The Physical Properties of Mixtures with Special Reference to Viscosity, with an Additional Paper, The Constitution of Phlobatannins

The property of viscosity is possessed, by any fluid, and. although the methods of investigation are widely different in each case, it may therefore be examined, in either liquids or gases, or in solutions or mixtures, as long as only a single phase is present.In this thesis, work is described on the viscosities of various types of mixtures; they are, briefly, (1) solution mixtures, where various degrees of reaction may be expected between the substances in solution; (2) mixtures of gases with vapours; (3) emulsions, which, though strictly speaking not single phase liquid mixtures, are yet as a rule sufficiently homogeneous to permit of the measurement of viscosity. Part I of this thesis contains the results obtai

Chandra Observations and the Nature of the Anomalous Arms of NGC 4258 (M106)

This paper presents high resolution X-ray observations with Chandra of NGC 4258 and infers the nature of the so called ``anomalous arms'' in this galaxy. The anomalous arms dominate the X-ray image; diffuse X-ray emission from the ``plateaux'' regions, seen in radio and H$\alpha$ imaging, is also found. X-ray spectra have been obtained at various locations along the anomalous arms and are well described by thermal (mekal) models with kT in the range 0.37 - 0.6 keV. The previously known kpc-scale radio jets are surrounded by cocoons of hot X-ray emitting gas for the first 350 pc of their length. The radio jets, seen in previous VLBA and VLA observations, propagate perpendicular to the compact nuclear gas disk (imaged in water vapor maser emission). The angle between the jets and the rotation axis of the galactic disk is 60$^{\circ}$. The jets shock the normal interstellar gas along the first 350 pc of their length, causing the hot, X-ray emitting cocoons noted above. At a height of z = 175 pc from the disk plane, the jets exit the normal gas disk and then propagate though the low density halo until they reach ``hot spots'' (at 870 pc and 1.7 kpc from the nucleus), which are seen in radio, optical line and X-ray emission. These jets must drive mass motions into the low density halo gas. This high velocity halo gas impacts on the dense galactic gas disk and shock heats it along and around a ``line of damage'', which is the projection of the jets onto the galactic gas disk as viewed down the galaxy disk rotation axis. However, because NGC 4258 is highly inclined ($i$ = 64$^{\circ}$), the ``line of damage'' projects on the sky in a different direction to the jets themselves. We calculate the expected p.a. of the ``line of damage'' on the sky and find that it coincides with the anomalous arms to within 2$^{\circ}$. (Abstract truncated). Comment: 12 pages plus 9 figures, to be published in the Astrophysical Journal, v560, nr 1, pt 1 (Oct 10, 2001 issue

Inclined Gas Disks in the Lenticular Seyfert Galaxy NGC 5252

We discuss the morphology and kinematics of the extended gas in the type 2 Seyfert galaxy NGC 5252 based on Hubble Space Telescope (HST) WFPC2 continuum and emission-line images (including a new [O III] λ5007 image) and a ground-based Fabry-Perot (F-P) velocity map of the ionized gas. The fine-scale morphology of the ionized gas in this galaxy's very extended (~40 kpc) ionization bicone consists of a complex network of filamentary strands. The new WFPC2 [O III] image also reveals more detail in the circumnuclear (~3 kpc) gas disk than is seen in the Hα + [N II] image presented previously by Tsvetanov and coworkers. The F-P velocity map shows an obvious antisymmetry of the velocity field of the ionized gas across the nucleus. We conclude that there are three dynamical components to the extended gas in NGC 5252. Two of these components are gas disks aligned with the stellar disk, one rotating with the stars and the other counterrotating. The third component is the circumnuclear gas disk seen in the HST observations and its extension to larger scales; this disk has an inclination of ~40° and a kinematic major axis in P.A. ~ 90°-135°, some 80°-125° from the major axis of the stellar disk. This simple model of two inclined rotating disks, superposed along the line of sight, describes well the seemingly complex kinematics observed in the optical emission lines and the H I 21 cm radio maps. The large misalignment between the second disk and the stellar disk suggests that the gas distribution, and possibly the nuclear activity, in NGC 5252 may have resulted from a galaxy merger event. The absence of significant radial motions, together with the well-defined ionization cones, strongly suggests that the gas is photoionized by a compact nuclear source rather than being ionized in situ by shock waves in a large-scale outflow

