On the application of frequency selective common mode feedback for multifrequency EIT

Common mode voltages are frequently a problem in electrical impedance tomography (EIT) and other bioimpedance applications. To reduce their amplitude common mode feedback is employed. Formalised analyses of both current and voltage feedback is presented in this paper for current drives. Common mode effects due to imbalances caused by the current drives, the electrode connections to the body load and the introduction of the body impedance to ground are considered. Frequency selective narrowband common mode feedback previously proposed to provide feedback stability is examined. As a step towards multifrequency applications the use of narrowband feedback is experimentally demonstrated for two simultaneous current drives. Measured results using standard available components show a reduction of 62dB for current feedback and 31dB for voltage feedback. Frequencies ranged from 50 kHz to 1 MHz

High Efficiency Power Management Unit for Implantable Optical-Electrical Stimulators

Battery-less active implantable devices are of interest because they offer longer life span and eliminate costly battery replacement surgical interventions. This is possible as a result of advances in inductive power transfer and development of power management circuits to maximize the overall power transfer and provide various voltage levels for multi-functional implantable devices. Rehabilitation therapy using optical stimulation of genetically modified peripheral neurons requires high current loads. Standard rectification topologies are inefficient and have associated voltage drops unsuited for miniaturized implants. This paper presents an integrated power management unit (PMU) for an optical-electrical stimulator to be used in the treatment of motor neurone disease. It includes a power-efficient regulating rectifier with a novel body biased high-speed comparator providing 3.3 V for the operation of the stimulator, a 3-stage latch-up charge pump with 12 V output for the input stage of the optical-electrical stimulator, and 1.8 V for digital control logic. The chip was fabricated in a 0.18 μm CMOS process. Measured results show that for a regulated output of 3.3 V delivering 30.3 mW power, the peak power conversion efficiency is 84.2% at 6.78 MHz inductive link tunable frequency reducing to 70.3% at 13.56 MHz. The charge pump with on chip capacitors has 90.9% measured voltage conversion efficiency

Tensor Perturbations in Quantum Cosmological Backgrounds

In the description of the dynamics of tensor perturbations on a homogeneous and isotropic background cosmological model, it is well known that a simple Hamiltonian can be obtained if one assumes that the background metric satisfies Einstein classical field equations. This makes it possible to analyze the quantum evolution of the perturbations since their dynamics depends only on this classical background. In this paper, we show that this simple Hamiltonian can also be obtained from the Einstein-Hilbert lagrangian without making use of any assumption about the dynamics of the background metric. In particular, it can be used in situations where the background metric is also quantized, hence providing a substantial simplification over the direct approach originally developed by Halliwell and Hawking.Comment: 24 pages, JHEP forma

A platform for the discovery of new macrolide antibiotics.

The chemical modification of structurally complex fermentation products, a process known as semisynthesis, has been an important tool in the discovery and manufacture of antibiotics for the treatment of various infectious diseases. However, many of the therapeutics obtained in this way are no longer effective, because bacterial resistance to these compounds has developed. Here we present a practical, fully synthetic route to macrolide antibiotics by the convergent assembly of simple chemical building blocks, enabling the synthesis of diverse structures not accessible by traditional semisynthetic approaches. More than 300 new macrolide antibiotic candidates, as well as the clinical candidate solithromycin, have been synthesized using our convergent approach. Evaluation of these compounds against a panel of pathogenic bacteria revealed that the majority of these structures had antibiotic activity, some efficacious against strains resistant to macrolides in current use. The chemistry we describe here provides a platform for the discovery of new macrolide antibiotics and may also serve as the basis for their manufacture

Spatial-Temporal Modeling of the Association between Air Pollution Exposure and Preterm Birth: Identifying Critical Windows of Exposure

Exposure to high levels of air pollution during the pregnancy is associated with increased probability of preterm birth (PTB), a major cause of infant morbidity and mortality. New statistical methodology is required to specifically determine when a particular pollutant impacts the PTB outcome, to determine the role of different pollutants, and to characterize the spatial variability in these results. We develop a new Bayesian spatial model for PTB which identifies susceptible windows throughout the pregnancy jointly for multiple pollutants (PM2.5, ozone) while allowing these windows to vary continuously across space and time. We geo-code vital record birth data from Texas (2002–2004) and link them with standard pollution monitoring data and a newly introduced EPA product of calibrated air pollution model output. We apply the fully spatial model to a region of 13 counties in eastern Texas consisting of highly urban as well as rural areas. Our results indicate significant signal in the first two trimesters of pregnancy with differe0nt pollutants leading to different critical windows. Introducing the spatial aspect uncovers critical windows previously unidentified when space is ignored. A proper inference procedure is introduced to correctly analyze these windows

Bayesian spatial-temporal model for cardiac congenital anomalies and ambient air pollution risk assessment: BAYESIAN MODEL FOR CARDIAC CONGENITAL ANOMALIES

We introduce a Bayesian spatial-temporal hierarchical multivariate probit regression model that identifies weeks during the first trimester of pregnancy which are impactful in terms of cardiac congenital anomaly development. The model is able to consider multiple pollutants and a multivariate cardiac anomaly grouping outcome jointly while allowing the critical windows to vary in a continuous manner across time and space. We utilize a dataset of numerical chemical model output which contains information regarding multiple species of PM2.5. Our introduction of an innovative spatial-temporal semiparametric prior distribution for the pollution risk effects allows for greater flexibility to identify critical weeks during pregnancy which are missed when more standard models are applied. The multivariate kernel stick-breaking prior is extended to include space and time simultaneously in both the locations and the masses in order to accommodate complex data settings. Simulation study results suggest that our prior distribution has the flexibility to outperform competitor models in a number of data settings. When applied to the geo-coded Texas birth data, weeks 3, 7 and 8 of the pregnancy are identified as being impactful in terms of cardiac defect development for multiple pollutants across the spatial domain

Adiabatic versus isocurvature non-Gaussianity

We study the extent to which one can distinguish primordial non-Gaussianity (NG) arising from adiabatic and isocurvature perturbations. We make a joint analysis of different NG models based on various inflationary scenarios: local-type and equilateral-type NG from adiabatic perturbations and local-type and quadratic-type NG from isocurvature perturbations together with a foreground contamination by point sources. We separate the Fisher information of the bispectrum of cosmic microwave background temperature and polarization maps by l for the skew spectrum estimator introduced by Munshi and Heavens to study the scale dependence of the signal-to-noise ratio of different NG components and their correlations. We find that the adiabatic and the isocurvature modes are strongly correlated, though the phase difference of acoustic oscillations helps to distinguish them. The correlation between local- and equilateral-type is weak, but the two isocurvature modes are too strongly correlated to be discriminated. Point source contamination, to the extent to which it can be regarded as white noise, can be almost completely separated from the primordial components for l > 100. Including correlations among the different components, we find that the errors of the NG parameters increase by 20-30 per cent for the Wilkinson Microwave Anisotropy Probe 5-year observation, but ~=5 per cent for Planck observations