Novel solid-phase extraction protocol for 11-nor-9-carboxy-delta9-tetrahydrocannabinol from urine samples employing a polymeric mixed-mode cation-exchange resin, Strata-X-C, suitable for gas chromatography-mass spectrometry or liquid chromatography-mass spectrometry analysis

A novel solid-phase extraction (SPE) method was developed for extraction and cleanup of 11-nor-9-carboxy-delta9-tetrahydrocannabinol (THC-COOH), the major metabolite of the active principle of marijuana, delta9-tetrahydrocannabinol, from urine samples. The protocol utilizes a polymeric mixed-mode cationic sorbent, Strata-X-C, which exhibits strong retention for the metabolite facilitating a more rigorous organic wash to eliminate matrix components/endogenous materials. Acetonitrile containing acetic acid was used as the elution solvent and is compatible with both LC-MS and GC-MS modes of analysis. The hydrophobic retention of Strata-X-C was demonstrated to be higher than a neutral polymeric sorbent, Strata-X, of the same backbone but devoid of the cation-exchange moiety (sulfonic acid), by LC studies employing homologous paraben probes. Simultaneously, the polar (non-ionic) interaction capability of Strata-X-C is also greater than that of Strata-X, as assessed through regioisomeric nitrophenol probes. These two features enable the metabolite to be retained strongly on Strata-X-C. Good linearity and precision was obtained for THC-COOH by GC-MS analysis of its trimethylsilyl derivative in the range 1-50 ng. A simplified room temperature instantaneous derivatization procedure was developed that is suitable for high-throughput screening of THC-COOH.     

Design and validation of a vacuum assisted anchorage for the uniaxial tensile testing of soft materials

Current commercial tensile testing systems use spring-loaded or other compression-based grips to clamp materials in place posing a problem for very soft or delicate materials that cannot withstand this mechanical clamping force. In order to perform uniaxial tensile tests on soft tissues or materials, we have created a novel vacuum-assisted anchor (VAA). Fibrin gels were subjected to uniaxial extension, and the testing data was used to determine material mechanical properties. Utilizing the VAA, we achieved successful tensile breaks of soft fibrin gels while finding statistically significant differences between the mechanical properties of gels fabricated at two different fibrinogen concentrations.     

PAMAM-containing semiconducting polymers: Effect of dendritic side chains on optoelectronic and solid-state properties

Dendronized polymers are a particularly interesting platform for the preparation of advanced semiconductors given their high degree of functionalization, monodispersity, and bulkiness. Despite advantageous features, the incorporation of dendritic moieties in semiconducting polymers is still relatively underexplored, and the impact on the optoelectronic, thermomechanical, and solid-state properties are difficult to predict. This work focuses on the incorporation of polyamidoamine (PAMAM) dendritic side chains to semicrystalline polymers based on diketopyrrolopyrrole. Using a versatile synthetic strategy based on the azide-alkyne Huisgen 1,3-dipolar cycloaddition, dendronized semiconducting polymers were prepared and the effect of the dendritic side chains on different properties were carefully characterized using different techniques. The dendritic side chains were found to reduce aggregation and crystallinity of the polymers in thin films. PAMAM-containing semiconducting polymers were also shown to have good charge transport properties in organic field-effect transistors, within the same order of magnitude to that of diketopyrrolopyrrole-based polymers bearing branched alkyl chains. This new design approach is particularly interesting to develop advanced semiconducting polymers given its synthetic versatility and the structural diversity of the dendronized moieties. Furthermore, the utilization of dendritic moieties in semiconducting polymers is a promising approach to fine-tune the thermomechanical properties toward semiconducting polymers for next-generation organic electronics.     

Fluorescence Detection of Single‐Nucleotide Polymorphisms with a Single,Self‐Complementary,Triple‐Stem DNA Probe

Singled out for its singularity : In a single‐step, single‐component, fluorescence‐based method for the detection of single‐nucleotide polymorphisms at room temperature, the sensor is comprised of a single, self‐complementary DNA strand that forms a triple‐stem structure. The large conformational change that occurs upon binding to perfectly matched (PM) targets results in a significant increase in fluorescence (see picture; F=fluorophore, Q=quencher).

