bluuebunny/crossref_metadata_2025 huggingface dataset:
Sample size re‐estimation: recent developments and practical considerations
Authors: Gould A. Lawrence
Published: August 2002

Interim findings of a clinical trial often will be useful for increasing the sample size if necessary to provide the required power against the null hypothesis when the alternative hypothesis is true. Strategies for carrying out the interim examination that have been described over the past several years include ‘internal pilot studies’, blinded interim sample size adjustment and conditional power. Simulation studies show that the alternative methods generally control the type I error rate satisfactorily, although the power properties are more variable. The important issues associated with sample size re‐estimation are strategic, not numeric. Clearly expressed regulatory preferences suggest that methods not requiring unblinding the data before completion of the trial would be most appropriate. Extending a trial has its risks. The investigators/patients enrolled later in the course of a trial are not necessarily the same as those recruited/entered early. Re‐activating the enrolment process may be sufficiently complicated and expensive to justify enrolling more investigators/patients at the outset. Since sample size re‐estimation adjusts the sample size on the basis of variability while efficacy interim analysis adjusts the sample size based on the basis of estimated effect size, both principles can be used in the same trial. Sample size re‐estimation may not be advisable for trials involving extended follow‐up of individual patients or, more generally, when the follow‐up time is long relative to the recruitment time. In such cases, it may be better to estimate the sample size conservatively and introduce an interim efficacy evaluation. Copyright © 2001 John Wiley & Sons, Ltd.
Sample size recalculation using conditional power
Authors: Denne Jonathan S.
Published: August 2002

The sample size required to achieve a given power at a prespecified absolute difference in mean response may depend on one or more nuisance parameters, which are usually unknown. Proposed methods for using an internal pilot to recalculate the sample size using estimates of these parameters have been well studied. Most of these methods ignore the fact that data on the parameter of interest from within this internal pilot will contribute towards the value of the final test statistic. We propose a method which involves recalculating the target sample size by computing the number of further observations required to maintain the probability of rejecting the null hypothesis at the end of the study under the prespecified absolute difference in mean response conditional on the data observed so far. We do this within the framework of a two‐group error‐spending sequential test, modified so as to prevent inflation of the type I error rate. Copyright © 2001 John Wiley & Sons, Ltd.
Exact inference for categorical data: recent advances and continuing controversies
Authors: Agresti Alan
Published: August 2002

Methods for exact small‐sample analyses with categorical data have been increasingly well developed in recent years. A variety of exact methods exist, primarily using the approach that eliminates unknown parameters by conditioning on their sufficient statistics. In addition, a variety of algorithms now exist for implementing the methods. This paper briefly summarizes the exact approaches and describes recent developments. Controversy continues about the appropriateness of some exact methods, primarily relating to their conservative nature because of discreteness. This issue is examined for two simple problems in which discreteness can be severe – interval estimation of a proportion and the odds ratio. In general, adjusted exact methods based on the mid‐P‐value seem a reasonable way of reducing the severity of this problem. Copyright © 2001 John Wiley & Sons, Ltd.
Zero‐inflated Poisson regression with random effects to evaluate an occupational injury prevention programme
Authors: Yau Kelvin K. W. , Lee Andy H.
Published: August 2002

This study presents a zero‐inflated Poisson regression model with random effects to evaluate a manual handling injury prevention strategy trialled within the cleaning services department of a 600 bed public hospital between 1992 and 1995. The hospital had been experiencing high annual rates of compensable injuries of which over 60 per cent were attributed to manual handling. The strategy employed Workplace Risk Assessment Teams (WRATS) that utilized a workplace risk identification, assessment and control approach to manual handling injury hazard reduction. The WRATS programme was an intervention trial, covering the 1988–1995 financial years. In the course of compiling injury counts, it was found that the data exhibited an excess of zeros, in the context that the majority of cleaners did not suffer any injuries. This phenomenon is typical of data encountered in the occupational health discipline. We propose a zero‐inflated random effects Poisson regression model to analyse such longitudinal count data with extra zeros. The WRATS intervention and other concomitant information on individual cleaners are considered as fixed effects in the model. The results provide statistical evidence showing the value of the WRATS programme. In addition, the methods can be applied to assess the effectiveness of intervention trials on populations at high risk of manual handling injury or indeed of injury from other hazards. Copyright © 2001 John Wiley & Sons, Ltd.
A general family of distributions for longitudinal dependence with special reference to event histories
Authors: Lindsey J. K.
Published: August 2002

Event histories play an increasingly important role in medical studies. Examples include times between recurrences of tumours, as with bladder cancer, and between repeated infections, as with chronic granulotomous disease. A general method for generating new distributions is proposed by introducing an intensity function into a density. This procedure yields, as special cases, several distributions already proposed in the literature. The families of distributions based on the Pareto distribution are of particular interest for event history analysis because of their relationship to the Laplace transform of a gamma distribution. They can yield multivariate distributions, with longitudinal (serial) dependence by a procedure similar to updating in the Kalman filter and with uniform dependence in a similar way to copulas. For longitudinal dependence, several such updating procedures are proposed. Copyright © 2001 John Wiley & Sons, Ltd.
On the inappropriateness of an EM algorithm based procedure for blinded sample size re‐estimation
Authors: Friede Tim , Kieser Meinhard
Published: August 2002

