bluuebunny/crossref_metadata_2025 huggingface dataset:
Dual roles of glucose in the freeze-tolerant earthwormDendrobaena octaedra: cryoprotection and fuel for metabolism
Authors: Calderon Sofia , Holmstrup Martin , Westh Peter , Overgaard Johannes
Published: February 2009

Ectothermic animals inhabiting the subarctic and temperate regions have evolved strategies to deal with periods of continuous frost during winter. The earthworm Dendrobaena octaedra is freeze tolerant and accumulates large concentrations of glucose upon freezing. The present study investigates the roles of glucose accumulation for long-term freeze tolerance in worms kept frozen at –2°C for 47 days. During this period, worms were sampled periodically for determination of survival and for measurements of glucose,glycogen, lactate, alanine and succinate. In addition we performed calorimetric measurements to assess metabolic rate of frozen and unfrozen worms. Long-term freezing was associated with a gradual depletion of glucose and worms that succumbed during this period were always characterised by low glucose and glycogen levels. The anaerobic waste products lactate and alanine increased slightly whereas succinate levels remained constant. However, it is argued that other waste products (particularly propionate) could be the primary end product of a continued anaerobic metabolism. Calorimetric measures of the metabolic rate of frozen worms were in accord with values calculated from the reduction in glucose assuming that most (∼90%) glucose was metabolised anaerobically. Both estimates of metabolic rate demonstrated a 10-fold metabolic depression associated with freezing. Thus, in addition to the suspected role of glucose as cryoprotectant, the present study demonstrates that glucose accumulation is vital to ensure substrate for long-term anaerobic metabolism in frozen worms. On the basis of the estimated metabolite levels, we calculate that the combined effect of metabolic depression and large glucose stores enables a projected 3 months survival of freezing at –2°C of the `average' D. octaedra. Such conditions are very likely to occur in the northern distribution ranges of this stress-tolerant earthworm.
Roles of PER immunoreactive neurons in circadian rhythms and photoperiodism in the blow fly, Protophormia terraenovae
Authors: Shiga Sakiko , Numata Hideharu
Published: February 2009

Several hypothetical models suggest that the circadian clock system is involved in the photoperiodic clock mechanisms in insects. However, there is no evidence for this at a neuronal level. In the present study, whether circadian clock neurons were involved in photoperiodism was examined by surgical ablation of small area in the brain and by immunocytochemical analysis in the blow fly Protophormia terraenovae. Five types of PER-immunoreactive cells, dorsal lateral neurons (LNd), large ventral lateral neurons (l-LNv), small ventral lateral neurons(s-LNv), lateral dorsal neurons (DNl) and medial dorsal neurons (DNm) were found, corresponding to period-expressing neurons in Drosophila melanogaster. Four l-LNvs and four s-LNvs were bilaterally double-labelled with antisera against pigment-dispersing factor (PDF) and PER. When the anterior base of the medulla in the optic lobe, where PDF-immunoreactive somata (l-LNv and s-LNv) are located, was bilaterally ablated, 55% of flies showed arrhythmic or obscure activity patterns under constant darkness. Percentages of flies exhibiting a rhythmic activity pattern decreased along with the number of small PDF-immunoreactive somata (i.e. s-Lnv). When regions containing small PDF somata (s-LNv)were bilaterally ablated, flies did not discriminate photoperiod, and diapause incidences were 48% under long-day and 55% under short-day conditions. The results suggest that circadian clock neurons, s-LNvs, driving behavioural rhythms might also be involved in photoperiodism, and that circadian behavioural rhythms and photoperiodism share neural elements in their underlying mechanisms.
Generation Expansion Planning of Stand-Alone Micro-Power Systems under Uncertainty Using Advanced Planning Methodology
Authors: Khodayar M. E. , Rahimi-Kian A. , Ehsan M.
Published: February 2009

In this paper a strategic planning framework for selecting the best configuration and capacity of different power generating technologies including renewable energy resources in stand-alone micro-power systems is proposed. The proposed framework is composed of three decision making techniques to identify the most feasible and efficient plans according to attributes and uncertain parameters in the planning environment. The framework considers the robustness and risk analysis of different plans exposed to uncertainties in the planning environment and selects the configurations that meet the objectives with the least risk exposure. The proposed methodology is implemented as a case study of a stand-alone micro-power system for a small region in Iran.
Application of Amberlite IRA-402 Modified by Means of 2-(p-Sulphophenylazo)-1,8-dihydroxy-3,6-naphthalene Disulphonate for the Recovery of Cu(II), Co(II), Cd(II), Ni(II), Mn(II) and Fe(III) Ions
Authors: Leszczyńska-Wawrzkiewicz Monika , Hubicki Zbigniew
Published: February 2009

