bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiple imputation to estimate the association between eyes in disease progression with interval‐censored data
Authors: Glynn Robert J. , Rosner Bernard 
Published: October 2004

AbstractIn many ophthalmologic studies, progression of diseases such as diabetic retinopathy, age‐related maculopathy, cataract, and glaucoma is only noted when each eye is examined at intervals that commonly vary between subjects. Such data are often analysed using continuous time survival methods with observed progression assumed to occur at the end of the interval. Tied times of progression can lead to substantial bias in estimation of the association between progression in right and left eyes. We describe a multiple imputation strategy to create multiple data sets without ties, based on drawing interval‐censored progression times from a parametric gamma frailty model that accounts for continuous and discrete covariates. We illustrate the method with data from 478 patients with insulin‐dependent diabetes mellitus who were followed for progression of diabetic retinopathy in the Sorbinil Retinopathy Trial. Resolution of tied failure times allows for valid estimation of the hazard of progression in one eye given the progression status of the other eye. A simulation study suggests that the method performs well. Results highlight the advantage of multiple imputation that data imputed under one model can be analysed under several alternative models. Copyright © 2004 John Wiley & Sons, Ltd.
Adjusting the generalized ROC curve for covariates
Authors: Schisterman Enrique F. , Faraggi David , Reiser Benjamin 
Published: October 2004

AbstractReceiver operating characteristic (ROC) curves and in particular the area under the curve (AUC), are widely used to examine the effectiveness of diagnostic markers. Diagnostic markers and their corresponding ROC curves can be strongly influenced by covariate variables. When several diagnostic markers are available, they can be combined by a best linear combination such that the area under the ROC curve of the combination is maximized among all possible linear combinations. In this paper we discuss covariate effects on this linear combination assuming that the multiple markers, possibly transformed, follow a multivariate normal distribution. The ROC curve of this linear combination when markers are adjusted for covariates is estimated and approximate confidence intervals for the corresponding AUC are derived. An example of two biomarkers of coronary heart disease for which covariate information on age and gender is available is used to illustrate this methodology. Copyright © 2004 John Wiley & Sons, Ltd.
Power and sample size determination when assessing the clinical relevance of trial results by ‘responder analyses’
Authors: Kieser Meinhard , Röhmel Joachim , Friede Tim 
Published: October 2004

AbstractA fundamental issue in regulatory decision making is the assessment of the benefit/risk profile of a compound. In order to do this, establishing the existence of a treatment effect by a significance test is not sufficient, but the clinical relevance of a potential benefit must also be taken into account. A number of regulatory guidelines propose that clinical relevance should be assessed by considering the rate of responders, i.e. the proportion of patients who are observed to achieve an apparently meaningful benefit. In this paper, we present methods for planning clinical trials that aim at demonstrating both statistical and clinical significance in superiority trials. Procedures based on analytical calculations are derived for normally distributed data and the case of a single endpoint as well as multiple primary outcomes. A bootstrap procedure is proposed that can be applied to non‐normal data. Application is illustrated by a clinical trial in Alzheimer's disease. Copyright © 2004 John Wiley & Sons, Ltd.
Sample size formula for proportional hazards modelling of competing risks
Authors: Latouche Aurélien , Porcher Raphaël , Chevret Sylvie 
Published: October 2004

AbstractTo test the effect of a therapeutic or prognostic factor on the occurrence of a particular cause of failure in the presence of other causes, the interest has shifted in some studies from the modelling of the cause‐specific hazard to that of the subdistribution hazard. We present approximate sample size formulas for the proportional hazards modelling of competing risk subdistribution, considering either independent or correlated covariates. The validity of these approximate formulas is investigated through numerical simulations. Two illustrations are provided, a randomized clinical trial, and a prospective prognostic study. Copyright © 2004 John Wiley & Sons, Ltd.
Placebo‐free designs for evaluating new mental health treatments: the use of adaptive treatment strategies
Authors: Dawson Ree , Lavori Philip W. 
Published: October 2004

