bluuebunny/crossref_metadata_2025 huggingface dataset:
The polymyalgia rheumatica activity score in daily use: Proposal for a definition of remission
Authors: Leeb Burkhard F. , Rintelen Bernhard , Sautner Judith , Fassl Christian , Bird Howard A.
Published: May 2007

Objective

To confirm the reliability and applicability of the Polymyalgia Rheumatica Disease Activity Score (PMR‐AS), and to establish a threshold for remission.

Methods

First, 78 patients with PMR (50 women/28 men, mean age 65.97 years) were enrolled in a cross‐sectional evaluation. The PMR‐AS, patient's satisfaction with disease status (PATSAT; range 1–5), erythrocyte sedimentation rate (ESR; first hour), and a visual analog scale of patients' general health assessment (VAS patient global; range 0–100) were recorded. Subsequently, another 39 PMR patients (24 women/15 men, mean age 68.12 years) were followed longitudinally. Relationships between the PMR‐AS, PATSAT, ESR, and VAS patient global were analyzed by the Kruskal‐Wallis test, Spearman's rank correlation, and kappa statistics. PMR‐AS values in patients with a PATSAT score of 1 and a VAS patient global <10 formed the basis to establish a remission threshold.

Results

PMR‐AS values were significantly related to PATSAT (P < 0.001), VAS patient global (P < 0.001), and ESR (P < 0.01). PATSAT and VAS patient global were reasonably different (κ = 0.226). The median PMR‐AS score in patients with PATSAT score 1 and VAS patient global <10 was 0.7 (range 0–3.3), and the respective 75th percentile was 1.3. To enhance applicability, a range from 0 to 1.5 was proposed to define remission in PMR. The median ESR in these patients was 10 mm/hour (range 3–28), indicating external validity.

Conclusion

We demonstrated the reliability, validity, and applicability of the PMR‐AS in daily routine. Moreover, we proposed a remission threshold (0–1.5) founded on patient‐dependent parameters.
Measuring disease activity and functionality during pregnancy in patients with rheumatoid arthritis
Authors: de Man Yaël A. , Hazes Johanna M. W. , van de Geijn Fleur E. , Krommenhoek Catharina , Dolhain Radboud J. E. M.
Published: May 2007

Objective

Pregnancy has a favorable effect on the course of rheumatoid arthritis (RA), although the magnitude of this effect is equivocal because RA assessment tools have never been validated in pregnancy. The goal of this study was to assess how pregnancy influences the scoring of the Disease Activity Score in 28 joints (DAS28) and the Health Assessment Questionnaire (HAQ), and how both scores perform in pregnant patients with RA.

Methods

Thirty‐two healthy women and 30 pregnant patients with RA were prospectively studied during pregnancy and at postpartum. At each trimester and postpartum the components of the DAS28 (global health [GH], erythrocyte sedimentation rate [ESR], and C‐reactive protein level [CRP]) and HAQ scores were determined. Maximal influences of healthy pregnancy on each component of the DAS28 were calculated. The performances of different DAS28 scores and the HAQ were also determined in RA patients. Furthermore, variants of the HAQ were developed within the HAQ scoring rules.

Results

The components of the DAS28 were influenced by healthy pregnancy, with average increases in DAS28 score of 0.22 (GH), 1.1 (ESR), and 0.25 (CRP). The DAS28 calculated with CRP (DAS28‐CRP) and without GH performed the best in pregnant RA patients. In healthy pregnancy, the median HAQ increased to 0.50 in the third trimester and was reduced by the HAQ variants to 0.25.

Conclusion

Pregnancy considerably influences the scoring of the DAS28 and HAQ. RA disease activity in pregnant patients should preferably be calculated with DAS28‐CRP without GH. Even with HAQ variants, influences of pregnancy on the assessment of functionality cannot be precluded.
Clinical features and outcome of pediatric Wegener's granulomatosis
Authors: Akikusa J. D. , Schneider R. , Harvey E. A. , Hebert D. , Thorner P. S. , Laxer R. M. , Silverman E. D.
Published: May 2007

Objective

Wegener's granulomatosis (WG) is a predominantly small‐vessel vasculitis associated with antineutrophil cytoplasmic antibodies (ANCAs). There are few reports describing its clinical features and outcome in children. We report on the experience at a single tertiary referral center over 21 years.

Methods

We conducted a retrospective chart review of all patients diagnosed with WG at The Hospital for Sick Children between 1984 and 2005.

Results

Twenty‐five patients were identified. Median age at diagnosis and median followup were 14.5 years and 32.7 months, respectively. Male‐to‐female ratio was 1:4. Median duration of symptoms before diagnosis was 2 months. Of 22 patients, 21 were ANCA positive during their disease course (classic ANCA 78.9%). Constitutional symptoms were the most common clinical feature at presentation (24 of 25). Glomerulonephritis was present in 22 patients at presentation. Only 1 of 11 patients who presented with or developed renal impairment had normalization of serum creatinine. Upper airway involvement occurred in 21 patients at presentation and 24 over followup; only 1 had subglottic stenosis. Twenty patients had initial pulmonary involvement, most commonly nodules (44%) and pulmonary hemorrhage (44%). Five patients required ventilation for pulmonary hemorrhage. Four patients (16%) had venous thrombotic events (VTEs). Treatment included prednisone (100%), cyclophosphamide (76%), azathioprine (40%), and methotrexate (32%).

Conclusion

Pediatric WG typically presents in adolescence and has a female predominance. Glomerulonephritis and pulmonary disease are common at diagnosis and frequently present as a pulmonary‐renal syndrome. Loss of renal function is common and rarely completely reversible. As in adults, children with WG are at risk of VTEs.
Participation in patient self‐management programs
Authors: Bruce Bonnie , Lorig Kate , Laurent Diana
Published: May 2007

Objective

Participation in evidenced‐based arthritis self‐management programs (SMPs) has not been well documented. The purpose of this study was to investigate the participation rate and participant characteristics in a closed cohort of subjects in a geographic region where arthritis SMPs have been offered multiple times and continuously for 2 decades.

