bluuebunny/crossref_metadata_2025 huggingface dataset:
Motor-evoked potentials are facilitated during perceptual identification of hand position in healthy subjects and stroke patients
Authors: Lackner Eva , Hummelsheim Horst
Published: August 2003

Objective: To delineate the facilitatory and/or inhibitory influence of relevant and irrelevant sensory afferent information to the motor cortex. The study is based on the assumption that sensorimotor coupling is crucial for motor learning and recovery.

Design: The interaction of a standard transcranial magnetic stimulus (TMS) with the facilitatory and/or inhibitory influence that proprioceptive afferent information exerts on the motor cortex was investigated.

Setting: A neurological rehabilitation hospital.

Subjects: Sixteen healthy subjects and 14 stroke patients.

Main outcome measures: Amplitudes and latencies of motor-evoked potentials (MEPs) recorded from the extensor carpi radialis muscle. The influence of a sensory discrimination task was compared with the influence of a sensory input irrelevant for the task and to a verbal memory task. Recordings were taken after the hand had been moved passively in one of four different positions.

Results: In the first trial, TMS was applied without any demand on the subjects. In the second trial, subjects were asked to identify the respective hand position and in the third trial a noun presented at a respective hand position had to be memorized and reproduced after TMS. The sensory discrimination task exerted by far the most prominent facilitatory effect on MEP amplitudes and latencies. An unspecific, albeit reproducible influence on MEP amplitudes was observed when a noun presented at a respective hand position had to be remembered.

Conclusions: Using a neurophysiological approach the study demonstrates that a sensory discrimination task based on relevant afferent information to motor centres of the brain forms a prominent facilitatory intervention for those muscle groups that are involved in the task. This holds true for healthy subjects and for hemiparetic stroke patients.
Further evidence for the agreement between patients with stroke and their proxies on the Frenchay Activities Index
Authors: Tooth Leigh R , McKenna Kryss T , Smith Melinda
Published: August 2003

Objective: To determine item, subscale and total score agreement on the Frenchay Activities Index (FAI) between stroke patients and proxies six months after discharge from rehabilitation.

Design: Prospective study design.

Setting/subjects: Fifty patient–proxy pairs, interviewed separately, in the patient's residence.

Main outcome measures: Modified FAI using 13 items. Individual FAI items, subscales and total score agreement as measured by weighted kappa and intraclass correlation coefficients (ICC).

Results: Excellent agreement was found for the total FAI (ICC 0.87, 95% confidence interval (CI) 0.78–0.93), and domestic (ICC 0.85, 95% CI 0.73–0.91) and outdoor (ICC 0.87, 95% CI 0.78–0.95) subscales, with moderate agreement found for the work/leisure subscale (ICC 0.63, 95% CI 0.34–0.78). For the individual FAI items, good, moderate, fair and poor agreement was found for five, three, four and one item, respectively. The best agreement was for objective items of preparing meals, washing-up, washing clothes, shopping and driving. The poorest agreement was for participation in hobbies, social outings and heavy housework. Scoring biases associated with patient or proxy demographic characteristics were found. Female proxies, and those who were spouses, scored patients lower on domestic activities; male patients, and those who were younger, scored themselves higher on outdoor activities and higher patient FIM scores were positively correlated with higher FAI scores.

Conclusions: While total and subscale agreement on the FAI was high, individual item agreement varied. Proxy scores should be used with caution due to bias.
Arm and leg impairments and disabilities after stroke rehabilitation: relation to handicap
Authors: Desrosiers Johanne , Malouin Francine , Bourbonnais Daniel , Richards Carol L , Rochette Annie , Bravo Gina
Published: August 2003

Objectives: (1) To examine the relationships between measures of impairment and disability for the arm and leg with a measure of handicap and (2) to identify the impairment or disability most strongly related to handicap situations.

Design: Prospective cohort study.

Setting: Intensive functional rehabilitation unit and community.

Patients: One hundred and two persons who had a stroke.

Main outcome measures: Arm and leg impairments and disabilities were evaluated with reliable and valid tests at discharge from rehabilitation. Six months later, handicap situations were evaluated with the Assessments of Life Habits (LIFE-H).

Results: Arm and leg impairments and disabilities are correlated with handicap situations. Disability of the leg is more strongly associated with handicap than arm disability. Arm and leg disabilities are not statistically more strongly related to handicap than arm and leg impairments.

Conclusions: The high correlations found between handicap situations and the impairment and disability measures of the leg provide new information that support the importance of mobility to promote integration after stroke.
A fluidity scale for evaluating the motor strategy of the rise-to-walk task after stroke
Authors: Malouin Francine , McFadyen Bradford , Dion Lise , Richards Carol L
Published: August 2003

Objective: (1) To develop an ordinal scale (content validity) for assessing ‘uidity of the rise-to-walk task (RTW); (2) to examine the concurrent validity of the ‘uidity scale; (3) to study the inter-rater reliability of the scale.

Design: A group of physical therapists participated in the scale development (content validity); a cross-sectional design was used to study the agreement between the ‘uidity scale and the ‘uidity index (criterion measure) obtained with the instrumented method (concurrent validity) and to examine the inter-rater reliability of the scale.

