On using an approximate noncentral t-distribution in determining a one-side upper limit for future sample relative reproducibility standard deviations

For future sample relative reproducibility standard deviations (RSD(R)), collaboratively obtained under a completely randomized model (CRM), a new formula for determining a one-tailed 100p% upper limit (kappap) for such RSD(R) values was developed based on an approximate noncentral t-distribution with degrees of freedom obtained using Satterthwaite's adjustment. The accuracy of kappap was assessed by comparing kappap and its probability levels with similar values associated with a Monte Carlo simulation and with those obtained using another formula (gammap) that was developed for the same purpose but based on a normal approximation.     

Determining a one-tailed upper limit for future sample relative reproducibility standard deviations

A formula was developed to determine a one-tailed 100p% upper limit for future sample percent relative reproducibility standard deviations (RSD(R),%= 100s(R)/y), where S(R) is the sample reproducibility standard deviation, which is the square root of a linear combination of the sample repeatability variance (s(r)2) plus the sample laboratory-to-laboratory variance (s(L)2), i.e., S(R) = s(L)2, and y is the sample mean. The future RSD(R),% is expected to arise from a population of potential RSD(R),% values whose true mean is zeta(R),% = 100sigmaR, where sigmaR and mu are the population reproducibility standard deviation and mean, respectively.     

Thermal and mechanical properties of electrospun PMMA,PVC, Nylon 6, and Nylon 6,6

Poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC), Nylon 6, and Nylon 6,6 have been electrospun successfully. The nanofibers have been characterized by scanning electron microscopy (SEM), confirming the presence of bead free and fiber‐bead free morphologies. Thermogravimetric analysis (TGA) indicated differences between the thermal stability of PMMA nanofibers and PMMA powder. However, no significant differences were observed between the starting physical form (powder or pellet) of PVC, Nylon 6 and Nylon 6,6, and their corresponding electrospun nanofibers. Differential scanning calorimetry (DSC) demonstrated a lower glass transition temperature (T_g) and water absorption for PMMA electrospun nanofibers. Furthermore, electrospun Nylon 6 and Nylon 6,6 had a slight decrease in crystallinity. Tensile testing was performed on the electrospun nanofibers to obtain the Young modulus, peak stress, strain at break, and energy to break, revealing that the non‐woven mats obtained had modest mechanical properties that need to be enhanced. Copyright © 2007 John Wiley & Sons, Ltd.     

Reactions of activated aryl sydnones with electrophiles

Electrophilic substitution on the aryl or sydnone ring of some ortho-substituted activated N-aryl-sydnones is reported.