Quantitative effects of acquisition duration and temporal resolution on the measurement accuracy of prostate dynamic contrast-enhanced MRI data: a phantom study

Objectives

The aim of this study was to investigate the effect of the temporal resolution (T _res) and acquisition duration (AD) on the measurement accuracy of contrast concentration–time curves (CTCs), and derived phenomenological and pharmacokinetic parameter values, in a dynamic contrast-enhanced MRI experiment using a novel phantom test device.

Materials and methods

‘Ground truth’ CTCs were established using a highly precise optical imaging system. These precisely known CTCs were produced in an anthropomorphic environment, which mimicked the male pelvic region, and presented to the MRI scanner for measurement. The T _res was varied in the range [2–24.4 s] and the AD in the range [30–600 s], and the effects on the measurement accuracy were quantified.

Results

For wash-in parameter measurements, large underestimation errors (up to 40%) were found using T _res values ≥16.3 s; however, the measured wash-out rate did not vary greatly across all T _res values tested. Errors in derived K ^trans and v _e values were below 14 and 12% for acquisitions with {T _res ≤ 8.1 s, AD ≥ 360 s} and {T _res ≤ 16.3 s, AD ≥ 360 s}, respectively, but increased dramatically outside these ranges.

Conclusions

Errors in measured wash-in, wash-out, K ^trans, and v _e parameters were minimised using T _res ≤ 8.1 s and AD ≥ 360 s, with large errors recorded outside of this range.

     

Turbine airfoil degradation in the persian gulf war

Helicopter turbine engines used in the Desert Shield and Desert Storm operations experienced excessive sand ingestion. Fine particles were able to bypass filters and proceed through the combustor or cooling gaspaths. The first-stage turbine vanes were impacted with viscous silicate particles, forming a deposit on the leading-edge root platform and resulting in overheating and oxidation. The chemistry of the raw sand determines that of the ingested powders, the deposits, and the material reactions.     

Structure-guided SCHEMA recombination of distantly related beta-lactamases

We constructed a library of beta-lactamases by recombining three naturally occurring homologs (TEM-1, PSE-4, SED-1) that share 34-42% sequence identity. Most chimeras created by recombining such distantly related proteins are unfolded due to unfavorable side-chain interactions that destabilize the folded structure. To enhance the fraction of properly folded chimeras, we designed the library using SCHEMA, a structure-guided approach to choosing the least disruptive crossover locations. Recombination at seven selected crossover positions generated 6561 chimeric sequences that differ from their closest parent at an average of 66 positions. Of 553 unique characterized chimeras, 111 (20%) retained beta-lactamase activity; the library contains hundreds more novel beta-lactamases. The functional chimeras share as little as 70% sequence identity with any known sequence and are characterized by low SCHEMA disruption (E) compared to the average nonfunctional chimera. Furthermore, many nonfunctional chimeras with low E are readily rescued by low error-rate random mutagenesis or by the introduction of a known stabilizing mutation (TEM-1 M182T). These results show that structure-guided recombination effectively generates a family of diverse, folded proteins even when the parents exhibit only 34% sequence identity. Furthermore, the fraction of sequences that encode folded and functional proteins can be enhanced by utilizing previously stabilized parental sequences.     

The Influence of Copper-Containing Additives on Oil Oxidation and Corrosion

The effects of transition metals in either catalyzing or inhibiting oil oxidation in the liquid phase have been extensively reported in the literature. However, little attention has been paid to the surface films formed as by-products of these reactions. In this paper, the authors investigated surface films for the important case of copper-containing additives influencing the oxidation of oil that contacts a steel surface. Copper naphthenate in solution was found to inhibit oil oxidation and to form copper-containing precipitates and deposits on the steel surface. The surface films formed were characterized by X-ray photoelectron spectroscopy, Auger spectroscopy and scanning electron microscopy. The precipitates showed a unique morphology of spherical particles several microns in diameter. A high level of copper naphthenate was found to prevent corrosion of the steel surface.     

Category-based errors and the accessibility of unbiased spatial memories: A retrieval model.

