bluuebunny/crossref_metadata_2025 huggingface dataset:
Mammaglobin as a Novel Breast Cancer Biomarker: Multigene Reverse Transcription-PCR Assay and Sandwich ELISA
Authors: Zehentner Barbara K , Persing David H , Deme Amadou , Toure Papa , Hawes Stephen E , Brooks Lisa , Feng Qinghua , Hayes Dawn C , Critichlow Cathy W , Houghton Raymond L , Kiviat Nancy B
Published: September 2004

Background: The aim of this study was to examine the potential usefulness of a mammaglobin multigene reverse transcription-PCR (RT-PCR) assay and a mammaglobin sandwich ELISA as diagnostic tools in breast cancer.

Methods: We studied peripheral blood samples from 147 untreated Senegalese women with biopsy-confirmed breast cancer and gathered patient information regarding demographic, and clinical staging of disease. The samples were tested for mammaglobin and three breast cancer-associated gene transcripts by a multigene real-time RT-PCR assay and for serum mammaglobin protein by a sandwich ELISA assay.

Results: In 77% of the breast cancer blood samples, a positive signal was obtained in the multigene RT-PCR assay detecting mammaglobin and three complementary transcribed genes. Fifty samples from healthy female donors tested negative. Significant correlations were found between mammaglobin protein in serum, presence of mammaglobin mRNA-expressing cells in blood, stage of disease, and tumor size. Circulating mammaglobin protein was detected in 68% of the breast cancer sera, and was increased in 38% in comparison with a mixed control population. The RT-PCR assay and the ELISA for mammaglobin produced a combined sensitivity of 84% and specificity of 97%.

Conclusion: The ELISA and RT-PCR for mammaglobin and mammaglobin-producing cells could be valuable tools for diagnosis and prognosis of breast cancer.
Analysis of Pyrimidine Synthesis “de Novo” Intermediates in Urine and Dried Urine Filter- Paper Strips with HPLC–Electrospray Tandem Mass Spectrometry
Authors: van Kuilenburg André B P , van Lenthe Henk , Löffler Monika , van Gennip Albert H
Published: September 2004

Background: The concentrations of the pyrimidine “de novo” metabolites and their degradation products in urine are useful indicators for the diagnosis of an inborn error of the pyrimidine de novo pathway or a urea-cycle defect. Until now, no procedure was available that allowed the analysis of all of these metabolites in a single analytical run. We describe a rapid, specific method to measure these metabolites by HPLC–tandem mass spectrometry.

Methods: Urine or urine-soaked filter-paper strips were used to measure N-carbamyl-aspartate, dihydroorotate, orotate, orotidine, uridine, and uracil. Reversed-phase HPLC was combined with electrospray ionization tandem mass spectrometry, and detection was performed by multiple-reaction monitoring. Stable-isotope-labeled reference compounds were used as internal standards.

Results: All pyrimidine de novo metabolites and their degradation products were measured within a single analytical run of 14 min with lower limits of detection of 0.4–3 μmol/L. The intra- and interassay variation for urine with added compounds was 1.2–5% for urines and 2–9% for filter-paper extracts of the urines. Recoveries of the added metabolites were 97–106% for urine samples and 97–115% for filter-paper extracts of the urines. Analysis of urine samples from patients with a urea-cycle defect or pyrimidine degradation defect showed an aberrant metabolic profile when compared with controls.

Conclusion: HPLC with electrospray ionization tandem mass spectrometry allows rapid testing for disorders affecting the pyrimidine de novo pathway. The use of filter-paper strips could facilitate collection, transport, and storage of urine samples.
Historical Development and Future Prospects of Structural Silicone Sealants in China
Authors: Wang Y-L , Wang H-M , Wu L-M
Published: September 2004

In China, the first four-sided structurally glazed curtain wall building, the Beijing Great Wall Hotel, was constructed in 1987. Since then, glass curtain wall buildings have become popular, and it is estimated that about 5 million m2 of coated glass are fabricated and installed by way of Structural Silicone Glazing (SSG) every year. Structural silicone sealants from Dow Corning and General Electric (GE) held the largest share of China's market until 1998. China developed and decreed its own national standard GB 16776-1997 for structural silicone sealants that is comparable with ASTM C 1184 but that has more stringent requirements in terms of tensile strength and adhesion to substrates. All structural silicone sealants, whether they are manufactured domestically or overseas, are required to be approved by the Chinese government based on the GB 16776 specification, and only certified products are permitted for use in Chinese glass curtain wall engineering. There are currently eight foreign structural silicone sealants and ten domestic products approved for installation of glass curtain walls in China. This paper covers China's market, national standard, and prospects of structural silicone sealants.
Properties of 20% Cold-Worked 316 Stainless Steel Irradiated at Low Dose Rate
Authors: Allen TR , Tsai H , Cole JI , Ohta J , Dohi K , Kusanagi H
Published: September 2004

