Electromagnetic KY production from the proton in a Regge-plus-resonance approach

A Regge-plus-resonance (RPR) description of the p(\gamma,K)Y and p(e,e'K)Y processes (Y = \Lambda, \Sigma^{0,+}) is presented. The proposed reaction amplitude consists of Regge-trajectory exchanges in the t channel, supplemented with a limited selection of s-channel resonance diagrams. The RPR framework contains a considerably smaller number of free parameters than a typical effective-Lagrangian model. Nevertheless, it provides an acceptable overall description of the photo- and electroproduction observables over an extensive photon energy range. It is shown that the electroproduction response functions and polarization observables are particularly useful for fine-tuning both the background and resonance parameters.Comment: 4 pages, 3 figures, Proceedings for IX International Conference on Hypernuclear and Strange Particle Physics (HYP2006), October 10-14 2006, Main

Electroproduction of kaons from the proton in a Regge-plus-resonance approach

We present a Regge-plus-resonance (RPR) description of the p(e,e'K^+)Y processes (Y=\Lambda,\Sigma^0) in the resonance region. The background contributions to the RPR amplitude are constrained by the high-energy p(\gamma, K^+)Y data. As a result, the number of free model parameters in the resonance region is considerably reduced compared to typical effective-Lagrangian approaches. We compare a selection of RPR model variants, originally constructed to describe $KY$ photoproduction, with the world electroproduction database. The electromagnetic form factors of the intermediate N^*s and $\Delta^*s are computed in the Bonn constituent-quark model. With this input, we find a reasonable description of the p(e,e'K^+)Y data without adding or readjusting any parameters. It is demonstrated that the electroproduction response functions are extremely useful for fine-tuning both the background and resonant contributions to the reaction dynamics.Comment: 14 pages, 7 figures; added discussion on double counting in the RPR model; accepted for publication in Phys. Lett.

Electromagnetic form factors of hyperons in a relativistic quark model

The relativistically covariant constituent quark model developed by the Bonn group is used to compute the EM form factors of strange baryons. We present form-factor results for the ground-state and some excited hyperons. The computed magnetic moments agree well with the experimental values and the magnetic form factors follow a dipole $Q^2$ dependence.Comment: 4 pages, 1 figure, Proceedings for NSTAR '04 conference in Grenoble, France, March 24-27, 2004 (World Scientific

Forward-angle K+ Lambda photoproduction in a Regge-plus-resonance approach

We present an effective-Lagrangian description for forward-angle K+ Lambda photoproduction from the proton, valid for photon lab energies from threshold up to 16 GeV. The high-energy part of the amplitude is modeled in terms of t-channel Regge-trajectory exchange. The sensitivity of the calculated observables to the Regge-trajectory phase is investigated in detail. The model is extended towards the resonance region by adding a number of s-channel resonances to the t-channel background. The proposed hybrid ``Regge-plus-resonance'' (RPR) approach allows one to exploit the p(gamma,K+)Lambda data in their entirety, resulting in stronger constraints on both the background and resonance couplings. The high-energy data can be used to fix the background contributions, leaving the resonance couplings as the sole free parameters in the resonance region. We compare various implementations of the RPR model, and explore to what extent the description of the data can be improved by introducing the ``new'' resonances D13(1900) and P11(1900). Despite its limited number of free parameters, the proposed RPR approach provides an efficient description of the p(gamma,K+)Lambda dynamics in and beyond the resonance region.Comment: 31 pages, 9 figures, accepted for publication in PRC. Section IIIB modified to include the most recent data; discussion of results and conclusions changed accordingl

Regge-plus-resonance treatment of the p(gamma,K^+)Sigma^0 and p(gamma,K^0)Sigma^+ reactions at forward kaon angles

An effective-Lagrangian framework for K Sigma photoproduction from the proton is presented. The proposed model is applicable at forward kaon angles and photon lab energies from threshold up to 16 GeV. The high-energy part of the p(gamma,K^+)Sigma^0 and p(gamma,K^0)Sigma^+ amplitudes is expressed in terms of Regge-trajectory exchange in the t channel. By supplementing this Regge background with a number of s-channel resonances, the model is extended towards the resonance region. The resulting ``Regge-plus-resonance'' (RPR) approach has the advantage that the background contributions involve only a few parameters, which can be largely constrained by the high-energy data. This work compares various implementations of the RPR model, and explores which resonance contributions are required to fit the data presently at hand. It is demonstrated that, through the inclusion of one K and two K* trajectories, the RPR framework provides an efficient and unified description of the K^+ Sigma^0 and K^0 Sigma^+ photoproduction channels over an extensive energy range.Comment: 33 pages, 15 figures; added discussion on new double-polarization data (Cx and Cz) in Section I

