Multifidelity optimization under uncertainty for a tailless aircraft

This paper presents a multifidelity method for optimization under uncertainty for aerospace problems. In this work, the effectiveness of the method is demonstrated for the robust optimization of a tailless aircraft that is based on the Boeing Insitu ScanEagle. Aircraft design is often affected by uncertainties in manufacturing and operating conditions. Accounting for uncertainties during optimization ensures a robust design that is more likely to meet performance requirements. Designing robust systems can be computationally prohibitive due to the numerous evaluations of expensive-to-evaluate high-fidelity numerical models required to estimate system-level statistics at each optimization iteration. This work uses a multifidelity Monte Carlo approach to estimate the mean and the variance of the system outputs for robust optimization. The method uses control variates to exploit multiple fidelities and optimally allocates resources to different fidelities to minimize the variance in the estimates for a given budget. The results for the ScanEagle application show that the proposed multifidelity method achieves substantial speed-ups as compared to a regular Monte-Carlo-based robust optimization.United States. Air Force. Office of Scientific Research. Multidisciplinary University Research Initiative (FA9550-15-1-0038

Ectopic cardiovascular fat in middle-aged men: effects of race/ethnicity, overall and central adiposity. The ERA JUMP study.

Background/objectivesHigher volumes of ectopic cardiovascular fat (ECF) are associated with greater risk of coronary heart disease (CHD). Identifying factors that are associated with ECF volumes may lead to new preventive efforts to reduce risk of CHD. Significant racial/ethnic differences exist for overall and central adiposity measures, which are known to be associated with ECF volumes. Whether racial/ethnic differences also exist for ECF volumes and their associations with these adiposity measures remain unclear.Subjects/methodsBody mass index (BMI), computerized tomography-measured ECF volumes (epicardial, pericardial and their summation) and visceral adipose tissue (VAT) were examined in a community-based sample of 1199 middle-aged men (24.2% Caucasians, 7.0% African-Americans, 23.6% Japanese-Americans, 22.0% Japanese, 23.2% Koreans).ResultsSignificant racial/ethnic differences existed in ECF volumes and their relationships with BMI and VAT. ECF volumes were the highest among Japanese-Americans and the lowest among African-Americans. The associations of BMI and VAT with ECF differed by racial/ethnic groups. Compared with Caucasians, for each 1-unit increase in BMI, African-Americans had lower, whereas Koreans had higher increases in ECF volumes (P-values<0.05 for both). Meanwhile, compared with Caucasians, for each 1-unit increase in log-transformed VAT, African-Americans, Japanese-Americans and Japanese had similar increases, whereas Koreans had a lower increase in ECF volumes (P-value<0.05).ConclusionsRacial/ethnic groups differed in their propensity to accumulate ECF at increasing level of overall and central adiposity. Future studies should evaluate whether reducing central adiposity or overall weight will decrease ECF volumes more in certain racial/ethnic groups. Evaluating these questions might help in designing race-specific prevention strategy of CHD risk associated with higher ECF

Kinetic analysis of copper(I)/feringa-phosphoramidite catalysed AlEt3 1,4-addition to cyclohex-2-en-1-one

ReactIR studies of mixtures of AlEt3 (A) and cyclohex-2-en-1-one (CX) in Et2O indicate immediate formation of the Lewis acid-base complex (CX.A) at -40 oC (K = 12.0 M-1, ΔGo react -1.1 kcal mol-1). Copper(I) catalysts, derived from pre-catalytic Cu(OAc)2 (up to 5 mol- %) and (R,S,S)-P(binaphtholate){N(CHMePh)2} [Feringa’s ligand (L), up to 5 mol-%] convert CX.A (0.04-0.3 M) into its 1,4-addition product enolate (E) within 2000 sec at -40 oC. Kinetic studies (ReactIR and chiral GC) of CX.A, CX and (R)-3-ethylcyclohexanone (P, the H+ quench product of enolate E) show that the true catalyst is formed in the first 300 sec and this subsequently provides P in 82% ee. This true catalyst converts CX.A to E with a rate law [Cu]1.5[L]0.66[CX.A]1 when [L]/[Cu] ≤ 3.5. Above this ligand ratio inhibition by added ligand with order [L]-2.5 is observed. A rate determining step (rds) of Cu3L2(CX.A)2 stoichiometry is shown to be most consistent with the rate law. The presence of the enolate in the active catalyst (Graphical Abstract) best accounts for the reaction’s induction period and molecularity as [E] ≡ [CX.A]. Catalysis proceeds through a ‘shuttling mechanism’ between two C2 symmetry related ground state intermediates. Each turnover consumes one equivalent of CX.A, expels one molecule of E and forms the new Cu-Et bond needed for the next cycle (Graphic Abstract). The observed ligand (L) inhibition and a non-linear ligand Lee effect on the ee of P are all well simulated by the kinetic model. DFT studies [ωB97X-D/SRSC] support coordination of CX.A to the groundstate Cu-trimer and its rapid conversion to E

