bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth, ion content, gas exchange, and water relations of wheat genotypes differing in salt tolerances
Authors: El-Hendawy Salah E. , Hu Yuncai , Schmidhalter Urs
Published: February 2005

Although the mechanisms of salt tolerance in plants have received much attention for many years, genotypic differences influencing salt tolerance still remain uncertain. To investigate the key physiological factors associated with genotypic differences in salt tolerance of wheat and their relationship to salt stress, 13 wheat genotypes from Egypt, Australia, India, and Germany, that differ in their salt tolerances, were grown in a greenhouse in soils of 4 different salinity levels (control, 50, 100, and 150 mm NaCl). Relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), photosynthesis, chlorophyll content (SPAD value), and leaf water relations were measured at Days 45 and 60 after sowing. Mineral nutrient content in leaves and stems was determined at Day 45 and final harvest. Salinity reduced RGR, NAR, photosynthetic rate, stomatal conductance, water and osmotic potentials, and K+ and Ca2+ content in stems and leaves at all times, whereas it increased leaf respiration, and Na+ and Cl– content in leaves and stems. LAR was not affected by salinity and the effect of salinity on SPAD value was genotype-dependent. Growth of salt-tolerant genotypes (Sakha 8, Sakha 93, and Kharchia) was affected by salinity primarily due to a decline in photosynthetic capacity rather than a reduction in leaf area, whereas NAR was the more important factor in determining RGR of moderately tolerant and salt-sensitive genotypes. We conclude that Na+ and Cl– exclusion did not always reflect the salt tolerance, whereas K+ in the leaves and Ca2+ in the leaves and stems were closely associated with genotypic differences in salt tolerance among the 13 genotypes even at Day 45. Calcium content showed a greater difference in salt tolerance among the genotypes than did K+ content. The genotypic variation in salt tolerance was also observed for the parameters involved in photosynthesis, and water and osmotic potentials, but not for turgor pressure.
Agronomic evaluation of a tiller inhibition gene (tin) in wheat. II. Growth and partitioning of assimilate
Authors: Duggan B. L. , Richards R. A. , van Herwaarden A. F.
Published: February 2005

Wheats with reduced tillering have been proposed for areas regularly subject to a terminal drought. A wheat plant with a genetic disposition to produce fewer stems is now possible through the introgression of a gene that inhibits tillering (tin). This study was conducted to determine the effect of the tin gene on the dynamics of tillering, light interception, and dry-matter production and partitioning in several different cultivars of wheat. Commercial cultivars and their near-isogenic pairs differing in the presence of the tin gene were grown in well-watered tubes and also in the field in south-eastern Australia where terminal drought is common. Tiller number, light interception, leaf area index (LAI), biomass, and the partitioning of biomass were recorded at various intervals throughout the growing season. Water-soluble carbohydrate (WSC) levels in the stems of field-grown plants were also determined in some environments at anthesis and maturity. In tubes and in field environments, lines with the tin gene produced tillers at the same rate as their free tillering counterparts but ceased tillering sooner. Under conditions where the free tillering lines produced over 1000 shoots/m2, lines containing the tin gene produced 600 shoots/m2. However, by maturity, fertile spike numbers were 350 and 450/m2 for lines with and without the tin gene, respectively. Despite the large difference in tillering, there were only small differences in LAI, light interception throughout the season, and biomass. There were small differences in the proportional allocation of biomass, and the tin lines partitioned more of their biomass towards spikes at anthesis and stored more WSC in stems. Dry weight distribution varied with genetic background, but in general the tin gene increased leaf area ratio and root to shoot ratio but decreased specific leaf area. It is concluded that the tin gene may be advantageous under terminal drought. This would come from the reduced light interception prior to anthesis and thereby potential for greater transpiration during grain filling as well as a greater capacity for stem carbohydrate storage and remobilisation. These factors are consistent with a greater harvest index and kernel weight associated with lines containing the tin gene.
The effect of boron tolerance, deep ripping with gypsum, and water supply on subsoil water extraction of cereals on an alkaline soil
Authors: Nuttall J. G. , Armstrong R. D. , Connor D. J.
Published: February 2005

Crop adaptation to edaphic constraints has focussed largely on increasing boron (B) tolerance in cereals, targeted to alkaline soils with high boron content. However, recent studies have implicated several other physicochemical constraints, such as salinity and sodicity, in reduced grain yields of cereals by restricting water extraction in the subsoil. Consequently, the value of B-tolerance may be limited on soils where multiple constraints exist. To test the contribution of B-tolerance where multiple constraints exist, near-isogenic lines of wheat and barley differing in B-tolerance were used, where growth and water extraction by crops in large intact cores, extracted from a Calcarosol profile, were measured. The effect of subsoil disturbance (deep ripping) and growing-season water supply was also investigated. Use of B-tolerant crops did not increase use of subsoil water or grain yield. Wheat and barley extracted soil water down to 0.6 m depth but not below 0.8 m. The soil B concentration of these 2 layers was equivalent (29 ν. 31 mg/kg), whereas salinity [(ECe) 7.2 ν. 8.1 dS/m] and sodicity [(ESP) 22 ν. 29%] both increased significantly with depth, implying that these 2 latter properties had a greater effect than B. Deep ripping with gypsum had no effect on grain yield. Wheat and barley grown under high water supply outyielded their counterparts grown under low water supply, although grain yield per unit of applied water for the crops under low water was 1.5 times that of the crops under high water regime. The results suggest that high salinity and sodicity, rather than B, were exerting the major effects on water extraction of wheat and barley from the deep subsoil, thus negating the effect of crop B-tolerance where multiple constraints exist. This highlights the need to breed cultivars with increased sodium tolerance, pyramided with current B-tolerance, for those crops targeted to many alkaline soils.
Photochemical efficiency is an important component of ecophysiological variation of Cistus albidus between habitats in south-east Spain
Authors: Grant Olga M. , Incoll Lynton D.
Published: February 2005

