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MIT Open Access Articles
Mostrando recursos 41 - 60 de 13,318
Measurement of the low-mass Drell-Yan differential cross section at √s = 7 TeV using the ATLAS detector - Taylor, Frank E.
The differential cross section for the process Z/γ [superscript ∗] → ℓℓ (ℓ = e, μ) as a function of dilepton invariant mass is measured in pp collisions at √s = 7 TeV at the LHC using the ATLAS detector. The measurement is performed in the e and μ channels for invariant masses between 26 GeV and 66 GeV using an integrated luminosity of 1.6 fb[superscript −1] collected in 2011 and these measurements are combined. The analysis is extended to invariant masses as low as 12 GeV in the muon channel using 35 pb[superscript −1] of data collected in 2010....
Search for top quark decays t → qH with H → γγ using the ATLAS detector - Taylor, Frank E.
A search is performed for flavour-changing neutral currents in the decay of a top quark to an up-type (c, u) quark and a Higgs boson, where the Higgs boson decays to two photons. The proton-proton collision data set used corresponds to 4.7 fb[superscript −1] at √s = 7 TeV and 20.3 fb[superscript −1] at √s = 8 TeV collected by the ATLAS experiment at the LHC. Top quark pair events are searched for in which one top quark decays to qH and the other decays to bW. Both the hadronic and the leptonic decay modes of the W boson are...
Measurement of charged particle multiplicities and densities in pp collisions at √s = 7 TeV in the forward region - Counts, Ian Thomas Hunt; Ilten, Philip James; Williams, Michael
Charged particle multiplicities are studied in proton–proton collisions in the forward region at a centre-of-mass energy of √s = 7 TeV with data collected by the LHCb detector. The forward spectrometer allows access to a kinematic range of 2.0 < η < 4.8 in pseudorapidity, momenta greater than 2 GeV/ c and transverse momenta greater than 0.2 GeV/ c. The measurements are performed using events with at least one charged particle in the kinematic acceptance. The results are presented as functions of pseudorapidity and transverse momentum and are compared to predictions from several Monte Carlo event generators.
Search for direct top squark pair production in events with a Z boson, b-jets and missing transverse momentum in √s = 8 TeV pp collisions with the ATLAS detector - Taylor, Frank E.
A search is presented for direct top squark pair production using events with at least two leptons including a same-flavour opposite-sign pair with invariant mass consistent with the Z boson mass, jets tagged as originating from b-quarks and missing transverse momentum. The analysis is performed with proton–proton collision data at √s = 8\ TeV collected with the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of 20.3 fb[superscript −1]. No excess beyond the Standard Model expectation is observed. Interpretations of the results are provided in models based on the direct pair production of the heavier top...
The differential production cross section of the ϕ(1020) meson in √s = 7 TeV pp collisions measured with the ATLAS detector - Taylor, Frank E.
A measurement is presented of the ϕ × BR(ϕ → K[superscript +]K[superscript −]) production cross section at √s = 7 TeV using pp collision data corresponding to an integrated luminosity of 383 μb[superscript −1], collected with the ATLAS experiment at the LHC. Selection of ϕ (1020) mesons is based on the identification of charged kaons by their energy loss in the pixel detector. The differential cross section is measured as a function of the transverse momentum, p[subscript T,ϕ], and rapidity, y[subscript ϕ], of the ϕ (1020) meson in the fiducial region 500 \(1200 MeV, |y[subscript ϕ]| < 0.8, kaon p[subscript...
Non-Gated Laser Induced Breakdown Spectroscopy Provides a Powerful Segmentation Tool on Concomitant Treatment of Characteristic and Continuum Emission - Myakalwar, Ashwin Kumar; Dingari, Narahara Chari; Dasari, Ramachandra Rao; Barman, Ishan; Gundawar, Manoj Kumar
We demonstrate the application of non-gated laser induced breakdown spectroscopy (LIBS) for characterization and classification of organic materials with similar chemical composition. While use of such a system introduces substantive continuum background in the spectral dataset, we show that appropriate treatment of the continuum and characteristic emission results in accurate discrimination of pharmaceutical formulations of similar stoichiometry. Specifically, our results suggest that near-perfect classification can be obtained by employing suitable multivariate analysis on the acquired spectra, without prior removal of the continuum background. Indeed, we conjecture that pre-processing in the form of background removal may introduce spurious features in the...
