bluuebunny/crossref_metadata_2025 huggingface dataset:
The need for European Union information amongst women in the United Kingdom: results of a survey
Authors: Marcella Rita
Published: November 2002

This paper describes the results of an exploratory survey by questionnaire distributed via a variety of information agencies, designed to investigate women’s information needs and patterns of information‐seeking behaviour in relation to the European Union. The results explore women’s attitudes to information and its value to them in a range of different life contexts, as well as their use of information agencies and of information and communications technologies. The results show that women value information highly and that they search for and use a wide range of categories of information in relation to education and their professional and personal life. Findings also suggest that respondents tend to predict high levels of future use of European information, in particular in relation to democratic participation and self development. Women were conscious of barriers to information access and suggested a
range of measures that might improve access. They were generally positive about participating in training in the use of electronic networks and about the likelihood of their using networks to access information about the European Union.
Semiotics and indexing: an analysis of the subject indexing process
Authors: Mai Jens‐Erik
Published: November 2002

This paper explains at least some of the major problems related to the subject indexing process and proposes a new approach to understanding the process, which is ordinarily described as a process that takes a number of steps. The subject is first determined, then it is described in a few sentences and, lastly, the description of the subject is converted into the indexing language. It is argued that this typical approach characteristically lacks an understanding of what the central nature of the process is. Indexing is not a neutral and objective representation of a document’s subject matter but the representation of an interpretation of a document for future use. Semiotics is offered here as a framework for understanding the “interpretative” nature of the subject indexing process. By placing this process within Peirce’s semiotic framework of ideas and terminology, a more detailed description of the process is offered which shows that the uncertainty generally associated with this process is created by the fact that the indexer goes through a number of steps and creates the subject matter of the document during this process. The creation of the subject matter is based on the indexer’s social and cultural context. The paper offers an explanation of what occurs in the indexing process and suggests that there is only little certainty to its result.
Consistency of textual expression in newspaper articles: an argument for semantically based query expansion
Authors: Lehtokangas Raija , Järvelin Kalervo
Published: November 2002

This article investigates how consistent different newspapers are in their choice of words when writing about the same news events. News articles on the same news events were taken from three Finnish newspapers and compared in regard to their central concepts and words representing the concepts in the news texts. Consistency figures were calculated for each set of three articles (the total number of sets was sixty). Inconsistency in words and concepts was found between news articles from different newspapers. The mean value of consistency calculated on the basis of words was 65 per cent; this however depended on the article length. For short news wires consistency was 83 per cent while for long articles it was only 47 per cent. At the concept level, consistency was considerably higher, ranging from 92 per cent to 97 per cent between short and long articles. The articles also represented three categories of topic (event, process and opinion). Statistically significant differences in consistency were found in regard to length but not in regard to the categories of topic. We argue that the expression inconsistency is a clear sign of a retrieval problem and that query expansion based on semantic relationships can significantly improve retrieval performance on free‐text sources.
An evaluation of the information needs and practices of part‐time and distance‐learning students in the context of educational and social change through lifelong learning
Authors: Rowland Fytton , Rubbert Iris
Published: November 2002

The information needs and practices of part‐time and distancelearning students in higher education (HE) in the UK outside the Open University (OU) have been evaluated. In recent years, the government has pointed out the importance of individuals engaging in lifelong learning initiatives, in order to remain competitive in a globalised economy which draws increasingly on cumulative
knowledge creation. In response, the HE sector in the UK offers a growing number of its programmes on a part‐time and/or distance‐learning basis for students who can remain in full‐ or part‐time employment while studying for their qualifications. We trace the history of adult education with its corresponding study modes, and set the experience of students within the wider framework of educational change in the information society. We distributed a questionnaire and conducted telephone and face‐to‐face interviews with a substantial sample of part‐time and distance learners. Based on our research findings, we question whether the information‐gathering
practices of part‐time and distance‐learning students best reflect the pedagogical concept of lifelong learning. Our results show that university libraries considered in our sample often do not cater for the specialised needs of part‐time and distance learners, which leads to an increasing use of the Internet and employer resources as a substitute for traditional information channels. Students have major problems coping with the complexity of the WWW, and we make recommendations on how to improve existing information services in HE.
A user‐centred approach to the evaluation of a hybrid library project
Authors: Jackson Maureen
Published: November 2002

The Hybrid Library of the Future (HyLiFe) project was funded by the Joint Information Services Council (JISC) for higher education in the UK and it focused on the users of the hybrid library. This article outlines the user‐centred approach used in evaluating the project. While the evaluation of HyLiFe diverged from much standard practice in performance measurement, the work of researchers into performance measures for the electronic library proved invaluable to the HyLiFe evaluation officer.
Records management and the capture of tacit knowledge
Authors: Sanderson Martin
Published: November 2002

