1,376 research outputs found
The Geographic Structure of Milk Hauling Cost and Efficiencies in New York State
R.B. 94-03A survey of the milk haulers in the Northeast was conducted in June 1992 to assess the status of the industry. Detailed information on characteristics of the hauling businesses as well as the equipment operated was collected. Data submitted by milk haulers with New York addresses was isolated from the survey data set and analyzed on a regional basis. Some of the general topics addressed include the number, size, and location of hauling businesses, wages paid to hired drivers, and the cost of milk hauling equipment. A section is devoted to measures of hauling efficiency. Two sections review the costs involved in milk hauling, the first of which is more general in its approach. The second cost-based section investigates differences in hauling costs between small-and large-sized milk haulers
Calcareous nannofossils and Mesozoic Oceanic Anoxic Events
Twenty-five years ago, Mesozoic oceanic anoxic events (OAEs) were documented and formalised as intervals of widespread to global deposition of organic matter. The Toarcian, Early Aptian (OAE1a) and latest Cenomanian (OAE2) OAEs are truly global in nature, commonly carbonate-poor, and typically represented by organic carbon-rich black shales. In some areas, these OAEs are also characterised by abundant radiolarian-sands and silts. They are associated withnegative and positive excursions in the 87Sr/86Sr record, in addition to large global carbon-isotope anomalies in carbonateand/or organic matter, caused by a major perturbation of the global carbon budget. Increased rates of volcanism during theformation of the Ontong Java (and Manihiki) and Caribbean Plates, and the Karoo-Ferrar Traps, are believed to havecaused the geological responses associated with OAE1a, OAE2, and the Toarcian OAE, respectively. Excess volcanogenic CO2 in the atmosphere most probably turned the climate into a greenhouse mode, accelerating continental weathering and increasing nutrient content in oceanic surface-waters via river run-off. Higher fertility in the global ocean was also probably triggered directly by submarine igneous events that introduced enormous quantities of biolimiting metals within hydrothermal plumes. Because Mesozoic OAEs are often represented by carbonate-poor sediments, quantitative studies of calcareous nannofossils have been applied to explore (a) the causes and effects of igneous/tectonic events and climate changes, relative to nannofloral increases and crises, as well as (b) dissolution events, and (c) diagenetic modifications.
Characterization of calcareous nannofloras in OAE intervals can improve our understanding of the marine ecosystem and biological processes such as photosynthesis (biological pump) and biomineralisation (carbonate pump) that affect the organic and inorganic carbon cycle, as well as adsorption of atmospheric CO2 in the oceans. Types and rates of nannoplankton production and evolution are interpreted to trace the impact of major palaeoceanographic and palaeoclimatic events. In selected sections, it has been documented that calcareous nannofloras rapidly reacted to new conditions of fertility and higher pCO2 by drastically reducing calcification. As in the modern oceans, during OAEs the increase of nutrients and atmospheric CO2 induced higher abundances of nannoplankton producing small placoliths and inhibited the deep-photic zone nannoconids and schizosphaerellids. Similarly to the \u2018nannoconid crisis\u2019 preceding deposition of the Early Aptian OAE1a black shales, a \u2018schizosphaerellid crisis\u2019 is detected prior to the Toarcian OAE. Both OAEs are further characterised by a rapid nannofloral speciation, beginning approximately 1.5 myr before the OAE, but without extinctions. Global changes during the latest Cenomanian OAE 2 exerted different influences on calcareous nannoplankton that experienced a turnover due to most extreme environmental conditions. This event, in fact, was a time of extinctions followed by originations within calcareous nannofossils. Precise timing of the events before, during and after OAE1a, OAE2 and the Toarcian OAE indicates that they were intervals of enhanced oceanic productivity and that anoxia/dysoxia post-dated biotic changes
1,3 dipolar cycloadditions of azides on enamines: more than 50 years in a “Click”
High resolution spatial analyses of trace elements in coccoliths reveal new insights into element incorporation in coccolithophore calcite
Change in the earth system and calcareous nannofossil evolution: does any linkage exist? An example from the Late Jurassic Tethys Ocean
In the Late Jurassic calcareous nannoplankton experienced a progressive increase in diversity, abundance and degree of calcification, culminating in the Middle Tithonian \u2013 Berriasian interval (Calcareous Nannofossils Zone NJK and NK1 \u2013 Bralower et al., 1989). Were there any linkages between calcareous nannoplankton evolution and geologic, palaeoceanographic or palaeoclimatic events?
Upper Oxfordian - Berriasian selected sections from the Southern Alps (N Italy) have been analyzed for calcareous nannofossil biostratigraphy, relative and absolute abundances and palaeofluxes. Data were compared with litho-magneto-chemostratigraphy and available information on the tectonic, palaeoceanographic and palaeoclimatic regime.
