bluuebunny/crossref_metadata_2025 huggingface dataset:
Constitutive model for quasi‐static deformation of metallic sandwich cores
Authors: Xue Zhenyu , Hutchinson John W.
Published: October 2004

All‐metal sandwich construction holds promise for significant improvements in stiffness, strength and blast resistance for built‐up plate structures. Analysis of the performance of sandwich plates under various loads, static and dynamic, requires modelling of face sheets and core with some fidelity. While it is possible to model full geometric details of the core for a few selected problems, this is unnecessary and unrealistic for larger complex structures under general loadings. In this paper, a continuum constitutive model is proposed as an alternative means of modelling the core. The constitutive model falls within the framework of a compressible rate‐independent, anisotropic elastic–plastic solid. The general form of the model is presented, along with algorithmic aspects of its implementation in a finite element code, and selected problems are solved which benchmark the code against existing codes for limiting cases and which illustrate features specific to compressible cores. Three core geometries (pyramidal truss, folded plate, and square honeycomb) are considered in some detail. The validity of the approach is established by comparing numerical finite element simulations using the model with those obtained by a full three‐dimensional meshing of the core geometry for each of the three types of cores for a clamped sandwich plate subject to uniform pressure load. Limitations of the model are also discussed. Copyright © 2004 John Wiley & Sons, Ltd.
Cracking particles: a simplified meshfree method for arbitrary evolving cracks
Authors: Rabczuk T. , Belytschko T.
Published: October 2004

A new approach for modelling discrete cracks in meshfree methods is described. In this method, the crack can be arbitrarily oriented, but its growth is represented discretely by activation of crack surfaces at individual particles, so no representation of the crack's topology is needed. The crack is modelled by a local enrichment of the test and trial functions with a sign function (a variant of the Heaviside step function), so that the discontinuities are along the direction of the crack. The discontinuity consists of cylindrical planes centred at the particles in three dimensions, lines centred at the particles in two dimensions. The model is applied to several 2D problems and compared to experimental data. Copyright © 2004 John Wiley & Sons, Ltd.
Supersensitivity due to uncertain boundary conditions
Authors: Xiu Dongbin , Karniadakis George Em
Published: October 2004

We study the viscous Burgers' equation subject to perturbations on the boundary conditions. Two kinds of perturbations are considered: deterministic and random. For deterministic perturbations, we show that small perturbations can result in O(1) changes in the location of the transition layer. For random perturbations, we solve the stochastic Burgers' equation using different approaches. First, we employ the Jacobi‐polynomial‐chaos, which is a subset of the generalized polynomial chaos for stochastic modeling. Converged numerical results are reported (up to seven significant digits), and we observe similar ‘stochastic supersensitivity’ for the mean location of the transition layer. Subsequently, we employ up to fourth‐order perturbation expansions. We show that even with small random inputs, the resolution of the perturbation method is relatively poor due to the larger stochastic responses in the output. Two types of distributions are considered: uniform distribution and a ‘truncated’ Gaussian distribution with no tails. Various solution statistics, including the spatial evolution of probability density function at steady state, are studied. Copyright © 2004 John Wiley & Sons, Ltd.
The cytoskeleton in neurodegenerative diseases
Authors: Cairns Nigel J , Lee Virginia M‐Y , Trojanowski John Q
Published: October 2004