The purpose of this paper is to consider the question ‘is it necessary and appropriate for records managers to play a role in identifying and capturing tacit knowledge into records and maintaining them accordingly, and by doing so safeguarding the organisation’s intellectual assets, moving human capital into structural capital’? Nonaka emphasises that tacit knowledge is a main source for creating new knowledge and continuous innovation. The need for, and ability of, organisations to capture tacit knowledge remains a disputed academic issue. Considering Nonaka’s hierarchy of data → information → knowledge, the need for a reverse movement from knowledge → information seems to be a fair and logical conclusion. Making the case for capturing tacit knowledge, this paper goes on to discuss some of the implications for records management and records managers. There are no easy solutions on offer for the successful capture and re‐use of tacit knowledge but questions are raised about the role of records managers. Developing relevant skills and taking responsibility for helping organisations with this strategic goal, thereby contributing to some core aspirations of our employers, should be an exciting prospect and worthwhile activity.
Appraisal based on organic functional analysis: a case study in an electronic records environment
Authors: Carvalho Cristina
Published: November 2002

This article is a shortened version of a Master’s dissertation for the Liverpool University Centre for Archive Studies. It deals with issues of appraisal. Such issues involve fundamental concepts on what records are, why they are kept, and their life cycle. The answers to these questions were sought and found in the history of archives, and in the specialist literature. The theory and the methodology adopted were then applied to a case study of a recently established organisation in Lisbon, which has, at the core of its business, information in electronic format.
Profiling brand‐piracy‐prone consumers: an exploratory study in Hong Kong’s clothing industry
Authors: Phau Ian , Prendergast Gerard , Hing Chuen Leung
Published: November 2002

This research profiles consumers of pirated products, specifically pirated brands of clothing. Utilising a structured questionnaire and counter‐biasing statements, results from face‐to‐face street‐intercept interviews showed that low spenders on pirated brands of clothing are mainly people aged 19 to 24 with a blue‐collar occupation, relatively low monthly income, secondary education level, and no children. High spenders on pirated brands are in the age bracket 25‐34 with white‐collar jobs, a monthly income of HK$10,000‐HK$19,999, tertiary or university education, and children. Consumers identify pirated brands of clothing usually by lower price and buying location, but price was not the sole determinant for purchase. Finally, they bought the pirated brands mainly for private use. Based on these results, the paper makes recommendations to original brand manufacturers and policy makers for combating pirated products.
A detailed study calculating the cost of preparing a collection
Authors: Aktuglu Ziynet
Published: November 2002

Preparing a collection is a costly process when compared with mass production. Although it is a short‐run process, there are high unit costs due to the need for ordering knitted or woven material, and making necessary preparations for print and stitch patterns. All of these factors increase the cost of collection samples. Because the amount of material to be used for the preparation of the collection is small, having the material knitted or woven, or having it dyed, if it is raw, is more expensive compared with mass production. However, if the company trusts its own collection and receives positive feedback from its customers, it may consider using the material for production and keep the orders at a high level, thus decreasing the unit price. The purpose of this study is to put forward methods of calculating expenses for preparing a collection and collection costs. It also presents a sample application using present‐day values to give a comparison of collection samples with mass production samples. This makes it possible to come up with the most profitable production techniques. For this purpose, 40 T‐shirt designs were made; of these, ten models with different production features were carefully selected. Production steps were classified and the cost for each step was then calculated. By adding the cost of each step together, unit model cost was found. The collection cost was determined in the same way. It has been observed that the costs increase according to the raw material, auxiliary equipment, accessories, side processes and labour.
“Did you hear what Tommy Hilfiger said?” Urban legend, urban fashion and African‐American generation Xers
Authors: McNeil Kimberly R. , Johnson Olenda E. , Johnson Ann Y.
Published: November 2002

The purpose of this study is to examine the influence of an urban folktale on the purchasing intentions and buying behaviour of the consumer. Specifically, it examines a rumour involving fashion designer Tommy Hilfiger, in which he purportedly made disparaging statements about African‐Americans. A survey of African‐American generation Xers revealed a relationship between the rumour and the decision to purchase Tommy Hilfiger clothing. Implications of the findings are discussed.
Quality in international clothing supply chains: cost versus quality
Authors: Popp Andrew , Ruckman J.E. , Rowe H.
Published: November 2002

Building on a series of earlier studies of the relationship between quality and international clothing supply chains, this paper focuses on the role of independent test houses in order to further explore the tensions between cost and quality imperatives operating in the process of internationalisation. The paper, using qualitative data derived from semi‐structured face‐to‐face interviews, first establishes a theoretical perspective on the position of testing and the test house in the supply chain, before turning to an examination of the cultural attributes of test houses, retailers and manufacturers. This approach allows for an assessment of the value accorded to quality issues. The paper concludes by stressing the dominance of the cost imperative.
Service‐enhanced manufacturing: a study of perceived service quality of apparel manufacturers
Authors: Kin‐man To Chester , Leung Chun‐sun
Published: November 2002

