3,832 research outputs found
Evaluation of some phenolic extracts against aphids (Aphis craccivora) Koch under laboratory conditions
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
Increased lymph node yield in colorectal cancer is not necessarily associated with a greater number of lymph node positive cancers
Peer reviewedPublisher PD
Nanosized Supramolecular Coordination Polymers Derived from Divalent Metal Ions, 4-Pyridylacetate and Auxiliary Ligands Containing Nitrogen and Phosphorus Donors
A series of coordination polymers of Co(II), Ni(II), Cu(II) or Cd(II) comprising 4-pyridylacetate (pya) and certain auxiliary ligands including benzimidazole (Hbzim), 1,10-phenanthroline (phen), 2,2'-bipyridine (2,2'-bipy), 2-amino-4-methylthiazole (A-Mtz), quinazole (Quz), 2,5-dimethylpyrazine (dpmz), bis(diphenylphosphino)methane (dpm), 1,2-bis(diphenylphosphino)ethane (dpe) and 1,3-bis(diphenylphosphino) propane (dpp) were prepared and characterized by spectroscopic, magnetic and thermal techniques. In these coordination polymers 4-pyridylacetate coordinates to the metal ions in a monodentate fashion through the carboxylate oxygens and/or the pyridyl nitrogen. Octahedral structures around the metal ions were suggested for all the complexes. The kinetic analyses of the thermal decomposition of the complexes were studied using the Coats-Redfern equation. The kinetic and thermodynamic parameters of the thermal decomposition were also calculated and discussed. From the X-ray powder diffraction data, the crystal parameters as well as the particle sizes (15.7-18.7 nm) of the complexes could be evaluated. Some of the compounds exhibit catalytic activity. The biological activity of the compounds was screened as well.
DOI: http://dx.doi.org/10.17807/orbital.v13i1.155
Magnetically Torqued Thin Accretion Disks
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
Izrada i značajke tankih polikristaliničnih hetero-spojeva n-Cd0.9Zn0.1S/p-CuGa0.3In0.7Se2
CuGa0.3In0.7Se2 polycrystalline thin films were prepared by thermal evaporation under vacuum of about 10-4Pa, with a deposition rate of about 200 nm/min. The selenization of these films at 723 K improves their properties. The activation energy as well as the optical energy gap of the investigated samples decreased with annealing and selenization. Polycrystalline thin film n-Cd0.9Zn0.1S/p-CuGa0.3In0.7Se2 heterojunctions were fabricated and the current density - voltage and capacitance - voltage characteristics of the junction were studied. The heterojunctions were exposed to light, and under illumination of 1000 mWcm-2, the open circuit voltage was 580 mV, the short circuit current density 4.8 mAcm-2, the fill factor 0.682 and the electrical conversion efficiency was 1.898% for cells of active area of 1 cm2.Tanke polikristalinične slojeve CuGa0.3In0.7Se2 pripremali smo naparavanjem u vakuumu oko 10−4 Pa, brzinom polaganja oko 200 nm/min. Seleniranje tih slojeva na 723 K poboljšava im svojstva. Aktivacijska energija i optički energijski procijep smanjuju se opuštanjem i seleniranjem. Pripremali smo i polikristalinične tankoslojne hetero-spojeve n-Cd0.9Zn0.1S/p-CuGa0.3In0.7Se2 i proučavali njihova značajke: gustoća struje – napon i kapacitet – napon. Ćelije ploštine 1 cm2 heterospojeva osvijetlili smo svjetlošću jakosti 1000 mW/cm2 i izmjerili napon otvorenog kruga od 580 mV, gustoću struje kratkog spoja 4.8 mAcm−2 , faktor punjenja 0.682 i učinkovitost pretvorbe 1.898%
Reactivity of Some Transition Metal Complexes of Anthranilic Acid with Leucine and Monochloroacetic Acid
Six mixed ligand complexes of [M(Anth) (Leu)] . nH20 and [M(Anth) (Clac)] types, where M=Co, Ni and Cu; n e=O, 2 or 4; Anth e anthranilate and Leu e leucinate, have been prepared. They were characterized on the basis of their analyses, infrared and UV-VIS spectra, magnetic and thermal measurements. All the compounds were found to have presumably distorted octahedral configurations. The polymeric structure of the complexes is indicated by their insolubility and high thermal stability
"Propeller" Regime of Disk Accretion to Rapidly Rotating Stars
We present results of axisymmetic magnetohydrodynamic simulations of the
interaction of a rapidly-rotating, magnetized star with an accretion disk. The
disk is considered to have a finite viscosity and magnetic diffusivity. The
main parameters of the system are the star's angular velocity and magnetic
moment, and the disk's viscosity, diffusivity. We focus on the "propeller"
regime where the inner radius of the disk is larger than the corotation radius.
