bluuebunny/crossref_metadata_2025 huggingface dataset:
A distributed autonomous approach for bulk power system restoration by means of multi‐agent system
Authors: Nagata Takeshi , Tahara Yoshiki , Kunisa Daisuke , Fujita Hideki
Published: April 2008

In recent years, the electric utility industry worldwide has been facing pressure to be deregulated. Also, the risk of blackout in large areas will increase. Actually, it is still vivid in our memory that the northeastern United States and southern Canada suffered the worst blackout in history. Consequently, a method to find the optimal solution rapidly is needed all the more. In this paper, we propose a new multi‐agent method for a bulk power system restoration. In order to demonstrate the capability of the proposed multi‐agent system, it has been applied to a model bulk power system, which consists of three local areas including 12 generating units and 12 loads, and three remote areas with 12 loads. A large number of simulations are carried out on this model network with changing conditions. The simulation results show that the proposed multi‐agent approach is effective and promising. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(1): 69–76, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20485
Development of Y‐branch joint for 275‐kV XLPE and fluid‐filled cable
Authors: Goto Takeshi , Yamashita Makoto , Sakamaki Masatoshi
Published: April 2008

When a new UHV substation is built in an urban region, generally, an existing underground transmission line will be diverted and drawn into the new substation. Compared with the latter construction method, enormous cost reduction of switching facilities and cable construction is expected when applying a Y‐branch joint (YJ) which is able to serve as a three‐way joint. The YJ has already been applied for 154‐kV‐class circuit, but it has not been investigated for 275‐kV‐class circuit. Since both XLPE and oil‐filled cable are presently used in 275‐kV‐class underground cable line, a universal design YJ for both cables has been investigated. The YJ was applied in a compact design which was based on our sophisticated electrical stress control technology for 500‐kV prefabricated‐type joint. Furthermore, the design was based on its prefabricated assembling technology. The YJ was verified as to its electrical and mechanical performance as 275‐kV cable joint by completion of its assembling test and a long‐term electrical test. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 18–24, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20514
An adaptive and reliable system based on interdependence between agents
Authors: Tanimoto Akifumi , Matsumoto Keinosuke , Mori Naoki
Published: April 2008

A multiagent system (MAS) has recently gained public attention as a technique to solve competition and cooperation in distributed systems. However, MAS's vulnerability due to the propagation of failures prevents its application to a large‐scale system. This paper proposes a general composition technique to improve its reliability easily applied to the existent MAS. The proposed system monitors messages between agents to detect undesirable behaviors (failures). Collecting related information, the system generates global information of interdependence between agents and expresses it in a graph. This interdependence graph enables us to detect or predict undesirable behaviors. This paper also shows that the system can optimize performance of MAS and improve adaptively its reliability under complicated and dynamic environment by applying the global information acquired from analysis of the interdependence graph to a replication system. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(1): 62–68, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20517
Cooperative allocation of SVR and SVC for voltage fluctuation in case of connecting distributed generators
Authors: Sugimoto Junjiro , Yokoyama Ryuichi , Fujita Goro , Fukuyama Yoshikazu
Published: April 2008

This paper presents a method for cooperative allocation of step voltage regulators (SVRs) and static var compensators (SVCs) when some distributed generators (DGs) are installed in a distribution system. In the proposed method, reactive tabu search (RTS) with multiple structures and functions is applied. First, the allocations of the SVRs are selected optimally and then the tap positions of the SVRs are optimized by the RTS. Finally, the locations of the SVC are chosen in order to enhance the voltage profile in the distribution network. The proposed method enables us to take account of the installation cost of both SVRs and SVCs as an economic criterion, of the upper and lower voltage limit at each node, and also of the upper limit of line currents as constraints. By applying the proposed method to a practical distribution test system (IEEE 34 Node Test Feeder Model), it is verified that this method is efficient in allocating SVRs and SVCs at minimum cost and in regulating the system voltages within an appropriate range after introducing DGs into the distribution system. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 10–17, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20639
A DC micro‐grid for superhigh‐quality electric power distribution
Authors: Kakigano Hiroaki , Miura Yushi , Ise Toshifumi , Uchida Ryohei
Published: April 2008

The “DC Micro‐grid” is a novel power system using DC distribution in order to provide superhigh‐quality electric power. The DC distribution system is suitable for DC output distributed generation techniques such as photovoltaic and fuel cells, and energy storage forms such as batteries and electric double‐layer capacitors. The power is distributed through a DC distribution line and converted to the required AC or DC voltage by converters placed near loads. The load‐side converters do not need transformers due to the choice of the proper distributed DC voltage. The spread converter scheme helps to assure high‐quality power supply. Even if a short circuit occurs on one load side, it does not affect other loads. In this paper, we propose a DC micro‐grid configuration and converter control methods for generation and energy storage. Computer simulation results demonstrate seamless operation during turn‐on and turn‐off of distributed generation, transients at the times of connecting and disconnecting operation with the bulk power system, and stability against sudden large load variations. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(1): 34–42, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20641
Detection of weak radiation involving generation and progress of water tree
Authors: Kumazawa Takao , Taniguchi Ryouichi
Published: April 2008