Setting: Rehabilitation centre.

Subjects: Nineteen persons with a chronic stroke and 19 age and gender-matched healthy subjects.

Main outcome measures: For the validation study: the ‘uidity index (FI) and the scores from the ‘uidity scale; for the inter-rater reliability study: duration of the RTW task and ‘uidity scores.

Results: The FI values did not overlap across categories of the scale and the relationship between FI values and the ‘uidity scores was 0.99. The weighted kappa (kw) indicated a substantial level of agreement between the new raters (kw = 0.78) and between the new raters and the expert rater (kw = 0.71). Corresponding mean intraclass correlation coefficients for the RTW duration were 0.95.

Conclusion: These results indicate that the descriptors of the scale provided a gradation of ‘uidity comparable to the gold standard measure (FI) and that trained clinicians can use the ‘uidity scale with a substantial level of reliability. The RTW task is a simple clinical tool for assessing mobility and motor strategies (locomotor co-ordination) in patients presenting varying degrees of motor recovery after stroke.
Pain in a Swedish spinal cord injury population
Authors: Budh Cecilia Norrbrink , Lund Iréne , Ertzgaard Per , Holtz Anders , Hultling Claes , Levi Richard , Werhagen Lars , Lundeberg Thomas
Published: August 2003

Objective: To describe pain and associated variables in a prevalence group of persons with a sustained spinal cord injury (SCI) in the Swedish capital and its surroundings.

Setting: Spinalis SCI Unit (outpatient clinic), Stockholm, Sweden. Design: Assessment over a 12-month period in a yearly health control.

Subjects: Four hundred and fifty-six SCI patients.

Results: Two hundred and ninety-one out of 456 SCI patients (63.7%) suffered from pain, and in 45.7% of these it was classified as being neurogenic. Aching pain was the most used descriptor (38.5%). The onset of pain was commonly within three months (73.5%). In 70.4% of patients pain occurred below the level of the lesion. Most patients identified pain as coming from one (55.0%) or two (28.2%) body regions. Rating of the general pain intensity on a visual analogue scale (VAS) was 46 out of 100 and rating of the worst pain intensity was 78 out of 100. Ninety-four out of 276 patients (32.3%) considered that their quality of life was significantly affected by pain.

Conclusion: Pain was most common in patients with incomplete lesions (ASIA impairment grade D) and there was a correlation between pain and higher mean age at injury and between pain and female gender.
A guide to clinically relevant drug interactions in oncology
Authors: Lam Masha S H , Ignoffo Robert J
Published: August 2003

This paper presents an overview of new information on clinically relevant drug-drug interactions, particular focuses on negative drug interactions in oncology. We have generated a concise table of drug-drug interactions that provides a synopsis of the clinical outcome of the interaction along with a recommendation for management. We have also generated other tables that describe specific interactions with methotrexate and dosing guidelines for cytotoxic drugs in the presence of renal or hepatic dysfunction. Since warfarin is one of the non-anticancer drugs that is commonly used in cancer patients for the treatment and prevention of venous thromboembolism, its interactions with other anticancer drugs that have been reported in literatures were also reviewed in this paper. In general, drug interactions observed in cancer patients may be categorized into pharmacokinetic, pharmacodynamic and pharmaceutic interactions. Pharmacokinetic interactions involve one drug altering the absorption, distribution, metabolism, or excretion of another drug. Interpatient variability in the pharmacokinetic profile of many anticancer agents often complicates the predictability of the antitumor response and toxicities. Among four pharmacokinetic characteristics, drug interactions involving hepatic metabolism is probably the most common and important mechanism responsible for oncologic drug interactions. For example, several anticancer drugs including taxanes, vinca alkaloids, and irinotecan are known to be metabolized by cytochrome CYP3A4. Enzyme-inducing anticonvulsants have been shown to significantly decrease the plasma levels of these anticancer drugs, thereby compromising the anti-tumor effects. N ephrotoxicity or changes in hepatic function caused by some anticancer drugs (e.g., cisplatin, asparaginase) may also have an impact on the pharmacokinetics of the interacting agents. Pharmacodynamic interactions may occur when two or more drugs acting at a common receptor-binding site impact on the pharmacologic action of the object drug, without influencing the pharmacokinetics of each interacting agent. In clinical setting, a decrease of antitumor efficacy was observed in breast cell lines when gemcitabine or vinorelbine were used in combination with paclitaxel. On the other hand, a decreased incidence of thrombocytopenia was seen in patients receiving combination of carboplatin and palcitaxel compared to those receiving carboplatin alone. The third type of drug-drug interaction is known as pharmaceutic interaction. When one drug may alter the physical or chemical compatibility of another drug that utlimately leads to a change in appearance of the solution or a decrease of effectiveness of the drug due to drug inactivation or degradation.
Stability and compatibility of 5-fluorouracil infusions in the Braun Easypump®
Authors: Roberts Sarah , Sewell Graham J
Published: August 2003

Objective. The aim of this study was to determine the stability and compatibility of `high strength’ (50 mg/mL) and `normal strength’ (25 mg/mL) 5-fluorouracil (5-FU); the latter prepared from 50 mg/mL 5-FU in either 0.9% sodium chloride or 5% glucose diluents and filled into the Braun Easy-pumpÒ (also known as the Homepump Fresenius). Studies were conducted under storage (48C or 258C) and in-use (318C) conditions.

