bluuebunny/crossref_metadata_2025 huggingface dataset:
SOLVING TIME-DEPENDENT EQUATIONS OF SCHRÖDINGER-TYPE USING MAPPED INFINITE ELEMENTS
Authors: DUQUE JAIRO
Published: June 2005

We present a general technique to solve one-dimensional time-dependent Schrödinger-type equations. A mapped infinite elements approach is used to eliminate spurious reflections of outgoing wave packets from the boundaries of the interval of interest. This procedure leads to more precise solutions because the space coordinates are discretized to approximate the solution in the entire physical domain. We show its utility giving numerical results on three typical examples: a bounded short-range potential; the unbounded potential of a particle in a dc field; and a Hamiltonian with an intrinsic time dependence like the Hamiltonian of a charged particle in an ac electromagnetic field.
PERCOLATION PROPERTIES AND UNIVERSALITY CLASS OF A MULTIFRACTAL RANDOM TILING
Authors: PEREIRA M. G. , CORSO G. , LUCENA L. S. , FREITAS J. E.
Published: June 2005

We study percolation as a critical phenomenon on a random multifractal support. The scaling exponent β related to the mass of the infinite cluster and the fractal dimension of the percolating cluster df are quantities that have the same value as the ones from the standard two-dimensional regular lattice percolation. The scaling exponent ν related to the correlation length is sensitive to the local anisotropy and assumes a value different from standard percolation. We compare our results with those obtained from the percolation on a deterministic multifractal support. The analysis of ν indicates that the deterministic multifractal is more anisotropic than the random multifractal. We also analyze connections with correlated percolation problems and discuss some possible applications.
SELF-SIMILARITY IN NONCLASSICAL TRANSMISSION THROUGH A FIBONACCI SEQUENCE OF GAUSSIAN BARRIERS
Authors: MANGA RAO V. S. C. , PRASAD M. D. , GUPTA S. D.
Published: June 2005

We study quantum mechanical scattering by one-dimensional sequence of Gaussian barriers and calculate the transmission through such systems. We illustrate the physical aspects of resonance states and their coupling with the example of two and three barriers. Finally, we consider Fibonacci sequences of such barriers to demonstrate the properties of scaling, multifractality and self-similarity. These results are compared with those of periodic structures. All the calculations are based on the transfer matrix approach resulting from a fine segmentation of each barrier.
SPLITTING AND TRAPPING OF BOSE-CONDENSED GASES IN MULTI-WELLS
Authors: LIU M. , WEN L. H. , SHE L. , CHEN A. X. , XIONG H. W. , ZHAN M. S.
Published: June 2005

For the Bose-condensed gas in a one-dimensional optical lattice, several far-off resonant laser beams are used to split and trap the matter wavepacket after switching off both the magnetic trap and optical lattices. In the presence of two far-off resonant laser beams which are not symmetric about the centre of the matter wavepacket, we propose an experimental scheme to observe the collision between two side peaks after switching off the magnetic trap and optical lattice. We also discuss an experimental scheme to realize a coherent splitting and trapping of the matter wavepacket which has potential application in atom optics.
THE LOSS OF FIDELITY DUE TO QUANTUM LEAKAGE FOR JOSEPHSON CHARGE QUBITS
Authors: LIANG XIAN-TING , XIONG YONG-JIAN
Published: June 2005

In this paper we calculate the loss of fidelity due to quantum leakage for the Josephson charge qubit (JCQ). In this investigation the characteristic values and characteristic states of the Mathieu equation are used. It is shown that for present typical parameters of JCQ, E J /E ch ~ 0.02, the loss of the fidelity per elementary operation is about 10-4 which satisfies DiVincenzo's low decoherence criterion. By appropriately improving the designs of the Josephson junction, namely, decreasing E J /E ch to ~ 0.01, the loss of fidelity per elementary operation can decrease even smaller to 10-5. The first-order nonadiabatic correction is also obtained by using the approach.
STUDY OF ELECTRICAL TRANSPORT AND AC SUSCEPTIBILITY IN LaMn1-xCuxO3
Authors: KAR MANORANJAN , RAVI S.
Published: June 2005

LaMn 1-x Cu x O 3 compounds have been prepared in single phase form for x = 0 to 0.30. X-ray diffraction patterns recorded at room temperature could be mostly refined using Pbnm space group. Paramagnetic-to-ferromagnetic transitions have been observed up to x = 0.30, from ac susceptibility measurements. Metal–insulator transition in the vicinity of ferromagnetic transition temperature has been observed for x = 0.05 and the resistivity data in the metallic region could be explained in terms of electron–electron and electron–magnon scattering mechanisms. Further increase in Cu-doping beyond x = 0.05 leads to systematic decrease in ferromagnetic transition temperature and ultimately ferromagnetism is destroyed for x = 0.40. The resistivity data of all samples except x = 0.05 exhibit semiconducting behaviors and they could be mostly explained using the adiabatic small polaron hopping model.
HIGH-PRESSURE STRUCTURE STUDY OF CuBa2Ca3Cu4O10 + δ SUPERCONDUCTOR
Authors: QIN X. M. , YU Y. , ZHANG G. M. , LI F. Y. , LIU J. , JIN C. Q.
Published: June 2005

In-situ high-pressure energy dispersive X-ray diffraction measurements on CuBa 2- Ca 3 Cu 4 O 10 + δ (Cu-1234) have been performed by using diamond anvil cell (DAC) device with synchrotron radiation. The results suggest that the crystal structure of Cu-1234 superconductor is stable under pressures up to 34 GPa at room temperature. According to the Birch–Murnaghan equation of state, the bulk modulus is obtained to be ~ 150 GPa.
PREPARATION AND MANIPULATION OF MODE-LOCKED TWO-PHOTON STATE
Authors: LU Y. J. , HUANG F. , OU Z. Y.
Published: June 2005