AbstractThe dominant pre‐marketing clinical trial in psychopharmacology is a non‐equivalence design that randomizes patients to one of three treatments: an accepted standard, the innovation (new drug), or placebo, with the main efficacy comparison being innovation vs placebo. The reasons behind the choice of placebo control in new drug development include anticipated small effect size for active‐controlled comparisons and the sufficiency of demonstrated treatment effect (new drug vs placebo) for regulatory approval. These reasons have led to great reliance on placebo control in drug evaluation studies, despite the ethical controversy over the use of placebo when there are known effective standard treatments. While the use of placebo controls has been widely debated, a less considered aspect of the usual placebo‐controlled non‐equivalence design is the disparity between the decisions that it supports and those that pervade clinical practice. We propose an alternative approach that randomizes one group of patients to an adaptive treatment strategy that exemplifies the adaptive nature of clinical decision‐making in the treatment of ongoing mental health disorders. The basic idea is to compare the adaptive strategy, which uses a patient's outcomes to date to determine when to switch from an initial treatment (e.g. an accepted standard) to an alternative (e.g. the new) treatment, to fixed trials of either treatment option. We state the conditions under which the adaptive treatment RCT is attractive to implement and the requirements for doing so. Copyright © 2004 John Wiley & Sons, Ltd.
Responsiveness of interoperating components
Authors: Reed J. N. , Sinclair J. E. , Roscoe A. W. 
Published: October 2004

Abstract.

This paper investigates the issue of responsiveness of interoperating components: one not causing the other to deadlock. This is obviously related to the question of whether the two deadlock when put in parallel. However, it is different in that we require that a specific process
P
is not itself blocked by a plugin
Q
when it could otherwise have progressed, instead of asking that either process can always proceed (deadlock freedom). The issue becomes yet more subtle when dealing with processes which can nondeterministically block, either through graceful termination or unfortunate deadlock. The relational predicate, that is, binary relation on processes, which we provide is refinement-closed. This is significant as it allows components to be developed independently. In addition, it can be mechanically verified. The contribution of this paper is to identify the issue of responsiveness; to define appropriate properties; to demonstrate the suitability of these properties and consider how they can be mechanically verified. The notation used is CSP with automatic model-checking provided by the FDR tool.
Case studies in novel narial anatomy: 3. Structure and function of the nasal cavity of saiga (Artiodactyla: Bovidae: Saiga tatarica)
Authors: Clifford Andrew B. , Witmer Lawrence M. 
Published: October 2004

AbstractMuch of the narial anatomy of the enigmatic antelope Saiga tatarica has been described by previous workers. However, the anatomy of the nasal cavity and the causally associated osteological correlates of proboscis structure require closer attention, because these data are integral for both a more comprehensive understanding of saiga functional morphology and more robust reconstructions of proboscis structure in fossil taxa. Saiga and outgroup specimens were subjected to X‐ray computed tomographic (CT) imaging, gross dissection and skeletonization. The nasal cavity of saiga is characterized by an enlarged nasal vestibule and basal conchal fold. Many structures (e.g. turbinates, lateral cartilages, mucosal folds, nasolacrimal duct) are retracted caudally to a small area in the caudodorsal part of the nasal cavity proper. The enlarged vestibule is associated laterally and ventrally with paired sacs. The nasal septum is largely membranous and contains a large patch of cavernous tissue that serves as a dynamic baffle modifying the flow of inspired air. Bones comprising the narial margin have modified attachment sites for buccinator group muscles and the reduced lateral cartilages. The premaxilla is greatly modified by the enlarged musculature associated with nasolabial fusion. Maintenance of the topological relationships of narial structures compared to bovid outgroups has resulted in a nasal cavity with much larger area for seromucous glands of the vestibule as well as narial musculature capable of controlling the aperture of the nasal cavity. Maxillolabial muscles and the lateralis nasi act together both to compress the nasal cavity and to control the dilation of the nostrils such that air flow through the cavity is highly modified relative to bovid outgroups. The lateral vestibular recess is an outpocketing of the nasal vestibule that produces supplementary seromucous secretions and seems to have no homologue among outgroups. The enlarged nasal vestibule, lateral vestibular recess, repositioned basal fold, and septal cavernous mass are regarded as a coordinated adaptation to dusty habitats, such that nasal air flow can be dynamically regulated allowing for collection of inspired particulates in the vestibule and thus cleansing of air destined for the lungs.
Urinary chemosignals in giant pandas (Ailuropoda melanoleuca): seasonal and developmental effects on signal discrimination
Authors: White A. M. , Swaisgood R. R. , Zhang H. 
Published: October 2004

