Dentro as técnicas de controle do movimento atômico utilizando pressão de radiação, aprisionamento tem merecido maior destaque por produzir amostras de átomos mais frios (temperaturas da ordem de &#956K), com altas densidades e confinadas em pequenas regiões do espaço. Devido a essas motivações, tem sido grande o esforço para desenvolver e caracterizar estas armadilhas atômicas. Uma das mais eficientes armadilhas de átomos neutros construídas até agora é a armadilha magneto-óptica. O átomo uma vez capturado por este tipo de armadilha passa por um intenso processo de desaceleração via efeito Doppler e acaba por ficar confinado no poço de potencial gerado pela interação com o campo magnético. O número e a densidade de átomos aprisionados, o tamanho da nuvem e o processo de carga possuem forte dependência com os parâmetros da armadilha, tais como: Este trabalho trata da caracterização de uma armadilha deste tipo para átomos de sódio através de um estudo sistemático para descobrir as condições de sua melhor performance. Paralelamente a este estudo, desenvolvemos modelos teóricos para entender em detalhe os processos de produção dessas nuvens de átomos aprisionados e as forças envolvidas neste tipo de material que é esse gás super resfriado. / Among the various atomic motion control techniques using radiation pressure magneto-optic trapping has been looked at with great enthusiasm because it produces samples of cold atoms (temperatures about &#956K), with high densities and confined in small regions of space. Due to these motivations the efforts for developing and characterizing these atoms traps has been high. Once the atom is captured by the magneto-optic trap, it goes through an intense process of desacceleration via Doppler Effect and ends up confined in the potential well genered by the interaction with the magnetically Field. The number and the density of the trapped atoms, the size of the cloud and the loading process are strongly related to trap parameters, such as: magnetic Field gradient, laser beam intensity and background vapor temperature. This work deals with the characterization of a trap of this kind for sodium atoms through a systematic study, in order to discover the conditions for a better performance. At the same time theoretical models are developed in order to understand in depth the atomic forces involved in the production of a new kind of material which is this highly refrigerated gas.

We present a novel method of in situ magnetic field mapping related to the Hanle effect. This method uses the change in spatial radiation pattern of scattered light, which we call a 'directional Hanle effect,' rather than the loss of polarization more commonly associated with the Hanle effect. It is particularly well suited for fields in a magneto-optical trap (MOT), requiring only the addition of a narrow slit and a camera to typical MOT components. The use of this method is demonstrated by measuring the gradient through, and location of, the zero-point of the field in our strontium MOT.

This thesis presents an in-depth study into the characterization and enhancement of a metastable neon laser cooled and trapped atomic beam. The apparatus consists of a standard Zeeman slowed atomic beam loaded into a magneto-optical trap and was designed for applications to electron scattering experiments and photoionization. The efficiency of the metastable neon atomic source was investigated to determine the ideal cathode type for maximum metastable production and optimal atomic beam velocity haracteristics. A series of characterization measurements were performed on the MOT, and the trap volume and population were investigated for a range of trapping and slowing laser intensities and detunings, together with the MOT and Zeeman slower magnetic fields. The volume measurements were compared to standard Doppler theory and it was found that the Doppler model inadequately explained the trap behaviour. It was found that the MOT population characteristics were governed by two processes: two-body losses that limit the trap population at high densities, and the efficiency of the atom capture process which limits the operational range of the MOT over the various parameters. The trap temperature was determined to be 1.3mK via a time-of-flight technique. This was nearly twice that predicted by Doppler theory and the lack of agreement once again suggests the inadequacies in the Doppler theory to correctly model the experiment. The application of the MOT to the photoionization cross-section measurement of the (2p53p)3D3 state of neon was investigated. The MOT decay technique was utilized to measure cross-section values of o351 = 2.9+0.2 -0.3 x 10 -18cm2 and o363 = 3.1 +0.3 -0.4 x 10-18cm2 at the wavelengths of 351nm and 363nm respectively. This is an increase in accuracy of around a factor of five from previous measurements and it was found that the results agreed well with the values predicted by current theories.

