1,621 research outputs found
Dirac quasinormal modes for a 4-dimensional Lifshitz Black Hole
We study the quasinormal modes of fermionic perturbations for an
asymptotically Lifshitz black hole in 4-dimensions with dynamical exponent z=2
and plane topology for the transverse section, and we find analytically and
numerically the quasinormal modes for massless fermionic fields by using the
improved asymptotic iteration method and the Horowitz-Hubeny method. The
quasinormal frequencies are purely imaginary and negative, which guarantees the
stability of these black holes under massless fermionic field perturbations.
Remarkably, both numerical methods yield consistent results; i.e., both methods
converge to the exact quasinormal frequencies; however, the improved asymptotic
iteration method converges in a fewer number of iterations. Also, we find
analytically the quasinormal modes for massive fermionic fields for the mode
with lowest angular momentum. In this case, the quasinormal frequencies are
purely imaginary and negative, which guarantees the stability of these black
holes under fermionic field perturbations. Moreover, we show that the lowest
quasinormal frequencies have real and imaginary parts for the mode with higher
angular momentum by using the improved asymptotic iteration method.Comment: Version accepted for publication in EPJC. arXiv admin note: text
overlap with arXiv:1306.597
Antimicrobial and antioxidant potentials of essential oil and acetone extract of Myristica fragrans Houtt. (aril part)
The antifungal, antibacterial, and antioxidant potentials of essential oil and acetone extract were carried out by different techniques. In poison food medium method, the essential oil showed complete zones of inhibition against Fusarium graminearum at the all tested doses. For other tested fungi and bacteria, they gave good to moderate zone inhibition. The antioxidant activity was evaluated by measuring peroxide, thiobarbituric acid and total carbonyl values of rapeseed oil at fixed time intervals. Both the extract and essential oil showed strong antioxidant activity in comparison with butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). In addition, their inhibitory action in linoleic acid system was studied by monitoring peroxide concentration in emulsion during incubation. The results were well correlated with above values. Their radical scavenging capacity was carried out on 2,2′-diphenyl-1-picrylhydracyl (DPPH) radicalm, and they showed strong scavenging activity in comparison with synthetic antioxidants. Their reducing power was also determined, which also proved strong antioxidant capacity of essential oil and extract. Gas chromatographic-mass spectroscopy studies on essential oil resulted in the identification of 49 components representing 96.49% of the total amount, and the major component was sabinene (20.22%), followed by terpinen-4-ol (12.08%), safrole (10.32%), α-pinene (9.7%), β-phellandrene (6.56%), and γ-terpinene (5.93%). The acetone extract showed the presence of 23 components representing 71.66% of the total amount. The major components were isocroweacin (18.92%), elemicin (17.68%), methoxyeugenol (8.13%), linoleic acid (4.12%), dehydrodiisoeugenol (4.06%), palmitic acid (2.8%), and trans-isoeugenol (2.76%). © 2005 Institute of Food Technologists.Fil: Singh, Gurdip. Deen Dayal Upadhyay Gorakhpur University India; IndiaFil: Marimuthu, P.. Deen Dayal Upadhyay Gorakhpur University India; IndiaFil: De Heluani, Carola S.. Universidad Nacional de Tucumán; ArgentinaFil: Catalan, Cesar Atilio Nazareno. Universidad Nacional de Tucumán; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Tucumán. Instituto de QuÃmica del Noroeste. Universidad Nacional de Tucumán. Facultad de BioquÃmica, QuÃmica y Farmacia. Instituto de QuÃmica del Noroeste; Argentin
Fractal dimension and size scaling of domains in thin films of multiferroic BiFeO3
We have analyzed the morphology of ferroelectric domains in very thin films
of multiferroic BiFeO3. Unlike the more common stripe domains observed in
thicker films BiFeO3 or in other ferroics, the domains tend not to be straight,
but irregular in shape, with significant domain wall roughening leading to a
fractal dimensionality. Also contrary to what is usually observed in other
ferroics, the domain size appears not to scale as the square root of the film
thickness. A model is proposed in which the observed domain size as a function
of film thickness can be directly linked to the fractal dimension of the
domains.Comment: 4 pages, 3 figure
Emergency Light with Dark Switch and Motion Sensor
The general objective of this research was to make an alternative means of producing light by the use of some simple materials at home. The specific objective of the study was to construct lighting system for emergency purposes which can use at schools, offices, hotels, hospitals and even in our homes. This study also aims to develop more suitable and efficient lighting system which uses motion sensor and dark sensor for switching devices. In this study, there are some advantages considered: (1) equipped with dark sensor which only activates standby light when the light in the surrounding is not sufficient during power outage; (2) equipped with motion sensors for switching device which will activate it brightness if there’s a presence of motion within an angle of 120 degrees and a maximum distance of 7 meters; (3) can give high frequency of emergency lighting during power outage. As the result of the study, this gadget only operates in dark surroundings and can give higher brightness if motion is sensed in a given angle and distance. To this end, this initial study formulated theories which stated that this gadget consumes less amount of energy and can operates automatically without directly controlled by a person
Multi-epoch Doppler tomography and polarimetry of QQ Vul
We present multi-epoch high-resolution spectroscopy and photoelectric polarimetry of the long-period polar (AM Herculis star) QQ Vul. The blue emission lines show several distinct components, the sharpest of which can unequivocally be assigned to the illuminated hemisphere of the secondary star and used to trace its orbital motion. This narrow emission line can be used in combination with Nai-absorption lines from the photosphere of the companion to build a stable long-term ephemeris for the star: inferior conjunction of the companion occurs at HJD = 244 8446.4710(5)+E×0. d 15452011(11). The polarization curves are dissimilar at different epochs, thus supporting the idea of fundamental changes of the accretion geometry, e.g. between one- and two-pole accretion modes. The linear polarization pulses display a random scatter by 0.2 phase units and are not suitable for the determination of the binary period. The polarization data suggest that the magnetic (dipolar) axis has a co-latitude of 23 ◦ , an azimuth of −50 ◦, and an orbital inclination between 50 ◦ and 70 ◦. Doppler images of blue emission and red absorption lines show a clear separatio
