bluuebunny/crossref_metadata_2025 huggingface dataset:
DeepC: The New Deep Water AUV Generation
Authors: Hornfeld Willi
Published: January 2009

The development of real Autonomous Underwater Vehicles (AUVs) represents a very particular challenge which is being tackled within the scope of the German co-operation project DeepC (www.deepc-auv.de), reaching the middle of the project time frame. The aim of this project is to develop a fully autonomous underwater vehicle for great diving depths, long mission times and a modular design with the following main features: • Mission depth till 4000 m (Crush: 6000 m); • Weight in air 2.4 t; • Cruise speed 4 kts; • Maximum speed 6 kts; • Mission time up to 60 hours; • Operating range up to 400 km; • Payloads ≥ 250 kg. The subjects of vehicle structure, maximum manoeuvrability, electrical power generation, storage and distribution, intelligent behaviour and precise navigation are some of the crucial aspects for the development of such an underwater vehicle. The high speed and manoeuvrability are rendered possible by two horizontal drive systems and four thrusters for transverse and vertical thrust. Electrical motors that are pressure-neutral up to depths of 7000 m are provided for propulsion. A battery-buffered PEM H2/O2 fuel cell whose functionality offers numerous advantages over other systems is used to generate the electrical power needed for DeepC operation. The storage of the reactants hydrogen and oxygen, the trimming-neutral accommodation of the residual water produced, the temperature management and especially also safety problems in connection with the possible development of oxyhydrogen gas are, however, a problem when the AUV is operated independently from an external air supply. Mission management systems perform vehicle guidance, assure intelligent behaviour in special situations, provide a degradation mode for emergencies and/or plan missions independently with due consideration to the targets set. Without external support, the navigation system must allow precise AUV navigation over longer periods of time. Mission-specific sensor systems support vehicle guidance, avoid collisions and perform the actual measuring tasks. Due to a modular payload concept, the vehicle can be easily used for a lot of different missions with a very low amount of mobilisation and demobilisation. The paper describes the current development status in general and the technological highlights like fuel cell, intelligent behaviour, etc. in particular, gives an outlook into the future and shows examples of applications.
First-Generation Wave Power Plants: Current Status and R&D Requirements
Authors: Falca˜o A. F. de O.
Published: January 2009

After some introductory considerations on the wave energy resource and the technology for its utilization, the paper concentrates on the more mature devices developed to be located on the shoreline or near shore (the so-called first generation devices), especially those that have reached the stage of full-sized prototype deployed in open sea waters. Apart from a brief reference to the shoreline TAPCHAN converter, the rest of the paper is devoted mostly to the oscillating water column (OWC). The principal factors affecting the technological development and the economics are analysed, taking into consideration the experience from existing prototypes: device siting, hydrodynamics and structure geometry, structural design and construction, power take-off equipment (turbine, electrical generator) and control. Special attention is devoted to two critical factors: civil construction and ways of reducing its costs, and air turbine conception and performance. The paper concludes with some perspectives on first generation wave energy technology.
A Study on Structural Response Behavior and Strength of Long Submerged Floating Structures With Tension Legs in Waves
Authors: Katsura Shinji , Tsubogo Takashi , Masaoka Koji , Okada Hiroo , Marutani Jun-Ichi
Published: January 2009

In this paper a submerged floating structure with tension legs is dealt with, the hydro-elastic response of which in long waves is investigated as a part of basic studies on marine space utilization structures. The analytical method is applied to the submerged floating structure. Then, the hydro-elastic characteristics of a floating structure model with a submerged plate and tension legs in regular long waves are investigated numerically. Next, in order to demonstrate the validity of theoretical results an experimental study is carried out for a basic model in regular waves. It was found that experimental results for the frequency response amplitude are in good correspondence to theoretical results in the low frequency range. Finally, characteristics of hydro-elastic responses of a 1,000m-class submerged floating structure under trial design are also investigated applying the above method.
TomX: High-Energy Tomographic X-Ray for In-Service Inspection of Flexible Pipeline Systems
Authors: Daaland Alf , Soldal Ragnvald , Loetveit Svein Are , Hagemann Christian
Published: January 2009

The applications of flexible pipes are increasing, and so is the demand for good inspection methods and integrity assessment tools, both from Operators and Authorities. Leakage or damage to the pipe on topsides could lead to an increased safety risk, uncontrolled shutdowns, longer system downtime and major financial loss. For several years, the Norwegian oil company, Statoil, has investigated the feasibility of developing x-ray computed tomography (CT) systems for on-site inspection of flexible pipelines. Special consideration has been given to the end fitting area on topsides. The development led to the foundation of the company TomX AS in 2001. With contributions from Statoil, Aker Kvaerner and NUI, the company has focused on studies and tests to confirm the feasibility of CT technology for inspection of flexible pipes. Much effort has been concentrated on proving that it is possible to get high quality CT images of flexible pipes and end fittings on topsides. The detection criteria are defined as flaws in the pressure barrier, as defined by the Statoil R&D group. The flaw size gives an estimate of the remaining lifetime of the flexible pipes. Until now, no non-destructive, non-intrusive inspection method has been able to inspect the pressure barrier. Tests with computed tomography show that this can become a unique way of getting reliable information about all layers in a flexible pipe, including the pressure barrier. Results from these tests are presented and discussed in this paper. Furthermore, possible analysis methods are introduced. ACT inspection tool is made up of a high-energy x-ray source, a detector array and a highly accurate mechanical system. Limited access on offshore installations, high demands for accuracy and radiation safety put strict requirements on the design of the tool. Prototype design for offshore inspection and inspection in conjunction with the Factory Acceptance Test (FAT) of the flexible pipe end fitting is presented and operational challenges are assessed.
Reliability Aspects of Corrosion in Oil Storage Tanks
Authors: Ramos Alfonso J. , Bea Robert G.
Published: January 2009

