741 research outputs found
Do personality traits predict post-traumatic stress?: a prospective study in civilians experiencing air attacks
Publisher version available from: http://journals.cambridge.org
Overriding Intrinsic Reactivity in Aliphatic CâH Oxidation: Preferential C3/C4 Oxidation of Aliphatic Ammonium Substrates
The site-selective CâH oxidation of unactivated positions in aliphatic ammonium chains poses a tremendous synthetic challenge, for which a solution has not yet been found. Here, we report the preferential oxidation of the strongly deactivated C3/C4 positions of aliphatic ammonium substrates by employing a novel supramolecular catalyst. This chimeric catalyst was synthesized by linking the well-explored catalytic moiety Fe(pdp) to an alkyl ammonium binding molecular tweezer. The results highlight the vast potential of overriding the intrinsic reactivity in chemical reactions by guiding catalysis using supramolecular host structures that enable a precise orientation of the substrates
Influence of Fertilization System on Wheat Yields in Terms of Global Climate Change
Over the last few decades, wheat production, both in Serbia and worldwide, has been practiced under characteristic agrometeorological conditions. It has generally been affected by specific strongly marked agrometeorological and climate extremes, most notably extreme temperature and drought events during critical periods in the growing season, which mostly had a negative impact on the growth, development and yield of wheat in Central Serbia.This paper presents results and discussion on both the potential effect of climate change on winter wheat yield and the possibility to alleviate it through an appropriately adjusted fertilization system.The present study on the effect of different rates and ratios of NPK fertilizers on grain yield in seven winter wheat cultivars under different (dry and ânormalâ) conditions during the year was conducted in a long-term field experiment at the Small Grains Research Centre in Kragujevac over a period of seven years (2000/01-2006/07).Depending on the fertilization treatment, the average yield reduction in dry years showed 50% variation relative to ânormalâ years. The highest reduction in grain yield and other productive traits of wheat in dry years was observed in the treatment involving nitrogen nutrition, particularly lower application rates. As compared to the non-treated control, the use of complete NPK fertilization having an increased amount of phosphorus resulted in the lowest yield reduction during the dry years that were unfavorable for winter wheat production. The average grain yield reduction in dry years was lowest in wheat cultivar Matica and highest in Kg-100, respectively
Decoherence due to contacts in ballistic nanostructures
The active region of a ballistic nanostructure is an open quantum-mechanical
system, whose nonunitary evolution (decoherence) towards a nonequilibrium
steady state is determined by carrier injection from the contacts. The purpose
of this paper is to provide a simple theoretical description of the
contact-induced decoherence in ballistic nanostructures, which is established
within the framework of the open systems theory. The active region's evolution
in the presence of contacts is generally non-Markovian. However, if the
contacts' energy relaxation due to electron-electron scattering is sufficiently
fast, then the contacts can be considered memoryless on timescales coarsened
over their energy relaxation time, and the evolution of the current-limiting
active region can be considered Markovian. Therefore, we first derive a general
Markovian map in the presence of a memoryless environment, by coarse-graining
the exact short-time non-Markovian dynamics of an abstract open system over the
environment memory-loss time, and we give the requirements for the validity of
this map. We then introduce a model contact-active region interaction that
describes carrier injection from the contacts for a generic two-terminal
ballistic nanostructure. Starting from this model interaction and using the
Markovian dynamics derived by coarse-graining over the effective memory-loss
time of the contacts, we derive the formulas for the nonequilibrium
steady-state distribution functions of the forward and backward propagating
states in the nanostructure's active region. On the example of a double-barrier
tunneling structure, the present approach yields an I-V curve with all the
prominent resonant features. The relationship to the Landauer-B\"{u}ttiker
formalism is also discussed, as well as the inclusion of scattering.Comment: Published versio
Bimodal Electrochemiluminescence Microscopy of Single Cells
Electrochemiluminescence (ECL) microscopy is an emerging technique with new applications such as imaging of single entities and cells. Herein, we have developed a bimodal and bicolor approach to record both positive ECL (PECL: light-emitting object on dark background) and shadow label-free ECL (SECL: nonemissive object shadowing the background luminescence) images of single cells. This bimodal approach is the result of the simultaneous emissions of [Ru(bpy)3]2+ used to label the cellular membrane (PECL) and [Ir(sppy)3]3- dissolved in solution (SECL). By spectrally resolving the ECL emission wavelengths, we recorded the images of the same cells in both PECL and SECL modes using the [Ru(bpy)3]2+ (?max = 620 nm) and [Ir(sppy)3]3- (?max = 515 nm) luminescence, respectively. PECL shows the distribution of the [Ru(bpy)3]2+ labels attached to the cellular membrane, whereas SECL reflects the local diffusional hindrance of the ECL reagents by each cell. The high sensitivity and surface-confined features of the reported approach are demonstrated by imaging cell-cell contacts during the mitosis process. Furthermore, the comparison of PECL and SECL images demonstrates the differential diffusion of tri-n-propylamine and [Ir(sppy)3]3- through the permeabilized cell membranes. Consequently, this dual approach enables the imaging of the morphology of the cell adhering on the surface and can significantly contribute to multimodal ECL imaging and bioassays with different luminescent systems