2-( p-Sulphophenylazo)-1,8-dihydroxy-3,6-naphthalene disulphonate (SPADNS), an aromatic complexing agent, may be loaded onto the styrene–divinylbenzene matrix of a strongly basic anion-exchanger in order to obtain a chelating resin. The uptake of Cu(II), Co(II), Cd(II), Ni(II), Mn(II) and Fe(III) ions on Amberlite IRA-402 modified by SPADNS was studied at 25°C. Phase contact time, acid addition (HCl, H2SO4 or CH3COOH) and temperature are the factors which determine SPADNS sorption when the batch technique is employed. The total and working ion-exchange capacities as well as the recovery factors for SPADNS were calculated.
Investigation of the Factors Affecting the Removal of an Acid Dye from Aqueous Solution by Adsorption Using Bentonite and Sepiolite
Authors: Bilgiç Ceyda
Published: February 2009

The effects of some factors on the adsorption of an Acid dye (Acid Blue 193, AB 193) from aqueous solution onto bentonite and sepiolite samples were studied. These factors were saturation of the samples with cations (Na+ and Ca2+), the pH and the ionic strength of the dye solution. The Langmuir and Freundlich adsorption models were used to describe the equilibrium isotherm and determine the isotherm constants for each of the samples. The Langmuir model agreed very well with the experimental data. Cation saturation led to an increase in the adsorption capacities of the samples. In addition, the adsorption capacities decreased with increasing pH of the dye solution and increased with increasing ionic strength. The maximum adsorption capacity of both the bentonite and sepiolite samples towards the cationic dye Methylene Blue (MB) was higher than that towards the anionic dye AB 193.
Super-Energy-Saving Dewatering Method for High-Specific-Surface-Area Fuels by Using Dimethyl Ether
Authors: Kanda Hideki
Published: February 2009

There is a growing need for the economical dewatering of high-specific-surface-area fuels containing large amounts of water, such as coal and sewage sludge. The principle underlying conventional dewatering methods is evaporation of the water content by heating the fuels to a high temperature, but this approach consumes a considerable amount of energy. The Central Research Institute of the Electric Power Industry (CRIEPI) has developed a method for the extraction of this water through the use of dimethyl ether (DME), which liquefies at ordinary temperatures under the influence of a slight pressure. In this method, the water content in the fuel is extracted into the liquefied DME for separation from the fuel. After dewatering, the DME is depressurised, and subsequently vaporised, thereby leaving the separated water. Dewatering with an input energy of only 1109 kJ/kg water under ordinary conditions has been demonstrated theoretically.
Frequency Response from Wind Turbines
Authors: Ekanayake J.B. , Jenkins N. , Strbac G.
Published: February 2009

The frequency response that can be provided by Doubly Fed Induction Generators (DFIG) and Full Power Converters (FPC) based wind turbines during the first 30 sec after a frequency event was investigated. A simplified model, which can be used for frequency studies on a single bus equivalent of the power system, was developed. Studies were carried out on the present and projected 2020 Great Britain power systems. The frequency deviation of the GB system with and without the frequency response of the wind turbines was simulated. It was shown that variable speed wind turbines with suitable controls can make an important contribution to frequency response.
Fluid Structure Interaction of Wind Turbine Airfoils
Authors: Guerri Ouahiba , Hamdouni Aziz , Sakout Anas
Published: February 2009

Flow induced vibrations of two airfoils used in wind turbine blades are investigated by a strong coupled fluid structure interaction approach. The method is based on a general Computational Fluid Dynamics (CFD) code that solves the Navier-Stokes equations defined in Arbitrary Lagrangian Eulerian (ALE) coordinates by a finite volume method. A straightforward technique is implemented in a user subroutine for the coupling of the CFD code to a structural dynamics program to determine the airfoil displacements due to the aerodynamics forces and for updating the grid at each time step. Simulations are carried out for a free pitch oscillating airfoil and for a combined pitch and vertical oscillating airfoil. Beforehand, the problem of the flow around a forced pitch oscillating airfoil is considered to check the reliability of the moving mesh technique and the CFD computations. All computations are performed in 2D, incompressible and low Reynolds number flows.
Design and Power Characterization of a Novel Vertical Axis Wind Energy Conversion System (VAWECS)
Authors: Sankar Terrence , Tiryakioğlu Murat
Published: February 2009

The power output characteristics of a novel vertical axis wind turbine system were investigated via computational fluid dynamics. The system was tested at seven wind velocities. Results showed that the efficiency of the new system increases with increasing wind velocities up to approximately 30 m/s, after which the efficiency remains constant at 0.45. Moreover it was found that system reacts more quickly to changes in wind velocity once it is in motion and reaches a steady state. A new equation was developed to predict the power generation as a function of time and wind velocity. The use of the equation in predicting power performance is discussed in the paper.
Development of a New Cold-Formed Steel Building System
Authors: Darcy Greg , Mahendran Mahen
Published: February 2009

