Volume 5 Issue 4 March 2007

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https://doi.org/10.33697/ajur.2007.001

Raison d’etre: American Journal of Undergraduate Research

https://doi.org/10.33697/ajur.2007.002

Author(s):

C. C. Chancey

Affiliation:

American Journal of Undergraduate Research, University of Northern Iowa, Cedar Falls, Iowa 50614-0150 USA


Particle Beam Waist Location in Plasma Wakefield Acceleration: Introduction and Background

https://doi.org/10.33697/ajur.2007.003

Author(s):

Adrian Down

Affiliation:

Department of Physics, University of California, Berkeley, California 94720-7300 USA

ABSTRACT:

The role of beam waist location in interactions between a plasma and a particle beam is not yet fully understood. Nonlinear effects with the plasma make an analysis of such interactions difficult. Five simulations are presented in this report, with the waist location of a beam of ultra-relativistic electrons propagating through one meter of self-ionized lithium plasma. The simulation parameters are chosen to model the recent experiment 167 at the Stanford Linear Accelerator, relevant to the design of future plasma wakefield accelerating afterburners. It is found that beams focused near the point of entry into the plasma propagate further into the plasma and accelerate witness particles to a greater maximum energy before disintegrating. These results could indicate that ion channel formation is dependent on the drive beam waist location and that the plasma accelerating medium can have an observable effect on the focusing of the drive beam.


Impaired Spatial Learning and Reduced MK-801 Associated Behavioral Deficits in Rodents Following Early Postnatal Exposure to Low-level Lead

https://doi.org/10.33697/ajur.2007.004

Author(s):

Jing Guo

Affiliation:

Department of Life Sciences, University of Toronto, 1265 Military Trail, Toronto, Ontario M1C 1A4 CANADA

ABSTRACT:

The current research aimed to investigate the effects of early postnatal exposure to low-level lead on the spatial learning of Long-Evans Hooded rats tested in the Morris water maze. To explore possible neurotoxic actions of lead on the N-methyl-D-aspartate (NMDA) receptors, the non-competitive NMDA receptor antagonist (+)-5-methyl-10,11-dihydroxy-5h- dibenzo(a,d)cyclohepten-5,10-imine (MK-801) was used. Two-day-old pups were randomly assigned to 0.1% lead carbonate diet or control diet and weaned onto regular food on postnatal day (PND) 23. Spatial acquisition was assessed from PND 24 to PND 27. Thirty minutes prior to behavioral testing, rats received an intraperitoneal (i.p.) injection of 0.1% MK-801 or saline. In the saline treatment group, Pb-exposed rats exhibited significantly longer overall mean escape latencies than those on the control diet, replicating the impaired spatial learning of Pb-exposed animals tested at a young age. Although MK-801 injection severely impaired animals’ water maze performance regardless of diet, it affected the performance of Pb-exposed animals to a lesser extent than animals on the control diet. No main effects of diet and drug were found for probe trials on PND 28 and PND 36, but interestingly, lead diet/MK-801 animals performed significantly better than control diet/MK-801 animals during the first probe trial. Unfortunately, MK-801 not only caused animals to display higher activity levels in the activity box, but also significantly impaired animals’ performance in the cued trial, suggesting non-specific sensorimotor deficits induced by MK-801 treatment might be responsible for animals’ poor performance. However, a significant drug by diet interaction in the escape latencies and the significantly better probe trial performance of Pb-exposed animals within the MK-801 treatment group imply that lead exposure actually alleviated behavioral deficits induced by MK-801 injection, providing evidence for a possible interaction between lead and MK-801 at the molecular level.


Electrochemical Behavior of Hexacyano Iron (III/II) in Frozen Aqueous Electrolytes

https://doi.org/10.33697/ajur.2007.005

Author(s):

Leslie S. Books, Cherie Harris, and Kasem K. Kasem

Affiliation:

Department of Natural, Information and Mathematical Sciences, Indiana University Kokomo, Kokomo, Indiana 46904-9003 USA

ABSTRACT:

Electrochemical studies in phases that have been solidified by freezing were carried out. A 5 mM [Fe(CN)6]-3/-4 [Hexacyano Iron(III/II)] in either aqueous 0.1M KCl or in Agar gel containing 0.1 M KCl Agar were the two phase systems subject to this study. Formation of pristine ice crystals (salt free) in pure aqueous electrolyte explains smaller ΔEp recorded in frozen agar than that in absence of Agar. Furthermore, greater capacitive current was observed in frozen agar compared to that in frozen aqueous electrolyte. The results also indicates that while a liquid-like layer (≈ 4 time the value of √2Dt) is formed in frozen aqueous electrolyte at electrode/ electrolyte interface, opposite observation were recorded in frozen agar electrolyte. This evident from the thin-layer electrochemical outcome generated in frozen electrolyte, and low diffusion coefficient determined under these conditions. Deviations from the liquid state behavior at room temperature were explained on the assumption that freezing created conditions similar to those caused by application of high pressure on liquid electrochemical systems. Some kinetic data related to these systems were determined and recorded.