8,004 research outputs found
Computation of Kolmogorov's Constant in Magnetohydrodynamic Turbulence
In this paper we calculate Kolmogorov's constant for magnetohydrodynamic
turbulence to one loop order in perturbation theory using the direct
interaction approximation technique of Kraichnan. We have computed the
constants for various , i.e., fluid to magnetic energy ratios
when the normalized cross helicity is zero. We find that increases from
1.47 to 4.12 as we go from fully fluid case to a situation when , then it decreases to 3.55 in a fully magnetic limit .
When , we find that .Comment: Latex, 10 pages, no figures, To appear in Euro. Phys. Lett., 199
Nonlinear electrostatic oscillations in a cold magnetized electron-positron plasma
We study the spatio-temporal evolution of the nonlinear electrostatic
oscillations in a cold magnetized electron-positron (e-p) plasma using both
analytics and simulations. Using a perturbative method we demonstrate that the
nonlinear solutions change significantly when a pure electrostatic mode is
excited at the linear level instead of a mixed upper-hybrid and zero-frequency
mode that is considered in a recent study. The pure electrostatic oscillations
undergo phase mixing nonlinearly. However, the presence of the magnetic field
significantly delays the phase-mixing compared to that observed in the
corresponding unmagnetized plasma. Using 1D PIC simulations we then analyze the
damping of the primary modes of the pure oscillations in detail and infer the
dependence of the phase-mixing time on the magnetic field and the amplitude of
the oscillations. The results are remarkably different from those found for the
mixed upper-hybrid mode mentioned above. Exploiting the symmetry of the e-p
plasma we then explain a generalized symmetry of our non-linear solutions. The
symmetry allows us to construct a unique nonlinear solution up to the second
order which does not show any signature of phase mixing but results in a
nonlinear wave traveling at upper-hybrid frequency. Our investigations have
relevance for laboratory/astrophysical e-p plasmas
Nanomaterial integration in micro LED technology: Enhancing efficiency and applications
The micro-light emitting diode (µLED) technology is poised to revolutionise display applications through the introduction of nanomaterials and Group III-nitride nanostructures. This review charts state-of-the-art in this important area of micro-LEDs by highlighting their key roles, progress and concerns. The review encompasses details from various types of nanomaterials to the complexity of gallium nitride (GaN) and III nitride nanostructures. The necessity to integrate nanomaterials with III-nitride structures to create effective displays that could disrupt industries was emphasised in this review. Commercialisation challenges and the economic enhancement of micro-LED integration into display applications using monolithic integrated devices have also been discussed. Furthermore, different approaches in micro-LED development are discussed from top-down and bottom-up approaches. The last part of the review focuses on nanomaterials employed in the production of micro-LED displays. It also highlights the combination of III-V LEDs with silicon LCDs and perovskite-based micro-LED displays. There is evidence that efficiency and performance have improved significantly since the inception of the use of nanomaterials in manufacturing these
Biochemical genetic polymorphism in Indian mackerel (Rastrelliger kanagurta)
Six enzymes glucose 6 phosphate dehydrogenase (G6PD), xanthene de hydrogenase (XDH), alcohol dehydrogenase
(ADH), peroxidase (PO), lactate dehydrogenase (LDH) and isocitric dehydrogenase (lDH) were examined to discover the
genetic variation in Indian mackerel through polyacrylamide gel electrophoresis. A significant difference in allelic frequency at XDH locus was observed between the eachin and Thotapally populations. Thotapally stocks exhibited a significant
deviation (P< 0.05) from Hardy weinberg equillibrium. The proportion of polymorphic Joci was 0.777. The coefficient of
identity and the genetic distance estimated were 0.9262 and 0.076 respectively
Biochemical genetic polymorphism in the Indian mackerel Rastrelliger kanagurta from Mangalore region
Electrophoresis is the modern and most
popular technique used for studying the genetic
variability within and among the populations of
plants and animals. Genetically controlled tissue
enzymes are the most suitable parameters for
genetic variability studies. In the present study
Polyacrylamide Gel Electrophoresis was used to
study the genetic variability in Indian mackerel
Bio-efficacy of tank mixed herbicides for control of complex weed flora in soybean (Glycine max L. Merril)