It is well known that generation and progress of water trees in XLPE cables are strongly enhanced by inorganic impurities. We have investigated the effect of such impurities in the water treeing process and reported the experimental results as follows: (1) the anomalous increase or decrease in several kinds of inorganic elements was observed in water treed XLPE samples, (2) a distinctive relationship was found for the mass numbers for the elements, and (3) the isotopic content of the elements such as Zn deviated over 6% from the naturally occurring level. These results suggest that some unknown phenomena play a role in the formation of water trees, such as cold fusion or nuclear transmutation in condensed matter. In order to study the relationship between water trees and these phenomena, we attempted to detect neutrons, γ‐rays, or X‐rays accompanying the generation and progress of water trees in XLPE samples. In the experiments, weak and burst‐like radiation, apparently low‐energy γ‐rays or X‐rays, was often detected by BF3 and/or CdZnTe counter. The radiation tended to be detected in the samples with a large number of water trees generated by supplying sufficient amounts of inorganic cations. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 1–9, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20672
A tower model for lightning overvoltage studies based on the result of an FDTD simulation
Authors: Noda Taku
Published: April 2008

This paper describes a method for deriving a transmission tower model for EMTP lightning overvoltage studies from a numerical electromagnetic field simulation result obtained by the FDTD (Finite Difference Time Domain) method. The FDTD simulations carried out in this paper take into account the following items which have been ignored or oversimplified in previously presented simulations: (i) resistivity of the ground soil; (ii) arms, major slant elements, and foundations of the tower; (iii) development speed of the lightning return stroke. For validation purpose a pulse test of a 500‐kV transmission tower is simulated, and a comparison with the measured result shows that the present FDTD simulation gives a sufficiently accurate result. Using this validated FDTD‐based simulation method the insulator‐string voltages of a tower for lightning strokes are calculated, and based on the simulation result the parameter values of the proposed tower model for EMTP studies are determined in a systematic way. Since previously presented models include trial‐and‐error process in the parameter determination, it can be said that the proposed model is more general in this regard. As an illustrative example, the 500‐kV transmission tower mentioned above is modeled, and it is shown that the derived model closely reproduces the FDTD simulation result. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(1): 8–20, 2008; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/eej.20675
Assessment of detachment and sediment transport capacity of runoff by field experiments on a silt loam soil
Authors: Schiettecatte W. , Verbist K. , Gabriels D.
Published: April 2008

The detachment capacity (Dc) and transport capacity (Tc) of overland flow are important variables in the assessment of soil erosion. They determine respectively the lower and upper limit of sediment transport by runoff and therefore control detachment and deposition pro‐cesses. In this study, the detachment and transport capacity of runoff was investigated by rainfall simulations and overland flow experiments on small field plots. On the bare field plots, it was found that Tc was strongly related to total runoff discharge. This was also observed for the plots covered by maize residues, but Tc was less due to the lower runoff velocity. A simple regression equation was derived to estimate Tc for both bare and covered soil. Comparing our observations with Tc equations mentioned in the literature revealed that Tc equations based on laboratory experiments overestimated, on average, our measurements. Although Tc can be assessed more easily in laboratory experiments, the applicability of the results to field conditions remains questionable. Detachment by runoff was also related to total runoff discharge. The Dc values were, however, 4–50 times smaller than the Tc at corresponding high and low runoff discharge. This indicates that detachment by runoff constitutes only part of the transported sediment. Interrill erosion supplies an important additional amount of sediment. In this study, however, only sealed soils were considered. In the case of freshly tilled, loose soils, the Dc of runoff may be larger, resulting in a larger contribution to the total soil loss. Copyright © 2008 John Wiley & Sons, Ltd.
A new sampler for extracting bed material sediment from sand and gravel beds in navigable rivers
Authors: Singer Michael Bliss
Published: April 2008

Grain‐size distributions of bed material sediment in large alluvial rivers are required in various scientific and management applications, but characterizing gravel beds in navigable rivers is hampered by difficulties in sediment extraction. The newly developed and preliminarily tested sampler reported here can extract sediment from a range of riverbeds. The 36 × 23 × 28 cm stainless steel toothed sampler is deployed from and dragged downstream by the weight of a jet boat, and it improves upon previous samplers that are unable to penetrate gravel bed surfaces, have small apertures, and/or cannot retain fine sediment. The presented sampler was used to extract 167 bed material sediment samples of up to 16 kg (dry weight) with an average sample size of ∼6 kg from 67 cross‐sections spanning 160 river kilometres along the Sacramento River. It was also tested at three sites on a subaerial bar to compare surface, subsurface, and sampler distributions. Sampler penetration is ∼5 cm. The device collects individual samples that satisfy the criterion for bed material sediment whereby the largest particle comprises no more than 5% of the total sample mass in gravel and sand beds, except where the degree of surface armouring is large (e.g. armor ratios >> 2) and where more than 10% of bed material sediment is composed of grains larger than 64 mm. When aggregated samples exceed 15 kg, all satisfy the criterion whereby the largest particle comprises no more than 1% of the total sample mass. Samples closely resemble surface size distributions, except where armouring is strong. The sampler should be subject to more rigorous field testing, but many of its current limitations are expected to become negligible with the advent a larger, heavier version of the sampling device. Copyright © 2008 John Wiley & Sons, Ltd.
Adaptive radio resource management in an integrated GPRS/UMTS service network
Authors: Chen Jiann‐Liang , Pan Shih‐Wei , Chen Ming‐Chiao , Huang Yueh‐Min
Published: April 2008

