Search for L5 Earth Trojans with DECam

Most of the major planets in the Solar System support populations of co-orbiting bodies, known as Trojans, at their L4 and L5 Lagrange points. In contrast, Earth has only one known co-orbiting companion. This paper presents the results from a search for Earth Trojans using the DECam instrument on the Blanco Telescope at CTIO. This search found no additional Trojans in spite of greater coverage compared to previous surveys of the L5 point. Therefore, the main result of this work is to place the most stringent constraints to date on the population of Earth Trojans. These constraints depend on assumptions regarding the underlying population properties, especially the slope of the magnitude distribution (which in turn depends on the size and albedo distributions of the objects). For standard assumptions, we calculate upper limits to a 90% confidence limit on the L5 population of N ET < 1 for magnitude H < 15.5, N ET =60-85 for H < 19.7, and N ET = 97 for H=20.4. This latter magnitude limit corresponds to Trojans ∼300 m in size for albedo 0.15. At H=19.7, these upper limits are consistent with previous L4 Earth Trojan constraints and significantly improve L5 constraints.

New peat bog record of atmospheric lead pollution in Switzerland: Pb concentrations, enrichment factors, isotopic composition, and organolead species

A peat core collected at Etang de la Gruère, an ombrotrophic bog in the Jura Mountains of Switzerland, was analyzed for organolead species (DEL, TEL, DML, and TML) using GC-MIP AES, Pb isotopes using TIMS, and total Pb using XRF and age-dated using 210Pb. The earliest occurrence of quantifiable alkyllead is found at a depth of 24 cm, which is dated at AD 1946 +/- 3; this finding is consistent with the introduction of leaded gasoline in Switzerland in 1947. The maximum concentration of alkyllead (2.89 ng/g) is found at 5 cm, which is dated at AD 1988 +/- 2. This same sample yielded 206Pb/207Pb = 1.1254, which is the least radiogenic value in the entire 2K core and comparable to the isotopic composition of Pb in leaded gasoline. The highest concentrations of DML (906 ng/g) and DEL (1906 ng/g) also were found in this sample. Total alkyllead never accounts for more than 0.02% of total Pb in any given sample. The spatial and temporal variations in organolead species is matched by the changes in the isotopic composition of Pb over the same interval. Despite this, the decline in anthropogenic Pb pre-dates the maximum in total alkyllead and minimum 206Pb/207Pb, indicating that atmospheric Pb emissions had already begun their decline prior to the introduction of unleaded gasoline. In fact the decline in anthropogenic Pb was probably in response to the introduction of legislation, first in Germany and later in the European Union, establishing a maximum allowable concentration of Pb in gasoline.

Comparison of three coupled gas chromatographic detectors (MS, MIP-AES, ICP-TOFMS) for organolead speciation analysis

An automatic unit for the screening of rainwater is used for the determination of organolead compounds using different detectors coupled to a gas chromatograph. A systematic overview is given of the advantages and disadvantages of several detectors (electron ionization mass spectrometry, EI-MS; microwave induced plasma atomic emission spectrometry, MIP-AES; and inductively coupled plasma time-of-flight mass spectrometry, ICP-TOFMS, for the speciation of organolead compounds on the basis of sensitivity, selectivity and reliability. C60 fullerene and RP-C18 were used as sorbent materials for these compounds. The primary assets of the fullerene sorbent, as compared to C18 sorbent, are high sensitivity and selectivity resulting from efficient adsorption due to large surface area and interstitial volume. Among the detection systems, GC/ ICP-TOFMS is the most sensitive, with absolute detection limits of approximately 15 fg of organolead compounds (as lead) using 5-mL sample volumes. Except for diethyllead, similar sensitivities were obtained by MIP-AES. GC/MS is intrinsically the most specific option, because the species are detected directly from molecular information. The precision is similar for all detectors. The screening of rainwater from different locations showed that samples collected in countries in which leaded gasolines are now banned contain organolead species at concentrations below 2 pg/ mL, levels that can be detected only for sample volumes of 25 mL and using MIP-AES or ICP-TOFMS as detectors, their determination being impossible by GC/MS.

Gas chromatography--inductively coupled plasma--time-of-flight mass spectrometry for the speciation analysis of organolead compounds in environmental water samples

The application of inductively coupled plasma--time-of-flight mass spectrometry for the speciation analysis of organolead compounds in environmental waters is described. Construction of the transfer line was achieved by means of a relatively simple and rapid coupling procedure. Derivatization of the ionic lead species was achieved by in-situ propylation with sodium tetrapropylborate; simultaneous extraction of the derivatized compounds in hexane was followed by separation and detection by capillary gas chromatography hyphenated to inductively coupled plasma-time-of-flight mass spectrometry. Detection limits for the different organolead species ranged from 10 to 15 fg (as Pb), corresponding to procedural detection limits between 50 and 75 ng L(-1), on the basis of a 50 mL snow sample, extraction with 200 microL hexane, and subsequent injection of 1 microL of the organic extract on to the column. The accuracy of the system was confirmed by additional analysis of the water samples by capillary gas chromatography coupled with microwave-induced plasma-atomic-emission spectrometry and the analysis of a standard reference material CRM 605 (road dust) with a certified content of trimethyllead.

