scholarly journals Small Sample Dating in China

Radiocarbon ◽  
1994 ◽  
Vol 36 (1) ◽  
pp. 47-49 ◽  
Author(s):  
Weijian Zhou ◽  
M. J. Head ◽  
Lauri Kaihola
Keyword(s):  
Liquid Scintillation ◽  
Small Sample ◽  
Quaternary Geology ◽  
Liquid Scintillation Spectrometer ◽  
Large Sample ◽  
National University ◽  
Dating Method ◽  
Age Limit

The Xi'an Laboratory of Loess and Quaternary Geology has developed a small sample 14C dating facility consisting of a Wallac 1220 Quantulus™ liquid scintillation spectrometer, and a miniature benzene synthesis line based on the synthesis procedures used at the Australian National University (ANU). This line can produce ca. 0.3-ml benzene samples, which are then measured for 14C activity using 0.3-ml Teflon vials developed by Wallac Oy. The counting performance of the Quantulus™ spectrometer using 0.3-ml vials has been evaluated, and a potential age limit of ca. 45,000 BP has been obtained for samples containing up to 250 mg carbon. This dating facility fills the gap between large sample (2.4–6 g carbon) and microsample (<1 mg carbon) handling to form a 14C dating method sequence.

scholarly journals High heterogeneity undermines generalization of differential expression results in RNA-Seq analysis

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Weitong Cui ◽  
Huaru Xue ◽  
Lei Wei ◽  
Jinghua Jin ◽  
Xuewen Tian ◽  
...  
Keyword(s):  
Gene Expression ◽  
Differential Expression ◽  
Small Sample ◽  
Differentially Expressed ◽  
Cancer Type ◽  
Rna Seq ◽  
Sample Sizes ◽  
Large Sample ◽  
Expression Levels ◽  
Gene Expression Levels

Abstract Background RNA sequencing (RNA-Seq) has been widely applied in oncology for monitoring transcriptome changes. However, the emerging problem that high variation of gene expression levels caused by tumor heterogeneity may affect the reproducibility of differential expression (DE) results has rarely been studied. Here, we investigated the reproducibility of DE results for any given number of biological replicates between 3 and 24 and explored why a great many differentially expressed genes (DEGs) were not reproducible. Results Our findings demonstrate that poor reproducibility of DE results exists not only for small sample sizes, but also for relatively large sample sizes. Quite a few of the DEGs detected are specific to the samples in use, rather than genuinely differentially expressed under different conditions. Poor reproducibility of DE results is mainly caused by high variation of gene expression levels for the same gene in different samples. Even though biological variation may account for much of the high variation of gene expression levels, the effect of outlier count data also needs to be treated seriously, as outlier data severely interfere with DE analysis. Conclusions High heterogeneity exists not only in tumor tissue samples of each cancer type studied, but also in normal samples. High heterogeneity leads to poor reproducibility of DEGs, undermining generalization of differential expression results. Therefore, it is necessary to use large sample sizes (at least 10 if possible) in RNA-Seq experimental designs to reduce the impact of biological variability and DE results should be interpreted cautiously unless soundly validated.

Randomization Inference for Accounting Researchers

2021 ◽  
Author(s):  
Roger M White ◽  
Matthew D. Webb
Keyword(s):  
Small Sample ◽  
Short Paper ◽  
Large Sample ◽  
Randomization Inference

In this short paper we summarize and promote randomization inference for accounting researchers. We discuss applications of randomization inference in both small sample and large sample settings, and we include several examples from our own work. We also provide guidance and sample code to researchers looking to implement randomization inference, as well as caveats to consider.

Direct Liquid Scintillation Radioassay of14C-Labeled Herbicides in Soil

Weed Science ◽  
1972 ◽  
Vol 20 (3) ◽  
pp. 215-219 ◽  
Author(s):  
T. L. Lavy ◽  
C. G. Messersmith ◽  
H. W. Knoche
Keyword(s):  
Liquid Scintillation Counting ◽  
Liquid Scintillation ◽  
Scintillation Counter ◽  
Soil Samples ◽  
Scintillation Counting ◽  
Liquid Scintillation Spectrometer ◽  
Single Extraction ◽  
Anisic Acid ◽  
Extraction Processes ◽  
Scintillation Vial

A liquid scintillation counting solution was developed which optimized the direct assay efficiencies of14C-labeled 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), 3,6-dichloro-o-anisic acid (dicamba), and α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) in soil. In this counting technique, 3-g soil samples containing14C-labeled herbicide were placed directly into a liquid scintillation vial containing a phosphorescent counting solution. Samples were shaken and allowed to settle before assaying using a liquid scintillation spectrometer. This direct radioassay was as efficient or more efficient than double or single extraction processes. Automatic external standardization in conjunction with the liquid scintillation counter was an effective tool for estimating the14C present in soil samples.

scholarly journals Instituto Venezolano de Investigaciones Cientificas Natural Radiocarbon Measurements III

