A current driven instability in parallel, relativistic shocks

Recently, Bell has reanalysed the problem of wave excitation by cosmic rays propagating in the pre-cursor region of a supernova remnant shock front. He pointed out a strong, non-resonant, current-driven instability that had been overlooked in the kinetic treatments, and suggested that it is responsible for substantial amplification of the ambient magnetic field. Magnetic field amplification is also an important issue in the problem of the formation and structure of relativistic shock fronts, particularly in relation to models of gamma-ray bursts. We have therefore generalised the linear analysis to apply to this case, assuming a relativistic background plasma and a monoenergetic, unidirectional incoming proton beam. We find essentially the same non-resonant instability noticed by Bell, and show that also under GRB conditions, it grows much faster than the resonant waves. We quantify the extent to which thermal effects in the background plasma limit the maximum growth rate.Comment: 8 pages, 1 figur

Morfološka ispitivanja mozga kanadske lasice (Mustela vison)

The mink is a strict carnivore and a seasonal breeder, which may be used as an experimental model for other carnivores. Using anatomical methods, 32 brains of the N. American mink were examined. It was found that the brain consists of four ventricles. Also, it was noted that the posterior horn was missing and that the olfactory recess was present in the lateral ventricle, a large-size interthalamic connection was present in the third ventricle, and a flat, necklace like bottom in the fourth ventricle. Only recently, the ins and outs of the mink’s anatomical structure have begun to absorb the attention of anatomists. Apparently, it is related to the fact that fury animals, among them the mink, are being domesticated. For this reason and because of easy access to the material, the purpose of brain dissection is to familiarize with the three dimensional structure of the brain and teach one of the great methods of studying the brain: looking at its structure.Kanadska lasica je karnivor, koji jednom godišnje daje 4-5 mladunaca, koji se koriste kao eksperimentalni model. Za anatomska ispitivanja, koristili smo 32 mozga oba pola kanadske lasice. Utvrdili smo da se u mozgu nalaze 4 komore, kao i kod ostalih sisara. Ustanovili smo da posteriorni rog bočne komore nedostaje, kao i da postoji olfaktorni izdanak bočne komore. Šira površina između talamusa je takodje ustanovljena u trećoj moždanoj komori, kao i udubljenje četvrte moždane komore. U poslednje vreme kao eksperimentalna životinja, kanadska lasica postaje predmet interesovanja anatoma kao i naučnih istraživača u velikom broju laboratorija. Takođe, divlje životinje postaju sve više domestifikovane, a među njima je i kanadska lasica

Diferencijacija prednjeg krila medonosne pčele iz Srbije

In this study, 12 morphological characteristics were measured on worker bee samples collected from seven different locations covering the territory of Republic Serbia. The measurement of 11 angles on the front wing and cubital index was done with stereo microscope Leica XTL-3400D, and software package IL 1009 in accordance with the standard method. The results showed significant differences between the groups of bees and investigation of angles on the forewing could be contributed to a clearer separation of groups of bees inside domestic population.U ovom istraživanju mereno je 12 morfoloških karakteristika prednjeg krila pčela radilica u skladu sa metodama Ruttner i sar. (1978). Uzorci pčela radilica su prikupljeni sa 7 različitih lokacija čime su pokriveni glavni pčelarski regioni na teritoriji Republike Srbije. Morfometrijska istraživanja pokazala su da pčele iz Zapadno Bačkog regiona u Vojvodini imaju najveću vrednost uglova B4 (113,17º), D7 (100,10º), E9 (24,28º), K19 (79,60º) i najveći kubitalni indeks (2,92). Iste pčele se na osnovu multivarijantne diskriminantne analize najviše razlikuju od grupe pčela sa Kosova. Na osnovu analize varijanse, utvrđeno je da postoji vrlo značajna razlika (P lt 0.01) u 7 morfoloških karakteristika između grupa pčela sa izabranih lokaliteta. Može se zaključiti da utvrđene vrednosti za ispitivane karaktere ukazuju na postojanje značajne varijabilnosti i impliciraju na postojanje subpopulacija uslovljenih delovanjem čoveka

Far-infrared spectroscopy of PbTe doped with iron

Far infrared reflection spectra, at room and liquid nitrogen temperature, of PbTe single crystals doped with iron are presented. Plasma minima were observed at about 160 cm–1 and 180 cm–1 for room and liquid nitrogen temperature, respectively. Using the reflectivity diagrams and their minima the values of the hole concentrations and their mobility at both temperatures were calculated and compared with galvanomagnetic measurements. All these results indicated that when PbTe is doped with a small concentration of Fe, the hole concentration is reduced by one order of magnitude and the free carrier mobility is larger when compared to pure PbTe

A Search for the Most Massive Galaxies. III. Global and Central Structure

We used the Advanced Camera for Surveys on board the Hubble Space Telescope to obtain high resolution i-band images of the centers of 23 single galaxies, which were selected because they have SDSS velocity dispersions larger than 350 km/s. The surface brightness profiles of the most luminous of these objects (M_i<-24) have well-resolved `cores' on scales of 150-1000 pc, and share similar properties to BCGs. The total luminosity of the galaxy is a better predictor of the core size than is the velocity dispersion. The correlations of luminosity and velocity dispersion with core size agree with those seen in previous studies of galaxy cores. Because of high velocity dispersions, our sample of galaxies can be expected to harbor the most massive black holes, and thus have large cores with large amounts of mass ejection. The mass-deficits inferred from core-Sersic fits to the surface-brightness profiles are approximately double the black-hole masses inferred from the M_bh-sigma relation and the same as those inferred from the M_bh-L relation. The less luminous galaxies (M_i>-23) tend to have steeper `power-law' inner profiles, higher-ellipticity, diskier isophotes, and bulge-to-total ratios of order 0.5 -- all of which suggest that they are `fast-rotators' and rotational motions could have contaminated the velocity dispersion estimate. There are obvious dust features within about 300 pc of the center in about 35% of the sample, predominantly in power-law rather than core galaxies.Comment: 27 Pages, 22 Figures, 2 Tables, Accepted for Publication in MNRA

