bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of upper gastrointestinal endoscopy with routine standardized endoscopic biopsy in AIDS
Authors: Cappellanes Carlos A. , Hashiba Kiyoshi , Brasil Horus A. , D’Assunção Marco A. , Moribe Daniel , Armellini Savèrio , Hassegawa Renato T. , Câmara Lopes Luiz H.
Published: March 2003

Background:

The purpose of this study is to identify lesions in the esophagus, stomach and duodenal bulb in patients with AIDS through endoscopy, and to correlate the results obtained with the histophatological study of standardized endoscopic biopsies of the esophagus, stomach and duodenal bulb.

Methods:

Eight standardized endoscopic biopsies were taken at every endoscopic examination: two from the distal segment of the esophagus, two from the body of the stomach, two from the gastric antrum and two from the duodenal bulb. The biopsies specimens were stained with H&E, Ziehl‐Nielsen‐Faraco, Giemsa and periodic acid‐schiff dyes. The avidin‐biotin‐peroxidase method was used for the immunohistochemical study.

Results:

Endoscopy with standardized endoscopic biopsies of the upper gastrointestinal tract in patients with AIDS demonstrated specific findings in the esophagus at 24.1% of cases, 16.1% in the stomach and 8.0% in the duodenal bulb. Endoscopy with standardized endoscopic biopsies of the gastrointestinal tract in patients with AIDS, even with normal endoscopic appearance, displayed specific findings in the stomach at 27.7% and in the duodenal bulb at 27.7%.

Conclusion:

Quite often, the endoscopic features in the esophagus, stomach and duodenal bulb in patients with AIDS do not appear to be associated with pathogens identified in them. Although we do not have data at this time, this series opens the discussion and shows that, even in patients with AIDS presenting a normal endoscopic finding, performing standardized endoscopic biopsies for the detection of opportunistic infections in various segments of the gastrointestinal tract could be very important.
Echocardiographic risk stratification for ischemic stroke in non‐rheumatic atrial fibrillation: Importance of aortic plaques detected by transesophageal echocardiography*
Authors: Matsumura Yoshihisa , Fukui Takayuki , Osaki Yasushi , Sato Kyoko , Yabe Toshikazu , Doi Yoshinori
Published: March 2003

Background: The aim of the present paper was to assess the prevalence of atherosclerotic aortic plaques in non‐rheumatic atrial fibrillation and their relation to ischemic stroke. Although aortic plaques are frequently seen in the elderly, their significance remains unclear in relation to ischemic stroke in patients with atrial fibrillation.

Methods: Transesophageal echocardiography was performed on 56 patients (age 61 ± 10 years) with atrial fibrillation. The aorta was divided into two segments (i.e. the proximal aorta that includes the ascending aorta and the aortic arch proximal to the ostium of the left subclavian artery, and the distal aorta that is the descending aorta distal to the left subclavian artery). Thickened intima = 3 mm in thickness was defined as aortic plaques.

Results: Ischemic stroke was found in 14 of the 56 patients. Aortic plaques were detected
in 25 of the 56 patients. All of these 25 patients had aortic plaques in the proximal
aorta, and 17 of them also had aortic plaques in the distal aorta. Ischemic stroke
was found in 11 of the 25 patients (44%) with aortic plaques, and three of
the 31 patients (10%) without aortic plaques (P < 0.01). Conversely,
aortic plaques were detected in 11 of the 14 patients (79%) with ischemic
stroke, and in 14 of the 42 patients (33%) without (P < 0.01).
The patients with ischemic stroke had a larger left atrium (47 ± 5 vs
43 ± 6 mm; P < 0.05) than those without. Aortic plaques were a correlate
only of previous ischemic stroke (P < 0.05) by multiple logistic regression analysis.

Conclusions: Atherosclerotic aortic plaques detected by transesophageal echocardio‐graphy are a correlate of previous ischemic stroke in patients with non‐rheumatic atrial fibrillation.
Factors associated with ADL dependence: A comparative study of residential care home and community‐dwelling elderly in Japan
Authors: Ho Han Kwee , Matsubayashi Kozo , Wada Taizo , Kimura Miyuki , Kita Toru , Saijoh Kiyofumi
Published: March 2003

Background:  Since the start of Long Term Nursing Insurance in Japan in April 2000, there has been much discussion about and emphasis on leading healthy and active twilight years, without ever being bedridden if possible. In an attempt to address some of these concerns, this comparative study examines the factors associated with dependence in the activities of daily living (ADL) in two samples of elderly people living in two different environments.

Methods:  In this cross‐sectional, self‐reported study, 262 and 968 elderly people from a residential care home and Yogo town completed a 65‐item questionnaire. Questions pertaining to ADL, medical and social history, quality of life (QOL) and the 15‐item Geriatric Depression Scale were included in the questionnaire. Using logistic regression model, factors associated with ADL dependence were determined.

Results:  In the residential care home group, age, female gender, instrumental ADL, communication‐related ability, history of falls, stroke, and osteoarthropathy, depressive tendency and low satisfaction with life emerged as the factors associated with ADL dependence, after multivariate logistic regression. The corresponding factors in the community‐dwelling elderly group were age, depressive tendency, history of osteoarthropathy, and low sense of health.

