Dynamic mesh refinement for discrete models of jet electro-hydrodynamics

Nowadays, several models of unidimensional fluid jets exploit discrete element methods. In some cases, as for models aiming at describing the electrospinning nanofabrication process of polymer fibers, discrete element methods suffer a non constant resolution of the jet representation. We develop a dynamic mesh-refinement method for the numerical study of the electro-hydrodynamic behavior of charged jets using discrete element methods. To this purpose, we import ideas and techniques from the string method originally developed in the framework of free-energy landscape simulations. The mesh-refined discrete element method is demonstrated for the case of electrospinning applications.Comment: 16 pages, 7 figures in Journal of Computational Science, 201

Self-crimping bicomponent nanofibres electrospun from polyacrylonitrile and elastomeric polyurethane

Two polymer solutions were brought together via a microfluidic device and subjected to an electrospinning process. The two polymer solutions flowed into the microfluidic channel side-by-side with very little intermixing due to their laminar nature. High speed stretching of the polymer solutions resulted in side-by-side bicomponent fibres. The electrospun nanofibres exhibited an extremely high propensity to self-crimp when an elastomeric polymer (polyurethane) and a normal polymer (polyacrylonitrile PAN) were involved in the electrospinning process. The formation of self-crimping fibre morphology was attributed to the differential shrinkage of the two polymers.<br /

Refined repetitive searches and long identical multi-species elements in mammals and plants : Insights into structure, function and evolution

All of the information necessary to reproduce a living organism is contained in the DNA of its genome. Within the genomic sequence, there are subsequences called genes that are transcribed into RNA and translated into proteins which control cellular function. The genomes of many different organisms, including human, have already been sequenced and many more are currently in progress. Also, there are concurrent projects to annotate the genes from these genomes. Once annotated, cross-species comparisons of both gene sequence and gene annotation terms are possible, which can facilitate knowledge discovery. This dissertation introduces our work in this area. For example, our newly-developed refined repetitive sequence searches were used to identify a potentially new phase-variable site in Haemophilus influenzae based on information previously reported from Helicobacter pylori. The genome of an organism is inherited from its parents and is, in turn, passed on to its descendants. Determinative DNA sequences, both intragenic and intergenic, are often very highly conserved between diverging species over time. In fact, many of these sequences have been exactly conserved in multiple species throughout evolution. Once these sequences can be comprehensively identified in a set of genomes, they can be studied in more detail. This dissertation introduces our work in this area as well. For instance, several previously unreported long identical multi-species elements (LIMEs) were identified and studied in mammals. Also, the comprehensive set of LIMEs in six large plant genomes are identified and extensively characterized in terms structure, function and evolution

Sonoelectrochemical synthesis of submicron metal powders

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 46-48).Pulsed sonoelectrochemical synthesis is a widely used technique for producing nanoparticles. In this technique, alternating pulses of electric current and power ultrasound are applied to an electrochemical cell to create and suspend particles in the electrolyte. The pulsed technique largely separates the particle morphology defining physical action of electrochemistry and ultrasound. Despite the large body of work characterizing the pulsed method, surprisingly little is written about the behavior of particles in the continuous case, where electric current and ultrasound are simultaneously present. In this thesis, continuous ultrasound assisted electrochemical synthesis of nanoparticles is established. Potentially useful mechanisms for particle size and shape control in continuous reactors are discussed. A continuous sonoelectrochemical reactor was designed and demonstrated to produce submicron copper powders. Improvements to the batch reactor design are proposed to extend the technique to a flow reactor useful for commercial production of submicron metal powders.by Joseph Reneker.S.M

Investigation of transportation innovations for food delivery and truck platoons

Studies find that low-income areas are underserved by food retailers and have less access to healthy food, contributing to health disparities. A section of this thesis examines micromobility, drones, and ridesharing that may be suited to deliver food. Using estimated capacities and delivery speeds of several transportation modes, quantitative analysis showed that micromobility is a feasible means of delivery for short-distance, small-quantity orders. Vehicles were the only suitable option once quantity or distance increases, with trucks being the only option for large deliveries of food. Regarding trucks, autonomous truck platooning has potential benefits such as energy savings, increased capacity, and improved safety. A section of this thesis discusses the novel issue of driver behavior interacting with truck platoons in work zones. This research investigates the effects of education, platoon signage, and the number of platooned trucks using a federated simulator study. The study found that education and the use of signage showed increased driver efficiency near platoons. There was a 13 percent increase in speed and 30 percent decrease in distance following a 2-truck platoon after education. Driver speed also increased by at least 14 percent and following distance increased by at least 24 percent, with signage added. Post-simulator survey results showed drivers strongly agree that education helps to clarify how to react to platoons. 90 percent of drivers admitted it is safer to not overtake the platoon, yet only 62 percent indicated they would follow it. Using the results of this research, transportation agencies could formulate policies better accommodate truck platoons as the technology grows.Includes bibliographical references