Methods

Data were from osteoarthritis (OA) and rheumatoid arthritis subjects participating in the Arthritis, Rheumatism, and Aging Medical Information System (ARAMIS) who resided in the San Francisco (SF) Bay area who had responded to questions about ever participating in an SMP. Differences between participants and nonparticipants were examined by t‐tests and chi‐square tests.

Results

Questions added to the Health Assessment Questionnaire were returned by 1,176 patients; 618 resided in the SF Bay area. Of the SF Bay area sample, 41.9% had participated in an SMP. Small group SMPs, which had been offered multiple times, in diverse settings, continuously over the past 2 decades, were attended by the highest proportion (28%) of participants. Characteristics of participants and nonparticipants in the SF Bay area were similar (∼70 years old, 15 years of education, and the majority had OA [∼72%]). However, a higher proportion of participants were white (88% versus 82%; P = 0.046) and female (82% versus 73%; P < 0.05).

Conclusion

When arthritis SMPs were offered multiple times in diverse settings and continuously over many years, >40% of the cohort was reached. More research is needed with larger samples and different geographic regions to identify participation rates in more diverse populations.
Clinical outcomes, quality of life, and diagnostic uncertainty in the first year of polymyalgia rheumatica
Authors: Hutchings Andrew , Hollywood Jane , Lamping Donna L. , Pease Colin T. , Chakravarty Kuntal , Silverman Barbara , Choy Ernest H. S. , Scott David G. I. , Hazleman Brian L. , Bourke Brian , Gendi Nagui , Dasgupta Bhaskar
Published: May 2007

Objective

To evaluate the impact of polymyalgia rheumatica (PMR) on clinical outcomes and quality of life (QOL); the relationship between laboratory measures and clinical outcomes, and changes in QOL; and agreement between rheumatologists in confirming the initial diagnosis.

Methods

We conducted a prospective study of 129 participants in 8 hospitals in England who met a modified version of the Jones and Hazleman criteria and had not started steroid therapy. The main outcome measures were response to steroids after 3 weeks (minimum 50% improvement in proximal pain, morning stiffness <30 minutes, acute‐phase response not elevated), relapses, QOL as measured by the Short Form 36 and Health Assessment Questionnaire, and diagnosis reassessment at 1 year.

Results

At 3 weeks, 55% of participants failed to meet our definition of a complete response to steroid therapy. Both physical and mental QOL at presentation were substantially lower than general population norms and improved by 12.6 (95% confidence interval [95% CI] 10.8, 14.4) and 11.2 (95% CI 8.5, 13.8) points, respectively, at 1 year. Proximal pain and longer morning stiffness were significantly associated with lower physical QOL during followup, whereas erythrocyte sedimentation rate was most strongly associated with lower mental QOL during followup. There was moderate agreement between clinicians in confirming the PMR diagnosis (kappa coefficients 0.49–0.65).

Conclusion

PMR is a heterogeneous disease with a major impact on QOL. Ongoing monitoring should include disease activity based on symptoms, emergence of alternative diagnoses, and early referral of atypical and severe cases.
Responder criteria for operant and cognitive–behavioral treatment of fibromyalgia syndrome
Authors: Thieme Kati , Turk Dennis C. , Flor Herta
Published: May 2007

Objective

To predict the effects of cognitive–behavioral therapy (CBT) and operant–behavioral therapy (OBT) in fibromyalgia syndrome (FMS).

Methods

A total of 125 patients who fulfilled the American College of Rheumatology FMS criteria were randomly assigned to CBT (n = 42), OBT (n = 43), or attention placebo (AP; n = 40). The pretreatment to 12‐month followup reliability change index was used to determine clinically meaningful changes in pain intensity and physical impairment. Multinominal logistic regression analyses were used to determine the predictors of improvement in pain intensity and physical impairment for the entire sample. Analyses of variance were computed to compare the characteristics of responders and nonresponders in each of the 3 interventions.

Results

At the 12‐month followup, 53.5%, 45.2%, and 5% of patients in the OBT, CBT, and AP groups, respectively, reported clinically meaningful improvements in pain intensity. Similarly, 58.1%, 38.1%, and 7.5% of patients treated with OBT, CBT, and AP, respectively, reported clinically significant improvements in physical impairment. Prior to treatment, the OBT physical impairment responders displayed significantly more pain behaviors, physical impairment, physician visits, solicitous spouse behaviors, and level of catastrophizing compared with nonresponders. The CBT physical impairment responders, compared with nonresponders, reported higher levels of affective distress, lower coping, less solicitous spouse behavior, and lower pain behaviors.

Conclusion

The results of this study suggest that pretreatment patient characteristics are important predictors of treatment response and may serve as a basis for matching treatments to patient characteristics. Prospective outcome studies are needed to confirm whether the tailoring of treatment actually leads to better outcomes for patients with FMS.
Joint proprioception, muscle strength, and functional ability in patients with osteoarthritis of the knee
Authors: van der Esch M. , Steultjens M. , Harlaar J. , Knol D. , Lems W. , Dekker J.
Published: May 2007

Objective

To test the hypotheses that poor knee joint proprioception is related to limitations in functional ability, and poor proprioception aggravates the impact of muscle weakness on limitations in functional ability in osteoarthritis (OA) of the knee.

