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‘It’s complicated’: Professional opacity, duality, and ambiguity—A response to Noordegraaf (2020). JOURNAL OF PROFESSIONS AND ORGANIZATION 2021. [DOI: 10.1093/jpo/joab006] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
In this comment to Noordegraaf’s ‘Protective or connective professionalism? How connected professionals can (still) act as autonomous and authoritative experts’, we argue that Noordegraaf has contributed significant insights into the development of contemporary professionalism. However, we argue for a less binary and more complex view of forms of professionalism, and for finding ways of understanding professionalism grounded in a relational view of everyday professional work. The first section (by Johan Alvehus) suggests that Noordegraaf’s ‘connective professionalism’ is primarily about new ways of strengthening professionalism’s protective shields by maintaining functional ambiguity and transparent opacity around professional jurisdictions. The second section (by Amalya Oliver and Netta Avnoon) argues for viewing professionalism on a range of protection–connection and offers an approach for understanding how connective and protective models co-occur. Both commentaries thus take a relational, dynamic, and somewhat skeptical view on the reproduction and maintenance of professionalism.
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Reducing the cost of knowledge exchange in consortia: network analyses of multiple relations. JOURNAL OF TECHNOLOGY TRANSFER 2021. [DOI: 10.1007/s10961-021-09858-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Organizational creativity‐innovation process and breakthrough under time constraints: Mid‐point transformation. CREATIVITY AND INNOVATION MANAGEMENT 2019. [DOI: 10.1111/caim.12326] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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The multi-level process of trust and learning in university–industry innovation collaborations. JOURNAL OF TECHNOLOGY TRANSFER 2019. [DOI: 10.1007/s10961-019-09721-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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From academic laboratory to the market: Disclosed and undisclosed narratives of commercialization. SOCIAL STUDIES OF SCIENCE 2017; 47:33-52. [PMID: 28195026 DOI: 10.1177/0306312716667647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This paper examines how the Weizmann Institute of Science has been telling the story of the successful commercialization of a scientific invention, through its corporate communication channels, from the early 1970s to today. The paper aims to shed light on the transformation processes by which intellectual-property-based commercialization activities have become widely institutionalized in universities all over the world, and on the complexities, ambiguities and tensions surrounding this transition. We look at the story of the scientific invention of Copolymer-1 at the Weizmann Institute of Science and its licensing to Teva Pharmaceutical Industries, which subsequently developed the highly successful drug Copaxone for the treatment of multiple sclerosis. We argue that, in its tellings and retellings of the story of Copolymer-1, the Weizmann Institute has created narratives that serve to legitimize the institution of academic patenting in Israel.
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Shifts in the organization and profession of academic science: the impact of IPR and technology transfer. JOURNAL OF PROFESSIONS AND ORGANIZATION 2017. [DOI: 10.1093/jpo/jow012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Networking Network Studies: An Analysis of Conceptual Configurations in the Study of Inter-organizational Relationships. ORGANIZATION STUDIES 2016. [DOI: 10.1177/017084069801900402] [Citation(s) in RCA: 256] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Given the recent accumulation of research on inter-organizational relations and networks and the current fragmentation of the field, it is time to take stock and explore the achievements of, and future challenges for, this field of study. On the basis of a network analysis of the 158 articles on inter-organizational relations and networks that were published in four leading journals from 1980 to 1996, this paper empirically explores the linkages among, and configurations of, core theories and concepts underlying earlier empirical research on inter-organizational relations and networks. We identify core, as well as peripheral, areas of research interest in the field and point out areas of overlap and consolidation. Moreover, our empirical analysis shows that the field segments into four substantive research perspectives, namely social network, power and control, institutional, and institutional economics and strategy clusters. In sum, we suggest an innovative, empirically grounded approach towards a literature review that aims at a synopsis of a field of study and highlights possibly fruitful avenues for future research.