Refined repetitive sequence searches utilizing a fast hash function and cross species information retrievals

BACKGROUND: Searching for small tandem/disperse repetitive DNA sequences streamlines many biomedical research processes. For instance, whole genomic array analysis in yeast has revealed 22 PHO-regulated genes. The promoter regions of all but one of them contain at least one of the two core Pho4p binding sites, CACGTG and CACGTT. In humans, microsatellites play a role in a number of rare neurodegenerative diseases such as spinocerebellar ataxia type 1 (SCA1). SCA1 is a hereditary neurodegenerative disease caused by an expanded CAG repeat in the coding sequence of the gene. In bacterial pathogens, microsatellites are proposed to regulate expression of some virulence factors. For example, bacteria commonly generate intra-strain diversity through phase variation which is strongly associated with virulence determinants. A recent analysis of the complete sequences of the Helicobacter pylori strains 26695 and J99 has identified 46 putative phase-variable genes among the two genomes through their association with homopolymeric tracts and dinucleotide repeats. Life scientists are increasingly interested in studying the function of small sequences of DNA. However, current search algorithms often generate thousands of matches – most of which are irrelevant to the researcher. RESULTS: We present our hash function as well as our search algorithm to locate small sequences of DNA within multiple genomes. Our system applies information retrieval algorithms to discover knowledge of cross-species conservation of repeat sequences. We discuss our incorporation of the Gene Ontology (GO) database into these algorithms. We conduct an exhaustive time analysis of our system for various repetitive sequence lengths. For instance, a search for eight bases of sequence within 3.224 GBases on 49 different chromosomes takes 1.147 seconds on average. To illustrate the relevance of the search results, we conduct a search with and without added annotation terms for the yeast Pho4p binding sites, CACGTG and CACGTT. Also, a cross-species search is presented to illustrate how potential hidden correlations in genomic data can be quickly discerned. The findings in one species are used as a catalyst to discover something new in another species. These experiments also demonstrate that our system performs well while searching multiple genomes – without the main memory constraints present in other systems. CONCLUSION: We present a time-efficient algorithm to locate small segments of DNA and concurrently to search the annotation data accompanying the sequence. Genome-wide searches for short sequences often return hundreds of hits. Our experiments show that subsequently searching the annotation data can refine and focus the results for the user. Our algorithms are also space-efficient in terms of main memory requirements. Source code is available upon request

BIMBINGAN PRANIKAH SEBAGAI PENYADARAN FUNGSI SEORANG SUAMI BERDASARKAN MAZMUR 128:1-6

The purpose of marriage is to achieve a harmonious and happy family life. In reality, often domestic harmony and happiness do not materialize due to the misunderstanding of family members regarding their roles and functions in the family. Psalm 128:1-6 becomes an important part of the Bible which talks about the necessity of a man playing the role of a husband to build happiness in the family because it must be delivered at the time of premarital counseling. This study uses qualitative research with a literature study approach (Library Research), and specifically, in examining Psalm 128:1-6 the author uses a hermeneutic approach with the grammatical-historical approach to finding the meaning of the selected text. The findings in the study revealed that an understanding of the self-concept of a happy family that focuses on the role of a man as a husband must be built through premarital guidance. Therefore, premarital guidance is an absolute requirement to be carried out before entering into marriage

Polymer based nanocomposites with nanofibers and exfoliated clay

Polymer solutions, containing clay sheets, were electrospun into nanofibers and microfibers that contained clay sheets inside. Controllable removal of polymer by plasma etching from the surface of fibers revealed the arrangement of clay. The shape, flexibility, size distribution and arrangement of clay sheets were observed by transmission and scanning electron microscopy. The clay sheets were partially aligned in big fibers with normal direction of clay sheets perpendicular to fiber axis. Crumpling of clay sheets inside fibers was observed when the fiber diameter was comparable to the lateral size of clay sheets. Single sheets of clay were observed both by catching clay sheets dispersed in water with electrospun nanofiber mats and by the deliberate removal of most of the polymer in the fibers. Thin, flexible gas barrier films, that are reasonably strong, were assembled from clay sheets and polymer nanofibers. Structure of composite films was characterized with scanning electron microscopy. Continuous film of clay sheets were physically attached to the surface of fiber mats. Spincoating film of polymer and clay sheets was reinforced by electrospun fiber scaffold. Certain alignment of clay sheets was observed in the vicinity of fibers

Enterprise knowledge portals: two projects in the United States Department of the Navy

Two projects in the US Department of the Navy to develop enterprise portals for facilitating knowledge discovery and dissemination are discussed. The authors describe efforts within a global organization to capitalize on current knowledge management concepts and technologies for knowledge access and sharing in order to provide users with more personalized, responsive and integrated information systems. The Next Generation Library supports knowledge management and networking objectives, as well as providing high-quality content access at the desktop. The Naval Postgraduate School Knowledge Portal, still under development, is designed to link internal administrative databases with current message traffic and external scholarly information resources