4,521 research outputs found

    On the formation of current sheets in response to the compression or expansion of a potential magnetic field

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    The compression or expansion of a magnetic field that is initially potential is considered. It was recently suggested by Janse & Low [2009, ApJ, 690, 1089] that, following the volumetric deformation, the relevant lowest energy state for the magnetic field is another potential magnetic field that in general contains tangential discontinuities (current sheets). Here we examine this scenario directly using a numerical relaxation method that exactly preserves the topology of the magnetic field. It is found that of the magnetic fields discussed by Janse & Low, only those containing magnetic null points develop current singularities during an ideal relaxation, while the magnetic fields without null points relax toward smooth force-free equilibria with finite non-zero current.Comment: Accepted for publication in Ap

    Evaluation of some phenolic extracts against aphids (Aphis craccivora) Koch under laboratory conditions

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    Local farmers worldwide have complained in recent years that insect pests have become resistant to the majority of insecticides, owing to pesticide abuse. In addition, highly poisonous and harmful substances may cause health and environmental dangers. Friendly alternatives such as plant extracts are the main targets as substituents to synthetic pesticides. The present study aimed to extract total phenols from some plants and evaluate their efficacy on aphids, Aphis craccivora, under laboratory conditions. Four methanolic plant extracts from Punica granatum, Lantana camara, Portulaca oleracea and Ziziphus jujuba, containing phenolic components were evaluated against A. craccivora through: slide dipping, spraying, and leaf dipping techniques. Generally, positive relationships between the concentrations of the tested phenolic extracts and their mortality percentages were noticed in the case of slide dipping and spraying techniques. Conversely, no biological efficacy was found using the leaf dipping technique. The descending order of effectiveness of the tested extracts depending on their EC50 values was 0.017, 0.321, 1.142 and 16.114 ppm for Z. jujuba, P. oleraceae P. granatum and L. comara, respectively, in the case of the slide dipping technique. In contrast, P. granatum, L. camara, P. oleraceae and Z. jujuba had EC50 values of 0.0023, 0.017, 0.321 and 2.3409 ppm, respectively, in the case of the spraying technique. Additionally, a direct proportion was found between mortality percentages and treatment period for plant extracts under study with both techniques. After formulation and completion of additional essential field research, phenols isolated from the plants under study could be employed to combat A. craccivora

    The Optimization of Microbus-Based Public Transportation Facilities in Jayapura City

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    Public transport services will work well if there is a balance between supply and demand. The research aimed to analyze the performance and the needs for the number of public transportation facilities based on the microbuses in Jayapura City. The types of the public transports, which would be discussed, were the microbuses which operated in 12 routes of the total routes of 26 in Jayapura city; those were B1, B2, B3, B4, J1, J2, K, I1, E, G, IA and I. The analyses of the performance and the demand for number of public transports were analyzed based on the load factor and the break event in accordance with the value of the vehicles operating costs (BOK) in setting tariffs. The research results indicated that the standard performance value of the public transport route code of K, I1, G, IA were categorized as less, while the routes of B1, B2, B3, B4, J1, J2, E and IB were categorized as medium. The microbuses demand was only 50% of the total microbuses now operating in Jayapura city

    On the rotational dynamics of magnetically threaded disks around neutron stars

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    We investigate the rotational dynamics of disk accretion around a strongly magnetized neutron star with an aligned dipole field. The magnetospheric field is assumed to thread the disk plasma both inside and outside the corotation radius. As a result of disk-star interaction, the magnetic torque on the disk affects the structure of accretion flow to yield the observed spin- up or spin- down rates for a source of given fastness, magnetic field strength, and mass accretion rate. Within the model we obtain a prescription for the dynamical viscosity of such magnetically modified solutions for a Keplerian disk. We then use this prescription to find a model solution for the rotation rate profile throughout the entire disk, including the non-Keplerian inner disk. We find that the non-Keplerian angular velocity transition region is not necessarily narrow for a source of given spin state. The boundary layer approximation, as in the standard magnetically threaded disk model, holds only in the case of dynamical viscosity decreasing all the way to the innermost edge of the disk. These results are applied to several observed disk-fed X-ray pulsars that have exhibited quasi-periodic oscillations (QPOs). The QPO frequencies provide a constraint on the fastness parameter and enable one to determine uniquely the width of the angular velocity transition zone for each source within model assumptions. We discuss the implications of these results on the value of the critical fastness parameter for a magnetized star in spin equilibrium. Applications of our model are also made with relevant parameters from recent numerical simulations of quasi-stationary disk - magnetized star interactions

    Effect of Mobility on the Quality of Life among Older Adults in Geriatric Home at Makkah Al-Mukarramah

