scholarly journals Viscosity and Large-Scale Magnetic Fields from Accretion Disc Dynamos

1997 ◽  
Vol 163 ◽  
pp. 190-200
Author(s):  
Christopher A. Tout
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Small Scale ◽  
Cascade Process ◽  
Jet Formation ◽  
Magnetohydrodynamic Turbulence ◽  
Discs Large ◽  
Scale Field ◽  
Large Scale Field ◽  
Nova Outbursts

AbstractWe review those processes associated with accretion discs that are probably influenced by magnetic fields, specifically, accretiondisc viscosity, energy dissipation and jet formation. We consider how magnetic instabilities in the disc can lead to a self-sustaining dynamical dynamo and how this is manifested as magnetohydrodynamic turbulence in numerical simulations. We show that currently these models do not fit with observational constraints imposed by dwarf-nova outbursts. We also show that the drop in ionisation fraction does not lead to the apparently necessary drop in viscosity in quiescent cataclysmic variable discs. Large-scale magnetic fields are required to launch and collimate jets form discs. We describe an inverse cascade process that can construct sufficient large-scale field from small-scale field generated by a dynamo.

scholarly journals Global magnetic fields: variation of solar minima

2011 ◽  
Vol 7 (S286) ◽  
pp. 113-122
Author(s):  
Andrey G. Tlatov ◽  
Vladimir N. Obridko
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Sunspot Cycle ◽  
Magnetic Activity ◽  
Small Scale ◽  
The Sun ◽  
Large Scale Magnetic Field ◽  
Scale Field ◽  
Large Scale Field

AbstractThe topology of the large-scale magnetic field of the Sun and its role in the development of magnetic activity were investigated using Hα charts of the Sun in the period 1887-2011. We have considered the indices characterizing the minimum activity epoch, according to the data of large-scale magnetic fields. Such indices include: dipole-octopole index, area and average latitude of the field with dominant polarity in each hemisphere and others. We studied the correlation between these indices and the amplitude of the following sunspot cycle, and the relation between the duration of the cycle of large-scale magnetic fields and the duration of the sunspot cycle.The comparative analysis of the solar corona during the minimum epochs in activity cycles 12 to 24 shows that the large-scale magnetic field has been slow and steadily changing during the past 130 years. The reasons for the variations in the solar coronal structure and its relation with long-term variations in the geomagnetic indices, solar wind and Gleissberg cycle are discussed.We also discuss the origin of the large-scale magnetic field. Perhaps the large-scale field leads to the generation of small-scale bipolar ephemeral regions, which in turn support the large-scale field. The existence of two dynamos: a dynamo of sunspots and a surface dynamo can explain phenomena such as long periods of sunspot minima, permanent dynamo in stars and the geomagnetic field.

scholarly journals A Field Efficacy Evaluation of In2Care Mosquito Traps in Comparison with Routine Integrated Vector Management at Reducing Aedes aegypti

2021 ◽  
Vol 37 (4) ◽  
pp. 242-249
Author(s):  
Eva A. Buckner ◽  
Katie F. Williams ◽  
Samantha Ramirez ◽  
Constance Darrisaw ◽  
Juliana M. Carrillo ◽  
...  
Keyword(s):  
Aedes Aegypti ◽  
Large Scale ◽  
Pathogen Transmission ◽  
Small Scale ◽  
Integrated Vector Management ◽  
Control Programs ◽  
Vector Management ◽  
Scale Field ◽  
Large Scale Field ◽  
Eggs And Larvae

