Toward a comprehensive mechanism for methanol pyrolysis

A single kinetic mechanism for methanol pyrolysis is tested against multiple sets of experimental data for the first time. Data are considered from static, flow, and shock tube reactors, covering temperatures of 973 to 2000 K and pressures of 0.3 to 1 atmosphere. The model results are highly sensitive to the rates of unimolecular fuel decomposition and of various chain termination reactions that remove CH₂OH and H radicals, as well as to experimental temperature uncertainties. The secondary fuel decomposition reaction CH₃OH = CH₂OH + H, which has previously been included only in mechanisms for high temperature conditions, is found to have a significant effect at low temperatures as well, through radical recombination. The reaction CH₃O + C = CH₃ + CO₂, rather than CH₃OH + H = CH₃ + H₂O, is found to be the dominant source of CH₃ at low temperatures. The reverse of CH₃ + OH = CH₂OH + H is important to CH₃ production at high temperatures.     

Ultrasonic heating of the skull

Comparatively simple analysis shows that diagnostic ultrasound devices, in some cases, may approach output levels that can produce significant heating of tissues, particularly if the propagation path includes bone. Experimental tests of these predictions using rodents show that temperature increments of the order of 3 degrees C/W/cm2 are produced in skull bone with sharply focused fields at medically relevant frequencies.     

Interactions of DNA with graphene and sensing applications of graphene field-effect transistor devices: A review

Graphene field-effect transistors (GFET) have emerged as powerful detection platforms enabled by the advent of chemical vapor deposition (CVD) production of the unique atomically thin 2D material on a large scale. DNA aptamers, short target-specific oligonucleotides, are excellent sensor moieties for GFETs due to their strong affinity to graphene, relatively short chain-length, selectivity, and a high degree of analyte variability. However, the interaction between DNA and graphene is not fully understood, leading to questions about the structure of surface-bound DNA, including the morphology of DNA nanostructures and the nature of the electronic response seen from analyte binding. This review critically evaluates recent insights into the nature of the DNA graphene interaction and its affect on sensor viability for DNA, small molecules, and proteins with respect to previously established sensing methods. We first discuss the sorption of DNA to graphene to introduce the interactions and forces acting in DNA based GFET devices and how these forces can potentially affect the performance of increasingly popular DNA aptamers and even future DNA nanostructures as sensor substrates. Next, we discuss the novel use of GFETs to detect DNA and the underlying electronic phenomena that are typically used as benchmarks for characterizing the analyte response of these devices. Finally, we address the use of DNA aptamers to increase the selectivity of GFET sensors for small molecules and proteins and compare them with other, state of the art, detection methods.     

Fat crystallisation at oil–water interfaces

This review focuses on recent advances in the understanding of lipid crystallisation at or in the vicinity of an interface in emulsified systems and the consequences regarding stability, structure and thermal behaviour. Amphiphilic molecules such as emulsifiers are preferably adsorbed at the interface. Such molecules are known for their ability to interact with triglycerides under certain conditions. In the same manner that inorganic crystals grown on an organic matrix see their nucleation, morphology and structure controlled by the underlying matrix, recent studies report a templating effect linked to the presence of emulsifiers at the oil/water interface. Emulsifiers affect fat crystallisation and fat crystal behaviour in numerous ways, acting as impurities seeding nucleation and, in some cases, retarding or enhancing polymorphic transitions towards more stable forms. This understanding is of crucial importance for the design of stable structures within emulsions, regardless of whether the system is oil or water continuous. In this paper, crystallisation mechanisms are briefly described, as well as recent technical advances that allow the study of crystallisation and crystal forms. Indeed, the study of the interface and of its effect on lipid crystallisation in emulsions has been limited for a long time by the lack of in-situ investigative techniques. This review also highlights reported interfacial effects in food and pharmaceutical emulsion systems. These effects are strongly linked to the presence of emulsifiers at the interface and their effects on crystallisation kinetics, and crystal morphology and stability.     

SERS detection of streptavidin/biotin monolayer assemblies

A two-dimensional array of gold nanotriangles inscribed onto glass coverslips were optimized for the surface-enhanced Raman detection of streptavidin/biotin monolayer assemblies. The nanostructures were fabricated by electron beam lithography, and its optical parameters were optimized to be probed under a Raman microscope with a linearly polarized He-Ne laser with an excitation wavelength of λ = 632.8 nm. The platforms were first tested against a monolayer of biotinylated alkanethiols (BAT) functionalized over the gold nanostructure, showing that good-quality spectra could be acquired with a short acquisition time. The supramolecular interaction of streptavidin (strep) with BAT showed subsequent modification of the Raman spectrum that implies a change in the secondary structure of the host biomolecule (streptavidin). Compared to gold surfaces without nanoscale structures, the local enhancement that results from our nanostructured surfaces allows one to detect the vibrational signal of monolayers within a time on the order of seconds and under modest laser intensity, further demonstrating the utility of using plasmonic metallic nanostructures for molecular recognition.     

Aryl-aryl bond formation by the fluoride-free cross-coupling of aryldisiloxanes with aryl bromides

The prevalence of the biaryl structural motif in biologically interesting and synthetically important molecules has inspired considerable interest in the development of methods for aryl-aryl bond formation. Herein we describe a novel strategy for this process involving the fluoride-free, palladium-catalysed cross-coupling of readily accessible aryldisiloxanes and aryl bromides. Using a statistical-based optimisation process, preparatively useful reaction conditions were formulated to allow the cross-coupling of a wide range of different substrates. This methodology represents an attractive, cost-efficient, flexible and robust alternative to the traditional transition-metal-catalysed routes typically used to generate molecules containing the privileged biaryl scaffold.     

A measurement of the azimuthal angle dependence of the process ep → enπ+ near threshold

The azimuthal angle dependence of the process ep → enπ⁺ has been measured by detecting the electron and neutron in coincidence. Data are presented for momentum transfers (?k²) between 0.08 and 0.32 $\text{(}\text{GeV}\text{c}\text{)}{}^2$ and at energies close to threshold. Fixed-t dispersion relation models give predictionsin good qualitative agreement with the data.     

Nitro group participation in the formation of heterocycles

Benzoyl bromide (2-nitrophenyl) hydrazone (2) was treated with sodium ethoxide and ethyl cyanoacetate and two unexpected products were obtained. These products were ultimately shown to be 6-bromo-3-phenyl-1,2,4-benzotriazine (32) and 5-bromo-2-phenylbenzoxazole (38), by comparison with authentic samples which were synthesized. A mechanism is presented for the formation of these two heterocyclic systems (32 and 38) from 2.     

Interaction of O2 with Pt(100): I. Equilibrium measurements

Two newly discovered phases on the Pt(100) surface produced by the adsorption of oxygen have been investigated using Rutherford baekscattering (RBS), nuclear microanalysis (NMA), work function changes (Δφ) and LEED. One phase is associated with the oxygensaturated surface (0.63 ± 0.03 monolayers0.81 × 10¹⁵ O atoms cm^?2), where a very complex LEED pattern is observed; the other is observed at an average coverage of 0.44 ± 0.05 monolayers and gives rise to a (3 × 1) LEED pattern (when observed at room temperature). For both surfaces, RBS measurements indicate large (? 0.025 nm) Pt atom displacements. Also discussed is a new method for preparing the “clean” (1 × 1)-Pt(100) surface without the need for NO adsorption/decomposition.