bluuebunny/crossref_metadata_2025_split huggingface dataset:
Applied geophysical inversion
Authors: Ellis R. G. , Oldenburg D. W. 
Published: April 2007

SummaryUsing the 2-D DC-resistivity tomography experiment as an example, we examine some of the difficulties inherently associated with constructing a single maximally smooth model as a solution to a geophysical inverse problem. We argue that this conventional approach yields at best only a single model from a myriad of possible models and at worst produces a model which, although having minimum structure, frequently has little useful relation to the earth that gave rise to the observed data. In fact in applied geophysics it is usual to have significant prior information which is to be supplemented by further geophysical experiments. With this perspective we suggest an alternate approach to geophysical inverse problems which emphasizes the prior information and includes the data from the geopysical experiment as a supplementary constraint. To this end we take all available prior information and construct an inversion algorithm which, given an arbitrary starting model and the absence of any data, will produce a preconceived earth model and then introduce the observed data into the inversion to determine how the prior earth model is influenced by the supplementary geophysical data.
Immunohistochemical identification of renal lysozyme during allograft rejection in man
Authors: KLOCKARS M. , REITAMO S. , COLLAN Y. 
Published: April 2007

An immunoperoxidase staining method was used to identify lysozyme in biopsy or transplantectomy specimens of human renal allografts during reversible and irreversible rejection of the grafts. Proximal tubules in apparently functioning nephrons showed lysozyme staining. In irreversibly rejected grafts, infiltrating mononuclear phagocytes in and near peritubular and glomerular capillaries also stained intensely for lysozyme. In acute necrotizing arteritis, lysozyme‐positive cells (mononuclear phagocytes) infiltrated the blood vessel wall. The presence of infiltrating lysozyme‐positive cells in the transplant was consistent with poor graft survival.The variation in lysozyme staining of proximal tubular cells apparently was a reflection of the differences in the reabsorption capacity of the tubular cells, attributable to the tubular dysfunction of renal allografts. The infiltrating lysozyme‐positive cells probably contribute to the increased urinary excretion of lysozyme during acute rejection.
Sinus histiocytosis with massive lymphadenopathy in Rwanda: report of eight cases with immunohistochemical and ultrastructural studies
Authors: NGENDAHAYO P. , ROELS H. , QUATACKER J. , BODDAERT J. , NTABOMUVRA V. , MBONYINGABO P. 
Published: April 2007

The clinico‐pathological, immunohistochemical and ultrastructural features of eight cases of sinus histiocytosis with massive lymphadenopathy (SHML) recorded in Rwanda from 1975 to 1980 are reported.The main histopathological features were a massive enlargement of the lymph node sinuses which were filled with large histiocytes, a great number of which phagocytosed blood cells, especially lymphocytes, and an important proliferation of plasma cells in the medullary cords. The pathogenesis of this syndrome is discussed, particularly the role of immunological disorders challenged by a chronic, but non‐specific, infectious state. The ultrastructural study revealed no micro‐organisms and no Langerhans’ granules. Immunohistochemical staining revealed two interesting features: the presence of immunoglobulins in the cytoplasm of the histiocytes indicating the presence of an immune phagocytosis and the absence of lysozyme and α1‐antichymotrypsin (α1‐AC) from the histiocytes. The significance of the latter phenomenon is still unknown.
Benign epithelial neoplasms of the appendix: classification and clinical associations
Authors: WILLIAMS G.R. , BOULAY C.E.H.DU , ROCHE W.R. 
Published: April 2007

The nomenclature of non‐carcinoid epithelial proliferations of the appendix is confused and many of the terms used have no histogenetic basis. A classification based on the well‐established diagnostic categories of colonic epithelial polyps has been proposed recently. We have applied this classification to 42 benign epithelial lesions of the appendix in order to determine its suitability for routine diagnostic use, and in order to determine the prognosis of patients with these lesions.All lesions could be classified as either hyperplastic, adenomatous, mixed hyperplastic/adenomatous or dilated appendices. Six cases were associated with a synchronous carcinoma of the colon with all types of appendiceal histology being represented. Follow‐up of the remainder of the patients revealed two subsequent colonic carcinomas, at 3 and 6 years post‐appendicectomy respectively. In both of these patients, the appendix had shown adenomatous epithelium. We suggest that adenomas of the appendix may have a similar prognostic significance to adenomas elsewhere in the large bowel.
Expression of mutant p53 gene in squamous carcinoma arising in patients with recessive dystrophic epidermolysis bullosa
Authors: SLATER S.D. , McGRATH J.A. , HOBBS C. , EADY R.A.J. , McKEE P.H. 
Published: April 2007