A new cold-formed steel building system was developed recently that has no conventional frames, purlins or girts. As it uses a new structural system, the load paths and the structural behaviour are unknown. Therefore a series of non-destructive and destructive full scale tests of a 5.4 m × 5.4 m × 2.3 m steel building was conducted under simulated wind uplift and racking loads. The test results showed that in its present state, this new building system needed modification for its intended purpose. The structural behaviour of the proposed structure was also investigated using finite element analyses. Based on these full sale tests and finite element analyses, suitable structural improvements were proposed to the new building system. This paper presents the essential details of the proposed cold-formed steel building system, the full scale tests and the finite element analyses as well as the important results including the details of an improved building system.
Development of the 2005 Edition of the Australian/New Zealand Standard for Cold-Formed Steel Structures AS/NZS 4600
Authors: Hancock G. J.
Published: February 2009

The paper describes the new developments in the Australian/New Zealand standard AS/NZS 4600. The developments are based mainly on research in Australia and the USA. They include new rules for high strength steel, the new Direct Strength Method of design as an alternative to the Effective Width Method and many other detailed changes including design of unstiffened compression elements under stress gradient. The standard is based mainly on the North American Specification published in 2001 with a 2004 Supplement but with special rules for high strength steels as produced in Australia including rules for distortional buckling and welding of high strength steel.
Development of Cold-Formed Steel Portal Frames with PRY Sections
Authors: Kwon Young Bong , Chung Hyun Suk , Kim Gap Deuk
Published: February 2009

A series of column, beam, and connection tests for portal frames which consisted of closed cold-formed steel PRY sections as columns and rafters were carried out. Firstly the compressive and the flexural strengths of the PRY sections were investigated, and secondly the structural behavior of the connections including the moment-rotation relation, the yield and the ultimate moment capacities of the connections were studied. The connection test specimens consisted of column-base, column-to-rafter, and rafter-to-rafter connections. The main testing parameters of the connection tests were the thickness and the shape of mild steel connectors, which were important for the proposed attachment system of wall panels. The connection test results were compared with those achieved by using advanced analysis procedures. The semi-rigid connection concept was considered appropriate for the analyses of the portal frames using the secant stiffness of the connections, which were estimated from the measured moment-rotation curves of the connections tested. Simple formulae for the shear resistances of the screwed connections were also proposed after calibrated with test results. The performance of the portal frame with PRY sections was investigated through the full scale tests.
Numerical Simulation of the Sound Radiated by a Turbulent Vortex Ring
Authors: Ran Hongyu , Colonius Tim
Published: February 2009

The acoustic field radiated by a turbulent vortex ring is studied. Direct Numerical Simulations (DNS) of the fully compressible, three-dimensional Navier-Stokes equations are used to generate an axisymmetric vortex ring to which 3D stochastic disturbances are added. The disturbances cause instability and turbulent transition of the vortex ring. Detailed information about temporal evolution of sound pressure level, spectrum and directivity associated with modes of oscillation and their turbulent breakdown are investigated. The peak frequency agrees well with experiments, and the modal directivities agree well with predictions of vortex sound theory. Based on the self-similar decay of the turbulent near field, the self-similar decay of the sound field is investigated. We also explore the connections with jet noise by modeling the jet as a de-correlated train of vortex rings.
Mechanisms of Jet Noise Generation: Classical Theories and Recent Developments
Authors: Viswanathan K.
Published: February 2009

Lighthill's acoustic analogy and several variants of it have been used to interpret, analyze and explain measured data. In this paper, the validity of the main tenets of the classical theories is examined. This assessment is facilitated by a new comprehensive aeroacoustic database. The overall sound power level does not exactly follow the eighth power of velocity ( Vj/a), but has a weak dependence on jet temperature. It has been believed that an additional source of noise, with either sixth or fourth power variation with velocity, appears for heated jets; there is also a supposed change in spectral shape at 90°, even though effects associated with convection and flow/acoustic interaction are negligible at that angle. The new data indicate that the velocity exponent for overall power is close to eight even at a very high stagnation temperature ratio of 3.2. Moreover, the spectral shape is invariant with jet Mach number and jet temperature. A careful assessment of Tanna's database, which provided the rationale and justification for many of the theoretical models, reveals that this database is unreliable and exhibits incorrect spectral trends. A fundamental tenet of the classical theories, based on both the formalisms of Lighthill-Ffowcs Williams and Lilley, is the notion of moving sources. This idea immediately leads to a Doppler shift for frequency and a convective amplification factor for the noise radiated to the aft angles. It is demonstrated with the new database that there is no experimental evidence for these conjectured effects of moving sources. The jet temperature ratio (static or stagnation), in addition to jet velocity Vj/a, is an independent controlling parameter. New scaling laws that are valid for all angles have been developed with the current database. There are no multiplicative factors with adjustable constants for the spectrum functions; the spectrum function and the velocity exponent depend on the jet temperature ratio and the radiation angle. This relation represents the main difference between the current and the classical formulations. A single exponent collapses the entire spectrum from jets with different Vj/a, but at fixed jet temperature ratio. Therefore, there is no experimental evidence for the main classical ideas of jet noise, as consisting of multi-poles and moving sources, as they are inconsistent with the new data. The idea of two distinct sources that are related to the fine-scale and large-scale turbulence of the jet plume has been investigated. Experimental evidence for the importance of the noise from large coherent structures even at low velocities is offered. The observation at lower and large aft angles of distinct characteristics in, (1) the far field spectral shapes, (2) the directivities of the peak Strouhal number and the OASPL, (3) the directivity of the velocity exponent, and (4) the polar and azimuthal correlations of the farfield pressure, provides strong evidence to support the above view of two different sources of jet noise.
Configuration of and Interaction Between Information Security Technologies: The Case of Firewalls and Intrusion Detection Systems
Authors: Cavusoglu Huseyin , Raghunathan Srinivasan , Cavusoglu Hasan
Published: February 2009

