bluuebunny/crossref_metadata_2025 huggingface dataset:
An Investigation on the Synchronization Regime of a Single Cylinder in Cross-Flow Subject to Harmonic Oscillations
Authors: Pinto Waldir Terra , Vitola Marcelo Arau´jo , Levi Carlos Antoˆnio
Published: May 2009

This work presents a numerical study on the synchronization regime of a single cylinder subject to forced harmonic motion in the transverse direction of the flow. The study is carried out for a circular cylinder for Reynolds number around 500. The forced harmonic amplitude to diameter ratio is 0.22 and the forced frequency varies from 0.2 to 4.8 Hz. The Navier-Stokes equations are solved in a non-staggered grid using a sixth-order compact difference schemes to evaluate the spatial derivatives, a low-storage third-order Runge-Kutta scheme for time integration. The cylinder is represented using a feedback force methodology. The results are compared with experimental data obtained in a water tunnel. Results show clearly that synchronization phenomenon in the fundamental frequency as well as to its super and sub-harmonics.
Hatch Seal Design Parameters for Manned Submersibles
Authors: Henkener Jerry A. , Johnson Donald W.
Published: May 2009

Southwest Research Institute conducted a test program on the 26-inch diameter hatch seal o-ring for a manned submersible vehicle. The tests measured o-ring extrusion at pressure differentials across the seal of up to 1560 psig and gaps between the sealing surfaces of up to 0.110 inches. This paper presents a test protocol for determining the maximum gap that a given size o-ring can seal at a given pressure. This paper also presents charts of extrusion vs. seal gap and addresses the potential for o-ring damage when the sealed joint is depressurized. The test results were used in the design of the hatch seal for the U.S. Navy Pressurized Rescue Module and represent the first industry-wide o-ring design data for face seals in large diameter mechanical joints that do not close with pressure.
Development and Qualification of Pipeline Welding Procedures for Strain Based Design
Authors: Hukle Martin W. , Lillig Dan B. , Newbury Brian D. , Dwyer John , Horn Agnes Marie
Published: May 2009

This paper reviews the specific testing methodologies implemented for the qualification of mechanized pulsed gas metal arc welding (PGMAW) procedures for strain based design applications. The qualified welding procedures were used during recent construction of an offshore pipeline subject to potential ice scour with an initial design target of 4% tensile strain capacity. This paper addresses the integrated development of linepipe specifications, large scale validation testing, weld procedure development, and finally, the verification of robustness through full scale pressurized testing of actual girth welds on project pipe material. The qualification sequence, from linepipe specification development through final full scale girth weld proof test is described.
Wave Distributions and Sampling Variability
Authors: Hagen O̸istein
Published: May 2009

The paper describes the effect of sampling variability on the predicted extreme individual wave height and the predicted extreme individual crests height for long return periods, such as for the 100-year maximum wave height and 100-year maximum crest height. We show that the effect of sampling variability is different for individual crest or wave height as compared to for significant wave height. The short term wave statistics is modeled by the Forristall crest height distribution and the Forristall wave height distribution [3,4]. Samples from the 3-hour Weibull distribution are simulated for 100.000 years period, and the 100-year extreme values for wave heights and crest heights determined for respectively 20 minute and 3 hour sea states. The simulations are compared to results obtained by probabilistic analysis. The paper shows that state of the art analysis approaches using the Forristall distributions give about unbiased estimates for extreme individual crest or wave height if implemented appropriately. Direct application of the Forristall distributions for 3-hour sea state parameters give long term extremes that are biased low, and it is shown how the short term distributions can be modified such that consistent results for 20 minute and 3 hour sea states are obtained. These modified distributions are expected applicable for predictions based on hindcast sea state statistics and for the environmental contour approach.
Correlation of Phased Array Inspection and Fatigue Performance of FSW Joints
Authors: Caravaca Delphine S. , Bird Colin R. , Beamish Kathryn , Maddox Stephen
Published: May 2009

Friction Stir Welding (FSW) of aluminium alloys is now an establish joining technique and there is increasing application of FSW to joining of critical components and structures. Much emphasis has been placed on optimising tool design and process parameters to ensure joint quality but flaws may still be created in the production environment if the limits of the “process window” are exceeded. There is a requirement to understand the type of flaws that may be generated, and their causes, when welding conditions deviate from the optimum. This paper has taken a step forward in NDT knowledge. This paper presents the result of an integrated project correlating NDT performance against fatigue performance for AL 2024 T3 butt welds.
Full Scale Monitoring Marco Polo Tension Leg Platform
Authors: van Dijk Radboud , van den Boom Henk
Published: May 2009

Installed 160 miles South of New Orleans in 1300 m of water, the Marco Polo Tension Leg Platform is subjected to an extensive monitoring campaign to benchmark design data and methods. The purpose of the full scale monitoring campaign is to evaluate the design in operation exposed to hurricane and loop-current conditions. Interests comprise the high and low frequency modes of motion, the fatigue loading of the platform and the dynamic behavior of the tendons and risers with focus on vortex induced vibrations. To evaluate these results wind, wave and current conditions are closely monitored. The monitoring system was in operation during the passage of hurricanes Ivan, Katrina and Rita. Although Marco Polo was extremely close to the center of these severe hurricanes, no significant damage was inflicted to the platform, even though wind speeds in excess of 138 mph and maximum wave heights over 28 m were measured. However, very valuable data was collected on the wave, wind, current, as well as on the response of the TLP during the Hurricane conditions.
Large Scale Airlift Experiments for Application to Deep Ocean Mining
Authors: Doyle Richard L. , Halkyard John E.
Published: May 2009

