bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of recycled polyethylene/ chitosan composites: the effect of polyethylene-graft-maleic anhydride
Authors: Salmah H. , Azieyanti A.N.
Published: December 2010

The surface of recycled polyethylene (RPE)/chitosan composites was modified with polyethylene-graft-maleic anhydride (MAPE). The mechanical properties, water absorption, morphology, and thermal properties were investigated. The composites with MAPE improved tensile strength and Young’s modulus but reduced elongation at break and water absorption. Scanning electron microscopy study of the tensile fracture surface of composites indicated that the presence of MAPE increased the interfacial interaction between chitosan and RPE matrix. The incorporation of MAPE improved the thermal stability and crystallinity of RPE/chitosan composites.
Does One More Medication Help? Effect of Adding Another Anticonvulsant in Childhood Epilepsy
Authors: Desai Jay , Mitchell Wendy G.
Published: December 2010

Objectives: To study adding an anticonvulsant in children with uncontrolled epilepsy on ≥1 appropriate anticonvulsants. Methods: Chart review, patients with intractable epilepsy in a neurology clinic July 1, 2004 to December 31, 2007. Inclusion: Children on ≥1 stable anticonvulsant who had a second, third, or fourth anticonvulsant added. Exclusions: Noncompliance, subtherapeutic doses, and/or serum anticonvulsant levels, inappropriate anticonvulsant for seizure type, inadequate documentation, infantile spasms, or significant dosage changes in the baseline anticonvulsant(s) over the follow-up period. Patients were followed until further therapeutic changes occurred or September 30, 2008, whichever came first. Outcome: ≥50% decrease in seizure frequency. Results: Charts reviewed: 1886. Patients who met criteria: 84. Time to assessment: 4 weeks to 42 months (median = 7 months). ≥50% reduction in seizure frequency: 35 of 52 patients with second agent added; 5 of 30 patients with third agent added (P = .0001). Conclusions: Worthwhile seizure reduction is reasonably likely with the addition of a second anticonvulsant, but much less likely with the addition of third anticonvulsant.
Methylphenidate has dose-dependent negative effects on rat spermatogenesis: decreased round spermatids and testicular weight and increased p53 expression and apoptosis
Authors: Cansu Ali , Ekinci Özgür , Ekinci Özalp , Serdaroglu Ayse , Erdoğan Deniz , Coşkun Zafer Kutay , Gürgen Seren Gulsen
Published: December 2010

In the present study, we aimed to evaluate the possible effects of methylphenidate on rat testes. Forty-two Wistar rats were randomly distributed into three experimental groups of 14 rats each. For 90 days, each group via gavage received the following: group 1 = tap water (control group), group 2 = 5 mg/kg/day of ritalin (methylphenidate, MPH), and group 3 = 10 mg/kg/day of ritalin. After sacrificing the animals, the body weights as well as the absolute and relative testicular weights were measured. Testes were sampled, fixed, and processed and, by histopathological examination, quantitative morphometric analysis of Sertoli cells, spermatocytes, and spermatids was performed in stages II, V, and XII. Immunohistochemistry was performed for transforming growth factor (TGF)-β1 and p53, and the apoptotic index was assessed through the TUNEL method. Group 2 had a reduction of round spermatids in stage II. Group 3 had reduction in both stage II and stage V spermatids, as well as lower testicular weight. The p53 expression was increased in group 3. In groups 2 and 3, the TGF-β1 expression was reduced and the apoptotic index by TUNEL was increased. Body weights remained stable on either group. Our results showed that methylphenidate might negatively affect spermatogenesis not only by reducing testicular weight and amount of round spermatids but also by increasing apoptotic death and p53 activation. The findings of the study, however, must be cautiously interpreted.
Failure of the Adipocytokine, Resistin, to Protect the Heart From Ischemia-Reperfusion Injury
Authors: Smith Christopher C. T. , Lim Shiang Y. , Wynne Abigail M. , Sivaraman Vivek , Davidson Sean M. , Mocanu Mihaela M. , Hausenloy Derek J. , Yellon Derek M.
Published: December 2010

Experimental studies have linked the adipocytokines with acute cardioprotection. Whether the adipocytokine, resistin, confers protection is, however, debatable. In the current study, the actions of resistin, administered at reperfusion, were investigated in in vivo and in vitro rodent and in vitro human models of myocardial ischemia-reperfusion (I/R) injury. Resistin did not reduce infarct size in Langendorff-perfused rat hearts or murine hearts perfused in vivo. Resistin also did not protect human atrial muscle subjected to hypoxia-reoxygenation. Although cyclosporin A delayed mitochondrial permeability transition pore (MPTP) opening in murine cardiomyocytes, resistin was ineffective. Western blot analysis revealed that resistin treatment was associated with enhanced phosphorylation of Akt, at both the serine-473 (+ 51.9%, P = .01) and threonine-308 (+107%, P < .01) phosphorylation sites, although not to the extent seen with ischemic preconditioning (+132.5%, P = .002 and +389.1%, P < .01, respectively). We conclude that resistin administered at reperfusion at concentrations/doses equivalent to normal (upper end) and pathological serum levels does not protect against I/R injury or inhibit MPTP opening.
Older Adults’ Perceptions of Physical Activity and Cognitive Health: Implications for Health Communication
Authors: Price Anna E. , Corwin Sara J. , Friedman Daniela B. , Laditka Sarah B. , Colabianchi Natalie , Montgomery Kara M.
Published: December 2010