The article describes the quantum properties of mode-locked two-photon state generated through either a Fabry–Perot cavity or a sub-threshold optical parametric oscillator. It is shown that the time correlation function of such a state exhibits a comb-like structure. Different approaches to observe this comb-like feature are thoroughly discussed. The experiment demonstrates several different quantum interference effects with a mode-locked two-photon state. An analysis of the experiment leads to a new control technique of two-photon interference and to a better understanding of time-entangled two-photon state. A novel quantum information coding is predicted if such a state is mixed with a single-mode wide band two-photon state.
THE MAGNETIC AND ELECTRICAL PROPERTIES OF RARE-EARTH Sm3+ SUBSTITUTED Bi1.7Pb0.3Sr2Ca2-xSmxCu3O12 SYSTEM
Authors: EKİCİBİL AHMET , COŞKUN ATILLA , ÖZÇELİK BEKIR , KIYMAÇ KERIM
Published: June 2005

In the present work, the magnetic properties of high-Tc Bi 1.7 Pb 0.3 Sr 2 Ca 2-x Sm x Cu 3 O 12 system (x = 0.03) have been investigated, for different temperatures below Tc. Substitution of Sm 3+ for Ca 2+ is found to change the superconducting properties of the system, despite the weak paramagnetic nature of the Sm 3+ ion. The dc magnetization measurements performed on the compound reveal that the superconducting regions decrease with increasing temperature and magnetic field. The results are explained on the basis of a possible reduction of hole concentration with trivalent rare-earth ion substitution, and also on the basis of the magnetic nature of the substituted Sm 3+ ions.
QUANTUM DIFFUSION ON A DYNAMICALLY DISORDERED AND HARMONICALLY DRIVEN LATTICE WITH STATIC BIAS: DECOHERENCE
Authors: SINGH NAVINDER , KUMAR N.
Published: June 2005

We revisit the problem of quantum diffusion of a particle moving on a lattice with dynamical disorder. Decoherence, essential for the diffusive motion, is introduced via a set of Lindblad operators, known to guarantee per se the positivity, Hermiticity and the trace-class nature of the reduced density matrix, are derived and solved analytically for several transport quantities of interest. For the special Hermitian choice of the Lindblad operators projected onto the lattice sites, we recover several known results, obtained by others, e.g. through the stochastic Liouville equation using phenomenological damping terms for the off-diagonal density-matrix elements. An interesting result that we obtained is for the case of a 1D lattice with static potential bias and a time-harmonic modulation (ac drive) of its transition-matrix element, where the diffusion coefficient shows an oscillatory behavior as function of the drive amplitude and frequency — clearly, a Wannier–Stark ladder signature. The question of dissipation is also briefly discussed.
USING THE EVENT CALCULUS FOR TRACKING THE NORMATIVE STATE OF CONTRACTS
Authors: FARRELL ANDREW D. H. , SERGOT MAREK J. , SALLÉ MATHIAS , BARTOLINI CLAUDIO
Published: June 2005

In this work, we have been principally concerned with the representation of contracts so that their normative state may be tracked in an automated fashion over their deployment lifetime. The normative state of a contract, at a particular time, is the aggregation of instances of normative relations that hold between contract parties at that time, plus the current values of contract variables. The effects of contract events on the normative state of a contract are specified using an XML formalization of the Event Calculus, called ecXML. We use an example mail service agreement from the domain of web services to ground the discussion of our work. We give a characterization of the agreement according to the normative concepts of obligation, power and permission, and show how the ecXML representation may be used to track the state of the agreement, according to a narrative of contract events. We also give a description of a state tracking architecture, and a contract deployment tool, both of which have been implemented in the course of our work.
TRANSFORMING AGREEMENTS INTO CONTRACTS
Authors: HOFFNER YIGAL , FIELD SIMON
Published: June 2005

During the life cycle of a service consumer-provider relationship, agreements are reached in a variety of areas covering technical, service, business and legal issues. Although some of these agreements may be viewed as legally binding, it is unlikely that any of them will constitute a legal contract in the full sense of the word. It is often expedient to gather these agreements and create a legal contract out of them. Automating this process of contract generation can speed up the process and reduce the cost of legal expenses. In fact, the process of automated contract generation can also be useful outside the realm of web services, when agreements are made directly among people.

We propose a way of transforming such agreements into contracts in a dynamic, efficient and speedy manner, using advanced forms of matchmaking technology in a novel way. This complements the other directions in which the agreements are to be used, namely configuration, instantiation, enactment supervision and relationship termination and evaluation.
PRESERVING TRADE SECRETS BETWEEN COMPETITORS IN B2B INTERACTIONS
Authors: MALIK ZAKI , BOUGUETTAYA ATHMAN
Published: June 2005

In this paper, we propose an approach for preserving trade secrets in B2B interactions among competitors. Customer information exchanged during Business-to-Business (B2B) collaborations is usually considered as a business asset not to be freely shared with other businesses. This customer information is in essence a business trade secret. The full automation of B2B interactions is now possible because of the wide deployment of such technologies as Web services. However, these advances also create greater opportunities for businesses in acquiring sensitive customer data from other transacting businesses, thus creating an impediment for potential B2B collaboration between competitors. This calls for techniques to protect disclosure of sensitive data. Our approach leverages psycholinguistic knowledge to perturb data to computationally impede the disclosure of privileged customer information. We present an analytical model and a set of experiments to demonstrate the robustness of the proposed techniques.
APPLYING THE 3C MODEL TO GROUPWARE DEVELOPMENT
Authors: FUKS HUGO , RAPOSO ALBERTO B. , GEROSA MARCO A. , LUCENA CARLOS J. P.
Published: June 2005

