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Megafaunal burrows were detected in boxcores from the two cites in the bathyal north-east Atlantic, which was analysed to asses the significance to sediment radiotracer profiles and organic composition. The result showed that (super 210)Pb(sub excess) and organic content indicated a phytodetrital origin, and extended linear bands of faecal pellets were present in three boxcars at 13-17 cm dept. The results suggest that 'catching' of phytodetritus and subsurface deposition of faeces are two mechanisms for the rapid, deep burial of relatively fresh organic matter.

Biodistribution studies of a water-soluble radioactive metallofullerene compound have been conducted using BALB/c mice. To this end, a sample containing [Ho.sub.x]@[C.sub.82] (x = 1, 2) was purified and derivatized to prepare the water-soluble metallofullerol, [Ho.sub.x]@[C.sub.82][(OH).sub.y]. This metallofullerol was then neutron-activated (165Ho[n,[Gamma]]166Ho) to prepare the 166[Ho.sub.x]@[C.sub.82][(OH).sub.y] analog as a radiotracer, which was monitored, after intravenous administration, for up to 48 hours by using dissection radioanalysis, and its biodistribution was compared with a control compound, [Na.sub.2][166Ho(DTPA)([H.sub.2]O)]. Results showed selective localization of the 166[Ho.sub.x]@[C.sub.82][(OH).sub.y] tracer in the liver but with slow clearance, as well as uptake by bone without clearance. In contrast, excretion of the control compound was nearly quantitative after 1 hour. The fate of 166Ho was also explored by a metabolism study of 166[Ho.sub.x]@[C.sub.82][(OH).sub.y] in Fischer rats. Results indicated 20% excretion of intact 166[Ho.sub.x]@[C.sub.82][(OH).sub.y] within 5 days. The present findings demonstrate the feasibility of using water-solubilized metallofullerene radiotracers to monitor the fate of fullerene-based materials in animals, and suggest that water-solubilized fullerene materials, in general, may be useful components in drug design.

The Miocene Tonga forearc has been found to contain low grade contact metamorphism produced by the paleothermal flux. Researchers have discovered that the paleothermal flux was responsible for the presence of oxygen isotopic compositions of clay minerals in the same site. These isotopic compositions were formed in an iron-chlorite-corrensite paragenesis environment capable of generating temperatures of up to 200 deg Celcius.

Introduction Effective management of ground water resources requires reliable information on the rates and patterns of ground water recharge and flow. For simple, relatively homogeneous aquifers, such information is often [...]

The tracers 129I and 137Cs were measured in 1993 in the Barents and Kara Seas and western Arctic Ocean. Findings indicated that the tracers were in excess of fallout levels, owing mainly to inputs of Atlantic-origin water contaminated by discharges from the Sellafield and La Hague nuclear reprocessing plants. Elevated levels of the tracers were also found in halocline and Atlantic layer water in the Makarov and Canada Basins, reflecting the labelling of these water masses by discharges from the European reprocessing plants.

Methods utilizing activated charcoal for separating radiolabeled sugars from each other and from water are described. The first method alleviates a practical limitation for use of tritiated sugars as a tracer in planta. Tritium exchange with water can now be readily quantified because the method allows a more rapid separation of sugars and water than has been previously described. A spin column containing activated charcoal and powdered cellulose retained ([is greater than] 99%) sucrose during elution ([is greater than] 99%) of ³[H.sub.2]O in water rinses. The retained sucrose could then he eluted (95%) from the column by rinsing with aqueous methanol. The second method partially resolves another limitation in the use of radiolabeled sugars as tracers in planta. We can now ascertain the spatial distribution of various radiolabeled sugars within particular organs. Charcoal filter paper was used to adsorb sucrose and hexose sugars for development of differential autoradiographs of sugars blotted from stem cross-sections of sorghum (Sorghum bicolor [L.] Moench). The hexose sugars were selectively removed during rinsing of the charcoal paper in water. Autoradiography was performed before and after rinsing. The autoradiographic image obtained before rinsing reflected the presence on the blot of both radiolabeled sucrose and hexose sugars. In comparison, the image obtained after rinsing no longer reflected the presence of radiolabeled hexose sugars. These methods help refine studies of carbon dynamics in plants by enhancing our ability to detect in planta movement of sugars through particular metabolic pathways and to detect the spatial distribution within organs of particular radiolabeled sugars., Soluble sugars constitute the principal form of translocated photoassimilate and are a major form of stored assimilate. Radiolabeled sugars supplied through photoassimilation Of [sup.14][CO.sub.2] are often used in exploring the [...]

The use of feces is proposed for examining isotopic abundance in large, free-ranging wild mammals in doubly labeled water method-based energy metabolism studies. Four female reindeer were examined in summer and in winter to test if feces can be employed in measuring isotopic marker concentrations. Results reveal no major differences in rate constants, dilution spaces, total energy expenditure and rates of CO2 production.

