bluuebunny/crossref_metadata_2025 huggingface dataset:
Stepwise Variable Selection in Classification Problems
Authors: Farver T. B. , Dunn O. J.
Published: April 2007

Two variable selection procedures are evaluated for classification problems: a forward stepwise discrimination procedure, and a stepwise procedure preceded by a preliminary screening of variables on the basis of individual t statistics. Expected probability of correct classification is used as the measure of performance. A comparison is made of the procedures using samples from multi‐variate normal populations and from several nonnormal populations.

The study demonstrated some situations where the use of all variables is preferable to the use of a stepwise discriminant procedure stopping after a few steps, though usually the latter procedure was superior in performance. However where the stepwise procedure performed better than using all variables, the modified stepwise procedure performed still better. The use of modified stepwise procedures in which not all the covariances of the problem need be estimated seems promising.
A Program for the WILCOXON Signed Ranks Test
Authors: Berchtold H.
Published: April 2007

A BASIC‐program for the computation of the Wilcoxon test statistic is introduced. It is more simple than the usual ones, because it is based on a more simple kind of computation.
Das Gesetz der absoluten Geschwindigkeiten biologischer Prozesse
Authors: Trinchee K.
Published: April 2007

The dependency of the velocity of biological processes from the temperature is described by the “Law of absolute velocity of biological processes”, which has only the individual parameters energy of activation ΔE, and the universal constant C. The law holds for all biological processes and is expressed by the equation:magnified imagewhere C is:magnified image.
Properties and Application of the Location‐Test V (n, k)
Authors: Rey G.
Published: April 2007

The present paper is concerned with the properties of a test statistic V(n, k) to test location differences in the one‐sample case with known hypothetical distribution G(x). The test is similar to the WILCOXON two‐sample statistic after replacement of the second sample by quantiles of the hypothetical distribution. A comparison with the exact distribution of V(n, k) shows that an approximation by means of the normal distribution provides good results even for small sample sizes. The V‐test is unbiased against one‐tailed alternatives and it is consistent with a restriction which is hardly relevant in practical applications.

With regard to the application we are interested especially in the power and robustness against extreme observations for small sample size n. It is shown that in a normal distribution with known standard deviation V(n, k) is more powerful than STUDENT's t for small n and more robust in the sense considered here.

The test statistic is based on grouping of the observations into classes of equal expected frequency. A generalization to arbitrary classes provides an essential extension of applicability such as to discrete distributions and to situations where only relative frequencies of G(x) in fixed classes are known.
The Design and Analysis of Twin Animal Experiments
Authors: Longmuir J. , Raktoe B. L.
Published: April 2007

The experimental design used in twin studies on veal calves at the University of Guelph during the years 1965–1968 combined split trials with uniformity trials on each treatment. Each replicate consisted of four twin pairs. Both members of one pair selected at random were put on treatment 1, both members of another pair were put on treatment 2, and the remaining two pairs were “split” with one twin from each pair randomly assigned to each treatment. There were a number of replicates of this basic design over the course of the experiment. The objective of this paper is: (i) to determine the feasibility of an overall analysis of the given design, (ii) to determine an accurate method for assessing treatment effects, and (iii) to find an efficient method for detecting the presence of treatment Xpair interaction.
Percentage Points of MultivariatetDistribution with Zero Correlations and their Application
Authors: Chen Hubert J.
Published: April 2007

Thek‐variatetdistribution plays an important role in the application of Multiple Comparison Procedures, Ranking and Selection Procedures, and Estimation of Ranked Parameters. This distribution was considered by several authors in the past and is now widely used. In this paper, tables of some percentage points of the multivariatetdistribution are tabulated for given probability level γ = 0.80, 0.90, 0.95, and 0.99; population sizek= 2(1)20; and degrees of freedomv=2(1) 30(5)60 with common correlation coefficient ϱ = 0. The accuracy of the percentage points is specifically determined (and is up to the fourth decimal place). An application of these tables is considered for interval estimation of the largest mean ofk(≧2) normal populations.
BAYESian Approach to the Prediction of the Restricted Range in the Censored Samples from the Exponential Population
Authors: Lingappaiah G. S.
Published: April 2007

k independent samples 0, 1, 2,…,k – 1 (or stages 0, 1,…. k – 1) are available from the exponential population. Each of k – 1 samples, except the sample 0 are censored both above and below. Restricted range is defined as the difference between largest and the smallest among the available observations. Prediction of this restricted range at stage k (in the future sample k) on the basis of the restricted ranges at earlier 1, 2,…k – 1 stages is attempted by obtaining the predictive distribution of this range at stage k. Probability that the variance at stage k is smaller than that at stage k – 1, is evaluated along with the probability integral. An illustrative example is given with simulated samples.
Signed‐Rank Tests in the Presence of Ties (with extended tables)
Authors: Buck W.
Published: April 2007

