Productivity of Macrophytes in Marion Lake, British Columbia

1970 ◽  
Vol 27 (1) ◽  
pp. 71-81 ◽  
Author(s):  
Gordon S. Davies
Keyword(s):  
British Columbia ◽  
Liquid Scintillation ◽  
Primary Producers ◽  
Phytoplankton Productivity ◽  
Weight Method ◽  
Total Productivity ◽  
Organic Weight

The in situ productivity of both the phytoplankton and the macrophytes in Marion Lake, B.C., was determined from April 1966 through September 1966, by using 14C techniques. The uptake of NaH14CO3 was measured in selected macrophytes by enclosing them in Plexiglas chambers. These plants were then combusted in oxygen, and the 14CO2 was absorbed in toluene-POPOP-ethanolamine. Radioassay was accomplished by liquid scintillation. In addition to the 14C method, an organic weight method was used to measure macrophytic productivity.The productivity of the macrophytes was always higher than that of the phytoplankton. There was a considerable difference in the estimates of the macrophyte productivity arrived at by the two different methods, and reasons for this are discussed.The total productivity of the lake is very low when compared with lakes of similar latitudes because of low phytoplankton productivity. It is concluded that in Marion Lake the macrophytes are more important primary producers than the phytoplankton.The difficulty of comparing data between this and other studies is discussed, and the need for standardization of methods is emphasized.

scholarly journals Dating the End of the Neolithic in an Eastern Sahara Oasis: Modeling Absolute Chronology

Radiocarbon ◽  
2012 ◽  
Vol 54 (3-4) ◽  
pp. 305-318 ◽  
Author(s):  
Michel Wuttmann ◽  
François Briois ◽  
Béatrix Midant-Reynes ◽  
Tiphaine Dachy
Keyword(s):  
Bayesian Modeling ◽  
Liquid Scintillation ◽  
Nile Valley ◽  
Archaeological Remains ◽  
Middle Holocene ◽  
Cultural Complex ◽  
Scintillation Method ◽  
First Time ◽  
Ostrich Eggshell

The Neolithic site KS043, excavated by the Institut français d'archéologie orientale (IFAO), is situated in the southern basin of the Kharga Oasis (Egypt). It is one of the very few stratified prehistoric sites of the eastern Sahara. The archaeological remains were found near artesian springs that provided water for pastoralists during the dry Middle Holocene. In situ settlement features provided well-preserved material (charcoal, ashy sediment, ostrich eggshell) sufficient to perform radiocarbon dating in the IFAO laboratory in Cairo by the conventional liquid scintillation method. In 2 cases, ostrich eggshell and charcoal within the same in situ context gave significantly different results of, respectively, ∼600 and ∼1200 yr younger dates for the ostrich eggshells. The strong discrepancy is here highlighted for the first time and we suggest that it may be linked with postdepositional phenomena in the vicinity of the artesian springs. A thorough review of 14C dates available for the Holocene in eastern Sahara shows that ostrich eggshells have been widely used. They seem slightly more prone to be discarded than other material but were never the object of a particular study in this context. Bayesian modeling shows that the Neolithic occupation at site KS043 spans a range from 5000 to 3950 cal BC (and concentrated around 4600–4350 cal BC). Characteristic flint tools and pottery relate this occupation to the end of the Neolithic and show links with the Tasian culture, confirming the timing of the presence of this cultural complex in the desert before its appearance in the Nile Valley.

scholarly journals High-Sensitivity Radiocarbon Dating in the 50,000 to 70,000 bp Range without Isotopic Enrichment

Radiocarbon ◽  
1992 ◽  
Vol 34 (3) ◽  
pp. 351-359 ◽  
Author(s):  
Austin Long ◽  
Robert M. Kalin
Keyword(s):  
Memory Effect ◽  
Liquid Scintillation ◽  
High Sensitivity ◽  
Isotopic Enrichment ◽  
Counting System ◽  
Systematic Analysis ◽  
Critical Elements ◽  
Background Material ◽  
Acetylene Production

Calculations show the possibility of detecting 14C remaining after 10 or 11 decay half-lives in natural materials, such as wood, using commercially available liquid scintillation (LS) detectors. Assuming in-situ14C production has contributed insignificantly to the measured 14C, one can calculate finite ages approaching 70 ka. In practice, defensible finite age determinations involve careful considerations of several critical elements in the procedure. These critical elements are: 1) the integrity of the sample itself, in terms of younger contaminants and of in situ-produced 14C; 2) the availability of “dead” background material; 3) chemical blank in laboratory preparation of, in this case, benzene; and 4) stability of background and efficiency of the LS counting system. High-sensitivity 14C dating reveals a low level of memory effect 14C in benzene synthesized in the laboratory from anthracite or marble. This level of 14C activity is equivalent to that found in 53 ka old wood, and thus, is not distinguishable from petrochemical benzene used in routine dating. If careful control of laboratory conditions can maintain this 14C blank constant, reproducible dating beyond 53 ka would be possible. Although we have not completed a systematic analysis of the origins of memory effect, lithium reactors used in acetylene production and organic solvents in wood pretreatment are likely sources.

