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Results 401 - 450 of 492
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Bowring S A - - 1995
The Archean crust contains direct geochemical information of the Earth's early planetary differentiation. A major outstanding question in the Earth sciences is whether the volume of continental crust today represents nearly all that formed over Earth's history or whether its rates of creation and destruction have been approximately balanced since ...
Ishibe T - - 1995
Inhaled nitric oxide (NO) is used for the treatment of pulmonary hypertension as a selective pulmonary vasodilator. However, NO is oxidized rapidly to the more toxic nitrogen dioxide (NO2). Elimination of NO2 from inspired gas is essential for safe clinical use NO. We therefore investigated the efficacy of soda lime ...
Raj A B - - 1995
The efficacy for the euthanasia of day-old chicks of mixtures of carbon dioxide and air, or carbon dioxide and argon containing 1, 2 or 5 per cent residual oxygen, or argon containing 1 or 2 per cent residual oxygen was tested in three experiments. The time to the onset of ...
Weisler M I - - 1995
The prehistoric settlement of the Pacific Ocean has intrigued scholars and stimulated anthropological debate for the past two centuries. Colonized over a few millennia during the mid to late Holocene, the islands of the Pacific--displaying a wide diversity of geological and biotic variability--provided the stage for endless "natural experiments" in ...
Maurette M - - 1995
"Interplanetary Dust Particles" with sizes approximately 10 micrometers collected in the stratosphere (IDPs), as well as much larger "giant" micrometeorites retrieved from Antarctic ice melt water (AMMs), are mostly composed of unequilibrated assemblages of minerals, thus being related to primitive unequilibrated meteorites. Two independent evaluations of the mass flux of ...
Mitchell C A - - 1994
Long-duration future habitation of space involving great distances from Earth and/or large crew sizes (eg, lunar outpost, Mars base) will require a controlled ecological life-support system (CELSS) to simultaneously revitalize atmosphere (liberate oxygen and fix carbon dioxide), purify water (via transpiration), and generate human food (for a vegetarian diet). Photosynthetic ...
Chesler M - - 1994
The extracellular pH of the brain is subject to shifts during neural activity. To understand these pH changes, it is necessary to measure [H+], [HCO3-], [CO3(2-)] and [CO2]. In principle, this can be accomplished using CO3(2-) and pH-sensitive microelectrodes; however, interference from HCO3- and Cl-, and physiological changes in [HCO3-], ...
Hedge A - - 1994
The effect of alternative smoking policies, which prohibited or restricted smoking, on indoor air quality was studied in 27 air-conditioned office buildings. Carbon monoxide, carbon dioxide, respirable particulates, formaldehyde, ultraviolet particulate matter (u.v.PM), nicotine, air temperature, relative humidity and illumination were measured at eight sample sites in each building. Smoking ...
Shelef M - - 1994
In 1970, before the implementation of strict controls on emissions in motor vehicle exhaust gas (MVEG), the annual USA incidence of fatal accidents by carbon monoxide in the MVEG was approximately 800 and that of suicides approximately 2000 (somewhat less than 10% of total suicides). In 1987, there were approximately ...
Kumagai H - - 1994
The biosynthesis of antitumor antibiotic cytogenin, 3-hydroxymethyl-6-methoxy-8-hydroxy-isocoumarin, was studied by feeding 14C- or 13C-labeled compounds to culture of the producing organism, Streptoverticillium eurocidicum MI43-37F11. 14C-Acetate and 14C-methionine were efficiently incorporated into cytogenin as precursors. 13C NMR studies proved that the carbon skeleton of cytogenin is derived from pentaketide intermediate due ...
Havens K E - - 1994
An in-situ experiment was performed to quantify the impacts of copper sulfate on plankton structure and carbon dynamics. Plankton were exposed to 140 microg litre(-1) copper in quadruplicate mesocosms. Community structure was monitored for 14 days by microscopical counts and compared with untreated controls. Carbon dynamics were assessed by tracer ...
Simpkins C O - - 1994
The effect of the stress-induced, cysteine-rich protein, metallothionein I (MT), on oxygen consumption by rat liver mitochondria was studied. Using a Clark-type oxygen electrode we found that electron transport from succinate to oxygen was enhanced by MT whereas ADP-initiated oxygen consumption was inhibited by MT. The MT effect was concentration ...
