Isolated unstable Weibel modes in unmagnetized plasmas with tunable asymmetry

In this letter, an initially unmagnetized pair plasma with asymmetric velocity distributions is investigated where any unstable Weibel mode must be isolated, with discrete values for the growth rates and the unstable wavenumbers. For both a non-relativistic distribution with thermal spread and a high-relativistic two-stream distribution it is shown that isolated modes are excited and that, as the asymmetry tends to zero, the growth rate remains finite, as long as the distribution function is not precisely symmetric.Comment: Comments: references adde

A double peaked pulse profile observed in GX 1+4

The hard X-ray pulsar GX 1+4 was observed several times in the last few years with a pair of balloon-borne Xenon filled Multi-cell Proportional Counters (XMPC). In a balloon flight made on 22 March 1995, the source was detected in a bright state, the average observed source count rate being $8.0\pm0.2/s$ per detector. X-ray pulsations with a period of $121.9\pm0.1$ s were detected in the source with a broad double peak pulse feature. When observed in December 1993 with the same instrument, the pulse profile of GX 1+4 showed a single peak. This change in the pulse profile to a double pulse structure in about 15 months indicates either activation of the opposite pole of the neutron star if the magnetic field is asymmetric or possibly a change in the beam pattern, from a pencil beam to a fan beam. Assuming a fan beam configuration, the pulse profile is used to find the inclinations of the magnetic axis and the viewing axis with the spin axis. The derived angles support the GINGA observations of a dip in the pulse profile which was resolved to have a local maximum in one of the observations and was explained with resonance scattering of cyclotron line energy photons by the accretion column (Makishima et al., \markcite{maki1988}, Dotani et al., \markcite{dotani1989}.). Compared to our previous observation of the same source with the same telescope (Rao et al., \markcite{rao1994}) a period change rate of $0.72 \pm 0.40 s/yr$ is obtained which is the lowest rate of change of period for this source since its discovery. Average pulse fraction in the hard X-ray range is low (30%), consistent with its anti correlation with luminosity as reported by us earlier (Rao et al., \markcite{rao1994}) and the observed spectrum is very hard (power law photon index $1.67\pm0.12$).Comment: 10 pages, to appear in A&

X-ray properties of the microquasar GRS 1915+105 during a variability class transition

We present a detailed X-ray study of the microquasar GRS 1915+105 during a variability class transition observed in 2000 June with the PPCs of the Indian X-ray Astronomy Experiment. We supplement this observation with data from the RXTE archives. The source made a transition from a steady low-hard state to a regular oscillatory behaviour in the light curve known as bursts or class `rho' (Belloni et al. 2000) between 2000 May 11 and 17 and reverted back to the low-hard state on 2000 June 27. A gradual change in the burst recurrence time from about 75 s to about 40 s was observed which then increased to about 120 s during the ~ 40 days of class `rho'. The regular bursts disappeared from the X-ray light curves and the class transition was observed to occur within 1.5 hours on 2000 June 27 with the PPCs. A correlation is found between the observed QPO frequency at 5-8 Hz in the quiescent phase and the average X-ray intensity of the source during the class `rho'. We notice a strong similarity between the properties of the source during the class `rho' and those during the oscillatory phase of the observations of class `alpha'. From the timing and spectral analysis, it is found that the observed properties of the source over tens of days during the class `rho' are identical to those over a time scale of a few hundreds of seconds in the class `alpha'. Examining the light curves from the beginning of the RXTE/PCA and RXTE/ASM observations, it is found that the change of state from radio-quiet low-hard state to high state occurs through the X-ray classes `rho' and `alpha' which appear together during the state transition. It is further inferred that the source switches from low-hard state to the class `rho' through the intermediate class `alpha'.Comment: 10 pages with 9 figures, LaTex. To be appeared in MNRA

A single molecule switch based on two Pd nanocrystals linked by a conjugated dithiol

Tunneling spectroscopy measurements have been carried out on a single molecule device formed by two Pd nanocrystals (dia, $\sim$5 nm) electronically coupled by a conducting molecule, dimercaptodiphenylacetylene. The I-V data, obtained by positioning the tip over a nanocrystal electrode, exhibit negative differential resistance (NDR) on a background M-I-M characteristics. The NDR feature occurs at $\sim$0.67 V at 300 K and shifts to a higher bias of 1.93 V at 90 K. When the tip is held in the middle region of the device, a coulomb blockade region is observed ($\pm\sim$0.3 V).Comment: Accepted in Praman

In vivo antioxidant and hepatoprotective potential of Glycyrrhiza glabra extract on carbon tetra chloride (CCl4) induced oxidative-stress mediated hepatotoxicity

