Effect of addition of saccharides on gelation of aqueous poly(vinyl alcohol) solutions

The properties of poly(vinyl alcohol) (PVA) hydrogels containing saccharides (D ‐xylose, D ‐fructose, D ‐glucose, and maltose) were examined. The effect of the addition of saccharides to PVA hydrogels on their melting temperatures was remarkable when the gels were chilled at 0°C with saccharide contents above 40 g/dL. Particularly, the melting temperature was the highest for PVA hydrogels with glucose and above 73°C at the polymer concentrations above 6 g/dL. Namely, the enthalpy of the thermal dissociation of the junctions of the spatial network ΔH was the highest of the four saccharides (glucose > fructose > maltose > xylose) and 150 kJ/mol for the hydrogels with the glucose content of 60 g/dL. The uniform preservation of saccharides and water in their gels were the highest for the gels with fructose during standing for a long time in air after freeze‐drying. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1298–1303, 1999     

Tailoring Silicon Nitride Surface Chemistry for Facilitating Odontogenic Differentiation of Rat Dental Pulp Cells

Silicon nitride (Si₃N₄) can facilitate bone formation; hence, it is used as a biomaterial in orthopedics. Nevertheless, its usability for dentistry is unexplored. The aim of the present study was to investigate the effect of Si₃N₄ granules for the proliferation and odontogenic differentiation of rat dental pulp cells (rDPCs). Four different types of Si₃N₄ granules were prepared, which underwent different treatments to form pristine as-synthesized Si₃N₄, chemically treated Si₃N₄, thermally treated Si₃N₄, and Si₃N₄ sintered with 3 wt.% yttrium oxide (Y₂O₃). rDPCs were cultured on or around the Si₃N₄ granular beds. Compared with the other three types of Si₃N₄ granules, the sintered Si₃N₄ granules significantly promoted cellular attachment, upregulated the expression of odontogenic marker genes (Dentin Matrix Acidic Phosphoprotein 1 and Dentin Sialophosphoprotein) in the early phase, and enhanced the formation of mineralization nodules. Furthermore, the water contact angle of sintered Si₃N₄ was also greatly increased to 40°. These results suggest that the sintering process for Si₃N₄ with Y₂O₃ positively altered the surface properties of pristine as-synthesized Si₃N₄ granules, thereby facilitating the odontogenic differentiation of rDPCs. Thus, the introduction of a sintering treatment for Si₃N₄ granules is likely to facilitate their use in the clinical application of dentistry.     

Electrochemical and structural influence on BaZr0.8Y0.2O3-δ from manganese,cobalt, and iron oxide additives

Proton conductive BaZr_0.8Y_0.2O_3−δ (BZY20) is a promising electrolyte candidate with perspective application in electrochemical devices, including fuel cells, electrolyzer cells. Mn, Fe, and Co are commonly incorporated into BZY20, to improve the sinterability (CoO), or due to possible inter-diffusion by calcining with cathode materials (eg, La_1−xSr_xMnO_3−δ, La_1−xSr_xCo_1−yFe_yO_3−δ) for cell preparation. This work was performed to investigate the influence of Mn, Fe, and Co on the structural and electrochemical properties of BZY20. As reported in literature, the sinterability of BZY20 was improved by adding CoO. XANES analysis shows that Mn, Fe, and Co are possibly incorporated into the perovskite crystal structure of BZY20, and are partially reduced when the samples were exposed to hydrogen at 600°C for 24 hours. However, through electrochemical analysis, we found that all these three elements decrease both the proton conductivity and transport numbers of proton conduction of BZY20. Therefore, the BZY20 electrolyte should be carefully handled to avoid the incorporation of these transition metal elements, to fabricate the cells with high performance.     

Analysis of packet loss in transport layer over ATM networks

In asynchronous transfer mode (ATM) networks, when cells are lost due to congestion, packets containing the lost cells should be retransmitted in the transport layer, which manages the end-to-end communication. The probability that a packet contains at least one lost cell depends on the packet length. It is thus very likely that the performance of the end-to-end communication is influenced by the packet length. In this paper, we analyse packet loss probability and the achievable maximum throughput when a block of data is divided into packets of fixed size and the lost packets are retransmitted based on the selective repeat automatic repeat request (ARQ). Through this analysis, we examine the effect of packet length and peak cell transmission rate on the performance measures mentioned above. © 1997 John Wiley & Sons, Ltd.     

Melting,regelling, and remelting of poly(vinyl alcohol) hydrogels

The melting behaviors of hydrogels of syndiotacticity-rich poly(vinyl alcohol) (s-PVA), derived from vinyl trifluoroacetate, during heating at various rates of rising temperature were examined. For the hydrogels with the polymer concentrations above 5 g/dL chilled at the temperatures of 0 ∼ 40°C, the melting temperature increased with a decrease in the rate of rising temperature. During rising temperature at lower rates, the phase separation with spinodal decomposition progressed even in gels and the microcrystals, which play an important role as the junction points, propagated to thermally more stable size. The small, broad exothermic peaks during rising temperature of s-PVA hydrogels in DSC thermograms was found at the temperature ranges of 10 ∼ 30 and 45 ∼ 60°C. © 1996 John Wiley & Sons, Inc.     