Abundant abnormal aggregates of cytoskeletal proteins are neuropathological signatures of many neurodegenerative diseases that are broadly classified by filamentous aggregates of neuronal intermediate filament (IF) proteins, or by inclusions containing the microtubule‐associated protein (MAP) tau. The discovery of mutations in neuronal IF and tau genes firmly establishes the importance of neuronal IF proteins and tau in the pathogenesis of neurodegenerative diseases. Multiple IF gene mutations are pathogenic for Charcot–Marie–Tooth (CMT) disease and amyotrophic lateral sclerosis (ALS)—in addition to those in the copper/zinc superoxide dismutase‐1 (SOD1) gene. Tau gene mutations are pathogenic for frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP‐17), and tau polymorphisms are genetic risk factors for sporadic progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). Thus, IF and tau abnormalities are linked directly to the aetiology and pathogenesis of neurodegenerative diseases. In vitro and transgenic animal models are being used to demonstrate that different mutations impair protein function, promote tau fibrilization, or perturb tau gene splicing, leading to aberrant and distinct tau aggregates. For recognition of these disorders at neuropathological examination, immunohistochemistry is needed, and this may be combined with biochemistry and molecular genetics to properly determine the nosology of a particular case. As reviewed here, the identification of molecular genetic defects and biochemical alterations in cytoskeletal proteins of human neurodegenerative diseases has facilitated experimental studies and will promote the development of assays of molecules which inhibit abnormal neuronal IF and tau protein inclusions. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Die lines in plastics extrusion: Film blowing experiments and numerical simulation
Authors: Ding Fan , Giacomin A. Jeffrey
Published: October 2004

Die lines are annoying surface striations that can destroy extrudate aesthetics and compromise product properties. The available literature on die lines has been previously reviewed to explore how die lines arise and how to minimize them. Many factors have been found to influence die line formation. Some techniques are effective in suppressing die lines, mainly discovered through manufacturing experience. Here, we first briefly introduce how to measure and characterize die lines (die line metrology). Film blowing experiments are then conducted to study how various die defects, material properties and operating conditions affect die lines. The empirical relations between die lines and die defects, material properties and operating conditions are explored using dimensionless groups. We also investigate the fluid mechanics in die line formation. The free surface flow of polymer melt leaving the die lips is simulated. The qualitative relations between die defects and die lines are explored. The results are compared with film blowing experiments. Finally, new ways to suppress die lines and prospects for future studies are proposed. Polym. Eng. Sci. 44:1811–1827, 2004. © 2004 Society of Plastics Engineers.
Flow and heat transfer simulation of injection molding with microstructures
Authors: Yu Liyong , Lee L. James , Koelling Kurt W.
Published: October 2004

Injection molding has been used for mass production of polymer products with microstructures. Conventional Hele‐Shaw 2.5D midplane simulation is unable to describe the flow pattern correctly. It tends to over‐predict the effects of microstructures on global flow patterns. For the unidirectional flow, an x‐z planar based on the general momentum equation is able to achieve better accuracy and to retrieve more detailed flow and heat transfer information around the microstructures. A hybrid numerical technique is developed, which can significantly reduce the nodes and computation time, and yet provide good flow simulation around the microstructures. The mold‐melt heat transfer coefficient and injection speed are shown to be very important factors in determining the filling depth in microstructures. A decrease of the heat transfer coefficient and the occurrence of wall‐slip are likely in microchannels. Polym. Eng. Sci. 44:1866–1876, 2004. © 2004 Society of Plastics Engineers.
A study on the characteristics of antiplasticized polycarbonates and their optical disk substrates
Authors: Ueda Masaya
Published: October 2004

The characteristics of antiplasticized polycarbonates (PC) and their optical disk substrates were investigated. Meta‐terphenyl (m‐tPh) was chosen as an antiplasticizer. Blends of PC with small amounts of added m‐tPh were injection molded to form optical disk substrates. The flow properties of the blends were significantly improved by the common plasticizing effect of antiplasticizer at the melt state. The effect also induced reduction in internal stress, causing birefringence of the substrate. The increased stiffness and decreased glass transition temperature of the antiplasticized PC caused better flatness of the substrate and better microreplication of the groove geometry, respectively. It also resulted in embrittlement of the substrates, known to be a typical characteristic of antiplasticization. The antiplasticizer decreased the water absorption of the blends and also caused increased stiffness of the blends. The increased stiffness was associated with the elimination of secondary mechanical loss transition at low temperatures. From these results, the ideal viscoelastic property behavior of a polymer for an optical disk substrate to achieve better microreplication, better flatness, and low birefringence was proposed; that is, exhibiting lower modulus above glass transition temperature and higher modulus at the regions below glass transition temperature for the polymer of interest. Polym. Eng. Sci. 44:1877–1884, 2004. © 2004 Society of Plastics Engineers.
Bubble nucleation and growth in polymer solutions
Authors: Kim Ki Young , Kang Sung Lin , Kwak Ho‐Young
Published: October 2004