Deep ocean mining for manganese nodules was the subject of extensive research and development in the 1970s. Recently, the discovery of very rich massive sulfide deposits in deep water has sparked renewed interest in this technology. This paper will report the results of a series of experiments conducted in the late 1970s to validate predictions for the performance of airlift pumping for an ocean mining application. The paper will discuss the sensitivity of airlift performance to proper flow regime maintenance and the comparison between experiments and theory. Implications on full scale system design and control will be discussed.
Calibration of Partial Safety Factors Through the Inverse FORM Method
Authors: Silva-Gonza´lez Francisco L.
Published: May 2009

A calibration method which uses the so-called inverse FORM approach is proposed. The objective is to find the design point on a hypersphere in U-space, whose radius is the target reliability index, which maximizes the response that the structural system must withstand. Once the design point is determined, the safety factors can be calculated. It is demonstrated that the computational cost of the proposed method is less than the computational cost of traditional calibration techniques. The proposed method is illustrated by means of three examples: parabolic, Eurocode and suction caisson design equations.
Strain Measurement on Riser Pipe Compared With Model Test and Calculation
Authors: Maeda Katsuya , Takahashi Ichihiko , Itoh Kazuaki , Kokubun Kentaroh , Ohuchi Kazuyuki , Masuda Satoshi , Uto Shotaro
Published: May 2009

For pumping up deep ocean water, a SPAR type floating structure with a steel riser pipe was installed in Sagami Bay, Japan, in 2003. The riser pipe, which is 175 m long and 1.0 m in diameter, was connected to the floating structure by two mooring chains. At the middle height of the riser pipe, strain gages were attached on the pipe surface so that they faced to 8 directions at equal angles. The authors measured not only strains but also motions of the floating structure and wave and current conditions from 2003 to 2005. From these measured results in actual sea, it was found that the strains (or stresses) of the riser pipe are mostly concerned with motions of the floating structures, more than wave and current conditions. In order to make clear this phenomenon, the authors carried out forced oscillation tests by using a reduced riser pipe model in the Deep-sea Basin in National Maritime Research Institute, along with some numerical simulations based on FEM. In this paper, we show the results of the model tests and numerical simulations compared with the measured results in actual sea.
A Semi Submersible in Combined Extreme Waves and Current: Comparison of Model Tests and Existing Software
Authors: Bratland Anne Katrine , Haver Sverre , Stansberg Carl Trygve , Zhang Fuwei , Allers Joachim , Krokstad Jo̸rgen , Ersdal Svein
Published: May 2009

Floating production systems are often exposed to combined waves and current. Normally, the effects from a steady current are neglected in the calculation methods for dynamic loads and motions. In some parts of the world the current velocities can be so large that neglecting wave-current interaction effects is questionable. Computer programs that handle wave-current interaction have been available for decades. However, so far very little results have been documented which validate the theories. Model test results for a semi submersible in extreme North Sea waves are presented, with and without current. The comparison with wave-current interaction computer models shows that the effect is generally over-estimated for the present case with a mean current velocity equal to 1.3 m/sec.
Field Measurement and Modelling of the Material Cycle in the Cultivation Pond of Penaeid Shrimp Penaeus Japonicus
Authors: Kitazawa Daisuke , Hakuta Keiichiro , Yamayoshi Nobuyuki , Tabeta Shigeru
Published: May 2009

Field measurement and modelling of the material cycle are carried out for the cultivation pond of penaeid shrimp Penaeus japonicus. The main purpose of the present study is to investigate the sustainability of coastal shrimp aquaculture, which is increasingly being questioned due to many problems like disease, excessive nutrient enrichment, and low levels of dissolved oxygen tension. Despite the great economic importance of shrimps and their suitability to aquaculture, little is known about the material cycle through the cultivation pond. Additionally, the collapse of shrimp aquaculture in most tropical countries may be attributed to the lack of ecological, biological, and environmental understanding. Hence field measurement of water quality is conducted in the shrimp cultivation pond, which locates in the Kyushu district of Japan. Various environmental factors such as water temperature, salinity, and the concentrations of dissolved oxygen, nutrients, and chlorophyll a are monitored for the water in the pond and that drawn from the outer sea during November and December of 2006. In addition to field measurement, one dimensional numerical model is developed for the shrimp cultivation pond to understand the material cycle through the pond in a quantitative manner. The numerical model consists of physical, lower trophic-level ecosystem, and shrimp growth submodels. The numerical values of physical and physiological parameters are calibrated to achieve the best agreement between observed and simulated results. By integrating results from field measurement and numerical simulation, it is revealed that the quality of water in the cultivation pond is quite different from that drawn from the outer sea. In particular the concentration of chlorophyll a is much higher in the cultivation pond due to large primary production. The results of the numerical simulation show that the high productivity is attributed partly to the activities of shrimps. The information from field measurement and the simulated results of the developed numerical model are useful to optimize the food quantity and quality, the population density of shrimps, and the design of watermills or the other equipments to improve the water quality for sustainable use of coastal shrimp cultivation pond.
Mathematical and Experimental Analysis of Schooling Behavior During Growth in Juvenile Chub Mackerel: Considerations of Population Density and Space Limitation
Authors: Suzuki Katsuya , Torisawa Shinsuke , Takagi Tsutomu
Published: May 2009