ABSTRACT Aedes aegypti is the predominant vector of dengue, chikungunya, and Zika viruses. This mosquito is difficult to control with conventional methods due to its container-inhabiting behavior and resistance to insecticides. Autodissemination of pyriproxyfen (PPF), a potent larvicide, has shown promise as an additional tool to control Aedes species in small-scale field trials. However, few large-scale field evaluations have been conducted. We undertook a 6-month-long large-scale field study to compare the effectiveness and operational feasibility of using In2Care Mosquito Traps (In2Care Traps, commercially available Aedes traps with PPF and Beauveria bassiana) compared to an integrated vector management (IVM) strategy consisting of source reduction, larviciding, and adulticiding for controlling Ae. aegypti eggs, larvae, and adults. We found that while the difference between treatments was only statistically significant for eggs and larvae (P < 0.05 for eggs and larvae and P > 0.05 for adults), the use of In2Care Traps alone resulted in 60%, 57%, and 57% fewer eggs, larvae, and adults, respectively, collected from that site compared to the IVM site. However, In2Care Trap deployment and maintenance were more time consuming and labor intensive than the IVM strategy. Thus, using In2Care Traps alone as a control method for large areas (e.g., >20 ha) may be less practical for control programs with the capacity to conduct ground and aerial larviciding and adulticiding. Based on our study results, we conclude that In2Care Traps are effective at suppressing Ae. aegypti and have the most potential for use in areas without sophisticated control programs and within IVM programs to target hotspots with high population levels and/or risk of Aedes-borne pathogen transmission.

scholarly journals Off-Site Lime Stabilisation as an Option to Treat Pit Latrine Faecal Sludge for Emergency and Existing On-Site Sanitation Systems

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Wilson Greya ◽  
Bernard Thole ◽  
Catherine Anderson ◽  
Flavius Kamwani ◽  
Jan Spit ◽  
...  
Keyword(s):  
Large Scale ◽  
Buffer Capacity ◽  
Hydrated Lime ◽  
Field Trials ◽  
Small Scale ◽  
E Coli ◽  
Scale Field ◽  
Large Scale Field ◽  
Sanitation Systems ◽  
Faecal Sludge

Off-site lime stabilisation for treating faecal sludge was assessed by undertaking small-scale (35 L) and large-scale (600 L) field trials in Blantyre, Malawi. Hydrated lime was dosed to maintain pH 10, pH 10.5, pH 11, pH 11.5, and pH 12 depending on the buffer capacity of the faecal sludge in the four replica small-scale field trials. Significant reduction of E. coli to below the detection limit of 104 CFU/100 mL within 1 hour of treatment was reported for pH > 11. Based on the small-scale findings, large-scale field trials were conducted and greater than 3 log removal of E. coli was observed under pH 12 conditions. Therefore, based on the study, off-site lime stabilisation by dosing lime in the range of 10–35% w/w (dry solid basis), depending on the buffer capacity and solids content of the sludge to maintain pH > 11, can be used to sanitise faecal sludge during emergencies, as well as for existing on-site sanitation systems.

Methanol masers and magnetic field in IRAS18089-1732

2017 ◽  
Vol 13 (S336) ◽  
pp. 285-286
Author(s):  
Daria Dall’Olio ◽  
W. H. T. Vlemmings ◽  
G. Surcis ◽  
H. Beuther ◽  
B. Lankhaar ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
High Mass ◽  
Small Scale ◽  
Star Forming ◽  
Large Scale Field ◽  
The Impact ◽  
Theoretical Simulations ◽  
The Magnetic Field

AbstractTheoretical simulations have shown that magnetic fields play an important role in massive star formation: they can suppress fragmentation in the star forming cloud, enhance accretion via disc and regulate outflows and jets. However, models require specific magnetic configurations and need more observational constraints to properly test the impact of magnetic fields. We investigate the magnetic field structure of the massive protostar IRAS18089-1732, analysing 6.7 GHz CH3OH maser MERLIN observations. IRAS18089-1732 is a well studied high mass protostar, showing a hot core chemistry, an accretion disc and a bipolar outflow. An ordered magnetic field oriented around its disc has been detected from previous observations of polarised dust. This gives us the chance to investigate how the magnetic field at the small scale probed by masers relates to the large scale field probed by the dust.

scholarly journals PENGEMBANGAN MEDIA PANLINTARMATIKA (PAPAN PERKALIAN PINTAR MATEMATIKA) MATERI PERKALIAN UNTUK SISWA SEKOLAH DASAR

2021 ◽  
Vol 2 (1) ◽  
pp. 41-47
Author(s):  
Hasna Nur Afifah ◽  
Meita Fitrianawati
Keyword(s):  
Data Analysis ◽  
Field Test ◽  
Large Scale ◽  
Field Testing ◽  
Small Scale ◽  
Quantitative Data Analysis ◽  
Scale Field ◽  
Large Scale Field ◽  
The Media ◽  
Information Collecting