Two types of magnetohydrodynamic flows have been found as a result of
simulations: "weak" and "strong" propellers. The strong propeller is
characterized by a powerful disk wind and a collimated magnetically dominated
outflow or jet from the star. The weak propeller have only weak outflows. We
investigated the time-averaged characteristics of the interaction between the
main elements of the system, the star, the disk, the wind from the disk, and
the jet. Rates of exchange of mass and angular momentum between the elements of
the system are derived as a function of the main parameters. The propeller
mechanism may be responsible for the fast spinning-down of the classical T
Tauri stars in the initial stages of their evolution, and for the spinning-down
of accreting millisecond pulsars.Comment: 18 pages, 16 figures, ApJ (accepted), added references, corrected
typos; see animation at
http://astrosun2.astro.cornell.edu/us-rus/disk_prop.ht
Locus of Control as Budget Slack Moderator: The Role of Ethical Leadership and Budget Participation
The current study investigates the impact of Budget Participation and Ethical Leadership on Budget Slack. Further, the study investigates how Locus of Control serves as a moderator. The study sample includes bankers working in the Egyptian banking sector. The study deployed an electronic survey. Of the 384 total distributed questionnaires 275 were retrieved, with a response rate of 71.6%. The final sample for the statistical analysis was 251 questionnaires after all exclusions. For testing hypothesis about the relationship between the study variables simple and multiple regression models were adapted. The study results revealed a negative and significant impact of Ethical Leadership on Budget Slack, while Budget Participation was found to affect Budget Slack behaviour positively and significantly. Furthermore, our study revealed that Locus of Control partially and negatively moderating the correlation between Ethical Leadership and Budget slack. These findings contribute to the organizational behavior and management accounting literature, representing one of the first studies to examine this interdisciplinary relationship and confirm the moderating roles identified in African and Middle Eastern contexts
Force-Free Models of Magnetically Linked Star-Disk Systems
Disk accretion onto a magnetized star occurs in a variety of astrophysical
contexts, from young stars to X-ray pulsars. The magnetohydrodynamic
interaction between the stellar field and the accreting matter can have a
strong effect on the disk structure, the transfer of mass and angular momentum
between the disk and the star, and the production of bipolar outflows, e.g.,
plasma jets. We study a key element of this interaction - the time evolution of
the magnetic field configuration brought about by the relative rotation between
the disk and the star - using simplified, largely semianalytic, models. We
first discuss the rapid inflation and opening up of the magnetic field lines in
the corona above the accretion disk, which is caused by the differential
rotation twisting. Then we consider additional physical effects that tend to
limit this expansion, such as the effect of plasma inertia and the possibility
of reconnection in the disk's corona, the latter possibly leading to repeated
cycles in the evolution. We also derive the condition for the existence of a
steady state for a resistive disk and conclude that a steady state
configuration is not realistically possible. Finally, we generalize our
analysis of the opening of magnetic field lines by using a non-self-similar
numerical model that applies to an arbitrarily rotating (e.g. keplerian) disk.Comment: 75 pages, 22 figures, 2 tables. Submitted to Astrophysical Journa
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