bluuebunny/crossref_metadata_2025 huggingface dataset:
A randomized controlled trial to measure the effectiveness of a sacral wedge in preventing postoperative back pain following trans‐urethral resection of the prostate (TURP) in lithotomy position
Authors: Pietrocola Peter , Riley Robin G , Beanland Christine J , Kelly Catherine , Radnell Jenny
Published: November 2004

Background.  Postoperative back pain is a common, yet under reported, complication of surgery. Previous studies, although small in number, have indicated that the use of a sacral wedge is effective in reducing the incidence of postoperative back pain.

Aim.  The aim of the study was to test the hypothesis that the intra‐operative use of a sacral wedge would decrease the incidence of postoperative back pain in patients undergoing trans‐urethral resection of the prostate in lithotomy position.

Methods.  The design of the study was a randomized controlled trial involving the use of a sacral wedge intra‐operatively in a male population undergoing trans‐urethral resection of the prostate. A total of 236 participants was recruited to the study and allocated to the control or intervention group by block randomization. All patients selected one of three different sized sacral wedges for use during surgery. Data were collected preoperatively, intra‐operatively and at postoperative days 2 and 4 and the tools included a structured questionnaire, Oswestry Disability Questionnaire, a visual analogue scale to measure pain intensity and a body map to record its location.

Results.  Fifty‐two per cent of participants reported having a history of back pain and point prevalence on admission to hospital was 27%. Twenty‐eight per cent of participants experienced back pain on day 2 postoperatively and this decreased to 14% on day 4. There was no significant difference between the control and intervention groups. The severity of back pain increased after surgery. Postoperatively there were reports of back pain from participants who had not reported a history of back pain before their admission for surgery.

Conclusions.  In contrast to other studies we found no evidence to support the use of a sacral wedge intra‐operatively to reduce the incidence of postoperative back pain.

Relevance to clinical practice.  Despite the non‐significant results, the high level of postoperative back pain stills draws attention to the need to develop strategies to reduce its incidence.
Liver transplant patients: their experience in the intensive care unit. A phenomenological study
Authors: Del Barrio Miriam , Lacunza Mª Mar , Armendariz Ana Carmen , Margall Mª Angeles , Asiain Mª Carmen
Published: November 2004

Background.  The nurses’ knowledge of patients’ experiences contributes to gaining a deeper understanding of their health process, which will help to provide a better foundation for nursing care. The patients’ experiences in the intensive care unit are singular; liver transplant patients constitute a specific group, because generally their admission to the intensive care unit marks the first step towards recovery of their health after a process in which they have lived in fear because their illness was reaching a more or less terminal stage.

Aim.  To describe the liver transplant patient's experience in the intensive care unit.

Design.  Phenomenological descriptive qualitative study.

Method.  In‐depth interviews were carried out with a sample of 10 patients. The interviews were audiotaped and transcribed verbatim. The transcripts were analyzed using the method devised by Giorgi and modified by Baker.

Results.  After the data were analyzed, a general description emerged, which includes five themes reflecting the essence of what this group of patients experienced: preconceived ideas marked the way they approached transplant; captured impressions of the intensive care unit's environment and experienced sensations; their perception of the caring behaviour of the nursing staff; support from the social environment (family) and religious beliefs; and their preconceived idea of the intensive care unit contrasted with their lived experience.

Conclusion.  This research enabled us to gain in‐depth knowledge of the liver transplant patient's lived experience of the intensive care unit. Nurses can optimize the nursing care plan for this group of patients based on these results.

Relevance to clinical practice.  Awareness of the importance that these participants gave to discomfort caused in their basic needs should lead nurses to pay special attention to the nursing interventions to help with these needs. As a result of this research, nurses and other professionals in the intensive care unit know that patients have an immediate sense of positive change. This enables us to reinforce this perception, reminding them frequently that they have already had their transplant and they are progressing well, thereby aiding their recovery. With regard to the social support of liver transplant patients, nurses must facilitate the presence of family members at the patient's bedside, as participants stated that the only support they needed was that of their family.
Meaning of spirituality: implications for nursing practice
Authors: McSherry Wilfred , Cash Keith , Ross Linda
Published: November 2004

Background.  This research outlines some preliminary findings emerging from a grounded theory investigation into the ‘meaning of spirituality’. These initial results raise some important questions about the terminology and language that nurses use regarding the term spirituality. It seems that many of the policy directives and statutory guidelines make two major assumptions regarding ‘spirituality’. Firstly, patients and nurses are aware and understand the concept, and secondly, patients may require their spiritual needs to be met. These preliminary findings suggest that a dichotomy is emerging between professional assumption and patient expectation regarding the meaning of spirituality.

Aim.  The study had one broad research aim, to gain a deeper insight into how patients, nurses, and people from the major world religions understand the concept of ‘spirituality’.

Design.  A qualitative research design was used involving a grounded theory method of inquiry. It was felt that this qualitative method would aid the investigation of this subjective dimension of peoples’ existence, enabling existing theoretical constructs and arguments to be tested.