The ecophysiology of Cistus albidus L. plants in a variety of habitats in south-east Spain was measured in situ over the course of a year, to determine whether physiological variation occurs between populations growing in sites exposed to differing temperature and precipitation. Not all the observed variation could be explained by differing contemporary meteorological conditions. In particular, plants at the driest site maintained much higher photochemical efficiency through the summer and autumn than plants at the other sites, and also showed higher stomatal conductance after the autumn rains. Principal component analysis identified photochemical efficiency as the greatest source of variation between populations. Such variation may represent the result of differing selection in populations that have been exposed to different prevailing conditions of mean temperature, precipitation or atmospheric humidity, for long periods of time.
Spatio‐visual memory of children with specific language impairment: evidence for generalized processing problems
Authors: Bavin Edith L. , Wilson Peter H. , Maruff Paul , Sleeman Felicity
Published: February 2005

Background: Children with Specific language Impairment (SLI) have problems with verbal memory, particularly with tasks that have more processing demands. They also have slower speeds of responding for some tasks.

Aims: To identify the extent to which young children with SLI would differ in performance from age‐matched non‐impaired children on a set of spatio‐visual memory tasks. It was predicted that if memory limitations of children with SLI extend beyond the verbal domain to other domains, their performance would be significantly poorer on the spatio‐visual tasks than that of the comparison group. It was also predicted that they would be slower in responding.

Methods & Procedures: Six spatio‐visual tasks were used to compare the performance of 21 children with SLI, with a mean age of 54.1 months, and 21 age‐matched non‐impaired children. The tasks ranged in difficulty from simple recall to a search‐based working memory task. All tasks were administered though a laptop computer and responses were non‐verbal using a touch screen.

Outcomes & Results: The children with SLI were not significantly slower than the comparison group. However, they were significantly less accurate than the comparison group in recalling patterns, but not in recalling locations. The accuracy for both groups was lower on spatial recall than on pattern recall. The children with SLI were also significantly less able to learn to associate a particular pattern with a particular location, and to have a shorter spatial span. However, on a spatial search task testing working memory, the groups did not differ significantly.

Conclusions: The results indicate that the memory limitations of children with SLI are not restricted to verbal memory, and this fact has implications for its aetiology. Intervention programmes for young children with SLI need to extend beyond language in order to help them develop strategies for processing information in different situations.
Binding of Anti‐HIV Drugs to Human Serum Albumin
Authors: Bocedi Alessio , Notaril Stefania , Narciso Pasquale , Bolli Alessandro , Fasano Mauro , Ascenzi Paolo
Published: February 2005

Human serum albumin (HSA), the most prominent protein in plasma, is best known for its exceptional ligand (i.e., drug) binding capacity. Here, values of the dissociation equilibrium constant (Kd) for the binding of HIV protease and reverse transcriptase inhibitors to HSA are reported. The binding of abacavir, atazanavir, didanosine, efavirenz, emtricitabine, lamivudine, nelfinavir, nevirapine, ritonavir, saquinavir, stavudine, zalcitabine, and zidovudine to the Sudlow site I (i.e., the warfarin cleft) located in the subdomain IIA involves the alteration of the HSA structure around Trp214 and induces intrinsic tryptophan fluorescence quenching. Accordingly, ibuprofen that primarily binds to the Sudlow site II located in the subdomain IIIA does not affect the HSA intrinsic tryptophan fluorescence and the binding of anti‐HIV drugs to the Sudlow site I. Accounting for the physiological concentration of HSA (= 7.0 × 10‐4 M), the average anti‐HIV drug concentration in plasma (= 1.0 × 10‐4 M), and Kd values for the binding of anti‐HIV drugs to HSA (ranging between 4.4 × 10‐5 M and 3.8 × 10‐4 M), it appears that the fraction of HIV protease and reverse transcriptase inhibitors bound to HSA ranges between 63% and 91%. This represents a significant drawback in the anti‐HIV therapy and management, the anti‐HIV drug concentration required to achieve 90% protease and reverse transcriptase inhibition in the presence of plasma proteins appears to be at least one order of magnitude higher than that required in their absence.
IUBMB Life, 56: 609‐614, 2004
HIV Protease Inhibitors‐induced Atherosclerosis: Prevention by α‐Tocopherol
Authors: Munteanu Adelina , Ricciarelli Roberta , Zingg Jean‐Marc
Published: February 2005

