bluuebunny/crossref_metadata_2025 huggingface dataset:
Photosystem I acceptor side limitation is a prerequisite for the reversible decrease in the maximum extent of P700 oxidation after short‐term chilling in the light in four plant species with different chilling sensitivities
Authors: Kim Jin‐Hong , Kim Sun‐Ju , Cho Sung Ho , Chow Wah Soon , Lee Choon‐Hwan
Published: January 2005

Changes in the extent of P700 oxidation (P700+) were investigated after chilling of barley, rice, pumpkin, and cucumber leaf segments at 4°C for 1 h under light with various photon flux densities. At 50 µmol photons m−2 s−1, the decrease in P700+ was observed only in cucumber, but at 150 µmol photons m−2 s−1, it was found in all plants except barley, revealing their expected chilling sensitivities. However, the decrease in P700+ by this short‐term chilling was reversible in the presence of 3‐(3′,4′‐dichlorophenyl)‐1,1‐dimethylurea or methyl viologen, and it did not show any causal relationship with the decrease in the electron transfer rate nor with the down‐regulation of photosystem II through the accumulation of zeaxanthin and the development of non‐photochemical quenching. These results led to the suggestion that photosystem I (PSI) acceptor side limitation is a prerequisite for the decrease of P700+. Furthermore, PSI acceptor side limitation could be mainly due to limitation of electron‐sink pathways such as CO2 assimilation and ascorbate–glutathione cycle, because treatment with glycolaldehyde which inhibits the former pathway, and with KCN which inhibits both pathways, decreased P700+ by 20–30% in barley leaves after chilling in the light.
Combining ability analysis and correlation between breeding values in true potato seed
Authors: Ortiz R. , Golmirzaie A. M.
Published: January 2005

True potato seed (TPS) requires the selection of appropriate parents for developing hybrid offspring. Parents for routine crossing schemes need to be selected according to their combining ability. Hierarchical and factorial mating designs provide a mean values to assess the general combining ability (GCA) of clones included in crossing schemes. Furthermore, specific combining ability (SCA) may be investigated using the factorial mating design. The aim of this research was to determine the combining ability of clones included in early and intermediate TPS breeding populations developed by the Centro Internacional de la Papa (CIP). Likewise, correlations between breeding values (or additive genetic correlation, pA) were calculated. Two hierarchical mating designs (in both the early and intermediate populations) and one factorial mating design (in the intermediate population) were evaluated in two contrasting Peruvian locations (La Molina ‐ coastal desert, and San Ramon, warm humid tropics). Plant and tuber characteristics were recorded in these experiments. Significant GCA was observed for tuber yield in all experiments. The male's pA between plant vigour after transplanting and tuber yield was significant, thereby suggesting that offspring with early vigorous growth are high yielding. Plant vigour was also correlated with tuber set, but only among the breeding value of female parents, which suggests that high tuber yield could be achieved because offspring with early, vigorous growth have many tubers. High tuber yielding hybrids can be obtained by choosing parents with significant GCA, whose tuber yield can also be further enhanced if the crosses have a significant SCA.
Transfer of powdery mildew resistance from Brassica carinata to Brassica oleracea through embryo rescue
Authors: Tonguç M. , Griffiths P. D.
Published: January 2005

Interspecific hybrid plants and backcross 1 (BC1) progeny were produced through sexual crosses and embryo rescue between Brassica carinata accession PI 360883 and B. oleracea cvs Titleist’and‘Cecile’to transfer resistance to powdery mildew to B. oleracea. Four interspecific hybrids were obtained through application of embryo rescue from crosses with B. carinata as the maternal parent, and their interspecific nature confirmed through plant morphology and random amplified polymorphic DNA (RAPD) analysis. Twenty‐one BC1 plants were obtained through sexual crosses and embryo rescue although embryo rescue was not necessary to produce first backcross generation plants between interspecific hybrids and B. oleracea. All interspecific hybrids and eight of the BC1 plants were resistant to powdery mildew.
Helminthosporium leaf blight resistance and agronomic performance of wheat genotypes across warm regions of South Asia
Authors: Sharma R. C. , Duveiller E. , Ahmed F. , Arun B. , Bhandari D. , Bhatta M. R. , Chand R. , Chaurasiya P. C. P. , Gharti D. B. , Hossain M. H. , Joshi A. K. , Mahto B. N. , Malaker P. K. , Reza M. A. , Rahman M. , Samad M. A. , Shaheed M. A. , Siddique A. B. , Singh A. K. , Singh K. P. , Singh R. N. , Singh S. P.
Published: January 2005

