Broad-band polarization conversion from a finite periodic structure in the microwave regime

Copyright © 2004 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters 84 (2004) and may be found at http://link.aip.org/link/?APPLAB/84/849/1A reflection grating demonstrating extraordinarily broad-band polarization conversion in a nondiffractive regime has been studied at microwave frequencies. This single-element structure has been fabricated by electrolessly plating a metallic layer onto a stereo-lithographically produced resin profile. Angle-dependent microwave reflectivity data collected from the grating indicates polarization conversion of greater than 80% over a spectral bandwidth equivalent to the entire visible regime (factor of 2 in frequency). This supports an earlier publication in which it was predicted that a broad-band polarization converter could be created from a suitably profiled diffraction grating

Should I keep studying? Consequences of a decision to stop learning in young and older adults

In situations of cognitive overload, the role of a metacognitive decision to stop learning is of utmost importance. We investigated how young and older adults decide to stop learning as a strategy for maximizing memory performance when they face to-be-learned material exceeding their memory capability. People may decide to stop learning for two main reasons: they experience a growing feeling of disfluency as a learning episode progresses and/or they perceive such a decision to be beneficial for future memory performance. In Experiments 1 and 2, participants studied lists of 50 words. The majority of young and older adults stopped learning in conditions where they were allowed to do so. This decision, counterintuitively, decreased the number of recalled words. Crucially, a similar number of young and older adults stopped the presentation of to-be-remembered material, and both age groups suffered comparable consequences in their memory performance. In Experiments 3a and 3b, participants read an experimental scenario and decided whether they would stop learning based on this description alone. People in different age groups predicted their metacognitive decisions similarly. However, participants’ forecasted performance did not reflect the negative influence of these decisions. Regardless of their age, people tend to make a suboptimal decision to stop learning, unaware of its negative consequences. Together, our results suggest that young and older adults can exert metamemory control to similar degrees even though their decisions may not be beneficial for memory performance. (PsycInfo Database Record (c) 2021 APA, all rights reserved

Precipitation Type Specific Radar Reflectivity-Rain Rate Relationships for Warsaw, Poland

Penelitian ini bertujuan untuk mengetahui peningkatan penguasaan konsep dan kemampuan literasi sains siswa dengan menggunakan model pembelajaran kontekstual berbantuan multimedia. Metode dan desain penelitian yang digunakan adalah quasi experiment dengan pretest-posttest control group design. Subjek penelitiannya adalah kelas XI di kabupaten Subang, Jawa-Barat. Hasil penelitian menunjukkan Model Pembelajaran Kontekstual berbantuan multimedia secara signifikan mampu meningkatkan penguasaan konsep dan kemampuan literasi sains siswa. Peningkatan penguasaan konsep siswa dengan nilai N-Gain 0.50 (kategori sedang) untuk kelas eksperimen dan 0,30 (kategori sedang) untuk kelas kontrol. Peningkatan kemampuan literasi sains siswa dengan nilai N-Gain 0.45 (kategori sedang) untuk kelas eksperimen dan 0,30 (kategori sedang) untuk kelas kontrol. This study aims to determine the concepts mastery and skills increase scientific literacy of students by using multimedia-assisted contextual learning model. The method used quasi experiment with pretest-posttest control group design. Subjects of study are class XI in Subang districts, West-Java. The result of study showed that contextual model’s aided by multimedia significantly enhance student’s concepts mastery and skills scientific literacy. The enhancement of student’s concepts mastery with N-Gain value is 0.50 (medium category) for experiment class and 0,30 (medium category) for control class. The enhancement of student's skills scientific literacy with N-Gain value is 0.45 (medium category) for experiment class and 0,30 (medium category) for control class

Evaluation of acidogenesis products’ effect on biogas production performed with metagenomics and isotopic approaches

