## Recursos de colección

#### DSpace at MIT (103.668 recursos)

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MIT Open Access Articles

1. #### Measurement of CP Violation Parameters in B[superscript 0] → D K[superscript * 0] Decays

Counts, Ian Thomas Hunt; Ilten, Philip J; Williams, Michael
An analysis of B[superscript 0]→DK[superscript ∗0] decays is presented, where D represents an admixture of D[superscript 0] and [bar over D][superscript 0] mesons reconstructed in four separate final states: K[superscript -]π[superscript +], π[superscript -]K[superscript +], K[superscript +]K[superscript -] and π[superscript +]π[superscript -]. The data sample corresponds to 3.0fb[superscript -1] of proton-proton collision, collected by the LHCb experiment. Measurements of several observables are performed, including CP asymmetries. The most precise determination is presented of r[subscript B](DK[superscript ∗0]), the magnitude of the ratio of the amplitudes of the decay B[superscript 0]→DK[superscript +]π[superscript -] with a b→u or a b→c transition, in a...

2. #### Natural language based financial forecasting: a survey

Cambria, Erik; Xing, Frank Z.; Welsch, Roy E
Natural language processing (NLP), or the pragmatic research perspective of computational linguistics, has become increasingly powerful due to data availability and various techniques developed in the past decade. This increasing capability makes it possible to capture sentiments more accurately and semantics in a more nuanced way. Naturally, many applications are starting to seek improvements by adopting cutting-edge NLP techniques. Financial forecasting is no exception. As a result, articles that leverage NLP techniques to predict financial markets are fast accumulating, gradually establishing the research field of natural language based financial forecasting (NLFF), or from the application perspective, stock market prediction. This...

3. #### Nonhomogeneous Time Mixed Integer Linear Programming Formulation for Traffic Signal Control

Guilliard, Iain; Sanner, Scott; Trevizan, Felipe W.; Williams, Brian C
Urban traffc congestion is on the increase worldwide; therefore, it is critical to maximize the capacity and throughput of the existing road infrastructure with optimized traffc signal control. For that purpose, this paper builds on the body of work in mixed integer linear programming (MILP) approaches that attempt to optimize traffc signal control jointly over an entire traffc network and specifcally on improving the scalability of these methods for large numbers of intersections. The primary insight in this work stems from the fact that MILP-based approaches to traffc control used in a receding horizon control manner (that replan at fxed...

4. #### Multifidelity DDDAS Methods with Application to a Self-aware Aerospace Vehicle

Allaire, D.; Kordonowy, D.; Lecerf, Marc A.; Mainini, Laura; Willcox, Karen E
A self-aware aerospace vehicle can dynamically adapt the way it performs missions by gathering information about itself and its surroundings and responding intelligently. We consider the specific challenge of an unmanned aerial vehicle that can dynamically and autonomously sense its structural state and re-plan its mission according to its estimated current structural health. The challenge is to achieve each of these tasks in real time-executing online models and exploiting dynamic data streams-while also accounting for uncertainty. Our approach combines information from physics-based models, simulated offline to build a scenario library, together with dynamic sensor data in order to estimate current...

5. #### Reducing CO2 from cars in the European Union

Löschel, Andreas; von Graevenitz, Kathrine; Koesler, Simon; Paltsev, Sergey; Chen, Yen-Heng; Karplus, Valerie Jean; Kishimoto, Paul Natsuo; Reilly, John M
The European Union (EU) recently adopted CO2 emissions mandates for new passenger cars, requiring steady reductions to 95 gCO2/km in 2021. We use a multi-sector computable general equilibrium (CGE) model, which includes a private transportation sector with an empirically-based parameterization of the relationship between income growth and demand for vehicle miles traveled. The model also includes representation of fleet turnover, and opportunities for fuel use and emissions abatement, including representation of electric vehicles. We analyze the impact of the mandates on oil demand, CO2 emissions, and economic welfare, and compare the results to an emission trading scenario that achieves identical emissions...

6. #### Opening up the QCD axion window

Agrawal, Prateek; Marques-Tavares, Gustavo; Xue, Wei
We present a new mechanism to deplete the energy density of the QCD axion, making decay constants as high as f[subscript a] ≃ 1017 GeV viable for generic initial conditions. In our setup, the axion couples to a massless dark photon with a coupling that is moderately stronger than the axion coupling to gluons. Dark photons are produced copiously through a tachyonic instability when the axion field starts oscillating, and an exponential suppression of the axion density can be achieved. For a large part of the parameter space this dark radiation component of the universe can be observable in upcoming...