Methods

Sixty‐three patients with symptomatic OA of the knee were tested. Proprioceptive acuity was assessed by establishing the joint motion detection threshold (JMDT) in the anteroposterior direction. Muscle strength was measured using a computer‐driven isokinetic dynamometer. Functional ability was assessed by the 100‐meter walking test, the Get Up and Go (GUG) test, and the Western Ontario and McMaster Universities Osteoarthritis Index physical function (WOMAC‐PF) questionnaire. Correlation analyses were performed to assess the relationship between proprioception, muscle strength, and functional ability. Regression analyses were performed to assess the impact of proprioception on the relationship between muscle strength and functional ability.

Results

Poor proprioception (high JMDT) was related to more limitation in functional ability (walking time r = 0.30, P < 0.05; GUG time r = 0.30, P < 0.05; WOMAC‐PF r = 0.26, P <0.05). In regression analyses, the interaction between proprioception and muscle strength was significantly related to functional ability (walking time, P < 0.001 and GUG time, P < 0.001) but not to WOMAC‐PF score (P = 0.625). In patients with poor proprioception, reduction of muscle strength was associated with more severe deterioration of functional ability than in patients with accurate proprioception.

Conclusion

Patients with poor proprioception show more limitation in functional ability, but this relationship is rather weak. In patients with poor proprioception, muscle weakness has a stronger impact on limitations in functional ability than in patients with accurate proprioception.
Benefits of intensive resistance training in patients with chronic polymyositis or dermatomyositis
Authors: Alexanderson Helene , Dastmalchi Maryam , Esbjörnsson‐Liljedahl Mona , Opava Christina H. , Lundberg Ingrid E.
Published: May 2007

Objective

To investigate the benefits and safety of an intensive muscular training program in patients with chronic polymyositis (PM) and dermatomyositis (DM).

Methods

Nine patients with chronic PM or DM (median age 53 years, range 44–61) were included. Assessments of impairment (10–15 voluntary repetition maximum [VRM], the Functional Index 2 [FI‐2], the Grippit, and pain rated on the Borg CR‐10 scale), activity limitation (Myositis Activities Profile), and participation restriction (patients' disease impact on well‐being) were performed 4 weeks prior to baseline, at baseline, and after 7 weeks of exercise. A 6‐item core set of disease activity measures was administered and muscle biopsy samples of vastus lateralis were obtained at baseline and after 7 weeks of exercise. Response criteria at an individual level were set for disability and disease activity. The patients exercised 3 days per week for 7 weeks on loads allowing 10 VRM.

Results

On a group level there were no significant differences between assessments at 4 weeks before baseline compared with baseline. The group improved significantly regarding 10–15 VRM and FI‐2 at 7 weeks compared with baseline (P < 0.05). All patients were responders with respect to impairment and 2 were activity limitation responders whereas participation restriction remained unchanged in all. Two patients were responders with reduced disease activity and no patient had signs of increased muscle inflammation in the muscle biopsy sample after 7 weeks of exercise.

Conclusion

Patients with chronic, stable PM and DM can perform this intensive resistive exercise program with beneficial effects on impairment and activity limitation without increased muscle inflammation.
Estimating the probability of radiographic osteoarthritis in the older patient with knee pain
Authors: Peat George , Thomas Elaine , Duncan Rachel , Wood Laurence , Wilkie Ross , Hill Jonathan , Hay Elaine M. , Croft Peter
Published: May 2007

Objective

To determine whether clinical information can practically rule in or rule out the presence of radiographic osteoarthritis in older adults with knee pain.

Methods

We conducted a cross‐sectional diagnostic study involving 695 adults ages ≥50 years reporting knee pain within the last year identified by postal survey and attending a research clinic. Potential indicators of radiographic osteoarthritis were gathered by self‐complete questionnaires, clinical interview, and physical examination. Participants underwent plain radiography (posteroanterior, skyline, and lateral views). Radiographic osteoarthritis was defined as the presence of definite osteophytes in at least 1 joint compartment of the index knee.

Results

Independent predictors of radiographic osteoarthritis were age, sex, body mass index, absence of whole leg pain, traumatic onset, difficulty descending stairs, palpable effusion, fixed‐flexion deformity, restricted‐flexion range of motion, and crepitus. Using this model, 245 participants had a predicted probability ≥80% (practical rule in), of whom 231 (94%) actually had radiographic osteoarthritis (specificity 93%). Twenty‐one participants had a predicted probability <20% (practical rule out), of whom only 2 (10%) had radiographic osteoarthritis (sensitivity 99.6%). The predicted probability of radiographic osteoarthritis for the remaining 429 participants fell into an intermediate category (20–79%).

Conclusion

Simple clinical information can be used to estimate the probability of radiographic osteoarthritis in individual patients. However, for the majority of community‐dwelling older adults with knee pain this method enables the presence of radiographic osteoarthritis to be neither confidently ruled in nor ruled out. Prospective validation and updating of these findings in an independent sample is required.
Cost‐utility analysis of a multidisciplinary job retention vocational rehabilitation program in patients with chronic arthritis at risk of job loss
Authors: van den Hout Wilbert B. , de Buck Petronella D. M. , Vliet Vlieland Theodora P. M.
Published: May 2007

Objective

To estimate from a societal perspective the cost‐utility of a multidisciplinary job retention vocational rehabilitation program compared with usual care in patients with chronic rheumatic diseases at risk of job loss.

Methods

Patients (n = 121) were randomly assigned to either the vocational rehabilitation program or usual outpatient care initiated by the treating rheumatologist. Followup lasted for 2 years. Program costs were estimated using time registrations and other societal costs using quarterly cost questionnaires filled out by the patients. To estimate quality‐adjusted life years, utility was assessed using the EuroQol classification system, EuroQol rating scale, Short Form 6D, and Time Trade‐Off.