When planning a clinical trial the sample size calculation is commonly based on ana prioriestimate of the variance of the outcome variable. Misspecification of the variance can have substantial impact on the power of the trial. It is therefore attractive to update the planning assumptions during the ongoing trial using an internal estimate of the variance. For this purpose, an EM algorithm based procedure for blinded variance estimation was proposed for normally distributed data. Various simulation studies suggest a number of appealing properties of this procedure. In contrast, we show that (i) the estimates provided by this procedure depend on the initialization, (ii) the stopping rule used is inadequate to guarantee that the algorithm converges against the maximum likelihood estimator, and (iii) the procedure corresponds to the special case of simple randomization which, however, in clinical trials is rarely applied. Further, we show that maximum likelihood estimation leads to no reasonable results for blinded sample size re‐estimation due to bias and high variability. The problem is illustrated by a clinical trial in asthma. Copyright © 2002 John Wiley & Sons, Ltd.
Motivation, cognitions and traits: predicting occupational health, well‐being and performance
Authors: Code Sharon , Langan‐Fox Janice
Published: August 2002

Past research on vulnerability/resistance to occupational stress and strain has focused predominantly on personality defined at the trait or dispositional level (e.g. Type A Behaviour Pattern, Locus of Control, Dispositional Optimism and Negative Affectivity). This is problematic for two reasons. First, within the current, prevailing integrative view of personality there are three main elements: motivation, cognitions, and traits (Winter, 1996; McAdams, 2000). The second problem is that there are two branches that together define personality psychology as a discipline: (a) the nomothetic or ‘individual difference’ approach; and (b) the ‘ideographic’ approach, that is the structure and organization of personality at the individual level (Epstein, 1994), yet trait theory—and especially the ‘Big Five’ model—have paid little attention to the latter, a trend that is also evident in the occupational stress literature. The central thesis of the current paper is that motivation, cognitions and traits should contribute more variance to the stress–strain relationship than trait personality alone. A preliminary model is presented and recommendations for future research provided. Copyright © 2001 John Wiley & Sons, Ltd.
Alliance entrepreneurship and firm market performance
Authors: Sarkar MB , Echambadi RAJ , Harrison Jeffrey S.
Published: August 2002

This paper extends entrepreneurship into the domain of alliances, and investigates the effect of alliance proactiveness on market‐based firm performance (defined in terms of sales growth, market share, market development and product development). Alliance proactiveness is defined as the extent to which an organization engages in identifying and responding to partnering opportunities. The effect of alliance proactiveness on performance is tested within a contingency framework, with size and perceived environmental uncertainty as moderators, and using data from 182 firms. We estimated the model using partial least squares. Results indicate that alliance proactiveness leads to superior market‐based performance, and that this effect is stronger for small firms and in unstable market environments. Copyright © 2001 John Wiley & Sons, Ltd.
A resource‐based view of manufacturing strategy and the relationship to manufacturing performance
Authors: Schroeder Roger G. , Bates Kimberly A. , Junttila Mikko A.
Published: August 2002

This paper examines manufacturing strategy from the perspective of the resource‐based view of the firm. It explores the role of resources and capabilities in manufacturing plants that cannot be easily duplicated, and for which ready substitutes are not available. Such resources and capabilities are formed by employees' internal learning based on cross‐training and suggestion systems, external learning from customers and suppliers, and proprietary processes and equipment developed by the firm. Based on data from 164 manufacturing plants, the paper empirically demonstrates that competitive advantage in manufacturing (as measured by superior plant performance) results from proprietary processes and equipment which, in turn, is driven by external and internal learning. The implication is that resources such as standard equipment and employees with generic skills obtainable in factor markets are not as effective in achieving high levels of plant performance, since they are freely available to competitors. The paper also demonstrates the important role of internal and external learning in developing resources that are imperfectly imitable and difficult to duplicate. Copyright © 2002 John Wiley & Sons, Ltd.
An object‐oriented design for graph visualization
Authors: Marshall M. S. , Herman I. , Melançon G.
Published: August 2002

Many applications, from everyday file system browsers to visual programming tools, require the display of network and graph structures. The Graph Visualization Framework (GVF) (available at http://www.cwi.nl/InfoVisu/GVF) is an architecture that supports the tasks common to most graph browsers and editors. This article gives a brief overview of the design of the GVF and focuses on the core classes that are used to represent and manipulate graphs. The design of the core classes is justified by the requirements for navigation and visualization. Copyright © 2001 John Wiley & Sons, Ltd.
Tool integration for flexible simulation of distributed algorithms
Authors: Khanvilkar Shashank , Shatz Sol M.
Published: August 2002

