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MIT Open Access Articles

Mostrando recursos 1 - 20 de 22.260

  1. Rapid MPN-Qpcr Screening for Pathogens in Air, Soil, Water, and Agricultural Produce

    Orlofsky, Ezra; Benami, Maya; Gross, Amit; Gillor, Osnat; Dutt, Michelle M.
    A sensitive, high-throughput, and cost-effective method for screening bacterial pathogens in the environment was developed. A variety of environmental samples, including aerosols, soil of various types (sand, sand/clay mix, and clay), wastewater, and vegetable surface (modeled by tomato), were concomitantly spiked with Salmonella enterica and/or Pseudomonas aeruginosa to determine recovery rates and limits of detection. The various matrices were first enriched with a general pre-enrichment broth in a dilution series and then enumerated by most probable number (MPN) estimation using quantitative PCR for rapid screening of amplicon presence. Soil and aerosols were then tested in non-spiked environmental samples, as these...

  2. An effective field theory for forward scattering and factorization violation

    Rothstein, Ira Z.; Stewart, Iain W
    Starting with QCD, we derive an effective field theory description for forward scattering and factorization violation as part of the soft-collinear effective field theory (SCET) for high energy scattering. These phenomena are mediated by long distance Glauber gluon exchanges, which are static in time, localized in the longitudinal distance, and act as a kernel for forward scattering where |t| ≪ s. In hard scattering, Glauber gluons can induce corrections which invalidate factorization. With SCET, Glauber exchange graphs can be calculated explicitly, and are distinct from graphs involving soft, collinear, or ultrasoft gluons. We derive a complete basis of operators which...

  3. David Schmittlein on Marketing

    Schmittlein, David C
    At the request of Customer Needs and Solutions, David Schmittlein, a marketing professor and the John C. Head III Dean of the MIT Sloan School of Management, reflects on a few wide-ranging issues raised by the Journal’s editorial board members. The interview was conducted by Catherine Tucker, a marketing professor at MIT Sloan School of Management and a member of the editorial board, on behalf of the Journal on Dec. 5, 2013. Excerpts of this interview are printed here, and the full videotaped interview is available in the public domain.

  4. Detecting meaning in RSVP at 13 ms per picture

    Wyble, Brad; Potter, Mary C; Hagmann, Carl; McCourt, Emily Sarah
    The visual system is exquisitely adapted to the task of extracting conceptual information from visual input with every new eye fixation, three or four times a second. Here we assess the minimum viewing time needed for visual comprehension, using rapid serial visual presentation (RSVP) of a series of six or 12 pictures presented at between 13 and 80 ms per picture, with no interstimulus interval. Participants were to detect a picture specified by a name (e.g., smiling couple) that was given just before or immediately after the sequence. Detection improved with increasing duration and was better when the name was...

  5. Aerosol-Assisted Plasma Deposition of Hydrophobic Polycations Makes Surfaces Highly Antimicrobial

    Liu, Harris; Kim, Yoojeong; Mello, Kerrianne; Lovaasen, John; Shah, Apoorva; Rice, Norman; Pappas, Daphne; Yim, Jacqueline H.; Klibanov, Alexander M
    The currently used multistep chemical synthesis for making surfaces antimicrobial by attaching to them hydrophobic polycations is replaced herein by an aerosol-assisted plasma deposition procedure. To this end, N,N-hexyl,methyl-PEI (HMPEI) is directly plasma-coated onto a glass surface. The resultant immobilized HMPEI coating has been thoroughly characterized and shown to be robust, bactericidal against Escherichia coli, and virucidal against human influenza virus.

  6. Human manual control performance in hyper-gravity

    Newman, Michael C.; Merfeld, Daniel M.; Young, Laurence R.; Clark, Torin K; Oman, Charles M
    Hyper-gravity provides a unique environment to study how misperceptions impact control of orientation relative to gravity. Previous studies have found that static and dynamic roll tilts are perceptually overestimated in hyper-gravity. The current investigation quantifies how this influences control of orientation. We utilized a long-radius centrifuge to study manual control performance in hyper-gravity. In the dark, subjects were tasked with nulling out a pseudo-random roll disturbance on the cab of the centrifuge using a rotational hand controller to command their roll rate in order to remain perceptually upright. The task was performed in 1, 1.5, and 2 G’s of net...

  7. Advances in electrospun carbon fiber-based electrochemical sensing platforms for bioanalytical applications

    Mao, Xianwen; Hatton, Trevor Alan; Tian, Wenda; Rutledge, Gregory C
    Electrochemical sensing is an efficient and inexpensive method for detection of a range of chemicals of biological, clinical, and environmental interest. Carbon materials-based electrodes are commonly employed for the development of electrochemical sensors because of their low cost, biocompatibility, and facile electron transfer kinetics. Electrospun carbon fibers (ECFs), prepared by electrospinning of a polymeric precursor and subsequent thermal treatment, have emerged as promising carbon systems for biosensing applications since the electrochemical properties of these carbon fibers can be easily modified by processing conditions and post-treatment. This review addresses recent progress in the use of ECFs for sensor fabrication and analyte...

