bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance- and safety-enhanced lentiviral vectors containing the human interferon-β scaffold attachment region and the chicken β-globin insulator
Authors: Ramezani Ali , Hawley Teresa S. , Hawley Robert G.
Published: February 2003

Retroviral vectors are the most efficient means of stable gene delivery to hematopoietic stem cells (HSCs). However, transgene expression from retroviral vectors is frequently subject to the negative influence of chromosomal sequences flanking the site of integration. Toward the development of autonomous transgene expression cassettes, we inserted the human interferon-β scaffold attachment region (IFN-SAR) and the chicken β-globin 5′ DNase I hypersensitive site 4 (5′HS4) insulator both separately and together into a series of self-inactivating (SIN) lentiviral vector backbones. Transduced cells of the human CD34+ hematopoietic progenitor line KG1a—pooled populations as well as individual clones harboring single integrants—were analyzed for reporter expression during culture periods of up to 4 months. Vectors carrying both the 5′HS4 insulator and the IFN-SAR consistently outperformed control vectors without inserts as well as vectors carrying either element alone. The performance of a set of vectors containing the murine stem cell virus long terminal repeat as an internal promoter was subsequently assessed during in vitro monocytic differentiation of transduced primary human CD34+ cord blood cells. Similar to what was observed in the KG1a hematopoietic progenitor cell model, optimal reporter expression in primary monocytes was obtained with the vector bearing both regulatory elements. These findings indicate that the 5′HS4/IFN-SAR combination is particularly effective at maintaining open chromatin domains permissive for high-level transgene expression at early and late stages of hematopoietic development, and thus could be of utility in HSC-directed retroviral vector–mediated gene transfer applications.
Chronic lymphocytic leukemias utilizing the VH3-21 gene display highly restricted Vλ2-14 gene use and homologous CDR3s: implicating recognition of a common antigen epitope
Authors: Tobin Gerard , Thunberg Ulf , Johnson Anna , Eriksson Inger , Söderberg Ola , Karlsson Karin , Merup Mats , Juliusson Gunnar , Vilpo Juhani , Enblad Gunilla , Sundström Christer , Roos Göran , Rosenquist Richard
Published: February 2003

The immunoglobulin variable heavy chain (IgVH) gene mutation status is an important prognostic factor in chronic lymphocytic leukemia (CLL), since cases with mutated VH genes show significantly longer survival than unmutated cases. Recently, we reported a preferential use of the VH3-21 gene in mutated CLL and showed that mutated VH3-21 cases had an inferior overall survival compared with other mutated CLL. In order to further characterize this subset, we performed VH gene analysis in 265 CLL cases and identified 31 VH3-21 cases (11.7%); 21 cases had mutated and 10 cases unmutated VH genes. Regardless of VH gene mutation status, a poor overall survival was found in the VH3-21 cases with a median survival of 83 months. These survival data confirm that VH3-21 cases do not fit into the general prognostic grouping of mutated and unmutated CLL. A large fraction of VH3-21 cases also demonstrated unique features with shorter lengths of the third complementarity determining region (CDR3) and CDR3s with highly homologous amino acid sequences. Furthermore, the VH3-21 cases showed a striking dominance of λ light chain expression, and analysis of the Igλ gene rearrangements revealed highly restricted use of the Vλ2-14/Jλ3 genes in the majority of cases. Taken together, our new findings strengthen the suggestion that VH3-21–using cases comprise a new CLL entity, irrespective of VH gene mutation status, and implicate that a common antigen epitope, perhaps of pathogenic significance, is recognized by the highly homologous VH3-21/Vλ2-14 Ig molecules expressed in individual tumors.
Mechanisms and implications of platelet discoid shape
Authors: Italiano Joseph E. , Bergmeier Wolfgang , Tiwari Sanjay , Falet Hervé , Hartwig John H. , Hoffmeister Karin M. , André Patrick , Wagner Denisa D. , Shivdasani Ramesh A.
Published: February 2003

The platelet marginal band consists of a single peripheral microtubule (MT) that is wound in 8 to 12 coils and maintains discoid cell shape. About 90% of β-tubulin in the marginal band is of the divergent, megakaryocyte (MK)/platelet-restricted β1 isoform. β1-tubulin–null mice show reduced proplatelet formation, thrombocytopenia, and platelet spherocytosis. Here, we show that structural abnormalities in resting β1-tubulin—/— platelets include frequent kinks and breaks in the marginal band. Platelets derived from mice lacking the transcription factor GATA1 show similar defects, probably as a direct consequence of absent β1-tubulin. β1-tubulin+/— platelets have normal ratios of β-tubulin isotypes but the marginal band is half the normal thickness, which is sufficient to maintain elliptical cell shape. Thus, a threshold 50% or less of the normal amount of β1-tubulin is required to preserve marginal band integrity and cell shape. β1-tubulin—/— platelets have normal size and contents and show no defects in serotonin release or aggregation. Accordingly, the apparently isolated spherocytosis allows investigation of the role of discoid platelet shape in hemostasis. On agonist stimulation, the disorganized MTs in β1-tubulin—/— platelets fail to condense into central rings and instead are dispersed in short bundles and linear arrays. Nevertheless, intravital microscopy and flow chamber studies demonstrate full functionality of these spherocytic platelets under physiologic shear conditions. Together, these findings highlight the essential requirements of the MK/platelet-restricted β1-tubulin isoform in platelet structure and suggest that spherocytosis does not impair many aspects of platelet function.
Human cytomegalovirus immediate-early mRNAemia versus pp65 antigenemia for guiding pre-emptive therapy in children and young adults undergoing hematopoietic stem cell transplantation: a prospective, randomized, open-label trial
Authors: Gerna Giuseppe , Lilleri Daniele , Baldanti Fausto , Torsellini Maria , Giorgiani Giovanna , Zecca Marco , De Stefano Piero , Middeldorp Jaap , Locatelli Franco , Revello M. Grazia
Published: February 2003