Methods. In the first study, the stability of 5-FU 50 mg/mL (undiluted) was determined in the EasypumpÒ at 258C and 318C over time intervals of 0, 1, 3, 5, 7, 14 and 21 days. In the second study, the stability of 25 mg/mL 5-FU diluted in 5% glucose and 0.9% sodium chloride for injection in the EasypumpÒ was determined after incubation at 48C for 0, 7 and 14 days and at 258C and 318C for 0, 1, 3, 5, 7, 14 and 21 days. For each time/temperature interval, the infusions were monitored for precipitation, colour change, pH, moisture loss, subvisual particulate levels (selected intervals) and chemical stability to assess for compatibility with the device.

Results. No significant changes in physical or chemical stability occurred in diluted solutions (25 mg/mL) over 14 days at 48C or 21 days at 258C and 318C or in the undiluted solutions (50 mg/mL) over 21 days at 258C and 318C, and 5-FU demonstrated suitable stability in the test devices.
Is pegfilgrastim appropriate for the treatment of established febrile neutropenia?
Authors: Stanford Brad L , Zondor Stacey D , Cobos Everardo
Published: August 2003

Objective. To report a case where both pegfilgrastim and filgrastim were considered in the treatment of febrile neutropenia in a hospitalized patient and assess the most cost-effective option.

Case summary. A 77-year-old white female was diagnosed with squamous cell carcinoma of the anus and adjuvant chemotherapy was ordered. She subsequently developed Grade 4 neutropenia, a wound infection and her Eastern Cooperative Oncology Group (ECOG) performance status declined to 4. Antibiotics were started and growth factor therapy was considered as part of her treatment. Filgrastim 480 g subcutaneously every day was chosen and her absolute neutrophil count (ANC) recovered after seven days of therapy.

Discussion. This case illustrates the potential cost benefits of using filgrastim over pegfilgrastim in hospitalized patients. The choice of filgrastim in our patient resulted in only seven days of filgrastim therapy at a cost of $2205.70. A 6 mg dose of pegfilgrastim is priced similarly to 10 days of filgrastim 480 g, therefore a cost savings of $744.01 was realized in our patient.

Conclusions. Filgrastim is the most appropriate growth factor for the treatment of established high-risk febrile neutropenia given that the ANC can be monitored on a daily basis and therapy can be discontinued upon recovery.
Mechanical properties of rat soleus aponeurosis and tendon during variable recruitmentin situ
Authors: Monti Ryan J. , Roy Roland R. , Zhong Hui , Edgerton V. R.
Published: August 2003

The in vitro mechanical properties of tendons are well described,whereas little data exist for conditions mimicking those found in vivo. Descriptions of the in situ mechanical properties of aponeuroses are more common, but the results are variable. Our goal was to examine the mechanical properties of these tissues under conditions mimicking the in vivo state. Tissue strains were measured in the rat(Rattus norvegicus) soleus muscle directly from the spacing of metal markers implanted within the tissues of interest using an X-ray video microscope. Strains were measured for the tendon and three regions (proximal,middle and distal) of the aponeurosis. Muscle stimulation was accomplished through isolated ventral rootlets, allowing force to be graded in seven repeatable increments independent of muscle-tendon unit length. Peak strains(during maximal tetanic contraction at optimum length; Po)were ∼5% in tendon and ∼12% in all regions of the aponeurosis. At forces above 50% of Po, tissue stiffness was nearly constant in all regions, and a pronounced toe region was observed only at forces below ∼25% of Po. Stiffness increased in all regions as the muscle-tendon unit was lengthened. These results suggest that using mechanical properties measured ex vivo or during single contractile events in situ to estimate the in vivo behavior of tendon and aponeurosis may lead to errors in estimating the distribution of strain among the contractile and series elastic elements of the muscle.
Lung ventilation during treadmill locomotion in a terrestrial turtle,Terrapene carolina
Authors: Landberg Tobias , Mailhot Jeffrey D. , Brainerd Elizabeth L.
Published: August 2003

