Home About us Contact
|
Home About us Contact | ||
|
|
||
Conventional Means (conventional + mean)
Selected AbstractsEnvironmental power analysis , a new perspectiveENVIRONMETRICS, Issue 5 2001David R. Fox Abstract Power analysis and sample-size determination are related tools that have recently gained popularity in the environmental sciences. Their indiscriminate application, however, can lead to wildly misleading results. This is particularly true in environmental monitoring and assessment, where the quality and nature of data is such that the implicit assumptions underpinning power and sample-size calculations are difficult to justify. When the assumptions are reasonably met these statistical techniques provide researchers with an important capability for the allocation of scarce and expensive resources to detect putative impact or change. Conventional analyses are predicated on a general linear model and normal distribution theory with statistical tests of environmental impact couched in terms of changes in a population mean. While these are ,optimal' statistical tests (uniformly most powerful), they nevertheless pose considerable practical difficulties for the researcher. Compounding this difficulty is the subsequent analysis of the data and the impost of a decision framework that commences with an assumption of ,no effect'. This assumption is only discarded when the sample data indicate demonstrable evidence to the contrary. The alternative (,green') view is that any anthropogenic activity has an impact on the environment and therefore a more realistic initial position is to assume that the environment is already impacted. In this article we examine these issues and provide a re-formulation of conventional mean-based hypotheses in terms of population percentiles. Prior information or belief concerning the probability of exceeding a criterion is incorporated into the power analysis using a Bayesian approach. Finally, a new statistic is introduced which attempts to balance the overall power regardless of the decision framework adopted. Copyright © 2001 John Wiley & Sons, Ltd. [source] A pilot study comparing the effectiveness of conventional training and virtual reality simulation in the skills acquisition of junior dental studentsEUROPEAN JOURNAL OF DENTAL EDUCATION, Issue 1 2003Frank Quinn The use of virtual reality (VR) in the training of operative dentistry is a recent innovation and little research has been published on its efficacy compared to conventional training methods. To evaluate possible benefits, junior undergraduate dental students were randomly assigned to one of three groups: group 1 as taught by conventional means only; group 2 as trained by conventional means combined with VR repetition and reinforcement (with access to a human instructor for operative advice); and group 3 as trained by conventional means combined with VR repetition and reinforcement, but without instructor evaluation/advice, which was only supplied via the VR-associated software. At the end of the research period, all groups executed two class 1 preparations that were evaluated blindly by ,expert' trainers, under traditional criteria (outline, retention, smoothness, depth, wall angulation and cavity margin index). Analyses of resulting scores indicated a lack of significant differences between the three groups except for scores for the category of ,outline form', for group 2, which produced significantly lower (i.e. better) scores than the conventionally trained group. A statistical comparison between scores from two ,expert' examiners indicated lack of agreement, despite identical written and visual criteria being used for evaluation by both. Both examiners, however, generally showed similar trends in evaluation. An anonymous questionnaire suggested that students recognized the benefits of VR training (e.g. ready access to assessment, error identification and how they can be corrected), but the majority felt that it would not replace conventional training methods (95%), although participants recognized the potential for development of VR systems in dentistry. The most common reasons cited for the preference of conventional training were excessive critical feedback (55%), lack of personal contact (50%) and technical hardware difficulties (20%) associated with VR-based training. [source] Anterior cranial base reconstruction using free tissue transfer: Changing trends,HEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 2 2003Joseph Califano MD Abstract Introduction. A consecutive series of 135 patients undergoing resection for malignant tumors involving the anterior cranial base between 1976 and 1999 was reviewed. Patient and Methods. In the years from 1976,1991, free-tissue transfer was used in 5 of 76 or 6.6% of cases, whereas free-tissue reconstruction was used in 24 of 59 or 40% of cases in the years 1992,1999. Of those cases reconstructed with free-tissue transfer in 1976,1991, 60% (three of five) underwent a complex resection defined as involving dura, brain, or more than one major structure adjacent to skull base. Of those patients reconstructed with conventional (pericranial or pericranial/galeal) pedicled flaps in this time period, 35% (25 of 71) underwent a complex resection. From 1992,1999, 75% (18 of 24) of patients reconstructed with free-tissue transfer received a complex resection, whereas only 6% (2 of 35) of patients reconstructed by other means received a complex resection. Outcomes. For those patients reconstructed by free-tissue transfer, there were