Carbon nanotube fiber microelectrodes: design, characterization, and optimization

We report on the preparation and interesting electrochemical behavior of carbon nanotube fiber microelectrodes (CNTFM). By combining the advantages of carbon nanotubes (CNT) with those of fiber electrodes, this type of microelectrode differs from CNT modified or CNT containing composite electrodes, because it's made of only CNT without any other components like additives or binders. The active CNT surface is easily regenerated. The performance of CNTFMs has been characterized, among others, by surface modification with phosphomolybdic acid. It is shown that adsorption behavior of these catalyst molecules is highly improved with a controlled orientation of CNT. A better CNT alignment inside the fiber can be achieved by a hot stretching procedure.     

Reaction of N-Acetylcysteine with Cu2+: Appearance of Intermediates with High Free Radical Scavenging Activity: Implications for Anti-/Pro-Oxidant Properties of Thiols

We studied the kinetics of the reaction of N-acetyl-l-cysteine (NAC or RSH) with cupric ions at an equimolar ratio of the reactants in aqueous acid solution (pH 1.4–2) using UV/Vis absorption and circular dichroism (CD) spectroscopies. Cu²⁺ showed a strong catalytic effect on the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) radical (ABTSr) consumption and autoxidation of NAC. Difference spectra revealed the formation of intermediates with absorption maxima at 233 and 302 nm (ε₃₀₂/Cu > 8 × 10³ M⁻¹ cm⁻¹) and two positive Cotton effects centered at 284 and 302 nm. These intermediates accumulate during the first, O₂-independent, phase of the NAC autoxidation. The autocatalytic production of another chiral intermediate, characterized by two positive Cotton effects at 280 and 333 nm and an intense negative one at 305 nm, was observed in the second reaction phase. The intermediates are rapidly oxidized by added ABTSr; otherwise, they are stable for hours in the reaction solution, undergoing a slow pH- and O₂-dependent photosensitive decay. The kinetic and spectral data are consistent with proposed structures of the intermediates as disulfide-bridged dicopper(I) complexes of types cis-/trans-Cu^I₂(RS)₂(RSSR) and Cu^I₂(RSSR)₂. The electronic transitions observed in the UV/Vis and CD spectra are tentatively attributed to Cu(I) → disulfide charge transfer with an interaction of the transition dipole moments (exciton coupling). The catalytic activity of the intermediates as potential O₂ activators via Cu(II) peroxo-complexes is discussed. A mechanism for autocatalytic oxidation of Cu(I)–thiolates promoted by a growing electronically coupled –[Cu^I₂(RSSR)]_n– polymer is suggested. The obtained results are in line with other reported observations regarding copper-catalyzed autoxidation of thiols and provide new insight into these complicated, not yet fully understood systems. The proposed hypotheses point to the importance of the Cu(I)–disulfide interaction, which may have a profound impact on biological systems.     

Ash decline assessment in emerald ash borer-infested regions: A test of tree-level, hyperspectral technologies

The emerald ash borer (EAB) is an exotic insect pest currently threatening ash species in the Great Lakes region. Because of the potential impact on forests in this area, multiple government agencies are currently focusing their efforts on developing new technologies to detect, monitor and control this insect pest. Previous work has shown that hyperspectral remote sensing technologies can produce detailed maps of forest health and species abundance on a landscape scale. This study examines the capability of a commercially available sensor (SpecTIR VNIR) to map ash decline due to exotic EAB infestations in Michigan and Ohio. A 6-term linear regression equation based on known stress- and chlorophyll-sensitive indices was able to predict decline on a continuous 0- to 10 scale with an r-squared of 0.71 and an average jackknifed residual of 0.61. Treated as an integer, decline was predicted to within one class with 97% accuracy. The ability of this instrument to assess decline below class 4 (when dieback and transparency reach levels first noticeable in the field) is based upon pre-visual reductions in chlorophyll content and function that are characteristic of early stress. The identification of early stress is critical in containing newly introduced exotics such as EAB. While this decline prediction technique is not stress- or species-specific, it will enable land managers to assess and monitor detailed forest health across the landscape.     

Differences in characteristics of pellets prepared by different pelletization methods

Pellets are currently a very popular dosage form for oral application. They can be prepared by several pelletization techniques. Extrusion/spheronization, commonly used in the pharmaceutical industry, and modern agglomeration in a rotoprocessor were the methods chosen for pellet preparation in our study. Theophylline (in 10% to 65% concentration) was the model drug, lactose monohydrate was used as filler, microcrystalline cellulose Avicel® PH 101 was thespheronization enhancer, and the wetting agent was purified water. Both techniques led to the formation of pellets of appropriate shape and mechanical properties. Pellets of a higher density, hardness, lower friability, and slightly slower dissolution profiles were obtained by extrusion/spheronization. This method of pelletization also led to production of particles with narrower size distribution and bigger yield of pellets with the requested size.     