Results

As part of the vocational rehabilitation program, patients on average had a total of 7.1 consultations and the total time spent by the multidisciplinary team was 12.7 hours per patient. Program costs were estimated at €1,426, of which ∼20% were time and travel costs incurred by the patients. No significant differences were found in other health care consumption, productivity, or quality‐adjusted life years. Program costs were outweighed by total savings on other health care and nonhealth care costs, but not significantly.

Conclusion

From a societal perspective, it remains unclear whether the program reduces or increases total costs. Further research on effective vocational rehabilitation is warranted, with special attention to early detection of work problems and the collaboration between health care and vocational rehabilitation services.
Arthritis symptoms, the work environment, and the future: measuring perceived job strain among employed persons with arthritis
Authors: Gignac Monique A. M. , Sutton Deborah , Badley Elizabeth M.
Published: May 2007

Objective

To develop a measure of job strain related to differing aspects of working with arthritis and to examine the demographic, illness, work context, and psychosocial variables associated with it.

Methods

Study participants were 292 employed individuals with osteoarthritis or inflammatory arthritis. Participants were from wave 3 of a 4‐wave longitudinal study examining coping and adaptation efforts used to remain employed. Participants completed an interview‐administered structured questionnaire, including a Chronic Illness Job Strain Scale (CIJSS) and questions on demographic (e.g., age, sex), illness and disability (e.g., disease type, pain, activity limitations), work context (e.g., job type, job control), and psychosocial variables (e.g., arthritis‐work spillover, coworker/managerial support, job perceptions). Principal component analysis and multiple linear regression were used to analyze the data.

Results

A single factor solution emerged for the CIJSS. The scale had an internal reliability of 0.95. Greater job strain was reported for future uncertainty, balancing multiple roles, and difficulties accepting the disease than for current workplace conditions. Participants with inflammatory arthritis, more frequent severe pain, greater workplace activity limitations, fewer hours of work, less coworker support, and greater arthritis‐work spillover reported greater job strain.

Conclusion

The findings underscore the diverse areas that contribute to perceptions of job strain and suggest that existing models of job strain do not adequately capture the stress experienced by individuals working with chronic illnesses or the factors associated with job strain. Measures similar to the CIJSS can enhance the tools researchers and clinicians have available to examine the impact of arthritis in individuals' lives.
Schmorl's nodes: Common, highly heritable, and related to lumbar disc disease
Authors: Williams F. M. K. , Manek N. J. , Sambrook P. N. , Spector T. D. , Macgregor A. J.
Published: May 2007

Objective

Schmorl's nodes (SN) are common, but little is known of their relationship with degenerative change and back pain or genetic and environmental factors influencing their expression. We studied healthy female twin volunteers to determine the prevalence and clinical features associated with SN.

Methods

Serial sagittal T1‐ and T2‐weighted magnetic resonance images of the lower thoracic and lumbar spine were analyzed in 516 healthy female twins (150 monozygotic and 366 dizygotic). The images were scored for lumbar degenerative change. Presence of SN was noted at cranial and caudal vertebral levels T9 to L5. Data on physical activity and back pain were collected by questionnaire. Heritability of SN was calculated using variance components modeling.

Results

SN were found in 30% of subjects. Of the 374 SN, 153 (41%) were in the lumbar spine and 221 (59%) were in the thoracic spine. SN heritability was >70%. There was a positive association between SN and lumbar disc disease (LDD). SN were more frequent in subjects with back pain (for ≥2 SN: odds ratio [OR] 2.68, 95% confidence interval [95% CI] 1.11–6.47, P = 0.03), but this was largely accounted for by the association of SN with LDD (OR 1.97, 95% CI 0.78–5.0, P = 0.15 adjusted for LDD). No independent association of SN with back pain was identified.

Conclusion

SN are common in middle‐aged women and are strongly genetically determined. They are associated with lumbar degenerative change, which is a risk factor for back pain, but are not themselves an independent risk factor for back pain.
The predictive ability of serum α‐fetoprotein for hepatocellular carcinoma is linked with the characteristics of the target population at surveillance
Authors: Huo Teh‐Ia , Hsia Cheng‐Yuan , Chu Chi‐Jen , Huang Yi‐Hsiang , Lui Wing‐Yiu , Wu Jaw‐Ching , Lee Pui‐Ching , Chi Chin‐Wen , Lee Shou‐Dong
Published: May 2007

Background

Serum α‐fetoprotein (AFP) is the most important tumor marker for hepatocellular carcinoma (HCC). The reported predictive accuracy of AFP for HCC widely varied. This study investigated the factors contributory to the heterogeneity of the ability of AFP to detect HCC.

Methods

A total of 1,135 patients were categorized into four groups: HCC undergoing surgical resection (n = 248), chronic hepatitis B (CHB, n = 413), chronic hepatitis C (CHC, n = 207), and liver cirrhosis (LC, n = 267). The area under the receiver operating characteristic curve (AUC) was estimated in different combinations.

Results

The AUC was the highest when HCC patients were co‐analyzed with patients with LC (0.805), followed by co‐analyzing patients with CHB (0.797) and CHC (0.740). The optimal cutoffs for AFP were between 26 and 32 ng/ml. Patients with tumor size ≤3 cm had a lower positive predictive value (PPV, 30%) compared to patients with tumor size >3 cm (46%), and HBsAg‐negative and anti‐HCV‐positive patients had the lowest PPV (38%) compared to other groups (60%, 100%, and 82%) at a cutoff at 20 ng/ml. The AUC was lower for hepatitis B‐negative subjects (0.684 and 0.509), compared to hepatitis B‐positive subjects (0.826 and 0.806) stratified by the status of HCV. Elevated ALT >80 U/L and HCC independently predicted increased (>20 ng/ml) AFP levels.