Helminthosporium leaf blight (HLB) is the most important disease constraint to wheat (Triticum aestivum L.) cultivation in the eastern Gangetic Plains of South Asia. A Helminthosporium Monitoring Nursery (HMN) including potential adapted and exotic sources of HLB resistance was developed in Bangladesh, India and Nepal to assess the stability of genetic resistance across locations. The 8th, 9th and 10th HMN assessed the HLB resistance and agronomic traits of 17 wheat genotypes across 20 environments of Bangladesh, India and Nepal in the 1999‐2000, 2000‐2001 and 2001‐2002 cropping seasons, respectively. The area under the disease progress curve (AUDPC) for HLB, grain yield, thousand‐kernel weight (TKW), days to heading, days to maturity, and plant height were examined. The 17 genotypes showed a range of variability for disease and agronomic characters. Disease severity (AUDPC) differed in the 3 years and showed the highest values in 2002. The increase in AUDPC in 2002 caused the lowest grain yield, with an average 18% reduction due to HLB. A few genotypes (SW 89‐5422, Yangmai‐6 and Ning 8201) appeared to have stable HLB resistance across environments. However, most of the higher‐yielding genotypes, except BL 1883, were unstable. The results suggest that careful selection of HLB resistance with acceptable grain yield, TKW and plant height may be possible using the wheat genotypes included in the HMN.
Estimates of additive and dominance effects for Fusarium head blight resistance of winter triticale
Authors: Oettler G. , Heinrich N. , Miedaner T.
Published: January 2005

The most effective strategy to control Fusarium head blight (FHB), a devastating disease of small‐grain cereals, is breeding resistant cultivars. This resistance study of F1 crosses, F2 and backcross generations of triticale estimates heterosis, general and specific combining ability (GCA, SCA), additive and dominance effects and compares parents with segregating generations. The genetic material consisted of 10 parents with their 45 F1 crosses and of six parents with their 15 F2 progeny and backcrosses to each parent. Genotypes were grown in various environments and artificially inoculated with an aggressive isolate of F. culmorum. FHB was assessed, by visual rating, as the mean of four to five individual ratings of disease development. Heterosis for FHB was of little importance. The correlation between the FHB rating of F1 crosses and their mid‐parent performance was close. GCA was the predominant source of variation, although the significance of the SCA variance also implied non‐additive allelic interaction. The preponderance of additive gene effects is encouraging for increasing resistance by a recurrent selection programme. The relationship between the GCA effect of a parent and its per se performance was close, which gives the possibility of predicting FHB resistance in F1 crosses. Additive effects were predominant in the F2 progeny and also in the backcrosses. Transgressive segregants could not be detected. Searching for them should be postponed to the F3 or later generations.
Evaluating genetic relationships in seed impatiens, Impatiens walleriana, using AFLP profiling
Authors: Carr J. , Korban S. S.
Published: January 2005

Although seed impatiens is the leading bedding plant in the US, little work has been conducted on evaluating the genetic variability present in this crop. In this study, amplified fragment length polymorphism technology was utilized to determine the level of polymorphism present across 20 commercial cultivars of seed impatiens, to assess their genetic variability, and to investigate their genetic relatedness. A total of eight EcoRI and MseI primer combinations were used for polymerase chain reaction amplification. Fluorescence‐labelled amplification products were subjected to electrophoresis and then analysed using an automated sequencer. High levels of polymorphism were detected among all 20 cultivars for all primer combinations tested. Gower's Genetic Dissimilarity estimates for the entire set of cultivars ranged from 1.000 to 0.316. The dendogram generated from these dissimilarity data revealed a number of groupings, including one major division which placed all of the cultivars into one of two groups. The implications of these results on genetic variability, genotypic relationships and genetic diversity in seed impatiens is discussed.
An AFLP‐based linkage map of Zoysiagrass (Zoysia japonica)
Authors: Cai H. , Inoue M. , Yuyama N. , Nakayama S.
Published: January 2005

To construct an amplified‐fragment length polymorphism (AFLP)‐based molecular linkage map of zoysiagrass, the selfed progenies of a clone consisting of 78 individuals were analysed using 471 AFLP markers derived from 126 PstI/MseI primer combinations. Of these markers, 364 were grouped into 26 linkage groups. The maps covered a total length of 932.5 cM, with an average spacing of 2.6 cM between markers. This information proves useful for gene targeting, quantitative trait loci mapping, and marker‐assisted selection in zoysiagrass.
Late heading of perennial ryegrass caused by introducing an Arabidopsis homeobox gene
Authors: van der Valk P. , Proveniers M. C. G. , Pertijs J. H. , Lamers J. T. W. H. , van Dun C. M. P. , Smeekens J. C. M.
Published: January 2005

Perennial ryegrass (Lolium perenne L.) is the most important temperate forage grass species. Unfortunately, the nutritional value of perennial ryegrass declines as maturity progresses, mainly because of a high concentration of poorly digestible compounds in inflorescences. Therefore, the development of forage‐type ryegrass varieties with extended vegetative growth is of interest for agriculture. To delay floral transition in perennial ryegrass the Arabidopsis ATH1 gene driven by the maize ubiquitin promoter, the rice actin promoter or the rice OSH1 promoter, respectively was introduced. In ATH1‐expressing plants heading was delayed, and in a number of cases the plants never flowered at all. Such non‐ or late‐heading was accompanied by the outgrowth of normally quiescent lateral meristems into extra leaves, resulting in a leafy growth habit. When eventually heading, these plants generally produced a reduced number of inflorescences. These observations suggest that ATH1‐mediated delay of heading may be useful to improve fodder quality of perennial ryegrass.
A simple method to control the seed purity of japonica hybrid rice varieties using PCR‐based markers
Authors: Komori T. , Nitta N.
Published: January 2005