Methods.  The constant comparative method was used throughout the data collection and analysis. Analysis was undertaken at two levels, ‘overview analysis’ and ‘line‐by‐line analysis’. This enabled the creation of categories and central themes.

Results.  Constant comparative analysis resulted in the formation of several categories and central themes. Two categories presented and discussed in detail are ‘definitions of spirituality’, and ‘diverse perceptions of spirituality’.

Conclusion.  It would seem that there is now an urgent need for nursing to evaluate and perhaps adjust its vision regarding what constitutes spirituality. Such an approach may serve to reduce the gap between policy and public expectation.

Relevance to clinical practice.  It seems that there may be no ‘precise’ terminology associated with the language used to define spirituality, raising possible implications for nursing practice and nurse education.
An exploration of the factors that influence the implementation of evidence into practice
Authors: Rycroft‐Malone Jo , Harvey Gill , Seers Kate , Kitson Alison , McCormack Brendan , Titchen Angie
Published: November 2004

Background.  The challenges of implementing evidence‐based practice are complex and varied. Against this background a framework has been developed to represent the multiple factors that may influence the implementation of evidence into practice. It is proposed that successful implementation is dependent upon the nature of the evidence being used, the quality of context, and, the type of facilitation required to enable the change process. This study sets out to scrutinize the elements of the framework through empirical enquiry.

Aims and objectives.  The aim of the study was to address the following questions:  • What factors do practitioners identify as the most important in enabling implementation of evidence into practice?

 • What are the factors practitioners identify that mediate the implementation of evidence into practice?

 • Do the concepts of evidence, context and facilitation constitute the key elements of a framework for getting evidence into practice?

Design and methods.  The study was conducted in two phases. Phase 1: Exploratory focus groups (n = 2) were conducted to inform the development of an interview guide. This was used with individual key informants in case study sites. Phase 2: Two sites with on‐going or recent implementation projects were studied. Within sites semi‐structured interviews were conducted (n = 17).

Results.  A number of key issues in relation to the implementation of evidence into practice emerged including: the nature and role of evidence, relevance and fit with organizational and practice issues, multi‐professional relationships and collaboration, role of the project lead and resources.

Conclusions.  The results are discussed with reference to the wider literature and in relation to the on‐going development of the framework. Crucially the growing body of evidence reveals that a focus on individual approaches to implementing evidence‐based practice, such as skilling‐up practitioners to appraise research evidence, will be ineffective by themselves.

Relevance to clinical practice.  Key elements that require attention in implementing evidence into practice are presented and may provide a useful checklist for future implementation and evaluation projects.
The Practice of Participatory Planning at Mapoon Aboriginal Settlement: Towards Community Control, Ownership and Autonomy
Authors: MORAN MARK F.
Published: November 2004

The practice of participatory planning in discrete Indigenous settlements has been established since the early 1990s. In addition to technical and economic goals, participatory planning also seeks community development outcomes, including community control, ownership and autonomy. This paper presents an evaluation of one such planning project, conducted at Mapoon in 1995. The Plan successfully improved physical infrastructure and housing, but had mixed success in terms of community development. Despite various efforts to follow participatory processes, the Plan was essentially a passing event, community control progressively diminished after its completion, and outcomes fell short of notions of ownership and autonomy. This suggests some misunderstandings between the practice of participatory planning and the workings of governance.
Gender and Life Course in the Narratives of Melbourne's High‐rise Housing Developers
Authors: FINCHER RUTH
Published: November 2004

Socially constructed ideas about the life course, sometimes encompassing gender relations, have long informed the views of those within the housing development industry about who should be housed where in the city, living what sorts of lives. Drawing on the findings of a recent study of developers’ narratives about the construction of expensive, high‐rise housing in central Melbourne, a relatively new form of dwelling even in this part of the metropolitan area, several themes are found to characterise the taken‐for‐granted ways in which these city‐builders view the gendered life courses of housing consumers. Developers’ narratives oppose the suburban ‘home’ to the high‐rise ‘lifestyle’, consider central city high‐rise residences as appropriate only for people without families, and see women, separately from the couples they make up with men, only as potential victims requiring the security that high‐rise apartment living is said to provide. These narratives reiterate the characteristics of an essentialised ‘empty nester’, or ‘young professional’ housing consumer, who is envisaged to occupy the new housing and is defined according to life course stage and gender. The developers’ partial and narrow accounts of the likely consumers of this high‐rise housing is one factor amongst many that explains the building of precincts of high‐rise housing that have limited facilities for children and for pursuits other than consumption of the individual ‘lifestyle’.
Is Sydney a Divided City Ethnically?
Authors: POULSEN MICHAEL , JOHNSTON RON , FORREST JAMES
Published: November 2004