To assess the effects of long-term, low-dose-rate neutron exposure, tensile, hardness, and fracture properties were measured, and microstructural characterization was performed on irradiated 20% cold-worked Type 316 stainless steel. Samples were prepared from reactor core components retrieved from the EBR-II reactor following final shutdown. Sample locations were chosen to cover a dose range of 1–56 dpa at temperatures from 371–390°C and dose rates from 0.8–3.3 × 10−7 dpa/s. Irradiation caused hardening, with the ultimate tensile strength (UTS) reaching about 800 MPa near 20 dpa and appearing to saturate at higher doses. The yield strength (YS) follows approximately the same trend as the ultimate tensile strength. The work-hardening capability of the material decreases with increasing dose. While the material retained respectable ductility at 20 dpa, the uniform and total elongation decreased to <1 and <3%, respectively, at 47 dpa. Fracture in the 30 dpa specimen is mainly ductile but with local regions of mixed-mode failure, consisting mainly of dimples and microvoids. The fracture surface of the higher-exposure 47 dpa specimen displays more brittle features. Changes in yield strength predicted from the microstructural components are roughly consistent with the measured changes in yield strength.
New Methodologies for Developing Radiation Embrittlement Models and Trend Curves of the Charpy Impact Test Data
Authors: Wang JA , Rao NSV
Published: September 2004

A new methodology is developed for the prediction of RPV embrittlement that utilizes a combination of domain models and nonlinear estimators including neural networks and nearest neighbor regressions. The Power Reactor Embrittlement Database is used in this study. The results from newly developed nearest neighbor projective fuser indicate that the combined embrittlement predictor achieved about 67.3% and 52.4% reductions in the uncertainties for General Electric Boiling Water Reactor plate and weld data compared to Regulatory Guide 1.99, Revision 2, respectively. The implications of irradiation temperature effects to the development of radiation embrittlement models are then discussed. A new methodology that incorporates the chemical compositions into the Charpy trend curve is also developed. The purpose of this new fitting procedure is to generate a new multi-space topography that can properly reflect the inhomogeneity of the surveillance materials and utilize this multi-space trend surface to link and project the surveillance test results to that of reactor pressure vessel steels.
The Macro-Microscopic Numerical Simulation of the Mechanical Behavior of CFCC with Matrix Anisotropic Damage by Homogenization Method
Authors: Luo D , Takezono S , Tao K , Minamoto H
Published: September 2004

In this paper, a damage constitutive model based on a micro-mechanical approach is established and used to predict the macro-microscopic elastic-brittle mechanical behavior of continuous fiber reinforced ceramic matrix composites (CFCC). Anisotropic damage is applied to describe the matrix phase damage which reflects all types of damage such as nucleation and coalescence of voids and micro-cracks that the matrix material undergoes. The asymptotic expansion homogenization method is used to obtain the effective mechanical properties of composites and to derive the homogenized damage elastic concentration factor and the gross stiffness matrix of unidirectional and cross-ply laminate composite materials. Internal variables are introduced to describe the evolution of the damage state and the degradation of the material stiffness. Using the proposed theory, the unidirectional composite and the cross-ply laminate composites with /03/90/03/, /03/902/03/, and /03/903/03/ stacking sequences are analyzed, and the numerical results are consistent with those of the experiments.
Extension of a Microstructure-Based Fatigue Crack Growth Model for Predicting Fatigue Life Variability
Authors: Enright MP , Chan KS
Published: September 2004

Most of the existing crack growth models rely on empirical constants derived from curve fits of data at specific test conditions. Although statistical information can be obtained for many of these constants, multiple experimental tests typically must be performed to represent the wide range of the response. In this paper, an alternative approach is presented that links fatigue crack growth parameters to material and microstructural size parameters via a microstructure-based fatigue crack growth (FCG) model. In addition, variation of initial crack size due to microstructural variation is modeled in terms of a crack-size-based fatigue crack initiation model. Variations of microstructural parameters are described in terms of a probabilistic framework. The probabilistic, microstructure-based, FCG approach is illustrated for a Ni-based superalloy in which the influence of changes in the main descriptors of the individual microstructural parameters on initial crack size, crack growth rate, and fatigue life is shown. Stochastic model results are compared with existing experimental data to illustrate the feasibility of the approach for predicting da/dN variability due to microstructure variations.
Application of Probabilistic Fracture Mechanics in Structural Design of Magnet Component Parts Operating Under Cyclic Loads at Cryogenic Temperatures
Authors: Yatomi M , Nyilas A , Portone A , Sborchia C , Mitchell N , Nikbin K
Published: September 2004

This paper presents a methodology for the use of probabilistic fracture mechanics concepts to estimate the design fatigue life and reliability of structural materials used in superconducting coils and magnet intercoil components of the International Thermonuclear Experimental Reactor (ITER). The orbitally welded conductor jackets of superconducting coils are subjected to fluctuating tensile stresses. The paper uses fatigue crack growth (FCGR) data at 7K from type 316LN stainless steel, in parent and weld material conditions, to predict fatigue crack growth rates using Monte Carlo analysis. Two stages are considered in which scatter could be quantified in the analysis. Initially, the unknown in crack length is taken as a stochastic variable. Secondly, the model assumes that the scatter observed in the correlation of the FCGR data versus ΔK is directly due to factors such as testing methods, measurement, material, and geometric variability and can therefore be quantified statistically. Either a normal or lognormal distribution of the scatter is assumed depending on the parameter. The purpose of this approach is to illustrate some of the advantages over a deterministic approach that most design codes use. An example is presented that compares the design life of a conductor jacket section containing a single crack and multiple cracks. A comparison of a sensitivity analysis for multiple cracks, for failure times at probabilities of 1 % and 0.001 %, with times calculated from a deterministic analysis using appropriate safety factors, suggests that the deterministic analysis give less conservative failure times.
Developing a Performance-Based Joint Sealant Specification for Airport PCC Pavements
Authors: Lacasse MA , Masson JF
Published: September 2004