Proper configuration of security technologies is critical to balance the needs for access and protection of information. The common practice of using a layered security architecture that has multiple technologies amplifies the need for proper configuration because the configuration decision about one security technology has ramifications for the configuration decisions about others. Furthermore, security technologies rely on each other for their operations, thereby affecting each other's contribution. In this paper we study configuration of and interaction between a firewall and intrusion detection systems (IDS). We show that deploying a technology, whether it is the firewall or the IDS, could hurt the firm if the configuration is not optimized for the firm's environment. A more serious consequence of deploying the two technologies with suboptimal configurations is that even if the firm could benefit when each is deployed alone, the firm could be hurt by deploying both. Configuring the IDS and the firewall optimally eliminates the conflict between them, ensuring that if the firm benefits from deploying each of these technologies when deployed alone, it will always benefit from deploying both. When optimally configured, we find that these technologies complement or substitute each other. Furthermore, we find that while the optimal configuration of an IDS does not change whether it is deployed alone or together with a firewall, the optimal configuration of a firewall has a lower detection rate (i.e., allowing more access) when it is deployed with an IDS than when deployed alone. Our results highlight the complex interactions between firewall and IDS technologies when they are used together in a security architecture, and, hence, the need for proper configuration to benefit from these technologies.
Research Note—Investments in Information Technology: Indirect Effects and Information Technology Intensity
Authors: Mittal Neeraj , Nault Barrie R.
Published: February 2009

Many studies measure the value of information technology (IT) by focusing on how much value is added rather than on the mechanisms that drive value addition. We argue that value from IT arises not only directly through changes in the factor input mix but also indirectly through IT-enabled augmentation of non-IT inputs and changes in the underlying production technology. We develop an augmented form of the Cobb-Douglas production function to separate and measure different productivity-enhancing effects of IT. Using industry-level data from the manufacturing sector, we find evidence that both direct and indirect effects of IT are significant. Partitioning industries into IT-intensive and non-IT-intensive, we find that the indirect effects of IT predominate in the IT-intensive sector. In contrast, the direct effects of IT predominate in the non-IT intensive sector. These results indicate structural differences in the role of IT in production between industries that are IT-intensive and those that are not. The implication for decision-makers is that for IT-intensive industries the gains from IT come primarily through indirect effects such as the augmentation of non-IT capital and labor.
Demand Heterogeneity in IT Infrastructure Services: Modeling and Evaluation of a Dynamic Approach to Defining Service Levels
Authors: Sen Sagnika , Raghu T. S. , Vinze Ajay
Published: February 2009

A key feature of service-oriented models of information technology is the promise of prespecified quality levels enforceable via service level agreements (SLAs). This poses difficult management problems when considerable variability exists in user preferences and service demand within any organization. Because variance in expectations impact service levels, effective pricing and resource allocation mechanisms are needed to deliver services at the promised quality level. In this paper, we propose a mechanism for SLA formulation that is responsive to demand fluctuations and user preference variance, with the objective of maximizing organizational welfare of the participants. This formulation features a dynamic priority based price-penalty scheme targeted to individual users. An analytical model is presented and evaluated for effectiveness of a proposed dynamic priority-based pricing scheme vis-à-vis a baseline fixed-price single-quality level SLA. Simulations using data from an existing SLA is used to provide evidence that the proposed dynamic pricing scheme is likely to be more effective than a fixed-price approach from a system welfare perspective.
Complementarities Between Organizational IT Architecture and Governance Structure
Authors: Tiwana Amrit , Konsynski Benn
Published: February 2009

This study addresses the theoretically neglected interplay between organizational information technology (IT) architecture and IT governance structure in shaping IT alignment. We theoretically develop the idea that IT architecture modularity helps sustain IT alignment by increasing IT agility, and that decentralization of IT governance strengthens this relationship. IT architecture therefore complements IT governance structure. Tests of the proposed mediated-moderation model using data from 223 organizations support these ideas. Implications for theory and practice are also discussed.
Approximation Algorithms for the Supplier's Supply Chain Scheduling Problem to Minimize Delivery and Inventory Holding Costs
Authors: Selvarajah Esaignani , Steiner George
Published: February 2009