We begin with a review of the areas of application of the signed‐rank tests (SRTs) and we conclude that the results are exact only if no ties of non‐null differences exist. In order to apply the SRTs according to WILCOXON and according to PRATT also in the presence of ties, by assigning midranks, we derive their null distributions. As special cases the null distributions for the problem without ties are obtained. In order to save the practising statistician the time‐consuming calculations of the distribution functions, we compute tables of critical values (for reasons of volume they will be published as part of the reprints only). For N0 = 0 (1) 5 null differences and M = = 1(1) 10 non‐null differences the critical values of all distributions with all possible tie vectors are calculated. Instructions are provided and an example serves to illustrate the use of the table. The extension of the tables are obtained by means of counting formulas given in the text. Approximations are provided in order to make the application of tests possible for larger samples as well. It is shown that the approximation of the null distribution in the presence of ties by the null distributions under the assumption of no ties in some cases overstates and sometimes understates the exact rejection probability. For N0 = 0 (1) 10 and M = 1 (1) 10 all distributions with all possible tie vectors for the SRTs with WILCOXON and PRATT ranking are examined with respect to the lattice type of the test statistic. The result is given in table 6. It is evident that the portion of PRATT‐distributions with lattice character decreases as the number of null differences increases. Continuity corrections are obtained for the asymptotic normal distribution which take into account the lattice character of the distribution of the test statistic.
Development and Applications of Five New Water Quality Indices
Authors: Schaeffer D. J. , Janardan K. G.
Published: April 2007

Two indices, P1 and I, employing ranked data and following the beta distribution, are described. These indices, which are true statistical measures of water quality, can be used with any set of parameters. Further, these indices correlate highly with biological and subjective‐engineering assessments of water quality.

Three indices, employing raw data and based on the chi‐square distribution, are described. Two of these, B1 and B2, do not have sufficient discrimination to serve as general measures of water quality, although they have use in specific circumstances. The index C has been found to be a measure of excessive variability (at a station), and can be used to quantitatively compare the (data) variability among stations.

The five indices described here are evaluated against a set of operational criteria which a mathematically sound index should meet.
A Concise Formula to Compute General Orthogonal Contrast Coefficients
Authors: Ackermann H.
Published: April 2007

A proof is given of a general formula conjectured by ABTto calculate the values of orthogonal polynomials for the case of nonequidistant levels and unequal numbers of observations. Also, a general derivation of the contrast coefficients is given on the basis of the conditions of orthogonality only. The practicality of the formulae with regard to applications in analysis of variance and regression analysis is stressed.
On the Reduction of Bias of Ratio Estimator to a Desired Degree
Authors: Singh M.
Published: April 2007

This paper advocates a procedure of obtaining an estimator (as a linear combination of a set of ratio estimators) whose bias can be reduced to a desired degree of sample size without any additional loss in efficiency.
A Modified MANN‐WHITNEY Test with Improved Asymptotic Relative Efficiency
Authors: Berchtold H.
Published: April 2007

A slight modification of the MANN‐WHITNEY test is introduced here. When the underlying distribution is normal the ARE of the modified test with respect to t‐test is 99.22% (MANN‐WHITNEY test: 95.45%). The lower bound of the ARE of the modified test is 92.50% for all distributions with a continuous density function and a finite variance (MANN‐WHITNEY test: 86.4%).
Sample Sizes for Testing Equality of Location Parameters of Two Exponential Distributions
Authors: Rasch D. , Schultz J.
Published: April 2007

A table for determining minimal sample sizes n1 = n2 = n for testing the hypothesis of equality of location parameters a4 and a2 of two two‐parametric exponential distributions for a first kind risk α=0,01 and 0,05 are given in such a way that the second kind risk β≦β0 as long as |a1–a>2|>d.
Mathematical Models for the Spread and Control of Foot‐and‐Mouth Disease During the 1973 Epidemic in Austria
Authors: Kláring W. J. , Timischl W.
Published: April 2007

Two models are studied to describe the spread of foot‐and‐mouth disease during the 1973 epidemic in Austria. The models are modifications of a three‐class‐model (due to KERMACK and MCKENDRICK) taking into account the special character of the disease as well as control methods (stamping‐out‐method, vaccination programs).
Estimation of Sheet Thickness Distributions from Linear and Plane Sections
Authors: Cruz‐Orive L. M.
Published: April 2007

A biological “membrane” or a “barrier” can often be modelled by a sheet, namely a portion of space comprised between two smooth, quasi‐parallel faces, such that sheet thickness is in general variable but very small in relation to face extent. Sheet thickness measurements are often of interest to the morphometrist, the physiologist and the pathologist. In the present paper, some stereological techniques are developed for estimating true sheet thickness distributions, and their moments, from the apparent thickness or intercept length measurements obtained, respectively, via random plane or linear sections. An important premise for the models to work is that of isotropic random (‘non‐preferential’) sheet orientation relative to the sectioning probe.
Nonparametric Estimation of Population Density for Line Transect Sampling Using FOURIER Series
Authors: Crain B. R. , Burnham K. P. , Anderson D. R. , Lake J. L.
Published: April 2007

A nonparametric, robust density estimation method is explored for the analysis of right‐angle distances from a transect line to the objects sighted. The method is based on the FOURIER series expansion of a probability density function over an interval. With only mild assumptions, a general population density estimator of wide applicability is obtained.
On the Construction of Balanced and Partially Balanced Ternary Design
Authors: Sinha Kishore , Saha G. M.
Published: April 2007

A method of constructing balanced and partially balanced ternary designs from balanced and partially balanced incomplete block designs, respectively, and two methods of constructing partially balanced ternary designs from association schemes are obtained. Two new and efficient balanced ternary designs havingK<VandR≦ 20 are obtained by the first method.
Moment Analysis for the Probit Model of Directional Selection
Authors: Chen Kuang‐Ho
Published: April 2007

An iteration relation is given for the moments of the surviving individuals after probit directional selection if the individuals before selection are normally distributed. The proportion, mean, variance, skewness, and kurtosis are expressed in closed form.
Segmented linear regression models applied to the analysis of data from a cross‐sectional growth experiment
Authors: Monti K. L. , Koch G. G. , Sawyer J.
Published: April 2007

Several different methods of analysis are applied to data consisting of weight measurements, taken at specified post‐treatment times, of harvested thyroids from rats given one of four treatments. Previous studies of this type of data indicated that the growth is initially rapid, and that a second phase of less rapid growth is followed by a final phase in which little additional growth occurs. The data are further characterized by increasing variance through time.