The molecular cluster model for homogeneous bubble nucleation was extended to predict the bubble nucleation events in elastomers, polymers and polymer solutions. For nucleation in elastomers and polymers, the strain energy overcome by a critical bubble during growth period was also considered. The calculation results for the number of bubbles nucleated are in good agreement with observed results. Further, the growing of the critical bubble by the diffusion process in a viscoelastic medium was treated by an integral method for the concentration boundary layer. The calculated cell sizes depending on the initial saturation pressure are in close agreement with the observed sizes. The governing equations developed in this study may be used in polymer processing of microcellular foams. Polym. Eng. Sci. 44:1890–1899, 2004. © 2004 Society of Plastics Engineers.
Synthesis and gas barrier characterization of poly(ethylene isophthalate)
Authors: Kotek Richard , Pang Kyeong , Schmidt Ben , Tonelli Alan
Published: October 2004

Poly(ethylene isophthalate) (PEI) was synthesized for this research with essentially a condensation polymerization of isophthalic acid and ethylene glycol catalyzed by zinc acetate and antimony trioxide. Several samples were obtained, and their characteristics were observed and compared with poly(ethylene terephthalate) (PET). The synthesized PEI samples were chemically identified by 1H NMR. Thermal analysis with differential scanning calorimetry (DSC) yielded results that indicate the samples were primarily amorphous, with a glass‐transition temperature of 55–60 °C. Molecular weights of these PEI samples were also obtained through intrinsic viscosity measurements (Mark–Houwink equation). Molecular weights varied with conditions of the polymerization, and the highest molecular weight achieved was 21,000 g/mol. Finally, the diffusion coefficient, solubility, and permeability of CO2 gas in PEI were measured and found to be substantially lower than in PET, as anticipated from their isomeric chemical structures. This is because in PET the phenyl rings are substituted in the para (1,4) positions, which allows for their facile flipping, effectively permitting gases to pass through. However, the meta‐substituted phenyl rings in PEI do not permit such ring flipping, and thus PEI may be more suitable for barrier applications. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4247–4254, 2004
The Interaction between Otto Fuel II and Aqueous Hydroxylammonium Perchlorate (HAP), Part I: Initial Observations and Time‐to‐Event Measurements
Authors: Bellerby John M. , Blackman Christopher S.
Published: October 2004

Investigations have shown that a violent event (normally auto‐ignition) occurs after a relatively short period of time when the two immiscible liquids Otto Fuel II and 82% aqueous hydroxylammonium perchlorate (HAP) come into contact at temperatures between 30 °C and 50 °C. Under quiescent conditions the time from initial contact to an event (time‐to‐event) depends on the relative volumes of the liquids as well as the temperature but there is no significant difference between the time‐to‐event recorded in an open container and that recorded in a sealed container at the same temperature. It is concluded that key reactions in the build up to an event are taking place in both the Otto Fuel II and in the HAP solution.
Enantiomer discrimination of peptides by tandem mass spectrometry: influence of the peptide sequence on chiral recognition
Authors: Czerwenka Christoph , Lindner Wolfgang
Published: October 2004