Objective: This study aimed to evaluate the antioxidant and hepatoprotective potential of Glycyrrhiza glabra hydromethanolic root extract against carbon tetra chloride (CCl4) induced oxidative-stress mediated hepatotoxicity in liver tissue of Swiss albino mice.Background: Medicinal plants play a vital role for the development of new drugs. Glycyrrhiza glabra is a widely used medicinal plant. It has many phyto-constituents and active components, which can be used for many diseases.Methods: For the antioxidant and hepatoprotective study, measurement of GSH, CAT, LPO bio-markers in Liver tissue of Swiss albino mice were taken. The animals were divided in six different groups each having 4 mice. The requisite dose of CCl4 was dissolved in appropriate solvent (1.5ml/kg body wt) and administrated as single i.p. dose per mice after 6 hr of last treatment of extract to the animals in each group. Mice were received orally administration of extract up to 7 days. Positive Control group received single i.p. injection of 1.5ml/kg body wt CCl4 in 0.9% saline.Results: The results suggest that, the crude extract of root of G. glabra at the doses of 300 and 600mg/kg body wt. expressed significant hepatoprotective potential against CCl4 induced oxidative stress mediated hepatotoxicity in student ‘t’ test (p<0.05) at dose dependent manner in the Liver tissue of Swiss albino mice. G. glabra root extract alone has not induced hepatotoxicity.Conclusion: Based on this study, It may be concluded that Glycyrrhiza glabra root extract possess hepatoprotective potential in Swiss albino mice.

Different types of X-ray bursts from GRS 1915+105 and their origin

We report the X-ray observations of the Galactic X-ray transient source GRS 1915+105 with the PPCs of the Indian X-ray Astronomy Experiment(IXAE) onboard the Indian satellite IRS-P3 during 1997 June - August, which have revealed the presence of four types of intense X-ray bursts. All the observed bursts have a slow exponential rise, a sharp linear decay, and they can broadly be put in two classes: irregular and quasi-regular bursts in one class, and regular bursts in another class. The regular bursts are found to have two distinct time scales and they persist over extended durations. There is a strong correlation between the preceding quiescent time and the burst duration for the quasi-regular and irregular bursts. No such correlation is found for the regular bursts. The ratio of average flux during the burst time to the average flux during the quiescent phase is high and variable for the quasi- regular and irregular bursts while it is low and constant for the regular bursts. We suggest that the peculiar bursts that we have seen are charact- eristic of the change of state of the source. The source can switch back and forth between the low-hard state and the high-soft state near critical accretion rates in a very short time scale. A test of the model is presented using the publicly available 13-60 keV RXTE/PCA data for irregular and regular bursts concurrent with our observations.Comment: 13 pages, 12 figures, Accepted in APJ, emulateapj style use

Anticarcinogenic potential of Withania coagulans fruit against skin papilomagenesis in swiss albino mice

Withania coagulans belongs to family Solanaceae and its beries are commonly known to be as good vegetable rennet. It has been reported to have withanolides which are known to be as a group of steroidal lactones found among members of Solanaceae. Withanolides are reported to have antitumor, antibacterial, anti-inflammatory, immune-suppressive, cyto-toxicity and antiulcer activities. In the present study, the anti-carcinogenic activity of Withania coagulans of aqueous and methanolic fruit extracts was investigated on DMBA induced skin papillomagenesis. Single topical application of 7,12-dimethylbenzanthracene (DMBA) of 100&mu;g/100&mu;l acetone, was given and one week later promoted by repeated application of Croton oil (1% in acetone/twice in a week ) till the end of experiment (16 weeks) in Swiss albino mice. Single topical application of Methanolic and Aqueous extract of Withania coagulans at the dose 1000mg/kg body weight along with DMBA+ Croton oil was found&nbsp; effective in decreasing cumulative no. of papillomas, tumor yield, tumor incidence and tumor burden as compared to the Control group i.e. DMBA and Croton oil. Histo-pathological studies also showed positive results of the Withania coagulans extracts against DMBA as promoter and Croton oil as stimulator of causing papillomagenesis. Histological sections in all the groups show marked papillomatosis, hypergranulosis and hyperkeratosis with papillary projections but in the control group papilloma consisted of fibro-vascular core with lump of epithelia showing mild dysplasia, the signs of malignancy were prominent showing Keratinous pearl and&nbsp; full thick dysplasia containing fibro-vascular core with lining epithelia. The tumor incidence in methanolic extract group are found statistically significant (p&lt;0.05) in comparison to control group

Evolving temporal association rules with genetic algorithms

A novel framework for mining temporal association rules by discovering itemsets with a genetic algorithm is introduced. Metaheuristics have been applied to association rule mining, we show the efficacy of extending this to another variant - temporal association rule mining. Our framework is an enhancement to existing temporal association rule mining methods as it employs a genetic algorithm to simultaneously search the rule space and temporal space. A methodology for validating the ability of the proposed framework isolates target temporal itemsets in synthetic datasets. The Iterative Rule Learning method successfully discovers these targets in datasets with varying levels of difficulty