bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence de la remise en exploitation de taillis-sous-futaie sur la faune entomologique | Influence of Renewed Coppicing with Standards on the Entomological Fauna
Authors: Barbalat Sylvie , Gétaz Daniel
Published: May 2007

This study estimates the influence of renewed coppicing with standards on the abundance and diversity of four beetle families(Buprestidae, Cerambycidae, Lucanidae and phytophagous Scarabaeidae) in a forest where this practice was abandoned. The study was conducted from mid-May to mid-August 1998 in the region of Ferreyres - Moiry (VD). Eight sites were chosen for the sampling of these insects, which were captured by means of window and water traps.

Coppicing with standards is very favourable to these beetles, which are often thermophilous. In such places, they find stumps and branch heaps, which are suitable for the development of their larvae. On the contrary, in abandoned coppice, the abundance and diversity of the selected beetles are very low. This kind of forest is extremely dark and unsuitable for thermophi-lous species. Renewed coppicing with standards is, therefore, very recommendable. It creates very favourable biotopes for the beetles, where they find both light and deadwood and which, to a certain extent, recreate the biotopes naturally formed by the fall of old trees in primitive forests.
Das Jungwaldpflegemodell Baden-Württemberg | The Baden-Württemberg Model of Juvenile Forest Tending
Authors: Kenk Georg
Published: May 2007

The frame conditions for the treatment of forest stands are subject to constant change due to the production factors. Examples.of Baden-Württemberg are investigated and show to what extent ‹biological automation› affects the stands, among others, financially.
Vom Forst zum Wald. Entwicklungstendenzen im naturnahen Waldbau | From a Production-Oriented Forest to a Multipurpose Forest. New Trends in Near-Natural Silviculture
Authors: Hockenjos Wolf
Published: May 2007

Concepts of near-natural forestry are in great demand these days. Most German forest administrations and private forest enterprises attach great importance to being as «near-natural» as possible. This should allow them to make the most of biological rationalisation. The concept of near-natural forestry is widely accepted, especially by conservationists. However, it is much too early to analyse how successful near-natural forestry has been to date, and therefore to decide whether an era of genuine near-natural forest management has really begun.

Despite wide-spread recognition, near-natural forestry is jeopardised by mechanised timber harvesting, and particularly by the large-timber harvester. The risk is that machines, which are currently just one element of the timber harvest will gain in importance and gradually become the decisive element. The forest would then be forced to meet the needs of machinery, not the other way round. Forests would consequently become so inhospitable that they would bear no resemblance to the sylvan image conjured up by potential visitors. This could mean taking a huge step backwards: from a near-natural forest to a forest dominated by machinery. The model of multipurpose forest management would become less viable, and the forest would become divided into areas for production, and separate areas for recreation and ecology. The consequences of technical intervention need to be carefully considered, if near-natural forestry is not to become a thing of the past.
Das schweizerische Mittelland und seine Biodiversität (Essay) | The Swiss plateau and its biodiversity
Authors: Broggi Mario F.
Published: May 2007

When it comes to preserving biodiversity, agriculture and forestry play a key role. The National Science Foundation study published in 1989 on «Minimum requirements of semi-natural areas within the cultural landscape»identified considerable deficiencies for species diversity in the Swiss plateau.

The agricultural policy reform introduced in the 1990’s should have met those concerns more directly. Despite new measures such as direct payments and despite high financial investments, during the last several years species diversity within the favored agricultural areas has hardly increased and the Swiss plateau has stayed a species-poor region. However, regarding the forest, conditions within the Swiss plateau are considered to be more favorable. The forest owners and forest enterprises are operating in public areas which, to a certain degree,put constraints on the intensity of management. For the forest, the deficits of highest concern are the insufficient establishment of forest reserves, the lack of diverse structures and the deficiencies of old growth and deadwood. Recently, the request for timber has increased rapidly. In order that the biodiversity does not lose its qualities, ecological standards for forest management are to be defined. The author recommends the development and implementation of an action plan for a national biodiversity strategy which covers the entire living space.
Phänologie – ein Biomonitoring und seine Anwendungen | Phenology – a bio-monitoring and its applications
Authors: Defila Claudio , Jeanneret François
Published: May 2007

Phenology studies the seasonally recurring growth and development of living creatures and abiotic phenomenon. It deals with observing the dates of plant developmental phases (from leafing to leaf fall), of bird migrations(arrival and takeoff of migratory birds), or frost occurrence and freezing of water courses and other phenomenon. Plant phenology is well suited as an indicator for bio-monitoring of environmental changes, such as actual climate warming, as organisms reflect the integrated reaction to the environment. In Switzerland Meteo-Swiss has run a national phenological observation network since 1951 that includes all regions and altitudinal belts, while a whole range of special networks operate for specific objectives: for example work in schools. The international and global cooperation in phenology starts gradually. In Europe, actively working groups prepare a standardization of observations and a central pool base for the observation data. At the moment, phenology serves above all as an indicator for the influence of climate warming on vegetation, but is also applied to frost warnings, pollen forecasts or for the optimization of plant protection in agriculture.
Expression of multiple catechol‐o‐methyltransferase (COMT) mRNA variants in human brain
Authors: Tunbridge Elizabeth M. , Lane Tracy A. , Harrison Paul J.
Published: May 2007