Conclusion:  Age and female gender were the two non‐modifiable risk factors associated with ADL dependence. Stroke, followed by osteoarthropathy and falls were the main medical conditions predisposing to functional dependence. Dependence in instrumental ADL, independence in communication‐related ADL, depressive tendency and components of QOL were factors associated with ADL dependence. Awareness of these factors not only helps to identify at‐risk patients, to initiate preventive measures and to promote disability‐delaying activities, but also helps in the holistic management of geriatric patients.
Evaluation of amylase and lipase in the diagnosis of acute pancreatitis
Authors: Treacy John , Williams Anthony , Bais Renz , Willson Krysten , Worthley Christopher , Reece John , Bessell Justin , Thomas David
Published: March 2003

Background: The diagnosis of acute pancreatitis relies heavily on a raised amylase.

Methods: In the present study patients were prospectively categorized, without knowledge of pancreatic enzyme levels, into acute pancreatitis (AP; n = 51), disease controls (n = 35), indeterminate as to pancreatitis (n = 189) or exclusions (non‐pancreatitis diseases where amylase may be elevated; n = 53).

Results: Enzyme levels were analysed by receiver operator characteristics (ROC) curves, with specificity > 80%. Day 1 serum lipase gave the greatest diagnostic accuracy (area under ROC curve = 0.128; P = 0.041 vs serum amylase). At the calculated diagnostic threshold of 208 U/L, lipase gave a sensitivity of 67% and a specificity of 97%. Other diagnostic thresholds (day 1) were: serum total amylase, 176 U/L (ROC 0.104, sensitivity 45%, specificity 97%), urinary total amylase, 550 U/L (ROC 0.108, sensitivity 62%, specificity 97%) and serum pancreatic isoamylase, 41 U/L (ROC 0.107, sensitivity 63%, specificity 85%). At delayed diagnosis (3 days) no enzyme was superior to lipase. The combination of lipase and amylase did not increase diagnostic accuracy.

Conclusion: Serum lipase is recommended for diagnosis of AP, both early and late in the disease. Although highly specific when elevated, all pancreatic enzymes have low sensitivity for diagnosis.
Optimal position for a cervical collar incision: A prospective study
Authors: Jancewicz Stephen , Sidhu Stan , Jalaludin Bin , Campbell Peter
Published: March 2003

Background: The descriptions of the optimal method for placing a cervical collar incision for thyroidectomy or parathyroidectomy are varied. It has been our impression that a collar incision marked in the neutral upright neck, migrates superiorly relative to the sternal notch when the patient is placed in the supine position. The aim of this study was to investigate the validity of this impression and to assess whether this is influenced by patient factors and/or pathology.

Methods: Fifty patients undergoing either thyroid or parathyroid surgery had a planned incision marked 1 finger‐breadth (17 mm) above the sternal notch when sitting in the upright position. When placed in the supine position, with neck extended, the distance from the sternal notch to the marked incision was remeasured. Patient variables such as body mass index, height, weight and neck circumference were documented prospectively and data were recorded on operative details and tumour pathology.

Results: The collar incision marked in the neutral upright neck, migrated
on average 21 mm superiorly once the patient was placed supine with the neck extended
(P = 0. 0001 ).The extent of migration was independent of all patient factors, type of operation and thyroid or parathyroid pathology.

Conclusions: Migration of a proposed cervical collar incision does occur. An inappropriately placed incision may lead to excessive scarring if it is too low, or unusual prominence if it is too high. We believe a good position for marking such an incision is 1 fingerbreadth above the sternal notch with the patient in a neutral, upright position.
Antibiotic prophylaxis in elective colorectal surgery
Authors: Gul Yunus A. , Lian Lee H. , Jabar Faisal M. , Moissinac Kevin
Published: March 2003

Background: Antibiotics are often administered in elective colorectal surgery to prevent wound infection. The tendency for surgeons to prolong the administration of prophylactic antibiotic therapy in the postoperative period is a well‐known fact. The aim of this study was to elucidate the pattern of prophylactic antibiotic utilization in elective colorectal surgery and to determine if evidence‐based medicine is employed in relation to this practice.

Methods: A cross‐sectional study encompassing general surgeons performing elective colorectal surgery was performed. Questionnaires were distributed to 144 surgeons (national, academic and private health care). Questions pertaining to the type, timing and duration of antibiotic administration were asked. The prevalence of wound infection audit rate and whether or not there were specific guidelines related to antibiotic administration were also determined.

Results: The response rate obtained was 67% (n = 96). Although evidence from the current medical literature and recommended national guidelines support the use of single‐dose prophylactic antibiotics, 72% of the respondents used more than a single dose. Forty surgeons (42%) claimed that their prescribing practice was supported by the medical literature, 31 respondents (32%) based their practice on hospital guidelines and personal preference was cited as a reason by 21 surgeons (22%). The remaining four respondents (4%) used a similar scheduling policy to that practiced by their colleagues in relation to antibiotic administration. There was no significant difference in antibiotic dose scheduling between national, private and university academic institutions (P = 0.85).

