27,890 research outputs found
Introduction to special section: Hawaii Scientific Drilling Project
Intraplate or "hot spot" volcanic island chains, exemplified by Hawaii, play an important role in plate tectonic theory as reference points for absolute plate motions, but the origin of these volcanoes is not explained by the plate tectonic paradigm [Engebretson et al., 1985; Molnar and Stock, 1987; Morgan, 1971, 1981, 1983; Wilson, 1963]. The most widely held view is that these chains of volcanoes form from magma generated by decompression melting of localized, buoyant upwellings in the mantle [Ribe and Christensen, 1994; Richards et al., 1988; Sleep, 1990; Watson and McKenzie, 1991] . These upwellings, or "plumes," are believed to originate at boundary layers in the mantle (e.g., at the core-mantle boundary or near the boundary at-670 km between the upper and lower mantle), and the cause of the buoyancy may be both compositional and thermal [Campbell and Griffiths, 1990; Griffiths, 1986; Richards et al., 1988; Watson and McKenzie, 1991]. Mantle plumes are responsible for about 10% of the Earth's heat loss and constitute an important mechanism for cycling mass from the deep mantle to the Earth's surface. Studies of the chemical and isotopic compositions of lavas from intraplate volcanoes, especially ocean island volcanoes, have contributed significantly to our knowledge of magma genesis in the mantle [Carmichael et al., 1974; Macdonald et al., 1983] and the compositional heterogeneity of the mantle [Allègre et al., 1983; Hart, 1988; Hart et al., 1986; Kurz et al., 1983]. Of particular importance is the identification of distinct compositional end members in the mantle, the origin and distribution of which provide insight into the long-term differentiation of the mantle-crust system, the recycling of oceanic crust and continental sediment into the mantle, and the history of the lithosphere [Allègre et al., 1995; Farley et al., 1992; Hart, 1988; Hofmann and White, 1982; McKenzie and O'Nions, 1983; Weaver, 1991; Zindler and Hart, 1986]
Deep drilling into a Hawaiian volcano
Hawaiian volcanoes are the most comprehensively
studied on Earth. Nevertheless, most
of the eruptive history of each one is inaccessible
because it is buried by younger lava
flows or is exposed only below sea level. For
those parts of Hawaiian volcanoes above sea
level, erosion typically exposes only a few
hundred meters of buried lavas (out of a total
thickness of up to 10 km or more).Available
samples of submarine lavas extend the time
intervals of individual volcanoes that can be
studied. However, the histories of individual
Hawaiian volcanoes during most of their ~1-million-year passages across the zone of melt
production are largely unknown
Anaesthetic breathing circuit obstruction due to blockage of tracheal tube connector by a foreign body - two cases
Publisher's copy made available with the permission of the publisher© 1999 Australian Society of AnaesthetistsTwo cases are presented which illustrate the disastrous consequences possible when an anaesthetic breathing circuit is obstructed by a foreign body. Despite reports of previous similar cases, work practices and equipment manufacture or design continue to allow for such events to occur. The importance of both pre-anaesthetic testing of the entire circuit including attachments such as the tracheal tube connector and filters, and the removal of these parts should obstruction occur, is emphasised. Use of “clear” transparent breathing circuit components and opaque or brightly coloured packaging and caps which could potentially cause obstruction should decrease the incidence and facilitate the diagnosis of this problem.M.J. Foreman, D. G. Moye
Operator monotones, the reduction criterion and the relative entropy
We introduce the theory of operator monotone functions and employ it to
derive a new inequality relating the quantum relative entropy and the quantum
conditional entropy. We present applications of this new inequality and in
particular we prove a new lower bound on the relative entropy of entanglement
and other properties of entanglement measures.Comment: Final version accepted for publication, added references in reference
[1] and [13
Growth Performance of Holstein Dairy Calves Supplemented with a Probiotic
Administration of antibiotics in both therapeutic
and sub-therapeutic doses has been the standard practice for dealing with pathogenic bacteria problems in
farm animals since the 1940s. Several types of antibiotics
are currently used to promote weight gain and feed
efficiency in domestic livestock. There is growing concern that the use of antibiotics as growth promoters may
result in the development of resistant populations of
pathogenic bacteria and, in turn, influence the therapeutic use of antibiotics. The indiscriminate and improper
use of antibiotics in food-producing animals could result
in the presence of residues in milk, meat, and other
animal food products consumed by humans. One possible alternative to antibiotics is the use of probiotics.