Population density and space limitation have proven important considerations for both fisheries management and aquaculture, resulting in intense interest in the development of new techniques and technologies for management and hatchery applications. To investigate the effects of space limitation and population density on the schooling behavior of fish, we examined the schooling behavior of captive juvenile chub mackerel. Three groups of fish were collected; collections were made at 18, 42, and 73 days post-hatch (dph) at which mean body lengths were 2.28, 8.83, and 11.4 cm, respectively. The two-dimensional movement of individuals during 200-s observation periods was digitized and processed. A mathematical model based on Newton’s second law of motion was used to quantify the forces dominating schooling behavior. The forces of swimming motion were quantified for each fish in a school as the propulsive force due to the swimming ability of each fish, the interactive force used to keep the proper distance and maintain similar velocity with neighboring fish, and the repulsive force used to keep a proper distance from the wall. The magnitude of the repulsive force was minimized in the 18-dph school, maximized in the 42-dph school, and decreased in the 73-dph school. The magnitudes of the propulsive and interactive forces increased with growth. Thus, the interactive force, which was critical for school formation and maintenance appears to reduce the importance of the repulsive force and causes the decline in the repulsive force between 18 and 73 dph.
Response-Based Estimation of Sea State Parameters
Authors: Nielsen Ulrik D.
Published: May 2009

Reliable estimation of the on-site sea state parameters is essential to decision support systems for safe navigation of ships. The sea state parameters can be estimated by Bayesian Modelling which uses complex-valued frequency response functions (FRF) to estimate the wave spectrum on the basis of measured ship responses. It is therefore interesting to investigate how the filtering aspect, introduced by FRF, affects the final outcome of the estimation procedures. The paper contains a study based on numerical generated time series, and the study shows that filtering has an influence on the estimations, since high frequency components of the wave excitations are not estimated as accurately as lower frequency components. Moreover, the paper investigates how the final outcome of the Bayesian Modelling is influenced by the accuracy of the FRF. Thus, full-scale data is analysed by use of FRF calculated by a 3-D time domain code and by closed-form (analytical) expressions, respectively. Based on comparisons with wave radar measurements and satellite measurements it is seen that the wave estimations based on closed-form expressions exhibit a reasonable energy content, but the distribution of energy appears to be incorrect.
A Fundamental Study About an Activity Trend of NPO of the Seaside Chosen by a Private Sector Management System
Authors: Hirao Naoyuki , Kondo Takeo , Yamamoto Kazukiyo , Arai Masato , Ochi Yasuhito
Published: May 2009

Conventionally, the institutions which Autonomy owns do not consider the space requirement that the institution is located in. Therefore, there was not one effective inflection that only an administration method grieved at in all institutions. In 2005, By Local Government Act revision, A management method of the institution which a Autonomy owned was changed of from “Management Trust System” to “A Private Sector Management System”. By this law revision, Regulation was relaxed, and private enterprise/NPO is able to have come to enter it. With it, each institution plays a role as every space, and it is hoped that it is inflected effectively as a high institution of specialty. In this study, I ascertain an activity trend of NPO juridical person and an element of a private sector management system choice requirement, I am aimed at arriving at means to use institutions of Autonomy functionally.
Case History of Multiphase Pump Applications in California Thermal Heavy Oil Operations
Authors: Corless Robert J. , Hasan Asad
Published: May 2009

Chevron North America Exploration and Production (CNAEP) has successfully used Multiphase Pumps (MPP) in its thermally enhanced heavy oil operations in San Joaquin Valley, California since March 2000. MPP’s are used to transfer produced fluids, solids, gas and sometimes steam. These pumps allowed Chevron to eliminate the need for numerous field tanks, gas pipelines, vapor recovery facilities and permits associated with thermally enhanced heavy oil operations. This case history will discuss three different applications of MPP’s used for boosting flowing wells, boosting rod pump wells and finally used as charge pumps for Heater Treaters to solve reliability issues. This paper will discuss the advantages and disadvantages of these installations and share lessons learned regarding design and maintenance. Specific design issues to be discussed include operating conditions, seals, metallurgy and control philosophy as well as design considerations for new pump installations.
Using Dynamics Measurements While Drilling to Detect Lithology Changes and to Model Drilling Dynamics
Authors: Reckmann Hanno , Jogi Pushkar , Herbig Christian
Published: May 2009

