An extension of a uniqueness theorem of J. A. Goldstein

AbstractA general uniqueness theorem for the abstract Cauchy problem x′(t) = f(t, x(t)); x(t) = P(t) + o(μ(t)) as t ↓ 0 is proved extending a result due to Goldstein. Applications of this theorem to a partial differential equation of a generalized Euler-Poisson-Darboux type are also discussed

Global crop yield response to extreme heat stress under multiple climate change futures

Extreme heat stress during the crop reproductive period can be critical for crop productivity. Projected changes in the frequency and severity of extreme climatic events are expected to negatively impact crop yields and global food production. This study applies the global crop model PEGASUS to quantify, for the first time at the global scale, impacts of extreme heat stress on maize, spring wheat and soybean yields resulting from 72 climate change scenarios for the 21st century. Our results project maize to face progressively worse impacts under a range of RCPs but spring wheat and soybean to improve globally through to the 2080s due to CO2 fertilization effects, even though parts of the tropic and sub-tropic regions could face substantial yield declines. We find extreme heat stress at anthesis (HSA) by the 2080s (relative to the 1980s) under RCP 8.5, taking into account CO2 fertilization effects, could double global losses of maize yield (ΔY = −12.8 ± 6.7% versus − 7.0 ± 5.3% without HSA), reduce projected gains in spring wheat yield by half (ΔY = 34.3 ± 13.5% versus 72.0 ± 10.9% without HSA) and in soybean yield by a quarter (ΔY = 15.3 ± 26.5% versus 20.4 ± 22.1% without HSA). The range reflects uncertainty due to differences between climate model scenarios; soybean exhibits both positive and negative impacts, maize is generally negative and spring wheat generally positive. Furthermore, when assuming CO2 fertilization effects to be negligible, we observe drastic climate mitigation policy as in RCP 2.6 could avoid more than 80% of the global average yield losses otherwise expected by the 2080s under RCP 8.5. We show large disparities in climate impacts across regions and find extreme heat stress adversely affects major producing regions and lower income countries

Many shades of gray - The context-dependent performance of organic agriculture

Organic agriculture is often proposed as a more sustainable alternative to current conventional agriculture. We assess the current understanding of the costs and benefits of organic agriculture across multiple production, environmental, producer, and consumer dimensions.Organic agriculture shows many potential benefits (including higher biodiversity and improved soil and water quality per unit area, enhanced profitability, and higher nutritional value) as well as many potential costs including lower yields and higher consumer prices. However, numerous important dimensions have high uncertainty, particularly the environmental performance when controlling for lower organic yields, but also yield stability, soil erosion, water use, and labor conditions.We identify conditions that influence the relative performance of organic systems, highlighting areas for increased research and policy support

Dynamically generated patterns in dense suspensions of active filaments

We use Langevin dynamics simulations to study dynamical behaviour of a dense planar layer of active semi-flexible filaments. Using the strength of active force and the thermal persistence length as parameters, we map a detailed phase diagram and identify several non-equilibrium phases in this system. In addition to a slowly flowing melt phase, we observe that for sufficiently high activity, collective flow accompanied by signatures of local polar and nematic order appears in the system. This state is also characterised by strong density fluctuations. Furthermore, we identify an activity-driven cross-over from this state of coherently flowing bundles of filaments to a phase with no global flow, formed by individual filaments coiled into rotating spirals. This suggests a mechanism where the system responds to activity by changing the shape of active agents, an effect with no analogue in systems of active particles without internal degrees of freedom.Comment: extended and updated versio

Looma Lesson Planner

Looma Lesson Planner is a web application that allows its users, experienced educators, to select, organize, and present existing classroom materials and educational content in the format of a custom-made lesson plan. Looma, an all-in-one computer developed by non-profit organization VillageTech Solutions, is designed for school teachers in rural Nepal, India. It provides them with basic access to textbooks, activities, and digital media that may be relevant in meeting Nepal\u27s curriculum requirements. However, Looma did not initially include a simple interface for teachers to connect many different forms of content together into cohesive, custom lesson plans. Our application presents and organizes Looma\u27s existing content in an accessible, user-friendly manner, and allows the teacher to create reusable lesson plans from this content. The application utilizes HTML5, CSS3, PHP, MongoDB, and JavaScript to create a simple, user-friendly, WYSIWYG design. The application\u27s goal is to remove a key technical barrier that Looma currently poses on teachers, and to create a seamless classroom experience for the teachers and their students. Going forward, we plan on working with VillageTech Solutions to integrate our application with Looma\u27s operating system. Once we have completed this task, VillageTech Solutions will use Looma and our web application to conduct user testing with teachers in Nepal. We are also finalizing both a technical guide and a user manual for VillageTech Solutions that will outline our code structure and illustrate how to use the web application, respectively