Conclusions: These results suggest that a significant proportion of surgeons administer excessive and unnecessary doses of antibiotics in elective colorectal surgery. Further studies are required to uncover the reasons but lack of appropriate guidelines and failure to exercise evidence‐based medicine are major factors that account for this practice.
Radiation therapy following nodal surgery for melanoma: An analysis of late toxicity
Authors: Burmeister B. H. , Smithers B. M. , Davis S. , Spry N. , Johnson C. , Krawitz H. , Baumann K. C.
Published: March 2003

Background: The role of adjuvant radiation therapy following resection of malignant melanoma involving regional lymph nodes remains controversial. There is no published randomized trial comparing surgery alone to surgery with postoperative radiation therapy that shows a benefit in terms of local control. Some retrospective studies, however, suggest that radiation given postoperatively reduces local recurrence. One of the obstacles to patients routinely being offered radiation therapy is the concern over the added late toxicity that may occur. The present article is a report of the first 130 patients of a prospective phase II multicentre study in Australia and New Zealand.

Methods: The study was aimed at patients who had had a resection of melanoma in regional nodes or in a regional node basin. The patients were given adjuvant radiation therapy to a recommended dose of 48 Gy in 20 fractions over 4 weeks using accepted radiation techniques for each of the major node sites. This report describes the late toxicity of the treatment received by these patients.

Results: The results of late toxicity experienced in the study were acceptable.

Conclusion:  The regimen of radiation therapy used could form the basis for the treatment arm of a randomized trial.
Impact of splenectomy on circulating T‐lymphocyte subsets in stage III gastric cancer
Authors: Cho Min Young , Kroh Matthew D. , Joh Yong Geul , Suh Sung Ock
Published: March 2003

Background:  The role of splenectomy remains unclear in patients with gastric cancer who undergo total gastrectomy. The aim of this study was to prospectively evaluate the impact of splenectomy on circulating T‐lymphocyte subsets and survival in advanced gastric cancer.

Methods:  Analysis of lymphocyte subsets was performed in 40 patients with American Joint Committee on Cancer (AJCC) stage III gastric adenocarcinoma located on the upper one‐third of the stomach, who underwent a curative total gastrectomy with or without splenectomy. Circulating T‐lymphocyte subsets were measured on venous blood by using flow cytometry and monoclonal antibodies at preoperative day 1, and postoperative months 1, 3, 6, 12 and 18.

Results:  The proportion of lymphocytes and the values of CD3, CD8, CD16 and CD25 subsets were higher in the splenectomy group of patients at postoperative month 3. In the spleen preservation group at the same point of treatment, the proportion of granulocytes and the values of CD4 and CD4 : CD8 ratio were higher. Except for CD16 levels, all T‐lymphocyte subsets showed no sig­nificant difference between splenectomy and spleen preservation groups after postoperative month 3. Increased CD16 levels in the splenectomy group were not associated with improvement in patients’ 5‐year survival rates.

Conclusion:  These results suggest that the long‐term impact of splenectomy does not play an important role in postoperative quantitative changes of circulating T‐lymphocyte subsets of patients with stage III gastric cancer who have undergone total gastrectomy. Furthermore, splenectomy does not give a prognostic benefit, based on tumour recurrence and survival of patients with proximal one‐third gastric cancer who undergo total gastrectomy.
Survey of current cementing techniques in total knee replacement
Authors: Lutz Michael John , Halliday Brett Richard
Published: March 2003

Background:  Current techniques in total knee replacement (TKR) vary greatly. Cementing techniques in TKR are no exception. Identification of current trends would aid ongoing research into future developments.

Methods:  A questionnaire was sent to all orthopaedic surgeons in Queensland, Australia. A range of factors influencing cementing techniques for the tibial plateau were investigated.

Results:  Eighty‐five percent of questionnaires were returned. Ninety‐one percent of surgeons regularly cement the tibial plateau, 90% use some form of lavage prior to cement application, 95% of surgeons apply cement by hand only. Techniques aimed at increasing cement penetration (cement gun, intraosseous suction) are used infrequently.

Conclusions:  In contrast to total hip replacement, measures are not often taken to ensure that there is penetration of cement or a complete cement mantle into the tibial plateau in TKR. This may be because of a perceived lack of evidence in modern literature. This study also illustrates the wide variation in technique in a relatively common orthopaedic operation.
Changing pattern of adrenalectomy at a tertiary referral centre 1970−2000
Authors: Sidhu Stan , Bambach Christopher , Pillinger Stephen , Reeve Thomas , Stokes Gordon , Robinson Bruce , Delbridge Leigh
Published: March 2003

Background:  In 1987, a report from this unit described the changing indications for open adrenalectomy over a 15‐year period. The indications for adrenalectomy had switched from it being the principal therapeutic procedure used in advanced breast cancer in the early 1970s, to being predominately performed for Cushing's disease or incidental, asymptomatic, adrenal masses by the early 1980s. The aim of the present study was to evaluate the changes in the presentation and management of adrenal disease in the last 15 years and to compare these findings with our previously published results.