Within the last decade of the twentieth century, the apparel industry in Hong Kong has been undergoing drastic changes. These changes mainly stem from the challenges of process globalization, which has led to manufacturers shifting a majority of production processes to countries that entail better cost‐competitive advantages, while retaining crucial planning and decision‐making services centrally. Industrialists, educators and even the Government have made a great deal of effort to enhance the provision of high quality service in an attempt to transform the industry strategically into a centre of service excellence in the South‐East Asian region. However, without accredited standard and reference points, the measuring and monitoring of quality in manufacture‐related service is very vague and perplexing. In this paper, the authors first review the extant literature for measuring perceived quality in service provision and then explore the respective implementation issues. A Servqual scale in three‐column format, adapted from the service quality measurement scale proposed by Parasuraman (1995), is used to survey the opinion of international buying offices and to assess the Hong Kong apparel manufacturers’service performance. Two expectation‐discrepancy standards in Service Adequacy and Service Superiority are constructed to measure the service deficiency (gaps). As a result the authors learnt that there are empirical differences between what is perceived in the existing manufacturer’s service performance and what the buyer side really desires. The paper concludes with a discussion of the Servqual modelling operational implications and future research directions.
Cutting With High-Pressure Ammonia Jets for Demilitarization of Chemical Weapons
Authors: Hashish Mohamed , Miller Paul L.
Published: November 2002

This paper presents a study on using high-pressure ammonia and abrasive ammonia jets for cutting and washout of chemical weapons. The work focused on chemical rocket M55 simulants. A test chamber was built to cut M60 training and M61 practice rockets at Redstone Arsenal by Teledyne-Commodore who developed a complete destruction process using alkali metals dissolved in anhydrous ammonia to form the aggressive solvated electron technology (SET™) solution. The rocket is loaded in a rotary chuck and stationary cutting/piercing nozzles were used to cut and drill through the rocket. This approach was found to be effective due to minimizing the number of moving parts. High-pressure direct drive and intensifier pumps were developed for this application. It was found that intensifier-based pumps are more suitable for robust field use. The abrasive ammonia jets performed well for cutting the rocket metal shell (aluminum and steel) casing as well as the outside fiberglass case. A wash-out-ammonia jet lance has also been found to completely wash out the simulant materials. Over 20 rockets were successfully cut by Teledyne personnel without any incidents. It was concluded that the use of anhydrous ammonia has numerous advantages over conventional water for chemical weapon demilitarization applications.
Avoiding Thermoacoustic Vibration in Burner/Furnace Systems
Authors: Eisinger Frantisek L. , Sullivan Robert E.
Published: November 2002

Burner/furnace systems are generally sensitive to thermoacoustic vibration due to the presence of large temperature differentials between the cold burner air and the hot furnace gases. The systems are predicted to vibrate when the temperature ratio between the hot and cold components reaches a critical value and when the acoustic mode shape of the combined system develops into a Rijke or a Sondhauss tube type. Original full-scale large-utility steam generator systems which vibrated in operation and modified systems resisting the vibration are described and explained. Guidelines for designing systems resistant to thermoacoustic vibration are also given to aid the designers.
Analysis of the Thermal Hydraulic Consequences Following Common Mode Pump Seizure in a Nuclear Power Plant
Authors: Chatterjee B. , Gupta S. K. , Kushwaha H. S. , Raj V. Venkat
Published: November 2002

In nuclear power plants, the primary heat transport system (PHTS) is designed according to ASME Section 3 Division 1. The PHTS together with Primary Coolant Pumps (PCPs) is designed so that the integrity under safe shutdown earthquake (SSE) is maintained. However, the operability under SSE may not be ensured. There might be a possibility of seizure of PCPs under SSE. The pump seizure has two thermal hydraulic effects. The flow sharply reduces and the kinetic energy of the fluid gets converted into pressure pulses. The magnitude of the pulse depends on the locked pump rotor flow resistance. The reduction in the flow affects the heat transfer in the core and the steam generator in different ways. This mismatch between the heat received and rejected by the PHTS results in high system pressure inspite of relief valves. This paper presents and discusses the aforementioned two effects for the case of a PHWR. The study shows that the peak pressure reached during the transient is much higher than the operating pressure. The system integrity may be affected if the peak pressure is significantly higher than the design pressure.
Weld Characterization and Residual Stress Measurements for TC-128B Steel Plate
Authors: Sutton M. A. , Abdelmajid I. , Zhao W. , Wang D. , Hubbard C.
Published: November 2002

