Harry Hess and sea-floor spreading

Harry Hess's hypothesis of sea-floor spreading brought together his long-standing interests in island arcs, oceanic topography, and the oceanic crust. The one unique feature of Hess's hypothesis was the origin of the oceanic crust as a hydration rind on the top of the mantle -- an idea that was not well received, even by the early converts to sea-floor spreading. Hess never changed his mind on this issue, and his stubbornness illuminates the logic of his discovery. Published and archival records show that 1) Hess became convinced the oceanic crust was a hydration rind as early as mid 1958, when he was still a fixist, 2) he devised sea-floor spreading in 1960 to reconcile the hydration-rind model with the newly discovered, high heat flow at oceanic ridge crests, and 3) Hess's new mobilist solution did the least amount of violence to his older fixist solution

A passive vibration-cancelling isolation mount

An analysis of an idealized passive vibration-cancelling two-terminal mount with one degree of freedom at each mechanical terminal isolating a nonrigid machine from a nonrigid foundation is presented. To evaluate a vibration-cancelling (VC) mount, its effectiveness as a function of frequency is compared with the effectiveness of both conventional and compound mounts isolating a rigid machine from a nonrigid foundation. The comparisons indicate that a carefully designed and manufactured VC mount should provide substantially greater vibration reduction at its cancellation frequency than either a conventional or compound mount having the same low frequency stiffness, i.e., stiffness at the natural frequency of the machine mount system

High MRSA Carriage Rate among Nursing Microbiology Students

Staphylococcus aureus is a common cause of disease, particularly in colonized persons. Although methicillin-resistant S. aureus (MRSA) infections have become increasingly reported, populationbased studies of students preparing for the health professions having S. aureus and MRSA colonization are lacking. We have found that students in microbiology classes having more contact with individuals in a healthcare setting are more likely to carry MRSA in their nares and axilla. The classes who had the highest rate of MRSA carriage during the school year, 2013-2014, were those with nursing students, who had a greater exposure to clinical settings and nursing homes. The class which had the highest rate of S. aureus carriage, had nearly 50% of the infected students had been involved a clinical setting. Since the majority of the students in the nursing and biology courses are looking to pursue a career in medicine, this sampling was very beneficial to inform them and others if they were a carrier of S. aureus and MRSA and the preventative measures to reduce the risk of infection

Double simple-harmonic-oscillator formulation of the thermal equilibrium of a fluid interacting with a coherent source of phonons

A formulation is given for a collection of phonons (sound) in a fluid at a non-zero temperature which uses the simple harmonic oscillator twice; one to give a stochastic thermal 'noise' process and the other which generates a coherent Glauber state of phonons. Simple thermodynamic observables are calculated and the acoustic two point function, 'contrast' is presented. The role of 'coherence' in an equilibrium system is clarified by these results and the simple harmonic oscillator is a key structure in both the formulation and the calculations

Analysis of a fixed-pitch X-wing rotor employing lower surface blowing

Lower surface blowing (LSB) is investigated as an alternative to the variable blade pitch requirement for the X-wing Circulation Control (CC) rotor concept. Addition trailing edge blowing slots on the lower surfaces of CC airfoils provide a bidirectional lift capability that effectively doubles the control range. The operational requirements of this rotor system are detailed and compared to the projected performance attributes of LSB airfoils. Analysis shows that, aerodynamically, LSB supplies a fixed pitch rotor system with the equivalent lift efficiency and rotor control of present CC rotor designs that employ variable blade pitch. Aerodynamic demands of bidirectional lift production are predicted to be within the capabilities of current CC airfoil design methodology. Emphasis in this analysis is given to the high speed rotary wing flight regime unique to stoppable rotor aircraft. The impact of a fixed pitch restriction in hover and low speed flight is briefly discussed

Hierarchical Nearest-Neighbor Gaussian Process Models for Large Geostatistical Datasets

Spatial process models for analyzing geostatistical data entail computations that become prohibitive as the number of spatial locations become large. This manuscript develops a class of highly scalable Nearest Neighbor Gaussian Process (NNGP) models to provide fully model-based inference for large geostatistical datasets. We establish that the NNGP is a well-defined spatial process providing legitimate finite-dimensional Gaussian densities with sparse precision matrices. We embed the NNGP as a sparsity-inducing prior within a rich hierarchical modeling framework and outline how computationally efficient Markov chain Monte Carlo (MCMC) algorithms can be executed without storing or decomposing large matrices. The floating point operations (flops) per iteration of this algorithm is linear in the number of spatial locations, thereby rendering substantial scalability. We illustrate the computational and inferential benefits of the NNGP over competing methods using simulation studies and also analyze forest biomass from a massive United States Forest Inventory dataset at a scale that precludes alternative dimension-reducing methods

Development of novel polymeric nanoparticles with tailored architectures and functionalities/

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 41-47).Developing a modular synthetic route to a combinatorial library of functional nanoparticles for applications like drug delivery is one of the main interests of our group. To this end, we have envisioned a novel nanoparticle architecture called a brush-arm star polymer (BASP), which has polymer brushes on the periphery shielding the core. Such nanoparticles were synthesized by, first, "graft-through" ring-opening metathesis polymerization (ROMP) of a norbornene-macromonomer to create the brush-arms, and second, cross-linking the arms with a bis-norbornene cross-linker to afford star polymers via the "arm-first" star polymer method. Functionality can be installed into the macromonomer (MM) or crosslinker preand post-polymerization. We took advantage of the highly efficient third-generation Grubbs catalyst to polymerize a polyethylene glycol (PEG) macromonomer (MM) and a bisnorbornene nitrobenzyloxycarbonyl (NBOC) photocleavable cross-linker to cross-link the brush-arms, which led to low-dispersity (Đ \=1.52) BASPs, while the more rigid RAFT initiator crosslinker led to low-dispersity (Đ </=1.05) BASPs. Finally, doxorubicin-loaded, photocleavable drug vector BASPs were synthesized from azide-functionalized BASPs. Copper-catalyzed azide-alkyne cycloaddition (CuAAC) was utilized to covalently link doxorubicin to the azide BASPs, post-polymerization. These BASPs degraded and simultaneously released their drug payload upon UV irradiation. MTT assays were conducted with these nanoparticles on MCF-7 human breast cancer cells and were shown to be non-toxic before UV irradiation and toxic afterward.by Alan O. Burts.S.M