Hemocompatibility of diamondlike carbon–metal composite thin films

We have investigated the hemocompatibility of diamondlike carbon–silver composite and diamondlike carbon–titanium composite thin films prepared using a multicomponent target pulsed laser deposition process. These materials were examined using transmission electron microscopy, Raman spectroscopy, nanoindentation, electrochemical charge transfer testing, and platelet adhesion testing. Cross-sectional transmission electron microscopy revealed that silver self-assembles into nanoparticle arrays within the diamondlike carbon matrix in the diamondlike carbon–silver composite film. On the other hand, titanium self-assembles into alternating nanometer-thick titanium carbide layers within the diamondlike carbon matrix in the diamondlike carbon–titanium composite film. The hemocompatibility of these materials was examined using electrochemical charge transfer testing and platelet adhesion testing. A few small, widely scattered crystals were observed on the surface of the unalloyed diamondlike carbon film exposed to platelet rich plasma. On the other hand, dense fibrin networks with densely aggregated platelets were observed on the surfaces of diamondlike carbon–silver and diamondlike carbon–titanium composite thin films exposed to platelet rich plasma. Electrochemical testing revealed that the time constant for the diamondlike carbon thin film (λ = 1) was significantly higher than those for the diamondlike carbon–silver and diamondlike carbon–titanium composite thin films. These results suggest possible uses for diamondlike carbon thin films and diamondlike carbon–metal composite thin films as coatings in next generation cardiovascular implants.     

Toward faster inference of micron-scale axon diameters using Monte Carlo simulations

Object

Recent advances have allowed oscillating gradient (OG) diffusion MRI to infer the sizes of micron-scale axon diameters. Here the effects on the precision of the inferred diameters are studied when reducing the number of images collected to reduce imaging time for clinical feasibility.

Materials and methods

Monte Carlo simulations of cosine OG sequences (50–1000 Hz) using a two-compartment model on a parallel cylinder (diameters 1–5 μm) geometry were conducted. Temporal diffusion spectroscopy was used to infer axon diameters. Three different gradient sets were simulated with different combinations of gradient strengths.

Results

Five frequencies were adequate for d = 3–5 μm with single-sized cylinders and for effective mean axon diameters greater than 2 μm for cylinders with a distributions of diameters. There was some improvement in precision for d = 1–2 μm with 10 frequencies. It is better to repeat measurements at higher gradient strengths than to use a range of gradient strengths. The improvement tended to be greatest when using fewer frequencies and was especially noticeable at very high gradient strengths.

Conclusion

Images can be collected with fewer gradient strengths and frequencies without sacrificing the precision of the measurements. This could be useful in reducing imaging time so that OG techniques can be used in clinical settings.

     

Comparison of anaerobic dechlorinating enrichment cultures maintained on tetrachloroethene,trichloroethene, cis-dichloroethene and vinyl chloride

An anaerobic mixed microbial culture was enriched from soil and groundwater taken from a site contaminated with trichloroethene (TCE). This enrichment culture was divided into four subcultures amended separately with either perchloroethene (PCE), TCE, cis-dichloroethene (cDCE) or vinyl chloride (VC). In each of the four subcultures, the chlorinated ethenes were rapidly, consistently, and completely converted to ethene at rates of 30-50 micromol/l of culture per day, or an average 160 micro-electron equivalents/l of culture per day. These cultures were capable of sustained and rapid dechlorination of VC, and could not dechlorinate 1,2-dichloroethane, differentiating them from Dehalococcoides ethenogenes, the only known isolate capable of complete dechlorination of PCE to ethene. Chloroform (CF) and 1,1,1-trichloroethane, frequent groundwater co-contaminants with TCE and PCE, inhibited chlorinated ethene dechlorination. Most strongly inhibited was the final conversion of VC to ethene, with complete inhibition occurring at an aqueous CF concentration of 2.5 microM. Differences in rates and community composition developed between the different subcultures, including the loss of the VC enrichment culture's ability to dechlorinate PCE. Denaturing gradient gel electrophoresis of amplified bacterial 16S rRNA gene fragments identified three different DNA sequences in the enrichment cultures, all phylogenetically related to D. ethenogenes. Based on the PCR-DGGE results and substrate utilization patterns, it is apparent that significant mechanistic differences exist between each step of dechlorination from TCE to ethene, especially for the last important dechlorination step from VC to ethene.     

Three-dimensional nonwoven scaffolds from a novel biodegradable poly(ester amide) for tissue engineering applications

Biodegradable polyesters are established biomaterials in medicine due to their chemical characteristics and options for material processing. A main problem, however, is the release of acid degradation products during biodegradation with severe local pH-drops and inflammatory reactions. Polyesteramides, in contrast, show a less prominent pH-drop during degradation. In this study, we developed a simple, reproducible synthesis of the poly(ester amide) (PEA) type C starting from ε-caprolactame, 1,4-butanediol, and adipic acid in a one-batch two-step reaction and conducted the manufacturing of PEA-derived 3D textile scaffolds applicable for tissue engineering purposes. The thermal and mechanical properties of PEA-type C were analysed and the structural conformity of different batches was confirmed by NMR spectroscopy and size exclusion chromatography. The polymer was formed into nonwovens by textile manufacturing. Cytotoxicity tests and X-ray photoelectron spectroscopy (XPS) were used to analyze the effect of scaffold extraction before cell seeding. The manufactured carriers were seeded with human preadipocytes and examined for cellular proliferation and differentiation. The production of PEA type C successfully occurred via simultaneous ring-opening polymerization of ε-caprolactame and polycondensation with 1,4-butanediol and adipic acid at 250 °C under high-vacuum. Soxhlet extraction allowed optimal cleaning of nonwoven scaffolds. Extracted PEA-derived matrices were capable of allowing good adherence, proliferation, and differentiation of preadipocytes. These results are encouraging and guidance towards an optimally prepared nonwoven carrier applicable for clinical use. K. Hemmrich and J. Salber have contributed equally.     