Low-molecular-weight organoiodine and organobromine compounds released by polar macroalgae--the influence of abiotic factors

The influence of temperature, light, salinity and nutrient availability on the release of volatile halogenated hydrocarbons was investigated in the Antarctic red macroalgal species Gymnogongrus antarcticus Skottsberg. Compared to standard culture condition, an increase in the release rates of iodocompounds was generally found for the exposure of the alga to altered environmental conditions. Macroalgae exhibited higher release rates after adaptation for two months to the changed factors, than after short-term exposure. Monitoring the release rates during a 24 h incubation period (8.25 h light, 15.75 h darkness) showed that changes between light and dark periods had no influence on the release of volatile halocarbons. Compounds like bromoform and 1-iodobutane exhibited constant release rates during the 24 h period. The formation mechanisms and biological role of volatile organohalogens are discussed. Although marine macroalgae are not considered to be the major source of biogenically-produced volatile organohalogens, they contribute significantly to the bromine and iodine cycles in the environment. Under possible environmental changes like global warming and uncontrolled entrophication of the oceans their significance may be increase.

Lead concentrations and isotopic signatures in vintages of French wine between 1950 and 1991

Vintages of French wine from 1950 to 1991 were analyzed for lead isotopes and concentrations to investigate whether they might be used to archive the isotopic composition of the anthropogenic lead in aerosols to which the vineyard was exposed. Early vintages (1950-1980) contained 78-227 ng/g of lead with 206Pb/207Pb ratios between 1.152 and 1.173, while the later vintages displayed significantly lower concentrations and a smaller range of isotopic ratios. The concentration of trimethyl lead, which is associated with automobile emissions, was found to be poorly correlated with total lead in the wines, suggesting that automobile aerosols were not a significant source of the lead. This result was supported by lead isotope data which showed a poor correlation with the available petrol and aerosol data. To identify its origin lead isotopes were measured in vineyard aerosols, soil particles, bottle caps, corks, and brass components used to dispense the wine. Although a dominant source could not be identified there was some evidence to suggest that brass which had a high lead concentration was a significant contributor. Because the lead contribution from the processing of wine was probably relatively high in the past it is unlikely that old vintages of wine will be a suitable archive for lead isotopes in aerosols.

Speciation analysis of organolead compounds in wine by capillary gas chromatography/microwave-induced-plasma atomic emission spectrometry

A method was developed for the speciation analysis of ionic organolead compounds in wine. The analytes were extracted as diethyldithiocarbamate complexes into hexane and propylated with a Grignard reagent. The derivatized extract was analyzed by capillary gas chromatography/microwave-induced-plasma atomic emission spectrometry. The method of standard additions was used for calibration to correct for variable recoveries and signal enhancements. Red, rosé, and white wines from southern France were analyzed. Trimethyllead was the ubiquitous species. The wines made from grapes grown close to industrial zones showed elevated concentrations of ethyllead species. The concentrations of methyllead and ethyllead found in wines were compared with the concentrations of organolead found in rain water and plant sap collected in the viticultural regions. The ratio of methyllead to ethyllead in wines greatly exceeded the same ratio found in atmospheric deposits.

Renal secretion of inactive renin and extraction of angiotensin II in renal artery stenosis in man: factors determining renal vein renin ratio

Triplicate blood samples were obtained, without stimulation, simultaneously from the aorta and both renal veins in 24 untreated hypertensive patients with unilateral renal artery stenosis. Across the affected kidney the plasma concentrations of active renin, inactive renin and angiotensin II increased by 363% (P less than 0.001), 80% (P less than 0.05) and 100% (P less than 0.05) respectively. Thus the affected kidney was secreting both active and inactive renin, while appreciable quantities of angiotensin II were generated across the renal circulation on that side. Across the contralateral unaffected kidney there were no significant changes in concentration of active or inactive renin, indicating net suppression of secretion of both forms of renin. Plasma angiotensin II concentration was however markedly reduced, to 50% of the arterial value (P less than 0.001), in the contralateral renal vein, demonstrating renal extraction of angiotensin II. In 14 patients renal plasma flow was also measured. The ratio of active renin concentration between the two renal veins correlated more closely with the renal plasma flow to the affected kidney (r = -0.81; P less than 0.01) than with renin secretion rate on that side (r = +0.37; NS). Thus reduction in renal blood flow rather than increase in renin secretion appeared to be the major determinant of renal vein renin ratio.