Storage tanks are critical elements within oil facilities not because of their failure rate, but because of their critical function and the high environmental consequences when they fail. The presented analysis allows determining the probability of failure of storage tanks considering the most probable failure scenarios of this equipment. The utilized methodology considers the uncertainties associated with material degradation mechanism such as general corrosion, pitting and cracking induced by corrosion. The analytical formulations of the time dependant degradation of the isolated mechanisms and the system conformed by the conjunction of them are considered. Obtained results allow determining the contribution of the individual scenarios in the system reliability. Additionally, the probability of failure results and the maintenance cost are used to determine the optimum inspection time based on minimum costs criterion.
Monitoring Axial Strain in Synthetic Fiber Mooring Ropes Using Polymeric Optical Fibers
Authors: Smith D. Barton , Williams Jerry G.
Published: January 2009

Synthetic fiber ropes constructed of polyester are providing an important new technology for mooring deep-water drilling and production platforms. Considerable effort is being directed toward advancing and qualifying this enabling and cost-effective technology. To date, synthetic fiber mooring ropes have been successfully deployed in Brazil and they have seen limited service in the Gulf of Mexico. Synthetic fiber mooring ropes have high strength-to-weight ratios and possess adequate stiffness, but they are much more susceptible to damage than their steel counterparts. Future safe deployment of synthetic fiber mooring ropes would be significantly enhanced if a reliable technique were available to monitor the performance of the ropes in service and thus provide an early warning of the loss of structural integrity. Test data in the open literature indicates that the strain in the rope at failure is essentially a constant independent of load path or history. Measurement of the accumulated strain in the rope should thus provide a reliable benchmark with which to estimate the remaining life and establish criteria for rope recertification or retirement. This paper discusses the results of research and development activities aimed at developing a reliable, robust method for monitoring strain in braided and twisted strand Synthetic Fiber Mooring Ropes [1]. The strain transducer is a polymeric optical fiber, integrated into the mooring rope and interrogated with Optical Time-Domain Reflectometry (OTDR) to measure changes in its length as the optical fiber and rope are stressed. The method provides a direct measurement of large axial strains. Strains measured in polymeric optical fibers exhibit good one-to-one correlation with applied strains within the test range studied (10% or less, typically). The integrated polymeric optical fiber has been shown to withstand large numbers of repeated cycles to high strains without failure and to accurately track the hysteresis exhibited by polyester rope. Results are reported for tests conducted with polymeric optical fibers integrated into typical mooring rope elements.
A Nearshore Wave Energy Atlas for Portugal
Authors: Pontes M. T. , Aguiar R. , Oliveira Pires H.
Published: January 2009

The nearshore wave energy resource in Portugal has been assessed through the development of ONDATLAS. This is an electronic atlas, compatible with Internet access, containing comprehensive wave climate and wave energy statistics for 78 points at about 20 m water depth spaced variably ca. 5 km to 30 km, 5 points at deep water and 2 points at open ocean locations. The data were produced by a third-generation wind-wave model, complemented by an inverse-ray model that computes the directional spectra transformation from open ocean to the near-shore. Shoaling, refraction, bottom dissipation and shelter by the coastline and/or neighbouring islands are taken into account. ONDATLAS statistics comprise yearly and monthly values, variability and probability data for significant wave height, energy (mean) period, peak period and wave power, and directional histograms for wave and power direction. Joint probability distributions for various combinations of the above parameters are also available, as well as extreme values and return period for wave height and period parameters. A summary of the detailed verification of this model using long-term buoy measurements at four sites is presented. The main characteristics of ONDATLAS are described. The strong spatial variability that wave conditions exhibit at the coastal area are illustrated and a brief assessment of the nearshore resource at the Portugal mainland is presented.
Multi-Tube Model Application in Riser Installation/Completion Sequence Simulation Analysis
Authors: Chang Roger , Smedley Marcus
Published: January 2009