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Responses by Professional Organizations to Multiple and Ambiguous Institutional Environments: The Case of AIDS. ORGANIZATION STUDIES 2016. [DOI: 10.1177/017084069601700405] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In this paper we examine responses to multiple and ambiguous pressures gener ated by the environmental threat of AIDS. Using an institutional theory frame work and insights from professional dominance theory, we develop a two- dimensional typology, incorporating the belief systems of important constituents and the degree of institutional rules, to explain the patterns of organizational adoption of AIDS-related policies and related professional prac tices. Hypotheses are tested with data from a national survey of hospitals ( n= 506), with interviews from administrators and chiefs of medicine. Results sup port the usefulness of the explanatory schema for patterns of organizational policy adoption; the schema also provides a stronger explanation of pro fessional behaviour patterns than does the existence of policies requiring such behaviour. Theoretical and practical implications of the findings for professional organizations in the context of environmental threats are discussed.
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A Fresh Look at How Professions Take Shape: Dual-directed Networking Dynamics and Social Boundaries. ORGANIZATION STUDIES 2016. [DOI: 10.1177/0170840607076278] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Understanding boundary-spanning activities such as interorganizational alliances and professional/organizational integration requires clarity about what boundaries are being spanned and how they were constructed. We approach this goal by drawing on social identity theory and institutional theory to develop a process model, whereby inward- and outward-directed networking activities combine to build the social boundaries marking exclusive membership and proprietary domain. Four stages in the process are demonstrated, using two longitudinal case studies of emerging professions: the Jewish legal profession in Israel and physician executives in the USA. Despite the cases' contextual differences, analysis of networking activities supports propositions based on the model.
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Abstract
Strategic alliances in the biotechnology industry are used as an inter-organizational learning device, in addition to their ability to provide financial resources, vertical and horizontal integration facilities, and legitimacy to dedicated biotechnology firms (DBFs). However, despite the advantages associated with strategic alliances, the literature accounts for hazards and disadvantages as well. This paper analyzes the relationship between organizational life-cycle and the formation of strategic alliances based on a population of 554 new biotechnology firms (DBFs) in a 15-year period. Using event history analysis, this study tests two propositions: that the inability of DBFs to form strategic alliances will be associated with organizational death and that firm growth will make it possible to reduce network learning through alliances (exploration stage of learning), allowing the firm to enter a period of internalized learning (exploitation). These propositions are supported by the data. The findings showed that lack of alliances is associated with organizational death, that learning through alliances is not a cumulative process, and that firm life-cycle alliance formation is not linear. Although alliance-based learning is vital to biotechnology firms at the early stages of their formation, when learning is associated with exploration, at later phases of the life-cycle, learning is internally exploited through intrafirm networks. The results also provide some evidence that another phase of external, network based, learning follows.
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Three Levels of Networking for Sourcing Intellectual Capital in Biotechnology. INTERNATIONAL STUDIES OF MANAGEMENT & ORGANIZATION 2016. [DOI: 10.1080/00208825.1997.11656719] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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The Albert Einstein archives digitization project: opening hidden treasures. LIBRARY HI TECH 2014. [DOI: 10.1108/lht-07-2013-0084] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Purpose
– The purpose of this paper is to present the organizational and technological processes and strategic choices that led to the successful digitization project of the Albert Einstein Archives.
Design/methodology/approach
– This is a case study of the major challenges that were associated with the project. These include: the integration of the archives in the academic environment; the management of a project of such magnitude within the university organization and between different stakeholders and the technological aspects of the project and user experience.
Findings
– A digitization project requires not only the archival staff expertise but also information specialists, IT staff, analysts and usually the digitization staff for processing the archival material. Finding the common language between all the professionals involved as well as building a good strategic plan are the keys to a successful project.
Research limitations/implications
– The planning and implementation of such a project requires a significant budget, manpower project management, hardware, software and intra- and inter-organizational cooperation and coordination.
Originality/value
– The phenomenon of digitizing unique and exclusive archival data by universities is becoming an innovative contribution of hidden goods to the public at large. This paper offers strategic insights for the planning of similar digitizing projects, particularly in an academic environment.
