University of Massachusetts Amherst

About: University of Massachusetts Amherst is a education organization based out in Amherst Center, Massachusetts, United States. It is known for research contribution in the topics: Population & Galaxy. The organization has 37274 authors who have published 83965 publications receiving 3834996 citations. The organization is also known as: UMass Amherst & Massachusetts State College.

A survey of loss functions for semantic segmentation

Abstract: Image Segmentation has been an active field of research as it has a wide range of applications, ranging from automated disease detection to self driving cars. In the past five years, various papers came up with different objective loss functions used in different cases such as biased data, sparse segmentation, etc. In this paper, we have summarized some of the well-known loss functions widely used for Image Segmentation and listed out the cases where their usage can help in fast and better convergence of a model. Furthermore, we have also introduced a new log-cosh dice loss function and compared its performance on NBFS skull-segmentation open source data-set with widely used loss functions. We also showcased that certain loss functions perform well across all data-sets and can be taken as a good baseline choice in unknown data distribution scenarios.

Capillary wrinkling of floating thin polymer films.

Abstract: A freely floating polymer film, tens of nanometers in thickness, wrinkles under the capillary force exerted by a drop of water placed on its surface. The wrinkling pattern is characterized by the number and length of the wrinkles. The dependence of the number of wrinkles on the elastic properties of the film and on the capillary force exerted by the drop confirms recent theoretical predictions on the selection of a pattern with a well-defined length scale in the wrinkling instability. We combined scaling relations that were developed for the length of the wrinkles with those for the number of wrinkles to construct a metrology for measuring the elasticity and thickness of ultrathin films that relies on no more than a dish of fluid and a low-magnification microscope. We validated this method on polymer films modified by plasticizer. The relaxation of the wrinkles affords a simple method to study the viscoelastic response of ultrathin films.

Humic Substances as a Mediator for Microbially Catalyzed Metal Reduction

Abstract: The potential for humic substances to serve as a terminal electron acceptor in microbial respiration and to function as an electron shuttle between Fe(III)-reducing microorganisms and insoluble Fe(III) oxides was investigated. The Fe(III)-reducing microorganism Geobacter metallireducens conserved energy to support growth from electron transport to humics as evidenced by continued oxidation of acetate to carbon dioxide after as many as nine transfers in a medium with acetate as the electron donor and soil humic acids as the electron acceptor. Growth of G. metallireducens with poorly crystalline Fe(III) oxide as the electron acceptor was greatly stimulated by the addition of as little as 100 μM of the humics analog, anthraquinone-2,6-disulfonate. Other quinones investigated, including lawsone, menadione, and anthraquinone-2-sulfonate, also stimulated Fe(III) oxide reduction. A wide phylogenetic diversity of microorganisms capable of Fe(III) reduction were also able to transfer electrons to humics. Microorganisms which can not reduce Fe(III) could not reduce humics. Humics stimulated the reduction of structural Fe(III) in clay and the crystalline Fe(III) forms, goethite and hematite. These results demonstrate that electron shuttling between Fe(III)-reducing microorganisms and Fe(III) via humics not only accelerates the microbial reduction of poorly crystalline Fe(III) oxide, but also can facilitate the reduction of Fe(III) forms that are not typically reduced by microorganisms in the absence of humics. Addition of humic substances to enhance electron shuttling between Fe(III)-reducing microorganisms and Fe(III) oxides may be a useful strategy to stimulate the remediation of soils and sediments contaminated with organic or metal pollutants. Huminstoffe als Vermittler bei der mikrobiell katalysierten Metallreduktion Es wurde untersucht, inwieweit Huminstoffe als terminale Elektronenakzeptoren bei der mikrobiellen Atmung und als Vermittler bei der Elektronenubertragung zwischen Fe(III)-reduzierenden Mikroorganismen und unloslichen Fe(III)-oxiden fungieren konnen. Das Fe(III)-reduzierende Bakterium Geobacter metallireducens gewinnt Energie zum Wachstum aus der Elektronenubertragung auf Huminstoffe. Das wurde offensichtlich, als nach 9 aufeinanderfolgenden Transfers des Bakteriums auf frisches Medium mit Acetat als Elektronendonor und Boden-Huminstoff als Elektronenakzeptor seine Fahigkeit zur Oxidation von Acetat zu CO2 erhalten blieb. Das Wachstum von G. metallireducens mit niedrigkristallinem Fe(III)-oxid als Elektronenakzeptor konnte durch den Zusatz des Huminstoff-Analogen Anthrachinon-2,6-disulfonat bereits in Konzentrationen von 100 μmol/L deutlich stimuliert werden. Auch weitere untersuchte Chinone wie z.B. Lawson (2-Hydroxy-1,4-naphthochinon), Menadion (2-Methyl-1,4-naphthochinon) und Anthrachinon-2-sulfonat stimulierten die Fe(III)-oxid-Reduktion. Eine grose Anzahl phylogenetisch unterschiedlicher Mikroorganismen, die zur Fe(III)-Reduktion befahigt sind, zeigten gleichzeitig die Fahigkeit zum Elektronentransfer auf Huminstoffe. Zur Fe(III)-Reduktion nicht befahigte Mikroorganismen konnten auch Huminstoffe nicht reduzieren. Durch Huminstoffe konnte die Reduktion von Fe(III) stimuliert werden, das in die Struktur von Tonmineralen und in kristalline Formen des Fe(III)-oxids, Goethit und Hamatit, eingebaut ist. Diese Ergebnisse zeigen, das durch die vermittelnde Funktion der Huminstoffe bei der Elektronenubertragung zwischen Fe(III)-reduzierenden Mikroorganismen und Fe(III) nicht nur die mikrobielle Reduktion von niedrigkristallinem Fe(III)-oxid beschleunigt wird, sondern auch die Reduktion von solchen Formen des Fe(III) erleichtert wird, welche im allgemeinen in Abwesenheit von Huminstoffen durch Fe(III)-reduzierende Mikroorganismen nicht reduziert werden. Die Zugabe von Huminstoffen zur Verbesserung der Elektronenubertragung zwischen Fe(III)-reduzierenden Mikroorganismen und Fe(III)-oxiden konnte eine nutzliche Strategie zur Stimulierung der Sanierung von mit organischen oder metallischen Kontaminanten verunreinigten Boden und Sedimenten sein.

A Thematic Guide to Optimality Theory

Abstract: This book describes Optimality Theory from the top down, explaining and exploring the central premises of OT and the results of their praxis Examples are drawn from phonology, morphology, and syntax, but the emphasis throughout is on the theory rather than the examples, on understanding what is special about OT and on equipping readers to apply it, extend it, and critique it in their own areas of interest To enhance the book's usefulness for researchers in allied disciplines, the topdown view of OT extends to work on first- and second-language acquisition, phonetics and functional phonology, computational linguistics, historical linguistics, and sociolinguistics Furthermore, to situate OT for those coming from other traditions, this book also contains much discussion of OT's intellectual origins, its predecessors, and its contemporary competitors Each chapter concludes with extensive suggestions for further reading, classified by topics, and supplemented by a massive bibliography (over 800 items) The book ends with a list of frequently asked questions about Optimality Theory, with brief answers and pointers to a fuller treatment in the text