Cytoplasmic male sterility (CMS) by the cms‐bo cytoplasm and its restoration by the nuclear restorer gene, Rf‐1, are used for seed production of japonica hybrid rice varieties. To produce pure hybrid seeds, a prerequisite is to properly manage the seed purity of parental lines, especially CMS lines. In this study, three dominant polymerase chain reaction (PCR)‐based markers (M1, M2 and M3) were developed to detect mutual contamination in seed batches of CMS lines, maintainer lines, restorer lines and hybrids. M1 detected the mitochondrial sequence that was present in the cytoplasm of common japonica varieties and absent in the cms‐bo cytoplasm. M2 and M3 detected the chromosomal sequence related to the Rf‐1 allele in restorer lines and the rf‐1 allele in common japonica varieties, respectively. By the strategic use of these markers, japonica hybrids and their parental lines could be efficiently distinguished from each other. Furthermore, sensitivity tests for the three markers with a series of crude DNA samples prepared from polished grains demonstrated that these markers could detect one contaminating grain among 500 or 1000 grains. Therefore, the bulk PCR analyses with the markers developed here probably make it possible to control the seed purity of japonica hybrids properly by selecting appropriate seed batches of their parental lines quickly and efficiently.
Efficient low‐cost DNA extraction and multiplex fluorescent PCR method for marker‐assisted selection in breeding
Authors: Frey J. E. , Frey B. , Sauer C. , Kellerhals M.
Published: January 2005

Marker‐assisted selection (MAS) is an increasingly important tool in current breeding efforts for improved crop plants and animal breeds. It enables detection of favourable alleles in early developmental stages and thus may result in substantial cost savings. Until now, however, the high costs of the required chemicals and materials, together with the still very labour‐intensive methods, have been an obstacle to widespread application of MAS. A new multiplex‐polymerase chain reaction (PCR)‐based method has been developed for reliable low‐cost, high‐throughput screening. By its use 3366 apple seedlings were screened with an average hands‐on time from DNA extraction to data ready for analysis of < 4 h per 96 plants, and at a cost below US$ 0.5 per marker per plant. Factors that have a strong effect on segregation ratios such as elevated levels of outcrossing are easily detected, as a significant correlation was observed between deviation from expected segregation ratios in some affected markers and the level of outcrossing in a cross. The new method is suitable for many crop species and, provided that suitable buffers are used for DNA extraction, for animals too.
Molecular evaluation of genetic variability in wild populations of mulberry (Morus serrata Roxb.)
Authors: Vijayan K. , Kar P. K. , Tikader A. , Srivastava P. P. , Awasthi A. K. , Thangavelu K. , Saratchandra B.
Published: January 2005

Sixteen populations of the wild mulberry, Morus serrata Roxb., were analysed for their genetic diversity with the aim of using them in introgressive breeding programmes with cultivated relatives. Five genets from each population were collected from different natural populations of M. serrata present in Uttaranchal and Himachal Pradesh in India, and diversity of morpho‐anatomical traits and inter‐simple sequence repeat (ISSR) markers were studied. Significant amounts of genetic diversity were observed among these populations for morpho‐anatomical as well as DNA markers. The 17 ISSR primers generated a total of 95 DNA markers, 51 of which were polymorphic, revealing 67% polymorphism among the populations. The pair‐wise genetic distance, estimated from these DNA markers varied from 0.091 between Urgam‐3 and Kathpuria to 0.258 between Dakrakao‐1 and Dunda with an average genetic distance of 0.165. Clustering analysis grouped these 16 populations into three broad groups. The grouping showed a moderate correlation with the geographical distances. Based on the morphological traits and molecular genetic variability, plants of Urgam‐1, Bhowali farm, Nainitikar, Dunda or Korwa‐2 can be selected for breeding and conservation programmes.
Introgression of disease resistance genes from Arachis kempff‐mercadoi into cultivated groundnut
Authors: Mallikarjuna N. , Pande S. , Jadhav D. R. , Sastri D. C. , Rao J. N.
Published: January 2005

Arachis kempff‐mercadoi is a wild species from the section Arachis. All kempff‐mercadoi accessions originate from the Santa Cruz province of Bolivia and they represent Arachis species with the A genome. From molecular analysis it was found that although cultivated A. hypogaea is made up of A and B genomes, A. kempff‐mercadoi may not be as closely related to it as are some of the other A genome species. Arachis kempff‐mercadoi is of interest because it has multiple disease resistance. It was crossed with a Spanish A. hypogaea cultivar which is susceptible to foliar diseases and to the insect pest Spodoptera litura. The success rate of the cross A. hypogaea (2n = 40) ×A. kempff‐mercadoi (2n = 20) was very low, but it could be increased by culturing immature seeds in vitro. Although the hybrids were triploids, a few fertile pollen grains were obtained due to the formation of restitution nuclei in the F1 plants. Interspecific derivatives at the BC2F2 generation were scored for early leaf spot, late leaf spot and to Spodoptera damage. Screening results showed that 29% of the derivatives had both early and late leaf spot resistance and that less than 5% of the derivatives had resistance to both the foliar diseases and to Spodoptera.
Development and characterization of interspecific hybrids of Trifolium alexandrinum×T. apertum using embryo rescue
Authors: Malaviya D. R. , Roy A. K. , Kaushal P. , Kumar B. , Tiwari A. , Lorenzoni C.
Published: January 2005

