906 research outputs found
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Investigation of Radar Propagation in Buildings: A 10 Billion Element Cartesian-Mesh FETD Simulation
In this paper large scale full-wave simulations are performed to investigate radar wave propagation inside buildings. In principle, a radar system combined with sophisticated numerical methods for inverse problems can be used to determine the internal structure of a building. The composition of the walls (cinder block, re-bar) may effect the propagation of the radar waves in a complicated manner. In order to provide a benchmark solution of radar propagation in buildings, including the effects of typical cinder block and re-bar, we performed large scale full wave simulations using a Finite Element Time Domain (FETD) method. This particular FETD implementation is tuned for the special case of an orthogonal Cartesian mesh and hence resembles FDTD in accuracy and efficiency. The method was implemented on a general-purpose massively parallel computer. In this paper we briefly describe the radar propagation problem, the FETD implementation, and we present results of simulations that used over 10 billion elements
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A parallel computer implementation of fast low-rank QR approximation of the Biot-Savart law
In this paper we present a low-rank QR method for evaluating the discrete Biot-Savart law on parallel computers. It is assumed that the known current density and the unknown magnetic field are both expressed in a finite element expansion, and we wish to compute the degrees-of-freedom (DOF) in the basis function expansion of the magnetic field. The matrix that maps the current DOF to the field DOF is full, but if the spatial domain is properly partitioned the matrix can be written as a block matrix, with blocks representing distant interactions being low rank and having a compressed QR representation. The matrix partitioning is determined by the number of processors, the rank of each block (i.e. the compression) is determined by the specific geometry and is computed dynamically. In this paper we provide the algorithmic details and present computational results for large-scale computations
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3D Vectorial Time Domain Computational Integrated Photonics
The design of integrated photonic structures poses considerable challenges. 3D-Time-Domain design tools are fundamental in enabling technologies such as all-optical logic, photonic bandgap sensors, THz imaging, and fast radiation diagnostics. Such technologies are essential to LLNL and WFO sponsors for a broad range of applications: encryption for communications and surveillance sensors (NSA, NAI and IDIV/PAT); high density optical interconnects for high-performance computing (ASCI); high-bandwidth instrumentation for NIF diagnostics; micro-sensor development for weapon miniaturization within the Stockpile Stewardship and DNT programs; and applications within HSO for CBNP detection devices. While there exist a number of photonics simulation tools on the market, they primarily model devices of interest to the communications industry. We saw the need to extend our previous software to match the Laboratory's unique emerging needs. These include modeling novel material effects (such as those of radiation induced carrier concentrations on refractive index) and device configurations (RadTracker bulk optics with radiation induced details, Optical Logic edge emitting lasers with lateral optical inputs). In addition we foresaw significant advantages to expanding our own internal simulation codes: parallel supercomputing could be incorporated from the start, and the simulation source code would be accessible for modification and extension. This work addressed Engineering's Simulation Technology Focus Area, specifically photonics. Problems addressed from the Engineering roadmap of the time included modeling the Auston switch (an important THz source/receiver), modeling Vertical Cavity Surface Emitting Lasers (VCSELs, which had been envisioned as part of fast radiation sensors), and multi-scale modeling of optical systems (for a variety of applications). We proposed to develop novel techniques to numerically solve the 3D multi-scale propagation problem for both the microchip laser logic devices as well as devices characterized by electromagnetic (EM) propagation in nonlinear materials with time-varying parameters. The deliverables for this project were extended versions of the laser logic device code Quench2D and the EM propagation code EMsolve with new modules containing the novel solutions incorporated by taking advantage of the existing software interface and structured computational modules. Our approach was multi-faceted since no single methodology can always satisfy the tradeoff between model runtime and accuracy requirements. We divided the problems to be solved into two main categories: those that required Full Wave Methods and those that could be modeled using Approximate Methods. Full Wave techniques are useful in situations where Maxwell's equations are not separable (or the problem is small in space and time), while approximate techniques can treat many of the remaining cases
The effect of monomer evaporation on a simple model of submonolayer growth
We present a model for thin film growth by particle deposition that takes
into account the possible evaporation of the particles deposited on the
surface. Our model focuses on the formation of two-dimensional structures. We
find that the presence of evaporation can dramatically affect the growth
kinetics of the film, and can give rise to regimes characterized by different
``growth'' exponents and island size distributions. Our results are obtained by
extensive computer simulations as well as through a simple scaling approach and
the analysis of rate equations describing the system. We carefully discuss the
relationship of our model with previous studies by Venables and Stoyanov of the
same physical situation, and we show that our analysis is more general.Comment: 41 pages including figures, Revtex, to be published in Physical
Review
The single morpheme -ed/-en of the English past/passive