The enantiomer discrimination of peptides by electrospray ionization tandem mass spectrometry is described. A cinchona alkaloid derivative, tert‐butylcarbamoylquinine, is used as chiral selector. The chiral selector forms diastereomeric complexes with the peptide enantiomers in the liquid phase (methanolic solution), which are then transferred to the gas phase, where their dissociation behaviour is studied in an ion‐trap mass spectrometer. Different degrees of dissociation of the diastereomeric complexes allow for the discrimination of the peptide enantiomers. The influence of the peptide sequence on enantiomer discrimination is discussed and molecular recognition information is derived by comparing the results obtained for related peptides. For dipeptides, small amino acid residues at the N‐terminus and bulky side chains at the C‐terminus were found to enhance chiral recognition, while for tripeptides the effects were rather irregular. Copyright © 2004 John Wiley & Sons, Ltd.
Sequence‐ and site‐specific photodissociation at 266 nm of protonated synthetic polypeptides containing a tryptophanyl residue
Authors: Oh Joo Yeon , Moon Jeong Hee , Kim Myung Soo
Published: October 2004

Photodissociation at 266 nm of protonated synthetic polypeptides containing a tryptophanyl residue was investigated using a homebuilt tandem time‐of‐flight mass spectrometer equipped with a matrix‐assisted laser desorption/ionization source. Efficient photodissociation of the protonated peptides was demonstrated. Most of the intense peaks in the laser‐induced tandem mass spectra were sequence ions. Furthermore, sequence ions due to cleavages at all the peptide bonds were observed; this is a feature of the technique that is particularly useful for peptide sequencing. Fragmentations at both ends of the tryptophanyl residue were especially prevalent, which can be useful for location of the tryptophanyl chromophore in a peptide. Copyright © 2004 John Wiley & Sons, Ltd.
The cores of random hypergraphs with a given degree sequence
Authors: Cooper Colin
Published: October 2004

We study random r‐uniform n vertex hypergraphs with fixed degree sequence d = (d1…,dn), maximum degree Δ = o(n1/24) and total degree θn, where θ is bounded. We give the size, number of edges and degree sequence of the κ ≥ 2) up to a whp error of O(n2/3 Δ4/3 log n). In the case of graphs (r = 2) we give further structural details such as the number of tree components and, for the case of smooth degree sequences, the size of the mantle. We give various examples, such as the cores of r‐uniform hypergraphs with a near Poisson degree sequence, and an improved upper bound for the first linear dependence among the columns in the independent column model of random Boolean matrices. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 25, 2004
Bootstrap confidence intervals for medical costs with censored observations
Authors: Jiang Hongyu , Zhou Xiao‐Hua
Published: October 2004

Medical costs data with administratively censored observations often arise in cost‐effectiveness studies of treatments for life‐threatening diseases. Mean of medical costs incurred from the start of a treatment until death or a certain time point after the implementation of treatment is frequently of interest. In many situations, due to the skewed nature of the cost distribution and non‐uniform rate of cost accumulation over time, the currently available normal approximation confidence interval has poor coverage accuracy. In this paper, we propose a bootstrap confidence interval for the mean of medical costs with censored observations. In simulation studies, we show that the proposed bootstrap confidence interval had much better coverage accuracy than the normal approximation one when medical costs had a skewed distribution. When there is light censoring on medical costs (≤25 per cent), we found that the bootstrap confidence interval based on the simple weighted estimator is preferred due to its simplicity and good coverage accuracy. For heavily censored cost data (censoring rate ≥30 per cent) with larger sample sizes (n≥200), the bootstrap confidence intervals based on the partitioned estimator has superior performance in terms of both efficiency and coverage accuracy. We also illustrate the use of our methods in a real example. Copyright © 2004 John Wiley & Sons, Ltd.
Accounting for leadtime in cohort studies: evaluating when to initiate HIV therapies
Authors: Cole Stephen R. , Li Rui , Anastos Kathryn , Detels Roger , Young Mary , Chmiel Joan S. , Muñoz Alvaro
Published: October 2004

