1,989 research outputs found
Kidney cell electrophoresis in space flight: Rationale, methods, results and flow cytometry applications
Cultures of human embryonic kidney cells consistently contain an electrophoretically separable subpopulation of cells that produce high levels of urokinase and have an electrophoretic mobility about 85 percent as high as that of the most mobile human embryonic kidney cells. This subpopulation is rich in large epithelioid cells that have relatively little internal structure. When resolution and throughput are adequate, free fluid electrophoresis can be used to isolate a broad band of low mobility cells which also produces high levels of plasminogen activators (PAs). In the course of performing this, it was discovered that all electrophoretic subpopulations of cultured human embryonic kidney cells produce some PAs and that separate subpopulations produce high quantities of different types of PA's. This information and the development of sensitive assays for this project have provided new insights into cell secretion mechanisms related to fibrinolysis. These advances would probably not have been made without the NASA program to explore fundamental questions of free fluid electrophoresis in space
Can be gravitational waves markers for an extra-dimension?
The main issue of the present letter is to fix specific features (which turn
out being independent of extradimension size) of gravitational waves generated
before a dimensional compactification process. Valuable is the possibility to
detect our prediction from gravitational wave experiment without high energy
laboratory investigation. In particular we show how gravitational waves can
bring information on the number of Universe dimensions. Within the framework of
Kaluza-Klein hypotheses, a different morphology arises between waves generated
before than the compactification process settled down and ordinary
4-dimensional waves. In the former case the scalar and tensor degrees of
freedom can not be resolved. As a consequence if were detected gravitational
waves having the feature here predicted (anomalous polarization amplitudes),
then they would be reliable markers for the existence of an extra dimension.Comment: 5 pages, two figure, to appear on Int. Journ. Mod. Phys.
Quantum Theory Approach for Neutron Single and Double-Slit Diffraction
We provide a quantum approach description of neutron single and double-slit
diffraction, with specific attention to the cold neutron diffraction (\AA) carried out by Zeilinger et al. in 1988. We find the
theoretical results are good agreement with experimental data.Comment: 10 page
Zur Ablagerung der industriellen Abprodukte: 14. Mitteilung: Beitrag zur Ablagerung von Chrom(VI)-Verbindungen in einer gemischten Schadstoffdeponie
Die Hercynia publiziert Originalbeiträge mit dem Schwerpunkt Ökologie (mit ihren vielseitigen Aspekten der Biodiversität), Botanik, Zoologie, Geologie und Geografie, den anwendungsorientierten Bereichen des Natur- und Umweltschutzes, sowie der Land- und Forstwirtschaft
High-Resolution Imaging of Molecular Gas and Dust in the Antennae (NGC 4038/39): Super Giant Molecular Complexes
We present new aperture synthesis CO maps of the Antennae (NGC 4038/39)
obtained with the Caltech Millimeter Array. These sensitive images show
molecular emission associated with the two nuclei and a partial ring of star
formation to the west of NGC 4038, as well as revealing the large extent of the
extra-nuclear region of star formation (the ``overlap region''), which
dominates the CO emission from this system. The largest molecular complexes
have masses of 3-6x10^8 M_sun, typically an order of magnitude larger than the
largest structures seen to date in more quiescent galaxy disks. The extremely
red luminous star clusters identified previously with HST are well-correlated
with the CO emission, which supports the conclusion that they are highly
embedded young objects rather than old globular clusters. There is an excellent
correlation between the CO emission and the 15 micron emission seen with ISO,
particularly for the brightest regions. The most massive complexes in the
overlap region have similar [NeIII]/[NeII] ratios, which implies that all these
regions are forming many massive stars. However, only the brightest
mid-infrared peak shows strong, rising continuum emission longward of 10
microns, indicative of very small dust grains heated to high temperatures by
their proximity to nearby luminous stars. Since these grains are expected to be
removed rapidly from the immediate environment of the massive stars, it is
possible that this region contains very young (< 1 Myr) sites of star
formation. Alternatively, fresh dust grains could be driven into the sphere of
influence of the massive stars, perhaps by the bulk motions of two giant
molecular complexes. The kinematics and morphology of the CO emission in this
region provide some support for this second scenario.Comment: Accepted for publication in The Astrophysical Journal, 13 pages, 5
figures, higher quality color images available at
http://www.astro.cornell.edu/staff/vassilis/papers/ngc4038_co.ps.g
What Powers Ultra-luminous IRAS Galaxies?
