10 results on '"Herbert, L. C."'
Search Results
2. Site U1541.
- Author
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Winckler, G., Lamy, F., Zarikian, C. A. Alvarez, Arz, H. W., Basak, C., Brombacher, A., Esper, O. M., Farmer, J. R., Gottschalk, J., Herbert, L. C., Iwasaki, S., Lawson, V. J., Lembke-Jene, L., Lo, L., Malinverno, E., Michel, E., Middleton, J. L., Moretti, S., Moy, C. M., and Ravelo, A. C.
- Subjects
CARBON cycle ,BIOLOGICAL productivity ,ICE sheets ,OCEAN temperature - Published
- 2021
- Full Text
- View/download PDF
3. Expedition 383 methods.
- Author
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Winckler, G., Lamy, F., Zarikian, C. A. Alvarez, Arz, H. W., Basak, C., Brombacher, A., Esper, O. M., Farmer, J. R., Gottschalk, J., Herbert, L. C., Iwasaki, S., Lawson, V. J., Lembke-Jene, L., Lo, L., Malinverno, E., Michel, E., Middleton, J. L., Moretti, S., Moy, C. M., and Ravelo, A. C.
- Subjects
ICE sheets ,CARBON cycle ,GLOBAL Positioning System ,INFORMATION retrieval - Published
- 2021
- Full Text
- View/download PDF
4. Expedition 383 summary.
- Author
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Winckler, G., Lamy, F., Zarikian, C. A. Alvarez, Arz, H. W., Basak, C., Brombacher, A., Esper, O. M., Farmer, J. R., Gottschalk, J., Herbert, L. C., Iwasaki, S., Lawson, V. J., Lembke-Jene, L., Lo, L., Malinverno, E., Michel, E., Middleton, J. L., Moretti, S., Moy, C. M., and Ravelo, A. C.
- Subjects
ANTARCTIC Circumpolar Current ,CARBON cycle ,BIOLOGICAL productivity ,ICE sheets ,PALEOCEANOGRAPHY - Abstract
The Antarctic Circumpolar Current (ACC), the world's strongest zonal current system, connects all three major ocean basins of the global ocean and therefore integrates and responds to global climate variability. Its flow is largely driven by strong westerly winds and is constricted to its narrowest extent in the Drake Passage. Fresh and cold Pacific surface and intermediate water flowing through the Drake Passage (cold-water route) and warm Indian Ocean water masses flowing through the Agulhas region (warmwater route) are critical for the South Atlantic contribution to Meridional Overturning Circulation changes. Furthermore, physical and biological processes associated with the ACC affect the strength of the ocean carbon pump and therefore are critical to feedbacks linking atmospheric CO2 concentrations, ocean circulation, and climate/cryosphere on a global scale. In contrast to the Atlantic and Indian sectors of the ACC, and with the exception of drill cores from the Antarctic continental margin and off New Zealand, there are no deep-sea drilling paleoceanographic records from the Pacific sector of the ACC. To advance our understanding of Miocene to Holocene atmosphere-ocean-cryosphere dynamics in the Pacific and their implications for regional and global climate and atmospheric CO2, International Ocean Discovery Program Expedition 383 recovered sedimentary sequences at (1) three sites in the central South Pacific (CSP) (U1539, U1540, and U1541), (2) two sites at the Chilean margin (U1542 and U1544), and (3) one site from the pelagic eastern South Pacific (U1543) close to the entrance to the Drake Passage. Because of persistently stormy conditions and the resulting bad weather avoidance, we were not successful in recovering the originally planned Proposed Site CSP-3A in the Polar Frontal Zone of the CSP. The drilled sediments at Sites U1541 and U1543 reach back to the late Miocene, and those at Site U1540 reach back to the early Pliocene. High sedimentation rate sequences reaching back to the early Pleistocene (Site U1539) and the late Pleistocene (Sites U1542 and U1544) were recovered in both the CSP and at the Chilean margin. Taken together, the sites represent a depth transect from ~1100 m at Chilean margin Site U1542 to ~4070 m at CSP Site U1539 and allow investigation of changes in the vertical structure of the ACC, a key issue for understanding the role of the Southern Ocean in the global carbon cycle. The sites are located at latitudes and water depths where sediments will allow the application of a wide range of siliciclastic-, carbonate-, and opalbased proxies to address our objectives of reconstructing, with unprecedented stratigraphic detail, surface to deep-ocean variations and their relation to atmosphere and cryosphere changes. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
5. Complex Microbial Communities Drive Iron and Sulfur Cycling in Arctic Fjord Sediments.
- Author
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Buongiorno, J., Herbert, L. C., Wehrmann, L. M., Michaud, A. B., Laufer, K., Røy, H., Jørgensen, B. B., Szynkiewicz, A., Faiia, A., Yeager, K. M., Schindler, K., and Lloyd, K. G.