In the search for better protocols of preemptive therapy of human cytomegalovirus (HCMV) infection in hematopoietic stem cell transplant (HSCT) recipients, we conducted a randomized trial comparing antigenemia with the nucleic acid sequence–based assay (NASBA) for determination of HCMV immediate-early messenger RNA (IEmRNA) as the guiding assay for initiation of pre-emptive antiviral treatment. In the IEmRNA arm, antiviral therapy was started upon IEmRNA positivity confirmed the following day, whereas in the antigenemia arm, therapy was started in the presence of either at least 2 pp65-positive leukocytes/2 × 105 examined or a single positive leukocyte confirmed the following day. In both arms, treatment was stopped upon 2 consecutive negative results. All patients were monitored for 3 months after HSCT. The primary end point of the study was duration of anti-HCMV therapy. On the whole, 80 children (41 in the IEmRNA and 39 in the antigenemia arm), recipients of transplants from either a relative or an unrelated donor, completed the study. No patient developed HCMV disease. In the IEmRNA arm, the incidence of HCMV infection was higher compared to the antigenemia arm (80% vs 51%, respectively, P = .0069), as well as the percentage of treated patients (66% vs 44%, respectively, P = .045). However, the percentage of relapses and treated relapses was comparable in the 2 arms. There was no significant difference in median duration of therapy per patient. Although these data indicate that IEmRNA determination does not offer advantages in terms of treatment duration, it can safely replace antigenemia, while semiautomation is the major advantage of the NASBA procedure.
Nucleolar localization of RPS19 protein in normal cells and mislocalization due to mutations in the nucleolar localization signals in 2 Diamond-Blackfan anemia patients: potential insights into pathophysiology
Authors: Da Costa Lydie , Tchernia Gil , Gascard Philippe , Lo Annie , Meerpohl Joerg , Niemeyer Charlotte , Chasis Joel-Anne , Fixler Jason , Mohandas Narla
Published: February 2003

Ribosomal protein S19 (RPS19) is frequently mutated in Diamond-Blackfan anemia (DBA), a rare congenital hypoplastic anemia. Recent studies have shown that RPS19 expression decreases during terminal erythroid differentiation. Currently no information is available on the subcellular localization of normal RPS19 and the potential effects of various RPS19 mutations on cellular localization. In the present study, using wild-type and mutant RPS19 cDNA, we explored the subcellular distribution of normal and mutant proteins in a fibroblast cell line (Cos-7 cells). RPS19 was detected primarily in the nucleus, and more specifically in the nucleoli, where RPS19 colocalized with the nucleolar protein nucleolin. Using various N-terminal and C-terminal deletion constructs, we identified 2 nucleolar localization signals (NoSs) in RPS19: the first comprising amino acids Met1 to Arg16 in the NH2-terminus and the second comprising Gly120 to Asn142 in the COOH-terminus. Importantly, 2 mutations identified in DBA patients, Val15Phe and Gly127Gln, each of which localized to 1 of the 2 NoS, failed to localize RPS19 to the nucleolus. In addition to their mislocalization, there was a dramatic decrease in the expression of the 2 mutant proteins compared to the wild type. This decrease in protein expression was specific for the mutant RPS19, since expression of other proteins was normal. The present findings enable us to document the nucleolar localization signals in RPS19 and help define the phenotypic consequences of some mutations in RPS19 in DBA.
Unrelated cord blood transplantation for adult patients with advanced myelodysplastic syndrome
Authors: Ooi Jun , Iseki Tohru , Takahashi Satoshi , Tomonari Akira , Ishii Koji , Takasugi Kashiya , Shimohakamada Yoko , Ohno Nobuhiro , Uchimaru Kaoru , Nagamura Fumitaka , Tojo Arinobu , Asano Shigetaka
Published: February 2003

