We consider modified versions of a cell population model for periodic chemotherapy treatment of tumors. These models contain both proliferating and quiescent cells, and treats the transitions between the two types of cells. Our models are defined by replacing the loss term function, μ(t, c), in Webb's model by a constant. This corresponds to having a constant infusion of the drug rather than having a periodic chemotherapy treatment. We compare our results with those of Webb who shows that shorter periods of treatment are advantageous.

This thesis focuses on two of the major challenges of carbon nanotube (CNT) research: understanding the growth mechanism of nanotubes by chemical vapour deposition (CVD) and the positioning of nanotubes on surfaces. The mechanism of growth of single–walled nanotubes (SWNTs) has been studied in two ways. Firstly, a novel iron nanoparticle catalyst for the production of single–walled nanotubes was developed. CVD conditions were established that produced high quality tubes. These optimised CVD conditions were then used as the basis of several comparative CVD experiments showing that the quality of nanotubes and the yield of carbon depended on the availability of carbon to react. The availability could be controlled by the varying concentration of methane in the gas phase or the residence time of the methane over the catalyst. Evidence is presented that the diameters of the tubes produced were affected by the availability of methane. A second mechanistic investigation was carried out to study the validity of the previously proposed ring addition mechanism for the growth of carbon nanotubes from camphor. In this mechanism, the formation of tubes is thought to occur through the addition of preformed carbon rings: so it would be expected that there would be a relationship between the molecular structure of the precursor and the resulting SWNTs. To explore this relationship, comparative CVDs were carried out to produce SWNTs with several different cyclic and acyclic compounds similar in structure to camphor. The vapour pressure and the chemical stability of the precursor were found to be important to the formation of nanotubes, while the compound’s structure was not related to the quality of tubes produced. The lack of a relationship between the structure of the precursor and the production of SWNTs suggests that preformed rings are not vital to the production of SWNTs. Differences in the growth of SWNT from benzene and methane were related to the stability of each compound. In particular, differences in the distributions of the diameters of the tubes formed from methane and benzene have been observed. These differences have been explained in terms of the relative kinetic stabilities of these molecules, and in terms of a competition between end–cap and sidewall growth. Positioning of nanotubes on surfaces has been explored using two approaches. In the first approach, commercially obtained SWNTs were functionalized by a sulfur plasma so that the products would form bonds with gold surfaces. The nanotubes were found to selectively deposit themselves onto gold surfaces from ethanolic dispersions of the functionalized samples. This selective deposition of the nanotubes allowed the production of prototype carbon nanotube field–effect transistors with higher device yields than were obtained with unfunctionalized tubes. In a second approach to positioning of carbon nanotubes, the growth of tubes on surfaces by CVD was explored. Iron nitrate and different magnesium compounds were dip–coated onto SiO2 surfaces so that MgO supported–Fe catalysts would be formed by calcination. SWNTs were grown on the surfaces by CVD. Surface area measurements of the equivalent powdered catalysts showed that a high surface area was vital to produce dense growth of high quality SWNTs. The morphology of the surface was also found to play a key role in the growth of the tubes. Patterned growth of carbon nanotubes was accomplished using soft lithography techniques to control the localization of catalyst deposition onto a surface. A long calcination step (10 h, 950 °C) before CVD, was found to improve the quality of nanotubes grown. Catalysts that had been calcined for 10 hours were also found to produce smaller diameter nanotubes than uncalcined samples. The formation of smaller diameter tubes was explained in terms of the formation of MgFe2O4 alloys, consistent with results reported previously in the literature. In addition, Raman spectroscopy of the calcined catalysts with 3% w/w loadings of Fe was used to confirm directly the presence of MgFe2O4.

The application of auto focus, using an optical beam deflection technique, to existing live cell interferometry measurements was developed and examined. The benefit to relevant experiments, currently being performed, is shown as well as its performance across various magnifications. Enough information is given so that the system can be reproduced to fit any end users needs.

Nanopore-based resistive pulse sensing represents an important class of single-molecule measurements. It provides information about many molecules of interest (i.e. DNA, proteins, peptides, clusters, polymers, etc.) without the need for labeling. Two experiments that are especially well suited for studying with nanopore sensors are DNA sequencing and DNA-protein force measurements. This thesis will describe progress that has been made in both areas. DNA sequencing has become an active area of research for stochastic single-molecule sensing, with many researchers striving for the ultimate goal of single-molecule de novo DNA sequencing. One intriguing method towards that goal involves the use of a DNA exonuclease or polymerase enzyme, which when attached close to the mouth of a pore, leads to cleavage of individual DNA nucleotide bases for loading into the pore for sensing. Though this method seems promising, the end goal has been elusive because the nucleotide motion is dominated by diffusion over the relevant length scales. This limits the likelihood of the cleaved nucleotide entering the pore to be characterized. The first part of this thesis will describe a method for addressing this problem, where it is shown that increasing the nucleotide capture probability can be achieved by lowering the bulk diffusion coefficient relative to the pore diffusion coefficient. The second part of this thesis will describe the design and implementation of a new type of sensor that combines a biological nanopore experimental apparatus with optical tweezers. The goal of this apparatus is to develop a means to independently measure the force on a charged molecule inside of the pore. The setup will be thoroughly described, and preliminary results showing that it is possible to optically trap a micron sized bead within a few microns of an isolated biological nanopore while simultaneously making current measurements through that pore will be presented. This will enable force measurements on DNA molecules tethered to the bead, which opens the door for the study of molecular force interactions between DNA and biological nanopores, DNA-bound protein interactions that cause diseased states, and controlled translocation of DNA through biological nanopores.