Prolonged treatments with inhibitors of human immunodeficiency (HIV)‐encoded protease (ARPI) have been reported to induce early atherosclerotic events. Our in vitro study indicates that α‐tocopherol may prevent drug‐induced premature atherosclerosis since it interferes with CD36 scavenger receptor over‐expression induced by ritonavir in monocytes. The mechanism of CD36 upregulation by ritonavir involves inhibition of the ubiquitin‐proteasome system and α‐tocopherol is able to normalize proteasome activity. These findings suggest that ARPI combined with early α‐tocopherol supplementation may decrease the drug‐induced atherosclerotic risk.
IUBMB Life, 56: 629‐631, 2004
N-myristoylation determines dual targeting of mammalian NADH-cytochrome b(5) reductase to ER and mitochondrial outer membranes by a mechanism of kinetic partitioning
Authors: Colombo Sara , Longhi Renato , Alcaro Stefano , Ortuso Francesco , Sprocati Teresa , Flora Adriano , Borgese Nica
Published: February 2005

Mammalian NADH-cytochrome b(5) reductase (b5R) is an N-myristoylated protein that is dually targeted to ER and mitochondrial outer membranes. The N-linked myristate is not required for anchorage to membranes because a stretch of hydrophobic amino acids close to the NH2 terminus guarantees a tight interaction of the protein with the phospholipid bilayer. Instead, the fatty acid is required for targeting of b5R to mitochondria because a nonmyristoylated mutant is exclusively localized to the ER. Here, we have investigated the mechanism by which N-linked myristate affects b5R targeting. We find that myristoylation interferes with interaction of the nascent chain with signal recognition particle, so that a portion of the nascent chains escapes from cotranslational integration into the ER and can be post-translationally targeted to the mitochondrial outer membrane. Thus, competition between two cotranslational events, binding of signal recognition particle and modification by N-myristoylation, determines the site of translation and the localization of b5R.
Regulation of the interaction between PIPKIγ and talin by proline-directed protein kinases
Authors: Lee Sang Yoon , Voronov Sergey , Letinic Kresimir , Nairn Angus C. , Di Paolo Gilbert , De Camilli Pietro
Published: February 2005

The interaction of talin with phosphatidylinositol(4) phosphate 5 kinase type Iγ (PIPKIγ) regulates PI(4,5)P2 synthesis at synapses and at focal adhesions. Here, we show that phosphorylation of serine 650 (S650) within the talin-binding sequence of human PIPKIγ blocks this interaction. At synapses, S650 is phosphorylated by p35/Cdk5 and mitogen-activated protein kinase at rest, and dephosphorylated by calcineurin upon stimulation. S650 is also a substrate for cyclin B1/Cdk1 and its phosphorylation in mitosis correlates with focal adhesion disassembly. Phosphorylation by Src of the tyrosine adjacent to S650 (Y649 in human PIPKIγ) was shown to enhance PIPKIγ targeting to focal adhesions (Ling, K., R.L. Doughman, V.V. Iyer, A.J. Firestone, S.F. Bairstow, D.F. Mosher, M.D. Schaller, and R.A. Anderson. 2003. J. Cell Biol. 163:1339–1349). We find that Y649 phosphorylation does not stimulate directly PIPKIγ binding to talin, but may do so indirectly by inhibiting S650 phosphorylation. Conversely, S650 phosphorylation inhibits Y649 phosphorylation by Src. The opposite effects of the phosphorylation of Y649 and S650 likely play a critical role in regulating synaptic function as well as the balance between cell adhesion and cell motility.
Sunday Driver links axonal transport to damage signaling
Authors: Cavalli Valeria , Kujala Pekka , Klumperman Judith , Goldstein Lawrence S.B.
Published: February 2005

Neurons transmit long-range biochemical signals between cell bodies and distant axonal sites or termini. To test the hypothesis that signaling molecules are hitchhikers on axonal vesicles, we focused on the c-Jun NH2-terminal kinase (JNK) scaffolding protein Sunday Driver (syd), which has been proposed to link the molecular motor protein kinesin-1 to axonal vesicles. We found that syd and JNK3 are present on vesicular structures in axons, are transported in both the anterograde and retrograde axonal transport pathways, and interact with kinesin-I and the dynactin complex. Nerve injury induces local activation of JNK, primarily within axons, and activated JNK and syd are then transported primarily retrogradely. In axons, syd and activated JNK colocalize with p150Glued, a subunit of the dynactin complex, and with dynein. Finally, we found that injury induces an enhanced interaction between syd and dynactin. Thus, a mobile axonal JNK–syd complex may generate a transport-dependent axonal damage surveillance system.
The de novo centriole assembly pathway in HeLa cells
Authors: La Terra Sabrina , English Christopher N. , Hergert Polla , McEwen Bruce F. , Sluder Greenfield , Khodjakov Alexey
Published: February 2005

