812 research outputs found
Cosmic Rays origin studies in the W 44 region with Fermi-LAT and MAGIC observations
No full textW44 is a well-known Supernova Remnant (SNR) observed in high-energy gamma-rays, widely studied to investigate cosmic ray (CR) acceleration. Several analyses of the W44 surroundings showed the presence of a gamma-ray emission offset from the radio SNR shell. This emission is thought to originate from escaped high-energy CRs. We present a detailed analysis of the W44 region as seen by Fermi-LAT, focusing on the spatial and spectral characteristics of both W44 SNR and its surroundings. The spatial analysis was limited to energies above 1 GeV in order to exploit the improved angular resolution of the instrument, deriving a detailed description of the region morphology. The spectral analysis was extended down to 100 MeV, favouring the hadronic origin of gamma-rays. Observations of the North-Western region of W44 were conducted with the MAGIC telescopes in the very-high-energy gamma-ray band. We analysed MAGIC data above 130 GeV exploiting the spatial information derived from the Fermi-LAT analysis above 1 GeV. Here we show the results of both analyses and the combined Fermi-LAT and MAGIC spectra. An interpretation model was developed, assuming that the gamma-ray emission from the surroundings is due to clouds located near W44 and illuminated by CRs escaping along the SNR’s magnetic field lines, thus obtaining constraining information on the diffusion coefficient of the escaped CRs
Ruskin traduzido: Sesame and Lilies por Proust e Catalán
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão, Programa de Pós-Graduação em Literatura, Florianópolis, 2009.Este trabalho parte da análise das traduções da obra Sesame and Lilies, de John Ruskin, para o francês e para o castelhano para fazer um exame de questões ligadas ao gênero ensaístico, à tradução de ensaios e à autoria. Para isso, analisarei a tradução de Marcel Proust para o francês e seu paratexto e a tradução para o castelhano feita por Miguel Catalán e o respectivo paratexto.This study analises the translations of Sesame and Lilies, by John Ruskin, into French and Spanish in order to examine issues related to the essay as a literary genre, to the translation of essays and to authorship. This exam will be carried out by analising the translation into French by Marcel Proust and its paratext and the translation into Spanish by Miguel Catalán, accompanied by its paratext
Addressing the challenges of climate change risks and adaptation in coastal areas: A review
No full textClimate change is and will continue altering the world's coasts, which are the most densely populated and economically active areas on earth and home for highly valuable ecosystems. While there is considerable relevant research, in the authors' experience this problem remains challenging for coastal engineering. This paper reviews important challenges in this respect and identifies three key actions to address them: (a) refocusing traditional practice towards more climate-aware approaches; (b) developing more comprehensive risk frameworks that include the multi-dimensionality and non-stationarity of their components and consideration of uncertainty; and (c) building bridges between risk assessment and adaptation theory and practice. We conclude that the way forward includes numerous activities including increased observations; the attribution of coastal impacts to their drivers; enhanced climate projections and their integration into impact models; more impact assessments at the local scale; dynamic projections of spatially-distributed exposure and vulnerability; and the exploration of inherently adaptive options. Given the complexity of the possible solutions, more practical guidance is required.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Coastal Engineerin
On the Efficiency of Staggered C-Grid Discretization for the Inviscid Shallow Water Equations from the Perspective of Nonstandard Calculus
No full textThis paper provides a rationale for the commonly observed numerical efficiency of staggered C-grid discretizations for solving the inviscid shallow water equations. In particular, using the key concepts of nonstandard calculus, we aim to show that the grid staggering of the primitive variables (surface elevation and normal velocity components) is capable of dealing with flow discontinuities. After a brief introduction of hyperreals through the notion of infinitesimal increments, a nonstandard rendition of the governing equations is derived that essentially turns into a finite procedure and permits a convenient way of modeling the hydraulic jumps in open channel flow. A central result of this paper is that the discrete formulations thus obtained are distinguished by the topological structures of the solution fields and subsequently provide a natural framework for the staggered discretization of the governing equations. Another key of the present study is to demonstrate that the discretization naturally regularizes the solution of the inviscid flow passing through the hydraulic jump without the need of non-physical dissipation. The underlying justification is provided by analytically studying the distributions of the flow variables across an infinitesimal thin hydraulic jump along with the use of hyperreal Heaviside step functions. This main finding is shown to be useful to comprehend the importance of the application of staggered finite difference schemes to accurately predict rapidly varying free-surface flows. A numerical experiment is provided to confirm this result.Environmental Fluid Mechanic
Atomistic simulation of carbide formation in ferrite