Exploring Universal Patterns in Human Home-Work Commuting from Mobile Phone Data - Kung, Kevin S.; Greco, Kael; Sobolevsky, Stanislav; Ratti, Carlo
Home-work commuting has always attracted significant research attention because of its impact on human mobility. One of the key assumptions in this domain of study is the universal uniformity of commute times. However, a true comparison of commute patterns has often been hindered by the intrinsic differences in data collection methods, which make observation from different countries potentially biased and unreliable. In the present work, we approach this problem through the use of mobile phone call detail records (CDRs), which offers a consistent method for investigating mobility patterns in wholly different parts of the world. We apply our analysis to...
Clinical Validation of an Ultra High-Throughput Spiral Microfluidics for the Detection and Enrichment of Viable Circulating Tumor Cells - Khoo, Bee Luan; Warkiani, Majid Ebrahimi; Tan, Daniel Shao-Weng; Bhagat, Ali Asgar S.; Irwin, Darryl; Lau, Dawn Pingxi; Lim, Alvin S. T.; Lim, Kiat Hon; Krisna, Sai Sakktee; Lim, Wan-Teck; Yap, Yoon Sim; Lee, Soo Chin; Soo, Ross A.; Han, Jongyoon; Lim, Chwee Teck
Circulating tumor cells (CTCs) are cancer cells that can be isolated via liquid biopsy from blood and can be phenotypically and genetically characterized to provide critical information for guiding cancer treatment. Current analysis of CTCs is hindered by the throughput, selectivity and specificity of devices or assays used in CTC detection and isolation.
Here, we enriched and characterized putative CTCs from blood samples of patients with both advanced stage metastatic breast and lung cancers using a novel multiplexed spiral microfluidic chip. This system detected putative CTCs under high sensitivity (100%, n = 56) (Breast cancer samples: 12–1275 CTCs/ml; Lung cancer...
Feasibility of the Assessment of Cholesterol Crystals in Human Macrophages Using Micro Optical Coherence Tomography - Kashiwagi, Manabu; Liu, Linbo; Chu, Kengyeh K.; Sun, Chen-Hsin; Tanaka, Atsushi; Gardecki, Joseph A.; Tearney, Guillermo J.
The presence of cholesterol crystals is a hallmark of atherosclerosis, but until recently, such crystals have been considered to be passive components of necrotic plaque cores. Recent studies have demonstrated that phagocytosis of cholesterol crystals by macrophages may actively precipitate plaque progression via an inflammatory pathway, emphasizing the need for methods to study the interaction between macrophages and crystalline cholesterol. In this study, we demonstrate the feasibility of detecting cholesterol in macrophages in situ using Micro-Optical Coherence Tomography (µOCT), an imaging modality we have recently developed with 1-µm resolution. Macrophages containing cholesterol crystals frequently demonstrated highly scattering constituents in their...
The Structure of RdDddP from Roseobacter denitrificans Reveals That DMSP Lyases in the DddP-Family Are Metalloenzymes - Hehemann, Jan-Hendrik; Law, Adrienne; Redecke, Lars; Boraston, Alisdair B.
Marine microbes degrade dimethylsulfoniopropionate (DMSP), which is produced in large quantities by marine algae and plants, with DMSP lyases into acrylate and the gas dimethyl sulfide (DMS). Approximately 10% of the DMS vents from the sea into the atmosphere and this emission returns sulfur, which arrives in the sea through rivers and runoff, back to terrestrial systems via clouds and rain. Despite their key role in this sulfur cycle DMSP lyases are poorly understood at the molecular level. Here we report the first X-ray crystal structure of the putative DMSP lyase RdDddP from Roseobacter denitrificans, which belongs to the abundant...
Premarket Safety and Efficacy Studies for ADHD Medications in Children - Bourgeois, Florence T.; Kim, Jeong Min; Mandl, Kenneth David
Attention-deficit hyperactivity disorder (ADHD) is a chronic condition and pharmacotherapy is the mainstay of treatment, with a variety of ADHD medications available to patients. However, it is unclear to what extent the long-term safety and efficacy of ADHD drugs have been evaluated prior to their market authorization. We aimed to quantify the number of participants studied and their length of exposure in ADHD drug trials prior to marketing.
