Determination of cobalt by catalytic-adsorptive differential pulse voltammetry

A novel method is described for the determination of cobalt(II) by differential pulse voltammetry, based on accumulation of a cobalt complex, [CoSCNNO]⁺, on a hanging mercury drop electrode, followed by measurement of the catalytic current of the adsorbed complex. The effects of various experimental parameters on the catalytic current were investigated. The current was found to be linear for 0.3 nM to 100 nM Co, with a detection limit of 70 pM (4.1 ng l⁻¹) and a relative standard deviation of 1.6% for 50 nM Co (n = 25). The developed method showed considerable selectivity against nickel and zinc. A possible mechanism of the reduction process is proposed.     

Isolation and identification of surface-bound acetone enolate on Ni(111)

A surface-bound acetone enolate species has been synthesized on Ni(111) between 260 and 340 K by two different routes catalyzed by surface Ni and O atoms: deprotonation of acetone and deacetylation of acetylacetone. The reaction pathways and surface species have been identified using reflection absorption infrared spectroscopy (RAIRS) in combination with isotopic substitution and density functional theory (DFT) calculations. Acetone enolate exhibits characteristic vibrational absorption bands at 1260, 1353, and 1545 cm-1 arising from mixed modes that involve CC stretching, CH3 bending, and CO stretching. This work conclusively proves the existence of stable acetone enolate species on a metal single-crystal surface and provides its first detailed characterization.     

Characterization of Capsicum annuum Recombinant α- and β-Tubulin

There are several conditions which might modulate polymerization to produce polymers having normal lattice structure. In the absence of 1 mM MgCl₂ the assembly was reduced by 36% in Capsicum annuum tubulin (CAnm tubulin). There was no significant difference in the final assembly formation in the presence of 5% to 10% glycerol. However, nucleation rate was slow and apparent study state was achieved lately in the presence of 10% glycerol. Taxol at 100 μM concentration increased 23% tubulin assembly. One millimolar CaCl₂, ≥1% dimethyl sulfoxide (DMSO) and physiologically low temperature reduced CAnm tubulin assembly. A value of 0.089 mg/ml was obtained as critical concentration for polymerization. Benomyl significantly reduced the number of cysteine residues accessible to 5,5’-dithiobis-(2-nitrobenzoic acid); there were 4.77?±?0.21 and 3.49?±?0.35 residues accessible per tubulin dimer in the presence of 50 and 100 μM benomyl respectively.     

Three-component carboformylation: α-quaternary aldehyde synthesis via Co(iii)-catalysed sequential C–H bond addition to dienes and acetic formic anhydride

All carbon α-quaternary aldehydes are prepared via Co(iii)-catalysed sequential C–H bond addition to dienes and acetic formic anhydride, representing a rare example of intermolecular carboformylation. A wide range of internally substituted dienes containing diverse functionality can be employed in this reaction, affording complex α-quaternary aldehydes that would not be accessible via hydroformylation approaches. Mechanistic investigations, including control reactions and deuterium labeling studies, establish a catalytic cycle that accounts for formyl group introduction with an uncommon 1,3-addition selectivity to the conjugated diene. Investigations into the role of the uniquely effective additive Proton Sponge® were also conducted, leading to the observation of a putative, intermediate Co(i) tetramethylfulvene complex at low temperatures via NMR spectroscopy. The synthetic utility of the aldehyde products is demonstrated by various transformations, including proline-catalysed asymmetric aldol addition, reductive amination, and the asymmetric synthesis of amines using tert-butanesulfinamide technology.

Co(iii)-catalysed sequential C–H bond addition to dienes and acetic formic anhydride results in a rare example of intermolecular carboformylation, generating versatile α-quaternary aldehyde products that are inaccessible via hydroformylation methods.     

Numerical characterization of ultraviolet ink fluid agglomeration and the surfactant effect in nanoinkjet printing

Ultraviolet (UV) ink is a major ink type used in additive manufacturing via 3D inkjet printing. A major challenge in nanoinkjet printing is ink agglomeration. Among the UV ink components, oligomers have the highest tendency to agglomerate which can agitate the stability and quality of the printing fluid and possibly lead to nanoscale nozzle clogging. In this work, the first numerical study on the UV ink fluid, UV ink is modeled by using dissipative particle dynamics to study mesoscale agglomeration. The constituents of the ink model are composed of polystyrene and polyethylene glycol as photopolymers, BZP as a photoinitiator, and SDS as a surfactant. Styrene is a prevalent and established commercial photopolymer in present 3D inkjet applications, while ethylene glycol is a photopolymer known to improve ink viscosity. The morphological characteristics of the UV ink are studied here, where the results for different models from four cases considered here show how the kind of photopolymers and their constituent ratios affect the agglomeration morphology of the fluidic system. The existence of both oligomers and monomers results in mutual morphological benefits against agglomeration, while the photoinitiator occurs between photopolymers. In addition, we find that the surfactant can reduce the average size of agglomeration and improve the dispersion uniformity by increasing the number of agglomerates. These results highlight the important role additives can play to prevent, reduce, and control various forms of agglomeration to achieve enhanced nanoinkjet printing quality. Copyright © 2017 John Wiley & Sons, Ltd.     