Recent claims that Sydney's ethnic residential concentrations are a permanent feature and that the city is rapidly turning into a city bifurcated along an ethnic divide cannot be sustained by the evidence. An understanding of multicultural policies as they operate in Australia, and of segregation as essentially a transitory phenomenon there, suggests that social bifurcation is unlikely to occur. Immigrant concentrations in the poor suburbs are nothing new, and do not imply the entrapment of ethnic groups. While immigrant residential concentrations are increasing in size, commensurate with the influx of large numbers of migrants from non‐English speaking backgrounds over the past 30 years, the evidence suggests that claims of bifurcation are a product of the usage of birthplace data, the aggregation of ethnic groups into just two groups and a failure to take account of the degree of mixing. Evidence from both birthplace and ancestry data using different levels of ethnic aggregation and more appropriate analyses shows that Sydney is dominated by an intermixing of different ethnic groups with each other and with the host society, and not by high levels of ethnic segregation. Ancestry data from the 2001 Census show the spatial assimilation into the host society of the grandchildren, but less so the children, of immigrants in Sydney with similar rates for both the white non‐Anglo‐Celtic and the Asian populations.
Self‐concept and perception of early mother and father behavior in normal and antisocial adolescents
Authors: ÖSTGÅRD‐YBRANDT H. , ARMELIUS B.‐Å.
Published: November 2004

This study examines the self‐concept and perceptions of early parental behavior in a group of 277 normal adolescents with respect to differences in age (12–18 years) and gender. A group of 30 antisocial adolescents of similar age (13–19 years) were included as a comparison group. The study was a cross‐sectional questionnaire study and the Swedish translation of the Structural Analysis of Social Behavior (SASB) introject and mother/father questionnaires were used as measures of self‐ and parental concepts. Multivariate analyses of variance show that the normal adolescent self‐concept and perception of early parental behavior are positive and that there are no age or gender differences. The early behavior of the mother is perceived more positively than that of the father. A positive self‐concept is related to a positive perception of the parent's early behavior. The antisocial group of adolescents shows a more autonomous and negative self‐concept and more negative perception of early parental behaviors. This was true especially in the group of antisocial girls. The conclusion from the study is that there is no evidence of a chaotic self‐concept or tumultuous changes in the perceptions of early parental behavior during normal adolescence, but that an antisocial way of life might be reflected in a more negative and autonomous self‐concept and in more negative perceptions of early parental behavior during adolescence.
Accounting Choice, Home Bias, and U.S. Investment in Non‐U.S. Firms
Authors: BRADSHAW MARK T. , BUSHEE BRIAN J. , MILLER GREGORY S.
Published: November 2004

This paper examines the relation between accounting choice and U.S. institutional investor ownership in non‐U.S. firms. We predict that U.S. investors exhibit home bias in their preference for accounting methods conforming to U.S. Generally Accepted Accounting Principles (GAAP) because such methods are more familiar, reduce information processing costs, and are perceived as higher quality. We find that firms exhibiting higher levels (changes) of U.S. GAAP conformity have greater levels (changes) of U.S. institutional ownership. Lead‐lag regressions suggest that increases in U.S. GAAP conformity precede increases in U.S. investment, but changes in U.S. institutional holdings do not precede changes in accounting methods. We also find that the positive relation between U.S. GAAP conformity and U.S. investment holds regardless of a firm's visibility to U.S. investors (e.g., American Depositary Receipt listing, stock index membership, analyst following, firm size). However, we find that U.S. GAAP conformity has a significantly greater impact among firms already visible to U.S. investors.
How Informed Are Actively Trading Institutional Investors? Evidence from Their Trading Behavior before a Break in a String of Consecutive Earnings Increases
Authors: KE BIN , PETRONI KATHY
Published: November 2004

We examine whether transient institutional investors (i.e., institutions that trade actively to maximize short‐term profits) have information that allows them to predict a break in a string of consecutive quarterly earnings increases and thereby avoid the economically significant negative stock price response associated with the break announcement. We show that transient institutions predict the break at least one quarter in advance of the break quarter. We also provide evidence that is consistent with transient institutions obtaining information regarding the impending break from private communications with management.
Bureaucratic Posture: On the Need for a Composite Theory of Bureaucratic Behavior
Authors: Wise Lois Recascino
Published: November 2004

This article examines the underlying assumptions and main findings of four streams of research on bureaucratic postures. It explores the utility of each school of thought for understanding how perspectives on bureaucratic postures are associated with the advancement of the public interest and bureaucratic performance. A main conclusion is that, although limited in scope of application, each stream has merit. Nonetheless, the existing research is too narrow: The field needs to consider a more complex model of bureaucratic behavior that draws from these four fields to offer a framework that is widely applicable to the range of motives for work found in the public bureaucracy and the variety of behaviors that individuals exhibit. Some attributes that may characterize such a model are sketched out.
Desperately Seeking Selznick: Cooptation and the Dark Side of Public Management in Networks
Authors: O'Toole Laurence J. , Meier Kenneth J.
Published: November 2004