Murphy C E CE - - 1993
The transport and cycling of tritium in the environment can be understood in terms of the role of hydrogen in the environment. Physical and chemical isotopic effects, while present in some transport mechanisms and chemical reactions, are not important factors in environmental tritium dynamics. In addition, because of the role ...
Lal D - - 1993
We present calculations of rates of production of several nuclides in the Martian atmosphere and in the regolith due to nuclear interactions of cosmic ray and radiogenic particles and consider their implications to the evolutionary history of Mars. Nuclides selected are those which, considering their chemical properties, may be useful ...
Auer D E - - 1993
Total plasma carbon dioxide (TCO2) concentrations were measured in Standardbred horses to determine criteria to discriminate between normal horses and horses with excessive TCO2 concentrations on raceday. TCO2 concentrations from stabled horses were distributed normally with a mean of 30.2 mmol/L and a standard deviation of 1.2 (n = 192) ...
Kronberg S L - - 1993
Leafy spurge (Euphorbia esula) is an introduced forb that is invading western rangelands. Goats (Capra hircus) readily graze the plant, but cattle (Bos tarus) generally and sheep (Ovis aries) locally appear to develop conditioned flavor aversions to leafy spurge. They either avoid the plant entirely or graze it reluctantly. We ...
Kasting J F - - 1993
Ideas about atmospheric composition and climate on the early Earth have evolved considerably over the last 30 years, but many uncertainties still remain. It is generally agreed that the atmosphere contained little or no free oxygen initially and that oxygen concentrations increased markedly near 2.0 billion years ago, but the ...
Herman D C - - 1993
An environmental actinomycetes, capable of utilizing p-nitrophenol as its sole carbon and nitrogen source, was starved for an 8-week period and showed no reduction in its ability to biodegrade p-nitrophenol. Microscopic examination revealed that starvation of the bacterium resulted in the fragmentation of filaments into individual cells.
Larsen C S - - 1992
Measurement of carbon and nitrogen stable isotope ratios (delta 13C and delta 15N) in samples of human bone collagen (n = 93) from a temporal series of four prehistoric (early preagricultural, late preagricultural, early agricultural, late agricultural) and two historic (early contact, late contact) periods from the Georgia Bight, a ...
Allen H - - 1992
Carbon monoxide poisoning is a well recognized, but uncommon hazard of sport and inshore diving, which occurs either as a result of a faulty air compressor or from air contamination by the exhaust of nearby petrol engines. The incidence of carbon monoxide poisoning may be under-reported as it may mimic ...
Liu Z - - 1992
Carbon monoxide (CO) was employed to assess the role of ferrous hemoproteins in the vasodilation and biotransformation of glyceryl trinitrate (GTN) in rabbit aortic strips. These tissues were contracted submaximally with phenylephrine, exposed to CO for 5 min, and then incubated with 0.5 microM [1,3(14) C]GTN in the presence of ...
Atanasov P - - 1992
Amperometric biosensors for the determination of beta-D-glucose have been constructed. They were based on a porous matrix of carbon blacks--'Ketjenblack' (KB) and 'Shawinigan black' (SB) wet-proofed with polytetrafluorethylene. Glucose-sensitive elements were prepared by subsequent adsorptional immobilization of 1,1'-dimethylferrocene (DMFc) and nickel-ocene (Nc) on 'Shawinigan black' or tetracyanoquinodimethane (TCNQ) on 'Ketjenblack' ...
Kaiserman M J - - 1992
Thirty-one Canadian brands of fine-cut tobaccos for roll-your-own cigarettes (RYOs) were evaluated under standard conditions using mandated tube and filter combinations. Results indicate no evidence of a significant difference in the amounts of tar, nicotine, and carbon monoxide produced by the 31 brands. In addition, the data emphasize that it ...
Kline D L - - 1991
Field studies were conducted to determine the responses of mosquitoes associated with irrigated riceland in Arkansas to 1-octen-3-ol (octenol), carbon dioxide (CO2) and combinations of both. Octenol was released at 4.1 (wick in) and 41.1 (wick out) mg/h and CO2 at 200, 500 and 1,000 ml/min. Octenol alone did not ...