Over the last two decades, considerable research has been done in distributed operating systems, which can be attributed to faster processors and better communication technologies. A distributed operating system requires distributed algorithms to provide basic operating system functionality likemutual exclusion,deadlock detection, etc. A number of such algorithms have been proposed in the literature. Traditionally, these distributed algorithms have been presented in a theoretical way, with limited attempts to simulate actual working models. This paper discusses our experience in simulating distributed algorithms with the aid of some existing tools, including OPNET and Xplot. We discuss our efforts to define a basic model‐based framework for rapid simulation and visualization, and illustrate how we used this framework to evaluate some classic algorithms. We have also shown how the performance of different algorithms can be compared based on some collected statistics. To keep the focus of this paper on the approach itself, and our experience with tool integration, we only discuss some relatively simple models. Yet, the approach can be applied to more complex algorithm specifications. Copyright © 2001 John Wiley & Sons, Ltd.
We enter the twenty‐first century with schooling designed in the nineteenth
Authors: Banathy Bela H.
Published: August 2002

Recognizing that the current system of schooling is grounded in – and was designed for – the industrial machine age of the nineteenth century, this paper brings into focus the necessity of designing new systems of learning and human development that are in‐sync with the new realities of the information/knowledge age and are capable to co‐evolve with the emerging society of the new century. The paper offers an approach to the design and self‐organization of these new systems. In closing, two educational images are projected; one stands for ‘the new story of education’, the other depicts ‘the old story.’ Copyright © 2001 John Wiley & Sons, Ltd.
Non‐trivial solutions to theN‐person Prisoners' Dilemma
Authors: Szilagyi Miklos N. , Szilagyi Zoltan C.
Published: August 2002

We have developed a new agent‐based simulation tool to model social dilemmas for the case of a large number of not necessarily rational decision‐makers (Szilagyi and Szilagyi,2000). The combination of various personalities with stochastic learning makes it possible to simulate the multi‐person Prisoners' Dilemma game for realistic situations. A variety of personality profiles and their arbitrary combinations can be represented, including agents whose probability of cooperation changes by an amount proportional to its reward from the environment. For the case of such agents the game has non‐trivial but remarkably regular solutions. We discuss a method and present an algorithm for making accurate advance predictions of these solutions. We also propose our model as a viable approach for the study of populations of cells, organisms, groups, organizations, communities, and societies. It may lead to better understanding of the evolution of cooperation in living organisms, international alliances, sports teams, and large organizations. Copyright © 2002 John Wiley & Sons, Ltd.
Lateral ligament: Its anatomy and clinical importance
Authors: Takahashi Takashi , Ueno Masashi , Azekura Kaoru , Ohta Hirotoshi
Published: August 2002

Since Miles proposed abdominoperineal excision as a radical surgery for rectal cancer in 1908, surgeons have recognized the lateral ligament in the pararectal space of their patients and attached clinical importance to it, although anatomists did not describe any such configuration in cadavers. By analyzing an experience of 421 lower rectal cancer cases at the Cancer Institute Hospital in Tokyo, discussion of the lateral ligament was focused on its relationship to the fascial arrangements in the pelvis, the pelvic autonomic nervous system, and the lymphatic drainage of the rectum. The lateral ligament is not an anatomical term, but a clinical or surgical one. It exists in a living pelvis as a condensation of connective tissue around the middle rectal artery and is divided into two segments by the inferior hypogastric nerve plexus inside it and the visceral endopelvic fascia around it. The lateral ligament is a pathway of blood vessels and nerve fibers toward the rectum and lymphatic vessels from the lower rectum toward the iliac lymph nodes. Therefore, the lateral ligament plays a critical role in surgery for lower rectal cancer in two respects: the anatomic extent of resection for curing rectal cancer, and the preservation of sexual function. Semin. Surg. Oncol. 19:386–395, 2000. © 2000 Wiley‐Liss, Inc.
Long‐lasting synaptic modification in the rat hippocampus resulting from NMDA receptor blockade during development
Authors: Bellinger Frederick P. , Wilce Peter A. , Bedi Kuldip S. , Wilson Peter
Published: August 2002

Recent reports have suggested that proper maturation of synapses in the hippocampus requires activation of NMDA receptors. We previously demonstrated that neonatal ethanol exposure results in a lasting reduction in synaptic strength in the hippocampus. To determine if this reduction was due to ethanol's effects on NMDA receptors, we investigated long‐term changes in synaptic properties resulting from administration of NMDA receptor antagonists to neonatal animals. Rats were injected daily from PND 4–9 with either the noncompetitive NMDA receptor antagonist MK‐801, the competitive NMDA receptor antagonist CPP, or the AMPA receptor antagonist NBQX. Control rats were either injected daily with physiological saline during the same period or left to develop normally. Hippocampal slices were prepared from nembutal‐anesthetized animals between PND 35 and PND 40. The maximum pEPSP and PS values were not significantly different between controls and NMDA antagonist‐treated animals. However, slices from animals injected with NMDA receptor antagonists required higher stimulus currents to attain comparable pEPSPs. The ratio of the slope of the pEPSP to the amplitude of the presynaptic volley was also reduced, as were pEPSP responses to specific stimulus currents. None of these effects were observed in slices prepared from animals treated with the AMPA receptor antagonist NBQX. Glutamate receptor antagonism did not produce lasting changes in long‐term potentiation or paired‐pulse facilitation. These results indicate activation of NMDA receptors during development is necessary for proper development of synapses. Synapse 43:95–101, 2002. © 2001 Wiley‐Liss, Inc.
Co‐localization of active caspase‐3 and DNA fragmentation (TUNEL) in normal and hyperthermia‐induced abnormal mouse development
Authors: Umpierre Carmen C. , Little Sally A. , Mirkes Philip E.
Published: August 2002

Background

Previous work has shown that caspase‐3 activation and DNA fragmentation, two hallmarks of apoptosis, are induced in day 9 mouse embryos exposed to hyperthermia (43°C); however, the methods used to assess caspase‐3 activation (Western blot) and DNA fragmentation (gel electrophoresis) did not allow these apoptotic events to be localized to specific cells within the embryo.

