Semi-relativistic charge-current density operator

The charge-current density and two-photon operators consistent with a single-particle semi-relativistic Hamiltonian are derived within a suitable functional derivative formalism which preserves gauge invariance. An application to electron scattering is presented and results are compared with a fully relativistic case and the non-relativistic cases corrected through fourth order in M^{-1}.Comment: 20 pages, 3 postscript figures, typos correcte

Photocouplings of nucleon resonances with gluon and pion exchange currents

Photocouplings for the nucleon resonances most relevant to total photoabsorption are calculated in a constituent quark model including gluon and pion exchange. The sensitivity of the results to the different ingredients of the model is discussed.Comment: 23 pages including 9 tables, LaTe

Dynamics and optical absorption of electronic excitations under the influence of coloured noise

For a model dimer the influence of vibrational degrees of freedom on electronic excitations is described by a dichotomic Markov process with coloured noise. Within this model the energy transport between the two units of the dimer, especially the transition between coherent and incoherent motion is discussed. Furthermore the optical absorption line shape is evaluated for various values of the model parameters

Electroexcitation of the P33(1232), P11(1440), D13(1520), S11(1535) at Q^2=0.4 and 0.65(GeV/c)^2

Using two approaches: dispersion relations and isobar model, we have analyzed recent high precision CLAS data on cross sections of \pi^0, \pi^+, and \eta electroproduction on protons, and the longitudinally polarized electron beam asymmetry for p(\vec{e},e'p)\pi^0 and p(\vec{e},e'n)\pi^+. The contributions of the resonances P33(1232), P11(1440), D13(1520), S11(1535) to \pi electroproduction and S11(1535) to \eta electroproduction are found. The results obtained in the two approaches are in good agreement with each other. There is also good agreement between amplitudes of the \gamma^* N \to S11(1535) transition found in \pi and \eta electroproduction. For the first time accurate results are obtained for the longitudinal amplitudes of the P11(1440), D13(1520) and S11(1535) electroexcitation on protons.Comment: 9 pages, 9 figure

Quality Control Methods for Optimal BCR-ABL1 Clinical Testing in Human Whole Blood Samples

Reliable breakpoint cluster region (BCR)–Abelson (ABL) 1 measurement is essential for optimal management of chronic myelogenous leukemia. There is a need to optimize quality control, sensitivity, and reliability of methods used to measure a major molecular response and/or treatment failure. The effects of room temperature storage time, different primers, and RNA input in the reverse transcription (RT) reaction on BCR-ABL1 and β-glucuronidase (GUSB) cDNA yield were assessed in whole blood samples mixed with K562 cells. BCR-ABL1 was measured relative to GUSB to control for sample loading, and each gene was measured relative to known numbers of respective internal standard molecules to control for variation in quality and quantity of reagents, thermal cycler conditions, and presence of PCR inhibitors. Clinical sample and reference material measurements with this test were concordant with results reported by other laboratories. BCR-ABL1 per 103 GUSB values were significantly reduced (P = 0.004) after 48-hour storage. Gene-specific primers yielded more BCR-ABL1 cDNA than random hexamers at each RNA input. In addition, increasing RNA inhibited the RT reaction with random hexamers but not with gene-specific primers. Consequently, the yield of BCR-ABL1 was higher with gene-specific RT primers at all RNA inputs tested, increasing to as much as 158-fold. We conclude that optimal measurement of BCR-ABL1 per 103 GUSB in whole blood is obtained when gene-specific primers are used in RT and samples are analyzed within 24 hours after blood collection

Baryon Current Matrix Elements in a Light-Front Framework

Current matrix elements and observables for electro- and photo-excitation of baryons from the nucleon are studied in a light-front framework. Relativistic effects are estimated by comparison to a nonrelativistic model, where we use simple basis states to represent the baryon wavefunctions. Sizeable relativistic effects are found for certain transitions, for example, to radial excitations such as that conventionally used to describe to the Roper resonance. A systematic study shows that the violation of rotational covariance of the baryon transition matrix elements stemming from the use of one-body currents is generally small.Comment: 32 pages, LaTeX, 10 postscript figures, uses epsf.sty; figures uuencoded with uufiles (or available by request in .ps or hardcopy form

Photo- and Electroproduction of Eta Mesons

Eta photo- and electroproduction off the nucleon is investigated in an effective lagrangian approach that contains Born terms and both vector meson and nucleon resonance contributions. In particular, we review and develop the formalism for coincidence experiments with polarization degrees of freedom. The different response functions appearing in single and double polarization experiments have been studied. We will present calculations for structure functions and kinematical conditions that are most sensitive to details of the lagrangian, in particular with regard to contributions of nucleon resonances beyond the dominant $S_{11}$(1535) resonance.Comment: 24 pages RevTeX/LaTeX2.09, NFSS1, 13 figures (in separate file (tar,gzip and uue)), accepted for publication in Z. Phys.

Longitudinal Transitions Of Baryon Resonances in Constituent Quark Model

A longitudinal transition operator that satisfies the gauge invariance requirement is introduced in constituent quark model. The corresponding longitudinal transitions between the nucleon and baryon resonances are calculated. We show that the study of the longitudinal coupling plays an important role in understanding the structure of baryons.Comment: 13 pages with 5 figures in ps. file can be obtained from autho