An Evaluation of the Health and Safety Education of Montague County, Texas, Schools

Health is a primary objective of modern education. It was named as the first of the seven cardinal principles of education. Over a period of years the health and safety of the school children have gradually become more firmly fixed as a part of the school program. Modern schools, when adequately staffed and administered, provide experiences in healthful daily living, an opportunity to become acquainted with good health services, a chance to learn something about the care of ones own body, the maintenance of health, and the prevention of disease. Thus the schools have come to contribute to community health through their planned programs of health service and through cooperation with other health and safety agencies

Blasts and shocks in the disc of NGC 4258

We present integral field spectroscopic observations of the central region of the active galaxy NGC 4258 obtained with the fibre IFU system INTEGRAL. We have been able to detect cold neutral gas by means of the interstellar NaD doublet absorption and to trace its distribution and kinematics with respect to the underlying disc. The neutral gas is blue-shifted with projected velocities in the 120--370 km/s range. We have also detected peculiar kinematics in part of the ionized gas in this region by means of a careful kinematic decomposition. The bipolar spatial distribution of the broader component is roughly coincident with the morphology of the X-ray diffuse emission. The kinematics of this gas can be explained in terms of expansion at very high (projected) velocities of up to 300 km/s. The observations also reveal the existence of a strip of neutral gas, parallel to the major kinematic axis, that is nearly coincident with a region of very high [SII]/H$\alpha$ ratio tracing the shocked gas. Our observations are consistent with the jet model presented by \cite{wilsonetal01} in which a cocoon originating from the nuclear jet is shocking the gas in the galaxy disc. Alternatively, our observations are also consistent with the bipolar hypershell model of \cite{Sofue80} and \cite{SofueandVogler01}. On balance, we prefer the latter model as the most likely explanation for the puzzling features of this peculiar object.Comment: 7 pages, 10 colour figures. Accepted for publication in MNRAS

The braided jets in the spiral galaxy NGC 4258

We have used the Hawaii Imaging Fabry-Perot Interferometer to synthesize 44,000 Hα and [N II] emission-line profiles at velocity resolution 68 km s-1 FWHM across the disk of the nearby Seyfert/LINER galaxy NGC 4258, including the prominent "four-branched jet" that extends to 10 and 5 kpc radii in the radio continuum and optical emission lines, respectively. A long-slit spectrum, which includes the emission lines Hα, [N II] λλ6548, 6583 and [S II] λλ6717, 6731, has also been obtained along the jets. These data are used for a comprehensive kinematic study of the galaxy. The disk velocity field is best fitted with a model that incorporates elliptical, bar-forced streaming motions, as suggested by the H I and CO kinematics. Velocity dispersions along the SE jet average 80 km s-1, compared to 40 km s-1 in the H II regions. This broadening arises from a helical, braided structure of three intertwined plasma streams, as inferred from both the spatial and kinematic structure of the jet. The emission-line profiles split into two distinct velocity systems with separations 300 ± 30 km s-1 within 1.7 kpc of the nucleus along the midaxis of the braid pattern. Gaussian decomposition of the line profiles show that the internal velocity dispersion of each helical strand is ≈100 km s-1. We observe two cycles of the triple-braid pattern, with wavelength ≈1.4 kpc and side-to-side amplitude ≈400 pc. If the braided streams represent ballistic motion of gas ejected from orbiting objects, the outflow velocity is ≈2000 km s-1. The masses and separations of the compact objects would be ≈3 × 106 M⊙ and ≈6 pc (0″.2), respectively. However, the emission-line velocity field of the SE jet suggests that the gas moves along the helices, perhaps as a result of fluid instabilities at the interface between the jet and the interstellar medium or of motion along magnetic flux tubes. We show that the NNW jet follows a clear channel between molecular cloud complexes, and exhibits several emission-line "hot spots" and bends where it interacts with the surrounding molecular gas. High-velocity gas in the SE and NW radio "plateaus" probably results from earlier ejections of gas from the nucleus in these directions, with the jet nozzle having precessed to its present orientation. We find that the jets have total ionized mass 1.5 × 106 M⊙ (1 cm-3/ne) and [N II] λ6583/Hα ratios consistent with shock excita-tion. An Einstein HRI image reveals X-ray emission from the nucleus and SE jet. We show that the jet's X-ray emission may be interpreted as thermal bremsstrahlung from hot, shocked jet gas

