No description available.

No description available.

This thesis contains two major components of research: numerical simulation of optical-parametric amplification cross correlation of Frequency-Resolved Optical Gating (OPA-XFROG) and numerical simulation of GRENOUILLE and its related issues. Recently, an extremely sensitive technique--OPA-XFROG has been developed. A short pump pulse serves as the gate by parametrically amplifying a short segment of the signal pulse in a nonlinear crystal. High optical parametric gain makes possible the complete measurement of ultraweak, ultrashort light pulses. Unlike interferometric methods, it does not carry prohibitively restrictive requirements, such as perfect mode-matching, perfect spatial coherence, highly stable absolute phase, and a same-spectrum reference pulse. We simulate the OPA-XFROG technique and show that by a proper choice of the nonlinear crystal and the noncollinear mixing geometry it is possible to match the group velocities of the pump, signal, and idler pulses, which permits the use of relatively thick crystals to achieve high gain without measurement distortion. Gain bandwidths of ~100 nm are possible, limited by group velocity dispersion. In the second part of the thesis, we numerically simulate the performance of the ultrasimple ultrashort laser pulse measurement device- GRENOUILLE. While simple in practice, GRENOUILLE has many theoretical subtleties because it involves the second-harmonic generation of relatively tightly focused and broadband pulses. In addition, these processes occur in a thick crystal, in which the phase-matching bandwidth is deliberately made narrow compared to the pulse bandwidth. We developed a model that include all sum-frequency-generation processes, both collinear and noncollinear. We also include dispersion using the Sellmeier equation for the crystal BBO. Working in the frequency domain, we compute the GRENOUILLE trace for practical-and impractical-examples and show that accurate measurements are easily obtained for properly designed devices. For pulses far outside a GRENOUILLE's operating range (on the long side), we numerically deconvolve the GRENOUILLE trace with the response function of GRENOUILLE to improve its spectral resolution. In the last part of the thesis, we simulate the second harmonic generation with tightly focused beams by use of lens. Thus, we are able to explain the `weird' focusing effect that has been a `puzzles' for us in the GRENOUILLE measurement.

Rhei Rhizoma, also named as rhubarb or Da Huang, has been used widely in oriental traditional medicine in treating constipation and edema. However, though much affection has been paid to the make of components on pharmaceutical mechanisms, few studies have been conducted to reveal chemical and physical mechanism of these effects. Studies have shown that diarrhea causes imbalance of chloride and sodium ion movements via epithelium, we wondered if similar mechanism may apply to Rhei Rhizoma, a herbal drug which has been used to treat constipation in oriental medicine for thousands of years. The measurement of short-circuit current (Isc) has been used widely to estimate the ion transportation between mucosal and serosal side of epithelium. In this study, we used Ussing chamber technique to examine the alternation in membrane potential and short-circuit currents. The result shows, at default, the Isc of frog skin we used was at 59.23¡Ó5.58£gA/cm², and the conductance was at 1.11¡Ó0.50£gA/cm²¡EmV. The lnjection of 1ml RRE to mucosal side of the frog skin leaded to a 90% elevation of the Isc. Followed by the application of Amiloride (sodium channel inhibitor) and Chlorothiazide (chloride channel inhibitor) to mucosal side of the epithelial skin, the observed Isc were then reduced 136% and 33% respectively. If RRE were applied after the adding of Amiloride or Chlorothiazide to the frog skin, then the Isc of the skin elevated only 24% and 70% respectively. These results show that Rhei Rhizoma Extract (RRE) significantly increases Isc upon application to the mucosal side of the skin epithelium. Amiloride and Chlorothiazide will both inhibit the Isc induced by RRE, indicating activation of chloride channel and Amiloride-sensitive sodium channel of the epithelial tissue by RRE. After the regular Ringer solution used in the preparation was replaced by Na-free and Cl-free Ringer solution, the inhibition of Isc by RRE application could still be observed although the inhibition was trivia. These results indicate that RRE acts dominantly on mucosa side of the epithelium and can be used to enhance sodium transport and to stimulate the secretion of Cl- in the epithelium.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

No description available.

