Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / A technique capable of describing in detail the various phenomena arising in the limit of low energy photons because of the polarization of the vacuum is obtained by quantizing the gauge invariant effective interaction Lagrangian. This approach then permits the use of the standard covariant calculational tools of Quantum Electro-dynamics. We first apply this technique to the computation of the differential cross section for low energy photon-photon scattering. The well known Euler cross section is thereby derived in a direct manner. As a second example, the probability of the triple breakup of a free photon because of vacuum polarization is explicitly shown to vanish. This, however, is primarily due to the kinematics of the photon breakup. For a third application we calculate the differential cross section for the scattering of a low energy photon from the Coulomb field of a nucleus, that is, Delbruck scattering. Here the exact low energy differential cross section is obtained. However, though the present technique determines completely the angular dependence, it is necessary to introduce a momentum cutoff in the Coulomb field in order to obtain a finite value for the coefficient in front of the angular dependence. A comparison of the resulting expression for the cross section with that for forward scattering given by Rohrlich and Gluckstern (1952) gives the numerical value of this coefficient. A brief comparison between the angular distribution for Delbruck scattering and that for a combination of an electric and magnetic dipole radiator is presented. / 2031-01-01

Macrophages are key orchestrators of the innate immune response with a dynamic role in the promotion and resolution of inflammation. Macrophage polarization to a pro-inflammatory or anti-inflammatory phenotype must be tightly controlled to maintain appropriate responses to stimuli as well as to maintain tissue homeostasis. The nutrient and energy sensor Mammalian Target of Rapamycin (mTOR) integrates upstream signals from the PI3K/Akt pathway to orchestrate cellular protein, lipid, and glucose metabolism. This key metabolic pathway has been implicated in T-helper cell skewing and in the innate immune regulation. The mechanisms of innate immune regulation by mTOR are currently unclear as most studies use pharmacological inhibitors with potential off target effects. In this study, we use a novel model of TSC1 deficiency in myeloid lineage cells to elucidate a role for mTOR in macrophage polarization. We show, for the first time, that Tsc1-deficiency and constitutive mTORC1 activity in macrophages leads to a marked defect in M2 polarization when stimulated with the Th2 cytokine IL-4. Tsc1-deficient macrophages display attenuated Akt signaling in response to IL-4 consistent with negative feedback of mTORC1 on upstream IRS2/PI3K signaling, and we demonstrate that this parallel signaling pathway is critical for induction of a subset of M2 markers. Tsc1-deficient macrophages fail to upregulate the M2 genes Pgc-1!, Arg-1, Fizz-1, and Mgl1 in addition to other M2 markers despite normal STAT6 signaling in response to IL-4. Consistent with downregulation of Pgc-1!, Tsc1-deficient macrophages also display defects in fatty acid metabolism and mitchochondrial biogenesis. Furthermore, LPS stimulation in Tsc-1 deficient macrophages leads to an enhanced inflammatory response with increased production of pro-inflammatory cytokines. We believe that Tsc1-deficient macrophages are a model of constitutive mTORC1 activity akin to obesity, where chronic nutrient excess leads to increases in mTORC1 activity, attenuation of IRS/PI3K/Akt signaling, and defective M2 polarization of macrophages in metabolic tissues.