Most literature on public‐sector networks focuses on how to build and manage systems and ignores the political problems that networks can create for organizations. This article argues that individual network nodes can work to bias the organization's actions in ways that benefit the organization's more advantaged clientele. The argument is supported by an analysis of performance data from 500 organizations over a five‐year period. A classic theoretical point is supported in a systematic empirical investigation. While networks can greatly benefit the organization, they have a dark side that managers and scholars need to consider more seriously.
Sexual Harassment in the Federal Workplace Revisited: Influences on Sexual Harassment by Gender
Authors: Jackson Robert A. , Newman Meredith A.
Published: November 2004

Using data from the U.S. Merit Systems Protection Board's most recent survey on sexual harassment, this study examines influences on sexual harassment in the federal workplace. We investigate the effect of workers’sociodemographic characteristics, aspects of their daily work environment (the sex of the supervisor and female/male ratio of coworkers), and agency location. Drawing on a variety of theoretical models and addressing a limitation of a previous study, we assess whether and how influences on sexual harassment differ for men and women. Not only does the likelihood of sexual harassment differ for men and women, but the determinants of harassment differ as well. Women are more likely to indicate receipt of unwanted sexual attention as their ratio of male coworkers increases, and men are more likely to indicate its receipt as their ratio of female coworkers increases. We also find differential effects for sex of supervisor, age, education, and job type, among other variables. Our analyses highlight that gender conditions the influences on sexual harassment.
Beyond Ethical Codes: The Management of Integrity in the Netherlands Tax and Customs Administration
Authors: van Blijswijk Jacques A.M. , van Breukelen Richard C.J. , Franklin Aimee L. , Raadschelders Jos C.N. , Slump Pier
Published: November 2004

Trust in government is foundering. Ethics codes have limited utility in bolstering public trust, and a clear correlation between such codes and changed behavior must still be established. They are a means for external oversight, but they do nothing in terms of providing an internal moral compass. To rebuild trust in government, employees must also act with integrity. Actions that are both ethical and carried out with integrity are necessary—neither is sufficient. Acknowledging this, the Dutch Tax Administration undertook a two‐pronged approach focused on the management of integrity as a means to codify the operational ethics of the organization, as well as to foster shared values and behaviors. This approach is noteworthy because it guides behaviors while retaining street‐level discretion. It also is the first step toward creating a bureaucracy of mutual relationships that creates an ongoing moral consciousness serving both democracy and efficiency not only through control, but also through self‐reflection, interaction, and association.
Globalization, Governance, and the Future of Public Administration: Can We Make Sense Out of the Fog of Rhetoric Surrounding the Terminology?
Authors: Klingner Donald E.
Published: November 2004

Books reviewed in this article:

Daniel Yergin and Joseph Stanislaw, The Commanding Heights: The Battle between Government and the Marketplace That Is Remaking the Modern World

Joseph Stiglitz, Globalization and Its Discontents

Miles Kahler and David Lake, eds., Governance in a Global Economy

Joseph Nye, Jr. and John Donahue, eds., Governance in a Globalizing World
Using Parallel Strategies to Promote Change: Forest Policymaking under George W. Bush
Authors: Vaughn Jacqueline , Cortner Hanna
Published: November 2004

This study of policy change examines the parallel strategies the administration of President George W. Bush has used to substantially alter the direction of forest policy during his first term. Using the Healthy Forests Initiative as a case study, this analysis explains how, by framing the problem of wildfires and forest health in terms of process and pointing blame at environmental groups misusing appeal procedures, the administration was able to emphasize process, rather than the content of existing forest policy. It also provided a reasonable explanation for the president to take a lead in seeking both legislative as well as regulatory change. We contend that the use of two parallel policymaking paths—legislative and administrative—enabled the president to pursue policy change more rapidly, and, from a strategic standpoint, more effectively, than by relying upon the legislative process alone. We offer that the Bush administration's approach to changing forest policy represents a redirection that is likely to serve as a template for further environmental policy change.
A System‐of‐Systems Perspective for Public Policy Decisions
Authors: DeLaurentis Dan , Callaway Robert K. “CAB”
Published: November 2004

Problems of increasing complexity are facing decision makers within government and industry, and the key characteristic of these problems is that they are of system‐of‐systems type. With multiple, heterogeneous, distributed systems involved (including policies and economies as well as technologies), effective analysis for decision‐support quickly becomes unmanageable within the “stovepipe” context that still characterizes many organizations in the research and development community. There is not a process/field of study in place that can enable us to systematically solve these types of problems, exemplified by the Next Generation Transportation System. While indeed numerous tools are available to help, they cannot be used effectively because the people who build and understand the tools all speak different languages. Much confusion still remains about words and phrases for system‐of‐systems type problems, let alone the best modeling approaches for dealing with them. While pockets of organizational restructuring may address this challenge for particular projects, there is a lack of systematic thinking at the basic level about how to address the challenges. This paper recommends that intellectual, financial, and institutional resources be invested for the purpose of initiating and nurturing a field of study that will enable us to better address this important type of problem. The future of transportation serves as a motivating example of a multidomain, system‐of‐systems problem of critical importance to the nation and in need of effective decision‐support. The analogy of creating better maps and “navigation aids” for decision makers will be employed, emphasizing that, when navigating a minefield, knowing where not to go is the key factor in successfully traversing the terrain (i.e., making wise decisions).
Spektr: A computational tool for x‐ray spectral analysis and imaging system optimization
Authors: Siewerdsen J. H. , Waese A. M. , Moseley D. J. , Richard S. , Jaffray D. A.
Published: November 2004