J.A.M. is currently receiving a research fellowship from the Dystrophic Epidermolysis Bullosa Research Association (DEBRA).Epidermolysis bullosa, a rare genodermatosis, is characterized by increased skin fragility manifest as blistering and sometimes accompanied by scarring. The latter is particularly severe in the recessive dystrophic variant and may be complicated by the development of squamous carcinoma in up to 30% of patients. We have studied 23 such tumours in six patients with this variant, with an anti‐serum to p53 protein. Twenty‐six per cent of the squamous carcinomas labelled positively for mutant‐type p53 protein. This low figure, however, reflects the large number of well‐differentiated tumours in this series, where 14 out of 15 were negative. In the moderate to poorly differentiated examples the positivity rate was 63%. Of the three patients in the latter category, one has died from disseminated tumour and another has widespread metastases. The findings support the hypothesis that mutant p53 protein expression correlates with poorer tumour differentiation. They also suggest a possible correlation between p53 protein expression and tumour behaviour.
Design of human trials in progressive renal failure
Authors: BECKER Gavin J 
Published: April 2007

Summary: Future studies aimed at testing therapies to prevent progression of renal failure have much to learn from the past successful and unsuccessful attempts. Given the insensitivity of all other methods, the proper index of renal function for study of progression of renal failure should be radioisotope glomerular filtration marker clearance. Randomized prospective controlled studies are required, and statistical analysis should be designed to allow consideration for patient drop out and covariants.Since compensatory mechanisms come into place as soon as there is any nephron damage, more attention should be paid to studying the progression of renal failure from a normal glomerular filtration rate (GFR) until there is an elevated plasma creatinine level. This suggestion is supported by four under‐lying concepts: (i) overall GFR does not fall until about 23% of nephrons are destroyed; (ii) if progression is multifactorial, the later in the progress the more likely that more factors are present to confound issues; (iii) this may allow study of greater patient numbers, since patients who have had renal biopsy or ultrasound diagnosis can be entered before the plasma creatinine is abnormal; (iv) in early stages of disease, issues of concurrent treatment may be less difficult (e.g. diet, phosphate control, hypertension).With diabetes, prognosis and progression has been related to proteinuria. In non‐diabetic disease proteinuria has been related to progression, but the effect of alleviation of proteinuria on prognosis has not been intensively studied. There is a need to study the relationships between proteinuria and progression, particularly in early renal disease.At present most therapies are based upon observations in the partially ablated rat model. Other animal models should be developed, and the details of early mechanisms in the rat further clarified. Since we believe progression is likely to be multifactorial in pathogenesis, combination therapies may be required to optimally reduce progression.
A FINITE ELEMENT ANALYSIS OF A CRACK GROWING UNDER CYCLIC LOADING
Authors: Wästberg Stig 
Published: April 2007

Abstract—Crack growth under cyclic loading has been studied by the finite element method. The calculation was made for plane stress conditions. The crack tip zone was modelled as a cohesive zone.The displacement of the free crack surface during unloading was found to be governed by the surrounding continuum and was independent of the details in the fracture zone. This means that crack closure upon unloading is directly related to the ultimate separation, of the cohesive zone, which in turn controls the residual plastic deformation left in the wake of the growing crack.If the distance over which closure takes place is rather small, closure may be very difficult to detect by the compliance technique.
FATIGUE CRACK GROWTH LAWS FOR BRITTLE AND DUCTILE MATERIALS INCLUDING THE EFFECTS OF STATIC MODES AND ELASTIC‐PLASTIC DEFORMATION
Authors: Chell G. G. 
Published: April 2007