We identified all ADHD medications approved by the Food and Drug Administration (FDA) and extracted data on clinical trials performed by the sponsor and used by the FDA to evaluate the drug’s clinical...
Decoherence and degradation of squeezed states in quantum filter cavities - Kwee, P.; Miller, John; Isogai, Tomoki; Barsotti, Lisa; Evans, Matthew J.
Squeezed states of light have been successfully employed in interferometric gravitational-wave detectors to reduce quantum noise, thus becoming one of the most promising options for extending the astrophysical reach of the generation of detectors currently under construction worldwide. In these advanced instruments, quantum noise will limit sensitivity over the entire detection band. Therefore, to obtain the greatest benefit from squeezing, the injected squeezed state must be filtered using a long-storage-time optical resonator, or “filter cavity,” so as to realize a frequency-dependent rotation of the squeezed quadrature. While the ultimate performance of a filter cavity is determined by its storage time,...
A Systematic Approach to Modeling Impedances and Current Distribution in Planar Magnetics - Chen, Minjie; Araghchini, Mohammad; Afridi, Khurram K.; Lang, Jeffrey H.; Sullivan, Charles R.; Perreault, David J.
Planar magnetic components using printed-circuit-board windings are attractive due to their high repeatability, good thermal performance and usefulness for realizing intricate winding patterns. To enable higher system integration at high switching frequency, more sophisticated methods that can rapidly and accurately model planar magnetics are needed. This paper develops a lumped circuit model that captures the impact of skin and proximity effects on current distribution and electromagnetic fields in planar magnetics. This enables accurate predictions of impedances, losses, stored reactive energy and current sharing among parallel windings. This lumped model is also a circuit domain representation of electromagnetic interactions. It can...
The Influence of Operational Cost on Estimation - Tulabandhula, Theja; Rudin, Cynthia
This work concerns the way that statistical models are used to make decisions. In particular, we aim to merge the way estimation algorithms are designed with how they are used for a subsequent task. Our methodology considers the operational cost of carrying out a policy, based on a predictive model. The operational cost becomes a regularization term in the learning algorithm’s objective function, allowing either an optimistic or pessimistic view of possible costs. Limiting the operational cost reduces the hypothesis space for the predictive model, and can thus improve generalization. We show that different types of operational problems can lead...
Non-Parametric Approximate Dynamic Programming via the Kernel Method - Bhat, Nikhil; Farias, Vivek F.; Moallemi, Ciamac C.
This paper presents a novel non-parametric approximate dynamic programming (ADP) algorithm that enjoys graceful approximation and sample complexity guarantees. In particular, we establish both theoretically and computationally that our proposal can serve as a viable alternative to state-of-the-art parametric ADP algorithms, freeing the designer from carefully specifying an approximation architecture. We accomplish this by developing a kernel-based mathematical program for ADP. Via a computational study on a controlled queueing network, we show that our procedure is competitive with parametric ADP approaches.
Retardation of arsenic transport through a Pleistocene aquifer - van Geen, Alexander; Bostick, Benjamín C.; Thi Kim Trang, Pham; Lan, Vi Mai; Mai, Nguyen-Ngoc; Manh, Phu Dao; Viet, Pham Hung; Radloff, Kathleen; Aziz, Zahid; Mey, Jacob L.; Stahl, Mason; Harvey, Charles F.; Oates, Peter; Weinman, Beth; Stengel, Caroline; Frei, Felix; Kipfer, Rolf; Berg, Michael
Groundwater drawn daily from shallow alluvial sands by millions of wells over large areas of south and southeast Asia exposes an estimated population of over a hundred million people to toxic levels of arsenic1. Holocene aquifers are the source of widespread arsenic poisoning across the region2, 3. In contrast, Pleistocene sands deposited in this region more than 12,000 years ago mostly do not host groundwater with high levels of arsenic. Pleistocene aquifers are increasingly used as a safe source of drinking water4 and it is therefore important to understand under what conditions low levels of arsenic can be maintained. Here...