Experimental Characterization of On-Chip Single and Double-Coupling Spiral Inductors

Experimental investigations on on-chip single and double-coupling square spiral inductors on silicon substrate are performed. For each pair of double-coupling inductors, they have the same edge distance, but with different turn numbers. Based on the measured S-parameters using de-embedding procedure, the inductance and Q-factor of the single square inductor are examined at first, and good agreement is obtained in the extracted inductance, compared to the predicted values using a closed-form series inductance equation. While for double-coupling spiral inductors, the smaller the product of two turn numbers, the weaker coupling will be, and in particular at low frequencies.     

Proteomic Evaluation of Biomarkers to Determine the Postmortem Interval

Proteomics separates and analyzes proteins for investigation at the cellular level in regard to disease processing by analyzing the proteins’ expression, function, structure, post-translational modification, and protein–protein interaction. In general forensic investigations, the postmortem interval was evaluated by measuring changes in body temperature after death, along with forensic entomological knowledge. These investigations may be restrictive and subjective because of external factors. The objectives of this study are to sort biomarker candidates and develop a direct postmortem-interval characterization method using proteomics through analyzing and tracking down proteins in the deceased that change in accordance with the postmortem interval. The liver and heart tissues of rats were collected for protein extraction in the 24-h interval following death, and two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis was conducted based on the isoelectric point and the molecular weight for separation. To validate protein spot changes on the gel, the stained electrophoresis gels were scanned and converted to digital images. Through image analysis, 14 liver proteins and 12 heart proteins were sorted and classified into four groups based on pattern changes. These proteins containing spots were extracted from the gel and analyzed by high-performance liquid chromatography with tandem mass spectrometry. Finally, 26 protein postmortem-interval relevant biomarker candidates were identified using software. Some of the proteins were muscle proteins while others were oxidation-related proteins. This study presents a new approach to the postmortem-interval research using proteomics and could be substituted for postmortem-interval evaluation.     

Silver sulfide/poly(3-hydroxybutyrate) nanocomposites: Thermal stability and kinetic analysis of thermal degradation

The non-isothermal degradation of poly(3-hydroxybutyrate) (PHB) and silver sulfide/poly(3-hydroxybutyrate) (Ag₂S/PHB) nanocomposites was investigated using thermogravimetric (TG) analysis. In the composite materials, Ag₂S caused the degradation of PHB at a lower temperature as opposed to that of neat PHB. Moreover, an increase Ag₂S loading in the PHB decreased the onset temperature (T_onset) of thermal degradation, whereas it was raised upon augmenting the heating rate. From Kissinger plots, the observed trend of the degradation activation energy, E_d, was attributed to polymer-particle surface interactions and the agglomeration of Ag₂S. The thermal degradation rate constant, k, was linearly related to the Ag₂S loading in PHB. Thus, the Ag₂S nanoparticles effectively catalyzed the thermal degradation of PHB in the Ag₂S/PHB nanocomposites. Differential scanning calorimetry (DSC) data also supported the catalytic property of Ag₂S.     

The absolute instability of boundary-layer flow over viscoelastic walls

The linear stability of boundary-layer flow over a viscoelastic-layer wall is considered. A companion matrix technique is used to formulate the stability problem as a linear matrix eigenvalue problem for complex frequency and all the eigenvalues may be determined without any initial guess values. The eigenvalues are compared with those obtained with an accurate shooting method. The instability character of the boundary-layer flow is further investigated with the purpose of finding the conditions under which the instability of the flow could become absolute. The mapping technique of Kupferet al. (1987) is used to identify the occurrence of absolute instability eigenvalues. Absolute instabilities are discovered for cases of soft damped wall over certain ranges of Reynolds number. The effects of wall material stiffness, damping coefficient, thickness of layer, and Reynolds number on the occurrence of absolute instability are examined and presented.     

Nondestructive evaluation of nanoscale structures: inverse scattering approach

In this paper, we demonstrate how subwavelength images of nanoscale structures can be obtained from the measurements of electromagnetic fields scattered by the objects, via an enhanced inverse scattering approach, which takes into account the multiple-scattering effect and allows the detectors to be placed in the far field. Specifically, the method is a combination of the transverse electric (TE) incidence and the subspace-based optimization method (SOM). It is observed that a wide continuous range of integer values of leading singular values can yield satisfactory reconstruction results, and even if the antennas for radiating and receiving the electromagnetic wave can only be arranged on one side of the scatterers, due to the limitation in the real world, the proposed method is still capable of achieving high resolution for the reconstructed patterns with rapid convergence rates and robust immunity to high noise corruption (33%).