Applications of nuclear analytical techniques in human nutrition research as exemplified by research programmes of the international atomic energy agency

In human nutrition research, nuclear analytical techniques, particularly neutron activation analysis (NAA), are used mainly for thein vitro study of trace elements. According to work sponsored by the IAEA, up to 15 trace elements and 5 minor elements of nutritional interest may be determined in biological materials by NAA with good accuracy and precision. A programme is described in which NAA was used for the determination of 14 trace elements and one minor element in human milk. NAA also plays an important role in the certification of reference materials for nutritional studies.     

Beyond electronegativity and local hardness: Higher-order equalization criteria for determination of a ground-state electron density

Higher-order global softnesses, local softnesses, and softness kernels are defined along with their hardness inverses. The local hardness equalization principle recently derived by the authors is extended to arbitrary order. The resulting hierarchy of equalization principles indicates that the electronegativity/chemical potential, local hardness, and local hyperhardnesses all are constant when evaluated for the ground-state electron density. The new equalization principles can be used to test whether a trial electron density is an accurate approximation to the true ground-state density and to discover molecules with desired reactive properties, as encapsulated by their chemical reactivity indicators.     

Nutritional supplements cross-contaminated and faked with doping substances

Since 1999 several groups have analyzed nutritional supplements with mass spectrometric methods (GC/MS, LC/MS/MS) for contaminations and adulterations with doping substances. These investigations showed that nutritional supplements contained prohibited stimulants as ephedrines, caffeine, methylenedioxymetamphetamie and sibutramine, which were not declared on the labels. An international study performed in 2001 and 2002 on 634 nutritional supplements that were purchased in 13 different countries showed that about 15% of the nonhormonal nutritional supplements were contaminated with anabolic-androgenic steroids (mainly prohormones). Since 2002, also products intentionally faked with high amounts of 'classic' anabolic steroids such as metandienone, stanozolol, boldenone, dehydrochloromethyl-testosterone, oxandrolone etc. have been detected on the nutritional supplement market. These anabolic steroids were not declared on the labels either. The sources of these anabolic steroids are probably Chinese pharmaceutical companies, which sell bulk material of anabolic steroids. In 2005 vitamin C, multivitamin and magnesium tablets were confiscated, which contained cross-contaminations of stanozolol and metandienone. Since 2002 new 'designer' steroids such as prostanozol, methasterone, androstatrienedione etc. have been offered on the nutritional supplement market. In the near future also cross-contaminations with these steroids are expected. Recently a nutritional supplement for weight loss was found to contain the beta2-agonist clenbuterol. The application of such nutritional supplements is connected with a high risk of inadvertent doping cases and a health risk. For the detection of new 'designer' steroids in nutritional supplements, mass spectrometric strategies (GC/MS, LC/MS/MS) are presented.     

Accreditation for United States environmental laboratories

 There is currently no national program for recognition of United States environmental laboratories. This situation should change sometime in 1998 as environmental testing laboratories should be able to apply for accreditation in the United States via a system developed by the National Environmental Laboratory Accreditation Conference (NELAC). NELAC is an organization whose purpose is to establish performance standards for accrediting environmental laboratories. Laboratories to be accredited will be required to demonstrate qualifications of testing personnel, pass on-site inspections, perform satisfactorily on proficiency test samples, and meet specified quality assurance standards.     

Simultaneous OH and Schlieren visualization of premixed flames at the lean blow-out limit

The structure of an air-propane premixed flame was studied experimentally at the lean flammability limit, using Schlieren photography synchronized with OH-imaging done with the Planar Laser Induced Fluorescence (PLIF) technique. The flame was studied in a wide range of fuel equivalence ratios. Various steps in the process of the flame destabilization were investigated, including partial lift-off, stable lift-off, and final blow-out conditions. The flame structure was visualized for each stage showing the transition from a flame held at the nozzle to a flame held by the flow structures. In order to study the latter conditions in more detail the flame was acoustically excited at the preferred mode frequency generating large, stable, coherent structures in the core region. The modified flame structure was visualized to understand the interaction between the flame and vortical flow dynamics.It is shown that for the flow conditions when the flame cannot be stabilized at the nozzle, a new anchoring point is reached at the location of the initial vortex roll-up in the jet shear layer. At this point the flow reversal and transition to turbulence produce stagnation points with relatively low local velocities and velocity gradients where the flame can be stabilized. When the flame jet is being forced at the jet most unstable frequency, large coherent structures are formed and the flame is stabilized intermittently on these vortices.     

The bootstrap: Some large sample theory and connections with robustness

The bootstrap, discussed by Efron (1979, 1981), is a powerful tool for the nonparametric estimation of sampling distributions and asymptotic standard errors. We demonstrate consistency of the bootstrap distribution estimates for a general class of robust differentiable statistical functionals. Our conditions for consistency of the bootstrap are variants of previously considered criteria for robustness of the associated statistics. A general example shows that, for almost any location statistic, consistency of the bootstrap variance estimator requires a tail condition on the distribution from which samples are taken. A modification of Efron's estimator of standard error is shown to circumvent this problem.     

Alkynyl germatranes as alternative reagents for the preparation of biarylethynes

Arylalkynyl germatranes react with aryl chlorides and triflates to give the corresponding biarylethynes in good yield. The reaction proceeds under mild conditions in the presence of a palladium phosphine catalyst and fluoride ions.     

Thin-layer chromatography--postsource-decay matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of small drug molecules

The structural analysis of small drug molecules by directly coupling thin-layer chromatography (TLC) with postsource-decay (PSD) matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is reported. The applicability of this technique is shown using two examples: the TLC-PSD MALDI analysis of two representatives of nonsteroidal antiinflammatory drugs (tenoxicam and piroxicam) and the analysis of the pharmaceutically active compound UK-137,457 and one of its related substances UK-124,912. The matrices alpha-cyano-4-hydroxycinnamic acid (alpha-CHCA) and graphite are used to investigate the effect of the precursor ion selection on the TLC-PSD MALDI spectra of the drug molecules studied. Although alpha-CHCA enhances the [M+H]+ ion formation graphite produces in general only sodium adducts. Structural differentiation of tenoxicam and piroxicam is possible only by selecting the sodium adduct of both drug molecules as precursor ions. In the case of the TLC-PSD MALDI analysis of UK-137,457 and its related substance UK-124,912 at the 1% level, the PSD spectra obtained in alpha-CHCA by selecting the protonated adduct of the small molecules as precursor ions shows distinguishable dissociation patterns containing structurally significant information.     

Determination of iodine in Asian diets by epithermal and radiochemical neutron activation analysis

Samples of diets from China, Japan, Korea, India, Pakistan and Philippines were analyzed using epithermal and radiochemical neutron activation analysis (ENAA and RNAA, respectively) within the framework of the IAEA project “Reference Asian Man”. The RNAA procedure was based on alkaline-oxidative fusion followed by extraction of elemental iodine in chloroform. The analytical methods employed are discussed in terms of detection limits and uncertainties of the results obtained. For quality control purposes a number of NIST biological reference materials, namely diets and foods were analyzed. Results for the diet samples indicate that achieving the WHO recommended daily allowance for iodine may be a problem in most of the above given countries. This revised version was published online in August 2006 with corrections to the Cover Date.