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In this study, a 1:1 addition reaction using 1,1-diphenylethylene (DPE) derivatives, referred to as the "living anionic addition reaction", was established to regulate the sequence of vinyl compounds having negligible homopolymerizability. The stoichiometric and successive addition reaction between a DPE anion and more reactive DPE derivatives proceeded quantitatively when the electrophilicity of the DPE derivatives was sufficiently enhanced by electron-withdrawing groups such as (trimethylsilyl)ethynyl and acyl groups. The relative electrophilicity of the DPE derivatives was predicted by Hammett's law and the β-carbon chemical shifts of the carbon-carbon double bonds. AB- and ABC-type chain-end sequence-controlled polystyrenes with well-defined structures were synthesized by reacting two or three DPE derivatives with difunctional anionic living polystyrene in increasing order of their electrophilicity in a one-pot reaction.

Active collagen oligopeptides (ACOP) are bioactive collagen-derived peptides detected by a recently-established ELISA. To facilitate studies of the function and metabolism of these products, this study aims to determine which of these peptides is recognized by a novel anti-ACOP antibody used in this ELISA. We then investigate the effect of collagen peptide (CP) ingestion and exercise on urinary ACOP concentrations in a cohort of university student athletes using colorimetric, LC–MS/MS, and ELISA. We observed that the antibody showed strong cross-reactivity to Pro-Hyp and Gly-Pro-Hyp and weak cross-reactivity to commercial CP. CP ingestion increased the urinary level of ACOP over time, which correlated highly with urinary levels of peptide forms of Hyp and Pro-Hyp. Physical activity significantly decreased the urinary ACOP level. This study demonstrates changes in urinary ACOP following oral CP intake and physical activity using ELISA with the novel anti-ACOP antibody. Thus, ACOP may be useful as a new biomarker for collagen metabolism., Article number: 13527 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/.

Genome wide studies indicate that vascular endothelial growth factor A (VEGF) is associated with osteoarthritis (OA), and increased VEGF expression correlates with increased disease severity. VEGF is also a chondrocyte survival factor during development and essential for bone formation, skeletal growth and postnatal homeostasis. This raises questions of how the important embryonic and postnatal functions of VEGF can be reconciled with an apparently destructive role in OA. Addressing these questions, we find that VEGF acts as a survival factor in growth plate chondrocytes during development but only up until a few weeks after birth in mice. It is also required for postnatal differentiation of articular chondrocytes and the timely ossification of bones in joint regions. In surgically induced knee OA in mice, a model of post-traumatic OA in humans, increased expression of VEGF is associated with catabolic processes in chondrocytes and synovial cells. Conditional knock-down of Vegf attenuates induced OA. Intra-articular anti-VEGF antibodies suppress OA progression, reduce levels of phosphorylated VEGFR2 in articular chondrocytes and synovial cells and reduce levels of phosphorylated VEGFR1 in dorsal root ganglia. Finally, oral administration of the VEGFR2 kinase inhibitor Vandetanib attenuates OA progression.

Increased vascular endothelial growth factor (VEGF) levels are associated with osteoarthritis (OA) progression. Indeed, VEGF appears to be involved in OA-specific pathologies including cartilage degeneration, osteophyte formation, subchondral bone cysts and sclerosis, synovitis, and pain. Moreover, a wide range of studies suggest that inhibition of VEGF signaling reduces OA progression. This review highlights both the potential significance of VEGF in OA pathology and pain, as well as potential benefits of inhibition of VEGF and its receptors as an OA treatment. With the emergence of the clinical use of anti-VEGF therapy outside of OA, both as high-dose systemic treatments and low-dose local treatments, these particular therapies are now more widely understood. Currently, there is no established disease-modifying drug available for patients with OA, which warrants continued study of the inhibition of VEGF signaling in OA, as stand-alone or adjuvant therapy. © 2016 American Society for Bone and Mineral Research.

