Three Poems

Three Poems by Biljana D. Obradovic Update: January Appointment Postponed I’ve Been Here Before Safe in the US of

On the Validity and Applicability of Models of Negative Capacitance and Implications for MOS Applications

The observation of room temperature sub-60 mV/dec subthreshold slope (SS) in MOSFETs with ferroelectric (FE) layers in the gate stacks or in series with the gate has attracted much attention. Recently, we modeled this effect in the framework of a FE polarization switching model. However, there is a large amount of literature attributing this effect to a stabilization of quasi-static (QS) negative capacitance (NC) in the FE. The technological implications of a stabilized non-switching (NS) QSNC model vs a FE switching model are vastly different; the latter precluding applications to sub-60 mV/dec SS scaled CMOS due to speed limitations and power dissipated in switching. In this letter, we provide a thorough analysis assessing the foundations of models of QSNC, identifying which specific assumptions (ansatz) may be unlikely or unphysical, and analyzing their applicability. We show that it is not reasonable to expect QSNC for two separate capacitors connected in series (with a metal plate between dielectric (DE) and FE layers). We propose a model clarifying under which conditions a QS "apparent NC" for a FE layer in a FE-DE bi-layer stack may be observed, quantifying the requirements of strong interface polarization coupling in addition to capacitance matching. In this regime, our model suggests the FE layer does not behave as a NC layer, simply, the coupling leads to both the DE and FE behaving as high-k DE with similar permittivities. This may be useful for scaled EOT devices but does not lead to sub-60 mV/dec SS.Comment: Version published in Appl. Phys. Let

Viewing the efficiency of chaos control

This paper aims to cast some new light on controlling chaos using the OGY- and the Zero-Spectral-Radius methods. In deriving those methods we use a generalized procedure differing from the usual ones. This procedure allows us to conveniently treat maps to be controlled bringing the orbit to both various saddles and to sources with both real and complex eigenvalues. We demonstrate the procedure and the subsequent control on a variety of maps. We evaluate the control by examining the basins of attraction of the relevant controlled systems graphically and in some cases analytically

Application of the Method of Trigonometrical Substitution in Solving Problems

The use of trigonometric substitution in solving algebraic problems aims to establish a relationship between different branches of mathematics, namely: algebra and trigonometry. It is important to instill in students courage and resourcefulness in finding ways to solve problems not only in the immediate environment of the conditions, but also in a wider, sometimes unexpected area. Trigonometric substitution is one of many substitution methods of integration where a function or expression in a given integral is replaced by trigonometric functions such as sin, cos, tan, etc. Integration by replacement is a good and easiest approach that anyone can make. It is used when we replace the function, whose derivative is already included in the given integral function. This simplifies the function and gives a function of simple integrals that we can easily integrate. It is also known as u-substitution or reverse chain rule Or in other words, using this method, we can easily evaluate integrals and antiderivatives

Modeling Single Electron Transfer in Si:P Double Quantum Dots

Solid-state systems such as P donors in Si have considerable potential for realization of scalable quantum computation. Recent experimental work in this area has focused on implanted Si:P double quantum dots (DQDs) that represent a preliminary step towards the realization of single donor charge-based qubits. This paper focuses on the techniques involved in analyzing the charge transfer within such DQD devices and understanding the impact of fabrication parameters on this process. We show that misalignment between the buried dots and surface gates affects the charge transfer behavior and identify some of the challenges posed by reducing the size of the metallic dot to the few donor regime.Comment: 11 pages, 7 figures, submitted to Nanotechnolog

Characterization of the “frequent exacerbator phenotype” in bronchiectasis

Rationale: Exacerbations are key events in the natural history of bronchiectasis, but clinical predictors and outcomes of patients with frequently exacerbating disease are not well described. Objectives: To establish if there is a \u201cfrequent exacerbator phenotype\u201d in bronchiectasis and the impact of exacerbations on long-term clinical outcomes. Methods: We studied patients with bronchiectasis enrolled from 10 clinical centers in Europe and Israel, with up to 5 years of follow-up. Patients were categorized by baseline exacerbation frequency (zero, one, two, or three or more per year). The repeatability of exacerbation status was assessed, as well as the independent impact of exacerbation history on hospitalizations, quality of life, and mortality. Measurements and Main Results: A total of 2,572 patients were included. Frequent exacerbations were the strongest predictor of future exacerbation frequency, suggesting a consistent phenotype.The incident rate ratios for future exacerbations were 1.73 (95% confidence interval [CI], 1.47-2.02; P, 0.0001) for one exacerbation per year, 3.14 (95% CI, 2.70-3.66; P, 0.0001) for two exacerbations, and 5.97 (95% CI, 5.27-6.78; P, 0.0001) for patients with three or more exacerbations per year at baseline. Additional independent predictors of future exacerbation frequency were Haemophilus influenzae and Pseudomonas aeruginosa infection, FEV1, radiological severity of disease, and coexisting chronic obstructive pulmonary disease. Patients with frequently exacerbating disease had worse quality of life and were more likely to be hospitalized during followup. Mortality over up to 5 years of follow-up increased with increasing exacerbation frequency. Conclusions: The frequent exacerbator phenotype in bronchiectasis is consistent over time and shows high disease severity, poor quality of life, and increased mortality during follow-up

Fourier Density Approximation for Belief Propagation in Wireless Sensor Networks

Many distributed inference problems in wireless sensor networks can be represented by probabilistic graphical models, where belief propagation, an iterative message passing algorithm provides a promising solution. In order to make the algorithm efficient and accurate, messages which carry the belief information from one node to the others should be formulated in an appropriate format. This paper presents two belief propagation algorithms where non-linear and non-Gaussian beliefs are approximated by Fourier density approximations, which significantly reduces power consumptions in the belief computation and transmission. We use self-localization in wireless sensor networks as an example to illustrate the performance of this method

The independent contribution of <i>Pseudomonas aeruginosa</i> infection to long-term clinical outcomes in bronchiectasis

Pseudomonas aeruginosa is responsible for chronic infection in many bronchiectasis patients but it is not known whether it is associated with worse clinical outcomes independent of the underlying severity of disease. This study analysed data from 2596 bronchiectasis patients included from 10 different bronchiectasis clinical centres across Europe and Israel, with a 5-year follow-up period. Prevalence of P. aeruginosa chronic infection and its independent impact on exacerbations, hospitalisations, quality of life and mortality was assessed. The prevalence of P. aeruginosa chronic infection was 15.0% (n=389). P. aeruginosa was associated with a higher mortality in a univariate analysis (hazard ratio (HR) 2.02; 95% (confidence interval) CI 1.53-2.66; p&lt;0.0001) but an independent impact on mortality was not found in a multivariate analysis (HR 0.98; 95% CI 0.70-1.36; p=0.89). P. aeruginosa was independently associated with increased mortality only in patients with frequent exacerbations (two or more per year) (HR 2.03; 95% CI 1.36-3.03; p=0.001). An independent association with worse quality of life of 7.46 points (95% CI 2.93-12.00; p=0.001) was found in a multivariable linear regression. P. aeruginosa was therefore found to be independently associated with exacerbation frequency, hospital admissions and worse quality of life. Mortality was increased in patients with P. aeruginosa particularly in the presence of frequent exacerbations