Gelling of cryogenic oxidizers Final report, 5 May 1965 - 4 Sep. 1966

Freeze dry methods for preparation of ultrafine, particle size lithium fluoride for cryogenic oxidizer

Microtubule dynamics depart from wormlike chain model

Thermal shape fluctuations of grafted microtubules were studied using high resolution particle tracking of attached fluorescent beads. First mode relaxation times were extracted from the mean square displacement in the transverse coordinate. For microtubules shorter than 10 um, the relaxation times were found to follow an L^2 dependence instead of L^4 as expected from the standard wormlike chain model. This length dependence is shown to result from a complex length dependence of the bending stiffness which can be understood as a result of the molecular architecture of microtubules. For microtubules shorter than 5 um, high drag coefficients indicate contributions from internal friction to the fluctuation dynamics.Comment: 4 pages, 4 figures. Updated content, added reference, corrected typo

Dynamical Response of Nanomechanical Oscillators in Immiscible Viscous Fluid for in vitro Biomolecular Recognition

Dynamical response of nanomechanical cantilever structures immersed in a viscous fluid is important to in vitro single-molecule force spectroscopy, biomolecular recognition of disease-specific proteins, and the detection of microscopic dynamics of proteins. Here we study the stochastic response of biofunctionalized nanomechanical cantilevers beam in a viscous fluid. Using the fluctuation-dissipation theorem we derive an exact expression for the spectral density of the displacement and a linear approximation for the resonance frequency shift. We find that in a viscous solution the frequency shift of the nanoscale cantilever is determined by surface stress generated by biomolecular interaction with negligible contributions from mass loading.Comment: 4 pages, 2 figures, RevTex4. See http://nano.bu.edu/ for related paper

The Detection of Unsteady Flow Separation with Bioinspired Hair-Cell Sensors

Biologists hypothesize that thousands of micro-scale hairs found on bat wings function as a network of air-flow sensors as part of a biological feedback flow control loop. In this work, we investigate hair-cell sensors as a means of detecting flow features in an unsteady separating flow over a cylinder. Individual hair-cell sensors were modeled using an Euler-Bernoulli beam equation forced by the fluid flow. When multiple sensor simulations are combined into an array of hair-cells, the response is shown to detect the onset and span of flow reversal, the upstream movement of the point of zero wall shear-stress, and the formation and growth of eddies near the wall of a cylinder. A linear algebraic hair-cell model, written as a function of the flow velocity, is also derived and shown to capture the same features as the hair-cell array simulatio

Liquid-like behaviour of gold nanowire bridges

A combination of Focused Ion Beam (FIB) and Reactive Ion Etch (RIE) was used to fabricate free standing gold nanowire bridges with radii of 30 nm and below. These were subjected to point loading to failure at their mid-points using an Atomic Force Microscope (AFM), providing strength and deformation data. The results demonstrate a dimensionally dependent transition from conventional solid metallic properties to liquid-like behaviour including the unexpected reformation of a fractured bridge. The work reveals mechanical and materials properties of nanowires which could have significant impact on nanofabrication processes and nanotechnology devices such as Nano Electro Mechanical Systems (NEMS)

Human Empathy as a Basis for Cross-Cultural Healthcare Design

The goal of our project was to work in collaboration with the people of Dwenase, Ghana to improve their health center using a human-centered co-design process. Human-centered means empathizing with the local people, allowing designers to visualize and understand the effects that potential solutions could have on the community. Additionally, co-design is working with the community to develop solutions together, since they know best what they need and what will work. We aimed to blend together contributions from the community - the “local experts” - with that of the “academic experts” to create the best possible solution

Statics and Dynamics of the Wormlike Bundle Model

Bundles of filamentous polymers are primary structural components of a broad range of cytoskeletal structures, and their mechanical properties play key roles in cellular functions ranging from locomotion to mechanotransduction and fertilization. We give a detailed derivation of a wormlike bundle model as a generic description for the statics and dynamics of polymer bundles consisting of semiflexible polymers interconnected by crosslinking agents. The elastic degrees of freedom include bending as well as twist deformations of the filaments and shear deformation of the crosslinks. We show that a competition between the elastic properties of the filaments and those of the crosslinks leads to renormalized effective bend and twist rigidities that become mode-number dependent. The strength and character of this dependence is found to vary with bundle architecture, such as the arrangement of filaments in the cross section and pretwist. We discuss two paradigmatic cases of bundle architecture, a uniform arrangement of filaments as found in F-actin bundles and a shell-like architecture as characteristic for microtubules. Each architecture is found to have its own universal ratio of maximal to minimal bending rigidity, independent of the specific type of crosslink induced filament coupling; our predictions are in reasonable agreement with available experimental data for microtubules. Moreover, we analyze the predictions of the wormlike bundle model for experimental observables such as the tangent-tangent correlation function and dynamic response and correlation functions. Finally, we analyze the effect of pretwist (helicity) on the mechanical properties of bundles. We predict that microtubules with different number of protofilaments should have distinct variations in their effective bending rigidity

Teachers Beliefs and Predictors of Response to Verbal, Physical and Relational Bullying Behavior in Preschool Classrooms

Relatively few research studies exist on bullying in preschool classrooms despite research indicating bullying roles can be formed at the preschool level. The purpose of this study was to examine preschoolers’ teachers’ beliefs about the existence of bullying in classrooms, and the factors likely to predict teachers’ response towards bullying behavior. Results revealed that teachers’ empathy, perception of seriousness, and response significantly predicted preschoolers’ verbal, physical, and relational bullying behaviors. The findings of the study highlight the need for advocacy and interventions in preschool classrooms

IPO Earnings Forecast, Corporate Governance and Earnings Management——Empirical study based on the IPO of A-share Mainboard companies

IPO盈利预测披露的问题一直以来都获得了众多学者的重视，因为它对于资本市场有着十分重大的意义。对投资者来说，IPO盈利预测代表着公司对于未来经营业绩的一种预期和描述，向广大投资者提供了支撑决策的信息，提升了市场对于公司的信心，降低了上市公司内部管理者与外部利益相关者之间的信息不对称，帮助投资者进行股票估值和投资决策。因此IPO盈利预测可以提高整个市场的信息效率。但是IPO盈利预测也会带来一个负面的问题，那就是管理层为了迎合预测而进行的盈余管理。 随着我国IPO盈利预测披露制度由强制性转变成了自愿性披露，IPO公司可以自愿选择是否披露盈利预测，这就可能导致披露预测的公司为了降低预测误差而有更强...The disclosure of IPO earnings forecast has always been a focus of study because it is significant for the capital market. For investors, IPO earnings forecast represents the expextation and description for the company’s performance in the future, which provides information for the investors for decision-making, enhances the confidence the market has for the company, reduces information asymmetry...学位：管理学硕士院系专业：管理学院_会计学学号：1752012115111