scholarly journals Prescribing practices of endocrine therapy for ductal carcinoma in situ in British Columbia

2018 ◽  
Vol 25 (2) ◽  
pp. 133 ◽  
Author(s):  
A.T. Chaudhry ◽  
T.A. Koulis ◽  
C. Speers ◽  
R.A. Olson
Keyword(s):  
British Columbia ◽  
Endocrine Therapy ◽  
Ductal Carcinoma In Situ ◽  
Carcinoma In Situ ◽  
Ductal Carcinoma ◽  
Population Based ◽  
Cox Regression Analysis ◽  
Treatment Centre ◽  
Er Status

Purpose The mainstay of treatment for ductal carcinoma in situ (dcis) involves surgery in the form of mastectomy or lumpectomy. Inconsistency in the use of endocrine therapy (et) for dcis is evident worldwide. We sought to assess the variation in et prescribing for patients with dcis across a population-based radiotherapy (rt) program and to identify variables that predict its use.Methods Data from a breast cancer database were obtained for women diagnosed with dcis in British Columbia from 2009 to 2014. Associations between et use and patient characteristics were assessed by chi-square test and multilevel multivariate logistic regression. The Kaplan–Meier method, with propensity score matching and Cox regression analysis, was used to assess the effects of et on overall survival (os) and relapse-free survival (rfs).Results For the 2336 dcis patients included in the study, et use was 13% in dcis patients overall, and 17% in patients with estrogen receptor–positive (er+) tumours treated with breast-conserving surgery and rt. Significant variation in et use by treatment centre was observed (range: 8%–23%; p < 0.001), and prescription of et by individual oncologists varied in the range 0%–40%. After controlling for confounding factors, age less than 50 years [odds ratio (or): 1.72; p = 0.01], treatment centre, er+ status (or: 5.33; p < 0.001), and rt use (or: 1.77; p < 0.001) were significant predictors of et use. No difference in os or rfs with the use of et was observed.Conclusions In this population-based analysis, 13% of patients with dcis in British Columbia received et, with variation by treatment centre (8%–23%) and individual oncologist (0%–40%). Age less than 50 years, er+ status, and rt use were most associated with et use.

scholarly journals In situ response of Antarctic under-ice primary producers to experimentally altered pH

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Vonda J. Cummings ◽  
Neill G. Barr ◽  
Rod G. Budd ◽  
Peter M. Marriott ◽  
Karl A. Safi ◽  
...  
Keyword(s):  
Primary Producers

scholarly journals British Museum Natural Radiocarbon Measurements XXII

Radiocarbon ◽  
1991 ◽  
Vol 33 (1) ◽  
pp. 51-68 ◽  
Author(s):  
Janet Ambers ◽  
Keith Matthews ◽  
Sheridan Bowman
Keyword(s):  
Humic Acid ◽  
Humic Acids ◽  
Chlorine Dioxide ◽  
Liquid Scintillation Counting ◽  
Liquid Scintillation ◽  
British Museum ◽  
Scintillation Counting ◽  
Dilute Acid ◽  
Organic Fraction

The following list consists of dates, obtained by liquid scintillation counting of benzene, for archaeologic samples mostly measured between June 1987 and October 1989.Charcoal and grain samples were pretreated with 1M HCl followed by washing in water and, where considered necessary, with dilute alkali for the removal of humic acids. Wood samples were treated either in the same way, or, where large enough, were reduced to cellulose by the action of chlorine dioxide produced in situ. All antler and bone samples were treated with cold dilute acid. The term ‘collagen’ is used throughout to mean the acid insoluble organic fraction produced by this treatment. Peat samples were treated with dilute acid and alkali to separate the humin and humic acid fractions, which were dated individually.