We report the results of unrelated cord blood transplantation (CBT) for 13 adult patients with advanced myelodysplastic syndrome (MDS). The median age was 40 years, the median weight was 51 kg, and the median number of infused nucleated cells was 2.43 × 107/kg. Twelve patients had myeloid reconstitution, and the median time to more than 0.5 × 109/L (5 × 108/L) absolute neutrophil count was 22.5 days. A self-sustained platelet count more than 50 × 109/L was achieved in 11 patients at a median time of 49 days. Acute graft versus host disease (GVHD) occurred in 9 of 12 evaluable patients and chronic GVHD in 8 of 11 evaluable patients. Ten patients are alive and free of disease at between 171 and 1558 days after transplantation. The probability of disease-free survival at 2 years was 76.2%. These results suggest that adult advanced MDS patients without suitable related or unrelated bone marrow donors should be considered as candidates for CBT.
Asthma self-management programmes in a population of Italian children: a multicentric study. Italian Study Group on Asthma Self-Management Programmes
Authors: Ronchetti R , Indinnimeo L , Bonci E , Corrias A , Evans D , Hindi-Alexander M , Midulla F , Pulejo R , Villa MP
Published: February 2003

This study was designed to answer three main questions: 1) Does asthma self-management education reduce asthma morbidity? 2) Are the two programmes "Living With Asthma" and "Open Airways" equally effective in doing so? 3) Is a shortened version of these programmes (4 weeks) as effective as the longer original programme (8 weeks)? Twelve Italian centres of paediatric bronchopneumology selected 312 children with asthma, who were stratified by disease severity, gender and age, and then randomly assigned to an Experimental group which received an educational programme or to a Comparison group, which did not. Of the 312 children selected, 209 (114 Experimental and 95 Comparison) completed the educational protocol and a 1 year follow-up. Data recorded during the last 2 months of follow-up, 10 months after the educational intervention, showed that the Experimental group required significantly fewer emergency treatments: this reduction was more evident in the more severe asthma cases. In the Experimental, but not in the Comparison group, patients with more severe asthma consumed more medications than patients with milder asthma "Open Airways" yielded, in some cases, better results than "Living with Asthma": but a type 2 error is possible. The standard and the shortened programmes proved equally effective. In conclusion, following education, regardless of receiving a short or long educational programme, asthma patients use emergency care services less and use medications more appropriately in comparison with standard care without education. This suggests that short educational programmes can be highly cost-effective in children with asthma.
Training with supplemental oxygen in patients with COPD and hypoxaemia at peak exercise
Authors: Rooyackers JM , Dekhuijzen PN , Van Herwaarden CL , Folgering HT
Published: February 2003

Supplemental oxygen has acute beneficial effects on exercise performance in patients with chronic obstructive pulmonary disease (COPD). The purpose of this study was to investigate whether oxygen-supplemented training enhances the effects of training while breathing room air in patients with severe COPD. A randomized controlled trial was performed in 24 patients with severe COPD who developed hypoxaemia during incremental cycle exercise (arterial oxygen saturation (Sa,O2) <90% at peak exercise). All patients participated in an in-patient pulmonary rehabilitation programme of 10 weeks duration. They were assigned either to general exercise training while breathing room air (GET/RA group: forced expiratory volume in one second (FEV1) 38% of predicted; arterial oxygen tension (Pa,O2) 10.5 kPa at rest; Pa,O2 7.3 kPa at peak exercise), or to GET while breathing supplemental oxygen (GET/O2 group: FEV1 29% pred; Pa,O2 10.2 kPa at rest; Pa,O2 7.2 kPa at peak exercise). Sa,O2 was not allowed to fall below 90% during the training. The effects on exercise performance while breathing air and oxygen, and on quality of life were compared. Maximum workload (Wmax) significantly increased in the GET/RA group (mean (SD) 17 (15) W, p<0.01), but not in the GET/O2 group (7 (25) W). Six minute walking distance (6MWD), stair-climbing, weight-lifting exercise (all while breathing room air) and quality of life significantly increased in both groups. Acute administration of oxygen improved exercise performance before and after training. Training significantly increased Wmax, peak carbon dioxide production (V'CO2) and 6MWD while breathing oxygen in both groups. Differences between groups were not significant. Pulmonary rehabilitation improved exercise performance and quality of life in both groups. Supplementation of oxygen during the training did not add to the effects of training on room air.
Is outcome from ARDS related to the severity of respiratory failure?
Authors: Ferring M , Vincent JL
Published: February 2003

The characteristics and outcome of acute respiratory distress syndrome (ARDS) may have changed with time. Some studies have reported that mortality is more commonly related to the development of sepsis/multiple organ failure (MOF), and others that it is related to the severity of acute respiratory failure (ARF). The present study evaluates the relative importance of the two phenomena in a large series of patients. The clinical and biological data of all patients who developed ARDS during a 26 month period (January 1993 until February 1995) in our intensive care unit (ICU) were reviewed retrospectively. A total of 129 patients developed ARDS during the study period, representing an incidence of 2.4% of all ICU admissions. The mortality rate was 52%. The primary cause of death was sepsis/MOF (49%), followed by respiratory failure (16%), cardiac failure or arrhythmias (15%), neurological failure (10%), and other causes (8%). The mortality rate was related to age and degree of organ failure. MOF was not always a cause of late death, since half the deaths occurred within 5 days after admission. In addition, mortality was higher in septic than in nonseptic patients, and lower in trauma and surgical than in medical patients. We conclude that sepsis/multiple organ failure is still the most common cause of death in acute respiratory distress syndrome. Improvements in outcome of acute respiratory distress syndrome may depend more on treatment of sepsis and multiple organ failure than on oxygenation measures.
Physiologically based indices of volumetric capnography in patients receiving mechanical ventilation
Authors: Romero PV , Lucangelo U , Lopez Aguilar J , Fernandez R , Blanch L
Published: February 2003