Changes in active and inactive renin and in angiotensin II across the kidney in essential hypertension and renal artery stenosis

Investigations were performed in 26 patients with essential hypertension and 24 with unilateral renal artery stenosis. In each patient blood was drawn simultaneously and in triplicate, from both renal veins and aorta, for measurement of plasma concentrations of active and inactive renin and of angiotensin II. In 19 patients estimates of individual renal plasma flow were obtained in order to calculate secretion rates for active and inactive renin, and to assess the contribution of renin secretion rate and of renal plasma flow to the renal vein renin ratio. In patients with essential hypertension there was evidence that the kidney secreted active renin (18% mean increase in renal vein concentration above that of arterial plasma; P less than 0.001), but no evidence of secretion of inactive renin (4% mean increase; NS). There was a tendency for the kidney to extract angiotensin II (8% mean decrease in renal vein concentration below that of arterial plasma; P = 0.07). The affected kidney in patients with renal artery stenosis showed marked secretion of active renin (364% mean increase; P less than 0.001) and also secreted inactive renin (80% mean increase; P less than 0.05) with net generation of angiotensin II across the renal circulation (100% mean increase; P less than 0.05). The contralateral kidney exhibited suppressed secretion of active renin (3% mean increase; NS) with no evidence of secretion of inactive renin (2% mean increase; NS), and marked extraction of angiotensin II (50% mean decrease; P less than 0.001). The correlation between combined secretion rate of active renin by both kidneys and the arterial concentration of active renin in patients with essential and renovascular hypertension taken together was strongly positive (r = 0.82; P less than 0.01). The same correlation for inactive renin was weak (r = 0.32; NS). The correlation between the combined secretion rates of active renin by both kidneys and the circulating plasma concentration of angiotensin II (r = +0.60; P less than 0.05) was both significant and positive. By contrast, the total 'secretion' rate of angiotensin II by both kidneys was inversely related to arterial plasma angiotensin II (r = -0.92; P less than 0.001). This latter relationship suggests an important role for the kidney in clearing angiotensin II from the circulation, this being more marked the higher the arterial angiotensin II concentration.(ABSTRACT TRUNCATED AT 400 WORDS)

Two families of abl-related transcripts in human haematopoietic cells differing in their homology to v-abl

The transforming gene of the Abelson murine leukaemia virus, v-abl, contains two open reading frames (orf). The 5' orf encodes a tyrosine-specific protein kinase while the 3' orf has the capacity to code for an 18,000 Mr protein. However, no 3' orf product has yet been identified. Using probes capable of distinguishing between the 5' and 3' orfs of v-abl, we have examined the abl-related transcripts present in human haematopoietic cells and leukaemia-derived cell lines, including the chronic myeloid leukaemia-derived cell line K562. Our results indicate that transcripts of 6 kb, 7 kb and 8 kb (kilobase, 10(3) base-pairs) show strong homology to v-abl 5' protein kinase-encoding orf sequences, but are devoid of any sequences from the v-abl 3' orf. In addition, transcripts of 5 kb, 3 kb, 1.6 kb and 1.4 kb, reacting with both 5' orf and 3' orf probes, were observed. The latter species, with coding sequences from both the tyrosine kinase and the putative 18,000 Mr protein, must be transcribed from the human c-abl gene as this is apparently the only human gene containing sequences homologous to the v-abl 3' orf. The 6 kb, 7 kb and 8 kb transcripts may arise either from the c-abl gene through differential splicing, or from one of the three other regions of the human genome with sequences homologous to the 5' orf of v-abl. Examination of genomic DNA from the K562 cell line revealed that the amplification of abl-related sequences, which is presumed to result in the elevated levels of the 8 kb transcript found in this cell line, does not involve sequences homologous to the v-abl 3' orf. This lends credence to the idea that the 8 kb transcript may derive from an abl-related gene other than c-abl. While the significance of the 3' orf of v-abl remains unknown, the data presented strongly suggest the existence of at least two distinct abl-related proteins in human haematopoietic cells.

Children's brain tumour cells produce RNA particles with incomplete retrovirus characteristics

Short-term cultures of cells from human rain tumours have been reported to synthesise RNA particles of density in the range characteristic of C type RNA retroviruses, with associated DNA polymerase activity. Fresh tumour cells obtained from 6 children with astrocytoma and 7 children with medulloblastoma, together with one sample of normal brain tissue and normal leukocytes from brain tumour patients were assayed by several characteristics for the primate retrovirus. 1 or 6 (17%) astrocytomas and 4 of 7 (57%) medulloblastomas released RNA particles which banded in sucrose gradients at a density of 1.16-1.18 g/cm3 together with a short segment of DNA, which was eliminated by prior ribonuclease treatment and two proteins of 28k and 16k daltons. These findings were compatible with the presence of a primate retrovirus. Immune coprecipitation of 125I-labelled proteins from the 1.16-1.18 g/cm3 gradient region failed to show any reactivity with antisera to p28 core antigens or the p70 reverse transcriptase antigens of simian sarcoma virus, baboon endogenous virus or Mason Pfizer virus. Assays for DNA polymerase activity in culture supernatant fluid showed only a low amount of activity with template preferences not characteristic of the retroviral reverse transcriptase enzyme.