The limb girdles and lungs of turtles are both located within the bony shell, and therefore limb movements during locomotion could affect breathing performance. A mechanical conflict between locomotion and lung ventilation has been reported in adult green sea turtles, Chelonia mydas, in which breathing stops during terrestrial locomotion and resumes during pauses between bouts of locomotion. We measured lung ventilation during treadmill locomotion using pneumotach masks in three individual Terrapene carolina (mass 304-416 g) and found no consistent mechanical effects of locomotion on breathing performance. Relatively small tidal volumes(2.2±1.4 ml breath-1; mean ± s.d., N=3 individuals) coupled with high breath frequencies(36.6±26.4 breaths min-1; mean ± s.d., N=3 individuals) during locomotion yield mass-specific minute volumes that are higher than any previously reported for turtles (264±64 ml min kg-1; mean ± s.d., N=3 individuals). Minute volume was higher during locomotion than during recovery from exercise(P<0.01; paired t-test), and tidal volumes measured during locomotion were not significantly different from values measured during brief pauses between locomotor bouts or during recovery from exercise(P>0.05; two-way ANOVA). Since locomotion does not appear to conflict with breathing performance, the mechanism of lung ventilation must be either independent of, or coupled to, the stride cycle. The timing of peak airflow from breaths occurring during locomotion does not show any fixed phase relationship with the stride cycle. Additionally, the peak values of inhalatory and exhalatory airflow rates do not differ consistently with respect to the stride cycle. Together, these data indicate that T. carolina is not using respiratory-locomotor coupling and limb and girdle movements do not contribute to lung ventilation during locomotion. X-ray video recordings indicate that lung ventilation is achieved via bilateral activity of the transverse (exhalatory) and oblique (inhalatory) abdominal muscles. This specialized abdominal ventilation mechanism may have originally circumvented a mechanical conflict between breathing and locomotion in the ancestor of turtles and subsequently allowed the ribs to abandon their role in lung ventilation and to fuse to form the shell.
Nitric oxide mediates seasonal muscle potentiation in clam gills
Authors: Gainey Louis F. , Greenberg Michael J.
Published: August 2003

The physiology and timing of gill muscle potentiation were explored in the clam Mercenaria mercenaria. When isolated demibranchs were exposed twice (with an intervening wash) to the same concentration of 5-hydroxytryptamine, the second contraction was larger than the first. This potentiation was seasonal: it was present from November through June, and absent from July through October. Potentiation was not affected by the geographic origin of the clams, nor by their acclimation temperature. Potentiation was inhibited by the nitric oxide synthase (NOS) inhibitor l-NAME and mimicked by the nitric oxide (NO) donor DEANO. During the season of potentiation, immunoreactive NOS appeared in the gill muscles and the gill filament epithelium, but during the off-season, the enzyme occurred at the base of the gill filaments. Potentiation was inhibited by ODQ,which inhibits soluble guanylate cyclase (sGC), and it was mimicked by dibutyryl-cGMP, an analog of cyclic GMP (cGMP). Moreover, potentiation was inhibited by the protein kinase G (PKG) inhibitor Rp-8-CPT-cGMPS. During the season of potentiation, immunoreactive sGC was concentrated in the gill muscles and the gill filament epithelium; but during the off-season,immunoreactive sGC was found in the gill filament epithelium. These data suggest that the potentiation of gill muscle is mediated by a NO/cGMP/PKG signaling pathway.
Sex differences in the thermoregulation and evaporative water loss of a heterothermic bat,Lasiurus cinereus,during its spring migration
Authors: Cryan Paul M. , Wolf Blair O.
Published: August 2003

This study quantifies sex differences in thermoregulation and water loss of a small (20-35 g) insectivorous heterothermic mammal, the hoary bat Lasiurus cinereus, during its spring migration. We measured body temperature, metabolic rate and evaporative water loss, and calculated wet thermal conductance, for bats exposed to air temperatures ranging from 0 to 40°C for periods of 2-5 h. Pregnant females maintained normothermic body temperatures (35.7±0.7°C; mean ± s.e.m.)independent of air temperature. In contrast, males became torpid during the majority (68%) of exposures to air temperatures <25°C. The thermal neutral zone (TNZ) ranged between approximately 30°C and 34°C in both sexes and, within the TNZ, females had lower mass-specific metabolic rates(6.1±0.2 mW g-1) than males (9.0±0.9 mW g-1). Wet thermal conductance values in torpid bats (0.7±0.5 mW g-1 deg.-1) were lower than those of normothermic individuals (1.1±0.3 mW g-1 deg.-1). Mass-specific rates of evaporative water loss in males were consistently higher than in females at most air temperatures and rates of water loss in torpid bats were 63±6% of normothermic values. These results suggest that male and pregnant female L. cinereus employ different thermoregulatory strategies during their spring migration. Females defend normothermic body temperatures, presumably to expedite embryonic growth, while males use torpor, presumably to minimize energy and water deficits. These variable thermoregulatory strategies may reflect continental differences in the summer distribution of the sexes.
Form and function of the bulbus arteriosus in yellowfin tuna (Thunnus albacares), bigeye tuna (Thunnus obesus) and blue marlin(Makaira nigricans): static properties
Authors: Braun Marvin H. , Brill Richard W. , Gosline John M. , Jones David R.
Published: August 2003

