Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1996. / Includes bibliographical references (leaves 66-68). / by Jian Tang. / M.S.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1941. / MIT copy bound with: An investigation of the anode effect in vacuum tube electrometers / Herman A. Affel, Jr. 1941. / Includes bibliographical references (leaf 20). / by Donald Brown Cameron. / B.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2001. / Includes bibliographical references (leaves 48-52). / W-Pair and Single-W production events are observed at LEP, the Large Electron Positron collider at CERN, using the L3 detector. All decay channels are considered, and data taken in the years 1998 and 1999, with electron-positron collision centre-of-mass energies from 189 GeV to 202 GeV are analysed. The integrated luminosity of the analysed data corresponds to approximately 400pb-1, and a total of approximately 5000 W-pair events and 100 single-W events are selected. The observed cross sections of these W production processes and the differential distributions of the event shapes are then used to measure the couplings of Wbosons with Z bosons and photons. Emphasis is placed on the unambiguous and efficient combination of the information from the different production and decay channels. For the couplings in the model in which gauge invariance is realised linearly, the following results are obtained ... where the errors shown are statistical, systematic and theoretical respectively. All results show consistency with expectations from the Standard Model. / by Yoshiyuki Uchida. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2012. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (p. 147-150). / N-body simulations have revealed a wealth of information about dark matter halos but their results are largely empirical. Here we attempt to shed light on simulation results by using a combination of analytic and numerical methods. First we generalize an analytic model of halo formation, known as Secondary Infall, to include the effects of tidal torque. Given this model we compare its predictions for halo profiles to simulation results and infer that angular momentum plays an important role in setting the structure of dark matter profiles at small radii. Next, we focus on explaining the origin of universality in halos. We find evidence that diffusion -- which can potentially lead to universality -- occurs during halo evolution and is partially sourced by external torques from large scale structure. This is surprising given that the halo is nonlinear and typically thought to be unaffected by neighboring structures. Last, we describe promising ways to analytically describe the evolution of nonlinear halos using a Fokker-Planck formalism. / by Phillip Gregory Zukin. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 177-188). / The Qweak experiment measures the parity violating asymmetry in elastic e[upper script right arrow]p scattering at Q² = 0.02455 (GeV/c)² with a 180 [mu]A and 88.7% longitudinally polarized electron beam of 1.165 GeV and a 34.4 cm liquid hydrogen target in experimental Hall C at Jefferson Lab. As the Q² at the Qweak experiment is much lower than all previous experiments, the Qweak measurement can be considered as the first direct determination of the weak charge of the proton, Qp/w, which is related to the weak mixing angle, sin2 [theta]w, an important Standard Model parameter. The preliminary and blinded asymmetry of the Run 2 data set, which constitutes approximately 60% of all the data collected in the experiment, is Aep/PV = -232.7 +/- 8.7 (stat) +/- 6.4 (syst) ppb. The value of Qp/w obtained by fitting this blinded asymmetry and earlier parity violating electron scattering (PVES) data at higher Q² is Qp/w (PVES) = 0.0705 +/- 0.0051. When combining this result with the ¹³³Cs atomic parity violation (APV) measurement, further constraints can be placed on the neutral weak quark coupling constants C₁u and C₁d. The combined PVES and APV analysis yields the blinded neutron's weak charge to be Qn/w (PVES+APV) = -0.9798 +/- 0.0065. The Qweak experiment also measures the parity violating asymmetry in nonresonance inelastic e[upper script right arrow]p scattering at Q² ~/= 0.09 (GeV/c)² with 3.35 GeV electron beams to provide inputs for the [gamma]Z box calculation. The preliminary measured inelastic asymmetry is Aep/inelastic-PV = 2.91 +/- 0.35 ppm. / by Fang Guo. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 171-178). / Binary systems composed of compact objects (neutron stars and black holes) radiate gravitational waves (GWs). The prospect of detecting these GWs using ground and space based experiments has made it imperative to understand the dynamics of such compact binaries. This work describes several advances in our ability to model compact binaries and extract the rich science they encode. A major part of this dissertation focuses on the subset of binaries composed of a massive, central black hole (105 - 10SM®) and a much smaller compact object (1 - 100M®). The emission of gravitational energy from such extreme mass ratio inspirals (EMRIs) forces the separation between the two components to shrink, leading to their merger. We treat the smaller object as a point-like particle on the stationary space-time of the larger black hole. The EMRI problem can be broken down into two related parts: (i) A determination of the inspiral trajectory followed by the smaller object, and (ii) A characterization of the gravitational waveforms that result from such an inspiral. The initial part of this work discusses the development of a numerical algorithm that solves for the GWs that result from the perturbations generated by the smaller object. It accepts any reasonable inspiral trajectory as an input and produces the resulting waveforms with an accuracy greater than 99%. Next, we present a technique to model the part of the inspiral trajectory that immediately precedes the final plunge of smaller object into the massive black hole. Along with earlier research, this enables us to compute the smaller object's complete inspiral trajectory. / (cont.) We now have a versatile toolkit that can model GWs from EMRIs. Finally, we present another application of this work. GWs carry linear momentum away from a binary. Integrating the lost momentum leaves an asymmetric binary with a non-zero recoil velocity after merger. We compute the recoils from EMRIs and extrapolate them to comparable mass binaries. We find that extrapolating perturbation theory gives results that agree well with those from numerical relativity, but require far less computation time. / by Pranesh Adhyam Sundararajan. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 141-146). / Each individual cell is a highly dynamic and complex system. Characterizing dynamics of gene expression and signal transduction is essential to understand what underlie the behavior of the cell and has stimulated much interest in systems biology. However, traditional techniques based on population averages 'wash out' crucial dynamics that are either out of phase among cells or are driven by stochastic cellular components[34]. In this work, we combined time-lapse microscopy, quantitative image analysis and fluorescent protein reporters, which allowed us to directly observe multiple cellular components over time in individual cells. In conjunction with mathematical models, we have investigated three dynamical systems, two of which are based on a long-term genealogical tracking method. First, we found that stochastic switching between different gene expression states in budding yeast is heritable[29]. This striking behavior only became evident using genealogical information from growing colonies. Our model based on burst induced correlation can explain the bulk of our results. In the next system investigated, we explored the interaction between biological oscillators. Especially, we used an abstract model to describe and predict the synchronization of cell cycles by the circadian clock. Simultaneous measurement of both circadian dynamics and cell cycle dynamics in individual cyanobacteria cells revealed the direct relationships between these two biological clocks and thus provided a clear evidence of 'circadian gating', in which circadian rhythms regulate the timing of cell divisions. Lastly, we studied the robustness of the network dynamics to the sequence changes and the changes of gene expression levels of embedding proteins by characterizing dynamic response of the well-conserved mitogen-activated protein kinase (MAPK) cascade to osmotic shock, combining experimental measurements and theoretical models. / by Qiong Yang. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2006. / Includes bibliographical references (p. 61-63). / In this thesis, we demonstrate a functioning planar radio frequency, three-rod Paul Trap, loaded with Yb+ ions that have been photoionized from a source of neutral atoms, which were cooled in a magneto-optical trap. Planar ion traps have only recently been successfully loaded[1], and never from a cold ion source. Additionally, ionizing directly from a MOT allows for isotope selection. / by Brendan John Shields. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 130-135). / The Karlsruhe Tritium Neutrino (KATRIN) experiment is a tritium beta decay experiment designed to make a direct, model independent measurement of the electron neutrino mass. To accomplish this task, the experiment employs precisely defined electric and magnetic fields for particle transport and mass spectroscopy. In order to simulate particle trajectories in the experiment, it is essential to have methods for calculating these fields quickly and accurately. The application of the methods of direct elliptic integral calculation, zonal harmonic expansion and interpolation from an adaptive-refinement field mesh is described within the object-oriented KatrinField framework, as well as an analysis of their comparative strengths and weaknesses in reproducing the electromagnetic fields found in KATRIN. / by Thomas Joseph Corona. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 203-215). / Studies of chromosomes have a long history. Since late XIX century, microscopy studies have revealed that chromosomal organization as seen by light microscopy is different among organisms, cell types, or stages of the cell cycle. However, the internal organization of chromosomes at scales below the diffraction limit largely remained unexplored. Recently, genomic techniques to measure contacts between genomic regions were developed; the most advanced of them, Hi-C, measures probabilities of contact between all pairs of genomic regions. Throughout my Ph.D, we have been developing methods to analyze Hi-C data, and to infer principles of chromosomal organization from the contact map provided by Hi-C. As a first step, we developed a toolset to map, analyze, and correct the Hi-C data. We then we performed polymer simulations that implement hypothetical principles of chromosomal organization and compared them to the Hi-C data. We showed that mitotic chromosomes in humans are not organized hierarchically, as thought previously, and are likely folded as an array of consecutive chromosomal loops. In the bacterium Caulobacter Crescentus, we showed that the chromosome is organized as a dense array of supercoiled plectonemes interspersed by highly transcribed regions free of plectonemes. Finally, for human interphase chromosomes, we showed that the equilibrium state of a long unknoted polymer chain is inconsistent with the observed properties of chromosomes. / by Maksim Imakaev. / Ph. D.