Chan Chi Wang = 宇宙微波背景輻射中之溫度與偏振各向不同性 / 陳志宏. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 94-98). / Text in English; abstracts in English and Chinese. / Chan Chi Wang = Yu zhou wei bo bei jing fu she zhong zhi wen du yu pian zhen ge xiang bu tong xing / Chen Zhihong. / Chapter 1 --- Overviewing modern cosmology --- p.1 / Chapter 1.1 --- Discoveries in Cosmology --- p.1 / Chapter 1.2 --- The Cosmological Model --- p.2 / Chapter 1.2.1 --- Cosmic Expansion --- p.3 / Chapter 1.2.2 --- The Metric and Friedmann Cosmology --- p.4 / Chapter 1.2.3 --- Thermodynamics of Matter and Radiation --- p.7 / Chapter 1.2.4 --- Timeline of the universe --- p.11 / Chapter 1.3 --- Formation of CMB and Its Anisotropics --- p.17 / Chapter 1.3.1 --- CMB --- p.17 / Chapter 1.3.2 --- CMB anisotropics --- p.18 / Chapter 1.4 --- Motivation and Thesis Outline --- p.21 / Chapter 2 --- The Recombination process --- p.23 / Chapter 2.1 --- The Saha approximation --- p.23 / Chapter 2.2 --- The Peebles recombination --- p.25 / Chapter 2.3 --- The RECFAST calculation --- p.28 / Chapter 3 --- The Boltzmann equations --- p.32 / Chapter 3.1 --- Boltzmann Equation for Photons --- p.33 / Chapter 3.1.1 --- Collision Term --- p.36 / Chapter 3.2 --- Boltzmann Equations for Matter --- p.37 / Chapter 3.2.1 --- Cold Dark Matter (CDM) --- p.37 / Chapter 3.2.2 --- Baryons --- p.38 / Chapter 3.3 --- Summary --- p.40 / Chapter 4 --- Formalism of CMB Anisotropies Calculation --- p.42 / Chapter 4.1 --- CMB Temperature Spectrum --- p.42 / Chapter 4.1.1 --- The Tight-coupling Solution --- p.43 / Chapter 4.1.2 --- Silk Damping --- p.45 / Chapter 4.1.3 --- The Free-Streaming Solution for fully decoupled cosmic fluid --- p.45 / Chapter 4.2 --- CMB Polarization Spectrum --- p.47 / Chapter 4.2.1 --- The E-mode and B-mode extractions --- p.48 / Chapter 4.3 --- The CMBFAST code --- p.50 / Chapter 4.4 --- Dependences on ionization history --- p.51 / Chapter 4.4.1 --- Recombination history --- p.53 / Chapter 4.4.2 --- Reionization history --- p.57 / Chapter 5 --- Softening of Equation of State during Recombination --- p.59 / Chapter 5.1 --- Recombination Revisited --- p.60 / Chapter 5.2 --- EOS softening by Recombination --- p.62 / Chapter 5.3 --- Numerical Results --- p.64 / Chapter 5.4 --- Summary and Discussions --- p.72 / Chapter 6 --- Time Varying Fundamental Constants --- p.74 / Chapter 6.1 --- Background --- p.74 / Chapter 6.1.1 --- Validity of time-varying fundamental constants --- p.76 / Chapter 6.1.2 --- The problem of units --- p.77 / Chapter 6.2 --- Theory --- p.78 / Chapter 6.3 --- Results --- p.79 / Chapter 6.3.1 --- Changing the electric charge --- p.80 / Chapter 6.3.2 --- Changing the electron mass --- p.82 / Chapter 6.3.3 --- Changing the cosmological constant --- p.85 / Chapter 6.3.4 --- Changing the speed of light --- p.87 / Chapter 6.4 --- Some concluding notes --- p.90 / Chapter 7 --- Conclusion --- p.92 / Bibliography --- p.94

In an effort to investigate the role of turbulence in near-forward scattering, laboratory measurements of scattering on turbulent flow were carried out in a Rayleigh-Bénard convective tank. Particle Image Velocimetry and profiling thermistor temperature measurements are used to characterize the turbulent flow through determination of the large scale flow features, turbulent kinetic energy dissipation rates, and thermal dissipation rates. Polarized diffractometer measurements allow for determination of the turbulence-induced depolarization rate, which is comparable to that observed with polarimetric lidar. Measurements were made over a range of turbulent strengths, with Rayleigh number between 10^8 and 3*10^9, and with turbulent parameters corresponding to those characteristic of the oceanic mixed layer. Results show that the turbulence-induced depolarization rate is indirectly proportional to the strength of the turbulent flow, suggesting that light beam depolarization from turbulent flow may contain useful information regarding the smallest length scales of turbulent flow.

We present, for the first time, methods to model and control the polarization of the output lightwave of a bidirectional fiber-optic system, in which the lightwave propagates through polarization control elements in both directions. Using the dynamic eigenstate (DES) principle, we built model to simulate the behavior of the polarization evolution. In a bidirectional system with one control element, we extracted system parameters from experimental data and achieved less than 3% angular deviation between modeled and experimental state of polarization (SOP). The theory was further validated by varying the input SOP to the bidirectional system. Our method can be extended to predict the SOP of a system with multiple actuators. Furthermore, combining our deterministic control method and a feedback loop, we are able to control the output SOP to be within a mean angular deviation of 5.5% from the target SOP, with as few as three iterations.