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Beliefs about social responsibility at work: comparisons between managers and non-managers over time and cross-nationally. ACTA ACUST UNITED AC 2013. [DOI: 10.1111/beer.12015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Shifts in guidelines for ethical scientific conduct: how public and private organizations create and change norms of research integrity. SOCIAL STUDIES OF SCIENCE 2009; 39:137-155. [PMID: 19569428 DOI: 10.1177/0306312708097659] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We analyze the activities and actors involved in articulating and diffusing guidelines for ethical scientific conduct from 1975 to the present. We use a theoretical framework of institutional change at the organizational-field level to examine the co-evolution of the structure of the organizational field of 'scientific research' and its institutional logic. Public agencies have long provided funding to US universities to support faculty research, expecting that implicit norms of scientific conduct would guide behavior. Growing publicity about research fraud in the late 1960s and early 1970s triggered a shift from implicit norms to explicit behavioral proscriptions, with strong administrative oversight. As private sources of research funding exert new pressures on research behavior, public-private partnerships are emerging to articulate explicit, yet voluntary prescriptive norms of research integrity. The analysis demonstrates the co-evolution and co-dependence of changes in the identity and strength of influential actors in the field of scientific research and changes in the norms of scientific conduct. We examine how the normative guidelines have been constructed over time, illustrating the persistence of earlier norms as the foundation for current guidelines. We conclude with implications for future research conduct.
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Book Review: Tobias Gössling, Leon Oerlemans, Rob Jansen (eds.) Inside Networks: A Process View on Multi-organizational Partnerships, Alliances and Networks Edward Elgar: Cheltenham 2007. 0-84542-784-X. ORGANIZATION STUDIES 2009. [DOI: 10.1177/0170840608101793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Comparison of Brown Midrib-6 and -18 Forage Sorghum with Conventional Sorghum and Corn Silage in Diets of Lactating Dairy Cows. J Dairy Sci 2004; 87:637-44. [PMID: 15202648 DOI: 10.3168/jds.s0022-0302(04)73206-3] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Total mixed rations containing conventional forage sorghum, brown midrib (bmr)-6 forage sorghum, bmr-18 forage sorghum, or corn silage were fed to Holstein dairy cows to determine the effect on lactation, ruminal fermentation, and total tract nutrient digestion. Sixteen multiparous cows (4 ruminally fistulated; 124 d in milk) were assigned to 1 of 4 diets in a replicated Latin square design with 4-wk periods (21-d adaptation and 7 d of collection). Diets consisted of 40% test silage, 10% alfalfa silage, and 50% concentrate mix (dry basis). Acid detergent lignin concentration was reduced by 21 and 13%, respectively, for the bmr-6 and bmr-18 sorghum silages when compared with the conventional sorghum. Dry matter intake was not affected by diet. Production of 4% fat-corrected milk was greatest for cows fed bmr-6 (33.7 kg/d) and corn silage (33.3 kg/d), was least for cows fed the conventional sorghum (29.1 kg/d), and was intermediate for cows fed the bmr-18 sorghum (31.2 kg/d), which did not differ from any other diet. Total tract neutral detergent fiber (NDF) digestibility was greatest for the bmr-6 sorghum (54.4%) and corn silage (54.1%) diets and was lower for the conventional (40.8%) and bmr-18 sorghum (47.9%) diets. In situ extent of NDF digestion was greatest for the bmr-6 sorghum (76.4%) and corn silage (79.0%) diets, least for the conventional sorghum diet (70.4%), and intermediate for the bmr-18 sorghum silage diet (73.1%), which was not different from the other diets. Results of this study indicate that the bmr-6 sorghum hybrid outperformed the conventional sorghum hybrid; the bmr-18 sorghum was intermediate between conventional and bmr-6 in most cases. Additionally, the bmr-6 hybrid resulted in lactational performance equivalent to the corn hybrid used in this study. There are important compositional differences among bmr forage sorghum hybrids that need to be characterized to predict animal response accurately.
