Production of “in house” reference materials for ELISA screening of bovine urine and liver samples for clenbuterol

Clenbuterol screening of bovines is done by analysis of urine, for monitoring living animals, and liver, for monitoring animals after slaughter. ELISA has generally been used as the main method for these purposes. Nevertheless, in Europe, methods must be validated according to Commission Decision (EC) 657/2007 criteria, i.e. by use of reference materials. Production of “in house” reference materials is a possibility, but the homogeneity, storage temperature, and period of stability of these materials must be investigated in the laboratory itself. This paper reports GC–MS evaluation of an “in-house”-produced batch of aliquots of bovine urine and liver, fortified with 10.0 ng/ml and 10.0 ng/g clenbuterol, respectively, and stored at ?20 °C and at ?60 °C. For urine stored for 20 weeks at ?20 °C and at 60 °C the stability of clenbuterol was proved at the 95% confidence level. For liver, however, it was demonstrated at the same confidence level that clenbuterol was highly unstable during storage for 20 weeks at either of the temperatures studied.     

Defects generated by irradiation with gamma rays in lead doped KCl–KBr mixed single crystals

In this work we report the behavior of solid solutions of lead-doped KCl–KBr mixed single crystals subjected to gamma irradiation. Various composition of KCl_1−xBr_x (x=0.02, 0.35, 0.50, 0.65, 0.85) doped with 20–40 ppm of Pb²⁺ were used and exposed to ionizing radiation. The defect production seems to be correlated with the observed increasing integrated thermoluminescence glow curve as a function of irradiation at high 10 kGy dose as well as in the low 2.2–130 dose Gy range. The analysis shows the potential use of these mixed crystals as radiation detector. The defects generated by irradiation were monitored by the optical absorption spectrum and the thermally stimulated luminescence.     

Regular Score Tests of Independence in Multivariate Extreme Values

The score tests of independence in multivariate extreme values derived by Tawn (Tawn, J.A., “Bivariate extreme value theory: models and estimation,” Biometrika 75, 397–415, 1988) and Ledford and Tawn (Ledford, A.W. and Tawn, J.A., “Statistics for near independence in multivariate extreme values,” Biometrika 83, 169–187, 1996) have non-regular properties that arise due to violations of the usual regularity conditions of maximum likelihood. Two distinct types of regularity violation are encountered in each of their likelihood frameworks: independence within the underlying model corresponding to a boundary point of the parameter space and the score function having an infinite second moment. For applications, the second form of regularity violation has the more important consequences, as it results in score statistics with non-standard normalisation and poor rates of convergence. The corresponding tests are difficult to use in practical situations because their asymptotic properties are unrepresentative of their behaviour for the sample sizes typical of applications, and extensive simulations may be needed in order to evaluate adequately their null distribution. Overcoming this difficulty is the primary focus of this paper. We propose a modification to the likelihood based approaches used by Tawn (Tawn, J.A., “Bivariate extreme value theory: models and estimation,” Biometrika 75, 397–415, 1988) and Ledford and Tawn (Ledford, A.W. and Tawn, J.A., “Statistics for near independence in multivariate extreme values,” Biometrika 83, 169–187, 1996) that provides asymptotically normal score tests of independence with regular normalisation and rapid convergence. The resulting tests are straightforward to implement and are beneficial in practical situations with realistic amounts of data. AMS 2000 Subject Classification Primary—60G70 Secondary—62H15     

Solving capacitated facility location problems by Fenchel cutting planes

In this paper, we apply the Fenchel cutting planes methodology to Capacitated Facility Location problems. We select a suitable knapsack structure from which depth cuts can be obtained. Moreover, we simultaneously obtain a primal heuristic solution. The lower and upper bounds achieved by our procedure are compared with those provided by Lagrangean relaxation of the demand constraints. As the computational results show the Fenchel cutting planes methodology outperforms the Lagrangean one, both in the obtaining of the bounds and in the effectiveness of the branch and bound algorithm using each relaxation as the initial formulation.     

Amino‐functionalized latex particles obtained by a multistep method: Development of a new immunoreagent

Cationic latex particles with surface amino groups were prepared by a multistep batch emulsion polymerization. In the first one, two or three steps, monodisperse cationic latex particles to be used as the seed were synthesized. In the third and fourth steps, the amino‐functionalized monomer aminoethylmethacrylate hydrochloride was used to synthesize the final functionalized latex particles. Three different azo initiators 2,2′‐azobisisobutyramidine dihydrochloride, 2,2′‐azobisdimethylenisobutyramidine dihydrochloride, and 2,2′‐azobisisobutyronitrile were used as initiators. Hexadecyltrimethylammonium bromide was the emulsifier. To characterize the final latices, conversions were obtained gravimetrically, and particle size distributions and average particle diameters were determined by transmission electron microscopy and photon correlation spectroscopy. The amount of amino groups was determined by conductimetric titrations. Colloidal aspects were ascertained by measuring the electrophoretic mobilities. Activation of these particles with glutaraldehyde produced an efficient reagent for latex‐enhanced immunoassay. The covalent coupling efficiency (protein covalently bound with respect to the total amount of protein adsorbed) was compressed between 50 and 80%. The developed immunoreagent was applied to the measurement of serum ferritin concentration in a new turbidimetric procedure that was compared with a commercial nephelometric method; the results obtained with both methods demonstrated that the two procedures correlated well (r = 0.992). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2404–2411, 2003     

A new sulfate acid polymorph of 1,3‐dihydrobenzotriazole

A new sulfate acid polymorph of 1,3‐dihydrobenzotriazole, viz. 1,3‐dihydrobenzotriazolium hydrogensulfate, C₆H₆N₃⁺·HSO₄⁻, differs from an existing polymorph in that the polymeric interaction between the HSO₄⁻ anions, together with different classical (D—H...A) and nonclassical (C—H...A) interactions, changes the space group.     

Secondary molecular mobility in amorphous ethyl cellulose: Aging effects and degree of co‐operativity

The secondary relaxations in amorphous ethyl cellulose are studied using thermally stimulated depolarization currents (TSDCs) in the temperature region from 165 °C (108 K) up to 145 °C (418 K). The influence of aging on the current peaks of the secondary relaxation is discussed, and it is concluded that some modes of motion of this mobility are aging independent, while others are affected by aging. A particular attention is focused on the discussion of the degree of co‐operativity of the motional modes of the secondary relaxation. The conclusion to be driven from the obtained TSDC results is that the aging‐independent motional modes, as well as those that are aging dependent, do not show any appreciable co‐operative character. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 820–829, 2009