Quantum bits with polyacetylene

The dynamics of a polyacetylene single chain as a system for possible physical implementations of quantum bits is determined. This novel proposition is studied by varying intensity and duration of application of an electric field as well as the intensity, number, and position in the polymer chain of impurity molecules. The behavior of soliton pairs, whose associated energy levels form the quantum bit, is analyzed. The chain is modeled by a modified Pariser-Parr-Pople Hamiltonian extended to include the effects of an external electric field and the parameters of the impurity molecules. The effect of the variation of the field and impurities on the separation of the energy levels associated with soliton pairs is analyzed by numerical integration of the equations of motion. Two different approaches for controlling the separation of levels are presented, and their features compared. First, the use of changes in the electric field to control the distance (and ultimately coupling) between two solitons moving freely on the chain or captured by the potential generated by the impurity molecules. Second, the change in the intensity of the impurities alone, with no application of an external field. We have found that the effect of the use of the field on the separation of levels is much smaller than the one obtained by changes in the parameters of the impurity molecules, which eventually led us to achieve quantum bit behavior in a polyacetylene chain. The influence of the field and impurity parameters in the energy levels is determined, as well as their role in the coupling of the two solitons on the chain. Critical values for distance between solitons, intensity of field, and impurities that determine whether a pair of solitons can work as a quantum bit are obtained.     

Controlled clustering and enhanced stability of polymer-coated magnetic nanoparticles

The clustering and stability of magnetic nanoparticles coated with random copolymers of acrylic acid, styrenesulfonic acid, and vinylsulfonic acid has been studied. Clusters larger than 50 nm are formed when the coatings are made using too low or too high molecular weight polymers or using insufficient amounts of polymer. Low-molecular-weight polymers result in thin coatings that do not sufficiently screen van der Waals attractive forces, while high-molecular-weight polymers bridge between particles, and insufficient polymer results in bare patches on the magnetite surface. The stability of the resulting clusters is poor, but when an insufficient polymer is used as primary coating, and a secondary polymer is added to coat remaining bare magnetite, the clusters are stable in high salt concentrations (>5 M NaCl), while retaining the necessary cluster size for efficient magnetic recovery. The magnetite cores were characterized by TEM and vibrating sample magnetometry, while the clusters were characterized by dynamic light scattering. The clustering and stability are interpreted in terms of the particle-particle interaction forces, and the optimal polymer size can be predicted well on the basis of these forces and the solution structure and hydrophobicity of the polymer. The size of aggregates formed by limited polymer can be predicted with a diffusion-limited colloidal aggregation model modified with a sticking probability based on fractional coating of the magnetite cores.     

A mathematical electron

A particle (m) is represented by a Ricci-flat Schwarzschild-basedanalytic enerel (“energy+ ixelectric charge”) geometry X with fundamental form:ds ²=g _αβ dx ^β =(1-2m/r)dt²?(1?2m/r)^?1 dr ² ?r ²(dθ²+sin²θd?²), wherex ^γ=(t, r, θ,?), m=m+ie isenerel, m is rest energy (or mass), and e is electric charge. A unitary vectoru _α and a scalarφ are defined inX by means of the postulated constitutive equation: φu _αβ u ^β+φ_α=0. The normalization condition is postulated as: $$m = \kappa \smallint _0^\pi \smallint _0^\pi \smallint _{ - a}^a \phi \rho g^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} u^0 dr{\text{ }}d\theta {\text{ }}d\varphi $$ whereρ=(R _αβγδ R ^αβγδ )^1/2 is an enerel density function,?=m ²/?c is a normalization constant and also a fine-structure constant,gdetg _αβ =?r ⁴sin² θ, andR _αβγδ is the Riemann curvature tensor formed with complexg _αβ . These equations yield the charge e=0.0855115... of a purely mathematicaleltron (m)=(ie) of radiusa.     

Complexes of Zn(2+), Cd(2+), and Hg(2+) with 2-(alpha-Hydroxybenzyl)thiamine Monophosphate Chloride