The multi-tube modeling scheme has been increasingly used in the industry to model top-tensioned risers due to the growing application of concentric, dual casing riser systems. One of the major advantages of using a multi-tube modeling scheme over the conventional composite modeling scheme is the former’s ability to simulate the installation/completion sequence. From the analysis, the inner riser strings preloads can be determined so that the potential inner string bulking problem can be avoided when the riser is in production. Since these preloads will alter the tension distribution among riser strings, any riser analysis without considering them will not produce the correct results. This paper presents the application of the multi-tube modeling scheme in simulating the riser installation/completion sequence to determine the inner strings preloads. The difficulties associated with this unique analysis are identified, and the analysis methodologies used to overcome these difficulties are explained. There are quite a few steps in the riser running procedure, and if every riser analysis has to include all of these steps to faithfully model what the real riser experiences, it would present a tremendous burden to the analyst. A simplified 3-step analysis is proposed and the results are compared with the full-steps results. Also presented is the comparison of the tension distribution among riser strings between analyses with and without the preloads to demonstrate the importance of this kind of analysis.
Limit States for Deepwater Flowlines and Risers: Review of the Research Activities at the Submarine Technology Laboratory/COPPE
Authors: Estefen S. F. , Netto T. A. , Pasqualino I. P.
Published: January 2009

Research activities related to the limit states of flowlines and risers conducted at the Submarine Technology Laboratory / COPPE in cooperation with PETROBRAS are presented. The motivation for most of the research programs is associated with deepwater challenges arising from the rigid pipe installations at Campos Basin. Initially ultimate strength of intact pipes are investigated together with aspects related to residual strength, buckling propagation and buckle arrestors. Based on the experimental results numerical models have been correlated in order to be used to generate results for full scale steel pipes. Ultimate strength curves have been then produced as well as the analytical equation representative of these curves. Experimental tests of buckling propagation for small and large scale pipes have also been performed to obtain the bias factor for different equations proposed in the literature. Based on this study an equation for propagation pressure has been recommended. In addition, ring and cylinder buckle arrestors have been tested in order to propose an expression relating crossing over pressure with the arrestor geometries. An overview of the studies aiming at establishing the influence of the reeling method of installation on the failure modes of flowlines and steel catenary risers is presented. It is emphasized the influence of cross-section ovality and weld defect amplification due to plastic bending on collapse pressure and fatigue life, respectively. Finally, the development of a new concept of sandwich pipe for ultra deepwater, combining structural resistance and thermal insulation is discussed.
The Shadow Effect on the Dynamics of a Shuttle Tanker Connected in Tandem With a FPSO
Authors: Fucatu Carlos H. , Nishimoto Kazuo
Published: January 2009

The ship based Floating Production Storage and Offloading system (FPSO) has been largely used in the recent offshore oil exploration. In most of the cases the oil stored in FPSO is offloaded to a shuttle ship that is connected by a hawser in tandem configuration. The problem of dynamic instability that arises in several ship mooring systems, like SPM and SMS subjected to the environmental forces, may also be present in the tandem system. Although the tandem mooring is a common procedure in the offshore oil industry, there are few publications related to the theme. Among these, there are none concerned with the environmental forces interference caused by FPSO on shuttle ship, here called as shadow effect. It is well known that the dynamic behaviour of a moored ship, in particular SPM system, is hardly affected by the environmental forces. Therefore, it is expected that shadow effect on the environmental forces acting on the shuttle ship will cause great influence in its dynamic behaviour, and consequently in the dynamics of whole FPSO-shuttle system. These phenomena could be observed in experiments with single point moored shuttle ships with and without the FPSO in upstream position. Therefore, the shadow effect should be considered in analysis of dynamic behaviour of two ships connected in tandem. Among the commercial simulators that analyse tandem systems there are none that consider shadow effect, making their analysis different from the real world. This paper presents an empirical model of the current shadow effect. The model was implemented in a numerical simulator, named DYNASIM. The comparison between numerical results and experimental one showed that the proposed model is effective.
The Riser System Challenge for 1,800 Meters: Roncador Field, Offshore, Brazil
Authors: Correˆa da Silva Renato Marques , Mourelle Marcio Martins , Teixeira da Gama Lima Jose´ Maurico , Ferreira Rodrigues Francisco Henrique
Published: January 2009

The paper presents a general overview of the technological challenge posed by the development of the phase 2, module 1A of Roncador field, offshore, Brazil. The field, discovered in 1996, encompasses reserves of 2.1 billion barrels of oil equivalent and is being developed in phases. This second phase, module 1A will be developed using solutions that will be among the world’s larger semi-submersible floating production unit displacement of more than 80,000 tons named Petrobras 52 (P-52). The platform will be moored in 1,800 meters (5905 ft) water depth. Peak production rates are targeted at 180,000 barrels per day (28,618m3/day) of oil and 130 million cubic feet per day (3.7 million m3/day) of natural gas. In addition to oil and associated gas processing capability to export and gas-lift, the unit will provide facilities capable of injecting up to 302,000 barrels per day (48,000 m3/day) of water. The subsea system was devised with all wells wet completed and directly connected to the production unit through around 44 SCRs (steel catenary risers) as base case. Moreover, alternative riser solutions such as flexible and hybrid risers are being screened and should be considered in the construction and installation bid. The gas lift system was defined through three subsea manifolds in order to narrow down the number of risers. The oil and gas export system was envisaged to be done through large diameter pipeline up to a shallow water fixed jacket hub facility which is linked with shore refinery pipeline network. The platform is scheduled for initial production in 2006. The feasibility study for the second phase, module 1A was performed in the third quarter of 2001. The main challenge was to produce an appraisal that mitigates the technology risk and also provides enough robustness to guarantee an attractive return rate. The unique field proven technology available to be considered in the feasibility study for the riser system as base case was the steel catenary riser system. On the other hand, other technologies were also investigated such as the riser tower system — similar to Girassol, West Africa; flexible riser system — to be qualified and the sub surface buoy, an in house solution. This paper describes the technical approach used into the feasibility in-house study that established the design base for the base case as well as the alternatives.
Equivalent Waves for Sea Loads on Ship Structures
Authors: Folso Lise , Rizzuto Enrico
Published: January 2009