Vascular abnormalities in the eye are the leading cause of many forms of inherited and acquired human blindness. Loss-of-function mutations in the Wnt-binding co-receptor LRP5 leads to aberrant ocular vascularization and loss of vision in genetic disorders such as osteoporosis-pseudoglioma syndrome. The canonical Wnt-β-catenin pathway is known to regulate retinal vascular development. However, it is unclear what precise role LPR5 plays in this process. Here, we show that loss of LRP5 function in mice causes retinal hypovascularization during development as well as retinal neovascularization in adulthood with disorganized and leaky vessels. Using a highly specific Flk1-CreBreier line for vascular endothelial cells, together with several genetic models, we demonstrate that loss of endothelium-derived LRP5 recapitulates the retinal vascular defects in Lrp5-/- mice. In addition, restoring LRP5 function only in endothelial cells in Lrp5-/- mice rescues their retinal vascular abnormalities. Furthermore, we show that retinal vascularization is regulated by LRP5 in a dosage dependent manner and does not depend on LRP6. Our study provides the first direct evidence that endothelium-derived LRP5 is both necessary and sufficient to mediate its critical role in the development and maintenance of retinal vasculature.

Background Platelet-rich plasma (PRP) therapy has become an increasingly popular treatment for orthopaedics and sports-related injuries, and various clinically available PRP preparation methods exist. However, the differences in PRP quality among numerous preparation methods remain unclear. Specifically, the benefit of including leukocytes in the PRP product remains controversial, and few studies have been conducted to evaluate the effects of the interaction between platelets and leukocytes on the growth factor concentrations. The aim of the present study was to compare the biological characteristics of PRPs focusing on the leukocyte concentration and composition. Methods Leucocyte rich (LR)-PRP, leucocyte poor (LP)-PRP, and pure-PRP were prepared from the peripheral blood of 6 healthy male volunteers (mean age: 31.3 years). The concentrations of platelets, leukocytes, erythrocytes, growth factors (transforming growth factor-beta 1: TGF-β1; fibroblast growth factor-basic: FGF-b; platelet-derived growth factor-BB: PDGF-BB; vascular endothelial growth factor: VEGF) and matrix metalloproteinase-9 (MMP-9) from each of the PRP samples were measured. Considering the interaction between platelets and leukocytes, correlations between platelets/leukocytes and growth factors/MMP-9 were analyzed using partial correlation coefficients. Results The platelet concentration did not differ among the three PRP preparation methods. Conversely, the leukocyte concentration was dramatically different: 14.9 ± 4.5 (10 3 /μl) in LR-PRP, 2.4 ± 1.3 (10 3 /μl) in LP-PRP, 0.2 ± 0.2 (10 3 /μl) in pure-PRP. The platelet concentration positively correlated with all growth factors. On the other hand, the leukocyte concentration positively correlated with PDGF-BB and the VEGF concentration, while it negatively correlated with FGF-b. Regarding catabolic factors, the MMP-9 concentration strongly correlated with the leukocyte concentration, while there was no correlation between the platelet and MMP-9 concentrations. Conclusions These findings demonstrate that leukocytes strongly influence the quality of PRPs. Therefore, modifying the PRP preparation method according to the pathology is essential to achieve better clinical results with PRP therapy.

The sympathetic nervous system suppresses bone mass by mechanisms that remain incompletely elucidated. Using cell-based and murine genetics approaches, we show that this activity of the sympathetic nervous system requires osteopontin (OPN), a cytokine and one of the major members of the noncollagenous extracellular matrix proteins of bone. In this work, we found that the stimulation of the sympathetic tone by isoproterenol increased the level of OPN expression in the plasma and bone and that mice lacking OPN (OPN-KO) suppressed the isoproterenol-induced bone loss by preventing reduced osteoblastic and enhanced osteoclastic activities. In addition, we found that OPN is necessary for changes in the expression of genes related to bone resorption and bone formation that are induced by activation of the sympathetic tone. At the cellular level, we showed that intracellular OPN modulated the capacity of the β2-adrenergic receptor to generate cAMP with a corresponding modulation of cAMP-response element binding (CREB) phosphorylation and associated transcriptional events inside the cell. Our results indicate that OPN plays a critical role in sympathetic tone regulation of bone mass and that this OPN regulation is taking place through modulation of the β2-adrenergic receptor/cAMP signaling system.