The primary purpose of the analysis is to study the effect of the treatments at the end of the study period. One‐way analysis of variance tests among groups are performed on each day, but the results are not particularly helpful. However, results from two‐way analyses of variance (over subsets of days and groups) are consistent with the three phase model and accordingly indicate significant group differences during each. Finally, maximum likelihood methods are used to fit a three part segmented linear regression model.
A method for determining the statistical significance of mutation frequencies
Authors: Traut H.
Published: April 2007

A method is devised for determining the statistical significance of the difference between a mutation frequency observed after treatment with a potential mutagen and its control frequency. This procedure, however, can be used only when the respective control value is based on large and reliable material (“stable” controls), a requirement that seems to be met in at least part of the systems used for mutagenesis screening. The procedure proposed has some advantages when compared with the 2 and the KASTENBAUM‐BOWMAN test, the most important one being that it can be employed when these two tests cannot (because of expected frequencies <5 in the 2 test and limited tabulations of the N and p values in the KASTENBAUM‐BOWMAN test). After explaining the procedure, an instruction how to carry it out is presented and illustrated by two examples (recessive sex‐linked lethal mutations in Drosophila melanogaster and dicentric chromosomes in human lymphocytes).
Ein fortran‐unterprogramm zur qnadratischen optimierung von mixturen
Authors: Crecknagel R.‐D.
Published: April 2007

A FORTRAN‐Subroutine is given to solve an optimization problem connected with the quadratic canonical mixture polynomial of SCHEFFÉ (1958).

Two numerical examples demonstrate the use of the procedure. Some remarks about practical experience with the program in fermentation to optimize the compound of nutrient media are added.
Model building and testing for the change‐over design
Authors: Zimmermann H. , Rahlfs W.
Published: April 2007

The two‐period cross‐over design is discussed within the framework of univariate and multivariate analysis of variance technique; the relations between both procedures are explained. It is shown that all hypotheses of interest can be tested if the design is regarded as a special case of a repeated measurement design. Some features of the n‐period change‐over design are explained by discussing the model and hypotheses of a three‐period design.
Comparing two independent binomial proportions by a modified chi square test
Authors: Schouten H. J. A. , Molenaar I. W. , Van Strik R. , Boomsma A.
Published: April 2007

When using the chi square test to compare the proportions of successes in two independent binomial samples, a new continuity correction is proposed, which equals half the size of the smaller sample. Exact computations of unconditional tail‐probabilities, together with a theoretical argument, show that this correction is more appropriate than the YATES correction. This version of the chi square test is still conservative, but less so, and as a consequence more powerful, than the YATES corrected test.
Note on a binomial test against sectoral preference of circular observations
Authors: Lehmacher W. , Lienert G. A.
Published: April 2007

A binomial test is proposed to test the nullhypothesis of uniform distribution of circular observations against the alternative of sectoral preference where the sector in which the observations are expected to cluster must be chosen prior to sampling. This binomial test against sectoral preference is illustrated by an example from psychopharmacology. The method is modified for comparing the sectoral proportions of two independent as well as two paired samples of circular observations.
On the combination of equality and inequality restrictions on regression coefficients
Authors: Toutenburg H.
Published: April 2007

The paper gives a method for using equality and inequality restrictions simultaneously. This is done by combining the estimator for linear equality restrictions and the minimax linear estimator principle which was developed for inequality restraints.

The result is a ridge‐type estimator, namely a biased so‐to‐speak minimax‐linear estimator (MMLE) which dominates the classical MMLE in the sense of smaller MSE.
A remark on a paper by misra
Authors: Kabe D. G.
Published: April 2007

MISRA (1978) sets confidence intervals for a double linear compound of multivariate normal regression coefficients by using ROY'S maximum root test criterion. The exact test statistic to be used is STUDENT'St.Thetstatistic gives narrower confidence bounds than those given by ROY's maximum root statistic. A result given by MORRISON (1975, p. 18, equation 10) for profile analysis is also obtained by using the STUDENT'Sttest.
A confidence interval for the unknown value of the regressor with given expectation of the regressand in model I of linear regression
Authors: Kuhnert D. , Horn M.
Published: April 2007

In the case of model I of linear regression there is derived a confidence interval for that xo where the “true line” will reach a given value yo. The interval can be given by the intersections between the line y = yo and the hyperbolas providing pointwise confidence intervals of the expectations of y.
Systematic designs for experiments with mixtures
Authors: Goel B. S.
Published: April 2007

In this paper systematic designs for experiments with mixtures are developed. The plan of analysis of the experiment is discussed for a quadratic model of SCHEFF É (1958) forq‐component mixture with orthogonal polynomials of third degree describing the time trends.
Determination of tsumacide residues in vegetable samples using a flow‐injection chemiluminescence method
Authors: Liu Haiyan , Hao Yuhong , Ren Juanjuan , He Pingang , Fang Yuzhi
Published: April 2007