Genetic structure and diversity of the selfing model grass Brachypodium stacei (Poaceae) in Western Mediterranean: out of the Iberian Peninsula and into the islands
Annual Mediterranean species of the genus Brachypodiurn are promising model plants for energy crops since their selfing nature and short-life cycles are an advantage in breeding programs. The false brome, B. distachyon, has already been sequenced and new genomic initiatives have triggered the de-novo genuine sequencing of its close relatives such as B. stacei, a species that was until recently mistaken for B. distachyon. However, the success of these initiatives hinges on detailed knowledge about the distribution of genetic variation within and among populations for the effective use of germplasm in la breeding program. Understanding population genetic diversity and genetic structure is also an important prerequisite for designing effective experimental populations for genomic wide studies. However, population genetic data are still limited in B. stacei. We therefore selected and amplified 10 nuclear microsatellite markers to depict patterns of population structure and genetic variation 13 among 181 individuals from 19 populations of B. stacei occurring in its predominant range, the western Mediterranean area: mainland Iberian Peninsula, continental Balearic Islands and oceanic Canary Islands. Our genetic results support the occurrence of a predominant selfing system with extremely high levels of homozygosity across the analyzed populations. Despite the low level of genetic variation found, two different genetic clusters were retrieved, one clustering all SE Iberian mainland populations and the island of Minorca and another one grouping all SE Iberian mainland populations, the Canary Islands and all Majorcan populations except one that clustered with the former group. These results, together with a high sharing of alleles (89%) suggest different colonization routes from the mainland Iberian Peninsula into the islands. A recent colonization scenario could explain the relatively low levels of genetic diversity and low number of alleles found in the Canary Islands populations while older colonization events are hypothesized to explain the high genetic diversity values found in the Majorcan populations. Our study provides widely applicable information about geographical patterns of genetic variation in B. stacei. Among others, the genetic pattern and the existence of local alleles will need to be adequately reflected in the germplasm collection of B. stacei for efficient genome wide association studies
Genetic relatedness and taxonomy in closely related species of Hedysarum (Fabaceae)
A multidisciplinary study, engaging morphological, carpological and molecular data, has been performed to investigate the genetic relatedness and taxonomic boundaries of the close species Hedysarum gmelinii, H. setigerum and H. chaiyrakanicum (Fabaceae) with overlapped distribution areas in southern Siberia. The diagnostic features of these legume species are analyzed and discussed, including their macro- and micromorphological characteristics, seed coat ornamentation and inter-simple sequence repeat (ISSR) profiles. The morphometric features, pod and seed microsculpture traits of H. chaiyrakanicum and the ISSR patterns of the three species have been determined for the first time. Sprout, leaf, calyx, corolla, and stem rachis measurements, leaflet indumentum type and ISSR patterns significantly discriminate H. chaiyrakanicum from the other two species, whereas plant height, lengths of stem and leaf, and length and width of leaflet show opposite ranges of variation for H. gmelinii and H. setigerum though none of them is reliable in species identification. Ornamentation of seed coat and ISSR patterns does not differ significantly in the species. Therefore, our study supports the separate taxonomic treatment of H. chaiyrakanicum and the subordination of the cryptic species H. setigerum within H. gmelinii
Design and Performance Evaluation of a Directional Telescopic Microphone for Enhanced Environmental Sound Capture
A directional telescopic microphone is composed of two parts. One is the pick-up circuit made up of 34 different length aluminum tubes to respond in a specific frequency. The use of a sensitive FET mic is to pick up a sound from a direction. The signal from the FET mic will be feed to the microphone preamplifier in order to amplify the signal. The Equalization and Attenuation circuit is responsible for the balancing and boosting the low and high frequency. The pick-up signal can be easily recordedto a device through the recording unit or can be heard through the speaker, driven by a power amplifier in order to set up the signal. The main purpose of the gadget is to be used in an environmental study. This can pick up sound that was not normally heard by human ear in a specify distance
Strain gradient induced polarization in SrTiO3 single crystals
Piezoelectricity is inherent only in noncentrosymmetric materials, but a
piezoelectric response can also be obtained in centrosymmetric crystals if
subjected to inhomogeneous deformation. This phenomenon, known as
flexoelectricity, affects the functional properties of insulators, particularly
thin films of high permittivity materials. We have measured
strain-gradient-induced polarization in single crystals of paraelectric
SrTiO as a function of temperature and orientation down to and below the
105 K phase transition. Estimates were obtained for all the components of the
flexoelectric tensor, and calculations based on these indicate that local
polarization around defects in SrTiO may exceed the largest ferroelectric
polarizations. A sign reversal of the flexoelectric response detected below the
phase transition suggests that the ferroelastic domain walls of SrTiO may
be polar.Comment: 4 pages, 3 figures, 1 tabl
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