Schnurri (Shn)-2 is a transcriptional modulator of bone formation and bone resorption and its deficiency causes low turnover state with higher cancellous bone mass due to the defects in osteoclasts that exceeds the defects in osteoblasts in mice. We addressed whether such low turnover of bone remodeling in Shn2 deficiency may be modulated in the absence of estrogen that induces high turnover state in vivo. Ovariectomy reduced bone mass in wild type compared to sham operated control mice and such reduction in bone mass was also observed in Shn2 deficient mice. However, due to the high levels of basal bone mass in Shn2 deficient mice, the bone mass levels after ovariectomy were still comparable to sham operated wild-type mice. Analysis indicated that estrogen depletion increased bone resorption at similar levels in wild type and Shn2 deficient mice though the basal levels of osteoclast number was slightly lower in Shn2-deficient mice. In contrast, basal levels of bone marrow cell mineralization in cultures were low in Shn2-deficeint mice while estrogen depletion increased the mineralization levels to those that were comparable to sham wild type. This indicates that Shn2-deficient mice maintain bone mass at the levels comparable to wild-type sham mice even after ovariectomy-induced bone loss and this correlates with the high levels of mineralization activity in bone marrow cells after ovariectomy. J. Cell. Physiol. 226: 573–578, 2011. © 2010 Wiley-Liss, Inc.

Multinuclear complexes consisting of metal ions and a bis(terpyridyl) ligand were covalently bound to carbon substrates. The bonding of the complexes is initiated by the bonding of phenylterpyridine (PT) on the substrates using its in-situ-generated diazonium derivative, followed by stepwise coordination of the metal ions and the ligand on it. The bonding of the PT and the formation of the multinuclear complexes were confirmed by XPS, AFM, and CV measurements. The heterogeneous rate constant (k) at the Co complex-substrate interface was evaluated by chronoamperometry (CA). The estimated high k = (2.9-3.6) x 10(3) s(-1)) would be attributed to the C-C bond at the interface without interrupting the conjugation. These multinuclear complexes bound to the carbon substrates can facilitate electron transfer from redox species such as enzymes.

Ultrafast dynamics of vibrational energy transfer in overlayers of D2O and CO on Pt(111) have been investigated by femtosecond time-resolved (TR) IR−visible sum-frequency-generation (SFG) spectrosc...

The mechanism of cycloaddition reaction between ethylene and the Si dimer on Si (100) is discussed from our recent experimental results using high-resolution electron energy loss spectroscopy and valence photoelectron spectroscopy at ~50 K. The weakly adsorbed π-complex state is identified as a precursor for di-σ bond formation and the activation barrier is roughly estimated to be ~0.2 eV. A different reaction route may exist since a di-σ species is also observed at low temperature. Using cycloaddition reaction, unsaturated organic molecules are chemically attached to the dimer on Si (100), and the adsorbed species are relatively stable. Thus, scanning tunneling spectroscopy (STS) measurements of a single adsorbed molecule can be carried out at room temperature. We report the STS results of 2-butyne adsorbed on Si (100).