7. #### Iterative regularization for learning with convex loss functions

Lin, Junhong; Zhou, Ding-Xuan; Rosasco, Lorenzo
We consider the problem of supervised learning with convex loss functions and propose a new form of iterative regularization based on the subgradient method. Unlike other regularization approaches, in iterative regularization no constraint or penalization is considered, and generalization is achieved by (early) stopping an empirical iteration. We consider a nonparametric setting, in the framework of reproducing kernel Hilbert spaces, and prove consistency and finite sample bounds on the excess risk under general regularity conditions. Our study provides a new class of efficient regularized learning algorithms and gives insights on the interplay between statistics and optimization in machine learning.

8. #### Anthropogenic Space Weather

Balogh, A.; Gombosi, T. I.; Baker, D. N.; Huba, J. D.; Lanzerotti, L. J.; Erickson, Philip J
Anthropogenic effects on the space environment started in the late 19th century and reached their peak in the 1960s when high-altitude nuclear explosions were carried out by the USA and the Soviet Union. These explosions created artificial radiation belts near Earth that resulted in major damages to several satellites. Another, unexpected impact of the high-altitude nuclear tests was the electromagnetic pulse (EMP) that can have devastating effects over a large geographic area (as large as the continental United States). Other anthropogenic impacts on the space environment include chemical release experiments, high-frequency wave heating of the ionosphere and the interaction of...

9. #### 50th Anniversary Perspective: Conducting/Semiconducting Conjugated Polymers. A Personal Perspective on the Past and the Future

Swager, Timothy M
It has been about 40 years since the field of organic conducting polymers was ignited by the demonstration of metallic conductivity in polyacetylene. A retrospective view of this research area suggests some areas remain ripe for discovery/innovation. The breadth of activities is too large to be comprehensive; hence, selected seminal, as well as some personal, contributions will be used to illustrate concepts and anecdotal ways to think about conducting polymer systems. This Perspective can serve as a tutorial for newcomers to the field and will also remind experts about results from the past. It begins with some history and simple...

10. #### Feedforward architectures driven by inhibitory interactions

Billeh, Yazan N.; Schaub, Michael T.
Directed information transmission is paramount for many social, physical, and biological systems. For neural systems, scientists have studied this problem under the paradigm of feedforward networks for decades. In most models of feedforward networks, activity is exclusively driven by excitatory neurons and the wiring patterns between them, while inhibitory neurons play only a stabilizing role for the network dynamics. Motivated by recent experimental discoveries of hippocampal circuitry, cortical circuitry, and the diversity of inhibitory neurons throughout the brain, here we illustrate that one can construct such networks even if the connectivity between the excitatory units in the system remains random....

11. #### Random contractions and sampling for hypergraph and hedge connectivity

Panigrahi, Debmalya; Ghaffari, Mohsen; Karger, David R
We initiate the study of hedge connectivity of undirected graphs, motivated by dependent edge failures in real-world networks. In this model, edges are partitioned into groups called hedges that fail together. The hedge connectivity of a graph is the minimum number of hedges whose removal disconnects the graph. We give a polynomial-time approximation scheme and a quasi-polynomial exact algorithm for hedge connectivity. This provides strong evidence that the hedge connectivity problem is tractable, which contrasts with prior work that established the intractability of the corresponding s−t min-cut problem. Our techniques also yield new combinatorial and algorithmic results in hypergraph connectivity....

12. #### Impact of MicroRNA Levels, Target-Site Complementarity, and Cooperativity on Competing Endogenous RNA-Regulated Gene Expression

Denzler, Rémy; Title, Alexandra C.; Stoffel, Markus; McGeary, Sean Edward; Agarwal, Vikram; Bartel, David
Expression changes of competing endogenous RNAs (ceRNAs) have been proposed to influence microRNA (miRNA) activity and thereby regulate other transcripts containing miRNA-binding sites. Here, we find that although miRNA levels define the extent of repression, they have little effect on the magnitude of the ceRNA expression change required to observe derepression. Canonical 6-nt sites, which typically mediate modest repression, can nonetheless compete for miRNA binding, with potency ∼20% of that observed for canonical 8-nt sites. In aggregate, low-affinity/background sites also contribute to competition. Sites with extensive additional complementarity can appear as more potent, but only because they induce miRNA degradation....