Conclusions

Serum AFP had a fairly stable predictive accuracy for HCC, with an optimal cutoff around 30 ng/ml. ALT level, viral status, and tumor size may significantly confound its ability to detect HCC. J. Surg. Oncol. 2007;95:645–651. © 2007 Wiley‐Liss, Inc.
Hessian‐based model reduction for large‐scale systems with initial‐condition inputs
Authors: Bashir O. , Willcox K. , Ghattas O. , van Bloemen Waanders B. , Hill J.
Published: May 2007

Reduced‐order models that are able to approximate output quantities of interest of high‐fidelity computational models over a wide range of input parameters play an important role in making tractable large‐scale optimal design, optimal control, and inverse problem applications. We consider the problem of determining a reduced model of an initial value problem that spans all important initial conditions, and pose the task of determining appropriate training sets for reduced‐basis construction as a sequence of optimization problems. We show that, under certain assumptions, these optimization problems have an explicit solution in the form of an eigenvalue problem, yielding an efficient model reduction algorithm that scales well to systems with states of high dimension. Furthermore, tight upper bounds are given for the error in the outputs of the reduced models. The reduction methodology is demonstrated for a large‐scale contaminant transport problem. Copyright © 2007 John Wiley & Sons, Ltd.
Comparison of reusable and single‐use plastic and paper shipping containers for distribution of fresh pineapples
Authors: Chonhenchob Vanee , Kamhangwong Damrongpol , Singh S. Paul
Published: May 2007

This paper presents the effects of different packaging systems and fruit orientation on bruising and pre‐cooling time of pineapples during distribution. The package types studied were reusable plastic containers, single‐use paper corrugated containers and plastic foam containers (FCs). Simulated vibration tests were performed to evaluate the shipping containers on their protective performances. After the vibration tests, pineapples were evaluated for bruise damage and decay during storage for 5 days. Pineapple fleshes were also evaluated for bruise volume and changes in colour, firmness, total soluble solids content (TSS) and titratable acidity (TA) after storage of 5 days. Bruise damage was more intense as the storage time increased. Package types had significant effects (p ≤ 0.05) on bruise damage of pineapples. The corrugated containers showed the best protective performance for pineapples, while the FCs showed the worst. The corrugated containers with paperboard partitions showed the lowest damage levels as compared to other package types studied. Foam‐net cushion reduced bruise damage of pineapples. L values and firmness of pineapple flesh were highly associated with degree of bruising. The results suggested that slight bruising on the skin may signify severe bruising on the flesh and bruising accelerated decay in pineapples. Orientation did not show a significant effect (p ≤ 0.05) on bruising. The highest pre‐cooling rates were observed in the reusable plastic containers, while the slowest rates were observed in the single‐use paper containers. The results indicated that careful handling in the proper packaging with optimum cushion can minimize bruise damage and decay of pineapples after shipments. Copyright © 2007 John Wiley & Sons, Ltd.
Deterministisches Chaos im Experiment
Authors: Brun E.
Published: May 2007

Quantitative Indikatoren für deterministisches Chaos werden am Beispiel des modulierten Kernresonanz (NMR)‐Lasers diskutiert und aus experimentellen Daten numerisch bestimmt. Die Ausgangssignale des Lasers werden dazu stroboskopisch abgetastet, dann digitalisiert und als lange Zeitserien von Meßpunkten im Computer gespeichert. Phasendiagramme des Lasers, die aus den Bifurkationsdiagrammen konstruiert werden, zeigen eine reichhaltige Phänomenologie auf den Routen ins Chaos. Fraktale Dimensionen, metrische Entropien und Lyapunov‐Exponenten werden für ausgewählte seltsame Attraktoren des NMR‐Lasers mit hoher Präzision numerisch, in Funktion der Einbettungsdimension, berechnet. Die Resultate illustrieren Möglichkeiten und Grenzen moderner Verfahren der Dimensionsanalyse mit diskreten Meßreihen.
On the Definition of Chaos
Authors: Kirchgraber U. , Stoffer D.
Published: May 2007

In dieser Arbeit werden fünf Definitionen für Chaos, welche in der Literatur über diskrete dynamische Systeme beschrieben werden, diskutiert. Es wird bewiesen, daß diese Chaosdefinitionen invariant sind gegenüber topologischer Konjugation. Sodann wird gezeigt, daß die sog. Schatteneigenschaft die fundamentalste der fünf Definitionen ist: sie impliziert Chaos im Sinne des Münzwurfs, im Sinne von Devaney, im Sinne von Li‐Yorke und im Sinne von Bernoulli. Zur Illustration werden folgende Beispiele besprochen: Torusautomorphismen, sog. snap‐back repellors, transversale homokline Punkte. Überdies beschreiben wir einige Verallgemeinerungen auf nicht‐autonome diskrete dynamische Systeme mit Anwendung auf nichtperiodische Differentialgleichungen.
Optimal Design of Sandwich Plates with a Rigid Obstacle
Authors: Lovíšek J.
Published: May 2007

Wir studieren ein optimales Steuer‐Problem, gesteuert durch eine Variationsungleichung und wenden es auf Sandwich‐Platten an. Die Existenz einer optimalen Lösung für Sandwich‐Platten, d. h. einer optimalen variablen Dicke der Außenschicht wird bewiesen. Zu diesem Zweck wird eine Variations‐Formulierung in der Sprache der Variationsungleichungen angewandt.
Eine einheitliche statische und dynamische Stabilitätstheorie für Pfadverfolgungsalgorithmen in der numerischen Festkörpermechanik
Authors: Krätzig W. B.
Published: May 2007

