Optical rheology for live cell membranes

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (leaves 24-25).We present a novel optical methodology including both instrumentation and theory aimed at retrieving the full viscoelastic information of cell membrane material properties. Red blood cells (RBC) are chosen for this study because of their simple structure, which consists of a bi-layer cell membrane supported by a cytoskeleton enclosing a homogeneous fluid. The full complex modulus of RBC in terms of temporal frequency and spatial frequency is retrieved 'without contact, for the first time to our knowledge. Sub-nanometer sensitivity diffraction phase and fluorescence microscopy (DPF) quantifies non-invasively three dimensional morphological information of live cell with high speed. The fluctuation dissipation theory and generalized Stokes-Einstein relationship provide the complex modulus associated with the cell membrane, in a spatially-resolved manner. This information is used to retrieve the dynamic and spatial behavior of red blood cell membranes during the process of shape deterioration. The viscoelasticity results on RBC strongly correlate with cell morphology. Thus, we find that the cell evolution from a normal, doughnut shape to a spheroid can be interpreted from a viscoelastic point of view as a liquid-solid transition.by YongKeun Park.S.M

User innovation in Internet businesses

Thesis (S.M.)--Massachusetts Institute of Technology, System Design and Management Program, 2007.Includes bibliographical references (leaf 39).This paper examines the concept of user innovation, how this concept has been applied to internet businesses, and behaviors and motivation of the users who have participated in user innovative activities for internet businesses. This thesis presents definitions and characteristics of both user innovation activities in web businesses. As a major research method, a survey is conducted to identify the trend and phenomenon of current user innovation activities on the web. Major discoveries from the web user innovation survey are two. First, most lead users who participate in user innovation activity in the web businesses do not significantly differ by gender, age, or profession. Second, most lead users participate in user innovation activities for social-networking purpose as well as the goal of contributing to society. User innovations are seldom oriented or initiated from financial benefit purpose as similar as many traditional user innovations are formed for non financial benefit reasons. Internet businesses can leverage these findings to bring a user innovation to their business more effectively.by Jin Suk Park.S.M

The Cosmological Constant and Horava-Lifshitz Gravity

Horava-Lifshitz theory of gravity with detailed balance is plagued by the presence of a negative bare (or geometrical) cosmological constant which makes its cosmology clash with observations. We argue that adding the effects of the large vacuum energy of quantum matter fields, this bare cosmological constant can be approximately compensated to account for the small observed (total) cosmological constant. Even though we cannot address the fine-tuning problem in this way, we are able to establish a relation between the smallness of observed cosmological constant and the length scale at which dimension 4 corrections to the Einstein gravity become significant for cosmology. This scale turns out to be approximately 5 times the Planck length for an (almost) vanishing observed cosmological constant and we therefore argue that its smallness guarantees that Lorentz invariance is broken only at very small scales. We are also able to provide a first rough estimation for the infrared values of the parameters of the theory $\mu$ and $Lambda_w$.Comment: 9 pages, Late

Metal waste forms from the electrometallurgical treatment of spent nuclear fuel

Stainless steel-zirconium alloys are being developed for the disposal of radioactive metal isotopes isolated using an electrometallurgical treatment technique to treat spent nuclear fuel. The nominal waste forms are stainless steel-15 wt% zirconium alloy and zirconium-8 wt% stainless steel alloy. These alloys are generated in yttria crucibles by melting the starting materials at 1,600 C under an argon atmosphere. This paper discusses the microstructures, corrosion and mechanical test results, and thermophysical properties of the metal waste form alloys

Intel: Tick-Tock product development cadence

Thesis (S.M.)--Massachusetts Institute of Technology, System Design and Management Program, 2008.Includes bibliographical references (p. 124-142).This thesis investigates on changes in semiconductor industry's product development methodology by following Intel's product development from year 2000. Intel was challenged by customer's preference change, competitors new enhanced product, internet bubble burst economy, and miss steps in the business strategy. Dynamics of these challenges drove Intel to develop a new product strategy: Tick-Tock product cadence. The paper discusses reasons why Intel landed at the Tick-tock strategy and results how strong product portfolio Intel ended up constructing. The thesis further discusses how the new "Global Product Development" strategy evolves, which can take advantage of TickTock cadence and deliver it to the next level helped from the effective GPD and systems engineering deployment.by Cheolmin Park.S.M

Equations for filling factor estimation in opal matrix

We consider two equations for the filling factor estimation of infiltrated zinc oxide (ZnO) in silica (SiO_2) opal and gallium nitride in ZnO opal. The first equation is based on the effective medium approximation, while the second one - on Maxwell-Garnett approximation. The comparison between two filling factors shows that both equations can be equally used for the estimation of the quantity of infiltrated nanocrystals inside opal matrix.Comment: 14 pages, 7 figures, 1 table. Addendum to the article: http://arxiv.org/abs/physics/050815

Broadening of band-gap in photonic crystals with optically saturated media

Due to strong absorption of the incident light, the media with high refractive index are considered restrictive for applications in photonic crystals (PhCs). The possibility to resolve this problem by optical saturation effectively minimizing the absorption of the PhC medium is discussed. Such approach might be promising for the significant broadening of the photonic band-gap.Comment: 10 page

Learning for informative path planning

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 104-108).Through the combined use of regression techniques, we will learn models of the uncertainty propagation efficiently and accurately to replace computationally intensive Monte- Carlo simulations in informative path planning. This will enable us to decrease the uncertainty of the weather estimates more than current methods by enabling the evaluation of many more candidate paths given the same amount of resources. The learning method and the path planning method will be validated by the numerical experiments using the Lorenz-2003 model [32], an idealized weather model.by Sooho Park.S.M

A self-tuning mechanism in (3+p)d gravity-scalar theory

We present a new type of self-tuning mechanism for ($3+p$)d brane world models in the framework of gravity-scalar theory. This new type of self-tuning mechanism exhibits a remarkable feature. In the limit $g_s \to 0$, $g_s$ being the string coupling, the geometry of bulk spacetime remains virtually unchanged by an introduction of the Standard Model(SM)-brane, and consequently it is virtually unaffected by quantum fluctuations of SM fields with support on the SM-brane. Such a feature can be obtained by introducing Neveu-Schwarz(NS)-brane as a background brane on which our SM-brane is to be set. Indeed, field equations naturally suggest the existence of the background NS-brane. Among the given such models, of the most interest is the case with $\Lambda=0$, where $\Lambda$ represents the bulk cosmological constant. This model contains a pair of coincident branes (of the SM- and the NS-branes), one of which is a codimension-2 brane placed at the origin of 2d transverse space ($\equiv \Sigma_2$), another a codimension-1 brane placed at the edge of $\Sigma_2$. These two branes are (anti) T-duals of each other, and one of them may be identified as our SM-brane plus the background NS-brane. In the presence of the background NS-brane (and in the absence of $\Lambda$), the 2d transverse space $\Sigma_2$ becomes an orbifold $R_2 /Z_n$ with an appropriate deficit angle. But this is only possible if the ($3+p$)d Planck scale $M_{3+p}$ and the string scale $M_s$($\equiv 1/\sqrt{\alpha^{\prime}}$) are of the same order, which accords with the hierarchy assumption \cite{1,2,3} that the electroweak scale $m_{EW}$ is the only short distance scale existing in nature