AbstractAs a solitary species, giant pandas Ailuropoda melanoleuca have a chemical communication system that allows for avoidance with conspecifics throughout most of the year and facilitates breeding during their brief reproductive period. To date, most studies have focused on adults during the breeding season, but much remains to be learned about developmental and seasonal effects on chemical communication. Here, using odour discrimination methodology, we examine these contextual influences on chemosignalling in giant pandas for the first time. During the breeding season both adult and subadult giant pandas overtly discriminated conspecific sex using chemical cues in urine. Male urine was consistently investigated more than female urine by pandas across all age‐sex categories. This preference for male urine was observed for both adult and subadult urine donors, indicating that adult levels of reproductive hormones are not necessary for the production of sex‐specific urinary odour cues. By contrast, giant pandas did not overtly discriminate sex during the non‐breeding season. This finding underscores that negative results for discrimination studies need to be interpreted with caution, as many contextual factors may influence overt expression of this ability. Evidence points to seasonal changes in motivation, rather than in the availability of sex‐specific chemical cues in urine, as the causal factor for changing odour discrimination patterns. These and other findings are discussed in the light of the potential role that discrimination of odour plays in the regulation of competitive and reproductive interactions in nature.
A histological study of emu (Dromaius novaehollandiae) skin
Authors: Weir Kristy A. , Lunam Christine A. 
Published: October 2004

AbstractThe skin of the emu Dromaius novaehollandiae is described in its entirety by light microscopy for the first time, therefore providing a basis for comparison with the integument of volant birds. The epidermal and dermal layers have a similar arrangement to other avian species. The concentration of lipid spheres in the basal layer of the epidermis is unique to emus. Although no differences in collagen density with depth of the dermis were observed, collagen bundle diameter is significantly smaller in the stratum superficial compared to the stratum compactum (P=0.001). The extensive stratum laxum, comprised predominantly of adipose tissue, may be an evolutionary adaptation to support the large feathers and also enhance insulation against ambient subzero temperatures. Males have a significantly thicker cellular epidermis (P=0.024) and stratum compactum (P=0.04) than females. In contrast, females have denser collagen (P=0.04) within the stratum superficial and stratum compactum.
Relative timing of ontogenetic events in primates
Authors: King Stephen J. 
Published: October 2004

AbstractHeterochrony is commonly proposed as a mechanism producing evolutionary changes, and some researchers identify two ways that heterochrony may be conceptualized.‘Growth heterochrony’ examines ancestor‐to‐descendant differences in the ontogeny of size relative to shape, while 'sequence heterochrony’ focuses on differences in the order of occurrence of events during ontogeny. Methods introduced here are allied with sequence heterochrony in that ontogeny is modelled as if it were a sequence of events; however, events are differently defined in this study. Using data from 16 primate species, I demonstrate that discriminant function analysis of data on developmental timing provides an additional tool for exploring the relationship between ontogeny and phylogeny. Patterns in the timing of tooth eruption, craniofacial sutural closure, and postcranial epiphyseal fusion can be used to classify individuals of all ages to their correct taxon. Taxon differences in these patterns can be characterized and described by interpreting correlations between discriminant functions and developmental events. Discriminant analysis has the advantages of: (1) being applicable to taxa for which there are too few individuals to be able to reconstruct ontogenetic sequences, including fossil species; (2) preserving intraspecific developmental variation during analysis; (3) being sensitive to very subtle differences in ontogenetic timing.
Respiratory turbinates of canids and felids: a quantitative comparison
Authors: Van Valkenburgh Blaire , Theodor Jessica , Friscia Anthony , Pollack Ari , Rowe Timothy 
Published: October 2004

