bluuebunny/crossref_metadata_2025 huggingface dataset:
Autoeficacia y escolaridad como predictores de la información sobre VIH/SIDA en mujeres
Authors: Landero René , González Mónica Teresa
Published: February 2003

El objetivo del presente estudio fue medir el nivel de información que tienen las mujeres sobre el VIH/SIDA y las variables que influyen en dicho nivel (escolaridady autoeficacia), en una muestra de mujeres “amas de casa” (n=75), que pertenecen a grupos de promotoras voluntarias. Para tal propósito, se utilizó el diseño correlational de tipo transeccional. Los resultados más relevantes indicaron una correlación positiva entre la información básica sobre el VIH/SIDA y las variables de autoeficacia general, autoeficacia en prevención con la pareja sexual y escolaridad. En lo que respecta a los resultados de la regresión múltiple, se concluyó que el 27.4% de la varianza de la variable dependiente es explicadapor las variables predictoras.
Vínculos de apego con los padres y relaciones con los iguales durante la adolescencia
Authors: Sánchez-Queija Inmaculada , Oliva Alfredo
Published: February 2003

Las interconexiones entre diferentes tipos de relaciones sociales es un tema que viene suscitando mucho interés entre los investigadores del desarrollo social. En el presente artículo analizamos la relación que existe entre el recuerdo de los vínculos de apego que los adolescentes establecieron con su padre y/o madre y el tipo de relación que mantienen con sus iguales. Con este objetivo, 513 adolescentes con edades comprendidas entre los 13 y los 19 años, completaron un cuestionario sobre las relaciones con sus progenitoresy sus iguales. Los resultados muestran que aquellos chicos y chicas que recuerdan relaciones con sus progenitores basadas en el afecto, la comunicación y la estimulación de la autonomía son quienes mejores relaciones afectivas desarrollan con los amigos en general o con el mejor amigo en particular durante los años adolescentes. Al mismo tiempo encontramos que aunque existe bastante coincidencia entre el vínculo que el adolescente establece con el padre y con la madre, en los casos en que el vínculo no coincide, basta con que exista un vínculo seguro con uno de los dosprogenitorespara que exista una relación positiva con los iguales.
Percepción del riesgo en contextos culturales diferentes
Authors: Aragonés Juan Ignacio , Talayero Fernando , Moyano Emilio
Published: February 2003

Desde las teorías culturales se sostiene que las fuentes de riesgo se perciben dependiendo del sistema de creencias y valores de cada cultura. De acuerdo con esta idea en este trabajo se utiliza una metodología de carácter psicométrico para llevar a cabo tres estudios sobre percepción del riesgo en donde se hacen dos comparaciones entre una muestra de sujetos españoles y otra de chilenos. En el primer estudio se obtienen aquellas fuentes de riesgo más destacadas por la sociedad chilena a partir de una muestra de 105 sujetos. En un segundo trabajo se compara el mapa de riesgos de dos muestras de españoles y chilenos, con igual número de participantes (N=56) obtenido a partir de 66 fuentes de riesgo. Finalmente, se estudian las diferencias en la estimación de la magnitud de 24 fuentes de riesgo entre dos muestras de españoles (N=100) y chilenos (N=84). A lo) largo del artículo se hacen referencias a la importancia de los aspectos culturales correspondientes a cada una de las muestras y a los posibles sesgos que producen las diferencias.
VEGF inhibits T-cell development and may contribute to tumor-induced immune suppression
Authors: Ohm Joyce E. , Gabrilovich Dmitry I. , Sempowski Gregory D. , Kisseleva Ekaterina , Parman Kelly S. , Nadaf Sorena , Carbone David P.
Published: February 2003

T-cell defects and premature thymic atrophy occur in cancer patients and tumor-bearing animals. We demonstrate that exposure of mice to recombinant vascular endothelial growth factor (VEGF) at concentrations similar to those observed in advanced stage cancer patients reproduces this profound thymic atrophy and is highlighted by a dramatic reduction in CD4+/CD8+ thymocytes. We find that VEGF does not induce thymocyte apoptosis, but instead rapidly decreases the number of the earliest observable progenitors in the thymus. VEGF does not inhibit thymocyte development in fetal thymic organ culture, further suggesting a prethymic effect. We also demonstrate that bone marrow progenitors from animals infused with recombinant VEGF and transferred to irradiated untreated animals recolonize the thymus more efficiently than progenitors from control animals. This suggests that VEGF exposure is associated with an increased population of thymus-committed progenitors in the bone marrow. We hypothesize that pathophysiologically relevant concentrations of VEGF may block the differentiation and/or emigration of these progenitors resulting in the observed thymic atrophy. Removal of VEGF via cessation of infusion or adoptive transfer of progenitors to a congenic host induces a preferential commitment of lymphoid progenitors to the T lineage and results in a restoration of the normal composition and cellularity of the thymus. These data demonstrate that at pathophysiologic concentrations, VEGF interferes with the development of T cells from early hematopoetic progenitor cells and this may contribute to tumor-associated immune deficiencies.
IL-15 is an essential mediator of peripheral NK-cell homeostasis
Authors: Ranson Thomas , Vosshenrich Christian A. J. , Corcuff Erwan , Richard Odile , Müller Werner , Di Santo James P.
Published: February 2003

