202,769 research outputs found
Invalidation of the Kelvin Force in Ferrofluids
Direct and unambiguous experimental evidence for the magnetic force density
being of the form in a certain geometry - rather than being the
Kelvin force - is provided for the first time. (M is the
magnetization, H the field, and B the flux density.)Comment: 4 pages, 4 figure
XPS and AFM study of interaction of organosilane and sizing with e-glass fibre surface
Organosilanes are often used in commercial sizings for glass fibres to provide wettability with the resin and promote strong interfacial adhesion to the matrix in a fibre reinforced polymer composite. The silane treatment is introduced as part of a complex deposition from an aqueous emulsion immediately at the spinaret and determines the optimum properties of the cured composite. To understand the interaction of organosilanes contained in sizings for glass surfaces, XPS was used to investigate the adsorption of γ-aminopropyltriethoxysilane (APS) from a simple sizing system containing a polyurethane (PU) film former. It has been found that both APS and the sizing (containing APS and PU) deposits on E-glass fibre surfaces contained components of differing hydrolytic stability. The differences observed in the AFM images of APS coated E-glass fibres before and after water extraction also confirmed that the APS deposit contained components with different water solubility
Interactions of satellite-speed helium atoms with satellite surfaces. 2: Energy distributions of reflected helium atoms
Energy transfer in collisions of satellite-speed (7,000 m/sec) helium atoms with a cleaned 6061-T6 satellite-type aluminum surface was investigated using the molecular-beam technique. The amount of energy transferred was determined from the measured energy of the molecular-beam and the measured spatial and energy distributions of the reflected atoms. Spatial distributions of helium atoms scattered from a 6061-T6 aluminum surface were measured. The scattering pattern exhibits a prominent backscattering, probably due to the gross surface roughness and/or the relative lattice softness of the aluminum surface. Energy distributions of reflected helium atoms from the same surface were measured for six different incidence angles. For each incidence angle, distributions were measured at approximately sixty scattering positions. At a given scattering position, the energy spectra of the reflected helium atoms and the background gas were obtained using the retarding-field energy analyzer
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Relativistic Ab initio Study On PtF and HePtF
The electronic structures and spectroscopic constants of the first three low-lying electronic states (Omega = 1/2, 3/2, and 5/2) of the linear HePtF complex were investigated by highly accurate relativistic ab initio methods, in which the spin-orbit coupling was taken into account, and compared with the results of PtF. It shows that the complex is significantly different from the typical van der Waals systems because of short He-Pt bond distances (1.80 similar to 1.87 angstrom), large He-Pt stretching frequencies (500 similar to 600 cm(-1)), considerable binding energies (1400 similar to 2500 cm(-1) with corrections), and a small electron transfer from helium (about 0.06). However, the topological analysis of the electron density distribution indicates that there is strong van der Waals interaction in the He-Pt bond instead of weak covalent one.Welch Foundation F-100Chemistr
Similarity of ionized gas nebulae around unobscured and obscured quasars
Quasar feedback is suspected to play a key role in the evolution of massive
galaxies, by removing or reheating gas in quasar host galaxies and thus
limiting the amount of star formation. In this paper we continue our
investigation of quasar-driven winds on galaxy-wide scales. We conduct Gemini
Integral Field Unit spectroscopy of a sample of luminous unobscured (type 1)
quasars, to determine the morphology and kinematics of ionized gas around these
objects, predominantly via observations of the [O III]5007 emission line. We
find that ionized gas nebulae extend out to ~13 kpc from the quasar, that they
are smooth and round, and that their kinematics are inconsistent with gas in
dynamical equilibrium with the host galaxy. The observed morphological and
kinematic properties are strikingly similar to those of ionized gas around
obscured (type 2) quasars with matched [O III] luminosity, with marginal
evidence that nebulae around unobscured quasars are slightly more compact.