Catechol‐o‐methyltransferase (COMT) is important for modulating dopamine levels, prefrontal cortex (PFC) function, and several psychiatric phenotypes. A single COMT mRNA has been described in human brain, which gives rise to membrane‐bound (MB)‐ and soluble (S)‐COMT proteins. In addition, we have recently described a novel COMT protein isoform in the human PFC, suggesting that there are more COMT gene products expressed than are currently appreciated. Therefore, we have investigated whether variant COMT mRNAs are present in human brain. We used reverse transcription‐PCR (RT‐PCR) to screen systematically for variant COMT mRNAs in human frontal cortex. Intron‐spanning primers were used for exon‐to‐exon PCR reactions; additionally, specific primers were designed to sequences in the NCBI Aceview database. The identity of amplicons was confirmed by sequencing, and their regional distributions and 3′ untranslated regions (UTRs) were characterised using RT‐PCR. We detected 7 COMT variant mRNAs, resulting from both insertions and deletions within the known COMT brain transcript. Several of the variants alter the predicted coding sequence. Three of these variants correspond to sequences within the Aceview database and could be reliably amplified, while the remaining four do not correspond to any expressed sequence tags and were amplified only once. The regional distributions of these transcripts are described. The results demonstrate multiple COMT mRNAs in human brain, revealing an additional complexity to the biology of COMT. The alternate gene products may be of significant functional importance, and differentially impacted by polymorphisms within the COMT gene. © 2007 Wiley‐Liss, Inc.
Transparent photo‐curable co‐polyacrylate/silica nanocomposites prepared by sol‐gel process
Authors: Chou Yen‐Chun , Wang Yu‐Young , Hsieh T.‐E.
Published: May 2007

This work prepared the highly transparent photo‐curable co‐polyacrylate/silica nanocomposites by using sol‐gel process. The FTIR and 13C NMR analyses indicated that during the sol‐gel process, the hybrid precursors transform into composites containing nanometer‐scale silica particles and crosslinked esters/anhydrides. Transmission electron microscopy (TEM) revealed that the silica particles within the average size of 11.5 nm uniformly distributed in the nanocomposite specimen containing about 10 wt % of Si. The nanocomposite specimens exhibited satisfactory thermal stability that they had 5% weight loss decomposition temperatures higher than 150°C and coefficient of thermal expansion (CTE) less than 35 ppm/°C. Analysis via derivative thermogravimetry (DTG) indicated that the crosslinked esters/anhydrides might influence the thermal stability of nanocomposite samples. The UV‐visible spectroscopy indicated that the nanocomposite resins possess transmittance higher than 80% in visible light region. Permeability test revealed a higher moisture permeation resistance for nanocomposite samples, which indicated that the implantation of nano‐scale silica particles in polymer matrix forms effective barrier to moisture penetration. Adhesion test of nanocomposite samples on glass substrate showed at least twofold improvement of adhesion strength compared with oligomer. This evidenced that the silica and the hydrophilic segments in nanocomposite resins might form interchains hydrogen bonds with the OH groups on the surface of glass so the substantial enhancement of adhesion strength could be achieved. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Novel modification of cyanate ester by epoxidized polysiloxane
Authors: Yang Chunzhuang , Gu Aijuan , Song Hongwei , Fang Zhongbin Xu'Zhengping , Tong Lifang
Published: May 2007

A novel modification of cyanate ester (CE) resin by epoxidized polysiloxane (E‐Si) has been developed, and the modified system is coded as CE/E‐Si. E‐Si was prepared by the reactions among octamethylcyclotetrasiloxane, hexamethyldisiloxane, (3‐aminopropyl)‐methyldiethoxysilane, and diglycidyl ether of bisphenol‐A resin. Six formulations were designed to evaluate the effect of the weight ratio between CE and E‐Si on performance parameters. Results reveal that the addition of E‐Si in CE resin cannot only significantly decrease the curing temperature of the CE resin but also improve the water resistance and toughness of original CE resin. Moreover, these positive effects increase with the increase of E‐Si concentration in CE/E‐Si systems. Thermal property investigation shows that the glass‐transition temperature and initial degradation temperature of CE/E‐Si systems are lower than that of original CE resin. For the flexural properties of the CE/E‐Si systems, the E‐Si concentration in the system exists a threshold, that is, when the E‐Si concentration is smaller than the threshold, original CE and CE/E‐Si systems have similar flexural properties, whereas when the E‐Si concentration is higher than the threshold, CE/E‐Si systems have lower flexural properties than original CE resin. All these changes of properties are closely correlated to the structure alteration from neat CE to CE/E‐Si networks. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Microwave absorbing rubber composites containing carbon black and aluminum powder
Authors: Tanrattanakul Varaporn , Bunchuay Attapon
Published: May 2007