Messages promoting physical activity (PA) to maintain cognitive health (CH) may increase PA and enhance CH among older persons. This study examined older adults’ perceptions of PA and CH. We conducted 10 focus groups with irregularly active older Black and White women and men ( N = 55), ages 65 to 74 in South Carolina. Constant comparison methods compared themes by gender and race/ethnicity groups. Most participants perceived cognitive decline as a severe threat, and they were primarily concerned about losing their independence. Most reported feeling susceptible to cognitive decline. Although most recognized the link between PA and CH, several White men said the association was not clear. Participants recommended a wide range of PA amounts needed to achieve CH benefits. Many suggested that evidence of PA benefits for CH would enhance message credibility. Participants suggested messages be paired with social support to increase PA. Results suggest a need for evidence-based, credible communication promoting PA and CH.
Critical literacy in a primary multiliteracies classroom: The Hurricane Group
Authors: Silvers Penny , Shorey Mary , Crafton Linda
Published: December 2010

This qualitative research presents an expanded perspective of literacy practices in which young students engage in multiple literacies while exploring personal inquiries about Hurricane Katrina in New Orleans, LA. An extended classroom example and analysis taken from a broader research project focusing on early multiliteracies, illustrates the ability of young students to ask critical questions, explore alternative perspectives, and engage in multimodal responses to construct and communicate meaning as they take social action. Narrative inquiry and discourse analysis provide insight into ways that primary children engage in authentic inquiry from a critical, social justice perspective. They also show how traditional early childhood curriculum can focus on social issues through critical framing. This classroom example demonstrates students’ increasing ability to use a range of multimodal tools to accomplish mutually agreed socially relevant goals within a classroom community of practice.
Young writers’ construction of agency
Authors: Fisher Ros
Published: December 2010

This paper considers young learners’ construction of agency in the context of classroom writing lessons. It draws on data from the Esmée Fairbairn-funded project, From Talk to Text: Using Talk to Support Writing, which investigated the relationship between talk and writing in early years classrooms. The paper reports on results from in-depth interviews with pairs of children in six classrooms in the south of England. It is argued that, although human beings have the ability to shape and influence their lives, this capacity is circumscribed by the context within which their activity is located. In order to examine human agency, it is necessary to explore the social contexts and cultural tools that shape the development of human ways of acting. Data presented here indicate a sense of agency in young writers’ classroom choices but raise questions about the efficacy of these choices.
Developing an alternative epistemology of practice: Teachers’ action research as critical pedagogy
Authors: Guy Wamba Nathalis
Published: December 2010

My struggle to promote critical consciousness, dialogue, creative and critical thinking and collaboration in my class led me to turn the classroom into a lab where I would experiment with action research as pedagogy. I began my course by asking students what they wanted, what would they contribute and how we will implement their recommendations. More importantly I invited them to be my co-inquirers in what they perceived to be a radical approach to instruction. This article is an account of what took place specifically the way we all experienced the process.
Action research literature 2008—2010: Themes and trends
Authors: Dick Bob
Published: December 2010

This is the fourth in a series of two-yearly reviews of action research books and edited collections. After an overview of the general action research literature I gather together other relevant literature under the following headings: educational action research, appreciative inquiry, community research and engagement, rural and regional development, organizational and systemic applications, and action learning. The review concludes with a brief examination of other relevant literature, and a tentative look to the future of action research.
Trends in Management of Phlegmasia Cerulea Dolens
Authors: Chinsakchai Khamin , ten Duis Kaj , Moll Frans L. , de Borst Gert J.
Published: December 2010

Phlegmasia cerulea dolens (PCD) is a fulminant condition of acute massive venous thrombosis that may result in major amputation or death unless treated in an early phase. Guidelines for treatment are still not clearly documented. As a consequence, physicians might have limited knowledge of this potential life-threatening condition and its clinical course. Therefore, the purpose of this review was to analyze and summarize clinical manifestations and proposed diagnostic approach, factors that affect the outcome of PCD, and the evolution of management and therapeutic options. Underlying malignancy, pulmonary embolism, and PCD severity are the vital factors that predict the outcome of PCD. In the last decades, treatment options have remained largely unchanged. Published evidence shows that advances in minimally invasive techniques have not yet resulted in outcome improvements compared with traditional surgical thrombectomy. Treatment seems to depend on grading the severity of this condition and experience of the surgeon.
Imagining the face of a nation: Scotland, modernity and the places of memory
Authors: Blaikie Andrew
Published: December 2010