The binding sites of Zn(2+), Cd(2+), and Hg(2+) in complexes with 2-(alpha-hydroxybenzyl)thiamine monophosphate chloride, (LH)(+)Cl(-), have been investigated in the solid state [2-(alpha-hydroxybenzyl)thiamin monophosphate chloride monoprotonated at the phosphate group and protonated at N(1)' is denoted as (LH)(+)Cl(-); therefore, the ligand monoprotonated at the phosphate group and deprotonated at N(1)' is L]. Complexes of formulae MLCl(2), M(LH)Cl(3), and (MCl(4))(2)(-)(LH)(2)(+) (M = Zn(2+), Cd(2+), and Hg(2+)) were isolated in aqueous and methanolic solutions, depending on pH. The crystal structure of the complex of formula HgL(2)Cl(2) was solved, together with that of the free ligand (LH)(+)Cl(-), by X-ray crystallography. HgL(2)Cl(2) crystallizes in C2/c, with a = 32.968(6) ?, b = 7.477(2) ?, c = 21.471(4) ?, beta = 118.19(1) degrees, V = 4665(2) ?(3), and Z = 4. (LH)(+)Cl(-) crystallizes in Cc, with a = 10.951(3) ?, b = 17.579(4) ?, c = 13.373(3) ?, beta = 105.36(2) degrees, V = 2482.4(10) ?(3), and Z = 4. Mercury(II) binds to the N(1') of the pyrimidine ring. Both ligands are in the S conformation [Phi(T) = -98.1(9) degrees and Phi(P) = 176.1(10) degrees for HgL(2)Cl(2) and Phi(T) = 104.1(5) degrees and Phi(P) = 171.9(6) degrees for (LH)(+)Cl(-)]. (31)P and (13)C NMR spectra, together with vibrational spectra (IR/Raman), are used to deduce the binding sites of the metal and the protonation states of the ligand at various pH values. It is found that solid-state (31)P NMR spectroscopy is particularly useful in characterizing these complexes as the (31)P shielding tensors are sensitive to the state of the phosphate group. On the other hand, the (31)P NMR spectra indicate that direct bonding between Zn(2+) and Cd(2+) to the phosphate can occur under certain preparation conditions. Solid-state (13)C NMR and vibrational (IR/Raman) spectroscopic results are also in agreement with the other techniques.     

Consequence of boar edible tissue consumption on urinary profiles of nandrolone metabolites. I. Mass spectrometric detection and quantification of 19-norandrosterone and 19-noretiocholanolone in human urine

For the first time in the field of steroid residues in humans, demonstration of 19-norandrosterone (19-NA: 3alpha-hydroxy-5alpha-estran-17-one) and 19-noretiocholanolone (19-NE: 3alpha-hydroxy-5beta-estran-17-one) excretion in urine subsequent to boar consumption is reported. Three male volunteers agreed to consume 310 g of tissues from the edible parts (meat, liver, heart and kidney) of a boar. The three individuals delivered urine samples before and during 24 h after meal intake. After deconjugation of phase II metabolites, purification and specific derivatisation of target metabolites, the urinary extracts were analysed by mass spectrometry. Identification was carried out using measurements obtained by gas chromatography/high resolution mass spectrometry (GC/HRMS) (R = 7000) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) (positive electrospray ionisation (ESI+)). Quantification was realised using a quadrupole mass filter. 19-NA and 19-NE concentrations in urine reached 3.1 to 7.5 microg/L nearby 10 hours after boar tissue consumption. Levels returned to endogenous values 24 hours after. These two steroids are usually exploited to confirm the exogenous administration of 19-nortestosterone (19-NT: 17beta-hydroxyestr-4-en-3-one), especially in the antidoping field. We have thus proved that eating tissues of non-castrated male pork (in which 17beta-nandrolone is present) might induce some false accusations of the abuse of nandrolone in antidoping.     

Unexpected photolysis of the sunscreen octinoxate in the presence of the sunscreen avobenzone

A major concern raised about photostability studies of sunscreen products is that the photodegradation of sunscreens does not readily translate into changes in product performance. This study examines the correlation between photochemical degradation of sunscreen agents and changes in protection provided by sunscreen films. Films of a commercial sunscreen product containing avobenzone, oxybenzone and octinoxate were irradiated using a fluorescent UV-A phototherapy lamp with additional UV-B blocking filter. Periodically, during irradiation the transmittances of the films were measured and samples collected for chemical analysis of the sunscreen agents using high-performance liquid chromatography techniques. The results show that UV-induced changes in UV transmittance of sunscreen films correlate with changes in concentration of sunscreen agents. In a parallel experiment, we also irradiated a thin film of the same product in the cavity of an electron spin resonance (ESR) spectrometer. We report the concomitant photolysis of avobenzone and octinoxate that predominates over expected E/Z photoisomerization and that irradiation of a film of this product produced free radicals detected by ESR spectroscopy that persisted even after exposure had ended.     

A two-point condition for characterizing the exponential distribution by means of identifically distributed properties related to order statistics

Let X₁, X₂, ..., X_n be independent and identically distributed random variables subject to a continuous distribution function F. Let X_1∶n, X_2∶n, ..., X_n∶n denote the corresponding order statistics. Write

Solution multistability in first-order nonlinear differential delay equations

The dependence of solution behavior to perturbations of the initial function (IF) in a class of nonlinear differential delay equations (DDEs) is investigated. The structure of basins of attraction of multistable limit cycles is investigated. These basins can possess complex structure at all scales measurable numerically although this is not necessarily the case. Sensitive dependence of the asymptotic solution to perturbations in the initial function is also observed experimentally using a task specific electronic analog computer designed to investigate the dynamics of an integrable first-order DDE.