Methods:  Information was gathered from a prospective database of all patients undergoing adrenalectomy in the University of Sydney Endocrine Surgical Unit at Royal North Shore Hospital from 1 January 1987 to 31 December 2000. Information was obtained on patient presentation, diagnostic investigations, indications for surgery, procedure performed and surgical outcomes. Prior to 1987, information was gathered by retrospective review of case notes of patients who had undergone adrenalectomy at Royal North Shore Hospital. During the period from 1 January 1970 to 31 December 2000, 236 patients underwent adrenalectomy. Excluding the 68 adrenalectomies performed for breast cancer, left 168 patients who underwent adrenalectomy for functional or non‐­functional masses. There were 97 (58%) women and 71 (42%) men, with a mean age of 48 years.

Results:  Of the 168 patients, the principal indications for surgery were hyperaldosteronism (32%), phaeochromocytoma (20%), hypercortisolism (20%), incidentaloma (16%), carcinoma (6%) and other reasons (6%). Examination of the number of cases in each pathological group for the periods 1970−1986 and 1987−2000, revealed an 8‐fold increase in the number of operations for hyper­aldosteronism, and a 3‐fold increase in cases of phaeochromocytoma. The number of operations for the other pathological groups remained steady. The annual incidence of adrenalectomy in the hospital has steadily risen since 1990, with a linear increase in the adrenalectomy rate since the introduction of laparoscopic adrenalectomy in 1995. There were fewer complications in either the open or laparoscopic group since 1987 compared with the pre‐1987 cohort.

Conclusions:  In the past 5 years, there has been a linear increase in the number of adrenalectomies performed in this unit for hyperaldosteronism and to a lesser extent phaeochromocytoma. This is a reflection of increased clinical awareness, improved diagnostic modalities and the advent of laparoscopic adrenalectomy.
David Murray Morton: Father figure of surgery at St Vincent's Hospital, bush lawyer and thwarted reformer of the medico‐legal system
Authors: Vellar Ivo D.
Published: March 2003

When the first Golden Age of surgery at St Vincent's Hospital Melbourne (a period covering the first 25 years of the twentieth century) is discussed, the names that spring to mind are usually those of Sir Thomas Dunhill, Sir Hugh Devine, Sir Douglas Shields and Julian Smith. A name which is often overlooked, and by now almost forgotten, is that of David Murray Morton. Murray ­Morton's career both as a medical student, general practitioner, anaesthetist and surgeon coincided with a revolution in the practice of medicine. He witnessed the progression from Listerian antisepsis to asepsis in surgical practice, the improvements in anaesthesia, the introduction of antibiotics and, before he died in 1959, the beginnings of organ transplants and open heart surgery. Morton was fond of saying that he grew up with the hospital. From the time of his first appointment as an anaesthetist in l896 to the time of his retirement from St Vincent's as senior surgeon in 1931, Morton, admired by all as a highly competent surgeon and a man of incorruptible probity, can rightly be described as the father figure of surgery during the formative years of St Vincent's Hospital. His innate sense of justice and fair play formed the basis of his distinguished tenure of the Presidency of the Medical Defence Association of Victoria, where his constructive attempts at reform of the medico‐legal system were only thwarted by the predictable opposition of the legal profession and politicians.
Sentinel lymph node biopsy for squamous cell carcinoma of the anal canal
Authors: Rabbitt Philippa , Pathma‐Nathan Nimilan , Collinson Trevor , Hewett Peter , Rieger Nicholas
Published: March 2003

Background:  The current Trans‐Tasman Radiation Oncology Group (TROG) protocol for T1 and T2 anal cancers is combination chemotherapy and radiotherapy excluding the inguinal region from the field. Several centres worldwide irradiate both inguinal regions as there is a small incidence of involvement with early stage tumours. The presence of inguinal lymph node metastases is not accurately detected using clinical and most radiological assessment modalities. We have developed a method of sampling the sentinel node in the groin using established node mapping techniques.

Methods:  A combination of radio‐labelled Antimony Sulphide and Patent Blue dye injected around the anal cancer enable identification of the sentinel node in the groin, using a gamma probe and direct visualization of the blue node.

Results:  This technique has been used in four patients. A groin sentinel node was identified and removed in three of these, with pathological assessment excluding metastatic disease in the inguinal region. The fourth patient had a sentinel node mapped to a meso‐rectal node. This was not sampled.

Conclusions:  The application of this effective technique will allow accurate staging of anal cancers to better plan future treatment regimes.
Serum interleukin‐6 measurement in the diagnosis of acute appendicitis
Authors: Gürleyik Günay , Gürleyik Emin , Çetinkaya Fuat , Unalmiser Selcuk
Published: March 2003

Background:  Many attempts have been made to determine ways of decreasing the negative laparotomy rate after a clinical diagnosis of acute appendicitis. The aim of the present study was to determine the effectiveness of serum interleukin‐6 (IL‐6) concentration in the diagnosis of appendicitis, and in the prevention of non‐therapeutic laparotomy in patients with right iliac fossa pain.

Methods:  Serum IL‐6 concentrations were measured at admission in 77 consecutive patients who were operated on for the treatment of acute appendicitis. The final diagnosis was established by histopathological examination. The sensitivity, specificity and accuracy of IL‐6 concentrations in the diagnosis of appendicitis were calculated.