Several indices of ventilatory heterogeneity can be identified from the expiratory CO2 partial pressure or CO2 elimination versus volume curves. The aims of this study were: 1) to analyse several computerizable indices of volumetric capnography in order to detect ventilatory disturbances; and 2) to establish the relationship between those indices and respiratory system mechanics in subjects with normal lungs and in patients with acute respiratory distress syndrome (ARDS), both receiving mechanical ventilation. We studied six normal subjects and five patients with early ARDS mechanically ventilated at three levels of tidal volume (VT). Respiratory system mechanics were assessed by end-expiratory and end-inspiratory occlusion methods, respectively. We determined Phase III slopes, Fletcher's efficiency index, Bohr's dead space (VD,Bohr/VT), and the ratio of alveolar ejection volume to tidal volume (VAE/VT) from expiratory capnograms, as a function of expired volume. Differences between normal subjects and ARDS patients were significant both for capnographic and mechanical parameters. Changes in VT significantly altered capnographic indices in normal subjects, but failed to change ventilatory mechanics and VAE/VT in ARDS patients. After adjusting for breathing pattern, VAE/VT exhibited the best correlation with the mechanical parameters. In conclusion, volumetric capnography, and, specifically, the ratio of alveolar ejection volume to tidal volume allows evaluation and monitoring of ventilatory disturbances in patients with adult respiratory distress syndrome.
A system to generate simultaneous forced oscillation and continuous positive airway pressure
Authors: Farre R , Rotger M , Montserrat JM , Navajas D
Published: February 2003

Assessment of airway obstruction in patients with obstructive sleep apnoea (OSA) subjected to continuous positive airway pressure (CPAP) may be carried out using the forced oscillation technique (FOT). To facilitate routine application of forced oscillation (FO) in sleep studies, our aim was to design a system capable of generating CPAP and applying FOT simultaneously. We constructed a prototype CPAP + FO generator by connecting a specially designed electromagnetic valve in parallel with a conventional blower. The capacity of the prototype to generate forced oscillation (5 Hz +/- 1 hPa) was tested by connecting it to a model simulating spontaneous breathing. The response of the prototype for target CPAPs of 5, 10 and 15 hPa and imposed sinusoidal breathing with peak flow up to 0.75 L x s(-1) was excellent when compared with that reported for commercially available CPAP generators. The applicability of the prototype was tested by applying it to assess airway obstruction in four patients with OSA during sleep. We conclude that the generator designed is able to apply continuous positive airway pressure and forced oscillation simultaneously. The system could be useful for automatic and noninvasive assessment of airway obstruction in patients with obstructive sleep apnoea subjected to continuous positive airway pressure. Future development of the generator may be helpful in implementing a set-up for automatic titration of continuous positive airway pressure.
Current aspects of spontaneous pneumothorax
Authors: Schramel FM , Postmus PE , Vanderschueren RG
Published: February 2003

Although spontaneous pneumothoraces have been recognized and treated for almost 180 yrs, new aspects have emerged concerning pathogenesis, diagnostic procedures and treatment modalities. In spite of the fact that blebs and bullae are frequently found in patients with primary spontaneous pneumothorax, they seldom seem to be the actual cause of the pneumothorax. Inflammatory changes in the distal airways play an important role in the occurrence of the pneumothorax during transpulmonary pressure changes. The value of the routine use of additional expiratory chest radiographs in diagnosing pneumothoraces has been doubted in previous studies. In this review, the diagnostic yield from additional expiratory chest radiographs is analysed. The role of previous pneumothoraces at presentation and the presence of blebs and bullae are discussed in predicting future recurrences and choosing appropriate treatment for optimal cost-effectiveness. Recommendations are made regarding treatment of primary and secondary spontaneous pneumothorax.
Combining cognitive therapy with medication in bipolar disorder
Authors: Watkins Edward
Published: February 2003

Although mood stabilisers have substantially improved the treatment of bipolar disorder, recent studies suggest that treatment with lithium is not as effective as originally claimed. Furthermore, patients still have high rates of relapse even when prescribed medication. Recent research has shown that poor coping strategies in response to bipolar prodromes and disruptions of sleep and social routines increase the risk of relapse. Combining a psychosocial approach with medication may improve the rate of relapse prevention. Cognitive therapy teaches patients better self-monitoring and coping skills and is therefore an appropriate means of minimising psychosocial risk factors for relapse. Recent randomised controlled trials suggest that combined medication and cognitive therapy significantly reduce bipolar relapse compared with medication alone.
Appraisal for consultant medical staff
Authors: Brown Nick , Parry Elizabeth , Oyebode Femi
Published: February 2003