The juxtaposition of heart and gills in teleost fish means that the Windkessel function characteristic of the whole mammalian arterial tree has to be subserved by the extremely short ventral aorta and bulbus arteriosus. Over the functional pressure range, arteries from blue marlin (Makaira nigricans) and yellowfin tuna (Thunnus albacares) have J-shaped pressure-volume (P-V) loops, while bulbi from the same species have r-shaped P-V loops, with a steep initial rise followed by a compliant plateau phase. The steep initial rise in pressure is due to the geometry of the lumen. The interactions between radius, pressure and tension require a large initial pressure to open the bulbar lumen for flow. The plateau is due to the unique organization of the bulbar wall. The large elastin:collagen ratio, limited amount of collagen arranged cirumferentially, lack of elastin lamellae and low hydrophobicity of the elastin itself all combine to lower stiffness, increase extensibility and allow efficient recoil. Even though the modulus of bulbus material is much lower than that of an artery, at large volumes the overall stiffness of the bulbus increases rapidly. The morphological features that give rise to the special inflation characteristics of the bulbus help to extend flow and maintain pressure during diastole.
Blubber and buoyancy: monitoring the body condition of free-ranging seals using simple dive characteristics
Authors: Biuw Martin , McConnell Bernie , Bradshaw Corey J. A. , Burton Harry , Fedak Mike
Published: August 2003

Elephant seals regularly perform dives during which they spend a large proportion of time drifting passively through the water column. The rate of vertical change in depth during these `drift' dives is largely a result of the proportion of lipid tissue in the body, with fatter seals having higher (more positive or less negative) drift rates compared with leaner seals. We examined the temporal changes in drift rates of 24 newly weaned southern elephant seal(Mirounga leonina) pups during their first trip to sea to determine if this easily recorded dive characteristic can be used to continuously monitor changes in body composition of seals throughout their foraging trips. All seals demonstrated a similar trend over time: drift rates were initially positive but decreased steadily over the first 30-50 days after departure(Phase 1), corresponding to seals becoming gradually less buoyant. Over the following ∼100 days (Phase 2), drift rates again increased gradually,while during the last ∼20-45 days (Phase 3) drift rates either remained constant or decreased slightly. The daily rate of change in drift rate was negatively related to the daily rate of horizontal displacement (daily travel rate), and daily travel rates of more than ∼80 km were almost exclusively associated with negative changes in drift rate. We developed a mechanistic model based on body compositions and morphometrics measured in the field,published values for the density of seawater and various body components, and values of drag coefficients for objects of different shapes. We used this model to examine the theoretical relationships between drift rate and body composition and carried out a sensitivity analysis to quantify errors and biases caused by varying model parameters. While variations in seawater density and uncertainties in estimated body surface area and volume are unlikely to result in errors in estimated lipid content of more than±2.5%, variations in drag coefficient can lead to errors of ≥10%. Finally, we compared the lipid contents predicted by our model with the lipid contents measured using isotopically labelled water and found a strong positive correlation. The best-fitting model suggests that the drag coefficient of seals while drifting passively is between ∼0.49 (roughly corresponding to a sphere-shaped object) and 0.69 (a prolate spheroid), and we were able to estimate relative lipid content to within approximately±2% lipid. Our results suggest that this simple method can be used to estimate the changes in lipid content of free-ranging seals while at sea and may help improve our understanding of the foraging strategies of these important marine predators.
On the press fit of a crankpin into a circular web in pressed-up crankshafts
Authors: Strozzi A , Vaccari P
Published: August 2003

The contact stresses induced by press-fitting a crankpin into a crankweb bore in pressed-up crankshafts are analysed for crankwebs possessing a circular geometry. The three-dimensional nature of this problem is reduced to a plane model, where the crankweb is described in terms of an eccentrically bored disc of uniform thickness, while the crankpin is idealized as an annular ring. Two different approaches are employed. Firstly, an elastic plane finite element analysis is carried out for this contact problem. Secondly, based upon the results of the numerical study, three variously approximated plane analytical models are developed. The contact pressure and the circumferential stress by the web bore are investigated, as well as the transmissible torque, where normalized diagrams are provided exploring a variety of disc-type crankweb geometries. Finally, selected three-dimensional finite element results are discussed, which highlight the limits of a plane model.
The relationship between the Dang Van criterion and the traditional bulk fatigue criteria
Authors: Peridas G , Korsunsky A. M , Hills D. A
Published: August 2003

A formal relationship is established between the traditional bulk fatigue criteria such as the Goodman rule and the Sines criterion, and the recent crack initiation criterion of Dang Van. The constants implied by the Dang Van procedure may be formally connected to the fatigue limit and mean stress dependence given by the Goodman rule, under conditions of uniaxial loading. The biaxial fatigue criterion of Sines is also compared with the Dang Van procedure. The similarity in the approaches may be further extended to permit finite initiation times to be estimated by the Dang Van criterion when the fatigue limit is exceeded.
On the analysis of singular stress fields Part 2: Application to complete slipping contacts
Authors: Tur M , Fuenmayor J , Mugadu A , Hills D. A
Published: August 2003