A system suitable for studying interactions between ⁸⁷Rb Rydberg atoms and metal surfaces has been constructed. This thesis describes the design and construction of the apparatus, and some test results. Atoms in a vapor cell magneto-optical trap are transferred to a macroscopic Ioffe-Pritchard trap, where they will be RF evaporatively cooled and loaded into a magnetic microtrap (atom chip). Confinement of cold clouds at controllable distances (5–200 μm)} from a metal surface is possible. The effects of atom-surface interactions can be studied with Rydberg atom spectroscopy. Some functionality of the apparatus has been demonstrated. Approximately 1.5×10⁷ atoms were loaded into a mirror MOT, and about 6×10⁶ atoms were optically pumped to the |F=2, m_F=2> hyperfine ground state and confined in a macroscopic Ioffe-Pritchard trap. The temperature of the cloud in the trap was 42 ± 5 μK, and the 1/e lifetime is 1–1.5 s. Forced RF evaporation has been used to measure the magnetic field at the trap minimum, but RF evaporative cooling has not yet been demonstrated.

A system suitable for studying interactions between ⁸⁷Rb Rydberg atoms and metal surfaces has been constructed. This thesis describes the design and construction of the apparatus, and some test results. Atoms in a vapor cell magneto-optical trap are transferred to a macroscopic Ioffe-Pritchard trap, where they will be RF evaporatively cooled and loaded into a magnetic microtrap (atom chip). Confinement of cold clouds at controllable distances (5–200 μm)} from a metal surface is possible. The effects of atom-surface interactions can be studied with Rydberg atom spectroscopy. Some functionality of the apparatus has been demonstrated. Approximately 1.5×10⁷ atoms were loaded into a mirror MOT, and about 6×10⁶ atoms were optically pumped to the |F=2, m_F=2> hyperfine ground state and confined in a macroscopic Ioffe-Pritchard trap. The temperature of the cloud in the trap was 42 ± 5 μK, and the 1/e lifetime is 1–1.5 s. Forced RF evaporation has been used to measure the magnetic field at the trap minimum, but RF evaporative cooling has not yet been demonstrated.

No description available.

The tumor microenvironment is a tangled web of multiple cell types, extracellular matrix components, and a multitude of cell signaling pathways frequently contribute to poor outcomes, which make cancer the second leading killer in the United States. A better understanding of how these constituents interact will inevitably facilitate development of novel cancer therapeutics and diagnostics. To advance scientific discovery towards this goal, innovative experimental techniques are required. In this dissertation, new research methods for probing cell communication at a single to multi cell level within 3D models of the tumor microenvironment are presented. Optical trapping, composite nanocapsules (i.e., gold-coated liposomes), and 3D cell culture models were the foundation for the development of these research tools. The first aim of this dissertation was to optimize our ability to optically manipulate gold-coated liposomes for the purpose of delivering molecular content to cells. The second aim was to apply optical manipulation of gold-coated liposomes to quantitatively deliver signaling molecules into a single cell to activate communication. The third aim was to develop a 3D model of the tumor microenvironment and demonstrate cell communication within this physiologically accurate architecture. The basis for this work was gold-coated liposomes' strong plasmon resonance with visible to near infrared (NIR) wavelengths of light, which enabled photo-thermal conversion and optical trapping. To identify preferred conditions for optical manipulation of gold-coated liposomes for delivering content into cells, gold-coated liposomes made with different dielectric properties were optically trapped under various laser modulation schemes and thoroughly characterized, enabled by high speed (kHz) imaging. Application of this technique was realized by precise delivery of molecular agents into a single cell (i.e., optical injection). As a demonstration of optical injection, the NIR trapping beam was utilized to propel gold-coated liposomes encapsulating inositol trisphosphate (IP3) into a single cell to initiate calcium (Ca²⁺) signaling. In another method for intracellular delivery, cells were preloaded with similar gold-coated liposomes, internalized by macropinocytosis, and then exposed to on-resonant laser light to trigger on-demand release of IP3 to activate Ca²⁺ signaling. Lastly, a 3D cell culture model of ovarian cancer microenvironment was developed as a platform for interrogating cell signaling. The in vitro model comprised human ovarian cancerous epithelial cells grown upon a collagen and human fibroblast stroma recapitulating architecture of human tissue. Gold-coated liposomes encapsulating signaling molecules, optical manipulation, and a 3D model of ovarian cancer, a trio of versatile experimental tools opens new opportunities for studying the tumor microenvironment.