Background: During the acetogenic step of anaerobic digestion, the products of acidogenesis are oxidized to substrates for methanogenesis: hydrogen, carbon dioxide and acetate. Acetogenesis and methanogenesis are highly interconnected processes due to the syntrophic associations between acetogenic bacteria and hydrogenotrophic methanogens, allowing the whole process to become thermodynamically favorable. The aim of this study is to determine the influence of the dominant acidic products on the metabolic pathways of methane formation and to find a core microbiome and substrate-specific species in a mixed biogas-producing system. Results: Four methane-producing microbial communities were fed with artificial media having one dominant component, respectively, lactate, butyrate, propionate and acetate, for 896 days in 3.5-L Up-flow Anaerobic Sludge Blanket (UASB) bioreactors. All the microbial communities showed moderately different methane production and utilization of the substrates. Analyses of stable carbon isotope composition of the fermentation gas and the substrates showed differences in average values of δ13C(CH4) and δ13C(CO2) revealing that acetate and lactate strongly favored the acetotrophic pathway, while butyrate and propionate favored the hydrogenotrophic pathway of methane formation. Genome-centric metagenomic analysis recovered 234 Metagenome Assembled Genomes (MAGs), including 31 archaeal and 203 bacterial species, mostly unknown and uncultivable. MAGs accounted for 54%–67% of the entire microbial community (depending on the bioreactor) and evidenced that the microbiome is extremely complex in terms of the number of species. The core microbiome was composed of Methanothrix soehngenii (the most abundant), Methanoculleus sp., unknown Bacteroidales and Spirochaetaceae. Relative abundance analysis of all the samples revealed microbes having substrate preferences. Substrate-specific species were mostly unknown and not predominant in the microbial communities. Conclusions: In this experimental system, the dominant fermentation products subjected to methanogenesis moderately modified the final effect of bioreactor performance. At the molecular level, a different contribution of acetotrophic and hydrogenotrophic pathways for methane production, a very high level of new species recovered, and a moderate variability in microbial composition depending on substrate availability were evidenced. Propionate was not a factor ceasing methane production. All these findings are relevant because lactate, acetate, propionate and butyrate are the universal products of acidogenesis, regardless of feedstock

Tensions in the periphery: Dependence and the trajectory of a low-cost productive model in the Central and Eastern European automotive industry

This article analyses the productive strategy adopted by Renault for its Dacia plant in Romania. It proposes a detailed analysis of the conditions for the success of the Logan project – Renault’s radical approach to the concept of the low-cost automobile. We look into both market- and production-related aspects that have made the Logan work and highlight the tensions sparked by Renault’s drive to capitalize on its favourable market situation as well as the success achieved by Dacia’s workers in defending their interests. In particular, we emphasize the company governance compromises that have shaped industrial relations at Dacia over the past decades and show how in recent years the maintaining of such a compromise has come increasingly into question due to threats by automation and relocation in a context of constantly rising wages and improving working conditions. Finally, we discuss the strategic dilemmas facing both management and labour and their possible resolutions, as well as the relevance of the Dacia case for understanding the future of Central and Eastern Europe as a peripheral region attracting automotive foreign direct investments

A Comparison of Depression and Anxiety among University Students in Nine Countries during the COVID-19 Pandemic.

The mental health of young adults, particularly students, is at high risk during the COVID-19 pandemic. The purpose of this studywas to examine differences inmental health between university students in nine countries during the pandemic. The study encompassed 2349 university students (69% female) from Colombia, the Czech Republic (Czechia), Germany, Israel, Poland, Russia, Slovenia, Turkey, and Ukraine. Participants underwent the following tests: Patient Health Questionnaire (PHQ-8), Generalized Anxiety Disorder (GAD-7), Exposure to COVID-19 (EC-19), Perceived Impact of Coronavirus (PIC) on students’ well-being, PhysicalActivity (PA), andGeneral Self-ReportedHealth (GSRH). The one-wayANOVAshowed significant differences between countries. The highest depression and anxiety risk occurred in Turkey, the lowest depression in the Czech Republic and the lowest anxiety in Germany. The 2 independence test showed that EC-19, PIC, and GSRHwere associatedwith anxiety and depression inmost of the countries, whereas PA was associated in less than half of the countries. Logistic regression showed distinct risk factors for each country. Gender and EC-19 were the most frequent predictors of depression and anxiety across the countries. The role of gender and PA for depression and anxiety is not universal and depends on cross-cultural differences. Students’mental health should be addressed froma cross-cultural perspective