Studies have consistently shown a spatial memory bias such that a target location is remembered toward the prototypical location of the region to which the target belongs, indicating a blending between the target’s specific information and the generic information of its region. The authors investigated whether people retain a veridical representation of a target location after a delay by determining the locus of the blending (during encoding, delay, or retrieval). To examine accessibility to the original target location, they used a recognition task, which is less demanding than the traditional reproduction procedure. The results showed that participants were able to recognize the original position of a target over their own biased recalled position after both a short (1,500 ms) and a longer (5,000 ms) delay. These findings reveal that spatial memories can be undistorted despite distorted recall responses. Results are discussed in terms of J. Huttenlocher, L. V. Hedges, and S. Duncan’s (1991) category adjustment model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chemical Ecology of the Defense of Two Nymphalid Butterfly Larvae Against Ants

We analyzed the behavioral responses of the ants Camponotus rufipes and Solenopsis geminata towards all instars of Dione junio and Abananote hylonome. We also analyzed ant behavior towards hexane extracts of larvae and extracts of the spines and neck glands of the fifth instars of both species and identified the chemical compounds present. Larvae of both species were repellent to ants from the first instar onward. Later instars survived ant attacks better than earlier instars. The spines and neck glands of the larvae influenced the behavior of C. rufipes. The chemical compounds contained in the hexane extracts of whole first and fifth instars and in the spines and neck glands of fifth instars were principally carboxylic acids and terpenes. Further bioassays confirmed the repellent effect of some of these acids toward ants.     

Partially observed epidemics in wildlife hosts: modelling an outbreak of dolphin morbillivirus in the northwestern Atlantic,June 2013–2014

Morbilliviruses cause major mortality in marine mammals, but the dynamics of transmission and persistence are ill understood compared to terrestrial counterparts such as measles; this is especially true for epidemics in cetaceans. However, the recent outbreak of dolphin morbillivirus in the northwestern Atlantic Ocean can provide new insights into the epidemiology and spatio-temporal spread of this pathogen. To deal with uncertainties surrounding the ecology of this system (only stranded animals were observed), we develop a statistical framework that can extract key information about the underlying transmission process given only sparse data. Our self-exciting Poisson process model suggests that individuals are infectious for at most 24 days and can transfer infection up to two latitude degrees (220 km) within this time. In addition, the effective reproduction number is generally below one, but reaches 2.6 during a period of heightened stranding numbers near Virginia Beach, Virginia, in summer 2013. Network analysis suggests local movements dominate spatial spread, with seasonal migration facilitating wider dissemination along the coast. Finally, a low virus transmission rate or high levels of pre-existing immunity can explain the lack of viral spread into the Gulf of Mexico. More generally, our approach illustrates novel methodologies for analysing very indirectly observed epidemics.     

Neighborhood Cohesion as a Buffer Against Hostile Maternal Parenting.

This study explored the moderating effects of children's neighborhoods on the link between hostile parenting and externalizing behavior. Participants were 1st- or 2nd-grade children in an urban northeastern community. Children were administered the Parenting and Neighborhood scales of the Child Puppet Interview, and mothers completed questionnaires on neighborhood quality and parenting practices. Census tract measures of neighborhood quality and teachers' reports of children's externalizing behavior also were obtained. Results indicated that children's and mothers' perceptions of neighborhood involvement-cohesion buffered the link between hostile parenting and externalizing problems. Children's externalizing behavior was unrelated to census tract variables. Findings highlight the protective effect of neighborhood social cohesion and the utility of including young children's perspectives in research on neighborhoods and families. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive behavioral guided self-help for the treatment of recurrent binge eating.

Objective: Despite proven efficacy of cognitive behavioral therapy (CBT) for treating eating disorders with binge eating as the core symptom, few patients receive CBT in clinical practice. Our blended efficacy–effectiveness study sought to evaluate whether a manual-based guided self-help form of CBT (CBT-GSH), delivered in 8 sessions in a health maintenance organization setting over a 12-week period by master's-level interventionists, is more effective than treatment as usual (TAU). Method: In all, 123 individuals (mean age = 37.2; 91.9% female, 96.7% non-Hispanic White) were randomized, including 10.6% with bulimia nervosa (BN), 48% with binge eating disorder (BED), and 41.4% with recurrent binge eating in the absence of BN or BED. Baseline, posttreatment, and 6- and 12-month follow-up data were used in intent-to-treat analyses. Results: At 12-month follow-up, CBT-GSH resulted in greater abstinence from binge eating (64.2%) than TAU (44.6%; number needed to treat = 5), as measured by the Eating Disorder Examination (EDE). Secondary outcomes reflected greater improvements in the CBT-GSH group in dietary restraint (d = 0.30); eating, shape, and weight concern (ds = 0.54, 1.01, 0.49, respectively; measured by the EDE Questionnaire); depression (d = 0.56; Beck Depression Inventory); and social adjustment (d = 0.58; Work and Social Adjustment Scale), but not weight change. Conclusions: CBT-GSH is a viable first-line treatment option for the majority of patients with recurrent binge eating who do not meet diagnostic criteria for BN or anorexia nervosa. (PsycINFO Database Record (c) 2010 APA, all rights reserved)