Welding is the primary joining process used in the construction and repair of railroad tank cars. Since recent federal regulations have emphasized the need for fatigue life analyses, and since most fatigue cracks and fractures in tank car structures are initiated in the vicinity of welds, there is a need to quantify the effect of tank car weld residual stresses on crack propagation and fracture. Thus, for the first time, the enclosed work reports neutron diffraction results for all six components of the three-dimensional residual stress field on a transverse weld cross section in a 5/8-in. (16.3-mm) thick, TC128-B steel widely used in the construction of pressurized railroad tank cars. Results for a nonheat- treated specimen indicate that (a) the residual effective stress ranges from 36 ksi (250 MPa) to 64 ksi (450 MPa) in the overmatched weld region, (b) the longitudinal residual stress approaches 120% of the uniaxial yield stress in the base material, and (c) the residual shear stresses are of the same order as the smaller principal residual stresses in the weld region.
Correlation of Test and FEA Results for the Nonlinear Behavior of Straight Pipes and Elbows
Authors: Tan Ying , Matzen Vernon C. , Yu Lixin
Published: November 2002

This paper summarizes the literature on reconciliation of finite element analyses with in-plane bending experiments on piping elbows. It then describes in detail two four-point-bending tests on straight pipes and two in-plane bending tests on elbows and the corresponding nonlinear finite element analyses. Using a new procedure for obtaining a stress-strain curve for stainless steel using only values for E,Sy, and Su and a representative stress-strain curve from a test on a similar material specimen, the nonlinear responses of the piping components tested are shown to be simulated more accurately than previously published results.
Separated Flow Transition Under Simulated Low-Pressure Turbine Airfoil Conditions—Part 2: Turbulence Spectra
Authors: Volino Ralph J.
Published: November 2002

Spectral analysis was used to investigate boundary layer separation, transition and reattachment under low-pressure turbine airfoil conditions. Cases with Reynolds numbers ranging from 25,000 to 300,000 (based on suction surface length and exit velocity) have been considered at low (0.5%) and high (9% inlet) free-stream turbulence levels. Spectra of the fluctuating streamwise velocity and the turbulent shear stress are presented. The spectra for the low free-stream turbulence cases are characterized by sharp peaks. The high free-stream turbulence case spectra exhibit more broadband peaks, but these peaks are centered at the same frequencies observed in the corresponding low turbulence cases. The frequencies of the peaks suggest that a Tollmien-Schlichting instability mechanism drives transition, even in the high turbulence cases. The turbulent shear stress spectra proved particularly valuable for detection of the early growth of the instability. The predictable nature of the instability may prove useful for future flow control work.
Optimum Strain Gage Application to Bladed Assemblies
Authors: Szwedowicz J. , Senn S. M. , Abhari R. S.
Published: November 2002

Optimum placements of the strain gages assure reliable vibration measurements of structural components such as rotating blades. Within the framework of cyclic vibration theory, a novel approach has been developed for computation of the optimum gage positions on tuned bladed disks regarding the determined sensitivity, orthogonality, gradient and distance criteria. The utilized genetic algorithm optimization tool allows for an effective numerical search of suitable solutions of the defined optimization function. A rotating impeller disk represented by a cyclic finite element model demonstrates the application of this method. The present technique can be easily applied to other structural components requiring optimal strain gage instrumentation.
The Use of Sweep and Dihedral in Multistage Axial Flow Compressor Blading—Part I: University Research and Methods Development
Authors: Gallimore Simon J. , Bolger John J. , Cumpsty Nicholas A. , Taylor Mark J. , Wright Peter I. , Place James M. M.
Published: November 2002

This paper describes the introduction of 3-D blade designs into the core compressors for the Rolls-Royce Trent engine with particular emphasis on the use of sweep and dihedral in the rotor designs. It follows the development of the basic ideas in a university research project, through multistage low-speed model testing, to the application to high pressure engine compressors. An essential element of the project was the use of multistage CFD and some of the development of the method to allow the designs to take place is also discussed. The first part of the paper concentrates on the university-based research and the methods development. The second part describes additional low-speed multistage design and testing and the high-speed engine compressor design and test.
Micro Air Injection and Its Unsteady Response in a Low-Speed Axial Compressor
Authors: Nie Chaoqun , Xu Gang , Cheng Xiaobin , Chen Jingyi
Published: November 2002

A new approach, steady micro air injection from the casing, is proposed to improve the stability of a three-stage low-speed axial compression system. Although the injection rate is designated to be only a few ten thousandth of the compressor flow rate, such an injection is able to trigger the unsteady response and thus lower the mass flow rate at stall for up to 5.83%. At the same time, it keeps the steady compressor characteristic with no injection unchanged. In order to verify that the compressor response is indeed unsteady, experiments at various injection configurations are performed, which include different injection angles, axial gaps between injector and blade leading edge, radial penetration of injector and the amount of injected air. Evidences of the unsteady response are further demonstrated through dynamic signal analysis using a wavelet-based method to show the behavior of early flow disturbances under the influence of injection. Numerical analyses performed at near stall condition show that the tip clearance vortices do response to the micro-injection, and thus delay the inception of stall.
Alternative Fatigue Lifetime Prediction Formulations for Variable-Amplitude Loading
Authors: Nijssen R. P. L. , van Delft D. R. V. , van Wingerde A. M.
Published: November 2002