Despite recent progress to develop a performance-based specification for bituminous sealants applied to asphalt concrete (AC) roadways and runways, a performance-based specification for cold-applied joint sealants for Portland cement concrete (PCC) aprons, taxiways, and parking areas has yet to be mapped and developed. Unique in-service conditions exist on these PCC pavements, where sealants are not only exposed to climatic effects and heavy traffic loads, but also to jet fuel and de-icing fluids. Installation and maintenance conditions are also unique in that it is often necessary to install or replace joint sealants at night or in a very short time so that aircraft traffic disruption is avoided. Hence, special consideration must be provided to ascertain that joint sealants are effective and durable. Recent studies on joint and crack sealants used on airport pavements that experience cold climates indicate that current specifications do not necessarily allow for the selection of durable sealants, and therefore sealant failure can be rapid. To address the issue of premature failure and to extend joint sealant service life, the elements of a performance-based specification for cold-applied joint sealants for PCC airport pavements is reviewed. The benefits of such a specification include the selection of joint sealants for specific local needs, reduced airport pavement maintenance costs, and extended airport PCC pavement service life.
Issues Related to the Mechanical Property Characterization of Sealants
Authors: White CC , Hunston DL
Published: September 2004

Quantification of the mechanical properties of cured sealant is complicated by the presence of the Mullins effect. This paper examines the Mullins effect using five different sealants encompassing the range of properties and formulations found in commercial sealants. Three main observations include: the Mullins effect was observed in all sealant formulations studied, the Mullins effect was observed in both tension and compression strains, and there was a recovery of the Mullins effect after sufficient periods of time between repeated loading cycles. Simple rules were formulated to describe the Mullins effect. Moreover, the tests show that understanding the Mullins effect is crucial in characterizing the mechanical properties of a sealant.
Identification of Crystalline Behavior on Macroscopic Response and Local Strain Field Analysis: Application to Alpha Zirconium Alloys
Authors: Gélébart L , Crépin J , Dexet M , Sauzay M , Roos A
Published: September 2004

The purpose of this paper is to present an identification method of the crystalline behavior of a material from a mechanical test performed on a polycrystalline sample. Because of the lack of knowledge about its crystalline behavior, this method is applied to a Zirconium alloy. This identification is based on a finite element modeling of the microstructure, and the results are compared to both the macroscopic and the microscopic experimental results. On the microscopic scale, the plastic strains are obtained using a micro-extensometry technique and the crystalline orientation using an EBSD technique. In order to validate the method, an identification is performed with only two free parameters: the evolutions of the macroscopic and microscopic errors appear to be regular and exhibit a well-defined minimum so that the parameters can be clearly identified.
Effect of Fabrication Variables on Irradiation Response of Crack Growth Resistance of Zr-2.5Nb
Authors: Coleman CE , Theaker JR , Kidd KV
Published: September 2004

Specimens of pressure tubes made from Zr-2.5Nb by various fabrication routes were irradiated in research reactors to evaluate the response of their fracture toughness (represented by crack growth resistance, dJ/da) at 250°C to irradiation by fast neutrons (E > 1 MeV). The reference route consists of melting Kroll sponge and some recycled material, primary hot-working, extrusion at 815°C, and cold-working 27 %. Tubes made from ingots that were melted four times (quadruple melting) are initially tougher than tubes made from ingots that have been melted twice (double melting), and after irradiation the former retain close to 50 % of their original crack growth resistance while the latter retain less than 30 % of theirs. The high toughness and its retention in the quadruple melted material are attributed to low concentrations of chlorine. Tubes made from electrolytic powder contain fluorine rather than chlorine. Fluorine is less damaging than chlorine. Crack growth resistance and its retention with irradiation of tubes made from electrolytic powder are intermediate between those of tubes made from quadruple and double melted sponge. Lowering the amount of cold-work is beneficial, and the toughness of tubes made with less than 27 % cold-work correlates well with strength, both before and after irradiation. Lowering the extrusion temperature produces strong, tough tubes, but these tubes lose much of their crack growth resistance with irradiation. This loss in toughness is not associated with material chemistry but with a high sensitivity to strength.
High Cycle Variable Amplitude Fatigue of a Nodular Cast Iron
Authors: Marquis GB , Rabb BR , Karjalainen-Roikonen P
Published: September 2004

