Bonnor-type Black Dihole Solution in Brans-Dicke-Maxwell Theory

It was originally thought that Bonnor's solution in Einstein-Maxwell theory describes a singular point-like magnetic dipole. Lately, however, it has been demonstrated that indeed it may describe a black {\it dihole}, i.e., a pair of static, oppositely-charged extremal black holes with regular horizons. Motivated particularly by this new interpretation, in the present work, the construction and extensive analysis of a solution in the context of the Brans-Dicke-Maxwell theory representing a black dihole are attempted. It has been known for some time that the solution-generating algorithm of Singh and Rai produces stationary, axisymmetric, charged solutions in Brans-Dicke-Maxwell theory from the known such solutions in Einstein-Maxwell theory. Thus this algorithm of Singh and Rai's is employed in order to construct a Bonnor-type magnetic black dihole solution in Brans-Dicke-Maxwell theory from the known Bonnor solution in Einstein-Maxwell theory. The peculiar feature of the new solution including internal infinity nature of the symmetry axis and its stability issue have been discussed in full detail.Comment: 29 pages, Revtex4, Int. J. Mod. Phys. A (IJMPA), in pres

The Stream-Stream Collision after the Tidal Disruption of a Star Around a Massive Black Hole

A star can be tidally disrupted around a massive black hole. It has been known that the debris forms a precessing stream, which may collide with itself. The stream collision is a key process determining the subsequent evolution of the stellar debris: if the orbital energy is efficiently dissipated, the debris will eventually form a circular disk (or torus). In this paper, we have numerically studied such stream collision resulting from the encounter between a 10^6 Msun black hole and a 1 Msun normal star with a pericenter radius of 100 Rsun. A simple treatment for radiative cooling has been adopted for both optically thick and thin regions. We have found that approximately 10 to 15% of the initial kinetic energy of the streams is converted into thermal energy during the collision. The angular momentum of the incoming stream is increased by a factor of 2 to 3, and such increase, together with the decrease in kinetic energy, significantly helps the circularization process. Initial luminosity burst due to the collision may reach as high as 10^41 erg/sec in 10^4 sec, after which the luminosity increases again (but slowly this time) to a steady value of a few 10^40 erg/sec in a few times of 10^5 sec. The radiation from the system is expected to be close to Planckian with effective temperature of \~10^5K.Comment: 19 pages including 12 figures; Accepted for publication in Ap

Demonstration of improved sensitivity of echo interferometers to gravitational acceleration

We have developed two configurations of an echo interferometer that rely on standing wave excitation of a laser-cooled sample of rubidium atoms that measures acceleration. For a two-pulse configuration, the interferometer signal is modulated at the recoil frequency and exhibits a sinusoidal frequency chirp as a function of pulse spacing. For a three-pulse stimulated echo configuration, the signal is observed without recoil modulation and exhibits a modulation at a single frequency. The three-pulse configuration is less sensitive to effects of vibrations and magnetic field curvature leading to a longer experimental timescale. For both configurations of the atom interferometer (AI), we show that a measurement of acceleration with a statistical precision of 0.5% can be realized by analyzing the shape of the echo envelope that has a temporal duration of a few microseconds. Using the two-pulse AI, we obtain measurements of acceleration that are statistically precise to 6 parts per million (ppm) on a 25 ms timescale. Using the three-pulse AI, we obtain measurements of acceleration that are statistically precise to 0.4 ppm on a timescale of 50 ms. A further statistical enhancement is achieved by analyzing the data across the echo envelope to improve the statistical precision to 75 parts per billion (ppb). We discuss methods for reducing prominent systematic effects due to a magnetized vacuum chamber and improving the signal-to-noise ratio. Simulations of both AI configurations with a timescale of 300 ms reached in a non-magnetic vacuum chamber suggest that an optimized experiment with improved vibration isolation and atoms selected in the mF = 0 state can result in measurements of g statistically precise to 0.3 pbb for the two-pulse AI and 0.6 ppb for the three-pulse AI.Comment: 17 pages, 9 figures, 3 table

N-Body Simulations of Compact Young Clusters near the Galactic Center

We investigate the dynamical evolution of compact young star clusters (CYCs) near the Galactic center (GC) using Aarseth's Nbody6 codes. The relatively small number of stars in the cluster (5,000-20,000) makes real-number N-body simulations for these clusters feasible on current workstations. Using Fokker-Planck (F-P) models, Kim, Morris, & Lee (1999) have made a survey of cluster lifetimes for various initial conditions, and have found that clusters with a mass <~ 2x10^4 Msun evaporate in ~10 Myr. These results were, however, to be confirmed by N-body simulations because some extreme cluster conditions, such as strong tidal forces and a large stellar mass range participating in the dynamical evolution, might violate assumptions made in F-P models. Here we find that, in most cases, the CYC lifetimes of previous F-P calculations are 5-30% shorter than those from the present N-body simulations. The comparison of projected number density profiles and stellar mass functions between N-body simulations and HST/NICMOS observations by Figer et al. (1999) suggests that the current tidal radius of the Arches cluster is ~1.0 pc, and the following parameters for the initial conditions of that cluster: total mass of 2x10^4 Msun and mass function slope for intermediate-to-massive stars of 1.75 (the Salpeter function has 2.35). We also find that the lower stellar mass limit, the presence of primordial binaries, the amount of initial mass segregation, and the choice of initial density profile (King or Plummer models) do not significantly affect the dynamical evolution of CYCs.Comment: 20 pages including 6 figures, To appear in ApJ, Dec 20 issu