A set of computational tools are presented that allow convenient calculation of x‐ray spectra, selection of elemental and compound filters, and calculation of beam quality characteristics, such as half‐value layer, mR/mAs, and fluence per unit exposure. The TASMIP model of Boone and Seibert is adapted to a library of high‐level language (Matlab™) functions and shown to agree with experimental measurements across a wide range of kVp and beam filtration. Modeling of beam filtration is facilitated by a convenient, extensible database of mass and mass‐energy attenuation coefficients compiled from the National Institute of Standards and Technology. The functions and database were integrated in a graphical user interface and made available online at http://www.aip.org/epaps/epaps.html. The functionality of the toolset and potential for investigation of imaging system optimization was illustrated in theoretical calculations of imaging performance across a broad range of kVp, filter material type, and filter thickness for direct and indirect‐detection flat‐panel imagers. The calculations reveal a number of nontrivial effects in the energy response of such detectors that may not have been guessed from simple K‐edge filter techniques, and point to a variety of compelling hypotheses regarding choice of beam filtration that warrant future investigation.
Fast and robust computation of colon centerline in CT colonography
Authors: Frimmel Hans , Näppi Janne , Yoshida Hiroyuki
Published: November 2004

Although several methods for generating the centerline of a colon from CT colonographic scans have been proposed, in general they are time‐consuming and do not take into account that the images of the colon may be of nonoptimal quality, with collapsed regions, and stool within the colon. Furthermore, the colonic lumen or wall, which is often used as a basis for computation of a centerline, is not always precisely segmented. In this study, we have developed an algorithm for computation of a colon centerline that is fast compared to the centerline algorithms presented in the reviewed literature, and that relies little on a complete colon segments identification. The proposed algorithm first extracts local maxima in a distance map of a segmented colonic lumen. The maxima are considered to be nodes in a set of graphs, and are iteratively linked together, based on a set of connection criteria, giving a minimum distance spanning tree. The connection criteria are computed from the distance from object boundary, the Euclidean distance between nodes and the voxel values on the pathway between pairs of nodes. After the last iteration, redundant branches are removed and end segments are recovered for each remaining graph. A subset of the initial maxima is used for distinguishing between the colon and noncolonic centerline segments among the set of graphs, giving the final centerline representation. A phantom study showed that, with respect to phantom variations, the algorithm achieved nearly constant computation time except for the most extreme setting . The algorithm successfully found all, or most of, the centerline . Displacement from optimum varied with colon diameter . By use of 40 CT colonographic scans, the computer‐generated centerlines were compared with the centerlines generated by three radiologists. The similarity was measured based on percent coverage and average displacement. The computer‐generated centerlines, when compared with human‐generated centerlines, had approximately the same displacement as when the human‐generated centerlines were compared among each other ( versus ). The coverage of the computer‐generated centerlines was slightly less than that of the human‐generated centerlines (92% versus 94%). The 40 centerlines were, on average, computed in 10.5 seconds, including computation time for the distance transform, with an Intel Pentium‐based computer, as compared with 12–17 seconds or more (excluding computation time for the distance transform needed) per centerline as reported in other studies.
Monte Carlo source model for photon beam radiotherapy: photon source characteristics
Authors: Fix Michael K. , Keall Paul J. , Dawson Kathryn , Siebers Jeffrey V.
Published: November 2004

A major barrier to widespread clinical implementation of Monte Carlo dose calculation is the difficulty in characterizing the radiation source within a generalized source model. This work aims to develop a generalized three‐component source model (target, primary collimator, flattening filter) for 6‐ and photon beams that match full phase‐space data (PSD). Subsource by subsource comparison of dose distributions, using either source PSD or the source model as input, allows accurate source characterization and has the potential to ease the commissioning procedure, since it is possible to obtain information about which subsource needs to be tuned. This source model is unique in that, compared to previous source models, it retains additional correlations among PS variables, which improves accuracy at nonstandard source‐to‐surface distances (SSDs). In our study, three‐dimensional (3D) dose calculations were performed for SSDs ranging from 50 to and for field sizes from to as well as a field off axis in each direction. The 3D dose distributions, using either full PSD or the source model as input, were compared in terms of dose‐difference and distance‐to‐agreement. With this model, over 99% of the voxels agreed within or for the target, within 2% or for the primary collimator, and within or for the flattening filter in all cases studied. For the dose distributions, 99% of the dose voxels agreed within 1% or when the combined source model—including a charged particle source and the full PSD as input—was used. The accurate and general characterization of each photon source and knowledge of the subsource dose distributions should facilitate source model commissioning procedures by allowing scaling the histogram distributions representing the subsources to be tuned.
Demonstration of enhanced ‐edge angiography using a cerium target x‐ray generator
Authors: Sato Eiichi , Tanaka Etsuro , Mori Hidezo , Kawai Toshiaki , Ichimaru Toshio , Sato Shigehiro , Takayama Kazuyoshi , Ido Hideaki
Published: November 2004

