1,444 research outputs found
Attractor Solutions in f(T) Cosmology
In this paper, we explore the cosmological implications of interacting dark
energy model in a torsion based gravity namely . Assuming dark energy
interacts with dark matter and radiation components, we examine the stability
of this model by choosing different forms of interaction terms. We consider
three different forms of dark energy: cosmological constant, quintessence and
phantom energy. We then obtain several attractor solutions for each dark energy
model interacting with other components. This model successfully explains the
coincidence problem via the interacting dark energy scenario.Comment: 10 pages, 23 figures, version accepted for publication in European
Physical Journal C (2012
Solvable K-essence Cosmologies and Modified Chaplygin Gas Unified Models of Dark Energy and Dark Matter
This paper is devoted to the investigation of modified Chaplygin gas model in
the context of solvable k-essence cosmologies. For this purpose, we construct
equations of state parameter of this model for some particular values of the
parameter . The graphical behavior of these equations are also discussed by
using power law form of potential. The relationship between k-essence and
modified Chaplygin gas model shows viable results in the dark energy scenario.
We conclude that the universe behaves as a cosmological constant, quintessence
phase or phantom phase depending upon .Comment: 14 pages, 6 figure
Cholinesterase inhibitors from heartwood of artocarpus fulvicortex F. M. Jarret (Moraceae)
Cholinesterase inhibition activities were screened on crude extracts and isolated compounds of the heartwood of Artocarpus fulvicortex. Phytochemical studies on the heartwood of A. fulvicortex have resulted in the isolation of one flavonoid, one stilbenoid and two triterpenes. Their structures were determined by spectroscopic analysis as catechin (1), oxyresveratrol (2), lupeol-3-acetate (3) and friedelin (4). All isolates were evaluated for the first time for anti-cholinesterase activity. Inhibition of acetylcholinesterase (AChE), tested by Ellman’s method and modified TLC bioautographic assay showed catechin (1) and oxyresvetratrol (2) were active agents with detection limit of 2 mM. The microplate assay was carried out using butyrylcholinesterase (BChe) to further confirmed that catechin (1) and oxyresvetratrol (2) displayed positive cholinesterase activity with IC50 values 50.0 mM and 6.25 mM respectively in dose dependent manner
Resolution of dark matter problem in f(T) gravity
In this paper, we attempt to resolve the dark matter problem in f(T) gravity.
Specifically, from our model we successfully obtain the flat rotation curves of
galaxies containing dark matter. Further, we obtain the density profile of dark
matter in galaxies. Comparison of our analytical results shows that our
torsion-based toy model for dark matter is in good agreement with empirical
data-based models. It shows that we can address the dark matter as an effect of
torsion of the space.Comment: 14 pages, 3 figure
Development of wireless-based low-cost current controlled stimulator for patients with spinal cord injuries
A spinal cord injury (SCI) has a severe impact on
human life in general as well as on the physical status and
condition. The use of electrical signals to restore the function of
paralyzed muscles is called functional electrical stimulation
(FES). FES is a promising way to restore mobility to SCI by
applying low-level electrical current to the paralyzed muscles so
as to enhance that person’s ability to function and live
independently. However, due to the limited number of
commercially available FES assisted exerciser systems and their
rather high cost, the conventional devices are unaffordable for
most peoples. It also inconvenient because of wired based system
that creates a limitation in performing exercise. Thus, this
project is concerned with the development of low-cost current
controlled stimulator mainly for the paraplegic subjects. The
developed device should be based on a microcontroller, wireless
based system using Zigbee module, voltage-to-current converter
circuit and should produce proper monophasic and biphasic
current pulses, pulse trains, arbitrary current waveforms, and a
trigger output for FES applications. The performances of the
device will be assessed through simulation study and validated
through experimental work. This device will be developed as in
the new technique of the stimulator development with low cost
and one of the contributing factors in Rehabilitation Engineering
for patients with SCI
Development of wireless-based low-cost current controlled stimulator for patients with spinal cord injuries
A spinal cord injury (SCI) has a severe impact on
human life in general as well as on the physical status and
condition. The use of electrical signals to restore the function of
paralyzed muscles is called functional electrical stimulation
(FES). FES is a promising way to restore mobility to SCI by
applying low-level electrical current to the paralyzed muscles so
as to enhance that person’s ability to function and live
independently. However, due to the limited number of
commercially available FES assisted exerciser systems and their
rather high cost, the conventional devices are unaffordable for
most peoples. It also inconvenient because of wired based system
that creates a limitation in performing exercise. Thus, this
project is concerned with the development of low-cost current
controlled stimulator mainly for the paraplegic subjects. The
developed device should be based on a microcontroller, wireless
based system using Zigbee module, voltage-to-current converter
circuit and should produce proper monophasic and biphasic
current pulses, pulse trains, arbitrary current waveforms, and a
trigger output for FES applications. The performances of the
device will be assessed through simulation study and validated
through experimental work. This device will be developed as in
the new technique of the stimulator development with low cost
and one of the contributing factors in Rehabilitation Engineering
for patients with SCI
Interacting entropy-corrected new agegraphic dark energy in Brans-Dicke cosmology
Motivated by a recent work of one of us [1], we extend it by using quantum
(or entropy) corrected new agegraphic dark energy in the Brans-Dicke cosmology.
The correction terms are motivated from the loop quantum gravity which is one
of the competitive theories of quantum gravity. Taking the non-flat background
spacetime along with the conformal age of the universe as the length scale, we
derive the dynamical equation of state of dark energy and the deceleration
parameter. An important consequence of this study is the phantom divide
scenario with entropy-corrected new agegraphic dark energy. Moreover, we assume
a system of dark matter, radiation and dark energy, while the later interacts
only with dark matter. We obtain some essential expressions related with dark
energy dynamics. The cosmic coincidence problem is also resolved in our model.Comment: 16 pages, no figure, accepted for publication in Gen. Relativ. Gra
Transformation of 2,4, 6-Trinitrotoluene (TNT) by Immobilized and Resting Cells of Arthrobacter SP.
Arthrobacter sp. transformed 2,4,6-trinitrotoluene (TNT) into two isomeric monoaminodinitrotoluenes viz, 4-amino-2,6-dinitrotoluene (4-ADNT), 2-amino- 4,6 –dinitrotoluene (2-ADNT) and also 2,4- diamino-6- nitrotoluene (2,4-DANT) under aerobic resting cell conditions. Experiments were carried out at 30° C (±1°C) in phosphate buffer with 60 mg per liter TNT at a pH of 7.2 (±0.2). Complete transformation of TNT occurred within 36 hours, yielding a mixture of monoaminodinitrotoluenes and diaminonitrotoluene. The major component was found to be 4-ADNT. Under the same experimental conditions, transformations were studied using barium alginate immobilized cells of Arthrobacter sp. Appropriate controls were run simultaneously. In both the cases, reactions were monitored every six hours by thin-layer chromatography (TLC) and gas chromatography (GC). The products were identified by gas chromatography coupled with mass spectrometry (GC-MS). Immobilization of Arthrobacter sp. in barium alginate resulted in more efficient TNT transformations, which were complete in 24 hours. The immobilized cells could be utilized at least for eight cycles and a decrease in rate of transformation was observed with each cycle
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