Low-pressure CO2 sorption in poly(vinyl benzoate) conditioned to high-pressure CO2

Sorption of CO₂ in poly(vinyl benzoate) was gravimetrically measured at pressures up to 1 atm. Sorption isotherms were determined above and below the glass transition temperature T_g from 5 to 85°C. The isotherms were analyzed by the dual-mode sorption model assuming that the plasticizing effect of sorbed CO₂ is negligible at this pressure range. The solubilities and Henry's law dissolution parameters were compared with those obtained by the high-pressure sorption and permeation measurements. Henry's law dissolution parameters were in good agreement with one another. However, the solubilities first determined here were smaller than those determined by the high-pressure sorption experiment at the same temperature. It was clear that the Langmuir capacity of the present specimen was smaller in spite of similar high-pressure CO₂ exposure. Relaxation of the polymer was expected to be one of the reasons. This expectation was confirmed from the observation and analysis of sorption isotherms after two kinds of treatments. After annealing above T_g, the Langmuir capacity was shown to be decreased to 1/2 or even to 1/3 from the sorption isotherms below 45°C. This means that the conditioning to the high-pressure CO₂ surely has a large effect on the nature of glassy polymer. Just after high-pressure CO₂ exposure at 25°C, increased solubility was observed. Furthermore, the slow decrease of solubility, that is, the decrease of conditioning effect, was also followed from the continual measurements at 25°C. This result reflects not only the characteristic of sorption capacity after high-pressure CO₂ exposure, but also the relaxation of polymer in glassy state.     

Measurements of plastic strain around indentations caused by the impact of round and angular particles, and the origin of erosion

The aim of this paper is to examine plastic strain distributions around indentations and to consider the mechanisms of erosion damage caused by solid particle impact. A WC ball and an angular SiC particle of 3 mm in diameter were used to compare the effect of particle shape on plastic strain. Measurements of principal shearing strain distributions around the indentations were performed on surfaces of aluminum, iron and cast iron at impact angles of 20°, 30°, 40°, 60° and 90° at impact velocities from 50 to 200 m s⁻¹. It was found that the impact angle dependence was roughly consistent with the maximum principal shearing strain and erosion damage data, which have been published in previous papers and obtained during additional works in this study. The surface topography of the impact craters suggested that depth, contact area and volume of indentation are affected by the particle density and the hardness of both particle and target material. Measurements of volume ratio of lips to craters proved that material removal did not necessarily occur at a single impact of the WC ball, but occurred at the impact of the angular SiC particle at low impact angles. It is concluded that the origin of erosion is probably attributed to the conjoint actions of high plastic strains followed by subsequent removal and the cutting process caused by particle impact.     

Enhanced centralized management of gateways using redirection-based rules sharing for mobile network virtualization

One of the current issues in the peer-to-peer streaming systems is to supply sufficient upload bandwidth for continuous streaming of high-quality video channels. The helpers as upload bandwidth boosters can improve the streaming capacity of system, so that the imbalance of upload bandwidth between different video channel overlays is compensated. With the deployment of helpers as an intermediate level between server and peers, building and maintaining the optimal peer-helper topology becomes a challenging task since the one-directional nature of video streaming from the helpers to users makes the well-known reciprocity-based algorithms useless. Because of selfish behavior of peers and lack of a central authority among them, selection of helpers requires implicit coordination. In this paper, we design a decentralized, stochastic approximation helper selection mechanism which is adaptable to supply and demand pattern of various video channels. Our regret-tracking-based solution for allowing peers to strategically exploit their shared resources is guaranteed to converge to the correlated equilibria (CE) among the helper selection strategies. Online convergence to the set of CE is achieved through the regret-tracking algorithm which tracks the equilibrium in the presence of stochastic dynamics of helpers’ bandwidth. The resulting CE can help to select proper cooperation policies. Simulation results demonstrate that our algorithm achieves good convergence, load distribution on helpers and sustainable streaming rates for peers.     

Ag nanorod arrays tailored for surface-enhanced Raman imaging in the near-infrared region

Using a dynamic oblique angle deposition technique, we demonstrate the direct formation of Ag nanorods with quasi-parallel major axes on a template layer of oxide having a strongly anisotropic surface morphology. The optical properties of the nanorods are tuned by varying the deposition conditions without any pre-?or post-treatment, and the resulting Ag nanorod arrays exhibit high surface-enhanced Raman scattering (SERS) activity. In addition to high macroscopic uniformity over a large area, our nanorod arrays contain a high density of isolated nanorods. Using the optimum Ag nanorod arrays, the SERS imaging of the microdroplets of a rhodamine 6G solution is successfully demonstrated. The space resolution of the imaging is of the order of at least a few μm. These features are suitable for the SERS imaging of biomaterials.     

Further Characterization of 394-GHz Gyrotron FU CW GII with Additional PID Control System for 600-MHz DNP-SSNMR Spectroscopy

A 394-GHz gyrotron, FU CW GII, has been designed at the University of Fukui, Japan, for dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR) experiments at 600-MHz ¹H resonant frequency. After installation at the Institute for Protein Research (IPR), Osaka University, Japan, a PID feedback control system was equipped to regulate the electron gun heater current for stabilization of the electron beam current, which ultimately achieved stabilization of output power when operating in continuous wave (CW) mode. During exploration to further optimize operating conditions, a continuous tuning bandwidth of approximately 1 GHz was observed by varying the operating voltage at a fixed magnetic field. In the frequency range required for positive DNP enhancement, the output power was improved by increasing the magnetic field and the operating voltage from their initial operational settings. In addition, fine tuning of output frequency by varying the cavity cooling water temperature was demonstrated. These operating conditions and ancillary enhancements are expected to contribute to further enhancement of SSNMR signal.     