An equivalent wave system is defined as a simple sinusoidal wave, which is meant to be representative of a complex extreme load situation. The present paper discusses three different ways of selecting an Equivalent Wave System. The implications of the different hypotheses at the basis of the selection are discussed and the outcomes in terms of maximization of single responses and of combinations of different types of responses are analysed. The extension of the concept of equivalent wave to fatigue life evaluations is also discussed, pointing out the different perspective from which a reference load situation is to be sought in this case.
Numerical Simulation of Nonlinear Wave Diffraction by a Vertical Cylinder in a Narrow Flume, Wide Tank, and Infinitely Wide Tank
Authors: Mansour Alaa M. , Williams A. Neil
Published: January 2009

In this paper, a three dimensional numerical wave tank model has been used to simulate fully nonlinear wave diffraction by a uniform vertical circular cylinder. The cylinder has been placed in a narrow flume of a width equal to four times the cylinder diameter. The runup and the hydrodynamic forces on the cylinder has been compared to the results when a similar cylinder is placed in a similar tank but with a width equal to sixteen times the cylinder diameter. The model has been further extended by applying an open boundary condition to the side-walls to simulate an infinitely wide tank and hence more realistically simulate open sea condition. The proposed open boundary condition in the lateral direction is based on coupling of two prescribed boundary conditions, namely, numerical beach and Orlanski boundary conditions. The use of this coupled boundary condition has been found to be very efficient in eliminating any significant wave reflection from the side-walls back into the computational domain.
On the Profile of Large Ocean Waves
Authors: Guedes Soares C. , Pascoal R.
Published: January 2009

Wave data obtained from simulations in an offshore basin and from field measurements were used to provide an assessment of the adequacy of describing the most likely time trace profile around large ocean wave crests based on the information provided by the autocorrelation function. It was concluded that the model is adequate in linear cases, but in high sea states, where nonlinear behaviour is apparent it starts becoming less appropriate.
Study of Flow Behavior in a Vibrating Pipe on Offshore Platform
Authors: Li Dezhong , Mei Ning , Su Jian
Published: January 2009

The purpose of this paper is to study flow behavior in a vibrating pipe on offshore platform. The mathematical model of unsteady, incompressible, viscous flow in a vibrating pipe is established according to the basic theory of oscillating fluid mechanics. The governing equations of flow are decomposed into a system for steady flow and another for flow oscillation, with the equations of the differential coefficients of flow parameters solved by using the parametric polynomial method. Velocity and pressure distributions are obtained for different flow conditions. Numerical results indicate that the flow behavior in the vibrating pipe on offshore platform is strongly affected by fluid properties and the pipe structure. A good agreement is obtained when comparing the results with the variational solution in constant cross-section, which shows that the method proposed in this work is effective for studying flow behavior in a vibrating pipe on offshore platform.
Comparison of Simulated and Measured Wind Forces on Offshore Tower Structure
Authors: Bjo̸rset Arve , Leira Bernt J. , Igland Ragnar T.
Published: January 2009

For flare towers or other types of slender structures mounted on offshore platforms, evaluation of the forces caused by static and dynamic wind action is of key importance for proper design. The drag coefficient is one of the main parameters to be specified for calculation of these forces. However, for complex lattice towers the drag coefficient is in general difficult to assess. The present paper outlines a procedure for estimation of wind forces and drag coefficients based on numerical simulation of the flow and pressure field around such structures. An example tower is considered for which measurements from wind tunnel tests also are available. The actual tower consists of four columns connected by transverse braces. The computer analysis is performed by the use of the computer code Navsim, which is developed for two-dimensional CFD-analysis.
Detection of Rogue Waves From Space
Authors: Lehner Susanne , Schulz-Stellenfleth Johannes , Niedermeier Andreas , Nieto Borge Jose Carlos
Published: January 2009

