Synthesis of Optically Active Dendrimers Having Chiral Bisphosphine as a Core

Summary First and second generation chiral dendrimers P-1G1, P-2G1, P-1G2 and P-2G2 containing chiral bisphosphine as a core were synthesized via a reaction of chiral bisphosphine compound (S,S)-1 with benzyl ether dendrons. This is the first example of chiral dendrimers containing chiral phosphorus atoms. To investigate the effect of chiral phosphorus atoms on their conformations, optically inactive dendrimer P′-2G1 was synthesized as well using optically inactive initiator 1′ which was the mixture of rac-1 ((S,S)-1 and (R,R)-1) and meso-1. Their structures were characterized by ¹H, ¹³C, ³¹P NMR, and HRMS. According to CD measurement, optically active dendrimers exhibited the Cotton effect induced by the chirality of phosphorus atoms, while optically inactive dendrimer P′-2G1 showed no Cotton effect.     

Biomaterial-Assisted Regenerative Medicine

This review aims to show case recent regenerative medicine based on biomaterial technologies. Regenerative medicine has arousing substantial interest throughout the world, with “The enhancement of cell activity” one of the essential concepts for the development of regenerative medicine. For example, drug research on drug screening is an important field of regenerative medicine, with the purpose of efficient evaluation of drug effects. It is crucial to enhance cell activity in the body for drug research because the difference in cell condition between in vitro and in vivo leads to a gap in drug evaluation. Biomaterial technology is essential for the further development of regenerative medicine because biomaterials effectively support cell culture or cell transplantation with high cell viability or activity. For example, biomaterial-based cell culture and drug screening could obtain information similar to preclinical or clinical studies. In the case of in vivo studies, biomaterials can assist cell activity, such as natural healing potential, leading to efficient tissue repair of damaged tissue. Therefore, regenerative medicine combined with biomaterials has been noted. For the research of biomaterial-based regenerative medicine, the research objective of regenerative medicine should link to the properties of the biomaterial used in the study. This review introduces regenerative medicine with biomaterial.     

Computed tomography reconstruction from two transmission measurements for iodine-marked cancer detection

The authors invented the transXend detector, which measures X-rays as electric currents, and then gives the energy distribution of the X-rays after an unfolding process. In a previous paper, it was shown that the material thickness distributions can be estimated with the transXend detector by using reference points plotted from the electric current ratios, such as the I ₂/I ₁ ? I ₃/I ₁ graph, where I_i denotes the electric current measured by the i-th segment of the transXend detector. In this paper, the tomographic images of iodine, aluminum, and the acrylic those surround the other two materials are reconstructed from their material thickness distributions, which are estimated from two X-ray incidence directions. The X-ray event ratios are also used to estimate the material thickness distributions.     

Possible Alterations in ��-Synuclein, the Non-Amyloidogenic Homologue of ��-Synuclein, during Progression of Sporadic ��-Synucleinopathies

α-Synucleinopathies are neurodegenerative disorders that are characterized by progressive decline of motor and non-motor dysfunctions. α-Synuclein (αS) has been shown to play a causative role in neurodegeneration, but the pathogenic mechanisms are still unclear. Thus, there are no radical therapies that can halt or reverse the disease’s progression. β-Synuclein (βS), the non-amyloidogenic homologue of αS, ameliorates the neurodegeneration phenotype of αS in transgenic (tg) mouse models, as well as in cell free and cell culture systems, which suggests that βS might be a negative regulator of neurodegeneration caused by αS, and that “loss of function” of βS might be involved in progression of α-synucleinopathies. Alternatively, it is possible that “toxic gain of function” of wild type βS occurs during the pathogenesis of sporadic α-synucleinopathies, since tg mice expressing dementia with Lewy bodies-linked P123H βS develop progressive neurodegeneration phenotypes, such as axonal pathology and dementia. In this short review, we emphasize the aspects of “toxic gain of function” of wild type βS during the pathogenesis of sporadic α-synucleinopathies.     

Monitoring of acrylamide concentrations in potato chips in Japan between 2006 and 2010

Acrylamide levels in commercially available potato chips in Japan were monitored between August 2006 and June 2010 using the xanthydrol derivative gas chromatography-mass spectrometry (GC-MS) method. Seasonal and annual changes in acrylamide concentrations were determined. Nationwide bimonthly sampling of potato chips was carried out using a four-level design, and seasonal variations were detected in which the minimum acrylamide concentration was observed in August, and the maximum between February and June. Seasonal variations became less apparent after August 2008 as a result of annual effects and/or mitigation measures taken by the potato chip producers. Sampling uncertainties were separated into time-to-time, city-to-city, and lot-to-lot variation, and the largest variation was shown to be lot-to-lot including bag-to-bag.     

