Design of a CMOS active electrode IC for wearable electrical impedance tomography systems

This paper describes the design of an active electrode integrated circuit (IC) for a wearable electrical impedance tomography (EIT) system required for real time monitoring of neonatal lung function. The IC comprises a wideband high power current driver (up to 6 mAp-p output current), a low noise voltage amplifier and two shape sensor buffers. The IC has been designed in a 0.35-μm CMOS technology. It operates from ±9 V power supplies and occupies a total die area of 5 mm2. Post-layout simulations are presented

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

Natural Double Inflation in Supergravity

We propose a natural double inflation model in supergravity. In this model, chaotic inflation first takes place by virtue of the Nambu-Goldstone-like shift symmetry, which guarantees the absence of the exponential factor in the potential for the inflaton field. During chaotic inflation, an initial value of the second inflation (new inflation) is set. In this model, the initial value of new inflation can be adequately far from the local maximum of the potential for new inflation due to the small linear term of the inflaton in the K\"ahler potential. Therefore, the primordial fluctuations within the present horizon scale may be attributed to both inflations; that is, the first chaotic inflation produces the primordial fluctuations on the large cosmological scales while the second new inflation on the smaller scales. The successive decay of the inflaton for new inflation leads to a reheating temperature low enough to avoid the overproduction of gravitinos in a wide range of the gravitino mass.Comment: 13 pages, to appear in Phys. Rev.

Adiabatic and entropy perturbations propagation in a bouncing Universe

By studying some bouncing universe models dominated by a specific class of hydrodynamical fluids, we show that the primordial cosmological perturbations may propagate smoothly through a general relativistic bounce. We also find that the purely adiabatic modes, although almost always fruitfully investigated in all other contexts in cosmology, are meaningless in the bounce or null energy condition (NEC) violation cases since the entropy modes can never be neglected in these situations: the adiabatic modes exhibit a fake divergence that is compensated in the total Bardeen gravitational potential by inclusion of the entropy perturbations.Comment: 25 pages, no figure, LaTe

Estimated Maternal Pesticide Exposure from Drinking Water and Heart Defects in Offspring

Our objective was to examine the relationship between estimated maternal exposure to pesticides in public drinking water and the risk of congenital heart defects (CHD). We used mixed-effects logistic regression to analyze data from 18,291 nonsyndromic cases with heart defects from the Texas Birth Defects Registry and 4414 randomly-selected controls delivered in Texas from 1999 through 2005. Water district-level pesticide exposure was estimated by linking each maternal residential address to the corresponding public water supply district’s measured atrazine levels. We repeated analyses among independent subjects from the National Birth Defects Prevention Study (NBDPS) (1620 nonsyndromic cases with heart defects and 1335 controls delivered from 1999 through 2005). No positive associations were observed between high versus low atrazine level and eight CHD subtypes or all included heart defects combined. These findings should be interpreted with caution, in light of potential misclassification and relatively large proportions of subjects with missing atrazine data. Thus, more consistent and complete monitoring and reporting of drinking water contaminants will aid in better understanding the relationships between pesticide water contaminants and birth defects

Hypospadias and maternal exposure to atrazine via drinking water in the National Birth Defects Prevention study

Background Hypospadias is a relatively common birth defect affecting the male urinary tract. It has been suggested that exposure to endocrine disrupting chemicals might increase the risk of hypospadias by interrupting normal urethral development. Methods Using data from the National Birth Defects Prevention Study, a population-based case-control study, we considered the role of maternal exposure to atrazine, a widely used herbicide and potential endocrine disruptor, via drinking water in the etiology of 2nd and 3rd degree hypospadias. We used data on 343 hypospadias cases and 1,422 male controls in North Carolina, Arkansas, Iowa, and Texas from 1998–2005. Using catchment level stream and groundwater contaminant models from the US Geological Survey, we estimated atrazine concentrations in public water supplies and in private wells. We assigned case and control mothers to public water supplies based on geocoded maternal address during the critical window of exposure for hypospadias (i.e., gestational weeks 6–16). Using maternal questionnaire data about water consumption and drinking water, we estimated a surrogate for total maternal consumption of atrazine via drinking water. We then included additional maternal covariates, including age, race/ethnicity, parity, and plurality, in logistic regression analyses to consider an association between atrazine and hypospadias. Results When controlling for maternal characteristics, any association between hypospadias and daily maternal atrazine exposure during the critical window of genitourinary development was found to be weak or null (odds ratio for atrazine in drinking water = 1. 00, 95 % CI = 0.97 to 1.03 per 0.04 μg/day increase; odds ratio for maternal consumption = 1.02, 95 % CI = 0.99 to 1.05; per 0.05 μg/day increase). Conclusions While the association that we observed was weak, our results suggest that additional research into a possible association between atrazine and hypospadias occurrence, using a more sensitive exposure metric, would be useful