     

Microbial adhesion to zirconium alloys

We present data and analyses concerning the adhesion of clinically relevant Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa (bacteria) and Candida albicans (yeast) to Zircaloy-2 (Zry-2) and Zircadyne-705 (Zr705) surfaces. These zirconium-based materials are similar to those now being used in total hip and knee replacements. Here we study clinical strains of microbes under shaken and stationary exposure conditions, and their ability to adhere to Zr surfaces having different oxide thicknesses. We use X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), viable counts, endotoxin assays, and statistical analysis methods, and demonstrate a predictive model for microbial adhesion based on XPS data.     

Facile Synthesis and Theoretical Conformation Analysis of a Triazine‐Based Double‐Decker Rotor Molecule with Three Anthracene Blades

The facile synthesis of a rotor‐shaped compound with two stacked triazine units, which are symmetrically connected by three anthracene blades through oxygen linkers, is presented. This new double‐decker, which is a potential monomer for two‐dimensional polymerization, was synthesized by using readily available, cheap building blocks, exploiting the known selectivity difference for the nucleophilic substitution of cyanuric chloride. The crystal structure of a C_3h symmetric rotor‐shaped compound with 9,10‐dihydroanthracene blades, which is a direct precursor to the targeted monomer, and the crystal structure of the new double‐decker with the desired C_3h symmetry, are also reported. The synthetic efforts were preceded by a computational analysis, which was triggered by the question of conformational stability of the potential monomer. Two stable conformers could be found, and the barrier for the transition path in the gas phase between these conformers was determined by quantum chemical calculations. Exploratory Born–Oppenheimer molecular‐dynamics simulations revealed a strong influence of solvent–solute interactions on the stability of the conformers, which resulted in an energetic preference of the C_3h symmetric conformation of the double‐decker.     

A new method for the covalent attachment of DNA to a surface for single-molecule studies

Attachments between DNA and a surface or bead are often necessary for single-molecule studies of DNA and DNA-protein interactions. In single-molecule mechanical studies using optical or magnetic tweezers, such attachments must be able to withstand the applied forces. Here we present a new method for covalently attaching DNA to a glass surface, which uses N-hydroxysuccinimide (NHS) modified PEG that is suitable for high-force single-molecule mechanical studies. A glass surface is coated with silane-PEG-NHS and DNA is covalently linked through a reaction between the NHS group and an amine modified nucleotide that has been incorporated into the DNA. After DNA attachment, non-reacted NHS groups are hydrolyzed leaving a PEG-covered surface which has the added benefit of reducing non-specific surface interactions. This method permits specific binding of the DNA to the surface through a covalent bond. At the DNA end not attached to the surface, we attach a streptavidin-coated polystyrene bead and measure force-versus-extension using an optical trap. We show that our method allows a tethered DNA molecule to be pulled through its overstretching transition (> 60pN) multiple times. We anticipate this simple yet powerful method will be useful for many researchers.     

A model and approach to the challenge posed by optimal power systems planning

Currently, there is a need to plan and analyze the electric power transmission system in greater detail and over larger geographic areas. Existing models approach the problem from different perspectives. Each model addresses different aspects of and has different approximations to the optimal planning process. In order to scope out the huge challenge of optimal transmission planning, this paper presents a new modeling approach for inter-regional planning and investment in a competitive environment. This modeling approach incorporates the detailed generator, topology and operational aspects found in production cost planning models into a larger framework that can find optimal sets of transmission expansion projects. The framework proposed here can be used in an auction to award investment contracts or as a part of a more general policy analysis. The solution yields the set of transmission projects that have the highest expected benefits, while also representing generic generation expansions under the same objective. The model is a two-stage, mixed-integer, multi-period, N-1-reliable model with investment, unit commitment, and transmission switching. The combination of combinatorial, stochastic and operational elements means this model may be computationally intractable without judicious modelling aggregations or approximations to reduce its size and complexity. Nevertheless we show via a dual problem that analysing the economics and sensitivity of the solution is computationally more straightforward.