Where is an object before you look at it?

According to the standard interpretation of quantum mechanics (QM), no meaning can be assigned to the statement that a particle has a precise value of any one of the variables describing its physical propertes before having interacted with a suitable measuring instrument. On the other hand, it is well known that QM tends to classical statistical mechanics (CSM) when a suitable classical limit is performed. One may ask therefore how is it that in this limit, the statement, meaningless in QM, that a given variable has always a precise value independently of having been measured, gradually becomes meaningful. In other words, one may ask how can it be that QM, which is a theory describing the intrinsically probabilistic properties of a quantum object, becomes a statistical theory describing a probabilistic knowledge of intrinsically well determined properties of classical objects.In the present paper we try to answer to this question and show that an inconsistency arises between the conventional interpretation of CSM which presupposes objectively existing Newtonian trajectories, and the standard interpretation of QM. We conclude that the latter needs revisiting unnless we wish to adopt a strictly subjective conception of the world around us, implying that macroscopic objects as well are not localized anywhere before we look at them.     

Super Toeplitz operators and non-perturbative deformation quantization of supermanifolds

The purpose of this paper is to construct non-perturbative deformation quantizations of the algebras of smooth functions on Poisson supermanifolds. For the examplesU ^1¦1 andC ^m¦n , algebras of super Toeplitz operators are defined with respect to certain Hilbert spaces of superholomorphic functions. Generators and relations for these algebras are given. The algebras can be thought of as algebras of quantized functions, and deformation conditions are proven which demonstrate the recovery of the super Poisson structures in a semi-classical limit.Supported in part by the Department of Energy under grant DE-FG02-88ER25065Supported in part by the Italian National Institute for Nuclear Physics (INFN)     

Blue silver: a very sensitive colloidal Coomassie G-250 staining for proteome analysis

A modified Neuhoff's colloidal Coomassie Blue G-250 stain is reported, dubbed "blue silver" on account of its considerably higher sensitivity, approaching the one of conventional silver staining. The main modifications, as compared to Neuhoff's protocol, were: a 20% increment in dye concentration (from 0.1% up to 0.12%) and a much higher level of phosphoric acid in the recipe (from 2% up to 10%). The "blue silver" exhibits a much faster dye uptake (80% during the first hour of coloration, vs. none with a commercial preparation from Sigma). Even at equilibrium (24 h staining), the "blue silver" exhibits a much higher sensitivity than all other recipes, approaching (but lower than) the one of the classical silver stain. Measurements of stain sensitivity after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of bovine serum albumin (BSA) gave a detection limit (signal-to-noise ratio > 3) of 1 ng in a single zone. The somewhat lower sensitivity of "blue silver" as compared to classical silvering protocols in the presence of aldehydes is amply compensated for by its full compatibility with mass spectrometry of eluted polypeptide chains, after a two-dimensional map analysis, thus confirming that no dye is covalently bound (or permanently modifies) to any residue in the proteinaceous material. It is believed that the higher level of phosphoric acid in the recipe, thus its lower final pH, helps in protonating the last dissociated residues of Asp and Glu in the polypeptide coils, thus greatly favoring ionic anchoring of dye molecules to the protein moiety. Such a binding, though, must be followed by considerable hydrophobic association with the aromatic and hydrophobic residues along the polypeptide backbone.     

Validating automated analytical instruments to meet regulatory and quality standard requirements

Analytical laboratories are more and more faced to meet official regulatory requirements as described in FDA and EPA good laboratory practice, good automated laboratory practice and good manufacturing practice regulations or to officially establish quality systems, such as specified in the ISO 9000 Series quality standards, in the ISO Guide 25 or in the EN 45001 guidelines. The impact on analytical instrumentation will be the requirement for stringent validation of analytical equipment and methods which increase the overall analysis costs. An overview is presented on the validation requirements using e.g. gas chromatography, high performance liquid chromatography, capillary electrophoresis and UV-visible spectroscopy and on the strategy to meet such needs at minimal extra costs with the help of an instrument vendor. It is recommended to use instrument hardware that has already built-in tools for self-verification and which is to be validated at the vendor's site. Performance testing in the user's laboratory is done using standard operating procedures as supplied with the instrument. If resources in the user's laboratory are limited, the performance verification is done by the vendor. Software and the entire computer system is validated prior to shipment at the vendor's site. Acceptance testing is done in the user's environment following the vendor recommendations. Analytical methods are validated automatically at the end of method development using a dedicated software. The software can be customized such that it can also be used for daily automated system suitability testing. Security and integrity of analytical data are ensured by saving the raw data together with instrument conditions and instrument log-books in check-sum protected binary register files for long-term archiving.     