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    Background: Mobility limitations are common in older adults, affecting the physical, psychological, and social aspects of an older adult's life. The term quality of life (QOL) references the general well-being of individuals and societies. The term is used in a wide range of contexts, including the fields of international development, healthcare, and politics. Quality of life should not be confused with the concept of standard of living, which is based primarily on income. Instead, standard indicators of the quality of life include not only wealth and employment but also the built environment, physical and mental health, education, recreation and leisure time, and social belonging Quality of life (QOL) is aboard concept affected in a complex way by the person’s physical health, psychological state, social relationship, and the relationship to salient feature of the environment. Aim: This study aimed to assess the nature of relationship between mobility on QOL in older adults through assessing the older adults’ mobility, Activity of daily living (ADL) and QOL. Subjects and methods: A descriptive study was conducted on a convenient sample of 75 older adults in Social Care Home at Makkah AL-Mukarramah. Tools of data collection were an interview questionnaire form to collect socio-demographic characteristics, Elderly Mobility Scale (EMS), WHOQOL-BREF, and ADL. Results: The current study revealed that nearly half of older adults their ages ranged from (>75- 85 years) and more than two thirds of them had osteoarthritis, hypertension, diabetes mellitus, and urinary incontinence, more than half of the study sample were received assistance in bathing, dressing, and continence and more than half of subjects feeds themselves without assistance. Conclusion: There is a strong positively relationship between QOL, ADL, and elderly mobility (EM). Most of the older adults at geriatric home are completely dependent in ADL and mobility. Also there was highly statistically significant difference between QOL and EM. Recommendation: Training exercise must be provided upon initial range of motion of older adult, and encourage the older adult to applied ADLs.Key words: Mobility, Quality of Life, Older Adult and Geriatric Home

    Synthesis, Characterization and Application of Nano-adsorbent Materials in the Sorption of Pb(II), Ni(II), Co(II), Mn(II), Li(I) from Aqueous Solution

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    In this study, nano-adsorbent materials were synthesized from two different precursors by thermal activation technique. The first was the synthesizing of nano-zinc silicate from chemical reagents of zinc oxide and commercial silica gel. The second was the preparation of nano-pore size activated carbon from different biomass. The synthesized nano-adsorbent materials were characterized by different techniques; Surface Area, FTIR, XRD and SEM. The prepared nano-adsorbent materials were applied in the sorption and separation of some heavy metals from aqueous solution. These metals includes; Pb (II), Ni(II), Co(II), Mn(II) and Li(I). Some factors affecting on the sorption process (e.g. contact time and pH) were investigated. It was found that: the nano-zinc silicate (of ratio 1:1 thermally treated at 700 0C) and nano-pores activated carbon (prepared from saw dust impregnated with 70% H3PO4 overnight, then heated to 500 0C in presence of steam for 80 min.) were the best samples for sorption and separation of concerned heavy metals

    Magnetically Torqued Thin Accretion Disks

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    We compute the properties of a geometrically thin, steady accretion disk surrounding a central rotating, magnetized star. The magnetosphere is assumed to entrain the disk over a wide range of radii. The model is simplified in that we adopt two (alternate) ad hoc, but plausible, expressions for the azimuthal component of the magnetic field as a function of radial distance. We find a solution for the angular velocity profile tending to corotation close to the central star, and smoothly matching a Keplerian curve at a radius where the viscous stress vanishes. The value of this ''transition'' radius is nearly the same for both of our adopted B-field models. We then solve analytically for the torques on the central star and for the disk luminosity due to gravity and magnetic torques. When expressed in a dimensionless form, the resulting quantities depend on one parameter alone, the ratio of the transition radius to the corotation radius. For rapid rotators, the accretion disk may be powered mostly by spin-down of the central star. These results are independent of the viscosity prescription in the disk. We also solve for the disk structure for the special case of an optically thick alpha disk. Our results are applicable to a range of astrophysical systems including accreting neutron stars, intermediate polar cataclysmic variables, and T Tauri systems.Comment: 9 sharper figs, updated reference

    Adrenocortical status in infants and children with sepsis and septic shock

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    AbstractBackgroundThe benefit from corticosteroids remains controversial in sepsis and septic shock and the presence of adrenal insufficiency (AI) has been proposed to justify steroid use.AimTo determine adrenal state and its relation with outcome in critical children admitted with sepsis to PICU of Cairo University, Children Hospital.MethodsThirty cases with sepsis and septic shock were studied. Cortisol levels (CL) were estimated at baseline and after high-dose short ACTH stimulation in those patients and in 30 matched controls. Absolute AI was defined as basal CL<7μg/dl and peak CL<18μg/dl. Relative AI was diagnosed if cortisol increment after stimulation is <9μg/dl.ResultsOverall mortality of cases was 50%. The mean CL at baseline in cases was higher than that of controls (51.39μg/dl vs. 12.83μg/dl, p=0.000). The mean CL 60min after ACTH stimulation was higher than that of controls (73.38μg/dl vs. 32.80μg/dl, p=0.000). The median of %rise in cases was lower than that of controls (45.3% vs. 151.7%). There was a positive correlation between basal and post-stimulation cortisol with number of system failure, inotropic support duration, mechanical ventilation days, and CO2 level in blood. There was a negative correlation between basal and post stimulation cortisol with blood pH and HCO3.ConclusionRAI is common with severe sepsis/septic shock. It is associated with more inotropic support and has higher mortality. Studies are warranted to determine whether corticosteroid therapy has a survival benefit in children with RAI and catecholamine resistant septic shock
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