Relationships between modernity and national identity raise issues of how place is remembered morally and visually. This article considers aspects of cultural output in Scotland during the 1930s. While the romantic, rural emphasis of travelogue imagery evaded urbanization, the important literary nationalists Edwin Muir and Hugh MacDiarmid produced nightmare visions of a country defiled by industrialization and imperialism. Against this, the pioneering film-maker John Grierson celebrated modernity as a process of continuity rather than rupture through an ongoing inheritance of national values. Their differing evaluations of alienation and belonging have contributed to stereotypes of place that figure iconographically in the national consciousness as sites of memory, thereby eliding the experience of non-iconographic places while compromising the ways in which individual accounts may be recollected through the modern social imaginary.
Exposure to life-writing as an impact on autobiographical memory
Authors: Harbus Antonina
Published: December 2010

This article combines narrative and genre theory with recent studies of memory processing and reporting to propose that contact with published biography and autobiography, both direct and indirect, has an influence on autobiographical narrative, memory and self-formation. Exposure to durable and pervasive modes of life-writing, transmitted culturally, provides frameworks for meaning-making that normalize certain narrative structures and shape the content and organization of autobiographical memory. This article traces the transfer of conventions found in life-writing genres in recently reported autobiographical memory studies, to argue that further consideration should be given in empirical research contexts to the impact of cultural and educational factors on memory.
Evi-1 is a transcriptional target of mixed-lineage leukemia oncoproteins in hematopoietic stem cells
Authors: Arai Shunya , Yoshimi Akihide , Shimabe Munetake , Ichikawa Motoshi , Nakagawa Masahiro , Imai Yoichi , Goyama Susumu , Kurokawa Mineo
Published: December 2010

Ecotropic viral integration site-1 (Evi-1) is a nuclear transcription factor that plays an essential role in the regulation of hematopoietic stem cells. Aberrant expression of Evi-1 has been reported in up to 10% of patients with acute myeloid leukemia and is a diagnostic marker that predicts a poor outcome. Although chromosomal rearrangement involving the Evi-1 gene is one of the major causes of Evi-1 activation, overexpression of Evi-1 is detected in a subgroup of acute myeloid leukemia patients without any chromosomal abnormalities, which indicates the presence of other mechanisms for Evi-1 activation. In this study, we found that Evi-1 is frequently up-regulated in bone marrow cells transformed by the mixed-lineage leukemia (MLL) chimeric genes MLL-ENL or MLL-AF9. Analysis of the Evi-1 gene promoter region revealed that MLL-ENL activates transcription of Evi-1. MLL-ENL–mediated up-regulation of Evi-1 occurs exclusively in the undifferentiated hematopoietic population, in which Evi-1 particularly contributes to the propagation of MLL-ENL–immortalized cells. Furthermore, gene-expression analysis of human acute myeloid leukemia cases demonstrated the stem cell–like gene-expression signature of MLL-rearranged leukemia with high levels of Evi-1. Our findings indicate that Evi-1 is one of the targets of MLL oncoproteins and is selectively activated in hematopoietic stem cell–derived MLL leukemic cells.
How I treat LGL leukemia
Authors: Lamy Thierry , Loughran Thomas P.
Published: December 2010

Large granular lymphocyte (LGL) leukemia is characterized by a clonal expansion of either CD3+ cytotoxic T or CD3− NK cells. Prominent clinical features of T-LGL leukemia include neutropenia, anemia and rheumatoid arthritis (RA). The terminal effector memory phenotype (CD3+/CD45RA+/CD62L−CD57+) of T-LGL suggests a pivotal chronic antigen-driven immune response. LGL survival is then promoted by platelet-derived growth factor and interleukin-15, resulting in global dysregulation of apoptosis and resistance to normal pathways of activation-induced cell death. These pathogenic features explain why treatment of T-LGL leukemia is based on immunosuppressive therapy. The majority of these patients eventually need treatment because of severe or symptomatic neutropenia, anemia, or RA. No standard therapy has been established because of the absence of large prospective trials. The authors use low-dose methotrexate initially for T-LGL leukemia patients with neutropenia and/or RA. We recommend either methotrexate or oral cyclophosphamide as initial therapy for anemia. If treatment is not successful, patients are switched to either the other agent or cyclosporine. The majority of patients experience an indolent clinical course. Deaths infrequently occur because of infections related to severe neutropenia. As there are no curative therapeutic modalities for T-LGL leukemia, new treatment options are needed.
Dentin matrix protein 1 induces membrane expression of VE-cadherin on endothelial cells and inhibits VEGF-induced angiogenesis by blocking VEGFR-2 phosphorylation
Authors: Pirotte Sophie , Lamour Virginie , Lambert Vincent , Alvarez Gonzalez Maria-Luz , Ormenese Sandra , Noël Agnès , Mottet Denis , Castronovo Vincent , Bellahcène Akeila
Published: December 2010