The stress state adjacent to the edge of a complete slipping contact has an implied elastic singularity. Using an asymptotic approach the order of this singularity, and hence the spatial distribution of the local stress field, may be found. The region over which it characterizes the full field solution is found by defining a generalized stress intensity factor K*. In practice, this requires a finite element (FE) analysis. However, the use of isoparametric elements leads to convergence problems which may be circumvented by using special singular elements which incorporate the required shape function. Here, these elements are applied to a complete contact problem for which there is an analytical solution, for comparison purposes, i.e. a rigid square-ended punch sliding along an elastic half-plane. It is shown that the singular elements are able to reproduce the singular field accurately, and that they significantly accelerate convergence when compared with a conventional mesh of isoparametric elements. Additionally, a comparison between the asymptotic and FE solutions reveals the domain over which the process (plastic) zone is controlled by the singular solution. The implications of the technique for defining the fretting fatigue strength of complete contacts will be discussed.
Shape optimization of two-dimensional anisotropic structures using the boundary element method
Authors: Tafreshi A
Published: August 2003

A shape optimization procedure is developed, using the boundary element method, for two-dimensional anisotropic structures to minimize weight while satisfying certain constraints upon stresses and geometry. A directly differentiated form of boundary integral equation with respect to geometric design variables is used to calculate shape design sensitivities of anisotropic materials. The boundary element method is very suitable for shape optimization and in comparison with the finite element method needs much fewer data, related only to the boundary of the structure being considered. Because a directly differentiated form of the boundary integral equation can be used to determine the derivatives of the objective and constraint functions, the accuracy of computation is very high. Because of the non-linear nature of weight and stresses, the numerical optimization method used in the program is the feasible direction approach, together with the golden section method for the one-dimensional search. Three example problems with anisotropic material properties are presented to demonstrate the applications of this general-purpose program.
Experimental determination of impact tensile properties of adhesive butt joints with the split Hopkinson bar
Authors: Yokoyama T
Published: August 2003

The tensile strength and energy absorption of adhesive butt joints at high rates of loading are determined with a tensile split Hopkinson bar using a cylindrical specimen. A commercially available single-component cyanoacrylate adhesive (instantaneous adhesive) and two different adherend materials are used in the adhesion tests. The impact tensile strength of the cyanoacrylate adhesive butt joints is determined from the applied tensile stress history at failure initiation. The impact absorbed energy is obtained by numerical integration of dynamic tensile load-adhesive deformation data. Comparative tension tests at low and intermediate rates of loading are performed on an Instron testing machine. An axisymmetric finite element analysis is carried out to investigate the stress distributions in the adhesive layer of the cyanoacrylate adhesive butt joints. The effects of loading rate, adherend material and adhesive layer thickness on the tensile strength and energy absorption of the cyanoacrylate adhesive butt joints are examined in detail. It is shown that the joint tensile strength increases significantly with increasing loading rate and is greatly affected by both the adhesive layer thickness and the adherend materials. The limitations of the technique are discussed.
Stress concentration factors in square and circular cross-sectioned bars with axial slots
Authors: Hyde T H , Notarangelo G , Pappalettere C , Sun W
Published: August 2003

The stress concentration factors (SCFs) in the region of a slot, with semicircular ends, in square and circular cross-sectioned bars have been obtained using the finite element (FE) method. Results are presented for torsion, bending (in two different directions) and axial loading. The effects of the length and width of the slot on the magnitudes and positions of the SCFs were investigated; the overall dimensions of the bars were kept constant. The choice of appropriate nominal stresses for defining the SCFs was given careful consideration. The choice of nominal stress for the torsion case is shown to be of particular importance. The SCFs due to torsion are found to be higher than those due to bending and axial loading. Also, except for short slots, the SCFs due to axial loading are lower than the SCFs caused by the most severe bending case.
An investigation for control of residual stress in roller-straightened rails
Authors: Srimani S L , Basu J
Published: August 2003

The cold roller straightening operation is the most critical process for the development of residual stress in rails during manufacturing. Knowledge of the residual stress in ‘as-manufactured’ rails is important for evaluation of the fatigue behaviour of rails during actual use. While experimental investigations have been reported on the induced residual stress in rails, the formulation of an appropriate simulated model for computation of the residual stress generated during the roller straightening process is still in the developmental stage. In the present investigation, an attempt has been made to develop a simulated model using the finite element (FE) method to evaluate the residual stress and to reduce its magnitude by controlling the relevant parameters of the straightening operation. The straightness of the finished rail has also been examined, and a suitable procedure for examination of the straightness of finished rails is indicated. Process parameters are recommended for reducing the residual stress in ‘as-manufactured’ rails while maintaining their straightness within specified limits.
Study on the transient response and wavelet time—frequency feature of a cracked rotor passage through a subcritical speed
Authors: Zou J , Chen J , Niu J. C , Geng Z. M
Published: August 2003

The dynamic model in dimensionless form of the transient response of a cracked rotor system is derived, which is based on the simple hinge crack model. By numerical simulation, the transient responses of the uncracked rotor and the cracked rotor are obtained and the subharmonic resonance of the cracked rotor is analysed. The influence of the unbalance, the inhabiting angle and the stiffness variation on the transient response is investigated. The wavelet time-frequency features of the cracked rotor and the uncracked rotor are studied, and the difference between them is discussed. The numerical simulation demonstrates that the wavelet analysis algorithm is valid for the identification of cracked rotor.
Determination of creep curves from multiple hardening-relaxation testing
Authors: Zhan Z , Tong J
Published: August 2003