An X-ray view of the active nucleus in NGC 4258

XMM-Newton observed the Seyfert 1.9 galaxy NGC 4258 in December 2000. At energies above 2 keV a hard nuclear point source is resolved that can be fitted by a highly absorbed power-law spectrum (NH = (8.0+-0.4)x10^22 cm^-2, photon index 1.64+-0.08) with an unabsorbed luminosity of 7.5x10^40erg/s in the 2-10 keV band. No narrow iron Kalpha emission line is detected (90% upper limit of equivalent width EW ~40 eV). The nuclear emission flux was observed to remain constant over the observation. A short archival Chandra observation taken in March 2000 further constrains the hard emission to a point source coincident with the radio nucleus. A point source ~3" southwest of the nucleus does not contribute significantly. Spectral results of the Chandra nuclear source are comparable (within the limited statistics) to the XMM-Newton parameters. The comparison of our iron line upper limit with reported detections indicates variability of the line EW. These results can be explained by the relatively low nuclear absorption of NGC 4258 (which is in the range expected for its intermediate Seyfert type) and some variability of the absorbing material. Reflection components as proposed to explain the large iron line EW of highly absorbed Seyfert 2 galaxies and/or variations in the accretion disk are however imposed by the time variability of the iron line flux.Comment: 6 pages, 5 figures, accepted for publication in A&

The Soft X-ray Spectrum from NGC 1068 Observed with LETGS on Chandra

Using the combined spectral and spatial resolving power of the Low Energy Transmission Grating (LETGS) on board Chandra, we obtain separate spectra from the bright central source of NGC 1068 (Primary region), and from a fainter bright spot 4" to the NE (Secondary region). Both spectra are dominated by line emission from H- and He-like ions of C through S, and from Fe L-shell ions, but also include narrow radiative recombination continua, indicating that most of the soft X-ray emission arises in low-temperature (kT few eV) photoionized plasma. We confirm the conclusions of Kinkhabwala et al. (2002), based on XMM-Newton RGS observations, that the entire nuclear spectrum can be explained by recombination/radiative cascade following photoionization, and radiative decay following photoexcitation, with no evidence for hot, collisionally ionized plasma. In addition, this model also provides an excellent fit to the spectrum of the Secondary region, albeit with radial column densities a factor of three lower, as would be expected given its distance from the source of the ionizing continuum. The remarkable overlap and kinematical agreement of the optical and X-ray line emission, coupled with the need for a distribution of ionization parameter to explain the X-ray spectra, collectively imply the presence of a distribution of densities (over a few orders of magnitude) at each radius in the ionization cone. Relative abundances of all elements are consistent with Solar abundance, except for N, which is 2-3 times Solar. The long wavelength spectrum beyond 30 A is rich of L-shell transitions of Mg, Si, S, and Ar, and M-shell transitions of Fe. The velocity dispersion decreases with increasing ionization parameter, as deduced from these long wavelength lines and the Fe-L shell lines.Comment: 12 pages, 11 figures, accepted for publication in Astronomy and Astrophysic