It has been reported that nontransformed mammalian cells become arrested during G1 in the absence of centrioles (Hinchcliffe, E., F. Miller, M. Cham, A. Khodjakov, and G. Sluder. 2001. Science. 291:1547–1550). Here, we show that removal of resident centrioles (by laser ablation or needle microsurgery) does not impede cell cycle progression in HeLa cells. HeLa cells born without centrosomes, later, assemble a variable number of centrioles de novo. Centriole assembly begins with the formation of small centrin aggregates that appear during the S phase. These, initially amorphous “precentrioles” become morphologically recognizable centrioles before mitosis. De novo–assembled centrioles mature (i.e., gain abilities to organize microtubules and replicate) in the next cell cycle. This maturation is not simply a time-dependent phenomenon, because de novo–formed centrioles do not mature if they are assembled in S phase–arrested cells. By selectively ablating only one centriole at a time, we find that the presence of a single centriole inhibits the assembly of additional centrioles, indicating that centrioles have an activity that suppresses the de novo pathway.
Conservation of boundary extension mechanisms between plants and animals
Authors: Mathur Jaideep
Published: February 2005

Locomotion clearly sets plants and animals apart. However, recent studies in higher plants reveal cell-biological and molecular features similar to those observed at the leading edge of animal cells and suggest conservation of boundary extension mechanisms between motile animal cells and nonmotile plant cells.
Divalent Cation Sensitivity of BK Channel Activation Supports the Existence of Three Distinct Binding Sites
Authors: Zeng Xu-Hui , Xia Xiao-Ming , Lingle Christopher J.
Published: February 2005

Mutational analyses have suggested that BK channels are regulated by three distinct divalent cation-dependent regulatory mechanisms arising from the cytosolic COOH terminus of the pore-forming α subunit. Two mechanisms account for physiological regulation of BK channels by μM Ca2+. The third may mediate physiological regulation by mM Mg2+. Mutation of five aspartate residues (5D5N) within the so-called Ca2+ bowl removes a portion of a higher affinity Ca2+ dependence, while mutation of D362A/D367A in the first RCK domain also removes some higher affinity Ca2+ dependence. Together, 5D5N and D362A/D367A remove all effects of Ca2+ up through 1 mM while E399A removes a portion of low affinity regulation by Ca2+/Mg2+. If each proposed regulatory effect involves a distinct divalent cation binding site, the divalent cation selectivity of the actual site that defines each mechanism might differ. By examination of the ability of various divalent cations to activate currents in constructs with mutationally altered regulatory mechanisms, here we show that each putative regulatory mechanism exhibits a unique sensitivity to divalent cations. Regulation mediated by the Ca2+ bowl can be activated by Ca2+ and Sr2+, while regulation defined by D362/D367 can be activated by Ca2+, Sr2+, and Cd2+. Mn2+, Co2+, and Ni2+ produce little observable effect through the high affinity regulatory mechanisms, while all six divalent cations enhance activation through the low affinity mechanism defined by residue E399. Furthermore, each type of mutation affects kinetic properties of BK channels in distinct ways. The Ca2+ bowl mainly accelerates activation of BK channels at low [Ca2+], while the D362/D367-related high affinity site influences both activation and deactivation over the range of 10–300 μM Ca2+. The major kinetic effect of the E399-related low affinity mechanism is to slow deactivation at mM Mg2+ or Ca2+. The results support the view that three distinct divalent-cation binding sites mediate regulation of BK channels.
Symmetric functions and the phase problem in crystallography
Authors: Buhler J. , Reichstein Z.
Published: February 2005

The calculation of crystal structure from X-ray diffraction data requires that the phases of the “structure factors” (Fourier coefficients) determined by scattering be deduced from the absolute values of those structure factors. Motivated by a question of Herbert Hauptman, we consider the problem of determining phases by direct algebraic means in the case of crystal structures withnnequal atoms in the unit cell, withnnsmall. We rephrase the problem as a question about multiplicative invariants for a particular finite group action. We show that the absolute values form a generating set for the field of invariants of this action, and consider the problem of making this theorem constructive and practical; the most promising approach for deriving explicit formulas uses SAGBI bases.
Homological algebra for the representation Green functor for abelian groups
Authors: Ventura Joana
Published: February 2005

In this paper we compute some derived functors

Ext
\operatorname {Ext}

of the internal homomorphism functor in the category of modules over the representation Green functor. This internal homomorphism functor is the left adjoint of the box product. When the group is a cyclic

2
2

-group, we construct a projective resolution of the module fixed point functor, and that allows a direct computation of the graded Green functor

Ext
\operatorname {Ext}

. When the group is

G
=

Z

/

2
×

Z

/

2

G=\mathbb {Z}/2\times \mathbb {Z}/2

, we can still build a projective resolution, but we do not have explicit formulas for the differentials. The resolution is built from long exact sequences of projective modules over the representation functor for the subgroups of

G
G

by using exact functors between these categories of modules. This induces a filtration which gives a spectral sequence which converges to the desired

Ext
\operatorname {Ext}

functors.
Smoothness of equisingular families of curves
Authors: Keilen Thomas
Published: February 2005

Francesco Severi (1921) showed that equisingular families of plane nodal curves are T-smooth, i.e. smooth of the expected dimension, whenever they are non-empty. For families with more complicated singularities this is no longer true. Given a divisor

D
D

on a smooth projective surface

Σ
\Sigma

it thus makes sense to look for conditions which ensure that the family

V

|

D

|

i
r
r

(

S

1

,
…
,

S

r

)