Today's 2G/2.5G systems are designed to achieve 90‐‐95 per cent coverage. Most operators plan to construct 3G base stations on previous 2G/2.5G stations. Consequently, integrated radio resource management (RRM) is comprised of timeslot‐limited and interference‐limited systems. To improve capacity, this study presents a novel resource management based on timeslot utilisation in an integrated general packet radio service/universal mobile telecommunications systems (GPRS/UMTS) service network. Although this approach gives UMTS high priority for sending data services, it also makes voice services available over general system for mobile communications (GSM). Experiments are performed to analyse the system performance, and indicate two observations. (1) The proportion of data sessions that obtain the required bandwidth is 90 per cent, and the average loss ratio is 1 per cent; the average delay time is qualified to support real‐time services, except for data services in GSM/GPRS. (2) For a heavy load, UMTS and GPRS share the traffic loads efficiently, so the increase in the integrated system capacity is 7.14 per cent and 13.33 per cent for the 64 and 128 kbps data services, respectively. Copyright © 2008 John Wiley & Sons, Ltd.
Genetic association tests in the presence of epistasis or gene‐environment interaction
Authors: Wang Kai
Published: April 2008

A genetic variant is very likely to manifest its effect on disease through its main effect as well as through its interaction with other genetic variants or environmental factors. Power to detect genetic variants can be greatly improved by modeling their main effects and their interaction effects through a common set of parameters or “generalized association parameters” (Chatterjee et al. [2006] Am. J. Hum. Genet. 79:1002–1016) because of the reduced number of degrees of freedom. Following this idea, I propose two models that extend the work by Chatterjee and colleagues. Particularly, I consider not only the case of relatively weak interaction effect compared to the main effect but also the case of relatively weak main effect. This latter case is perhaps more relevant to genetic association studies. The proposed methods are invariant to the choice of the allele for scoring genotypes or the choice of the reference genotype score. For each model, the asymptotic distribution of the likelihood ratio statistic is derived. Simulation studies suggest that the proposed methods are more powerful than existing ones under certain circumstances. Genet. Epidemiol. 2008. © 2008 Wiley‐Liss, Inc.
The impact of using different imputation methods for missing quality of life scores on the estimation of the cost‐effectiveness of lung‐volume‐reduction surgery
Authors: Blough David K. , Ramsey Scott , Sullivan Sean D. , Yusen Roger
Published: April 2008

A post hoc analysis of data from a prospective cost‐effectiveness analysis (CEA) conducted alongside a randomized controlled trial (National Emphysema Treatment Trial – NETT) was used to assess the impact of using different imputation methods for missing quality of life data on the estimation of the incremental cost‐effectiveness ratio (ICER). The NETT compared lung‐volume‐reduction surgery plus medical therapy with medical therapy alone in patients with severe chronic obstructive pulmonary disease due to emphysema. One thousand sixty‐six patients were followed for up to 3 years after randomization. The cost per quality‐adjusted life‐year gained was obtained, computing costs from a societal perspective and using the self‐administered Quality of Well Being questionnaire to measure quality of life. Different methods of imputation resulted in substantial differences in ICERs as well as differences in estimates of the uncertainty in the point estimates as reflected in the CEA acceptability curves. Paradoxically, the use of a conservative single imputation method resulted in relatively less uncertainty (anticonservative) about the ICER. Owing to the effects of different imputation methods for missing quality of life data on the estimation of the ICER, we recommend use of a minimum of two imputation methods that always include multiple imputation. Copyright © 2008 John Wiley & Sons, Ltd.
The effects of stochastic demand and expense preference behaviour on public hospital costs and excess capacity
Authors: Lovell C. A. Knox , Rodríguez‐Álvarez Ana , Wall Alan
Published: April 2008

The literature to date on the effect of demand uncertainty on public hospital costs and excess capacity has not taken into account the role of expense preference behaviour. Similarly, the research on expense preference behaviour has not taken demand uncertainty into account. In this paper, we argue that both demand uncertainty and expense preference behaviour may affect public hospital costs and excess capacity and that ignoring either of these effects may lead to biased parameter estimates and misleading inference. To show this, we extend the analysis of Rodríguez‐Álvarez and Lovell (Health Econ. 2004; 13: 157–169) by incorporating demand uncertainty into the technology to account for the hospital activity of providing standby capacity or insurance against the unexpected demand. We find that demand uncertainty in Spanish public hospitals affects hospital production decisions and increases costs. Our results also show that overcapitalization in these hospitals can be explained by hospitals providing insurance demand when faced with demand uncertainty. We also find evidence of expense preference behaviour. We conclude that both stochastic demand and expense preference behaviour should be taken into account when analysing hospital costs and production. Copyright © 2008 John Wiley & Sons, Ltd.
Globally optimal trial design for local decision making
Authors: Eckermann Simon , Willan Andrew R.
Published: April 2008

