bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of zeolitization on the volume-change behaviour of kaolinitic soils
Authors: Sivapullaiah P V , Manju M
Published: October 2006

An attempt has been made to study the effect of zeolite formation on the volume-change behaviour of kaolinitic soil. This is studied in terms of two criteria, namely concentration and period of interaction. Conventional consolidation tests have been carried out to determine the extent of change in swell and compressibility of kaolinitic soils remoulded with water and inundated with an alkali solution. It was observed that abnormal swell occurs during unloading when specimens were inundated with a 4N alkali solution. While allowing a longer interaction period at 6.25 kPa, it was found that swelling in kaolinitic soils is induced after time lags of 30 and 15 days on inundation with 1N and 4N alkali solutions, respectively. Equilibrium is reached after 50–70 days in kaolinitic soils, however, and loading was undertaken later. A 16% swelling was observed in kaolinitic soils when inundated with a 4N alkali solution, indicating that zeolitization of kaolinite results in swelling at the seating load provided the period of interaction is sufficient. X-ray diffraction studies confirm the formation of zeolite.Key words: alkali, consolidation, kaolinite, swelling, X-ray diffraction, zeolite.
Evaluation of relative density profiles of sand fill at a reclaimed site
Authors: Chang Ming-Fang , Yu Gu , Na Yung-Mook , Choa Victor
Published: October 2006

The determination of relative density is an important part of site characterization for reclaimed sand fill. In practice, a direct determination of the relative density profile is not always possible, and very often one has to resort to indirect methods using in situ tests, such as the cone penetration test. The usefulness of the indirect method is strongly affected by the validity of available correlations. This investigation compares relative density profiles of reclaimed sand fill created from a marine sand by two distinctively different placement methods at the Changi East reclamation site in Singapore as obtained using both the direct and indirect methods. For reclaimed fill, the relative density profile is found to be predominantly influenced by the method of sand placement, although the basic characteristics of the sand also have an effect. Existing correlations developed in calibration chamber tests for indirect evaluation of relative density from the cone resistance in silicate sand are found to provide a slight underestimate of the relative density in direct-dumped fill in Changi, mainly because of the high compressibility of the marine sand. On the other hand, inadequate consideration of overconsolidation and variation in particle size from the specific placement process have led to an overestimate of the relative density in hydraulically placed sand fill in Changi using similarly derived correlations.Key words: in situ density, relative density, sand, land reclamation, cone penetration test, sand placement.
Incorporating set-up into reliability-based design of driven piles in clay
Authors: Yang Luo , Liang Robert
Published: October 2006

A statistical database is developed to describe the increase in pile axial capacity with time, known as set-up, when piles are driven into clay. Based on the collected pile testing data, pile set-up is significant and continues to develop for a long time after pile installation. The statistical database shows that normal distribution can be used to properly describe the probabilistic characteristics of predicted set-up capacity by the Skov and Denver equation. The main objective of this paper is to incorporate the set-up effect into a reliability-based load and resistance factor design (LRFD) of driven piles. The statistical parameters for set-up effect combined with the previously documented statistics of load and resistance can be systematically accounted for in the framework of reliability-based analysis using the first-order reliability method (FORM). Separate resistance factors are obtained to account for different degrees of uncertainties associated with measured short-term capacity and predicted set-up capacity at various reliability levels. The incorporation of set-up effect in LRFD can improve the prediction of design capacity of driven piles. Thus, pile length or numbers of pile could be reduced and economical design of driven piles could be achieved.Key words: driven piles, set-up, reliability, load and resistance factor design (LRFD), first-order reliability method (FORM).
Diving behaviour of Cuvier’s (Ziphius cavirostris) and Blainville’s (Mesoplodon densirostris) beaked whales in Hawai‘i
Authors: Baird Robin W. , Webster Daniel L. , McSweeney Daniel J. , Ligon Allan D. , Schorr Gregory S. , Barlow Jay
Published: October 2006

Beaked whales (family Ziphiidae) are thought to be among the longest and deepest diving mammals, and some species appear to be prone to mass-strand in response to high-intensity sonar. We studied diving behaviour of Cuvier’s ( Ziphius cavirostris G. Cuvier, 1823) and Blainville’s ( Mesoplodon densirostris (Blainville, 1817)) beaked whales in Hawaiian waters using suction-cup-attached time–depth recorders. Six whales, two Cuvier’s and four Blainville’s, were tagged and 41 h of dive data were collected. While Cuvier’s beaked whales were found in significantly deeper water depths (median depth = 2079 m) than Blainville’s beaked whales (median depth = 922 m), several aspects of diving were similar between the two species: (i) both regularly dove for 48–68 min to depths greater than 800 m (maximum 1408 m for Blainville’s and 1450 m for Cuvier’s); (ii) ascent rates for long/deep dives were substantially slower than descent rates, while for shorter dives there were no consistent differences; and (iii) both spent prolonged periods of time (66–155 min) in the upper 50 m of the water column. Based on time intervals between dives for the Cuvier’s beaked whales, such long dives were likely aerobic, but both species appeared to prepare for long dives by spending extended periods of time near the surface.
Habitat use and behaviour of Greater Snow Geese during movements from nesting to brood-rearing areas
Authors: Mainguy J. , Gauthier G. , Giroux J.-F. , Duclos I.
Published: October 2006