Results:  The negative laparotomy rate was 17% (13/77) in this series. The IL‐6 level was elevated in seven of 13 patients (54%; false positive) with a normal appendix. The IL‐6 level was normal in 10/64 patients (16%; false negative) with acute appendicitis. The IL‐6 level was highly elevated in all patients with perforated appendicitis. The sensitivity, specificity, accuracy, and positive and negative predictive values were calculated as 84, 46, 78, and 89 and 38%, respectively.

Conclusions:  Unacceptably high false negative and positive rates decrease the accuracy of the serum IL‐6 test for appendicitis. Serum IL‐6 measurement is not of benefit in increasing the accuracy of the diagnosis of appendicitis. Serum IL‐6 results are not useful for preventing negative laparotomies in the majority of patients with right iliac fossa pain.
A NEW MULTIPARAMETER APPROACH TO THE PREDICTION OF FATIGUE CRACK GROWTH
Authors: Soboyejo  , Ni  , Li  , Soboyejo  , Knott
Published: March 2003

A new multiparameter approach is proposed for the prediction of the combined effects of multiple variables on fatigue crack growth. The method, which is based on multiple linear regression analysis, involves the statistical formulation of mathematical expressions for the crack growth rate, da/dN, as a function of multiple variables, e.g. stress intensity factor range, ΔK, crack closure stress intensity factor, Kcl , and stress ratio, R. A general empirical approach is proposed for the estimation of the fatigue crack growth rate as a function of the above variables. The predictive capability of the empirical approach is then verified by comparing predicted and measured fatigue crack growth and crack growth rate data obtained from tests on a quenched and tempered Q1N (HY80) pressure vessel steel. Error ranges and reliability functions are presented within a probabilistic mechanics framework, and the implications of the results are discussed for the development of generalized fatigue life prediction methods.
FATIGUE CRACK GROWTH IN TWO ADVANCED TITANIUM ALLOYS UNDER CONSTANT AND VARIABLE AMPLITUDE LOADING AT 25 AND 175 °C
Authors: Stephens  , Stephens  , Albertson  , Veit
Published: March 2003

Fatigue crack growth of β‐21S and Ti‐62222 in sheet form was investigated under constant and miniTWIST flight spectra loading conditions at 25 and 175 °C. Variable amplitude results were compared with life calculations performed using NASA/FLAGRO software and constant amplitude fatigue crack growth results. Single tensile overloads under constant ΔKwere performed to evaluate load interaction effects. Constant amplitude results showed that fatigue crack growth resistance was slightly better for Ti‐62222 than β‐21S at 25 and 175 °C. The presence of crack closure under various conditions caused moderate shifts in the fatigue crack growth data. Under miniTWIST flight spectra loading, Ti‐62222 exhibited a greater extension in life in comparison to the β‐21S at elevated temperature, consistent with the NASA/FLAGRO calculations. This was also consistent with the single tensile overloads where 25 °C tests were comparable for both materials, while at 175 °C, delay cycles were greater by a factor of almost three for Ti‐62222. Extensive secondary cracking in Ti‐62222 at elevated temperature accounted for the extended fatigue lives.
THE FAILURE OF LIGAMENTS DUE TO MULTIPLE‐SITE DAMAGE USING INTERACTIONS OF DUGDALE‐TYPE CRACKS
Authors: Kuang JH , Chen CK
Published: March 2003

A self‐similar, narrow‐strip Dugdale model is invoked to determine interactive crack tip plastic zones. Symmetric collinear multiple‐site damage (MSD) cracks are considered for the coalescence of plastic zones between adjacent cracks. The Swift’s ligament failure criterion is employed to predict the residual strength with or without considering the interaction between Dugdale‐type plastic zones. Better agreement is achieved between the calculated results and experimental data if the interaction between the plastic zones is implemented in a computing scheme.
STATISTICAL ANALYSIS OF DEFECTS FOR FATIGUE STRENGTH PREDICTION AND QUALITY CONTROL OF MATERIALS
Authors: Beretta S , Murakami Y
Published: March 2003

A wide range of studies and experimental evidence have shown that the lower bound of fatigue properties can be correctly predicted by considering the maximum occurring defect size. The estimate of this dimension can be done by analysing the defect sizes using the statistics of extremes.

The scope of this paper is to discuss and investigate the two key points in a successful application of this technique: the first is the choice of statistical method for the analysis of data; the second is the knowledge of the minimum number of defects needed to obtain a good estimate of extreme defects.

The results obtained in this study allow one to formulate a procedure for estimating the extreme defects with a precision suitable for fatigue strength prediction.
TRANSIENT RESPONSE OF A CRACKED INFINITE PIEZOELECTRIC STRIP UNDER ANTI‐PLANE IMPACT
Authors: Yu  , Chen
Published: March 2003

By using the well‐established integral transform methodology, the dynamic response of stress and electric displacement around a finite crack in an infinite piezoelectric strip are investigated under anti‐plane impact. The dynamic intensity factors of stress and electric displacement are obtained analytically. The results show that the dynamic electric field will promote or retard the propagation of the crack at different stages of the loading process. On the other hand, the response of the electric field is coherent with the applied electric load and independent of the external mechanical load. The result obtained for the anti‐plane impact of a cracked infinite piezoelectric ceramic can be regarded as a special case of the present work when the width of the strip tends to infinity.
AN ALTERNATIVE ANALYTICAL APPROXIMATION OF THECtPARAMETER
Authors: Adefris  , McDowell  , Saxena
Published: March 2003

