20,268 research outputs found
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A Red Tide Monitoring Program for Texas Coastal Waters
This is the final report for the red tide monitoring project conducted at The University of
Texas at Austin Marine Science Institute (UTMSI) and covers the period from 1 Nov. 1998 to 10
April 2000. The study was designed to examine the seasonal dynamics of the toxic red tide
dinoflagellate Karenia brevis (Davis) G. Hansen and Moestrup at 5 locations off the Texas coast.
The work was conducted in collaboration with the Texas Parks and Wildlife Department
(TPWD) utilizing bimonthly finfish surveys (Coastal Fisheries Division) to collect samples. The
samples were shipped to UTMSI for chl a, nutrient, and cell count analyses.
Significant interannual variability occurred in the temperature and salinity fields.
Temperature was lowest in Jan.-Feb. of each year and increased. In general, the 5 stations
showed little concordance with each other. There was no annual pattern in nutrient distributions.
Individual stations appeared to reflect local inputs, rather than coast wide events. The only
exception was a generalized silicate increase noted in Feb-April 2001 at all stations except
Brazos Santiago near Brownsville.
Karenia brevis was observed sporadically along the coast during the winter and most
observations were limited to the summer/fall months. The sporadic occurrences and numerous
"no cells" observations do not support the hypothesis that a year round resident red tide
population exists in the Texas coastal zone. It appears that are transported into the area by large
scale oceanographic features. The mechanism for this remains unknown.
A minor red tide occurred along South Padre Island in Oct./Nov 1999. The bloom
advected south into Mexico, and no further fish kills were noted in 1999. However, K. brevis
occurred sporadically along the coast during this time. These events suggest that K. brevis may
be seeded into the area from further offshore regularly at very low levels. Until fish-killing
populations develop, it likely remains undetected. One major red tide event occurred during
2000 that affected the entire Texas coast. A small red tide occurred along South Padre Island in
July, 2000 but disappeared after moving north to Padre Island National Seashore. Fish-killing
concentrations of K. brevis were first detected in mid August off Sabine Pass in the north and
moved south along the coast over the following months. However, low level occurrences of K.
brevis were found at intermediate stations well before the main red tide advected into the region,
and were nearly coincident with the initial observations off Sabine Pass. It is impossible from
this data to determine if the July bloom in south Texas was related to the events off Sabine, but
there is a possibility that offshore continental shelf currents may well be transporting cells north
from Mexico into northern Texas waters.
Another toxic species closely related to K. brevis has been seen at reasonably high
abundance. This species, Karenia mikimotoi, is toxic to fish and has been reported to co-occur
with K. brevis in blooms. Maximum abundance of this species was 6000 cells L-1, and appeared
to exhibit a distinct increase and decline in population levels at 3 different stations.Marine Scienc
Labor Market Policies and Employment Duration: The Effects of Labor Market Reform in Argentina
Over the last few years, the debate on labor market reform has been at the center of economic policy debate in Argentina. This debate has been fueled by the sustained growth in the unemployment rate observed during the decade. One of the major targets of the attack on labor market regulation has been high dismissal costs. Attempts to reduce dismissal costs for all existing jobs have faced strong opposition. As a compromise, and to stimulate job creation, employment promotion contracts for new jobs were introduced in 1995. These contracts are limited to a fixed term ranging from three months to two years.
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Duration and Risk of Unemployment in Argentina
After a decade of structural reforms, unemployment rates have tripled in Argentina. This paper is concerned with the measurement of unemployment risk and its distribution. We show the importance of considering re-incidence in the measurement of unemployment risk and develop a methodolgy to do that. Our estimates for Argentina show that, though the typical unemployment spell is short, once re-incidence is taken into account, unemployment risk is high, has risen substantially in the last decade and is shared very unequally in the labor force. This counters the established view that unemployment is a small risk, short-duration phenomenon, which arises when re-incidence is not considered.http://deepblue.lib.umich.edu/bitstream/2027.42/39861/3/wp476.pd
Towards a Unified Framework for Declarative Structured Communications
We present a unified framework for the declarative analysis of structured
communications. By relying on a (timed) concurrent constraint programming
language, we show that in addition to the usual operational techniques from
process calculi, the analysis of structured communications can elegantly
exploit logic-based reasoning techniques. We introduce a declarative
interpretation of the language for structured communications proposed by Honda,
Vasconcelos, and Kubo. Distinguishing features of our approach are: the
possibility of including partial information (constraints) in the session
model; the use of explicit time for reasoning about session duration and
expiration; a tight correspondence with logic, which formally relates session
execution and linear-time temporal logic formulas
RECONSTITUTION OF ALLOPHYCOCYANIN FROM Mastigocladus laminosus WITH ISOLATED LINKER POLYPEPTIDE
The core linker polypeptide Lc 8.9 was isolated from Mastigocladus laminosus and purified on a preparative scale. A method for the reconstitution of allophycocyanin (AP)âlinker complexes from isolated polypeptides was developed. The complex (αAP(ÎČAP)3 Lc 8.9 was reconstituted and compared to (αAPÎČAP) and (αAPÎČAP)3 by sucrose density gradient ultracentrifugation, absorption, fluorescence emission and circular dichroism spectroscopy. Differences in the spectra of reconstituted and of directly isolated AP complexes are discussed
Bacteriochlorophyll aggregates in positively charged micelles
Micellar complexes were prepared from bacteriochlorophyll a and bacteriopheophytin a with the cationic detergents, cetyltrimethyl ammonium bromide and cetylpyridinium chloride. These complexes have spectroscopic properties (absorption, circular dichroism) which are very different from the ones formed with non-ionic detergents like Triton X-100, and also with anionic detergents. Bacteriochlorophyll a forms two complexes: One is blue-shifted and has excitonically coupled Qy transitions. The second one is extremely red-shifted. The unusual properties are suggested to result from interactions of the positively charged head-group of the detergent with the tetrapyrrole
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