There is a requirement that appraisal of consultants will have been introduced by all National Health Service (NHS) trusts from April 2001. The implication is that all consultants would have had their first annual appraisals by the end of March 2002. In this paper, the authors discuss the development of appraisal as a concept and the societal context in which it has arisen in medicine. They introduce the format for conducting appraisal within NHS trusts and discuss the likely benefits and possible limitations of appraisal.
Antipsychotic-induced hyperprolactinaemia in women: pathophysiology, severity and consequences
Authors: Wieck A. , Haddad P. M.
Published: February 2003

Background

Hyperprolactinaemia has for decades been an inevitable and neglected side-effect of antipsychotic medication. The recent introduction of prolactin-sparing antipsychotic agents makes a re-examination of this problem timely.

Aims

To review the literature on antipsychotic-induced hyperprolactinaemia and its consequences.

Method

A search was made of the Medline database (1966–2002) for key articles, supplemented by cross-referencing.

Results

During antipsychotic treatment prolactin concentrations can rise to ten times normal levels or above, and existing data indicate that 17–78% of female patients have amenorrhoea with or without galactorrhoea. Survey data, however, suggest that clinicians underestimate the prevalence of these conditions. Long-term consequences of antipsychotic-related hypo-oestrogenism require further research but are likely to include premature bone loss.

Conclusions

Antipsychotic-induced hyperprolactinaemia should become a focus of interest in the drug treatment of psychiatric patients.
Neurocognitive impairment in drug-free patients with major depressive disorder
Authors: Porter Richard J. , Gallagher Peter , Thompson Jill M. , Young Allan H.
Published: February 2003

Background

Although neurocognitive impairment has been widely reported in major depressive disorder (MDD), confounding factors, such as the effects of psychotropic medication, have rarely been controlled for.

Aims

To examine neurocognitive function in medication-free patients with MDD and healthy controls.

Method

Forty-four patients meeting DSM–IV criteria for MDD, all psychotropic-medication-free for at least 6 weeks, and 44 demographically matched, healthy comparison subjects completed a comprehensive neurocognitive battery.

Results

Patients with depression were impaired significantly in a range of cognitive domains, including attention and executive function and visuospatial learning and memory, compared with controls. Motor and psychomotor functions were intact. Severity of depression correlated with learning and memory performance, but not executive function.

Conclusions

Pronounced neurocognitive impairment was found in this sample of young adult out-patients with MDD. This is not attributable to the confounding effects of psychotropic medication and could therefore provide an objective marker of brain dysfunction in depression.
Service innovations: the Orchard Clinic: Scotland's first medium secure unit
Authors: Nelson D.
Published: February 2003

The development of forensic psychiatry provision in Scotland lags behind that in other parts of the United Kingdom. Until recently, there were no medium secure units in the country and mentally disordered offenders (MDOs) requiring such care had to be managed in intensive psychiatric care unit (IPCU) settings. In November 2000, The Orchard Clinic, a medium secure unit sited at the Royal Edinburgh Hospital, was opened. This paper discusses the background to this development, the government policies setting out plans for the care, services and support of MDOs in Scotland, progress and work of the new unit to date and plans for developments in other parts of Scotland.
Acute hospital care in inner London: splitting from mental health services in the community
Authors: Dratcu Luiz , Grandison Alistair , Adkin Antony
Published: February 2003

Acute hospital care in psychiatry has been described as inefficient and disorganised (Muijen, 1999). Worrying as it may be, this is neither new nor surprising. Following the closure of large mental institutions and the advent of community care, hospital services were supposed to provide acute in-patient care as part of a wider system. Long-term needs of patients in the community should henceforth be met by community services that would be fully equipped and resourced to undertake this task. However, it was not long before acute wards were overwhelmed by occupancy rates of 100% and above, particularly in inner cites (Powell et al, 1995). The reason for the ‘bed crisis' that followed seems essentially twofold: community services were neither equipped nor resourced as required, and the number of acute beds was not adjusted to the ensuing demand. As hospital care has come to represent the only option for many patients whose needs could not be met in the community, acute wards have become overcrowded and ‘a bizarre and illogical mixture … of old and young, male and female, psychotic and depressed, retarded and agitated and voluntary and detained’ (Muijen, 1999).
A survey of referrers' satisfaction with a regional forensic psychiatric service: what do they want?
Authors: Papanastassiou Maria , Roche Sean , Boyle John , Baxter Richard , Chesterman Paul
Published: February 2003

Aims and Method

The perceptions and expectations by referrers of assessments performed by a medium secure unit were examined in order to ascertain areas for possible improvement. All referrals to two teams at the North West Thames Regional Secure Unit were monitored over a 6-month period. A self-report questionnaire was sent to each referrer, in cases where an assessment and forensic report had been completed.

Results

Assessments and forensic reports were completed (and questionnaires sent to referrers) in 63% of total referrals (32 out of 51). The response rate to the questionnaire was 81% (26 out of 32). Many referrers wanted the assessments and report to be completed in 2 weeks. Most referrers were satisfied with the quality of the report received and the majority were happy with the risk assessment.