All English regular verbs and about half its irregular verbs have the same form for the finite past tense and the past participle. The finite past tense is different from the participle only for a closed class of about 100 irregular verbs. These latter can be analyzed by a lexical device of wide-ranging applicability called Alternative Realization. All other Past forms of Vs, finite and non-finite, can then be derived from a single morpheme -ed which appears in two contexts: one when V is finite and one when it is selected by a semantically empty stative verb, have or be. There is also a third use of -ed to form passive participles, in both verbal and adjectival passives.The paper presents a formalized system of selection features for lexical items including but going beyond classical subcategorization. This system permits formulating a single full lexical entry for the suffix -ed that covers all its uses. The final version of this entry exemplifies how to specify Alternative Realization, uninterpretability of categories and disjunctive contexts, and independently justifies each of these notations
Coumarins and pyranocoumarins, potential novel pharmacophores for inhibition ofmeasles virus replication
A series of coumarin and pyranocoumarin analogues were evaluated in vitro for antiviral efficacy against measles virus (MV), strain Chicago. Of the 22 compounds tested for inhibition, six were found to have selectivity indices greater than 10. These were compounds 5-hydroxy-7-propionyloxy- 4-propylcoumarin (2a), 5,7-bis(tosyloxy)-4- propylcoumarin (7); 5-hydroxy-4-propyl-7-tosyloxy- coumarin (8); 6,6-dimethyl-9-propionyloxy-4- propyl-2H,6H-benzo[1,2-b:3,4-b′]dipyran-2-one (9); 6,6-dimethyl-9-pivaloyloxy-4-propyl-2H,6Hbenzo[ 1,2-b:3,4-b′]dipyran-2-one (10); and 7,8-cis- 10,11,12-trans-4-propyl-6,6,10,11-tetramethyl- 7,8,9-trihydroxy-2H,6H,12H-benzo[1,2-b:3,4-b′:5,6- b′′]tripyran-2-one (18). Three of the active drugs were propyl coumarin analogues (2a, 7 and 8), two were dipyranone or chromeno-coumarins (9 and 10), and one was a benzotripyranone with a coumarin nucleus (18). Some appeared to be rather specific and potent inhibitors of MV with EC50 values ranging from 0.2 to 50 μg/ml and the majority of the EC50 values being less than 5 μg/ml. The compounds inhibited an additional nine strains of MV, and in virucidal tests the drugs did not physically disrupt the virion to inhibit virus replication. The inhibitory activity for one of the compounds tested (7) was somewhat dependent on virus concentration and it was still active when added to cells up to 24 h after virus exposure. When used in combination with ribavirin, compound 7 appeared not to profoundly affect the antiviral efficacy of ribavirin or its cell-associated toxicity. However, a slightly antagonistic MVinhibitory effect was observed at the highest concentration of ribavirin used in combination with most concentrations of compound 7 tested. This and related compounds may be valuable leads in the development of a potent and selective class of MV inhibitors that could be used in future in the clinic
GeneMatch: A novel recruitment registry using at‐home APOE genotyping to enhance referrals to Alzheimer’s prevention studies
IntroductionRecruitment for Alzheimer’s disease (AD) prevention research studies is challenging because of lack of awareness among cognitively healthy adults coupled with the high screen fail rate due to participants not having a genetic risk factor or biomarker evidence of the disease. Participant recruitment registries offer one solution for efficiently and effectively identifying, characterizing, and connecting potential eligible volunteers to studies.MethodsIndividuals aged 55‐75 years who live in the United States and self‐report not having a diagnosis of cognitive impairment such as MCI or dementia are eligible to join GeneMatch. Participants enroll online and are provided a cheek swab kit for DNA extraction and apolipoprotein E (APOE) genotyping. Participants are not told their APOE results, although the results may be used in part to help match participants to AD prevention studies.ResultsAs of August 2018, 75,351 participants had joined GeneMatch. Nearly 30% of participants have one APOE4 allele, and approximately 3% have two APOE4 alleles. The percentages of APOE4 heterozygotes and homozygotes are inversely associated with age (P < .001).DiscussionGeneMatch, the first trial‐independent research enrollment program designed to recruit and refer cognitively healthy adults to AD prevention studies based in part on APOE test results, provides a novel mechanism to accelerate prescreening and enrollment for AD prevention trials.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152681/1/alzjjalz201812007.pd
Standardized Outcome Measurement for Patients With Coronary Artery Disease: Consensus From the International Consortium for Health Outcomes Measurement (ICHOM)
Coronary artery disease (CAD) outcomes consistently improve when they are routinely measured and provided back to physicians and hospitals. The International Consortium for Health Outcomes Measurement (ICHOM) established a Working Group to define a standard set of outcome measures and risk factors of CAD care. Members were drawn from 4 continents and 6 countries. Using a modified Delphi method, the Group defined who should be tracked, what should be measured, and when such measurements should be performed. Thirteen specific outcomes were chosen, including acute complications occurring within 30 days of acute myocardial infarction, coronary artery bypass grafting surgery, or percutaneous coronary intervention; and longitudinal outcomes for up to 5 years for patient‐reported health status (Seattle Angina Questionnaire [SAQ‐7], elements of Rose Dyspnea Score, and Patient Health Questionnaire [PHQ‐2]), cardiovascular hospital admissions, cardiovascular procedures, renal failure, and mortality. Baseline demographic, cardiovascular disease, and comorbidity information is included to improve the interpretability of comparisons
First GPS Baseline Results from the North Andes
The CASA UNO GPS (Global Positioning System) experiment (January-February 1988) has provided the first epoch baseline measurements for the study of plate motions and crustal deformation in and around the North Andes. Two dimensional horizontal baseline repeatabilities are as good as 5 parts in 108 for short baselines (100-1000km), and better than3 parts in 108 for long baselines (\u3e1000km). Vertical repeatabilities are typically 4 -6 cm, with a weak dependence on baseline length. The expected rate of plate convergence across the Colombia Trench is 6-8 cm/yr, which should be detectable by the repeat experiment planned for 1991. Expected deformation rates within the North Andes are of the order of 1 cm/yr, which may be detectable with the 1991 experiment
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