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Roles of Akt/PKB and IKK complex in constitutive induction of NF-kappaB in hepatocellular carcinomas of transforming growth factor alpha/c-myc transgenic mice. Hepatology 2001; 34:32-41. [PMID: 11431731 DOI: 10.1053/jhep.2001.25270] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
NF-kappaB regulates liver cell death during development, regeneration, and neoplastic transformation. For example, we showed that oncogenic Ras- or Raf-mediated transformation of rat liver epithelial cells (RLEs) led to altered NF-kappaB regulation through IKK complex activation, which rendered these cells more resistant to TGF-beta1-induced apoptosis. Thus, based on these findings, we sought to determine whether NF-kappaB could also be involved in tumor growth of liver cells in vivo. Hepatocellular carcinomas (HCCs) derived from bitransgenic mice harboring TGF-alpha and c-myc transgenes targeted specifically to the liver were compared with HCCs from c-myc single transgenic mice. Tumors from bitransgenic mice are characterized by a higher frequency of appearance, lower apoptotic index, and a higher rate of cell proliferation. Here we show that NF-kappaB is activated in HCCs of double TGF-alpha/c-myc transgenic mice, but not of c-myc single transgenic mice, suggesting that TGF-alpha mediates induction of NF-kappaB. Activation of the IKK complex was observed in the HCCs of double TGF-alpha/c-myc transgenic mice, implicating this pathway in NF-kappaB induction. Lastly, activation of the Akt/protein kinase B (PKB), which has recently been implicated in NF-kappaB activation by PDGF, TNF-alpha, and Ras, was also observed. Importantly, human HCC cell lines similarly displayed NF-kappaB activation. Thus, these studies elucidate an anti-apoptotic mechanism by a TGF-alpha-Akt/PKB-IKK pathway, which likely contributes to survival and proliferation, thereby accelerating c-myc-induced liver neoplastic development in vivo.
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Abstract
Conformal dynamic arc (CD-ARC) and intensity modulated arc treatments (IMAT) are both treatment modalities where the multileaf collimator (MLC) can change leaf position dynamically during gantry rotation. These treatment techniques can be used to generate complex isodose distributions, similar to those used in fix-gantry intensity modulation. However, a beam-hold delay cannot be used during CD-ARC or IMAT treatments to reduce spatial error. Consequently, a certain amount of leaf position error will have to be accepted in order to make the treatment deliverable. Measurements of leaf position accuracy were taken with leaf velocities ranging from 0.3 to 3.0 cm/s. The average and maximum leaf position errors were measured, and a least-squares linear regression analysis was performed on the measured data to determine the MLC velocity error coefficient. The average position errors range from 0.03 to 0.21 cm, with the largest deviations occurring at the maximum achievable leaf velocity (3.0 cm/s). The measured MLC velocity error coefficient was 0.0674 s for a collimator rotation of 0 degrees and 0.0681 s for a collimator rotation of 90 degrees. The distribution in leaf position error between the 0 degrees and 90 degrees collimator rotations was within statistical uncertainty. A simple formula was developed based on these results for estimating the velocity-dependent dosimetric error. Using this technique, a dosimetric error index for plan evaluation can be calculated from the treatment time and the dynamic MLC leaf controller file.
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Role of the IkappaB kinase complex in oncogenic Ras- and Raf-mediated transformation of rat liver epithelial cells. Mol Cell Biol 2000; 20:5381-91. [PMID: 10891479 PMCID: PMC85990 DOI: 10.1128/mcb.20.15.5381-5391.2000] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
NF-kappaB/Rel factors have been implicated in the regulation of liver cell death during development, after partial hepatectomy, and in hepatocytes in culture. Rat liver epithelial cells (RLEs) display many biochemical and ultrastructural characteristics of oval cells, which are multipotent cells that can differentiate into mature hepatocytes. While untransformed RLEs undergo growth arrest and apoptosis in response to transforming growth factor beta1 (TGF-beta1) treatment, oncogenic Ras- or Raf-transformed RLEs are insensitive to TGF-beta1-mediated growth arrest. Here we have tested the hypothesis that Ras- or Raf-transformed RLEs have altered NF-kappaB regulation, leading to this resistance to TGF-beta1. We show that classical NF-kappaB is aberrantly activated in Ras- or Raf-transformed RLEs, due to increased phosphorylation and degradation of IkappaB-alpha protein. Inhibition of NF-kappaB activity with a dominant negative form of IkappaB-alpha restored TGF-beta1-mediated cell killing of transformed RLEs. IKK activity mediates this hyperphosphorylation of IkappaB-alpha protein. As judged by kinase assays and transfection of dominant negative IKK-1 and IKK-2 expression vectors, NF-kappaB activation by Ras appeared to be mediated by both IKK-1 and IKK-2, while Raf-induced NF-kappaB activation was mediated by IKK-2. NF-kappaB activation in the Ras-transformed cells was mediated by both the Raf and phosphatidylinositol 3-kinase pathways, while in the Raf-transformed cells, NF-kappaB induction was mediated by the mitogen-activated protein kinase cascade. Last, inhibition of either IKK-1 or IKK-2 reduced focus-forming activity in Ras-transformed RLEs. Overall, these studies elucidate a mechanism that contributes to the process of transformation of liver cells by oncogene Ras and Raf through the IkappaB kinase complex leading to constitutive activation of NF-kappaB.