Commonly reported comparisons of differences in disease progression according to disease staging at therapy initiation may be subject to bias if they do not account for the time it took the deferred group to reach the latter stage (that is, leadtime) and for previous events in those who initiate therapy at late stage (that is, unseen fast progressors). To estimate the impact of deferring initiation of highly active antiretroviral therapies (HAART) on time to clinical AIDS in the context of data from observational cohort studies, we describe a method that capitalizes on data from a pre‐HAART period to multiply impute estimated leadtimes and the unseen events among fast progressors. After accounting for leadtime and the unseen events, data from two large cohort studies (N=739) indicate that deferring HAART initiation until CD4 is below 200 cells/mm3was detrimental compared to initiating between 201 and 350 (hazard ratio=1.97; 95 percent confidence interval [CI] 1.09, 3.54), and that failure to account for leadtime resulted in a 38 per cent higher hazard ratio. In contrast, initiating HAART between 201 and 350 did not increase the hazard of AIDS compared to initiating with CD4 between 351 and 500cells/mm3(hazard ratio=0.70; 95 per cent CI 0.35, 1.42). Methods presented here offer an approach to analysing prevalent cohort studies and provide procedures to maximize the usefulness of observational data. Copyright © 2004 John Wiley & Sons, Ltd.
Comparing regression methods for the two‐stage clonal expansion model of carcinogenesis
Authors: Kaiser J. C. , Heidenreich W. F.
Published: October 2004

In the statistical analysis of cohort data with risk estimation models, both Poisson and individual likelihood regressions are widely used methods of parameter estimation. In this paper, their performance has been tested with the biologically motivated two‐stage clonal expansion (TSCE) model of carcinogenesis. To exclude inevitable uncertainties of existing data, cohorts with simple individual exposure history have been created by Monte Carlo simulation. To generate some similar properties of atomic bomb survivors and radon‐exposed mine workers, both acute and protracted exposure patterns have been generated. Then the capacity of the two regression methods has been compared to retrieve a priori known model parameters from the simulated cohort data. For simple models with smooth hazard functions, the parameter estimates from both methods come close to their true values. However, for models with strongly discontinuous functions which are generated by the cell mutation process of transformation, the Poisson regression method fails to produce reliable estimates. This behaviour is explained by the construction of class averages during data stratification. Thereby, some indispensable information on the individual exposure history was destroyed. It could not be repaired by countermeasures such as the refinement of Poisson classes or a more adequate choice of Poisson groups. Although this choice might still exist we were unable to discover it. In contrast to this, the individual likelihood regression technique was found to work reliably for all considered versions of the TSCE model. Copyright © 2004 John Wiley & Sons, Ltd.
Residual analysis in linear regression models with an interval‐censored covariate
Authors: Topp Rebekka , Gómez Guadalupe
Published: October 2004

Residual analysis is a useful class of techniques for the evaluation of the goodness of a fitted model. Checking the underlying assumptions is important since most linear regression estimators require a correctly specified regression function and independent and identically distributed errors to be consistent. For uncensored data, the examination of the residuals of the fitted model is a standard tool for checking whether or not the underlying model assumptions hold. Such analysis has not been widely developed for censored data. Hillis (Statistics in Medicine1995;14:2023–2036) developed a residual plot for model checking when the response variable of a linear model is right‐censored, and Gómezet al. (Statistics in Medicine2003;22:409–425) proposed residuals in models with interval‐censored covariates. In this paper, we propose a new definition of residuals for linear models that incorporate interval‐censored covariates. This definition can be also applied when the response variable is interval‐censored. These new residuals are shown to perform better in model checking than other types of residuals in this context. We illustrate them with a data set from an AIDS clinical trial study. Copyright © 2004 John Wiley & Sons, Ltd.
Multiple imputation to estimate the association between eyes in disease progression with interval‐censored data
Authors: Glynn Robert J. , Rosner Bernard
Published: October 2004