Clinical Implications

Referrers want forensic assessments to be of a high quality and to be performed quickly. Recommendations for service development are suggested.
A study of cutting forces and surface finish in high-speed machining of AISI H13 tool steel using carbide tools with TiAIN based coatings
Authors: Mativenga P T , Hon K K B
Published: February 2003

High-speed machining (HSM) has emerged as a key technology in rapid tooling and manufacturing applications. In this study, the effect of increased spindle speeds on surface finish is examined. Physical vapour deposition (PVD) coated ball-nose micrograin carbide tools are used in finishing cuts for spindle speeds up to 42 000 r/min and a real-time force acquisition system is used to study the orthogonal forces. The importance of orthogonal force components to surface finish prediction and control is explored. The results show that Fz axial force has a very strong correlation with surface finish and that increased spindle speeds lead to far superior surface finish. Multilayer TiAIN coated carbides were found to generate the best surface finish while the uncoated tool and TiAIN + WC/C lubricant coating led to a severe degradation of surface finish at increased spindle speeds.
Pressure-based in-process measurement by the null method for automatic compensation of wheel wear during surface grinding
Authors: Furutani K , Hieu N T , Ohguro N , Nakamura T
Published: February 2003

This paper deals with automatic compensation of grinding wheel wear in wet grinding by pressure-based in-process measurement. A pressure sensor is set close to a grinding wheel with a small gap. When grinding fluid is dragged into the gap by the rotation, the wear of the grinding wheel can be predicted by using hydrodynamic pressure that has been generated, which corresponds to the gap thickness and topography of the surface. This method was applied to a numerically controlled surface grinding machine. Some characteristics of the pressure were measured. The pressure sensor was repositioned to keep the pressure constant with the null method. The spindle was also repositioned according to the sensor displacement, which was equal to the worn thickness of the grinding wheel. The error of the ground depth with compensation was less than the feeding step for the compensation. The measurement performance by the null method was compared with that obtained without compensation, with compensation by a deflection method and by the contact method.
Dynamic characteristics of a drill in the drilling process
Authors: Huang B W
Published: February 2003

The dynamic characteristics of high-speed drilling were investigated in this study. To improve quality and produce a higher production rate, the dynamic characteristics of the drilling process need to be studied. A pre-twisted beam is used to simulate the drill. The moving Winkler-type elastic foundation is used to approximate the drilling process. A time-dependent vibration model for drilling is presented. The spinning speed, pre-twisted angle and thrust force effects of the drill are considered. The numerical analysis indicates that the natural frequency is suddenly reduced as the drill moves into a workpiece.
Quality assurance for concave-arc ball-end milling cutters
Authors: Chen W-F , Lai H-Y , Chen C-K
Published: February 2003

This paper presents a systematic modelling procedure for assessing the profile quality of concave-arc ball-end (CABE) milling cutters with a cylindrical shank. CABE milling cutters are widely used in three-axis numerical control (NC) machines for producing dies and moulds of complicated surface features. Evaluation of the contour quality of the CABE milling cutter is crucial in enhancing machining accuracy and efficiency. In order adequately to describe the shape of the clamped cutter, the centre-line axis of the minimum circumscribed cylinder of the cylinder shank is taken as the referenced datum axis. The minimum circumscribed concave-arc revolving surface and the minimum circumscribed spherical surface are carefully derived in sequence. The profile errors and tolerances are estimated. The quality of the CABE milling cutter is assured by using the proposed modelling procedure, and several numerical examples are presented to illustrate its effectiveness. The results indicate that the present method is feasible and can be extended to enhance the quality of various revolving cutters.
The practical application of design risk assessment models
Authors: Crossland R , Williams J Sims , McMahon C
Published: February 2003

This paper describes three case studies of the application of quantitative design risk assessment methods in practice. The studies arose out of a survey of risk practice in design which showed that leading edge companies use quantitative methods of risk assessment in assessing both project risk, which may be defined as the risk to cost and time-scale, and technical risk, which may be defined as the risk that the designed artefact will not meet its functional requirements. The first case study concerns a coastal defence programme and is primarily concerned with technical risk. The second study is concerned with the installation of a replacement bridge and is primarily concerned with project risk. The final study describes an aerospace engine design programme that involved both technical and project risks The paper first presents a generic overview of the risk management process and then describes, for each of the three study domains, how risk is identified, how risk assessment is carried out, including prioritization and uncertainty modelling, what risk treatment steps are undertaken and how risks are monitored. Outcomes in the three studies are shown to be a whole-life cost-benefit uncertainty model for assessing design alternatives, a method for incorporating uncertainty into task criticality as well as task duration in the activity network for a design project and a method for aggregating uncertainty in design attributes over the basic product model.
Design and application of hybrid software for modelling die components and the die assembly
Authors: Singh R , Sekhon G S
Published: February 2003