A Comparison of Liquid Scintillation and Geiger–Müller Estimates of Primary Productivity in an in situ Experiment

1973 ◽  
Vol 30 (5) ◽  
pp. 708-711 ◽  
Author(s):  
F. J. Ward ◽  
Masami Nakanishi
Keyword(s):  
Light Intensity ◽  
Surface Area ◽  
Primary Productivity ◽  
Liquid Scintillation ◽  
Lake Biwa ◽  
In Situ Experiment ◽  
M Estimate ◽  
M Estimates ◽  
Loss Rates

For an in situ experiment conducted in Shiozu Bay, Lake Biwa, Japan, primary productivity estimates from liquid scintillation radioactivity counts of wet algae were generally higher than those from Geiger–Müller radioactivity counts of desiccated algae. Values at 0 m were similar, the G–M estimate at 0.5 m was 10% higher, but from 3 to 13 m the liquid scintillation values ranged from 11 to 33% higher than G–M estimates. The 20-m estimates were low and similar. Differences were caused primarily by 14C losses during desiccation prior to G–M counting. Increasing loss rates between 0.5 and 3.0 m may have been caused by decreasing light intensity. On the basis of surface area, the estimate from liquid scintillation data was 27% greater than that obtained from G–M data.

The Sisters Creek Formation: Pleistocene sediments representing a nonglacial interval in southwestern British Columbia at about 18 ka

1995 ◽  
Vol 32 (6) ◽  
pp. 758-767 ◽  
Author(s):  
Stephen R. Hicock ◽  
Olav B. Lian
Keyword(s):  
British Columbia ◽  
Glacial Maximum ◽  
Time Space ◽  
Late Wisconsinan ◽  
Sand And Gravel ◽  
New Time

Sisters Creek Formation is formally defined, stratotypes are established for it, and the time–space chart is updated for the Fraser Lowland, southwestern British Columbia. The Sisters Creek is a Pleistocene formation comprising in situ and reworked organic-rich sediments, and nonorganic silt, sand, and gravel. The formation was deposited during the Port Moody interstade (within the Late Wisconsinan Fraser Glaciation; δ18O stage 2) between the Coquitlam stade (early Fraser Glaciation) and the main Vashon stadial maximum that occurred about 14.5 ka. The Sisters Creek Formation represents a glacial recession in southwestern British Columbia that generally coincided with the timing of the last global glacial maximum. The new time–space chart implies that, in Fraser Lowland, the Fraser Glaciation represents the rapid advances and retreats of glacial lobes issuing from surrounding mountains, which remained ice-covered during interstades.

scholarly journals In Situ Cultured Bacterial Diversity from Iron Curtain Cave, Chilliwack, British Columbia, Canada

Diversity ◽  
2017 ◽  
Vol 9 (3) ◽  
pp. 36 ◽  
Author(s):  
Soumya Ghosh ◽  
Elise Paine ◽  
Rob Wall ◽  
Gabrielle Kam ◽  
Tanna Lauriente ◽  
...  
Keyword(s):  
British Columbia ◽  
Bacterial Diversity ◽  
Iron Curtain

scholarly journals Estimates of New and Total Productivity in Central Long Island Sound from In Situ Measurements of Nitrate and Dissolved Oxygen

2012 ◽  
Vol 36 (1) ◽  
pp. 74-97 ◽  
Author(s):  
James R. Collins ◽  
Peter A. Raymond ◽  
W. Frank Bohlen ◽  
Mary M. Howard-Strobel
Keyword(s):  
Dissolved Oxygen ◽  
Long Island ◽  
Long Island Sound ◽  
In Situ Measurements ◽  
Total Productivity ◽  
Island Sound

Aspects of Histology in Macoma Carlottensis (Bivalvia: Tellinidae) and In Situ Histopathology Related to Mine-Tailings Discharge

1989 ◽  
Vol 69 (2) ◽  
pp. 447-464 ◽  
Author(s):  
Doug A. Bright ◽  
Derek V. Ellis
Keyword(s):  
British Columbia ◽  
Coastal Waters ◽  
Mine Tailings ◽  
Western United States ◽  
Left Valve ◽  
Sediment Particle ◽  
Surface Deposit ◽  
Sediment Particle Size ◽  
Current Exposure

Macoma carlottensis Whiteaves, 1880 is abundant (up to approximately 350 nr2) in subtidal infaunal communities on the continental shelf of western United States (Lie & Kelly, 1970; Word, 1979) and in British Columbia fjords (Ellis, 1969). Of thirteen different species of Macoma identified from the coastal waters of southern British Columbia, M. carlottensis is the most tolerant to variations in water depth, sediment particle size, current exposure, and salinity (Dunnill & Ellis, 1969). Observations of the species maintained in sediment trays in our laboratory suggest thatM. carlottensis is an infaunal, primarily sub-surface deposit feeder which generally lies at a depth of 1-4 cm with its left valve downwards. Filter feeding was observed in some instances as indicated by extension of the siphons from 0-5-3 cm above the substrate.

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