What sets the magnetic field strength and cycle period in solar-type stars?

Two fundamental properties of stellar magnetic fields have been determined by observations for solar-like stars with different Rossby numbers (Ro), namely, the magnetic field strength and the magnetic cycle period. The field strength exhibits two regimes: 1) for fast rotation it is independent of Ro, 2) for slow rotation it decays with Ro following a power law. For the magnetic cycle period two regimes of activity, the active and inactive branches, also have been identified. For both of them, the longer the rotation period, the longer the activity cycle. Using global dynamo simulations of solar like stars with Rossby numbers between ~0.4 and ~2, this paper explores the relevance of rotational shear layers in determining these observational properties. Our results, consistent with non-linear alpha^2-Omega dynamos, show that the total magnetic field strength is independent of the rotation period. Yet at surface levels, the origin of the magnetic field is determined by Ro. While for Ro<1 it is generated in the convection zone, for Ro>1 strong toroidal fields are generated at the tachocline and rapidly emerge towards the surface. In agreement with the observations, the magnetic cycle period increases with the rotational period. However, a bifurcation is observed for Ro~1, separating a regime where oscillatory dynamos operate mainly in the convection zone, from the regime where the tachocline has a predominant role. In the latter the cycles are believed to result from the periodic energy exchange between the dynamo and the magneto-shear instabilities developing in the tachocline and the radiative interior.Comment: 43 pages, 14 figures, accepted for publication in The Astrophysical Journa

Techniques for Enhancing and Maintaining Electrical Efficiency of Photovoltaic Systems

Demand for electricity generation from solar energy, which is a clean and renewable resource, is increasing day by day. It is desirable that the panel surface temperature is not excessively hot while generating electricity with PVT panels. High temperature causes thermal degradation and panel electric efficiency decrease. There are many studies in the literature about active thermal cooling of PVT panels used for electricity generation as well as for storing thermal energy. In this study, a review was made on methods developed to increase the thermal and electrical efficiencies of PVT panels

Rheology of high-performance cement pastes: effect of calcined kaolin

The search for a quality of concrete is a major concern in Algeria especially after the 2003 earthquake (East- Algeria). So it's necessary to improve the properties of concrete using fine particles such as mineral additions as a solution. These are currently used in the concrete to develop its performance and reduce consumption of clinker. This reduction will contribute to economic and easy way to solve problems related to the environment. In this work, an experimental rheological investigation was conducted to evaluate the performances of Algerian metakaolin MK on cement pastes. The latter is obtained from calcined natural kaolin found in large amounts in eastern Algeria (Tamazert- Milia). Several rheological tests were carried out by using the stress controlled rheometer AR2000, on the fresh cement pastes incorporating 0%, 5%, 10%, 15% and 20% of MK. The effects of metakaolin on the rheological behaviour of pastes were discussed. The parameters such as shear stress, viscosity, compliance, loss and storage shear modulus were evaluated by means of rheological techniques of both flow test, oscillatory and creep dynamic tests. The study in dynamic mode allow to give information on the evolution of the paste structure related to practically interesting problems such as workability. The results obtained have shown that the metakaolin improves the flowability and exhibits viscous rheological behaviour of cement pastes compared to the elastic behaviour of control paste (0%MK). Moreover, the creep test has shown that MK exhibits a viscoelastic liquid behaviour of cement pastes compared to a viscoelastic solid behaviour of control paste. In addition, it seems that the replacement rate of 10% of MK is an optimum for better rheological behavior of cement pastes. The rheological tests give promising results that encourage the use of metakaolin as component for a high performance concrete designated for industry

Context of STEM Integration in Schools: Views from In-service Science Teachers

This is the final version of the article. Available from ISER publications via the DOI in this record.This study explores science teachers' views regarding Science, Technology, Engineering and Mathematics (STEM) pedagogy and its interdisciplinary nature. It also seeks to identify teachers' views on the contextual factors that facilitate and hinder such pedagogy in their schools. Qualitative methodologies were used through focus group discussions and an interview protocol. From the specific contextual issues that were highlighted in the findings, was teacher self-efficacy, pedagogical-knowledge, issues related to establishing a collaborative school culture and familiarity to STEM education among school administrators, students and parents. Findings expressed teachers' concerns of their under- preparedness to enact STEM practices and illustrated that engineering is the least mentioned discipline to be integrated with science. The study ends with recommendations that could lead to develop a professional development model to enact STEM education in schools based on valuing partnership with universities and industries as a necessary step for enacting a STEM integrated model.This research was conducted as part of the professional development for in-service Science and mathematics teachers Research group with support of the Excellence Research Centre of Science and Mathematics Education - King Saudi University, Kingdom of Saudi Arabia

Adaptation Algorithm and Theory Based on Generalized Discrepancy

We present a new algorithm for domain adaptation improving upon a discrepancy minimization algorithm previously shown to outperform a number of algorithms for this task. Unlike many previous algorithms for domain adaptation, our algorithm does not consist of a fixed reweighting of the losses over the training sample. We show that our algorithm benefits from a solid theoretical foundation and more favorable learning bounds than discrepancy minimization. We present a detailed description of our algorithm and give several efficient solutions for solving its optimization problem. We also report the results of several experiments showing that it outperforms discrepancy minimization