Roundup is a commonly used pesticide applied to agriculture and forest habitats. In Canada and parts of the North Eastern United States, these areas are generally optimal for amphibians due to the presence of small, ephemeral water bodies. While Roundup has been shown to have no adverse effects on a number of species, amphibians are one of the few groups who show high sensitivity to Roundup. My research aims to determine how an acute sub-lethal dose of Roundup affects several different facets of larvae development in wood frogs (Lithobates sylvaticus). In Chapter 2 I examined the effect of Roundup on amphibian development. Groups of tadpoles were treated with Roundup (0.5 mg a.e./L) for four days at three different times in their development (Gosner stage 26, 31-32 and 37-38), while a control group was maintained in similar conditions without Roundup. Pictures were taken every four days until tadpoles reached metamorphosis. Changes in development, body area or length were assessed, along with metamorphic endpoints, such as timing of metamorphosis and weight. Although there was no differential effect of Roundup on tadpole growth or weight, there was a slight, non-ecologically relevant, delay in development in tadpoles treated with Roundup at stage 26. The delay was not detectable in the second half of the experiment, indicating that compensatory mechanisms allowed those individuals to recover. Neither time to metamorphosis or weight at metamorphosis were affected by an environmentally relevant exposure to Roundup. In Chapter 3 I focused on the effect of Roundup on crucial behaviours related to the ability of larval amphibians to detect and avoid predation threats. I demonstrated that being exposed to Roundup for one hour eliminated the response of larval wood frogs to cues from injured conspecifics (i.e. cues known to elicit dramatic anti-predator responses in a wide variety of aquatic species). Tadpoles that were maintained in clean water and exposed to a combination of injured conspecific cues and Roundup, did not exhibit a decrease in movement, when compared to control tadpoles. This result indicates that Roundup deactivates the alarm function of the injured conspecific cues. However, it is possible that both the cues and the animal would be affected by Roundup. In Chapter 3 I also demonstrated that tadpoles that were exposed to Roundup as embryos had reduced basal movement rates. The results of this thesis illustrate that an environmentally relevant concentration of Roundup (0.5 mg a.e./L), does not negatively affect the development of tadpoles. The studies outlined in this thesis suggest that at this exposure concentration, behaviour acts as a more sensitive endpoint, than more traditional morphologic endpoints.

No description available.

The movements of Western Chorus Frogs (Pseudacris, triseriata triseriata) were studied from March, 1970, to March, 1971, at the Robert H. and Esther L. Cooper Woodland Area near Muncie, Delaware County, Indiana. The objectives of the study were to determine: (1) the time and rate of dispersal from the breeding pool; (2) the day-to-day movements, including the time and minimal distance traveled; (3) the preferred cover or microhabitat; and (4) the site of hibernation.Seventy-three Chorus Frogs were tagged with approximately 50 μc Co60 and toe-clipped, and each was released at its capture site. The frogs were then sought at intervals by surveying the area with a portable survey meter equipped with a scintillation probe. The location of each recovered specimen and a description of the recapture site was recorded.Sixty-two individual specimens were recaptured at least one time. The number of recaptures for each specimen was variable, and the maximum number of recaptures for a single specimen was 26 times. In all, 324 recoveries of tagged specimens were made. The tagged specimens graduallybecame lost to the investigator, and the last specimen was found on August 4. The longest period of contact for an individual frog was 134 days.Some Chorus Frogs began leaving the breeding pools soon after the first eggs were observed on April 1. The exodus appeared to be gradual as a few (one to eight) additional tagged specimens were found out of the pools throughout April and early May. Four of these specimens returned at least once to their original pool and seventeen frogs entered a second pool.From a single attempt to monitor the overnight activities of these frogs, it appears that they remain quiescent during the daylight hours and become active between dusk and dawn.The minimal distances traveled by the tagged, specimens during the study are more a function of the length of the contact period and the number of recaptures than of the activity of the frogs. The average rate of movement for all of the specimens over the entire study period was 11.3 feet/day. However, the fastest observed rate of movement for a single specimen between two recapture sites was 138 feet/day. The greatest straight distance any specimen was found from its original pool was 700 feet. Most recaptures were within 500 feet of the pools where the specimens were tagged.In 213 (91.3%) of the 234 recaptures made daylight hours after the frogs left the breeding pools,the frogs were hidden in the leaf litter of the woods or dead grasses of the grassland. In the remaining recaptures the frogs were hidden under small objects. The frogs seemed to prefer moist rather than dry or wet cover, but this is possibly more a reflection of conditions at the time of the study than a preference on the part of the frogs.The gradual disappearance of the tagged frogs from the study area, the woodland situation of the breeding pools, and the concentration of searching efforts in the vicinity of the pools prevented the determination of the preferred habitat type (woodland or grassland). Also, because of the loss of all tagged specimens by the end of summer, hibernating sites were not located.There is evidence that the gradual disappearance of tagged specimens may be explained by predation or movement of the frogs underground or out of the study area. Other frogs lost their cobalt wires and could no longer be located.