TheCtparameter has proven very useful in correlations of creep crack growth behaviour under both transient and steady state creep conditions. In this paper, we investigate the implications of adopting a different definition of the creep zone based on an absolute measure of creep strain rather than a measure that is relative to the elastic strain. The analytical equations for small‐scale creep and transition times from small‐scale creep to extensive creep conditions are derived for theCtparameter using this alternative definition, considering both primary and secondary creep strain. It is shown that this alternative definition gives a reasonable starting point for the theory, approximately in accordance with the transient evolution of theCtparameter based on the more conventional definition of the creep zone, and removes the somewhat artificial limit of applicability imparted by the classical creep zone definition used in creep fracture mechanics. Accordingly, diffusional creep processes with a power law exponentn ≤ 3 are admitted in theCtdescription.
EVOLUTION OF TRANSVERSE MATRIX CRACKING IN CROSS‐PLY LAMINATES
Authors: Qu  , Hoiseth
Published: March 2003

The objective of this paper is to develop a micromechanics model for the onset and subsequent multiplication of transverse cracks in the 90° layers of a cross‐ply laminate under uniaxial tension. The micromechanics study of transverse matrix cracking is performed by a combination of finite element and analytical analyses. Based on the Griffith fracture criterion, the evolution of transverse matrix crack density is predicted. The prediction compares well with existing experimental data in the literature. Analytical expressions of the non‐linear effective stress–strain curves are also obtained for a wide range of material systems. In addition, an analytical expression of the effective stiffness is derived based on the differential self‐consistent method. The analytical results agree very well with the finite element calculations.
Retrogression, reaging and residual stresses in 7010 forgings
Authors: Robinson J.S. , Tanner D.A. , Whelan S.D.
Published: March 2003

Open die forgings of the aluminium alloy 7010 (DTD5636) have been retrogressed at temperatures between 200 and 240 °C and then reaged (RRA). Tensile, fracture toughness and stress corrosion cracking values are reported. Retrogression at 200 °C offers the most promising combination of properties, and the long retrogression time of approx. 2500 s will enable thick sections to be treated. Residual stresses induced during quenching are also predicted, and initial experimental results suggest that some stress relief occurs during the retrogression heat treatment.
X‐ray diffraction studies on fatigue crack plastic zones developed under plane strain state conditions
Authors: Dias  , Lebrun  , Bignonnet
Published: March 2003

An overview of the X‐ray fractography technique, as performed on fatigue crack surfaces of several steels and Al‐alloys under different loading conditions, is presented. The plastic zone sizes of fatigue cracks, for plane strain conditions, are measured from the in‐depth distribution of residual stresses and X‐ray diffraction peak broadening. In addition to the usual monotonic plastic zone size determination methodology, a model for the estimation of the reverse plastic zone size was established in the case of fatigue softening materials. Monotonic and cyclic plastic zone sizes are related to the stress intensity by, respectively, rpm = α  (Kmax /σys )2 and rpc = α  (ΔK/2σ′ys )2. The α‐value, in the monotonic plastic zone size equation, increases as the yield strength of the material increases, following the relationship α = 0.196  [σys /(129 + 0.928σys )]2. The α‐value versus σys evolution has been understood through the influence of the hardening rate of materials on the plastic zone size. X‐ray fractography has been applied to actual failure analyses to predict some aspects of the actual loadings.
A methodology and criterion for acrylic bone cement fatigue tests
Authors: Cristofolini L. , Minari C. , Viceconti M.
Published: March 2003

Acrylic bone cement is used as a fixing device in total hip arthroplasty and it is based on polymethyl‐methacrylate. Fatigue failure of the cement is the primary cause of loosening of cemented arthroplasties. Pores form in the acrylic material during mixing and curing, and an analysis of the fatigue life of the cement requires the elimination of the critical macropores, defined as having a diameter > 1 mm, which may bias the outcome of tests. Previous workers have rejected fatigue specimens either on a qualitative basis or at a specified pore size level. However various different thresholds have been considered but currently there is no quantitative criterion to define them. This investigation proposes a quantitative criterion for establishing a critical macropore size rejection threshold for fatigue specimens, and discusses the effectiveness of this criterion based on fatigue tests of radiopaque cement specimens.
Industrial experiences of FE‐based fatigue life predictions of welded automotive structures
Authors: Fermér M. , Svensson H.
Published: March 2003

Mechanical finite element analyses of welded structures are performed on a daily basis in the automotive industry. One objective is to estimate the fatigue strength, which for thin sheet structures is given mainly by the strength of the joints. This article gives some insight into the dimensioning process, with special focus on fatigue analysis of spot welds and seam welds in thin‐walled car body structures made of steel. Experiences from daily use at Volvo Car Corporation, limitations of methods, future and on‐going work are discussed.
Application of decohesive model with mixed damage scale in fracture analysis of composite materials
Authors: Chen J. , New A.
Published: March 2003