This paper describes the design and application of hybrid modelling software for assisting die designers working in small and medium-sized sheet metal enterprises. The proposed procedure utilizes AutoLISP and AutoCAD for fast modelling of die components and the die assembly. The proposed die modelling software AUDIEDR comprises seven modules, namely DIEMOD, STRPRMOD, BPPPPMOD, BDSTMOD, TDSTMOD, BDIEASS and TDIEASS. The interfacing of AutoLISP with AutoCAD facilitates automatic drafting of die components and the die assembly. The software is written in AutoLISP and is loaded in the prompt area of AutoCAD. The program allows the user firstly to model the blank drawing. It then prompts the user to pick pregenerated data files for each die component and automatically models the die components and the die assembly using the above-mentioned modules sequentially. The chief feature of the software is its facility of interfacing die design with drafting. The software can be operated in a Windows environment on a PC/AT. An illustrative example has been included to demonstrate the usefulness of the proposed system. The software also helps create a library of die components. The modelling system can be modified depending upon the requirements of the specific shop floor. The low cost of the system makes it affordable for planners working in small and medium-sized enterprises.
An investigation of stability and pattern formation in reaming
Authors: Epureanu B I
Published: February 2003

One of the important factors affecting the quality of a surface manufactured by reaming is chatter. In this paper, chatter is investigated by means of a numerical linear stability analysis. The trajectory of the centre of the tool is discretized in time and an eigenvalue problem is solved to determine the formation and evolution of patterns on the manufactured surface. The pattern forming process is shown to be unstable under certain circumstances. The unstable patterns lead to a wavy profile of the workpiece, as often observed in practice. In contrast, the stable patterns are shown to disappear during reaming due to the exponential decrease in their magnitude, thus leading to a fixed location for the centre of the tool and a circular final profile of the workpiece. The unstable patterns grow in magnitude until non-linear effects become important and limit their growth. Some of these important non-linear phenomena are analysed. Specifically, the non-linear analysis is based on the limited allowed slope of the profile of the workpiece. Numerical examples for a typical reaming system are presented and the final patterns obtained are shown to be similar to experimental observations.
On the construction of a general numerical tyre shear force model from limited data
Authors: Sharp R S , Bettella M
Published: February 2003

The extension of very limited tyre shear force and moment measured results to allow the modelling and simulation of quite general motions of automobiles is discussed. Relying on a recently devised algorithm that has its basis in magic formula and parameter normalization methods, processes are devised for determining the necessary parameter values of the algorithm. The method is applied to two tyres that are substantially different in nature. Where data are lacking, fundamental knowledge of tyre mechanics is applied to the problem of obtaining the best values. Results are included to demonstrate the effectiveness of the processes. Datasets for the particular tyres treated and the algorithm itself are included.
Determination of the crash pulse and optimization of the crash components using the response surface approximate optimization
Authors: Hong U P , Park G J
Published: February 2003

Computational occupant analysis has been performed with a pre-determined crash pulse which is produced from a real test. The involved crash components are designed on the basis of the results of the analysis. This method has limitations in that the design does not have much freedom. However, if a good crash pulse is proposed, the occupant's injuries can be reduced more effciently and the body structure can be modified to generate the crash pulse. A good crash pulse is a deceleration curve that minimizes injuries to unrestrained occupants. In this research, a preferable crash pulse is generated by an optimization method called the response surface approximate optimization (RSAO). RSAO is a modified algorithm from a response surface method. The crash pulse is determined to minimize occupant injury while the related physics are satisfied. An RSAO in a commercial code is utilized by interfacing it with an in-house occupant analysis program called SAFE (safety analysis for occupant crash environment). Design of the involved components is carried out on the basis of the generated crash pulse by optimization. The RSAO is also used in this design process. The advantages of the RSAO are investigated as opposed to other design methods, and the results are compared and discussed.
Fluidized bed combustion systems for power generation and other industrial applications
Authors: Minchener A. J.
Published: February 2003

Fluidized bed combustion (FBC) in various forms has been used to burn all types of coal, coal waste and a wide variety of other fuels, either singly or cofired with coal. FBC boilers are currently available commercially in the capacity range from 1 MWth to over 250 MWe and continue to be adopted for a variety of commercial, industrial and power generation applications. There are two main derivatives of FBC, namely bubbling fluidized bed combustion (BFBC) and circulating fluidized bed combustion (CFBC). There are also several hybrid systems and pressurized versions of both BFBC and CFBC. The status of these different systems, with some now fully commercial and some still under development, is described, with projections made for future development requirements and market opportunities.
PF-fired supercritical power plant
Authors: Chew P. E.
Published: February 2003

