The mass spectra of N-acyliminopyridinium and isoquinolinium betaines

The mass spectral fragmentation behaviour of N-acyliminopyridinium and isoquinolinium betaines has been investigated. Major fragmentations of the pyridinium betaines can be rationalized in terms of charge localization on the pyridinium nitrogen. The most prominent process is α-cleavage followed by loss of NCO to furnish a pyridine ion. The electron-impact induced fragmentation of N-benzoyliminopyridinium betaine (I) was compared with that of thermolysis. The completely analogous behaviour has been observed in the corresponding isoquinolinium betaines.     

Quenching of a photosensitized dye through single-electron transfer from trivalent phosphorus compounds

Various types of trivalent phosphorus compounds 1 undergo single-electron transfer (SET) to the photoexcited state of rhodamine 6G (Rho+*) in aqueous acetonitrile to quench the fluorescence from Rho+*. The rate constants kp for the overall SET process were determined by the Stern-Volmer method. The rate is nearly constant at a diffusion-controlled limit in the region of E1/2(1) < 1.3 V (vs Ag/Ag+), whereas log kp depends linearly on E1/2(1) in the region of E1/2(1) > 1.3 V, the slope of the correlation line being -alphaF/RT with alpha = 0.2. The potential at which the change in dependence of log kp on E1/2(1) occurs (1.3 V) is in accordance with the value of E1/2(Rho+*) (1.22 V) that has been obtained experimentally. Thus, the SET step is exothermic when E1/2(1) < 1.3 V and endothermic when E1/2(1) > 1.3 V. The alpha-value (0.2) obtained in the endothermic region shows that the SET step from 1 to Rho+* is irreversible in this region. Trivalent phosphorus radical cation 1*+ generated in the SET step undergoes an ionic reaction with water in the solvent rapidly enough to make the SET step irreversible. In contrast, the SET from amines 2 and alkoxybenzenes 3 to Rho+* is reversible when the SET step is endothermic, meaning that the radical cations 2*+ and 3*+ generated in the SET step undergo rapid "back SET" in the ground state to regenerate 2 and 3.     

Determination of mercapturic acids in urine by solid-phase extraction followed by liquid chromatography-electrospray ionization mass spectrometry

A novel method for the determination of five kinds of mercapturic acids, found in urine as metabolites of alkylbenzenes, based on liquid chromatography-electrospray ionization mass spectrometry is described. A solid-phase extraction procedure was used for the extraction of the mercapturic acids from urine and the separation was performed on a reversed-phase C30 column. The detection limits were in the range 2.4-3.2 ng ml-1.     

Improvement of capillary zone electrophoresis sensitivity with artificial seawater as the background electrolyte utilizing transient isotachophoresis for the determination of nitrate and nitrate ions in seawater

We describe capillary zone electrophoresis (CZE) with transient isotachophoresis (ITP) for the determination of low concentrations of nitrite and nitrate ions in seawater. Bromide-free artificial seawater was adopted as background electrolyte (BGE) to eliminate the interference of high concentrations of salts in seawater. To reverse the electroosmotic flow (EOF), 3 mM cetyltrimethylammonium chloride (CTAC) was added to the BGE. High concentrations of chlorate were added to sample solutions as the terminating ion to generate the ITP process before the CZE separation. In general, the stacking effect increased with increasing amounts of chlorate injected into the capillary. The limits of detection (LODs) for nitrite and nitrate were 0.063 and 0.033 mg/L when the chlorate concentration was 600 and 200 mM, respectively; these were half of those obtained by CZE without the transient ITP. The LODs were obtained at a signal to noise ratio (S/N) of 3. The relative standard deviations (RSD, n = 10) of the peak areas for these ions were 3.2 and 2.9%. The RSDs of peak heights for these ions were 1.6 and 2.1%. The RSDs of migration times for these ions were 0.67 and 0.46%.     

Optimum conditions for effective use of the terminating ion in transient isotachophoresis for capillary zone electrophoretic determination of nitrite and nitrate in seawater,with artificial seawater as background electrolyte

We have examined transient isotachophoresis (ITP) conditions, e.g. the nature of the terminating ion, its concentration, and the injection procedure, to improve the limit of detection (LOD) for determination of nitrite and nitrate in seawater by capillary zone electrophoresis (CZE). Artificial seawater containing 3.0 mmol L(-1) cetyltrimethylammonium chloride (CTAC) was used as background electrolyte (BGE). After sample injection 600 mmol L(-1) acetate was separately injected into the capillary as the terminating ion for transient ITP. The LOD for nitrite and nitrate, obtained at a signal-to-noise ratio (S/N) of 3, were 15 and 7.0 microg L(-1) (as nitrogen), respectively. Relative standard deviations (RSD) of peak area for nitrite and nitrate were 7.3 and 0.8%, respectively, and the RSD of peak height were 5.7 and 1.2%, respectively, when the concentrations of nitrite and nitrate were 0.05 and 0.25 mg L(-1). The RSD of migration time for these ions was 0.2%. The proposed method was applied to the determination of nitrite and nitrate in seawater samples. The results for nitrite were nearly in agreement with those obtained by naphthylethylenediamine spectrophotometric analysis (SPA; correlation coefficient 0.9041).     

