bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cytoskeletal control of sperm release in Chara contraria
Authors: Jin Qiaojun , Hasenstein Karl H. 
Published: February 2009

Abstract
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

Abstract
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.
Stress-Triaxiality in Zr-2.5Nb Pressure Tube Materials
Authors: Leitch B. W. , St. Lawrence S. 
Published: February 2009

Abstract
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

AbstractIn 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

AbstractThe 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.
Fatigue Life and Inelastic Strain Response under Complex Histories for an Alloy Steel
Authors: Dowling NE 
Published: February 2009

AbstractFor 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

Abstract
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.
Triaxial Testing of Nonreinforced Concrete Specimens
Authors: Hilsdorf HK , Lorman WR , Monfore GE 
Published: February 2009

Abstract
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

Abstract
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.
Finite Strain and the 0.01 Percent Offset Yield Strength
Authors: Wonsiewicz BC , Hart RR 
Published: February 2009

Abstract
The validity of the stress at 0.01 percent offset as an approximation to the elastic limit was evaluated for a high-strength material, textured copper-beryllium CA-172. Specimens were loaded in uniaxial tension and precise determinations were made of the load-extension diagram. In loading to a strain of 0.85 percent, offsets of ∼0.02 percent were observed with insignificant permanent strain (&lt;5 × 10−5) remaining on release of the load. Permanent strain of 0.01 percent occurred only after an offset of 0.05 percent and a strain of 1 percent. The nonlinearities observed correspond to previously reported higher-order elastic effects in copper. A priori corrections to the offset strength for elastic nonlinearities are impractical since the nonlinearities depend on both the higher-order elastic constants of the material and the preferred orientation. The limitations of the offset yield strengths are discussed and the suggestion made that dynamic energy absorption techniques be considered to measure the onset of plastic flow; that is, plastic strains of about 0.01 percent.
Comparison of Bending and Tension Tests in Creep of Sheet Metal
Authors: Duncan JL , Ragab AR 
Published: February 2009

Abstract
A technique is presented for obtaining creep data for thin sheets using a test in which the whole sheet is arranged as a cantilever loaded by its own weight. A theory is given for deriving creep parameters from measured deflection rates in two tests. A stress-strain rate curve is derived from a number of tests using the skeletal point method. Tensile and bending tests were performed on superplastic eutectoid Zn-Al sheet at room temperature which demonstrated the applicability of the bending test to obtain creep properties of superplastic alloys. Erratum to this paper appears in 2(1).
A Test Procedure for Determining the Resilient Properties of Granular Materials
Authors: Kalcheff IV , Hicks RG 
Published: February 2009

Abstract
The resilient response of highway materials has generally been considered to be a function of intensity, number, duration, and frequency of the stresses to which it has been subjected. To date, little research has been conducted to show the effects of these factors on the response of paving materials and from what has been done, the observed behavior varies from material to material.
The purpose of this investigation was to better define the effect of stress repetitions, load duration, frequency, and sequence on the resilient response of several crushed stone materials. Tests were carried out at two levels of density and moisture condition using a conventional triaxial cell. Repeated axial compressive stresses, as well as static ones, were applied under conditions of constant confining pressures. The resulting axial strains were measured.
Results from the tests indicated that the number of stress repetitions and stress sequence had little effect on the resilient behavior of granular materials. There was no evidence of a change in resilient behavior with changes in load duration or frequency. The significance of these findings is that the resilient response determined after 150 to 200 repetitions will provide a reasonable indication of resilient properties for a material subjected to a complex stress history. Findings also indicate that the response to stresses of different intensities can be measured in any sequence on a single sample. Furthermore, the response can be determined using either static or dynamic triaxial load tests.
Test procedures are formulated to provide the practicing engineer with a simple procedure for determining an estimate of the resilient properties of granular materials.
A Mathematical Description of the Elevated Temperature Flow Behavior of Type 304 Stainless Steel at High Strain Rates
Authors: Steichen JM 
Published: February 2009

Abstract
A mathematical description of the true stress-true strain tensile behavior of annealed Type 304 stainless steel has been completed for tests at strain rates from 3 × 10−5 to 1 × 102 s−1 and temperatures from 600 to 1600°F (316 to 871°C). This description provides an accurate method for predicting deformation behavior within this temperature and strain rate region. It formulates a means of describing materials properties which can be readily factored into design, performance, and safety analyses of structural components.