Chiral Lagrangians and the transition amplitude for radiative muon capture

The transition operator for the radiative capture of mesons mu minus by protons is constructed starting from a chiral Lagrangian of the N-pi-rho-a_1-omega system obtained within the approach of hidden local symmetries. The transition operator is gauge invariant and satisfies exactly the CVC and PCAC equations.Comment: 11 pages, 1 figure, LaTex, feynman, submitted to Few-Body System

Gauge symmetric delta(1232) couplings and the radiative muon capture in hydrogen

Using the difference between the gauge symmetric and standard pi-N-delta couplings, a contact pi-pi-N-N term, quadratic in the pi-N-delta coupling, is explicitly constructed. Besides, a contribution from the delta excitation mechanism to the photon spectrum for the radiative muon capture in hydrogen is derived from the gauge symmetric pi-N-delta and gamma-N-delta couplings. It is shown for the photon spectrum, studied recently experimentally, that the new spectrum is for the photon momentums k > 60 MeV by 4-10 % smaller than the one obtained from standardly used couplings with the on-shell deltas.Comment: 9 pages, 3 figure

Novel instrument for automated pKa determination by internal standard capillary electrophoresis

The internal standard capillary electrophoresis method (IS-CE) has been implemented in a novel sequential injection−capillary electrophoresis instrument for the high-throughput determination of acidity constants (pKa) regardless of aqueous solubility, number of pKa values, or structure. This instrument comprises a buffer creation system that automatically mixes within a few seconds four reagents for in situ creation of the separation electrolyte with a pH range of 2−13, ionic strength of 10−100 mM and organic solvent content from 0% to 40%. Combined with 1.2 kV/cm and a short effective length (15 cm to the UV detector) fast 20 s electrophoretic separations can be obtained. The low standard deviation of the replicates and the low variation compared to reference values show that this system can accurately determine acidity constants of drugs by IS-CE. A single pKa can be determined in 2 min and a set of 20 measurements in half an hour, allowing rapid, simple, and flexible determination of pKa values of pharmaceutical targets

Quantum Mechanics of Proca Fields

We construct the most general physically admissible positive-definite inner product on the space of Proca fields. Up to a trivial scaling this defines a five-parameter family of Lorentz invariant inner products that we use to construct a genuine Hilbert space for the quantum mechanics of Proca fields. If we identify the generator of time-translations with the Hamiltonian, we obtain a unitary quantum system that describes first-quantized Proca fields and does not involve the conventional restriction to the positive-frequency fields. We provide a rather comprehensive analysis of this system. In particular, we examine the conserved current density responsible for the conservation of the probabilities, explore the global gauge symmetry underlying the conservation of the probabilities, obtain a probability current density, construct position, momentum, helicity, spin, and angular momentum operators, and determine the localized Proca fields. We also compute the generalized parity (\cP), generalized time-reversal (\cT), and generalized charge or chirality (\cC) operators for this system and offer a physical interpretation for its \cP\cT-, \cC-, and \cC\cP\cT-symmetries.Comment: Published version, typos fixed, a change in symbol, 1 fi

Transient field-resolved reflectometry at 50-100 THz

Transient field-resolved spectroscopy enables studies of ultrafast dynamics in molecules, nanostructures, or solids with sub-cycle resolution, but previous work has so far concentrated on extracting the dielectric response at frequencies below 50 THz. Here, we implemented transient field-resolved reflectometry at 50-100 THz(3-6 mu m) with MHz repetition rate employing 800 nm few-cycle excitation pulses that provide sub-10 fs temporal resolution. The capabilities of the technique are demonstrated in studies of ultrafast photorefractive changes in semiconductors Ge and GaAs, where the high frequency range permits to explore the resonance-free Drude response. The extended frequency range in transient field-resolved spectroscopy can further enable studies with so far inaccessible transitions, including intramolecular vibrations in a large range of systems. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License

STUDIES ON KINETICS OF INHIBITION AND BINDING OF XIIIa BY A CROSS-REACTING ANTIFIBRINOGEN ANTIBODY*

Coagulation factor XIIIa, plasma transglutaminase(endo-g-glutamine:e-lysine transferase EC 2.3.2.13) cata-lyzes isopeptide bond formation between glutamine andlysine residues and rapidly cross-links fibrin clots. Amonoclonal antibody (5A2) directed to a fibrinogen Aa-chain segment 529 –539 was previously observed fromanalysis of end-stage plasma clots to block fibrina-chaincross-linking. This prompted the study of its effect onnonfibrinogen substrates, with the prospect that 5A2was inhibiting XIIIa directly. It inhibited XIIIa-cata-lyzed incorporation of the amine donor substrate dan-sylcadaverine into the glutamine acceptor dimethylca-sein in an uncompetitive manner with respect todimethylcasein utilization and competitively with re-spect to dansylcadaverine. Uncompetitive inhibitionwas also observed with the synthetic glutamine sub-strate, LGPGQSKVIG. Theoretically, uncompetitive in-hibition arises from preferential interaction of the in-hibitor with the enzyme-substrate complex but is alsofound to inhibitg-chain cross-linking. The conjunctionof the uncompetitive and competitive modes of inhibi-tion indicates in theory that this bireactant system in-volves an ordered reaction in which docking of the glu-tamine substrate precedes the amine exchange. Thepresence of substrate enhanced binding of 5A2 to XIIIa,an interaction deemed to occur through a C-terminalsegment of the XIIIa A-chain (643– 658,GSDMTVTVQFT-NPLKE), 55% of which comprises sequences occurring inthe fibrinogen epitope Aa-(529 –540) (GSESGIFTNTKE).Removal of the C-terminal domain from XIIIa abolishesthe inhibitory effect of 5A2 on activity. Crystallographicstudies on recombinant XIIIa place the segment 643– 658in the region of the groove through which glutaminesubstrates access the active site and have predicted thatfor catalysis, a conformational change may accompanyglutamine-substrate binding. The uncompetitive inhibi-tion and the substrate-dependent binding of 5A2 pro-vide evidence for the conformational change