Several distinct classes of surface receptors can, on ligand binding, transmit signals that modulate the survival, proliferation, and apoptosis of peripheral B, T, and natural killer (NK) cells. At the population level, dynamic changes in lymphocyte cell numbers are strictly regulated to maintain a steady state, a process referred to as homeostasis. Although several studies have investigated the signals that regulate B- and T-cell homeostasis, little is known about the mechanisms that control the survival and proliferation of peripheral NK cells. Using an adoptive transfer system, we have investigated the role of γc-dependent cytokines, in particular interleukin 7 (IL-7) and IL-15, and major histocompatibility complex (MHC) class I molecules in peripheral NK-cell homeostasis. We observed that IL-15 plays a dominant role in the survival of peripheral NK cells, via maintenance of the antiapoptotic factor Bcl-2. IL-15 availability, however, also plays an important role because endogenous NK cells in the recipient mice influence the behavior of adoptively transferred NK cells. Finally, although NK cells bear functional inhibitory Ly49 receptors for MHC class I molecules, the presence or absence of specific ligands on host cells did not influence the survival or homeostatic expansion of donor NK cells.
Obstructive sleep apnoea and diabetes mellitus: the role of cardiovascular autonomic neuropathy
Authors: Ficker J.H. , Dertinger S.H. , Siegfried W. , König H.J. , Pentz M. , Sailer D. , Katalinic A. , Hahn E.G.
Published: February 2003

Knowledge of conditions associated with an increased prevalence of obstructive sleep apnoea (OSA) may help to identify patients with OSA and might give some insight into the pathogenesis of OSA and its sequelae. A number of earlier, smaller studies hinted at an association between diabetic cardiovascular autonomic neuropathy (AN) and OSA. The present study was, therefore, conducted with the aim of establishing the prevalence of OSA in diabetics with AN and of determining whether OSA is more prevalent in diabetics with AN, than in those without.

We studied two groups of diabetic patients: 23 with and 25 without AN. All patients were evaluated for possible OSA (apnoea/hypopnoea index Š10) using initial ambulatory screening followed by polysomnography.

Six patients with AN (26%) were found to have OSA, but none of the patients without AN met the diagnostic criteria (p<0.01). When the patients with OSA were compared to those without, no differences were found in terms of age, sex, body mass index or diabetes type or duration.

In conclusion, about one in four diabetic patients with autonomic neuropathy suffers from OSA. Thus, obstructive sleep apnoea is more prevalent in diabetic patients with autonomic neuropathy, than in those without.
Cardiorespiratory consequences of sleep apnoea syndrome in patients with massive obesity
Authors: Laaban J-P. , Cassuto D. , Orvoën-Frija E. , Iliou M-C. , Mundler O. , Léger D. , Oppert J-M.
Published: February 2003

Assessment of cardiorespiratory consequences of sleep apnoea syndrome (SAS) is difficult owing to confounding factors, especially obesity, that are strongly associated with SAS. This study was designed to assess the cardiorespiratory consequences of SAS by comparing the results of a comprehensive cardiorespiratory evaluation in apnoeic and nonapnoeic patients with massive obesity.

In a retrospective chart-review study, we studied 60 patients with massive obesity defined by a body mass index (BMI) >40 kg·m-2, presenting no chronic respiratory disease, who underwent an extensive assessment of cardiorespiratory consequences of obesity, including overnight polysomnography, lung function tests, arterial blood gas analysis, evaluation of vascular risk factors, myocardial scintigraphy with dipyridamole stress-test, isotopic ventriculography, Doppler echocardiography and Holter electrocardiogram recording.

SAS defined by an apnoea + hypopnoea index (AHI) ≥10 was diagnosed in 42% of patients (25 out of 60). Mean±sdAHI of SAS-positive (SAS+) patients was 38±24. Age, BMI, ventilatory function parameters, prevalence of smoking history and diabetes mellitus did not differ significantly in SAS+versusSAS-negative (SAS-) groups. The following complications were observed more frequently in SAS+ than in SAS- patients: daytime hypoxaemia (35vs9%, p<0.02), pulmonary arterial hypertension (36vs7%, p<0.05) and increased interventricular septal thickness (50vs15%, p<0.03). No association was found between SAS on the one hand and systemic arterial hypertension, coronary artery disease, left ventricular dysfunction and nocturnal cardiac arrhythmias on the other.