no instances of flap loss. Comparison of these two time periods was notable for a similar patient composition in terms of age, histologic findings, and extent of resection. Major complication rates for patients who are reconstructed with free-tissue transfer for anterior cranial base resections (31%) are similar compared with patients who have been reconstructed with conventional pedicled flaps (35%). This was noted despite an increased extent and complexity of resection in those patients who underwent free-tissue transfer reconstruction (72%) compared with those patients reconstructed by more conventional means (26%) p < .001. Conclusion. In our institution, the use of vascularized, free-tissue transfer has replaced pedicled flaps as the preferred modality for reconstructing complex anterior cranial base defects involving resection of dura, brain, or multiple major structures adjacent to local skull base, including the orbit, palate, and other structures. Complication rates for patients reconstructed with free-tissue transfer techniques is similar to those patients reconstructed by conventional techniques, despite an increase in complexity of resection in this group. © 2002 Wiley Periodicals, Inc. Head Neck 24: 000,000, 2002 [source] Satellite rainfall climatology: a reviewINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 9 2001C. Kidd Abstract The monitoring of the world's climate using conventional means is well established, incorporating numerous historical data sets to ensure a long-term record. Parameters such as temperature have been quite accurately recorded over the last 200 years or so, but other parameters such as rainfall are less well recorded. This paper introduces satellite rainfall climatology and why it is important, not only from the longer term study of rainfall, but also for the future monitoring and estimation of rainfall. A summary of the range of satellites and their instruments is reviewed to provide a background to the techniques. These are discussed and their relative merits explored. Finally, examples of the techniques are shown, illustrating the applications to which the satellite-derived data sets may be put. Copyright © 2001 Royal Meteorological Society [source] Disruption of an exotic mutualism can improve management of an invasive plant: varroa mite, honeybees and biological control of Scotch broom Cytisus scoparius in New ZealandJOURNAL OF APPLIED ECOLOGY, Issue 2 2010Quentin Paynter Summary 1.,A seed-feeding biocontrol agent Bruchidius villosus was released in New Zealand (NZ) to control the invasive European shrub, broom Cytisus scoparius, in 1988 but it was subsequently considered unable to destroy sufficient seed to suppress broom populations. We hypothesized that an invasive mite Varroa destructor, which has caused honeybee decline in NZ, may cause pollinator limitation, so that the additional impact of B. villosus might now reach thresholds for population suppression. 2.,We performed manipulative pollination treatments and broad-scale surveys of pollination, seed rain and seed destruction by B. villosus to investigate how pollinator limitation and biocontrol interact throughout the NZ range of broom. 3.,The effect of reduced pollination in combination with seed-destruction was explored using a population model parameterized for NZ populations. 4.,Broom seed rain ranged from 59 to 21 416 seeds m,2 from 2004 to 2008, and was closely correlated with visitation frequency of honeybees and bumblebees. Infestation of broom seeds by B. villosus is expected to eventually reach 73% (the average rate observed at the localities adjacent to early release sites). 5.,The model demonstrated that 73% seed destruction, combined with an absence of honeybee pollination, could cause broom extinction at many sites and, where broom persists, reduce the intensity of treatment required to control broom by conventional means. 6.,Nevertheless, seed rain was predicted to be sufficient to maintain broom invasions over many sites in NZ, even in the presence of the varroa mite and B. villosus, largely due to the continued presence of commercial beehives that are treated for varroa mite infestation. 7.,Synthesis and applications. Reduced pollination through absence of honeybees can reduce broom seed set to levels at which biocontrol can be more effective. To capitalize on the impact of the varroa mite on feral honeybees, improved management of commercial beehives (for example, withdrawal of licences for beekeepers to locate hives on Department of Conservation land) could be used as part of a successful integrated broom management programme at many sites in NZ. [source] Combined thermotherapy and cryotherapy for efficient virus eradication: relation of virus distribution, subcellular changes, cell survival and viral RNA degradation in shoot tipsMOLECULAR PLANT PATHOLOGY, Issue 2 2008QIAOCHUN WANG SUMMARY Accumulation of viruses in vegetatively propagated plants causes heavy yield losses. Therefore, supply of virus-free planting materials is pivotal to sustainable crop production. In previous studies, Raspberry bushy dwarf virus (RBDV) was difficult to eradicate from raspberry (Rubus idaeus) using the conventional means of meristem tip culture. As shown in the present study, it was probably because this pollen-transmitted virus efficiently invades leaf primordia and all meristematic tissues except the least differentiated cells of the apical dome. Subjecting plants to thermotherapy prior to meristem tip culture heavily reduced viral RNA2, RNA3 and