Degradation of [14C]GlcDGD in the marine sediment by monitoring radioactivity in the aqueous and gas phase using liquid scintillation counting (LSC) techniques

An experiment was conceived in which we monitored degradation of GlcDGD. Independent of the fate of the [14C]glucosyl headgroup after hydrolysis from the glycerol backbone, the 14C enters the aqueous or gas phase whereas the intact lipid is insoluble and remains in the sediment phase. Total degradation of GlcDGD then is obtained by combining the increase of radioactivity in the aqueous and gaseous phases. We chose two different sediment to perform this experiment. One is from microbially actie surface sediment sampled in February 2010 from the upper tidal flat of the German Wadden Sea near Wremen (53° 38' 0N, 8° 29' 30E). The other one is deep subsurface sediments recovered from northern Cascadia Margin during Integrated Ocean Drilling Program Expedition 311 [site U1326, 138.2 meters below seafloor (mbsf), in situ temperature 20 °C, water depth 1,828 m. We performed both alive and killed control experiments for comparison. Surface and subsurface sediment slurry were incubated in the dark at in situ temperature, 4 °C and 20 °C for 300 d, respectively. The sterilized slurry was stored at 20 °C. All incubations were carried out under N2 headspace to ensure anaerobic conditions. The sampling frequency was high during the first half-month, i.e., after 1, 2, 7, and 14 d; thereafter, the sediment slurry was sampled every 2 months. At each time point, samples were taken in triplicate for radioactivity measurements. After 300 d of incubation, no significant changes of radioactivity in the aqueous phase were detected. This may be the result of either the rapid turnover of released [14C] glucose or the relatively high limit of detection caused by the slight solubility (equivalent to 2% of initial radioactivity) of GlcDGD in water. Therefore, total degradation of GlcDGD in the dataset was calculated by combining radioactivity of DIC, CH4, and CO2, leading to a minimum estimate.

Age determination and stable carbon isotope ratios of Neogloboquadrina pachyderma of IODP Hole 302-M0004C

The Integrated Ocean Drilling Program (IODP) Arctic Coring Expedition (ACEX) Hole 4C from the Lomonosov Ridge in the central Arctic Ocean recovered a continuous 18 m record of Quaternary foraminifera yielding evidence for seasonally ice-free interglacials during the Matuyama, progressive development of large glacials during the mid-Pleistocene transition (MPT) ~1.2-0.9 Ma, and the onset of high-amplitude 100-ka orbital cycles ~500 ka. Foraminiferal preservation in sediments from the Arctic is influenced by primary (sea ice, organic input, and other environmental conditions) and secondary factors (syndepositional, long-term pore water dissolution). Taking these into account, the ACEX 4C record shows distinct maxima in agglutinated foraminiferal abundance corresponding to several interglacials and deglacials between marine isotope stages (MIS) 13-37, and although less precise dating is available for older sediments, these trends appear to continue through the Matuyama. The MPT is characterized by nearly barren intervals during major glacials (MIS 12, 16, and 22-24) and faunal turnover (MIS 12-24). Abundant calcareous planktonic (mainly Neogloboquadrina pachyderma sin.) and benthic foraminifers occur mainly in interglacial intervals during the Brunhes and very rarely in the Matuyama. A distinct faunal transition from calcareous to agglutinated foraminifers 200-300 ka in ACEX 4C is comparable to that found in Arctic sediments from the Lomonosov, Alpha, and Northwind ridges and the Morris Jesup Rise. Down-core disappearance of calcareous taxa is probably related to either reduced sea ice cover prior to the last few 100-ka cycles, pore water dissolution, or both.

Farm labor fact book.

Mode of access: Internet.

The migratory farm labor problem in the United States : a report, together with individual views, to the Committee on Labor and Public Welfare, United States Senate, made by its Subcommittee on Migratory Labor, pursuant to S. Res. 267 (86th Cong., 2d sess.) a resolution authorizing a study of the problems of migratory labor.

Cover title.

Migratory labor. Hearings before the Subcommittee on Migratory Labor of the Committee on Labor and Public Welfare, United States Senate, Eighty-sixth Congress, first [-second] session, on S. 1085 [and other] bills ...

Hearings held Aug. 7, 1959-July 11, 1960 in various cities.

Migratory labor : hearings before the Subcommittee on Migratory Labor of the Committee on Labor and Public Welfare, United States Senate, Eighty-seventh Congress, first session, on S. 1123 [and other] bills ...

Hearings held Apr. 12, 1961 - Aug. 17, 1962.

Labor law and practice in Colombia

Bibliography: p. 87.

Labor law and practice in Ecuador /

Cover title.

Labor law and practice in Colombia /

Cover title.

Labor legislation of Ecuador /

"This translation of the labor laws of Ecuador was made under the direction of Ethel Y. Larson, of the Bureau of Labor Statistics."

Labor legislation of Paraguay /

"This translation of the labor laws of Paraguay was made under the direction of Ethel Y. Larson, of the Bureau of Labor Statistics."

Child labor and inadequate family income; preliminary report on a study of the work and welfare of children of agricultural laborers in Hidalgo County, Texas.

Cover title.

Immigrants and the American labor market /

Includes bibliographical references.

Labor legislation of Venezuela /

"This translation of the labor laws of Venezuela was made under the direction of Ethel Y. Larson, of the Bureau of Labor Statistics."