Many precocial birds make long-distance movements with their young after hatch to reach the best foraging sites. On Bylot Island, Nunavut, a large number of Greater Snow Goose ( Chen caerulescens atlantica L., 1758) families move 30 km from the main nesting colony (MNC) to reach the main brood-rearing area (MBR) soon after hatch. Geese moving from the MNC to the MBR generally rear lighter and smaller goslings than geese that avoid this movement by both nesting and rearing their brood at the MBR. In this study, we tested the hypotheses that use of low-quality habitats and an increase in the time spent walking at the expense of foraging during movements could explain the reduced growth of goslings in those families. We conducted visual observations to compare habitat use and selection as well as behaviour of geese during brood movements from the MNC to the MBR (i.e., at a transit area) with those of families that had already settled at the MBR. We also conducted aerial tracking to monitor habitat use of 16 radio-marked females during and after brood movements. Streams, wet polygons, and lakes, considered high-quality habitats in terms of feeding opportunities and predator refuges, were preferred, while upland, a low-quality habitat, was avoided at both the transit area and the MBR. However, broods were found in the upland habitat more often during movements than once settled on a rearing site. The behaviour of unmarked geese at the transit site did not differ from that of geese at the MBR. We suggest that reduced food intake in low-quality habitats during movements, but not the increase in time spent walking, may explain the reduction in growth observed at fledging in goslings moving from the MNC to the MBR.
Effects of Antenna Size and Configurations in Large-Area RF Plasma Production with Internal Low-Inductance Antenna Units
Authors: Deguchi Hiroshige , Yoneda Hitoshi , Kato Kenji , Kubota Kiyoshi , Hayashi Tsukasa , Ogata Kiyoshi , Ebe Akinori , Takenaka Kosuke , Setsuhara Yuichi
Published: October 2006

Recent trends of liquid crystal display (LCD) fabrication toward a significant enlargement of glass substrates require large-area plasma sources with a scale length exceeding 1 m. To meet this requirement, large-area plasma sources with internal low-inductance antenna (LIA) units have been developed for uniform processes, in which design principles for selecting antenna size and configurations in the multiple installation of the LIA units are established. In this study, the effects of antenna size were examined in terms of plasma production characteristics indicating small increase in plasma density with a decrease in antenna size (or antenna impedance). Furthermore, plasma density distributions with the LIA units were investigated to understand the nature of plasma diffusion, which can be utilized for designing plasma profiles with multiple LIA units. First, it was shown that the plasma density distributions followed exponential decay as a function of distance from the antenna. Secondly, the measured plasma density profiles with multiple LIA units were shown to agree well with those obtained by superposing those described by exponential functions, which can be utilized for prediction.
Spatial Structure of Waves and Plasma Uniformity in Planar Microwave Discharges
Authors: Yasaka Yasuyoshi , Sakae Atsushi , Sugimoto Naoki , Takeno Hiromasa , Hojo Hitoshi
Published: October 2006

The spatial structure of waves and plasma uniformity in microwave discharges using a multi-slotted planar antenna are investigated experimentally and by calculation. The wave field amplitude and phase are measured in the axial and azimuthal directions, and are compared with three-dimensional finite-difference time-domain calculation result. The wave mode in the plasma does not change with various densities, and, as a consequence, spatially uniform plasmas are obtained for a wide range of parameters being free from abrupt changes associated with surface wave eigenmodes.
Temporal Variations in Densities of Y, Ba, and Cu Atoms in Magnetron Sputtering Plasmas with YBaCuO Target
Authors: Gao Junsi , Sasaki Koichi
Published: October 2006

In this study, we used optical emission spectroscopy (OES) for examining the temporal variations in the densities of Y, Ba, and Cu atoms sputtered from a YBaCuO target in a magnetron plasma source. It was found that the densities of Y and Cu changed with the discharge period. In a low-pressure, low-power discharge, the temporal variations in the Y and Cu densities were small, whereas they became significant at a high pressure and a high power. Ten minutes after the initiation of the discharge, Y density decreased to 8% of the initial value at an rf power of 70 W and a gas pressure of 300 mTorr. On the other hand, the optical emission intensities from Ar and Ba were roughly constant during the same discharge period. The roughly constant Ar intensity indicates that electron density and electron temperature were almost constant. The discovery of temporal variations in the Y and Cu densities is important for optimizing the discharge parameters for the deposition of high-quality, high-critical-temperature (high-T
c) superconductor films.
Particle Simulation Study of Transition of Spatial Structure in a Plane-Parallel Hollow Cathode Discharge
Authors: Takahashi Toshiki , Goto Makoto , Kondoh Yoshiomi , Sheng Min , Mukaiyama Takeshi , Okada Tomio
Published: October 2006

A self-consistent Monte Carlo particle simulation is carried out to study a transition process of macroscopic spatial structure in a plane-parallel hollow cathode discharge filled with argon. The fine subslab technique and the weight probability method are introduced here. The photoelectric emission is considered. The simulation results show that the luminous structure of the discharge is rapidly changed after a step-increase in applied voltage, and eventually the discharge plasma seems to be sustained dominantly by secondary electrons (i.e., the γ effect) as judged from the potential profile. In the non-equilibrium transition phase, the electron energy distribution is found to consist of two components that are thermal electrons and the high-energy tail electrons.
Analysis of a Capacitively Coupled Dual-Frequency CF4Discharge
Authors: Donkó Z. , Petrović Z. Lj.
Published: October 2006