This paper introduces an approach based on the 3C (communication, coordination and cooperation) collaboration model to the development of collaborative systems. The 3C model is studied by means of a detailed analysis of each of its three elements, followed by a case study of a learningware application and the methodology of a web-based course, both designed based on this model. Moreover, this paper describes a component-based system architecture following this 3C approach.
The Effects of High-Tech Companies' Strategic Alliance Announcements on the Stock Prices of the Relevant Companies: A Comparative Analysis of Indirect Benefits for Taiwan's High-Tech Industry Versus Other Industries 1998–2002
Authors: Liang Chiung-Ju , Yao Ming-Li , Lin Jung-Chu
Published: June 2005

In recent years, the formation of strategic alliances has become an increasingly common trend among developing countries around the world. In spite of this, the numerous attempts to comprehensively review the research on the correlation between these strategic alliances and stock prices over the years have, by and large, limited their discussion to how the stock price of a corporation responds to its announcement that it is forming a strategic alliance. Only a few studies have, however, discussed the announcement's indirect impact on the stock prices of investing companies that have entered into such strategic alliances. It is for this reason that we conduct an event study and develop an empirical model to measure that indirect impact on the stock prices of investing companies engaging in strategic alliances with Taiwan's high-tech industry from 1998 to 2002, while also discussing the market's different responses in their stock prices according to various industrial types that have been used to classify these investing companies.
Insider Trading Activities Before the Simultaneous Announcements of Earnings and Dividends
Authors: Cheng Louis T. W. , Szeto Ricky W. F. , Leung T. Y.
Published: June 2005

We employ a sample of 3,177 events from Hong Kong industrial firms during the 1993–1999 period to examine insider trading activities around earnings and dividends announcements. By controlling for earnings management, special dividends, and other firm level financial indicators, we find that the presence of insider trading, its trading direction, and its trading intensity are related to the signals of these simultaneous earnings and dividends announcements. Various tests show that our findings are robust regardless of the proxies used for measuring insider trading activities, earnings, and dividend changes.
The Determinants and Implications of Matching Maturities
Authors: Jun Sang-Gyung , Jen Frank C.
Published: June 2005

Though maturity matching is a common practice in real finance, no academic study has been conducted yet on cross-sectional variations in the degree of maturity matching. This study derives hypotheses on the maturity matching and empirically tests them. We show that firms with a higher degree of maturity matching are more likely to stabilize equity values: they have lower stock return volatilities. We also show evidence supporting the existence of an optimal level of maturity matching. Though financially strong firms generally employ a higher degree of maturity matching, the relationship between financial strength and maturity matching is not monotonic.
Trading Patterns and Performance of Trader Types in Taiwan Futures Market
Authors: Lin Chao-Hsien , Hsu Hsinan , Chiang Chwan-Yi
Published: June 2005

By analyzing the behavior and performance of trader types in the Taiwan futures market, we find that the foreign investors, futures dealers and security dealers are positive feedback traders, whereas individuals are contrarians. Evidence shows that the foreign investors and security dealers earn significant profits. We conclude that they are information-based traders. Instead, the individuals and futures traders perform poorly. However, weak evidence reveals that futures dealers are behavioral-based traders. As it is also reported, the cumulative performance demonstrates that foreign investors are the clear winners and individuals are the clear losers in the Taiwan futures market.
The Market Reaction Around Ex-Dates of Stock Splits Before and After Decimalization
Authors: Chou Robin K. , Lee Wan-Chen , Chen Sheng-Syan
Published: June 2005

This paper examines the stock price behavior around the ex-split dates both before and after the decimalization on the New York Stock Exchange (NYSE). We find that the abnormal ex-split day returns decrease and the abnormal trading volume increases in the 1/16th and decimal pricing eras, relative to the 1/8th pricing era. These findings are consistent with the microstructure-based explanations for the ex-day price movements. Our study also supports the hypothesis that short-term traders perform arbitrage activities during the ex-split dates when transaction costs become lower after the tick size is reduced.
SYSTEMATIC CONSERVATION PLANNING IN THE CAPE FLORISTIC REGION AND SUCCULENT KAROO, SOUTH AFRICA: ENABLING SOUND SPATIAL PLANNING AND IMPROVED ENVIRONMENTAL ASSESSMENT
Authors: BROWNLIE SUSIE , DE VILLIERS CHARL , DRIVER AMANDA , JOB NANCY , VON HASE AMREI , MAZE KRISTAL
Published: June 2005

The Cape Floristic Region (CFR) and Succulent Karoo are global biodiversity hotspots. The CFR is one of six plant kingdoms worldwide. The CFR and most of the Succulent Karoo lie within South Africa. South Africa has ratified the Biodiversity Convention, and must accordingly safeguard its biodiversity. Environmental assessment (EA) can help to achieve this end. Environmental legislation in South Africa requires EA for activities at project, not strategic level. However, strategic environmental assessment has been mandatory since 2000 for preparing municipal spatial development frameworks (SDFs). By setting targets for ecosystem conservation and providing thresholds of significance, systematic conservation planning can make a significant contribution to the sound preparation of SDFs, and effective EA at planning and project levels. In South Africa, the integration of systematic conservation planning with spatial planning and EA is recent. Based on examples, the main challenges for the future are identified.
IMPACTS OF REGION-WIDE URBAN DEVELOPMENT ON BIODIVERSITY IN STRATEGIC ENVIRONMENTAL ASSESSMENT
Authors: BALFORS BERIT , MÖRTBERG ULLA , GONTIER MIKAEL , BROKKING PETER
Published: June 2005