- Subjects
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SULFUR cycle , *MICROBIAL communities , *FJORDS , *IRON , *GENE libraries - Abstract
Glacial retreat is changing biogeochemical cycling in the Arctic, where glacial runoff contributes iron for oceanic shelf primary production. We hypothesize that in Svalbard fjords, microbes catalyze intense iron and sulfur cycling in loworganic- matter sediments. This is because low organic matter limits sulfide generation, allowing iron mobility to the water column instead of precipitation as iron monosulfides. In this study, we tested this with high-depth-resolution 16S rRNA gene libraries in the upper 20 cm at two sites in Van Keulenfjorden, Svalbard. At the site closer to the glaciers, iron-reducing Desulfuromonadales, iron-oxidizing Gallionella and Mariprofundus, and sulfur-oxidizing Thiotrichales and Epsilonproteobacteria were abundant above a 12-cm depth. Below this depth, the relative abundances of sequences for sulfate-reducing Desulfobacteraceae and Desulfobulbaceae increased. At the outer station, the switch from iron-cycling clades to sulfate reducers occurred at shallower depths (~5 cm), corresponding to higher sulfate reduction rates. Relatively labile organic matter (shown by δ13C and C/N ratios) was more abundant at this outer site, and ordination analysis suggested that this affected microbial community structure in surface sediments. Network analysis revealed more correlations between predicted iron- and sulfur-cycling taxa and with uncultured clades proximal to the glacier. Together, these results suggest that complex microbial communities catalyze redox cycling of iron and sulfur, especially closer to the glacier, where sulfate reduction is limited due to low availability of organic matter. Diminished sulfate reduction in upper sediments enables iron to flux into the overlying water, where it may be transported to the shelf. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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6. Remobilization and uptake of N by newly planted apple (Malus domestica) trees in response to irrigation method and timing of N application.
- Author
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Neilsen, D., Millard, P., Herbert, L. C., Neilsen, G. H., Hogue, E. J., Parchomchuk, P., and Zebarth, B. J.
- Subjects
FOREST irrigation ,APPLES ,NITROGEN fertilizers ,PLANT fertilization ,ORCHARD management - Abstract
Environmentally sound management of N in apple orchards requires that N supply meets demand. In 1997, newly planted apple trees (Malus domesticaBorkh. var. Golden Delicious on M.9 rootstock) received daily applications of N for six weeks as Ca(15NO3)2 through a drip irrigation system at a concentration of 112 mg l−1 at 2–8, 5–11 or 8–14 weeks after planting. Irrigation water was applied either to meet estimated evaporative demand or at a fixed rate. In 1997, trees were harvested at 5, 8, 11 and 14 weeks after planting; and in 1998 at 3 weeks after full bloom. The amount of fertilizer N recovered was similar in trees in both irrigation treatments, but efficiency of fertilizer use was greater for trees receiving demand-controlled irrigation than fixed-rate irrigation. This was attributed to lower N inputs, greater retention time in the root zone and less N leaching in the demand-controlled irrigation treatments compared with fixed-rate irrigation treatments. Less fertilizer N was recovered by trees receiving an early application of N than a later application of N and this was related to the timing of N supply with respect to tree demand. Demand for root-supplied N was low until 11 weeks after planting, because early shoot and root growth was supported by N remobilized from woody tissue, which involved 55% of the total tree N content at planting. Rapid development of roots > 1 mm in diameter occurred between 11 and 14 weeks after planting, after remobilization ended, and was greater for trees receiving an early application of N than for trees receiving a later application of N. Late-season tree N demand was supplied by native soil N, and uptake and background soil solution N concentrations were higher for trees receiving demand-supplied irrigation compared with fixed-rate irrigation. Total annual N uptake by roots was unaffected by treatments and averaged 6–8 g tree−1. Nitrogen applications in 1997 affected growth and N partitioning in 1998. Trees receiving early applications of N had more flowers, spur leaves and bourse shoots than trees receiving later applications of N. Consequently, more N was remobilized into fruits in trees receiving early applications of N compared with fruits in trees receiving later applications of N. [ABSTRACT FROM PUBLISHER]
- Published
- 2001
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7. Letters.
- Author
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Greenfield, Peter, Wright, J. L., Eades, A., Long, Graham, Herbert, L. C., Corp, David, MacDonald, Jose, Stephens, D., Rimington, John, Ward, Ashley, Braid, Jim, Simpson, Jo, Howarth, Robert, and Rowland, Wendy
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LETTERS to the editor ,AGRICULTURE ,DAIRY farming ,ASSOCIATIONS, institutions, etc. - Abstract
Presents letters to the editor referencing articles and topics discussed in previous issues. Proposed requirements for cross-compliance for British growers to qualify for the new single farm payments from 2005; "Talking Point," by Geoffrey Hollis in the April 23, 2004 issue; Importance of the Milk Development Council and the National Dairy Council.