Nocturnal apnoeas in massive obesity may thus be associated with moderate daytime hypoxaemia, mild pulmonary arterial hypertension and moderate left ventricular hypertrophy, but not with severe cardiorespiratory complications.
Effect of inspiratory muscle training with an intermediate load on inspiratory power output in COPD
Authors: Villafranca C , Borzone G , Leiva A , Lisboa C
Published: February 2003

There is very little information about the effect of inspiratory muscle training on inspiratory flow (V'I) and thus on power output (PO) in patients with chronic obstructive pulmonary disease (COPD). In this study we aimed to evaluate the changes induced by training on the determinants of PO. Thirty one patients with severe COPD were randomly divided into: Group 1, trained with 30% maximal inspiratory pressure (PI,max); Group 2, with 10% PI,max; and Group 3 also trained with 30% PI,max, but the breathing pattern was evaluated while performing the training manoeuvres along inspiratory muscle training (IMT). All groups used a threshold device for 10 weeks. The PO for each of the loads during an incremental threshold test was evaluated prior to and after training. Maximal PO (POmax) increased in all groups, but the increment was higher in groups trained with 30% PI,max (p<0.005), mainly due to an increase in V'I. Group 3 showed a progressive increase in V'I (p<0.001) during the training manoeuvres in spite of an increase in load along IMT. In addition, the load after IMT was overcome with a shorter inspiratory time (tI) (p<0.02), a smaller tI/total duration of the respiratory cycle (t(tot)), (p<0.001) with no change in tidal volume or t(tot). The increment in POmax in this group correlated with the V'I generated while training (r=0.85; p<0.0001). We conclude that in patients with chronic obstructive pulmonary disease, the use of an intermediate threshold load for training improves power output mainly by increasing inspiratory flow, an effect consistent with an increase in shortening velocity of inspiratory muscles.
Mask intermittent positive pressure ventilation in chronic hypercapnic respiratory failure due to chronic obstructive pulmonary disease
Authors: Sivasothy P , Smith IE , Shneerson JM
Published: February 2003

Noninvasive ventilation in chronic obstructive pulmonary disease (COPD) has been shown to improve arterial blood gases but its long-term role has not been established. We retrospectively studied 26 consecutive patients with hypercapnic ventilatory failure due to COPD in whom oxygen therapy caused worsening hypercapnia (defined as a rise in the daytime arterial carbon dioxide tension (Pa,CO2) to >8.0 kPa or nocturnal transcutaneous carbon dioxide tension (Ptc,CO2) to >9 kPa). All were treated with mask ventilation (15 with nasal and 11 face masks) at night and during daytime naps. Additional oxygen therapy was required in 15 patients. The mean annualized death rate was 10.8% with a 1 and 3 yr survival of 92 and 68%, respectively. After 1 yr the median daytime Pa,CO2 had fallen by 1.35 kPa and the arterial oxygen tension (Pa,O2) had risen by 2.4 kPa. In subjects not using additional oxygen the median overnight Sa,O2 rose by 12% and the Ptc,CO2 fell by 2.8 kPa after 1 yr. The haematocrit was significantly less than pretreatment at 6 months and 1 yr. Quality of life in the domain of role limitation by physical health (measured using the SF-36 questionnaire) improved significantly at 6 months. Survival in this selected group with clinically stable airflow obstruction unable to tolerate oxygen therapy and treated with noninvasive mask ventilation is better than historical controls and is comparable to those able to tolerate oxygen therapy. Poor survival was associated with a low forced expiratory volume in one second, a low body mass index and a high nocturnal transcutaneous carbon dioxide tension. No difference in survival was found between those treated with mask intermittent positive pressure ventilation alone or with mask intermittent positive pressure and supplementary oxygen therapy.
Association between health-related quality of life and consultation for respiratory symptoms: results from the DIMCA programme
Authors: van den Boom G , Rutten-van Molken MP , Tirimanna PR , van Schayck CP , Folgering H , van Weel C
Published: February 2003

In general practice, diagnosis of chronic obstructive pulmonary disease (COPD) is hampered by underpresentation. A substantial proportion of subjects experiencing respiratory complaints do not consult their general practitioner (GP). In this study, the relationship between disease-specific quality of life and presentation of respiratory symptoms to a GP is investigated. A random sample from the general population (undiagnosed subjects) was screened for symptoms and objective signs of COPD (n=1,155). The lung function of subjects with symptoms of COPD was monitored for 6 months. During this period, 48 new COPD patients with a persistently reduced lung function (forced expiratory volume in one second (FEV1) less than or equal to the predicted value minus 2 SD) were detected. A disease-specific quality-of-life questionnaire (chronic respiratory questionnaire (CRQ)) was administered and clinical and GP consultation data were collected. Multivariate analysis showed that quality-of-life impairments due to dyspnoea and fatigue and variability in lung function (bronchial hyperresponsiveness, reversibility and peak expiratory flow rate variability) were related to medical consultation. Only 31% of the newly detected patients reported that they had ever visited their GP for respiratory complaints. A similarly low percentage was found in the rest of the sample (26%). It is concluded that the mere presence of respiratory symptoms or a (gradually) reduced lung function is insufficient reason for patients to seek medical help. Subjects are more likely to consult their general practitioner once their quality of everyday life is affected or they experience variability in lung function.
Effect of salmeterol on Haemophilus influenzae infection of respiratory mucosa in vitro
Authors: Dowling RB , Johnson M , Cole PJ , Wilson R
Published: February 2003