Probiotics can be defined as “live microbial feed supplements which beneficially affect the host animal by improving its intestinal microbial balance” (Fuller, 1989).
Probiotics introduce beneficial microorganisms into the
gut which act to maintain optimal conditions within the
gastrointestinal tract and inhibit the growth of pathogenic or other undesirable bacteria
Minimum Wages and Teen Employment: A Spatial Panel Approach
The authors employ spatial econometrics techniques and Annual Averages data from the U.S. Bureau of Labor Statistics for 1990-2004 to examine how changes in the minimum wage affect teen employment. Spatial econometrics techniques account for the fact that employment is correlated across states. Such correlation may exist if a change in the minimum wage in a state affects employment not only in its own state but also in other, neighboring states. The authors show that state minimum wages negatively affect teen employment to a larger degree than is found in studies that do not account for this correlation. Their results show a combined direct and indirect effect of minimum wages on teen employment to be -2.1% for a 10% increase in the real effective minimum wage. Ignoring spatial correlation underestimates the magnitude of the effect of minimum wages on teen employment.minimum wage, teen employment, spatial econometrics
Alaska mining and water quality
The Institute of Water Resources has sought financial assistance
for some time in an attempt to initiate research relative to the impact
of mining on water quality. Attempts were made as early as 1971 by Dr.
Timothy Tilsworth and later by Dr. Donald Cook and Dr. Sage Murphy.
These investigators anticipated growth in placer gold mining and the
development of natural resources in Alaska during a period of national
and environmental concern. The subsequent energy "crisis," the major
increase in the price of gold on the world market, and dwindling nonrenewable
resource supplies have resulted in large-scale mineral
exploration in Alaska. This exploration, coupled with development of
the trans-Alaska oil pipeline, has attracted considerable capital for
potential investment and development in Alaska. Expected industrial
growth has already started and major new projects are "just around the
corner."
Yet, as of 1976, no major research effort has occurred to determine
the extent of or potential for water quality impacts from mining operations
in Alaska. Recently a series of interdisciplinary research projects
have been completed in Canada; however, the application of Canadian data
to Alaskan problems is uncertain. Although, state and federal government
agencies have been advised and are aware of this potential problem
and lack of baseline data they have not sought out new information or
rational solutions. Even now, with deadlines of Public Law 92-500 at
hand, some regulatory agencies give the impression of attempting to
ignore the situation. Interim limitations are proposed and permits
are issued with no discernible rationale or basis. Data have not been
obtained relative to the Alaskan mining operations and thus are not
available for use in seeking solutions compatible with mining and environmental protection. Numbers appear to have been arbitrarily
assigned to permits and water quality standards. When permits are
issued, self-monitoring requirements are negligible or nonexistent.
Nor have regulatory agencies demonstrated the ability or inclination
to monitor mining operations or enforce permits and water quality
standards.
It was hoped that the project would bring together miners, environmentalists, and regulators in a cooperative effort to identify the
problems and seek solutions. The investigators recognized the political
sensitivity of the subject matter but proceeded optimistically.
Relatively good cooperation, though not total, occurred early in the
project. In April 1976, a symposium was held to exchange ideas and
determine the state-of-the-art. Although the symposium had good
attendance and an exchange of information occurred, the symposium
itself was somewhat of a disappointment. With few exceptions, the
participants aligned on one side or the other in preconceived fixed
positions. Some even chose not to attend and were therefore able to
avoid the issues. Little hard data was presented.