As a result of bit-rock interaction, downhole weight-on-bit, downhole torque, instantaneous downhole rotational speed and bit motion (acceleration and rate of penetration) are directly affected by the formations being drilled. Since these measurements react differently to different lithologies, and assuming that drilling problems do not effect these measurements, any changes in the measurements in some way will reflect changes in the properties of the lithology. If, based on these measurements, the lithology is assumed to have certain properties, then it is possible to derive models for the interaction between bit, formation and drillstring. With these models it is possible to simulate the dynamic behavior of the system including phenomena like stick-slip. Rate of penetration has long been used as a lithology indicator, and drilling models have been developed using surface measured drilling parameters to infer changes in lithology. With the advent of MWD measurements, significant improvements were made in the mathematical models by involving downhole torque. The model derived parameters were shown to be related to rock strength (drilling and shear strength) and proved to be good indicators of formation changes. Similar expressions in the form of simple bit models can be used in combination with a finite element model of the drillstring to simulate the dynamic behavior of the complete system. A significant improvement in this analysis can be affected by introducing measurements from the dynamics tool, such as instantaneous torque, weight and rotation rate, as well as the bit acceleration. These measurements provide not only static but also dynamic data which can be used to validate simulations and the underlying models. The present analysis explores the use of the dynamic measurements and the application of some drilling models in analyzing formation changes while drilling, and the use of these data and models in simulating drilling dynamics.
Implementing Agreement on Ocean Energy Systems
Authors: Pontes M. Teresa
Published: May 2009

The Implementing Agreement on Ocean Energy Systems is an International Energy Agency technical collaborative programme on ocean energy that was setup in 2001 by three countries. Presently it has 12 Member-Countries it being while others are showing interest to join. In this paper the activities that were carried out during the first five-year term, the benefits obtained and the recommendations for further work are presented. This is followed by the revised mission and strategy for the 2007–2011 term and the presentation of the planned work.
Numerical and Experimental Modeling of Direct-Drive Wave Energy Extraction Devices
Authors: Elwood David , Yim Solomon , Yokochi Alex , Rhinefrank Ken , Prudell Joe , Schacher Al , Hogan Peter , Vander Muelen Aaron , von Jouanne Annette , Brekken Ted
Published: May 2009

The solutions to today’s energy challenges need to be explored through alternative, renewable and clean energy sources to enable a diverse national energy resource plan. An extremely abundant and promising source of energy exists in the world’s oceans in the forms of wave, tidal, marine current, thermal (temperature gradient) and salinity. Among these forms, significant opportunities and benefits have been identified in the area of wave energy extraction. Waves have several advantages over other forms of renewable energy such as wind and solar, in that the waves are more available (seasonal, but more constant) and more predictable, thus enabling more straightforward and reliable integration into the electric utility grid. Wave energy also offers higher energy densities, enabling devices to extract more power from a smaller volume at consequent lower costs. However, many engineering challenges need to be overcome to ensure wave energy device survivability, reliability and maintainability, in addition to efficient and high quality power take-off systems. Optimizing wave energy technologies requires a multi-disciplinary team from areas such as Electrical, Chemical, Ocean, Civil and Mechanical Engineering, to enable innovative systems-level research and development. This paper presents some recent research developments on experimental and numerical modeling on direct-drive approaches and the associated devices designed to convert the motion of the ocean waves into electrical energy using point absorber wave energy converters. This research is focused on a simplification of processes, i.e., replacing systems using intermediate hydraulics or pneumatics with direct-drive approaches to allow generators to respond directly to the movement of the ocean by employing magnetic fields for contact-less mechanical energy transmission, and power electronics for efficient electrical energy extraction. The term “direct” drive describes the direct coupling of the buoy’s velocity and force to the generator without the use of hydraulic fluid or air. The wave energy buoy and spar are designed to efficiently capture ocean wave energy and transfer it to the generator. These buoys have been tested at the Oregon State University O.H. Hinsdale Wave Research Laboratory, with planned testing off the coast of Oregon. The paper will examine several direct-drive approaches, including electrical and mechanical design characteristics, describe the numerical modeling of the associated conceptual devices, prototype testing, and some ongoing research on the dynamics of buoy generator systems for design optimization.
Assessment of Free Surface Treatment Techniques and Turbulence Models Influence Using the Slightly Compressible Flow Simulation
Authors: Ciortan C. , Guedes Soares C. , Wanderley J.
Published: May 2009

A free surface, finite-difference code on collocated grids, using the Slightly Compressible Flow formulation, is used for simulating turbulent flow around a Wigley hull. Two free-surface treatment techniques are compared in terms of accuracy and influence on the flow parameters. The runs were performed in standard conditions of Froude numbers and the results were compared against experimental and numerical results. The initial version of the code used an interface-tracking technique and two turbulence models (Large Eddy Simulation and Baldwin-Lomax). The numerical scheme was marched in time using the factorized Beam and Warming implicit method. The second version of the code uses an interface-capturing technique. For the time being, the code uses a fixed grid on which the kinematic free surface equation is solved. The grid is identical to the initial grid used in the first set of formulations. Other changes in the code were necessary, the most important being the switch of the time-marching method to a 2nd order, explicit Runge-Kutta. The results show good agreement with the experimental results.
Time Domain Simulations of Side-by-Side Moored Vessels: Lessons Learnt From a Benchmark Test
Authors: Naciri Mamoun , Waals Olaf , de Wilde Jaap
Published: May 2009

