Bayesian Nonparametric Adaptive Control using Gaussian Processes

This technical report is a preprint of an article submitted to a journal.Most current Model Reference Adaptive Control (MRAC) methods rely on parametric adaptive elements, in which the number of parameters of the adaptive element are fixed a priori, often through expert judgment. An example of such an adaptive element are Radial Basis Function Networks (RBFNs), with RBF centers pre-allocated based on the expected operating domain. If the system operates outside of the expected operating domain, this adaptive element can become non-effective in capturing and canceling the uncertainty, thus rendering the adaptive controller only semi-global in nature. This paper investigates a Gaussian Process (GP) based Bayesian MRAC architecture (GP-MRAC), which leverages the power and flexibility of GP Bayesian nonparametric models of uncertainty. GP-MRAC does not require the centers to be preallocated, can inherently handle measurement noise, and enables MRAC to handle a broader set of uncertainties, including those that are defined as distributions over functions. We use stochastic stability arguments to show that GP-MRAC guarantees good closed loop performance with no prior domain knowledge of the uncertainty. Online implementable GP inference methods are compared in numerical simulations against RBFN-MRAC with preallocated centers and are shown to provide better tracking and improved long-term learning.This research was supported in part by ONR MURI Grant N000141110688 and NSF grant ECS #0846750

Systematic review and meta-analysis on certolizumab pegol for rheumatoid arthritis in adults

Background The appearance of tumor necrosis factor-alpha (TNFalpha) inhibitors dramatically changed the prognosis of rheumatoid arthritis. Certolizumab pegol (CZP) is a human Fab fragment of anti-TNFalpha monoclonal antibody which is approved for the treatment of rheumatoid arthritis. We performed a systematic review and meta-analysis, with Cochrane methodology, of the effects of CZP in rheumatoid arthritis. Objectives To assess the clinical benefits and harms of CZP in patients with rheumatoid arthritis. Methods We performed a search of electronic database (Cochrane Database, MEDLINE, EMBASE, Web of Knowledge and clinicaltrials.gov) until 26th September 2016. We searched for randomized controlled trials of CZP in rheumatoid arthritis compared to any other agent including placebo. Results 14 trials were included for the meta-analysis, 12 (5422 patients) in the pooled analysis for benefits and 14 (5499 patients) in the pooled analysis for safety. The overall possibility of bias seemed to be low but the quality of the evidence was low due to the risk of attrition bias. With the approved dose - CZP 200 mg subcutaneous every other week with the first three doses of 400 mg - CZP showed statistically significant improvements at 24 weeks compared to placebo in: ACR50 absolute improvement 27% (95% CI 20% to 33%), RR 3.8 (95% CI 2.42 to 5.95) and NNT=4 (95% CI 3 to 8); DAS28 <2.6 - original definition of remission - with RR 3.79 (95% CI 1.90 to 7.56); HAQ with -12% absolute improvement (95% CI -9% to -14%); and erosion score with -0.29% (95% CI -0.42% to -0.17%). There are also data available at 12 weeks with RR of 1.99 (95% CI 1.44 to 2.76) of achieving DAS28<2.6 with CZP 200 mg dose. The proportion of patients achieving DAS28<2.6 was still higher with CZP at 52 weeks with RR of 1.83 (95% CI 1.53 to 2.18). Serious adverse events were more frequent for CZP 200 mg dose with a RR of 1.47 (95% CI 1.13 to 1.91) and NNH of 32. There have been eight adverse events leading to death in CZP 200 mg group versus two in the control group (not statistically significant) and 10 patients developing tuberculosis versus two in the control group (not statistically significant). Conclusions There is low level evidence from randomized controlled trials that CZP as monotherapy or combined with methotrexate improved ACR50, DAS28, HAQ and joint damaged on x-ray. Adverse events were more frequent with active treatment

Lead halide perovskites: Challenges and opportunities in advanced synthesis and spectroscopy

Hybrid lead perovskites containing a mixture of organic and inorganic cations and anions have led to solar cell devices with performance and stability that are better than those of their single-halide analogs. 207Pb solid-state nuclear magnetic resonance and single-particle photoluminescence spectroscopies show that the structure and composition of mixed-halide and likely other hybrid lead perovskites are much more complex than previously thought and are highly dependent on their synthesis. While a majority of reports in the area focus on the construction of photovoltaic devices, this Perspective focuses instead on achieving a better understanding of the fundamental chemistry and photophysics of these materials, because this will aid not only in constructing improved devices but also in generating new uses for these unique materials

Aerosol light-scattering enhancement due to water uptake during the TCAP campaign

Aerosol optical properties were measured by the DOE/ARM (US Department of Energy Atmospheric Radiation Measurements) Program Mobile Facility during the Two-Column Aerosol Project (TCAP) campaign deployed at Cape Cod, Massachusetts, for a 1-year period (from summer 2012 to summer 2013). Measured optical properties included aerosol light-absorption coefficient (σap) at low relative humidity (RH) and aerosol light-scattering coefficient (σsp) at low and at RH values varying from 30 to 85%, approximately. Calculated variables included the single scattering albedo (SSA), the scattering Ångström exponent (SAE) and the scattering enhancement factor (f(RH)). Over the period of measurement, f(RH = 80%) had a mean value of 1.9 ± 0.3 and 1.8 ± 0.4 in the PM10 and PM1 fractions, respectively. Higher f(RH = 80%) values were observed for wind directions from 0 to 180° (marine sector) together with high SSA and low SAE values. The wind sector from 225 to 315° was identified as an anthropogenically influenced sector, and it was characterized by smaller, darker and less hygroscopic aerosols. For the marine sector, f(RH = 80%) was 2.2 compared with a value of 1.8 obtained for the anthropogenically influenced sector. The air-mass backward trajectory analysis agreed well with the wind sector analysis. It shows low cluster to cluster variability except for air masses coming from the Atlantic Ocean that showed higher hygroscopicity. Knowledge of the effect of RH on aerosol optical properties is of great importance for climate forcing calculations and for comparison of in situ measurements with satellite and remote sensing retrievals. In this sense, predictive capability of f(RH) for use in climate models would be enhanced if other aerosol parameters could be used as proxies to estimate hygroscopic growth. Toward this goal, we propose an exponential equation that successfully estimates aerosol hygroscopicity as a function of SSA at Cape Cod. Further work is needed to determine if the equation obtained is valid in other environments.This research was funded by the NOAA Climate Program using measurements funded by the US Department of Energy Atmospheric System Research program. The authors would like to express their gratitude to the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model. We would like to thank also the Openair project. G. Titos was funded by the Spanish Ministry of Economy and Competitiveness – Secretariat of Science, Innovation and Development under grants BES-2011-043721 and EEBB-I-13-06456, and projects P10-RNM-6299, CGL2010-18782 and EU INFRA-2010-1.1.16-262254