Fe K‐Edge X‐ray Absorption Fine Structure Determination of γ‐Al2O3‐Supported Iron‐Oxide Species

The structure of FeO_x species supported on γ‐Al₂O₃ was investigated by using Fe K‐edge X‐ray absorption fine structure (XAFS) and X‐ray diffraction (XRD) measurements. The samples were prepared through the impregnation of iron nitrate on Al₂O₃ and co‐gelation of aluminum and iron sulfates. The dependence of the XRD patterns on Fe loading revealed the formation of α‐Fe₂O₃ particles at an Fe loading of above 10 wt %, whereas the formation of iron‐oxide crystals was not observed at Fe loadings of less than 9.0 wt %. The Fe K‐edge XAFS was characterized by a clear pre‐edge peak, which indicated that the Fe?O coordination structure deviates from central symmetry and that the degree of Fe?O?Fe bond formation is significantly lower than that in bulk samples at low Fe loading (<9.0 wt %). Fe K‐edge extended XAFS oscillations of the samples with low Fe loadings were explained by assuming an isolated iron‐oxide monomer on the γ‐Al₂O₃ surface.     

Unconventional Magnetic and Resistive Hysteresis in an Iodine‐Bonded Molecular Conductor

Simultaneous manipulation of both spin and charge is a crucial issue in magnetic conductors. We report on a strong correlation between magnetism and conductivity in the iodine‐bonded molecular conductor (DIETSe)₂FeBr₂Cl₂ [DIETSe=diiodo(ethylenedithio)tetraselenafulvalene], which is the first molecular conductor showing a large hysteresis in both magnetic moment and magnetoresistance associated with a spin‐flop transition. Utilizing a mixed‐anion approach and iodine bonding interactions, we tailored a molecular conductor with random exchange interactions exhibiting unforeseen physical properties.     

An experimental study of flow-induced fiber orientation and concentration distributions in a concentrated suspension flow through a slit channel containing a cylinder

Flow-induced fiber orientation and concentration distributions were measured in a concentrated fiber suspension (CFS) and a dilute one (DFS). The channel has a thin slit geometry containing a circular cylinder. In the previous work, many researchers have qualitatively studied fiber orientation and concentration distributions in injection-molded products of fiber-reinforced plastics. In the present work, however, they are quantitatively estimated by direct observation of fibers in the concentrated suspension flow. For the CFS, some fibers rotate in an expansion part between the channel wall and the circular cylinder, and the fiber orientation becomes almost random state. On the other hand, fibers are perfectly aligned along the flow direction owing to the elongational flow near the centerline downstream of the cylinder. The fiber concentration has a flat distribution except near the channel wall and the centerline. For the DFS a minimum in the fiber concentration distribution was clearly observed on the centerline, and two peaks beside the centerline and near the channel wall. This characteristic distribution is caused by the fiber-wall and fiber-cylinder interactions. It is found that the obstacle such as the circular cylinder in the channel significantly affects the fiber orientation downstream of the obstacle for the CFD, while it affects the fiber concentration distribution for the DFS.     

Sequence Analysis for Alternating Copolymers by MALDI‐TOF‐MS: Importance of Initiator Selectivity for Comonomer Pair

A special initiator for metal‐catalyzed living radical polymerization facilitates sequence analyses by matrix‐assisted laser desorption/ionization time of flight mass spectrometry (MALDI‐TOF‐MS) of alternating copolymers from styrene and maleimide derivatives. The initiator is a malonate‐based alkyl halide (DEMM‐Br), in which two ester groups are attached on the carbon neighboring to bromide, and poor electron density of the radical species allows determination of next unit to the initiator in resultant alternating copolymers due to the selective initiation to styrene derivative. Thanks to the well‐defined α‐end group, sequence of the oligomeric products via radical copolymerization of PMS and EMI with DEMM‐Br can be more simply analyzed by MALDI‐TOF‐MS, and indeed the following are clarified: the crossover propagation is almost perfectly controlled regardless of the injection ratio; a minor error event of the disordered alternating sequence containing St–St sequential unit could take place; the minor error can be suppressed with an excess amount of maleimide.

     

Tractive performance of a bulldozer running on weak ground

To determine the tractive performance of a bulldozer running on weak ground in the driven state, the relations between driving force, drawbar pull, sinkage, eccentricity and slip ratio have been analysed together with each energy balance; effective input energy, sinkage deformation energy, slippage energy and drawbar pull energy. It is considered that the thrust is developed not only on the main straight part of the bottom track belt but also on parts of the front idler and rear sprocket, and the compaction resistance is calculated from the amount of slip sinkage. For a given vehicle and soil properties, it is determined that the drawbar pull increases directly with the slip ratio and reaches about 70% of the maximum driving force. The compaction resistance reaches about 13% of the maximum driving force. The sinkage of the rear sprocket, the eccentricity, and the trim angle increase with the increment of slip ratio due to the slip sinkage. These analytical results have been verified experimentally. After determining the optimum slip ratio to obtain a maximum effective tractive power, it is found that a larger optimum drawbar pull at optimum contact pressure could be obtained for a smaller eccentricity of vehicle center of gravity and a larger track length-width ratio under the same contact area.     