Time domain simulations are used extensively to assess the availability of turret moored terminals for offloading operations. The availability analysis provides a key input when assessing the economical viability of a project. In this context, it was deemed important to perform a benchmark study. Three programs have been used: AQWA-DRIFT - an ANSYS product maintained by Century Dynamics and used at SBM, LIFSIM and aNySIM both developed in MARIN. Five environments including wind, waves and current have been selected one of which with all components in-line and the remaining four with oblique wind and current. Simulations have been performed with identical input for the three programs. Results are compared statistically, but also in the time domain. Lessons learned will be discussed and areas of improvement identified.
A Literature Review of Risk Assessment of Ship-FPSO Collisions
Authors: Wang Ge , Pedersen Preben Terndrup
Published: May 2009

This paper reviews the latest research and analyses related to the risk assessment of ship-FPSO collision. The focus is placed on: existing criteria, FPSO collision accident, design scenarios for FPSO collision, mechanics of collision incidents, consequences and acceptance criteria. The research achievements of ships’ collision and grounding since 1990s are introduced. Issues specific to ship-FPSO collisions that deserve further development are addressed. The content of this paper is mainly drawn from the ISSC 2006 Specialist Committee V.1 on Collision and Grounding.
Offshore Standards: The Impact of Hurricanes Ivan/Katrina/Rita
Authors: Wisch David J. , Ward E. G.
Published: May 2009

Prior to the 2004 Hurricane Season, offshore practices and standards continued evolving incorporating new technology and experience. The disruption of the industry from damaged facilities and infrastructure was unprecedented. A critical review of the production disruption was undertaken to identify where standards may need to be adjusted to increase robustness in the future, where gaps may exist and what elements are outside traditional scope. The industry stakeholders responded with several interim guidelines coupled multi-year programs of investigation and update of standards. This paper will provide an assessment of the damage reviews, initial interim standards and the long range plans for upgrading infrastructure performance.
ISSC Technical Committee I.1 Environment
Authors: Hutchison Bruce L.
Published: May 2009

This paper presents highlights of the report of the 16th International Ship and Offshore Structure Congress (ISSC) I.1 Environment Committee presented in August 2006 in Southampton, UK. Subjects addressed include notable accomplishments in the study of the marine environment pertinent to the design and operation of ships and offshore structures. These include advances in the past three years with respect to sensing, modeling and analysis of environmental data, discussion of rogue waves, climate change and parametric roll, and recommendations for further research.
Collapse Behaviour of Damaged Panels With a Dimple Imperfection
Authors: Lui´s Rui M. , Witkowska Malgorzata , Guedes Soares C.
Published: May 2009

This paper deals with the influence that a localised damage induced dimple imperfection can have on the ability of a panel to resist in-plane compressive loads. A single damaged plate on a ship is not a severe problem, but if enough plates have been damaged then the ability of a panel to carry its intended load can be compromised. In this study a finite element non-linear analysis of panels having different geometry is carried out in order to identify the influence of various parameters on the collapse strength. The finite element model used is of a panel, 3 plates long and 3 plates across. It was found that the position of the dimple imperfection on the panel is an important factor, that the dimple imperfection not only reduces the collapse strength but induces a more violent collapse and that it has an influence over the mode of collapse.
Inhibition of Hedgehog Signaling Enhances Delivery of Chemotherapy in a Mouse Model of Pancreatic Cancer
Authors: Olive Kenneth P. , Jacobetz Michael A. , Davidson Christian J. , Gopinathan Aarthi , McIntyre Dominick , Honess Davina , Madhu Basetti , Goldgraben Mae A. , Caldwell Meredith E. , Allard David , Frese Kristopher K. , DeNicola Gina , Feig Christine , Combs Chelsea , Winter Stephen P. , Ireland-Zecchini Heather , Reichelt Stefanie , Howat William J. , Chang Alex , Dhara Mousumi , Wang Lifu , Rückert Felix , Grützmann Robert , Pilarsky Christian , Izeradjene Kamel , Hingorani Sunil R. , Huang Pearl , Davies Susan E. , Plunkett William , Egorin Merrill , Hruban Ralph H. , Whitebread Nigel , McGovern Karen , Adams Julian , Iacobuzio-Donahue Christine , Griffiths John , Tuveson David A.
Published: May 2009

It's All in the Delivery

Pancreatic cancer is almost universally associated with a poor prognosis, in part because the tumors are resistant to chemotherapeutic drugs. Working with a mouse tumor model that displays many features of the human disease,

Olive
et al.

(p.
1457
, published online 21 May; see the Perspective by

Olson and Hanahan

) found that the tumors were poorly vascularized, a factor likely to impede drug delivery. Treatment of the mice with the chemotherapeutic drug gemcitabine in combination with a drug that depletes tumor-associated stromal tissue led to an increase in tumor vasculature, enhanced delivery of gemcitabine, and a delay in disease progression. Thus, drugs targeting the tumor stroma may merit investigation as a way to enhance the efficacy of conventional chemotherapy for pancreatic cancer.
Beryllium Dimer—Caught in the Act of Bonding
Authors: Merritt Jeremy M. , Bondybey Vladimir E. , Heaven Michael C.
Published: May 2009

2 Be or Not 2 Be?

The beryllium dimer is a rather simple-looking compound, bridging two atoms of the fourth-lightest element. Yet it has long posed a frustrating challenge to theorists, because, to a first approximation, chemical bonding models suggest that it should not exist. In recent decades, calculations of ever-increasing sophistication have offered rationales for the two atoms' puzzling mutual attraction. Now

Merritt
et al.