Methods

To co‐localize active caspase‐3 and DNA fragmentation to specific cells, we used paraffin sections of day 13 mouse limb buds, sections of control and hyperthermia‐treated day 9 mouse embryos, and sequential immunohistochemical staining for caspase‐3 and TUNEL staining for DNA fragmentation. We used a primary rabbit antibody specific for the active, p17 subunit of caspase‐3 and a goat anti‐rabbit secondary antibody conjugated to Alexa 594 fluorochrome (red fluorescence) to localize active caspase‐3. To co‐localize DNA fragmentation, we subsequently processed the same sections by the TUNEL method using fluorescein‐labeled dUTP (green fluorescence).

Results

Using this dual labeling approach, we show that active caspase‐3 (caspase‐3 positive) and DNA fragmentation (TUNEL positive) occur in a sub‐population of interdigital mesenchyme cells of day 13 mouse limb buds. Using the same approach, we detected a small number of caspase‐3 positive and TUNEL‐positive cells in the central nervous system and in the mesenchyme of the first branchial arch of untreated day 9 mouse embryos. The number of caspase‐3 and TUNEL‐positive cells are greatly increased 5 hr after a brief exposure to hyperthermia (43°C, 13 min). Caspase‐3 and TUNEL‐positive cells were most abundant in the neuroepithelium of the developing central nervous system, mesenchyme of the first pharyngeal arch, and somitic mesoderm. In contrast, the heart, mesencephalic mesenchyme, and the visceral yolk sac contained few, if any, caspase‐3 and TUNEL‐positive cells.

Conclusions

This is the first demonstration that activation of caspase‐3 and DNA fragmentation co‐localize in cells programmed to die in the interdigital mesenchyme of day 13 limb buds and in the neuroepithelium and branchial arch mesenchyme of day 9 mouse embryos. Similarly, our results represent the first co‐localization of teratogen‐induced activation of caspase‐3 and DNA fragmentation in specific cells of early postimplantation mouse embryos, and confirm that cells of the developing central nervous system are acutely sensitive to the cell death‐inducing potential of hyperthermia, whereas cells of the heart are resistant. Finally, we show for the first time that, like cells of the heart, cells of the mesencephalic mesenchyme and the visceral yolk sac are also resistant to hyperthermia‐induced apoptosis. Teratology 63:134–143, 2001. © 2001 Wiley‐Liss, Inc.
Defining scholarship for the twenty‐first century
Authors: Diamond Robert M.
Published: August 2002

Many factors determine the definition of scholarship at any given time, including the discipline, the priorities of the institution and academic unit, and the interests of the individual. This chapter discusses these influences, traces recent developments in how we view the scholarly role of faculty members, and it recommends an institutional approach for bringing fairness and quality into faculty reward systems.
Testing the toxicity of influents to activated sludge plants with the Vibrio fischeri bioassay utilising a sludge matrix
Authors: Hoffmann Caroline , Christofi Nick
Published: August 2002

To protect the bioceonosis within activated sludge, a method of predicting the toxic effect of influents to the biological treatment stage of waste water treatment plants, based on DIN method 38412 L 34, has been developed. A population of the luminescent marine bacterium Vibrio fischeri was incorporated into a sludge testing matrix derived from a model laboratory and real activated sludge plants. The sludge was challenged with different concentrations of pure toxicants and complex aqueous samples, and light output by V. fischeri monitored. The results were compared to toxicant testing in the absence of sludge (standard test). The modified method was found to be less sensitive for some toxicants tested than the standard DIN and other bioluminescent tests, but considered more realistic as it provides buffering and takes into account sorption which can affect the sensitivity of the test towards some compounds. The method is comparable in terms of ease of use, speed, reproducibility and cost effectiveness to standard V. fischeri luminescence methods. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 422–427, 2001
Relative potencies of individual polycyclic aromatic hydrocarbons to induce dioxinlike and estrogenic responses in three cell lines
Authors: Villeneuve D. L. , Khim J. S. , Kannan K. , Giesy J. P.
Published: August 2002