Accurate prediction of lifetime is an increasingly important issue for wind turbine rotor blade materials. Coupon tests with the variable-amplitude standard loading sequences for wind turbines known as WISPER and WISPERX have indicated that the coupon lifetime can be overestimated by one or two orders of magnitude using conventional lifetime prediction formulations. In the actual design, this might be compensated for by conservative design factors covering other aspects such as environmental conditions. These conventional lifetime prediction formulations use Rainflow counting of the load history, a log-log SN-curve (stress- or strain amplitude versus cycles to failure) for R = −1, a linear Goodman diagram as a constant-life diagram, and Miner summation. In this work, possible alternative fatigue formulations to improve lifetime prediction under variable-amplitude loading are investigated. Results of WISPER and WISPERX variable-amplitude tests on a material representative of wind turbine rotor blades are used. Only alternatives for the SN-curve and the constant-life diagram are investigated; Rainflow counting and Miner summation are used in all predictions discussed here. None of the investigated SN-curves unites an apparent correlation of constant-amplitude data with an accurate and/or conservative lifetime prediction, when including them in a classical linear Goodman diagram. However, the lin-log- and log-log SN-curves do yield better predictions in combination with an alternative constant-life diagram.
Optimal Design of Horizontal-Axis Wind Turbines Using Blade-Element Theory and Evolutionary Computation
Authors: Benini Ernesto , Toffolo Andrea
Published: November 2002

This paper describes a multi-objective optimization method for the design of stall-regulated horizontal-axis wind turbines. Two modules are used for this purpose: an aerodynamic model implementing the blade-element theory and a multi-objective evolutionary algorithm. The former provides a sufficiently accurate solution of the flow field around the rotor disc; the latter handles the decision variables of the optimization problem, i.e., the main geometrical parameters of the rotor configuration, and promotes function optimization. The scope of the method is to achieve the best trade-off performance between two objectives: annual energy production per square meter of wind park (to be maximized) and cost of energy (to be minimized). Examples of the best solutions found by the method are described and their performance compared with those of commercial wind turbines.
Stress Analysis and Determination of Bolt Preload in Pipe Flange Connections With Gaskets Under Internal Pressure
Authors: Sawa Toshiyuki , Ogata Naofumi , Nishida Takahito
Published: November 2002

The stresses of a pipe flange connection with a spiral-wound gasket under internal pressure are analyzed taking account a nonlinearity and a hysteresis of the gasket by using an axisymmetric theory of elasticity and the finite element method (FEM). The leakage tests were also conducted using an actual pipe flange connection with a spiral-wound gasket. Using the contact stress distribution of the pipe flange connection with 3-in. nominal diameter under internal pressure and the tightness parameter, the values of the new gasket constants are obtained by taking into account the changes in the contact stress. A difference in the new gasket constants between the estimated values obtained from the actual pipe flange connection and the values obtained by the PVRC procedure is small. In addition, a method to determine the bolt preload for a given tightness parameter is demonstrated. The obtained results of the bolt preload for the pipe flange connection are in a fairly good agreement with those obtained by the PVRC procedure under a lower pressure application. However, a difference in the bolt preload is about 10% when an internal pressure is increased.
Development of high quantum efficiency flat panel detectors for portal imaging: Intrinsic spatial resolution
Authors: Pang G. , Rowlands J. A.
Published: November 2002

Recently developed flat panel detectors have been proven to have a much better image quality than conventional electronic portal imaging devices (EPIDs). They are, however, not yet the ideal systems for portal imaging application due to the low x‐ray absorption, i.e., low quantum efficiency (QE), which is typically on the order of 2–4 % as compared to the theoretical limit of 100%. The QE of current flat panel systems can be improved by significantly increasing the thickness of the energy conversion layer (i.e., amorphous selenium or phosphor screen). This, however, will be at the expense of a decrease in spatial resolution mainly due to x‐ray scatter in the conversion layer (and also the spread of optical photons in the case of phosphor screen). In this paper, we investigate theoretically the intrinsic spatial resolution of a high QE flat panel detector with a new energy conversion layer that is much denser and thicker than that of current flat panel systems. The modulation transfer function (MTF) of the system is calculated based on a theoretical model using a novel approach, which uses an analytical expression for absorbed dose. It is found that if appropriate materials are used for the conversion layer, then the intrinsic MTF of the high QE flat panel is better than that of current EPIDs, and in addition they have a high QE (e.g., ∼60%). Some general rules for the design of the conversion layer to achieve both high QE and high resolution as well as high DQE are also discussed.
Diffraction enhanced imaging contrast mechanisms in breast cancer specimens
Authors: Hasnah M. O. , Zhong Z. , Oltulu O. , Pisano E. , Johnston R. E. , Sayers D. , Thomlinson W. , Chapman D.
Published: November 2002