the coat protein in the shoot tips, but no virus-free plants were obtained. Therefore, a novel method including thermotherapy followed by cryotherapy was developed for efficient virus eradication. Heat treatment caused subcellular alterations such as enlargement of vacuoles in the more developed, virus-infected cells, which were largely eliminated following subsequent cryotherapy. Using this protocol, 20,36% of the treated shoot tips survived, 30,40% regenerated and up to 35% of the regenerated plants were virus-free, as tested by ELISA and reverse transcription loop-mediated isothermal amplification. Novel cellular and molecular insights into RBDV,host interactions and the factors influencing virus eradication were obtained, including invasion of shoot tips and meristematic tissues by RBDV, enhanced viral RNA degradation and increased sensitivity to freezing caused by thermotherapy, and subcellular changes and subsequent death of cells caused by cryotherapy. This novel procedure should be helpful with many virus,host combinations in which virus eradication by conventional means has proven difficult. [source] Virtual Reality and Interactive Simulation for Pain DistractionPAIN MEDICINE, Issue 2007Mark D. Wiederhold MD ABSTRACT Pain and discomfort are perceptible during many medical procedures. In the past, drugs have been the conventional means to alleviate pain, but in many instances, medications by themselves do not provide optimal results. Current advances are being made to control pain by integrating both the science of pain medications and the science of the human mind. Various psychological techniques, including distraction by virtual reality environments and the playing of video games, are being employed to treat pain. In virtual reality environments, an image is provided for the patient in a realistic, immersive manner devoid of distractions. This technology allows users to interact at many levels with the virtual environment, using many of their senses, and encourages them to become immersed in the virtual world they are experiencing. When immersion is high, much of the user's attention is focused on the virtual environment, leaving little attention left to focus on other things, such as pain. In this way virtual reality provides an effective medium for reproducing and/or enhancing the distractive qualities of guided imagery for the majority of the population who cannot visualize successfully. [source] Design Optimization of Blood Shearing Instrument by Computational Fluid DynamicsARTIFICIAL ORGANS, Issue 6 2005Jingchun Wu Abstract:, Rational design of blood-wetted devices requires a careful consideration of shear-induced trauma and activation of blood elements. Critical levels of shear exposure may be established in vitro through the use of devices specifically designed to prescribe both the magnitude and duration of shear exposure. However, it is exceptionally difficult to create a homogeneous shear-exposure history by conventional means. This study was undertaken to develop a Blood Shearing Instrument (BSI) with an optimized flow path which localized shear exposure within a rotating outer ring and a stationary conical spindle. By adjustment of the rotational speed and the gap dimension, the BSI is designed to generate shear stress magnitudes up to 1500 Pa for exposure time between 0.0015 and 0.20 s with a pressure drop of 100 mm Hg. Computational fluid dynamics (CFD) revealed that a flow path designed by first-order analysis and intuition exhibited unfavorable pressure gradient, vortices, and undesirable regions of reverse flow. An optimized design was evolved utilizing a parameterized geometric model and automatic mesh generation to eliminate vortices and reversal flow and to avoid unfavorable pressure gradients. Analysis of the flow and shear fields for the extreme limits of the shear gap demonstrated an improvement in homogeneity due to shape optimization and the limitations of an annular shear device for achieving completely uniform shear exposure. [source] Clinicopathological analysis of early gastric cancer with solitary lymph node metastasisBRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 11 2002Dr K. Arai Background: The sentinel node concept has not yet been established in gastric cancer. Methods: Fifty-four patients with early gastric cancer who had only one lymph node metastasis were regarded retrospectively as patients with a possible sentinel node metastasis, and the morphological features of these nodes were assessed. The level I nodes in seven patients with a possible skip metastasis at routine haematoxylin and eosin staining were re-examined using cytokeratin (CK) immunostaining. Results: The shape of the gastric cancer lesion could be examined in 53 of the patients; more than one-third (20 of 53) were microfocal type. Concerning the intranodal cancer foci, the marginal sinus type was found in 32 affected nodes, medullary sinus type in 14 and mixed type in seven. Forty-three per cent of suspected sentinel nodes were the largest in size among all nodes from the station. CK immunostaining of seven non-metastatic nodes with haematoxylin and eosin revealed that three were CK positive. Conclusion: These findings suggest that possible sentinel nodes detected by conventional means may not always be primary portions of any metastasis. Adoption of sentinel node biopsy in gastric cancer must await the development of improved procedures for diagnosis during surgery. © 2002 British Journal of Surgery Society Ltd [source] | |||||||||||||