A decohesive model using a mixed damage scale and using the total fracture energy to simulate the fracture process of composite materials has been developed in this article. The model assumes a bilinear interfacial decohesion function and is incorporated into an interface finite element developed as a user subroutine in the commercial FEA package ABAQUS. In comparison with traditional numerical methods in fracture mechanics, this approach can automatically predict the failure load, crack path and the residual stiffness of bodies undergoing the fracture process. Applications given in this paper are simulation of a typical fracture test with a double cantilever beam (DCB) specimen; modelling a stiffened composite laminated panel under four‐point bending and modelling a repaired composite sandwich panel under four‐point bending. Good correlation was seen between modelling predictions and experimental results.
R‐curve behaviour of friction stir welds in aluminium‐lithium alloy 2195
Authors: KRONINGER H. R. , REYNOLDS A. P.
Published: March 2003

ABSTRACT The fracture resistance of friction stir welds in 2195‐T8 is described in this paper. R‐curves were produced for several crack planes, parallel to the welding direction and situated at varying distances from the weld centreline. The friction stir weld was also characterized by hardness and tensile testing. Fracture resistance of the friction stir weld is compared to the base metal and to a variable polarity plasma arc weld. Results show that the material in and around the friction stir weld is tougher than the base metal and the variable polarity plasma arc weld. The friction stir weld fracture performance is discussed in the light of the observed hardness and fractographic data presented.
Experimental techniques for fracture instability toughness determination of unidirectional fibre metal laminates
Authors: CASTRODEZA E. M. , IPIÑA J. E. PEREZ , BASTIAN F. L.
Published: March 2003

ABSTRACT The aim of this work is to propose procedures for the measurement of the fracture toughness of fibre metal laminates (FMLs) reinforced with unidirectional fibres of aramid or glass. Experimental techniques for fracture toughness evaluation by using Compact (C(T)) and Single‐Edge Bend (SE(B)) specimens obeying ASTM standards are introduced. Procedures from the standard for thick metallic materials were modified in order to overcome problems, which can arise when testing FMLs – that is, specimen buckling, indentations and crack growth in planes other than the plane of the fatigue pre‐crack or notch. The methodology proposed was experimentally tested leading to satisfactory results.
Fatigue voids and their significance
Authors: SUNDER R. , PORTER W. J. , ASHBAUGH N. E.
Published: March 2003

ABSTRACT Fractures from tests on 2014‐T6511 and 2024‐T3 test coupons under specially designed programmed loading reveal voids with distinct fatigue markings. These ‘fatigue voids’ appear to form as a consequence of the separation of noncoherent secondary particulates from the matrix in early fatigue. The process of their formation is through the initiation, growth and coalescence of multiple interfacial cracks around the particulate. Such voids become visible on the fatigue fracture surface if and when the crack front advances through them. In vacuum, each fatigue void is the potential initiator of an embedded penny‐shaped crack. The one closest to the specimen surface is likely to become the dominant crack, indicating that fatigue voids appear to be the likely origins of the dominant crack in vacuum. In air, the dominant crack forms at the notch surface and grows much faster, giving less opportunity for multiple internal cracks to spawn off from the innumerable internal fatigue‐voids. Thus in air, fatigue voids do not appear to affect the fatigue process at low and intermediate growth rates. At high crack growth rates involving considerable crack tip shear, slip planes with particulate concentration offer the path of least resistance. This explains the increasing density of fatigue voids with growth rate. Very high growth rates signal the onset of a quasi‐static crack growth component that manifests itself through growing clusters of microvoid coalescence associated with static fracture. Fatigue voids are likely to form in other Al‐alloys with secondary noncoherent particulates. They have nothing in common with microvoids associated with ductile fracture.
Fibre reinforcement and fracture response in geopolymeric mortars
Authors: SILVA F. J. , THAUMATURGO C.
Published: March 2003

The inorganic polymeric cement called geopolymer or PSS, has been studied in recent years as a binder for mortar and concrete. The present work reports the fracture toughness studies in mortars made of PSS cement matrix reinforced by wollastonite microfibers (Ca(SiO3)). KI‐curves for PSS cement composites were determined according to the superposition asymptotic assumption and compared with reference Portland cement (PC) composites. The maximum toughness gain occurs in both composite systems with Vf = 2%. For higher fibre volumes (3 and 5%), KI values decrease, due to an increase in porosity. Microstructural analyses showed that toughening mechanisms, as debonding and pullout of the fibers, are more common in PSS cement composites than in the reference PC composites. The difference of toughness between PSS and PC cement (0% of fibers) is about 80%. This demonstrates the high performance of these geopolymeric materials.
Fracture mechanics and notch sensitivity
Authors: ATZORI B. , LAZZARIN P. , MENEGHETTI G.
Published: March 2003

A diagram valid for the analysis of the fatigue limit of cracks and notches centred in an infinite plate was recently proposed by the authors of the present work with the aim to make explicit the bridging at the fatigue limit between defect sensitivity (correlated to the length parameter a0, according to El Haddad–Topper–Smith's definition) and notch sensitivity (correlated to a*, where a* is a particular notch depth corresponding to the intersection between the ΔKth and Δσ0/Kt curves). The expression being valid, defect sensitivity and notch sensitivity were seen as two sides of the same medal. Such a diagram is now extended to finite size components by simply introducing the shape factor α commonly used in fracture mechanics. The obtained critical defect size is termed aD, which is a material and geometry dependent parameter, in order to distinguish it from a0, which is a material parameter. As a consequence the critical notch depth aN is introduced, such that . This results in the proposal of a ‘universal’ diagram able to summarize experimental data related to different materials, geometry and loading conditions. The diagram, the validity of which is checked by means of several results available in the literature, is applied both to the interpretation of the scale effect and to the surface finishing effect.
Long‐term fitness benefits of egg sex modification by the Seychelles warbler
Authors: Komdeur Jan
Published: March 2003

