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Ecological relationships between marine microorganisms and hydrocarbons in the OEI study area, Louisiana
Supported by Gulf Universities Research Consortium, Project #OE73HJMCataloged from imperfect copy: all after leaf 20 wantingSeven cruise projects were conducted in association with the Louisiana Offshore Ecological Investigation (OEI) to determine the relationships between microorganisms and hydrocarbons in surface waters. Techniques were developed to take surface samples and to determine bacterial numbers, hydrocarbon content, and the response of indigenous microorganisms to various added hydrocarbon molecules. The numbers of heterotrophic bacteria as determined by dilution techniques varied from 10 to 10,000 per ml. The hydrocarbon oxidizing organisms varied from 10 to 100,000 per liter with maxima in the month of January. Hydrocarbon concentrations varied from 0.03 to 0.6 micrograms per liter. There was no correlation between the numbers of oil degraders and hydrocarbon concentration found. This may be the result of the in situ low concentrations of hydrocarbons which would limit microbial response. The numbers of bacteria and hydrocarbons were similar to control areas in the eastern and western parts of the Gulf. BOD experiments conducted to measure the response of the microorganisms to various low and high molecular weight paraffinic and aromatic hydrocarbons indicated that all hydrocarbons were oxidized by some of the mixed indigenous microorganisms. These data suggest that an adequate inoculum was naturally present to respond to oil contamination in nature. The high numbers of hydrocarbon oxidizing microorganisms associated with January hydrographic data may indicate that the upland leaching and other contamination of hydrocarbons in the Mississippi River produce the noted microbial response for that month. The dominant saturated hydrocarbons and isoprenoids ranged from C-15 to C-41. Water from Timbalier Bay generally contained higher concentrations than offshore samples and exhibited a more pronounced odd-even preference in the range C-24 to C-33. GC-MS analysis of the dominant paraffins revealed a characteristic biomodal distribution dominated by C-17 and pristane and C-25 to C-35 with an unresolved envelope. No buildup of specific n-paraffin molecules was found, which data corresponded to BOD results of added hydrocarbons to indigenous microflora.Marine Scienc
On the Limitations of the Theory of the Positron
In a recent paper Dirac has suggested a further development
of his theory of the positron. Dirac here considers the
operators corresponding to charge and current density for
a system of electrons in which nearly all the negative energy states are full, and shows that in the presence of an arbitrary external electromagnetic field these operators may be divided into two terms: one of these is infinite, and
depends on the field but not on the state of the electrons;
the other is finite and determinate, and depends on the
field and on the electron state. Dirac makes the suggestion
that these second terms be regarded as giving the charge
and current density of the electron-positron distribution
(epd): i.e., that the formalism of his theory of the electron be modified by the subtraction from the operators for charge and current density of the infinite and field-dependent terms. This modification leaves unaltered the
Lorentz and gauge invariance of the theory and the validity
of the conservation law for charge and current. Because,
however, the way in which the operators are to be modified
depends upon the value of the electromagnetic field, the
method is not readily extended to take account of the field
produced by the epd; on the other hand, it gives for the
charge and current induced in the epd by an external field
finite and definite results, and thus constitutes in this
respect a true theoretical advance
A Budget and Accounting of Metals at z~0: Results from the COS-Halos Survey
We present a budget and accounting of metals in and around star-forming
galaxies at . We combine empirically derived star formation histories
with updated supernova and AGB yields and rates to estimate the total mass of
metals produced by galaxies with present-day stellar mass of
--. On the accounting side of the ledger, we
show that a surprisingly constant 20--25% mass fraction of produced metals
remain in galaxies' stars, interstellar gas and interstellar dust, with little
dependence of this fraction on the galaxy stellar mass (omitting those metals
immediately locked up in remnants). Thus, the bulk of metals are outside of
galaxies, produced in the progenitors of today's galaxies. The COS-Halos
survey is uniquely able to measure the mass of metals in the circumgalactic
medium (to impact parameters of kpc) of low-redshift
galaxies. Using these data, we map the distribution of CGM metals as traced by
both the highly ionized OVI ion and a suite of low-ionization species; combined
with constraints on circumgalactic dust and hotter X-ray emitting gas out to
similar impact parameters, we show that % of metals produced by
galaxies can be easily accounted for out to
150 kpc. With the current data, we cannot rule out a constant mass of metals