AbstractThe respiratory turbinates of mammals are complex bony plates within the nasal chamber that are covered with moist epithelium and provide an extensive surface area for the exchange of heat and water. Given their functional importance, maxilloturbinate size and structure are expected to vary predictably among species adapted to different environments. Here the first quantitative analysis is provided of maxilloturbinate structure based on high‐resolution computed tomography (CT) scans of the skulls of eight canid and seven felid species. The key parameters examined were the density of the maxilloturbinate bones within the nasal chamber and how that density varied along the air pathway. In both canids and felids, total maxilloturbinate chamber volume and bone volume increased with body size, with canids having c. 1.5–2.0 times the volume of maxilloturbinate than felids of similar size. In all species, the volume of the maxilloturbinates varies from rostral to caudal, with the peak volume occurring approximately midway, close to where airway cross‐sectional area is greatest. Interspecific differences among canids or felids in maxilloturbinate density were not consistent with adaptive explanations, i.e. the densest maxilloturbinates were not associated with species living in arid or cold habitats. Some of the observed variation in maxilloturbinate form might reflect a need for both low‐and high‐resistance pathways for airflow under alternative conditions.
A new species of Peripatopsis from South Africa, P. stelliporata, with observations on embryonic development and sperm degradation (Onychophora, Peripatopsidae)
Authors: Sherbon Beverley J. , Walker Muriel H. 
Published: October 2004

Abstract Peripatopsis stelliporata sp. nov. from South Africa is described. SEM observations are used to illustrate the similarities and differences between this species and Peripatopsis capensis Grube 1866. The most conspicuous differences in morphology between the two species relate to the structure of the last reduced pair of legs, and the male genital pore, which in P. stelliporata is stellate in shape. Maintaining P. stelliporata in culture allowed timings of births to be recorded and the onset of sexual maturity to be determined. Spermatophores were first noted when the males were c. 4 months old. Females were observed to give birth at 15 months of age. In any female the embryos are all at around the same stage of development, and females gave birth between February and May. Young were born singly or in pairs at intervals of several days. The appearance of the embryos of P. stelliporata and also those of P. capensis collected in 1996 and 1997 was unexpected, as they are transparent apart from the red pigmented gut running from the mouth to the anus. Previously observed embryos of P. capensis were opaque and unpigmented. In appearance these embryos have similarities to those of Opisthopatus cinctipes Purcell 1895, which exhibits a different pattern of embryonic development. Whether or not this difference in appearance of the embryos reflects a transition in the pattern of development is discussed. A modified key for South African Peripatopsidae incorporating P. stelliporata is presented.
A comparison of the bone density and morphology of giraffe (Giraffa camelopardalis) and buffalo (Syncerus caffer) skeletons
Authors: van Schalkwyk O. L. , Skinner J. D. , Mitchell G. 
Published: October 2004

AbstractUnique features of giraffe Giraffa camelopardalis anatomy are its long neck and slender long limbs. Its neck vertebrae should be light and have low density to make it manoeuvrable while the limb bones should have high density to provide the strength to support the giraffe's mass. Giraffes also have a very high vertical growth rate, a diet with a high Ca:P ratio, and a skeleton that constitutes a high proportion of its body mass. To investigate whether the giraffe skeleton is affected by its anatomy and biology, giraffe bone density and morphology were compared with those of African buffalo Syncerus caffer, an artiodactyl of similar mass, more conventional anatomy, a lower vertical growth rate, and different diet. Our results show that except for minor differences the density of giraffe bones is the same as that of buffaloes. Giraffe limb bones have a slightly greater diameter and much thicker walls than equivalent bones in buffaloes. Giraffe cervical vertebrae, unlike those in buffaloes, decrease in mass with cranial distance. We conclude that giraffe biology and anatomy do not affect bone deposition or density. However, other characteristics of their skeletons seem to be adaptations to their unique anatomy.
Chromosomal diversity in mole‐rats of the genus Cryptomys (Rodentia: Bathyergidae) from the Zambezian region: with descriptions of new karyotypes
Authors: Van Daele P. A. A. G. , Dammann P. , Meier J. L. , Kawalika M. , Van De Woestijne C. , Burda H. 
Published: October 2004