Value of information methods allows decision makers to identify efficient trial design following a principle of maximizing the expected value to decision makers of information from potential trial designs relative to their expected cost. However, in health technology assessment (HTA) the restrictive assumption has been made that, prospectively, there is only expected value of sample information from research commissioned within jurisdiction. This paper extends the framework for optimal trial design and decision making within jurisdiction to allow for optimal trial design across jurisdictions. This is illustrated in identifying an optimal trial design for decision making across the US, the UK and Australia for early versus late external cephalic version for pregnant women presenting in the breech position. The expected net gain from locally optimal trial designs of US$0.72M is shown to increase to US$1.14M with a globally optimal trial design. In general, the proposed method of globally optimal trial design improves on optimal trial design within jurisdictions by: (i) reflecting the global value of non‐rival information; (ii) allowing optimal allocation of trial sample across jurisdictions; (iii) avoiding market failure associated with free‐rider effects, sub‐optimal spreading of fixed costs and heterogeneity of trial information with multiple trials. Copyright © 2008 John Wiley & Sons, Ltd.
Potential barriers to the application of multi‐factor portfolio analysis in public hospitals: evidence from a pilot study in the Netherlands
Authors: Pavlova Milena , Tsiachristas Apostolos , Vermaeten Gerhard , Groot Wim
Published: April 2008

Portfolio analysis is a business management tool that can assist health care managers to develop new organizational strategies. The application of portfolio analysis to US hospital settings has been frequently reported. In Europe however, the application of this technique has received little attention, especially concerning public hospitals. Therefore, this paper examines the peculiarities of portfolio analysis and its applicability to the strategic management of European public hospitals. The analysis is based on a pilot application of a multi‐factor portfolio analysis in a Dutch university hospital. The nature of portfolio analysis and the steps in a multi‐factor portfolio analysis are reviewed along with the characteristics of the research setting. Based on these data, a multi‐factor portfolio model is developed and operationalized. The portfolio model is applied in a pilot investigation to analyze the market attractiveness and hospital strengths with regard to the provision of three orthopedic services: knee surgery, hip surgery, and arthroscopy. The pilot portfolio analysis is discussed to draw conclusions about potential barriers to the overall adoption of portfolio analysis in the management of a public hospital. Copyright © 2008 John Wiley & Sons, Ltd.
Cancer risk in people infected with human immunodeficiency virus in the United States
Authors: Engels Eric A. , Biggar Robert J. , Hall H. Irene , Cross Helene , Crutchfield Allison , Finch Jack L. , Grigg Rebecca , Hylton Tara , Pawlish Karen S. , McNeel Timothy S. , Goedert James J.
Published: April 2008

Data are limited regarding cancer risk in human immunodeficiency virus (HIV)‐infected persons with modest immunosuppression, before the onset of acquired immunodeficiency syndrome (AIDS). For some cancers, risk may be affected by highly active antiretroviral therapy (HAART) widely available since 1996. We linked HIV/AIDS and cancer registries in Colorado, Florida and New Jersey. Standardized incidence ratios (SIRs) compared cancer risk in HIV‐infected persons (initially AIDS‐free) during the 5‐year period after registration with the general population. Poisson regression was used to compare incidence across subgroups, adjusting for demographic factors. Among 57,350 HIV‐infected persons registered during 1991–2002 (median CD4 count 491 cells/mm3), 871 cancers occurred during follow‐up. Risk was elevated for Kaposi sarcoma (KS, SIR 1,300 [n = 173 cases]), non‐Hodgkin lymphoma (NHL, 7.3 [n = 203]), cervical cancer (2.9 [n = 28]) and several non‐AIDS‐defining malignancies, including Hodgkin lymphoma (5.6 [n = 36]) and cancers of the lung (2.6 [n = 109]) and liver (2.7 [n = 14]). KS and NHL incidence declined over time but nonetheless remained elevated in 1996–2002. Incidence increased in 1996–2002 compared to 1991–1995 for Hodgkin lymphoma (relative risk 2.7, 95%CI 1.0–7.1) and liver cancer (relative risk infinite, one‐sided 95%CI 1.1‐infinity). Non‐AIDS‐defining cancers comprised 31.4% of cancers in 1991–1995, versus 58.0% in 1996–2002. For KS and NHL, risk was inversely related to CD4 count, but these associations attenuated after 1996. We conclude that KS and NHL incidence declined markedly in recent years, likely reflecting HAART‐related improvements in immunity, while incidence of some non‐AIDS‐defining cancers increased. These trends have led to a shift in the spectrum of cancer among HIV‐infected persons. © 2008 Wiley‐Liss, Inc.
Mechanical behavior of human cortical bone in cycles of advancing tensile strain for two age groups
Authors: Nyman Jeffry S. , Roy Anuradha , Reyes Michael J. , Wang Xiaodu
Published: April 2008