In 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

Receiver 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

A 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

To 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

The 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

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

Much 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

As 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

The 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

Heterochrony 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

The 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

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

Unique 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

The 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.
SOCS proteins in T helper cell differentiation: implications for allergic disorders?
Authors: Inoue Hiromasa , Kubo Masato
Published: October 2004

Asthma, allergic rhinitis and atopic dermatitis are allergic immune disorders characterised by a predominance of T helper 2 (Th2) cells, the resulting elevation of allergen-specific IgE, and mast-cell- and basophil-associated inflammation. The cytokine environment at the site of the initial antigen stimulation determines the direction of Th-cell differentiation into Th1 or Th2 cells. The SOCS (suppressor of cytokine signalling) proteins are implicated in the control of the balance between Th1 and Th2 cells in this process. SOCS3 is predominantly expressed in Th2 cells and inhibits Th1 differentiation; conversely, SOCS5 is expressed predominantly in Th1 cells and inhibits Th2 differentiation. Here, we discuss the role of SOCS proteins in Th-cell differentiation and explore the potential of SOCS proteins as targets for therapeutic strategies in allergic disorders.
Lithium neuroprotection: molecular mechanisms and clinical implications
Authors: Rowe Michael K. , Chuang De-Maw
Published: October 2004

Lithium has emerged as a neuroprotective agent efficacious in preventing apoptosis-dependent cellular death. Lithium neuroprotection is provided through multiple, intersecting mechanisms, although how lithium interacts with these mechanisms is still under investigation. Lithium increases cell survival by inducing brain-derived neurotrophic factor and thereby stimulating activity in anti-apoptotic pathways, including the phosphatidylinositol 3-kinase/Akt and the mitogen-activated protein kinase pathways. In addition, lithium reduces pro-apoptotic function by directly and indirectly inhibiting glycogen synthase kinase-3β activity and indirectly inhibiting N-methyl-D-aspartate (NMDA)-receptor-mediated calcium influx. Lithium-induced regulation of anti- and pro-apoptotic pathways alters a wide variety of downstream effectors, including β-catenin, heat shock factor 1, activator protein 1, cAMP-response-element-binding protein, and the Bcl-2 protein family. Lithium neuroprotection has a wide variety of clinical implications. Beyond its present use in bipolar mood disorder, lithium's neuroprotective abilities imply that it could be used to treat or prevent brain damage following traumatic injury, such as stroke, and neurodegenerative diseases such as Huntington's and Alzheimer's diseases.
Intensivierung, Fokussierung und Verhaltensrelevanz
Authors: Neininger Bettina , Pulvermüller Friedemann , Elbert Thomas , Rockstroh Brigitte , Mohr Bettina , Mohr Bettina
Published: October 2004

Zusammenfassung: Gehirnwissenschaftliche Erkenntnisse der vergangenen Jahre haben neue neuropsychologische Therapieformen hervorgebracht, deren allgemeine Prinzipien sich mit den Termini Intensivierung, Verhaltensrelevanz und Fokussierung umreißen lassen (genannt Constraint-Induced Aphasia Therapy - CIA Therapie). Intensivierung der Therapie bedeutet, dass die Intervention mit besonders hoher Frequenz durchgeführt wird (engl.: massed practice). Die im therapeutischen Setting implementierten Interaktionstypen gleichen denjenigen im Alltag (behavioral relevance). “Fokussierung” heißt, dass der Patient durch Hilfsmittel und Regeln der therapeutischen Interaktion zu Handlungsweisen gebracht wird, die er aufgrund operanter Konditionierungen in Folge der Gehirnschädigung sonst vermeiden würde (constraints to avoid learned nonuse). In einer kontrollierten Effektivitätsstudie konnten wir beweisen, dass CIA Therapie auch bei chronischer Aphasie zu einer signifikanten Verbesserung der sprachlichen Leistungen führen kann. Wir gehen hier auf die historischen Wurzeln ein und diskutieren Fragen für zukünftige Forschungen.