Electrophoretic separation of human kidney cells at zero gravity

Electrophoretic isolation of cells results in a loss of resolution power caused by the sedimentation of the cells in the media. The results of an experiment to extract urokinase from human embryos during the Apollo Soyuz mission are presented and discussed

THE PROMISES AND REALITIES OF EVIDENCE-BASED PRACTICES: PERCEPTIONS FROM ASSESSMENT PERSONNEL

Assessment personnel are those individuals who work in the capacity of evaluation of students with disabilities, including, but not limited to, educational diagnosticians, educational examiners, psychometrists, and instructional specialists. These professionals are responsible for identifying strengths and weaknesses and for providing teachers with evidence-based recommendations that can be implemented in the classroom to improve performance of students with learning deficits. This qualitative study examines 19 educational diagnosticians’ perceptions related to the barriers and supports that impacted their ability to provide evidence-based recommendations for students who are learning disabled. Three categories of barriers to issuing successful evidence-based recommendations emerged as a result of the study: Knowledge of Evidence- Based Interventions, Time to Complete Assessments, and Support from Administrators and Teachers

Odd C-P contributions to diffractive processes

We investigate contributions to diffractive scattering, which are odd under C- and P-parity. Comparison of p-$\bar p$ and p-p scattering indicates that these odderon contributions are very small and we show how a diquark clustering in the proton can explain this effect. A good probe for the odderon exchange is the photo- and electroproduction of pseudo-scalar mesons. We concentrate on the pi^0 and show that the quasi elastic pi^0-production is again strongly suppressed for a diquark structure of the proton whereas the cross sections for diffractive proton dissociation are larger by orders of magnitude and rather independent of the proton structure.Comment: 18 pages, LaTex2e, graphicx package, 14 eps figures include

Gamma*Gamma* Reactions at High Energies

The total hadronic gamma*gamma* cross sections at high energy are calculated as a function of energy and photon virtuality in a model combining Regge exchange, the quark box diagram (a fixed pole in Regge language) and soft and hard pomeron exchanges evaluated in the context of dipole-dipole scattering. Good agreement is obtained with the data for the real gamma-gamma cross section and for the real photon structure function. However the model prediction for the gamma* gamma* cross section is too small. This is attributed to an incorrect extrapolation of the Q^2 dependence of the hard pomeron adopted here. Parametrising it independently shows that the hard part of the cross section can be well represented by a simple Regge pole with intercept ~ 1.3.Comment: 21 pages, 5 figure

The Missing Odderon

In contrast to theoretical expectations, experimental results at sqrt(s)=200 GeV for the reaction gamma p --> pi0 X show no evidence for odderon exchange. The upper limit on the cross section is an order of magnitude smaller than the theoretical estimate. It is argued that chiral symmetry leads to a large suppression, taking the thoeretical estimates well below the data. Two additional arguments are presented which may decrease the theoretical estimate further. The calculations are more sensitive to the assumptions made in evaluating the hadronic scattering amplitude than in the processes considered previously and lattice gauge calculations indicate that the odderon intercept may be appreciably lower than usually assumed. These two latter effects are particularly relevant for the reactions gamma p --> f2(1270)X and gamma p --> a2(1320)X for which the data upper limits are also below the theoretical predictions, but not so dramatically as for gamma p --> pi0 X.Comment: 12 pages, 3 figure

Diffractive color-dipole nucleon scattering

We determine the diffractive scattering amplitude of a color-dipole on a nucleon using a non-perturbative model of QCD which contains only parameters taken from low-energy physics. This allows to relate specific features of the confinement mechanisms with diffractive electro-production processes and structure functions. The agreement with phenomenological data is satisfactory.Comment: 7 pages, 5 eps-figures, uses eps