Formation of Ultrafine‐Grained Microstructure of Ti–6Al–4V Alloy by Hot Deformation of α′ Martensite Starting Microstructure

We have presented a formation of ultrafine‐grained microstructure (d_α ≈ 0.2 µm) of industrial Ti–6Al–4V alloy produced by the hot compression of a sample with the acicular α′ martensite starting microstructure. The hot‐deformation behavior was different from the case of the conventional (α + β) starting microstructure, that is, the phase transformation of α′/(α + β) during hot working enhanced the microstructural conversion, especially under the conditions of a low temperature and a high‐strain rate.     

Highly sensitive molecular detection with swift heavy ions

Various imaging techniques using microbeam have been applied in biology. Secondary ion mass spectrometry (SIMS) is one of the prominent tools for biological imaging; SIMS can provide data on molecular distribution in biological samples smaller than 1 μm. However, conventional SIMS has only low sensitivity for molecular ions; therefore there is a need for beams of more sensitive primary ions. Plasma desorption mass spectrometry (PDMS) is a method using high energy fission fragments from excitation of a ²⁵²Cf source, and it allows ionization of large molecules (typically up to 20 kDa) due to the dense electronic excitation. Although PDMS is not in use today because of the development of soft ionization methods, ionization induced by high energy ion collision still remains the only method which combines high spatial resolution and sensitive detection of large molecules. In this work, the secondary ion yield of amino acid and phospholipid was measured for 6 MeV Cu⁴⁺. The yields were compared to bismuth cluster ions, which achieve relatively high yield. It was confirmed that the swift heavy ion has a couple of hundred times higher yield for large molecules than bismuth cluster ions.     

Temperature dependence and fracture criterion of mixed mode I/II fracture toughness of phenolic resin for friction material

In this study, the temperature dependence of the mixed‐mode fracture toughness of the phenolic resin for friction materials is investigated. For pure mode I, the fracture toughness decreases as the temperature increases, and it increases again after showing its minimum value. For pure mode II, the fracture toughness shows a similar trend but has its minimum value at a higher temperature. The temperature dependence of the mixed‐mode fracture toughness varies depending on the mode mixity, which is attributed to the different sensitivity to the relaxation phenomenon. At room temperature, as the fracture toughness for pure mode I and II are almost the same, the fracture locus shows a circular arc. At elevated temperatures, the locus becomes smaller and noncircular. At high temperature, the fracture locus shows an elliptical arc, where the fracture toughness for pure mode II is smaller than that for mode I. An empirical fracture criterion based on the time‐temperature dependence of the resin is proposed, and the proposed method successfully predicts the fracture toughness under various conditions of the temperature, time, and mode mixity. The crack initiation angles, on the other hand, are almost consistent regardless of the temperature, which agree with the maximum hoop stress theory. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The impact of air contaminants on PEMFC performance and durability

The impact of air contaminants such as sulfur compounds (SO₂, H₂S) and nitrogen compounds (NO_x and NH₃) was investigated using subscale fuel cells. The severity of the effect of these impurities varies depending on the contaminants. Among air contaminants, sulfur compounds cause the most severe performance loss due to decrease of available Pt sites for oxygen reduction reaction (ORR). We found that sulfur compounds adsorbed on Pt surface tend to be oxidized to sulfate at 0.9 V and higher potentials. The cell performance can be recovered partially by excursions to high potentials due to increase of available Pt sites. Furthermore, flushing the cathode with high humidity gases results in almost complete recovery of the cell performance. We conclude that these recovery effects are due to oxidation/removal of the contaminants from the Pt surface.     

Ripple compensation for torque sensors built into harmonic drives

Harmonic drives include a mechanically flexible component which transmits load torque, and therefore, a torque sensor can be built into harmonic drives by cementing strain gages on a flexible component of the gear. However, a periodic sensing error called ripple is generated by deformation of a flexible component during the gear operation. The ripple signal cannot be sufficiently compensated by pairs of strain gages that produce opposite phase signals, because the strain gages cannot be exactly positioned on the desired locations. In this paper, we present a method to compensate the ripple by a new approach of tuning the ripple amplitudes for separate strain gages. The ripple, caused by positioning errors of the strain gages, can be perfectly compensated, and, therefore, the requirement for accurate strain gage positioning is reduced. The method does not need any online calculations, and consequently, the torque signal is not delayed. The minimum number of strain gages needed to compensate a given number of frequency components of a ripple is derived. Some experimental results are shown