- Published
- 2004
8. Effect of propylthiouracil treatment during prenatal and early postnatal development on the neocortex of rat pups.
- Author
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Behnam-Rassoli M, Herbert LC, Howard V, Pharoah PO, and Stanisstreet M
- Subjects
- Animals, Cell Count, Cerebral Cortex drug effects, Cerebral Cortex growth & development, Female, Litter Size drug effects, Maternal-Fetal Exchange, Neuroglia cytology, Neurons cytology, Pregnancy, Rats, Rats, Inbred Strains, Thyroxine pharmacology, Triiodothyronine pharmacology, Cerebral Cortex embryology, Propylthiouracil pharmacology
- Abstract
The effects of a pre- and postnatal hypothyroid environment on the development of the neocortex have been determined. Rats were treated with propylthiouracil (PTU) with or without thyroid hormone supplementation during pregnancy and throughout the early development of the pups. The Cavalieri method was used to provide an estimate of the volume of the neocortex, and a combination of the Cavalieri method and the 'disector' particle-counting method provided an unbiased estimate of the numbers of glia and neurons in the neocortex. In pups from non-treated rats the mean volume of the neocortex increased from 31.3 mm3 at 5 days postnatally to 191.5 mm3 at 20 days and then remained constant to day 48. Similarly, the mean number of glial cells increased from 5.2 x 10(6) at day 5 to 12.0 x 10(6) on day 20 and then remained constant to day 48. The mean number of neurons in the neocortex in the control condition was constant at about 14.6 x 10(6) from day 5 to day 48. PTU treatment during pregnancy and postnatal development significantly decreased the mean volume of the neocortex at all of the stages studied, for example from 31.3 to 23.3 mm3 (p less than 0.001) on day 5 and from 191.5 to 155.0 mm3 (p less than 0.001) on day 20. Supplementation with thyroxine (T4) or tri-iodothyronine partially reversed this at certain stages. For example, the mean volume of the neocortex at 48 days was 197.5 mm3 in control rats, 118.1 mm3 in PTU-treated rats and 169.3 mm3 in PTU-treated rats supplemented with T4. Within the neocortex, the volume of the neuropile was more severely affected than was the volume of the neuron cell bodies.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1991
- Full Text
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9. Effects of thyroid antagonists on rat embryos cultured in vitro.
- Author
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Stanisstreet M, Herbert LC, and Pharoah PO
- Subjects
- Animals, Hyperthyroidism drug therapy, In Vitro Techniques, Rats, Rats, Inbred Strains, Abnormalities, Drug-Induced etiology, Embryo, Mammalian drug effects, Ethylenethiourea adverse effects, Imidazoles adverse effects, Methimazole adverse effects
- Abstract
A literature review of individual pregnancies and recent surveys involving large cohorts reveal an association between congenital malformation and maternal hyperthyroidism, suggesting that some aspect of hyperthyroidism or its treatment might compromise the development of the fetus. Experiments have shown that the thyroid antagonist, ethylenethiourea (ETU), causes fetal malformations when administered to pregnant rats, but it is not known whether it is ETU or the imbalance in maternal thyroid hormone which it causes which is the teratogenic agent. Here we employ in vitro culture to determine the possible direct effects on rat embryos of two thyroid antagonists, ETU and methimazole (MMI), the latter being one which is used for treatment of thyrotoxicosis in humans. It was found that ETU can compromise the development of rat embryos in vitro, confirming that ETU has a direct effect on the rat embryo. It was also found that MMI can cause abnormal development of rat embryos in vitro, although the concentration at which MMI disturbs rat embryogenesis is higher than that which is reached in hyperthyroid patients treated with clinical doses of MMI or carbimazole.
- Published
- 1990
- Full Text
- View/download PDF
10. Metergoline as an alternative to bromocriptine in amenorrhoea.
- Author
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Hicks BH, Finer N, and Herbert LC
- Subjects
- Adult, Clinical Trials as Topic, Dose-Response Relationship, Drug, Double-Blind Method, Female, Follicle Stimulating Hormone blood, Humans, Luteinizing Hormone blood, Menstruation drug effects, Ovulation drug effects, Progesterone blood, Random Allocation, Time Factors, Amenorrhea drug therapy, Bromocriptine therapeutic use, Ergolines therapeutic use, Metergoline therapeutic use, Prolactin blood
- Abstract
The results of this study offer further evidence that metergoline is a valuable alternative to bromocriptine in the suppression of excessive prolactin secretion. Forty-nine hyperprolactinaemic and 44 normoprolactinaemic women with amenorrhoea took part in a double-blind trial to compare the efficacy of metergoline 12 mg/day and bromocriptine 7.5 mg/day in restoring menstruation and ovulation. All the women had normal results on conventional tomography of the sella turcica, normal gonadotrophin levels and normal androgen levels. In the hyperprolactinaemic group, metergoline and bromocriptine were equally effective, with 84 and 75% respectively achieving menstruation, and 76 and 67% respectively achieving ovulation, within 4 months. In the normoprolactinaemic group, 47% menstruated and 40% ovulated on metergoline, against comparative figures of 36 and 21% for bromocriptine and 20 and 13% for placebo, but the differences were not statistically significant. Side effects were not a major problem.
- Published
- 1984
- Full Text
- View/download PDF
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