(p.
1548
, published online 21 May; see the Perspective by

Bernath

) have used high-resolution spectroscopy to assemble, at last, a full experimental potential energy function describing the ground electronic state of Be
2
. The curve is unusually shallow at long bond lengths, deviating from the contour of more traditional molecular Morse potentials, and provides a detailed basis of comparison for future theoretical bonding frameworks.
IMAGE DENOISING BASED ON WAVELET SHRINKAGE USING NEIGHBOR AND LEVEL DEPENDENCY
Authors: CHO DONGWOOK , BUI TIEN D. , CHEN GUANGYI
Published: May 2009

Since Donoho et al. proposed the wavelet thresholding method for signal denoising, many different denoising approaches have been suggested. In this paper, we present three different wavelet shrinkage methods, namely NeighShrink, NeighSure and NeighLevel. NeighShrink thresholds the wavelet coefficients based on Donoho's universal threshold and the sum of the squares of all the wavelet coefficients within a neighborhood window. NeighSure adopts Stein's unbiased risk estimator (SURE) instead of the universal threshold of NeighShrink so as to obtain the optimal threshold with minimum risk for each subband. NeighLevel uses parent coefficients in a coarser level as well as neighbors in the same subband. We also apply a multiplying factor for the optimal universal threshold in order to get better denoising results. We found that the value of the constant is about the same for different kinds and sizes of images. Experimental results show that our methods give comparatively higher peak signal to noise ratio (PSNR), are much more efficient and have less visual artifacts compared to other methods.
DISCRETE WAVELET TRANSFORM APPLIED ON PERSONAL IDENTITY VERIFICATION WITH ECG SIGNAL
Authors: CHIU CHUANG-CHIEN , CHUANG CHOU-MIN , HSU CHIH-YU
Published: May 2009

The main purpose of this study is to present a novel personal authentication approach with the electrocardiogram (ECG) signal. The electrocardiogram is a recording of the electrical activity of the heart and the recorded signals can be used for individual verification because ECG signals of one person are never the same as those of others. The discrete wavelet transform was applied for extracting features that are the wavelet coefficients derived from digitized signals sampled from one-lead ECG signal. By the proposed approach applied on 35 normal subjects and 10 arrhythmia patients, the verification rate was 100% for normal subjects and 81% for arrhythmia patients. Furthermore, the performance of the ECG verification system was evaluated by the false acceptance rate (FAR) and false rejection rate (FRR). The FAR was 0.83% and FRR was 0.86% for a database containing only 35 normal subjects. When 10 arrhythmia patients were added into the database, FAR was 12.50% and FRR was 5.11%. The experimental results demonstrated that the proposed approach worked well for normal subjects. For this reason, it can be concluded that ECG used as a biometric measure for personal identity verification is feasible.
Serine proteases decrease intestinal epithelial ion permeability by activation of protein kinase Cζ
Authors: Swystun Veronica A. , Renaux Bernard , Moreau France , Wen Shoubin , Peplowski Michael A. , Hollenberg Morley D. , MacNaughton Wallace K.
Published: May 2009

Epithelial permeability to ions and larger molecules in the gut is essential for fluid balance, and its dysregulation contributes to intestinal pathology. We investigated the effect of digestive serine proteases on epithelial paracellular permeability. Trypsin, chymotrypsin, and elastase elicited sustained increases in transepithelial resistance (RTE) in polarized monolayers of three intestinal epithelial cell lines. This effect was reflected by decreases in paracellular conductances of Na+and Cl−and a concomitant decrease in permeability to 3,000 molecular weight dextran. The enzyme activities of the proteases were required, yet activators of known protease-activated receptors (PARs) did not reproduce the effect of these proteases on RTE. PKCζ isoform-specific inhibitor significantly reduced the trypsin-induced increase in RTEwhereas PKCζ activity was increased in cells treated with trypsin and chymotrypsin compared with control cells; this activity was reduced to control levels in the presence of PKCζ-specific inhibitor. Ca2+chelators and pharmacological inhibitors of cell signaling support the role for PKCζ in the protease-induced effect. Finally, we showed that treatment with the serine proteases increased occludin immunostaining and zonula occludin-1 coimmunoprecipitation with occludin in the detergent-insoluble fraction of cell lysates, and these increases were ablated by pretreatment with PKCζ-specific inhibitor. This finding indicates increased insertion of occludin into the cell junctional complex. These data demonstrate a role for serine proteases in the facilitation of epithelial barrier function through a mechanism that is independent of PARs and is mediated by activation of PKCζ.
Maternal arterial stiffness in pregnancies affected by preeclampsia
Authors: Kaihura Christina , Savvidou Makrina D. , Anderson James M. , McEniery Carmel M. , Nicolaides Kypros H.
Published: May 2009