Pulverized fuel firing is the dominant application of supercritical steam cycles. This has been driven by the aims of efficiency improvement and reduction in environmental emissions. The sensitivity of supercritical steam plant to operating conditions is reviewed and the improvements in operating plant efficiency achieved through increase in steam pressure and temperatures and other factors such as auxiliary power demand is illustrated. Steam temperatures have increased by about 40°C during the 1990s and this, together with an increase in main steam pressure and cycle improvement, have led to a net efficiency of 45 per cent (reduced to UK conditions) for the state-of-the-art plant at present. Plants with still more advanced conditions are under construction or are planned, with the prospect of plant efficiency of 50 per cent in the future. This will rely on continued improvement in materials and is supported by a number of European programmes. Some main difficulties in the design of boilers with advanced temperatures, in particular steam temperature at the furnace outlet, furnace tube arrangement, and materials for superheater and reheater outlet sections, are discussed and the state of advanced steam turbines is reviewed. The operational availability of the supercritical plant, at least in Europe, has improved such that it is little different to the subcritical plant. Similarly, significant improvements have been made in controlling emissions by refinement of flue gas clean-up systems and combustion technology.
The gravity pump: A new approach to a natural energy water pump
Authors: Young B
Published: February 2003

The double-acting gravity pump is an environmentally friendly, positive-displacement device for pumping surface water using the natural energy resource of falling water as its motive power. The genesis of this design of pump derived from a need to generate high delivery pressures for rural water supply projects in the developing world; pressures that were beyond the capacity of the conventional ram pump. The paper outlines the theory behind the operation of the gravity pump and goes on to describe an experimental programme carried out on a prototype in order to prove the concept. The results of the experiments confirm the theoretical analysis in all respects and the performance of any configuration of gravity pump may now be forecast with confidence. The paper describes a second prototype pump destined for field trials, which is currently in the course of a construction. This version incorporates a number of design improvements following from the experience gained in building and testing the first pump. Research and development of the gravity pump is supported by an Invention and Innovation Award from the National Endowment for Science, Technology and the Arts (NESTA).
Flow field, turbulence and critical condition at a horizontal water intake
Authors: Marghzar Sh. H. , Montazerin N , Rahimzadeh H
Published: February 2003

This paper presents a study on the flow structure and turbulence characteristics of a horizontal water intake. The geometry is a basic configuration that is instrumental in the validation of experimental and numerical procedures, which could then be developed to a more complex geometry with more complicated flow patterns. Parallel to the experimental investigations, a three-dimensional numerical code for the prediction of any gravitational turbulent flow has been developed. This code assumes a flat free surface, but allows pressure contours over it. The three velocity components and their fluctuations at different water depths inside the intake bay are measured with a laser Doppler anemometer. This is then used to show the transition from the approach channel to the pipe and its importance on the flow structure and critical condition. A notable feature is that the streamwise component of the velocity in the channel accelerates from upstream to reach the pipe velocity in a length that is limited to twice the pipe diameter. The turbulence intensity is an index that identifies positions where free surface and subsurface vortices may form. Measurements and predictions are possible for the critical condition and its corresponding water level. The notable observation is that critical condition in this symmetric intake occurs with no swirl at the free surface.
Survey of thermodynamic methods to improve the efficiency of coal-fired electricity generation
Authors: Rosen M. A. , Dincer I
Published: February 2003

Some of the more significant thermodynamic methods to improve the efficiency of coal-based electricity generation technologies are surveyed and examined, focusing on minor practical improvements that can be undertaken with limited effort and cost. Two categories of methods are examined. The first is efficiency-improvement techniques such as better maintenance and control, application of exergy and related analysis methods, and use of computer-based simulation, analysis, optimization, and design. The second category includes efficiency-improvement measures for devices, including steam generators, condensers, reheaters, and regenerative feedwater heaters. A case study is presented. It is concluded, for coal-fired electricity generation plants, that (i) many useful techniques exist (especially exergy analysis) and should be used for identifying and designing efficiency improvements, and (ii) the many possible measures to improve efficiency should be weighed against other factors and where appropriate implemented. Where larger efficiency increases are sought, improvements applicable over longer time frames and of a broader nature should be investigated.
Towards long length scale unsteady modelling in turbomachines
Authors: Xu L , Hynes T. P. , Denton J. D.
Published: February 2003

The modelling issue of long length scale unsteadiness in turbomachines is discussed in this paper and a new three-dimensional CFD method with a hierarchy of body force models is proposed. A program has been developed to deal with the long length scale problem using efficient coarse meshes and large time steps, together with body force models. The distributed viscous body force can be calculated either using a very simple viscous wall shear stress model or extracted from a ‘stand-alone’ three-dimensional single passage steady calculation using a fine mesh. By eliminating the need to compute fine viscous scales, the proposed method is several orders of magnitude more efficient than ‘standard’ fine mesh N-S unsteady calculations while maintaining respectable resolution down to the scale of blade-to-blade variation, including wake/potential interactions between blade rows. Two sample cases with high-frequency low-amplitude and low-frequency high-amplitude, respectively, are used to illustrate the accuracy of the model.
Prediction of NOX emissions in gas turbine combustors inclusive of the N2O contribution
Authors: Lentini D
Published: February 2003

A model is presented to account for NO emissions due to both the thermal and the nitrous oxide pathways, and to quantify emissions of N2O itself. The model is applied to a hypothetical combustor operating at typical take-off conditions, as high-pressure conditions are expected to emphasize the role of the nitrous oxide pathway. Predictions suggest that this pathway may turn out to be a significant source in such conditions, contributing about 15% to total NOx emissions.