The cerium target x‐ray generator is useful in order to perform enhanced ‐edge angiography using a cone beam because ‐series characteristic x rays from the cerium target are absorbed effectively by iodine‐based contrast mediums. The x‐ray generator consists of a main controller, a unit with a Cockcroft‐Walton circuit and a fixed anode x‐ray tube, and a personal computer. The tube is a glass‐enclosed diode with a cerium target and a ‐thick beryllium window. The maximum tube voltage and current were and , respectively, and the focal‐spot sizes were . Cerium lines were left using a barium sulfate filter, and the x‐ray intensity was at from the source with a tube voltage of , a current of , and an exposure time of . Angiography was performed with a computed radiography system using iodine‐based microspheres. In coronary angiography of nonliving animals, we observed fine blood vessels of approximately with high contrasts.
A filtered backprojection algorithm for cone beam reconstructionusing rotational filtering under helical source trajectory
Authors: Tang Xiangyang , Hsieh Jiang
Published: November 2004

With the evolution from multi‐detector‐row CT to cone beam (CB) volumetric CT, maintaining reconstruction accuracy becomes more challenging. To combat the severe artifacts caused by a large cone angle in CB volumetric CT, three‐dimensional reconstruction algorithms have to be utilized. In practice, filtered backprojection (FBP) reconstruction algorithms are more desirable due to their computational structure and image generation efficiency. One of the CB‐FBP reconstruction algorithms is the well‐known FDK algorithm that was originally derived for a circular x‐ray source trajectory by heuristically extending its two‐dimensional (2‐D) counterpart. Later on, a general CB‐FBP reconstruction algorithm was derived for noncircular, such as helical, source trajectories. It has been recognized that a filtering operation in the projection data along the tangential direction of a helical x‐ray source trajectory can significantly improve the reconstruction accuracy of helical CB volumetric CT. However, the tangential filtering encounters latitudinal data truncation, resulting in degraded noise characteristics or data manipulation inefficiency. A CB‐FBP reconstruction algorithm using one‐dimensional rotational filtering across detector rows (namely CB‐RFBP) is proposed in this paper. Although the proposed CB‐RFBP reconstruction algorithm is approximate, it approaches the reconstruction accuracy that can be achieved by exact helical CB‐FBP reconstruction algorithms for moderate cone angles. Unlike most exact CB‐FBP reconstruction algorithms in which the redundant data are usually discarded, the proposed CB‐RFBP reconstruction algorithm make use of all available projection data, resulting in significantly improved noise characteristics and dose efficiency. Moreover, the rotational filtering across detector rows not only survives the so‐called long object problem, but also avoids latitudinal data truncation existing in other helical CB‐FBP reconstruction algorithm in which a tangential filtering is carried out, providing better noise characteristics, dose efficiency and data manipulation efficiency.
The long‐term stability of amorphous silicon flat panel imaging devices for dosimetry purposes
Authors: Louwe R. J. W. , McDermott L. N. , Sonke J.‐J. , Tielenburg R. , Wendling M. , van Herk M. B. , Mijnheer B. J.
Published: November 2004

This study was carried out to determine the stability of the response of amorphous silicon ‐flat panel imagers for dosimetry applications. Measurements of the imager's response under reference conditions were performed on a regular basis for four detectors of the same manufacturer. We found that the ambient temperature influenced the dark‐field, while the gain of the imager signal was unaffected. Therefore, temperature fluctuations were corrected for by applying a “dynamic” dark‐field correction. This correction method also removed the influence of a small, irreversible increase of the dark‐field current, which was equal to 0.5% of the dynamic range of the imager per year and was probably caused by mild radiation damage to the array. By applying a dynamic dark‐field correction, excellent stability of the response over the entire panel of all imagers of 0.5% was obtained over an observation period up to . However, two imagers had to be replaced after several months. For one imager, an image segment stopped functioning, while the image quality of the other imager degraded significantly. We conclude that the tested EPIDs have a very stable response and are therefore well suited for dosimetry. We recommend, however, applying quality assurance tests dedicated to both imaging and dosimetry.
Development of high quantum efficiency, flat panel, thick detectors for megavoltage x‐ray imaging: A novel direct‐conversion design and its feasibility
Authors: Pang G. , Rowlands J. A.
Published: November 2004