吸収式冷凍機内の銅イオンの回収技術について検討し，以下に要約する結果を得た．(1) 実機における冷媒およびLiBr溶液中の銅イオンおよび酸化物の濃度および存在形態を調査し，銅イオンの回収技術の基礎データとした．(2) 電解による銅イオン回収法について検討し，カソード電極電位を－1.0～－0.6 V vs. SSEに保持することで効率良く銅イオンを捕捉回収できることを確認した．(3) 2 電極方式の銅イオン電解回収装置を試作した．実機にて適用，評価し，カソード電極に銅イオンが還元析出し，冷媒およびLiBr溶液中の銅イオンを目標レベルである1 mg dm－3以下に維持できることを検証した．(4) 活性金属電極を応用した置換型浄化フィルターを開発した．実験室および実機で冷媒および LiBr 溶液中の銅イオンおよび酸化物を目標レベル以下に維持できることを検証した．

We investigated the adsorption states and the reaction of vinyl bromide (CH2=CHBr) on Si(100)c(4×2), using high-resolution electron energy loss spectroscopy. We found that the chemisorption of this molecule occurs via a precursor state and a vinyl bromide molecule is di-σ bonded to the Si dimer on Si(100)c(4×2) in the chemisorption state. The precursor species are observed in the temperature range from 58 to 90 K. Judging from the vibrational spectra, we conclude that the structure of the precursor state is a three-atom intermediate state (π complex). The activation energy and the preexponential factor of the reaction from the precursor state to the chemisorption state are estimated to be 27.3 kJ/mol (283 meV) and 1.5 × 1013 s-1, respectively. The activation energy decreases with increasing the vinyl bromide coverage owing to the steric repulsion.

Adsorption of trimethylamine (TMA) on Si(100)c(4×2) has been studied using scanning tunneling microscopy (STM), valence photoelectron spectroscopy (PES), and high-resolution electron energy spectroscopy (HREELS) between 80 and 300 K. The TMA molecule is adsorbed nondissociatively only on the down dimer atom and appears as a triangle shaped bright protrusion in the occupied state STM image. The saturation coverage of TMA on Si(100) is estimated to be ∼0.25 ML (ML = one molecule per surface Si atom). The PES and HREELS results suggest that TMA is adsorbed through the N lone pair by forming an Si−N dative bond. The HREELS spectra indicate that the symmetry of adsorbed TMA is Cs and the molecular C3 axis is tilted from the surface normal. The stretching mode of the SiN dative bond is observed at 525 cm-1. Thus the combined STM, PES, and HREELS results indicate that the chemisorption of TMA on Si(100)c(4×2) occurs selectively on the down dimer atom via dative bonding. Hence, the TMA adsorption on Si(100)c(4×2)...

We have investigated the electronic states of clean and BF 3 adsorbed Si(100) surfaces at low temperature by means of high resolution Si 2p photoelectron spectroscopy. The peak intensities of upper atom and lower atom of the asymmetric dimer in Si 2p spectra do not change even at 30 K compared with those at higher temperature up to 300 K, indicating that the dimer is asymmetric in the ground state. In order to investigate chemical reactivity of asymmetric dimer on Si(100), a typical Lewis acid molecule BF 3 is adsorbed on Si(100). We have found that BF 3 molecules are dissociated into BF 2 and F on Si(100) and dissociated species (BF 2 and F) are adsorbed predominantly on the up dimer atoms of the asymmetric dimers.

The adsorbed states of 1,1,1-trifluoro-2-propanol (TFIP) molecule on Si(1 0 0) c(4 × 2) have been investigated by high resolution electron energy loss spectroscopy. TFIP is dissociatively adsorbed on Si(1 0 0) as CF 3 CH(O–Si)CH 3 and H–Si at 100 K. These species are stable up to 300 K. At 400 K, CF bonds start to be dissociated. At 800 K, all adsorbed species are decomposed into SiH, SiF, SiF 2 and residual carbon species. At 1050 K, the silicon carbide is formed.