Scaling theory for information networks

Networks distribute energy, materials and information to the components of a variety of natural and human-engineered systems, including organisms, brains, the Internet and microprocessors. Distribution networks enable the integrated and coordinated functioning of these systems, and they also constrain their design. The similar hierarchical branching networks observed in organisms and microprocessors are striking, given that the structure of organisms has evolved via natural selection, while microprocessors are designed by engineers. Metabolic scaling theory (MST) shows that the rate at which networks deliver energy to an organism is proportional to its mass raised to the 3/4 power. We show that computational systems are also characterized by nonlinear network scaling and use MST principles to characterize how information networks scale, focusing on how MST predicts properties of clock distribution networks in microprocessors. The MST equations are modified to account for variation in the size and density of transistors and terminal wires in microprocessors. Based on the scaling of the clock distribution network, we predict a set of trade-offs and performance properties that scale with chip size and the number of transistors. However, there are systematic deviations between power requirements on microprocessors and predictions derived directly from MST. These deviations are addressed by augmenting the model to account for decentralized flow in some microprocessor networks (e.g. in logic networks). More generally, we hypothesize a set of constraints between the size, power and performance of networked information systems including transistors on chips, hosts on the Internet and neurons in the brain.     

Are the memories of older adults positively biased?

There is disagreement in the literature about whether a "positivity effect" in memory performance exists in older adults. To assess the generalizability of the effect, the authors examined memory for autobiographical, picture, and word information in a group of younger (17-29 years old) and older (60-84 years old) adults. For the autobiographical memory task, the authors asked participants to produce 4 positive, 4 negative, and 4 neutral recent autobiographical memories and to recall these a week later. For the picture and word tasks, participants studied photos or words of different valences (positive, negative, neutral) and later remembered them on a free-recall test. The authors found significant correlations in memory performance, across task material, for recall of both positive and neutral valence autobiographical events, pictures, and words. When the authors examined accurate memories, they failed to find consistent evidence, across the different types of material, of a positivity effect in either age group. However, the false memory findings offer more consistent support for a positivity effect in older adults. During recall of all 3 types of material, older participants recalled more false positive than false negative memories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Does knowledge about attention-deficit/hyperactivity disorder impact teachers' reported behaviors and perceptions?

This study surveyed elementary school teachers in Melbourne, Australia to investigate their knowledge about attention-deficit/hyperactivity disorder (ADHD) and its impact on their reported behavior toward and perceptions of children with ADHD. Consistent with previous international findings, teachers demonstrated good overall knowledge about ADHD, with strengths in knowledge of symptoms/diagnosis and weaknesses in knowledge of causes and treatments. To investigate how knowledge impacted reported behaviors and perceptions, teachers also read vignettes of children with ADHD symptoms and rated their reactions to these children. In general, teachers with high, and to some extent average, knowledge about ADHD reported more helpful behaviors (e.g., help-seeking for their students) and perceptions (e.g., perceive the benefit of behavioral and educational treatments). However, teachers with high and average knowledge also predicted that these children would be more disruptive in the classroom, and reported having less confidence in their ability to manage these children. Implications and need for future research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fast comprehensive two-dimensional gas chromatography with cryogenic modulation

The fast separation of a mixture of 29 compounds by using comprehensive two-dimensional gas chromatography is reported. Capillary column sets with shorter lengths and smaller inner diameter in both the first and second dimensions have been tested, for both fast chiral and achiral separations. Fast chiral separations, which included enantiomer separations of limonene, linalool, citronellol, and alpha-isomethylionone, were achieved within 23 min, which corresponds to approximately 2-fold faster than analyses under conditions previously considered as normal. Fast achiral separations, which do not have the restriction of requiring a minimum quality of chiral resolution, were obtained within 5 min, which is markedly faster than separations on the normal column set under conditions more commonly employed. The achiral fast GC x GC method used a 5 m x 0.1 mm i.d. first dimension column, interfaced to a 0.3 m x 0.05 mm i.d. second column, with temperature program rate of 35 degrees C.min-1; a modulation period of 1 s was employed. Peak widths at baseline on the first column were a little over 1 s, while modulated peak widths at half-height recorded with a flame ionization detector operating at 200 Hz were approximately 30 ms. The benefits and limitations of GC x GC for fast chiral and achiral separations are reported and discussed.     

Improved scanning laser fundus imaging using polarimetry

We present a polarimetric technique to improve fundus images that notably simplifies and extends a previous procedure [Opt. Lett.27, 830 (2002)]. A generator of varying polarization states was incorporated into the illumination path of a confocal scanning laser ophthalmoscope. A series of four images, corresponding to independent incoming polarization states, were recorded. From these images, the spatially resolved elements of the top row of the Mueller matrix were computed. From these elements, images with the highest and lowest quality (according to different image quality metrics) were constructed, some of which provided improved visualization of fundus structures of clinical importance (vessels and optic nerve head). The metric values were better for these constructed images than for the initially recorded images and better than averaged images. Entropy is the metric that is most sensitive to differences in the image quality. Improved visualization of features could aid in the detection, localization, and tracking of ocular disease and may be applicable in other biomedical imaging.