Consequences of the Factorization Hypothesis in pbar p, pp, gamma p and gamma gamma Collisions

Using an eikonal analysis, we examine the validity of the factorization theorem for nucleon-nucleon, gamma p and gamma gamma collisions. As an example, using the additive quark model and meson vector dominance, we directly show that for all energies and values of the eikonal, that the factorization theorem sigma_{nn}/sigma_{gamma p} = sigma_{gamma p}/sigma_{gamma gamma} holds. We can also compute the survival probability of large rapidity gaps in high energy pbar p and pp collisions. We show that the survival probabilities are identical (at the same energy) for gamma p and gamma gamma collisions, as well as for nucleon-nucleon collisions. We further show that neither the factorization theorem nor the reaction-independence of the survival probabilities depends on the assumption of an additive quark model, but, more generally, depends on the opacity of the eikonal being independent of whether the reaction is n-n, gamma p or gamma gamma.Comment: 8 pages, Revtex, no figures. Expanded discussion, minor correction

Adaptation kinetics in bacterial chemotaxis

Cells of Escherichia coli, tethered to glass by a single flagellum, were subjected to constant flow of a medium containing the attractant alpha-methyl-DL-aspartate. The concentration of this chemical was varied with a programmable mixing apparatus over a range spanning the dissociation constant of the chemoreceptor at rates comparable to those experienced by cells swimming in spatial gradients. When an exponentially increasing ramp was turned on (a ramp that increases the chemoreceptor occupancy linearly), the rotational bias of the cells (the fraction of time spent spinning counterclockwise) changed rapidly to a higher stable level, which persisted for the duration of the ramp. The change in bias increased with ramp rate, i.e., with the time rate of change of chemoreceptor occupancy. This behavior can be accounted for by a model for adaptation involving proportional control, in which the flagellar motors respond to an error signal proportional to the difference between the current occupancy and the occupancy averaged over the recent past. Distributions of clockwise and counterclockwise rotation intervals were found to be exponential. This result cannot be explained by a response regular model in which transitions between rotational states are generated by threshold crossings of a regular subject to statistical fluctuation; this mechanism generates distributions with far too many long events. However, the data can be fit by a model in which transitions between rotational states are governed by first-order rate constants. The error signal acts as a bias regulator, controlling the values of these constants

Coordination of flagella on filamentous cells of Escherichia coli

Video techniques were used to study the coordination of different flagella on single filamentous cells of Escherichia coli. Filamentous, nonseptate cells were produced by introducing a cell division mutation into a strain that was polyhook but otherwise wild type for chemotaxis. Markers for its flagellar motors (ordinary polyhook cells that had been fixed with glutaraldehyde) were attached with antihook antibodies. The markers were driven alternately clockwise and counterclockwise, at angular velocities comparable to those observed when wild-type cells are tethered to glass. The directions of rotation of different markers on the same cell were not correlated; reversals of the flagellar motors occurred asynchronously. The bias of the motors (the fraction of time spent spinning counterclockwise) changed with time. Variations in bias were correlated, provided that the motors were within a few micrometers of one another. Thus, although the directions of rotation of flagellar motors are not controlled by a common intracellular signal, their biases are. This signal appears to have a limited range

The effects of a reading intervention with the spot-and-dot syllabication strategy in conjunction with the vowel pattern chart

This study investigated the effects of a 14-week reading intervention, which included using the Spot-and-Dot Syllabication Strategy (Cheyney and Cohen, 1999) in conjunction with an adjusted Vowel Pattern Chart (Cheyney and Cohen, 1999) with one student who attended a mid-western metropolitan literacy center. The student received instruction that allowed him to segment multisyllabic words through awareness of the vowel/syllable patterns. Pre- and posttest assessments were administered with the Reading Dr. Seuss Words!!! (Santa & Hoien, 1999) and the Power Pattern Placement Survey (Cheyney and Cohen, 1999). Posttest results showed he had significant improvement of p = 03 on Reading Dr. Seuss Words!!! (1999) and p = 01 on the Power Pattern Placement Survey (1999). These results show that the use of this intervention strategy helped this struggling reader recognize vowel/syllable patterns. Further research is needed to determine the effects of this intervention with small intervention groups and/or in a regular classroom environment

Determining the optimal exercise intensity level for adjunctive treatment of major depressive disorder

A clinical decision report using: Helgadóttir B, Hallgren M, Ekblom Ö, Forsell Y. Training fast or slow? Exercise for depression: A randomized controlled trial. Prev Med. 2016;91:123-131. https://doi.org/10.1016/j.ypmed.2016.08.011 for a patient seeking an exercise regimen to help with depressive symptoms

The life histories of platynothrus peltifer (Koch 1839) and damaeus clavipes (Hermann 1804)(Acarina:cryptostigmata) in soils of Pennine moorland

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The Comparative Effectiveness of Computer-Mediated Communication Supplemented Satellite Distance Education and Traditional Face-To-Face Education

Satellite distance education delivery typically has one main drawback -- limited student-to-student and student-to-instructor interaction. Telecommunications technology, more specifically computer-mediated communication (CMC), has made it possible for educational institutions to overcome this drawback. This research examines the comparative effectiveness of CMC supplemented satellite distance education delivery and traditional face-to-face education delivery. The three dependent variables that were measured to compare the two educational delivery methods included: performance, interaction, and attitude outcomes. Pre- and post-course instruments were administered in a non-equivalent quasi-experimental design to students enrolled in an Air Force Institute of Technology\u27s School of Systems and Logistics software engineering Professional Continuing Education course. Descriptive statistics and parametric tests were used to analyze these results (at alpha = .05). The parametric tests indicated that the distance education group and traditional group differed significantly on two demographic areas, educational level and self-rated computer proficiency, and on the pretest, final exam and overall course grades. The distance education and traditional group were not significantly different on pre-course attitudes towards computers, midterm exam grades, and post- course instructor and course ratings