We used the energy-selected-photoelectron photoion coincidence (ESPEPICO) method to study site-specific fragmentation caused by C:1s photoionization of 1,1,1-trifluoro-2-propanol-d1 [CF3CD(OH)CH3, TFIP-d1] on a Si(100) surface. High-resolution electron energy loss spectroscopy showed that TFIP-d1 is dissociatively chemisorbed like (CF3)(CH3)CDO–Si(100), and different chemical shifts at the three carbon sites were observed by photoelectron spectroscopy. The site-specific fragmentation evident in the ESPEPICO spectra of the sub-monolayer at room temperature indicates that the TFIP-d1 there has an O–Si bond oriented in the trans position with respect to the C–CF3 bond. Here we discuss the fragmentation processes in light of the results obtained with the ESPEPICO method and the Auger-electron photoion coincidence method.

The interface bonding between adsorbates (ethylene and benzene) and the Si(1 0 0)c(4×2) surface has been investigated by means of angle-dependent Si 2p high resolution photoelectron spectroscopy at 140 K, and several new quantitative properties have been obtained. Upon ethylene adsorption, a drastic decrease of up dimer and down dimer atom components (95%), and the appearance of a new component has been observed. This new component is assigned to the outer most Si atoms which are bonded to ethylene. The originally asymmetric Si dimer atoms become chemically equivalent upon adsorption. In the case of benzene, the decrease of up dimer and down dimer components is about 49% at the saturation coverage, and the unreacted dimers remain asymmetric. The charge transfer between adsorbed molecules and the Si(1 0 0)(2×1) surface has been estimated from the core-level shift and the nature of interface bonding including surface and second layer Si atoms is discussed.

Adsorbed states of cyclopentene on Si(100)(2×1) have been investigated by means of low energy electron diffraction (LEED), valence and Si 2p photoelectron spectroscopy (PES) using synchrotron radiation, and high-resolution electron energy loss spectroscopy (HREELS). Valence and Si 2p PES results indicate that the dangling bonds of the Si(100)(2×1) dimer and the π-bond of cyclopentene interact with each other, resulting in the formation of Si−C bonds. The valence electronic structure of adsorbed cyclopentene is similar to that of gas-phase cyclopentane. In addition, the HREELS spectra of cyclopentene on Si(100)(2×1) resemble the vibrational spectra of free cyclopentane and the cyclopentene di-σ bonded to Pt(111). Therefore, we conclude that cyclopentene is di-σ bonded to the Si(100)(2×1) surface and the molecular structure is similar to that of cyclopentane (all the carbon atoms are in sp3 state); the possible adsorbed structures are discussed. At saturation, 76% of the dimers are reacted, indicating that ...

We have studied the adsorption states of cyclohexene on Si(100)(2×1) by means of photoelectron spectroscopy (PES) and scanning tunneling microscopy (STM). PES results indicate the interaction between π bond of cyclohexene and the dangling bond of the dimer. Two adsorbed state are observed in STM images; one shows a symmetric protrusion, and another one is asymmetric and consists of some small protrusions. The former is assigned to the boat conformation of adsorbed cyclohexene, and the latter is assigned to the twist-boat conformation.

In order to elucidate the nature of the interface bonding between different molecules and a silicon surface, high resolution Si 2p photoelectron spectroscopy measurements were performed. After adsorption of unsaturated hydrocarbon molecules (ethylene, cyclopentene, and 1,4-cyclohexadiene), the peaks corresponding to the up and down atoms of surface asymmetric dimers vanished, while new peaks appeared between 215 and 398 meV relative to the bulk Si peak. These peaks are assigned to the di-σ Si–C bonds at the interface between the molecules and the surface. We can also estimate the amounts of reacted asymmetric dimers and the charge transfers from the peak intensities and the relative binding energies, respectively.

The adsorption state of 1,4-cyclohexadiene on a Si(100)(2×1) surface is studied with synchrotron radiation photoelectron spectroscopy (PES), high-resolution electron energy loss spectroscopy (HREEL...