The dioxinlike and estrogenic relative potencies (REPs) of 16 priority polycyclic aromatic hydrocarbons (PAHs), seven methylated PAHs, and two hydroxylated PAHs were examined using threein vitrocell bioassays. Anin vitro ethoxyresorufin‐O‐deethylase assay with PLHC‐1 fish hepatoma cells andin vitroluciferase assay with H4IIE‐luc recombinant rat hepatoma cells were used to evaluate dioxinlike potency. Anin vitroluciferase assay with MVLN, recombinant human breast carcinoma cells, was used to evaluate estrogenic potency. Seven of the 16 priority PAHs tested induced significant dioxinlike responses. Excluding outliers with large ranges of uncertainty, the dioxinlike REPs for the PAHs ranged from 10−6to 10−3. This is similar to the REPs reported for other xenobiotics of concern including polychlorinated naphthalenes (PCNs) and some polychlorinated biphenyls (PCBs). In general, REP estimates generated in this study were similar to those reported previously. However, a comparison of the estimates of total 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin equivalents derived using assay‐specific REPs with REPs reported in other studies indicated that the use of nonspecific REPs could lead to significant error in mass‐balance (potency‐balance) analyses. A 10‐h acid treatment completely destroyed the dioxinlike activity of a PAH mixture. Among the compounds tested, only benzo[a]anthracene and dibenz[a,h]anthracene induced significant responses in the MVLN bioassay. Relative estrogenic potencies were estimated to be approximately 10−7. Overall, this research contributes to the growing consensus regarding the dioxinlike potency of priority PAHs and PAH derivatives and provides some additional evidence about potentially estrogenic PAHs. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 128–137, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10041
A touch‐enabled system for multi‐resolution modeling and 3D painting‡
Authors: Ehmann Stephen A. , Gregory Arthur D. , Lin Ming C.
Published: August 2002

We present an intuitive system,inTouch, for interactively editing and painting a polygonal mesh using a force‐feedback device. An artist or a designer can use this system to create and refine a three‐dimensional multi‐resolution polygonal mesh. The appearance can be further enhanced by directly painting onto its surface. The system allows users to naturally create complex forms and patterns aided not only by visual feedback but also by their sense of touch. Copyright © 2001 John Wiley & Sons, Ltd.
Mobility culling: an efficient rendering algorithm using temporal coherence
Authors: Oh Kyoung‐Su , Shin Byeong‐Seok , Gil Shin Yeong
Published: August 2002

Interactive display of complex scenes is a challenging problem in computer graphics. Such current approaches as z‐buffer, level of detail and visibility culling have not fully used the temporal coherence between consecutive frames. When the viewing condition is fixed, the color and depth values of static polygons can be obtained from the result of the previous frame and only the remaining dynamic polygons require rendering. We present a method that enhances the speed of the conventional z‐buffer algorithm by exploiting the above temporal coherence. This algorithm is simple to combine with existing graphics hardware that supports the conventional z‐buffer algorithm. It can manipulate any scene suitable for the z‐buffer algorithm without preprocessing or human intervention. The rendering time is proportional to the number of dynamic polygons in each frame. Experimental results show that our method is faster than the conventional z‐buffer algorithm and the performance enhancement becomes higher as the fraction of static polygons increases. Copyright © 2001 John Wiley & Sons, Ltd.
Smart cell sectorization for third generation CDMA systems
Authors: Giuliano Romeo , Mazzenga Franco , Vatalaro Francesco
Published: August 2002

Smart antennas are a powerful means to provide the increased bandwidth efficiency needed to deliver advanced third generation (3G) interactive multimedia services anywhere and anytime. In this paper we focus on the development of smart antennas located at the base stations of a code division multiple access (CDMA) cellular system. First, we review the main characteristics of antenna array systems and highlight some issues related to the inclusion of smart antennas in a 3G CDMA system. A classification of the proposed beamforming techniques and a discussion on the advantages and drawbacks of smart antennas are provided. Then, we introduce an original smart antenna technique based on rotation and resizing of the available sectors much simpler than common smart antennas based on beamforming techniques addressing a specific user. We discuss on the impact of the proposed technique in the base station architecture. Finally, we provide simulation results in order to show the effectiveness of the proposed approach and to relate transmission performance to system parameters. It turns out that the smart sectorization technique provides significant capacity improvements under statistically uniform user distribution (up to about 80 per cent for data traffic). Copyright © 2002 John Wiley & Sons, Ltd.
Channel modeling for satellite and HAPS system design
Authors: Vázquez‐Castro M. , Pérez‐Fontán F. , Arbesser‐Rastburg B.
Published: August 2002

This paper reviews the state of the art and current trends towards 3G and 3G+ mobile satellite systems that are being planned in parallel or within the International Mobile Telecommunications (IMT‐2000) framework. The subject is firstly approached by introducing the key and enabling technologies both for satellites and high altitude platform stations. After having introduced an overall picture, another review is presented on physical layer research activities including propagation and channel modeling. Finally, the use of the reviewed channel models for Code Division Multiple Access system level analysis is introduced and some current efforts towards system design are presented. Copyright © 2002 John Wiley & Sons, Ltd.
Flap/lead–lag aeroelastic stability of wind turbine blades
Authors: Chaviaropoulos P. K.
Published: August 2002