V_{|D|}^{irr}\big (\mathcal {S}_1,\ldots ,\mathcal {S}_r\big )

of irreducible curves in the linear system

|

D

|

l

|D|_l

with precisely

r
r

singular points of types

S

1

,
…
,

S

r

\mathcal {S}_1,\ldots ,\mathcal {S}_r

is T-smooth. Considering different surfaces including the projective plane, general surfaces in

P

C

3

\mathbb {P}_{\mathbb {C}}^3

, products of curves and geometrically ruled surfaces, we produce a sufficient condition of the type
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="sigma-summation Underscript i equals 1 Overscript r Endscripts gamma Subscript alpha Baseline left-parenthesis script upper S Subscript i Baseline right-parenthesis greater-than gamma dot left-parenthesis upper D minus upper K Subscript normal upper Sigma Baseline right-parenthesis squared comma">

∑

i
=
1

r

γ
α

(

S

i

)
>
γ
⋅
(
D
−

K
Σ

)
2

,

\sum \limits _{i=1}^r\gamma _\alpha (\mathcal {S}_i) > \gamma \cdot (D- K_\Sigma )^2,

\]
where

γ
α

\gamma _\alpha

is some invariant of the singularity type and

γ
\gamma

is some constant. This generalises the results of Greuel, Lossen, and Shustin (2001) for the plane case, combining their methods and the method of Bogomolov instability. For many singularity types the

γ
α

\gamma _\alpha

-invariant leads to essentially better conditions than the invariants used by Greuel, Lossen, and Shustin (1997), and for most classes of geometrically ruled surfaces our results are the first known for T-smoothness at all.
Weighted rearrangement inequalities for local sharp maximal functions
Authors: Lerner Andrei
Published: February 2005

Several weighted rearrangement inequalities for uncentered and centered local sharp functions are proved. These results are applied to obtain new weighted weak-type and strong-type estimates for singular integrals. A self-improving property of sharp function inequalities is established.
Upper bounds for the number of solutions of a Diophantine equation
Authors: Garaev M.
Published: February 2005

We give upper bound estimates for the number of solutions of a certain diophantine equation. Our results can be applied to obtain new lower bound estimates for the

L
1

L_1

-norm of certain exponential sums.
The limit sets of Schottky quasiconformal groups are uniformly perfect
Authors: Li Xiaosheng
Published: February 2005

In this paper we study Schottky quasiconformal groups. We show that the limit sets of Schottky quasiconformal groups are uniformly perfect, and that the limit set of a given discrete non-elementary quasiconformal group has positive Hausdorff dimension.
Semiparametric Estimation of Proportional Mean Residual Life Model in Presence of Censoring
Authors: Chen Y. Q. , Jewell N. P. , Lei X. , Cheng S. C.
Published: February 2005

SummaryA mean residual life function is the average remaining life of a surviving subject, as it varies with time. The proportional mean residual life model was proposed byOakes and Dasu(1990,Biometrika77,409–410) in regression analysis to study its association with related covariates in absence of censoring. In this article, we develop some semiparametric estimation procedures to take censoring into account. The proposed methodology is evaluated via simulation studies, and further applied to a clinical trial of chemotherapy in postoperative radiotherapy of lung cancer patients.
Comparison of Maximum Statistics for Hypothesis Testing When a Nuisance Parameter Is Present only under the Alternative
Authors: Zheng Gang , Chen Zehua
Published: February 2005

Summary In many practical problems, a hypothesis testing involves a nuisance parameter which appears only under the alternative hypothesis. Davies (1977, Biometrika64, 247–254) proposed the maximum of the score statistics over the whole range of the nuisance parameter as a test statistic for this type of hypothesis testing. Freidlin, Podgor, and Gastwirth (1999, Biometrics55, 883–886) studied two other simpler maximum test statistics, the maximum of the score statistics at two extreme points of the nuisance parameter, and the maximum of the score statistics at three points of the nuisance parameter including the two extreme points. In this article, we compare the powers of these three maximum‐type statistics in the context of three genetic problems.
Bayesian Population Dynamics of Interacting Species: Great Gerbils and Fleas in Kazakhstan
Authors: Frigessi Arnoldo , Holden Marit , Marshall Clare , Viljugrein Hildegunn , Stenseth Nils Chr. , Holden Lars , Ageyev Vladimir , Klassovskiy Nikolay L.
Published: February 2005

SummaryWe propose a discrete‐time Bayesian hierarchical model for the population dynamics of the great gerbil–flea ecological system. The model accounts for the sampling variability arising from data originally collected for other purposes. The prior for the unknown population densities incorporates specific biological hypotheses regarding the interacting dynamics of the two species, as well as their life cycles, where density‐dependent effects are included. Posterior estimates are obtained via Markov chain Monte Carlo. The variance of the observed density estimates is a quadratic function of the unknown density. Our study indicates the presence of a density‐dependent growth rate for the gerbil population. For the flea population there is clear evidence of density‐dependent over‐summer net growth, which is dependent on the flea‐to‐gerbil ratio at the beginning of the reproductive summer. Over‐winter net growth is favored by high density. We estimate that on average 35% of the gerbil population survives the winter. Our study shows that hierarchical Bayesian models can be useful in extracting ecobiological information from observational data.
Quantile Regression Models with Multivariate Failure Time Data
Authors: Yin Guosheng , Cai Jianwen
Published: February 2005