This study aims to 1) find out the steps in developing Panlintarmatika learning media, 2) know the feasibility of developing Panlintarmatika learning media based on experts.  This study is a type of Research and Development (RD) research using the Borg and Gal model which consists of: (1) research and information collecting, (2) planning, (3) developing preliminary from a product, (4) prelimunary field testing,  (5) main product revision, (6) main field testing, (7) operational product revision (8) operational field testing.  The trial subjects used were 18 grade 2 students and teachers at SD N Kalangan.  Data collection techniques in the form of observation, interviews and questionnaires.  Data analysis includes quantitative data analysis and qualitative data analysis.  The results showed that the validation of the media experts received a score of 60 in the "Very good" category, the validation of the material experts received a score of 42 in the "Good" category and the learning expert received a score of 60 in the "Good" category.  The results of the small-scale field test students get a score of 100 with the category "Very Good" and the teacher gets a score of 94 with the category "Very Good".  Large-scale field test results students get a score of 100 with the category "Very Good" and the teacher scores 98 with a score of "Very Good" It can be concluded that the Panlintarmatika learning media is feasible and can be used as class 2 learning multiplication material

scholarly journals Advection/diffusion of large scale magnetic field in accretion disks

2009 ◽  
Vol 16 (1) ◽  
pp. 77-81 ◽  
Author(s):  
R. V. E. Lovelace ◽  
G. S. Bisnovatyi-Kogan ◽  
D. M. Rothstein
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Turbulent Viscosity ◽  
Pressure Ratio ◽  
Rotational Instability ◽  
Small Scale ◽  
Magnetic Diffusivity ◽  
Large Scale Magnetic Field ◽  
Scale Field ◽  
Large Scale Field

Abstract. Activity of the nuclei of galaxies and stellar mass systems involving disk accretion to black holes is thought to be due to (1) a small-scale turbulent magnetic field in the disk (due to the magneto-rotational instability or MRI) which gives a large viscosity enhancing accretion, and (2) a large-scale magnetic field which gives rise to matter outflows and/or electromagnetic jets from the disk which also enhances accretion. An important problem with this picture is that the enhanced viscosity is accompanied by an enhanced magnetic diffusivity which acts to prevent the build up of a significant large-scale field. Recent work has pointed out that the disk's surface layers are non-turbulent and thus highly conducting (or non-diffusive) because the MRI is suppressed high in the disk where the magnetic and radiation pressures are larger than the thermal pressure. Here, we calculate the vertical (z) profiles of the stationary accretion flows (with radial and azimuthal components), and the profiles of the large-scale, magnetic field taking into account the turbulent viscosity and diffusivity due to the MRI and the fact that the turbulence vanishes at the surface of the disk. We derive a sixth-order differential equation for the radial flow velocity vr(z) which depends mainly on the midplane thermal to magnetic pressure ratio β>1 and the Prandtl number of the turbulence P=viscosity/diffusivity. Boundary conditions at the disk surface take into account a possible magnetic wind or jet and allow for a surface current in the highly conducting surface layer. The stationary solutions we find indicate that a weak (β>1) large-scale field does not diffuse away as suggested by earlier work.

scholarly journals Pengembangan Alat Peraga Taktual Model Atom untuk Siswa Tunanetra Kelas VIII

INKLUSI ◽  
2014 ◽  
Vol 1 (2) ◽  
pp. 159
Author(s):  
Wahyu Triningsih ◽  
Winarti Winarti
Keyword(s):  
Large Scale ◽  
Student Response ◽  
Atomic Model ◽  
Small Scale ◽  
Product Analysis ◽  
Expert Teacher ◽  
Scale Field ◽  
Large Scale Field ◽  
Research Procedure ◽  
Grade 3

The research purposes to (1) produce atomic model tactual props and material guidance of atomic model for blind student on eight grade, (2) know quality of atomic model tactual props and material guidance of atomic model for blind student on eight grade, (3) know student response toward atomic model tactual props and material guidance of atomic model for blind student on eight grade.This is a developmental research based on a procedural model. The development procedure is based on the development research procedure by Puslitjaknov Team that is adapted from Borg and Gallresearch procedure with development steps such as (1) doing product analysis that will be developed, (2) developing preliminary product, (3) experts validation and revision, (4) small scale field test and product revision, and (5) large scale field and final product. Collecting data technique by a non test research instruments are developed by such as validation sheet, appraisal sheet and student response. The analyzing data technique is done by changing the quantitative data into qualitative data.This research produced an atomic model tactual props and material guidance for blind student on eight grade. Based on the appraisal of media expert, material expert, teacher, atomic and students this prop has a very good quality.