  8. Interval bounds on the solutions of semi-explicit index-one DAEs. Part 2: computation

    Scott, Joseph Kirk; Barton, Paul I
    This article presents two methods for computing interval bounds on the solutions of nonlinear, semi-explicit, index-one differential-algebraic equations (DAEs). Part 1 presents theoretical developments, while Part 2 discusses implementation and numerical examples. The primary theoretical contributions are (1) an interval inclusion test for existence and uniqueness of a solution, and (2) sufficient conditions, in terms of differential inequalities, for two functions to describe componentwise upper and lower bounds on this solution, point-wise in the independent variable. The first proposed method applies these results sequentially in a two-phase algorithm analogous to validated integration methods for ordinary differential equations (ODEs). The second...

  9. Interval bounds on the solutions of semi-explicit index-one DAEs. Part 1: analysis

    Scott, Joseph Kirk; Barton, Paul I
    This article presents two methods for computing interval bounds on the solutions of nonlinear, semi-explicit, index-one differential-algebraic equations (DAEs). Part 1 presents theoretical developments, while Part 2 discusses implementation and numerical examples. The primary theoretical contributions are (1) an interval inclusion test for existence and uniqueness of a solution, and (2) sufficient conditions, in terms of differential inequalities, for two functions to describe componentwise upper and lower bounds on this solution, point-wise in the independent variable. The first proposed method applies these results sequentially in a two-phase algorithm analogous to validated integration methods for ordinary differential equations. The second method...

  10. The impact of Southern Ocean residual upwelling on atmospheric CO[subscript 2] on centennial and millennial timescales

    Williams, Richard G.; Munday, David R.; Marshall, David P.; Lauderdale, Jonathan
    The Southern Ocean plays a pivotal role in climate change by exchanging heat and carbon, and provides the primary window for the global deep ocean to communicate with the atmosphere. There has been a widespread focus on explaining atmospheric CO[subscript 2] changes in terms of changes in wind forcing in the Southern Ocean. Here, we develop a dynamically-motivated metric, the residual upwelling, that measures the primary effect of Southern Ocean dynamics on atmospheric CO[subscript 2] on centennial to millennial timescales by determining the communication with the deep ocean. The metric encapsulates the combined, net effect of winds and air–sea buoyancy...

  11. Graph cuts with interacting edge weights: examples, approximations, and algorithms

    Bilmes, Jeff A.; Jegelka, Stefanie Sabrina
    We study an extension of the classical graph cut problem, wherein we replace the modular (sum of edge weights) cost function by a submodular set function defined over graph edges. Special cases of this problem have appeared in different applications in signal processing, machine learning, and computer vision. In this paper, we connect these applications via the generic formulation of “cooperative graph cuts”, for which we study complexity, algorithms, and connections to polymatroidal network flows. Finally, we compare the proposed algorithms empirically.

  12. Graph cuts with interacting edge weights: examples, approximations, and algorithms

    Bilmes, Jeff A.; Jegelka, Stefanie Sabrina
    We study an extension of the classical graph cut problem, wherein we replace the modular (sum of edge weights) cost function by a submodular set function defined over graph edges. Special cases of this problem have appeared in different applications in signal processing, machine learning, and computer vision. In this paper, we connect these applications via the generic formulation of “cooperative graph cuts”, for which we study complexity, algorithms, and connections to polymatroidal network flows. Finally, we compare the proposed algorithms empirically.

  13. Suzuki–Miyaura cross-coupling optimization enabled by automated feedback

    Reizman, Brandon Jacob; Wang, Yiming; Buchwald, Stephen Leffler; Jensen, Klavs F
    An automated, droplet-flow microfluidic system explores and optimizes Pd-catalyzed Suzuki–Miyaura cross-coupling reactions. A smart optimal DoE-based algorithm is implemented to increase the turnover number and yield of the catalytic system considering both discrete variables—palladacycle and ligand—and continuous variables—temperature, time, and loading—simultaneously. The use of feedback allows for experiments to be run with catalysts and under conditions more likely to produce an optimum; consequently complex reaction optimizations are completed within 96 experiments. Response surfaces predicting reaction performance near the optima are generated and validated. From the screening results, shared attributes of successful precatalysts are identified, leading to improved understanding of the...

  14. Suzuki–Miyaura cross-coupling optimization enabled by automated feedback

    Reizman, Brandon Jacob; Wang, Yiming; Buchwald, Stephen Leffler; Jensen, Klavs F
    An automated, droplet-flow microfluidic system explores and optimizes Pd-catalyzed Suzuki–Miyaura cross-coupling reactions. A smart optimal DoE-based algorithm is implemented to increase the turnover number and yield of the catalytic system considering both discrete variables—palladacycle and ligand—and continuous variables—temperature, time, and loading—simultaneously. The use of feedback allows for experiments to be run with catalysts and under conditions more likely to produce an optimum; consequently complex reaction optimizations are completed within 96 experiments. Response surfaces predicting reaction performance near the optima are generated and validated. From the screening results, shared attributes of successful precatalysts are identified, leading to improved understanding of the...