A sensitive, simple and rapid flow‐injection chemiluminescence (FI–CL) method is described to determine tsumacide pesticide residue based on the CL reaction of the alkaline degradation product of tsumacide with acidic KMnO4 when rhodamine 6G was present. Under the optimum conditions, the relative CL intensity is linear with the concentration of tsumacide in the range of 2.0 × 10−3–0.20 mg/L. The detection limit is 6.6 × 10−4 mg/L (3σ) and the relative standard deviation for 2.0 × 10−2 mg/L tsumacide solution was 2.28% (intra‐day) and 4.85% (inter‐day). The proposed method has been applied to determine the residue of tsumacide in vegetable samples and the recovery test is very satisfactory. Copyright © 2007 John Wiley & Sons, Ltd.
Flow‐injection determination of carbaryl and carbofuran based on KMnO4–Na2SO3 chemiluminescence detection
Authors: Waseem Amir , Yaqoob Mohammad , Nabi Abdul
Published: April 2007

A flow‐injection method is described for the determination of carbaryl and carbofuran. It was found that a strong chemiluminescence (CL) signal was generated when these pesticides were mixed with Na2SO3 and KMnO4 in acidic medium. Under the optimum experimental conditions, the enhanced CL intensity was linear, with the concentrations in the range 0.1–2.0 µg/mL (r2 = 0.9996 and 0.9993, n = 6) with relative standard deviation (n = 4) in the range 1.0–2.3%. The limits of detection (3σ blank) were 10 and 50 ng/mL, respectively, with a sample throughput of 180/h. The proposed method was applied to determine carbaryl and carbofuran in freshwaters with satisfactory results. Most metal and non‐metal ions and some pesticides, such as carbophenothion and aldicarb, do not interfere with the determination. Dinoseb, diazinon and malathion calibration graphs (in the range 0.2–2.0 µg/mL, r2 = 0.9966–0.9988, n = 6) were also established with relative standard deviations (n = 4) in the range 1.2–2.0% with limits of detection (3σ blank) in the range 100–300 ng/mL. Copyright © 2007 John Wiley & Sons, Ltd.
Few substitutions affect the bioluminescence spectra of Phrixotrix (Coleoptera: Phengodidae) luciferases: a site‐directed mutagenesis survey
Authors: Viviani Vadim R. , Arnoldi Frederico G. C. , Ogawa Florisbela T. , Brochetto‐Braga M.
Published: April 2007

Phrixotrix (railroad worm) luciferases produce bioluminescence in the green and red regions of the spectrum, depending on the location of the lanterns, and are the only luciferases naturally producing red bioluminescence. Comparison of the luciferase sequences showed a set of substitutions that could be involved in bioluminescence colour determination: (a) unique substitutions in the red luciferase replacing otherwise invariant residues; (b) conserved basic residues in the green–yellow emitting luciferases; and (c) an additional R353 residue in red‐emitting luciferase (Viviani et al., 1999). To investigate whether these sites have a functional role in bioluminescence colour determination, we performed a site‐directed mutagenesis. Natural substitutions in the region 220–344 and residues in the putative luciferin‐binding site were also investigated. With the exception of the previously identified substitution of R215 and T226 (Viviani et al., 2002), which display dramatic red‐shift effects on the spectrum of green–yellow‐emitting luciferases, only a few substitutions had a moderate effect on the spectrum of the green‐emitting luciferase. In contrast, no single substitution affected the spectrum of the red‐emitting luciferase. The results suggest that the identity of the active site residues is not so critical for determining red bioluminescence in PxRE luciferase. Rather, the conformation assumed during the emitting step could be critical to set up proper interactions with excited oxyluciferin. Copyright © 2007 John Wiley & Sons, Ltd.
Duplex Formation of the Simplified Nucleic Acid GNA
Authors: Schlegel Mark K. , Peritz Adam E. , Kittigowittana Krisada , Zhang Lilu , Meggers Eric
Published: April 2007

Glycol nucleic acid (GNA) has an acyclic backbone of propylene glycol nucleosides that are connected by phosphodiester bonds. This paper characterizes the duplex‐formation properties of this simplified nucleic acid. Although single and multiple GNA nucleotides are highly destabilizing if incorporated into DNA duplexes, the two enantiomeric oligomers (S)‐GNA and (R)‐GNA form antiparallel homoduplexes that are thermally and thermodynamically significantly more stable than analogous duplexes of DNA and RNA. The salt‐dependence and Watson–Crick‐pairing fidelity of GNA duplexes are similar to those of DNA duplexes, but, apparently, the 2′‐deoxyribonucleotide and the propylene glycol backbones are not compatible with each other. This conclusion is further supported by cross‐pairing experiments. Accordingly, both (S)‐ and (R)‐GNA strands do not generally pair with DNA. However, (S)‐GNA, but not (R)‐GNA, forms stable heteroduplexes with RNA in sequences that are low in G:C content. Altogether, the high stability and fidelity of GNA duplex formation in combination with the economical accessibility of propylene glycol building blocks for oligonucleotide synthesis render GNA an attractive candidate for the design of self‐assembling materials. They further suggest that GNA could be considered as a potential candidate for a predecessor of RNA during the evolution of life on Earth.
A Fluorogenic Peptide Containing the Processing Site of Human SARS Corona Virus S‐Protein: Kinetic Evaluation and NMR Structure Elucidation
Authors: Basak Ajoy , Mitra Abhijit , Basak Sarmistha , Pasko Carolyn , Chrétien Michel , Seaton Pamela
Published: April 2007

