Effects of crosslinker density on the polymer network structure in poly‐N,N‐dimethylacrylamide hydrogels

To investigate the effects of crosslinker density on the properties of hydrogels, compression tests, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Raman measurements were performed on poly‐N,N‐dimethylacrylamide hydrogels. The results of the compression tests showed that the Young's modulus increases as the crosslinker density increases. To understand the mechanism of the change in the mechanical properties, the structures of the polymer networks and water and the molecular vibrations were analyzed using SEM, DSC, and Raman methods. From the SEM images, it was found that the porosity estimated from the mesh size and cell density increases with increasing crosslinker density. In addition, the DSC and Raman results show that the thickness of the bound water increases as the porosity increases, although the density of the polymer chains in the porous wall remains nearly constant. The increase in the number density of polymer chains can be one of the mechanisms contributing to the increase in the mechanical strength of the hydrogels at lower crosslinker density below 5 mol %, as proposed by previous studies. At higher crosslinker density, however, the number density of polymer chains does not increase with increasing crosslinker density. The present results suggest that the bound water plays an important role in strengthening the hydrogel. The water structure may be one of the dominant factors governing the chemical and physical properties of hydrogels. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1017–1027     

Atomic correlation between adjacent graphene layers in double-wall carbon nanotubes

Atomic correlation between adjacent graphene layers was elucidated for double-wall carbon nanotubes (DWNTs) through a chiral index assignment of two nested nanotubes by high-resolution transmission electron microscopy. Our analysis provides a rather constant diameter difference close to 0.75 nm but no chiral angle correlation between the constituent nanotubes in the concentric DWNTs. The local atomic correlation as a commensurate graphene stacking was repeatedly found in eccentric DWNTs and circumscribed nanotubes, which should lead to elastic deformation and bundling of nanotubes.     

Risks of Muscle Atrophy in Patients with Malignant Lymphoma after Autologous Stem Cell Transplantation

Objective: Muscle atrophy is associated with autologous stem cell transplantation (ASCT)-related outcomes in patients with malignant lymphoma (ML). However, the impact of ASCT on muscle mass remains unclear in patients with ML. The aims of this study were to investigate changes in muscle mass and risk profiles for muscle atrophy after ASCT. Method: We enrolled 40 patients with refractory ML (age 58 [20-74] years, female/male 16/24, body mass index (BMI) 21.1 kg/m² [17.1-29.6]). Psoas muscle mass was assessed using the psoas muscle index (PMI) before and after ASCT. Statistical analysis used: Independent factors associated with a severe decrease rate of change in PMI were evaluated by decision-tree analysis, respectively. Results: PMI was significantly decreased after ASCT (4.61 vs. 4.55 cm²/m²; P=0.0425). According to the decision-tree analysis, the regimen was selected as the initial split. The rates of change in PMI were −5.57% and −3.97% for patients administered MCEC and LEED, respectively. In patients who were administered LEED, the second branching factor was BMI. In patients with BMI < 20.3 kg/m², the rate of change in PMI was −7.16%. On the other hand, the rate of change in PMI was 4.05% for patients with BMI ≥ 20.3 kg/m². Conclusion: We demonstrated that muscle mass decreased after ASCT in patients with ML. Patients who received MCEC and patients with low BMI were at risk for a decrease in muscle mass.     

An exact algorithm for the precedence-constrained single-machine scheduling problem

This study proposes an efficient exact algorithm for the precedence-constrained single-machine scheduling problem to minimize total job completion cost where machine idle time is forbidden. The proposed algorithm is based on the SSDP (Successive Sublimation Dynamic Programming) method and is an extension of the authors’ previous algorithms for the problem without precedence constraints. In this method, a lower bound is computed by solving a Lagrangian relaxation of the original problem via dynamic programming and then it is improved successively by adding constraints to the relaxation until the gap between the lower and upper bounds vanishes. Numerical experiments will show that the algorithm can solve all instances with up to 50 jobs of the precedence-constrained total weighted tardiness and total weighted earliness–tardiness problems, and most instances with 100 jobs of the former problem.     

