A new internal quality control chart based on biological variation

The instruments and analytical methods currently used in clinical laboratories today have better precision and stability than those used in the past. With the development of chemical and immunological methods and instrumentation technology, test precision has increased. However, the application of the Westgard multirule procedure to control sera in the Levey-Jennings chart may not be useful or cost-effective. We devised a new test-specific decision limit for accepting or rejecting runs based on the data of within-subject biological variation and prepared a control chart. We then applied these new limits and control chart to a group of tests performed in our laboratory. With the exception of the tests for albumin, total protein, and calcium, for which desirable performance standards could not be attained with the current technology and methodology, the application of these control limits was cost-effective and convenient. It is estimated that the value of healthy within-subject biological variations is constant, irrespective of the methodology, the area in which the study has been performed, and the number of subjects included in the study. We believe that control limits based on biological variation are reliable and cost-effective, and may be useful in modern and accredited laboratories.     

Iminosugar-ferrocene conjugates as potential anticancer agents

We prepared a series of new iminosugar-ferrocene hybrids displaying potent inhibition of fucosidase (bovine kidney) and inactivation of MDA-MB-231 breast cancer cells proliferation at low micromolar concentrations. The synthetic route brought to light an unprecedented isomerisation of a 2-ethanalylpyrrolidine.     

VUV Fourier-transform absorption study of the Lyman and Werner bands in D2

An extensive survey of the D(2) absorption spectrum has been performed with the high-resolution VUV Fourier-transform spectrometer employing synchrotron radiation. The frequency range of 90,000-119,000 cm(-1) covers the full depth of the potential wells of the B (1)Σ(u)(+), B' (1)Σ(u)(+), and C (1)Π(u) electronic states up to the D(1s) + D(2l) dissociation limit. Improved level energies of rovibrational levels have been determined up to respectively v = 51, v = 13, and v = 20. Highest resolution is achieved by probing absorption in a molecular gas jet with slit geometry, as well as in a liquid helium cooled static gas cell, resulting in line widths of ≈0.35 cm(-1). Extended calibration methods are employed to extract line positions of D(2) lines at absolute accuracies of 0.03 cm(-1). The D (1)Π(u) and B' (1)Σ(u)(+) electronic states correlate with the D(1s) + D(3l]) dissociation limit, but support a few vibrational levels below the second dissociation limit, respectively, v = 0-3 and v = 0-1, and are also included in the presented study. The complete set of resulting level energies is the most comprehensive and accurate data set for D(2). The observations are compared with previous studies, both experimental and theoretical.     

Single crystal growth and physical properties of superconducting ferro-pnictides Ba(Fe,Co)2As2 grown using self-flux and Bridgman techniques

We have employed the high temperature solutions growth technique and the Bridgman technique to grow cm-size high-quality single crystals of pristine BaFe₂As₂ (Ba122) and its Co-doped superconducting variants. In the first approach, self-flux (Fe, Co)As was used to achieve a homogeneous melt of composition Ba(Fe, Co)_3.1As_3.1 at T=1463 K. The melt was then cooled slowly under a temperature gradient in a double-wall crucible assembly to obtain large and flux-free single crystals of Ba(Fe, Co)₂As₂. In the second approach, single crystals were grown directly from a stoichiometric Ba(Fe, Co)₂As₂ melt at T=1723 K employing the Bridgman technique associated with a vertical tube furnace. Using both techniques single crystals with lateral dimensions up to 25×10 mm² and thickness up to 1 mm were obtained. Details of the two methods are given and a comparative study of the magnetic and transport properties of the single crystals obtained using the two methods is presented.     

Formation of the C-S-H Layer during early hydration of tricalcium silicate grains with different sizes

Portland cement is a mixture of solid phases which all react with water. Tricalcium silicate (Ca3SiO5) is its main component and is often used in model systems to study cement hydration. It is generally recognized that setting and hardening of cement are due to the formation, by a dissolution-precipitation process, of a calcium silicate hydrate (C-S-H) on anhydrous grains during Ca3SiO5 hydration. The purpose of this paper is to study the effect of Ca3SiO5 particle size on the nucleation-growth process of C-S-H. An experimental study of the rate of hydration by using different grain sizes under controlled conditions has been performed. The experimental data have been compared with results obtained by numerical simulation based on a particles-aggregation model. The thickness of the C-S-H layer when the reaction becomes limited by diffusion has been then estimated.     

Supramolecular binding of protonated amines to a receptor microgel in aqueous medium

Polyanionic microgels containing negatively charged tetrazole binding sites show supramolecular binding of various protonated amines (e.g. dibucaine and spermine) in a competitive aqueous medium at millimolar concentration.     

Towards standardization of external quality assessment schemes by using bias values based on biological variation

The precision and trueness of current instruments and methods in clinical laboratories is much better than in the past. However, the z-score and other comparison variables that are currently used in external quality assessment programs are based on relative data. Thus, they may change from program to program and also change over time within the same program and consequently may not be useful or cost-effective. We therefore devised a test-specific decision limit for accepting or rejecting test results based on a combination of the data of within- and between-subject biological variations. We then applied these limits to a group of tests performed in our laboratory and compared our results with those of external quality assessment programs. In addition, we combined external and internal quality control data on the same graph and prepared a two-dimensional graph for different levels of control sera. Inspection of all results of control sera on this new graph was more useful for decision making. We concluded that the z-score is not reliable for comparisons of test results in external quality assessment. As a substitute for this currently accepted practice, we assert that control limits based on biological variation are more reliable, and can be useful in the evaluation of both external and internal quality assessments and their combination on this new graph.     

Block copolymers and telechelic oligomers by end group reaction of polymethacrylates

Block copolymers and telechelic oligomers bearing methacrylate moities were obtained by means of a new highly selective end group reaction. Starting from polymethacrylates that were prepared by radical polymerization in the presence of mercaptanes as chain transfer agents, the resulting ester end group linked to the terminal tertiary carbon atom of the polymer backbone can be either transesterified or saponified selectively. The selectivity of the end group reactions was determined by MALDI-TOF-mass spectrometry. Polymethacrylate-b-poly(ethylene oxide)-, polymethacrylate-b-poly(methacrylic acid)- and polymethacrylate-b-polysiloxane-b-polymethacrylate-copolymers as well as α,ω-dihydroxy- and α,ω-dicarboxy-telechelic polymethacrylates were prepared by applying end group transesterification or end group saponification.