This is the first report on the development of interspecific hybrids between Trifolium alexandrinum and T. apertum using embryo rescue and characterization of F1 plants. T. apertum was used as the male parent and T. alexandrinum as the female parent. Development of interspecific hybrids under natural conditions is not successful and so embryo rescue was attempted. Of the several combinations tried, pollination 2 days after emasculation and embryos rescued 11 days after pollination was found to be the best. For embryo culture, EC3 medium consisting of MS basal supplemented with 2.3 μM kinetin and 3% sucrose was used. Germinated embryos were transferred to LSP3 medium 25 days after inoculation wherein most of the cultures showed multiple shoots that were split and subcultured on RL1 medium for rooting. After hardening, about 75% of hybrids were successfully transferred to the field. The hybrids, in general, showed morphological traits intermediate between the two parents; however, a few hybrids showed better growth than either parent. Some F1 plants were almost 3 weeks later in flowering than the female parent. Pollen fertility among these plants ranged from 78 to approximately 100%. Chromosomal associations at diakinesis and isozyme banding patterns for acid phosphatase (ACP), superoxide dismutase (SOD) and peroxidase also confirmed the hybrid nature of the plants.
Mechanism of crack path morphology and branching from small fatigue cracks under mixed loading
Authors: MURAKAMI Y. , TAKAHASHI K. , TOYAMA K.
Published: January 2005

In order to investigate the crack path in materials containing a small crack under mixed mode loading, reversed torsion and combined push–pull/torsion fatigue tests were carried out on 0.47% carbon steel specimens containing an initial small crack. The initial small cracks were introduced by a preliminary push–pull fatigue test using a specimen that contained an artificial small hole of 40 μm diameter/depth. Push–pull fatigue tests followed by reversed torsion, and reversed torsion followed by push–pull were carried out. Fatigue tests of combined push–pull/torsion followed by push–pull were also carried out to examine the effect of crack geometry, such as branching and kinking, on cumulative fatigue damage. Different crack growth behaviours due to different loading modes and sequences complicatedly influenced the fatigue crack path and eventually the cumulative fatigue damage. Thus, existing fatigue damage theories cannot be applied to the cases presented in this study. A single factory roof morphology was formed on the fracture surface of the specimen having an initial semielliptical surface crack under cyclic torsion. Taking the result into consideration, torsional fatigue tests of circumferentially cracked specimens were carried out to investigate the Mode III crack growth threshold and the formation mechanism of the factory roof. It was found that the factory‐roof pattern was formed by Mode I crack branching from small semielliptical cracks nucleated ahead of the circumferential crack tip. Thus, stress intensity factors at the semielliptical crack tip ahead of the circumferential crack tip were analysed to make the mechanism of crack branching from the semielliptical crack clear. The analysis shows that the Mode III stress intensity factor, KIII, at the deepest point of the semielliptical crack decreases with increase in the depth of semielliptical crack. It follows that as the shear crack growth becomes difficult at the semielliptical crack tip, crack branching starts at the major axis ends in the direction for Mode I growth, forming factory roof, due to ΔKIth < ΔKIIIth.
The relationship between process mechanisms and crack paths in friction stir welded 5083‐H321 and 5383‐H321 aluminium alloys
Authors: JAMES M. N. , BRADLEY G. R. , LOMBARD H. , HATTINGH D. G.
Published: January 2005

Friction stir (FS) welding is a relatively new solid‐state welding process that offers high levels of joint performance with minimal preparation and little post‐weld dressing. The high levels of plastic work induced in the weld zone produce a very fine grain size in the stirred region of the weld (e.g. the nugget), while the low heat input limits residual stresses to a low fraction of the proof strength of the weld metal. These effects are generally beneficial to weld dynamic performance. The peculiar thermomechanical history in the FS weld region leads, however, to particular defects with some unusual effects on crack path, whose occurrence depends partly on crack speed, or growth rate. This paper presents observations regarding specific influences of the FS welding process on crack paths and dynamic performance for 5083‐H321 and 5383‐H321 aluminium alloys, and proposes an explanation for the observations in terms of the weld microstructures and thermomechanical history. The insights presented in this paper can be used to inform optimisation of the weld process parameters, through on‐line feedback and control of tool geometry, force footprint, torque and temperature.
Stress distributions in notched structural components under pure bending and combined traction and bending
Authors: ATZORI B. , FILIPPI S. , LAZZARIN P. , BERTO F.
Published: January 2005

The availability of analytical expressions is often desirable in the analyses of fatigue crack initiation and early propagation. This paper presents approximate analytical expressions capable of describing the overall distribution of the maximum principal stress in finite size notched bodies subjected to bending and combined traction and bending. The formulae reported here represent an extension of an analytical complex function approach already presented in the literature, suitable for describing highly stressed zones surrounding the notch tip. Such an extension, derived by simply imposing global equilibrium conditions, enables us to increase the range of validity of the principal stress expression from the notch tip to the entire ligament width. The accuracy of the proposed expressions is tested against data from finite element analyses carried out on plates and bars weakened by semicircular, V‐ and U‐shaped notches. The agreement seems to be good.
Environmental and frequency effects on fatigue crack growth rate and paths in aluminium alloy
Authors: MICHEL S. A. , KIESELBACH R. , FIGLIOLINO M.
Published: January 2005