Summary As an alternative to the mean regression model, the quantile regression model has been studied extensively with independent failure time data. However, due to natural or artificial clustering, it is common to encounter multivariate failure time data in biomedical research where the intracluster correlation needs to be accounted for appropriately. For right‐censored correlated survival data, we investigate the quantile regression model and adapt an estimating equation approach for parameter estimation under the working independence assumption, as well as a weighted version for enhancing the efficiency. We show that the parameter estimates are consistent and asymptotically follow normal distributions. The variance estimation using asymptotic approximation involves nonparametric functional density estimation. We employ the bootstrap and perturbation resampling methods for the estimation of the variance–covariance matrix. We examine the proposed method for finite sample sizes through simulation studies, and illustrate it with data from a clinical trial on otitis media.
Modeling Association among Demographic Parameters in Analysis of Open Population Capture–Recapture Data
Authors: Link William A. , Barker Richard J.
Published: February 2005

Summary We present a hierarchical extension of the Cormack–Jolly–Seber (CJS) model for open population capture–recapture data. In addition to recaptures of marked animals, we model first captures of animals and losses on capture. The parameter set includes capture probabilities, survival rates, and birth rates. The survival rates and birth rates are treated as a random sample from a bivariate distribution, thus the model explicitly incorporates correlation in these demographic rates. A key feature of the model is that the likelihood function, which includes a CJS model factor, is expressed entirely in terms of identifiable parameters; losses on capture can be factored out of the model. Since the computational complexity of classical likelihood methods is prohibitive, we use Markov chain Monte Carlo in a Bayesian analysis. We describe an efficient candidate‐generation scheme for Metropolis–Hastings sampling of CJS models and extensions. The procedure is illustrated using mark‐recapture data for the moth Gonodontis bidentata.
Bayesian Monitoring of Clinical Trials with Failure‐Time Endpoints
Authors: Rosner Gary L.
Published: February 2005

SummaryThis article presents an aid for monitoring clinical trials with failure‐time endpoints based on the Bayesian nonparametric analyses of the data. The posterior distribution is a mixture of Dirichlet processes in the presence of censoring if one assumes a Dirichlet process prior for the survival distribution. Using Gibbs sampling, one can generate random samples from the posterior distribution. With samples from the posterior distributions of treatment‐specific survival curves, one can evaluate the current evidence in favor of stopping or continuing the trial based on summary statistics of these survival curves. Because the method is nonparametric, it can easily be used, for example, in situations where hazards cross or are suspected to cross and where relevant clinical decisions might be based on estimating when the integral between the curves might be expected to become positive and in favor of the new but toxic therapy. An example based on an actual trial illustrates the method.
A Sample Size Formula for the Supremum Log‐Rank Statistic
Authors: Eng Kevin Hasegawa , Kosorok Michael R.
Published: February 2005

Summary An advantage of the supremum log‐rank over the standard log‐rank statistic is an increased sensitivity to a wider variety of stochastic ordering alternatives. In this article, we develop a formula for sample size computation for studies utilizing the supremum log‐rank statistic. The idea is to base power on the proportional hazards alternative, so that the supremum log rank will have the same power as the standard log rank in the setting where the standard log rank is optimal. This results in a slight increase in sample size over that required for the standard log rank. For example, a 5.733% increase occurs for a two‐sided test having type I error 0.05 and power 0.80. This slight increase in sample size is offset by the significant gains in power the supremum log‐rank test achieves for a wide range of nonproportional hazards alternatives. A small simulation study is used for illustration. These results should facilitate the wider use of the supremum log‐rank statistic in clinical trials.
Regression Modeling of Competing Risks Data Based on Pseudovalues of the Cumulative Incidence Function
Authors: Klein John P. , Andersen Per Kragh
Published: February 2005

SummaryTypically, regression models for competing risks outcomes are based on proportional hazards models for the crude hazard rates. These estimates often do not agree with impressions drawn from plots of cumulative incidence functions for each level of a risk factor. We present a technique which models the cumulative incidence functions directly. The method is based on the pseudovalues from a jackknife statistic constructed from the cumulative incidence curve. These pseudovalues are used in a generalized estimating equation to obtain estimates of model parameters. We study the properties of this estimator and apply the technique to a study of the effect of alternative donors on relapse for patients given a bone marrow transplant for leukemia.
Iterative Partial Least Squares with Right‐Censored Data Analysis: A Comparison to Other Dimension Reduction Techniques
Authors: Huang Jie , Harrington David
Published: February 2005

SummaryIn the linear model with right‐censored responses and many potential explanatory variables, regression parameter estimates may be unstable or, when the covariates outnumber the uncensored observations, not estimable. We propose an iterative algorithm for partial least squares, based on the Buckley–James estimating equation, to estimate the covariate effect and predict the response for a future subject with a given set of covariates. We use a leave‐two‐out cross‐validation method for empirically selecting the number of components in the partial least‐squares fit that approximately minimizes the error in estimating the covariate effect of a future observation. Simulation studies compare the methods discussed here with other dimension reduction techniques. Data from the AIDS Clinical Trials Group protocol 333 are used to motivate the methodology.
Biometry, Biometrics, Biostatistics, Bioinformatics, … , Bio‐X
Authors: Molenberghs Geert
Published: February 2005

