Relativistic quantum mechanics over stochastic phase space

Stochastic quantum mechanics is a quantum theory in which the basic limitations of real-world measuring instruments, due to their intrinsically quantum nature, are taken into account. Among other things this leads to a new operational definition of space-time, called quantum space-time. Fundamental to this approach is the formulation of quantum mechanics over phase space rather than just over position or momentum space. A concept of extended particle is a natural outgrowth of this development. Gauge and internal symmetry have a natural place within the theory, and preliminary computations combining some old ideas due to Born with more recent ideas on symmetry breaking suggest that the theory could lead to a mass formula compatible with known data on the low-lying baryons.Supported in part by NSERC Grant, No. A8403.     

Initial 119Sn Mössbauer Spectroscopy and X-ray Diffractometry Investigations of Electrodeposited Tin-Chromium and Tin-Zinc-Chromium Alloys

¹¹⁹Sn conversion electron Mössbauer spectroscopy, X-ray diffractometry and energy dispersive X-ray analysis (EDAX) were employed to investigate microstructure, composition and phases present in as-electroplated Sn-Cr and Sn-Cr-Zn alloys deposited on copper substrates. In the Sn-Cr deposits Cu, -Sn, Cr-Sn phases can be identified by X-ray diffractometry. The phase composition is significantly different between the samples prepared with relatively higher and lower current densities. In the diffractograms of Sn-Cr-Zn deposits Cu, -Sn, Zn phases can be well identified. A small intensity amorphous peak is also present, which can perhaps be associated with the presence of some amorphous Zn and Sn alloy. ¹¹⁹Sn Mössbauer spectra of Sn-Cr deposits exhibit an asymmetric broad main line centered near the isomer shift characteristic of -Sn as well as they contain a small component near the zero velocity which can be attributed to a SnO₂ phase based upon its characteristic. ¹¹⁹Sn Mössbauer spectra of Sn-Cr-Zn deposits are roughly similar to those of Sn-Cr deposits although the Mössbauer parameters of the third phase are different and vary with the Zn content. The presence of SnO₂ on the surface mainly in the Sn-Cr samples can be attributed to the corrosion process in the air.     

In-out intermittency in partial differential equation and ordinary differential equation models

We find concrete evidence for a recently discovered form of intermittency, referred to as in-out intermittency, in both partial differential equation (PDE) and ordinary differential equation (ODE) models of mean field dynamos. This type of intermittency [introduced in P. Ashwin, E. Covas, and R. Tavakol, Nonlinearity 9, 563 (1999)] occurs in systems with invariant submanifolds and, as opposed to on-off intermittency which can also occur in skew product systems, it requires an absence of skew product structure. By this we mean that the dynamics on the attractor intermittent to the invariant manifold cannot be expressed simply as the dynamics on the invariant subspace forcing the transverse dynamics; the transverse dynamics will alter that tangential to the invariant subspace when one is far enough away from the invariant manifold. Since general systems with invariant submanifolds are not likely to have skew product structure, this type of behavior may be of physical relevance in a variety of dynamical settings. The models employed here to demonstrate in-out intermittency are axisymmetric mean-field dynamo models which are often used to study the observed large-scale magnetic variability in the Sun and solar-type stars. The occurrence of this type of intermittency in such models may be of interest in understanding some aspects of such variabilities. (c) 2001 American Institute of Physics.     

Quantitation of ortho‐cresyl phosphate adducts to butyrylcholinesterase in human serum by immunomagnetic‐UHPLC‐MS/MS

Tri‐ortho‐cresyl phosphate (ToCP) is an anti‐wear, flame retardant additive used in industrial lubricants, hydraulic fluids and gasoline. The neurotoxic effects of ToCP arise from the liver‐activated metabolite 2‐(o‐cresyl)‐4H‐1,3,2‐benzodioxaphosphoran‐2‐one (cresyl saligenin phosphate or CBDP), which inhibits esterase enzymes including butyrylcholinesterase (BChE). Following BChE adduction, CBDP undergoes hydrolysis to form the aged adduct ortho‐cresyl phosphoserine (oCP‐BChE), thus providing a biomarker of CBDP exposure. Previous studies have identified ToCP in aircraft cabin and cockpit air, but assessing human exposure has been hampered by the lack of a laboratory assay to confirm exposure. This work presents the development of an immunomagnetic‐UHPLC‐MS/MS method for the quantitation of unadducted BChE and the long‐term CBDP biomarker, oCP‐BChE, in human serum. The method has a reportable range from 2.0 ng/ml to 150 ng/ml, which is consistent with the sensitivity of methods used to detect organophosphorus nerve agent protein adducts. The assay demonstrated high intraday and interday accuracy (≥85%) and precision (RSD ≤ 15%) across the calibration range. The method was developed for future analyses of potential human exposure to CBDP. Analysis of human serum inhibited in vitro with CBDP demonstrated that the oCP‐BChE adduct was stable for at least 72 h at 4, 22 and 37 °C. Compared to a previously reported assay, this method requires 75% less sample volume, reduces analysis time by a factor of 20 and demonstrates a threefold improvement in sensitivity. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.     