scholarly journals Small-scale field assessment of efficacy of the autodissemination approach against Aedes sp. in an urban area

2020 ◽  
Author(s):  
Ahmad Mohiddin Mohd Ngesom ◽  
Hidayatulfathi Othman ◽  
Rawaida Bahauddin ◽  
Nazni Wasi Ahmad ◽  
Lee Han Lim ◽  
...  
Keyword(s):  
Vector Control ◽  
Large Scale ◽  
Field Trials ◽  
Control Programme ◽  
Small Scale ◽  
Vector Control Programme ◽  
Breeding Habitats ◽  
Scale Field ◽  
Large Scale Field ◽  
Future Evaluation

AbstractThis is the first study to evaluate the efficacy of an autodissemination approach, as suggested by WHO. Therefore, the efficacy of an autodissemination approach in small-scale field trials against wild Aedes sp. population was evaluated in an urbanized setting, Malaysia. Lethal ovitraps enhanced with pyriproxyfen were used to control Aedes sp. populations at treatment sites, with the autodissemination activity was assessed using the WHO larval bioassays. Lethal ovitraps enhanced with pyriproxyfen effectively reduced of Aedes sp. population. All autodissemination stations were shown to be visited by Aedes sp. mosquitoes with 100% complete inhibition against eggs and larvae development. In the larvae bioassay, pupae mortality ranged from 14 to 40%. Statistically, a significant reduction of Aedes sp. population in the treatment sites compared to the untreated areas. The study proved for the autodissemination of pyriproxyfen to breeding habitats by wild Aedes sp. This technique is highly potentially for vector control activities. Future evaluation should focus on large-scale field trials.Author SummarySince 2012, Dataran Automobil, Seksyen 15, Shah Alam, was declared as one of the dengue hotspot areas. Major vector control activities were conducted by government, NGOs, social communities, and local authorities, but the number still rising. We conducted a new invention of autodissemination concepts in this area by an entomological study on mosquito populations reduction and dispersal abilities of the technique. We found that the technique has proven to control mosquito populations, but the other factors such as epidemiology link still unclear and need further clarification. Our finding highlighted the effectiveness of autodissemination strategies that can be considered as one of the alternative tools in vector control programme.

scholarly journals Developing a training tool for beginner athletes in woodball

2021 ◽  
Author(s):  
Adi Wijayanto
Keyword(s):  
Large Scale ◽  
Descriptive Analysis ◽  
Field Trials ◽  
Small Scale ◽  
Quantitative Descriptive Analysis ◽  
Training Tool ◽  
Scale Field ◽  
Observation Instruments ◽  
Large Scale Field ◽  
Quantitative Descriptive

This research aimed to produce models of hitting practice tools, which could be used in training beginner woodball athletes in Indonesia. A process of research and development was followed after the model of Gall, Gall, & Borg (2007). Small-scale field trials were first conducted at Gerokgak Woodball Club (GWC), or GerokgakWoodball Club (GWC) Buleleng-Bali, involving 10 athletes (5 males and 5 females).These were followed by large-scale field trials conducted in Pengkab WoodballBuleleng, or Pengkab Woodball Buleleng-Bali, involving 20 athletes (10 males and 10females). Data gathered were both quantitative and qualitative. Quantitative descriptive analysis was employed with the (a) observation instruments/observations of the effectiveness of the tool development model; and (b) the athlete response questionnaire as part of the validation process. Qualitative descriptive analysis was applied to data gained from interviews, observations and fieldnotes in processing suggestions for improvement from material experts, media experts, and practitioners. This research produced an effective and appropriate hitting practice tool for beginners in woodball and a guide/instruction on how to use the tool. These wood practice products can be carried or moved in accordance with training needs (portable), can be used to train the consistency of the punch, increase the frequency of hitting exercises, in the open field (outdoor) or in the building (indoor). The wood practice tool can be used by athletes to practice short stroke, medium, long, or finishing/gating.

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