Accuracy of intraoral scanners versus traditional impressions: a rapid umbrella review

PURPOSE This study aimed to (1) report the trueness and precision of intraoral scanning (IOS) in dentistry based on recent secondary sources and to (2) appraise the reporting quality of the titles and abstracts of the included literature. MATERIALS AND METHODS This rapid overview searched the PubMed/Medline and Cochrane Database of Systematic Reviews in March 2021 to identify reviews reporting on the accuracy of IOS. The reference list from the eligible studies was also screened for identification of other potentially eligible studies. The inclusion criteria consisted of English language systematic reviews or meta-analyses published between 2019 and 2021. The exclusion criteria were primary studies, narrative review, and extraoral scanners. The assessment of reporting quality of abstracts of systematic reviews was performed using the reporting checklist PRISMA extension for Abstracts (PRISMA-A). This was a self-funded research project. RESULTS Out of the full text screened 25 records, 11 reviews were included. Most studies supported the IOS approach being as precise and accurate as the conventional one. Only one study significantly favored the conventional approach over the IOS, and two studies abstained from making a recommendation. The IOS was significantly superior to the traditional technique in terms of patient preference and time efficiency. After applying PRISMA-A, recommendations for improvements on titles and abstracts of future reviews of IOS and conventional impressions are provided. CONCLUSION Laboratory data indicated similar accuracy between IOS and conventional impressions, whereas clinical data found the same in less than 4-unit fixed dental prostheses. For more extensive definitive fixed solutions or removable prostheses, the conventional approach is recommended. IOS was superior in terms of patient preference and time reduction. More clinical trials are required to determine the clinical effectiveness of incorporating IOS in broader scenarios. Better quality of reporting secondary sources abstract is advised

Design, synthesis and potential anti-proliferative activity of some novel 4-aminoquinoline derivatives

Novel nineteen compounds based on a 4-aminoquinoline scaffold were designed and synthesized as potential anti-proliferative agents. The new compounds were N-substituted at the 4-position by aryl or heteroaryl 1-9, quinolin-3-yl 10, 2-methylquinolin-3-yl 11, thiazol-2-yl 12, and dapsone moieties 13, 14 and 18. Bis-compounds 15, 16 and 19 were also synthesized to assess their biological activity. All the newly synthesized comounds were tested for in vitro antiproliferative activity against the MCF-7 breast cancer cell line. Seventeen of the novel compounds showed higher activity than the reference drug doxorubicin. The corresponding 7-(trifluoromethyl)-N-(3,4,5-trimethoxyphenyl)quinolin-4-amine 1, N-(7-(trifluoromethyl)quinolin-4-yl)quinolin-3-amine (10), 2-methyl-N-(7-trifluorome-thyl)quinolin-4-yl)quinolin-3-amine (11) and N-(4-(4-aminophenylsulf-onyl)phenyl)-7-chloroquinolin-4-amine (13) were almost twice to thrice as potent as doxorubicin

Selection of pomegranate (Punica granatum L.) in south-eastern Tunisia

Tunisia is one of the main producers and exporters of pomegranate (Punica granatum L.) in the world. Due to its international importance, the selection of both quantitative and qualitative most desirable varieties has become a necessity. To select new cultivars that are most appropriate for commercial use, 21 accessions were collected from different regions of south-east Tunisia. 24 morphological characters of the tree and fruit were studied for each accession. This study has revealed considerable diversity especially concerning the tree vigor, the fruit size and color and the acidity of juice. Taking into account all comments, some trees are considered particularly efficient in south-eastern Tunisia.Key words: South-east Tunisia, Punica granatum L., selection, morphological characters

An experimental setup combining a highly sensitive detector forreaction products with a mass-selected cluster source andalow-temperature STM for advanced nanocatalysis measurements

We report on a home-built detector for catalytic reaction measurements offering good gas isolation from the surrounding ultrahigh vacuum components, high sensitivity for reaction products and a fast response time of 10ms enabling dynamic studies correlated to reactant gas pulses. The device is mounted in ultrahigh vacuum and combined with a low-temperature scanning tunneling microscope and a source for the deposition of mass-selected clusters. This combination allows for a direct correlation between surface morphology and catalytic properties of model catalysts. The performances of the new detector are illustrated by measurements on two model systems. Thermal desorption spectroscopy of CO carried out on morphologically well characterized Pt on TiO2(110)-(1×1) reveals several desorption features, which can be attributed to different surface sites. Catalytic CO oxidation performed by alternatingly pulsing isotopic CO and O2 on a Pt film on yttria stabilized zirconia reveals the CO or O rich temperature regimes. The CO2 production rate correlated with either one of the reactants can perfectly be reproduced by a kinetic reaction model giving access to the respective adsorption energie