Dentin matrix protein 1 (DMP1) is a member of the small integrin–binding ligand N-linked glycoprotein (SIBLING) family, a group of proteins initially described as mineralized extracellular matrices components. More recently, SIBLINGs have been implicated in several key steps of cancer progression, including angiogenesis. Although proangiogenic activities have been demonstrated for 2 SIBLINGs, the role of DMP1 in angiogenesis has not yet been addressed. We demonstrate that this extracellular matrix protein induced the expression of vascular endothelial cadherin (VE-cadherin), a key regulator of intercellular junctions and contact inhibition of growth of endothelial cells that is also known to modulate vascular endothelial growth factor receptor 2 (VEGFR-2) activity, the major high-affinity receptor for VEGF. DMP1 induced VE-cadherin and p27Kip1 expression followed by cell-cycle arrest in human umbilical vein endothelial cells (HUVECs) in a CD44-dependent manner. VEGF-induced proliferation, migration, and tubulogenesis responses were specifically blocked on DMP1 pretreatment of HUVECs. Indeed, after VE-cadherin induction, DMP1 inhibited VEGFR-2 phosphorylation and Src-mediated signaling. However, DMP1 did not interfere with basic fibroblast growth factor–induced angiogenesis. In vivo, DMP1 significantly reduced laser-induced choroidal neovascularization lesions and tumor-associated angiogenesis. These data enable us to put DMP1 on the angiogenic chessboard for the first time and to identify this protein as a new specific inhibitor of VEGF-induced angiogenesis.
Physiological homology betweenDrosophila melanogasterand vertebrate cardiovascular systems
Authors: Choma Michael A. , Suter Melissa J. , Vakoc Benjamin J. , Bouma Brett E. , Tearney Guillermo J.
Published: December 2010

The physiology of the Drosophila melanogaster cardiovascular system remains poorly characterized compared with its vertebrate counterparts. Basic measures of physiological performance remain unknown. It also is unclear whether subtle physiological defects observed in the human cardiovascular system can be reproduced in D. melanogaster. Here we characterize the cardiovascular physiology of D. melanogaster in its pre-pupal stage by using high-speed dye angiography and optical coherence tomography. The heart has vigorous pulsatile contractions that drive intracardiac, aortic and extracellular-extravascular hemolymph flow. Several physiological measures, including weight-adjusted cardiac output, body-length-adjusted aortic velocities and intracardiac shear forces, are similar to those in the closed vertebrate cardiovascular systems, including that of humans. Extracellular-extravascular flow in the pre-pupal D. melanogaster circulation drives convection-limited fluid transport. To demonstrate homology in heart dysfunction, we showed that, at the pre-pupal stage, a troponin I mutant, held-up2 (hdp2), has impaired systolic and diastolic heart wall velocities. Impaired heart wall velocities occur in the context of a non-dilated phenotype with a mildly depressed fractional shortening. We additionally derive receiver operating characteristic curves showing that heart wall velocity is a potentially powerful discriminator of systolic heart dysfunction. Our results demonstrate physiological homology and support the use of D. melanogaster as an animal model of complex cardiovascular disease.
Embryonic frog epidermis: a model for the study of cell-cell interactions in the development of mucociliary disease
Authors: Dubaissi Eamon , Papalopulu Nancy
Published: December 2010

Specialised epithelia such as mucociliary, secretory and transporting epithelia line all major organs, including the lung, gut and kidney. Malfunction of these epithelia is associated with many human diseases. The frog embryonic epidermis possesses mucus-secreting and multiciliated cells, and has served as an excellent model system for the biogenesis of cilia. However, ionic regulation is important for the function of all specialised epithelia and it is not clear how this is achieved in the embryonic frog epidermis. Here, we show that a third cell type develops alongside ciliated and mucus-secreting cells in the tadpole skin. These cells express high levels of ion channels and transporters; therefore, we suggest that they are analogous to ionocytes found in transporting epithelia such as the mammalian kidney. We show that frog ionocytes express the transcription factor foxi1e, which is required for the development of these cells. Depletion of ionocytes by foxi1e knockdown has detrimental effects on the development of multiciliated cells, which show fewer and aberrantly beating cilia. These results reveal a newly identified role for ionocytes and suggest that the frog embryonic skin is a model system that is particularly suited to studying the interactions of different cell types in mucociliary, as well as in secretory and transporting, epithelia.
A New Evolutionary Algorithm for a Class of Nonlinear Bilevel Programming Problems and Its Global Convergence
Authors: Wang Yuping , Li Hong , Dang Chuangyin
Published: December 2010