Therefore in samples of obscured and unobscured quasars carefully matched in [O
III] luminosity we find support for the standard geometry-based unification
model of active galactic nuclei, in that the intrinsic properties of quasars,
of their hosts and of their ionized gas appear to be very similar. Given the
apparent ubiquity of extended ionized regions, we are forced to conclude that
either the quasar is at least partially illuminating pre-existing gas or that
both samples of quasars are seen during advanced stages of quasar feedback. In
the latter case, we may be biased by our [O III]-based selection against
quasars in the early "blow-out" phase, for example due to dust obscuration.Comment: 17 pages, 10 figures, 2 tables. Published in MNRAS, 201
Researches on interactions of satellite-speed helium atoms with aluminum and quartz surfaces
Three major areas were experimentally studied: (1) energy transfer in collisions of satellite-speed (700 m/sec) helium atoms with a cleaned satellite-type aluminum surface was investigated using the molecular-beam technique. Spatial and energy distributions of reflected helium atoms were measured and analyzed, (2) The gross accommodation coefficient for a satellite-speed (7000 m/sec) helium beam entering a 2-inch-diameter aluminum spherical cavity was determined by measuring the exit velocity distribution of the leaving helium atoms using a metastable time-of-flight method. Results indicate that the 7000-m/sec satellite-speed helium atoms entering the cavity gain full accommodation with the room-temperature inner surface of the sphere through a large number of collisions before leaving the spherical cavity; and (3) the feasibility of producing a satellite-speed atomic hydrogen beam by arc-heating, for use in studies of interactions of satellite-surfaces with hydrogen atoms under laboratory conditions, was investigated. It was found that a stable arc-heated molecular hydrogen beam can be obtained using the arc-heater, and that a partially dissociated hydrogen beam can be produced. Photographs of laboratory equipment are shown
Probing a Very Narrow Boson with CDF and D0 Data
The CDF and D0 data of nearly 475 in the dilepton channel is
used to probe a recent class of models, Stueckelberg extensions of the Standard
Model (StSM), which predict a boson whose mass is of topological origin
with a very narrow decay width. A Drell-Yan analysis for dilepton production
via this shows that the current data put constraints on the parameter
space of the StSM. With a total integrated luminosity of ,
the very narrow can be discovered up to a mass of about 600 GeV. The StSM
will be very distinct since it can occur in the region where a
Randall-Sundrum graviton is excluded.Comment: 4 pages, 3 figure
Observations of Feedback from Radio-Quiet Quasars: I. Extents and Morphologies of Ionized Gas Nebulae
Black hole feedback -- the strong interaction between the energy output of
supermassive black holes and their surrounding environments -- is routinely
invoked to explain the absence of overly luminous galaxies, the black hole vs.
bulge correlations and the similarity of black hole accretion and star
formation histories. Yet direct probes of this process in action are scarce and
limited to small samples of active nuclei. We present Gemini IFU observations
of the distribution of ionized gas around luminous, obscured, radio-quiet (RQ)
quasars at z~0.5. We detect extended ionized gas nebulae via [O III]5007
emission in every case, with a mean diameter of 28 kpc. These nebulae are
nearly perfectly round. The regular morphologies of nebulae around RQ quasars
are in striking contrast with lumpy or elongated nebulae seen around radio
galaxies at low and high redshifts. We present the uniformly measured
size-luminosity relationship of [O III] nebulae around Seyfert 2 galaxies and
type 2 quasars spanning 6 orders of magnitude in luminosity and confirm the
flat slope of the correlation (R ~ L^{0.25+/-0.02}). We find a universal
behavior of the [O III]/H-beta ratio in our entire RQ quasar sample: it
persists at a constant value (~10) in the central regions, until reaching a
"break" isophotal radius ranging from 4 to 11 kpc where it starts to decrease.
We propose a model of clumpy nebulae in which clouds that produce line emission
transition from being ionization-bounded at small distances from the quasar to
being matter-bounded in the outer parts of the nebula, which qualitatively
explains the observed line ratio and surface brightness profiles. It is
striking that we see such smooth and round large-scale gas nebulosities in this
sample, which are inconsistent with illuminated merger debris and which we
suggest may be the signature of accretion energy from the nucleus reaching gas
at large scales.Comment: 44 pages, 11 figures, 3 tables. Accepted for publication in MNRA
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