A fatigue crack growth damage accumulation model is used to derive laws for the fatigue crack growth rates of brittle and ductile materials. The damage accumulated during cyclic loading is assumed to be proportional to the cyclic change in the plastic displacement in the crack tip yielded zone. The static mode contribution to the fatigue damage is assumed to be proportional to some power of the crack tip displacement. The laws are applicable in either the small or large scale yielding regimes provided that the stress ratio remains positive. Static modes are assumed to be controlled by the fracture toughness value in brittle materials, and by the gradient of the crack growth resistance curve in ductile materials. In the analysis of ductile materials it is assumed that the crack growth resistance of the material is not significantly altered by fatigue crack growth.The growth rate equations are expressed in terms of the near field value of theJ‐integral, i.e. the value which would be calculated from assuming the material deformed in a non‐linear elastic manner during the increasing load part of the fatigue cycle. Examples are given of the predictions of the growth law for ductile materials. It is predicted that after the initiation of stable tearing the crack growth rate, when expressed in terms of the cyclic change in the stress intensity factor, depends on both the structural geometry and the degree of crack tip plastic deformation. In both brittle and ductile materials the fatigue crack growth rate is predicted to accelerate as the failure criteria relevant to static crack instability are approached.
CREEP‐FATIGUE STUDIES UNDER A BIAXIAL STRESS STATE AT ELEVATED TEMPERATURE
Authors: Hamada Naomi , Sakane Masao , Ohnami Masateru 
Published: April 2007

AbstractIn order to study creep‐fatigue interactions under multiaxial stress states, both push‐pull and reversed torsion low‐cycle fatigue tests were carried out using an austenitic stainless steel, SUS 304, at 923 K in air. From the tests, it is concluded that the hold‐times introduced at the peak strain reduce low‐cycle fatigue lives in the push‐pull mode, but in the torsional mode they were not so harmful. This difference in the hold‐time effect is discussed from considerations of crack formation and propagation and the stress amplitude applied to the specimen.Both maximum principal strain range, Δε1, and the von Mises' equivalent strain range, Δεeq, provide a nearly adequate comparison base for the assessment of biaxial low‐cycle fatigue lives in tests without strain hold‐time but are inadequate for hold‐time tests. An equivalent stress range, Δσ*, which includes the effect of the stress parallel to the fatigue crack and which was previously proposed by the authors for no hold‐time tests, is applied to the hold‐time tests in the biaxial stress state. It is found that Δσ* is a good parameter for the correlation of biaxial low‐cycle fatigue data in both no hold‐time and hold‐time tests.
SHORT CRACK FATIGUE BEHAVIOUR IN A MEDIUM CARBON STEEL
Authors: Rios E. R. de los , Tang Z. , Miller K. J. 
Published: April 2007

AbstractThe initiation stage and short crack behaviour in torsional fatigue of a 0.4% C steel was investigated by a replication technique.The fatigue cracks initiated and propagated in the ferrite phase which is located at the prior austenite grain boundaries in the form of long allotriomorphs. At this stage of crack development it is proposed that crack growth rate depends on the extent and intensity of plasticity at the tip of the crack. Crack growth per cycle is correspondingly proportional to the strength of the slip band. The ferrite‐pearlite boundaries are strong barriers to crack propagation, which is manifested by a deceleration of growth and possible arrest. On raising the stress level the previously non‐propagating cracks may continue to grow by branching or joining with other cracks in the ferrite phase. This process is repeated until the stress fields of one or more dominant cracks attain a critical value to sustain continued growth that leads to failure.
CYCLIC DEFORMATION OF A1‐4%Cu ALLOY POLYCRYSTALS CONTAINING θ″ PRECIPITATES
Authors: Horibe Susumu , Lee Jia‐Kuen , Laird Campbell 
Published: April 2007

AbstractThe cyclic deformation of polycrystalline A1‐4%Cu alloy containing θ precipitates was investigated by strain controlled tests, and compared to monocrystalline cyclic behavior. The cyclic deformation of the polycrystals was found to depend on the grain size, and in coarse‐grained material (grain diameter = 1 mm) a definite plateau was observed in the cyclic stress‐strain (CSS) curve. In order to explore the relationship of cyclic behavior between single crystals and polycrystals, three available orientation factors were examined. This relationship can be interpreted by selection from the different types of orientation factors (Taylor factor, Sachs factor and Maximum Schmid factor), which operate to different degrees depending on the magnitude of the strain amplitude and the grain size.
FATIGUE GROWTH OF SURFACE CRACKS IN THE ELASTIC‐PLASTIC REGION
Authors: Obrtlík K. , PolÁk J. 
Published: April 2007