Unravelling daily human mobility motifs - Schneider, Christian M.; Belik, Vitaly; Couronne, Thomas; Smoreda, Zbigniew; Gonzalez, Marta C.
Human mobility is differentiated by time scales. While the mechanism for long time scales has been studied, the underlying mechanism on the daily scale is still unrevealed. Here, we uncover the mechanism responsible for the daily mobility patterns by analysing the temporal and spatial trajectories of thousands of persons as individual networks. Using the concept of motifs from network theory, we find only 17 unique networks are present in daily mobility and they follow simple rules. These networks, called here motifs, are sufficient to capture up to 90 per cent of the population in surveys and mobile phone datasets for...
Mutator/Hypermutable Fetal/Juvenile Metakaryotic Stem Cells and Human Colorectal Carcinogenesis - Kini, Lohith G.; Herrero-Jimenez, Pablo; Sanghvi, Jayodita; Gutierrez, Efren; Hensle, David; Kogel, John; Kusko, Rebecca; Rexer, Karl; Kurzweil, Ray; Refinetti, Paulo; Morgenthaler, Stephan; Koledova, Vera V.; Gostjeva, Elena V.; Thilly, William G.; Kamath, Tushar V.
Adult age-specific colorectal cancer incidence rates increase exponentially from maturity, reach a maximum, then decline in extreme old age. Armitage and Doll (1) postulated that the exponential increase resulted from “n” mutations occurring throughout adult life in normal “cells at risk” that initiated the growth of a preneoplastic colony in which subsequent “m” mutations promoted one of the preneoplastic “cells at risk” to form a lethal neoplasia. We have reported cytologic evidence that these “cells at risk” are fetal/juvenile organogenic, then preneoplastic metakaryotic stem cells. Metakaryotic cells display stem-like behaviors of both symmetric and asymmetric nuclear divisions and peculiarities such...
Retractions - Azoulay, Pierre; Furman, Jeffrey L.; Krieger, Joshua Lev; Murray, Fiona E.
To what extent does “false science” impact the rate and direction of scientific change? We examine the impact of over 1,100 scientific retractions on the citation trajectories of articles that are related to retracted papers in intellectual space but were published prior to the retraction event. Following retraction and relative to carefully selected controls, related articles experience a lasting five to ten percent decline in the rate of citations received. This penalty is more severe when the retracted article involves fraud or misconduct, rather than honest mistakes. In addition, we find that the arrival rate of new articles and funding...
Measurement of the triple-differential cross section for photon + jets production in proton-proton collisions at s√ = 7 TeV - Apyan, Aram; Bauer, Gerry P.; Busza, Wit; Cali, Ivan Amos; Chan, M.; Di Matteo, Leonardo; Dutta, Valentina; Gomez-Ceballos, Guillelmo; Goncharov, Maxim; Gulhan, Doga Can; Kim, Y.; Klute, Markus; Lai, Yue Shi; Levin, A.; Luckey, P. David; Ma, T.; Nahn, Steven; Paus, Christoph M. E.; Ralph, Duncan Kelley; Roland, Christof E.; Roland, Gunther M.; Stephans, George S. F.; Stoeckli, Fabian; Sumorok, Konstanty C.; Velicanu, Dragos Alexandru; Wolf, R.; Wyslouch, Boleslaw; Yang, M.; Yilmaz, Yetkin; Yoon, A. S.; Zanetti, Marco; Zhukova, Victoria; CMS Collaboration
A measurement of the triple-differential cross section, d[superscript 3]σ/(dp[superscript γ]Tdη[superscript γ]dη[superscript jet]) , in photon + jets final states using a data sample from proton-proton collisions at s√ = 7 TeV is presented. This sample corresponds to an integrated luminosity of 2.14 fb[superscript −1] collected by the CMS detector at the LHC. Photons and jets are reconstructed within a pseudorapidity range of |η| < 2.5, and are required to have transverse momenta in the range 40 < pjet[over]T < 300 GeV and pjet[over]T > 30 GeV, respectively. The measurements are compared to theoretical predictions from the sherpa leading-order QCD Monte...