The environmental and frequency effects on fatigue crack growth in aluminium alloys are studied theoretically and experimentally. 2024‐T351 and 7075‐T651 tested in corrosive environments (humid air or technically purified nitrogen) show a constant crack growth rate (da/dN) at low values of the effective stress intensity range (ΔKeff). Typical well‐known fits of this curve (da/dN vs ΔKeff) do not reflect the plateau‐like region. A new model of crack growth is presented, which physically attributes this region to the formation and subsequent fracture of a crack tip oxide layer. The thickness of this layer is measured with X‐ray photon electron spectroscopy. At higher loads, other mechanisms are understood to be active. The model parameters are determined from constant amplitude tests, and are valid for a given material and environment. In 7075‐T651 tested in nitrogen, with R= 0.1 and 83 Hz, unexpected macroscopical crack branching is observed when ΔKeff reaches approximately 3.0 MPa √m.
Review of the subsurface strain path approach to fatigue life assessment of components
Authors: SHATIL G.
Published: January 2005

Fatigue lives obtained from complex testing and monitoring of different components often involve some degree of discrepancy in results due to geometrical variations, even when they are tested under controlled conditions and have a similar surface cyclic strain range at the critical location. Recently, several fatigue models have been developed to improve the correlation of specimen lives using a critical ‘process zone’ that surrounds the damaged material. A review of such an approach is presented. The approach is based on critical subsurface strains and consists of a fatigue damage summation procedure in the affected area. The fatigue life‐prediction model is applied to two structural materials using three geometries subjected to biaxial cyclic stresses. These include notched bars, rhombic plates and car components. The subsurface strains are evaluated by using a detailed elastic–plastic finite element analysis, and by considering critical subsurface fatigue strain paths. It is shown that in the several cases investigated, the subsurface approach appears to improve life predictions.
A predictor–corrector scheme for the optimization of 3D crack front shapes
Authors: KOLK K. , KUHN G.
Published: January 2005

A predictor–corrector scheme is presented to improve the shape of 3D crack fronts within the 3D simulation of fatigue crack growth. This concept is fully functional for mode‐I, and an extension for mixed‐mode problems is presented. The whole procedure is embedded in an automatic incremental crack growth algorithm for arbitrary 3D problems with linear elastic material behaviour. The numerical simulation is based on the 3D dual boundary element method (Dual BEM) and on an optimized evaluation of very accurate stress intensity factors (SIFs) and T‐stresses. As part of the proposed predictor–corrector scheme, 3D singularities along the crack front especially in the vicinity of the intersection of the crack front and the boundary are considered. The knowledge of these singularities allows the specification of crack front shapes with bounded energy release rate. Numerical examples with complex cross‐sections are presented to show the efficiency of the proposed crack growth algorithm. The obtained results are in good agreement with recent experimental results.
Near‐threshold fatigue crack path in Al–Zn–Mg alloys
Authors: PETIT J.
Published: January 2005

This paper reviews the role of microstructure and environment on the path of fatigue cracks in a high purity Al‐4.5% wt Zn‐1.25% wt Mg alloy in the form of single crystals, bicrystals and polycrystals, and a commercial Al–Zn–Mg alloy type 7075 in three ageing conditions. Crack propagation rates were measured in air and in high vacuum, possible interactions of crack closure being uncoupled by considering data provided by tests performed with closure correction or in conditions without closure. The analysis of the experimental results is particularly focused on the role of the atmospheric environment on the crack path. The relation between the crack paths and the crack growth mechanisms is discussed on the basis of micrographic and micro‐fractographic observations and of mechanisms previously identified for the three basic crack propagation stages (stage I, stage I like and stage II) and for intergranular fatigue crack propagation.
Fatigue fracture planes and expected principal stress directions under biaxial variable amplitude loading
Authors: KAROLCZUK A. , MACHA E.
Published: January 2005

Fatigue behaviour under multiaxial variable amplitude loading can be examined by applying the failure criteria based on the critical plane approach. Positions of the critical plane can be determined in relation to the principal stress or strain directions. In the present paper, the expected directions of the principal stresses under proportional and non‐proportional loading have been obtained by averaging the instantaneous values of the Euler angles through special weight functions. The known weight functions based on stress parameters appear not to be efficient for each loading or material being analysed. Thus, the authors consider new weight functions based on energy parameters. The presented forms of weight functions are assessed by testing 18G2A steel specimens. It is concluded that the fatigue fracture plane position under multiaxial loading can efficiently be determined on the basis of an averaged direction of the maximum principal stress by employing a suitable weight function.
Fatigue crack path in Cu–Ni–Mo alloyed PM steel
Authors: BERGMARK A. , ALZATI L.
Published: January 2005