AbstractSurface crack growth has been studied in centre notched and smooth panels of low carbon steel under symmetric axial elastic‐plastic cyclic straining. The crack shape, followed by heat tinting, has been found to be approximately semi‐circular for crack radii 0.3–5 mm. Both smooth and notched specimens have been fatigued until fracture. The smallest notches of 0.1 mm in radius and depth approximately represent defects of a critical size under present loading conditions. Crack propagation rates have been measured and plotted vs ΔJ. Both present part through‐crack data and previous long through‐crack data in the elastic and the elastic‐plastic regions are compatible. A single dependence of dl/dN vs ΔJ is obtained.
EFFECTS OF AIR AND INERT ENVIRONMENTS ON THE NEAR THRESHOLD FATIGUE CRACK GROWTH BEHAVIOR OF ALLOY 718
Authors: Yuen J. L. , Schmidt C. G. , Roy P. 
Published: April 2007

AbstractThe near threshold fatigue crack growth behavior of alloy 718 was studied in air and helium environments at room temperature and at 538°C. Tests were performed at 100 Hz and at load ratios of 0.1 and 0.5. At room temperature and at 538°C, the ΔKth values in helium were lower than in air. The ΔKth values in air decreased with increasing load ratio. These results can be explained with a model that involves the accumulation of oxide in the crack which enhances crack closure. In the air tests, the oxide build‐up on the fatigue fracture surfaces at ΔKth was of the order of magnitude as the crack tip opening displacement. In the helium tests, no significant build‐up of oxide on the fracture surface at threshold was found.
THE VARIATION OF CRACK OPENING STRESS INTENSITY WITH TIME
Authors: Lei Ming jun , Yu Weikang , Gerberich W. W. 
Published: April 2007

AbstractIt was found that crack opening stress intensities are not constant after holding for various times in the unloaded state for iron and a sequence of Fe‐Si binary alloys. The crack opening level decreased with time first because of asperity creep and substructure relaxation, and then increased again with time due to reverse plastic zone relaxation allowing a new set of asperities to come into contact. It is demonstrated that the crack closure phenomenon is not only a result of residual plasticity, oxidation and asperities, but also is due to asperity creep and reverse plastic zone relaxation at the crack tip for low strength materials.
ANALYTICAL AND GRAPHICAL AIDS FOR THE FATIGUE DESIGN OF WELDMENTS
Authors: Yung J.‐Y. , Lawrence F. V. 
Published: April 2007

AbstractThere are four important attributes of weldments which, together with the magnitude of the fluctuating stresses applied, determine their resistance to metallic fatigue: the ratio of the applied or self‐induced axial and bending stresses; the severity of the discontinuity or notch which is an inherent property of the geometry of the joint; the notch‐root residual stresses which result from fabrication and subsequent use of the weldment; and the mechanical properties of the notch‐root material in which fatigue crack initiation and growth takes place. A simple version of a more elaborate analytical model of the fatigue behavior of weldments [1] is presented here which provides analytical and graphical design aids for design.
FATIGUE CRACK GROWTH UNDER MIXED MODES I AND II
Authors: Yokobori A. Toshimitsu , Yokobori Takeo , Sato Kiyoshi , Syoji Kazuo 
Published: April 2007

AbstractFatigue crack growth behaviour under mixed modes I and II was studied by applying in‐phase alternating tensile and torsional loading to a thin‐walled hollow cylindrical specimen with an initial crack.In the linear region of a log‐log plot where da/dN=A(ΔK)m, da/dN at first decreases with increasing ΔK110 component and then approaches a minimum close to the value of ΔK110/ΔK10∼ 0.58; here ΔK110/ΔK10 is the ratio of the initial ΔKII to the initial ΔK1., When ΔK110/ΔK10 increases further, da/dN increases. Under shear mode, da/dN becomes higher than that under mode I. The ΔK1, and ΔK11 components during fatigue crack growth under mixed mode loading increase and decrease, respectively, with an increase in da/dN In the low crack growth rate region the fatigue crack growth rates accelerate with an increase of the initial ΔK11 component, ΔK110. Fatigue life increases with increase of ΔK110/ΔK10 under the test condition of equivalent stress range being kept constant and the pre‐crack length being the same.
STRESS INTENSITY FACTORS FOR CRACKS IN NOTCHED FINITE PLATES SUBJECTED TO BIAXIAL LOADING
Authors: Xiao S. T. , Brown M. W. , Miller K. J. 
Published: April 2007