This paper provides a brief summary of life prediction methods for variable amplitude fatigue. Special attention is given to cracks propagating from nominally defect free components in the high cycle regime where a significant portion of the fatigue damage can be attributed to cycles with amplitude less than the fatigue limit observed under constant amplitude loading. Constant and variable amplitude fatigue data for a nodular cast iron are presented. An effective stress method for variable amplitude loaded similar to the Topper model is developed. Most model parameters are derived from constant amplitude S-N curves and the Haigh diagram, but two sets of long life variable amplitude tests are needed to derive the variable amplitude interaction parameters.
Effect of Transient Loads on Fatigue Crack Growth in Solution Treated and Aged Ti-62222 at −54, 25, and 175°C
Authors: Stephens RR , Stephens RI , Berge SC , Lemm DE , Glancey CD
Published: September 2004

Transient loads consisting of single tensile overloads and single tensile overloads followed by single compressive underloads were applied to Ti-62222 solution treated and aged titanium alloy at −54, 25, and 175°C. Tensile overload ratios were 2.0 and 2.5, and the compressive underload ratio was −0.5. Four reference steady state ΔKss values, using constant δK testing at R = 0.1, were investigated at each temperature. Cycles of delay, fatigue crack growth during delay, and minimum fatigue crack growth rate during a transient load were obtained for all tests. Cycles of delay ranged from zero to crack arrest. Higher tensile overloads caused greater delay cycles, and underloads were often detrimental. Low and high temperatures were primarily beneficial to delay cycles relative to those at room temperature. Crack growth delay distance was always greater than the pertinent reversed plastic zone size. Fatigue crack growth life predictions were made using FASTRAN III and AFGROW computer programs and produced both conservative and non-conservative results with more than half the predictions being within ±2 of the experimental results. Macro- and microfractography revealed surface crack closure, Mode II displacements, crack tip blunting, branching, and tunneling contributed to the transient fatigue crack growth behavior.
Prediction of Crack Growth Under Variable-Amplitude and Spectrum Loading in a Titanium Alloy
Authors: Newman JC , Phillips EP
Published: September 2004

The present paper is concerned with the application of a plasticity-induced crack-closure model, FASTRAN, to predict fatigue-crack growth under various load histories in a thin-sheet Ti-62222 STA titanium alloy. This alloy was a leading candidate for a metallic High-Speed-Civil-Transport (HSCT) aircraft in the United States. The crack-growth model was based on the Dugdale strip-yield model but modified to leave plastically deformed material in the wake of the advancing crack. The model includes the influence of “constraint” on the development of plasticity and closure during constant- and variable-amplitude load histories. The model was used to correlate crack-growth-rate data under constant-amplitude loading over a wide range in crack-growth rates and stress ratios at two service temperatures (room temperature and 175°C). Tests on repeated spike overloads were used to help establish the constraint variations in the model. The model was then used to predict crack growth under two simulated aircraft spectrum load histories at the two temperatures. The spectra were a commercial HSCT wing spectrum and the Mini-TWIST (transport wing spectrum). This paper will demonstrate how constraint plays a leading role in the retardation and acceleration effects that occur under variable-amplitude and spectrum loading. The model was able to calculate the effects of repeated spike overloads on crack growth at the two temperatures, generally within about ± 30%. Also, the predicted crack-growth behavior under the HSCT spectrum agreed well with test data (within 30%). However, the model under-predicted the fatigue-crack-growth behavior under the Mini-TWIST spectrum by about a factor-of-two. Some of the differences may be due to fretting-product-debris-induced closure or three-dimensional effects, such as free-surface closure, not included in the model. Further study is needed on life predictions under the Mini-TWIST flight spectrum.
Crack Growth and Closure Behavior of Short and Long Fatigue Cracks under Random Loading
Authors: Song JH , Kim C-Y , Lee S-Y
Published: September 2004

Crack growth and closure behavior of physically short and conventionally long cracks under random loading are extensively investigated, utilizing test results of 2024-T351 aluminum alloy obtained by performing narrow- and wide-band random loading tests for various stress ratios and random loading block lengths. A noise reduction method is developed to determine the crack opening load under random loading more easily, precisely, and economically. Crack growth rates are analyzed mainly in terms of the stress intensity factor range estimated by 2/PI correction proposed by Donald and Paris. The long and short cracks are very different in characteristics of closure behavior under random loading. Crack growth of short and long cracks under random loading can be well described by the crack closure concept. The effects of random spectrum or random block length on crack opening load and crack growth are not significant.
Comparison of the Rain Flow Algorithm and the Spectral Method for Fatigue Life Determination Under Uniaxial and Multiaxial Random Loading
Authors: Łagoda T , Macha E , Niesłony A
Published: September 2004

This paper presents the strain energy density parameter used for fatigue life calculation under random loading by two methods. The first method is based on schematization of energy parameter histories with the rain flow algorithm. The other one is based on moments of the power spectral density function of the energy parameter. The experimental data of fatigue tests of 10HNAP steel under constant amplitude and random uniaxial loading with non-gaussion probability distribution, zero mean value, and wide-band frequency spectrum used for comparison of the rain flow algorithm and the spectral method gave satisfactory results. Next, histories of the random stress tensor with normal probability distribution, wide-band frequency, and zero mean values corresponding to biaxial tension-compression, combined tension with torsion and triaxial loading with various correlation coefficients were generated, and the lifetime was calculated. It has been observed that both methods of fatigue life determination give almost the same results.
Spectrum Fatigue Testing and Small-Crack Life Prediction Analysis on a Coupon Similar to a Critical Design Detail of a CF188 Hornet Component
Authors: Yanishevsky M , Everett RA
Published: September 2004