Sex‐ratio theory states that if the fitness costs to the parents of producing one offspring's sex relative to the other are higher, parents should discount these costs by producing fewer individuals of the more costly sex. In the co‐operatively breeding Seychelles warbler (Acrocephalus sechellensis) mothers adaptively modify the sex of their single egg toward daughters, the helping sex, when living on territories with rich resources where helpers increase parental reproductive success, but toward sons, the dispersing sex, when living on territories where resources are scarce and/or no helping benefits accrue. By modifying offspring sex ratio, parents maximize their inclusive fitness benefits. Pairs in high‐quality territories gained significantly more inclusive fitness benefits (through helping and reproducing offspring) from the production of daughters than from sons, and vice versa in low‐quality territories (through reproducing offspring). Experimental manipulation of the offspring's sex shows that the consequences of sex allocation are adaptive for parents on high‐quality territories. On high‐quality territories with female production, breeding pairs raising step‐daughters gained significantly higher inclusive benefits (through indirect and direct fitness gains) than by raising step‐sons.
The macroecology of population dynamics: taxonomic and biogeographic patterns in population cycles
Authors: Kendall  , Prendergast  , Bjørnstad
Published: March 2003

Regular cycles in population abundance are fascinating phenomena, but are they common in natural populations? How are they distributed among taxa? Are there differences between different regions of the world, or along latitudinal gradients? Using the new Global Population Dynamics Database we analysed nearly 700 long (25 + years) time series of animal field populations, looking for large‐scale patterns in cycles. Nearly 30% of the time series were cyclic. Cycle incidence varied among taxonomic classes, being most common in mammal and fish populations, but only in fish did cycle incidence vary among orders. Cycles were equally common in European and North American populations, but were more common in Atlantic fish than Pacific fish. The incidence of cycles increased with latitude in mammals only. There was no latitudinal gradient in cycle period, but cycle amplitude declined with latitude in some groups of fish. Even after considering the biases in the data source and expected type I error, population cycles seem common enough to warrant ecological attention.
Organism–quartz interactions in structuring benthic communities: towards a marine bio‐mineralogy?
Authors: Cerrano C. , Arillo A. , Bavestrello G. , Benatti U. , Calcinai B. , Cattaneo‐Vietti R. , Cortesogno L. , Gaggero L. , Giovine M. , Puce S. , Sarà M.
Published: March 2003

Abiotic and biotic factors determine the distribution and structure of marine benthic communities but the processes invoked to explain such patterns are often inadequate. We demonstrate that the presence of quartz grains in sediments inhibits animal colonization on marine soft‐bottoms. We suggest that this phenomenon may be related to the oxidant properties of the quartz crystal surface derived by the generation of silicon‐based radicals due to water movement. The interaction between organisms and the crystallographic structure of substrata might play a neglected but important role in structuring coastal benthic communities.
Insects affect relationships between plant species richness and ecosystem processes
Authors: Mulder  , Koricheva  , Huss‐Danell  , Högberg  , Joshi
Published: March 2003

This study examined whether insects can alter relationships between plant species diversity and ecosystem function in grassland communities, by (i) altering biomass across a plant diversity gradient, (ii) altering relative abundances of plant species, or (iii) altering ecosystem function directly. We measured herbivore damage on seminatural grassland plots planted with 1, 2, 4, 8, or 12 plant species, and compared plant biomass in a subset of these plots with replicates in which insect levels were reduced. Plant biomass and herbivore damage increased with species richness. Reducing insect populations resulted in greater evenness of relative plant species abundances and revealed a strong positive relationship between plant species richness and above‐ground biomass. Reducing insects also changed the relationship between plant species richness and decomposition. Plant species mixtures and their relative abundances partially explained plant biomass results, but not decomposition results. These results suggest that insects can alter relationships between plant diversity and ecosystem processes through all three mechanisms.
Habitat and patch use by hyraxes: there’s no place like home?
Authors: Kotler B.P. , Brown J.S. , Knight M.H.
Published: March 2003

Models of central place foraging predict that animals should forage more thoroughly in resource patches located closer to the central place. Travel time, cost of transporting food back to the central place, and exposure to predators should all act to increase foraging costs with increasing distance from the refuge. We examined habitat and patch use in rock hyraxes (Procavia capensis) inhabiting a group of kopjes in a semiarid savanna, Augrabies Falls National Park, South Africa. We tested the prediction of more intense patch use closer to the central place by measuring giving‐up densities (GUDs) in experimental resource patches set at four different distances from the kopje and in two microhabitats differing in cover. Surprisingly, hyraxes had their lowest GUDs at intermediate distances from the kopje. These unexpected results suggest that the sentinel behaviour of hyraxes alters the probability of detection of predators for animals foraging away from the kopje.