The pericellular matrix (PCM) is a voluminous polymer network adhered to and surrounding many different types of mammalian cells, and which extends out into the environment outside the cell for distances ranging up to twenty microns. It is comprised of very long flexible polymers (hyaluronan) which are tethered to the cell surface and which have binding sites for large, highly charged bottle brush proteoglycans (aggrecan). The PCM plays an important role in many cell functions such as cell proliferation, cell adhesion, cell migration, and cancer development, however the precise way it influences these processes remains unclear. Three original biophysical tools are developed in this thesis in order to study the PCM: the quantitative particle exclusion assay (qPEA), optical force probe assay (OFPA), and exogenous fluorescent aggrecan mapping assays. These tools are used to measure the polymeric and biophysical properties of the matrix in order to make further advancements in the understanding the PCMs role in adhesion, transport to and from the cell surface, its purported function as a chemical micro-reservoir, as well as basic studies on the kinetics of its formation, turnover and maintenance. The qPEAs measure the penetration and distribution of sub-micron particles after they diffuse into the cell coat, where their distribution maps the interior structure of the PCM. The qPEA assays reveal that the PCM acts a sieve, separating incoming particles by their size, preventing micron sized particles from entering the PCM while allowing sub 100 nm particles to pass to the cell surface. The OFPA uses an optically-trapped bead to study the force response of the matrix as it encounters the probe. The assay not only reveals new details about the PCM such as the fact that it is larger than initially thought, having a two layer structure, but when combined with a polymer physics model which relates the observed equilibrium forces to an existing osmotic pressure gradient within the PCM, the OFPA studies produce the first discovery and measurement of the correlation length distribution in the cell coat. The OFPA and qPEA assays are also performed on cells modified with exogenous aggrecan, resulting in a model for possible proteoglycan mediated cell coat transformations. The fluorescent exogenous aggrecan assays measure the dynamics of the exogenous aggrecan binding to and releasing from the coat, revealing that the PCM can be rapidly modified by a changing environment, and quantitatively measure how the exogenous aggrecan modifies the existing PCM. Together, these assays provide an unprecedented look into the interior structure of the PCM, and the mechanisms responsible both for this structure and its modification.

abstract: In the frenzy of next generation genetic sequencing and proteomics, single-cell level analysis has begun to find its place in the crux of personalized medicine and cancer research. Single live cell 3D imaging technology is one of the most useful ways of providing spatial and morphological details inside living single cells. It provides a window to uncover the mysteries of protein structure and folding, as well as genetic expression over time, which will tremendously improve the state of the fields of biophysics and biomedical research. This thesis project specifically demonstrates a method for live single cell rotation required to image them in the single live cell CT imaging platform. The method of rotation proposed in this thesis uses dynamic optical traps generated by a phase-only spatial light modulator (SLM) to exert torque on a single mammalian cell. Laser patterns carrying the holographic information of the traps are delivered from the SLM through a transformation telescope into the objective lens and onto its focal plane to produce the desired optical trap "image". The phase information in the laser patterns being delivered are continuously altered by the SLM such that the structure of the wavefront produces two foci at opposite edges of the cell of interest that each moves along the circumference of the cell in opposite axial directions. Momentum generated by the motion of the foci exerts a torque on the cell, causing it to rotate. The viability of this method was demonstrated experimentally. Software was written using LabVIEW to control the display panel of the SLM. / Dissertation/Thesis / M.S. Bioengineering 2013