  15. Normal Evoked Response to Rapid Sequences of Tactile Pulses in Autism Spectrum Disorders

    Ganesan, Santosh; Khan, Sheraz; Garel, Keri-Lee A.; Hämäläinen, Matti S.; Kenet, Tal
    Autism spectrum disorder (ASD) is a developmental disorder diagnosed behaviorally, with many documented neurophysiological abnormalities in cortical response properties. While abnormal sensory processing is not considered core to the disorder, most ASD individuals report sensory processing abnormalities. Yet, the neurophysiological correlates of these abnormalities have not been fully mapped. In the auditory domain, studies have shown that cortical responses in the early auditory cortex in ASD are abnormal in multiple ways. In particular, it has been shown that individuals with ASD have abnormal cortical auditory evoked responses to rapid, but not slow, sequences of tones. In parallel, there is substantial...

  16. Normal Evoked Response to Rapid Sequences of Tactile Pulses in Autism Spectrum Disorders

    Ganesan, Santosh; Khan, Sheraz; Garel, Keri-Lee A.; Hämäläinen, Matti S.; Kenet, Tal
    Autism spectrum disorder (ASD) is a developmental disorder diagnosed behaviorally, with many documented neurophysiological abnormalities in cortical response properties. While abnormal sensory processing is not considered core to the disorder, most ASD individuals report sensory processing abnormalities. Yet, the neurophysiological correlates of these abnormalities have not been fully mapped. In the auditory domain, studies have shown that cortical responses in the early auditory cortex in ASD are abnormal in multiple ways. In particular, it has been shown that individuals with ASD have abnormal cortical auditory evoked responses to rapid, but not slow, sequences of tones. In parallel, there is substantial...

  17. Uncertainty in future agro-climate projections in the United States and benefits of greenhouse gas mitigation

    Snyder, Richard; Monier, Erwan; Monier, Liyi Xu
    Scientific challenges exist on how to extract information from the wide range of projected impacts simulated by crop models driven by climate ensembles. A stronger focus is required to understand and identify the mechanisms and drivers of projected changes in crop yield. In this study, we investigate the robustness of future projections of five metrics relevant to agriculture stakeholders (accumulated frost days, dry days, growing season length, plant heat stress and start of field operations). We use a large ensemble of climate simulations by the MIT IGSM-CAM integrated assessment model that accounts for the uncertainty associated with different emissions scenarios,...

  18. Uncertainty in future agro-climate projections in the United States and benefits of greenhouse gas mitigation

    Snyder, Richard; Monier, Erwan; Monier, Liyi Xu
    Scientific challenges exist on how to extract information from the wide range of projected impacts simulated by crop models driven by climate ensembles. A stronger focus is required to understand and identify the mechanisms and drivers of projected changes in crop yield. In this study, we investigate the robustness of future projections of five metrics relevant to agriculture stakeholders (accumulated frost days, dry days, growing season length, plant heat stress and start of field operations). We use a large ensemble of climate simulations by the MIT IGSM-CAM integrated assessment model that accounts for the uncertainty associated with different emissions scenarios,...

  19. Poly(glycoamidoamine) Brushes Formulated Nanomaterials for Systemic siRNA and mRNA Delivery in Vivo

    Abutbul-Ionita, Inbal; Danino, Dganit; DeRosa, Frank; Heartlein, Michael; Dong, Yizhou; Dorkin, Joseph Robert; Wang, Weiheng; Chang, Philip; Webber, Matthew; Tang, Benjamin C.; Yang, Jung H; Langer, Robert S; Anderson, Daniel Griffith
    Safe and effective delivery is required for siRNA and mRNA-based therapeutics to reach their potential. Here, we report on the development of poly(glycoamidoamine) brush nanoparticles as delivery vehicles for siRNA and mRNA. These polymers were capable of significant delivery of siRNA against FVII and mRNA-encoding erythropoietin (EPO) in mice. Importantly, these nanoparticles were well-tolerated at their effective dose based on analysis of tissue histology, systemic cytokine levels, and liver enzyme chemistry. The polymer brush nanoparticles reported here are promising for therapeutic applications.

  20. Poly(glycoamidoamine) Brushes Formulated Nanomaterials for Systemic siRNA and mRNA Delivery in Vivo

    Abutbul-Ionita, Inbal; Danino, Dganit; DeRosa, Frank; Heartlein, Michael; Dong, Yizhou; Dorkin, Joseph Robert; Wang, Weiheng; Chang, Philip; Webber, Matthew; Tang, Benjamin C.; Yang, Jung H; Langer, Robert S; Anderson, Daniel Griffith
    Safe and effective delivery is required for siRNA and mRNA-based therapeutics to reach their potential. Here, we report on the development of poly(glycoamidoamine) brush nanoparticles as delivery vehicles for siRNA and mRNA. These polymers were capable of significant delivery of siRNA against FVII and mRNA-encoding erythropoietin (EPO) in mice. Importantly, these nanoparticles were well-tolerated at their effective dose based on analysis of tissue histology, systemic cytokine levels, and liver enzyme chemistry. The polymer brush nanoparticles reported here are promising for therapeutic applications.

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