Formation of Aromatic and Other Unsaturated End Groups in Carboxymethyl Cellulose During Hot Alkaline Treatment

Carboxymethyl cellulose (CMC, DS 0.58) was treated in solutions of sodium hydroxide (0.001–1 M) at 95 °C. The treated (1–12 h) CMC samples were purified by dialysis and analyzed by UV spectroscopy and by UV resonance Raman spectroscopy (UVRRS) with excitation at 244 nm. A UV absorption maximum at 265 nm and a UVRR signal at 1650 cm⁻¹ were indicative of formation of -conjugated aldehyde end groups in CMC through -elimination. Another strong UVRR band at 1610 cm⁻¹ gave evidence on conversion of some of the -conjugated aldehyde end groups to alkali stable aromatic structures.     

Twice-punctured hyperbolic sphere with a conical singularity and generalized elliptic integral

We describe, in terms of generalized elliptic integrals, the hyperbolic metric of the twice-punctured sphere with one conical singularity of prescribed order. We also give several monotonicity properties of the metric and a couple of applications.     

Thermal Degradation of Cellulose Nanocrystals Deposited on Different Surfaces

Thermal degradation of cellulose nanocrystals deposited on flat solid surfaces was monitored by AFM coupled with analysis of obtained images using image processor. The nanocrystals deposited on TiO₂ substrate showed different degradation patterns compared to those deposited on the nanosized layer of amorphous cellulose. The degradation was complete within 20 minutes at 300 °C. The nanocrystal deposited on amorphous cellulose resisted the heat treatment up to 120 minutes. Visual comparison and analysis of the AFM images clearly demonstrated the impact of temperature on the degradation rate of the nanocrystals deposited on TiO₂ substrate.     

Evolution of microstructure and failure mechanism of lead-free solder interconnections in power cycling and thermal shock tests

Failure mechanisms of lead-free solder interconnections in power cycling and thermal shock tests have been investigated in this work. Even though there are some characteristic differences between the two tests, the failures in both cases were induced by recrystallization-assisted crack nucleation and propagation. The three major differences between the tests were: (i) minimum temperature during power cycling was considerably higher in comparison to thermal shock, (ii) the current flow in the power cycling test resulted in electromigration, and (iii) in the power cycling test heat originates locally from components themselves. These differences were also reflected in the test results in the following way: firstly, in the power cycling test the recrystallization occurred earlier than in the thermal shock test, mainly owing to the higher average temperature and secondly, the enhanced growth of intermetallic compound layer at the anode side due to the electromigration was observed during power cycling.     

Effect of Ni on the Formation of ${hbox {Cu}}_{6}{hbox {Sn}}_{5}$ and ${hbox {Cu}}_{3}{hbox {Sn}}$ Intermetallics

In this paper, the effect of Ni on the formation of Cu₆Sn₅ and Cu₃Sn intermetallics between tin and (Cu,Ni) substrates has been studied by making use of the thermodynamic assessment of the Sn-Cu-Ni system. The driving forces for the diffusion of the elements in the intermetallic layers were calculated as a function of Ni content. Assuming constant mobilities of component atoms, the results suggest that the diffusion fluxes of all the components in the (Cu, Ni)₆Sn₅ layer increase with increasing content of dissolved Ni, while the Cu and Sn fluxes in the (Cu, Ni)₃Sn layer decrease. Therefore, the dissolution of Ni retards the growth of (Cu, Ni)₃Sn. When the Ni content of the (Cu,Ni) substrate is high enough, the intermetallic compound growth in the reaction zones is dominated by (Cu, Ni)₆Sn₅, and the (Cu, Ni)₃Sn layer disappears gradually. The small thickness of (Cu, Ni)₃Sn is associated with large difference between Sn and Cu fluxes in (Cu, Ni)₃Sn that encourages also the "Kirk-endall void" formation. In addition, the calculated driving forces suggest that the growth rate of (Cu, Ni)₆Sn₅ should further increase if (Cu, Ni)₃Sn disappears, resulting in an unusually thick (Cu, Ni)₆Sn₅ layer. The results of thermodynamic calculations supplemented with diffusion kinetic considerations are in good agreements with recent experimental observations.     

Electrochemical oxidation of p-nitrophenol using graphene-modified electrodes, and a comparison to the performance of MWNT-based electrodes

The electrochemical oxidation of p-nitrophenol (p-NP) has been studied comparatively on a graphene modified electrode and a multiwall carbon nanotube (MWNT) electrode by using cyclic and differential pulse voltammetry. The sensors were fabricated by modifying screen-printed electrodes with graphene and MWNT nanomaterials, respectively, both dispersed in Nafion polymer. p-NP is irreversibly oxidized at +0.9?V (vs. the Ag/AgCl) in solutions of pH 7. The height and potential of the peaks depend on pH in the range from 5 to 11. In acidic media, p-NP yields a well-defined oxidation peak at +0.96?V which gradually increases in height with the concentration of the analyte. In case of differential pulse voltammetry in sulfuric acid solution, the sensitivity is practically the same for both electrodes. The modified electrodes display an unusually wide linear response (from 10???M to 0.62?mM of p-NP), with a detection limit of 0.6???M in case of the graphene electrode, and of 1.3???M in case of the MWNT electrode.

Influence of mesh deformation on the quality of large eddy simulations

The influence of mesh motion on the quality of large eddy simulation (LES) was studied in the present article. A three‐dimensional, turbulent pipe flow (Re_τ=360) was considered as a test case. Simulations with both stretching and static meshes were carried out in order to understand how mesh motion affects the turbulence statistics. The spatial filtering of static and moving mesh direct numerical simulation (DNS) data showed how an ideal LES would perform, while the comparison of DNS cases with static and moving meshes revealed that no significant numerical errors arise from the mesh motion when the simulation is fully resolved. The comparison of the filtered fields of the DNS with a moving mesh with the corresponding LES fields revealed different responses to mesh motion from different numerical approaches. A straightforward test was applied in order to verify that the moving mesh works consistently in LES: when the mesh is stretched in the streamwise direction, the moving mesh results should be in between the two extremal resolutions between which the mesh is stretched. Numerical investigations using four different LES approaches were carried out. In addition to the Smagorinsky model, three implicit LES approaches were used: linear interpolation (non‐dissipative), the Gamma limiter (dissipative), and the scale‐selective discretisation (slightly dissipative). The results indicate that while the Smagorinsky and the scale‐selective discretisation approaches produce results consistent with the resolution of the non‐static mesh, the implicit LES with linear interpolation or the Gamma scheme do not. Copyright © 2016 John Wiley & Sons, Ltd.