Variable Corticosteroid Sensitivity of Thymic Cortex and Medullary Peripheral-type Lymphoid Tissue in Myasthenia Gravis Patients: Structural and Functional Effects

The thymus has been studied in myasthenia gravis patients to assess the effects of previous immunosuppresslon on total yields of cell suspension, immunohistology and culture responses. The reduction in cell yields by pretreatment with corticosteroid was very variable. In 16 of 32 cases, cortical, medullary and total cell numbers were all greatly reduced (‘depleted cases'), whereas in the others, they were within or near the typical range for untreated myasthenics. Cortical thymocytes were even more depleted than precursor thymic blasts. Thus the interpatient differences in sensitivity to corticosteroid recently described for mature T cells also affected immature cortical thymocytes and their differentiating medullary progeny.In the medulla, mature (CD3+)T lymphocytes and germinal centres were enriched by the loss of cortex and appeared relatively healthy, but somewhat depopulated. Concomitantly, in-vitro T-cell responses to acetylcholine receptor (AChR) and production of anti-A ChR antibody and total IgG by thymic cells were usually well within the typical range (assessed per 106 cells). Moreover, the total productivity of the entire thymus was reduced almost entirely by the cellular depopulation rather than by decreased function per surviving cell. Thus the main actions of this alternate day therapy with corticosteroids were apparently on total peripheral cell numbers, and perhaps on activated cells and effector mechanisms too, and its thymic effects were inessentia

The TFOS International Workshop on Contact Lens Discomfort: Introduction

Nichols, J. J., Jones, L., Nelson, J. D., Stapleton, F., Sullivan, D. A., & Willcox, M. D. P. (2013). The TFOS International Workshop on Contact Lens Discomfort: Introduction. Investigative Opthalmology & Visual Science, 54(11), TFOS1. https://doi.org/10.1167/iovs.13-13195For many years, the contact lens field had focused on safety associated with contact lens wear—and for good reason, given the lack of understanding of the risk factors and etiology of serious complications such as microbial keratitis. However, as knowledge came to light on these complications through the 1980s and 1990s, it allowed for practitioners to become more comfortable managing these complications, along with the introduction of products that helped reduce or prevent some of these problems. It was during this time, beginning in the mid-1980s, that the field itself became cognizant of the issues associated with comfort, or discomfort, during contact lens wear. Since that time, we have witnessed the field (and industry) shift its attention toward understanding the issue of contact lens discomfort (CLD). Contact lens discomfort is a substantial and burdensome problem experienced frequently by contact lens wearers. It is well established that most contact lens wearers experience CLD, at least occasionally, although many experience CLD to such a severity that they feel compelled to alter their wearing habits. Common, although palliative at best, treatments include the periodic use of rewetting drops, contact lens removal, contact lens refitting (using different lens designs or materials or replacement schedules), and changes in the contact lens care solutions or regimens, in addition to other less commonly used approaches including topical or systemic medications, alterations in diet, and punctal plugs. Ultimately, CLD is the primary factor associated with permanent discontinuation from contact lens wear. Given the importance of the issue of CLD to both patients and practitioners alike, the time was right to move the field forward by taking steps to bring global consensus to our current understanding of this condition.Supported by unrestricted financial support from Alcon (title sponsor), Allergan, Bausch & Lomb, Santen, Menicon, Vistakon, Laboratoires Théa, Optima, Oculus, CooperVision, and Contact Lens Spectrum

Doublet structures in quantum well absorption spectra due to Fano-related interference

In this theoretical investigation we predict an unusual interaction between a discrete state and a continuum of states, which is closely related to the case of Fano-interference. It occurs in a GaAs/AlxGa1-xAs quantum well between the lowest light-hole exciton and the continuum of the second heavy-hole exciton. Unlike the typical case for Fano-resonance, the discrete state here is outside the continuum; we use uniaxial stress to tune its position with respect to the onset of the continuum. State-of-the art calculations of absorption spectra show that as the discrete state approaches the continuum, a doublet structure forms which reveals anticrossing behaviour. The minimum separation energy of the anticrossing depends characteristically on the well width and is unusually large for narrow wells. This offers striking evidence for the strong underlying valence-band mixing. Moreover, it proves that previous explanations of similar doublets in experimental data, employing simple two-state models, are incomplete.Comment: 21 pages, 5 figures and 5 equations. Accepted for publication in Physical Review