Interlaboratory assessment of measurement precision and bias in the coulometric Karl Fischer determination of water

The precision and bias of the coulometric Karl Fischer ASTM method D1533-00 have been assessed in a collaborative ASTM round robin program for a group of 34 laboratories. The test materials used in this study included water saturated 1-octanol (WSO), water saturated 1-butanol (WSB), and a series of new and used transformer oil samples. Fundamental systematic biases have been demonstrated in the accuracy of the measurement of water in the WSO, WSB, and transformer oil samples. The systematic bias in the measurement of the WSO and WSB standards indicates that for some laboratories either the instruments were not accurate or the quantity of the standard was not measured accurately. A second type of systematic bias consisted of measurement errors associated with the selection of the Karl Fischer solvent that was used with each instrument, and this was superimposed upon the error in the measurement of the water in the standards. Using the statistical calculation method ASTM D 6300 the repeatability and reproducibility for water in transformer oil were found to be 7 mg/kg and 14 mg/kg respectively. The method detection limit of water was 8 mg/kg oil. The method bias was estimated based on the National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 2890, WSO, since no suitable reference material for water in transformer oil was available for this study.     

Meson production in p + d reactions

Total and differential cross sections for the reactions p + d → ³He + m ⁰ with m=π, η and p + d → ³H+π⁺ were measured with the GEM detector at COSY for beam momenta between threshold and the maximum of the corresponding baryon resonance. For both reactions a strong forward-backward asymmetry was found. The data were compared with model calculations. The aspect of isospin symmetry breaking is studied. Representing the GEM Collaboration     

A Complete Rewrite System and Normal Forms for (S) reg

The ( . ) _reg construction was introduced in order to make an arbitrary semigroup S divide a regular semigroup (S) _reg which shares some important properties with S (e.g., finiteness, subgroups, torsion bounds, J -order structure). We show that (S) _reg can be described by a rather simple complete string rewrite system , as a consequence of which we obtain a new proof of the normal form theorem for (S) _reg . The new proof of the normal form theorem is conceptually simpler than the previous proofs.     

Preparation of tetra-Boc-protected polymyxin B nonapeptide

A method for the selective tetra-Boc-protection of polymyxin B nonapeptide (PMBN) has been developed. Boc-ON selectively protects the amino side chains of the four diaminobutyric acid (Dab) residues in the presence of the N-terminal free amine.     

Quasi-identities of finite semigroups and symbolic dynamics

An algebra is inherently non-finitely (Q-)based if it is not a member of any locally finite (quasi-)variety, whose (quasi-)identities are finitely based. We prove that no finite semigroup is inherently non-finitely Q-based. This is in marked contrast to the case of varieties, where there are many inherently non-finitely based finite semigroups which have all been described by the second author. Research of both authors supported in part by NSF and the Center for Communication and Information Sciences of the University of Nebraska at Lincoln.     

Observation of forbidden transitions in the ν4 band of NH3: corrections to the ground state ΔK = 3 intervals

This paper presents a preliminary evaluation of the C rotational constant and coefficients of the operators P_z ²ⁿ up to n = 4 for NH₃ in the ground state. These constants are evaluated on the basis of the determination of 14 different ΔK = 3 ground state intervals obtained from measurement of many Δ(K - l) = 3 transitions observed in the ν₄ vibration rotation band. Corrections to the ground state term values for NH₃ are given as a function of K, thus permitting ΔK = 3 transitions to be determined with accuracies comparable to those of normal allowed transitions. The perturbation which gives rise to the observed transitions is large, but has not been treated in previous analyses of the ν₄-2ν₂ bands.