within this fixed physical radius. This census provides a crucial boundary
condition for the eventual fate of metals in galaxy evolution models.Comment: 19 pages, 12 figures, 2 tables. ApJ, in pres
Black hole formation in perfect fluid collapse
We construct here a special class of perfect fluid collapse models which
generalizes the homogeneous dust collapse solution in order to include non-zero
pressures and inhomogeneities into evolution. It is shown that a black hole is
necessarily generated as end product of continued gravitational collapse,
rather than a naked singularity. We examine the nature of the central
singularity forming as a result of endless collapse and it is shown that no
non-spacelike trajectories can escape from the central singularity. Our results
provide some insights into how the dynamical collapse works, and into the
possible formulations of the cosmic censorship hypothesis, which is as yet a
major unsolved problem in black hole physics.Comment: Revtex4, To appear in Physical Review
Juan de Fuca slab geometry and its relation to Wadati-Benioff zone seismicity
A new model of the subducted Juan de Fuca plate beneath western North America allows first-order correlations between the occurrence of Wadati-Benioff zone earthquakes and slab geometry, temperature, and hydration state. The geo-referenced 3D model, constructed from weighted control points, integrates depth information from earthquake locations and regional seismic velocity studies. We use the model to separate earthquakes that occur in the Cascadia forearc from those that occur within the underlying Juan de Fuca plate and thereby reveal previously obscured details regarding the spatial distribution of earthquakes. Seismicity within the slab is most prevalent where the slab is warped beneath northwestern California and western Washington suggesting that slab flexure, in addition to expected metamorphic dehydration processes, promotes earthquake occurrence within the subducted oceanic plate. Earthquake patterns beneath western Vancouver Island are consistent with slab dehydration processes. Conversely, the lack of slab earthquakes beneath western Oregon is consistent with an anhydrous slab. Double-differenced relocated seismicity resolves a double seismic zone within the slab beneath northwestern California that strongly constrains the location of the plate interface and delineates a cluster of seismicity 10 km above the surface that includes the 1992 M7.1 Mendocino earthquake. We infer that this earthquake ruptured a surface within the Cascadia accretionary margin above the Juan de Fuca plate. We further speculate that this earthquake is associated with a detached fragment of former Farallon plate. Other subsurface tectonic elements within the forearc may have the potential to generate similar damaging earthquakes
Monitoring SO2 emission at the Soufriere Hills Volcano: implications for changes in erruptive conditions
FLWINinfo:eu-repo/semantics/publishe
Evolving Einstein's Field Equations with Matter: The ``Hydro without Hydro'' Test
We include matter sources in Einstein's field equations and show that our
recently proposed 3+1 evolution scheme can stably evolve strong-field
solutions. We insert in our code known matter solutions, namely the
Oppenheimer-Volkoff solution for a static star and the Oppenheimer-Snyder
solution for homogeneous dust sphere collapse to a black hole, and evolve the
gravitational field equations. We find that we can evolve stably static,
strong-field stars for arbitrarily long times and can follow dust sphere
collapse accurately well past black hole formation. These tests are useful
diagnostics for fully self-consistent, stable hydrodynamical simulations in 3+1
general relativity. Moreover, they suggest a successive approximation scheme
for determining gravitational waveforms from strong-field sources dominated by
longitudinal fields, like binary neutron stars: approximate quasi-equilibrium
models can serve as sources for the transverse field equations, which can be
evolved without having to re-solve the hydrodynamical equations (``hydro
without hydro'').Comment: 4 postscript figures. Submitted to Phys. Rev. D15 as a Brief Repor
On the Role of Initial Data in the Gravitational Collapse of Inhomogeneous Dust
We consider here the gravitational collapse of a spherically symmetric
inhomogeneous dust cloud described by the Tolman-Bondi models. By studying a
general class of these models, we find that the end state of the collapse is
either a black hole or a naked singularity, depending on the parameters of the
initial density distribution, which are , the initial central density
of the massive body, and , the initial boundary. The collapse ends in a
black hole if the dimensionless quantity constructed out of this
initial data is greater than 0.0113, and it ends in a naked singularity if
is less than this number. A simple interpretation of this result can be
given in terms of the strength of the gravitational potential at the starting
epoch of the collapse.Comment: Original title changed, numerical range of naked singularity
corrected. Plain Tex File. 14 pages. To appear in Physical Review
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