We present particle-in-cell simulations of capacitively-coupled CF4RF discharges. For establishing the discharge plasma high frequency sources of either 13.56 or 100 MHz are used, while a low frequency 0.7–1.0 MHz source is applied for biasing. The simulation results demonstrate that an efficient decoupling between the plasma and the biasing sources can be achieved by optimizing the choice of frequencies. The decoupling is observed by a small effect of varying of the biasing voltages of the RF sources on properties of the bulk of the plasma and the flux of the CF3+ions hitting the electrodes, while the mean energy of ions increases with the biasing voltage. The 100 MHz/1 MHz case allows setting of these ion properties in an especially wide range. For high values of the low-(biasing) frequency RF voltage a small flux of energetic negative ions is also observed at the electrodes.
Numerical Calculation of Implanted Nitrogen Diffusion in SUS304 during Plasma-Based Ion Implantation
Authors: Akamatsu Hiroshi , Hattori Hiroyuki
Published: October 2006

Two-dimensional temperature rising in an austenitic stainless steel SUS304 trench object with plasma-based ion implantation (PBII) was numerically simulated, where the thermal input on the surface of the trench structure was derived from the calculation of plasma sheath evolution. The difference in temperature distribution was a few Kelvin although the convex corner of the trench had a larger thermal flux than the concave corner. Using the calculated temporal evolution of object temperature, we numerically studied the diffusion of implanted nitrogen ions in the SUS304 trench surface heated by PBII. In addition, the formation of the expanded austenitic phase γ'N-Fe, which can enhance the hardness of the material, is discussed on the basis of the calculated depth profile of the implanted nitrogen.
Measurements of Electron Collision Cross Sections of Relevance to Plasma and Gas Discharge Physics
Authors: Brunger Michael J. , Cho Hyuck , Tanaka Hiroshi , Buckman Stephen J.
Published: October 2006

Recent advances in the measurement of electron collisions with atoms and molecules are discussed and illustrated through their application to a range of targets of relevance to plasma and discharge technologies. Techniques that are discussed include, laser cooling and trapping, time-of flight spectroscopy, large angle scattering, and conventional energy loss spectroscopy. Their application to targets such as metastable helium, chloro- and flouro-carbons, SF6and H2O are presented. Future studies involving molecular radical species are also discussed.
Plasma Diagnostics and Thrust Performance Analysis of a Microwave-Excited Microplasma Thruster
Authors: Takao Yoshinori , Ono Kouichi , Takahashi Kazuo , Eriguchi Koji
Published: October 2006

A microwave-excited microplasma source for a miniature electrothermal thruster has been investigated by optical emission spectroscopy and an electrostatic probe. The microplasma source is made of a dielectric tube 10 mm long and 1.5 mm in inner diameter, producing high temperature Ar plasmas in the pressure range from 5 to 40 kPa. Plasma diagnostics showed that higher microwave frequencies and dielectric constants resulted in desirable plasma characteristics: electron densities of 1017–1019 m-3 and rotational temperatures of 700–1800 K at microwave powers below 10 W. Moreover, the temperature increased toward the exit of the plasma chamber where a micronozzle is equipped. Numerical analysis of thrust performance based on the plasma diagnostics indicated that smaller throat diameters of the micronozzle produced better thrust performances: thrusts of 0.98–1.2 mN and specific impulses of 67–81 s.
Polishing Characteristics of Silicon Carbide by Plasma Chemical Vaporization Machining
Authors: Sano Yasuhisa , Watanabe Masayo , Yamamura Kazuya , Yamauchi Kazuto , Ishida Takeshi , Arima Kenta , Kubota Akihisa , Mori Yuzo
Published: October 2006

Silicon carbide (SiC) is expected to be a promising semiconductor material for high-temperature, high-frequency, high-power and energy-saving applications. However, it is so hard and so chemically stable that there is no efficient method of machining it without causing damage to the machined surface. Plasma chemical vaporization machining (PCVM) is a gas-phase chemical etching method in which reactive species generated in atmospheric-pressure plasma are used. PCVM has a high removal rate equivalent to those of conventional machining methods such as grinding and lapping, because the radical density in atmospheric-pressure plasma is much higher than that in normal low-pressure plasma. In this paper, the polishing characteristics of silicon carbide by PCVM are described. As a result, a high machining rate (approximately 0.18 mm/min) and a very smooth surface (below 2 nm peak-to-valley in a 500 nm square area) are achieved.
Low-Hydrogen-Content Silicon Nitride Deposited at Room Temperature by Inductively Coupled Plasma Deposition
Authors: Zhou Haiping , Elgaid Khaled , Wilkinson Chris , Thayne Iain
Published: October 2006

A novel room-temperature inductively coupled plasma chemical vapour deposition (ICP–CVD) technique has been developed, which yielded high-quality silicon nitride (SiN) films with a hydrogen content of less than 3 at. %. The chemical composition and bonding of the films were analysed by energy dispersive X-ray (EDX) analysis, secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The film optical indexes measured by ellipsometry were well correlated with film composition. Very little plasma-induced damage was observed on Van de Pauw samples of GaAs-based high-electron-mobility transistor (HEMT) layer structures grown by molecular beam epitaxy (MBE). Breakdown electric field >4×106 V cm-1 was observed for an ultrathin 5 nm room-temperature-grown ICP–CVD SiN film embedded in a metal-insulator-metal (MIM) capacitor structure. This technique has been successfully incorporated into the III–V MMIC process flow to provide significant flexibility towards realising array-based MMICs.
Corrosion Resistance of High Hardness TiN Coatings Prepared by Gas Tunnel Type Plasma Reactive Spraying
Authors: Kobayashi Akira , Jiang Wei
Published: October 2006