A novel charge transfer label was developed based on the utilization of trans-1-[p-(N,N-dimethylamino)phenyl]-trans-4-(p-nitrophenyl)-1,3-butadiene (NND) as starting material. The synthesis of the NND analogs was based on the reaction of NND to potassium tert-butoxide in DMF solution. The resulting analogs of NND exhibited a phenolic handle for linkage to the anomeric center of the carbohydrate. The fluorescent tag responded to solvent polarity and was applicable to a wide variety of protein labelling events involving restricted protein binding.

Receptor subtypes of pharmacological interest are often characterized by studies in which a particular radiolabelled ligand is competitively displaced from its binding sites, either by its unlabelled analogue (homologous displacement), or by different, unlabelled, ligands (heterologous displacement). In this article, Stephane Swillens, Magali Waelbroeck and Philippe Champeil emphasize the fact that a single homologous displacement curve is generally unable to reveal that the radioligand binds to a heterogeneous receptor population. Overlooking this heterogeneity may, in turn, dramatically affect interpretation of heterologous displacement curves displaying more than one receptor type for the unlabelled ligand: neither the binding affinities of the ligands for the different receptors, nor the proportion of these receptors, can be estimated reliably.

Radon-222 (Rn-222) and chloride may be used as tracers of the infiltration of river water into alluvial aquifers. This was proven by a study which was conducted in an alluvial aquifer in France which is partly recharged by the nearby Lot River. The quality of water taken from some wells in the area had deteriorated, and tracers were needed to understand the dynamic conditions affecting the biogeochemical reactions in the aquifer. Rn-222 was used to trace the infiltration path, while chloride was used to quantify river and groundwater mixing.

An analysis of the time scales of magmatic processes is presented. The analysis tests initial Sr isotopic compositions of glass and mineral separates taken from the Bishop Tuff in Long Valley, CA. It is shown that a substantial isotopic heterogeneity exists. The heterogenous characteristic is exhibited between eruptive units and between glass and phenocryst stages of each unit. Variations were generated by magmatic processes.

Isotopic data for Quaternary volcanic centers from lat 17.5 degrees to 22 degrees S in northern Chile provide evidence for crustal contributions to arc magma genesis in the central Andes and delineate basement domains. Crustal thickness, distance from trench, height of volcanic edifices above the seismically active subduction zone, and sediment supply to the trench are all constant along this segment of the arc. The only significant variable is crustal age (Paleozoic in the south, Proterozoic in the north). Pb isotopic compositions of Quaternary lavas in the northern sector are lower (206Pb/204Pb = 17.89-18.28) and Sr and O isotope ratios are less variable (87Sr/86Sr = 0.7058-0.7077, delta-18-O = +6.5 0/00-+8.4 0/00) than in the southern sector (206Pb/204Pb = 18.59-18.79, 87Sr/86Sr = 0.7053-0.7083, delta-18-O = +6.4 0/00-+9.3 0/00) for rocks similar in bulk composition, from 53 to 74 wt% SiO2. Together, these features are interpreted to reflect interaction of magmas with crustal contaminants of different isotopic character, rather than changes in the mantle source of central Andean arc magmas resulting from either subduction erosion or involvement of old enriched lithosphere.

The preparation of three functionalized perfluorophenyl azides (PFPAs) with azido and iodo units in the same aryl ring and two PFPAs with azido and iodo units in different aryl rings represents two new methods of introducing iodine into PFPA photolabeling reagents. Similarly, three new trifluorophenyl azides promote the entry of a tritium atom into the ring system without disrupting the photochemistry of PFPAs. Moreover, the photolysis studies of methyl 4-azido-2-iodo-3,5,6-trifluorobenzoate and methyl 3-(4-azido-2,3,5, 6-tetrafluorobenzamido)-5-iodobenzoate show iodinated PFPAs perform better CH and NH insertion than nonfluorinated intermediates.

Byline: V. Shaiju, S. Sharma, Rajesh. Kumar, B. Sarin Medical cyclotron is a particle accelerator used in producing short lived radiotracers such as [sup] 18 F, [sup] 11 C, [sup] [...]

Paleoclimatologists who study the tiny air bubbles trapped in ice cores are very lucky. They can observe the composition of Earth's past atmosphere over hundreds of thousands of years and [...]

In diagnostic medicine, radiotracers are used to image molecules in the body by methods such as positron emission tomography. Radionuclides such as carbon-11, nitrogen-13 or fluorine-18 are incorporated into molecules [...]

Geologists gathered for a conference between Jun 10-14, 1991, to discuss ways to predict future climate changes. Among the topics discussed were continental isotopic indicators of climate histories (CIICs), often found in lake sediments. Some presentations showed that the variety of useful CIICs goes beyond the widely used isotopes of hydrogen, carbon, and oxygen. A map of the global distribution of the isotopic composition of rainfall was used to interpret past continental climates.