Search results for "HECK"

Exploring the influence of vegetation cover, sediment storage capacity and channel dimensions on stone check dam conditions and effectiveness in a la…

2018

Abstract Check dams are widely used for soil conservation at the watershed scale. When structurally sound, these engineering control works retain sediment as planned. However, there is limited information describing the influence of site characteristics on post-construction condition including structural stability and sediment retention capacity. More specifically, the effects of channel morphology, check dam geometry and vegetation characteristics as potentially influencing factors on sediment retention capacity at the watershed level are poorly understood. Thus, an investigation applying field and remotely sensed measurements, multi-regression models, redundancy and sensitivity analysis, …

Pedagogical experiments with MathCheck in university teaching

2019

MathCheck is a relatively new online tool that gives students feedback on their solutions to elementary university mathematics and theoretical computer science exercises. MathCheck was designed with constructivism learning theory in mind and it differs from other online tools as it checks the solutions step by step and shows a counter-example if the step is incorrect. It has been in student use since the autumn of 2015 and under design-based research from the first online day. The main research questions of this study are the following. 1) How can the usage of MathCheck support the aspects of conceptual understanding and procedural fluency of constructivism learning? 2) How can MathCheck em…

From Benzofurans to Indoles: Palladium-Catalyzed Reductive Ring-Opening and Closure via β-Phenoxide Elimination

2018

International audience; Benzofurans can undergo ring-opening by a palladium-catalyzed process resulting in C−O bond breaking. Benzofuran-tethered 2-iodoanilines give synthetically interesting 2-(3-indolylmethyl)phenols in an overall reductive process. Mechanistic studies suggest that this unusual reaction proceeds by carbopalladation of benzofuran giving a 3-palladated 2,3-dihydrobenzofuran intermediate, which then fragments by an uncommon trans-elimination of the phenoxide group β to the metal. In this transformation, N,N-diisopropylethylamine (DIPEA) acts as a base and as a reducing agent: it regenerates palladium(0) from palladium(II), thus allowing catalytic turnover.

IVANOVA, una possibile metodologia per la Information Literacy

Polypyrrole–palladium nanoparticles composite as efficient catalyst for Suzuki–Miyaura coupling

2012

International audience; Synthesis of a new hybrid material (Pd/PPy) composed of polypyrrole globules with uniformly incorporated Pd nanoparticles via direct redox reaction between pyrrole and Pd(NH3)(4)Cl-2 in water has been recently reported (V.A. Zinovyeva, M.A.Vorotyntsev, I. Bezverkhyy, D. Chaumont, J.-C. Hierso, Adv. Funct. Mater. 21 (2011) 1064-1075). In the actual study, this procedure has been extended to synthesize a series of Pd/PPy powders with variable palladium content and morphological parameters. Depending on the monomer-to-oxidant ratio in reaction mixture, average diameters of Pd and PPy particles may change in the ranges of 1.25-1.45 and 27-62 nm, respectively, the Pd conc…

An overview of the Ephydridae (Diptera) of Saudi Arabia

2019

Despite the species richness of Ephydridae world-wide (2000 species) and its prominent environmental roles as a minor pest and as a food for wildlife, only 13 species have been recorded from Saudi Arabia. Between 2012 and 2016, a biodiversity study of Diptera was conducted at Jazan, Asir, and Najran in south-western Saudi Arabia, at 22 sites, was performed mainly using Malaise traps and sweep nets. In this study, 43 known species of Ephydridae were identified, 37 of them for the first time from southwestern Saudi Arabia and 16 from Arabian Peninsula. This brings the total number of Ephydridae species in Saudi Arabia to 49 (including previous records). There were a further four species, whic…

Formal verification of a Cooperative Automatic Repeat reQuest MAC protocol

2012

Author's version of an article published in the journal: Computer Standards & Interfaces. Also available from the publisher at: http://dx.doi.org/10.1016/j.csi.2011.12.001 Cooperative communications, in which a relay node helps the source node to deliver its packets to the destination node, are able to obtain significant benefits in terms of transmission reliability, coverage extension and energy efficiency. A Cooperative Automatic Repeat reQuest (C-ARQ) MAC protocol has been recently proposed to exploit cooperative diversity at the MAC layer. in this paper, we validate the integrity and the validity of the C-ARQ protocol using formal methods. The protocol logic is modeled in SDL and implem…

Adoption of a COVID-19 Contact Tracing App Among Older Internet Users in Finland

2022

The outbreak of the COVID-19 pandemic created an unequal need for limiting physical contacts and tracing possible exposures to a novel coronavirus. Smartphone-based contact tracing applications (CTAs) were presented as a vehicle for stopping virus transmission chains and supporting the work of contact tracing teams. In this study, older adults’ adoption of a CTA was studied using socioeconomic background factors, satisfaction with health, and the measure of digital activity as predictors. The data were drawn from a larger questionnaire survey targeted at older internet users. A subsample of older Finnish internet users (N = 723) was analyzed using a logistic regression model. Results showed…

Study of the cytolethal distending toxin (CDT)-activated cell cycle checkpoint. Involvement of the CHK2 kinase.

2001

AbstractThe bacterial cytolethal distending toxin (CDT) triggers a G2/M cell cycle arrest in eukaryotic cells by inhibiting the CDC25C phosphatase-dependent CDK1 dephosphorylation and activation. We report that upon CDT treatment CDC25C is fully sequestered in the cytoplasmic compartment, an effect that is reminiscent of DNA damage-dependent checkpoint activation. We show that the checkpoint kinase CHK2, an upstream regulator of CDC25C, is phosphorylated and activated after CDT treatment. In contrast to what is observed with other DNA damaging agents, we demonstrate that the activation of CHK2 can only take place during S-phase. Use of wortmannin and caffeine suggests that this effect is no…

Yeast Dun1 Kinase Regulates Ribonucleotide Reductase Inhibitor Sml1 in Response to Iron Deficiency

2014

Iron is an essential micronutrient for all eukaryotic organisms because it participates as a redox-active cofactor in many biological processes, including DNA replication and repair. Eukaryotic ribonucleotide reductases (RNRs) are Fe-dependent enzymes that catalyze deoxyribonucleoside diphosphate (dNDP) synthesis. We show here that the levels of the Sml1 protein, a yeast RNR large-subunit inhibitor, specifically decrease in response to both nutritional and genetic Fe deficiencies in a Dun1-dependent but Mec1/Rad53- and Aft1-independent manner. The decline of Sml1 protein levels upon Fe starvation depends on Dun1 forkhead-associated and kinase domains, the 26S proteasome, and the vacuolar pr…