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Clinical application of digitally-reconstructed radiographs generated from magnetic resonance imaging for intracranial lesions. Int J Radiat Oncol Biol Phys 1999; 45:797-802. [PMID: 10524436 DOI: 10.1016/s0360-3016(99)00173-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
PURPOSE The purpose of this work is to demonstrate the clinical utility of magnetic resonance (MR) imaging-based digitally reconstructed radiographs (DRRs) for the setup and verification of patients with intracranial lesions. METHODS AND MATERIALS MR images of 16 patients with various intracranial lesions were obtained for treatment planning and virtual simulation. Five-millimeter-thick contiguous T1-weighted postcontrast transverse slices were obtained using a standard head coil in a General Electric Signa 1.5T MR scanner. MR-DRRs were generated using the "pseudo density" technique on an existing treatment planning computer without any special modifications. Anterior and lateral verification films were taken for each patient for visual comparison with MR-based DRRs. RESULTS Visual alignment with bony landmarks, including the orbits, frontal sinus, sphenoid sinus, auditory meatus, nasal bone, vomer bone, mastoid process, and the cranium were used by physicians, physicists, and therapists to verify patient positioning. Misalignments from 3 to 10 mm were visually identified and corrected using this technique. CONCLUSION A method for visually utilizing MR-based DRRs during simulation has been developed and clinically implemented. The quality of MR-DRRs generated using this technique is such that physicians, physicists, and therapists can easily and routinely compare MR-DRRs side-by-side with simulation films.
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Abstract
Respiratory gating has only recently been applied to conventional external beam radiotherapy. In order for respiratory gating to be used clinically, an evaluation of the dosimetric effects of small units of delivered dose must be performed. The purpose of this study is to systematically evaluate the effect of various gating sequences on x-ray central axis output, ionization ratios (nominal accelerating potential), beam flatness, and beam symmetry. Measurements were taken for 6 and 18 MV photons on a linear accelerator that generates the gate by using a gridded electron gun to stop the electron flow to the wave-guide. The beam output, energy, flatness, and symmetry did not vary by more than 0.8 percent in most of the gating sequences. The maximum output deviations (0.8 percent), flatness deviations (1.9 percent), and symmetry deviations (0.8 percent) occurred when a low number of monitor units (<5 MU) were delivered in the gating window. Although these deviations are not clinically significant, each linear accelerator should be evaluated carefully before clinical implementation.