When the leader's objective function of a nonlinear bilevel programming problem is nondifferentiable and the follower's problem of it is nonconvex, the existing algorithms cannot solve the problem. In this paper, a new effective evolutionary algorithm is proposed for this class of nonlinear bilevel programming problems. First, based on the leader's objective function, a new fitness function is proposed that can be easily used to evaluate the quality of different types of potential solutions. Then, based on Latin squares, an efficient crossover operator is constructed that has the ability of local search. Furthermore, a new mutation operator is designed by using some good search directions so that the offspring can approach a global optimal solution quickly. To solve the follower's problem efficiently, we apply some efficient deterministic optimization algorithms in the MATLAB Toolbox to search for its solutions. The asymptotically global convergence of the algorithm is proved. Numerical experiments on 25 test problems show that the proposed algorithm has a better performance than the compared algorithms on most of the test problems and is effective and efficient.
A Time Bucket Formulation for the Traveling Salesman Problem with Time Windows
Authors: Dash Sanjeeb , Günlük Oktay , Lodi Andrea , Tramontani Andrea
Published: December 2010

The traveling salesman problem with time windows (TSPTW) is the problem of finding a minimum-cost path visiting a set of cities exactly once, where each city must be visited within a given time window. We present an extended formulation for the problem based on partitioning the time windows into subwindows that we call buckets. We present cutting planes for this formulation that are computationally more effective than the ones known in the literature because they exploit the division of the time windows into buckets. To obtain a good partition of the time windows, we propose an iterative linear programming (LP)-based procedure that may produce buckets of different sizes. The LP relaxation of this formulation yields strong lower bounds for the TSPTW and provides a good starting point for our branch-and-cut algorithm. We also present encouraging computational results on hard test problems from the literature, namely, asymmetric instances arising from a practical scheduling application, as well as randomly generated symmetric instances. In particular, we solve a number of previously unsolved benchmark instances.
Economic Interpretation of Probabilities Estimated by Maximum Likelihood or Score
Authors: Johnstone D. J.
Published: December 2010

The conventional method of estimating a probability prediction model by maximum likelihood (MLE) is a form of maximum score estimation with economic meaning. Of all the probabilities that a given model might have produced, those obtained by MLE yield maximum in-sample betting return to a log utility investor. Recognition of this affinity between MLE and log utility begs the wider methodological question of whether different decision makers benefit in different degrees from different probabilities. Probabilities produced by MLE can be either too conservative or too bold relative to those found by maximizing utility under more risk-tolerant or risk-averse score functions. A very (not very) risk-averse user, who bets characteristically small (large) fractions of wealth based on a conservative forecast, is bound to make a rapidly (slowly) increasing bet as the forecast probability becomes progressively bolder or more distant from the market probability. The effect of this interaction between risk aversion and forecast is that a highly risk-averse user may need a much bolder forecast to obtain the same certainty equivalent as a more risk-tolerant investor. It follows more broadly that professional forecasters should anticipate how a client with given risk aversion expects to gain from any given forecast, or forecast revision, before committing resources toward making a better informed (but still honest) forecast.

This paper was accepted by Peter Wakker, decision analysis.
Organizational Change and Employee Stress
Authors: Dahl Michael S.
Published: December 2010

This article analyzes the relationship between organizational change and employee health. It illuminates the potentially negative outcomes of change at the level of the employee. In addition, it relates to the ongoing debate over how employees react to and respond to organizational change. I hypothesize that change increases the risk of negative stress, and I test this hypothesis using a comprehensive panel data set of all stress-related medicine prescriptions for 92,860 employees working in 1,517 of the largest Danish organizations. The findings suggest that the risk of receiving stress-related medication increases significantly for employees at organizations that change, especially those that undergo broad simultaneous changes along several dimensions. Thus, organizational changes are associated with significant risks of employee health problems. These effects are further explored with respect to employees at different hierarchical levels as well as at firms of different sizes and from different sectors.

This paper was accepted by Jesper Sørensen, organizations.
OR PRACTICE—R&D Project Portfolio Analysis for the Semiconductor Industry
Authors: Gemici-Ozkan Banu , Wu S. David , Linderoth Jeffrey T. , Moore Jeffry E.
Published: December 2010

We introduce a decision-support framework for the research and development (R&D) portfolio selection problem faced by a major U.S. semiconductor manufacturer. R&D portfolio selection is of critical importance to high-tech operations such as semiconductors and pharmaceuticals, because it determines the blend of technological development the firm must invest in its R&D resources. This R&D investment leads to differentiating technologies that drive the firm's market position. We developed a general, three-phase decision-support structure for the R&D portfolio selection problem. First is the scenario generation phase, where we transform qualitative assessment and market foresight from senior executives and market analysts into quantitative data. This is combined with the company's financial data (e.g., revenue projections) to generate scenarios of potential project revenue outcomes. This is followed by the optimization phase, where a multistage stochastic program (SP) is solved to maximize expected operating income (OI) subject to risk, product interdependency, capacity, and resource allocation constraints. The optimization procedure generates an efficient frontier of portfolios at different OI (return) and risk levels. The refinement phase offers managerial insights through a variety of analysis tools that utilize the optimization results. For example, the robustness of the optimal portfolio with respect to the risk level, the variability of a portfolio's OI, and the resource level usage as a function of the optimal portfolio can be analyzed and compared to any qualitatively suggested portfolio of projects. The decision-support structure is implemented, tested, and validated with various real-world cases and managerial recommendations. We discuss our implementation experience using a case example, and we explain how the system is incorporated into the corporate R&D investment decisions.
Optimal Control of a Mean-Reverting Inventory
Authors: Cadenillas Abel , Lakner Peter , Pinedo Michael
Published: December 2010