Thick titanium nitride coatings, which have high hardness, were obtained by gas tunnel type plasma reactive spraying. In this study, the corrosion behavior of the thick TiN coatings was investigated using the electrochemical polarization measurement in 1 M hydrochloric (HCl) solution at room temperature of 295 K. The polarization curve of stainless steel (SUS304) was also measured in order to clarify the effect of corrosion resistance of TiN coatings on the substrates as protective layer. The results showed that the TiN coating could protect the substrate surface from corrosion. It also revealed that the corrosion resistance of TiN coatings was improved as the thickness of TiN coatings was increased.
Transparent Conductive Thin Film for Top Emitting Organic Light Emitting Diodes by Sputtering Method
Authors: Keum Min-Jong , Kim Kyung-Hwan
Published: October 2006

The indium tin oxide (ITO) cathode electrode of top emitting organic light emitting diodes (TOLEDs) was deposited by facing targets sputtering (FTS) method which can deposit thin films with low substrate damage. And it also use a plasma-free sputtering method in which substrate is located apart from plasma. So the temperature increase of substrate due to the bombardment of high-energy particles can be restrained. The ITO thin film which is a transparent electrode was deposited on the cell (Mg:Ag/LiF/EML/HTL/ITO) using two magnetic field such as concentrated magnetic field type and distributed magnetic field type, respectively. Also, the ITO thin films were deposited by sputtering current at working gas (Ar:O2 mixture gas) pressure 1 mTorr. Electrical and optical properties of ITO thin films which deposited on amorphous glass were measured and current–voltage (I–V) characteristics of ITO thin film on the cell were measured. In the results, the leakage-current density of ITO/cell prepared at concentrated magnetic filed type and distribution magnetic filed type showed about 1×10-3 mA/cm2 at -6 V and 1×10-5 mA/cm2 at -6 V, respectively.
Control the Shape of Buckling Micromachined Beam using Plasma Chemistry Bonding Technology
Authors: Su Wang Shen , Lee Sheng Ta , Lin Cheng Yu , Yip Ming Chuen , Tsai Ming Shih , Fang Weileun
Published: October 2006

In this study, we report a novel method for controlling the shape of a micromachined bridge (clamped-clamped beam) by plasma surface modification. In short, the microbridge can be tuned to either buckle upward or downward using plasma treatment. To demonstrate the feasibility of this approach, NH3 plasma treatments were employed to control the direction of buckling amplitude for a SiO2 microbridge. Furthermore, the shape of a buckling microbridge can also be adjusted by the same technique. The buckling profiles predicted by finite element analysis are in agreement with those determined from the measurement.
Low-Temperature Crystallization of Amorphous Silicon by Atmospheric-Pressure Plasma Treatment in H2/He or H2/Ar Mixture
Authors: Ohmi Hiromasa , Kakiuchi Hiroaki , Nishijima Kenichi , Watanabe Heiji , Yasutake Kiyoshi
Published: October 2006

To crystallize amorphous silicon (a-Si) films at temperatures less than 600 °C, we propose an atmospheric pressure plasma (APP) treatment method using a H2/He or H2/Ar mixture. An atmospheric-pressure stable-glow plasma was generated using a 150 MHz very high frequency power supply. After APP treatment, the Si films were characterized by reflection high-energy electron diffraction analysis, Fourier-transform infrared spectroscopy and scanning electron microscopy. In addition, optical emission spectroscopy (OES) was employed to study the plasma. In the case of treatment with the H2/He plasma, the crystallization of the a-Si films started with in negligible incubation time at a substrate temperature as low as 200 °C, and the resulting Si crystallites showed anisotropic morphology. It was found that a-Si layers still existed under the crystallized layers. This result suggests that crystallization of a-Si by APP was predominated by chemical interactions between atomic hydrogen in the plasma and the treated surface. However, in the case of treatment with the H2/Ar plasma, Si crystallites of the treated film did not show anisotropic morphology, and film peeling was partly observed in the treated area. Additionally, from the OES, emission lines from atomic hydrogen were hardly observed in the H2/Ar plasma. This implies that physical interactions between Ar atoms and the film surface play a significant role in the crystallization of a-Si.
An evaluation of combined geophysical and geotechnical methods to characterize beach thickness
Authors: Gunn D.A. , Pearson S.G. , Chambers J.E. , Nelder L.M. , Lee J.R. , Beamish D. , Busby J.P. , Tinsley R.D. , Tinsley W.H.
Published: October 2006

Beaches provide sediment stores and have an important role in the development of the coastline in response to climate change. Quantification of beach thickness and volume is required to assess coastal sediment transport budgets. Therefore, portable, rapid, non-invasive techniques are required to evaluate thickness where environmental sensitivities exclude invasive methods. Site methods and data are described for a toolbox of electrical, electromagnetic, seismic and mechanical based techniques that were evaluated at a coastal site at Easington, Yorkshire. Geophysical and geotechnical properties are shown to be dependent upon moisture content, porosity and lithology of the beach and the morphology of the beach–platform interface. Thickness interpretation, using an inexpensive geographic information system to integrate data, allowed these controls and relationships to be understood. Guidelines for efficient site practices, based upon this case history including procedures and techniques, are presented using a systematic approach. Field results indicated that a mixed sand and gravel beach is highly variable and cannot be represented in models as a homogeneous layer of variable thickness overlying a bedrock half-space.
Significance of a seepage face on flows to wells in unconfined aquifers
Authors: Rushton K.R.
Published: October 2006