Natural rubber (NR), epoxidized natural rubber (ENR), and chlorosulfonated polyethylene (CSM) composites filled with conductive carbon black and aluminum powder have been prepared by using a two‐roll mill. An electromagnetic interference shielding effectiveness of those rubber composites was carried out in the frequency range of 8–12GHz (X‐band microwave). The increase of filler loading enhanced shielding effectiveness of the rubber composites. Conductive carbon black was more effective in shielding than aluminum powder. Binary filler‐filled rubber composites showed higher shielding effectiveness than that of single filler‐filled rubber composites. It has been observed that the shielding effectiveness of these rubber composites could be ranked in the following order: ENR ≥ CSM > NR, whereas the mechanical properties of the rubber composites were in the order of CSM > ENR > NR. The correlation between shielding effectiveness and electrical conductivity as well as mechanical properties of the rubber composites are also discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Impregnation of silk sericin into polyester fibers using supercritical carbon dioxide
Authors: Kongdee Arunee , Okubayashi Satoko , Tabata Isao , Hori Teruo
Published: May 2007

Silk sericin was impregnated into polyester fabric using supercritical carbon dioxide (SCCO2) to overcome polyester hydrophobicity. The effects of sericin molecular weight, pH of sericin, solution and cosolvent types on sericin impregnation were investigated. Enzyme‐hydrolyzed, acid‐, based‐hydrolyzed sericin in SCCO2, and a 30 kDa sericin in SCCO2 modified with cosolvents such as water, methanol, 1‐propanol, and acetone; and a modifier: sodium hydroxide solution were used in this work. Impregnation of sericin in polyester was indicated by Fourier transform infrared spectrophotometry (FTIR) and dyeing with acid dye. Degradation of polyester fibers during SCCO2 process was indicated by scanning electron microscopy (SEM). Methylene blue dyeing was used to realize carboxyl group in polyester. The results showed no impregnation of sericin into polyester by using SCCO2 modified with cosolvents. However, sericin was impregnated into modified surface polyester since hydrophilic groups such as carboxyl and hydroxyl groups were regenerated by alkaline hydrolysis. Samples impregnated with hydrolyzed sericin showed high color strength of Supranolechtbordeaux B acid dye. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Monitoring process for attributes with quality deterioration and diagnosis errors
Authors: Trindade Anderson Laécio Galindo , Ho Linda Lee , da Costa Quinino Roberto
Published: May 2007

The aim of this paper is to present an online economical quality‐control procedure for attributes in a process subject to quality deterioration after random shift and misclassification errors during inspections. The process starts in control (State I) and, in a random time, it shifts to out of control (State II). Once at State II, the non‐conforming fraction increases according to a non‐decreasing function ψ(z), where z is the number of items produced after a shift. The monitoring procedure consists of inspecting a single item at every m produced items, which is examined r times independently to decide its condition. Once an inspected item is declared non‐conforming, the process is stopped and adjusted. A direct search technique is used to find the optimum parameters which minimize the expected cost function. The proposed model is illustrated by a numerical example. Copyright © 2007 John Wiley & Sons, Ltd.
Preventive maintenance for inspected systems with additive subexponential shock magnitudes
Authors: Frostig Esther , Kenzin Moshe
Published: May 2007

We examine the long‐run average availability and cost rate of a maintained system which deteriorates according to a random‐shock process. Shocks arrive according to a Poisson process. The system fails whenever the cumulative damage exceeds a given threshold. The system's failures are not self‐announcing, hence, failures must be detected via inspections. The system is inspected at periodic or exponentially distributed intervals. Systems are replaced by preventive maintenance or after failure (corrective maintenance), whichever occurs first. When the distribution function of the shock magnitudes belongs to the class of subexponential distributions, we obtain simple approximations for the availability and the cost rate. Copyright © 2007 John Wiley & Sons, Ltd.
When is Piece‐Wise Regression Really Necessary?
Authors: Onukogu I. B.
Published: May 2007

Results are obtained showing that when a response surface can be modelled as a single function, then a single regressor is more efficient and less biased than a segmented regression. However, if the surface is segmented, a segmented regressor is less biased than a single regressor. Areas of application are indicated.
A Generalization of the Intraclass Tau Correlation for Tied and Censored Data
Authors: Schemper M.
Published: May 2007

Intraclass tau correlations and a corresponding asymptotic permutation test have already been derived by WHITFIELD (1949), though for continuous data only. WHITFIELD'S concepts are now generalized for use with tied and censored data and a suggestion is made for the application of the methods to arbitrary and varying group sizes. Special attention is given to their application to dichotomous data. Extensive simulations confirming the safe use of the asymptotic test even for samples of moderate size are reported and calculated examples with data from twin‐births and kidney transplantations presented.
Studies on Tests Using Fisher's Tanh−1 Transformation for Spearman's “Rho” and Kendall's “Tau” in Small Samples
Authors: Bennett B. M. , Choe M. K.
Published: May 2007

A series of papers by FIELLER, PEARSON et al. (1957, 1961, 1962) were concerned with the use of FISHER'S tanh−1 transformation (=z) for SPEARMAN'S ‘rho’ and KENDALL'S ‘tau’ rank correlation coefficients. Under the assumption of bivariate normal samples, empirical results on the means and variances for z were obtained.