Preeclampsia (PE) is characterized by an aberrant maternal cardiovascular adaptation to pregnancy and increased cardiovascular risk later on in life. The aim of this study was to compare the maternal wave reflections and arterial stiffness in women with established PE and those with normotensive pregnancies, after systematic adjustment for known confounders. This was a cross-sectional study involving 69 normotensive, pregnant women and 54 women with established PE. Maternal wave reflection (augmentation index) and pulse wave velocity of the carotid-radial and carotid-femoral parts of the arterial tree were assessed noninvasively using applanation tonometry. The measurements were adjusted for maternal age, heart rate, mean arterial pressure, and aortic time to wave reflection and expressed as multiples of the median (MoM) of the control group. In the PE group, compared with controls, there was an increase in the median pulse wave velocity of both the carotid to femoral [1.1, interquartile rage (IQR) 1.0–1.3 MoM vs. 0.9, IQR 0.9–1.0 MoM; P < 0.0001] and carotid to radial (1.0, IQR 0.9–1.1 MoM vs. 0.9, IQR 0.9–1.0 MoM; P = 0.01) parts of the arterial tree. In contrast, there were no significant differences between the two groups in the median augmentation index (0.9, IQR 0.7–1.1 MoM vs. 1.0, IQR 0.5–1.8 MoM; P = 0.46). In conclusion, we found that established PE is characterized by increased maternal arterial stiffness but not altered maternal wave reflection.
Cross-Talk Between PKA and Akt Protects Endothelial Cells From Apoptosis in the Late Ischemic Preconditioning
Authors: Bellis Alessandro , Castaldo Diletta , Trimarco Valentina , Monti Maria Gaia , Chivasso Pierpaolo , Sadoshima Junichi , Trimarco Bruno , Morisco Carmine
Published: May 2009

Objective—

The aim of this study was to explore the molecular mechanisms involved in late preconditioning-induced cell protection in endothelial cells.

Methods and Results—

Preconditioning (PC) was induced by exposing bovine aortic endothelial cells (BAECs) to 3 cycles of 15 minutes of hypoxia followed by 15 minutes of reoxygenation. A 12-hour period of hypoxia induced cell death in 60% of BAECs (48±5% apoptosis, 12±4% necrosis). Early and late PC decreased hypoxia-induced apoptotic (25±5% and 28±4%, respectively) and necrotic (6±3%, and 8±2%, respectively) cell death. Consistently, hypoxia-induced caspase-3 cleavage was reduced by PC. Pretreatment with H89 (protein kinase A [PKA] inhibitor), LY294002 (phosphatidyl-inositol-3-kinase [PI3K] inhibitor), and N-acetyl-cysteine (antioxidant) abrogated late PC-induced cell protection, whereas inhibition of protein kinase C by Go6983, and of nitric oxide synthesis by L-NAME,1400W and bovine eNOS siRNA did not. In addition, in early and late PC, PKA physically interacted with the phosphorylated form of Akt, suggesting that PKA is required for Akt phosphorylation. Expression of PKA and Akt dominant negative mutants inhibited ischemic late PC-induced protection, indicating that these kinases play a key role in late PC-mediated cell protection.

Conclusions—

Late ischemic PC protects BAECs against hypoxia through PKA- and PI3K-dependent activation of Akt.
Peroxisome Proliferator-Activated Receptor δ Regulates Extracellular Matrix and Apoptosis of Vascular Smooth Muscle Cells Through the Activation of Transforming Growth Factor-β1/Smad3
Authors: Kim Hyo Jung , Kim Min Young , Jin Hana , Kim Hyun Joon , Kang Sang Soo , Kim Hye Jung , Lee Jae Heun , Chang Ki Churl , Hwang Jin-Yong , Yabe-Nishimura Chihiro , Kim Jin-Hoi , Seo Han Geuk
Published: May 2009

Homeostasis of the extracellular matrix and apoptosis of vascular smooth muscle cells (VSMCs) are key components in the regulation of the stability of atherosclerotic plaques. Here, we demonstrate that peroxisome proliferator-activated receptor (PPAR)δ regulates extracellular matrix synthesis and degradation through transforming growth factor-β1 and its effector, Smad3. Activation of PPARδ strongly amplified the expression of types I and III collagen, fibronectin, elastin, and TIMP-3 (tissue inhibitor of metalloproteinases 3), but not of TIMP-1, matrix metalloproteinase-2 or -9. The effect of PPARδ on the expression of type III collagen was dually regulated by the direct binding of PPARδ and Smad3 to a direct repeat-1 site and a Smad-binding element, respectively, in the type III collagen gene promoter. The activation of PPARδ attenuated apoptotic cell death in VSMCs induced by oxidized low-density lipoprotein, and similar antiapoptotic effects were observed on treatment of cells with exogenous type I and/or III collagen. Administration of a PPARδ ligand GW501516 to mice also suppressed elastase-induced cell death of aortic VSMCs. These results suggest that PPARδ-induced upregulation of extracellular matrix proteins exerts an antiapoptotic effect, thereby maintaining the stability of atherosclerotic plaques. Specific ligands of PPARδ may aid in the therapeutic intervention of atherosclerosis by improving plaque stability and patient prognosis.
Effects of Task-Oriented Circuit Class Training on Walking Competency After Stroke
Authors: Wevers Lotte , van de Port Ingrid , Vermue Mathijs , Mead Gillian , Kwakkel Gert
Published: May 2009

Background and Purpose—

There is increasing interest in the potential benefits of circuit class training after stroke, but its effectiveness is uncertain. Our aim was to systematically review randomized, controlled trials of task-oriented circuit class training on gait and gait-related activities in patients with stroke.