We have investigated the contrast mechanisms of the refraction angle, and the apparent absorption images obtained from the diffraction enhanced imaging technique (DEI) and have correlated them with the absorption contrast of conventional radiography. The contrast of both the DEI refraction angle image and the radiograph have the same dependence on density differences of the tissues in the visualization of cancer; in radiography these differences directly relate to the contrast while in the DEI refraction angle image it is the density difference and thickness gradient that gives the refraction angle. We show that the density difference of fibrils in breast cancer as measured by absorption images correlate well with the density difference derived from refraction angle images of DEI. In addition we find that the DEI apparent absorption image and the image obtained with the DEI system at the top of the reflectivity curve have much greater contrast than that of the normal radiograph (×8 to 33‐fold higher). This is due to the rejection of small angle scattering (extinction) from the fibrils enhancing the contrast.
Accelerating Monte Carlo simulations of radiation therapy dose distributions using wavelet threshold de‐noising
Authors: Deasy Joseph O. , Wickerhauser M. Victor , Picard Mathieu
Published: November 2002

The Monte Carlo dose calculation method works by simulating individual energetic photons or electrons as they traverse a digital representation of the patient anatomy. However, Monte Carlo results fluctuate until a large number of particles are simulated. We propose wavelet threshold de‐noising as a postprocessing step to accelerate convergence of Monte Carlo dose calculations. A sampled rough function (such as Monte Carlo noise) gives wavelet transform coefficients which are more nearly equal in amplitude than those of a sampled smooth function. Wavelet hard‐threshold de‐noising sets to zero those wavelet coefficients which fall below a threshold; the image is then reconstructed. We implemented the computationally efficient 9,7‐biorthogonal filters in the C language. Transform results were averaged over transform origin selections to reduce artifacts. A method for selecting best threshold values is described. The algorithm requires about 336 floating point arithmetic operations per dose grid point. We applied wavelet threshold de‐noising to two two‐dimensional dose distributions: a dose distribution generated by 10 MeV electrons incident on a water phantom with a step‐heterogeneity, and a slice from a lung heterogeneity phantom. Dose distributions were simulated using the Integrated Tiger Series Monte Carlo code. We studied threshold selection, resulting dose image smoothness, and resulting dose image accuracy as a function of the number of source particles. For both phantoms, with a suitable value of the threshold parameter, voxel‐to‐voxel noise was suppressed with little introduction of bias. The roughness of wavelet de‐noised dose distributions (according to a Laplacian metric) was nearly independent of the number of source electrons, though the accuracy of the de‐noised dose image improved with increasing numbers of source electrons. We conclude that wavelet shrinkage de‐noising is a promising method for effectively accelerating Monte Carlo dose calculations by factors of 2 or more.
Dosimetry of therapeutic photon beams using an extended dose range film
Authors: Esthappan Jacqueline , Mutic Sasa , Harms William B. , Dempsey James F. , Low Daniel A.
Published: November 2002

For intensity modulated radiation therapy (IMRT) dose distribution verification, multidimensional measurements are required to quantify the steep dose‐gradient regions. High resolution, two‐dimensional dose distributions can be measured using radiographic film. However, the photon energy response of film is known to be a function of depth, field size, and photon beam energy, potentially reducing the accuracy of dose distribution measurements. The dosimetric properties of the recently developed Kodak EDR2 film were investigated and compared to those of Kodak XV film. The dose responses of both film types to 6 MV and 18 MV photon beams were investigated for depths of 5 cm, 10 cm, and 15 cm and field sizes of 4×4 cm2 and 15×15 cm2. This analysis involved the determination of sensitometric curves for XV and EDR2 films, the determination of dose profiles from exposed XV and EDR2 films, and comparison of the film‐generated dose profiles to ionization chamber measurements. For the combinations of photon beam energy, depth, and field size investigated here, our results indicate that the sensitometric curves are nearly independent of field size and depth of calibration. For a field size of 4×4 cm2, a single sensitometric curve for either EDR2 and XV film can be used for the determination of relative dose profiles. For the larger field size, the sensitometric curve for EDR2 film is superior to XV film in regions where the dose falls below 20% of the central axis dose, due to the effects that the increased low energy scattered photon contributions have on film response. The limited field size and depth dependence of sensitometric data measured using EDR2 film, along with the inherently wide linear dose‐response range of EDR2 film, makes it better suited to the verification of IMRT dose distributions.
Beyond bixels: Generalizing the optimization parameters for intensity modulated radiation therapy
Authors: Markman Jerry , Low Daniel A. , Beavis Andrew W. , Deasy Joseph O.
Published: November 2002