We study the upstream supplier's batch scheduling problem in a supply chain, which was defined by Hall and Potts [Hall, N. G., C. N. Potts. 2003. Supply chain scheduling: Batching and delivery. Oper. Res. 51(4) 566–584]. The supplier has to manufacture multiple products and deliver them to customers in batches. There is an associated delivery cost with each batch. The objective of the supplier is to minimize the total inventory holding and delivery costs. We present simple approximation algorithms for this strongly NP-hard problem, which find a solution that is guaranteed to have a cost at most 3/2 times the minimum. We also prove that the approximation algorithms have worst-case bounds that vary parametrically with the data and that for realistic parameter values are much better than 3/2. The theoretical results are also supported by the findings of a computational study.
Next-Generation Sequencing: From Basic Research to Diagnostics
Authors: Voelkerding Karl V , Dames Shale A , Durtschi Jacob D
Published: February 2009

Background: For the past 30 years, the Sanger method has been the dominant approach and gold standard for DNA sequencing. The commercial launch of the first massively parallel pyrosequencing platform in 2005 ushered in the new era of high-throughput genomic analysis now referred to as next-generation sequencing (NGS).

Content: This review describes fundamental principles of commercially available NGS platforms. Although the platforms differ in their engineering configurations and sequencing chemistries, they share a technical paradigm in that sequencing of spatially separated, clonally amplified DNA templates or single DNA molecules is performed in a flow cell in a massively parallel manner. Through iterative cycles of polymerase-mediated nucleotide extensions or, in one approach, through successive oligonucleotide ligations, sequence outputs in the range of hundreds of megabases to gigabases are now obtained routinely. Highlighted in this review are the impact of NGS on basic research, bioinformatics considerations, and translation of this technology into clinical diagnostics. Also presented is a view into future technologies, including real-time single-molecule DNA sequencing and nanopore-based sequencing.

Summary: In the relatively short time frame since 2005, NGS has fundamentally altered genomics research and allowed investigators to conduct experiments that were previously not technically feasible or affordable. The various technologies that constitute this new paradigm continue to evolve, and further improvements in technology robustness and process streamlining will pave the path for translation into clinical diagnostics.
The MIQE Guidelines: Minimum Information for Publication of Quantitative Real-Time PCR Experiments
Authors: Bustin Stephen A , Benes Vladimir , Garson Jeremy A , Hellemans Jan , Huggett Jim , Kubista Mikael , Mueller Reinhold , Nolan Tania , Pfaffl Michael W , Shipley Gregory L , Vandesompele Jo , Wittwer Carl T
Published: February 2009

Background: Currently, a lack of consensus exists on how best to perform and interpret quantitative real-time PCR (qPCR) experiments. The problem is exacerbated by a lack of sufficient experimental detail in many publications, which impedes a reader’s ability to evaluate critically the quality of the results presented or to repeat the experiments.

Content: The Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE) guidelines target the reliability of results to help ensure the integrity of the scientific literature, promote consistency between laboratories, and increase experimental transparency. MIQE is a set of guidelines that describe the minimum information necessary for evaluating qPCR experiments. Included is a checklist to accompany the initial submission of a manuscript to the publisher. By providing all relevant experimental conditions and assay characteristics, reviewers can assess the validity of the protocols used. Full disclosure of all reagents, sequences, and analysis methods is necessary to enable other investigators to reproduce results. MIQE details should be published either in abbreviated form or as an online supplement.

Summary: Following these guidelines will encourage better experimental practice, allowing more reliable and unequivocal interpretation of qPCR results.
Cytoskeletal control of sperm release in Chara contraria
Authors: Jin Qiaojun , Hasenstein Karl H.
Published: February 2009

The spermatozoid release process from antheridial filaments of Chara contraria was studied using cytoskeletal drugs and ATPase inhibitors. The drugs did not change the onset of spermatozoid release, but affected other factors. The myosin ATPase inhibitor 2,3-butanedione monoxime (BDM) inhibited spermatozoid movement before release, and the microtubule (MT) inhibitor oryzalin and the F-actin inhibitor latrunculin B (LatB) accelerated spermatozoid movement after release. Spermatozoids released into 10 and 20 mM BDM solutions were completely immobile and the nucleus was deformed. None of the three drugs affected spermatozoid release rate, but they synchronized the release between individual antheridial filaments. After release, the size of the spiral-shaped spermatozoid increased over time. This size increase was reduced by oryzalin but increased by LatB. The data suggest that MTs and F-actin are involved in spermatozoid release and mobility in Chara contraria. The spiral shape of the nucleus of the spermatozoid is affected by both MTs and F-actin.
Comparison of different procedures for the extraction and partial purification of R-phycoerythrin from the red macroalga Grateloupia turuturu
Authors: Denis Claire , Ledorze Charline , Jaouen Pascal , Fleurence Joël
Published: February 2009