In urbanising regions, urban sprawl and infrastructure cause profound alterations of natural habitats. Initial decisions on urban expansion and major infrastructure investments are often made on a strategic level where the long-term development of a region is determined. For these types of decisions a strategic environmental assessment can be prepared. However, the lack of an adequate conceptual and methodological framework can pose a major problem for the prediction of impacts, not least concerning biodiversity. This paper will highlight the need for effective methods for biodiversity analysis at landscape and regional levels, with reference to the long-term urban development of the Stockholm and Mälaren regions. Problems of habitat loss, fragmentation and other impacts related to large-scale urbanisation and infrastructure developments will be addressed. GIS-based methods focusing on predictive ecological modelling will be discussed in a scenario context. The implementation of such methodologies in the strategic environmental assessment process would allow a better integration of biodiversity in planning and decision-making, further promoting a sustainable planning system.
STRATEGIC ENVIRONMENT ASSESSMENT AND BIOLOGICAL DIVERSITY CONSERVATION IN THE KOREAN HIGH-SPEED RAILWAY PROJECT
Authors: LEE SANG DON
Published: June 2005

Biological diversity (biodiversity) is an essential issue in conservation and environmental impact assessment (EIA). Though Korea is relatively small, the country harbours over 29,800 species, making biodiversity and ecosystem conservation a central issue when an EIA is undertaken during development site selection. Indeed, an unfavourable biodiversity evaluation can halt a proposed or in-progress development, creating a societal conflict between conservationists and developers. To solve this, the Strategic Environment Assessment (SEA) legislation was created in Korea to provide a systematic instrument for improving decision-making through early-stage environmental assessment. The SEA legislation was recently passed by the President's cabinet and is poised for implementation during 2005. Adoption of the SEA will facilitate better assessments of biodiversity during the early stages of the developmental process, preventing late-stage interruptions such as those seen in the Korean High-speed Railway Project (KHRP), which was recently halted due to poor biodiversity conservation around the development site. The original EIA of the KHRP did not appropriately address the biodiversity issues because most of the developmental plan had been set in place prior to evaluation of biodiversity in the affected areas. The KHRP caused leakage of mountain groundwater such that high elevation wetlands marked as ecosystem conservation areas by the Ministry of Environment became dry and lost their endemic amphibian species. Upon learning this, several national NGOs filed court cases on behalf of the Korean clawed salamander (Onachodaytylus fisheri), halting the project for some time. Thus, the lack of biodiversity consideration at the earliest stages of the KHRP created a social conflict. This paper examines how the implementation of an SEA during the KHRP would have minimised the social conflicts between biodiversity conservation and developmental processes.
BIODIVERSITY IN SEA FOR SPATIAL PLANS — EXPERIENCES FROM THE NETHERLANDS
Authors: KOLHOFF AREND , SLOOTWEG ROEL
Published: June 2005

This paper provides an overview of the way biodiversity issues are dealt with in strategic environmental assessment (SEA) for spatial plans in the Netherlands. Spatial plans are selected as subject of study because 50 percent of all SEA studies executed in the Netherlands are carried out for spatial plans. Secondly, these plans provide an overarching framework for multiple interventions with potential impacts on biodiversity. It is, therefore, important to pay particular attention to biodiversity at the strategic level of a spatial plan. The evaluation is based on five spatial plans that have been subject to SEA, two national plans, two provincial plans and one local plan. Based on these assessments a number of conclusions are presented on the assessment of biodiversity in SEA for spatial plans in the Netherlands. The evaluation of case studies on which this paper is based was undertaken to produce a submission to the Convention on Biological Diversity for the drafting of international guidelines on biodiversity in SEA.
STRENGTHENING BIODIVERSITY CONSERVATION THROUGH COMMUNITY-ORIENTED DEVELOPMENT PROJECTS: ENVIRONMENTAL REVIEW OF THE INDIA ECODEVELOPMENT PROJECT
Authors: RAJVANSHI ASHA
Published: June 2005

The India Ecodevelopment Project supported from Global Environmental Facility funds has been a major conservation initiative of the Government of India that was initiated in 1997 in seven protected areas (PAs) in the country. This project aimed to strengthen biodiversity conservation by establishing critical links between conservation and community well-being. The objective of environmental review of the project in the seven PA sites was to review the success of enabling strategies and interventions under the project in effectively addressing biodiversity conservation and optimising benefits to local communities through measurable improvements.

Strategic environmental assessment, along with other indicators of success that have been adopted worldwide for evaluating integrated conservation and development projects, was used for the environmental review of the project. The prioritisation of investments in activities under the project was found to be in accordance with the ecological profile and in conformity with the objectives of conservation in each PA. Although most of the activities identified under the project are beneficial and provide evidence of their positive impacts on biodiversity conservation, the project at large had pitfalls and success in varying proportions in different sites. The India Ecodevelopment Project has been particularly limited in scope to address biodiversity threats from unplanned development and incompatible landuse practices around PAs, which pose far more significant threats to conservation.
PRINCIPLES FOR THE USE OF STRATEGIC ENVIRONMENTAL ASSESSMENT AS A TOOL FOR PROMOTING THE CONSERVATION AND SUSTAINABLE USE OF BIODIVERSITY
Authors: TREWEEK JO , THERIVEL RIKI , THOMPSON STEWART , SLATER MARTIN
Published: June 2005

Strategic environmental assessment (SEA) has been identified as an important tool for helping to ensure that development is planned and implemented for the benefit of biodiversity by the Convention on Biological Diversity, the Ramsar Convention and the Convention for Migratory Species. SEA is seen as a way to overcome many limitations of project-level environmental impact assessment by allowing consideration of biodiversity at higher tiers of decision-making and planning.

