Bayesian uncertainty analysis with applications to turbulence modeling

In this paper, we apply Bayesian uncertainty quantification techniques to the processes of calibrating complex mathematical models and predicting quantities of interest (QoI's) with such models. These techniques also enable the systematic comparison of competing model classes. The processes of calibration and comparison constitute the building blocks of a larger validation process, the goal of which is to accept or reject a given mathematical model for the prediction of a particular QoI for a particular scenario. In this work, we take the first step in this process by applying the methodology to the analysis of the Spalart-Allmaras turbulence model in the context of incompressible, boundary layer flows. Three competing model classes based on the Spalart-Allmaras model are formulated, calibrated against experimental data, and used to issue a prediction with quantified uncertainty. The model classes are compared in terms of their posterior probabilities and their prediction of QoI's. The model posterior probability represents the relative plausibility of a model class given the data. Thus, it incorporates the model's ability to fit experimental observations. Alternatively, comparing models using the predicted QoI connects the process to the needs of decision makers that use the results of the model. We show that by using both the model plausibility and predicted QoI, one has the opportunity to reject some model classes after calibration, before subjecting the remaining classes to additional validation challenges.     

Three-dimensional magnetic focusing of superparamagnetic beads for on-chip agglutination assays

We present a new method for three-dimensional (3D) magneticfocusing of magnetic microparticles in a microfluidic system. On-chip magnetic particle manipulation in the microchannel is achieved by a high-gradient magnetic field generated by means of a micromachined field concentrator. The system allows retention of functionalized beads in a dense plug while flowing through buffer or analyte. Slowly reducing the magnetic retention force in the presence of a flow results in controlled release of the particles into a fine streamline with regular longitudinal interparticle spacing. Alignment at half-height of the channel is readily obtained through the symmetry of the magnetic field. A single lateral sheath flow is required to provide full 3D focusing of the microparticles in the middle of the microchannel with a maximum deviation of ±5 μm from the center position. With the use of this system, a new approach for performing an immunoagglutination assay on-chip has been implemented. Three-dimensional focusing allowed reliable counting of singlets and agglutinated doublets. We demonstrate the potential of the agglutination assay in a microfluidic format using a streptavidin/biotinylated bovine serum albumin (bBSA) model system. A detection limit of about 400 pg/mL (6 pM) is achieved.     

Time-independent,high electron mobility in thin PC61BM films: Relevance to organic photovoltaics

Ultrafast optical probing of electric field by means of electroabsorption combined with conventional photocurrent measurements was employed to investigate the drift and mobility dynamics of photo-generated charge carriers in the pristine PC₆₁BM film and in the blend with a merocyanine dye. Electrons passed a 40 nm thick PC₆₁BM film within a few picoseconds with time-independent and weakly dispersive mobility. The electron mobility is 1 cm²/(V s) at 1 MV/cm and an estimate of the zero-field mobility yields 5 ⋅ 10⁻² cm²/(V s). The initial electron mobility in the blend is of the order of 10⁻² cm²/(V s) and decreases rapidly. We conclude that electron motion in PC₆₁BM based organic bulk hetero-junction solar cells is limited by barriers between PC₆₁BM domains rather than by intrinsic PC₆₁BM properties.     

THE POISSON WAVELET TRANSFORM

This paper introduces a family of wavelet transforms based on the Poisson Transform. The wavelet transform maps L² (R)functions to a space described by two continuous variables, scale and translation, as well as a discrete index. Reconstruction in the wavelet domain can be done for each of the discrete indices. Additionally, a different reconstruction formula exists for the Poisson Transform domain. We develop the Poisson Wavelet Transform, present an example relevant to stable, over-damped, linear, time-invariant systems, and show the relationship between the Poisson Transform and the Poisson Wavelet Transform.     

Nicotine, cotinine, withdrawal, and craving patterns during smoking and nicotine nasal spray use: results from a pilot study with African American men.

Nicotine intake via smoking is highly variable. Individualized dosing of nicotine replacement therapy (NRT) may improve product efficacy, but a better understanding of the within-day and within-subject relationships between smoking, NRT use, nicotine and cotinine concentrations in blood, and cravings and withdrawal symptoms is needed to inform dosing algorithms. A pilot study was undertaken to collect data on these relationships and to assess the feasibility of the methods needed for this type of research, including a sophisticated statistical modeling technique (a two-part mixed-effects model with correlated random effects that accounts for clumping at zero). Because nicotine metabolism varies by gender and race, the sample was homogeneous with respect to these characteristics. In a within-subjects study, 27 African American adult male smokers carried a computerized cigarette dispenser for 1 week, capturing the time each cigarette was smoked. Subjects then entered an inpatient setting for 1 day of scheduled smoking (matched to data from the cigarette dispenser to create an ecologically valid schedule) and 4 days of ad libitum nicotine nasal spray use, while tobacco abstinent. Eight times per day, at 2-hour intervals, blood was drawn and ratings of cigarette cravings and withdrawal symptoms were obtained. On average, subjects used less than half of the manufacturer's recommended minimum daily dose of nicotine nasal spray. Large differences in nicotine and cotinine levels were observed between individuals. When predicting nicotine, cotinine, withdrawal, and cravings, we observed significant interactions between route of nicotine intake and a variety of independent variables.     