With the aim of solubilizing R-phycoerythrin from Grateloupia turuturu, we tested the efficiency of two extraction solutions (distilled water and phosphate buffer) on fresh and freeze-dried seaweeds. Three different methods enabling a partial purification of this pigment were also tested: ammonium sulfate precipitation, separation in aqueous two-phase systems, and ultrafiltration. The best extraction and partial purification conditions for R-phycoerythrin were observed from freeze-dried algae after application of the precipitation procedure (80% ammonium sulfate). This latter protocol appears to be efficient for separating R-phycoerythrin without denaturation from most proteins and other components (such as sugars) that limit the purification of phycobiliproteins.
Managing Virtual Teams: Strategies for Team Leaders
Authors: Lyons Rebecca , Priest Heather A. , Wildman Jessica L. , Salas Eduardo , Carnegie David
Published: February 2009

Organizations' increasing use of virtual teams has emphasized the importance of effective virtual team leadership. Yet the distribution of team members complicates typical leader functions, such as supervision and support, which the leader must now perform through technology. In this article, we present 10 strategies for managing virtual teams, focusing on the role of technology and training. Our hope is that these strategies will inform designers and guide them in developing collaborative support tools and procedures for these tools and in designing training for the use of these tools.
Stress-Triaxiality in Zr-2.5Nb Pressure Tube Materials
Authors: Leitch B. W. , St. Lawrence S.
Published: February 2009

The crack growth resistance of irradiated Zr-2.5Nb pressure tubes is controlled by the initiation of voids and their subsequent growth and coalescence. The presence of particles that contribute to void nucleation is determined by the operating conditions/history of the pressure tube and by the concentration of pre-existing species, which is a function of the manufacturing process. The susceptibility of the pressure tubes to void nucleation is determined by the number and distribution of particles, the deformation properties of the matrix, and the stress state at the crack tip. The effect of irradiation on zirconium material is to increase the yield stress but to reduce the work hardening ability of the matrix and to promote strain localization, which, in turn, leads to void nucleation. Void nucleation is also enhanced by high values of stress triaxiality at or near the crack tip. For irradiated pressure tube material, both small-scale curved compact tension specimens and large-scale burst test sections are used to characterize the crack growth resistance. However, the measured fracture toughness can depend on the specimen geometry due to differences in constraint. The present investigation uses three-dimensional finite element analyses to characterize stress triaxiality at the crack tip in these different specimen geometries. Results of the numerical analyses are compared to the experimental evidence that provide qualitative evidence of differences in stress triaxiality at the crack tip for different specimen geometries.
Sensitivity in Creep Crack Growth Predictions of Components Due to Variability in Deriving the Fracture Mechanics ParameterC*
Authors: Nikbin KM
Published: February 2009

In this paper the uncertainties in estimating C* creep fracture mechanics parameter, on component defect assessment, is considered. Comparisons of reference stress σref and the stress intensity factor K for a surface cracked plate under tension and bending and a pipe geometry under internal pressure and external bending using formulae from available codes of practices such as the R5/R6 [1-2], BS7901 [3] and A16 [4] are made with three-dimensional Finite Element (3D FE) analysis calculations. It is shown, using the same material properties and specimen dimensions, that the uncertainty associated with calculating σref could be as much as ±40% whereas for the stress intensity K it is about ±10%. The σref values are used to calculate C* using the mean properties of a base 316LN type stainless steel plate tested at 650 °C and a cross-weld P22 circumferentially welded pipe tested at 565 °C. Both the pipe and the plate were tested within a European collaborative programme ‘HIDA’ between (1996–2000) [5]. The tendency is that ‘global’ limit load analysis will give a lower and more conservative C* than the ‘local’ analysis. From the comparisons of the pipe and plate initial cracking rates, using different C* estimations, with standard creep crack growth rate data on compact tensions (CT) specimens, using the ASTME1457-2002 to evaluate C*, it is shown that predictions of cracking rates could vary by as much as two decades in magnitude. This inconsistency yields itself to an analysis based on an empirical model for predicting crack growth in components.
On the Identification of Critical Damage Mechanisms Parameters to Predict the Behavior of Charpy Specimens on the Upper Shelf
Authors: Poussard C , Sainte Catherine C , Forget P , Marini B
Published: February 2009

The use of sub-sized Charpy-V specimens to monitor the mechanical properties of reactor pressure vessel (RPV) steels is receiving increasing attention. It is motivated by the fact that a smaller amount of material can be used to obtain the fracture properties, which can be of great economical interest when dealing with activated materials. Prior to use reduced-size specimens, investigations are still necessary to verify that the properties obtained from sub-sized specimens are comparable to those obtained from standard size specimens. Amongst the approaches that are available, the local approach to failure, which combines a description of the material microstructure (void density, distance between inclusions…) and empirical observations, is a promising way to investigate the transferability of mechanical properties. It has been successfully used to describe the macroscopic behavior of a wide range of cracked or notched specimens and components of various dimensions but restricted so far to quasi-static loading conditions. The results discussed in the paper are focused on the upper shelf behavior of the French RPV material, equivalent to the American ASTM A508 Cl.3 material. Modeling of the material is achieved using the Rousselier coupled damage constitutive equations. This model is implemented in CAST3M, a general-purpose finite element code developed by the French Atomic Energy Agency. Comparisons between the numerical results and the experimental observations are given and the computed local temperature elevations and plastic strain rates discussed to explain the behavior of the specimens.
Computational Estimation of Multiaxial Yield Surface Using Microyield Percolation Analysis
Authors: Geltmacher AB , Everett RK , Matic P , Dyka CT
Published: February 2009