Human severe acute respiratory syndrome coronavirus (hSARS‐CoV) is the causative agent for SARS infection. Its surface glycoprotein (spike protein) is considered to be one of the prime targets for SARS therapeutics and intervention because its proteolytic maturation by a host protease is crucial for host–virus fusion. Using intramolecularly quenched fluorogenic (IQF) peptides based on hSARS‐CoV spike protein (Abz‐755Glu‐Gln‐Asp‐Arg‐Asn‐Thr‐Arg‐Glu‐Val‐Phe‐Ala‐Gln766‐Tyx‐NH2) and in vitro studies, we show that besides furin, other PCs, like PC5 and PC7, might also be involved in this cleavage event. Through kinetic measurements with recombinant PCs, we observed that the peptide was cleaved efficiently by both furin and PC5, but very poorly by PC7. The cleavage could be blocked by a PC‐inhibitor, α1‐PDX, in a dose‐dependent manner. Circular dichroism spectra indicated that this peptide possesses a high degree of sheet structure. Following cleavage by furin, the sheet content increased, possibly at the expense of turn and random structures. 1H NMR spectra from 2D COSY and ROESY experiments under physiological buffer and pH conditions indicated that this peptide possesses a structure with a turn at its C‐terminal segment, close to the cleavage site. The data suggest that the cleavable peptide bond is located within the most exposed domain; this is supported by the nearby turn structure. Several strong to weak NMR ROESY correlations were detected, and a 3D structure of the spike IQF peptide that contains the crucial cleavage site R761↓E has been proposed.
Mixed‐Metal (Platinum, Palladium), Mixed‐Pyrimidine (Uracil, Cytosine) Self‐Assembling Metallacalix[n]arenes: Dynamic Combinatorial Chemistry with Nucleobases and Metal Species
Authors: Gil Bardají Elisa , Freisinger Eva , Costisella Burkhard , Schalley Christoph A. , Brüning Wolfgang , Sabat Michal , Lippert Bernhard
Published: April 2007

Reactions between the mononuclear mixed‐nucleobase complex [Pt(en)(UH‐N1)(CH2‐N3)]+(1; en: ethylenediamine; UH‐N1: uracil monoanion bonded through the N1 atom; CH2‐N3: neutral cytosine bonded through the N3 atom) and [PdII(en)] or [PdII(2,2′‐bpy)] (2,2′‐bpy: 2,2′‐bipyridine) lead to libraries of compounds of different stoichiometries and different connectivities. In these compounds, the palladium entity binds to or cross‐links either the N3 sites of uracil and/or the N1 sites of cytosine, following deprotonation of these positions to give uracil dianions (U) and cytosine monoanions (CH). Cyclic species, which can be considered as metallacalix[n]arenes, have been detected in several cases, withnbeing 4 and 8. The complexity of the compounds formed not only results from the possibility of the two different nucleobases in building block1engaging in different connectivities with the Pd entities, but also from the potential for the formation of oligomers of different sizes and different conformations; in the case of cyclic tetranuclear Pt2Pd2species, this can, in principle, lead to the various arrangements (cone, partial cone, 1,2‐alternate, 1,3‐alternate) known from calix[4]arene chemistry. A further complication arises from the fact that, depending on the mutual orientation of the exocyclic groups of the two nucleobases (O2 and O4 of uracil, O2 and N4 of cytosine), these sites can be engaged in additional chelation of [PdII(en)] and [PdII(2,2′‐bpy)]. Thus, penta‐, hexa‐, and octanuclear complexes, Pt2Pd3, Pt2Pd4, and Pt2Pd6, derived from cyclic Pt2Pd2tetramers have been isolated and characterized.
Design and Non‐Covalent DNA Binding of Platinum(II) Metallacalix[4]arenes
Authors: Galindo Miguel A. , Olea David , Romero M. Angustias , Gómez Julio , del Castillo Pedro , Hannon Michael J. , Rodger Alison , Zamora Félix , Navarro Jorge A. R.
Published: April 2007

A set of cyclic tetranuclear complexes of the metallacalix[4]arene type with formula [{Pt(en)(L)}4]4+ (en=ethylenediamine; 2: LH=5‐chloro‐2‐hydroxypyrimidine (5‐Cl‐Hpymo); 3: LH=5‐bromo‐2‐hydroxypyrimidine (5‐Br‐Hpymo); 4: LH=5‐iodo‐2‐hydroxypyrimidine (5‐I‐Hpymo)) have been obtained from the reaction between cis‐protected square‐planar [Pt(en)(H2O)2]2+ metal entities and LH in aqueous media. Additionally, the binding properties of 2, 3, 4 and their congener [{Pt(en)(L)}4]4+ (1: LH=2‐hydroxypyrimidine (Hpymo)) with calf thymus‐DNA (ct‐DNA) have been studied by using different techniques including circular and linear dichroism (CD and LD, respectively) and UV‐visible absorbance spectroscopies, gel electrophoresis, fluorescence competitive‐binding studies and atomic force microscopy (AFM). The results are consistent with significant non‐covalent interactions taking place between the polynuclear cyclic species and ct‐DNA. Moreover, gel electrophoresis, linear dichroism titrations and AFM images of ct‐DNA with metallacalixarenes show ct‐DNA coiling at low metallacalixarene concentrations and upon subsequent increments in metallacalixarene concentration ct‐DNA can be seen to uncoil with concomitant formation of long and inflexible ct‐DNA structures.
Rational Synthetic Tuning between Itinerant Antiferromagnetism and Ferromagnetism in the Complex Boride Series Sc2FeRu5−nRhnB2 (0≤n≤5)
Authors: Fokwa Boniface P. T. , Lueken Heiko , Dronskowski Richard
Published: April 2007