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Abstract
L-Phenylacetylcarbinol (L-PAC) is the precursor for L-ephedrine and D-pseudoephedrine, alkaloids possessing alpha- and beta-adrenergic activity. The most commonly used method for production of L-PAC is a biological method whereby the enzyme pyruvate decarboxylase (PDC) decarboxylates pyruvate and then condenses the product with added benzaldehyde. The process may be undertaken by either whole cells or purified PDC. If whole cells are used, the biomass may be grown and allowed to synthesize endogenous pyruvate, or the cells may be used as a catalyst only, with both pyruvate and benzaldehyde being added. Several yeast species have been investigated with regard to L-PAC-producing potential; the most commonly used organisms are strains of Saccharomyces cerevisiae and Candida utilis. It was found that initial high production rates did not necessarily result in the highest final yields. Researchers then examined ways of improving the productivity of the process. The substrate, benzaldehyde, and the product, L-PAC, as well as the by-products, were found to be toxic to the biomass. Methods examined to reduce toxicity include modification of benzaldehyde dosing regimes, immobilization of biomass or purified enzymes, modification of benzaldehyde solubility and the use of two-phase reaction systems. Various means of modifying metabolism to enhance enzyme activity, relevant metabolic pathways and yield have been examined. Methods investigated include the use of respiratory quotient to influence pyruvate production and induce fermentative activity, reduced aeration to increase PDC activity, and carbohydrate feeding to modify glycolytic enzyme activity. The effect of temperature on L-PAC yield has been examined to identify conditions which provide the optimal balance between L-PAC and benzyl alcohol production, and L-PAC inactivation. However, relatively little work has been undertaken on the effect of medium composition on L-PAC yield.
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Dosimetric verification of two commercially available three-dimensional treatment planning systems using the TG 23 test package. Med Phys 1999; 26:1188-95. [PMID: 10435518 DOI: 10.1118/1.598614] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The Task Group 23 (TG-23) radiation treatment planning dosimetry verification package was used to evaluate the dosimetric accuracy of two commercially available treatment planning systems. The TG-23 test package contains experimentally measured beam data for two x-ray beams (4 and 18 MV) that can be used as input for 3D-RTP (three-dimensional radiation treatment planning) systems. Once the beam data is entered and modeled, a series of test cases are performed that isolate different aspects of the dose computational process. The computed values from the 3D-RTP system are compared against the measured dosimetry data, included in the package, for a set of comparison points within each test case. Both of the treatment planning systems that were studied provided excellent agreement between computed and measured doses. The cumulative 4 and 18 MV TG-23 test results for the convolution/superposition based planning system indicates that 96% of the dosimetric test points are within +/-2%, and 98% are within +/-3% of the tabulated TG-23 values. The dosimetric TG-23 test results for the pencil beam kernel based planning system are similar, with 96% of the test points falling within +/-2%, and 99% falling within +/-3% of the TG-23 measurements.
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Abstract
One major limitation of three-dimensional conformal radiation therapy that has not been adequately addressed is respiration-induced organ motion. During respiration, tumors in the abdomen can typically move from 1 to 3 centimeters. Because the size and shape of external radiation treatment fields do not change during treatment, the field size of the x-ray beam must be enlarged to encompass the tumor through the entire respiration cycle. Several manufacturers are developing respiratory gating systems. These systems allow the selective delivery of absorbed doses to moving target volumes in the abdomen during time intervals when the target volume is within the intended location. Before respiratory gated radiotherapy can be implemented clinically, the efficacy of the procedure must be justified. The magnitude of dosimetric and geometric uncertainties associated with respiratory motion must be identified to determine if gating can provide an advantage over conventional treatment techniques. In addition, clinical situations and specific types of cancer that could benefit from respiratory gating must also be identified.
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Ionization chamber, electrometer, linear accelerator, field size, and energy dependence of the polarity effect in electron dosimetry. Med Phys 1999; 26:214-9. [PMID: 10076977 DOI: 10.1118/1.598507] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Plane-parallel ionization chambers are the instrument of choice for use in electron calibration and dosimetry, but these chambers may exhibit large polarity effects. This study concentrates on measuring the dependence of the polarity error at various mean energies using different linear accelerator, field size, ion chamber, and electrometer combinations. The polarity error was shown to increase for all four ionization chambers as the mean energy at depth decreased, but was always less than one percent at d(max). Polarity error dependence was also observed for similar plane-parallel chambers, varying field sizes, and different linear accelerators, but no polarity error dependence was observed for similar cylindrical chambers and different electrometers. Measurements of the polarity error can be used to develop correction factors for future measurements that will help minimize the time spent performing electron dosimetry and calibrations. These correction factors can be used to calculate the correct reading without the need to reverse the chamber bias, thus reducing the number of measurements required.