Gamma-radiation induced agglomeration of chicken muscle myosin and actin

Radiolytic behaviour of the major vertebrate muscle proteins: fibril Jar myosin (rnolar mass, M-m = 520,000 g/mol) and filament fortning actin (M-m = 42,050 g/mol) was studied using a SDS-polyacrylamide gel electrophoresis and quantified by high precision laser-densitometry. In order to study the OH radical contribution to the radiation damage, purified chicken myosin and actin (4 muM) were prepared in N2O saturated solution and irradiated with 1-3 kGy at Co-60 gamma source. With respect to changes in the molecular mass, the only observed myosin and actin damage was dose dependent agglomeration of proteins. The corresponding radiation chemical yields of 5 x 10(-8) mol J(-1) and 6.3 x 10(-8) mol J(-1) were obtained for myosin and actin, respectively. This result confirmed that only the radiation-induced agglomeration is initiated with the reaction of the OH radical even in the situation where the OH radical concentration produced exceeds the protein concentration 500 times, thus enabling the multi-radical attack to occur

Comparative thermal buckling analysis of functionally graded plate

A thermal buckling analysis of functionally graded thick rectangular plates according to von Karman non-linear theory is presented. The material properties of the functionally graded plate, except for the Poisson's ratio, were assumed to be graded in the thickness direction, according to a power-law distribution, in terms of the volume fractions of the metal and ceramic constituents. Formulations of equilibrium and stability equations are derived using the high order shear deformation theory based on different types of shape functions. Analytical method for determination of the critical buckling temperature for uniform increase of temperature, linear and non-linear change of temperature across thickness of a plate is developed. Numerical results were obtained in MATLAB software using combinations of symbolic and numeric values. The paper presents comparative results of critical buckling temperature for different types of shape functions. The accuracy of the formulation presented is verified by comparing to results available from the literature

The ACS Virgo Cluster Survey III. Chandra and HST Observations of Low-Mass X-Ray Binaries and Globular Clusters in M87

The ACIS instrument on board the Chandra X-ray Observatory has been used to carry out the first systematic study of low-mass X-ray binaries (LMXBs) in M87. We identify 174 X-ray point-sources, of which ~150 are likely LMXBs. This LMXB catalog is combined with deep F475W and F850LP images taken with ACS on HST to examine the connection between LMXBs and globular clusters in M87. Of the 1688 globular clusters in our catalog, f_X = 3.6 +- 0.5% contain a LMXB and we find that the metal-rich clusters are 3 +- 1 times more likely to harbor a LMXB than their metal-poor counterparts. In agreement with previous findings for other galaxies, we find that brighter, more metal-rich clusters are more likely to contain a LMXB. For the first time, however, we are able to demonstrate that the probability, p_X, that a given cluster will contain a LMXB depends sensitively on the dynamical properties of the host cluster. Specifically, we use the HST images to measure the half-light radius, concentration index and central density, \rho_0, for each globular, and define a parameter, \Gamma, which is related to the tidal capture and binary-neutron star exchange rate. Our preferred form for p_X is then p_X \propto \Gamma \rho_0^{-0.42\pm0.11} (Z/Z_{\odot})^{0.33\pm0.1}. We argue that if the form of p_X is determined by dynamical processes, then the observed metallicity dependence is a consequence of an increased number of neutron stars per unit mass in metal-rich globular clusters. Finally, we find no compelling evidence for a break in the luminosity distribution of resolved X-ray point sources. Instead, the LMXB luminosity function is well described by a power law with an upper cutoff at L_X ~ 10^39 erg/s. (abridged)Comment: 23 pages, 21 figures. Accepted for publication in ApJ. Also available at http://www.physics.rutgers.edu/~pcote/acs/publications.htm

Testing general relativity and probing the merger history of massive black holes with LISA

Observations of binary inspirals with LISA will allow us to place bounds on alternative theories of gravity and to study the merger history of massive black holes (MBH). These possibilities rely on LISA's parameter estimation accuracy. We update previous studies of parameter estimation including non-precessional spin effects. We work both in Einstein's theory and in alternative theories of gravity of the scalar-tensor and massive-graviton types. Inclusion of non-precessional spin terms in MBH binaries has little effect on the angular resolution or on distance determination accuracy, but it degrades the estimation of the chirp mass and reduced mass by between one and two orders of magnitude. The bound on the coupling parameter of scalar-tensor gravity is significantly reduced by the presence of spin couplings, while the reduction in the graviton-mass bound is milder. LISA will measure the luminosity distance of MBHs to better than ~10% out to z~4 for a (10^6+10^6) Msun binary, and out to z~2 for a (10^7+10^7) Msun binary. The chirp mass of a MBH binary can always be determined with excellent accuracy. Ignoring spin effects, the reduced mass can be measured within ~1% out to z=10 and beyond for a (10^6+10^6) Msun binary, but only out to z~2 for a (10^7+10^7) Msun binary. Present-day MBH coalescence rate calculations indicate that most detectable events should originate at z~2-6: at these redshifts LISA can be used to measure the two black hole masses and their luminosity distance with sufficient accuracy to probe the merger history of MBHs. If the low-frequency LISA noise can only be trusted down to 10^-4 Hz, parameter estimation for MBHs (and LISA's ability to perform reliable cosmological observations) will be significantly degraded.Comment: 13 pages, 4 figures. Proceedings of GWDAW 9. Matches version accepted in Classical and Quantum Gravit