A field experiment was conducted at ZARS, Jhabua (M.P.) during kharif 2014 to find out most suitable and efficient method of weed control in soybean. The experiment consisted of nine treatments laid out in randomized block design with three replications. All the weed management practices led to significant reduction in density and dry matter of weeds as compared to weedy check. Two hand weeding (20 & 40 DAS) recorded lowest weed density (4.9/ m2), weed dry matter (22.35 g/m2) with highest weed control efficiency of 59.67% and found at par with the application of Chlorimuron Ethyl @ 9gm /ha + Quizalofop-p-ethyl @ 50 g /ha (density 5.48/ m2, dry matter 26.62 g/m2 and WCE of 51.97%) and Imazethapyr @ 35 g /ha + Imazamox @ 35 g/ha (density 6.13/ m2, dry matter 26.00 g/m2 and WCE of 53.08%). Maximum yield of 1782 kg/ha was recorded in two hand weeding (20 & 40 DAS) closely followed by Chlorimuron Ethyl @ 9gm /ha + Quizalofop-p-ethyl @ 50 g /ha (1723 kg/ha) and Imazethapyr @ 35 g / ha + Imazamox @ 35 g/ha (1697 kg/ha). Reduction in soybean yield in weedy check to be recorded is 38.78 per cent when compared to weed free and 36.68 per cent in comparison to Chlorimuron Ethyl @ 9gm /ha + Quizalofopp-ethyl @ 50 g /ha. However, highest Benefit to Cost ratio is recorded in Chlorimuron Ethyl +Quizalofop-p-ethyl (3.26) closely followed by Imazethapyr + Imazamox (3.22) and Weed free (3.21)
Emergence of small-scale magnetic flux in the quiet Sun
We study the evolution of a small-scale emerging flux region (EFR) in the
quiet Sun, from its emergence to its decay. We track processes and phenomena
across all atmospheric layers, explore their interrelations and compare our
findings with recent numerical modelling studies. We used imaging, spectral and
spectropolarimetric observations from space-borne and ground-based instruments.
The EFR appears next to the chromospheric network and shows all characteristics
predicted by numerical simulations. The total magnetic flux of the EFR exhibits
distinct evolutionary phases, namely an initial subtle increase, a fast
increase and expansion of the region area, a more gradual increase, and a slow
decay. During the initial stages, bright points coalesce, forming clusters of
positive- and negative-polarity in a largely bipolar configuration. During the
fast expansion, flux tubes make their way to the chromosphere, producing
pressure-driven absorption fronts, visible as blueshifted chromospheric
features. The connectivity of the quiet-Sun network gradually changes and part
of the existing network forms new connections with the EFR. A few minutes after
the bipole has reached its maximum magnetic flux, it brightens in soft X-rays
forming a coronal bright point, exhibiting episodic brightenings on top of a
long smooth increase. These coronal brightenings are also associated with
surge-like chromospheric features, which can be attributed to reconnection with
adjacent small-scale magnetic fields and the ambient magnetic field. The
emergence of magnetic flux even at the smallest scales can be the driver of a
series of energetic phenomena visible at various atmospheric heights and
temperature regimes. Multi-wavelength observations reveal a wealth of
mechanisms which produce diverse observable effects during the different
evolutionary stages of these small-scale structures.Comment: Accepted for publication in Astronomy & Astrophysics 14 pages, 14
figure
X-ray absorption spectroscopy and X-ray magnetic circular dichroism studies of transition-metal-co-doped ZnO nano-particles
We report on x-ray absorption spectroscopy (XAS) and x-ray magnetic circular
dichroism (XMCD) studies of the paramagnetic (Mn,Co)-co-doped ZnO and
ferromagnetic (Fe,Co)-co-doped ZnO nano-particles. Both the surface-sensitive
total-electron-yield mode and the bulk-sensitive total-fluorescence-yield mode
have been employed to extract the valence and spin states of the surface and
inner core regions of the nano-particles. XAS spectra reveal that significant
part of the doped Mn and Co atoms are found in the trivalent and tetravalent
state in particular in the surface region while majority of Fe atoms are found
in the trivalent state both in the inner core region and surface region. The
XMCD spectra show that the Fe ions in the surface region give rise to
the ferromagnetism while both the Co and Mn ions in the surface region show
only paramagnetic behaviors. The transition-metal atoms in the inner core
region do not show magnetic signals, meaning that they are
antiferromagnetically coupled. The present result combined with the previous
results on transition-metal-doped ZnO nano-particles and nano-wires suggest
that doped holes, probably due to Zn vacancy formation at the surfaces of the
nano-particles and nano-wires, rather than doped electrons are involved in the
occurrence of ferromagnetism in these systems.Comment: Proceedings of "XAFS theory and nanoparticles
- …