We present an ISO SWS and ISOPHOT-S, mid-infrared spectroscopic survey of 15
ultra-luminous IRAS galaxies. We combine the survey results with a detailed
case study, based on near-IR and mm imaging spectroscopy, of one of the sample
galaxies (UGC 5101). We compare the near- and mid-IR characteristics of these
ultra-luminous galaxies to ISO and literature data of thirty starburst and
active galactic nuclei (AGN), template galaxies. We find that
1) 70-80% of the ultra-luminous IRAS galaxies in our sample are predominantly
powered by recently formed massive stars. 20-30% are powered by a central AGN.
These conclusions are based on a new infrared 'diagnostic diagram' involving
the ratio of high to low excitation mid-IR emission lines on the one hand, and
on the strength of the 7.7um PAH feature on the other hand.
2) at least half of the sources probably have simultaneously an active
nucleus and starburst activity in a 1-2 kpc diameter circum-nuclear disk/ring.
3) the mid-infrared emitting regions are highly obscured. After correction
for these extinctions, we estimate that the star forming regions in ULIRGs have
ages between 10^7 and 10^8 years, similar to but somewhat larger than those
found in lower luminosity starburst galaxies.
4) in the sample we have studied there is no obvious trend for the AGN
component to dominate in the most compact, and thus most advanced mergers.
Instead, at any given time during the merger evolution, the time dependent
compression of the circum-nuclear interstellar gas, the accretion rate onto the
central black hole and the associated radiation efficiency may determine
whether star formation or AGN activity dominates the luminosity of the system.Comment: 63 pages postscript (ex. MS Word), 11 postscript and 2 gif figures,
submitted to ApJ. See also
http://www.mpe-garching.mpg.de/ISO/preprint/MPE-IR-97003.htm
Diffraction of complex molecules by structures made of light
We demonstrate that structures made of light can be used to coherently
control the motion of complex molecules. In particular, we show diffraction of
the fullerenes C60 and C70 at a thin grating based on a standing light wave. We
prove experimentally that the principles of this effect, well known from atom
optics, can be successfully extended to massive and large molecules which are
internally in a thermodynamic mixed state and which do not exhibit narrow
optical resonances. Our results will be important for the observation of
quantum interference with even larger and more complex objects.Comment: 4 pages, 3 figure
The Vlasov limit and its fluctuations for a system of particles which interact by means of a wave field
In two recent publications [Commun. PDE, vol.22, p.307--335 (1997), Commun.
Math. Phys., vol.203, p.1--19 (1999)], A. Komech, M. Kunze and H. Spohn studied
the joint dynamics of a classical point particle and a wave type generalization
of the Newtonian gravity potential, coupled in a regularized way. In the
present paper the many-body dynamics of this model is studied. The Vlasov
continuum limit is obtained in form equivalent to a weak law of large numbers.
We also establish a central limit theorem for the fluctuations around this
limit.Comment: 68 pages. Smaller corrections: two inequalities in sections 3 and two
inequalities in section 4, and definition of a Banach space in appendix A1.
Presentation of LLN and CLT in section 4.3 improved. Notation improve
Large-scale magnetic fields from inflation due to Chern-Simons-like effective interaction
We discuss the generation of large-scale magnetic fields due to the breaking
of the conformal invariance in the electromagnetic field through the -even
dimension-six Chern-Simons-like effective interaction with a fermion current in
inflationary cosmology. It is shown that the magnetic fields on 1Mpc scale with
the field strength of G at the present time can be generated even
for the scale of the effective interaction being the Planck scale.Comment: 13 pages, 2 figures, additional explanations include
Interaction of photons with plasmas and liquid metals: photoabsorption and scattering
Formulas to describe the photoabsorption and the photon scattering by a
plasma or a liquid metal are derived in a unified manner with each other. It is
shown how the nuclear motion, the free-electron motion and the core-electron
behaviour in each ion in the system determine the structure of photoabsorption
and scattering in an electron-ion mixture. The absorption cross section in the
dipole approximation consists of three terms which represent the absorption
caused by the nuclear motion, the absorption owing to the free-electron motion
producing optical conductivity or inverse Bremsstrahlung, and the absorption
ascribed to the core-electron behaviour in each ion with the Doppler
correction. Also, the photon scattering formula provides an analysis method for
experiments observing the ion-ion dynamical structure factor (DSF), the
electron-electron DSF giving plasma oscillations, and the core-electron DSF
yielding the X-ray Raman (Compton) scattering with a clear definition of the
background scattering for each experiment, in a unified manner. A formula for
anomalous X-ray scattering is also derived for a liquid metal. At the same
time, Thomson scattering in plasma physics is discussed from this general point
of view.Comment: LaTeX file: 18 pages without figur
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