Im folgenden wird eine allgemeine Theorie der Stabilität diskontinuierlicher Systeme auf der Grundlage von Pfadverfolgungsalgorithmen entwickelt. Ausgehend von der 1. Ljapunowschen Näherung für ein Kelvin‐Voigt‐Diskontinuum werden Stabilitätskriterien sowie Stabilitätsalgorithmen für zeitinvariante und zeitveränderliche Prozesse entwickelt, die ausschließlich auf numerisch verfügbaren, tangentialen Zustandsraumeigenschaften begründet sind. Die hergeleiteten Konzepte werden an Hand verschiedener Tragwerksantworten illustriert.
Heat Transfer in a Viscous Liquid Between Concentric Rotating Spheres
Authors: Bhatnagar R. K. , Vayo H. W.
Published: May 2007

Es wird das Problem der Wärmeübertragung in einem viskosen Fluid betrachtet. Das fluide Medium befindet sich zwischen einem Paar konzentrischer Kugelschalen, die mit unterschiedlicher Geschwindigkeit um ihre gemeinsame Achse rotieren. Die Lösungen für die dimensionslose Form der Energiegleichung, unter Einbeziehung der viskosen Dissipationsterme, werden für kleine Reynolds‐Zahlen erhalten. Zwei Typen der thermischen Randbedingungen werden verwendet, nämlich (i), wenn die Kugelschalen auf verschiedenen konstanten Temperaturen gehalten werden, und (ii) der Fall, wo eine Kugelschale auf konstanter Temperatur gehalten wird, während die andere thermisch isoliert wird. Der Störungsansatz wird benutzt, um die Lösungen abzuleiten, die für verschiedene Werte der Prandtl‐Zahl, Eckert‐Zahl und des Parameters, der das Verhältnis der Winkelgeschwindigkeiten der zwei Kugelschalen beschreibt, graphisch dargestellt werden. Einige interessante Eigenschaften des Temperaturfeldes werden aus diesen Diagrammen abgelesen.
On the Generalization of Mathews' Problem of the Vibrations of a Beam on Elastic Foundation
Authors: Bogacz R. , Krzyýśki T. , Popp K.
Published: May 2007

Die Bestimmung kritischer Parameter für die Stabilität hybrider Systeme mit fortschreitenden Wellen steht in Verbindung mit der Analyse der Bewegungen eines Balkens unter einer bewegten und oszillierenden Kraft. Untersucht werden die Schwingungen eines unendlich langen Timoshenko‐Balkens auf elastischer Bettung unter der Wirkung einer harmonisch zeitveränderlichen und mit konstanter Geschwindigkeit längs des Balkens bewegten Kraft. Die Lösung wird für den gesamten Frequenz‐Geschwindigkeitsbereich der Kraft angegeben. Die Ergebnisse für einen Bernoulli‐Euler‐Balken folgen als Grenzfall aus denen des Timoshenko‐Balkens.
Implicit Runge‐Kutta Methods with a Global Error Estimation for Stiff Differential Equations
Authors: Scholz S.
Published: May 2007

Die Parameter eines 2‐stufigen impliziten Runge‐Kutta‐Verfahrens mit globaler Fehlerschätzung nach Stetter werden so gewählt, daß die Fehlerschätzung nicht nur für h → 0 (d. h. in der transienten Phase), sondern – zumindest bei Problemen, die vom Prothero‐Robinson‐Modell repräsentiert werden – auch für h ≫ 0 (d. h. in der glatten Phase) zuverlässig sind.
Van der Pol‐Duffing Oscillators and Trigonometric Iteration
Authors: Schmidt G. , Dum R.
Published: May 2007

Für den van der Pol‐Duffing‐Schwinger mit nichtlinearen Rückstell‐, Dämpfungs‐ und/oder Selbsterregungskräften werden höhere analytische Näherungen mit einer Methode der trigonometrischen Iteration bestimmt, die einerseits zu leicht numerisch auswertbaren Amplituden‐Frequenz‐Formeln höherer Ordnung, andererseits zu näherungsweisen Startwerten für eine numerische Lösung der gekoppelten Fouriergleichungen mit der Powellmethode führen. Die Ergebnisse zeigen den Einfluß der Zwangserregung, der linearen und nichtlinearen Dämpfung und der Selbsterregung auf die Schwingungsamplituden und den Frequenzbereich, in dem große Amplituden existieren und Chaos einsetzen kann.
Computer Algebra Implementation of Lie Transforms for Hamiltonian Systems: Application to the Nonlinear Stability of L4
Authors: Coppola V. T. , Rand R. H.
Published: May 2007

Wir wenden die Methode der Lie‐Transformationen, eine Perturbationsmethode für Differentialgleichungen, auf eine allgemeine Klasse von Hamilton‐Systemen an, wobei wir uns der Computer‐Algebra bedienen. Dabei entwickeln wir (geschrieben in der Sprache der Koeffizienten im Ausgangssystem H) explizite Formeln zur Transformation des Systems in Birkhoffsche Normalform. Unter Anwendung eines Satzes von Arnold entwickeln wir explizite nichtlineare Stabilitätskriterien allein in der Sprache von H für Systeme, bei denen die lineare Stabilitätsanalyse nicht schlüssig ist. Nach der Bereitstellung zweier Beispiele wenden wir unsere Ergebnisse auf die nichtlineare Stabilität von L4 an, bei dem es sich um einen Dreieckspunkt im Dreikörperproblem mit zirkularen Restriktionen handelt. In L4 muß man sich des Satzes von Arnold bedienen, weil es nicht möglich ist, eine Liapunov‐Funktion zu finden.
Unsteady Potential Flow Past a Circular Cylinder with Permeable Surface
Authors: Wolfersdorf L.
Published: May 2007

Es wird ein neues mathematisches Modell für die instationäre ebene Potentialströmung einer reibungslosen inkompressiblen Flüssigkeit um einen Kreiszylinder mit poröser Oberfläche angegeben. Für den Fall eines linearen Filtrationsgesetzes mit konstantem Koeffizienten wird das Problem auf eine komplexe partielle Differentialgleichung erster Ordnung zurückgeführt, welche für grundlegende Anfangsbedingungen mit Hilfe einer Riccatischen Differentialgleichung gelöst werden kann.
Radiating Gas Flow Past a Slender Body with an Attached Shock Wave
Authors: Singh L. P. , Sharma V. D. , Ram R.
Published: May 2007