This paper presents results on the z transformation for small samples under a more general trivariate normal model, and reviews the accuracy of the variance and covariance approximations for z, as well as considerations on the resulting power of the tests using the z‐transformation.
Simultaneous Randomization Tests
Authors: Foutz R. V.
Published: May 2007

Randomization analyses have been developed for testing main effects and interactions in standard experimental designs. However, exact multiple comparisons procedures for these randomization analyses have received little attention. This article proposes a general procedure for constructing simultaneous randomization tests that have prescribed type I error rates. An application of the procedure does provide for multiple comparisons in the randomization analyses of designed experiments. This application is made to data collected in a biopharmaceutical experiment.
Interaction Contrast Disease Rates for Assessing Synergism (or Antagonism) in Multifactor—Multilevel Disease Risks
Authors: Rao B. Raja , Enterline Philip E.
Published: May 2007

In the present paper, the two‐factor‐two‐level disease risk case is briefly reviewed. We have defined, what we call, the marginal effect of an agent. This is the effect of an agent in the presence of a second agent. It is noted that the two agents are synergistic (or that synergism is present) if the marginal effect of an agent exceeds its individual effect. The difference ME(A) — E(A alone) is called the effect SA of an agent. A simple relationship has been established between the effects SA and SB of the two agents and the HOGAN et al. (1978) measure D (also called the Interaction Contrast Disease Rate (ICDR) by HAMILTON (1979)). This relationship shows that there can be no assymmetries at the two dichotomous risk level.

This discussion is extended to two disease risks each at several levels and to several disease risks each at several levels. In each case, a simple relationship has been established between the ICDR and the effects SAi (i = 1, 2,…, k) of these disease risks. Several numerical examples are worked out to illustrate the result.
On a Problem of Allocation of Sample Size in Stratified Random Sampling
Authors: Mukerjee Rahul , Rao T. J.
Published: May 2007

In this paper we shall consider the problem of judging how good an actual compromise allocation is compared to Neyman's optimum allocation for the case of stratified random sampling by obtaining a bound to the ratio of the corresponding variances. A solution to a more general version of the problem considered by COCHRAN (1977) and RAO (1983) has been obtained and the results have been empirically demonstrated.
New Constructions of BIB Designs
Authors: Kageyama S. , Mohan R. N.
Published: May 2007

A method of construction of certain balanced incomplete block (BIB) designs is defined from which we get new series of BIB designs.
Exact Calculation of Permutational Distributions for Two Dependent Samples I
Authors: Zimmermann H.
Published: May 2007

A simple Fortran subroutine is given for the calculation of permutational distributions. Important special cases are Fisher's randomization test, the Wilcoxon signed ranks test and the sign test. The algorithm works in polynomial time. Thus it can be used even for micro‐computers within justifiable time limits.
A Note on Variance Bounds for an Inverse Binomial Estimator
Authors: Sahai A.
Published: May 2007

BEST (1974) found the variance of the minimum variance unbiased estimator of the Bernoulli parameter with an inverse sample. Noting its intricacy MIKULSKI and SMITH (1976) found bounds on this variance. SATHE (1977) developed closer bounds on it. In this paper still closer upper bound on the variance is achieved using Jensen's inequality.
Augmented Partial Diallel Cross Based on Circulant Sample
Authors: Kaushik L. S. , Puri P. D.
Published: May 2007

At present, the parents are included in the experimental material for judging the performance of crosses over parents and for calculation of heterosis but they are ignored for combining ability analysis of Partial Diallel Crosses due to the non‐availability of the method of analysis for such designs. To satisfy the practical need of the breeders on one hand and to remove the statistical objections on the other hand, a method of analysis of Partial Diallel Crosses based on circulant sample including parents has been presented in this paper. A numerical example is given for llustration of technique.
A Comparison of Algorithms for the Computation of the Mann‐Whitney Test
Authors: Schuster E.
Published: May 2007

An algorithm is proposed for the computation of the Mann‐Whitney Test which only requires the separate ordering of the individual samples and is therefore more suitable than the usual one. It is also more suitable as to computation time than the algorithm described by KUMMER, 1981, if the two sample sizes are of the same magnitude.
The Evaluation of Roadside Surveys of Blood Alcohol Content in Drivers in the Absence of Correlative Information
Authors: Kannemann Klaus , Warren Reg
Published: May 2007

An evaluation methodology is outlined for roadside surveys of blood alcohol content in drivers, where correlative attributes are absent or at most weakly related to the alcohol levels. The methodology is based on concepts of statistical information theory, and may be extended into a continuous model of the distribution systems arising from such or similar surveys with voluntary participation.
A Reanalysis of Jaw Joint Data Using Incomplete Multidimensional Contingency Tables
Authors: Upton Graham J. G.
Published: May 2007

BÖRZSÖNYI(1981) presents an analysis of the relationship between jaw joint pains and noises using data taken from the work of SCHMIDand ZSCHEGE(1976). That analysis consisted of the study of the association in various 2×2 tables obtained by collapsing the data.