The capacity of bone for post‐yield energy dissipation decreases with age. To gain information on the causes of such a change, we examined age‐related changes in the mechanical behavior of human cadaveric bone as a function of progressive deformation. In this study, tensile specimens from tibiae of nine middle aged and eight elderly donors were loaded till failure in an incremental and cyclic (load‐dwell‐unload‐dwell‐reload) scheme. The elastic modulus, maximum stress, permanent strain, stress relaxation, permanent strain energy, elastic release strain energy, and hysteresis energy were determined in each loading cycle at incremental strains. Similar with previous work, the results of the present study also indicated that elderly bone failed at much lower strains compared to middle aged bone. However, no significant differences in the mechanical behavior of bone were observed between the two age groups except for the premature failure of elderly bone. After yielding, the energy dissipation and permanent strain of bone appeared to linearly increase with increasing strain applied, while nonlinear changes occurred in the modulus loss and stress relaxation with increasing strain. Moreover, stress relaxation tended to peak at 1% strain beyond which few elderly bone specimens survived. This study suggests that damaging mechanisms in bone vary with deformation, and aging affects the post‐yield mechanisms, thus giving rise to the age‐related differences in the mechanical properties of bone, especially the capacity of the tissue for energy dissipation. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Paracrine and juxtacrine lymphocyte enhancement of adherent macrophage and foreign body giant cell activation
Authors: Chang David T. , Colton Erica , Anderson James M.
Published: April 2008

Lymphocytes have been shown to be involved in modulating monocyte and macrophage behavior in the foreign body reaction. Lymphocyte effects on biomaterial‐adherent macrophage and foreign body giant cell (FBGC) behavior were further investigated by culturing monocytes alone or together with lymphocytes, either in direct co‐cultures or indirectly in transwells, on a series of polyethylene terephthalate‐based photograft co‐polymerized material surfaces displaying distinct hydrophobic, hydrophilic/neutral, hydrophilic/anionic, and hydrophilic/ cationic chemistries. After periods of 3, 7, and 10 days, cytokine production was quantified by enzyme‐linked immunosorbent assay and normalized to adherent macrophage/FBGC density to yield a measure of adherent macrophage/FBGC activation. Interactions with lymphocytes enhanced adherent macrophage and FBGC production of pro‐inflammatory IL‐1β, TNF‐α, IL‐6, IL‐8, and MIP‐1β on the hydrophobic and hydrophilic/cationic surfaces but had no effect on anti‐inflammatory IL‐10 production indicating lymphocytes promote a pro‐inflammatory response to biomaterials. Lymphocytes also did not significantly influence MMP‐9, TIMP‐1, and TIMP‐2 production. Interactions through indirect (paracrine) signaling showed a significant effect in enhancing adherent macrophage/FBGC activation at early time points whereas interactions via direct (juxtacrine) mechanisms dominated at later time points. Biomaterial surface chemistries differentially affected the observed responses as hydrophilic/neutral and hydrophilic/anionic surfaces, evoked the highest levels of activation relative to the other surfaces but did not facilitate lymphocyte enhancement of adherent macrophage/FBGC activation. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
L929 fibroblast and Saos‐2 osteoblast response to hydroxyapatite‐βTCP/agarose biomaterial
Authors: Alcaide María , Serrano M. Concepcion , Pagani Raffaella , Sánchez‐Salcedo Sandra , Nieto Alejandra , Vallet‐Regí María , Portolés M. Teresa
Published: April 2008

Biphasic calcium phosphate, a mixture of hydroxyapatite (HA) and β‐tricalcium phosphate (β‐TCP), has been successfully used as an excellent bone graft substitute because of the HA capacity for direct interaction with bone and the β‐TCP resorption properties. Agarose has been recently mixtured with ceramics as natural biodegradable binder to increase the biomaterial flexibility facilitating its placement into the bone defect. In this study, the behavior of L929 fibroblasts and Saos‐2 osteoblasts cultured on hydroxyapatite‐βTCP/agarose disks has been evaluated. Both cell types adhere and proliferate on the biomaterial surface maintaining their characteristic morphology. Transitory changes on cell cycle, size, and complexity are observed. The biomaterial induces apoptosis in Saos‐2 osteoblasts but not in fibroblasts. A transitory stimulation of fibroblast mitochondrial activity is observed. This effect remains in osteoblasts after 9 days of culture showing a higher sensitivity of this cell type. However, the intracellular reactive oxygen species content and the lactate dehydrogenase release of Saos‐2 osteoblasts indicate that hydroxyapatite‐βTCP/agarose does not induce oxidative stress in this cell type and confirm the integrity of the osteoblast plasma membrane. These results underline the good biocompatibility of hydroxyapatite‐βTCP/agarose disks and its potential utility for bone substitution and repair. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Chemical and topographical influence of hydroxyapatite and β‐tricalcium phosphate surfaces on human osteoblastic cell behavior
Authors: dos Santos E. A. , Farina M. , Soares G. A. , Anselme K.
Published: April 2008