AbstractStress intensity factors were calculated, based on Bueckner's principle for cracks in both infinite and finite plates with notches subjected to biaxial loading. Approximate Green's functions have been obtained by modifying two existing Green's functions, originally for unnotched plates. Values of stress intensity factors calculated using Bueckner's principle with the approximate Green's functions are in good agreement with published stress intensity factors for cracks in both infinite and finite plates containing a circular notch or an elliptical notch, previously found by the method of boundary collocation.
FATIGUE FAILURE AT STRESSES BELOW FATIGUE LIMIT
Authors: Iwasaki C. , Ikai Y. 
Published: April 2007

AbstractIn the present study, the authors have focused attention on the internal stress in a material. A stress applied to a specimen does not fully act to deform the material. The effective stress which actually acts on dislocations depends on the internal stress in the material. The origin of the internal stress is attributed here to the dislocation structure. From this viewpoint, fatigue tests were carried out and the following results were obtained:(1) The origins of the internal stress and the effective stress were clarified by means of a dislocation model.(2) The behaviour of the internal stress during the fatigue process showed clear differences between over‐stressed and under‐stressed states.(3) The concept of internal and effective stresses assists in our understanding of the fatigue phenomenon.(4) The mechanism of fatigue failure in the under‐stressed fatigue state was also studied, and the concept of an internal stress was applied to instances of practical fatigue situations.
NON‐DAMAGING NOTCHES IN FATIGUE*
Authors: Lukáš P. , Kunz L. , Weiss B. , Stickler R. 
Published: April 2007

AbstractThe fact that very small notches (cavities, holes, scratches, etc.) have no effect on the fatigue limit of metallic materials is well known. This paper presents both a qualitative explanation for the existence of non‐damaging notches and a quantitative derivation of their critical sizes. The condition for a notch (characterized by the stress concentration factor Kt and the notch root radius ρ) to be non‐damaging in a metallic material (characterized by a critical crack size l0) is(K2t− 1)ρ≤ 4.5 l0.The critical crack size can be expressed with good approximation in terms of the threshold stress intensity for fatigue crack growth and the plain fatigue limit. Therefore the above relation can be applied for an engineering evaluation of non‐damaging notches. Test results obtained for copper and a pressure vessel steel demonstrate the applicability of the proposed method.
LIMITATIONS OF LINEAR ELASTIC FRACTURE MECHANICS IN RESPECT OF SMALL FATIGUE CRACKS AND MICROSTRUCTURE
Authors: Tokaji Keiro , Ogawa Takeshi , Harada Yukio , Ando Zenji 
Published: April 2007

AbstractThe growth characteristics of small fatigue cracks were investigated under rotary bending in a low alloy steel prepared with two prior austenite grain sizes of 15 μm (fine grain) and 91 μm (coarse grain). The influence of grain boundaries on crack growth rate and the crack aspect ratio was examined, and the critical crack length above which linear elastic fracture mechanics (LEFM) is applicable was evaluated for a growing small crack. When the surface crack length is shorter than three grain diameters (3d), crack growth rates decrease near the grain boundaries. Aspect ratios are also affected by the microstructure and thus vary widely. Cracks longer than 3d are not influenced by the microstructure, but they grow faster than would be expected based on LEFM until their lengths reach 3d+ 150 μm. This behaviour may be attributed to the difference in crack closure between small cracks and large cracks. If the contribution of crack closure to the growth of small cracks can be established experimentally or analytically, the critical crack length above which LEFM is applicable would be 3d. However, because it is difficult to evaluate crack closure, 3d+ 150 μm is considered to be the critical crack length for engineering applications.