Space borne Synthetic aperture radar are able to provide high resolution measurements of ocean waves on a global scale. SAR is still the only instrument providing directional information on waves on a continuous basis in the open ocean. The present study uses a reprocessed data set of complex SAR images acquired by the European Remote Sensing satellite ERS-2 to estimate different wave parameters relevant for ship security. In addition, a new method is presented to derive two dimensional sea surface elevation fields from complex SAR data. The method permits to analyze wave fields in more detail than conventional SAR wave measurement techniques, which only estimate the wave spectrum. The technique provides parameters like maximum to significant wave height ratios, wave steepness, or the probability of wave breaking. Global maps and statistics of the new parameters are presented.
Reliability Based Fitness-for-Service Assessment of Corrosion Defects Using Different Burst Pressure Predictors and Different Inspection Techniques
Authors: Bea Robert , Beuker Thomas , Vargas Pedro
Published: January 2009

A comprehensive reliability based formulation is proposed for the assessment of the integrity of corroded pipelines. In this formulation, the inspection technique, the pipeline geometric and material characteristics, operational parameters, and Limit State model for burst are combined in a general approach. This approach is illustrated with application to evaluation of an in-service gas pipeline.
Time Simulations of Ocean-Going Structures in Extreme Waves
Authors: Pastoor Wouter , Helmers Jens Bloch , Bitner-Gregersen Elzbieta
Published: January 2009

A summary is presented on calculation procedures to determine extreme responses of ocean-going structures using nonlinear time domain simulations. As such nonlinear simulations are time consuming full scatter diagram assessments are not feasible. Advanced techniques are therefore required to assist in the selection of response critical sea states. Of particular importance is to what extend a few or even a single design sea state can be used to determine a lifetime design value. An overview of methods, which can be used to determine design sea states, is given and discussed. Secondly, if a design sea state is specified different approaches are possible to assess a response in that sea state. Regular, random irregular and conditioned irregular waves can be modeled, which affect both the accuracy and the computation time. Alternative extreme wave conditions are considered, in perspective to existing techniques, and the application of freak waves for response simulation is discussed. An example simulation is shown of a cruise-ship in a freak wave. In this example different phases are identified and the associated physical phenomena are discussed. Based on this study and the calculations, requirements for future research are formulated in order to use extreme/freak waves in response analyses and secondly to consider the use of freak waves in design procedures.
Current Issues and Considerations Regarding Trichomoniasis and Human Immunodeficiency Virus in African-Americans
Authors: Shafir Shira C. , Sorvillo Frank J. , Smith Lisa
Published: January 2009

Trichomonas vaginalis
has long been recognized as one of the most prevalent sexually transmitted infections. However, it is only in recent years that it has been appreciated that
Trichomonas
may play a critical role in amplifying human immunodeficiency virus (HIV) transmission. Given the evidence that
T. vaginalis
likely promotes HIV infection, the apparent high level of
Trichomonas
infection in the African-American community is cause for concern. Even if
T. vaginalis
increases the risk of HIV transmission by a small or modest amount, it translates into a sizable population effect since
Trichomonas
is so common in this community. Therefore, control of trichomoniasis may represent an important avenue of control for the prevention of HIV transmission, particularly among African-Americans.
Microbiology of Odontogenic Bacteremia: beyond Endocarditis
Authors: Parahitiyawa N. B. , Jin L. J. , Leung W. K. , Yam W. C. , Samaranayake L. P.
Published: January 2009

The human gingival niche is a unique microbial habitat. In this habitat, biofilm organisms exist in harmony, attached to either enamel or cemental surfaces of the tooth as well as to the crevicular epithelium, subjacent to a rich vascular plexus underneath. Due to this extraordinary anatomical juxtaposition, plaque biofilm bacteria have a ready portal of ingress into the systemic circulation in both health and disease. Yet the frequency, magnitude, and etiology of bacteremias due to oral origin and the consequent end organ infections are not clear and have not recently been evaluated. In this comprehensive review, we address the available literature on triggering events, incidence, and diversity of odontogenic bacteremias. The nature of the infective agents and end organ infections (other than endocarditis) is also described, with an emphasis on the challenge of establishing the link between odontogenic infections and related systemic, focal infections.
Update on the Human Broad Tapeworm (GenusDiphyllobothrium), Including Clinical Relevance
Authors: Scholz Tomáš , Garcia Hector H. , Kuchta Roman , Wicht Barbara
Published: January 2009

Tapeworms (Cestoda) continue to be an important cause of morbidity in humans worldwide. Diphyllobothriosis, a human disease caused by tapeworms of the genusDiphyllobothrium, is the most important fish-borne zoonosis caused by a cestode parasite. Up to 20 million humans are estimated to be infected worldwide. Besides humans, definitive hosts ofDiphyllobothriuminclude piscivorous birds and mammals, which represent a significant zoonotic reservoir. The second intermediate hosts include both freshwater and marine fish, especially anadromous species such as salmonids. The zoonosis occurs most commonly in countries where the consumption of raw or marinated fish is a frequent practice. Due to the increasing popularity of dishes utilizing uncooked fish, numerous cases of human infections have appeared recently, even in the most developed countries. As many as 14 valid species ofDiphyllobothriumcan cause human diphyllobothriosis, withD. latumandD. nihonkaiensebeing the most important pathogens. In this paper, all taxa from humans reported are reviewed, with brief information on their life history and their current distribution. Data on diagnostics, epidemiology, clinical relevance, and control of the disease are also summarized. The importance of reliable identification of human-infecting species with molecular tools (sequences of mitochondrial genes) as well as the necessity of epidemiological studies aimed at determining the sources of infections are pointed out.
Acute aortic syndrome: a new look at an old conundrum
Authors: Vilacosta I , Aragoncillo P , Cañadas V , Román J A San , Ferreirós J , Rodríguez E
Published: January 2009