Numerous studies have shown that small-crack methodology can be used to predict the total fatigue life of laboratory type (KT = 1 and 3) specimens under variable amplitude loading. Prior to investigating how well this fatigue life prediction capability could be extended to “real” aircraft structures, an intermediary step was taken where total fatigue life was predicted for a laboratory type specimen similar to a critical design detail in a fighter aircraft fuselage bulkhead. Using the small-crack analysis in the computer code called FASTRAN and assuming an initial crack size of 20 microns, the time to catastrophic failure of the test coupons was predicted to within 10% of the average test times.
Variable Amplitude Fatigue Crack Growth Using Digital Signal Processing Technology
Authors: Donald JK , George K
Published: September 2004

An automated variable amplitude fatigue crack growth system has been developed using digital signal processing (DSP) technology to provide waveform generation, command-feedback verification, and crack growth monitoring. The system is designed to interface with existing analog or digital closed-loop servo-hydraulic mechanical test systems. An important parameter in the control of variable amplitude testing is the effect of loading errors on the fatigue crack growth rate response. A damage parameter (Γ) has been incorporated to quantify the magnitude and effect of loading errors. In this paper, a FALSTAFF, Mini-TWIST, and truncated Mini-TWIST aircraft spectrum were applied to an M(T) crack growth sample to demonstrate the correlation between the damage parameter and fatigue life.
A Model for the Inclusion of Notch Plasticity Effects in Fatigue Crack Growth Analysis
Authors: Ball DL
Published: September 2004

Notches or other stress concentrations are by far the most common sites for the initiation and growth of fatigue cracks in aircraft structures. The growth of these cracks is directly influenced by the material stress-strain response in the vicinity of the notch. Specifically, when the applied (remote) stress is sufficient to cause local plastic deformation at the notch, the response (local) stresses can no longer be found using elastic stress concentration factors, and they become dependent on the prior loading history. This is to say that the response stresses can no longer be treated as state variables. The occurrence of fatigue crack growth at notches which experience local yielding one or more times during their design lifetime is, in fact, quite common in many cyclically loaded structures. Some of the assumptions inherent in “traditional” Linear Elastic Fracture Mechanics (LEFM) based fatigue crack growth analysis may be inappropriate for such problems. In particular, the assumption that the stress distribution on a critical plane remains proportional to the elastic distribution throughout the loading history becomes incorrect when one or more of the applied loads causes plastic deformation and introduces or alters a residual stress field in this region. This paper first describes an elastic-plastic stress-strain response algorithm which may be used to estimate response stress distributions on a critical plane on a cycle-by-cycle basis. This is followed by a discussion of the manner by which stress intensity factors may be calculated based on these response stress distributions using Green's functions. Finally, the use of these stress intensity factors for the calculation of crack growth rate and, ultimately, crack growth life, is demonstrated.
Study on Fatigue Design Loads for Ships Based on Crack Growth Analysis
Authors: Tomita Y , Hashimoto K , Osawa N , Terai K , Wang Y
Published: September 2004

Although ship structural members are designed to survive 20 years, fatigue crack damage still occurs, often starting very early in the ship's life, with some cracks growing quickly to considerable size. The primary factor causing variability is the sequence of the variable amplitude load cycle, and the others are welding irregularities on the weld toe and variations in mechanical properties in the material. In this paper, the load sequence effect on fatigue life variability is examined by the use of a fatigue design procedure proposed by the authors. It is found that the fatigue lives of ship structural members vary from several months to 20 years, strongly dependent on the sequence of sea state which ships encounter during ocean-going service. The worst possible loading sequence is elucidated for the fatigue life of the ship's hull. Sensitivity study of fatigue life is discussed.
High Cycle Fatigue Testing and Analysis Using Car Standard Sequence
Authors: Morel F , Ranganathan N
Published: September 2004

An original computer software package for controlling a servo-hydraulic machine was used to carry out uniaxial and biaxial variable amplitude loading tests on a high strength steel. Tension-compression and torsion uniaxial tests, as well as combined proportional tension-torsion tests were performed under the car loading sequence CARLOS used for fatigue strength investigations of car wheel suspension components. The number of sequences to crack nucleation was estimated by means of a crack front marking technique using very small amplitude cycles to generate marker bands on the fracture surface. The experimental data obtained from these tests were compared to the predictions of the fatigue life prediction method proposed by Morel and based on a microplasticity analysis. It was shown that all the predictions, though non-conservative, were within an acceptable scatter band.
Effect of Overloads and Underloads on Fatigue Crack Growth and Interaction Effects
Authors: Romeiro F , de Freitas M , Pommier S
Published: September 2004