Es wird ein nichtlineares Problem einer Gasströmung um einen spitzen Körper, bei der die Wärmestrahlung einen Einfluß hat, mit einer am Vorderteil vorhandenen Stoßwelle behandelt. Die Eigenschaften der Stoßwellen und des Strömungsfeldes hängen von drei wichtigen Parametern ab, nämlich vom Dickenparameter des Körpers, der Machzahl stromaufwärts und der Boltzmannschen Zahl. Die analytische Lösung für das Strömungsfeld wird bis zur zweiten Potenz des Dickenparameters abgeleitet. Die Form der Stoßwelle am Vorderteil wird hergeleitet. Die Ergebnisse zeigen, wie die Form der Stoßwelle durch das Verhältnis des Strahlungsverlusts zu einem typischen Körpermaß, der Boltzmannschen Zahl und der Machzahl stromaufwärts abhängt.
Die Auflösung schwach singulärer Fredholmscher Integralgleichungen mit angepaßten Quadraturen
Authors: Micke A.
Published: May 2007

Untersucht werden lineare Fredholmsche Integralgleichungen zweiter Art mit Kernen, die entlang beliebiger stetiger Kurven mit schwachen Singularitäten behaftet sind. Durch geeignete Transformationen werden sowohl der Kern als auch die Lösung in glatte Funktionen übergeführt. Zur Lösung der transformierten Integralgleichung werden Quadraturen vom Mehrfachinterpolationstyp benutzt, für deren Berechnung nur Funktionswerte des schwach singulären Kernes benötigt werden. Bedingungen für die Konvergenz des Verfahrens werden hergeleitet, und es wird eine spezielle Technik, die auf der Approximation mit Tschebyscheff‐Polynomen basiert, vorgestellt. Der Nutzen dieser Technik wird anhand numerischer Beispiele demonstriert.
Optimal Approximation of the Added Mass Matrix of Two Spheres of Unequal Radii by an Asymptotic Short Distance Expansion
Authors: Raszillier H. , Guiasu I. , Durst F.
Published: May 2007

An asymptotic expansion of the added mass matrix mA = {mij}i,j=i, 2 of two spheres of radii R1 R2, moving along the line of their centres in an ideal fluid (of zero vorticity) is given for small particle surface distances x (x → 0) to any order in x. The derivation starts from the classical essentially long distance expansion of mA, which is first converted by an inverse Mellin transformation into an integral representation. The expansion is deduced by the shift of the integration line in this representation and by the application of the residue theorem, and its asymptotic character is proved. The pointwise approximation of the matrix mA by a finite number of terms of the asymptotic expansion is investigated in terms of a suitably defined approximation error d(x) for the matrix element mij(x) and its n‐th order approximant m(x) (n = 0, 1,…). The minimum dij(x) of d(x) with respect to the order n is attained for a finite value n = n(x) because of the divergence of the expansion (lim d(x) = ∞ for any x > 0) and defines by it the order n = n(x) of the optimal approximant of mij(x).
equation image
, which describe the range of x where m(x) approximates mij with an error not larger than ϵ, are introduced, together with the set
equation image
which gives the distance range x where an approximation of mij(x) by the asymptotic expansion is possible within an error ϵ. By numerical computation the optimal approximation order n(x) and the sets D(ϵ) (n = 1,…, 11) are estimated. It turns out that n(x) is large compared to the highest order (n = 1) approximant m(x) computed previously, whereas the optimal ϵ‐approximation set Dij(ϵ) is typically by one order of magnitude larger than D(ϵ), the ϵ‐approximation set of the approximant m(x).
Nonlocal Qualitative and Quantitative Analysis of a Simple Shallow Shell Problem
Authors: Labisch F. K.
Published: May 2007

A nonlocal qualitative and quantitative analysis of a nonlinear problem is illustratively carried out for a shallow shell problem. The shell model is of “Marguerre” type and the problem is governed by a system of nonlinear partial differential equations. The complete nonlocal solution set is obtained equivalently by means of the boundary value problem and independently by means of each of the two genuinely dual variational problems, too. An identical morphological behaviour of the geometrically and of the statically approached complete solution set is proved. This implies a diffeomorphism between these sets and their identical stability behaviour. Thus the paradox connected with the different stability behaviour of the common solution points described by means of the two classical complementary variational problems is resolved for the considered problem. The solution set contains solution continua which are neither minimizers nor maximizers. Singular phenomena occur at any point of the involved complete degenerate solution set. This set is a natural extension of the notion of eigenvalues from linear to nonlocal nonlinear problems. The complete degenerate solution set introduced is indispensable in a nonlocal nonlinear morphology analysis. An exact numerical analysis is carried out in a space spanned by the first four active modes.
On the Velocities of Electromagnetic Shock Waves
Authors: Giannone A.
Published: May 2007

For a nonlinear problem in electrodynamics, the shock velocities are determined as eigenvalues of a matrix which results from the “average” of the field ahead and behind the shock. The shocks are studied by considering the corresponding eigenvectors.
Zur Eingrenzung des Lorenz‐Attraktors durch die Anwendung der nichtlokalen Reduktionsmethode und mit Hilfe von Vergleichssystemen zweiter Ordnung
Authors: Koksch N. , Leonov G. A. , Morozov A. V. , Ponomarenko D. V.
Published: May 2007