Why are [P(C6H5)4](+)N3- and [As(C6H5)4](+)N3- ionic salts and Sb(C6H5)4N3 and Bi(C6H5)4N3 covalent solids? A theoretical study provides an unexpected answer

A recent crystallographic study has shown that, in the solid state, P(C(6)H(5))(4)N(3) and As(C(6)H(5))(4)N(3) have ionic [M(C(6)H(5))(4)](+)N(3)(-)-type structures, whereas Sb(C(6)H(5))(4)N(3) exists as a pentacoordinated covalent solid. Using the results from density functional theory, lattice energy (VBT) calculations, sublimation energy estimates, and Born-Fajans-Haber cycles, it is shown that the maximum coordination numbers of the central atom M, the lattice energies of the ionic solids, and the sublimation energies of the covalent solids have no or little influence on the nature of the solids. Unexpectedly, the main factor determining whether the covalent or ionic structures are energetically favored is the first ionization potential of [M(C(6)H(5))(4)]. The calculations show that at ambient temperature the ionic structure is favored for P(C(6)H(5))(4)N(3) and the covalent structures are favored for Sb(C(6)H(5))(4)N(3) and Bi(C(6)H(5))(4)N(3), while As(C(6)H(5))(4)N(3) presents a borderline case.     

The Unexpected Base-Pairing Behavior of Cyanuric Acid in RNA and Ribose versus Cyanuric Acid Induced Helicene Assembly of Nucleic Acids: Implications for the Pre-RNA Paradigm

The cyanuric acid (CA) heterocycle forms supramolecular structures with adenine nucleobases/nucleosides and oligonucleotides, leading to speculation that they can act as forerunners to RNA. Herein, the assembly behavior of RNA containing CA and CA–ribose nucleoside was studied. Contrary to previous reports, CA in RNA and the CA-ribonucleoside resulted in destabilization of supramolecular assemblies, which led to a reevaluation of the CA–adenine hexameric rosette structure. An unprecedented noncovalent supramolecular helicene structure is proposed to account for the striking difference in behavior, which has implications for novel paradigms for reorganizing the structures of nucleic acids, the synthesis of long helicenes, and pre-RNA world paradigms. The results caution against extrapolating the self-assembly behavior of individual heterocycles from the level of monomers to oligomers because the base-paring properties of (non-)canonical nucleobases are impacted by the type of oligomeric backbone to which they are attached.     

Self‐Assembly of a Four‐Helix Bundle on a DNA Quadruplex

Come together : A novel method for assembling monomers and controlling structure of a de novo helix bundle protein is described. A guanine (G)‐rich oligodeoxynucleotide scaffold forms a hydrogen‐bonded DNA quadruplex in the presence of potassium counterions, thereby inducing a helical structure and fourfold stoichiometry in conjugated, amphiphilic peptide sequences. The DNA scaffold shows potential for rapidly assembling designed proteins.

     

An enhanced butyrylcholinesterase method to measure organophosphorus nerve agent exposure in humans

Organophosphorus nerve agent (OPNA) adducts to butyrylcholinesterase (BChE) can be used to confirm exposure in humans. A highly accurate method to detect G- and V-series OPNA adducts to BChE in 75 μL of filtered blood, serum, or plasma has been developed using immunomagnetic separation (IMS) coupled with liquid chromatography tandem mass spectrometry (LC-MS/MS). The reported IMS method captures >?88 % of the BChE in a specimen and corrects for matrix effects on peptide calibrators. The optimized method has been used to quantify baseline BChE levels (unadducted and OPNA-adducted) in a matched-set of serum, plasma, and whole blood (later processed in-house for plasma content) from 192 unexposed individuals to determine the interchangeability of the tested matrices. The results of these measurements demonstrate the ability to accurately measure BChE regardless of the format of the blood specimen received. Criteria for accepting or denying specimens were established through a series of sample stability and processing experiments. The results of these efforts are an optimized and rugged method that is transferrable to other laboratories and an increased understanding of the BChE biomarker in matrix.