Multiple hardening and relaxation tests have been carried out on a nickel-based superalloy at 650°C. The stress relaxation curves were obtained at selected strain levels, from which the plastic strain rates spanning three decades were obtained. Creep curves were simulated from the relaxation test results and compared reasonably well with those obtained from the creep tests. This method may be useful in the assessment of creep resistance, particularly during the material development stage.
Rotor vibration with auxiliary bearing contact in magnetic bearing systems Part 1: Synchronous dynamics
Authors: Keogh P S , Cole M O T
Published: August 2003

Magnetic bearing systems incorporate auxiliary bearings to prevent physical interaction between rotor and stator laminations. Rotor/auxiliary bearing contacts may occur when a magnetic bearing still retains a full control capability. To actively return the rotor to a non-contacting state it is essential to determine the manner in which contact events affect the rotor vibration signals used for position control. An analytical procedure is used to assess the nature of rotor contact modes under idealized contacts. Non-linearities arising from contact and magnetic bearing forces are then included in simulation studies involving rigid and flexible rotors to predict rotor response and evaluate rotor synchronous vibration components. An experimental flexible rotor/magnetic bearing facility is also used to validate the predictions. It is shown that changes in synchronous vibration amplitude and phase induced by contact events causes existing controllers to be ineffective in attenuating rotor displacements. These findings are used in Part 2 of the paper as a foundation for the design of new controllers that are able to recover rotor position control under a range of contact cases.
Rotor vibration with auxiliary bearing contact in magnetic bearing systems Part 2: Robust synchronous control for rotor position recovery
Authors: Cole M O T , Keogh P S
Published: August 2003

A number of conditions or events may produce rotor motion that involves contact with auxiliary bearings. Standard adaptive and closed-loop control strategies based on linear dynamics can cause instability when contact occurs, resulting in increased contact forces and vibration compared with the uncontrolled case. This paper introduces a method for robust control of synchronous vibration components that can maintain dynamic stability during interaction between the rotor and auxiliary bearings. The controllers are designed to minimize the severity and duration of contact and ensure that the rotor vibration returns to optimal levels, provided that sufficient control force capacity is available. Synthesis of controller gain matrices is based on a linear time-varying system model, which can be derived from either on-line identification routines or theoretical modelling and simulation. The controllers are tested experimentally on a flexible rotor system with magnetic bearings and are shown to restore rotor position control to optimal levels without further contact.
A one-dimensional analysis of rigid-body penetration with high-speed friction
Authors: Jones S E , Hughes M L , Toness O A , Davis R N
Published: August 2003

A new law for high-speed friction is presented in this paper. This law is based on observations made by several investigators regarding the asymptotic behaviour of sliding friction as the speed is increased. The new frictional effect is incorporated into the equations for rigid-body penetration to develop an analytical penetration theory. The new theory is applied to a series of penetration experiments for several steel projectiles into the same concrete target. The results confirm that the new frictional effect is a very promising addition to the theory of rigid-body penetration.
Formulation of laser-induced thermal stresses: Stress boundary at the surface
Authors: Yilbas B S , Al-Aqeeli N
Published: August 2003

Laser heating of solids results in a high-temperature gradient inside the substrate material. This, in turn, results in high stress levels in the region irradiated by a laser beam. In the present study, laser heating of solid substrate is formulated and a closed-form solution for the stress field inside the substrate material is obtained. Time exponentially decaying laser pulse intensity is employed in the analysis. In order to account for the recoil pressure effect on the resulting stress field, the stress boundary at the solid surface is employed in the analysis. The Laplace transformation method is used when deriving the closed-form solutions. It is found that a stress wave propagates into the solid bulk with a wave speed c1. The amplitude of the stress wave reduces as the distance from the substrate increases towards the solid bulk. The occurrence of peak stress inside the substrate material differes for the stress-free boundary and the stress boundary at the free surface cases.
An evolutionary shape optimization procedure for contact problems in mechanical designs
Authors: Li W , Li Q , Steven G P , Xie Y M
Published: August 2003

The finite element method (FEM) has been extensively applied to explore contact stress distributions in multi-body mechanical systems. Uneven contact stresses are often one of the main concerns of mechanical design engineers. By adopting the evolutionary structural optimization (ESO) concepts, this paper presents a non-gradient procedure for gradual shape redesign of prescribed contact interfaces. In this method, interfacial gaps are considered as design variables and contact stress deviations over design interfaces are set as the objective function. To deal with multiple contact region problems, two different design objectives, namely an individual criteria and a unified criteria, are formulated respectively. Several practical examples show that this method is effective for design problems consisting of single- or multiple-contact regions in mechanical systems, in which a uniform contact stress pattern is the desired optimality criterion.
Analytical approach for optimal design of a type of spherical parallel manipulator using dexterous performance indices
Authors: Huang T , Gosselin C M , Whitehouse D J , Chetwynd D G
Published: August 2003