This paper identifies some important principles that should be taken into account to ensure that biodiversity considerations are appropriately addressed in SEA, so that the conservation and sustainable use of biodiversity are pursued as fundamental objectives of strategic decision-making. The paper also sets out key considerations to take into account at different stages in the SEA process. The principles explored in this paper should be applicable in any country where SEA is practiced, even though legislation, methodologies and procedures vary widely.
15-F2t-isoprostane exacerbates myocardial ischemia-reperfusion injury of isolated rat hearts
Authors: Xia Zhengyuan , Kuo Kuo-Hsing , Godin David V. , Walker Michael J. , Tao Michelle C. Y. , Ansley David M.
Published: June 2005

Reactive oxygen species induce formation of 15-F2t-isoprostane (15-F2t-IsoP), a specific marker of in vivo lipid peroxidation, which is increased after myocardial ischemia and during the subsequent reperfusion. 15-F2t-IsoP possesses potent bioactivity under pathophysiological conditions. However, it remains unknown whether 15-F2t-IsoP, by itself, can influence myocardial ischemia-reperfusion injury (IRI). Adult rat hearts were perfused by the Langendorff technique with Krebs-Henseleit (KH) solution at a constant flow rate of 10 ml/min. 15-F2t-IsoP (100 nM), SQ-29548 (1 μM, SQ), a thromboxane receptor antagonist that can abolish the vasoconstrictor effect of 15-F2t-IsoP, 15-F2t-IsoP + SQ in KH, or KH alone (vehicle control) was applied for 10 min before induction of 40 min of global ischemia followed by 60 min of reperfusion. During ischemia, saline (control), 15-F2t-IsoP, 15-F2t-IsoP + SQ, or SQ in saline was perfused through the aorta at 60 μl/min. 15-F2t-IsoP, 15-F2t-IsoP + SQ, or SQ in KH was infused during the first 15 min of reperfusion. Coronary effluent endothelin-1 concentrations were significantly higher in the group treated with 15-F2t-IsoP than in the control group during ischemia and also in the later phase of reperfusion ( P < 0.05). Infusion of 15-F2t-IsoP increased release of cardiac-specific creatine kinase, reduced cardiac contractility during reperfusion, and increased myocardial infarct size relative to the control group. SQ abolished the deleterious effects of 15-F2t-IsoP. 15-F2t-IsoP exacerbates myocardial IRI and may, therefore, act as a mediator of IRI. 15-F2t-IsoP-induced endothelin-1 production during cardiac reperfusion may represent a mechanism underlying the deleterious actions of 15-F2t-IsoP.
Postconditioning via stuttering reperfusion limits myocardial infarct size in rabbit hearts: role of ERK1/2
Authors: Darling Chad E. , Jiang Rong , Maynard Michelle , Whittaker Peter , Vinten-Johansen Jakob , Przyklenk Karin
Published: June 2005

Emerging evidence suggests that restoration of blood flow in a stuttering manner may limit lethal myocardial ischemia-reperfusion injury. However, the mechanisms contributing to this phenomenon, termed postconditioning (post-C), remain poorly defined. Our aim was to test the hypothesis that activation of classic “survival kinases,” phosphatidylinositol 3-kinase (PI3-kinase) and/or extracellular signal-regulated kinase (ERK)1/2, may play a role in post-C-induced cardioprotection. In protocol 1, isolated buffer-perfused rabbit hearts underwent 30 min of sustained coronary artery occlusion and were randomized to receive abrupt reperfusion (controls) or four cycles of 30 s of reperfusion and 30 s of reocclusion before full restoration of flow (post-C). Protocol 2 was identical except control and postconditioned hearts received the PI3-kinase inhibitor LY-294002 ( protocol 2A) or the ERK1/2 antagonist PD-98059 ( protocol 2B) throughout the first 25 min of reperfusion, whereas in protocol 3, myocardial samples were obtained during the early minutes of reflow from additional control, postconditioned, and nonischemic sham hearts for the assessment, by standard immunoblotting, of phospho-Akt (downstream target of PI3-kinase) and phospho-ERK. Protocols 1 and 2 corroborated that infarct size (delineated by tetrazolium staining and expressed as a percent of risk region) was reduced in postconditioned hearts vs. control hearts and also revealed that post-C-induced cardioprotection was maintained despite LY-294002 treatment but was abrogated by PD-98059. These pharmacological data were supported by protocol 3, which showed increased immunoreactivity of phospho-ERK but not phospho-Akt with post-C. Thus our results implicate the involvement of ERK1/2 rather than PI3-kinase/Akt in the reduction of infarct size achieved with post-C.
Physical exercise capacity is associated with coronary and peripheral vascular function in healthy young adults
Authors: Hägg Ulrika , Wandt Birger , Bergström Göran , Volkmann Reinhard , Gan Li-ming
Published: June 2005