L'expérience de diffusion Compton profondément virtuelle sur le proton (DVCS) du Hall A a pris le faisceau d'électrons de 5,757 GeV polarisé du Jefferson Laboratory de septembre à décembre 2004. Elle a utilisé un spectromètre à haute résolution associé à un calorimètre électromagnétique en fluorure de plomb et à un détecteur de protons tous deux spécialement conçus pour fonctionner à une haute luminosité de 10 puissance 37cm puissance-2s puissance-1 permettant de signer les évènements exclusifs sans ambiguïté. Trois mesures ont été effectuées à x indice bjorken=0.32 constant pour 3 valeurs de Q puissance2 : 1.5 GeV carré, 1.91GeV carré, 2.32 GeV carré. Une électronique dédiée a aussi été mise en place permettant de résoudre l'empilement plus tard à l'analyse ainsi qu'un module de coïncidence électron-photon. Les données de la cinématique à 2.32 GeV carré et s=5.6 GeV carré ont permis d'extraire un résultat préliminaire pour la section efficace d'électrproduction exclusive de pi0 sur le proton

Photorefraction is a technique that has been used in the past two decades for pediatric vision screening. The technique uses a digital or photographic camera to capture the examinee‟s retinal reflex from a light source that is located near the camera‟s lens. It has the advantages of being objective, binocular and low cost, which make it a good candidate for pediatric screening when compared to other methods. Although many children have been screened using this technique in the U.S., its sensitivity and other disadvantages make it unacceptable for continued use. The Adaptive Photorefraction system (APS) was developed at the Center for Laser Applications (CLA) at the University of Tennessee Space Institute (UTSI) to correct the problems in the existing PS devices. APS was designed to determine quantitatively binocular refractive errors and strabismus and to accomplish these tasks objectively, without the need of medical professionals, and it is capable of performing these objectives and reporting the digitally recorded results within one- to-two minutes. In this dissertation, two APS prototypes were constructed, and measurements were performed using both an artificial eye and human subjects. Binocular measurements of refractive error were determined, and the effects of the variation of pupil-size and gaze angle were determined. After initial corrections for ocular scattering effects, measurement of the binocular refractive error of forty human subjects was achieved, and in the myopic region with uncertainty of the method was 0.6 diopter. Ocular alignment determinations were achieved, and using a novel cover-uncover test, strabismus detection was demonstrated.

This thesis presents results of theoretical modeling of x-ray and vibrational spectroscopies applied to liquid water and to CO adsorbed on a Ni(100) surface. The Reverse Monte Carlo method is used to search for  water structures that reproduce diffraction, IR/Raman and x-ray absorption by fitting them to experimental data and imposed constraints. Some of the structures are created to have a large fraction of broken hydrogen bonds because recent x-ray absorption and emission studies have been seen to support the existence of such structures. In the fitting procedure a fast way of computing the IR/Raman spectrum for an isolated OH stretch is used, where the frequency is represented by the electric field projected in the direction of the stretch coordinate. This method is critically evaluated by comparing it to quantum chemical cluster calculations. Furthermore, the x-ray emission spectrum of water is investigated, the modeling of which is complicated by the necessity of including vibrational effects in the spectrum calculations due to a dissociative intermediate state. Based on the Kramers-Heisenberg formula a new semi-classical method is developed to include vibrational effects in x-ray emission calculations. The method is seen to work very well for a one-dimensional test system. Moreover, x-ray absorption and emission are implemented in a periodic Density Functional Theory code which is applied to ice and to the surface adsorbate system CO on Ni(100). / Den här avhandlingen presenterar resultat av teoretisk modellering av röntgen- och vibrationella spektroskopier applicerade på flytande vatten och på CO adsorberat på en Ni(100) -yta. Reverse Monte Carlo-metoden används till att söka efter vattenstrukturer som reproducerar diffraktion, IR/Raman, röntgenabsorption och emission genom att anpassa strukturerna till experimentella data samt till pålagda restriktionsvillkor. Vissa av strukturerna är skapade så att de har en stor andel brutna vätebindningar eftersom nya röntgenabsorptions- och emissionsexperiment har setts stödja förekomsten av sådana strukturer. I anpassningsprocessen används en metod för att snabbt beräkna IR/Raman-spektrum för en isolerad OH-stretch, där frekvensen representeras av det elektriska fältet projicerat i stretch-koordinatens riktning.Vi utvärderar kritiskt denna metod genom att jämföra den med kvantkemiska klusterberäkningar. Vidare undersöks vattens röntgenemissionsspektrum, vars modellering kompliceras av nödvändigheten att inkludera vibrationella effekter i spektrumberäkningarna på grund av ett dissociativt intermediärt tillstånd. Baserat på Kramers-Heisenbergformeln utvecklas en ny semiklassisk metod som inkluderar vibrationella effekter. Metoden visar sig fungera mycket väl för ett endimensionellt testsystem. Dessutom implementerar vi röntgenabsorption och emission i en periodisk Täthetsfunktionalteorikod som vi sedan applicerar  på is och på ett ytadsorbatsystem: CO på Ni(100). / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript. Paper 6: Manuscript.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1151. Adviser: Mark J. Kushner. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3652. Adviser: Jonathan J. L. Higdon. Includes bibliographical references (leaves 201-208) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6874. Adviser: Kenneth S. Schweizer. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.