A Suggestion of Fractional-Order Controller for Flexible Spacecraft Attitude Control

A controller design method for flexible spacecraft attitude control isproposed. The system is first described by partial differential equationwith internal damping. Then the frequency response is analyzed, and thethree basic characteristics of the flexible system, namely, averagefunction, lower bound and upper bound are defined. On this basis, afractional-order controller is proposed, which functions as phasestabilization control for lower frequency and smoothly enters toamplitude stabilization at higher frequency by proper amplitudeattenuation. It is shown that the equivalent damping ratio increases inproportion to the square of frequency.     

Kinetics for the reaction of methine proton of an unsymmetrical tetradentate Schiff base complex of nickel(II) with N-chlorosuccinimide

The substitution reaction of the methine proton of an unsymmetrical tetradentate Schiff base complex of nickel(II) with N-chlorosuccinimide was kinetically studied in a dichloromethane solution. While the rate of chlorination was decreased by the addition of acetone or ether, the rate was significantly increased by the addition of ethanol. The rate of bromination was faster than that of chlorination. A four-centred intermediate was proposed for the halogenation reaction of the Schiff base nickel(II) complex.     

The reaction of perfluorobicyclic ethers and perfluorospiro-ethers with anhydrous aluminum chloride

Perfluorobicyclic ethers and perfluorospiroethers, all containing an oxolane skeleton, were treated with AlCl₃ in a heterogeneous manner to give the corresponding α,α,α′-trichlorinated and α,α-dichlorinated products, respectively. From perfluoroacetal compounds, for example, perfluoro(8-methoxy-7-oxabicyclo- [4.3.0]nonane), mono- and di-chlorinated products, i.e. perfluoro- (8-chloro-8-methoxy-7-oxabicyclo[4.3.0]nonane) and perfluoro- (8,8-dichloro-7-oxabicyclo[4.3.0]nonane) were obtained in good yields. The action of fuming sulfuric acid on these polychlorinated products led to the formation of the corresponding lactones. Perfluoro(6-chloro-7-oxa-8-oxobicyclo[4.3.0]nonane) was treated with (CH₃)₂NLi to give N,N-dimethylundecafluoro-2-oxocyclohexyl- acetamide.     

Development of a new radiation detector utilizing CNTs as anodes

A new gas-multiplication radiation detector utilizing CNTs as anodes is proposed. A very compact detector with good spatial and temporal resolutions might be built. The designing and development of a prototype detector is described. Argon gas or liquid is adopted as radiation-converting medium. The detector body can be evacuated and cooled down to liquid nitrogen temperature. Silicon wafers on which single-wall CNTs are grown are used as the detector anode.     

Synthesis and properties of hexakis(6-octyl-2-azulenyl)benzene as a multielectron redox system with liquid crystalline behavior

[structure: see text] This paper describes the cyclotrimerization reaction of di(2-azulenyl)acetylenes (2a,b) catalyzed by Co2(CO)8 to produce hexa(2-azulenyl)benzene derivatives (1a,b). The cyclooligomerization of 2a and 2b utilizing CpCo(CO)2 as a catalyst produced (eta5-cyclopentadienyl)[tetra(2-azulenyl)cyclobutadiene]cobalt complexes (3a,b). The redox behavior of hexakis(6-octyl-2-azulenyl)benzene (1b), bis(6-octyl-2-azulenyl)acetylene (2b), and the cobalt complexes 3a and 3b along with 6-octyl-2-phenylazulene (19) was examined by cyclic voltammetry (CV). The reduction of compound 1b exhibited multiple-electron transfers in one step upon CV with a reduction potential similar to that of compound 19. However, the CVs of compounds 2b, 3a, and 3b were characterized by stepwise waves because of the reduction of each azulene ring. The mesomorphic behaviors of 1b, 2b, and 19 were also studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction (XRD) techniques. A new series of azulene derivatives, 1b, 2b, and 19, substituted by a long alkyl chain at the 6-position shows mesomorphism with crystalline polymorphs. Compound 1b showed a large temperature range of hexagonal columnar mesophases (Col(ho)) from 115.5 to 199.9 degrees C. Compound 2b has rectangular columnar (Col(ro)), smectic E (S(E)), and nematic (N) mesophases. Compound 19 exhibited an S(E) mesophase.