Under constant amplitude loading a single variable (ΔK) is required in crack growth relationships. The transferability of fatigue laws, determined under constant amplitude loading, to variable amplitude fatigue requires at least an additional variable, whose evolution with crack length accounts for the interaction effects between cycles of different types. The crack opening level (Kop) is usually employed for this purpose because it can be determined from the experiments and compared with predictions from models or FEM analyses. This paper presents an analysis of fatigue crack growth on M(T) specimens of medium carbon steel specimens and using FEM analyses. The specimens are subjected to repeated blocks of cycles made up of one or several overloads separated by a variable number of baseline cycles. The experiments are simulated by FEM analyses, taking into account the cyclic plastic behavior of the low carbon steel. The main objective of this study is to better understand the mechanisms at the origin of interactions effects due to the presence of overloads (or underloads) at different locations of the block loading. It is concluded that the interaction effects are closely related to the cyclic plastic behavior of the material and namely to the Bauschinger effect.
Crack Initiation at a Notch under Constant and Selected Variable Amplitude Loading Conditions
Authors: Gérard N , Leroy R , Girard O , Ranganathan N
Published: September 2004

In a previous study, we showed that crack initiation life at a notch tip can be modeled as the micro crack propagation life from an initial microstructural defect up to a crack size of about 500 µm. This model is based upon the assumption that short cracks at a notch propagate without any significant closure effects. In our present experimental study, the results of fatigue tests to verify this hypothesis are presented and discussed.

The fatigue tests were conducted in ambient air on single edge notched specimens with a theoretical stress concentration factor of 3.14 on thin sheets of 1.2 mm thick Aluminum alloy 2024 T351. The test conditions studied are: constant amplitude tests at stress ratios of 0.1, 0.3, and 0.5 and variable amplitude tests using an extract from the TWIST spectrum. The tests were carried out at a nominal frequency of 10 Hz. At selected intervals, micro crack advance (if any) was determined using replicas. The measurements were made at the maximum stress for constant amplitude tests and at a chosen positive stress for variable amplitude tests (avoiding any overload). The smallest crack size detected is about 10 µm.
Epilepsy in Small-World Networks
Authors: Netoff Theoden I. , Clewley Robert , Arno Scott , Keck Tara , White John A.
Published: September 2004

In hippocampal slice models of epilepsy, two behaviors are seen: short bursts of electrical activity lasting 100 msec and seizure-like electrical activity lasting seconds. The bursts originate from the CA3 region, where there is a high degree of recurrent excitatory connections. Seizures originate from the CA1, where there are fewer recurrent connections. In attempting to explain this behavior, we simulated model networks of excitatory neurons using several types of model neurons. The model neurons were connected in a ring containing predominantly local connections and some long-distance random connections, resulting in a small-world network connectivity pattern. By changing parameters such as the synaptic strengths, number of synapses per neuron, proportion of local versus long-distance connections, we induced “normal,” “seizing,” and “bursting” behaviors. Based on these simulations, we made a simple mathematical description of these networks under well-defined assumptions. This mathematical description explains how specific changes in the topology or synaptic strength in the model cause transitions from normal to seizing and then to bursting. These behaviors appear to be general properties of excitatory networks.
In VivoMeasurement of Brain Extracellular Space Diffusion by Cortical Surface Photobleaching
Authors: Binder Devin K. , Papadopoulos Marios C. , Haggie Peter M. , Verkman A. S.
Published: September 2004

Molecular diffusion in the brain extracellular space (ECS) is an important determinant of neural function. We developed a brain surface photobleaching method to measure the diffusion of fluorescently labeled macromolecules in the ECS of the cerebral cortex. The ECS in mouse brain was labeled by exposure of the intact dura to fluorescein-dextrans (Mr4, 70, and 500 kDa). Fluorescein-dextran diffusion, detected by fluorescence recovery after laser-induced cortical photobleaching using confocal optics, was slowed approximately threefold in the brain ECS relative to solution. Cytotoxic brain edema (produced by water intoxication) or seizure activity (produced by convulsants) slowed diffusion by >10-fold and created dead-space microdomains in which free diffusion was prevented. The hindrance to diffusion was greater for the larger fluorescein-dextrans. Interestingly, slowed ECS diffusion preceded electroencephalographic seizure activity. In contrast to the slowed diffusion produced by brain edema and seizure activity, diffusion in the ECS was faster in mice lacking aquaporin-4 (AQP4), an astroglial water channel that facilitates fluid movement between cells and the ECS. Our results establish a minimally invasive method to quantify diffusion in the brain ECSin vivo, revealing stimulus-induced changes in molecular diffusion in the ECS with unprecedented spatial and temporal resolution. Thein vivomouse data provide evidence for: (1) dead-space ECS microdomains after brain swelling; (2) slowed molecular diffusion in the ECS as an early predictor of impending seizure activity; and (3) a novel role for AQP4 as a regulator of brain ECS.
Time-Resolved ESCA: a Novel Probe for Chemical Dynamics
Authors: Drescher Markus
Published: September 2004