A detailed qualitative fatigue crack path study is made on Ni–Cu alloyed powder metallurgy (PM) steel with Mo prealloyed base powder. The microstructure is characterized by upper bainitic cores of the base powder particles surrounded by a Cu‐rich martensite with islands of Ni‐rich austenite. Earlier observations have shown that the visible surface cracks do not pass through the Ni‐rich areas. The aim of the present study is to find the crack path in relation to the Cu‐rich martensite and the Ni‐rich austenite also below the surface. Successive grinding in steps of about 20 μm is made, and the surface crack in each level is recorded by light optical microscope (LOM). The main part of the crack path is found through high temperature bainite or along the interface between martensite and high temperature bainite. Ni‐rich austenite is surrounded by martensite that hinders the crack from entering into austenite. The result indicates that austenite as such is not a strong crack stopper.
Multiple surface crack propagation: numerical simulations and experimental tests
Authors: CITARELLA R. , PERRELLA M.
Published: January 2005

In‐house experimental observations of three‐dimensional fatigue crack growth are compared to numerical predictions by the Boundary Element code BEASY. Fracture analysis results for a complex geometry specimen, undergoing a general load spectrum, are presented with regard to three‐dimensional crack propagation and mode coupling effects. The specimens under consideration are cracked tension specimens, with a through‐crack or a quarter/semicircular crack that proceed inclined to the remote loading direction. Mixed mode conditions along the crack edge are characterized: the stress intensity factors are determined using the crack opening displacement (COD) method and the crack growth direction is computed by the minimum strain energy density criterion. Effects of specimen complex geometry, produced by a part‐through thickness hole near the initial saw‐cut notch, on fracture crack path are analysed. Moreover, multiple interacting three‐dimensional cracks are simulated correspondingly to experiments: a satisfactory agreement between numerical and experimental crack growth direction and crack growth rates are displayed.
The effects of loading waveform and microstructure on the fatigue response of Ti–6Al–2Sn–4Zn–2Mo alloy
Authors: SHANIAVSKI A. A.
Published: January 2005

A fractographic analysis was performed to estimate the crack‐growth period in specimens of Ti–6AL–2Sn–4Zn–2Mo–0.1Si titanium alloy with two types, α/β and β, of microstructure. The fatigue load cycle shape was triangular or trapezoidal. It was shown that a facetted pattern predominantly forms under the trapezoidal wave shape of cyclic loads for both the investigated microstructures. A special methodology was introduced for quantitative fractographic analysis in the case of locally formed fatigue striations between facetted patterns. Crack‐growth periods, estimated on the basis of the striation spacing measurements, were used to determine lifetime to failure for the tested specimens. The results of the performed investigations are briefly discussed and compared with experimental data.
A model for fatigue strength of welded lap joints
Authors: BERETTA S. , SALA G.
Published: January 2005

The most advanced structural frames of cars and motorcycles are made from welded box beams of aluminium alloys. A recent technological solution for the beams consists of press‐formed metal sheets joined by welded single‐lap joints. Because the frames undergo cyclic loading, the evaluation of the fatigue endurance of this kind of connections plays a crucial role in the development of the frames. The present research deals with the evaluation of the fatigue behaviour of welded lap joints, subjected to tensile and bending loads. Fractographic evidence and numerical analyses show that the fatigue strength is controlled by the presence of defects and inhomogeneities at the tip of the weld root. In particular, these defects, which appear to lie on the maximum Kθθ path, increase the stress intensity factor (SIF) at the weld root. Such an analysis, together with a statistical description of the population defects, allows us to develop a methodology to predict the fatigue strength of lap joints. A simple method for SIF computation based on finite‐element (FE) analyses and structural stresses at the lap joints is then presented.
Computational prediction of fatigue crack paths in ship structural details
Authors: SUMI Y. , MOHRI M. , KAWAMURA Y.
Published: January 2005

The characteristics of fatigue crack propagation and the remaining life assessment of ship structures are investigated focusing attention on a curved crack path due to the effects of welds, complicated stress distributions at three‐dimensional structural joints and structural redundancy. An advanced numerical simulation method is demonstrated for the remaining life assessment for curved crack propagation. The simulation method is based on a step‐by‐step finite‐element analysis. The crack path is predicted by the perturbation method with the local symmetry criterion, which gives a higher order approximation of the crack path, while the finite‐element re‐zoning is carried out by an improved paving method. Fatigue crack paths in the welded structural details of the transverse girder of a ship structure are investigated by experiments and simulation. The present method may offer an efficient simulation‐based tool for the design of critical details, which prevents the failure of the plates forming a compartment boundary.
Theoretical crack path prediction
Authors: RICHARD H. A. , FULLAND M. , SANDER M.
Published: January 2005

In many practical cases, the crack growth leads to abrupt failure of components and structures. For reasons of a reliable quantification of the endangerment due to sudden fracture of a component, therefore, it is of enormous importance to know the threshold values, the crack paths and the growth rates for the fatigue crack growth as well as the limiting values for the beginning of unstable crack growth (fracture toughness). This contribution deals with the complex problem of a—however initiated—crack, that is subjected to a mixed‐mode loading. It will present the hypotheses and concepts, which describe the superposition of Mode I and Mode II (plane mixed mode) as well as the superposition of all three modes (Mode I, II and III) for spatial loading conditions. Those concepts admit a quantitative appraisal of such crack situations and a characterization of possible crack paths.
The effect of microtexture evaluated by electron backscatter diffraction method on fatigue crack propagation behaviour in rolled copper film
Authors: SHIMIZU K. , TORII T.
Published: January 2005