Optimistically, some of the miners, environmentalists, and
regulators are prepared to resolve their differences. This report,
hopefully, will be of benefit to them. It is our experience that
miners and environmentalists share a love of the land that is uniquely
Alaska. We feel that technology is available for application to this
problem for those who care about doing the job right in the "last
frontier." Whether or not it will be effectively applied to protect
Alaska's water resources is a question which remains unanswered.The work upon which this report is based was supported in part by
funds provided by the United States Department of the Interior, Office
of Water Resources Research Act of 1964, Public Law 88-379, as amended
(Project A-055-ALAS)
USING CALLING ACTIVITY TO PREDICT CALLING ACTIVITY: A CASE STUDY WITH THE ENDANGERED HOUSTON TOAD (BUFO [ANAXYRUS] HOUSTONENSIS)
Understanding anuran calling activity patterns is important for maximizing efficiency and value of call survey data collection and analyses. Previous studies have primarily focused on identifying and quantifying abiotic variables that influence anuran calling activity, and investigating relationships between calling activity and population estimates. In this study we investigated the use of a predictor pond approach to guide call survey effort. In this approach, calling activity at a subset of breeding sites (e.g., ponds) is used as a predictor of calling activity at additional breeding sites, with the goal being to minimize sampling effort while simultaneously maximizing sampling efficiency. We explored the efficiency of this approach using call survey data collected on the endangered Houston Toad (Bufo [Anaxyrus] houstonensis) at 15 known breeding ponds over 9 survey years. We found that if calling activity at 3 predictor ponds was used to decide if additional call surveys would occur at the remaining 12 ponds, we would have hypothetically correctly assumed calling activity was not occurring at non-predictor ponds on 92.1% of survey nights, and we would have hypothetically detected 93.9% of the total number of detected individuals over the 9 survey years. We found the predictor pond approach performed well in our case study, and believe it could be a valuable tool for many anuran monitoring programs
Virus taxonomy: the database of the International Committee on Taxonomy of Viruses (ICTV)
The International Committee on Taxonomy of Viruses (ICTV) is charged with the task of developing, refining, and maintaining a universal virus taxonomy. This task encompasses the classification of virus species and higher-level taxa according to the genetic and biological properties of their members; naming virus taxa; maintaining a database detailing the currently approved taxonomy; and providing the database, supporting proposals, and other virus-related information from an open-access, public web site. The ICTV web site (http://ictv.global) provides access to the current taxonomy database in online and downloadable formats, and maintains a complete history of virus taxa back to the first release in 1971. The ICTV has also published the ICTV Report on Virus Taxonomy starting in 1971. This Report provides a comprehensive description of all virus taxa covering virus structure, genome structure, biology and phylogenetics. The ninth ICTV report, published in 2012, is available as an open-access online publication from the ICTV web site. The current, 10th report (http://ictv.global/report/), is being published online, and is replacing the previous hard-copy edition with a completely open access, continuously updated publication. No other database or resource exists that provides such a comprehensive, fully annotated compendium of information on virus taxa and taxonomy
The effect of fluorine on viscosities in the system Na2O-Al2O3-SiO2: implications for phonolites, trachytes and rhyolites
The effect of fluorine on melt viscosities of five compositions in the system Na2O-Al2O3-
SiO2h as been investigateda t one atmospherea nd 1000-1600'Cb y concentric-cylinder
viscometry. The compositions chosen were albite, jadeite and nepheline on the join
NaAlOlSiO2 and two others of the join at 75 mole percent SiO2, one peralkaline and one
peraluminous. All melt viscosities were independent of shear rate over two orders of
magnitude, indicating Newtonian behavior. All viscosity-temperature relationships were
Arrhenian within error. Fluorine reduces the viscosities and activation energies of all melts
investigated. The viscosity-reducing power of fluorine increases with the SiO2 content of
melts on the join NaAlO2-SiO2 and is a maximum at Na/Al (molar) = I for melts containing
75 mole percent SiO2. Fluorine and water have similar effects on aluminosilicate melt
viscosities, probably due to depolymerization of these melts by replacement of Si-O-(Si,
Al) bridges with Si-OH and Si-F bonds, respectively. Evidence from slag systems shows
that fluorine also reduces the viscosity of depolymerized silicate melts. The viscous flow of
phonolites, trachytes and rhyolites will be strongly afected by fluorine. It appears that
fluorine contents of igneous rocks may be combined with water in calculation schemes for
determining the viscosity of natural melts
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