Neste trabalho é apresentada a construção da montagem de um sistema experimental para resfriar átomos de estrôncio. A construção do sistema está focada no estudo do espalhamento coletivo em nuvens atômicas frias e ultrafrias por meio da teoria de Mie. O estrôncio é um elemento que conta com dois estágios de resfriamento, o primeiro utilizando a transição forte entre estados singletos ¹S₀-¹P ₁ de Γ = (2 π)32 MHz, e o segundo com uma transição fraca entre estados singleto e tripleto ¹S₀-³P₁ de Γ = (2 π)7,5 MHz. O objetivo deste trabalho é a construção do sistema para resfriar átomos de estrôncio utilizando a primeira transição. A construção do sistema se apresenta em várias partes, primeiro a construção do um forno como fonte de vapor de estrôncio, onde o estrôncio metálico é aquecido até uma temperatura T = 600°C. O forno conta com um sistema de microtubos encarregados de colimar o feixe atômico, estes microtubos tem um diâmetro interno D ≈ 180µm e um comprimento de 8mm. Depois da implementação do forno e do sistema de microtubos foi medido o perfil de velocidades transversais e a divergência do feixe atômico que sai do forno. A largura tem um valor wr = (2π)108 MHze a divergência do feixe de α ≈4,12. A segunda parte do sistema conta com a construção do desacelerador Zeeman, responsável por desacelerar os átomos do feixe atômico utilizando um feixe laser contrapropagante de λ=461 nm, circularmente polarizado e com uma dessintonização utilizada, após a caracterização do sistema, de Δ=(-2π)580MHz. Os átomos sentiram os efeitos da força de pressão radiativa dentro de um tubo de comprimento de 0,28m. Para compensar o efeito Doppler causado pelo movimento dos átomos foi utilizado um arranjo de bobinas em configuração spin flip para gerar o campo. A terceira e principal parte do sistema foi a construção da armadilha magnetoóptica (AMO). Onde os átomos que saem do desacelerador Zeeman são confinados e resfriados pela combinação de seis feixes contrapropagantes, dos quais três são retrorefletidos utilizando a transição Γ=(2π)32MHz. A dessintonia dos feixes após da caracterização do sistema foi de Δ=(-2π)39MHz. Depois da construção do sistema foi feita a primeira caracterição da armadilha magneto-óptica de átomos de estrôncio 88 em nosso grupo, onde obtivemos a temperatura dos átomos na armadilha para o eixo vertical da expansão foi de Tv=4.7mK e para o eixo horizontal de TH=4mK. Também foi medido o tempo de carga dos átomos na armadilha tcarga=0.15s como bombeamento óptico de estado ³P₂-³D₂. O tempo de vida foi de 0.3s e 0.03s com e sem bombeamento óptico, respectivamente. / This work presents the construction of the assembly of an experimental system for cooling strontium atoms. The construction of the system is focused on the collective scattering in atomic cold cloud and ultra cold using the Mie theory. The strontium is an element that permits two stage of cooling, the first using the strong transition between singlet states ¹S₀-¹P₁ of Γ=(2π) 32 MHz, and a second stages is the weak transition between singlet and triplet states ¹S₀-³P₁ de Γ=(2π) 7.5MHz. The objective of this work is building the system for cooling strontium atoms using the first transition. The construction of the system is presented in several parts. First is described the construction of oven as vapor source strontium, where the strontium metal is heated to Temperature Range T = 600°C. The oven has a microtubule system responsible for collimating the atomic beam, these microtubules has an internal diameter of D ≈ 180µm and a length of 8mm. After implementation of the oven system and the microtubes were measured transverse velocity profile and the divergence of the atomic beam that leaves the oven, the width value was f wr=(2π)108MHzand beam divergence value was α ≈ 4,12. The second part of the system relies on the construction of the Zeeman slower responsible for decelerating the atoms of the atomic beam using a laser beam antipropagating of λ = 461 nm nm with a circularly polarized , the detuning used after of the characterization of the system was Δ = (2π)580 MHz. Atoms felt the effects of pressure force radiative within a tube length of 0.28m to compensate the Doppler shift due to motion a of atoms used an arrangement of coils in configuration \"spin flip\" to generate the magnetic field to compensate this effect. The third and main part of the system was the construction of magneto-optical trap (MOT), the atoms coming out of the Zeeman decelerator are confined and cooled by a combination of six counterpropagating beams, three of which are retro reflected using the transition Γ = (2π)32MHz, the detuning of the beam after the characterization of the system was Δ = (-2π) 39 MHz and the opposite polarization for each pair of beam in the same direction. After the construction of the system was made the first magneto-optical trap of strontium atoms 88, the temperature of the trap was atoms to the vertical he expansion was Tv = 4.7mK and the horizontal axis TH = 4 mK 4, also was measured loading time of the atoms in the trap tcharge = 0.15s as optical pumping state ³P₂- ³D₂. The lifetime with and without optical pumping was tlife = 0.3s and tlife = 0.03s respectively.