Single crystals of the complex boride series Sc2FeRu5−nRhnB2 (n=1, 3, 4) were synthesized by arc‐melting the elements in water‐cooled copper crucibles under argon atmospheres and were chemically characterized by single‐crystal XRD and EDX analyses. The new compounds are isotypic and crystallize in the tetragonal space group P4/mbm with Z=2, adopting a substitutional variant of the Ti3Co5B2‐type structure. The magnetically active iron atoms are arranged in chains with intra‐ and interchain distances of about 3.02 and 6.60 Å, respectively. Strong ferromagnetic interactions are observed for both Sc2FeRuRh4B2 (64 valence electrons (VE), TC≈350 K, μa=3.1 μB) and Sc2FeRu2Rh3B2 (63 VE, TC≈300 K, μa=3.0 μB), whereas antiferromagnetic interactions are found in the case of Sc2FeRu4RhB2 (61 VE, TN≈10 K, μeff=3.2): The magnetism of the entire Sc2FeRu5−nRhnB2 (0≤n≤5) series is discussed based on the variable valence‐electron count and the resulting Fe–Fe bonding character, and it is also compared with other isoelectronic systems.
Electron Transfer and Structural Change: Distinguishing Concerted and Two‐Step Processes
Authors: Macías‐Ruvalcaba Norma A. , Evans Dennis H.
Published: April 2007

In electron‐transfer reactions accompanied by structural changes, the structural change can be concerted with electron transfer or can occur in a separate reaction either preceding or following the electron‐transfer step. In this paper we discuss ways of distinguishing concerted reactions from the latter two‐step type. Included are recent examples in which no intermediates have been detected in the reactions, thus precluding the direct assignment to the two‐step category. In these cases, other means are used to build support for the two‐step mechanism with respect to the concerted process. These include an example of structural change preceding electron transfer, a demonstration that the current models of concerted reactions cannot fit the voltammetric data, and a case in which an independent measure of the inner reorganization energy was used to show that the reaction could not be a concerted electron transfer and structural change.
Numerical solution of the small dispersion limit of Korteweg—de Vries and Whitham equations
Authors: Grava Tamara , Klein Christian
Published: April 2007

The Cauchy problem for the Korteweg—de Vries (KdV) equation with small dispersion of order ϵ2, ϵ ≪ 1, is characterized by the appearance of a zone of rapid, modulated oscillations of wavelength of order ϵ. These oscillations are approximately described by the elliptic solution of KdV where the amplitude, wave number, and frequency are not constant but evolve according to the Whitham equations. In this manuscript we give a quantitative analysis of the discrepancy between the numerical solution of the KdV equation in the small dispersion limit and the corresponding approximate solution for values of ϵ between 10−1 and 10−3. The numerical results are compatible with a difference of order ϵ close to the center within the “interior” of the Whitham oscillatory zone, of order ϵ1/3 at the left boundary outside the Whitham zone and of order √ϵ at the right boundary outside the Whitham zone. © 2007 Wiley Periodicals, Inc.
Stereoselective Electrocatalytic Oxidative Coupling of Phenylacetonitriles: Facile and Convenient Way to trans‐α,β‐Dicyanostilbenes
Authors: Elinson Michail N. , Dorofeev Alexander S. , Feducovich Sergey K. , Belyakov Pavel A. , Nikishin Gennady I.
Published: April 2007

Electrolysis of phenylacetonitriles in methanol in an undivided cell in the presence of sodium halides as mediators induces a stereoselective oxidative coupling process that results in the formation of trans‐α,β‐dicyanostilbenes in 60–85 % yield with 40–70 % current efficiency. The application of this efficient stereoselective electrocatalytic method to the formation of trans‐α,β‐dicyanostilbenes represents an environmentally benign synthetic strategy and is valuable from the viewpoint of large‐scale processes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Study of Radical Decarboxylation Toward Functionalization of Naphthoquinones
Authors: Commandeur Claude , Chalumeau Céline , Dessolin Jean , Laguerre Michel
Published: April 2007

In order to obtain functionalized naphthoquinones, a systematic study of the Kochi–Anderson procedure for the alkylation of quinones is presented. While linear amino acids of different lengths were good substrates for this decarboxylation procedure, chiral α‐amino acids were unsuccessful substrates. The best reaction conditions were evaluated with β‐alanine and then applied to a series of carboxylic acids to obtain chemical diversity on the naphthoquinones. We observed that the substitution of the acids is critical for the alkylation, and that it was possible to realize a double alkylation with 1,4‐naphthoquinone, even with different reactants. The Barton procedure was attempted on some substrates to compare with our results, but no reaction was observed, no matter which radical trap was used. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
CEC separation of heterocyclic amines using methacrylate monolithic columns
Authors: Barceló‐Barrachina Elena , Moyano Encarnación , Puignou Lluís , Galceran Maria Teresa
Published: April 2007