A numerical tool for investigating the aeroelastic stability of a single wind turbine blade subjected to combined flap/lead–lag motion is presented. Its development is motivated by recent concern about destructive edgewise vibrations of modern stall‐controlled blades. The stability tool employs a finite element formulation to discretize in space the structural and aerodynamic governing equations. Unsteady aerodynamics is considered by means of the extended ONERA lift and drag models. The mathematical form of these models allows for a combined treatment of dynamics and aerodynamics through the introduction of a so‐called ‘aeroelastic beam element’. This is an extended two‐node beam element having both deformation and aerodynamic degrees of freedom. Several linear and non‐linear versions of the stability tool are available, differing in the way that instantaneous lift and/or drag is treated. In the linear case, stability is investigated through eigenvalue analysis. Time domain integration is employed for non‐linear stability analysis. Results are presented and discussed for a 17 m stall‐controlled blade. Copyright © 2001 John Wiley & Sons, Ltd.
Endoscopy, assisted percutaneous repair of the Achilles tendon ruptures: a cadaveric and clinical study
Authors: Turgut Akın , Günal İzge , Maralcan Gökhan , Köse Nusret , Göktürk Erol
Published: August 2002

Endoscopy‐assisted percutaneous repair of Achilles tendon ruptures were investigated in a cadaveric and clinical study. Sixteen above‐knee fresh amputation specimens in which different types of Achilles tendon ruptures were created were repaired percutaneously with the visualization of the tendon ends by endoscopy. Neither malalignment nor damage to the neurovascular structures was observed. Eleven patients were treated in this way. No reruptures, wound problems, or neurovascular injury were observed. All patients returned to daily activities 10–11 weeks after the repair. This technique seems to overcome certain problems of conservative, surgical, or percutaneous repair of the Achilles tendon ruptures.
Preoperative Evaluation of Pancreatic Masses with Positron Emission Tomography Using 18F‐fluorodeoxyglucose: Diagnostic Limitations
Authors: Sendler Andreas , Avril Norbert , Helmberger Hermann , Stollfuß Jens , Weber Wolfgang , Bengel Frank , Schwaiger Markus , Roder Jürgen D. , Siewert J. Rüdiger
Published: August 2002

Identification of pancreatic cancer in patients presenting with an enlarged pancreatic mass is a major diagnostic problem. Positron emission tomography (PET) using the radiolabeled glucose analogue 18F‐fluorodeoxyglucose (FDG) has been suggested to provide excellent accuracy for noninvasive determination of suspicious pancreatic masses. We conducted a prospective study to verify these results. Forty‐two patients admitted for pancreatic surgery underwent PET scanning. Image analysis was based on visual film evaluation and quantification of regional tracer uptake. PET imaging was visually analyzed by three observers blinded for the results of other diagnostic tests; they qualitatively graded the scans using a five‐point scale (I = low to V = high) for the presence and intensity of focal FDG uptake. Diagnosis was proven by histology (n= 38) or follow‐up (n= 4). Furthermore, the results of PET were compared with helical computed tomography (CT) and conventional ultrasonography (US), done during the routine diagnostic workup before pancreatic cancer surgery. Regarding only the results with scores of IV and V as positive for representing definite malignancy yielded a sensitivity of 71% and a specificity of 64% for film reading. Quantification of regional tracer uptake contributed no significant diagnostic advantage for differentiation between benign and malignant tumors. Helical CT revealed a sensitivity of 74% and a specificity of 45.5% and abdominal US 56% and 50%, respectively. We concluded that PET imaging provides only fair diagnostic accuracy (69%) for characterizing enlarged pancreatic masses. PET does not allow exclusion of malignant tumors. In doubtful cases, the method must be combined with other imaging modalities, such as helical CT. The results indicate that the number of invasive procedures is not significantly reduced by PET imaging.
Improvement of Operative Mortality after Curative Resection for Gastric Cancer: Population‐based Study
Authors: Msika Simon , Benhamiche Anne‐Marie , Tazi Mohamed A. , Rat Patrick , Faivre Jean
Published: August 2002

It is not well known if the improvement in operative mortality after surgery for gastric cancer reported in hospital series can be extrapolated to the whole population. The aim of this study was to determine trends in operative mortality over a 20‐year period in a nonselected community‐based series of patients. A database of 648 patients with gastric cancer resected with curative intent between 1976 and 1995 in a region with a half‐million population was divided into two periods: 1976–1983 and 1984–1995. Nonconditional logistic regression was performed to estimate the independent effects of the studied factors. Operative mortality was higher during the 1976–1983 period than during the 1984–1995 period (17.1% vs. 7.1%; p < 0.0001). When comparing the two study periods, operative mortality decreased dramatically from 26.2% to 10.0% in patients over age 70, from 31.8% to 7.9% after total gastrectomy, and from 30.7% to 6.3% after proximal esophagogastrectomy. Operative mortality after total gastrectomy was nearly the same as that after distal gastrectomy (7.9% vs 5.9%) during the second study period. During the first study period, operative mortality was independently associated with age at diagnosis, type of gastrectomy, and to a lesser degree stage at diagnosis; during the second study period, only age and stage at diagnosis were associated with the risk of operative mortality. This study indicates that in this well defined population operative mortality after curative resection for gastric cancer has decreased during the last 20 years. The results should encourage aggressive management of patients with gastric cancer, even in patients over 70 years of age.
Evaluation of S‐100b as a Specific Marker for Neuronal Damage Due to Minor Head Trauma
Authors: Biberthaler Peter , Mussack Thomas , Wiedemann Ernst , Kanz Karl‐Georg , Koelsch Martin , Gippner‐Steppert Cornelia , Jochum Marianne
Published: August 2002