Electric and magnetic form factors of strange baryons

Predictions for the electromagnetic form factors of the Lambda$, Sigma and Xi hyperons are presented. The numerical calculations are performed within the framework of the fully relativistic constituent-quark model developed by the Bonn group. The computed magnetic moments compare favorably with the experimentally known values. Most magnetic form factors G_M(Q^2) can be parametrized in terms of a dipole with cutoff masses ranging from 0.79 to 1.14 GeV.Comment: 15 pages, 8 figures, 3 tables, submitted to Eur. Phys. J.

Comparison of methods to estimate the affected body surface area and the dosage of topical treatments in psoriasis and atopic dermatitis : the advantage of a picture‐based tool

Background: The accurate determination of the dosage of topical treatments is important given its repercussions on patient adherence and therapeutic efficacy. Up till now, the fingertip unit calculated by the rule of hands is considered the gold standard, although its use is associated with several drawbacks. Objective: To compare different methods to estimate the affected body surface area (BSA) and dosage of topical treatments in atopic dermatitis and psoriasis and investigate its reliability, user-friendliness and timing. Methods: In this study, we compared the reliability of three different methods: (i) the fingertip unit calculated by the 1% hand rule; (ii) a picture-based tool [termed Cutaneous Inflammatory Disease Extent Score (CIDES)]; and (iii) a digital drawing tool. Eleven observers scored 40 patients with psoriasis and eczema to assess the inter-rater and intrarater reliability. Timing was automatically recorded, and user-friendliness was investigated by a questionnaire. Results: An excellent intraclass correlation (ICC) was found for both inter-rater agreement and intrarater agreement for the picture-based tool (ICC = 0.92 and ICC = 0.96, respectively). The ICCs for drawing the area of involvement on a silhouette were 0.89 and 0.93, respectively. Finally, the rule of hands was associated with an increased inter-rater variability although an excellent intrarater agreement was found (ICC = 0.79 and 0.95, respectively). Automated calculation of the amount of topical treatment improved reliability, and CIDES was associated with the least variation. CIDES was considered the preferred method by all observers and was fast to perform (median: 30 s). Conclusion: A picture-based method offered the most advantages (in terms of reliability, speed and user-friendliness) to estimate the affected BSA and calculate the dosage of topical treatments

Quantitative proteomics analysis of the nuclear fraction of human CD4+ cells in the early phases of IL-4-induced Th2 differentiation

We used stable isotope labeling with 4-plex iTRAQ (isobaric tags for relative and absolute quantification) reagents and LC-MS/MS to investigate proteomic changes in the nucleus of activated human CD4(+) cells during the early stages of Th2 cell differentiation. The effects of IL-4 stimulation upon activated naïve CD4(+) cells were measured in the nuclear fractions from 6 and 24 h in three biological replicates, each using pooled cord blood samples derived from seven or more individuals. In these analyses, in the order of 800 proteins were detected with two or more peptides and quantified in three biological replicates. In addition to consistent differences observed with the nuclear localization/expression of established human Th2 and Th1 markers, there were changes that suggested the involvement of several proteins either only recently reported or otherwise not known in this context. These included SATB1 and among the novel changes detected and validated an IL-4-induced increase in the level of YB1. This unique data set from human cord blood CD4(+) T cells details an extensive list of protein determinations that compares with and complements previous data determined from the Jurkat cell nucleus.</p

Exclusive electroproduction of K+ Lambda and K+ Sigma^0 final states at Q^2 = 0.030-0.055 (GeV/c)^2

Cross section measurements of the exclusive p(e,e'K+)Lambda,Sigma^0 electroproduction reactions have been performed at the Mainz Microtron MAMI in the A1 spectrometer facility using for the first time the Kaos spectrometer for kaon detection. These processes were studied in a kinematical region not covered by any previous experiment. The nucleon was probed in its third resonance region with virtual photons of low four-momenta, Q^2= 0.030-0.055 (GeV/c)^2. The MAMI data indicate a smooth transition in Q^2 from photoproduction to electroproduction cross sections. Comparison with predictions of effective Lagrangian models based on the isobar approach reveal that strong longitudinal couplings of the virtual photon to the N* resonances can be excluded from these models.Comment: 16 pages, 7 figure