We present, for the first time, methods to model and control the polarization of the output lightwave of a bidirectional fiber-optic system, in which the lightwave propagates through polarization control elements in both directions. Using the dynamic eigenstate (DES) principle, we built model to simulate the behavior of the polarization evolution. In a bidirectional system with one control element, we extracted system parameters from experimental data and achieved less than 3% angular deviation between modeled and experimental state of polarization (SOP). The theory was further validated by varying the input SOP to the bidirectional system. Our method can be extended to predict the SOP of a system with multiple actuators. Furthermore, combining our deterministic control method and a feedback loop, we are able to control the output SOP to be within a mean angular deviation of 5.5% from the target SOP, with as few as three iterations.

In this thesis, Bi4Ti3O12 thin films are deposited on ITO/glass and Pt/Ti/SiO2/Si substrates using RF magnetron sputtering at room temperature and two kinds of targets with different compositions of Bi4Ti3O12 and Bi4Ti3O12+4wt% Bi2O3, respectively, and then heated by a rapid thermal annealing (RTA) process in an oxygen atmosphere. Three topics are focused in this research, they are: (1) to study the effects of different fabricated conditions and substrates on the physical and electrical characteristics of Bi4Ti3O12; (2) to investigate the influence of bismuth evaporation during thermal process on the characteristics of thin films, and seeking for the methods of bismuth compensation; and (3) applying the Bi4Ti3O12 film as the insulting layer of AC thin film electroluminescence device with the phosphor layer of ZnS:TbOF, and investigating the interaction between the two films. The experimental results indicate that intensities of X-ray diffraction (XRD) peaks of the films are evident when annealing at 650¢J for 15 min or at 700¢J for 10 min using RTA process, and the optimal properties of polycrystalline Bi4Ti3O12 thin films can be obtained at 700¢J for 15 min. No dielectric breakdown phenomenon of the films is detected in the filed of 500 kV/cm, and the leakage current density was lower than 10-6 A/cm2. The dielectric constant can attain to 307, and the loss factor is 0.02 at 1 kHz. The residual polarization and coercive field are 3.7 £gC/cm2 and 80 kV/cm with a sinusoidal wave of 500 Hz, respectively. The optical transmittance of the film is close to 100% at the wavelength of 550 nm. Scanning electronic microscopy (SEM) observation reveals that the microstructures, grain sizes and thicknesses of the thin films strongly dependent on the substrates, that is, the Pt/Ti/SiO2/Si substrate provides a more suitable interface layer than ITO/glass substrate for the growth of Bi4Ti3O12 thin films. The energy dispersive spectrometer (EDS) results indicate that the Bi/Ti atomic ratio of the films is less than that of target, which suggests that evaporation loss of bismuth occurs during the heating process. Whereas, this phenomenon occurs near the surface of thin film, it is not apparent in the inner of film. Excess 4wt% Bi2O3 additive in the target or additional Bi2O3 powder in the annealing process can compensate the loss of bismuth in the films, and improve the characteristics of thin films. Finally, the interdiffusion and chemical reactions take place among the element Bi, S and O at the interface during the deposition of ZnS:TbOF on Bi4Ti3O12 films, which degrades the optical transmittance of thin films. A 100 nm SiO2 buffer layer sandwiched between the ZnS:TbOF and Bi4Ti3O12 films can prevent the interdiffusion of the two layers, and enhance the optical transmittance and dielectric breakdown of Bi4Ti3O12 films.

Analysis and experimental results on a polarization independent electrooptic matched filter (EMF) with a center wavelength of 1.53 μm are reported. The EMF utilizes electrooptic phase-matched TE↔TM conversion in a Ti-diffused waveguide on a LiNbO3 substrate. The operation of the EMF to select an optical frequency channel is controlled by applying independent voltages to interdigital electrode sets cascaded along a single mode waveguide. The device is inherently polarization independent and has the potential for submicrosecond tuning. The number of selectable channels N is related to the number of electrode sets P by the formula / 2 1 N P = + . A matrix analysis is used to determine the TE↔TM conversion efficiency for the case that 8 P = and 5 N = . A driving circuit for the EMF was implemented using a digital-to-analog converter (DAC) array controlled from a personal computer (PC). Transmittance spectra of a filter produced in a LiNbO3 substrate are presented. A raised cosine weighting function applied along the 3.8 cm length of an EMF provides a sidelobe suppression level better than –17 dB with a 1.0 nm 3-dB bandwidth.

Thesis (M.S. in Combat Systems Technology)--Naval Postgraduate School, December 2003. / Thesis advisor(s): Alfred W. Cooper, Gamani Karunasiri. Includes bibliographical references (p. 83-84). Also available online.

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