Electron spectroscopy for chemical analysis (ESCA) is a well established tool for quantitative studies of the composition and the chemical environment of molecular systems. Recent developments in the generation and utilization of ultrashort X-ray pulses now add the dimension of time to this technique and will expand the possibilities of femtochemistry in terms of chemical selectivity, quality of information, and temporal resolution. The properties and capabilities of various X-ray pulse sources are discussed, along with their prospects for dynamical studies. Examples of time-resolved electron spectroscopy are presented in the femtosecond (1 fs = 10−15 s) as well as the attosecond (1 as = 10−18 s) regime, the latter marking the current ultimate limit for the time-resolution in pump-probe experiments.
Contributions of Multipolar Polarizabilities to the Isotropic and Anisotropic Light Scattering Induced by Molecular Interactions in Gaseous Sulfur Hexafluoride
Authors: El-Kader M.S.A. , El-Sheikh S.M. , Omran M.
Published: September 2004

The binary isotropic and anisotropic collision-induced light scattering spectra of the gaseous sulfur hexafluoride at room temperature are analyzed in terms of recent intermolecular potential and interaction-induced pair polarizability models, using quantum line-shapes computations. The spectra at relatively low frequencies are determined largely by the effect of bound and free transitions. At intermediate frequencies the spectra are sensitive to both the attractive part of the potential and the short-range part of the polarizability trace and anisotropy. The high frequency wings are discussed in terms of the collision-induced rotational Raman effect and estimates for the dipole–octopole polarizability E, is obtained and checked with recent ab initio theoretical value. Absolute zeroth moment of both spectra have been measured and compared with theoretical calculations using different models of the intermolecular potentials. Also, the temperature dependence of the pressure second virial coefficient, viscosity and thermal conductivity are also discussed for the proposed potentials. The results show that (M3SV) is the most accurate potential yet reported for this system.
The Dissolution of FeO and FeF3 in Cryolite
Authors: Šimko F. , Proks I. , Daněk V. , Boča M. , Chrenková M.
Published: September 2004

Theoretical derivation of relations valid for cryoscopic measurements in solvents with dystectic mode of melting (solvents, which undergo at melting a more or less extended thermal dissociation), when also chemical reaction between solvent and solute takes place, is presented. When one of the products of this chemical reaction is identical with the product of thermal dissociation of the solvent, arise the problem of defining the number of “foreign” substances, originating in the reaction. The presented approach shows that the partially dissociated solvent cannot distinguish as foreign substance between the own dissociation product and the originating one and made it easier to determine the nature of the probable chemical reaction.

The presented approach is applied in the systems Na3AlF6–FeO and Na3AlF6–FeF3, which are of great importance in the fundamentals of aluminium electrolysis.

In the system Na3AlF6–FeO for the dependence of the temperature of primary crystallization of cryolite on x(Na3AlF6) the equation

T
pc/K = 1014.4 + 267.86x(Na3AlF6)

was obtained, which yields for the Stortenberker’s correction factor the value k
St = 2.09. This means that dissolving FeO in cryolite two new particles are formed. This can be interpreted by the chemical reaction

2Na3AlF6 + FeO ⇔ Na2FeF4 + Na2Al2OF6 + 2NaF.

In the system Na3AlF6–FeF3 for the dependence of the temperature of primary crystallization of cryolite on x(Na3AlF6) the equation

T
pc/K = 1547.2 − 659.88x(Na3AlF6) + 394.99x
2 (Na3AlF6)

was obtained. For the Stortenbeker’s correction factor the value k
St = 1.02 was then calculated, which means that one new particle is created when FeF3 is dissolved in cryolite. The most probable reaction is

1.5Na3AlF6 + FeF3 ⇔ Na3FeF6 + 1.5NaAlF4.
Middle school victims of bullying: Who reports being bullied?
Authors: Unnever James D. , Cornell Dewey G.
Published: September 2004

This study examined factors that influence a student's decision to report being bullied at school. An anonymous survey of 2,437 students in six middle schools identified 898 students who had been bullied, including 25% who had not told anyone that they were bullied and 40% who had not told an adult about their victimization. We investigated chronicity and type of bullying, school climate, familial, demographic, and attitudinal factors that influenced victim reporting to anyone versus no one, to adults versus no one, and to adults versus peers. Logistic regression analyses indicated that reporting increased with the chronicity of victimization. Reporting was generally more frequent among girls than boys, and among lower grade levels. Students who perceived the school climate to be tolerant of bullying, and students who described their parents as using coercive discipline were less likely to report being bullied. Implications for improving victim reporting of bullying are discussed. Aggr. Behav. 30:373–388, 2004. © 2004 Wiley‐Liss, Inc.
Urinary testosterone metabolite levels and aggressive behaviors in male and female bonobos (Pan paniscus)
Authors: Sannen Adinda , Van Elsacker Linda , Heistermann Michael , Eens Marcel
Published: September 2004