Influence of Fertilization System on Wheat Yields in Terms of Global Climate Change
Over the last few decades, wheat production, both in Serbia and worldwide, has been practiced under characteristic agrometeorological conditions. It has generally been affected by specific strongly marked agrometeorological and climate extremes, most notably extreme temperature and drought events during critical periods in the growing season, which mostly had a negative impact on the growth, development and yield of wheat in Central Serbia.This paper presents results and discussion on both the potential effect of climate change on winter wheat yield and the possibility to alleviate it through an appropriately adjusted fertilization system.The present study on the effect of different rates and ratios of NPK fertilizers on grain yield in seven winter wheat cultivars under different (dry and ânormalâ) conditions during the year was conducted in a long-term field experiment at the Small Grains Research Centre in Kragujevac over a period of seven years (2000/01-2006/07).Depending on the fertilization treatment, the average yield reduction in dry years showed 50% variation relative to ânormalâ years. The highest reduction in grain yield and other productive traits of wheat in dry years was observed in the treatment involving nitrogen nutrition, particularly lower application rates. As compared to the non-treated control, the use of complete NPK fertilization having an increased amount of phosphorus resulted in the lowest yield reduction during the dry years that were unfavorable for winter wheat production. The average grain yield reduction in dry years was lowest in wheat cultivar Matica and highest in Kg-100, respectively
Rapid migration from traditional or hybrid to fully virtual education in the age of the coronavirus pandemic: challenges, experiences and views of college and university students
The abrupt outbreak of the coronavirus pandemic throughout the world in March 2020 resulted in the sudden closure of all schools, colleges and universities, institutions, and an unprecedented pivot to remote learning. Students and teachers were confronted with the overwhelming challenge of migrating from the traditional face-to-face or hybrid mode of education to fully virtual learning and assessment environments within an extremely short amount of time. This migration was exceptionally difficult, as it took place halfway through the academic or school year in most countries. While pandemic restrictions currently vary across different regions, the 2020-2021 academic session continues to pose challenges despite the experience gained. In addition to a review of the current state-of-the-art in relation to the effects of COVID-19 on teaching and learning, this paper reports on an empirical study carried out in 26 countries (from Asia, Europe, Africa and America), by 36 academics from 29 academic institutions. Through an extensive global survey of college and university students, information was collected about the challenges (technological, economic, psychological) faced by them, as a result of the pandemic. We also asked the studentsâ to offer their ideas and suggestions for further improvements in teaching and learning, as we look toward a post-COVID world. In this paper, we address issues relating to the availability of, and accessibility to, necessary digital technologies (e.g., learning and communication platforms), isolation, disconnection, and loneliness among students, the overall impact of the pandemic on learning and academic performance, and the reliability of assessment methods., cybercrime dangers and fake information. A total of 1005 responses to the survey were received and analysed. The results are presented in this paper together with reflections of the authors. The paper concludes with a summary of suggestions for process improvements in distance education, and the need for preventive preparedness in the post-COVID period
Organic Fertilizer Abrasive Grits Increase Soil Available Nitrogen, Plant Height, and Biomass
In organic cropping systems, airâpropelled abrasive grits can be used to control inârow weeds. If the applied abrasive grit is an approved organic fertilizer, these applications may serve a dual purpose of weed control and crop fertility. Laboratory soil incubations examined the N mineralization rates of several grit types with differing C/N ratios (Agra Grit [crushed walnut shells, 170:1], corncob grit [91:1], Sustane [composted turkey litter, 5.0:1], Phytaboost Plant Food [crushed and pelletized soybean meal, 5.0:1]). A greenhouse study determined plant wheat (Triticum aestivum L.), kale (Brassica napus pabluaria DC), and velvetleaf (Abutilon theophrasti Medik.) growth response in soils amended with these grits. The N mineralization rates varied by grit type, soil, and application rate. The N mineralized from Phytaboost within 56 d was similar among the amounts of N a whereas the amount of N mineralized from Sustane was inversely related to the amount of N applied. Agra Grit and corncob grit immobilized soil N due to their high C/N ratios. In soils amended with Sustane, plant height and biomass were 15â43% and 34â83% greater than for plants grown in soils with Agra Grit, corncob grit, and the nontreated soil. Applications of organic fertilizer as airâpropelled grit may improve crop growth; however, if weed control is imperfect, these grits may increase weed growth. Grits with high C/N ratios may immobilize soil available N but not affect plant growth
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