Andrew Clifford

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We present the application of a nonparametric method to performing functional principal component analysis for functional curve data that consist of measurements of a random trajectory for a sample of subjects. This design typically consists of an irregular grid of time points on which repeated measurements are taken for a number of subjects. We introduce(More)
Weanling mice were fed an amino acid-based diet supplemented with 0 or 11.3 mumol folic acid/kg diet for approximately 38 days to study behavior and neurochemistry in folate deficiency. After approximately 5 wk, mice fed the unsupplemented diet weighted approximately 70% as much those fed the supplemented diet. After 2 wk, mice fed the unsupplemented diet(More)
In a marker-trait association study we estimated the statistical significance of 65 single nucleotide polymorphisms (SNP) in 23 candidate genes on HDL levels of two independent Caucasian populations. Each population consisted of men and women and their HDL levels were adjusted for gender and body weight. We used a linear regression model. Selected genes(More)
BACKGROUND A quantitative understanding of human folate metabolism is needed. OBJECTIVE The objective was to quantify and interpret human folate metabolism as it might occur in vivo. DESIGN Adults (n = 13) received 0.5 nmol [(14)C]pteroylmonoglutamate (100 nCi radioactivity) plus 79.5 nmol pteroylmonoglutamate in water orally. (14)C was measured in(More)
The high-throughput Zn reduction method was developed and optimized for various biological/biomedical accelerator mass spectrometry (AMS) applications of mg of C size samples. However, high levels of background carbon from the high-throughput Zn reduction method were not suitable for sub-mg of C size samples in environmental, geochronology, and(More)
Biological and biomedical applications of accelerator mass spectrometry (AMS) use isotope ratio mass spectrometry to quantify minute amounts of long-lived radioisotopes such as (14)C. AMS target preparation involves first the oxidation of carbon (in sample of interest) to CO 2 and second the reduction of CO 2 to filamentous, fluffy, fuzzy, or firm(More)
Isotope tracer studies, particularly radiocarbon measurements, play a key role in biological, nutritional, and environmental research. Accelerator mass spectrometry (AMS) is now the most sensitive detection method for 14 C, but AMS is not widely used in kinetic studies of humans. Part of the reason is the expense, but costs would decrease if AMS were used(More)
The unit of ACE inhibitory activity of identified substances in the Abstract, Results and Discussion, and Table 3 should be corrected to (IC 50 , μM). The correct ACE inhibitory activities are as follows: The final sentence under the heading Sample Collections (in the Materials and Methods section) should read as follows: When 100 nCi of 14 C was dosed to(More)
Catalytic graphitization for (14)C-accelerator mass spectrometry ((14)C-AMS) produced various forms of elemental carbon. Our high-throughput Zn reduction method (C/Fe = 1:5, 500 degrees C, 3 h) produced the AMS target of graphite-coated iron powder (GCIP), a mix of nongraphitic carbon and Fe(3)C. Crystallinity of the AMS targets of GCIP (nongraphitic(More)
14 C has long been used as a tracer for quantifying the in vivo human metabolism of food components, biopharmaceuticals, and nutrients. Minute amounts (e1 Â 10-18 mol) of 14 C can be measured with high-throughput 14 C-accelerator mass spectrometry (HT 14 C-AMS) in isolated chemical extracts of biological, biomedical, and environmental samples. Availability(More)