Intensity modulated radiation therapy (IMRT) treatment planning systems optimize fluence distributions by subdividing the fluence distribution into rectangular bixels. The algorithms typically optimize the fluence intensity directly, often leading to fluence distributions with sharp discontinuities. These discontinuities may yield difficulties in delivery of the fluence distribution, leading to inaccurate dose delivery. We have developed a method for decoupling the bixel intensities from the optimization parameters; either by introducing optimization control points from which the bixel intensities are interpolated or by parametrizing the fluence distribution using basis functions. In either case, the number of optimization search parameters is reduced from the direct bixel optimization method. To illustrate the concept, the technique is applied to two‐dimensional idealized head and neck treatment plans. The interpolation algorithms investigated were nearest‐neighbor, linear and cubic spline, and radial basis functions serve as the basis function test. The interpolation and basis function optimization techniques were compared against the direct bixel calculation. The number of optimization parameters were significantly reduced relative to the bixel optimization, and this was evident in the reduction of computation time of as much as 58% from the full bixel optimization. The dose distributions obtained using the reduced optimization parameter sets were very similar to the full bixel optimization when examined by dose distributions, statistics, and dose‐volume histograms. To evaluate the sensitivity of the fluence calculations to spatial misalignment caused either by delivery errors or patient motion, the doses were recomputed with a 1 mm shift in each beam and compared to the unshifted distributions. Except for the nearest‐neighbor algorithm, the reduced optimization parameter dose distributions were generally less sensitive to spatial shifts than the bixel optimization. These results indicate that significant reductions in optimization parameter sets can be accomplished with a negligible reduction in dose distribution quality. The decreased parameters can result in a reduced optimization time, or can be used to allow an improved and consequently more computation‐intensive dose calculation for more accurate dose calculations during the optimization process. The basis functions may be generalized to model the accelerator motion for direct computation of the accelerator motion sequence, removing the need for developing an independent leaf sequence step.
The medical‐irradiation characteristics for neutron capture therapy at the Heavy Water Neutron Irradiation Facility of Kyoto University Research Reactor
Authors: Sakurai Yoshinori , Kobayashi Tooru
Published: November 2002

At the Heavy Water Neutron Irradiation Facility of the Kyoto University Research Reactor, the mix irradiation of thermal and epi‐thermal neutrons, and the solo irradiation of epi‐thermal neutrons are available additionally to the thermal neutron irradiation, and then the neutron capture therapy (NCT) at this facility became more flexible, after the update in 1996. The estimation of the depth dose distributions in NCT clinical irradiation, were performed for the standard irradiation modes of thermal, mixed and epi‐thermal neutrons, from the both sides of experiment and calculation. On the assumption that the concentration in tumor part was 40 ppm and the ratio of tumor to normal tissue was 3.5, the advantage depth were estimated to 5.4, 6.0, and 8.0, for the respective standard irradiation modes. It was confirmed that the various irradiation conditions can be selected according to the target‐volume conditions, such as size, depth, etc. Besides, in the viewpoint of the radiation shielding for patient, it was confirmed that the whole‐body exposure is effectively reduced by the new clinical collimators, compared with the old one.
Theoretical and experimental quantification of carotid plaque volume measurements made by three‐dimensional ultrasound using test phantoms
Authors: Landry Anthony , Fenster Aaron
Published: November 2002

An accurate technique that exhibits low variability has practical importance for the quantification of carotid plaque volume. Such a technique is necessary to monitor plaque progression or regression that may result in response to nonsurgical therapy. In this study, we investigate the accuracy and variability of plaque volume measurement by three‐dimensional ultrasound using vascular plaque phantoms over a range of 68.2 mm3 to 285.5 mm3. The agar plaques maintained a consistent cylindrical geometry with variations in the height, length, and echogenisity. The volume of each plaque was determined by water displacement. The three‐dimensional (3D) ultrasound (US) images were acquired with a mechanical scanning system which creates a 3D US Cartesian volume, that was manipulated and viewed in any orientation, from a collection of conventional parallel two‐dimensional (2D) US images. The plaque volumes were measured by serial 2D manual planimtery. The mean accuracy in plaque volume measurement was 3.1±0.9%. Variability in plaque volume measurement was calculated to be 4.0±1.0% and 5.1±1.4% for intraobserver and interobserver measurements, respectively. We have also developed a theoretical description for the variance in measurement of plaque volume using manual planimetry. Root‐mean‐square difference between experimentally and theoretically determined values of plaque volume fractional variance was 9%.
Clinical use of LiF:Mg,Cu,P: Critical evaluation of an ultrasensitive material for thermoluminescence dosimetry
Authors: Duggan Lisa
Published: November 2002