Motivated by empirical observations, we assume that the inventory level of a company follows a mean-reverting process. The objective of the management is to keep this inventory level as close as possible to a given target; there is a running cost associated with the difference between the actual inventory level and the target. If inventory deviates too much from the target, management may perform an intervention in the form of either a purchase or a sale of an amount of the goods. There are fixed and proportional costs associated with each intervention. The objective of this paper is to find the optimal inventory levels at which interventions should be performed as well as the magnitudes of the interventions to minimize the total cost. We solve this problem by applying the theory of stochastic impulse control. Our analysis yields the optimal policy, which at times exhibits a behavior that is not intuitive.
Algorithms for Scheduling Runway Operations Under Constrained Position Shifting
Authors: Balakrishnan Hamsa , Chandran Bala G.
Published: December 2010

The efficient operation of airports, and runways in particular, is critical to the throughput of the air transportation system as a whole. Scheduling arrivals and departures at runways is a complex problem that needs to address diverse and often competing considerations of efficiency, safety, and equity among airlines. One approach to runway scheduling that arises from operational and fairness considerations is that of constrained position shifting (CPS), which requires that an aircraft's position in the optimized sequence not deviate significantly from its position in the first-come-first-served sequence. This paper presents a class of scalable dynamic programming algorithms for runway scheduling under constrained position shifting and other system constraints. The results from a prototype implementation, which is fast enough to be used in real time, are also presented.
Do Firms Invest in Forecasting Efficiently? The Effect of Competition on Demand Forecast Investments and Supply Chain Coordination
Authors: Shin Hyoduk , Tunca Tunay I.
Published: December 2010

We study the effect of downstream competition on incentives for demand forecast investments in supply chains. We show that with common pricing schemes, such as wholesale price or two-part tariffs, downstream firms under Cournot competition overinvest in demand forecasting. Analyzing the determinants of overinvestment, we demonstrate that under wholesale price contracts and two-part tariffs, total demand forecast investment can be very significant, and as a result, the supply chain can suffer substantial losses. We show that an increased number of competing retailers and uncertainty in consumer demand tend to increase inefficiency, whereas increased consumer market size and demand forecast costs reduce the loss in supply chain surplus. We identify the causes of inefficiency, and to coordinate the channel with forecast investments, we explore contracts in the general class of market-based contracts used in practice. When retailers' forecast investments are not observable, such a contract that employs an index-price can fully coordinate the supply chain. When forecast investments are observable to others, however, the retailers engage in an “arms race” for forecast investment, which can result in a significant increase in overinvestment and reduction in supply chain surplus. Furthermore, in that case, simple market-based contracts cannot coordinate the supply chain. To solve this problem, we propose a uniform-price divisible-good auction-based contracting scheme, which can achieve full coordination when forecast investments are observable. We also demonstrate the desirable properties for implementability of our proposed coordinating contracting schemes, including incentive-compatible and reliable demand forecast information revelation by the retailers, and being regret-free.
OR FORUM—High Leverage Interventions: Three Cases of Defensive Action and Their Lessons for OR/MS Today
Authors: Lane David C.
Published: December 2010

This paper has two aims. First, to present cases in which scientists developed a defensive system for their homeland: Blackett and the air defense of Britain in WWII, Forrester and the SAGE system for North America in the Cold War, and Archimedes' work defending Syracuse during the Second Punic War. In each case the historical context and the individual's other achievements are outlined, and a description of the contribution's relationship to OR/MS is given.

The second aim is to consider some of the features the cases share and examine them in terms of contemporary OR/MS methodology. Particular reference is made to a recent analysis of the field's strengths and weaknesses. This allows both a critical appraisal of the field and a set of potential responses for strengthening it. Although a mixed set of lessons arise, the overall conclusion is that the cases are examples to build on and that OR/MS retains the ability to do high stakes work.
Balance Within and Across Domains: The Performance Implications of Exploration and Exploitation in Alliances
Authors: Lavie Dovev , Kang Jingoo , Rosenkopf Lori
Published: December 2010