Fully automated two-dimensional electrophoresis system for high-throughput protein analysis

We developed a fully automated electrophoresis system for rapid and highly reproducible protein analysis. All the two-dimensional (2D) electrophoresis procedures including isoelectric focusing (IEF), on-part protein staining, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and in situ protein detection were automatically completed. The system comprised Peltiert devices, high-voltage generating devices, electrodes, and three disposable polymethylmethacrylate (PMMA) parts for IEF, reaction chambers, and SDS-PAGE. Because of miniaturization of the IEF part, rapid IEF was achieved in 30 min. A gel with a tapered edge gel on the SDS-PAGE part realized a connection between the parts without use of a gluing material. A biaxial conveyer was employed for the part relocation, sample introduction, and washing processes to realize a low-maintenance and cost-effective automation system. Performances of the system and a commercial minigel system were compared in terms of detected number, resolution, and reproducibility of the protein spots. The system achieved high-resolution comparable to the minigel system despite shorter focusing time and smaller part dimensions. The resulting reproducibility was better or comparable to the performance of the minigel system. Complete 2D separation was achieved within 1.5 h. The system is practical, portable, and has automation capabilities.     

Probing the unfolding and refolding processes of carbonic anhydrase 2 using electrospray ionization mass spectrometry combined with pH jump

A novel method for proving the time course of the unfolding and refolding processes of metalloprotein bovine carbonic anhydrase 2 (CA2) is demonstrated using electrospray ionization mass spectrometry (ESI MS) combined with pH jumps between 3.6 and 4.4. The shift in mass accompanied by the release or coordination of a zinc ion and the change in the charge state distribution were measured to evaluate the folding process. The time course of the ESI mass spectra revealed the existence of four types of ions in the experimental system, i.e., lower charged apo-CA2 and holo-CA2 ions and higher charged apo-CA2 and holo-CA2 ions. The deconvolution spectrum of the ion peak ensemble for each type of ion was processed and time course plots of the relative intensities of the four ions were prepared in order to analyze the folding processes. These analyses revealed the coexistence of two folding states of the lower and higher charged apo-CA2 under the condition of pH 3.6. The lower and higher charged apoproteins spontaneously refolded to the lower charged holoprotein by a pH jump from 3.6 to 4.4 without the addition of an extra zinc ion. The higher charged holoprotein observed during both the unfolding and refolding processes was considered to be an intermediate of the change in folding. The present study indicates that ESI MS combined with pH jump would be a powerful method to probe the unfolding and refolding of proteins. This method simultaneously measures mass spectra and analyzes the folding processes as a function of time using deconvolution spectra constructed by selecting a suitable m/z range for the analysis from the peaks of charge state distributions.     

Rapid Desensitization of Lipolysis in the Visceral and Subcutaneous Adipocytes of Rats

In adipocytes, short and long term stimulation of β adrenergic receptors (βAR) induces the desensitization to catecholamines, leading to a decrease in the intracellular accumulation of cAMP, but the roles played by this in lipolysis is not clear. In this study, we assessed the catecholamine-induced desensitization of lipolysis and compared this in adipocytes isolated from visceral and subcutaneous fat tissues of rats. When adipocytes were pretreated with isoproterenol (ISO), the norepinephrine (NE)-induced lipolysis was significantly reduced dose- and time-dependently. A similar reduction of the lipolytic response was also found in NE-, dobutamine-, terbutaline- or BRL37344-induced lipolysis. The ISO- and each βAR agonist-induced lipolysis in the visceral fat was not only higher than in the subcutaneous fat, but also markedly reduced by ISO- or NE-pretreatment. These results showed that short-term treatment of three subtypes of βAR by each agonist induces a rapid reduction in the lipolytic response to βAR stimulation. This suggests some common mechanism for the rapid desensitization of βAR-agonist-induced lipolysis, in contrast with previous reports on the characteristics of βAR subtypes. In addition, the regional difference of adipose tissue not only in inducing lipolysis but also in rapid desensitization was also apparent.     

Dynamic control of the Q factor in a photonic crystal nanocavity

High-quality (Q) factor photonic-crystal nanocavities are currently the focus of much interest because they can strongly confine photons in a tiny space. Nanocavities with ultrahigh Q factors of up to 2,000,000 and modal volumes of a cubic wavelength have been realized. If the Q factor could be dynamically controlled within the lifetime of a photon, significant advances would be expected in areas of physics and engineering such as the slowing and/or stopping of light and quantum-information processing. For these applications, the transfer, storage and exchange of photons in nanocavity systems on such a timescale are highly desirable. Here, we present the first demonstration of dynamic control of the Q factor, by constructing a system composed of a nanocavity, a waveguide with nonlinear optical response and a photonic-crystal hetero-interface mirror. The Q factor of the nanocavity was successfully changed from approximately 3,000 to approximately 12,000 within picoseconds.