Using a fatigue‐testing method by which a fatigue crack can be propagated in a film adhered to cover an elliptical through‐hole in a base plate, annealed rolled copper films have been fatigued. The effects of rolling textures and annealing twin boundaries on fatigue crack propagation behaviour are discussed. The fatigue crack propagates in a large zigzag pattern in the TC specimen (crack perpendicular to the rolling direction), while the crack propagation path in the RC specimen (crack parallel to the rolling direction) is nearly straight. Further, the fatigue cracks propagate slower toward the perpendicular direction than toward the parallel direction. After fatigue testing, the crystallographic characteristic of rolling textures around the fatigue crack in the annealed film is analysed using the EBSD (electron backscatter diffraction) system. Because the annealing twin boundary is in the same plane as the slip of the face‐centred‐cubic metal, the fatigue crack tends to propagate along the slip line initiated along the annealing twin boundary.
Quantitative palaeoclimatic inference based on terrestrial mammal faunas
Authors: Fernández Manuel Hernández , Peláez‐Campomanes Pablo
Published: January 2005

Aim  The main goal of this paper is to propose a new tool, in the form of Quantitative Bioclimatic Models (QnBMs), for reconstructing past climates based on fossil mammal associations. As a case study, European climatic conditions during the basal early Pleistocene will be inferred using QnBMs.

Location  The study uses faunas throughout the world to develop a quantitative bioclimatic model, which is then applied to Quaternary faunas from Eurasia.

Methods  The models were constructed by applying multivariate linear regression to modern mammal faunas and climates from all over the world. The models were validated with a second group of modern faunas, which includes several from transitional zones between different climates (ecotones). To test the reliability of the method when applied to fossil associations, the results obtained for the Pleistocene have been compared with those obtained from palynology.

Results  Validation of the models shows that as many as 11 climatic factors can be inferred with high reliability using the regression models developed in this work. Comparisons of results in the late Pleistocene–Holocene of Barová (Czech Republic) between a palynological study and the quantitative bioclimatic analysis show a high degree of similarity. The results for the early Pleistocene show colder and drier climatic conditions for Europe than today.

Main conclusions  The application of the quantitative bioclimatic models to present day as well as Quaternary mammal faunas proves to be a useful tool for palaeoclimatic reconstruction during the Quaternary and probably most of the Neogene. Transfer functions are presented for a complete set of climatic factors, allowing a precise estimation of the climate in a locality from its mammal fauna.
Carbon sequestration rates in organic layers of boreal and temperate forest soils — Sweden as a case study
Authors: Akselsson Cecilia , Berg Björn , Meentemeyer Vernon , Westling Olle
Published: January 2005

Aim The aim of this work was to estimate C sequestration rates in the organic matter layer in Swedish forests.

Location  The region encompassed the forested area (23 × 106 ha) of Sweden ranging from about 55° N to 69° N.

Methods  We used the concept of limit values to estimate recalcitrant litter remains, and combined it with amount of litter fall. Four groups of tree species were identified (pine, spruce, birch and ‘other deciduous species’). Annual actual evapotranspiration (AET) was estimated for 5 × 5 km grids covering Sweden. For each grid, data of forested area and main species composition were available. The annual input of foliar litter into each grid was calculated using empirical relationships between AET and foliar litter fall in the four groups. Litter input was combined with average limit values for decomposition for the four groups of litter, based on empirical data. Finally, C sequestration rate was calculated using a constant factor of the C concentration in the litter decomposed to the limit value, thus forming soil organic matter (SOM).

Results  We obtained a value of 4.8 × 106 metric tons of C annually sequestered in SOM in soils of mature forests in Sweden, with an average of 180 kg ha−1 and a range from 40 to 410 kg ha−1. Norway spruce forests accumulated annually an average of 200 kg C ha−1. The pine and birch groups had an average of 150 kg ha−1 and for the group of other deciduous trees, which is limited to south Sweden, the C sequestration was around 400 kg ha−1.

Conclusions  There is a clear C sequestration gradient over Sweden with the highest C sequestration in the south‐west, mainly corresponding to the gradient in litter fall. The limit‐value method appears useful for scaling up to a regional level to describe the C sequestration in SOM. A development of the limit value approach in combination with process‐orientated dynamic models may have a predictive value.
Preserving biodiversity under current and future climates: a case study
Authors: W. Coulston John , Riitters Kurt H.
Published: January 2005

Aim  The conservation of biological and genetic diversity is a major goal of reserve systems at local, regional, and national levels. The International Union for the Conservation of Nature and Natural Resources suggests a 12% threshold (area basis) for adequate protection of biological and genetic diversity of a plant community. However, thresholds based on area may protect only a small portion of the total diversity if the locations are chosen without regard to the variation within the community. The objectives of this study were to demonstrate methods to apply a coarse‐filter approach for identifying gaps in the current reserve system of the Psuedotsuga menziesii (Douglas‐fir) forest type group based on current climatic conditions and a global climate change scenario.