In this paper, an analytical approach for the optimal design of a type of spherical parallel manipulator with symmetric geometry is investigated. Both the condition number and the behaviour of the direct Jacobian matrix associated with the initial configuration are optimized, resulting in a set of closed-form parametric relationships that enables a global optimal performance index to be achieved in the overall workspace. It has been concluded that the global optimal solution is located on the loci of local optimal solutions. The outcome confirms analytically the optimality of the orthogonal spherical parallel manipulator achieved using the numerical approach.
Effect of gap size and spacing on heat conduction between materials with irregularly spaced plane strip contacts
Authors: Manners W
Published: August 2003

A previous paper developed solutions for conductive heat flow in the x, y plane where there is a uniform flow at infinite values of y and where y = 0 represents the interface between two materials. This interface consists of an arbitrary pattern of perfectly conducting strips and non-conducting gaps. It was assumed that thermoelastic effects are negligible. The solution took the form of an equation with one unknown parameter per gap, which can be found by a simple process involving numerical integration. Using this method, the present paper gives solutions for a range of gap sizes and spacings. These are compared with approximate solutions determined by simplifying the general solutions sufficiently for them to be solved analytically. It is shown that the sizes of the gaps are the dominant parameters. The spacings are relatively unimportant unless two gaps are very close. The extent to which the approximate forms can be used to give solutions for random patterns of gaps, using the statistics of gap sizes, is discussed.
New approach to radial flow blower design to predict process parameters during operation at optimum conditions
Authors: Zaher M A
Published: August 2003

Industrial plants often have many process variable measurements. A method is used in this paper to work with a reduced number of variables. A design method is proposed used in evaluating the geometric dimensions of an impeller. The analysis utilizes numerical optimization. The purpose of the study is to predict the influence of the individual parameters of an impeller on radial blower head characteristics as a function of output at its nominal duty. A correlation between the parameters of the impeller was found in relation to the derivative of the theoretical head. This paper also attempts to provide a physical understanding of the process of loss generation. Two different impellers were chosen as a basis of calculation. One is of a compressor type and the other of a fan type.
The aerodynamic installation of optical fibres in telecommunication networks
Authors: McNeil D A , Addlesee A J , Taylor J
Published: August 2003

The installation of optical fibres for communication purposes is increasingly being carried out using a blowing technique. This study reviews the basis of the current design methods for this technique and proposes a new method based on a more traditional fluid mechanics approach. The method is used to demonstrate how far optical fibres can be blown and the stress levels likely to be encountered by them at various positions within their journey. The method will allow for future technological developments to be simulated by allowing for air drag on the fibre and the constraining tube wall to be treated differently.
Finite element analyses and experimental considerations of the deflection and failure behaviour of an asymmetric laminate composite bicycle handlebar
Authors: Chang R R
Published: August 2003

The deformation and first-ply failure load of an asymmetric laminate composite bicycle handlebar have been studied via both theoretical and experimental approaches. The composite bicycle handlebar tube is fabricated with outer main fibre layers and inner reinforcing fibre layers and is designed to predicted first-ply failure loads. Optimal angle-ply orientations of antisymmetric [θ-θ…]-s laminated tubes designed for maximum stiffness were investigated. A number of laminated composite bicycle handlebars were fabricated and subjected to static transverse bend testing. The first-ply failure loads of laminated composite bicycle handlebars tubes were determined using acoustic emission (AE). The failure modes of the bicycle handlebars were studied, and experimental results were used to verify the theoretical predictions. The experimental results have been proved to be efficient and effective in the theoretical prediction of first-ply failure loads of laminated composite bicycle handlebars.
Investigations on the fracturing of nanoparticle agglomerates—first results
Authors: Seipenbusch M , Froeschke S , Weber A P , Kasper G
Published: August 2003

The mechanical properties of nanoparticle agglomerates have been addressed in many studies. Agglomerates of nanoparticles grown by stochastic processes such as diffusion-limited cluster-cluster agglomeration represent fractal-like objects. These agglomerates are not in the most stable state, and delivering a certain minimum energy, i.e. the activation energy for restructuring, can induce rearrangement. However, in many applications of nanoparticles a high degree of dispersion in the carrier medium (gas or liquid) is desired. Thus, the fragmentation of the aggregates down to the primary particles would be optimal. Depending on the production process, the bond strength between the primary particles will exhibit a distribution that may range from weak van der Waals bonds to strong solid state necking. In the present study, the degree of fracturing as indicated by image analysis of electron micrographs from impacted agglomerates of nanoparticles of Ag and TiO2 was investigated. The influence of kinetic energy on fracturing was studied.
Recognition of two-phase flow patterns with the use of dynamic image analysis
Authors: Ulbrich R , Krótkiewicz M , Szmolke N , Anweiler S , Masiukiewicz M , Zajac D
Published: August 2003

This research work aimed at developing techniques for the recognition of two-phase flow patterns using image analysis. Flow was realized in a flat rectangular channel. Information recorded with a CCD camera, was analysed using the authors' own software. The change in the grey level value from the recorded flow realizations was investigated. The results of this analysis allowed identification of the two-phase flow structures obtained. Stochastic analysis of the fluidization process was also carried out.