No full textIn this study possible routes from dissolved M and C atoms to a M-C (M = Ti, Nb) cluster are studied. Using atomistic modelling to perform relaxation simulations and molecular dynamics (MD) simulations for the Fe-M-C ternary system, the formation of clusters is studied for M. Additionally the stability of M-C clusters is assessed. The clustering of M and C atoms as observed in experiments is also found in simulations. The initial clusters found in this work have a (Fe,M)C composition with a large Fe fraction. Moreover, structurally relaxed clusters reveal that there are growth pathways with a monotone decrease in Gibbs energy, suggesting that the highest energy barrier in the formation of M-C clusters is the diffusion barrier for the atoms forming the cluster. The development of M-C clusters as found in this study suggests a formation mechanism for nano-precipitation of carbides consisting of several steps; first a C cluster forms, then M atoms attach to the C cluster forming a (Fe,M)C cluster, and in the final step the (Fe,M)C cluster transforms to a NaCl-structured carbide.Team Marcel SluiterTeam Erik Offerma
Author response
No full textThe DEAH-box NTPase Prp43 and its cofactors Ntr1 and Ntr2 form the NTR complex and are required for disassembling intron-lariat spliceosomes (ILS) and defective earlier spliceosomes. However, the Prp43 binding site in the spliceosome and its target(s) are unknown. We show that Prp43 fused to Ntr1's G-patch motif (Prp43_Ntr1GP) is as efficient as the NTR in ILS disassembly, yielding identical dissociation products and recognizing its natural ILS target even in the absence of Ntr1's C-terminal-domain (CTD) and Ntr2. Unlike the NTR, Prp43_Ntr1GP disassembles earlier spliceosomal complexes (A, B, B(act)), indicating that Ntr2/Ntr1-CTD prevents NTR from disrupting properly assembled spliceosomes other than the ILS. The U2 snRNP-intron interaction is disrupted in all complexes by Prp43_Ntr1GP, and in the spliceosome contacts U2 proteins and the pre-mRNA, indicating that the U2 snRNP-intron interaction is Prp43's major target
Design of non-serial, non-parallel flexural transmissions as applied to a micro-machined MEMS tuning fork gyroscope
No full textThesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 99-105).The purpose of this work is to develop and implement design rules for flexures that emphasize directionality. This work is important for flexure designs that cannot be broken down into equivalent series or parallel components. The impact of this work is illustrated in the implementation of a high-performance micro-electromechanical system (MEMS) tuning fork gyroscope (TFG) that may be used for inertial navigation, automobile rollover detection, video games, and smartphones. These design rules build upon Freedom Actuation and Constraint Topologies (FACT), pseudo-rigid body modeling (PRBM), and constraint based-design (CBD) to include directionality. Flexural transmissions may be used to couple the motion of a plurality of stages to have different types (translations, rotations, and screws), different transmission ratios, and different directions on different axes. These design rules are implemented to create a MEMS TFG that exhibits coupled mass motions and decoupled mode shapes. A MEMS gyroscope was designed and modeled and a meso-scale prototype was made to verify the models and test sensitivity to fabrication errors. The design has 49% separation between desired and undesired modes. The meso-scale prototype and finite element analysis (FEA) suggest that the TFG design developed from these rules exhibits a 4x reduction in sensitivity to quadrature error.by Marcel Adam Craig Thomas.S.M
Stealing into print: fraud, plagiarism, and misconduct in scientific publishing
No full textFalse data published by a psychologist influence policies for treating the mentally retarded. A Nobel Prize-winning molecular biologist resigns the presidency of Rockefeller University in the wake of a scandal involving a co-author accused of fabricating data. A university investigating committee declares that almost half the published articles of a promising young radiologist are fraudulent.Incidents like these strike at the heart of the scientific enterprise and shake the confidence of a society accustomed to thinking of scientists as selfless seekers of truth. Marcel LaFollette's long-awaited book gives a penetrating examination of the world of scientific publishing in which such incidents of misconduct take place. Because influential scientific journals have been involved in the controversies, LaFollette focuses on the fragile "peer review" process - the editorial system of seeking pre-publication opinions from experts. She addresses the cultural glorification of science, which, combined with a scientist's thirst for achievement, can seem to make cheating worth the danger. She describes the great risks taken by the accusers - often scholars of less prestige and power than the accused - whom she calls "nemesis figures" for their relentless dedication to uncovering dishonesty.In sober warning, LaFollette notes that impatient calls from Congress, journalists, and taxpayers for greater accountability from scientists have important implications for the entire system of scientific research and communication.Provocative and learned, Stealing Into Print is certain to become the authoritative work on scientific fraud, invaluable to the scientific community, policy makers, and the general public
Formation and growth of transition metal carbides in ferrite
No full textCarbide nano-precipitates are commonly used to improve mechanical properties of steel. It has been experimentally observed that TiC, NbC, and VC carbide precipitates initially form as ‘plate-like’ particles oriented in the {1 0 0} planes of the ferrite lattice. These platelets share similarities with Guinier-Preston zones in Al-Cu alloys. The clustering of group IV and V transition metal atoms (M = Ti, Zr, Hf, V, Nb, Ta) in ferrite is studied using density functional theory. It is deduced that the transition metal carbides all form in a similar way. Furthermore, the transition from an initial M–C cluster to a NaCl-structured platelet to a NaCl-structured precipitate is examined through atomistic simulations using Modified Embedded Atom Method potentials. A route is established along which transition metal carbides form and transform into precipitates that possess the Baker-Nutting orientation relation with the ferrite matrix.Team Marcel SluiterTeam Erik Offerma
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