13. #### Widespread Influence of 3′-End Structures on Mammalian mRNA Processing and Stability

Wu, Xuebing; Bartel, David P.; Bartel, David
The physiological relevance of structures within mammalian mRNAs has been elusive, as these mRNAs are less folded in cells than in vitro and have predicted secondary structures no more stable than those of random sequences. Here, we investigate the possibility that mRNA structures facilitate the 3′-end processing of thousands of human mRNAs by juxtaposing poly(A) signals (PASs) and cleavage sites that are otherwise too far apart. We find that RNA structures are predicted to be more prevalent within these extended 3′-end regions than within PAS-upstream regions and indeed are substantially more folded within cells, as determined by intracellular probing. Analyses...

14. #### Search for Physics Beyond the Standard Model in Events with High-Momentum Higgs Bosons and Missing Transverse Momentum in Proton-Proton Collisions at 13 TeV

A search for physics beyond the standard model in events with one or more high-momentum Higgs bosons, H, decaying to pairs of b quarks in association with missing transverse momentum is presented. The data, corresponding to an integrated luminosity of 35.9  fb⁻¹, were collected with the CMS detector at the LHC in proton-proton collisions at the center-of-mass energy √s = 13  TeV. The analysis utilizes a new b quark tagging technique based on jet substructure to identify jets from H→bb[over ¯]. Events are categorized by the multiplicity of H-tagged jets, jet mass, and the missing transverse momentum. No significant deviation from standard...

15. #### “It Was Their Business to Know”: British Merchants and Mercantile Epistemology in the Eighteenth Century

Deringer, William P
This article explores the history of commercial epistemology during the first half of the eighteenth century in Britain. During that period, questions about the character of commerce as a field of knowledge—whether it was a simple or complex, how it related to commercial “interest,” and especially who possessed it—lay at the heart of political-economic debate. This article looks specifically at one set of attitudes about commercial epistemology, what I call mercantile epistemology, which came to dominate economic thinking from 1714 to roughly 1750. Mercantile epistemology was based on two pillars. The first was that commerce was a straight-forward, “common sense”...

16. #### Brian Regal. Searching for Sasquatch: Crackpots, Eggheads, and Cryptozoology.

Ritvo, Harriet
Cryptozoology has been described as the converse of paleontology: that is to say, paleontologists study creatures for which there is evidence, but which no one (at least no human who could leave a record) has ever seen, while cryptozoologists study creatures that have frequently been seen, but for which there is no evidence. Of course there are many other differences between these fields, including the one conspicuously, if facetiously, signaled in Brian Regal's subtitle. Paleontologists tend to be conventionally credentialed scientists; cryptozoologists, however, tend to be amateur enthusiasts. This dichotomy is especially marked among the subset of cryptozoologists who are...

17. #### The Courtiers’ Anatomists: Animals and Humans in Louis XIV’s Paris.

Ritvo, Harriet
rom the perspective even of stay-at-home European naturalists in the seventeenth century, the world kept getting bigger as increasing animal, vegetable, and mineral evidence of its breadth and variety poured into metropolitan centers. At the same time, the technology of the microscope and the virtuoso practice of dissection (of living animals as well as corpses—Anita Guerrini argues that these practices were perceived as less distinct by her subjects, and by their private and public audiences, than has subsequently become the case) turned the attention of anatomists to things that were small and hidden. Written with interdisciplinary erudition and insight, The...

18. #### Ca²⁺/Calmodulin-Dependent Protein Kinase II (CaMKII) β-Dependent Phosphorylation of GABAB1 Triggers Lysosomal Degradation of GABAB Receptors via Mind Bomb-2 (MIB2)-Mediated Lys-63-Linked Ubiquitination

Balakrishnan, Karthik; Grampp, Thomas; Benke, Dietmar; Zemoura, Khaled
The G protein-coupled GABAB receptors, constituted from GABAB1 and GABAB2 subunits, are important regulators of neuronal excitability by mediating long-lasting inhibition. One factor that determines receptor availability and thereby the strength of inhibition is regulated protein degradation. GABAB receptors are constitutively internalized from the plasma membrane and are either recycled to the cell surface or degraded in lysosomes. Lys-63-linked ubiquitination mediated by the E3 ligase Mind bomb-2 (MIB2) is the signal that sorts GABAB receptors to lysosomes. However, it is unknown how Lys-63-linked ubiquitination and thereby lysosomal degradation of the receptors is regulated. Here, we show that Ca2+/calmodulin-dependent protein kinase...