Stone J - - 1991
A suite of morphologically distinctive silicon carbide (SiC) grains from the Orgueil and Murchison carbonaceous chondrite meteorites contains Si and C of highly anomalous isotopic composition. All of the SiC grains in this suite are characterized by a distinctive platy morphology and roughly developed hexagonal crystal forms that allow them ...
Turnlund J R - - 1991
A number of minerals contained in foods are essential nutrients for humans, animals, and/or plants. While most vitamins are very well absorbed, most essential minerals are not. Usual absorption of minerals ranges from less than 1% to over 90%. The bioavailability of dietary minerals must be considered when determining whether ...
Dutkiewicz T - - 1991
For each environmental poison the index of harmfulness was calculated on the basis of quantitative evaluation of the following properties: emission of the substance to the environment (Fi), toxicity (F2), the population exposed (F3), exposure (F4), persistence of the substance in the environment (F5), secondary substances and mixtures (F6), bioaccumulation ...
Jasper J P - - 1990
Analyses of gases trapped in continental ice sheets have shown that the concentration of CO2 in the Earth's early atmosphere increased from 180 to 280 p.p.m. during the most recent glacial-interglacial transition. This change must have been driven by an increase in the concentration of CO2 dissolved in the mixed ...
Kennedy B V - - 1990
The isotopic compositions of animal tissues, minerals, and fluids reflect those of ingested food and water and inhaled gases. This relationship is illustrated by a review of data pertaining to five light elements of biological interest (carbon, nitrogen, hydrogen, oxygen, and sulphur). Processes affecting the isotopic composition of inorganic compounds ...
Skogerboe K J - - 1990
This instrumental method for total urinary nitrogen (TUN) is based on the principle of gas-phase chemiluminescence. Results correlate well with measurements of TUN by the Kjeldahl method, which has long provided the means to calculate nitrogen balances for nutritional management. In recent years, because of speed and convenience of measurement, ...
Schneider D A - - 1990
VO2max and the ventilatory threshold (Tvent) were measured during cycle ergometry (CE) and treadmill running (TR) in a group of 10 highly trained male triathletes. Tvent was indicated as the VO2 at which the ventilatory equivalent for oxygen increased without a marked rise in the ventilatory equivalent for carbon dioxide. ...
Shahkhalili Y - - 1990
The extent to which tea, cocoa and carob (foods rich in polyphenols) influence fecal nitrogen (N) excretion was investigated in rats. The studies took into account the methylxanthine contents of tea and cocoa as well as the poor digestibility of cocoa nitrogen. Balance measurements indicated that all three food sources ...
Grupe G - - 1990
Feeding habits of free-ranging martens (Martes martes and Martes foina) are evaluated by means of trace element and stable carbon isotope analyses of their skeletons. This investigation was carried out as an inter-disciplinary project of both wildlife biology and physical anthropology. As a result, data are obtained on the feeding ...
Doull J L - - 1990
Actinorhodin production in Streptomyces coelicolor A3(2) was relatively insensitive to the carbon source concentration but was elicited by nitrogen or phosphate depletion, or by a decline in the growth rate. In starch-glutamate media with nitrogen limitation, increasing the nitrogen supply delayed the onset of antibiotic synthesis and, at concentrations above ...
Duggins D O - - 1989
Kelps are highly productive seaweeds found along most temperate latitude coastlines, but the fate and importance of kelp production to nearshore ecosystems are largely unknown. The trophic role of kelp-derived carbon in a wide range of marine organisms was assessed by a natural experiment. Growth rates of benthic suspension feeders ...
Holtzapple M T - - 1989
Life support components are evaluated for application to an idealized closed life support system which includes an algal reactor for food production. Weight-based trade studies are reported as "break-even" time for replacing food stores with a regenerative bioreactor. It is concluded that closure of the life support gases (oxygen recovery) ...
Razis P A - - 1989
A random postal survey of 1528 anaesthetists in the UK was performed to assess their use of carbon dioxide in anaesthesia and opinion on its safety. Of 1100 replies (72% response rate), 60.9% used it daily and 77.1% would object to its exclusion from future anaesthetic machines. There was no ...