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Magnetic resonance imaging based digitally reconstructed radiographs, virtual simulation, and three-dimensional treatment planning for brain neoplasms. Med Phys 1998; 25:1928-34. [PMID: 9800700 DOI: 10.1118/1.598382] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Currently, patients with brain neoplasms must undergo both computed tomography (CT) and magnetic resonance (MR) imaging to take advantage of CT's density information and MR's soft tissue imaging capabilities. A method has been developed that allows virtual simulation, digitally reconstructed radiographs (DRRs), and 3-D treatment planning of patients with brain neoplasms to be generated using only one T1-weighted MR data set. DRRs of an anthropomorphic RANDO head phantom were generated using MR and CT imaging. The MR based DRRs provided structural information equivalent to CT based DRRs. The spatial linearity of CT and MR image sets was evaluated by measuring the percent distortion and spatial error. There was no statistical difference in spatial linearity or accuracy between the CT and MR image sets. MR and CT based treatment planning were compared using a variety of different treatment accessories, field sizes, photon energies, and gantry positions. Doses at various points throughout the head phantom were used as comparison points between CT based heterogeneous, CT based homogenous, and MR based homogenous treatment planning of the head phantom. Lithium fluoride thermoluminescent dosimeters were used to verify the dosimetric accuracy of MR based treatment planning by taking measurements at these points. For treatment plans with fields that pass through large air cavities, such as the maxillary sinus, homogenous treatment planning produces unacceptable dosimetric error (2%-4%). For treatment plans with fields that pass through the skull, MR homogenous treatment planning can be used with a dosimetric accuracy of +/- 2%.
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A network approach to outpatient service delivery systems: resources flow and system influence. Health Serv Res 1996; 30:771-89. [PMID: 8591929 PMCID: PMC1070092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
OBJECTIVE The study tests a path model for the effects on organizational influence of an organization's centrality in four resource exchange networks in order to gain insight into the network relations that may affect coordination and effectiveness of outpatient health and mental health service systems. DATA SOURCES Primary data are used from face-to-face interviews with the directors of every organization in the predefined service systems in three urbanized counties in Oregon. Each system consisted of 19 to 20 organizations. Data were collected during 1986 and 1987. STUDY DESIGN The path model contains five variables: the major dependent variable is attributed organizational influence; the independent variables are three sets of primary resource exchanges: funds allocation, client referrals, and client inflow. An intervening variable of general network contacts, as an informational resource, is modeled as an outcome of the three primary resource exchanges, as well as one of the predictors of influence. DATA COLLECTION Organizations were identified as system members through a modified snowball sampling procedure. Measures of organizational influence and centrality in each of the exchange networks were derived from interviews with all directors about their interactions with each organization in the system. Multiple regression analysis was used to test the path model. PRINCIPAL FINDINGS The most important resource in predicting centrality in a general contact network is centrality in a client referral network, while contacts and funds allocation centrality are significant predictors of organizational influence. CONCLUSIONS The organization with the greatest influence within the system (because of its ability to allocate funds) may not be the organization that takes the largest role in terms of coordinating routine contacts (because of its ability to refer clients). This disjuncture may signal a weakness in the coordination network and system effectiveness, since the more influential organization may not be the most knowledgeable one in terms of the needs of the system.
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Abstract
The impact resistance of chemically and thermally hardened glass lenses of 2.2- and 3.0-mm thicknesses was evaluated using a ballistic test. Each lens was edged and mounted into a spectacle frame, which was placed on a standard headform. A 6.5-mm steel ball was fired from an air gun at the center of the lens at increasing speeds until the lens broke. The multiple impact data were used to plot cumulative breakage curves. We found that heat-treated photochromic glass and heat-treated crown glass fail at similar missile speeds and that chemical treating considerably improves the impact resistance of crown glass but not of photochromic glass. The poorer performance of photochromic lenses indicates that they should not be prescribed when optimal impact protection is required. Plastic lenses show superior performance.
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Helix coil transitions of d(A)n-d(T)n, d(A-T)n-d(A-T)n, and d(A-A-T)n-d(A-T-T)n; evaluation of parameters governing DNA stability. Biopolymers 1977; 16:1115-37. [PMID: 861368 DOI: 10.1002/bip.1977.360160512] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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