Effects of ginseng treatment on neutrophil chemiluminescence and immunoglobulin G subclasses in a rat model of chronic Pseudomonas aeruginosa pneumonia

OBJECTIVE: To examine the effect of different concentrations of calcium on the contractile responses of isolated strips of rabbit bladder detrusor to various forms of stimulation after 2 h incubation in the presence of substrate and oxygen depletion (in vitro ischaemia), followed by 1 h of recovery. The resultant contractile responses were correlated with the level of lipid peroxidation as determined by malonedialdehyde (MDA) concentration. MATERIALS AND METHODS: Isolated strips of rabbit bladder detrusor smooth muscle were incubated in Tyrode's solution containing different concentrations of calcium (0-5.4 mmol/L). The effect of 2 h of incubation in oxygen- and substrate-free medium (in vitro ischaemia), followed by a 1-h incubation in the presence of oxygen and substrate, on the contractile responses to field stimulation, carbachol and KCl were determined. The effects of repetitive stimulation (15 s of stimulation at 32 Hz applied every 5 min during the 2-h experimental period) were also assessed. RESULTS: The contractile responses to all stimuli increased as the extracellular calcium concentration was increased from 0.6 to 5.4 mmol/L. A 2 h exposure to in vitro ischaemia, followed by a return to normal solution, resulted in a diminished response to all stimuli. This contractile dysfunction was least in the presence of calcium chelator (EGTA) and greatest in the presence of 5.4 mmol/L calcium. Repetitive stimulation during in vitro ischaemia also exacerbated the contractile dysfunction. Lipid peroxidation increased during in vitro ischaemia in proportion to the calcium concentration and was enhanced by repetitive stimulation during this period. Regardless of the incubation conditions, the reduction in the contractile response was significantly greater for field-stimulated tissues than for those stimulated with carbachol or KCl. CONCLUSIONS: These results show that the magnitude of contractile dysfunction induced by incubation in the presence of substrate and oxygen depletion is reduced in the presence of low calcium concentrations, increased in the presence of high calcium levels and increased in the presence of repetitive stimulation. In addition, the level of lipid peroxidation after the recovery period was proportional to the magnitude of contractile dysfunction present.     

Comparison of laser-wavelength operation for drilling of via holes in AlGaN/GaN HEMTs on SiC substrates

By using a frequency-tripled Nd:YVO₄ laser source (355 nm) for drilling through-wafer via holes in SiC substrates, we can reduce the surface contamination and achieve better smoothness inside the via holes compared to use of the more common 1064-nm Nd:YVO₄ laser. The sheet and contact resistance of AlGaN/GaN HEMT layers grown on SiC substrates were similar after formation of vias by 355-nm laser drilling to those of the undrilled reference sample. By sharp contrast, 1064-nm laser drilling produces significant redeposition of ablated material around the via and degrades the electrical properties of the HEMT layers.     

The Impact of the Sibling in Clinical Practice: Transference and Countertransference Dynamics.

For many years, the impact of sibling relationships on psychological development has been neglected in the literature, overshadowed by the role of the parent-child relationship. As a result, attention to sibling dynamics and sibling transference as valuable information for case formulation and treatment interventions has not been used to its maximum potential. The authors demonstrate how deliberate consideration of sibling dynamics as well as the transferences and countertransferences associated with those dynamics can facilitate treatment. Several important sibling dynamics are discussed, including siblings' influences on identity development; sibling rivalry, jealousy, envy, guilt, and resentment; and sibling attachment. The impact of sibling dynamics on adult love relationships is discussed, as are potential effects of sibling abuse and sibling bereavement. Examples of how these dynamics can manifest themselves in transference and countertransference reactions and suggestions for working with those dynamics are illustrated with clinical examples. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Absolute metabolite quantification by in vivo NMR spectroscopy: II. A multicentre trial of protocols for in vivo localised proton studies of human brain

We have performed a multicentre trial to assess the performance of three techniques for absolute quantification of cerebral metabolites using in vivo proton nuclear magnetic resonance (NMR). The techniques included were 1) an internal water standard method, 2) an external standard method based on phantom replacement, and 3) a more sophisticated method incorporating elements of both the internal and external standard approaches, together with compartmental analysis of brain water. Only the internal water standard technique could be readily implemented at all participating sites and gave acceptable precision and interlaboratory reproducibility. This method was insensitive to many of the experimental factors affecting the performance of the alternative techniques, including effects related to loading, standing waves and B1 inhomogeneities; and practical issues of phantom positioning, user expertise and examination duration. However, the internal water standard method assumes a value for the concentration of NMR-visible water within the spectroscopic volume of interest. In general, it is necessary to modify this assumed concentration on the basis of the grey matter, white matter and cerebrospinal fluid (CSF) content of the volume, and the NMR-visible water content of the grey and white matter fractions. Combining data from 11 sites, the concentrations of the principal NMR-visible metabolites in the brains of healthy subjects (age range 20-35 years) determined using the internal water standard method were (mean+/-SD): [NAA]=10.0+/-3.4 mM (n=53), [tCho]=1.9+/-1.0 mM (n=51), [Cr + PCr]=6.5+/-3.7 mM (n=51). Evidence of system instability and other sources of error at some participating sites reinforces the need for rigorous quality assurance in quantitative spectroscopy.