This paper views the data as being an incomplete portion of a 26table rather than as three 4×4 tables. The present formulation allows for more penetrating insights into the relations between pains, noises and side of mastication. The paper also presents a brief resumé of some new results appropriate to sparse two‐way contingency tables.
The Estimation of the Segregation Parameter when Ascertainment is not Complete
Authors: Shoukri M. , Ward R.
Published: May 2007

Procedures to estimate the genetic segregation parameter when ascertainment of families is incomplete, have previously relied on iterative computer algorithms since estimators with closed form are lacking. We now present the Minimum Variance Unbiased Estimator for the segregation parameter under any ascertainment probability. This estimator assumes a simple form when ascertainment is complete. We also present a simple estimator, akin to Li and Mantel's (1968) estimator, but without the restriction that ascertainment be complete. The performance of these estimators is compared with respect to asymptotic efficiency. We also provide tables that define the required number of families of a given size that need to be sampled to achieve a specific power for testing simple hypothesis on the segregation parameter.
The Method of Unweighted Means in Unbalanced Analysis of Variance
Authors: Knoke J. D.
Published: May 2007

For factorial experiments with unbalanced data the method of unweighted means is an alternate method of analysis which is computationally simpler than likelihood ratio based F‐tests. The quality of the null approximation to the F‐distribution of the statistic for the method of unweighted means and the power of this test relative to the likelihood ratio test are discussed. Recommendations are made of when in the course of data analysis the superior operating characteristics of the likelihood ratio test may not outweigh the computational simplicity of the method of unweighted means test.
Diagnostic Measures of Influence for s2
Authors: Steece Bert
Published: May 2007

We present three intuitive diagnostic measures for judging the influence that single or multiple observations exert on the estimates2, the mean square error. The three measures are shown to be equivalent statistics. We discuss distributional properties of these measures and conclude with an example.
Measures of Dispersion with Weights Based on Ranks
Authors: Bomsdorf E.
Published: May 2007

The measures of dispersion for ungrouped data proposed by Gini and Lienert, which are defined as the mean of the ranges of pairs and triplets of n values, are generalised. A family of measures of dispersion emerges with weights based on ranks instead of the measurements themselves.
Models of Independent Action for Combination Therapy
Authors: Korn E. L.
Published: May 2007

Two methods of applying Finney's concept of simple independent action are suggested for examining possible synergism in combination therapy. In one model the treatments act independently at one time to cure the disease. In the other model the treatments act independently continuously to prevent the disease from progressing to a terminal outcome. The implications of these models for the interaction terms of a proportional hazards model, a log‐linear model on death rates, and a logistic model are discussed.
A Model of Genome Size Dynamics During Speciation
Authors: Rodin S. N. , Berdnikov V. A. , Zharkikh A. A.
Published: May 2007

A model developed for the evolving size of the repetitive part of the eukaryote genome during speciation was subjected to analytical and computer treatment. The basic assumption of the model was that two classes of repetitive DNA contribute mainly to macroevolutionary changes in genome size: arrays of tandem repeats (ATR) changing through unequal crossover and mobile genetic elements (MGE) changing presumably through an integration mechanism of the Tn‐ and Is‐kind operating in bacteria. Within the framework of this model, the macroevolution of the MGE size is formally equivalent to that of the ATR in the particular case when shifts of chromatids have only one repeat out of register. This allowed us to consider genome size as a large set of various ATRs. The results obtained are as follows. If the duplication and deletion of repeats have unequal fixation probabilities during each speciation act, the predicted species distributions of genome size significantly deviate from the real ones; if they have equal fixation probabilities, there is a conformance between calculated and real distributions. In the latter case, the model reproduces the salient features of real distributions upon acceptance of 1) upper selective boundary nonspecifically limiting increase in genome size within the evolving taxonomic group and 2) non‐neutrality of variability in genome size with respect to speciation.
An Examination of the Conservative Nature of “Classical” Confidence Limits for a Proportion
Authors: Walters D. E.
Published: May 2007

The performance of the standard confidence limits for a proportion is studied over the entire range of proportions, and for various prescribed values of the nominal confidence coefficient. In the light of the conservative nature of these limits, modifications are suggested resulting in limits with average confidence coefficients close to the 95% nominal value. A comparison is made with a solution obtained from the application of Bayes's theorem to the problem.
Sequentially Rejective Test Procedures for Detecting Outlying Cells in One‐ and Two‐Sample Multinomial Experiments
Authors: Perli H.‐G. , Hommel G. , Lehmacher W.
Published: May 2007

For multiple testing of multinomial models in the case of one or two samples we propose using test procedures based on the principle described by MARCUS, PERITZ and GABRIEL (1976). These methods are based in each step of the sequentially rejective strategy on tests which exhaust the full α level (i.e. which are not conservative). The tests can be performed in a finite or asymptotic version.
On a Model for Hazard Rates
Authors: Paranjape Sharayu , Rajarshi M. B. , Gore A. P.
Published: May 2007