Radiocarbon ◽  
1967 ◽  
Vol 9 ◽  
pp. 237-245 ◽  
Author(s):  
M. A. Tamers
Keyword(s):  
Oxalic Acid ◽  
Count Rate ◽  
Radiocarbon Dating ◽  
Liquid Scintillation ◽  
Liquid Scintillation Spectrometer ◽  
Modern Standard

The dates reported here represent a portion of those determined in 1966, The Radiocarbon Dating Laboratory of the Instituto Venezolano de Investigaciones Científicas carries out a synthesis of benzene for each sample and detects the activity with a liquid scintillation spectrometer. For routine measurements, 3 cc synthesized benzene and 1 cc commercial toluene, with PPO and dimethyl-POPOP scintillators, are used in a special small counting vial. The modern standard is 95% of the NBS oxalic acid, which gives a net modern count rate of 23.9 cpm. The background is now 8.5 cpm.

Updating Existing Travel Simulation Models with Small-Sample Survey Data Using Parameter Scaling Methods

1997 ◽  
Vol 1607 (1) ◽  
pp. 55-61
Author(s):  
W. Thomas Walker ◽  
Scott H. Brady ◽  
Charles Taylor
Keyword(s):  
Survey Data ◽  
Primary Source ◽  
Simulation Models ◽  
Small Sample ◽  
Sample Survey ◽  
Secondary Source ◽  
Sample Surveys ◽  
Large Sample ◽  
Scaling Methods ◽  
Home Interview

The travel simulation models for many metropolitan areas were originally developed and calibrated with older large-sample travel surveys that can no longer be undertaken given today’s funding constraints. Small-sample travel surveys have been collected as part of model update activities required by the Intermodal Surface Transportation Efficiency Act and the Clean Air Act Amendments. Although providing useful information, these surveys are inadequate for calibrating elaborate simulation models by traditional techniques. Parameter transfer scaling based on small-sample surveys and other secondary source data can be a cost-effective alternative to large-sample surveys when existing models are being updated, particularly when the models tend to be robust and the required changes are relatively small. The use of parameter scaling methods to update the Delaware Valley Planning Commission’s existing travel simulation models is demonstrated. All available sources of data are incorporated into the update process including current survey data, census work trips from the Census Transportation Planning Package (CTPP), transit ridership checks, highway screenline counts, and Highway Performance Monitoring System travel estimates. A synopsis of experience with parameter scaling techniques including the model changes and resulting accuracy is provided. Overall, small-sample-based parameter scaling techniques were judged to be effective. The census CTPP data were evaluated versus the home interview and were found to be useful in the model recalibration effort as a source of small-area employment data by place of work and as a supplement to home interview data for model validation. However, a home interview survey is required as the primary source of travel data for both work and nonwork trips.

scholarly journals British Museum Natural Radiocarbon Measurements VI

Radiocarbon ◽  
1969 ◽  
Vol 11 (2) ◽  
pp. 278-294 ◽  
Author(s):  
Harold Barker ◽  
Richard Burleigh ◽  
Nigel Meeks
Keyword(s):  
Liquid Scintillation Counting ◽  
Liquid Scintillation ◽  
British Museum ◽  
Low Noise ◽  
Scintillation Counting ◽  
Statistical Accuracy ◽  
Liquid Scintillation Spectrometer ◽  
Long Term Stability ◽  
Replicate Measurements

Dates listed below are based on measurements made up to May 1968, and cover a period during which the technique of gas proportional counting using CO2 was gradually replaced by liquid scintillation counting using benzene. The gas counting measurements were carried out by the method and techniques previously described (Barker and Mackey, 1968) the only modifications being the replacement of some old electronic units by more stable solid-state equipment; proportional counting results are indicated in the text by (P) at the end of the relevant sample descriptions. Liquid scintillation counting, which is now the preferred method in this laboratory, is carried out using a Packard Tri-Carb liquid scintillation spectrometer model 3315/AES fitted with selected low-noise quartz-faced photomultipliers. Normally 3 ml of benzene is prepared from each sample. This is dissolved in 12 ml of scintillation grade toluene containing 5 gm/liter of scintillator (PPO) and the solution is measured in a standard low-potassium glass vial at a temperature of 0°C. Photomultiplier E.H.T., amplifier, and channel width settings are optimized for C14, and measurements are carried out at ca. 65% efficiency of detection for C14 to eliminate interference from any tritium which may be present in the benzene. Under these circumstances the background is approx. 8.6 cpm and the modern (95% Aox) is approx. 24.0 cpm. Samples are counted in groups of 3 to 5 together with background and modern reference samples and are measured for at least one week, the instrument being set to cycle at 100 min intervals. In this period, the counts accumulated are such that the background is always measured to a statistical accuracy of better than 1% and most other samples to a higher accuracy than this. Background and modern counts used in the calculation of each result are only those relevant to the period of measurement of that particular sample. Statistical analysis of groups of replicate measurements made under these conditions over a very long period of time has demonstrated the excellent long-term stability of the equipment and indicates that the technique is quite capable of achieving results of very high statistical accuracy when required.

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