In this paper we describe the analysis of the effects of the specific heat of a regenerator material on the refrigeration capacity of a 4K-GM (Gifford-McMahon) refrigerator. The findings revealed by the analysis are given below. When the specific heat of the regenerator material is changed from 1.5 J/(K·cm3) to 0.01 J/(K·cm3), the no-load temperature is changed from 2.11 K to 26.9 K. The lowest temperature that can be theoretically attained in this refrigerator is the temperature around the λ point of helium. It is sufficient for the regenerator material to provide a specific heat of 0.8 J/(K·cm3). The refrigeration capacity is found to be superior over a wider temperature range when the specific heat distribution is uniform than when it has a peak. When different kinds of regenerator materials are stacked, the material stacked at the cold part of the regenerator may have a low specific heat at high temperatures, but the material stacked at the hot part of the regenerator should have a high specific heat at low temperatures.

This paper describes the numerical simulation of a GM refrigerator operating at about 4K. The simulation model is composed of a regenerator, an expansion space, and a cooling stage. The volumetric change of the expansion space and the actual thermophysical properties of the working fluid, helium are considered. The basic equations are made up of one-dimensional fluid equations and an energy equation of the regenerator material and the cooling stage. The fluid equations are expressed in the general coordinate system of which a coordinate axis moves with time to take account of the volumetric change of the expansion space. These basic equations are differentiated by using the TVD MacCormack method. In order to verify the simulation model, the theoretical validity of the calculation results was checked and calculation results were compared with results of experiments. As a result it was confirmed that the simulation model is appropriate.

Hydrolysis constants of the zinc ion were measured at 25, 50, 75, 185, 200, and 225°C through the direct measurement of pH using pH sensors, especially of the yttria-stabilized zirconia membrane-ty...

Rare earth-ruthenium intermetallic compounds have been developed for ues as regenerator materials in helium liquefaction Gifford-McMahon refrigerators. These compounds show characteristically lower magnetic transition temperatures than other rare earth intermetallic compounds. The refrigeration capacity of GM refrigerators has been remarkably improved by the use of Ho1·5Er1·5Ru spheres as regenerator materials at the temperature range below 5K. This material posseses a large heat capacity even under magnetic fields of 0.5T in such a temperature range. Spherical powders of these materials were produced by a simple method named the “low pressure jet method, ” which offers good sphericity powders with smooth surface. Nozzle clogging is a serious problem in this method, but we have overcome this problem by reducing gas elements such as oxygen, fluorine, from starting materials.

Parathyroid hormone (PTH), the major calcium-regulating hormone, and norepinephrine (NE), the principal neurotransmitter of sympathetic nerves, regulate bone remodeling by activating distinct cell-surface G protein-coupled receptors in osteoblasts: the parathyroid hormone type 1 receptor (PTHR) and the β 2 -adrenergic receptor (β 2 AR), respectively. These receptors activate a common cAMP/PKA signal transduction pathway mediated through the stimulatory heterotrimeric G protein. Activation of β 2 AR via the sympathetic nervous system decreases bone formation and increases bone resorption. Conversely, daily injection of PTH (1–34), a regimen known as intermittent (i)PTH treatment, increases bone mass through the stimulation of trabecular and cortical bone formation and decreases fracture incidences in severe cases of osteoporosis. Here, we show that iPTH has no osteoanabolic activity in mice lacking the β 2 AR. β 2 AR deficiency suppressed both iPTH-induced increase in bone formation and resorption. We showed that the lack of β 2 AR blocks expression of iPTH-target genes involved in bone formation and resorption that are regulated by the cAMP/PKA pathway. These data implicate an unexpected functional interaction between PTHR and β 2 AR, two G protein-coupled receptors from distinct families, which control bone formation and PTH anabolism.

We have investigated the electronic states of the Si(100) surface at low temperature by means of high-resolution Si 2p photoelectron spectroscopy. The peak intensities of up and down atoms of the asymmetric dimer in Si 2p spectra do not change from 140 K to 55 K, showing that the number of asymmetric dimers is preserved. Therefore, we can conclude that the ground state of the dimer is asymmetric and the symmetric dimer images observed by scanning tunneling microscopy at this temperature range are due to extrinsic or dynamical intrinsic effects on the buckled dimer.