Most electronic portal imaging devices (EPIDs) developed to date, including recently developed flat panel systems, have low x‐ray absorption, i.e., low quantum efficiency (QE) of 2%–4% as compared to the theoretical limit of 100%. A significant increase of QE is desirable for applications such as a megavoltage cone‐beam computed tomography (MVCT) and megavoltage fluoroscopy. However, the spatial resolution of an imaging system usually decreases significantly with an increase of QE. The key to the success in the design of a high QE detector is therefore to maintain the spatial resolution. Recently, we demonstrated theoretically that it is possible to design a portal imaging detector with both high QE and high resolution [see Pang and Rowlands, Med. Phys. 29, 2274 (2002)]. In this paper, we introduce such a novel design consisting of a large number of microstructured plates (made by, e.g., photolithographic patterning of evaporated or electroplated layers) packed together and aligned with the incident x rays. On each plate, microstrip charge collectors are focused toward the x‐ray source to collect charges generated in the ionization medium (e.g., air or gas) surrounded by high‐density materials that act as x‐ray converters. The collected charges represent the x‐ray image and can be read out by various means, including a two‐dimensional (2‐D) active readout matrix. The QE, spatial resolution, and sensitivity of the detector have been calculated. It has been shown that the new design will have a QE of more than an order of magnitude higher and a spatial resolution equivalent to that of flat panel systems currently used for portal imaging. The new design is also quantum noise limited down to very low doses ( radiation pulses of the linear accelerator).
Dynamic Instability in a DNA-Segregating Prokaryotic Actin Homolog
Authors: Garner Ethan C. , Campbell Christopher S. , Mullins R. Dyche
Published: November 2004

Dynamic instability—the switching of a two-state polymer between phases of steady elongation and rapid shortening—is essential to the cellular function of eukaryotic microtubules, especially during chromosome segregation. Since the discovery of dynamic instability 20 years ago, no other biological polymer has been found to exhibit this behavior. Using total internal reflection fluorescence microscopy and fluorescence resonance energy transfer, we observe that the prokaryotic actin homolog ParM, whose assembly is required for the segregation of large, low–copy number plasmids, displays both dynamic instability and symmetrical, bidirectional polymerization. The dynamic instability of ParM is regulated by adenosine triphosphate (ATP) hydrolysis, and filaments are stabilized by a cap of ATP-bound monomers. ParM is not related to tubulin, so its dynamic instability must have arisen by convergent evolution driven by a set of common constraints on polymer-based segregation of DNA.
Jet and Accretion-Disk Emission Untangled in 3C 273
Authors: Grandi Paola , Palumbo Giorgio G. C.
Published: November 2004

A long-term spectral variability study of 3C 273 on data obtained by BeppoSAX allows us to decouple the beamed nonthermal (jet) and unbeamed thermal (accretion flow) radiation produced in the inner region of a radio-loud active galactic nucleus. Jet power, when compared with unbeamed radiation, increases with energy. The thermal component is generally overwhelmed by the nonthermal radiation, by a factor of 1.2 to 3 in the 2- to 10-keV range and up to a factor of 7 above 20 keV. In only one case, the accretion flow overcomes the jet, allowing the
K
α
iron line to emerge clearly over the continuum.
Structural Insights into the Assembly of the Type III Secretion Needle Complex
Authors: Marlovits Thomas C. , Kubori Tomoko , Sukhan Anand , Thomas Dennis R. , Galán Jorge E. , Unger Vinzenz M.
Published: November 2004

Type III secretion systems (TTSSs) mediate translocation of virulence factors into host cells. We report the 17-angstrom resolution structures of a central component of
Salmonella typhimurium
TTSS, the needle complex, and its assembly precursor, the bacterial envelope–anchored base. Both the base and the fully assembled needle complex adopted multiple oligomeric states in vivo, and needle assembly was accompanied by recruitment of the protein PrgJ as a structural component of the base. Moreover, conformational changes during needle assembly created scaffolds for anchoring both PrgJ and the needle substructure and may provide the basis for substrate-specificity switching during type III secretion.
Thinking About the Conscious Mind
Authors: Koch Christof
Published: November 2004

Mind
A Brief Introduction.
By John R. Searle
. Oxford University Press, New York, 2004. 336 pp. $22, £14.99. ISBN 0-19-515733-8. Fundamentals of Philosophy.

Writing for a broad, nonspecialist audience, the author argues against "all of the most famous and influential theories" in the philosophy of mind and for his interpretation of topics such as the mind-body problem, consciousness, and free will.
Uridine Addition After MicroRNA-Directed Cleavage
Authors: Shen Binzhang , Goodman Howard M.
Published: November 2004

One of the important roles of microRNA (miRNA) is to direct the cleavage of messenger RNA (mRNA). However, the mechanisms of decay of the cleaved mRNA products is not well understood. We show that miRNA-directed cleavage products in organisms as diverse as
Arabidopsis
, mouse, and Epstein-Barr virus have at their 3' ends a stretch (1 to 24 nucleotides) of oligouridine posttranscriptionally added downstream of the cleavage site. This 3' uridine addition, as shown for
Arabidopsis
, is correlated with decapping and 5' shortening of the cleaved products, suggesting a mechanistic step in the miRNA-directed mRNA decay mechanism.
Cation Exchange Reactions in Ionic Nanocrystals
Authors: Son Dong Hee , Hughes Steven M. , Yin Yadong , Paul Alivisatos A.
Published: November 2004

