not differ between the groups directly after the intervention or at 1 year of follow-up. Conclusions: The use of assistive technology seems to have transfer effects on reading ability and to be supportive, especially for students with the most severe difficulties. In addition, it increases motivation for overall schoolwork. Our experience also highlights the obstacles involved in measuring the ability to assimilate and communicate text.Implications for rehabilitations Assistive technology (AT) can be useful for children with reading disabilities to assimilating text as well as boosting their reading. Children with reading disability using AT increased reading performance as much as a norm group, i.e. the students enhanced their reading ability despite no training in traditional reading remediation. Children’s and adolescents’ motivation for schoolwork can be boosted when using AT as a complement for those with reading and writing disabilities

State-of-the-art capabilities in LPJ-GUESS

LPJ-GUESS is an advanced DGVM including detailed forest demography and management, croplands, wetlands, specialised arctic processes, emissions of nonCO2 GHGs and a highly flexible land-use change scheme which tracks transitions between different land-uses. It is the vegetation component of the EC-Earth CMIP6 ESM, the RCA-GUESS regional ESM, and also has a European mode operating at tree species level