The objective of this work was to evaluate the relative role of the calcium phosphate surface chemistry and surface topography on human osteoblast behavior. Highly dense phosphate ceramics (single‐phase hydroxyapatite HA and β‐tricalcium phosphates TCP) presenting two distinct nano roughnesses were produced. Some samples were gold‐sputter coated in order to conveniently mask the surface chemical effects (without modification of the original roughness) and to study the isolated effect of surface topography on cellular behavior. Our results indicated that the nanotopography of the studied ceramics had no effect on the cellular adhesion (cell spreading, focal contacts and stress fibers formation). On the contrary, strong topographical effects were verified on cell proliferation and differentiation. Moreover, the phosphate chemistry was responsible for changes in adhesion, proliferation and cell differentiation. On TCP, it was shown that the main influent parameter was surface chemistry, which negatively affected the initial cell adhesion but positively affected the subsequent stage of proliferation and differentiation. On HA, the main influent parameter was surface topography, which increased cell differentiation but lowered proliferation. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
On the assessment of oxidative and microstructural changes after in vivo degradation of historical UHMWPE knee components by means of vibrational spectroscopies and nanoindentation
Authors: Medel Francisco J. , Rimnac Clare M. , Kurtz Steven M.
Published: April 2008

This study reports on the suitability of different experimental techniques to evaluate chemical, microstructural, and mechanical changes associated with in vivo oxidation encountered in historical polyethylene components. To accomplish this aim, eight traceable tibial inserts were analyzed after revision surgery. The knee bearings were γ sterilized in air and implanted for an average of 11.5 years after a shelf life of no longer than 1 year. Characterization of oxidation and transvinylene indexes, crystallinity, amorphous, and intermediate phase fractions, along with hardness and surface modulus, were performed in transverse sections of each bearing using Fourier transform infrared spectroscopy, Raman spectroscopy, and nanoindentation, respectively. Generally, subsurface maxima in the crystallinity, oxidation index, and hardness were observed at a depth of about 1 mm in all of the bearings. The superior surfaces and anterior‐posterior faces of the inserts exhibited significantly higher oxidation and greater crystallinity than the inferior side. These observations suggest that the metallic tray may limit the access of molecular oxygen to the backside of the tibial inserts. We conclude that chemical, physical, and mechanical properties data confirm the occurrence of in vivo degradation in the long‐term implanted knee components following γ irradiation in air. Furthermore, infrared spectroscopy alone appeared to provide excellent insight into the oxidation and crystallization state of the in vivo oxidized polyethylene. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
The modification of PLA and PLGA using electron‐beam radiation
Authors: Leonard Dermot J. , Pick Louise T. , Farrar David F. , Dickson Glenn R. , Orr John F. , Buchanan Fraser J.
Published: April 2008

The degradable polymers polylactide (PLA) and polylactide‐co‐glycolide (PLGA) have found widespread use in modern medical practice. However, their slow degradation rates and tendency to lose strength before mass have caused problems. The aim of this study was to ascertain whether treatment with e‐beam radiation could address these problems. Samples of PLA and PLGA were manufactured and placed in layered stacks, 8.1 mm deep, before exposure to 50 kGy of e‐beam radiation from a 1.5 MeV accelerator. Gel permeation chromatography testing showed that the molecular weight of both materials was depth‐dependent following irradiation, with samples nearest to the treated surface showing a reduced molecular weight. Samples deeper than 5.4 mm were unaffected. Computer modeling of the transmission of a 1.5 MeV e‐beam in these materials corresponded well with these findings. An accelerated mass‐loss study of the treated materials found that the samples nearest the irradiated surface initiated mass loss earlier, and at later stages showed an increased percentage mass loss. It was concluded that e‐beam radiation could modify the degradation of bioabsorbable polymers to potentially improve their performance in medical devices, specifically for improved orthopedic fixation. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Anticoagulant surface modification of titanium via layer‐by‐layer assembly of collagen and sulfated chitosan multilayers
Authors: Li Quan‐Li , Huang Nan , Chen Jialong , Wan Guojiang , Zhao Ansa , Chen Junying , Wang Jin , Yang Ping , Leng Yongxiang
Published: April 2008

Extracellular matrix (ECM)‐like biomimetic surface modification of cardiovascular implants is a promising method for improving hemocompatibility. In the present work, collagen (Col) and sulfated chitosan (SCS) multilayers were coated on pure titanium using a layer‐by‐layer (LBL) self‐assembly technique. The Col‐SCS multilayer growth was carried out by first depositing a single layer of positively charged poly‐L‐lysine (PLL) on the NaOH‐treated titanium substrate (negatively charged surface), followed by alternate deposition of negatively charged SCS and positively charged Col, and terminated by an outermost layer of SCS. Platelet adhesion in vitro, partial activated thromboplastin time (APTT) and prothrombin time (PT) assays were used to evaluate the hemocompatibility of the Col‐SCS multilayer coated titanium. The multilayer processed surfaces displayed reduced platelet adhesion and activation, and prolonged clotting time of APTT and PT compared with untreated titanium. Thus, the approach described here may provide a basis for the preparation of modified titanium surfaces for application in cardiovascular implants. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Distribution of lipid nanocapsules in different cochlear cell populations after round window membrane permeation
Authors: Zou Jing , Saulnier Patrick , Perrier Thomas , Zhang Ya , Manninen Tommi , Toppila Esko , Pyykkö Ilmari
Published: April 2008