Objective Regeneration of bone requires the combination of appropriate drugs and an appropriate delivery system to control cell behavior. However, the delivery of multiple drugs to heal bone is complicated by the availability of carriers. The aim of this study was to explore a new system for delivery of a selective EP4 receptor agonist (EP4A) in combination with low-dose bone morphogenetic protein 2 (BMP-2). Methods Combined delivery of EP4A and BMP-2 was carried out with a nanogel-based scaffold in the shape of a disc, to repair critical-size circle-shaped bone defects in calvariae that otherwise did not heal spontaneously. Results Combination treatment with EP4A and low-dose BMP-2 in nanogel efficiently activated bone cells to regenerate calvarial bone by forming both outer and inner cortical plates as well as bone marrow tissue to regenerate a structure similar to that of intact calvaria. EP4A enhanced low-dose BMP-2–induced cell differentiation and activation of transcription events in osteoblasts. Conclusion These data indicate that combined delivery of EP4A and low-dose BMP-2 via nanogel-based hydrogel provides a new system for bone repair.

We investigated the adsorption states of 2-methylpropene and propene on Si(100)c(4 x 2) using low-temperature scanning tunneling microscopy. We have found that regioselective cycloaddition reactions (di-sigma bond formation) occur between the asymmetric alkene molecules and the asymmetric dimers on Si(100)c(4 x 2). First-principles calculations have elucidated that the regioselectivity is closely related to the structures of precursor species and these precursor species have carbocation-like features. Thus, we conclude that Markovnikov's rule is applicable for the cycloaddition of asymmetric alkene with the asymmetric dimer on Si(100)c(4 x 2).

We report the direct observation of a precursor state for the cycloaddition reaction (the di-sigma bond formation) of ethylene on Si(100)c(4 x 2) using high-resolution electron energy loss spectroscopy at low temperature, and the meta-stable precursor state is identified as a weakly bonded pi-complex type. The activation energy from the pi-complex precursor to the di-sigma bonded species is experimentally estimated to be 0.2 eV. First-principles calculations support the pi-complex precursor mediated cycloaddition reaction of ethylene on Si(100)c(4 x 2).

This paper describes the effects of thermal conductance in the cooling stage of a 4K-GM refrigerator on its refrigeration capacity. Calculation of the temperature difference between the gas and cooling stage in the expansion space of a 4K-GM refrigerator has shown that the thermal conductance between the gas and cooling stage is inadequate, and the heat transfer loss is too large to be ignored. Hence, we have made improvements in the shape and material of the cooling stage to increase thermal conductance, and have been successful in increasing refrigeration capacity at 4.2 K from 2.2 W to 3.0 W.

It is important for rotors of superconducting generators to maintain a stable flow pattern of liquid helium to prevent an accidental transition of superconducting field windings into the normal state. Liquid helium within the rotating helium pool of superconducting generators has two major flow patterns. One is a gravity dominant flow pattern and the other is a centrifugal force dominant flow pattern. The former has a flat horizontal surface of a liquid, and the latter has a cylindrical one. This paper describes the transition phenomena between these two flow patterns. The results of a visual experiment using water, fron 113 and silicon oil were presented in the first report of this paper. The second report at first describes experimental data of liquid helium obtained using a rotating helium pool, and then compares these experimental data with the results of a visual experiment.

This article describes the principal design features and performance test results of a three‐stage Gifford–McMahon cycle cryogenic refrigerator by which the authors have achieved a no‐load temperature of 3.3 K and succeeded in helium liquefaction. The refrigeration capacity was 20 mW at 4.2 K and the helium liquefaction rate was 10 cm3/h. The key point of the success is the selection of GdxEr1−xRh compounds as a regenerator material. This is the first time that a Gifford–McMahon refrigerator has liquefied helium without the use of a Joule–Thomson stage.