Cation exchange has been investigated in a wide range of nanocrystals of varying composition, size, and shape. Complete and fully reversible exchange occurs, and the rates of the reactions are much faster than in bulk cation exchange processes. A critical size has been identified below which the shapes of complex nanocrystals evolve toward the equilibrium shape with lowest energy during the exchange reaction. Above the critical size, the anion sublattice remains intact and the basic shapes of the initial nanocrystals are retained throughout the cation exchange. The size-dependent shape change can also be used to infer features of the microscopic mechanism.
Autophagy Defends Cells Against Invading Group A
Streptococcus
Authors: Nakagawa Ichiro , Amano Atsuo , Mizushima Noboru , Yamamoto Akitsugu , Yamaguchi Hitomi , Kamimoto Takahiro , Nara Atsuki , Funao Junko , Nakata Masanobu , Tsuda Kayoko , Hamada Shigeyuki , Yoshimori Tamotsu
Published: November 2004

We found that the autophagic machinery could effectively eliminate pathogenic group A
Streptococcus
(GAS) within nonphagocytic cells. After escaping from endosomes into the cytoplasm, GAS became enveloped by autophagosome-like compartments and were killed upon fusion of these compartments with lysosomes. In autophagy-deficient Atg5
–/–
cells, GAS survived, multiplied, and were released from the cells. Thus, the autophagic machinery can act as an innate defense system against invading pathogens.
Characterization of the Nodularin Synthetase Gene Cluster and Proposed Theory of the Evolution of Cyanobacterial Hepatotoxins
Authors: Moffitt Michelle C. , Neilan Brett A.
Published: November 2004

Nodularia spumigena
is a bloom-forming cyanobacterium which produces the hepatotoxin nodularin. The complete gene cluster encoding the enzymatic machinery required for the biosynthesis of nodularin in
N. spumigena
strain NSOR10 was sequenced and characterized. The 48-kb gene cluster consists of nine open reading frames (ORFs),
ndaA
to
ndaI
, which are transcribed from a bidirectional regulatory promoter region and encode nonribosomal peptide synthetase modules, polyketide synthase modules, and tailoring enzymes. The ORFs flanking the
nda
gene cluster in the genome of
N. spumigena
strain NSOR10 were identified, and one of them was found to encode a protein with homology to previously characterized transposases. Putative transposases are also associated with the structurally related microcystin synthetase (
mcy
) gene clusters derived from three cyanobacterial strains, indicating a possible mechanism for the distribution of these biosynthetic gene clusters between various cyanobacterial genera. We propose an alternative hypothesis for hepatotoxin evolution in cyanobacteria based on the results of comparative and phylogenetic analyses of the
nda
and
mcy
gene clusters. These analyses suggested that nodularin synthetase evolved from a microcystin synthetase progenitor. The identification of the nodularin biosynthetic gene cluster and evolution of hepatotoxicity in cyanobacteria reported in this study may be valuable for future studies on toxic cyanobacterial bloom formation. In addition, an appreciation of the natural evolution of nonribosomal biosynthetic pathways will be vital for future combinatorial engineering and rational design of novel metabolites and pharmaceuticals.
Dynamics of a Pasture Soil Microbial Community after Deposition of Cattle Urine Amended with [13C]Urea
Authors: Petersen Søren O. , Roslev Peter , Bol Roland
Published: November 2004

Within grazed pastures, urine patches are hot spots of nitrogen turnover, since dietary N surpluses are excreted mainly as urea in the urine. This short-term experiment investigated13C uptake in microbial lipids after simulated deposition of cattle urine at 10.0 and 17.1 g of urea C m−2. Confined field plots without or with cattle urine amendment were sampled after 4 and 14 days, and soil from 0- to 5-cm and 10- to 20-cm depths was analyzed for content and composition of phospholipid fatty acids (PLFAs) and for the distribution of urea-derived13C among individual PLFAs. Carbon dioxide emissions were quantified, and the contributions derived from urea were assessed. Initial changes in PLFA composition were greater at the lower level of urea, as revealed by a principal-component analysis. At the higher urea level, osmotic stress was indicated by the dynamics of cyclopropane fatty acids and branched-chain fatty acids. Incorporation of13C from [13C]urea was low but significant, and the largest amounts of urea-derived C were found in common fatty acids (i.e., 16:0, 16:1ω7c, and 18:1ω7) that would be consistent with growth of typical NH4+-oxidizing (Nitrosomonas) and NO2−-oxidizing (Nitrobacter) bacteria. Surprisingly, a 20‰ depletion of13C in the cyclopropane fatty acid cy17:0 was observed after 4 days, which was replaced by a 10 to 20‰ depletion of that in cy19:0 after 14 days. Possible reasons for this pattern are discussed. Autotrophic nitrifiers could not be implicated in urea hydrolysis to any large extent, but PLFA dynamics and the incorporation of urea-derived13C in PLFAs indicated a response of nitrifiers which differed between the two urea concentrations.