When pumping occurs from a well in an unconfined aquifer, a seepage face develops between the elevation where water table intercepts the well face and the water level in the well. The existence of a seepage face often leads to well yields which are less than values determined by conventional analysis. Using numerical models to represent the two-dimensional flow through an aquifer to a well bore, the distribution of inflows at the well face are determined; flows per unit depth (incremental flows) from the seepage face are normally less than those into the water column. Two case studies are examined; numerical model simulations show that as the pumping rate is increased and the water level in the well falls, incremental flows from the seepage face into the well bore are unchanged although incremental flows into the water column do increase. When pumping ceases from a well with a significant seepage face, rapid recovery of the well water level occurs, this allows estimates to be made of water table elevations at a pumping station; the methodology is illustrated by a field example.
Transporters as Channels
Authors: DeFelice Louis J. , Goswami Tapasree
Published: October 2006

This review investigates some key aspects of transport mechanisms and recent advances in our understanding of this ubiquitous cellular process. The prevailing model of cotransport is the alternating access model, which suggests that large conformational changes in the transporter protein accompany cotransport. This model rests on decades of research and has received substantial support because many transporter characteristics are explained using its premises. New experiments, however, have revealed the existence of channels in transporters, an idea that is in conflict with traditional models. The alternating access model is the subject of previous detailed reviews. Here we concentrate on the relatively recent data that document primarily the channel properties of transporters. In some cases, namely, the observation of single-transporter currents, the evidence is direct. In other cases the evidence—for example, from fluctuation analysis or transporter currents too large to be described as anything other than channel-like—is indirect. Although the existence of channels in transporters is not in doubt, we are far from understanding the significance of this property. In the online Supplemental Material , we review some pertinent aspects of ion channel theory and cotransport physiology to provide background for the channels and transporters presented here. We discuss the existence of channels in transporters, and we speculate on the biological significance of this newly unveiled property of transport proteins.
Early treatment of the pregnant guinea pig with IGFs promotes placental transport and nutrient partitioning near term
Authors: Sferruzzi-Perri Amanda N. , Owens Julie A. , Standen Prue , Taylor Robyn L. , Heinemann Gary K. , Robinson Jeffrey S. , Roberts Claire T.
Published: October 2006

Appropriate partitioning of nutrients between the mother and conceptus is a major determinant of pregnancy success, with placental transfer playing a key role. Insulin-like growth factors (IGFs) increase in the maternal circulation during early pregnancy and are predictive of fetal and placental growth. We have previously shown in the guinea pig that increasing maternal IGF abundance in early to midpregnancy enhances fetal growth and viability near term. We now show that this treatment promotes placental transport to the fetus, fetal substrate utilization, and nutrient partitioning near term. Pregnant guinea pigs were infused with IGF-I, IGF-II (both 1 mg·kg−1·day−1) or vehicle subcutaneously from days 20–38 of pregnancy (term = 69 days). Tissue uptake and placental transfer of the nonmetabolizable radio analogs [3H]methyl-d-glucose (MG) and [14C]aminoisobutyric acid (AIB) in vivo was measured on day 62. Early pregnancy exposure to elevated maternal IGF-I increased placental MG uptake by >70% ( P = 0.004), whereas each IGF increased fetal plasma MG concentrations by 40–50% ( P < 0.012). Both IGFs increased fetal tissue MG uptake ( P < 0.048), whereas IGF-I also increased AIB uptake by visceral organs ( P = 0.046). In the mother, earlier exposure to either IGF increased AIB uptake by visceral organs ( P < 0.014), whereas IGF-I also enhanced uptake of AIB by muscle ( P = 0.044) and MG uptake by visceral organs ( P = 0.016) and muscle ( P = 0.046). In conclusion, exogenous maternal IGFs in early pregnancy sustainedly increase maternal substrate utilization, placental transport of MG to the fetus, and fetal utilization of substrates near term. This was consistent with the previously observed increase in fetal growth and survival following IGF treatment.
Mechanism of insulin-stimulated clearance of plasma nonesterified fatty acids in humans
Authors: Carpentier André C. , Frisch Frédérique , Brassard Pascal , Lavoie François , Bourbonnais Annie , Cyr Denis , Giguère Robert , Baillargeon Jean-Patrice
Published: October 2006