High-performance liquid chromatography and capillary electrophoresis: methodological challenges for the determination of biologically relevant low-aliphatic aldehydes in human saliva

Tobacco smoke is involved in the pathogenesis of cardiovascular and respiratory diseases and also has a local toxic effect in the oral cavity. Low-aliphatic aldehydes, such as formaldehyde, acetaldehyde and acrolein, are among the main components of mainstream cigarette smoke and their local noxious and carcinogenic effects in the oral cavity and upper gastrointestinal tract are well-known. Although various studies have been performed so far to determine their content in cigarette smoke, none has included the direct measurement of these compounds in the saliva of smoking and nonsmoking subjects. Thus, in an attempt to verify whether typical chromatographic (high-performance liquid chromatography, HPLC) and/or electrophoretic (capillary electrophoresis, CE) techniques could be reliable methods for determining the levels of these analytes in human saliva, we submitted specimens obtained from a selected population of heavy, moderate, and nonsmoking subjects to HPLC and CE analyses. Both methods showed good reproducibility in terms of migration times and peak height and/or areas and had comparable linearity. Quantitative analyses performed on the specimens investigated evidenced a 3.5-fold increase of low-aliphatic aldehydes in saliva of nonsmoking subjects after they have smoked a single cigarette and a further 2-fold increase of these compounds in saliva of smokers with a daily consumption of 10 or more cigarettes.     

Extremely localized molecular orbitals: theory and applications

Orbitals that are extremely localized on molecular fragments represent a powerful tool for a number of purposes: to cite a few examples, they allow to reduce strongly the complexity of calculations on large systems and are easily transferable from one molecule to another, providing a suitable and efficient way to build up the electronic structure of large molecules. Recently, we have developed efficient algorithms to determine extremely localized molecular orbitals (ELMOs), which will be reviewed in this paper. As a rigorous localization is strictly connected to a reduction in the number of variational parameters, which reflects into an increased value of the associated energy with respect to the Hartree Fock value, we have developed a number of strategies to relax the wavefunction built up using transferred localized orbitals. The extreme localization has also been exploited in connection with the “Divide and Conquer” technique to determine the electron densities of large polypeptides assembled from orbitals computed on small model molecules. Moreover, we will discuss the recent application of the ELMOs in the framework of the hybrid QM/MM methods to describe the frontier region. We will also show that the ELMOs can be used to extract chemical interpretations from numerical results. A variety of applications will be presented.     

EPR support for the ketyl radical-anion "triggered" [3,3]-sigmatropic rearrangement

New physical evidence to support a ketyl radical-anion mechanism for the [3,3]-sigmatropic rearrangement is presented. With use of EPR spectroscopy, spectra are observed that can be attributed to 8, an acyl radical-anion species resulting from a [3,3]-rearrangement; this also functions as a key intermediate in the process. The spectrum of an additional paramagnetic species resulting from further addition of tin-centered radicals to the reaction product was also observed.     

5‐Substituted Benzothiophenes: Synthesis,Mechanism, and Kinetic Studies

The kinetics of the reaction of 4‐methoxythiophenoxyacetaldehyde diethyl acetal, 4‐nitrothiophenoxyacetaldehyde diethyl acetal, and 3‐methoxythiophenoxyacetaldehyde diethyl acetal in polyphosphoric acid has been explained. The kinetic behavior has been explained on the basis of aided simulation and on the basis of density functional theory calculations showing a different pathway for 4‐nitrothiophenoxyacetaldehyde diethyl acetal and for 4‐methoxythiophenoxyacetaldehyde diethyl acetal. In this last case, a very fast competing reaction to the dimerization product was observed.     

Selective Determination of Se4+ and Se6+ Using SPME and GC/MS

A method for the selective determination of Se⁴⁺ and Se⁶⁺ using solid phase microextraction (SPME) and GC/MS analysis is presented. Se⁴⁺ is selectively derivatized by reaction with 4,5-dichloro-1,2-phenylenediamine to form the corresponding piazselenolo complex, extracted by the SPME fiber, and determined by GC/MS. The RSD at a 5 μg/L concentration was 9.88% and the theoretical detection limit 6 ng/L. The method was employed to test real matrices; tap and river water were analyzed before and after spiking giving a recovery rate of 102% in river water and 97% in tap water.