Robust performance analysis for systems with structured uncertainty

This paper analyses robust performance measures for linear time-invariant systems with norm-bounded time-varying structured uncertainty. We consider two robust performance measures. One is the worst-case peak value of the error signal in response to the disturbance with a known energy. The other is the worst-case energy of the error signal in response to impulsive disturbance. In both cases, the ‘worst case’ is taken over all admissible uncertainties and disturbances. The notion of robust stability is Q-stability, or the scaled H_∞ norm bound. Our main results provide an upper bound for each of the robust performance measures in terms of a positive definite matrix which satisfies a linear matrix inequality (LMI) together with a scaling matrix. Hence, the best bound in this LMI formulation can be computed by convex programming.     

Activity measurement of the constituents in liquid Cu-Mg and Cu-Ca alloys with mass spectrometry

A mass spectrometer has been used to study activities of the constituents in liquid Cu-Mg and Cu-Ca alloys. Activities and heats of mixing have been determined from a series of measurements of the ratios of the ion current intensity of the solution components according to the Belton-Fruehan treatment. The activities in both systems exhibit negative deviation from ideality and tend to approach an ideal behavior at higher temperatures. The terms of RT ln γ _Cu and RT ln γ _Mg show very small temperature dependence within the present experimental range and agree well with the values reported by Garg et al. for the Cu-Mg system. The terms of RT ln γ _Ca and RT ln γ _Cu are independent of temperature and in excellent agreement with the values assessed by Risold et al. for the Cu-Ca system. Relative partial molar enthalpy and integral heat of mixing in the liquid Cu-Mg and Cu-Ca systems were also estimated. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium,” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS.     

Feeding Rhythm-Induced Hypothalamic Agouti-Related Protein Elevation via Glucocorticoids Leads to Insulin Resistance in Skeletal Muscle

Circadian phase shifts in peripheral clocks induced by changes in feeding rhythm often result in insulin resistance. However, whether the hypothalamic control system for energy metabolism is involved in the feeding rhythm-related development of insulin resistance is unknown. Here, we show the physiological significance and mechanism of the involvement of the agouti-related protein (AgRP) in evening feeding-associated alterations in insulin sensitivity. Evening feeding during the active dark period increased hypothalamic AgRP expression and skeletal muscle insulin resistance in mice. Inhibiting AgRP expression by administering an antisense oligo or a glucocorticoid receptor antagonist mitigated these effects. AgRP-producing neuron-specific glucocorticoid receptor-knockout (AgRP-GR-KO) mice had normal skeletal muscle insulin sensitivity even under evening feeding schedules. Hepatic vagotomy enhanced AgRP expression in the hypothalamus even during ad-lib feeding in wild-type mice but not in AgRP-GR-KO mice. The findings of this study indicate that feeding in the late active period may affect hypothalamic AgRP expression via glucocorticoids and induce skeletal muscle insulin resistance.     

Knee Osteoarthritis Progression Is Delayed in Silent Information Regulator 2 Ortholog 1 Knock-in Mice

Overexpression of silent information regulator 2 ortholog 1 (SIRT1) is associated with beneficial roles in aging-related diseases; however, the effects of SIRT1 overexpression on osteoarthritis (OA) progression have not yet been studied. The aim of this study was to investigate OA progression in SIRT1-KI mice using a mouse OA model. OA was induced via destabilization of the medial meniscus using 12-week-old SIRT1-KI and wild type (control) mice. OA progression was evaluated histologically based on the Osteoarthritis Research Society International (OARSI) score at 4, 8, 12, and 16 weeks after surgery. The production of SIRT1, type II collagen, MMP-13, ADAMTS-5, cleaved caspase 3, Poly (ADP-ribose) polymerase (PARP) p85, acetylated NF-κB p65, interleukin 1 beta (IL-1β), and IL-6 was examined via immunostaining. The OARSI scores were significantly lower in SIRT1-KI mice than those in control mice at 8, 12, and 16 weeks after surgery. The proportion of SIRT1 and type II collagen-positive-chondrocytes was significantly higher in SIRT1-KI mice than that in control mice. Moreover, the proportion of MMP-13-, ADAMTS-5-, cleaved caspase 3-, PARP p85-, acetylated NF-κB p65-, IL-1β-, and IL-6-positive chondrocytes was significantly lower in SIRT1-KI mice than that in control mice. The mechanically induced OA progression was delayed in SIRT1-KI mice compared to that in control mice. Therefore, overexpression of SIRT1 may represent a mechanism for delaying OA progression.     

Simulation of primary-slag melting behavior in the cohesive zone of a blast furnace, considering the effect of Al2O3, Fe t O, and basicity in the sinter ore

The alumina content in the iron ore imported to Japan is increasing year by year, and some problems in blast furnace operation, due to the use of the high-alumina-containing sinter, have already been reported. In order to clarify the mechanism of the harmful effect of alumina on the blast furnace operation, the behavior of the primary melt, which is formed in the sinter at the cohesive zone of the blast furnace, has been simulated by dripping slag through an iron or oxide funnel. The effects of basicity, Al₂O₃, and Fe _t O contents in the five slag systems on the dripping temperature and weight of slag remaining on the funnel have been discussed. It was found that the eutectic melt formed in the sinter would play an important role in the dripping behavior of the slag in the blast furnace through the fine poreosity of the reduced iron and ore particles. Al₂O₃ increased the weight of the slag remaining on the funnel, and its effect became very significant in the acidic and low-Fe _t O-containing slag. It was estimated that the increase of the weight of the slag remaining on the funnel by Al₂O₃ in the ore could result in a harmful effect on the permeability resistance and an indirect reduction rate of the sinter in the blast furnace.