Automated DNA fragment collection by capillary array gel electrophoresis in search of differentially expressed genes

An automatic DNA fragment collector using capillary array gel electrophoresis has been developed. A sheath flow technique is used for not only detection but also collection of DNA fragments. In a sheath flow cell, the DNA fragments separated by 16 capillaries flow independently into corresponding sampling capillaries. The fraction collector consists of 16 sampling trays and each sampling tray is set beneath each end of the sampling capillaries to collect the flow-through DNA fragments. Certain DNA fragments are automatically sorted by controlling the movement of the sampling trays according to the signals from the system. The collector experimentally separated two mixtures of polymerase chain reaction (PCR) products: one prepared by using eight different sizes (base lengths from 161 to 562) of DNAs; and the other prepared by a differential display (DD) method with cDNA fragments. Collected DNA fragments are amplified by PCR and measured by electrophoresis. DNA fragments with base length differences of one (base lengths 363 and 364) were successfully separated. A separated DNA fragment from the DD sample was also successfully sequenced. In addition, differentially expressed DNA fragments were automatically sorted by comparative analysis, in which two similar cDNA fragment groups, labeled by two different fluorophores, respectively, were analyzed in the same gel-filled capillary. These results show that the automatic DNA fragment collector is useful for gene hunting in research fields such as drug discovery and DNA diagnostics.     

Information in asset pricing: a wave function approach

This paper introduces a quantum‐like wave function as an information wave function. We show how the option pricing partial differential equation can be re‐written when we account for such information wave function. We use two stochastic differential equations, one of which relates to Nelson's hypothesis of Universal Brownian motion. We also provide for two examples which further highlight the proposed theory.     

Quadrupole oscillations in a quantum degenerate Bose–Fermi mixture

We study the collective dynamics in a degenerate Bose–Fermi mixture of ¹⁷⁴Yb and ¹⁷³Yb atoms. We excite collective oscillations by a sudden reduction of the trapping confinement and observe low m=0 quadrupole oscillations of condensates in ¹⁷⁴Yb. First the oscillations in ¹⁷⁴Yb atoms alone are investigated, and they are well described by the time-dependent Gross–Pitaevskii equation in the Thomas–Fermi approximation. Using the same procedure the quadrupole oscillations are excited for a ¹⁷⁴Yb–¹⁷³Yb Bose–Fermi mixture. In comparing data taken with and without fermionic ¹⁷³Yb atoms, the oscillation frequency of the quadrupole mode in the condensate decreases with the presence of ¹⁷³Yb atoms.     

Pressure-induced intermetallic valence transition in BiNiO3

The valence state change of BiNiO3 perovskite under pressure has been investigated by a powder neutron diffraction study and electronic-state calculations. At ambient pressure, BiNiO3 has the unusual charge distribution Bi(3+)(0.5)Bi(5+)(0.5)Ni(2+)O3 with ordering of Bi(3+) and Bi(5+)charges on the A sites of a highly distorted perovskite structure. High-pressure neutron diffraction measurements and bond valence sum calculations show that the pressure-induced melting of the charge disproportionated state leads to a simultaneous charge transfer from Ni to Bi, so that the high-pressure phase is metallic Bi(3+)Ni(3+)O3. This unprecedented charge transfer between A and B site cations coupled to electronic instabilities at both sites leads to a variety of ground states, and it is predicted that a Ni-charge disproportionated state should also be observable.     

Inside Back Cover: Integrated Soft Porosity and Electrical Properties of Conductive-on-Insulating Metal-Organic Framework Nanocrystals (Angew. Chem. Int. Ed. 35/2023)

A one-stone, two-bird method to integrate the soft porosity and electrical properties of distinct metal–organic frameworks (MOFs) into a single material involves the design of conductive-on-insulating MOF (cMOF-on-iMOF) heterostructures that allow for direct electrical control. Herein, we report the synthesis of cMOF-on-iMOF heterostructures using a seeded layer-by-layer method, in which the sorptive iMOF core is combined with chemiresistive cMOF shells. The resulting cMOF-on-iMOF heterostructures exhibit enhanced selective sorption of CO₂ compared to the pristine iMOF (298 K, 1 bar, S from 15.4 of ZIF-7 to 43.2–152.8). This enhancement is attributed to the porous interface formed by the hybridization of both frameworks at the molecular level. Furthermore, owing to the flexible structure of the iMOF core, the cMOF-on-iMOF heterostructures with semiconductive soft porous interfaces demonstrated high flexibility in sensing and electrical “shape memory” toward acetone and CO₂. This behavior was observed through the guest-induced structural changes of the iMOF core, as revealed by the operando synchrotron grazing incidence wide-angle X-ray scattering measurements.