Insulin increases plasma nonesterified fatty acid (NEFA) clearance in humans, but whether this is independent of change in plasma NEFA appearance is currently unknown. Nine nondiabetic men (age: 28 ± 3 yr, body mass index: 27.2 ± 1.7 kg/m2) underwent euglycemic clamps to maintain low (LINS) vs. high (HINS) physiological insulin levels for 6 h. An intravenous infusion of heparin + Intralipid (HI) was performed during 4 of the 6 h of the clamps (in the last 4 h at LINS and in the first 4 h at HINS), whereas saline infusion (SAL) was administered in the remaining 2 h to modulate plasma NEFA levels independently of plasma insulin levels. Four experimental conditions were obtained in each individual: LINS with saline (LINS/SAL) and with HI infusion (LINS/HI) and HINS with saline (HINS/SAL) and with HI infusion (HINS/HI). Plasma palmitate appearance during HINS/SAL was lower than during the three other experimental conditions ( P < 0.05). In contrast, plasma linoleate appearance, as expected, was increased by HI independently of insulin level ( P < 0.02). Plasma palmitate clearance during HINS/SAL was higher than LINS/SAL and LINS/HI ( P < 0.008), and this increase was blunted during HINS/HI. We observed a linear decrease in plasma palmitate clearance with increasing plasma NEFA appearance independent of insulin levels. Plasma NEFA levels increased exponentially with increase in plasma NEFA appearance. We conclude that insulin stimulates plasma NEFA clearance by reducing the endogenous appearance rate of NEFA. The relationship between plasma NEFA level and appearance rate is nonlinear.
Calcification of human vascular smooth muscle cells: associations with osteoprotegerin expression and acceleration by high-dose insulin
Authors: Olesen Ping , Nguyen Kirsten , Wogensen Lise , Ledet Thomas , Rasmussen Lars Melholt
Published: October 2006

Arterial medial calcifications occur often in diabetic individuals as part of the diabetic macroangiopathy. The pathogenesis is unknown, but the presence of calcifications predicts risk of cardiovascular events. We examined the effects of insulin on calcifying smooth muscle cells in vitro and measured the expression of the bone-related molecule osteoprotegerin (OPG). Human vascular smooth muscle cells (VSMCs) were grown from aorta from kidney donors. Induction of calcification was performed with β-glycerophosphate. The influence of insulin (200 μU/ml or 1,000 μU/ml) on calcification was judged by measuring calcium content in the cell layer and by von Kossa staining. OPG was measured in the medium by ELISA. Histochemistry was used for determination of alkaline phosphatase (ALP). Bone sialoprotein (BSP) and OPG mRNA expressions were done by RT-PCR. β-Glycerophosphate was able to induce calcification in human smooth muscle cells from a series of donors after variable time in culture. Decreased OPG amounts were observed from the cells during the accelerated calcification phase. High dose of insulin (1,000 μU/ml) accelerated the calcification, whereas lower concentrations (200 μU/ml) did not. Calcified cells expressed ALP and BSP activity in high levels. In conclusion, high concentration of insulin enhances in vitro-induced calcification in VSMCs. Altered OPG levels during the calcification raise the possibility that OPG may have a potent function in regulating the calcification process or it may represent a consequence of mineralization. Effects of insulin and modulations by OPG on the calcification process in arterial cells may play a role in the development of calcifications as part of the diabetic macroangiopathy.
Insulin regulation of glutathione and contractile phenotype in diabetic rat ventricular myocytes
Authors: Li Shumin , Li Xun , Li Yu-Long , Shao Chun-Hong , Bidasee Keshore R. , Rozanski George J.
Published: October 2006

Cardiovascular complications of diabetes mellitus involve oxidative stress and profound changes in reduced glutathione (GSH), an essential tripeptide that controls many redox-sensitive cell functions. This study examined regulation of GSH by insulin to identify mechanisms controlling cardiac redox state and to define the functional impact of GSH depletion. GSH was measured by fluorescence microscopy in ventricular myocytes isolated from Sprague-Dawley rats made diabetic by streptozotocin, and video and confocal microscopy were used to measure mechanical properties and Ca2+ transients, respectively. Spectrophotometric assays of tissue extracts were also done to measure the activities of enzymes that control GSH levels. Four weeks after injection of streptozotocin, mean GSH concentration ([GSH]) in isolated diabetic rat myocytes was ∼36% less than in control, correlating with decreased activities of two major enzymes regulating GSH levels: glutathione reductase and γ-glutamylcysteine synthetase. Treatment of diabetic rat myocytes with insulin normalized [GSH] after a delay of 3–4 h. A more rapid but transient upregulation of [GSH] occurred in myocytes treated with dichloroacetate, an activator of pyruvate dehydrogenase. Inhibitor experiments indicated that insulin normalized [GSH] via the pentose pathway and γ-glutamylcysteine synthetase, although the basal activity of glucose-6-phosphate dehydrogenase was not different between diabetic and control hearts. Diabetic rat myocytes were characterized by significant mechanical dysfunction that correlated with diminished and prolonged Ca2+ transients. This phenotype was reversed by in vitro treatment with insulin and also by exogenous GSH or N-acetylcysteine, a precursor of GSH. Our data suggest that insulin regulates GSH through pathways involving de novo GSH synthesis and reduction of its oxidized form. It is proposed that a key function of glucose metabolism in heart is to supply reducing equivalents required to maintain adequate GSH levels for the redox control of Ca2+ handling proteins and contraction.
Cardiovascular responses to oxygen inhalation after hemorrhage in anesthetized rats: hyperoxic vasoconstriction
Authors: Atkins James L. , Johnson Ken B. , Pearce Frederick J.
Published: October 2006