Haemophilus influenzae is a common bacterial pathogen causing human respiratory tract infections. We have previously shown that the beta2-agonist salmeterol reduces damage to the respiratory mucosa caused by Pseudomonas aeruginosa in vitro. We have now investigated the effect of salmeterol on H. influenzae infection of adenoid tissue in an organ culture by scanning electron microscopy. Tissue was preincubated with or without salmeterol (4x10(-7)M), prior to infection with H. influenzae and incubated for 12 or 24 h. Infected organ cultures had increased epithelial damage and decreased numbers of both ciliated and unciliated cells at 12h, which were significantly different (p < or = 0.01) from the controls at 24 h. Salmeterol (4x10(-7)M) significantly (p < or = 0.03) reduced damage and loss of ciliated cells in infected organ cultures at both 12 and 24, and significantly (p < or = 0.03) reduced loss of unciliated cells at 24 h. Salmeterol had no effect on the density of bacteria adhering to each individual mucosal feature or the total number of bacteria adhering to the organ culture. These results suggest that salmeterol protects the respiratory epithelium against Haemophilus influenzae-induced damage. The mechanism of salmeterol cytoprotection and its potential clinical relevance remain to be investigated.
Relationship between exhaled nitric oxide and airway hyperresponsiveness following experimental rhinovirus infection in asthmatic subjects
Authors: de Gouw HW , Grunberg K , Schot R , Kroes AC , Dick EC , Sterk PJ
Published: February 2003

Exhaled nitric oxide (NO) is elevated in asthmatics, and varies with disease severity. We postulated that a respiratory virus infection increases exhaled NO levels in asthma, and examined the relationship between the virus-induced changes in exhaled NO and in airway hyperresponsiveness to histamine. In a parallel study, seven patients underwent experimental rhinovirus 16 (RV16) inoculation at days 0 and 1, whilst seven patients received placebo. Exhaled NO was measured at baseline (day 0) and at days 1, 2 and 3 after inoculation. Histamine challenges were performed prior to (day -7) and after inoculation (day 3), and were expressed as provocative concentration causing a 20% fall in forced expiratory volume in one second (FEV1) (PC20). Following RV16 infection there was a significant increase in NO at days 2 and 3 as compared to baseline (median change (range): 4.2 (7.5) parts per billion (ppb), p=0.03, and 3.0 (10.1) ppb, p=0.02, respectively). Furthermore, PC20 decreased significantly following RV16 infection (mean+/-SD change in doubling dose: -0.65+/-0.54, p=0.02), whereas PC20 did not change in the placebo group (p=0.1). There was a significant correlation between the RV16-induced changes in exhaled NO levels at day 2 and the accompanying changes in PC20 at day 3 (rank correlation coefficient (rs): 0.86, p=0.01). Hence, the greater the increase in exhaled NO, the smaller the decrease in PC20. We conclude that rhinovirus infection increases exhaled nitric oxide levels in asthmatics, and that this increase is inversely associated with worsening of airway hyperresponsiveness to histamine. These results suggest that viral induction of nitric oxide synthase within the airways may play a protective role in exacerbations of asthma.
High dose rate endobronchial brachytherapy: results and complications in 189 patients
Authors: Taulelle M , Chauvet B , Vincent P , Felix-Faure C , Buciarelli B , Garcia R , Brewer Y , Reboul F
Published: February 2003

The purpose of this study was to determine the benefit of high dose rate endobronchial brachytherapy in the treatment of obstructive lung cancer. Between September 1990 and March 1995, 189 patients with bronchogenic carcinoma were treated with high dose rate endobronchial brachytherapy. Most patients (69.3%) had received prior treatment and presented with symptomatic bronchial obstruction due to either recurrent or residual endobronchial disease. A small group (12%) was medically unfit for either surgical resection or thoracic radiotherapy and benefited from endobronchial brachytherapy alone for small endobronchial tumours. The remainder of the patients had not been treated previously and endobronchial brachytherapy was performed for life-threatening symptoms requiring emergency obstruction relief before other therapy. Treatment was performed weekly and consisted of three to four 8 to 10 Gy fractions at a radius of 10 mm from the centre of the source. Major symptomatic relief was obtained for haemoptysis (74%), dyspnoea (54%), and cough (54%). Complete endoscopic response was observed in 54% of cases. Median survival was 7 months for the entire group. For small, strictly endobronchial tumours, complete response rate was 96%, median survival 17 months, and 30 month survival 46%, with a plateau starting at 18 months. Grade 3 to 4 toxicities occurred at a rate of 17% and included massive haemoptysis (n=13), bronchial stenosis (n=12), soft tissue necrosis (n=8), and bronchial fistula (n=3). By univariate analysis, no factor was found to be predictive of late pulmonary toxicity. The present study confirms the usefulness of endobronchial brachytherapy in alleviating symptoms caused by endobronchial recurrence of bronchogenic carcinoma. In addition, this therapy can be tried with curative intent in patients who present with small endobronchial tumours and are not candidates for other forms of therapy.
A childhood asthma death in a clinical trial: potential indicators of risk
Authors: Warner JO , Nikolaizik WH , Besley CR , Warner JA
Published: February 2003