Organizational research advocates that firms balance exploration and exploitation, yet it acknowledges inherent challenges in reconciling these opposing activities. To overcome these challenges, such research suggests that firms establish organizational separation between exploring and exploiting units or engage in temporal separation whereby they oscillate between exploration and exploitation over time. Nevertheless, these approaches entail resource allocation trade-offs and conflicting organizational routines, which may undermine organizational performance as firms seek to balance exploration and exploitation within a discrete field of organizational activity (i.e., domain). We posit that firms can overcome such impediments and enhance their performance if they explore in one domain while exploiting in another. Studying the alliance portfolios of software firms, we demonstrate that firms do not typically benefit from balancing exploration and exploitation within the function domain (technology versus marketing and production alliances) and structure domain (new versus prior partners). Nevertheless, firms that balance exploration and exploitation across these domains by engaging in research and development alliances while collaborating with their prior partners, or alternatively, by forming marketing and production alliances while seeking new partners, gain in profits and market value. Moreover, we reveal that increases in firm size that exacerbate resource allocation trade-offs and routine rigidity reinforce the benefits of balance across domains and the costs of balance within domains. Our domain separation approach offers new insights into how firms can benefit from balancing exploration and exploitation. What matters is not simply whether firms balance exploration and exploitation in their alliance formation decisions but the means by which they achieve such balance.
Status Inconsistency and Product Valuation in the California Wine Market
Authors: Zhao Wei , Zhou Xueguang
Published: December 2010

This study develops a theoretical model on the role of multidimensional status and status inconsistency in market evaluation processes. A product or an organization may acquire multiple status indicators in association with a multitude of market institutions. We argue that when status indicators are consistently positive, each exerts a greater positive effect on the valuation of a product or an organization; conversely, inconsistency among multiple indicators undermines the status claim. We test this theoretical proposition by examining patterns of product valuation in the California premium wine market. Our findings show that when an individual wine's tasting score rated by critics and another more general status indicator—classified appellation affiliation, extra designation on the label, or a winery's organizational status—are consistently positive, each makes a greater contribution to wine price. In contrast, when status indicators are inconsistent, the value of the positive status indicator is reduced. Our study explicates the scope conditions under which market status may yield different outcomes and sheds light on the interplay among status indicators in market valuation.
Dynamic Resource Capabilities: Managing Workforce Knowledge with a Technology Upgrade
Authors: Gaimon Cheryl , Özkan Gülru F. , Napoleon Karen
Published: December 2010

Although managers invest in new technology to improve performance, often the benefits sought are elusive while the costs incurred far exceed expectations. The literature offers insights to help explain this phenomenon. Evidence suggests that, while carefully considering the purchase cost, managers often underestimate the costs and planning necessary for proper implementation. Consequently, short-term problems arise and long-term benefits are not realized. A model is introduced that integrates workforce knowledge management with the technology upgrade decision. The manager upgrades technology or pursues general training of the workforce in response to depreciation in the ability of each resource to drive net income over time. Depreciation occurs because of changes in consumer preferences and competition. Although adding to technology capability, an upgrade makes a portion of workforce knowledge obsolete. The manager invests in preparatory training prior to the upgrade to reduce obsolescence. Whereas general training is pursued to respond to depreciation by enhancing the ability of the workforce to improve existing products or create new products, preparatory training is technology-specific and focused on preparing for a technology upgrade. We find that the rates of preparatory and general training follow entirely different paths over time. Conditions are given where a manager uses one training strategy as a substitute for or complement to the other. We show that training strategies are not only impacted by learning phenomena such as the rate of forgetting, but also by the rates of technology depreciation and advancement. We show how workforce learning phenomena impact the technology upgrade decision.
Corporate Governance and Stakeholder Opportunism
Authors: v. Werder Axel
Published: December 2010

Corporate governance has become one of the most prominent topics for management scholars, top executives, and regulators alike over the last couple of decades. Originally a domain of economics and finance (as well as law), the theme has spread to other areas such as strategic management and organization theory in recent years. This paper will first give a brief overview on major developments in the field of corporate governance. These developments encompass, on the one hand, the extension of the classical focus on formal systems and structures to perspectives that address behavioral as well as process issues. On the other hand, the terrain has been broadened from its traditional narrow interest in the principal agent problem between shareholders and management to the more comprehensive stakeholder approach of corporate governance. Building on these developments, this paper will subsequently elaborate on a further extension of the topic by emphasizing the concept of stakeholder opportunism. The classical principal agent problem results from possible opportunistic behavior of the management, which compromises the interests of the shareholders. However, as the notion of stakeholder opportunism points out, not only the management of a company can exercise opportunism; rather, all stakeholders of a company can (and will to some extent) have options to behave opportunistically and at the same time bear the risk of being victims of the opportunism of other stakeholders. This paper develops a conceptual framework for analyzing the determinants and dynamics of the various stakeholders' opportunism options and risks as well as of the actual opportunistic behavior of stakeholders. Employing this framework, implications of the notion of stakeholder opportunism for managers and regulators are discussed, and perspectives for further research are identified.
Network Exchange Patterns in Online Communities
Authors: Faraj Samer , Johnson Steven L.
Published: December 2010