SummaryRecent scientific evolutions force us to rethink our profession's position on the scientific map, in relation to our neighboring professions, the ones with which we traditionally have strong collaborative links as well as the newly emerging fields, but also within our own, diverse professional group. We will show that great inspiration can be drawn from our own history, in fact from the early days of the Society. A recent inspiring example has been set by the late Rob Kempton, who died suddenly just months before he was to become President of theInternational Biometric Society.
Spatial and temporal variation in the provisioning behaviour of female rockhopper penguins Eudyptes chrysocome filholi
Authors: Tremblay Yann , Cherel Yves
Published: February 2005

As seabirds are central place foragers during breeding, their provisioning behaviour and their ability to face variable energy demand from the chicks is expected to vary with environmental conditions. The provisioning behaviour of female rockhopper penguins Eudyptes chrysocome filholi was recorded over the chick‐rearing period at Kerguelen (KER) and Crozet (CRO) archipelagoes (two very distinct marine environments), using time‐depth recorders, or VHF transmitters coupled with an automatic recording station. No influences of the method have been found on the average foraging trip durations. Some previously undescribed short and multiple trips within a day were recorded using the automatic recording system. These multiple trips (6.8 h) were mostly performed with <5 days old chicks, a period during which feeding rates were the highest (1.1 meals per day), at both sites. During the brooding period, both KER and CRO females mainly performed daily trips of increasing duration (2 h longer at CRO) and at decreasing frequency. During the crèche compared to the brooding period, females from KER performed slightly fewer daily trips (0.6 per day) and more (<3 days) overnight trips, while females from CRO performed very few daily trips (0.1 per day) and more overnight trips, some of them being long trips lasting 5 to 29 days, mostly initiated during the transition between the brooding and the crèche periods. The result fit the hypothesis that long trips permit females to restore and/or maintain their body condition at more distant foraging places. It seemed that chick developement during the brooding period and environmental factors during the crèche period conditioned trip duration of females. Due to more long trips at CRO, the female feeding frequency was twice as high at KER than at CRO during the crèche period, while males participated in the feeding duties. Based on differences in female behaviour, we hypothesize that the male's contribution is likely to differ strongly from one site to another, and may buffer the possible decrease in female feeding frequency by feeding the chicks if food is less abundant.
Nest predation of grassland bird species increases with parental activity at the nest
Authors: Muchai Muchane , Plessis Morné A. du
Published: February 2005

Alexander Skutch predicted that nest predation will increase with activity at nests, and that predation should be greatest during the nestling stage when parents are feeding young. We tested this hypothesis using three ecologically similar grassland bird species nesting on the high altitude grasslands of Wakkerstroom, South Africa. Parental activity, measured as adult arrival and departure frequency from the nest, was greater during the nestling than incubation stage. Nest predation, however, did not increase with parental activity between these stages in all three study species. However, nest site effects could have confounded this result. We therefore conducted an experiment that controlled for parental activity (by reusing natural nests of the study species with artificial clutches) in order to test for nest site effects. Nests that had a high rate of predation when used by active parents had a correspondingly high rate of depredation when the same nests were reused with artificial clutches (i.e. after controlling for parental activity). This result supports the notion that variation in nest site quality is the primary factor affecting nest predation rate. We also tested whether high predation during incubation is related to nest site effects. Nest predation rates of experimental clutches placed in reused nests that had been originally (when active parents were present) depredated during incubation stage were significantly higher than those that were originally depredated during the nestling stage. Finally, once nest site effects were accounted for, nest predation showed a positive increase with parental activity during the nestling stage across species.
Tracking habitat use of a long‐distance migratory bird, the American redstart Setophaga ruticilla, using stable‐carbon isotopes in cellular blood
Authors: Norris D. Ryan , Marra Peter P. , Kyser T. Kurt , Ratcliffe Laurene M.
Published: February 2005

The successful use of stable isotopes to track migratory animals between different seasons of the annual cycle depends, in part, on the turnover rate of isotopes in sample tissue. We examined whether stable‐carbon isotopes in the blood of a long‐distance migratory bird, the American redstart Setophaga ruticilla, sampled upon arrival to the temperate breeding grounds could be used to track the quality of habitat used the previous season on the tropical wintering grounds. Stable‐carbon isotopes in red‐blood cells sampled upon arrival (δ13CRBC) were significantly less negative relative to: 1) plasma sampled upon arrival from the same individuals, 2) red‐blood cells of redstarts recaptured more than a month later on the breeding grounds, and 3) nestling feathers grown at the same breeding location. δ13CRBC was also significantly different between sexes, consistent with findings from the wintering grounds where sex‐biased habitat use is known to occur. Although individuals likely integrate some isotopic signatures during migration, we provide evidence that cellular blood can be used to track the relative habitat use of migratory birds during the wintering period. Non‐destructive methods of sampling stable‐isotopes, such as this, are particularly useful because it provides a technique for tracking the patterns of habitat use and/or geographic location of migratory animals. Such approaches allow researchers to understand how events throughout the annual cycle interact to influence population dynamics.
Some considerations on the interpretation of seabed images based on commercial 3D seismic in the Faroe‐Shetland Channel
Authors: Bulat J.
Published: February 2005