Short-term exercise training has been shown to improve cardiovascular function, whereas long-term effects of a physically active lifestyle, on coronary artery function in particular, are still not well studied. We explored possible relationships between physical exercise capacity and coronary and peripheral vascular function in healthy young adults. Twenty-nine healthy young male and female volunteers participated in the study. They underwent 1) basic clinical and echocardiographic characterization, 2) coronary flow velocity reserve (CFVR) measurement of the left anterior descending coronary artery (LAD), 3) common carotid artery (CCA) intima-media thickness (IMT) measurement, 4) assessment of CCA stiffness index (SI), 5) forearm flow-mediated vasodilation (FMD), and 6) submaximal exercise test. The calculated weight-adjusted maximal oxygen uptake capacity (V̇o2 maxc) was positively correlated to LAD CFVR and inversely correlated to IMT and SI. Also, subjects with high compared with moderate exercise capacity had higher FMD. In addition, subjects with LAD CFVR in the upper median had greater ratios between endothelium-dependent and -independent vasodilation in the forearm and lower SI in CCA. High exercise capacity due to a physically active lifestyle is associated with high coronary and peripheral artery function, indicating an early protective role of physical exercise for cardiovascular health.
GRO family chemokines are specialized for monocyte arrest from flow
Authors: Smith David F. , Galkina Elena , Ley Klaus , Huo Yuqing
Published: June 2005

Chemokines participate in various processes of monocyte recruitment including monocyte arrest and migration. Our group and others have demonstrated that growth-related oncogene (GRO)-α (CXCL1) can support monocyte arrest in models of inflammation. Here we employed a parallel plate-flow chamber and Transwell reconstitution assay to test whether GRO family chemokines were sufficient for Mono Mac 6 (a human monocytic cell line) and isolated human monocyte recruitment. Our study shows that 1) GRO-α, -β (CXCL2), and -γ (CXCL3) all act as arrest chemokines for monocyte adhesion on vascular cell adhesion molecule (VCAM)-1 under flow in the presence of P-selectin; 2) CXCR2 is the functional receptor for GRO-family chemokines in monocyte arrest; however, CXCR2 is not an arrest chemokine receptor in general, since epithelial neutrophil-activating peptide ENA-78 failed to arrest monocytes; 3) GRO-α, -β, and -γ all fail to increase intracellular free Ca2+or mediate monocyte chemotaxis; and 4) signaling through Gαiprotein, phosphoinositide 3-kinase, and actin polymerization but not Ca2+mobilization or the mitogen-activated kinases p38 and MAPK/extracellular signal-related kinase are necessary for GRO-α-mediated Mono Mac 6 cell arrest under flow. We conclude that the GRO-family chemokines are specialized monocyte-arrest chemokines. Their role in monocyte recruitment in inflammation can be inhibited by blocking CXCR2 function or downstream signaling events.
Effects of Na+ and K+ channel blockade on vulnerability to and termination of fibrillation in simulated normal cardiac tissue
Authors: Qu Zhilin , Weiss James N.
Published: June 2005

Na+ and K+ channel-blocking drugs have anti- and proarrhythmic effects. Their effects during fibrillation, however, remain poorly understood. We used computer simulation of a two-dimensional (2-D) structurally normal tissue model with phase I of the Luo-Rudy action potential model to study the effects of Na+ and K+ channel blockade on vulnerability to and termination of reentry in simulated multiple-wavelet and mother rotor fibrillation. Our main findings are as follows: 1) Na+ channel blockade decreased, whereas K+ channel blockade increased, the vulnerable window of reentry in heterogeneous 2-D tissue because of opposing effects on dynamical wave instability. 2) Na+ channel blockade increased the cycle length of reentry more than it increased refractoriness. In multiple-wavelet fibrillation, Na+ channel blockade first increased and then decreased the average duration or transient time () of fibrillation. In mother rotor fibrillation, Na+ channel blockade caused peripheral fibrillatory conduction block to resolve and the mother rotor to drift, leading to self-termination or sustained tachycardia. 3) K+ channel blockade increased dynamical instability by steepening action potential duration restitution. In multiple-wavelet fibrillation, this effect shortened  because of enhanced wave instability. In mother rotor fibrillation, this effect converted mother rotor fibrillation to multiple-wavelet fibrillation, which then could self-terminate. Our findings help illuminate, from a theoretical perspective, the possible underlying mechanisms of termination of different types of fibrillation by antiarrhythmic drugs.
Enhanced oxidative stress impairs cAMP-mediated dilation by reducing Kv channel function in small coronary arteries of diabetic rats
Authors: Bubolz Aaron H. , Li Hongwei , Wu Qingping , Liu Yanping
Published: June 2005

We have shown that short-term exposure of rat small coronary arteries (RSCAs) to high glucose enhances superoxide (O2−·) formation and impairs cAMP-mediated dilation by reducing voltage-gated K+ (Kv) channel function. However, it is not clear whether the impairment also occurs in diabetes mellitus (DM), where alternate mechanisms could mask or aggravate vasodilator dysfunction. RSCAs were isolated from control and streptozotocin-induced diabetic rats. Reduced constriction to 4-aminopyridine (4-AP) was observed in RSCAs from DM rats, indicating Kv channel impairment. Forskolin increased 4-AP-inhibitable K+ channel open-state probability and whole cell K+ current density in coronary myocytes from non-DM rats but had little effect on K+ current density in cells from DM rats. Diminished dilation to 8-bromo-cAMP, forskolin, or isoproterenol was observed in DM RSCAs. The attenuated dilation to forskolin or isoproterenol in DM RSCAs was partially restored by application of the superoxide dismutase mimetic manganese[III] tetrakis (4-benzoic acid) porphyrin. Histofluorescence studies using hydroethidine revealed a blockage of O2−· generation by the NADPH oxidase inhibitor apocynin in DM RSCAs. Sepiapterin, a precursor of tetrahydrobiopterin, had little effect on hyperglycemia-induced O2−· formation. Consistent with the findings from the concurrent fluorescence study, apocynin also partially restored the reduced dilator response to forskolin in DM RSCAs. Forskolin-induced cAMP production was unaltered in DM. We conclude that in diabetes, enhanced O2−· formation by activation of NADPH oxidase impairs cAMP-medicated dilation in RSCAs by inhibiting Kv channel activity.
The intrinsic circadian clock within the cardiomyocyte
Authors: Durgan David J. , Hotze Margaret A. , Tomlin Tara M. , Egbejimi Oluwaseun , Graveleau Christophe , Abel E. Dale , Shaw Chad A. , Bray Molly S. , Hardin Paul E. , Young Martin E.
Published: June 2005