This note proposes a new model for summarising data on survival distribution. A simple graphical method (or equivalently a linear‐regression‐based method) for estimation of parameters is given. The model is shown to describe adequately data on Survivorship of Starling Birds reported by LACK (1943) and data on power generators reported by DHILLON (1981). A comment is added to illustrate how one can obtain a goodness of fit statistic which has a chi‐squared distributions.
A Relationship Between two Fundamental Concepts in Drug Combination Theory
Authors: Wolf Th. , Unkelbach H. D.
Published: May 2007

Theories for the dose response analysis of drug combinations have been developed along two separate lines. In the first line, mainly followed by pharmacologists, the concept of “additivity” is of central importance. A corresponding central concept in the second line, which was mainly followed by biometricians, is that of “simple similarity”. We show that simple similarity implies additivity and we give a condition under which the reverse holds.
Analysis of Line × Tester Progenies Compared in Orthogonally Supplemented Efficiency Balanced Incomplete Block Design
Authors: Kaczmarek Z. , Kielczewska H. , Luczkiewicz T.
Published: May 2007

An analysis of experimental design is suggested for comparing progenies of lineXtester mating system. The line × tester mating system is an expanded top‐cross mating system, used frequently in practice. This system is of interest for breeders dealing with estimation and testing of general as well as specific combining abilities. In the suggested design, treatments, i.e. hybrids obtained in crosses, and testers are studied in orthogonally supplemented incomplete block design. Analysis of variance has been presented, estimators of expected values for progenies and for testers have been given, testing of hypotheses concerning contrasts of interest for progenies, lines and testers has been discussed. Estimators of effects of general and specific combining abilities as well as tests permitting for testing the significance of various genetic parameters, have also been given.
The Use of Combined Classifiers in Medical Functional Diagnostics
Authors: Wernecke K.‐D. , Unger S. , Kalb G.
Published: May 2007

In otological and ophthalmological functional diagnostics it is typical to record for a certain individual several similar biopotentials under different conditions of stimulation and/or to collect various potentials for the same individual.

Since the combination of these different data collected from a patient is of interest, coupling of the classification results obtained for each single data set seems desirable.

Based on sample classifiers, obtained by linear discriminance analysis, of acoustically or visually evoked potentials from selected patients an algorithm is proposed for their coupling, which logically links the various rules of allocation and is based on the principle of assignment by highest likelihood.

Furthermore, the procedure may be modified by inclusion of corresponding confidence intervals for the determined allocation frequencies.

The results obtained for the groups of patients investigated show a considerable improvement of classification as judged from the error rates being distinctly reduced after the coupling.
The Mathematical Theory of Taxonomic Keys
Authors: Leuschner D. , Sviridov A. V.
Published: May 2007

The mathematical theory of taxonomic keys and examples for its application are demonstrated.
How to Use the Two Sample t‐Test
Authors: Cressie N. A. C. , Whitford H. J.
Published: May 2007

This work discusses how two sample t‐tests behave when applied to data that may violate the classical statistical assumptions of independence, heteroscedasticity and Gaussianity. The usual two sample t‐statistic based on a pooled variance estimate and the Welch‐Aspin statistic are treated in detail. Practical “rules‐of‐thumb” are given along with their applications to various examples so that readers will easily be able to use such tests on their own data sets.
The Effect of Categorization on a Simple Analysis of Variance Model
Authors: Rayner J. C. W. , Dodds K. G. , Best D. J.
Published: May 2007

Many statistical procedures assume a continuous model in spite of the fact that observations are necessarily discrete. Here we consider a simple ANOVA model—one factor with fixed effects—and assess the effect of categorisation by simulating sizes and calculating asymptotic relative efficiencies. Even for severe categorisation the effects are small.
A Statistical Method for Comparison of Two Structures and Its Biological Applications
Authors: Rachman M. I. , Kozyakov S. Ja.
Published: May 2007

Some experimental methods applied to biological investigations allow to find a number q of homogeneous discrete components that determine a structure of the object in the study and the to establish the presence of some components from these q in compositions of other n objects. Such data form a nXq incidence matrix. In this paper a statistical approach is suggested for revealing the associated components in two different structures of the object. The procedure is based on joint consideration of two sampling incidence matrices. An application of this method is demonstrated by analysis of relationships between antigens and proteins of one strain of cyanobacteria. The method may be useful in different scientific areas, e.g. psychology, when direct experimental comparison of components from two structures is difficult.
Small Sample Properties of the Likelihood Estimator in Proportional Hazard Regression Models with Omitted Variables
Authors: Brännäs K. , Pohjanpalo J.
Published: May 2007

The paper deals with the effects of incorrectly omitted regressor variables in a parametric proportional hazard regression model. By studying conditions for equality between the estimators of correct and incorrect models it is demonstrated analytically that such cases are not to be expected in practise. A small sample Monte Carlo experiment indicates severe negative effects on the retained parameters both in terms of bias and mean square error.
Missing Techniques in Complete Diallel Crosses
Authors: Kaushik L. S. , Puri P. D.
Published: May 2007