Two methacrylate‐based monolithic columns, one with a negatively charged group (sulfonic group) and another with a new monomer N,N‐dimethylamino ethyl acrylate (DMAEA), were prepared and tested for the separation of basic compounds by CEC. This new monolithic stationary phase was prepared by the in situ polymerization of DMAEA with butyl methacrylate and ethylene dimethacrylate, using a ternary porogenic solvent consisting of water, 1‐propanol and 1,4‐butanediol. The performance of this column was evaluated by means of the analysis of a family of heterocyclic amines. Separation conditions such as pH, amount of organic modifier, ionic strength and elution mode (normal or counterdirectional flow) were studied. At the optimal running electrolyte composition, and using the counterdirectional mode, symmetrical electrochromatographic peaks were obtained, with the number of theoretical plates up to 30 000 and a good resolution between closely related peaks. The 2‐acrylamido‐2‐methyl‐1‐propane‐sulfonic acid column was used for CEC‐MS, taking advantage of the compatibility of its elution mode (normal flow) with the MS coupling.
Comparative studies of the interaction between ferulic acid and bovine serum albumin by ACE and surface plasmon resonance
Authors: Zhang Yintang , Xu Maotian , Du Ming , Zhou Feimeng
Published: April 2007

Affinity capillary electrophoresis (ACE) was used to study the interaction between ferulic acid (FA) and BSA. The interaction between FA and BSA was facilitated by injecting FA into a BSA‐containing running buffer. Both mobility ratio and mobility shift assays were performed to deduce the binding constant (Kb). However, the Kb value obtained with the mobility ratio assay was only ˜20% of that extracted from the mobility shift assay. The former assay yielded a Kb value (5.6 ± 0.4×104 M–1), which compares well with the result obtained with surface plasmon resonance (SPR) (5.1 ± 0.6×104 M–1). The discrepancy between the mobility ratio and mobility shift assays suggests that the data extrapolation from the mobility ratio should be more reliable for cases when both changes in the EOF and viscosity of the running buffer are important. The work demonstrates that ACE, a solution‐based technique, and SPR, a technique addressing interfacial processes, are highly complementary to each other and the comparative studies are confirmatory and allow binding constants to be accurately determined.
Selbstbewusst und exzellent
Authors: Schorn‐Schütte Luise
Published: April 2007

Bei der Förderung geisteswissenschaftlicher Forschung geht es um die Bewahrung spezifischer Exzellenzkriterien unter den veränderten Rahmenbedingungen knapper Ressourcen – nicht nur im Jahr der Geisteswissenschaften 2007
Dynamic patterns of latest Proterozoic‐Palaeozoic‐early Mesozoic marine biodiversity in South China
Authors: Jiayu Rong , Junxuan Fan , Miller Arnold I. , Guoxiang Li
Published: April 2007

Analyses of global biodiversity curves have been important for the interpretation of co‐evolution between organisms and environments through geological time. Global curves can be better understood if all the data collected from a multitude of palaeocontinents are analysed and explained separately. South China is a major block possessing more advantages for regional research than any of the other blocks in China. There exists a well‐developed succession of marine strata from the Ediacaran through to the Triassic with a relatively high resolution of bio‐ and chrono‐stratigraphy and an extensive marine fossil record. Stratigraphic occurrences of 5685 genera and 1386 families within 32 phyla or subphyla plus groups with uncertain affinities from this interval have been compiled by a large team of palaeontologists. With the exception of the Ediacaran, 50 time intervals with an average duration of 6.8 Ma are investigated. Diversity curves constructed at the levels of genus, family and order indicate that marine biodiversity peaked six times within the intervals: (1) Early Cambrian explosive radiation, (2) Early‐Mid Ordovician radiation mainly of the Paleozoic Evolutionary Fauna, (3) Early Silurian radiation, (4) late Early‐Mid Devonian radiation, (5) Mid‐Late Permian radiation and (6) Mid Triassic radiation chiefly of the Modern Evolutionary Fauna. Drops in biodiversity are controlled by various factors: (1) global catastrophes, which produced rapid losses of biodiversity during short time intervals; (2) global environmental perturbations with long term effects, as in the Carboniferous; (3) regional tectonics and palaeogeographical constraints, resulting in a lack of marine sedimentary rocks in many areas with biodiversity declining, as in the Wenlock; (4) unique sedimentary facies in large areas resulting in biodiversity losses, as in the Late Cambrian and (5) artifactual constraints associated with a lack of fossil record or low research intensity for some intervals, as in the period of about 30 Ma following the Early Cambrian explosive radiation. Copyright © 2007 John Wiley & Sons, Ltd.
Patterns of PIK3CA alterations in familial colorectal and endometrial carcinoma
Authors: Ollikainen Miina , Gylling Annette , Puputti Marjut , Nupponen Nina N. , Abdel‐Rahman Wael M. , Butzow Ralf , Peltomäki Päivi
Published: April 2007

While the phosphatidylinositol 3‐kinase (PI3K)/AKT signaling pathway is known to be activated in multiple sporadic cancers, the role of this pathway in familial tumors is mostly unknown. We searched for alterations in the catalytic domain of PI3K (PIK3CA), PTEN and KRAS, all of which may contribute to PI3K/AKT pathway activation, in a total of 160‐familial colorectal (CRC) and endometrial carcinomas (EC), stratified by the presence vs. absence of germline mutations in DNA mismatch repair (MMR) genes. PIK3CA alterations (consisting of point mutations or low‐level amplification, which were mutually exclusive with 1 exception) occurred in 10/70 (14%) of CRCs and 19/90 (21%) of ECs. Within ECs, amplification was significantly associated with the subgroup lacking germline mutations in MMR genes (familial site‐specific endometrial cancer) (p = 0.015). Decreased or lost PTEN expression was characteristic of endometrial tumourigenesis (51/81, 63%, in EC compared with 24/62, 39%, in CRC, p = 0.004) and KRAS mutations of colorectal tumourigenesis (19/70, 27% in CRC vs. 9/89, 10%, in EC, p = 0.006) regardless of the MMR gene mutation status. PIK3CA alterations frequently coexisted with PTEN or KRAS changes. Combined with published studies on sporadic tumors, our data broaden the understanding of the role for PI3K pathway genes in human tumorigenesis. © 2007 Wiley‐Liss, Inc.
Influence of VEGF‐A gene variation and protein levels in breast cancer susceptibility and severity
Authors: Balasubramanian Sabapathy P. , Cox Angelo , Cross Simon S. , Higham Sue E. , Brown Nicola J. , Reed Malcolm W.
Published: April 2007

