Limit of detection estimator for second-order bilinear calibration

A new approach is developed for estimating the limit of detection in second-order bilinear calibration with the generalized rank annihilation method (GRAM). The proposed estimator is based on recently derived expressions for prediction variance and bias. It follows the latest IUPAC recommendations in the sense that it concisely accounts for the probabilities of committing both types I and II errors, i.e. false positive and false negative declarations, respectively. The estimator has been extensively validated with simulated data, yielding promising results.     

Comparative Study of Influence of Experimental Configuration on Densities of Active Species in the Early Afterglows of N2/(0–2.5%)H2 HF Flowing Plasmas

Afterglows of mixed gas of N₂ and H₂(0–2.5%) flowing microwave discharges in a 5 mm diameter tube connected to a 5 L reactor via a tube of 1.8 cm diameter and 50 cm long, have been studied using optical emission spectroscopy. The obtained results at the entrance of the afterglow tube of 1.8 cm diameter: Short time afterglow (SA), (10^–3 s) and inside the 5 L reactor: Long time afterglow (LA), (10^–2 s) were then compared. It was found that, in N₂ at 2 Torr, 0.5 slpm, the active specie density ratios had a constant value of 10^–2 for N/N₂, but decreased respectively from 10^–3 to 10^–4 for N₂ (X,v?>?13)/N₂ and from 10^–6 to 10^–8 for N⁺₂ /N₂. By directly connecting the discharge tube inside the 5 L reactor, the density increases by 10 for N₂ (X,v?>?13) and by 10² for N₂⁺ by changing the afterglow from LA(10^?2 s) to a SA(10^–3 s). Moreover and by adding 1% of H₂ to N₂, the N/N₂ and H/H₂ ratios had constant values of 1% and 0.2% respectively. The SA(10^–3 s) appeared to be more efficient for surface treatments than the LA (10^–2 s).

     

Comprehensive Characterization of the Self-Folding Cavitand Dynamics

The conformational equilibria and guest exchange process of a resorcin[4]arene derived self-folding cavitand receptor have been characterized in detail by molecular dynamics simulations (MD) and ¹H EXSY NMR experiments. A multi-timescale strategy for exploring the fluxional behaviour of this system has been constructed, exploiting conventional MD and accelerated MD (aMD) techniques. The use of aMD allows the reconstruction of the folding/unfolding process of the receptor by sampling high-energy barrier processes unattainable by conventional MD simulations. We obtained MD trajectories sampling events occurring at different timescales from ns to s: 1) rearrangement of the directional hydrogen bond seam stabilizing the receptor, 2) folding/unfolding of the structure transiting partially open intermediates, and 3) guest departure from different folding stages. Most remarkably, reweighing of the biased aMD simulations provided kinetic barriers that are in very good agreement with those determined experimentally by ¹H NMR. These results constitute the first comprehensive characterization of the complex dynamic features of cavitand receptors. Our approach emerges as a valuable rational design tool for synthetic host-guest systems     

Operator spaces with few completely bounded maps

We construct several examples of Hilbertian operator spaces with few completely bounded maps. In particular, we give an example of a separable 1-Hilbertian operator space X₀ such that, whenever X is an infinite dimensional quotient of X₀, X is a subspace of X, and is a completely bounded map, then T=I_X+S, where S is compact Hilbert-Schmidt and ||S||₂/16||S||_cb||S||₂. Moreover, every infinite dimensional quotient of a subspace of X₀ fails the operator approximation property. We also show that every Banach space can be equipped with an operator space structure without the operator approximation property. Mathematics Subject Classification (2000):The first author was supported in part by the NSF grants DMS-9970369, 0296094, and 0200714.     

Neutral and dianionic iron and ruthenium 1,4-diphosphabutadiene complexes

Reaction of a tetraphenyl-1,2-diphosphinyl dianion with [FeCl2(THF)1.5] or [Ru(COD)(acac)2] yields dianionic complexes which further react with Ph3SnCl to afford the corresponding bis(1,4-diphosphabutadiene) complexes.     

Effect of non-significant proportional bias in the final measurement uncertainty

The trueness of an analytical method can be assessed by calculating the proportional bias of the method in terms of apparent recovery. If the apparent recovery does not differ significantly from one, the analytical method has not a significant bias. If this is the case, the bias is neglected and the uncertainty associated with this bias is included in the uncertainty budget of results. However, when assessing trueness there is always a probability of incorrectly concluding that the proportional bias is not significant. Therefore, the uncertainty of results may be underestimated. In this paper, we study how non-significant bias affects the uncertainty of analytical results. Moreover, we study how to avoid the underestimation of uncertainty by including the non-significant bias calculated in the uncertainty budget. To answer these questions, we have used the Monte-Carlo method to simulate the process of estimating the apparent recovery of a biased analytical method and, subsequently, the future results this method provides. The results of the simulation show that non-significant bias may underestimate the uncertainty of analytical results when bias contributes in more than 20% to the overall uncertainty. Uncertainty is specially underestimated when bias contributes in more than 50% to the overall uncertainty.