Duke Standards

Many papers report the fractionation of polystyrene latexes or mixtures thereof, as such commonly available spherical latex standards are an ideal system to test FFF setups or evaluations (for an example, see [362,401]). Recent coupling of Fl-FFF to MALLS enables a very high precision in particle size determinations. One example is shown in Fig. 31, where two Duke standard latex batches of a nominal size of 100 nm were investigated by Fl-FFF/M ALLS, underlining both separation power and resolution. Using traditional techniques such as photon correlation spectroscopy (PCS) and classic Fl-FFF detection, these samples seem to be identical. However, with Fl-FFF/MALLS, the batches could be separated as two discrete size distributions with a peak size that differed by 3 nm. However, it is not stated if a precise temperature control was maintained so that, critically considered, the observed differences could also have their origin in slight temperature... 

Fig. 31. Fl-FFF-MALLS particle size distribution for two Duke standard latexes of nominal size 100 nm but from two different batches. Reproduced from [374] with kind permission of John Wiley and Sons...

Standard polystyrene spheres are also available for calibration purposes from Gilson and Duke Standards. Stork Screens Inc. measure apertures and screen wire dimensions using wax impressions and the impressions are examined with an automatic image analyzer. 

CTIF - Centre Technique des Industries de la Fonderie, 44 Avenue de la Division Leclerc, F 92310 Sevres, France Duke Standards Co., 445 Sherman Avenue, Palo Alto, CA 94306, USA Eidgenossische Materialpriifungs - und Versuchsanstalt fiir Industrie Bauwesen und Gewerbe, Unterstr. 11, CH 900 St.Gallen BCR Community Bureau of Reference, 200 rue de la Loi, B - 1049 Brussel nil - International Trade and Industry Inspection Institute, 49-10,... 

Duke Standards Company, 445 Sherman Avenue, Palo Alto, California 94306. 

This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the National Research Council s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making its published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their review of this report Dr. Richard T. Barber (Duke University), Dr. Edward Boyle (Massachusetts Institute of Technology), Dr. Thomas S. Bianchi (Tulane University), Dr. Katherine H. Freeman (Penn State), Dr. Dennis A. Hansell (University... 

At the same time, the power and capabilities of standard PCs increased dramatically. The Richardsons (Richardson and Richardson, 1992) at Duke University developed molecular graphics programs to run on the Macintosh. In a dramatic development, the World Wide Web emerged. Roger Sayle created RasMol as part of his PhD dissertation at Oxford, and made the source code freely available on the web. This program allowed raster display of molecules on UNIX or PCs. The RasMol... 

Fay and Duke (23) approached the question of allelopathic expression from oats in a different way. They screened 3,000 accessions of Avena spp. germ plasm for output of scopoletin, a known inhibitor from oats. Some exuded up to three times as much scopoletin as a standard cultivar, and these were the most active in suppressing wild mustard [R taW-tca kabeA (D.C.) L.C. Wheeler] in sand culture. However, in loamy-sand soil this activity was lost. 

Monodisperse polystyrene (latex) spheres having a radius value in the range 30-100 run with a standard deviation of 8% or less characterizing the size uniformity. Such samples can be obtained from Duke Scientific Corp. as 3000 Series Nanospheres (www. dukescientific.com), Polymer Laboratories as PL-Latex Plain White (www.polymerlabs. com), and Polysciences, Inc., as Nanobead Traceable Size Standards (www.polysciences. com). 

AB), which are colored cross-linked dextran particles with defined buoyant densities, were used to determine the evolution and the final shape of the quasiequilibrium density gradients in TLF. Several samples of polystyrene (PS) latex microspheres (Duke Scientific Corporation, Palo Alto, CA), supplied by manufacturer as particle size standards, were used in focusing FFF experiments. 

Standard powders are available from Duke Scientific Corporation, 135D San Antonio Rd. Palo Alto, CA 94303. 

Gardon J, Boussinesq M, Kamgno J, Gardon-Wendel N, Demanga-Ngangue, Duke BO. Effects of standard and high doses of ivermectin on adult worms of Onchocerca volvulus, a randomised controlled trial. Lancet 2002 360(9328) 203-10. 

Flyim R, Roest M. Your guide to standardized herbal products. Prescott, AZ One World Press, 1995.3. Duke JA. CRC handbook of medicinal herbs. Boca Raton CRC Press, 1985. 

Standards and Samples. The polystyrene standards used were obtained from Duke Scientific (Palo Alto, CA) and Seradyn (Indianapolis, IN). 

For accurate work, the sieves may need to be calibrated. Four organizations prepare standard reference materials (SRM s) the National Institute of Standards and Technology (NIST), Bethesda, MD the Community Bureau of Reference (BCR), Brussels Whitehouse Reference Standards Brussels, and Duke Scientific, Palo Alto, CA. NIST uses glass beads and silicon nitride particles BCR uses quartz beads Whitehouse uses soda-lime glass and Duke uses polystyrene-divinylbenzene or glass spheres. NIST and BCR standards are expensive. Figure 37-31, p. 443, shows a set of standards. 

Nitrile based Olefinically unsaturated mers Corrosion resistant coatings Duke et al. U.S. Pat. 4,510,204, 1985 Standard Oil... 

Table 3. Results of PLS models for fresh Duke berry samples (r = coefficient of correlation RMSEC = root mean square of the standard error in calibration RMSEGV = root mean square of the standard error in cross-validation LV = latent variables). All data were preprocessed by second derivative of reduced and smoothed data.

American, the standard pronunciation of duke is /d uw k/, whereas in British English it is /d y uw k/. This generahsation covers all words with this pattern (witii the possible exception of news in which many Americans say the lyf). Hence tiiere is some important generalisation going on here. 

The particle size standards (PSS) used to test the dependence of the reflectance measurements to the particle size were purchased from Duke scientific. Table 2 shows the information on the particle size distribution (NIST mean diameter, standard deviation, a, and coefficient of variation) of the particles given by the manufacturer. 

Table 2. Polystyrene (ID 1-11) particle size standards from Duke Scientific...

Duke Scientific Corporation (NANOSPHERE SIZE STANDARDS)... 

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