The term acute aortic syndrome (AAS), coined several years ago, is now widely recognised. In the light of new findings in aortic pathology and in an era when modern imaging techniques are widely available and interventional management of AAS is increasing, some morphological and diagnostic aspects of acute aortic pathology have been examined and the syndrome updated. This article provides a new, comprehensive overview of the pathology, diagnosis, evolution and management of patients with AAS. As acute aortic disease is the most common fatal condition in patients with chest pain, prompt recognition and treatment is of paramount importance.
IL-4 regulates susceptibility to intestinal inflammation in murine food allergy
Authors: Cardoso Cristina R. , Provinciatto Pauline R. , Godoi Dannielle F. , Ferreira Beatriz R. , Teixeira Gerlinde , Rossi Marcos A. , Cunha Fernando Q. , Silva João S.
Published: January 2009

Allergies involve a state of immediate hypersensitivity to antigens, including food proteins. The mechanism underlying the initiation and development of allergic responses involves IL-4 that directly induces the differentiation of committed effector Th2 lymphocytes. Although it is clear that Th2 responses play a pivotal role in the development of allergic responses, it remains unclear which mechanisms are involved in the development of the intestinal damages observed in food allergy. Accordingly, this work aimed to study the role of Th2/IL-4-dependent responses in the development of food allergy and intestinal pathology. C57BL/6 wild-type (WT) and IL-4−/−mice were sensitized with peanut proteins, challenged with peanut seeds, and followed for the development of food allergy and intestinal inflammation. Results demonstrated that exposure to peanut seeds led to weight loss in WT but not in IL-4−/−mice that preserved gut integrity with no signs of mucosal inflammation. These animals presented increased levels of IgG2a in sera, suggesting a role for allergic antibodies in the pathogenesis of WT animals. Most importantly, results also showed that lack of IL-4 modulated gut mucosal response in food allergy through diminished expression of TNF-α mRNA, increased Th1 IFN-γ, IL-12p40, regulatory cytokines, and Foxp3, demonstrating their relevance in the control of allergic inflammatory processes, especially in the intestine. Finally, this study highlighted some of the complex mechanisms involved in the pathogenesis of allergic responses to food antigens in the gut, thereby providing valuable tools for directing novel therapeutic or preventive strategies to the control of allergic enteropathy.
Oxidant stress-induced liver injury in vivo: role of apoptosis, oncotic necrosis, and c-Jun NH2-terminal kinase activation
Authors: Hong Ji-Young , Lebofsky Margitta , Farhood Anwar , Jaeschke Hartmut
Published: January 2009

Oxidant stress is critically involved in various liver diseases. Superoxide formation causes c-Jun NH2-terminal kinase (JNK)- and caspase-dependent apoptosis in cultured hepatocytes. To verify these findings in vivo, male Fisher rats were treated with diquat and menadione. The oxidant stress induced by both compounds was confirmed by increased formation of glutathione disulfide and 4-hydroxynonenal protein adducts. Plasma alanine aminotransferase activities increased from 46 ± 4 U/l in controls to 955 ± 90 U/l at 6 h after diquat treatment. Hematoxylin and eosin staining of liver sections revealed large areas of necrotic cells at 3 and 6 h. DNA strandbreaks, evaluated with the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, showed clusters of TUNEL-positive cells, where the staining was predominantly cytosolic and the cells were swollen, indicating oncotic necrosis. There was no significant increase in caspase-3 activities or relevant release of DNA fragments into the cytosol at any time between 0 and 6 h after diquat treatment. Despite the activation of JNK after high doses of diquat, the JNK inhibitor SP-600125 did not protect against diquat-induced necrosis. Menadione alone did not cause liver injury, but, in combination with phorone and FeSO4, induced moderate oncotic necrosis. On the other hand, if animals were treated with galactosamine/endotoxin as positive control for apoptosis, caspase-3 activities were increased by 259%, the number of TUNEL-positive cells with apoptotic morphology was increased 103-fold, and DNA fragmentation was enhanced 6-fold. The data indicate that liver cell death initiated by diquat-induced superoxide formation in vivo is mediated predominantly by oncotic necrosis and is independent of JNK activation.
Transcriptional regulation of IL-6 in bile duct epithelia by extracellular ATP
Authors: Yu Jin , Sheung Nina , Soliman Elwy M. , Spirli Carlo , Dranoff Jonathan A.
Published: January 2009