Large-scale online communities rely on computer-mediated communication between participants, enabling them to sustain interactions and exchange on a scale hitherto unknown. Yet little research has focused on how these online communities sustain themselves and how their interactions are structured. In this paper, we theorize and empirically measure the network exchange patterns of long-duration sustainable online communities. We propose that participation dynamics follow specific forms of social exchange: direct reciprocity, indirect reciprocity, and preferential attachment. We integrate diverse findings about individual participation motivations by identifying how individual behavior manifests in network-level structures of online communities. We studied five online communities over 27 months and analyzed 38,483 interactions using exponential random graph (p*) models and mixed-effects analysis of covariance. In a test of competing models, we found that network exchange patterns in online community communication networks are characterized by direct reciprocity and indirect reciprocity patterns and, surprisingly, a tendency away from preferential attachment. Our findings undermine previous explanations that online exchange follows a power law distribution based on people wanting to connect to “popular” others in online communities. Our work contributes to theories of new organizational forms by identifying network exchange patterns that regulate participation and sustain online communities.
Sheehan's syndrome in modern times: a nationwide retrospective study in Iceland
Authors: Kristjansdottir Hallgerdur Lind , Bodvarsdottir Sigrun Perla , Sigurjonsdottir Helga Agusta
Published: December 2010

Background and objective

Half a century ago the prevalence of Sheehan's syndrome (SS) was 10–20 per 100 000 women. With better obstetric help the prevalence is assumed to have decreased, especially in developed countries. The aim of this study is to estimate the prevalence of SS in modern times in Iceland.

Design

We studied the prevalence of SS in 2009 in a nationwide retrospective population-based study.

Methods

All patients with diagnosed SS were identified, and information regarding obstetric care, clinical presentation and hormonal assays was collected. Correlation was calculated with Kendall's tau-b. Significance level: P<0.05.

Results

Eight women were identified with SS; thus, the prevalence of SS in 2009 was 5.1 per 100 000 women. The mean age at delivery and diagnosis was 33.0 and 36.6 respectively, resulting in a diagnostic delay (DD) of 1–240 months. Four women had low blood pressure during delivery, and five had massive blood loss (>1000 ml). Six had complicated deliveries. The most common clinical presentation was failure to lactate and failure to resume menstruation. The patients had three to five failing pituitary axis. There was no correlation between bleeding at delivery or the number of hormonal axes affected and DD.

Conclusion

The prevalence of SS in Iceland was higher than we expected in a country with modern obstetric care. Long DD and incidental diagnosis indicate that women might be lacking correct diagnosis and treatment, and thus the prevalence of SS is even higher. As SS is easily diagnosed and treatable, but can be life-threatening if unrecognised, doctors need to be aware of the disease.
Similarities, Differences, and Unknowns in Biology and Management of Three Parasitic Lampreys of North America
Authors: Clemens Benjamin J. , Binder Thomas R. , Docker Margaret F. , Moser Mary L. , Sower Stacia A.
Published: December 2010

Sea lampreys, Petromyzon marinus, are invasive to the Laurentian Great Lakes where they have decimated native fishes. Great Lakes sea lampreys have been subjected to control measures for several decades, and the drive to control them has led to major advances in understanding their biology and in informing management. In contrast, anadromous sea and Pacific (Entosphenus tridentatus) lampreys have co-evolved with their oceanic prey. Both of these anadromous lampreys are in decline, and a limited amount of information on their biology has stymied conservation. The tendency has been to make biological inferences about anadromous lampreys based on the Great Lakes sea lamprey without justifiable evidence. We identify areas in which key information is missing for the juvenile (parasitic feeding) phase and adult freshwater spawning migrations, and compare and contrast information for these lampreys. Our comparisons reveal major differences, some intriguing similarities, and key unknowns that will require empirical testing.

Resumen

la lamprea marina, Petromyzon marinus, es una especie invasiva de la región de los grandes lagos de los Estados Unidos de Norteamérica, en los cuales han diezmado las poblaciones de peces nativos. La lamprea marina de los grandes lagos ha sido sujeto de medidas de control por varias décadas y esta necesidad ha dado lugar a importantes avances en el entendimiento de su biología y manejo. En contraste, la lamprea anádroma y la del Pacífico (Entosphenus tridentatus) han co-evolucionado con sus presas oceánicas. Actualmente las poblaciones de ambas lampreas se encuentran en declive y la escasez de información sobre su biología ha interferido con su conservación. La tendencia ha sido hacer, sin evidencia que lo justifique, inferencias acerca de la lamprea del Pacífico sobre la base de lo que se conoce de la lamprea de los grandes lagos. Se identificaron áreas en las que se carece de información crítica de la fase juvenil (alimentación parasitaria) y de las migraciones reproductivas de los adultos y se comparó y contrastó información para estas lampreas. La comparación reveló diferencias significativas, algunas similitudes interesantes e interrogantes clave que demandarán de comprobación empírica.