Measurements of multiaxial properties of materials, such as yield surfaces, damage surfaces and fracture limit surfaces, are a time and resource intensive problem. For three-dimensional (3D) multiaxial yield of a complex microstructure, hundreds of points are required at different 3D strain states to define a full yield surface to the resolution required for constitutive model implementation. Experimental determination of the effects generated by a specific microstructure on a multiaxial yield surface is hindered by the inability to produce multiple specimens with the exact same microstructure or the inability to subject the same specimen to multiple stress or strain states without changing its response. Full nonlinear analysis of a specific microstructure for such a large set of points is also prohibitive, due to the time constraints of solving large, 3D nonlinear problems. A technique has been developed that uses high resolution 3D tomographic images and finite element simulations to track the development of microplastic connectivity for actual material microstructures in an 1100 aluminum/TiB2 particle composite. This information is then used to estimate the 3D multiaxial yield surface of the material in strain space for the imaged microstructures. The multiaxial yield surface is estimated using linear superposition and load scaling of three orthogonal displacement basis loads. Macroscopic yielding is defined as the percolation of microplastic elements across the model. Interval halving is used to solve for the scaling parameter, iterating to the value at which plastic flow percolation occurs and defining a point on the yield surface. Percolation can occur across one or more of the three directions defined by the model, but it need not occur simultaneously. A small selected set of nonlinear analyses is used as calibration for the estimated yield surface. The aim of this approach is to accelerate the process of building 3D multiaxial yield surfaces from microstructures and to gain insight into the material microstructure performance.
Multiaxial Fatigue Behavior of Oxidized and Unoxidized UHMWPE During Cyclic Small Punch Testing at Body Temperature
Authors: Villarraga ML , Edidin AA , Herr M , Kurtz SM
Published: February 2009

We hypothesized that oxidation would influence the resistance to fatigue crack initiation and propagation of Ultra-High molecular weight polyethylene (UHMWPE). We subjected tibial insert surrogates (ram extruded GUR 1050) to accelerated aging protocols following ASTM F 2003-00 (14, 21 and 28 days). Subsurface disc specimens from the control and aged materials at each time period were subjected to cyclic small punch loading to failure (modification of ASTM F 2183-02). A significant decrease in fatigue loading was observed, relative to the un-aged controls, starting at three weeks of accelerated aging. Furthermore, SEM examination of the failed aged specimens revealed a network of multiple secondary initiation sites, which was also confirmed by observation with endoscopy, and microCT. Thus, in contrast to the unoxidized highly crosslinked conventional materials evaluated previously, the oxidized materials failed by the initiation and propagation of cracks from numerous initiation sites with the brittle appearance increasing with oxidation time. These results suggest that oxidized UHMWPE exhibits a different fatigue crack initiation and propagation behavior compared to unoxidized virgin, and crosslinked UHMWPE. Future studies will be needed to increase our understanding of the clinically acceptable fatigue properties for new tibial bearing materials, such as highly crosslinked UHMWPEs.
Measurement of Pore Size and Porosity of Tissue Scaffolds
Authors: Tomlins P , Grant P , Mikhalovsky S , James S , Mikhalovska L
Published: February 2009

Tissue engineering involves seeding the patient's cells on to a three-dimensional temporary scaffold. It is becoming increasingly obvious that cells used to seed the scaffold have very specific requirements concerning the morphology and chemistry of the surface of the scaffold and its interconnectivity. A range of techniques has been examined in relation to key measurements such as pore size and porosity. Since capillary flow porometry measures a pore solely at its most constricted point, the method is unable to provide characterisation of other aspects of the pore. Scanning Electron Microscopy is limited to examining surface pores in ‘stiff’ scaffolds. Although cryo-SEM reduces the amount of ice-induced damage generated in ‘soft’ scaffolds upon freezing, the technique is limited to the same constraints. Images produced via scanning confocal microscopy are probably more representative of the true structure of the scaffold than that implied by cryo-SEM, although due to the diffuse nature of the image it is difficult to measure pore sizes.
Comparative Study of Bone Cell Culture Methods for Tissue Engineering Applications
Authors: Thomas CB , Kellam JF , Burg KJL
Published: February 2009

Cells are used in bone tissue engineering applications to facilitate new bone formation in implants. Enzymatic digestion and marrow removal by either centrifugal force or syringe are three methods used to isolate the cells for culture, but each technique has benefits and drawbacks. This comparative study evaluated the effects of the three cell isolation techniques on the attachment, proliferation, and mineralization of rat bone cells. Cells were isolated, seeded, and cultured following standard protocols for each isolation method. Quantitative assays to determine metabolic activity, lactic acid production, glucose consumption, and amounts of intracellular protein, alkaline phosphatase activity, and extracellular calcium were performed. In addition, cell morphology and viability were examined qualitatively. The results indicate that the cell isolation method affects the attachment, proliferation, and type of tissue formed by cells cultured under identical conditions.
Evaluation of Composite Failures through Fracture Signal Analysis
Authors: Mullin JV , Mehan RL
Published: February 2009