A 9 yr old girl with a history of eczema and asthma was admitted to our specialist asthma service and recruited into a trial designed to investigate systemic as well as therapeutic benefits of inhaled corticosteroids. Eight months after referral the patient died from an acute asthma attack. This childhood asthma death during an inhaled steroid trial has facilitated identification of risk factors. Despite good clinical response to inhaled corticosteroids, the patient was distinguishable from the other patients by: increased variability of the morning and evening peak flow rates; increased reactivity, though not sensitivity, to histamine; and an unprecedented rise in serum soluble interleukin-2 receptor levels immediately after commencing inhaled steroids. The immunological basis for corticosteroid resistance and immunohistochemical studies on postmortem specimens from asthma deaths suggest that T-cell activation markers may be indicators of the fatality prone asthmatic.
Bronchoalveolar lavage cell analysis in a child with chronic lipid pneumonia
Authors: Midulla F , Strappini PM , Ascoli V , Villa MP , Indinnimeo L , Falasca C , Martella S , Ronchetti R
Published: February 2003

In an asymptomatic 4 yr old child with radiographic evidence of parenchymal lung disease, bronchoalveolar lavage (BAL) yielded the diagnosis of chronic lipid pneumonia caused by chronic aspiration of mineral oil given as a laxative. BAL analysis showed a marked reduction in the total number of alveolar macrophages; almost 70% of these cells contained intracytoplasmic lipid vacuoles. It also disclosed lymphocytic (cytotoxic/suppressor) alveolitis. A high percentage of lymphocytes expressed antigen markers of activation (human leucocyte antigen (HLA)-DR), CD54 and CD25). BAL analysis 18 months after mineral oil intake revealed that lymphocytes bearing antigen markers of activation had markedly decreased whereas alveolar macrophages (normal and lipid-laden) had increased. A subsequent whole lung BAL was considered unnecessarily invasive in this otherwise healthy child.
Sources of nonlinearity and complexity in geomorphic systems
Authors: Phillips Jonathan D.
Published: February 2003

Nonlinearity is common in geomorphology, though not present or relevant in every geomorphic problem. It is often ignored, sometimes to the detriment of understanding surface processes and landforms. Nonlinearity opens up possibilities for complex behavior that are not possible in linear systems, though not all nonlinear systems are complex. Complex nonlinear dynamics have been documented in a number of geomorphic systems, thus nonlinear complexity is a characteristic of real-world landscapes, not just models. In at least some cases complex nonlinear dynamics can be directly linked to specific geomorphic processes and controls. Nonlinear complexities pose obstacles for some aspects of prediction in geomorphology, but provide opportunities and tools to enhance predictability in other respects. Methods and theories based on or grounded in complex nonlinear dynamics are useful to geomorphologists. These nonlinear frameworks can explain some phenomena not otherwise explained, provide better or more appropriate analytical tools, improve the interpretation of historical evidence and usefully inform modeling, experimental design, landscape management and environmental policy. It is also clear that no nonlinear formalism (and, as of yet, no other formalism) provides a universal meta-explanation for geomorphology. The sources of nonlinearity in geomorphic systems largely represent well-known geomorphic processes, controls and relationships that can be readily observed. A typology is presented, including thresholds, storage effects, saturation and depletion, self-reinforcing feedback, self-limiting processes, competitive feedbacks, multiple modes of adjustment, self-organization and hysteresis.
Biophysical remote sensing of arctic environments
Authors: Laidler Gita J. , Treitz Paul
Published: February 2003

Various remote sensing studies have been conducted to investigate methods and applications of vegetation mapping and analysis in arctic environments. The general purpose of these studies is to extract information on the spatial and temporal distribution of vegetation as required for tundra ecosystem and climate change studies. Because of the recent emphasis on understanding natural systems at large spatial scales, there has been an increasing interest in deriving biophysical variables from satellite data. Satellite remote sensing offers potential for extrapolating, or ‘scaling up’ biophysical measures derived from local sites, to landscape and even regional scales. The most common investigations include mapping spatial vegetation patterns or assessing biophysical tundra characteristics, using medium resolution satellite data. For instance, Landsat TM data have been shown to be useful for broad vegetation mapping and analysis, but not accurately representative of smaller vegetation communities or local spatial variation. It is anticipated, that high spatial resolution remote sensing data, now available from commercial remote sensing satellites, will provide the necessary sampling scale to link field data to remotely sensed reflectance data. As a result, it is expected that these data will improve the representation of biophysical variables over sparsely vegetated regions of the Arctic.
A review of rockfall mechanics and modelling approaches
Authors: Dorren Luuk K.A.
Published: February 2003