Adhesion and growth of vascular smooth muscle cells in cultures on bioactive RGD peptide-carrying polylactides

The surface of poly(l-lactide) (PLLA) films deposited on glass coverslips was modified with poly(dl-lactide) (PDLLA), or 1:4 mixtures of PDLLA and PDLLA-b-PEO block copolymers, in which either none, 5% or 20% of the copolymer molecules carried a synthetic extracellular matrix-derived ligand for integrin adhesion receptors, the GRGDSG oligopeptide, attached to the end of the PEO chain. The materials, perspective for vascular tissue engineering, were seeded with rat aortic smooth muscle cells (11,000 cells/cm²) and the adhesion, spreading, DNA synthesis and proliferation of these cells was followed on inert and bioactive surfaces. In 24-h-old cultures in serum-supplemented media, the number of cells adhering to the PDLLA-b-PEO copolymer was almost eight times lower than that on the control PDLLA surface. On the surfaces containing 5% and 20% GRGDSG-PEO-b-PDLLA copolymer, the number of cells increased 6- and 3-fold respectively, compared to the PDLLA-b-PEO copolymer alone. On PDLLA-b-PEO copolymer alone, the cells were typically round and non-spread, whereas on GRGDSG-modified surfaces the cell spreading areas approached those found on PDLLA, reaching values of 991 μm² and 611 μm² for 5% and 20% GRGDSG respectively, compared to 958 μm² for PDLLA. The cells on GRGDSG-grafted copolymers were able to form vinculin-containing focal adhesion plaques, to synthesize DNA and even proliferate in a serum-free medium, which indicates specific binding to the GRGDSG sequences through their adhesion receptors.     

Unlicensed driving and other related health risk behaviors: A study of Montana high school students

Purpose

Health risk behaviors tend to cluster in young people, not least among young drivers. Less is known about the health risk profile of young unlicensed drivers. This study investigates health risk behaviors among young unlicensed drivers compared to both their licensed and driving peers, and their non-driving peers.

Methods

High school students participating in the Youth Risk Behavior Surveillance System in Montana (US) and age-eligible to have a driver's license were studied (n = 5985), categorized according to their self-reported car driving and license practice (licensed driving, unlicensed driving, and non-driving). Ten health risk behaviors, of which four were related to car riding/driving, were considered. Multinomial logistic regression was used to compile sex-specific odds ratios (with 95% confidence intervals) of adopting those behaviors using licensed drivers as a reference and adjusting for age and race/ethnicity.

Results

Health risk behaviors tended to be more common among unlicensed drivers than other groups, although some behaviors were prevalent in all groups (i.e., alcohol use and lack of seat belt use). As a consequence, for both male and female students, there was a significant association between unlicensed driving and most health risk behaviors, except for being involved in a physical fight and riding with a drinking driver among female students.

Conclusions

Young unlicensed drivers are more likely than licensed drivers to adopt several health risk behaviors both in car driving/riding or otherwise, in particular alcohol use and cigarette smoking. This challenges any simplistic approach as unlicensed driving in youth is not an isolated act suggesting public health and traffic safety initiatives.     

The Effect of Thermal Pre-Treatment on Structure, Composition, Basicity and Catalytic Activity of Mg/Al Mixed Oxides

The goal of this work is to study the effect of thermal pre-treatment of Mg/Al mixed oxides (450–1,050 °C) on their structure, basicity and catalytic activity in transesterification of rapeseed oil. The catalytic activity of Mg/Al catalysts was shown to depend not only on the amount of basic sites, but also on crystallite size of MgO, specific surface area and population of medium/strong basic sites. Moreover, high stability of Mg/Al-550 was established by re-using the catalyst four times. It was associated with negligible magnesium leaching from the solid catalyst to liquid phases.     

Robust imaging of hippocampal inner structure at 7T: in vivo acquisition protocol and methodological choices

Objective

Motion-robust multi-slab imaging of hippocampal inner structure in vivo at 7T.

Materials and methods

Motion is a crucial issue for ultra-high resolution imaging, such as can be achieved with 7T MRI. An acquisition protocol was designed for imaging hippocampal inner structure at 7T. It relies on a compromise between anatomical details visibility and robustness to motion. In order to reduce acquisition time and motion artifacts, the full slab covering the hippocampus was split into separate slabs with lower acquisition time. A robust registration approach was implemented to combine the acquired slabs within a final 3D-consistent high-resolution slab covering the whole hippocampus. Evaluation was performed on 50 subjects overall, made of three groups of subjects acquired using three acquisition settings; it focused on three issues: visibility of hippocampal inner structure, robustness to motion artifacts and registration procedure performance.

Results

Overall, T2-weighted acquisitions with interleaved slabs proved robust. Multi-slab registration yielded high quality datasets in 96 % of the subjects, thus compatible with further analyses of hippocampal inner structure.

Conclusion

Multi-slab acquisition and registration setting is efficient for reducing acquisition time and consequently motion artifacts for ultra-high resolution imaging of the inner structure of the hippocampus.

     

O6-Methylguanine-Methyltransferase (MGMT) Promoter Methylation Status in Glioma Stem-Like Cells is Correlated to Temozolomide Sensitivity Under Differentiation-Promoting Conditions

Glioblastoma (GBM) is the most malignant type of primary brain tumor with a very poor prognosis. The actual standard protocol of treatment for GBM patients consists of radiotherapy and concomitant temozolomide (TMZ). However, the therapeutic efficacy of this treatment is limited due to tumor recurrence and TMZ resistance. Recently isolated, glioma stem-like cells (GSCs) are thought to represent the population of tumorigenic cells responsible for GBM resistance and recurrence following surgery and chemotherapy. In addition, MGMT (O6-methylguanine-methyltransferase) methylation is considered as one of the principal mechanisms contributing to TMZ sensitivity of GBM. In this study we have isolated GSCs from 10 adult GBM patients and investigated the relationship between MGMT methylation status and Temozolomide (TMZ) sensitivity of these lines grown either in stem-like or differentiation promoting conditions. Sensitivity to TMZ was significantly associated with MGMT methylation status in cells committed to differentiation but not in stem-like cells. In addition, patients harboring highly methylated MGMT promoters had a longer overall survival. These results reveal the importance of the differentiation process when considering the predictive value of MGMT status in GSCs for clinical response to TMZ.