The inflammatory cytokine IL-6 is essential for cell survival after liver injury. Bile duct epithelia (BDE) markedly upregulate IL-6 release after liver injury, but the mechanisms regulating this have not been defined. Purinergic signals induce multiple potent downstream effects in BDE, so the goals of this study were to determine whether extracellular ATP regulates BDE IL-6 transcription and to identify the molecular mechanisms regulating this process. Effects of extracellular nucleotides on IL-6 transcription in primary rat bile duct epithelia were assessed. The relative effects of cAMP and cytosolic calcium were determined by use of agonists and antagonists. The role of the cAMP response element (CRE) was determined by site-directed mutagenesis. We found that ATP potently upregulated IL-6 mRNA, and that the pharmacological profile for IL-6 upregulation was most consistent with the newly identified P2Y11receptor. This occurred in a cAMP-dependent and calcium-dependent fashion. The effect of cAMP and calcium agonists on IL-6 promoter activity was synergistic, and mutation of the IL-6 CRE blocked upregulation by ATP. Taken together, these data show that extracellular ATP acts through a mechanism involving a rat P2Y receptor functionally related to the P2Y11receptor, cAMP, and calcium signals and that the IL-6 promoter CRE to upregulate transcription of IL-6 in BDE. Since IL-6 has such critical importance in the liver, it is likely that this pathway is of great relevance to the understanding of hepatic response to injury.
Lymphatic pump-conduit duality: contraction of postnodal lymphatic vessels inhibits passive flow
Authors: Quick Christopher M. , Ngo Bruce L. , Venugopal Arun M. , Stewart Randolph H.
Published: January 2009

Lymphangions, the segments of lymphatic vessels between valves, exhibit structural characteristics in common with both ventricles and arteries. Although once viewed as passive conduits like arteries, it has become well established that lymphangions can actively pump lymph against an axial pressure gradient from low-pressure tissues to the great veins of the neck. A recently reported mathematical model, based on fundamental principles, predicted that lymphangions can transition from pump to conduit behavior when outlet pressure falls below inlet pressure. In this case, the axial pressure gradient becomes the major source of energy for the propulsion of lymph, despite the presence of cyclical contraction. In fact, flow is augmented when cyclical contractions are abolished. We therefore used an in vitro preparation to confirm these findings and to test the hypothesis that lymphangion contraction inhibits flow when outlet pressure falls below inlet pressure. Bovine postnodal mesenteric lymphatic vessels harvested from an abattoir were subjected to an inlet pressure of 5.0 cmH2O and an outlet pressure that decreased from 6.5 to 3.5 cmH2O under control conditions, stimulated with U-46619 (a thromboxane analog) and relaxed with calcium-free solution. Under control conditions, lymphatic flow markedly increased as outlet pressure fell below inlet pressure. In this case, the slopes of the flow versus axial pressure gradient increased with calcium-free conditions (61%, n = 8, P = 0.016) and decreased with U-46619 stimulation (21%, n = 5, P = 0.033). Our findings indicate that the stimulation of lymphatic contractility does indeed inhibit lymphatic flow when vessels act like conduits.
Left ventricular regional wall curvedness and wall stress in patients with ischemic dilated cardiomyopathy
Authors: Zhong Liang , Su Yi , Yeo Si-Yong , Tan Ru-San , Ghista Dhanjoo N. , Kassab Ghassan
Published: January 2009

Geometric remodeling of the left ventricle (LV) after myocardial infarction is associated with changes in myocardial wall stress. The objective of this study was to determine the regional curvatures and wall stress based on three-dimensional (3-D) reconstructions of the LV using MRI. Ten patients with ischemic dilated cardiomyopathy (IDCM) and 10 normal subjects underwent MRI scan. The IDCM patients also underwent delayed gadolinium-enhancement imaging to delineate the extent of myocardial infarct. Regional curvedness, local radii of curvature, and wall thickness were calculated. The percent curvedness change between end diastole and end systole was also calculated. In normal heart, a short- and long-axis two-dimensional analysis showed a 41 ± 11% and 45 ± 12% increase of the mean of peak systolic wall stress between basal and apical sections, respectively. However, 3-D analysis showed no significant difference in peak systolic wall stress from basal and apical sections ( P = 0.298, ANOVA). LV shape differed between IDCM patients and normal subjects in several ways: LV shape was more spherical (sphericity index = 0.62 ± 0.08 vs. 0.52 ± 0.06, P < 0.05), curvedness at end diastole (mean for 16 segments = 0.034 ± 0.0056 vs. 0.040 ± 0.0071 mm−1, P < 0.001) and end systole (mean for 16 segments = 0.037 ± 0.0068 vs. 0.067 ± 0.020 mm−1, P < 0.001) was affected by infarction, and peak systolic wall stress was significantly increased at each segment in IDCM patients. The 3-D quantification of regional wall stress by cardiac MRI provides more precise evaluation of cardiac mechanics. Identification of regional curvedness and wall stresses helps delineate the mechanisms of LV remodeling in IDCM and may help guide therapeutic LV restoration.
Phosphoinositide 3-kinase Akt signaling pathway interacts with protein kinase Cβ2 in the regulation of physiologic developmental hypertrophy and heart function
Authors: Rigor Debra L. , Bodyak Natalya , Bae Soochan , Choi Jun H. , Zhang Li , Ter-Ovanesyan Dmitry , He Zhiheng , McMullen Julie R. , Shioi Tetsuo , Izumo Seigo , King George L. , Kang Peter M.
Published: January 2009