Models can be useful tools to assess the risk posed by rockfall throughout relatively large mountainous areas (>500 km2), in order to improve protection of endangered residential areas and infrastructure. Therefore the purpose of this study was to summarize existing rockfall models and to propose modifications to make them suitable for predicting rockfall at a regional scale. First, the basic mechanics of rockfall are summarized, including knowledge of the main modes of motion: falling, bouncing and rolling. Secondly, existing models are divided in three groups: (1) empirical models, (2) process-based models and (3) Geophysical Information System (GIS)-based models. For each model type its basic principles and ability to predict rockfall runout zones are summarized. The final part is a discussion of how a model for predicting rockfall runout zones at a regional scale should be developed. A GIS-based distribution model is suggested that combines a detailed process-based model and a GIS. Potential rockfall source areas and falltracks are calculated by the GIS component of the model and the rockfall runout zones are calculated by the process-based component. In addition to this model, methods for the estimation of model parameters values at a regional scale have to be developed.
The development of a fast and robust computer model for metal rolling
Authors: Dixon A E , Yuen W Y D
Published: February 2003

A combined analytical/numerical solution method is developed to solve the equations that describe stresses in the plastic deformation of metal strip during rolling together with the resultant roll flattening. This gives a model that is more robust and computationally faster for the same accuracy than standard numerical schemes. Initially, the model assumes the elastically deformed rolls to be approximated by a circular arc profile when in contact with the strip, but it is later extended to calculate the deformed roll profile from the pressure profile through the roll gap. Both versions are suitable for on-line use in predicting the necessary roll force for the rolling of metal strip to a given thickness reduction.
Net shaping via aluminium foaming
Authors: Kathuria Y P
Published: February 2003

The marriage between net shaping and aluminium alloy foaming has given a new dimension to the rapid prototyping technique for manufacturing of the lightweight structure in the automotive and aerospace industries. The present paper is focused on laser-assisted aluminium foaming from a foamable precursor material and its possible applications in net shaping of three-dimensional structures. Preliminary results suggest that a pore size gradient and a density gradient exist in the structure as the processing condition changes. The foam has large pores and lower density for slow processing speed, in contrast with the fast processing speed with small pore size but higher density. For pilot-scale production of the foamed plates, sandwiches panel and localized foamed structure, specially intended for heat exchanger in the electronic industries, the laser foaming technique may be the most appropriate.
The effect of process parameters on cell morphology in cellular aluminium alloy fabricated by powder compression and the induction heating process
Authors: Youn S W , Kang C G
Published: February 2003

In a foaming process, accurate control of the foaming temperature and heating rate is very important in terms of reproducibility of mechanical properties. Generally, foaming of the precursor is performed in an electric furnace, which is preheated at temperatures higher than the desired temperature. In this case, accurate control of the precursor temperature is difficult. In this study, cellular aluminium alloy having a closed cell structure is fabricated by applying the powder compact method and an induction heating process. The induction heating process was used for foaming of the precursor in order to improve the reproducibility of mechanical properties. To establish the cellular aluminium fabrication conditions, the effects of process parameters such as the titanium hydride content (0.3-1.5 wt%), pressing pressure of the foamable precursor (50-150 kN) and the foaming temperature (610-690°C) on the pore morphology were investigated and porosities (%)-foaming temperature curves were obtained.
A review of conventional and modern single-point sheet metal forming methods
Authors: Hagan E , Jeswiet J
Published: February 2003

The use of computers in manufacturing has enabled the development of several new metal forming processes that are based upon older technologies. In this case modifications have been made to traditional forming methods such as conventional spinning and shear forming. These two processes are similar in that the deformation mechanism is localized to a small region under the forming tool. Recent advances in computing power have enabled this localized deformation to be accurately controlled and studied. Spinning, shear forming and flow forming are limited to forming parts that are symmetrical about the revolving lathe axis. Current research has been focused on forming non-symmetrical parts using computer numerical control (CNC) technology, without the need for costly dies. A comparison of traditional and modern forming methods is presented here in an attempt to illustrate the evolution of different incremental sheet metal forming techniques. Emphasis is placed on conventional spinning, shear forming and modern computer-controlled forming methods that are currently being studied.
Automatic redesign of assemblies for layered manufacturing
Authors: Wu J , Tan S T , Sze W S
Published: February 2003

In this paper, the characteristics and advantages of layered manufacturing are discussed. Based on the computer aided design (CAD) model of an existing assembly, a scheme of automatic redesign of the component parts of the assembly for layered manufacturing is proposed. By determining the physical assembly constraint graph and the physically fully constrained part groups of the assembly, pertinent component parts of the assembly are merged automatically into a single part. The redesigned part assembly contains a fewer number of component parts and a simpler assembly structure and could be fabricated as a whole in one step in a layered manufacturing machine. The redesign of a simple slider-crank mechanism assembly has been carried out to illustrate the proposed scheme, and further redesign issues are also discussed.
Experimental studies on the accuracy of wax patterns used in investment casting
Authors: Hock T S , Trevor S , Christodoulou P , Yarlagadda P K D V
Published: February 2003