Towards self-adaptive KPN applications on NoC-based MPSoCs

Self-adaptivity is the ability of a system to adapt itself dynamically to internal and external changes. Such a capability helps systems to meet the performance and quality goals, while judiciously using available resources. In this paper, we propose a framework to implement application level self-adaptation capabilities in KPN applications running on NoC-based MPSoCs. The monitor-controller-adapter mechanism is used at the application level. The monitor measures various parameters to check whether the system meets the assigned goals. The controller takes decisions to steer the system towards the goal, which are applied by the adapters. The proposed framework requires minimal modifications to the application code and offers ease of integration. It incorporates a generic adaptation controller based on fuzzy logic. We present the MJPEG encoder as a case study to demonstrate the effectiveness of the approach. Our results show that even if the parameters of the fuzzy controller are not tuned optimally, the adaptation convergence is achieved within reasonable time and error limits. Moreover, the incurred steady-state overhead due to the framework is 4% for average frame-rate, 3.5% for average bit-rate, and 0.5% for additional control data introduced in the network

Global trends in visibility: implications for dust sources

International audienceThere is a large uncertainty in the relative roles of human land use, climate change and carbon dioxide fertilization in changing desert dust source strength over the past 100 years, and the overall sign of human impacts on dust is not known. We used visibility data from meteorological stations in dusty regions to assess the anthropogenic impact on long term trends in desert dust emissions. Visibility data are available at thousands of stations globally from 1900 to the present, but we focused on 359 stations with more than 30 years of data in regions where mineral aerosols play a dominant role in visibility observations. We evaluated the 1974 to 2003 time period because most of these stations have reliable records only during this time. We first evaluated the visibility data against AERONET aerosol optical depth data, and found that only in dusty regions are the two moderately correlated. Correlation coefficients between visibility derived variables and AERONET optical depths indicate a moderate correlation (~0.47), consistent with capturing about 20% of the variability in optical depths. Two visibility derived variables appear to compare the best with AERONET observations: the fraction of observations with visibility less than 5 km (VIS5) and the surface extinction (EXT). Regional trends show that in many dusty places, VIS5 and EXT are statistically significantly correlated with the palmer drought severity index (based on precipitation and temperature) or surface wind speeds, consistent with dust temporal variability being largely driven by meteorology. This is especially true for North African and Chinese dust sources, but less true in the Middle East, Australia or South America, where there are not consistent patterns in the correlations. Climate indices such as El Nino or the North Atlantic Oscillation are not correlated with visibility derived variables in this analysis. There are few stations where visibility measures are correlated with cultivation or grazing estimates on a temporal basis, although this may be a function of the very coarse temporal resolution of the land use datasets. On the other hand, spatial analysis of the visibility data suggests that natural topographic lows are not correlated with visibility, but land use is correlated at a moderate level. This analysis is consistent with land use being important in some regions, but meteorology driving interannual variability during 1974?2003

CONVERSION OF SLUDGE BIOMASS INTO CATALYSTS: ENVIRONMENTAL TREATMENT APPLICATIONS

La força d'aquest objectiu de la recerca és l'ús de catalitzadors a base de fangs (SBC) per al tractament d'aigües residuals en els mètodes de tractament biològics i químics en condicions ambientalment acceptables. Aquesta investigació presenta una forma alternativa de reutilitzar els materials de rebuig de les plantes de tractament d'aigües residuals i el rendiment dels nous catalitzadors en les aplicacions de tractament de medi ambient, sobretot en els processos d'oxidació biològica i avançats (POA), com l'ozonització, reacció foto i oxidació amb aire humit catalítica. Aquest estudi inclou característiques importants com la carbonització, la impregnació del metall, la caracterització de la superfície, i el mecanisme de degradació dels contaminants en els processos de reacció biològics i oxidació. Els nanocompostos / TiO2 de carboni llots van ser sintetitzats per diferents mètodes clàssics i l'estudi del disseny i fabricació de materials fotocatalítics avançades en el marc de la nanociència es presenta.La fuerza de este objetivo de la investigación es el uso de catalizadores a base de lodos (SBC) para el tratamiento de aguas residuales en los métodos de tratamiento biológicos y químicos en condiciones ambientalmente aceptables. Esta investigación presenta una forma alternativa de reutilizar los materiales de desecho de las plantas de tratamiento de aguas residuales y el rendimiento de los nuevos catalizadores en las aplicaciones de tratamiento de medio ambiente, sobre todo en los procesos de oxidación biológica y avanzados (POA), como la ozonización, reacción foto y oxidación con aire húmedo catalítica. Este estudio incluye características importantes como la carbonización, la impregnación del metal, la caracterización de la superficie, y el mecanismo de degradación de los contaminantes en los procesos de reacción biológicos y oxidación. Los nanocompuestos / TiO2 de carbono lodos fueron sintetizados por diferentes métodos clásicos y el estudio del diseño y fabricación de materiales fotocatalíticos avanzadas en el marco de la nanociencia se presenta.The strength of this research aim is to use sludge-based catalysts (SBCs) for the treatment of wastewaters in the biological and chemical treatment methods at environmentally acceptable conditions. This research presents an alternative way to reuse waste materials from wastewater treatment plants and the performance of new catalysts in the environmental treatment applications, especially in the biological and advanced oxidation processes (AOPs) such as ozonation, photo reaction and catalytic wet air oxidation. This study includes important features such as carbonisation, metal impregnation, surface characterization, and degradation mechanism of pollutants on the biological and oxidative reaction processes. The sludge carbon/TiO2 nanocomposites were synthesized by different classical methods and the study of the design and fabrication of advanced photocatalytic materials in the framework of nanoscience is presented