Hearing loss is a major public health problem, and its treatment with traditional therapy strategies is often unsuccessful due to limited drug access deep in the temporal bone. Multifunctional nanoparticles that are targeted to specified cell populations, biodegradable, traceable in vivo, and equipped with controlled drug/gene release may resolve this problem. We developed lipid core nanocapsules (LNCs) with sizes below 50 nm. The aim of the present study is to evaluate the ability of the LNCs to pass through the round window membrane and reach inner ear targets. FITC was incorporated as a tag for the LNCs and Nile Red was encapsulated inside the oily core to assess the integrity of the LNCs. The capability of LNCs to pass through the round window membrane and the distribution of the LNCs inside the inner ear were evaluated in rats via confocal microscopy in combination with image analysis using ImageJ. After round window membrane administration, LNCs reached the spiral ganglion cells, nerve fibers, and spiral ligament fibrocytes within 30 min. The paracellular pathway was the main approach for LNC penetration of the round window membrane. LNCs can also reach the vestibule, middle ear mucosa, and the adjacent artery. Nuclear localization was detected in the spiral ganglion, though infrequently. These results suggest that LNCs are potential vectors for drug delivery into the spiral ganglion cells, nerve fibers, hair cells, and spiral ligament. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2008
Injectability of a bone filler system based on hydroxyapatite microspheres and a vehicle with in situ gel‐forming ability
Authors: Oliveira Serafim M. , Barrias Cristina C. , Almeida Isabel F. , Costa Paulo C. , Ferreira Maria R. Pena , Bahia Maria F. , Barbosa Mário A.
Published: April 2008

The aim of this study was to test the injectability of a bone filler system based on the combination of ceramic microspheres with a gel‐like vehicle, for noninvasive surgery. Porous hydroxyapatite microspheres with a uniform size and an average diameter of 535 ± 38 μm were prepared, and their compression strength and friability were tested. The sodium‐alginate solution with a concentration of 7.25% (w/v) was used as the vehicle. To promote its in situ gelation, calcium carbonate and D‐gluconic‐δ‐lactone were added to the solution. Microspheres were mixed with the vehicle at different percentages (20–40 wt %). Gelation times in the range of 8–20 min, were obtained, depending on the formulation. Mixtures of HAp microspheres with alginate solution at 7.25% originating a gel in 11 min present an adequate handling time to perform an injection. Their injectability was evaluated using an injection device commonly employed in vertebroplasty surgical procedures, coupled to a texturometer in compression mode. Using an extrusion rate of 0.1 mm/s, the force required to extrude any of the mixtures tested was lower than 100 N. For an extrusion rate of 1 mm/s mixtures with 40 wt % of microspheres were very difficult to inject. Mixtures with 35 wt % of microspheres presented the best compromise between injectability and compression strength of the gelled system. MicroCT analysis revealed a homogeneous distribution of the microspheres inside the vehicle, as well as full interconnection of the intra‐microspheres spaces. The compression strength for the gelled systems ranged from 80 kPa (gel itself) to 600 kPa (composite with 40 wt % of microspheres). © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2008
Preparation and characterization of interferon‐loaded magnetic biodegradable microspheres
Authors: Zhou Shaobing , Sun Jing , Sun Lin , Dai Yanqin , Liu Liping , Li Xiaohong , Wang Jianxin , Weng Jie , Jia Wenxiang , Zhang Zairong
Published: April 2008

In this work, magnetite (Fe3O4) nanoparticles with an average size 10 nm modified by sodium oleate were prepared by the modified controlled chemical coprecipitation method, which can be well dispersed in water and linked well with protein molecules because of the presence of —COOH on their surface. Then magnetic poly(lactic acid) (PLA) and poly(lactic‐co‐glycolic acid) (PLGA) microspheres containing interferon alpha‐2b (IFN‐a‐2b) were prepared by the modified water‐in‐oil‐in‐water solvent evaporation procedure. X‐ray powder diffraction analysis, particle size analysis, transmission electron microscopy, scanning electron microscopy, and vibrating‐sample magnetometer (VSM) analysis were carried out to examine phase composition, surface and interior morphology, size and size distribution, and magnetic properties of the magnetic microspheres. Also the effects of some important parameters on the magnetic biodegradable microspheres were investigated, such as magnetite dosage in the preparation system, stirring rate of the suspension medium, and concentration of the external aqueous phase. And the antiviral activity of IFN‐a‐2b encapsulated in the magnetic polymeric microspheres was evaluated by the vesicular stomatitis virus (VSV) cytopathicity inhibition assay. The results showed that the properties of IFN‐loaded magnetic PLGA and PLA microspheres were better than the conventional protein‐loaded polymeric microspheres, such as perfect magnetic properties, higher protein encapsulation efficiency, and less effect on the antiviral activity of protein. These indicated that the magnetic PLA and PLGA microspheres containing IFN‐a‐2b exhibited strong potential as targeted‐drug delivery vehicles, which could be rapidly localized to the immunization‐related tissues easily by an external magnetic field. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2008
Cancer chemoprevention and chemotherapy: Dietary polyphenols and signalling pathways
Authors: Ramos Sonia
Published: April 2008