Das Untersuchungsobjekt des vorliegenden Artikels ist das bekannte Lorenz‐System — die einfachste Galerkin‐Näherung der Navier‐Stokes‐Gleichungen für die Benard‐Aufgabe [1]. Auf der Grundlage der nichtlokalen Reduktionsmethode und auch mit Hilfe der Methode der Vergleichssysteme zweiter Ordnung [3, 4] wird die Menge im Phasenraum eingegrenzt, in dem sich der Attraktor befindet. Als Folgerung aus diesen Resultaten erhalten wir eine hinreichende Bedingung für das Fehlen von Separatrixschlingen beim Lorenz‐System. Es wird ein Vergleich der vorliegenden, analytisch erhaltenen Eingrenzungen des Attraktors mit den numerischen Ergebnissen von E. Lorenz durchgeführt. Die Arbeit ist eine Fortsetzung und Weiterentwicklung der Thematik aus [5, 6].
Error Estimates for the Approximate Solution of Linear Fixed Point Equations
Authors: Lippold G.
Published: May 2007

The defects which are caused by the solutions of approximate equations in the original equation provide an effective tool for the asymptotically exact estimation of approximation errors. Using these defects may be justified without uniformity restrictions on the underlying mesh sequences. As an example, asymptotically exact error estimates are investigated for the numerical solution of a one‐dimensional linear diffusion‐convection equation by means of finite elements.
Verschiedene Typen von Singularitäten einer Randwertaufgabe bei einem Modell einer Pipeline
Authors: Collatz L. , Grothkopf U. , Hayman W. K.
Published: May 2007

Ein einfaches Modell der Temperaturverteilung in einer Rohrwandung führt auf eine Randwertaufgabe der Potentialtheorie mit drei Typen von Singularitäten: Unstetigkeiten in den Randwerten, logarithmische Singularitäten und Pole. Die Aufgabe kann mittels elliptischer Funktionen in geschlossener Form gelöst werden; der Aufsatz soll aber auch zeigen, daß man ohne Kenntnis der strengen Lösung numerisch die gesuchte Lösung in relativ leicht erhältliche brauchbare und garantierbare Schranken einschließen kann.
Fitting of Experimental Yield Surfaces
Authors: Gupta N. K. , Meyers A.
Published: May 2007

To be able to describe experimentally observed deviations in the initial yield surface from the von Mises ellipse as well as translation, rotation and distortion of a subsequent yield surface, a function of the second and third invariants of the translated deviator stress tensor was proposed in an earlier paper [1]. This relationship is further considered, and the manner in which various encountered parameters influence the fitting of an experimentally determined yield surface, is discussed. The experimental data employed in illustrations is taken from literature.
Steady Flows of a Third Grade Fluid by Transformation Methods
Authors: Moro L. , Siddiqui M. A. , Kaloni P. N.
Published: May 2007

Solutions for the equations of motion of an incompressible third grade fluid are obtained by employing transformation methods. First, the hodograph transformation is applied to the equations to interchange the independent and dependent variables. Then a Legendre‐transform function is introduced and all equations are written in terms of this function and the conditions this function should satisfy are determined. Several illustrations of the method are considered and the results with the linear viscous fluid case are compared. It is noted that the results in the third grade fluid are considerably different from the corresponding results of the viscous fluid.
Construction of Center Manifolds
Authors: Knobloch H. W.
Published: May 2007

Given a pair of coupled differential equations ẋ = g(x, y), ẏ = h(x, y), x, y being vectors. The paper is concerned with existence and properties of invariant manifolds given in the form y = S(x), × ∈ M. The questions raised and partially answered differ from the standard content of center manifold theory in two respects. (i) The scenario is non‐local, i.e. the set M is not necessarily small. (ii) The manifold is supposed to satisfy side conditions, namely a boundary condition (S(x) = s(x) for × ∈ ∂M) and condition of inner stability (“inflowing”).
Stabilization by Noise Revisited
Authors: Arnold L.
Published: May 2007

Given a d × d matrix A and a d × k matrix B. We investigate how the stability behavior of ẋ = (A + BG(t)) × can be improved by a k × d matrix‐valued white noise process G(t). The analysis is based on the theory of Lyapunov exponents (exponential growth rates) and uses an averaging principle. It generalizes a result by the author and co‐workers for the case B = identity, in which the top Lyapunov exponent can be brought arbitrarily close to trace A/d by cleverly choosing G(t).
Generierung angepaßter dynamischer Ersatzsysteme mit Optimierungsprozeduren
Authors: Müller‐Slany H. H.
Published: May 2007

The analysis and simulation of elasto‐mechanical systems requires simple physical substitute models with reduced order in the form of lumped‐mass or multi‐body systems. Such models are generally found by heuristic methods, i.e. by a linear discretization of the distributed parameters of the real system. In the case of high condensation, these models show large errors in the mass‐geometrical and modal system properties and are thus only of limited use for simulation tasks. It will be shown how a hierarchical optimization procedure allows to establish an adapted model with given system properties for such modelling tasks.
Modellbildung und Simulation von elektromechanischen Drucksystemen
Authors: Lückel J. , Moritz W. , Wassmuth E. , Junker F.
Published: May 2007

Der Artikel beschreibt die Modellbildung und Simulation von elektromechanischen Drucksystemen, die nach dem ballistischen Funktionsprinzip arbeiten. Für das aus den Teilkomponenten Elektromagnetik und Mechanik bestehende Gesamtsystem werden physikalische Ersatzmodelle entwickelt und die mathematischen Beschreibungen abgeleitet. Hierbei ist es erforderlich, die transienten Vorgänge der Magnetik und die elastischen Systemkomponenten der Mechanik zu berücksichtigen. Anhand einiger ausgewählter Simulationsergebnisse, die sich aus der numerischen Lösung des nichtlinearen Differentialgleichungssystems ergeben, wird die Druckkopfdynamik verdeutlicht und ein Vergleich mit Meßergebnissen dargestellt.