Location  Western United States.

Method  We used an ecological envelope approach that was based on seven bioclimatic factors, two topographic factors, and two edaphic factors. Multivariate factor analysis was then used to reduce the envelope to two dimensions. The relative density of habitat and protected areas were identified in each part of the envelope based on the current climate and potential future climate. We used this information to identify gaps in the reserve system.

Results  Although the protected areas occurred in all parts of the envelope, most existed in colder and drier areas. This was true for both the current climate and potential future climate.

Main conclusion  To protect more of the ecological envelope, future conservation efforts would be most effective in western Oregon, north‐western Washington, and north‐western California.
Dimensions of quality upgrading
Authors: Dulleck Uwe , Foster Neil , Stehrer Robert , Woerz Julia
Published: January 2005

The impact of the Central and Eastern European (CEE) economies’ trade integration with European markets on CEE trade structures has been studied extensively. These studies frequently observe a quality upgrading of CEE exports. In this paper we consider three dimensions of quality upgrading: upgrading across industries, upgrading across different quality segments within industries and, finally, product upgrading within quality segments inside industries. For the analysis we partition industries into quality segments based on EU‐15 import unit values. The results for ten CEE countries (comprising the CEE‐5, the Baltics and South East Europe) and thirteen industries suggest fundamental differences, both across country groups and across the three different notions of quality upgrading. The CEE‐5 show no evidence of entering a ‘low‐quality trap’ in all three dimensions. By contrast, while there is a general catching‐up process across industries and inside quality segments, the second notion of low‐quality specialization may be applicable within the high‐tech industries to the performance for the Baltics and South East Europe as a group.
Poverty and informal economy participation
Authors: Kim Byung‐Yeon
Published: January 2005

This paper uses a household survey of the Romanian informal economy to analyse the effects of poverty on informal economy participation. We begin by developing a simple theoretical model, which shows that the participation is driven by low income and the gap between desired and actual income level. We then estimate the determinants of households’ participation in the informal economy. Empirical findings are consistent with the theoretical prediction. In addition, a positive association between husbands and wives working in the informal economy implies the deep poverty faced by a family whose head participates in the informal economy.
Genome conflict in the gramineae
Authors: Jones Neil , Pašakinskienė Izolda
Published: January 2005

The genomes of grasses and cereals include a diverse and large collection of selfish genetic elements, many of which are fossil relics of ancient origin. Some of these elements are active and, because of their selfish nature and the way in which they exist to perpetuate themselves, they cause a conflict for genomes both within and between species in hybrids and allopolyploids. The conflict arises from how the various elements may undergo ‘drive’, through transposition, centromere and neocentromere drive, and in mitotic and meiotic drive processes in supernumerary B chromosomes. Experimental and newly formed hybrids and polyploids, where new combinations of genomes are brought together for the first time, find themselves sharing a common nuclear and cytoplasmic environment, and they can respond with varying degrees of instability to adjust to their new partnerships. B chromosomes are harmful to fertility and to the physiology of the cells and plants that carry them. In this review we take a broad view of genome conflict, drawing together aspects arising from a range of genetic elements that have not hitherto been considered in their entirety, and we find some common themes linking these various elements in their activities.

Contents

Summary
391

I.
Introduction
391

II.
Intragenomic conflict
393

III.
Intergenomic conflict
401

IV.
Conclusions
405

Dedication
406

References
406
In touch: plant responses to mechanical stimuli
Authors: Braam Janet
Published: January 2005

Perception and response to mechanical stimuli are likely essential at the cellular and organismal levels. Elaborate and impressive touch responses of plants capture the imagination as such behaviors are unexpected in otherwise often quiescent creatures. Touch responses can turn plants into aggressors against animals, trapping and devouring them, and enable flowers to be active in ensuring crosspollination and shoots to climb to sunlit heights. Morphogenesis is also influenced by mechanical perturbations, including both dynamic environmental stimuli, such as wind, and constant forces, such as gravity. Even individual cells must sense turgor and wall integrity, and subcellular organelles can translocate in response to mechanical perturbations. Signaling molecules and hormones, including intracellular calcium, reactive oxygen species, octadecanoids and ethylene, have been implicated in touch responses. Remarkably, touch‐induced gene expression is widespread; more than 2.5% of Arabidopsis genes are rapidly up‐regulated in touch‐stimulated plants. Many of these genes encode calcium‐binding, cell wall modifying, defense, transcription factor and kinase proteins. With these genes as tools, molecular genetic methods may enable elucidation of mechanisms of touch perception, signal transduction and response regulation.

Contents

Summary
373

I.
Introduction
374

II.
Fast and fascinating – thigmonasty and thigmotropism
374

III.
Subcellular touch‐induced movements
382

IV.
Thigmomorphogenesis
382

V.
Discovery of the Arabidopsis TCH genes
384

VI.
Microarray identification of touch‐inducible genes
384

VII.
Regulation of TCH gene expression
385

Acknowledgements
386

References
386