Vascular endothelial growth factor‐A (VEGF‐A) plays an important role in tumour angiogenesis and cancer progression.VEGFgene variation may influence VEGF levels and therefore cancer susceptibility and progression. We studied the role ofVEGFsingle nucleotide polymorphisms and haplotypes in breast cancer susceptibility and severity. We also studied the relationships ofVEGFSNPs with circulating VEGF levels in healthy volunteers and protein expression in breast cancers. Single nucleotide polymorphisms (SNPs) in the regulatory regions of theVEGFgene were genotyped by high throughput methods in ∼500 breast cancer cases and 500 appropriate controls. Haplotype frequencies were inferred using methods based on the Expectation Maximisation algorithm. The effect ofVEGFgenotypes on serum and plasma VEGF levels were studied in another cohort of healthy individuals. A semi‐quantitative assessment of VEGF protein expression on tissue micro arrays (TMA) constructed from ∼300 breast cancer samples was performed and compared withVEGFgenotypes and with histopathological parameters and survival in breast cancer. The −460T/+405C/−7C/936C haplotype in the VEGF gene was found to be associated with decreased breast cancer risk (p= 0.029). The −7C>T polymorphism may influence overall breast cancer survival (p= 0.027). Individual polymorphisms however did not affect breast cancer susceptibility. There was no association between the individual polymorphisms and circulating VEGF levels in healthy volunteers and VEGF expression on the breast cancer micro array. VEGF expression in breast cancers was however associated with high grade (p= 0.002) and ER negative tumours (p= 0.03). © 2007 Wiley‐Liss, Inc.
m‐THPC‐mediated photodynamic therapy of malignant gliomas: Assessment of a new transfection strategy
Authors: Molinari Agnese , Bombelli Cecilia , Mannino Stefano , Stringaro Annarita , Toccacieli Laura , Calcabrini Annarica , Colone Marisa , Mangiola Annunziato , Maira Giulio , Luciani Paola , Mancini Giovanna , Arancia Giuseppe
Published: April 2007

Malignant gliomas represent the most common primary brain tumor: more than 50% of them are glioblastoma multiforme (GBM). Photodynamic therapy may offer a very good chance of targeted destruction of infiltrating GBM cells, thus increasing the survival time and recurrence‐free interval of GBM patients. Among photosensitizing agents, meta‐tetrahydroxyphenylchlorin (m‐THPC) is promising for the treatment of brain tumors. In previous studies, we investigated the transfection activity of dimyristoyl‐sn‐glycero‐phosphatidylcholine (DMPC) liposomes, containing a cationic gemini surfactant, loaded with m‐THPC on human colon adenocarcinoma and glioblastoma cell lines. In this paper, the uptake and the intracellular distribution of m‐THPC, loaded in several formulations of cationic liposomes, were analyzed, by making a comparison with those obtained using the same chlorin in the pharmaceutical form (Foscan®). Moreover, by cloning efficiency assay the potential therapeutic efficiency of chlorin delivered by liposome formulations was compared with that of the pharmaceutical compound, before and after irradiation with laser light at 652 nm. The obtained results indicated that cationic liposomes (i) transferred m‐THPC in glioblastoma cells more efficiently than pharmaceutical formulation; (ii) significantly (p < 0.001) increased the m‐THPC cytotoxic effect after laser irradiation; (iii) seemed to exert their cytotoxic action in the early phase of interaction with the cells, during adhesion to the plasma membrane. © 2007 Wiley‐Liss, Inc.
Anxiety affects the relationship between parents and their very low birth weight infants
Authors: Zelkowitz Phyllis , Bardin Claudette , Papageorgiou Apostolos
Published: April 2007

The goal of this study was to examine the medical and sociodemographic factors associated with parental anxiety following the birth of a very low birth weight infant (VLBW, below 1500 g), and to determine the impact of anxiety on the behavior of parents with their VLBW infants in the Neonatal Intensive Care Unit (NICU). The parents of 88 VLBW infants were recruited through the NICU of a tertiary‐care hospital, approximately 2 weeks following delivery. Parents completed self‐report questionnaires measuring anxiety, marital quality, and social support. Prior to discharge, each parent was observed twice during a feeding interaction with the infant. Maternal anxiety was greater when their infants were smaller in terms of birth weight and younger in gestational age. Maternal education, marital status, and country of origin, as well as social support and marital quality, were also associated with anxiety. Paternal anxiety was not related to socioeconomic status or infant medical risk, but was associated with country of origin, social support, and marital quality. For both mothers and fathers, anxiety was a better predictor of parental behavior than was infant medical risk. These findings suggest the need to intervene with anxious parents in order to promote satisfactory parent‐infant relationships.