Management of patients with minor head trauma (MHT) continues to be debated in the literature. Measurement of S‐100b in serum has been introduced into the discussion as an additional screening tool for intracerebral injuries because routine cranial computed tomography (CCT) of a large number of patients causes logistic difficulties, and the neurologic examination is often impaired by a high frequency of coincidental intoxication. The aim of our study was to determine the diagnostic value of measuring S‐100b in the serum of MHT patients to identify risk groups. Additional validity should be aquired by a comparison with plasma levels of polymorphonuclear neutrophil (PMN) elastase an established general trauma marker. A series of 52 patients with MHT were included in the prospective study. At admission the patients underwent a routine CCT scan to detect intracerebral lesions, and blood samples were drawn to investigate circulating levels of S‐100b and PMN elastase. For comparison, data for a positive control group of 10 severe head trauma patients (initial Glasgow Coma Scale score < 8) and for a negative control group with 20 healthy volunteers were obtained. The interval between MHT and admission to our hospital was 73.4 ± 47.0 minutes. The initial S‐100b serum levels of MHT patients were 0.470 ± 0.099 ng/ml, those of the positive control group were 7.16 ± 3.77 ng/ml, and those of the negative control group were 0.05 ± 0.01 ng/ml. Relevant pathologic CCT scans were detected in 28.8% of MHT patients; one patient of that group was subjected to immediate surgical intervention (1.9%). At a cut‐off point of 0.1 ng/ml, the sensitivity of positive S‐100b levels reached 100% and the specificity 40.5%. Plasma levels of PMN elastase reached 60.52 ± 10.75 ng/ml in the MHT group, 66.4 ± 14.92 ng/ml in the severely head‐injured group, and 23.26 ± 1.53 ng/ml in the negative control group. Serum levels of S‐100b seem to be a highly sensitive but not very specific marker for isolated neurotrauma. Measurement of this parameter may be helpful as an additional screening tool to identify high risk groups in the cohort of MHT patients.
Prospective Randomized Comparison of Open versus Laparoscopic Appendectomy in Men
Authors: Cox Michael R. , McCall John L. , Toouli James , Padbury Robert T.A. , Wilson Thomas G. , Wattchow David A. , Langcake Mary
Published: August 2002

A prospective, randomized trial was performed to compare open appendectomy with laparoscopic appendectomy in men with a clinical diagnosis of acute appendicitis. Sixty‐four patients with a median age of 25 years (range 18–84 years) were randomized to open appendectomy (n= 31) or laparoscopic (n= 33) appendectomy. Of the 64 men, 56 (87.5%) had appendicitis (27 open, 29 laparoscopic procedures). The mean operating times were 50.6 ± 3.7 minutes (± SEM) for open and 58.9 ± 4.0 minutes for laparoscopic appendectomy (p= 0.13). Five (15%) patients randomized to laparoscopic appendectomy had an open operation. The mean postoperative hospital stay was significantly longer for open appendectomy (3.8 ± 0.4 days) than for laparoscopic appendectomy (2.9 ± 0.3 days) (t= 2.05,df= 62,p= 0.045). The complication rate after open appendectomy (25.8%) was not significantly different from that after laparoscopic appendectomy (12.1%). There was a single postoperative death due to a pulmonary embolus in the laparoscopic group and a single death due to cardiac and renal failure in the open group. The mean time to return to normal activities was significantly longer following open appendectomy (19.7 ± 2.4 days) than after laparoscopic appendectomy (10.4 ± 0.9 days), (t= 3.75,df= 49,p= 0.001). In conclusion, laparoscopic appendectomy in men has significant advantages in terms of a more rapid recovery compared to open appendectomy. There were no significant disadvantages to laparoscopic appendectomy compared to open appendectomy.
Laparoscopic Colorectal Surgery: Ascending the Learning Curve
Authors: Reissman Petachia , Cohen Stephen , Weiss Eric G. , Wexner Steven D.
Published: August 2002