Gale J - - 1989
The photosynthesis and productivity of Lemna gibba were studied with a view to its use in Controlled Ecological Life Support Systems (CELSS). Photosynthesis of L. gibba floating on the nutrient solution could be driven by light coming from either above or below. Light from below was about 75% as effective ...
Oguchi M - - 1989
In CELSS (Controlled Ecological Life Support System), utilization of photosynthetic algae is an effective means for obtaining food and oxygen at the same time. We have chosen Spirulina, a blue-green alga, and have studied possibilities of algae utilization. We have developed an advanced algae cultivation system, which is able to ...
Woelders H - - 1988
The rate of ATP synthesis (JP) in isolated rat-liver mitochondria was strongly dependent on the magnitude of the protonmotive force (delta mu H+) across the mitochondrial inner membrane. Addition of different concentrations of various uncouplers or malonate to mitochondrial incubations in State 3 led to a depression of delta mu ...
Russell W L - - 1988
Micromonospora purpureochromogenes subsp. halotolerans was found to produce crisamicin C, a novel antibiotic, together with crisamicin A. Crisamicin C was purified by silica gel column chromatography and its physico-chemical properties, structure and biosynthesis were studied. Crisamicin C, mp 260 degrees C (dec), showed UV maxima at 392 (epsilon 9,497), 261 ...
Knowles C J - - 1988
Various microorganisms can produce (cyanogenesis) or degrade cyanide. They degrade cyanide either to detoxify it, or to use it as a source of nitrogen for growth. Significant amounts of cyanide are formed as a secondary metabolite by a wide range of fungi and a few bacteria by decarboxylation of glycine. ...
Kirkham A J - - 1988
1. We have compared rebreathing, breath-hold and mean alveolar methods of measuring alveolar carbon monoxide (CO), at levels similar to those found in smokers, as a preliminary to using them as indirect measures of carboxyhaemoglobin levels. In the present study alveolar CO levels were raised by rebreathing a 2% CO ...
Ong J T - - 1988
The in vitro release of lonapalene, a novel nonsteroidal antipsoriatic agent, was studied from two-phase emulsion-type ointment systems into a perfect sink of propylene carbonate at 32 degrees C. Lonapalene was completely solubilized in the ointments consisting of an internal phase of propylene carbonate (PC)-propylene glycol (PG) mixture dispersed within ...
Weber F L FL - - 1987
To determine how lactulose and lactulose plus neomycin might alter nitrogen metabolism in the colon we investigated the effect of these agents on the distribution of nitrogen in the bacterial, soluble, and fiber fractions of stool. The alterations in fecal nitrogen excretion were additionally correlated with changes in total body ...
Macintyre P E - - 1987
Meperidine has been used to suppress postanesthesia shivering. However, its efficacy to date has only been assessed by observation of visible shivering. We measured the effect of meperidine on oxygen consumption (VO2), carbon dioxide production (VCO2) and pulmonary gas exchange in 14 otherwise healthy patients shivering after general anesthesia. Meperidine ...
Laxen D P - - 1987
Annual mean sulphur dioxide concentrations measured at County Hall in central London between 1931 and 1985 showed no clear trend until 1963/64, when a steady decline set in. Results for a number of sites across London for the period 1964/65 to 1984/85 have been divided into three geographic zones: the ...
Oguchi M - - 1987
In order to reduce the cultivation area required for the growth of higher plants in space adoption of algae, which have a higher photosynthetic ability, seems very suitable for obtaining oxygen and food as a useful source of high quality protein. The preliminary cultivation experiment for determining optimum cultivation conditions ...
Westley J W - - 1986
Streptomyces sp. X-14873 (ATCC 31679) has been found to produce a number of secondary metabolites. Three have been identified as the novel actinomycins, X-14873B, C and D, each of which contains both proline and 3-hydroxy-5-methylproline. Potentially, the most important microbial product from this fermentation is the novel polyether antibiotic X-14873A ...
Severinghaus J W - - 1986
To calibrate an anesthetic mass spectrometer without the use of premixed gases and vapors in cylinders, we devised a gas mixer using fixed resistances of capillary needle tubings and adjustable needle valves to dilute test gases and vapors with oxygen. The dilution ratio was determined during each calibration by diluting ...
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