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Manipulation and Sorting of Cell-Laden Hydrogel Microcapsules Within Microfluidic EnvironmentDhingra, Karan 20 November 2019 (has links)
Encapsulating cells within semi-permeable hydrogel material has been shown to boost the therapeutic effectiveness of stem cell therapy in certain applications. Cell encapsulation promotes high retention and engraftment rates, and protects against attack from the immune system of the host, as these are challenges often seen in utilizing stem cells in suspension alone. Leveraging droplet-based microfluidics has yielded a platform capable of producing monodispersed microcapsules embedded with cells at high throughput, typically achieved by mixing an aqueous hydrogel solution that contains cells with an immiscible liquid (oil) in a flow focusing geometry. However, encapsulation using microfluidics results in randomized generation of empty and cell-laden microcapsules, following Poisson statistics, raising the need to institute a successful sorting mechanism, thereby increasing occupancy and ultimately purifying the desired sample. In this thesis we propose a sorting strategy by combining two conceptual mechanisms of electrophoresis (EP) and deterministic lateral displacement (DLD). Different varieties of microcapsules were characterized for EP and DLD respectively. Leveraging these differences was used in a device combining both of the concepts towards sorting of empty and cell-laden microcapsules.
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The effect of neutron excess and nuclear deformation on dipole strength functions below the neutron separation energy - nuclear resonance fluorescence experiments on 124,128,132,134 Xe at ELBE and HI gamma SMassarczyk, Ralph 28 October 2014 (has links) (PDF)
Within this thesis, nuclear resonance fluorescence experiments were analyzed which have been performed at the gamma ELBE facility of the Helmholtz-Zentrum Dresden-Rossendorf and the HI gamma S facility of the Triangle Universities Nuclear Laboratory. The dipole strength up to the neutron separation energy, its distribution as well as its split into electric and magnetic strength were determined. The influence of crucial nuclear parameters, like deformation and neutron excess, on the data was investigated.
For the first time a whole set of enriched gaseous targets was measured in the energy region close to the neutron separation threshold. At ELBE the scattering of photons on four different isotopes 124, 128, 132, 134 Xe was investigated by irradiating containers with enriched target material with a broad bremsstrahlung distribution. The endpoint energies were chosen to be 12MeV. This ensures excitations up to the neutron separation threshold. The two isotopes 128, 134 Xe were measured in an additional campaign at HI gamma S facility. The region below the threshold was explored in detail in these experiments. A second, more model-independent determination of the cross section was possible.
The work shows, how the measured spectra taken with high-purity germanium detectors, have to be corrected for several, partly overlapping effects in order to determine the complete excitation strength.
The calculation of different backgrounds, detector response functions and the influence of inelastic scattering constitute the main part of the presented work. With the help of GEANT4 simulations the amount of not-nuclear scattered photons was estimated. GEANT4 was also used to test the influence of the extended targets on the detection efficiency and response. The code gamma DEX, which calculates deexcitation schemes based on statistical assumptions, was updated and finally used for the unfolding of the spectrum.
The measured data is compared to different strength function models and a theoretical prediction based on a QRPA calculation. The summed strength is also set into comparison to other experimental data sets and a global trend for low-lying strength was found. This shows, that the nuclear deformation which has a large influence on the dipole strength above the threshold is only of minor impact for the strength at lower energies.
Instead of this, the neutron excess seems to be the dominating factor for the strength in the investigated energy region.
This work was supported by the German Research Foundation (DFG), Project No. SCHW883/1-1.
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The effect of neutron excess and nuclear deformation on dipole strength functions below the neutron separation energy - nuclear resonance fluorescence experiments on 124,128,132,134 Xe at ELBE and HI gamma SMassarczyk, Ralph 16 October 2014 (has links)
Within this thesis, nuclear resonance fluorescence experiments were analyzed which have been performed at the gamma ELBE facility of the Helmholtz-Zentrum Dresden-Rossendorf and the HI gamma S facility of the Triangle Universities Nuclear Laboratory. The dipole strength up to the neutron separation energy, its distribution as well as its split into electric and magnetic strength were determined. The influence of crucial nuclear parameters, like deformation and neutron excess, on the data was investigated.
For the first time a whole set of enriched gaseous targets was measured in the energy region close to the neutron separation threshold. At ELBE the scattering of photons on four different isotopes 124, 128, 132, 134 Xe was investigated by irradiating containers with enriched target material with a broad bremsstrahlung distribution. The endpoint energies were chosen to be 12MeV. This ensures excitations up to the neutron separation threshold. The two isotopes 128, 134 Xe were measured in an additional campaign at HI gamma S facility. The region below the threshold was explored in detail in these experiments. A second, more model-independent determination of the cross section was possible.
The work shows, how the measured spectra taken with high-purity germanium detectors, have to be corrected for several, partly overlapping effects in order to determine the complete excitation strength.
The calculation of different backgrounds, detector response functions and the influence of inelastic scattering constitute the main part of the presented work. With the help of GEANT4 simulations the amount of not-nuclear scattered photons was estimated. GEANT4 was also used to test the influence of the extended targets on the detection efficiency and response. The code gamma DEX, which calculates deexcitation schemes based on statistical assumptions, was updated and finally used for the unfolding of the spectrum.
The measured data is compared to different strength function models and a theoretical prediction based on a QRPA calculation. The summed strength is also set into comparison to other experimental data sets and a global trend for low-lying strength was found. This shows, that the nuclear deformation which has a large influence on the dipole strength above the threshold is only of minor impact for the strength at lower energies.
Instead of this, the neutron excess seems to be the dominating factor for the strength in the investigated energy region.
This work was supported by the German Research Foundation (DFG), Project No. SCHW883/1-1.
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