The aim of this study was to prospectively assess the results of our first 100 consecutive patients who underwent laparoscopic or laparoscopy‐assisted colorectal operations. The parameters studied included the type and length of procedure, intra‐ and postoperative complications, conversion to open surgery, length of ileus, and hospitalization. A total of 100 laparosopic and laparoscopy‐assisted procedures were performed between May 1991 and April 1994. The mean patient age was 49 years (12–88 years). The procedures included 36 total abdominal colectomies (TACs) (ileoanal reservoir 28, ileorectal anastomosis 6, end‐ileostomy 2), 39 segmental resections of the colon and small bowel, 8 resections of the rectum, 7 diverting stoma creations, 7 reversals of Hartmann’s procedure, and 3 other procedures. In seven cases (7%) the laparoscopic procedure was converted to a laparotomy. A group of 22 patients sustained 26 complications that included enterostomy (n= 5), hemorrhage (n= 6), intraabdominal abscess (n= 4), prolonged ileus (n= 4), wound infection (n= 2), anastomotic leak (n= 1), aspiration (n= 1), cardiac arrhythmia (n= 1), upper intestinal bleeding (n= 1), and postoperative small bowel obstruction (n= 1). There were no deaths. When divided into three equal, consecutive groups, the patients in the early (n= 33) and intermediate (n= 33) groups had a significantly higher complication rate (42% and 27%, respectively), than those in the late group (n= 34, 12%;p< 0.05). The complication rate in each group was also directly related to the number of TACs performed (18 in the early, 13 in the intermediate, and 5 in the late group). The overall complication rate in TAC cases was significantly higher (42%) when compared to that of all other procedures (segmental resection 9%, nonresectional 12%;p< 0.01). The mean operating time was 4 hours (2.5–6.5 hours) for TAC, 2.5 hours (1.5–5.5 hours) for segmental colonic resection, and 1.6 hours (1.0–2.5 hours) for the nonresectional procedures. The length of ileus was 3.5 days (2–7 days) after TAC, 3 days (2–7 days) after the segmental resections, and 2 days (1–4 days) after the nonresectional procedures. The mean hospital stay was 7.3 days (2–40 days): 8.4 (5–40), 7.0 (4–12), and 6.8 (2–11) days for the TAC, segmental resection, and nonresectional procedures, respectively. We conclude that the feasibility of laparoscopic colorectal surgery has been well established. The morbidity associated with laparoscopic colorectal surgery correlates with a steep learning curve but is also related to the type of procedure. TAC is associated with a higher complication rate than are other laparoscopic colorectal procedures.
Nutritional Support to Prevent and Treat Multiple Organ Failure
Authors: Bengmark Stig , Gianotti Luca
Published: August 2002

Enteral nutrition (EN) has several advantages over parenteral nutrition (PN) for postoperative/posttrauma patients. Modern technologies for tube‐feeding have made early EN possible. Jejunal tube‐feeding has advantages over gastric tube‐feeding: faster metabolic recovery, less vomiting, and less risk of regurgitation and aspiration. Immediate or early EN stimulates the splanchnic and hepatic circulations, improves mucosal blood flow, prevents intramucosal acidosis and permeability disturbances, and eliminates the need for stress ulcer prophylaxis. Saliva containing important antimicrobial substances and gastric acidity are important in sepsis prevention. Chewing, saliva, and gastric acidity support gastric nitric oxide (NO) release, important for mucosal blood flow, gastrointestinal (GI) motility, mucus formation, and bacteriostasis. An oral supply of NO‐donating substances and chewing of nitrate‐rich food, such as lettuce or spinach, can be useful. Oral and mucosa‐protective lipids are recommended. H2 blockers and saliva‐inhibiting drugs are avoided. Immediate EN should be given, starting with 25 ml/hr and increasing to 100 ml/hr over 24 to 48 hours. For the immunocompromised patient special attention should be given to the purity of water. Bottled water can contain bacteria such asPseudomonas. Food antioxidants such as glutathione, vitamin E, and β‐carotenes are important. Ingredients for the colonic mucosa are important. Approximately 10% of caloric need is satisfied by so‐called colonic food (prebiotics), fermented at the level of the colonic mucosa to produce colonic mucosa nutrients and to prevent gut origin sepsis. More than 10 g of fiber per day is recommended. The fermenting flora (probiotic flora) is deranged owing to disease or antibiotic treatment, and resupply of flora is important. A new concept of ecoimmune nutrition is presented for enteral supply of mucosa‐reconditioning ingredients: new surfactants, pseudomucus, fiber, amino acids such as arginine, and mucosa‐adheringLactobacillus plantarum299.
Laparoscopic Treatment of Gallbladder and Common Bile Duct Stones: A Prospective Study
Authors: Lezoche Emanuele , Paganini Alessandro M. , Carlei Francesco , Feliciotti Francesco , Lomanto Davide , Guerrieri Mario
Published: August 2002

The aim of this study was to investigate prospectively the feasibility, success rate, safety, and short‐term results of single‐stage laparoscopic treatment of gallstones and ductal stones in 100 consecutive, unselected patients. Common bile duct (CBD) stones were diagnosed at routine intraoperative cholangiography and choledochoscopy in 100 of 950 patients with gallstones undergoing laparoscopic cholecystectomy (LC). Unsuspected CBD stones were present in 39 patients (4.1% of 950; 39% of 100); 26 patients were referred for surgery after failed endoscopic sphinctertomy (ES) performed elsewhere. Transcystic duct CBD exploration (TC‐CBDE) was the procedure of choice. When it was not feasible, choledochotomy and direct CBD exploration (D‐CBDE) was performed. Use of biliary drainage was liberal. A completion cholangiogram was obtained for all patients. Laparoscopic treatment of CBD stones was successful in 96 patients: after TC‐CBDE in 63 and after D‐CBDE in 33. Four operations were converted to open surgery (4%). Retained stones, observed in five patients, were treated by ES in two cases and by percutaneous endoscopic/fluoroscopic lithotripsy in three. Minor morbidity included biloma (n = 2), port site infection (n = 2), and subumbilical hematoma (n = 1). Major morbidity was bile leakage from the cystic duct stump in two cases due to clips or transcystic duct drainage displacement, respectively. One elderly, high risk patient died after being referred for several failed attempts of endoscopic clearance; she died from cardiogenic shock 3 days after successful laparoscopic treatment. Laparoscopic CBD exploration is feasible and safe in most patients, with short‐term results that compare favorably with the results of sequential ES/LC reported in the literature.