Effect of drought stress on growth, proline and antioxidant enzyme activities of upland rice

Responses of eight upland rice (Oryza sativa L.) varieties subjected to different drought levels were investigated in laboratory to evaluate eight local upland rice varieties against five drought levels (0, -2, -4, -6, and -8 bars) at germination and early seedling growth stage of plant development. Data were analyzed statistically for growth parameters; shoot length, root length, and dry matter yield, and biochemical parameters; proline and antioxidant enzymes activity (catalase, superoxide dismutase and peroxidase), were measured. Experiment units were arranged factorial completely randomized design with four replications. The drought-tolerant variety, Pulot Wangi tolerated PEG at the highest drought level (-8 bar) and showed no significantly difference relation to control. However, drought-sensitive variety, Kusam was markedly affected even at the lowest drought level used. Concomitantly, the activity of antioxidant enzymes catalase, peroxidase and superoxide dismutase in the drought-tolerant varieties increased markedly during drought stress, while decreased by drought stress in the drought sensitive variety. Consequently, this led to a marked difference in the accumulation of proline in the upland rice varieties. It may be concluded that the activities of antioxidant enzymes and proline accumulation were associated with the dry mass production and consequently with the drought tolerance of the upland rice varieties

Cognitive decline heralds onset of symptomatic inherited prion disease

The clinical effectiveness of any disease-modifying treatment for prion disease, as for other neurodegenerative disorders, will depend on early treatment before damage to neural tissue is irrevocable. Thus, there is a need to identify markers that predict disease onset in healthy at-risk individuals. Whilst imaging and neurophysiological biomarkers have shown limited use in this regard, we recently reported progressive neurophysiological changes in individuals with the inherited prion disease mutation P102L. We have also previously demonstrated a signature pattern of fronto-parietal dysfunction in mild prion disease. Here we address whether these cognitive features anticipate the onset of symptoms in a unique sample of patients with inherited prion disease. In the cross-sectional analysis, we analysed the performance of patients at three time points in the course of disease onset: prior to symptoms (n = 27), onset of subjective symptoms without positive clinical findings (n = 8) and symptomatic with positive clinical findings (n = 24). In the longitudinal analysis, we analysed data from 24 patients who were presymptomatic at the time of recruitment and were followed up over a period of up to 17 years, of whom 16 remained healthy and eight converted to become symptomatic. In the cross-sectional analysis, the key finding was that, relative to a group of 25 healthy non-gene carrier controls, patients with subjective symptoms but without positive clinical findings were impaired on a smaller but similar set of tests (Trail Making Test part A, Stroop test, Performance IQ, gesture repetition, figure recall) to those previously found to be impaired in mild prion disease. In the longitudinal analysis, Trail Making Test parts A and B, Stroop test and Performance IQ scores significantly discriminated between patients who remained presymptomatic and those who converted, even before the converters reached criteria for formal diagnosis. Notably, performance on the Stroop test significantly discriminated between presymptomatic patients and converters before the onset of clinical symptoms [area under the curve = 0.83 (95% confidence interval, 0.62–1.00), P = 0.009]. Thus, we report here, for the first time, neuropsychological abnormalities in healthy patients prior to either symptom onset or clinical diagnosis of inherited prion disease. This constitutes an important component of an evolving profile of clinical and biomarker abnormalities in this crucial group for preventive medicine

Efficient computation of min and max sensor values in multihop networks

Consider a wireless sensor network (WSN) where a broadcast from a sensor node does not reach all sensor nodes in the network; such networks are often called multihop networks. Sensor nodes take sensor readings but individual sensor readings are not very important. It is important however to compute aggregated quantities of these sensor readings. The minimum and maximum of all sensor readings at an instant are often interesting because they indicate abnormal behavior, for example if the maximum temperature is very high then it may be that a fire has broken out. We propose an algorithm for computing the min or max of sensor readings in a multihop network. This algorithm has the particularly interesting property of having a time complexity that does not depend on the number of sensor nodes; only the network diameter and the range of the value domain of sensor readings matter

Equidistribution of zeros of holomorphic sections in the non compact setting

We consider N-tensor powers of a positive Hermitian line bundle L over a non-compact complex manifold X. In the compact case, B. Shiffman and S. Zelditch proved that the zeros of random sections become asymptotically uniformly distributed with respect to the natural measure coming from the curvature of L, as N tends to infinity. Under certain boundedness assumptions on the curvature of the canonical line bundle of X and on the Chern form of L we prove a non-compact version of this result. We give various applications, including the limiting distribution of zeros of cusp forms with respect to the principal congruence subgroups of SL2(Z) and to the hyperbolic measure, the higher dimensional case of arithmetic quotients and the case of orthogonal polynomials with weights at infinity. We also give estimates for the speed of convergence of the currents of integration on the zero-divisors.Comment: 25 pages; v.2 is a final update to agree with the published pape