A calcareous nannofossil increase in diversity, abundance and calcification occurred, inducing a major change in pelagic sedimentation from predominantly siliceous (Radiolarite fm. and lower part of the Rosso ad Aptici fm.) to mostly calcareous (upper part fo Rosso ad Aptici fm. and Maiolica fm.). In particular, an impressive speciation started in the Tithonian, including the first occurrence and early diversification of nannoliths and nannoconids. The increase in abundance of coccoliths and nannoliths affected the ocean carbonate system, especially because of the high rates of some nannolith calcification.
These nannoplankton evolutionary events occurred during times of low spreading rates, low pCO2, low Mg/Ca ratio, cool climatic conditions and relatively oligotrophic oceans. Available data suggest that calcareous phytoplankton was stimulated by environmental stability rather than perturbations. This is consistent with modern coccolithophorid distribution, showing highest diversity and abundance as well as calcification in stable oligotrophic oceanic areas.
A precise stratigraphic control allows to model the Late Jurassic nannofossil speciation episode and the abundance increase of high-calcified genera (Conusphaera, Polycostella, Faviconus, Nannoconus), evaluating environmental causes and consequences of evolution.
Preliminary results suggest that the Late Jurassic nannoplankton evolution was mostly controlled by the following factors: A) a decrease in pCO2 due to decreased spreading rate and/or increased weathering rate (87Sr/86Sr); B) a decrease in oceanic Mg/Ca ratio values promoting low Mg-CaCO3 and CaCO3 biomineralization (nannofossils fertilization sensu Stanley, 2006); C) cool climatic condition (Price, 1999)
On the influence of the mean-free-path parameter on intranuclear cascade calculations
In a recent letter GINOCCHIO and BLANN (2) compared results of intranuclear cascade model (ICM) calculations obtained either with a nucleon mean-free-path (mfp) in nuclear matter corresponding to free 3~-2C scattering cross-sections, or with a four times longer mfp. The latter assumption was reported to give far poorer agreement with the experimental data; and this conclusion was reported as evidence in favour of the use of the shorter mfp values in pre-equilibrium decay models, whose alternate formulations have been lately discussed at some length (2.6). We maintain tha t ICI~[ calculations performed with the free ~ ~ scatter mfp in general do not afford an accurate reproduction of the excitation functions of reactions induced by protons of some tens of MeV, and of the energy integrated spectra of the emitted particles. In fact, published results of ICM calculations have shown a systematic tendency to underestimate the emission of high-energy particles, and to overestimate compound-nucleus production. We made this statement, which agrees with an opinion already expressed by MILLER (D, on the basis of the findings of several works cited in ref. (2). Our belief is further supported by other results of BERTINI et al. (S) (e l . Specifically fig. 4 thereof), and even by the figures reported by the authors of ref. (1). However, in spite of such inadequacies of the ICM calculations, the model seems to retain a good measure of appeal as an intui t ive tool much in use for practical purposes
Mid-Cretaceous paleoenvironmental changes in the western Tethys
We present a continuous record of surface water temperature and fertility variations through the latest Barremian-Cenomanian interval (ca. 27 Myr) based on calcareous nannofossil abundances from the western Tethys. The nannofossil temperature index, calibrated with TEX86 sea surface temperatures, suggests that warmest (34-36 \ub0C) conditions were reached during oceanic anoxic event (OAE) 1a onset, the Aptian-Albian boundary interval hyperthermals (113, Kilian level and Urbino level OAE 1b) and during a ca. 4 Myr long phase in the middle Albian. Coolest temperatures (29 \ub0C) correspond instead to the late Aptian. Generally warm conditions characterized the Albian followed by a progressive cooling trend that started in the latest Albian (at the Marne a Fucoidi-Scaglia Bianca Formation transition). Temperate conditions occurred in the Cenomanian with frequent short-term variations highlighted by abundance peaks of the cold-water nannofossil species E. floralis and R. parvidentatum. Mid-Cretaceous surface water fertility was rather fluctuating and mostly independent from climatic conditions as well as from black shales intervals. Intense warming and fertility spikes were systematically associated only with black shales of OAE 1a and of the Aptian-Albian boundary hyperthermals. The Albian-Cenomanian rhythmic black shales are, in fact, associated with varying long-term climatic and fertility conditions. The similarity of western Tethys climatic and fertility fluctuations during OAE 1a, OAE 1b, the middle Albian and OAE 1d with nannofossil-based records from other basins indicated that these paleoenvironmental conditions were affecting the oceans at supra-regional to global scale
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