Oxygen inhalation is recommended for the initial care of trauma victims. The improved survival seen in early hemorrhage is normally associated with an increase in blood pressure. Although clinical use of oxygen can occur late after hemorrhage, the effects of late administration have not been specifically examined. Anesthetized rats were studied using an isobaric hemorrhage model with target pressures of either 70 or 40 mmHg. At various times after hemorrhage, the feedback control of the blood pressure was stopped and the inspired gas was changed from room air to 100% oxygen. The results show that shortly after hemorrhage to 70 mmHg, oxygen inhalation results in an increase in mean arterial blood pressure of 60 ± 3 mmHg, which is associated with a large increase in total peripheral resistance from 0.89 ± 0.05 to 1.25 ± 0.1 peripheral resistance units. The blood pressure response is essentially unchanged with time, and it is not altered by a 10-min exposure to NG-nitro-l-arginine methyl ester. At a target pressure of 40 mmHg, the initial blood pressure response to oxygen is the same, but it gradually decreases as the animal develops a lactic acidosis. We conclude that the therapeutic value of oxygen needs to be separately evaluated for late hemorrhage.
Cardiac hypertrophy in anion exchanger 1-null mutant mice with severe hemolytic anemia
Authors: Alvarez Bernardo V. , Kieller Dawn M. , Quon Anita L. , Robertson Murray , Casey Joseph R.
Published: October 2006

Anion exchanger 1 (AE1; SLC4A1), the plasma membrane Cl−/HCO3−exchanger of erythrocytes, is also expressed in heart. The aim of this study was to assess the role of AE1 in heart function through study of AE1-null (AE1−/−) mice, which manifest severe hemolytic anemia resulting from erythrocyte fragility. Heart weight-to-body weight ratios were significantly higher in the AE1−/−mice than in wild-type (AE1+/+) littermates at both 1–3 days postnatal (3.01 ± 0.38 vs. 1.45 ± 0.04) and at 7 days postnatal (9.45 ± 0.53 vs. 4.13 ± 0.41), indicating that loss of AE1 led to cardiac hypertrophy. Heterozygous (AE1+/−) mice had no signs of cardiac hypertrophy. Morphology of the adult AE1−/−mutant heart revealed an increased left ventricular mass, accompanied by increased collagen deposition and fibrosis. M-mode echocardiography revealed dysfunction of the AE1−/−hearts, including dilated left ventricle end diastole and systole and expanded left ventricular mass compared with AE1+/+hearts. Expression of intracellular pH-regulatory mechanisms in the hypertrophic myocardium of neonate AE1−/−mutant mice was indistinguishable from AE1+/−and AE1+/+mice, as assessed by quantitative real-time RT-PCR. Confocal immunofluorescence revealed that, in normal mouse myocardium, AE1 is sarcolemmal, whereas AE3 and slc26a6 are found both at the sarcolemma and in internal membranes (T tubules and sarcoplasmic reticulum). These results indicate that AE1−/−mice, which suffer from severe hemolytic anemia and spherocytosis, display cardiac hypertrophy and impaired cardiac function, reminiscent of findings in patients with hereditary abnormalities of red blood cells. No essential role for AE1 in heart function was found.
Very low-frequency blood pressure variability depends on voltage-gated L-type Ca2+channels in conscious rats
Authors: Langager Amanda M. , Hammerberg Bailey E. , Rotella Diane L. , Stauss Harald M.
Published: October 2006

The mechanisms generating high- frequency (HF) and low-frequency (LF) blood pressure variability (BPV) are reasonably well understood. However, little is known about the origin of very low-frequency (VLF) BPV. We tested the hypothesis that VLF BPV is generated by L-type Ca2+channel-dependent mechanisms. In conscious rats, arterial blood pressure was recorded during control conditions ( n = 8) and ganglionic blockade ( n = 7) while increasing doses (0.01–5.0 mg·100 μl−1·h−1) of the L-type Ca2+channel blocker nifedipine were infused intravenously. VLF (0.02–0.2 Hz), LF (0.2–0.6 Hz), and HF (0.6–3.0 Hz) BPV were assessed by spectral analysis of systolic blood pressure. During control conditions, nifedipine caused dose-dependent declines in VLF and LF BPV, whereas HF BPV was not affected. At the highest dose of nifedipine, VLF BPV was reduced by 86% compared with baseline, indicating that VLF BPV is largely mediated by L-type Ca2+channel-dependent mechanisms. VLF BPV appeared to be relatively more dependent on L-type Ca2+channels than LF BPV because lower doses of nifedipine were required to significantly reduce VLF BPV than to reduce LF BPV. Ganglionic blockade markedly reduced VLF and LF BPV and abolished the nifedipine-induced dose-dependent declines in VLF and LF BPV, suggesting that VLF and LF BPV require sympathetic activity to be evident. In conclusion, VLF BPV is largely mediated by L-type Ca2+channel-dependent mechanisms. We speculate that VLF BPV is generated by myogenic vascular responses to spontaneously occurring perturbations of blood pressure. Other factors, such as sympathetic nervous system activity, may elicit a permissive effect on VLF BPV by increasing vascular myogenic responsiveness.
Hyposmotic challenge inhibits inward rectifying K+ channels in cerebral arterial smooth muscle cells
Authors: Wu Bin-Nan , Luykenaar Kevin D. , Brayden Joseph E. , Giles Wayne R. , Corteling Randolph L. , Wiehler William B. , Welsh Donald G.
Published: October 2006