Radiation dosimetry is an essential part of optimization in medical exposures. However there are medical procedures that are particularly challenging for existing dosimetric techniques: neonatal radiography (low dose), mammography (low energy), cardiac catheterization (moving radiation fields), and brachytherapy using implanted radionuclides (steep dose gradients). Hence, the objectives of this thesis were to study the dosimetric characteristics of ultrasensitive LiF:Mg,Cu,P thermoluminescence dosimeters (TLDs) in radiation beams typical for both diagnostics and therapy, and develop procedures to implement this dosimeter into clinical practice for those selected scenarios. GR‐200 (SDDML, China) and MCP‐N (TLD Poland) TLDs were compared to other TLD materials (LiF:Mg,Ti, and tested for reproducibility, dose response (1 μGy to 500 Gy), photon energy response (10 keV to 18 MVp), light sensitivity (240–800 nm), long‐term stability (6 months) using different annealing cycles and glow curve deconvolution. A miniaturized TLD form (MCP‐Np) was developed by TLD Poland for the present investigations. Detection limit of GR‐200 and MCP‐Np was found to be less than 1 and 8 μGy, respectively, with dose response linear up to 18 Gy. To obtain adequate detection limits and precision, accurate temperature calibration of heating cycles and a dual‐anneal technique with dose history monitoring was performed. Energy response was similar for both materials within 5% and essentially uniform except for a minimum of 0.82 at 185 keV. LiF:Mg,Cu,P proved to be more suitable than LiF:Mg,Ti for dosimetry in low dose medical applications particularly when kilovoltage photons are to be used. The high sensitivity and resulting scope for miniaturization provided the opportunity to perform unique in vivo measurements within brachytherapy implants and for mammography.
Modeling the impact of treatment uncertainties in radiotherapy
Authors: Booth Jeremy T.
Published: November 2002

The aim of this thesis is to model the impact (dosimetric and radiobiological) of prostate radiotherapy treatment uncertainties and techniques for displaying potential dose errors. A Monte Carlo code is written to simulate both the treatment planning and delivery phases. Distributions of systematic organ motion, systematic positioning error, random organ motion, random positioning error, and interpatient cell sensitivity are taken from the literature. These distributions are used to sample the position and size of the prostate and rectum at each fraction of treatment. Dose to organ voxels are assigned from precalculated dose distributions (four‐field box using 6 MV photons with margins around the clinical target volume of 0.5, 1.0, and 1.5 cm). In particular, the poor estimation of prostate mean position from one planning CT series is investigated and shown to introduce large dose uncertainty. A convolution kernel is suggested that considers multiple pre‐treatment CT scans to better estimate mean prostate position. The radiobiological impact of the treatment uncertainties is evaluated in terms of tumor control probability for prostate, normal tissue complication probability for rectal bleeding and uncomplicated tumor control probability using established models. Local prostate control is highly sensitive to treatment uncertainties with inadequate margin size and to interpatient radiosensitivity. Rectal bleeding is more sensitive to margin size than to deformation. A number of ways to display the dosimetric uncertainty are presented. The display tools proposed allow the planner to consider potential variations in dose visually and may assist with margin size considerations.
Reconnecting Farms and Ecosystems-- If It Pays
Authors: Bent Andrew
Published: November 2002

The Farm as Natural Habitat
. Reconnecting Food Systems with Ecosystems. Dana L. Jackson and Laura L. Jackson, Eds. Island, Washington, DC, 2002. 312 pp. $50. ISBN 1-55963-846-X. Paper, $25. ISBN 1-55963-847-8.

The contributors argue for a sustainable agriculture that would feed us while protecting and restoring biodiversity in rural landscapes.
Simulation of Subduction Zone Seismicity by Dehydration of Serpentine
Authors: Dobson David P. , Meredith Philip G. , Boon Stephen A.
Published: November 2002

We measured acoustic emission energy during antigorite dehydration in a multianvil press from 1.5 to 8.5 gigapascals and 300° to 900°C. There was a strong acoustic emission signal on dehydration, and analysis of recovered samples revealed brittle deformation features associated with high pore-fluid pressures. These results demonstrate that intermediate depth (50 to 200 kilometers) seismicity can be generated by dehydration reactions in the subducting slab.
Structural Basis for the Transition from Initiation to Elongation Transcription in T7 RNA Polymerase
Authors: Yin Y. Whitney , Steitz Thomas A.
Published: November 2002

To make messenger RNA transcripts, bacteriophage T7 RNA polymerase (T7 RNAP) undergoes a transition from an initiation phase, which only makes short RNA fragments, to a stable elongation phase. We have determined at 2.1 angstrom resolution the crystal structure of a T7 RNAP elongation complex with 30 base pairs of duplex DNA containing a “transcription bubble” interacting with a 17-nucleotide RNA transcript. The transition from an initiation to an elongation complex is accompanied by a major refolding of the amino-terminal 300 residues. This results in loss of the promoter binding site, facilitating promoter clearance, and creates a tunnel that surrounds the RNA transcript after it peels off a seven–base pair heteroduplex. Formation of the exit tunnel explains the enhanced processivity of the elongation complex. Downstream duplex DNA binds to the fingers domain, and its orientation relative to upstream DNA in the initiation complex implies an unwinding that could facilitate formation of the open promoter complex.