The missing of observations in agricultural field experiments is quite common due to several natural hazards and at present no method of analysis of diallel crosses exists when one or two observations are missing. Therefore, the method of combining ability analysis of diallel crosses (including parents and reciprocals) for one and two missing observations based on TOPHAM (1956) model and using BARTLETT (1937) missing plot technique has been presented in this paper. The formulae for estimating genetical parameters, calculatings um of squares due to these parameters and for calculating variances due to the estimates of parameters have been presented. A numerical example have been given for illustrating the technique.
A Note on Estimation of Population Means Having Equal Coefficient of Variation on Successive Occasions
Authors: Sisodu B. V. S. , Singh Rajendba , Izatnagab Lv. R. I.
Published: May 2007

Following SEN & GERIG (1975) an estimator for the population mean on the current occasion is proposed. It has been shown that the estimator is more efficient than ‘mean per unit estimate’ for all kind of populations. The eetimatiors suggeated by SEN & GERIG (1976) and SEABM (1964) are also found to be relatively less efficient than the proposed estimator.
Sequential Analysis of Survival Times in Clinical Trials
Authors: Olschewski M. , Schumacher M.
Published: May 2007

This paper provides a synopsis of statistical methods which can be used for the sequential analysis of possibly censored survival times in clinical trials. Especially, results on the asymptotic behaviour of the Breslow‐Haug statistic and on the sequential version of the logrank statistic are presented in a standardized terminology. In addition, formulae for the explicit calculation of linear and square‐root boundaries for sequential plans are given and illustrated by an example. Practical problems of applying these methods when monitoring a fixed‐sample clinical trial as well as group sequential methods and calculation of P‐values are also discussed.
On the Performance of the SPRT for Correlation Coefficient: Normal and Mixtures of Normal Populations
Authors: Kocherlakota K. , Balakrishnan N. , Kocherlakota S.
Published: May 2007

The sequential probability ratio test (SPRT) for the correlation coefficient is examined in the normal and non‐normal situations. In the latter case, we evaluate the robustness of the normal procedure when sampling from the mixtures of normal distributions. Two models are introduced for this type of nonnormality. It is shown that in the case of moderate nonnormality, the normal procedure is robust while for extreme nonnormality, the normal procedure is not recommended.
On the Reliability of Bayesian Confidence Limits for a Difference of Two Proportions
Authors: Walters D. E.
Published: May 2007

A method is presented of deriving confidence limits for a difference of two proportions using Bayesian Theory. The reliability of the method is assessed for a selection of small sample sizes. A limited table of confidence limits is displayed.
Gram‐Schmidt Orthogonalization of Multinormal Variates: Applications in Genetics
Authors: Bonney G. E. , Kissling G. E.
Published: May 2007

The computation of an N‐variate normal density function requires the inversion of an N × N co‐variance matrix. Furthermore, if each mean depends on u unobservable factors, a mixture of uN N‐variate normal densities must be computed, making likelihood calculations impractical even for moderate N. The Gram‐Schmidt orthogonalization process is used to express a multinormal density as a product of univariate normal densities. When the pattern of the correlation matrix is taken into account the formulas may be considerably simplified. In some cases each of the orthogonal variates can be written as a linear combination of only a few of the original variates. Such results are crucial for applications of multinormal distributions and of mixtures of multinormal distributions. An intraclass correlation model and a genetic variance components model applicable to family data are discussed as examples.
A Simplified Newton Method for Computing the Factor Loadings in Maximum Likelihood Factor Analysis
Authors: Focke Joachim
Published: May 2007

A simplified Newton iteration scheme for computation of factor loadings in maximum likelihood factor analysis is described. It operates in the space of factor loadings and avoids eigenvalue problems. From this, a comparatively small computational effort results. Besides of the case of positive unique variances, also the Heywood case is considered, where some unique variances vanish. The ability of the proposed method is demonstrated in three examples, results and iteration process are compared with data given in literature.
Testing for Independence of Binary Responses
Authors: Fidler V. , de Jonge A. B.
Published: May 2007

In the context of experiments involving visual inspection of random dot patterns the problem of testing the null hypothesis of independence of binary responses is considered. A flexible model for dependence between binary responses is proposed. Two tests, optimal under different versions of the model, are derived. These two tests turn out to involve the same computations as the Wilcoxon two sample test and the runs test respectively.
Variance Calculations for Direct Adjusted Survival Curves, with Applications to Testing for No Treatment Effect
Authors: Gail M. H. , Byar D. P.
Published: May 2007