This study sought to define whether inward rectifying K+ (KIR) channels were modulated by vasoactive stimuli known to depolarize and constrict intact cerebral arteries. Using pressure myography and patch-clamp electrophysiology, initial experiments revealed a Ba2+-sensitive KIR current in cerebral arterial smooth muscle cells that was active over a physiological range of membrane potentials and whose inhibition led to arterial depolarization and constriction. Real-time PCR, Western blot, and immunohistochemical analyses established the expression of both KIR2.1 and KIR2.2 in cerebral arterial smooth muscle cells. Vasoconstrictor agonists known to depolarize and constrict rat cerebral arteries, including uridine triphosphate, U46619, and 5-HT, had no discernable effect on whole cell KIR activity. Control experiments confirmed that vasoconstrictor agonists could inhibit the voltage-dependent delayed rectifier K+ (KDR) current. In contrast to these observations, a hyposmotic challenge that activates mechanosensitive ion channels elicited a rapid and sustained inhibition of the KIR but not the KDR current. The hyposmotic-induced inhibition of KIR was 1) mimicked by phorbol-12-myristate-13-acetate, a PKC agonist; and 2) inhibited by calphostin C, a PKC inhibitor. These findings suggest that, by modulating PKC, mechanical stimuli can regulate KIR activity and consequently the electrical and mechanical state of intact cerebral arteries. We propose that the mechanoregulation of KIR channels plays a role in the development of myogenic tone.
Pregnancy prevents hypertensive remodeling and decreases myogenic reactivity in posterior cerebral arteries from Dahl salt-sensitive rats: a role in eclampsia?
Authors: Aukes Annet M. , Vitullo Lisa , Zeeman Gerda G. , Cipolla Marilyn J.
Published: October 2006

Previous studies have demonstrated that pregnancy prevents protective hypertension-induced remodeling of cerebral arteries using nitric oxide synthase (NOS) inhibition to raise mean arterial pressure (MAP). In the present study, we investigated whether this effect of pregnancy was specific to NOS inhibition by using the Dahl salt-sensitive (SS) rat as a model of hypertension. Nonpregnant ( n = 16) and late-pregnant ( n = 17) Dahl SS rats were fed either a high-salt diet (8% NaCl) to raise blood pressure or a low-salt diet (<0.7% NaCl). Third-order posterior cerebral arteries were isolated and pressurized in an arteriograph chamber to measure active responses to pressure and passive remodeling. Several vessels from each group were stained for protein gene product 9.5 to determine perivascular nerve density. Blood pressure was elevated in both groups on high salt. The elevated MAP was associated with significantly smaller active and passive diameters ( P < 0.05) and inward remodeling in the nonpregnant hypertensive group only. Whereas no structural changes were observed in the late-pregnant hypertensive animals, both late-pregnant groups had diminished myogenic reactivity ( P < 0.05). Nerve density in both the late-pregnant groups was significantly greater when compared with the nonpregnant groups, suggesting that pregnancy has a trophic influence on perivascular innervation of the posterior cerebral artery. However, hypertension lowered the nerve density in both nonpregnant and late-pregnant animals. It therefore appears that pregnancy has an overall effect to prevent hypertension-induced remodeling regardless of the mode of hypertension. This effect may predispose the brain to autoregulatory breakthrough, hyperperfusion, and eclampsia when MAP is elevated.
Pretreatment of adult bone marrow mesenchymal stem cells with cardiomyogenic growth factors and repair of the chronically infarcted myocardium
Authors: Bartunek Jozef , Croissant Jeffrey D. , Wijns William , Gofflot Stephanie , de Lavareille Aurore , Vanderheyden Marc , Kaluzhny Yulia , Mazouz Naïma , Willemsen Philippe , Penicka Martin , Mathieu Myrielle , Homsy Christian , De Bruyne Bernard , McEntee Kathleen , Lee Ike W. , Heyndrickx Guy R.
Published: October 2006

The in vivo cardiac differentiation and functional effects of unmodified adult bone marrow mesenchymal stem cells (MSCs) after myocardial infarction (MI) is controversial. We postulated that ex vivo pretreatment of autologous MSCs using cardiomyogenic growth factors will lead to cardiomyogenic specification and will result in superior biological and functional effects on cardiac regeneration of chronically infarcted myocardium. We used a chronic dog MI model generated by ligation of the coronary artery ( n = 30). Autologous dog bone marrow MSCs were isolated, culture expanded, and specified into a cardiac lineage by adding growth factors, including basic FGF, IGF-1, and bone morphogenetic protein-2. Dogs underwent cell injection >8 wk after the infarction and were randomized into two groups. Group A dogs ( n = 20) received MSCs specified with growth factors (147 ± 96 × 106), and group B ( n = 10) received unmodified MSCs (168 ± 24 × 106). After the growth factor treatment, MSCs stained positive for the early muscle and cardiac markers desmin, antimyocyte enhancer factor-2, and Nkx2–5. In group A dogs, prespecified MSCs colocalized with troponin I and cardiac myosin. At 12 wk, group A dogs showed a significantly larger increase in regional wall thickening of the infarcted territory (from 22 ± 8 to 32 ± 6% in group A; P < 0.05 vs. baseline and group B, and from 19 ± 7 to 21 ± 7% in group B, respectively) and a decrease in the wall motion score index (from 1.60 ± 0.05 to 1.35 ± 0.03 in group A; P < 0.05 vs. baseline and group B, and from 1.58 ± 0.07 vs. 1.56 ± 0.08 in group B, respectively). The biological ex vivo cardiomyogenic specification of adult MSCs before their transplantation is feasible and appears to improve their in vivo cardiac differentiation as well as the functional recovery in a dog model of the chronically infarcted myocardium.