AbstractThe genus Cryptomys contains a number of social, subterranean rodents that are widely distributed throughout sub‐Saharan Africa. Specimens of Cryptomys from 23 localities in south‐west Zambia were karyotyped using a standard staining protocol. A minimum of five metaphases per specimen was scored for 2n and the fundamental number (NF) was determined in females. Nine new karyotypes, which may represent several new species, were identified: (1) 2n= 42, NF = 78 (Dongo, Southern Province); (2) 2n= 44, NF = 76 (Salujinga, North‐western Province); (3) 2n= 45, NF = 78 (Lochinvar, Southern Province); (4) 2n= 52, NF = 86 (Chinyingi, North‐western Province); (5) 2n= 54, NF = 78 (Monze, Southern Province); (6) 2n= 56, NF = 76 (Watopa, North‐western Province); (7) 2n= 58, NF = 80 (Livingstone, Southern Province); (8) 2n= 58, NF = 86 (Senanga, Western Province); (9) 2n= 60, NF = 82 (Kataba, Western Province; type locality of C. damarensis micklemi.) Contrary to previous reports, the specimens from Kataba and Senanga on the left bank of the Zambezi do not correspond to C. damarensis and should be considered a separate species: C. micklemi (as confirmed by molecular analyses; Ingram, Burda & Honeycutt, 2004). According to the karyotype, C. damarensis occurs only on the right bank of the Zambezi River in the Western Province. In contrast to the high karyotypic variability on the right bank of the Kafue River, it was found that C anselli (2n= 68) is widely distributed throughout the Central province on the left bank of the Kafue River. The resulting pattern of occurrence of the different karyotypes correlates well with the extant river system configuration that separates most karyotypes. We hypothesize that geomorphological changes and in particular river system dynamics in recent geological times have played an important role in the chromosomal diversification and may have provided opportunities for speciation to occur.
TJ-II wave forms analysis with wavelets and support vector machines
Authors: Dormido-Canto S. , Farias G. , Dormido R. , Vega J. , Sánchez J. , Santos M. ,   The TJ-II Team
Published: October 2004

Since the fusion plasma experiment generates hundreds of signals, it is essential to have automatic mechanisms for searching similarities and retrieving of specific data in the wave form database. Wavelet transform (WT) is a transformation that allows one to map signals to spaces of lower dimensionality. Support vector machine (SVM) is a very effective method for general purpose pattern recognition. Given a set of input vectors which belong to two different classes, the SVM maps the inputs into a high-dimensional feature space through some nonlinear mapping, where an optimal separating hyperplane is constructed. In this work, the combined use of WT and SVM is proposed for searching and retrieving similar wave forms in the TJ-II database. In a first stage, plasma signals will be preprocessed by WT to reduce their dimensionality and to extract their main features. In the next stage, and using the smoothed signals produced by the WT, SVM will be applied to show up the efficiency of the proposed method to deal with the problem of sorting out thousands of fusion plasma signals.
From observation of several experiments, our WT+SVM method is very viable, and the results seems promising. However, we have further work to do. We have to finish the development of a Matlab toolbox for WT+SVM processing and to include new relevant features in the SVM inputs to improve the technique. We have also to make a better preprocessing of the input signals and to study the performance of other generic and self custom kernels. To reach it, and since the preprocessing stages are very time consuming, we are going to study the viability of using DSPs, RPGAs or parallel programming techniques to reduce the execution time.