Comparison of the traffic performance of a two-axle four wheel drive (4WD), rear wheel drive (RWD), and front wheel drive (FWD) vehicle on loose sandy sloped terrain

The traffic performances during driving and braking of a 5.88 kN weight wheeled vehicle with two-axle four wheel drive, rear wheel drive, and front wheel drive running up and down a loose sandy sloped terrain were compared by means of a simulation. For the given dimensions of the vehicle and the given terrain-wheel system constants, the relationship between the effective tractive and braking effort of the vehicle, the amount of sinkage of the front and rear wheels, the total amount of sinkage of the vehicle, and the slip ratio were calculated to estimate the optimum height of force of application and the optimum eccentricity of the center of gravity of the vehicle. It was observed that, during driving action, the maximum effective tractive effort of the four wheel drive vehicle (4WD) was larger than that of the rear wheel drive vehicle (RWD), which in turn was greater than that of the front wheel drive vehicle (FWD). During the braking action, the effective braking effort at skid -20% of the four wheel vehicle (4WB) was larger than that of the front wheel brake vehicle (FWB), in turn greater than that of the rear wheel brake vehicle (RWB), when the two-axle four wheel vehicle is moving up or down the loose sandy sloped terrain. The maximum terrain slope angle up which the two-axle wheeled vehicle is able to move during driving action was found to be about 0.067π rad for the 4WD vehicle, about 0.031π rad for the RWD vehicle, and about 0.017π rad for the FWD vehicle. The effective braking effort at skid-20% of 4WB, FWB and RWB was found to decrease with slope angle.     

Unprecedented Sequence Control and Sequence‐Driven Properties in a Series of AB‐Alternating Copolymers Consisting Solely of Acrylamide Units

Herein, we report a method to synthesize a series of alternating copolymers that consist exclusively of acrylamide units. Crucial to realizing this polymer synthesis is the design of a divinyl monomer that contains acrylate and acrylamide moieties connected by two activated ester bonds. This design, which is based on the reactivity ratio of the embedded vinyl groups, allows a “selective” cyclopolymerization, wherein the intramolecular and intermolecular propagation are repeated alternately under dilute conditions. The addition of an amine to the resulting cyclopolymers afforded two different acryl amide units, i.e., an amine‐substituted acryl amide and a 2‐hydroxy‐ethyl‐substituted acryl amide in alternating sequence. Using this method, we could furnish ten types of alternating copolymers; some of these exhibit unique properties in solution and in the bulk, which are different from those of the corresponding random copolymers, and we attributed the differences to the alternating sequence.     

Half‐Sandwich Iridium Complexes Bearing a Diprotic Glyoxime Ligand: Structural Diversity Induced by Reversible Deprotonation

Synthesis and deprotonation reactions of half‐sandwich iridium complexes bearing a vicinal dioxime ligand were studied. Treatment of [{Cp*IrCl(μ‐Cl)}₂] (Cp*=η⁵‐C₅Me₅) with dimethylglyoxime (LH₂) at an Ir:LH₂ ratio of 1:1 afforded the cationic dioxime iridium complex [Cp*IrCl(LH₂)]Cl ( 1 ). The chlorido complex 1 undergoes stepwise and reversible deprotonation with potassium carbonate to give the oxime–oximato complex [Cp*IrCl(LH)] ( 2 ) and the anionic dioximato(2?) complex K[Cp*IrCl(L)] ( 3 ) sequentially. Meanwhile, twofold deprotonation of the sulfato complex [Cp*Ir(SO₄)(LH₂)] ( 4 ) resulted in the formation of the oximato‐bridged dinuclear complex [{Cp*Ir(μ‐L)}₂] ( 5 ). X‐ray analyses disclosed their supramolecular structures with one‐dimensional infinite chain ( 1 and 2 ), hexagonal open channels ( 3 ), and a tetrameric rhomboid ( 4 ) featuring multiple intermolecular hydrogen bonds and electrostatic interactions.     

Unsymmetrical Pincer‐Type Ruthenium Complex Containing β‐Protic Pyrazole and N‐Heterocyclic Carbene Arms: Comparison of Brønsted Acidity of NH Groups in Second Coordination Sphere

A reaction of a 2‐(imidazol‐1‐yl)methyl‐6‐(pyrazol‐3‐yl)pyridine with [RuCl₂(PPh₃)₃] resulted in tautomerization of the imidazole unit to afford the unsymmetrical pincer‐type ruthenium complex 2 containing a protic pyrazole and N‐heterocyclic carbene (NHC) arms. Deprotonation of 2 with one equivalent of a base led to the formation of the NHC–pyrazolato complex 3 , indicating that the protic NHC arm is less acidic. When 2 was treated with two equivalents of a base under H₂ or in 2‐propanol, the hydrido complex 4 containing protic NHC and pyrazolato groups was obtained through metal–ligand cooperation.