This study presents the first data on the relationship between testosterone (T) and aggression in both sexes of the bonobo (Pan paniscus). Morning urinary concentrations of T metabolites (measured by immunoreactive 5α–androstane–17α–ol–3–one) were used to reflect T status. Results show that first, no correlation of T metabolite levels with any of the aggressive behaviors was found between individuals. Within an individual, T metabolite levels only correlated with a minority of aggressive behaviors. Hence, social factors are likely of major importance for the occurrence of aggression in this highly gregarious species, but certain intraindividual aspects of aggressive behavior are nevertheless related to T. A more detailed discussion of the results follows. Secondly, all correlations with T were similar for every individual, males and females, suggesting an analogous relationship in both sexes. Thirdly, our study confirms for bonobos that the measure of aggression used, the time scale at which the correlation is studied, and whether this is done on an inter‐ or intraindividual level, considerably affect results. Aggr. Behav. 30:425–434, 2004. © 2004 Wiley‐Liss, Inc.
Social‐cognitive mediators of the relation of environmental and emotion regulation factors to children's aggression
Authors: Musher‐Eizenman Dara R. , Boxer Paul , Danner Stephanie , Dubow Eric F. , Goldstein Sara E. , Heretick Donna M.L.
Published: September 2004

Tested a theoretical model in which social cognitions about aggression partially mediated the relation of environmental and emotion regulation factors to children's aggressive behavior. An ethnically diverse sample of 778 children (57% girls) in grades 4–6 from both urban and suburban schools participated. Measures included exposure to aggression (seeing/hearing about aggression, victimization), emotion regulation (impulsivity, anger control), social cognitions about aggression (self‐evaluation, self‐efficacy, retaliation approval, aggressive fantasizing, caring about consequences), and aggressive behavior. Results supported the hypothesis that social cognitions mediate the relations of exposure to aggression and anger control to aggressive behavior. Also, social cognitions about direct and indirect aggression differentially predicted the respective behaviors with which they are associated. That is, social cognitions about direct aggression were mediators of direct aggressive behavior, whereas social cognitions about indirect aggression were mediators of indirect aggressive behavior. Finally, gender moderated the relations among the variables such that for girls, retaliation approval beliefs were a strong mediator, whereas for boys, self‐evaluation was more important. Aggr. Behav. 30:389–408, 2004. © 2004 Wiley‐Liss, Inc.
Concurrent and prospective effects of multi‐dimensional aggression and anger on adolescent alcohol use
Authors: Swaim Randall C. , Deffenbacher Jerry L. , Wayman Jeffrey C.
Published: September 2004

This study examined the relationship between alcohol, anger, and aggression in high school students. Anger and three types of aggressive expression (verbal, physical toward people, and physical toward objects) were evaluated cross‐sectionally and prospectively, via structural equation modeling for relationships to alcohol use in Mexican American and white non‐Latino 9–10th (Time 1) and 11–12th grade (Time 2) students. At both times cross‐sectionally, anger and aggressive anger expression tended to correlate positively with alcohol use in each ethnicity/gender group. However, prospectively, aggressive forms of anger expression tended not to be related to alcohol use two years later. Only verbally aggressive anger expression was related to alcohol use two years later and then, only for Mexican American and white non‐Latino females. There was, therefore, little basis for causal links between aggressive anger expression and alcohol use in a general population of high school students. Aggress. Behav. 30:356–372, 2004. © 2004 Wiley‐Liss, Inc.
On new parametrization methods for the estimation of linear state–space models
Authors: Ribarits T. , Deistler M. , Hanzon B.
Published: September 2004

In this paper we introduce two variants of a new parametrization for state–space systems which we will both call separable least squares data driven local co‐ordinates (slsDDLC). SlsDDLC is obtained by modifying the parametrization by data driven local co‐ordinates (DDLC). These modifications lead to analogous parametrizations, and we show how they can be used for a suitably concentrated likelihood criterion function. The concentration step can be done by an ordinary or generalized least squares step. An obvious consequence is the reduced number of parameters in the iterative search algorithm. The application of the parametrizations to maximum likelihood identification is exemplified. Simulations indicate that the usage of slsDDLC for concentrated likelihood functions has numerical advantages as compared to the usage of the more commonly used echelon canonical form or conventional DDLC for the likelihood function. Copyright © 2004 John Wiley & Sons, Ltd.
Recursive subspace identification based on instrumental variable unconstrained quadratic optimization
Authors: Mercère G. , Lecoeuche S. , Lovera M.
Published: September 2004

The problem of the recursive formulation of the MOESP class of subspace identification algorithms is considered and two novel instrumental variable approaches are introduced. The first one leads to an RLS‐like implementation, the second to a gradient type iteration. The relative merits of both approaches are analysed and discussed, while simulation results are used to compare their performance with one of the existing techniques. Copyright © 2004 John Wiley & Sons, Ltd.
Optimal adaptive controller for systems with delay
Authors: Lo Kueiming , Kimura Hidenori
Published: September 2004

Stochastic adaptive d‐step‐ahead optimal control is analyzed in this paper. An adaptive controller using the least squares (LS) algorithm and an input matching technique is proposed to combine the globally convergent estimation character of the adaptive tracking and optimally‐based input specification behavior by using a d‐step‐ahead quadratic cost function. The identification convergence rate of the parameter estimation is based on the LS algorithm. With adaptive control, the d‐step‐ahead closed‐loop stochastic system is globally stable and the adaptive controller converges to the d‐step‐ahead optimal controller. Lastly, the consistency of parameter estimators is analyzed and the convergence rate of parameter estimation is obtained. Copyright © 2004 John Wiley & Sons, Ltd.