Circadian clocks are intracellular molecular mechanisms that allow the cell to anticipate the time of day. We have previously reported that the intact rat heart expresses the major components of the circadian clock, of which its rhythmic expression in vivo is consistent with the operation of a fully functional clock mechanism. The present study exposes oscillations of circadian clock genes [brain and arylhydrocarbon receptor nuclear translocator-like protein 1 ( bmal1), reverse strand of the c-erbaα gene ( rev-erbaα), period 2 ( per2), albumin D-element binding protein ( dbp)] for isolated adult rat cardiomyocytes in culture. Acute (2 h) and/or chronic (continuous) treatment of cardiomyocytes with FCS (50% and 2.5%, respectively) results in rhythmic expression of circadian clock genes with periodicities of 20–24 h. In contrast, cardiomyocytes cultured in the absence of serum exhibit dramatically dampened oscillations in bmal1 and dbp only. Zeitgebers (timekeepers) are factors that influence the timing of the circadian clock. Glucose, which has been previously shown to reactivate circadian clock gene oscillations in fibroblasts, has no effect on the expression of circadian clock genes in adult rat cardiomyocytes, either in the absence or presence of serum. Exposure of adult rat cardiomyocytes to the sympathetic neurotransmitter norephinephrine (10 μM) for 2 h reinitiates rhythmic expression of circadian clock genes in a serum-independent manner. Oscillations in circadian clock genes were associated with 24-h oscillations in the metabolic genes pyruvate dehydrogenase kinase 4 ( pdk4) and uncoupling protein 3 ( ucp3). In conclusion, these data suggest that the circadian clock operates within the myocytes of the heart and that this molecular mechanism persists under standard cell culture conditions (i.e., 2.5% serum). Furthermore, our data suggest that norepinephrine, unlike glucose, influences the timing of the circadian clock within the heart and that the circadian clock may be a novel mechanism regulating myocardial metabolism.
Relationship of diastolic intraventricular pressure gradients and aerobic capacity in patients with diastolic heart failure
Authors: Rovner Aleksandr , Greenberg Neil L. , Thomas James D. , Garcia Mario J.
Published: June 2005

We sought to elucidate the relationship between diastolic intraventricular pressure gradients (IVPG) and exercise tolerance in patients with heart failure using color M-mode Doppler. Diastolic dysfunction has been implicated as a cause of low aerobic potential in patients with heart failure. We previously validated a novel method to evaluate diastolic function that involves noninvasive measurement of IVPG using color M-mode Doppler data. Thirty-one patients with heart failure and 15 normal subjects were recruited. Echocardiograms were performed before and after metabolic treadmill stress testing. Color M-mode Doppler was used to determine the diastolic propagation velocity ( Vp) and IVPG off-line. Resting diastolic function indexes including myocardial relaxation velocity, Vp, and E/ Vp correlated well with V̇o2 max ( r = 0.8, 0.5, and −0.5, respectively, P < 0.001 for all). There was a statistically significant increase in Vp and IVPG in both groups after exercise, but the change in IVPG was higher in normal subjects compared with patients with heart failure (2.6 ± 0.8 vs. 1.1 ± 0.8 mmHg, P < 0.05). Increase in IVPG correlated with peak V̇o2 max ( r = 0.8, P < 0.001) and was the strongest predictor of exercise capacity. Myocardial relaxation is an important determinant of exercise aerobic capacity. In heart failure patients, impaired myocardial relaxation is associated with reduced diastolic suction force during exercise.
Estrogen potentiates vasopressin-induced contraction of female rat aorta by enhancing cyclooxygenase-2 and thromboxane function
Authors: Li Min , Stallone John N.
Published: June 2005

To determine the roles of estrogen and constrictor prostanoids in vasopressin (VP)-induced contraction of female rat aorta, vascular reactivity to VP was determined in thoracic aortas of intact, ovariectomized, and ovariectomized + estrogen-replaced female rats in the presence of indomethacin (Indo), NS-398, SQ-29,548, or vehicle control. The effects of estrogen on vascular reactivity to the thromboxane A2 analog U-46619 were also examined. Maximal contractile response to VP in intact female rats (5,567 ± 276 mg/mg of aortic ring wt) was markedly attenuated by ovariectomy (2,485 ± 394 mg; P < 0.001) and restored by estrogen replacement with 17β-estradiol (5,059 ± 194 mg; P > 0.1). Indo and NS-398 significantly attenuated maximal responses to VP in intact female rats to a similar extent [3,176 ± 179 ( P < 0.0001) and 3,258 ± 152 mg ( P < 0.0001), respectively]. Ovariectomy abolished and estrogen replacement restored the inhibitory effects of Indo, NS-398, and SQ-29,548. Contractile responses of rat aorta to U-46619 were significantly greater ( P < 0.0001) in females (5,040 ± 238 mg) than in males (3,679 ± 96 mg). Ovariectomy markedly attenuated (3,923 ± 84 mg; P < 0.01) and estrogen replacement restored (5,024 ± 155 mg; P > 0.1) responses to U-46619 in female aortas. These data reveal that estrogen is an important regulator of the contractile responses of female rat aorta to VP, which appears to potentiate both cyclooxygenase-2 and constrictor prostanoid function in the vascular wall.
Low-frequency oscillation of sympathetic nerve activity decreases during development of tilt-induced syncope preceding sympathetic withdrawal and bradycardia
Authors: Kamiya Atsunori , Hayano Junichiro , Kawada Toru , Michikami Daisaku , Yamamoto Kenta , Ariumi Hideto , Shimizu Syuji , Uemura Kazunori , Miyamoto Tadayoshi , Aiba Takeshi , Sunagawa Kenji , Sugimachi Masaru
Published: June 2005