This paper describes the use of acoustic monitoring techniques to identify specific failure mechanisms in composite materials. Because of their inherent complexity, composites exhibit a number of fracture modes depending on loading conditions and the properties and volume ratios of the constituents. The technique of fracture signature analysis attempts to use the frequency content and nature of the signals as a means for identifying specific critical events in the fracture process. Some of the difficulties associated with this technique are described together with a description of the techniques applied and results obtained with boron/epoxy.
Heat Transfer in Fibrous Materials
Authors: Bankvall C
Published: February 2009

In fibrous material different types of heat transfer are present: conduction in solid phase constituting the insulation, radiation in the material, and heat transfer in the gas confined in the insulation. In this report the mechanisms of heat transfer are calculated theoretically. These calculations are verified experimentally by measurements on a glass fiber insulation in a specially constructed guarded hot plate apparatus. It is shown that the theories give a complete and consistent explanation of the influence of the mechanisms of heat transfer on the effective thermal conductivity of fibrous material.
Four Aspects of Sheet Metal Formability and Their Assessment
Authors: Lee PK , Hsu TC
Published: February 2009

An attempt is made to define formability quantitatively. Owing to the complexity of the concept of formability, it is analysed and four aspects of formability are distinguished. They are: the formability of the material at a critical section, the formability of the material in general, process efficiency, and proportional increase in surface area. Distinction is thus made between formability (or ductility) of the material and the extent to which the ductility is exploited in particular processes. A method of quantitative assessment is proposed for each of the four aspects of formability and demonstrated with experimental results.
Influence of Specimen Size and Shape on Compression Perpendicular to the Grain of Green Messmate
Authors: Walsh PF
Published: February 2009

The results of some tests on the strength in compression perpendicular to the grain of green messmate specimens are reported. It is shown that the inclusion of a perimeter effect of absolute size on the bearing strength in partial area loading conditions.
Fatigue Life and Inelastic Strain Response under Complex Histories for an Alloy Steel
Authors: Dowling NE
Published: February 2009

For quenched and tempered SAE 4340 steel, the inelastic strains measured during complex stress-strain histories are observed to be larger than would be estimated from constant amplitude test results. Ignoring this effect can result in nonconservative fatigue life predictions. The effect is accounted for by basing fatigue life calculations on inelastic strain. A stress versus inelastic strain relationship is determined from incremental step tests. The inelastic strain versus cycles to failure relationship is employed, and at short lives is determined from constant amplitude tests. At long lives, either the short life data can be extrapolated, or initial and periodic overstrains should be imposed during the constant amplitude tests. Actual and calculated lives are compared for a variety of complex history fatigue tests on unnotched axially loaded specimens.
Determination of Resonant Vibration Frequency of Concrete by an Acoustic Impact Technique
Authors: Wang JCK , Auskern A , Horn W
Published: February 2009

A simple technique based on the acoustic impact method is described for measuring the longitudinal, transverse, and torsional vibration modes of concrete. The results are in excellent agreement with the standard ASTM C 215-60 procedure of forced vibration for determining the resonant frequencies. It is suggested that the acoustic impact method be considered an alternative to the standard technique.
Mechanization for Remolding Fine Grained Soils and for the Plastic Limit Test
Authors: Gay GCW , Kaiser W
Published: February 2009

Time and costs studies in 1965 showed that in soil mechanics laboratories 60 to 90 percent of the total costs of tests were labor costs. The reason for these high labor costs is there has been very little mechanization of soil mechanics laboratory tests.
Triaxial Testing of Nonreinforced Concrete Specimens
Authors: Hilsdorf HK , Lorman WR , Monfore GE
Published: February 2009

This report is a review of experimental procedures used and methods for presenting data obtained, in testing specimens of nonreinforced concrete under triaxial stress conditions. The report is mainly concerned with behavior of hardened concrete under triaxial compression; materials other than concrete, mortar, or cement paste are excluded.
An Analog Control System for an Inverted Torsion Pendulum
Authors: Willertz LE , Pradhan AH
Published: February 2009

An analog system has been designed, constructed, and tested for driving an inverted torsion pendulum used in determining damping and internal friction properties of materials. The system is capable of determining log decrements from the electrical characteristics of the system from 10−4 to 10−1 at stresses from 102 to 105 psi with the results being plotted directly by an X–Y recorder. Other variables can be plotted on the x axis in addition to stress, such as magnetic field strength, temperature, time, and axial loads to make this a valuable instrument in the field of metallurgical research. Initial results using this system have shown them to compare almost exactly with those obtained using the usual free decay method.