Commercial three‐dimensional (3D) seismic surveys now cover much of the continental slope and basin floor areas of the Faroe‐Shetland Channel. A mosaic of the seabed picks derived from these data sets and enhancement with visualisation techniques has resulted in detailed relief images of the seabed that testify to the action of a number of sedimentary processes such as glaciation, downslope and alongslope processes. The wealth of detail in these images is remarkable and extremely valuable for the identification and interpretation of seabed features. However, the level of detail can seduce the interpreter into treating the image purely as an aerial photograph. The interpreter needs to understand the limitations and artefacts inherent in such images to use them appropriately. This paper will present the major artefacts observed in the images and how certain aspects of 3D seismic survey acquisition and processing have contributed to their presence. The vertical and horizontal resolution of the images will also be discussed. Although primarily focused on seabed imagery these comments are equally pertinent to the application of 3D seismic surveys for shallower objectives than for which they were primarily designed.
Fluid flow impact on slope failure from 3D seismic data: a case study in the Storegga Slide
Authors: Bünz Stefan , Mienert Jürgen , Bryn Petter , Berg Kjell
Published: February 2005

Analysis of three‐dimensional (3D) seismic data from the headwall area of the Storegga Slide on the mid‐Norwegian margin provides new insights into buried mass movements and their failure mechanisms. These mass movements are located above the Ormen Lange dome, a Tertiary dome structure, which hosts a large gas reservoir. Slope instabilities occurred as early as the start of the Plio‐Pleistocene glacial–interglacial cycles. The 3D seismic data provide geophysical evidence for gas that leaks from the reservoir and migrates upward into the shallow geosphere. Sediments with increased gas content might have liquefied during mobilization of the sliding and show different flow mechanisms than sediments containing less gas. In areas where there is no evidence for gas, the sediments remained intact. This stability is inherited by overlying strata. The distribution of gas in the shallow subsurface (<600 m) may explain the shape of the lower Storegga headwall in the Ormen Lange area.
Pressure ulcers: implementation of evidence‐based nursing practice
Authors: Clarke Heather F. , Bradley Chris , Whytock Sandra , Handfield Shannon , Van Der Wal Rena , Gundry Sharon
Published: February 2005

Aims.  A 2‐year project was carried out to evaluate the use of multi‐component, computer‐assisted strategies for implementing clinical practice guidelines. This paper describes the implementation of the project and lessons learned. The evaluation and outcomes of implementing clinical practice guidelines to prevent and treat pressure ulcers will be reported in a separate paper.

Background.  The prevalence and incidence rates of pressure ulcers, coupled with the cost of treatment, constitute a substantial burden for our health care system. It is estimated that treating a pressure ulcer can increase nursing time up to 50%, and that treatment costs per ulcer can range from US$10,000 to $86,000, with median costs of $27,000. Although evidence‐based guidelines for prevention and optimum treatment of pressure ulcers have been developed, there is little empirical evidence about the effectiveness of implementation strategies.

Method.  The study was conducted across the continuum of care (primary, secondary and tertiary) in a Canadian urban Health Region involving seven health care organizations (acute, home and extended care). Trained surveyors (Registered Nurses) determined the prevalence and incidence of pressure ulcers among patients in these organizations. The use of a computerized decision‐support system assisted staff to select optimal, evidence‐based care strategies, record information and analyse individual and aggregate data.

Results.  Evaluation indicated an increase in knowledge relating to pressure ulcer prevention, treatment strategies, resources required, and the role of the interdisciplinary team. Lack of visible senior nurse leadership; time required to acquire computer skills and to implement new guidelines; and difficulties with the computer system were identified as barriers.

Conclusions.  There is a need for a comprehensive, supported and sustained approach to implementation of evidence‐based practice for pressure ulcer prevention and treatment, greater understanding of organization‐specific barriers, and mechanisms for addressing the barriers.
Cerebellar liponeurocytoma: Morphological, immunohistochemical, and ultrastructural study of a relapsed case
Authors: Buccoliero Anna Maria , Caldarella Adele , Bacci Stefano , Gallina Pasquale , Taddei Antonio , Di Lorenzo Nicola , Romagnoli Paolo , Taddei Gian Luigi
Published: February 2005

Cerebellar liponeurocytoma is a rare and newly identified neoplasm  found  in  adults  which  is  reputed  to  be benign. Its salient morphological characteristics are advanced neuronal/neurocytic differentiation, the presence of lipomatous areas, low mitotic rate, and the absence of necrosis, pleomorphism and vascular hyperplasia. Reported is a case of relapsing liponeurocytoma which occurred 3 and a half years after the radical excision of the primary lesion. Histopathological aggressive features (mitoses and a high proliferation index as evaluated by MIB‐1) were shown in the primary lesion and recurrence of the tumor. We suggest that liponeurocytoma is an uncertain malignant potential lesion when mitoses are present and the MIB‐1 positive cells are more than 10%.