Prevention of cancer through dietary intervention recently has received an increasing interest, and dietary polyphenols have become not only important potential chemopreventive, but also therapeutic, natural agents. Polyphenols have been reported to interfere at the initiation, promotion and progression of cancer. They might lead to the modulation of proteins in diverse pathways and require the integration of different signals for the final chemopreventive or therapeutic effect. Polyphenols have been demonstrated to act on multiple key elements in signal transduction pathways related to cellular proliferation, differentiation, apoptosis, inflammation, angiogenesis and metastasis; however, these molecular mechanisms of action are not completely characterized and many features remain to be elucidated. The aim of this review is to provide insights into the molecular basis of potential chemopreventive and therapeutic activities of dietary polyphenols with emphasis in their ability to control intracellular signalling cascades considered as relevant targets in a cancer preventive approach.
Fate of 14C‐acrylamide in roasted and ground coffee during storage
Authors: Baum Matthias , Böhm Nadine , Görlitz Jessica , Lantz Ingo , Merz Karl Heinz , Ternité Rüdiger , Eisenbrand Gerhard
Published: April 2008

Acrylamide (AA) is formed during heating of carbohydrate rich foods in the course of the Maillard reaction. AA has been classified as probably carcinogenic to humans. Storage experiments with roasted coffee have shown that AA levels decrease depending on storage time and temperature. In the present study the fate of AA lost during storage of roasted and ground (R&G) coffee was studied, using 14C‐labeled AA as radiotracer. Radiolabel was measured in coffee brew, filter residue, and volatiles. In the brew, total 14C‐label decreased during storage of R&G coffee, while activity in the filter residue built up concomitantly. [2,3‐14C]‐AA (14C‐AA) was the only 14C‐related water extractable low molecular compound in the brew detected by radio‐HPLC. No formation of volatile 14C‐AA‐related compounds was detected during storage and coffee brewing. Close to 90% of the radiolabel in the filter residue (spent R&G coffee, spent grounds) remained firmly bound to the matrix, largely resisting extraction by aqueous ammonia, ethyl acetate, chloroform, hexane, and sequential polyenzymatic digest. Furanthiols, which are abundant as aroma components in roasted coffee, have not been found to be involved in the formation of covalent AA adducts and thus do not contribute substantially to the decrease of AA during storage.
Clinical, sonographic, and epidemiologic features of second‐ and early third‐trimester spontaneous antepartum uterine rupture: a cohort study
Authors: Vaknin Zvi , Maymon Ron , Mendlovic Sonia , Barel Oshri , Herman Arie , Sherman Dan
Published: April 2008

Objective

To present prenatal findings and maternal and neonatal outcomes following second‐ and early third‐trimester spontaneous antepartum uterine rupture events in our institute.

Method

Charts of patients with full‐thickness second‐ or early third‐trimester symptomatic uterine ruptures locally treated between 1984 and 2007 were evaluated.

Results

There were seven events involving six women, all requiring emergency laparotomy, and cesarean section (CS). During the study period in our institute, there were 120 636 singleton deliveries (≥22 weeks' gestation), including 5 of our cases, while in 2 cases, the rupture occurred earlier (<22 weeks' gestation). The rupture occurred after ≥ 1 previous CSs in five cases. Six events were associated with abnormal placentation: placenta previa (n = 3), placenta percreta (n = 1), or both (n = 2). Other associated events included short, interpregnancy (IP) interval (n = 3) and past uterine rupture (n = 2). Pregnant women at gestational age ≥ 22 weeks, who had the combination of placenta previa, and previous CS (n = 3), had a higher chance for spontaneous symptomatic antepartum uterine rupture when compared to women with placenta previa without a previous CS (OR 29.3, 95% CI 1.5–569.3, p = 0.007). There were no maternal deaths. Three of the five viable neonates survived.

Conclusions

Spontaneous symptomatic second‐ or early third‐trimester uterine rupture in nonlaboring women is a very rare, obstetric emergency, which is hard to diagnose. Maternal and neonatal outcomes can be optimized by awareness of risk factors, recognition of clinical signs and symptoms, and availability of ultrasound to assist in establishing diagnosis, and enabling prompt surgical intervention. Copyright © 2008 John Wiley & Sons, Ltd.
Review and critical analysis of the morphology of random ionomers across many length scales
Authors: Grady Brian P.
Published: April 2008

This review presents a description of what is known about ionomer morphology. All papers on ionomer morphology are not included in this review; but all relevant questions about ionomer morphology are posed and answered as completely as possible. The review is critical; that is, reasons are given for morphologies that are deemed to be more or less likely. The review is organized along three length scales: sub‐nanometer, nanometer to 10 nm, and greater than 10 nm. Within each length scale, all three phases are considered: crystalline, amorphous, and ionic aggregate. The purity of the three phases, the arrangement of atoms in the three phases, the size and shape of the three phases, and their arrangements in space relative to each other are explored in this review. A model for the shape of aggregates in ionomers that have well‐ordered internal environments is presented. This model proposes that aggregates are fundamentally planar, but will “roll up” into tubes or other related structures in order to reduce the number of atoms at aggregate edges. This model was developed primarily based on the varied morphologies ionomers have shown in electron micrographs, but is consistent with other indirect measurements of ionomer morphology. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.