Sympathetic activation during orthostatic stress is accompanied by a marked increase in low-frequency (LF, ∼0.1-Hz) oscillation of sympathetic nerve activity (SNA) when arterial pressure (AP) is well maintained. However, LF oscillation of SNA during development of orthostatic neurally mediated syncope remains unknown. Ten healthy subjects who developed head-up tilt (HUT)-induced syncope and 10 age-matched nonsyncopal controls were studied. Nonstationary time-dependent changes in calf muscle SNA (MSNA, microneurography), R-R interval, and AP (finger photoplethysmography) variability during a 15-min 60° HUT test were assessed using complex demodulation. In both groups, HUT during the first 5 min increased heart rate, magnitude of MSNA, LF and respiratory high-frequency (HF) amplitudes of MSNA variability, and LF and HF amplitudes of AP variability but decreased HF amplitude of R-R interval variability (index of cardiac vagal nerve activity). In the nonsyncopal group, these changes were sustained throughout HUT. In the syncopal group, systolic AP decreased from 100 to 60 s before onset of syncope; LF amplitude of MSNA variability decreased, whereas magnitude of MSNA and LF amplitude of AP variability remained elevated. From 60 s before onset of syncope, MSNA and heart rate decreased, index of cardiac vagal nerve activity increased, and AP further decreased to the level at syncope. LF oscillation of MSNA variability decreased during development of orthostatic neurally mediated syncope, preceding sympathetic withdrawal, bradycardia, and severe hypotension, to the level at syncope.
Frequency-dependent regulation of cardiac Na+/Ca2+ exchanger
Authors: Omelchenko Alexander , Bouchard Ron , Shurraw Sabin , Trac Michael , Hnatowich Mark , Hryshko Larry V.
Published: June 2005

The activity of the cardiac Na+/Ca2+ exchanger (NCX1.1) undergoes continuous modulation during the contraction-relaxation cycle because of the accompanying changes in the electrochemical gradients for Na+ and Ca2+. In addition, NCX1.1 activity is also modulated via secondary, ionic regulatory mechanisms mediated by Na+ and Ca2+. In an effort to evaluate how ionic regulation influences exchange activity under pulsatile conditions, we studied the behavior of the cloned NCX1.1 during frequency-controlled changes in intracellular Na+ and Ca+ (Na[Formula: see text] and Ca[Formula: see text]). Na+/Ca2+ exchange activity was measured by the giant excised patch-clamp technique with conditions chosen to maximize the extent of Na+- and Ca2+-dependent ionic regulation so that the effects of variables such as pulse frequency and duration could be optimally discerned. We demonstrate that increasing the frequency or duration of solution pulses leads to a progressive decline in pure outward, but not pure inward, Na+/Ca2+ exchange current. However, when the exchanger is permitted to alternate between inward and outward transport modes, both current modes exhibit substantial levels of inactivation. Changes in regulatory Ca2+, or exposure of patches to limited proteolysis by α-chymotrypsin, reveal that this “coupling” is due to Na+-dependent inactivation originating from the outward current mode. Under physiological ionic conditions, however, evidence for modulation of exchange currents by Na[Formula: see text]-dependent inactivation was not apparent. The current approach provides a novel means for assessment of Na+/Ca2+ exchange ionic regulation that may ultimately prove useful in understanding its role under physiological and pathophysiological conditions.
Effects of acute and chronic nitric oxide inhibition in an experimental model of chronic pulmonary allergic inflammation in guinea pigs
Authors: Prado Carla M. , Leick-Maldonado Edna A. , Kasahara David I. , Capelozzi Vera L. , Martins Milton A. , Tibério Iolanda F. L. C.
Published: June 2005

Endogenously produced nitric oxide is a recognized regulator of physiological lung events, such as a neurotransmitter and a proinflammatory mediator. We tested the differences between chronic and acute nitric oxide inhibition by Nω-nitro-l-arginine methyl ester (l-NAME) treatment in lung mechanics, inflammation, and airway remodeling in an experimental asthma model in guinea pigs. Both acute and chronic l-NAME treatment reduced exhaled nitric oxide in sensitized animals ( P < 0.001). Chronic l-NAME treatment increased baseline and maximal responses after antigen challenge of respiratory system resistance and reduced peribronchial edema and mononuclear cells airway infiltration ( P < 0.05). Acute administration of l-NAME increased maximal values of respiratory system elastance and reduced mononuclear cells and eosinophils in airway wall ( P < 0.05). Chronic ovalbumin exposure resulted in airway wall thickening due to an increase in collagen content ( P < 0.005). Chronic nitric oxide inhibition increased collagen deposition in airway wall in sensitized animals ( P < 0.05). These data support the hypothesis that in this model nitric oxide acts as a bronchodilator, mainly in proximal airways. Furthermore, chronic nitric oxide inhibition was effective in reducing edema and mononuclear cells in airway wall. However, airway eosinophilic inflammation was unaltered by chronic l-NAME treatment. In addition, nitric oxide inhibition upregulates collagen deposition in airway walls.