Several investigators have recently constructed survival curves adjusted for imbalances in prognostic factors by a method which we call direct adjustment. We present methods for calculating variances of these direct adjusted survival curves and their differences. Estimates of the adjusted curves, their variances, and the variances of their differences are compared for non‐parametric (Kaplan‐Meier), semi‐parametric (Cox) and parametric (Weibull) models applied to censored exponential data. Semi‐parametric proportional hazards models were nearly fully efficient for estimating differences in adjusted curves, but parametric estimates of individual adjusted curves may be substantially more precise. Standardized differences between direct adjusted survival curves may be used to test the null hypothesis of no treatment effect. This procedure may prove especially useful when the proportional hazards assumption is questionable.
Estimation of Heritability for Samples from Non‐Normal Situations
Authors: Singhal R. A. , Jain J. P.
Published: May 2007

Mathematical expressions, to investigate the effects of mederate departure from normality assumption on the point estimate and on the probability of getting a negative estimate of genetic heritability, in a balanced situation, have been derived. The numerical results show that the point estimate is over sensitive whereas the probability of a negative estimate is insensitive to this violation.
Two‐Stage Least Squares Analysis of Hierarchical Linear Models
Authors: Onukogu I. B.
Published: May 2007

This paper has two major objectives. The first is to present a two‐stage least squares procedure for estimation of the parameters in a linear model whose parameters are in themselves linear functions of some hyperparameters. The second, and perhaps more important point, is that the new estimator can be shown to be generally more precise than either the Bayesian or the generalized single‐stage least squares estimator reported by LINDLEY and SMITH (1072).
The Asymptotic Covariance Matrix of the Maximum Likelihood Parameter Estimator in Conditional Poisson Log‐linear Models
Authors: Bonett D. G. , Bentler P. M. , Woodward J. A.
Published: May 2007

The asymptotic covariance matrix of the maximum likelihood estimator for the log‐linear model is given for a general class of conditional Poisson distributions which include the unconditional Poisson, multinomial and product‐multinomial, as special cases. The general conditions are given under which the maximum likelihood covariance matrix is equal to the covariance matrix of an equivalent closed‐form weighted least squares estimator.
A Classification of Trivariate Regression Models
Authors: Holling Heinz
Published: May 2007

The present study begins with a discussion of a topic frequently mentioned in the relevant literature, namely the division of multiple regression models with two predictors into five mutually excluding categories. The theoretical basis for this classification is criticized and a system of three mutually excluding categories is suggested which is free of the criticized inconsistencies.
Some Monte Carlo Studies on the Comparison of Several Means Under Heteroscedasticity and Robustness with Respect to Departure from Normality
Authors: Tan W. Y. , Tabatabai M. A.
Published: May 2007

By using Monte Carlo studies, this paper compares the Welch test, the James test and the Brown‐Forsythe test for comparing several means under heteroscedasticity. It appears that all the tests are quite robust with respect to departure from normality. The Brown‐Forsythe test is at least as good as the James test and the Welch test; but the differences are so small that the choice is immaterial for practical purposes.
A Two‐stage Procedure with Controlled Error Probabilities for Testing Bioequivalence
Authors: Srinivasan R. , Langenberg P.
Published: May 2007

The procedures currently used for testing the bioequivalence of two drug formulations achieve control over the error probability of erroneously accepting bioequivalence or over the probability of erroneous rejection, but not over both error probabilities. A two‐stage procedure that rectifies this drawback is presented, assuming that the performance of the drug is characterized by a normally distributed variate.
Unbiasedness of Iterated Aitken Estimators
Authors: Rao U. L. Gouranga
Published: May 2007

The iterated Aitken estimator of the parameter vector of the general linear model is shown to be unbiased on the assumption that the errors underlying the model follow a symmetric probability law with mean zero.
Variances and Asymptotic Distributions of Direct Standardized Rates
Authors: Cohen Arthur , Davis Linda J.
Published: May 2007

Formulas for the variance of direct standardized rates are given for three different sampling models. The three models are product multinomial models when population totals are fixed by design, or strata totals are fixed by design, or cell (each population—each stratum) totals are fixed by design. Asymptotic distributions are derived for each model. A discussion on the relevance and use of standardized rates and the need for distribution theory is also provided.
Searching for Optimal Block Designs when Block Effects are Random
Authors: Jones B.
Published: May 2007

An algorithm that searches for optimal block designs when block effects are random is described. Some situations in which such an algorithm will prove useful are considered. An illustrative example and some discussion are given.
Inference Based on Ranks with Tied Failure Time or Grouped Survival Data
Authors: Pettitt A. N.
Published: May 2007

Scores for the analysis of distinct failure time data using ranks are modified to deal with tied failure times or grouped data. Approximate techniques for inference for regression parameters are considered for ‘proportional odds’ and ‘proportional hazards’ survival data involving tied failures or grouped data. An illustration is given involving a two sample problem.
Alternatives to the Chi‐Square Test of Homogeneity in 2×2 Tables and to Fisher's Exact Test
Authors: Sachs L.
Published: May 2007

In comparing two independent binomial proportions by modified X2tests: Gart's modified likelihood‐ratio, Overall and Starbuck's “tailoredF”, Pearson's adjustedX2[=X2multiplied by (n‐ 1)/n] and its skewness‐corrected version proposed by Berchtold, it was found that the last two have error probabilities that in the mean are close to the significance level.