Investment casting is often used to produce fully functional prototype components from sacrificial patterns. These patterns (prototypes) may be made using specialized rapid prototyping techniques such as stereolithography or three-dimensional printing. When multiple functional prototypes are required, interim tools for making wax patterns are employed. The objective of this research work was to determine the precision and accuracy of wax patterns produced using several prototype tools. Linear contraction was used to determine the accuracy as a function of the wax injection parameters used in low-pressure injection moulding. Wax patterns were produced using polyurethane and silicone rubber tools. It has been shown that the accuracy of patterns from both tools is similar. However, silicone tools produce patterns with much higher contraction than those produced by polyurethane tools. Unconstrained patterns dimensions contracted as much as 3.44 ± 0.40 per cent and 1.70 ± 0.60 per cent for silicone and polyurethane tools respectively. The constrained dimensions contracted by 2.20 ± 0.20 per cent in the case of silicone tools and 1.40 ± 0.20 per cent in the case of polyurethane tools.
Design considerations for inspiratory muscle training systems
Authors: Caine M P , Waller T M , Wilcox A
Published: February 2003

Inspiratory muscle training can be used to strengthen the muscles employed when breathing in. This has been shown to benefit the exercise performance of a diverse group of users including elite sports people. Unfortunately, existing training devices do not provide an optimum training stimulus. The principal limitations of current devices are that they can only be used statically, i.e. not during exercise, and that the load they provide does not reflect the force generating capacity of the targeted muscle group. These limitations could be overcome if an ambulatory responsive loading technology were developed. Ambulatory training would allow users to ‘wear’ the training device while performing exercise, thereby ensuring that improvements to breathing are functionally relevant to the particular demands of a given sport or task. Responsive loading would ensure that the load applied to the inspiratory muscles is specific to the force-generating capacity of the inspiratory muscles during exercise. The purpose of the present project was to explore the feasibility of ambulatory responsive inspiratory muscle training. A series of potential design solutions were identified. This paper describes the design and development process undertaken and draws conclusions regarding the feasibility of ambulatory responsive inspiratory muscle training.
Noise from progressive multi-leaf springs and methods for its reduction
Authors: Kim S-S , Moon W , Yoo Y-I
Published: February 2003

The noise produced by progressive multi-leaf springs was investigated. Experiments on progressive multi-leaf springs indicated that the source of the noise was contact between the main and help springs. The contact between the two leaves was examined by numerical simulations of spring deformation with changes in the applied external load; these simulations were carried out using ABAQUS. The parameters that potentially influence the unexpected noise in the progressive multi-leaf spring were investigated through a review of the structural characteristics of the spring. Two candidates were then selected as potential main parameters influencing the observed noise: impact by an abrupt contact and friction between the main and help spring leaves. Consideration of the results of numerical simulations, noise measurements and other observations led to the conclusion that translational jumping of the contact point between the main and help spring leaves is the main mechanism causing the noises emanating from the progressive multi-leaf spring. Based on this conclusion, modification of the shape of the help spring leaf is proposed to eliminate the abrupt contact caused by a jump of the contact position. Experiments showed that the tapping noise was successfully eliminated by modifying the shape of a help spring leaf without a noticeable change in the spring stiffness.
A comparison of emerging time-triggered protocols for automotive X-by-wire control networks
Authors: Shaheen S , Heffernan D , Leen G
Published: February 2003

This paper compares the emerging time-triggered protocols that will find use in automotive control networks. At present there is no de facto standard in the automotive industry for in-vehicle networking based on the time-triggered model. As the industry is pushing towards incorporating X-by-wire technology (X standing for steer, brake, shift, etc.) for future cars, car manufacturers are working towards agreeing industry standards for X-by-wire control system applications. Currently there are four protocols based on the time-triggered paradigm which are competing for the X-by-wire automotive market. These protocols are TTCAN, TTP/C, Flex Ray and Byteflight.
Study of cycle-by-cycle variations of natural gas direct injection combustion using a rapid compression machine
Authors: Huang Z , Shiga S , Ueda T , Nakamura H , Ishima T , Obokata T , Tsue M , Kono M
Published: February 2003

Cycle-by-cycle variations of natural gas direct injection (CNG DI) combustion were studied by using a rapid compression machine. Results show that CNG DI combustion can realize high combustion stability with less cycle-by-cycle variation in the maximum pressure rise, the maximum rate of pressure rise and the maximum rate of heat release at the given equivalence ratios. Mixture stratification and fast flame propagation with the aid of turbulence produced by the high speed fuel jet are considered to be responsible for these behaviours. Cycle-by-cycle variations in combustion durations and combustion products present higher magnitudes than those of maximum pressure rise and maximum rate of heat release. Cycle-by-cycle variations of CO and unburned CH4 show an interdependence with the variation of the late combustion duration, and the variation of NO x shows an interdependence with the variation of the rapid combustion duration. Cycle-by-cycle variations are found to be insensitive to the equivalence ratios in CNG DI combustion.
An investigation into a state space model for an attenuator in automotive hydraulic systems
Authors: Lee J-C
Published: February 2003

