Multifunctional, Multimaterial Particle Fabrication Via an In-Fiber Fluid Instability

Spherical micro- and nano-particles have found widespread use in many various applications from paint to cosmetics to medicine. Due to the multiplicity of desired particle material(s), structure, size range, and functionality, many approaches exist for generating such particles. Bottom-up methods such as chemical synthesis have a high yield and work with a wide range of materials; however, these processes typically lead to large polydispersity and cannot produce structured particles. Top-down approaches such as microfluidics overcome the polydispersity issue and may produce a few different structures in particles, but at lower rates and only at the micro-scale. A method that can efficiently produce uniformly-sized, structured particles out of a variety of materials and at both the micro- and nano-scales does not yet exist. Over the past few years, I have developed an in-fiber particle fabrication method that relies on a surface tension-driven fluid instability, the Plateau-Rayleigh capillary instability (PRI). Thermal treatment of a multimaterial core/cladding fiber induces the PRI, causing the initially intact core to break up into a periodic array of uniformly-sized spherical particles. During this time, I have demonstrated that this method can produce particles from both polymers and glasses, in a multiplicity of structures, and from diameters of over 1 mm down to 20 nm. Furthermore, by using a stack-and-draw method, a high density of cores may be incorporated into a single fiber, making the in-fiber PRI approach a highly scalable process. Finally, I have shown that it is possible to add dopants to the particles to give them functionality. By structuring the particles, it is thus possible to fabricate multi-functional particles whose functionalities may be allocated arbitrarily throughout the volume of the particles

Mixing Enhancement in Serpentine Micromixers with a Non-Rectangular Cross-Section

In this numerical study, a new type of serpentine micromixer involving mixing units with a non-rectangular cross-section is investigated. Similar to other serpentine/spiral shaped micromixers, the design exploits the formation of transversal vortices (Dean flows) in pressure-driven systems, associated with the centrifugal forces experienced by the fluid as it is confined to move along curved geometries. In contrast with other previous designs, though, the use of non-rectangular cross-sections that change orientation between mixing units is exploited to control the center of rotation of the transversal flows formed. The associated extensional flows that thus develop between the mixing segments complement the existent rotational flows, leading to a more complex fluid motion. The fluid flow characteristics and associated mixing are determined numerically from computational solutions to Navier–Stokes equations and the concentration-diffusion equation. It is found that the performance of the investigated mixers exceeds that of simple serpentine channels with a more consistent behavior at low and high Reynolds numbers. An analysis of the mixing quality using an entropic mixing index indicates that maximum mixing can be achieved at Reynolds numbers as small as 20 in less than four serpentine mixing units

Miocene Burrows of Extinct Bear Dogs: Indication of Early Denning Behavior of Large Mammalian Carnivores

Partial skeletons of four species of extinct carnivores have been found in their dens excavated in the floodplain of an early Miocene ephemeral braided stream at Agate Fossil Beds National Monument, Nebraska. Bear dogs (Carnivora: Amphicyonidae) were the principal occupants; their den dimensions and body size are similar to those of living wolves and hyenas. Discovery of this predator community extends the record of denning behavior of large mammalian carnivores to the early Miocene, 20 million years ago

Tool for real-time distributed monitoring of home electricity consumption

Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (p. 51).This thesis presents SeeGreen, a system designed to enable easy collection of distributed information about power usage (quantity and quality) in residential facilities. In Europe many appliances are emerging that incorporate power measuring devices for power regulation. However, products for retrofitting old appliances or recording measurements from other power consuming devices are not available. Due to aging of appliances, varying consumer habits and appliance standby modes, estimating the power consumption behavior of a device is remarkably difficult. Products in "off' (or standby) modes consume an estimated ten percent of the electrical energy used in a house. With built in AC switches, SeeGreen has the capacity to minimize or even eliminate this unnecessary waste. Perhaps the largest downfall of modem monitoring systems is a lack of real-time (immediate) feedback about an appliance's consumption. Feedback of this nature highly encourages change in consumer behavior. SeeGreen facilitates reduced electricity consumption by providing information to consumers and automatic control devices.by Joshua Daniel Kaufman.M.Eng.and S.B

Efficient emulators of computer experiments using compactly supported correlation functions, with an application to cosmology

Statistical emulators of computer simulators have proven to be useful in a variety of applications. The widely adopted model for emulator building, using a Gaussian process model with strictly positive correlation function, is computationally intractable when the number of simulator evaluations is large. We propose a new model that uses a combination of low-order regression terms and compactly supported correlation functions to recreate the desired predictive behavior of the emulator at a fraction of the computational cost. Following the usual approach of taking the correlation to be a product of correlations in each input dimension, we show how to impose restrictions on the ranges of the correlations, giving sparsity, while also allowing the ranges to trade off against one another, thereby giving good predictive performance. We illustrate the method using data from a computer simulator of photometric redshift with 20,000 simulator evaluations and 80,000 predictions.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS489 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Western North Pacific Tropical Cyclone Formation and Structure Change in TCS-08 and TCS-08 Field Experiment Support

Long-term goals: The long-term goal of this project is to develop a better understanding of mesoscale and synoptic-scale processes associated with the entire life cycle of tropical cyclones in the western North Pacific. The inability to correctly identify tropical cyclone formation over the period of 24 h – 48 h poses a threat to shore and afloat assets across the western North Pacific. Furthermore, once a tropical cyclone has formed the predictability of structure changes during intensification of tropical cyclones is very low, which is due to complex physical processes that vary over a wide range of space and time scales. Periods of reduced predictability occur throughout the tropical cyclone life cycle, which includes the decaying stage. Because decaying tropical cyclones often transition to a fast-moving and rapidly- developing extratropical cyclone that may contain gale-, storm-, or hurricane-force winds, there is a need to improve understanding and prediction of the extratropical transition phase of a decaying tropical cyclone. The structural evolution of the transition from a tropical to an extratropical circulation involves rapid changes to the wind, cloud, and precipitation patterns that potentially impact maritime and shore-based facilities.N0001409WR2000

Amphiprion barberi, a new species of anemonefish (Pomacentridae) from Fiji, Tonga, and Samoa

Amphiprion barberi, a new species of anemonefish fish, is described from 46 specimens, 16.3-85.8 mm SL, collected at depths of 2-10 m from coral reefs of Fiji, Tonga, and Samoa. It is closely allied to A. melanopus, which is widely distributed in the western Pacific. The two species exhibit significant colour-pattern differences, including a mainly reddish orange body in A. barberi and dark brown or blackish body in A. melanopus. Adults of the new species also possess fewer spinules (11-19 versus 19-26) in the upper-opercular series than A. melanopus. Genetic data presented here confirms the separation of these species