The phosphoinositide 3-kinase (PI3-kinase)-protein kinase B (Akt) signaling pathway is essential in the induction of physiological cardiac hypertrophy. In contrast, protein kinase C β2 (PKCβ2) is implicated in the development of pathological cardiac hypertrophy and heart failure. Thus far, no clear association has been demonstrated between these two pathways. In this study, we examined the potential interaction between the PI3-kinase and PKCβ2 pathways by crossing transgenic mice with cardiac specific expression of PKCβ2, constitutively active (ca) PI3-kinase, and dominant-negative (dn) PI3-kinase. In caPI3-kinase/PKCβ2 and dnPI3-kinase/PKCβ2 double-transgenic mice, the heart weight-to-body weight ratios and cardiomyocyte sizes were similar to those observed in caPI3-kinase and dnPI3-kinase transgenic mice, respectively, suggesting that the regulation of physiological developmental hypertrophy via modulation of cardiomyocyte size proceeds through the PI3-kinase pathway. In addition, we observed that caPI3-kinase/PKCβ2 mice showed improved cardiac function while the function of dnPI3-kinase/PKCβ2 mice was similar to that of the PKCβ2 group. PKCβ2 protein levels in both dnPI3-kinase/PKCβ2 and PKCβ2 mice were significantly upregulated. Interestingly, however, PKCβ2 protein expression was significantly attenuated in caPI3-kinase/PKCβ2 mice. PI3-kinase activity measured by Akt phosphorylation was not affected by PKCβ2 overexpression. These data suggest a potential interaction between these two pathways in the heart, where PI3-kinase is predominantly responsible for the regulation of physiological developmental hypertrophy and may act as an upstream modulator of PKCβ2 with the potential for rescuing the pathological cardiac dysfunction induced by overexpression of PKCβ.
Temporal changes in expression of connexin 43 after load-induced hypertrophy in vitro
Authors: Bupha-Intr Tepmanas , Haizlip Kaylan M. , Janssen Paul M. L.
Published: January 2009

Upon remodeling of the ventricle after a provoking stimulus, such as hypertension, connections between adjacent myocytes may need to be “reformatted” to preserve a synchronization of excitation of the remodeling heart. In the mammalian heart, the protein connexin forms the gap junctions that allow electrical and chemical signaling communication between neighboring cells. We aim to elucidate whether mechanical load, in isolation, potentially changes the expression of connexin 43 (Cx43), the major isoform of the connexin family in the ventricle, and its phosphorylation. Cx43 expression levels and contractile function of multicellular rabbit cardiac preparations were assessed in a newly developed in vitro system that allows for the study of the transition of healthy multicellular rabbit myocardium to hypertrophied myocardium. We found that in mechanically loaded cardiac trabeculae, Cx43 levels remained stable for about 12 h and then rapidly declined. Phosphorylation at Ser368 declined much faster, being almost absent after 2 h of high-load conditions. No-load conditions did not affect Cx43 levels, nor did phosphorylation at Ser368. The downregulation of Cx43 under mechanical load did not correspond with the contractile changes that were observed. Furthermore, blocking paracrine activity of the muscle could only partially prevent the downregulation of Cx43. Additionally, no effect of mechanical loading on the expression of N-cadherin and zonula occludens-1 was observed, indicating a specificity of the connexin response. High mechanical load induced a rapid loss of Cx43 phosphorylation, followed by a decrease in Cx43 protein levels. Paracrine factors are partly responsible for the underlying mechanism of action, whereas no direct correlation to contractile ability was observed.
Impairment of the autonomic nervous function during decompression sickness in swine
Authors: Bai Yan , Mahon Richard T. , White Joseph C. , Brink Peter R. , Chon Ki H.
Published: January 2009

Dysautonomia has been observed in many cardiac diseases; however, its effect in decompression sickness (DCS) has not been well examined largely due to the difficulty in obtaining experimental data in human or animal subjects. In this study, we examine how DCS affects the autonomic nervous system's (ANS) dynamics in swine. Baseline and post-DCS electrocardiograms were obtained via telemetry recordings and compared. These data were analyzed using both the power spectrum method and our recently developed principal dynamic mode (PDM) analysis. PDM is able to separate the dynamic tones of the sympathetic and parasympathetic nervous systems. Both methods demonstrated a statistically significant decrease (>55%; P < 0.05) in the dynamics of both branches of the autonomic nervous system in the swine with DCS compared with the control condition. In cardiac diseases such as myocardial infarction, ANS imbalance is often associated with a significant increase in sympathetic tone, which may or may not be counterbalanced by parasympathetic nervous activity. However, the effect of DCS is such that both branches of the ANS are depressed >55% compared with the control condition, suggesting impairment, but not imbalance, of the ANS.