A hydraulic attenuator has been used in hydraulic active suspension systems of automotive vehicles to reduce high amplitude ripple pressure of a pump. The hydraulic attenuator considered in this study is so highly non-linear and of high order that the analysis in the time domain has been performed infrequently, although the frequency response analysis with the transfer matrix method was applicable. In this paper, a state space representation of the dynamics for a hydraulic attenuator is presented, utilizing the electrical analogy. The results of the experiment are compared with those of the simulation to validate the state space model proposed. The comparison reveals that the state space model proposed is practically applicable for estimating the dynamic responses of the hydraulic attenuator in the time domain.
Audible-frequency stiffness of a primary suspension isolator on a high-speed tilting bogie
Authors: Kari L
Published: February 2003

The preload-dependent dynamic stiffness of a primary suspension isolator on a high-speed tilting bogie is examined via measurements and modelling within an audible frequency range. The stiffness is found to depend strongly on both frequency and preload. The former displays some resonance phenomena, such as stiffness peaks and troughs, while the latter exhibits a steep low-frequency stiffness increase in addition to an anti-resonance peak shifting to a higher frequency with increased preload. The problems of simultaneously modelling the preload and frequency dependence are removed by adopting a frequency-dependent waveguide approach, assuming incompressible rubber with an Abel operator kernel as its shear relaxation function. The preload dependence is modelled by a non-linear shape factor based approach, using a globally equivalent preload configuration. All the translational stiffnesses are modelled, including the vertical, longitudinal and lateral directions, and the vertical stiffness results are compared to those of measurements in a specially designed test rig. Good agreement is obtained for a wide frequency domain-covering 100-600 Hz-using a minimum number of parameters and for a wide preload domain-from vanishing to the maximum in service, 90 kN.
Making deep reductions in CO2 emissions from coal-fired power plant using capture and storage of CO2
Authors: Freund P
Published: February 2003

Concerns about potentially dangerous changes in climate as a result of rising levels of greenhouse gases in the atmosphere are leading to restrictions on emissions of carbon dioxide (CO2), the principal anthropogenic greenhouse gas. The main source of CO2 emissions is fossil fuel combustion; power generation is the single largest contributor. Coal is widely used for power generation, but it releases approximately twice as much CO2 compared with the use of natural gas for each unit of electricity sent out. Emission reduction could be achieved by increasing the efficiency with which coal is burnt, or by switching to another fuel. These measures can achieve significant reductions in emissions, but, for deep reductions, more substantial changes would be required in the power plant. The technology for capture and storage of CO2 has been recognized in recent years as providing a means of cutting emissions from fossil fuel combustion by at least 80 per cent. Capture and storage is based on technology already in use for other purposes, so there is limited need for development, and the risk of application will be less than is typical for novel energy technologies. Hence, this seems to be a technology that could be deployed relatively rapidly to reduce emissions from fossil fuel fired plant. In this paper, the technology for capture and storage of CO2 will be reviewed, especially the costs and potential capacity for reducing emissions. Some barriers to implementation are identified, and work necessary to overcome them is discussed.
Coalbed methane extraction and utilization
Authors: Creedy D , Tilley H
Published: February 2003

Coalbed methane (CBM) is the generic name for all methane of coal seam origin. It is a natural gas formed by geological, or biological, processes in coal seams and generally consists predominantly of methane, but may also contain some higher alkanes and non-combustible gases. Methane is released whenever coal is de-stressed or fractured by mining. Methane is one of the main greenhouse gases contributing to global warming, therefore releasing it to atmosphere is an environmental hazard. However, it is also an important energy resource and can be recovered from operational coal mines, abandoned coal mines, and virgin (unmined) coal seams. Significant volumes of CBM are exploited worldwide for space heating, industrial processes, and power generation. This paper critically reviews the current UK and worldwide status of CBM extraction and utilization technologies building on a previous study funded through the Department of Trade and Industry's Cleaner Coal Technology Programme [1].
Coal gasification technologies
Authors: Hotchkiss R
Published: February 2003

This paper reviews coal gasification processes and technology. Sources of more detailed information in specific areas are suggested. The merits and disadvantages of incorporating coal gasification into power generation plants are discussed. The recent history of coal gasification technology and the current state of projects are summarized. The potential for large-scale coal gasification, small-scale coal gasification and cogasification of coal with biomass and/or wastes in the current economic climate is discussed.
Nonlinear balanced models for stratified fluids conserving Ertel–Rossby PV
Authors: Ziemia'Nski Micha Z. , Thorpe Alan J.
Published: February 2003

A derivation of consistent balanced models for stratified fluids conserving the Ertel–Rossby potential vorticity (PV) is presented. It is used to develop a set of balanced models incorporating new omega equations valid for flow regimes from synoptic scale to mesoscale. The models are developed for quasi‐Boussinesq and real atmospheres, and for adiabatic and frictionless as well as non‐conservative processes. The new omega equations allow the identification of additional forcing of the vertical velocity due to the ageostrophic and stability effects, and the modification of atmospheric response due to the non‐Boussinesq effects. It is shown that the new omega equation, valid beyond the limit of small Rossby number, allows for a subjective analysis of the vertical‐velocity forcing based on an approach involving the isentropic upgliding, Ertel–Rossby PV advection and boundary temperature advection. Copyright © 2003 Royal Meteorological Society