Rapid crack growth in a thermoelastic solid under mixed-mode thermomechanical loading

A two-dimensional steady-sate analysis of semi-infinite brittlecrack growth at a constant subcritical rate in an unboundedfully-coupled thermoelastic solid under mixed-mode thermomechanicalloading is made. The loading consists of normal and shear tractionsand heat fluxes applied as point sources (line loads in theout-of-plane direction). A related problem is solved exactly in an integral transformspace, and robust asymptotic forms used to reduce the originalproblem to a set of integral equations. The equations are partiallycoupled and exhibit operators of both Cauchy and Abel types,yet can be solved analytically. The temperature change field at a distance from the moving crackedge is then constructed, and its dominant term is found tobe controlled by the imposed heat fluxes. The role of this termis, indeed, enhanced if the heat fluxes serve to render thecrack as a net heat source/sink for the solid, as opposed tobeing a transmitter of heat across its plane. More generally,the influence of the thermoelastic coupling on this field, aswell as other functions, is found to increase with crack speed.     

Boryl (Hetero)aryne Precursors as Versatile Arylation Reagents: Synthesis through CH Activation and Orthogonal Reactivity

(Pinacolato)boryl ortho‐silyl(hetero)aryl triflates are presented as a new class of building blocks for arylation. They demonstrate unique versatility by delivering boronate or (hetero)aryne reactivity chemoselectively in a broad range of transformations. This approach enables the unprecedented postfunctionalization of fluoride‐activated (hetero)aryne precursors, for example, as substrates in transition‐metal catalysis, and offers valuable new possibilities for aryl boronate postfunctionalization without the use of specialized protecting groups.     

Palladium-catalyzed selective acyloxylation using sodium perborate as oxidant

Sodium perborate (SPB), a principal component of washing powders, was employed as an inexpensive and eco-friendly oxidant in the palladium-catalyzed C-H acyloxylation of alkenes in excellent regio- and stereochemistry. The reactions used anhydrides as acyloxy sources. The method applies to both terminal and internal alkenes, and even benzylic C-H oxidation.     

Synthesis of new microsensor coatings and their response to vapors-III Arylphosphonic acids, salts and esters

Phosphonic acids, phosphonate esters and cyclohexylammonium phosphonates, spray-coated onto surface acoustic wave (SAW) devices, were exposed to vapors of chloroethyl ethyl sulfide (CEES), dimethyl methylphosphonate (DMMP), and water. Changes in the resonance frequency of the device or the resistance of the coating were collected by computer-controlled data acquisition. Two of the esters showed major reversible and selective response to CEES, and one of the acids showed similar behavior with DMMP.     

A miniaturized and integrated gel post platform for multiparameter PCR detection of herpes simplex viruses from raw genital swabs

Herpes simplex virus (HSV) is one of the most prevalent viruses, with acute and recurrent infections in humans. The current gold standard for the diagnosis of HSV is viral culture which takes 2-14 days and has low sensitivity. In contrast, DNA amplification by polymerase chain reaction (PCR) can be performed within 1-2 h. We here describe a multiparameter PCR assay to simultaneously detect HSV-1 and HSV-2 DNA templates, together with integrated positive and negative controls, with product detection by melting curve analysis (MCA), in an array of semi-solid polyacrylamide gel posts. Each gel post is 0.67 μL in volume, and polymerized with all the components required for PCR. Both PCR and MCA can currently be performed in one hour and 20 min. Unprocessed genital swabs collected in universal transport medium were directly added to the reagents before or after polymerization, diffusing from atop the gel posts. The gel post platform detects HSV templates in as little as 2.5 nL of raw sample. In this study, 45 genital swab specimens were tested blindly as a preliminary validation of this platform. The concordance of PCR on gel posts with conventional PCR was 91%. The primer sequestration method introduced here (wherein different primers are placed in different sets of posts) enables the simultaneous detection of multiple pathogens for the same sample, together with positive and negative controls, on a single chip. This platform accepts unprocessed samples and is readily adaptable to detection of multiple different pathogens or biomarkers for point-of-care diagnostics.     

Stereoselective intermolecular allylic C-H trifluoroacetoxylation of functionalized alkenes

Pd-catalyzed allylic C-H trifluoroacetoxylation of substituted alkenes was performed using PhI(OCOCF(3))(2) as the oxidant and acyloxy source. Trifluoroacetoxylation of monosubstituted cyclopentenes and cyclohexenes proceeds with excellent regio- and diastereoselectivity. Studies with one of the possible (η(3)-allyl)Pd(II) intermediates suggest that the reaction proceeds via stereoselective formation of Pd(IV) intermediates and subsequent stereo- and regioselective reductive elimination of the product.     

Synthetic magnetic opals

We present studies of novel nanocomposites of BiNi impregnated into the structure of opals as well as inverse opals. Atomic force microscopy and high resolution elemental analyses show a highly ordered structure and uniform distribution of the BiNi filler in the matrix. These BiNi-based nanocomposites are found to exhibit distinct ferromagnetic-like ordering with transition temperature of about 675 K. As far as we know there exists no report in literature on any BiNi compound which is magnetic.     

Investigation of metal–buffer interactions using isothermal titration calorimetry

Isothermal titration calorimetry (ITC) and potentiometric titration (PT) methods were used to study the interactions of cobalt(II) and nickel(II) ions with buffer substances 2-(N-morpholino)ethanesulfonic acid (Mes), dimethylarsenic acid (Caco), and piperazine-N,N′-bis(2-ethanesulfonic acid) (Pipes). Based on the results of PT data, the stability constants were calculated for the metal–buffer complexes (T = 298.15 K, ionic strength I = 100 mM NaClO₄). Furthermore, calorimetric measurements (ITC) were run in 100 mM Mes, Caco, and Pipes solutions with pH 6, at 298.15 K. The enthalpies (ΔH) of the metal–buffer complexation reactions were calculated indirectly by displacement titration using nitrilotriacetic acid (H₃NTA) as a strong-binding, competitive ligand. Finally, to verify obtained results, the number of protons released by H₃NTA due to complexation of the cobalt(II) and nickel(II) ions was determined from calorimetric data and compared with results of calculations.     

Boryl (Hetero)aryne Precursors as Versatile Arylation Reagents: Synthesis through C?H Activation and Orthogonal Reactivity

(Pinacolato)boryl ortho‐silyl(hetero)aryl triflates are presented as a new class of building blocks for arylation. They demonstrate unique versatility by delivering boronate or (hetero)aryne reactivity chemoselectively in a broad range of transformations. This approach enables the unprecedented postfunctionalization of fluoride‐activated (hetero)aryne precursors, for example, as substrates in transition‐metal catalysis, and offers valuable new possibilities for aryl boronate postfunctionalization without the use of specialized protecting groups.