Methods—

A computer-aided literature search was performed to identify randomized, controlled trials in which the experimental group received task-oriented circuit class training focusing on the lower limb. Studies published up to March 2008 were included. The methodological quality of each study was assessed and studies with the same outcome variable were pooled by calculating the summary effect sizes using fixed or random effects models.

Results—

Six of the 445 studies screened, comprising 307 participants, were included. Physiotherapy Evidence Database scores ranged from 4 to 8 points with a median of 7.5 points. The meta-analysis demonstrated significant homogeneous summary effect sizes in favor of task-oriented circuit class training for walking distance (0.43; 95% CI, 0.17 to 0.68;
P
<0.001), gait speed (0.35; 95% CI, 0.08 to 0.62;
P
=0.012), and a timed up-and-go test (0.26; 95% CI, 0.00 to 0.51;
P
=0.047). Nonsignificant summary effect sizes in favor of task-oriented circuit class training were found for the step test and balance control.

Conclusions—

This meta-analysis supports the use of task-oriented circuit class training to improve gait and gait-related activities in patients with chronic stroke. Further research is needed to investigate the cost-effectiveness and its effects in the subacute phase after stroke, taking comorbidity into account, and to investigate how to help people maintain and improve their physical abilities after their rehabilitation program ends.
Relative and Cumulative Effects of Lipid and Blood Pressure Control in the Stroke Prevention by Aggressive Reduction in Cholesterol Levels Trial
Authors: Amarenco Pierre , Goldstein Larry B. , Messig Michael , O'Neill Blair J. , Callahan Alfred , Sillesen Henrik , Hennerici Michael G. , Zivin Justin A. , Welch K.M.A.
Published: May 2009

Background and Purpose—

The relative contributions of on-treatment low- and high-density lipoprotein cholesterol (LDL-C, HDL-C), triglycerides, and blood pressure (BP) control on the risk of recurrent stroke or major cardiovascular events in patients with stroke is not well defined.

Methods—

We randomized 4731 patients with recent stroke or transient ischemic attack and no known coronary heart disease to atorvastatin 80 mg per day or placebo.

Results—

After 4.9 years, at each level of LDL-C reduction, subjects with HDL-C value above the median or systolic BP below the median had greater reductions in stroke and major cardiovascular events and those with a reduction in triglycerides above the median or diastolic BP below the median showed similar trends. There were no statistical interactions between on-treatment LDL-C, HDL-C, triglycerides, and BP values. In a further exploratory analysis, optimal control was defined as LDL-C <70 mg per deciliter, HDL-C >50 mg per deciliter, triglycerides <150 mg per deciliter, and SBP/DBP <120/80 mm Hg. The risk of stroke decreased with as the level of control increased (hazard ratio [95% confidence interval] 0.98 [0.76 to 1.27], 0.78 [0.61 to 0.99], 0.62 [0.46 to 0.84], and 0.35 [0.13 to 0.96]) for those achieving optimal control of 1, 2, 3, or 4 factors as compared to none, respectively. Results were similar for major cardiovascular events.

Conclusions—

We found a cumulative effect of achieving optimal levels of LDL-C, HDL-C, triglycerides, and BP on the risk of recurrent stroke and major cardiovascular events. The protective effect of having a higher HDL-C was maintained at low levels of LDL-C.
Prevalence and Risk Factors Associated With Reversed Robin Hood Syndrome in Acute Ischemic Stroke
Authors: Alexandrov Andrei V. , Nguyen Huy Thang , Rubiera Marta , Alexandrov Anne W. , Zhao Limin , Heliopoulos Ioannis , Robinson Alice , DeWolfe Jennifer , Tsivgoulis Georgios
Published: May 2009

Background and Purpose—

Early deterioration can occur after acute stroke for a variety of reasons. We describe a hemodynamic steal and associated neurological deterioration, the reversed Robin Hood syndrome (RRHS). We aimed to investigate the frequency and factors associated with RRHS.

Methods—

Consecutive patients with acute cerebral ischemia underwent serial National Institutes of Health Stroke Scale and bilateral transcranial Doppler monitoring with breathholding. Steal magnitude (%) was calculated from transient mean flow velocity reduction in the affected arteries at the time of velocity increase in normal vessels. Excessive sleepiness and likelihood of sleep apnea were evaluated by the Epworth Sleepiness Scale and Berlin Questionnaire.

Results—

Among 153 patients (age, 61±14 years; 48% women; 21% transient ischemic attack) admitted within 48 hours from symptom onset, 21 (14%) had steal phenomenon (median steal magnitude, 20%; interquartile range, 11%; range, 6% to 45%), and 11 (7%) had RRHS. RRHS was most frequent in patients with proximal arterial occlusions (17% versus 1%;
P
<0.001). The following factors were independently (
P
<0.05) associated with RRHS (multivariate logistic regression model): male gender, younger age, persisting arterial occlusions, and excessive sleepiness (
P
<0.001). A 1-point increase in the Epworth Sleepiness Scale was independently related to an increased likelihood of RRHS of 36% (95% CI, 7% to 73%).

Conclusions—

RRHS and hemodynamic steal can be found in 7% and 14%, respectively, of consecutive patients with stroke without other known causes for deterioration. Patients with persisting arterial occlusions and excessive sleepiness can be particularly vulnerable to the steal.