bluuebunny/crossref_metadata_2025 huggingface dataset:
Overdispersion
Authors: Dean Charmaine B.
Published: October 2008

Count data analyzed under a Poisson assumption or data in the form of proportions analyzed under a binomial assumption often exhibit overdispersion, where the empirical variance in the data is greater than that predicted by the model. This entry illustrates how overdispersion may arise and discusses the consequences of ignoring it, in particular, the underestimation of standard errors of covariate effects. Straightforward methods for ascertaining whether overdispersion is evident are presented. Simple methods for incorporating overdispersion within the framework of quasi‐likelihood estimation are reviewed as well as generalized linear mixed models, which form a broad scheme for model‐based analysis when overdispersion is present.
Power Transformations
Authors: Atkinson A. C.
Published: October 2008

Simple regression analysis assumes normally distributed errors of constant variance. These assumptions may be more nearly satisfied by transformation of either the response variable, the explanatory variable(s), or both. In using the power transformation of Box and Cox, the power parameter may be estimated by maximum likelihood. This family of transformations includes the square root, logarithm, and reciprocal.
Regression
Authors: Farewell Vern T.
Published: October 2008

Statistical usage of the term regression is discussed.
Response Surface Methodology
Authors: Raghavarao D. , Altan S.
Published: October 2008

Response Surface Methodology (RSM) is used to determine the optimal setting givenkquantitative experimental factors. A preliminary first‐order experiment based on a Plackett–Berman design identifies important factors with a first pass estimate of the optimal point by means of the method of steepest ascent. This is followed by a confirmatory second‐order experiment using a suitable fractional factorial, Central Composite or Box–Behnken design. RSM identifies the optimal setting by estimating the coefficients of a polynomial equation describing the responses from thenexperimental runs, each run corresponding to a prescribed choice of factor combinations. The relationship betweennandk, the points in the experimental design and their properties in relation to orthogonality, rotatability, and uniform precision constitute the major part of the RSM.
Risk Assessment
Authors: Armitage Peter
Published: October 2008

The “risk” of a potentially dangerous hazard may be measured either by the probability of its occurrence (perhaps per unit time or unit of exposure), or by combining this with a measure of its severity. Risk assessment may involve estimation of these quantities, evaluation of their significance for individuals and communities, the extent to which individuals may differ in their perceptions of risks, and the measures taken by individuals and communities to reduce the impact of risks. These aspects are considered in turn.
Stratification
Authors: Gail Mitchell H.
Published: October 2008

Stratification refers in epidemiology, to a design that improves the efficiency of analytical procedures to control for confounding by causing controls to have the same distribution over strata defined by levels of potential confounders as cases in a case–control study or as the exposed cohort in a cohort study.
Wilcoxon Signed‐Rank Test
Authors: Woolson R. F.
Published: October 2008

This is a nonparametric test procedure for the analysis of matched‐pair data, based on differences, or for a single sample. The null hypothesis is that the differences, or individual observations in the single‐sample case, have a distribution centered about zero. The absolute values are ranked. The test statistic is the sum of the ranks for either the positive or the negative values. Examples and details, including large‐sample properties, are given.
Wilcoxon–Mann–Whitney Test
Authors: Moses Lincoln E.
Published: October 2008

This is a method of comparing the size of observations in two groups by ranking all the observations and comparing the average ranks of the two groups. The distribution theory is described. The test has high efficiency for the comparison of two normal distributions with the same variance, and is much better than thettest for some nonnormal distributions. Topics discussed include adjustment for tied data and the calculation of confidence limits for a difference in translation between the two distributions.
Prevention Trials
Authors: Prentice Ross L.
Published: October 2008

Randomized controlled trials provide the gold standard for assessing the health benefits and risks of preventive treatments or interventions. Such trials typically need to be very large‐scale and long‐term. Hence, cost and logistic considerations imply that few such trials can be conducted, and there is a need for careful hypothesis development and preliminary testing, prior to the initiation of a full‐scale disease prevention trial. Aspects of the design, conduct monitoring and analysis of prevention trials are reviewed, along with a discussion of differences from therapeutic trials, and of the interplay with observational studies. The National Institutes of Health‐sponsored Women's Health Initiative, which includes both a multi‐faceted prevention trial, and a large cohort study, among postmenopausal women, provides an illustration of prevention trial considerations and trade‐offs.
Quality of Life
Authors: Fairclough Diane L. , Ganz Patricia A.
Published: October 2008

In the health sciences, assessment of quality of life and other patient‐reported outcomes are now an integral component of patient‐focused research. Health‐related quality of life (HRQoL) is a multidimensional construct that assesses the extent to which one's usual or expected physical, emotional, and social well‐being are impacted by a medical condition or its treatment. HRQoL may be assessed using generic or disease‐specific instruments. These instruments consist of a set of questions, method of administration, instructions for administration, method of scoring and analysis, and interpretation. Validation of these instruments includes assessment of content validity, internal consistency, test–retest reliability, and discriminant and predictive validity. Some of the statistical issues that arise in the analysis of studies with HRQoL assessments are multiple endpoints, missing data (informative dropout), and interpretation (statistical versus clinical significance).
World Health Organization (
WHO
): Global Health Situation
Authors: Hapsara H. R.
Published: October 2008

WHO has responsibility for the global epidemiologic surveillance of disease, receiving information on outbreaks of communicable disease and distributing this information throughout the world. WHO is also responsible for the
International Health Regulations
, the International Classification of Diseases, and other standards, which together make international epidemiologic comparisons possible. WHO also publishes
World Health Statistics Quarterly
,
World Health Statistics Annual
,
World Health Report
. The thirtieth World Health Assembly decided that the main social target of governments and WHO in the coming decades should be “health for all” by the year 2000. Member states committed themselves to monitoring progress toward, and evaluating the attainment of, this common goal. The health‐for‐all monitoring and evaluation process is intended to establish a baseline of current health and socioeconomic conditions, against which progress toward defined targets and objectives can be measured. Periodic measurement should establish trends that will permit anticipation of future conditions, and enable planning for them. The Health Situation and Trend Assessment Program is at present responsible for global health situation analysis and projection; strengthening of country health information; and partnerships and coordination of epidemiology, statistics, and trend assessment. Global epidemiologic surveillance is under the responsibility of the Emerging and other Communicable Diseases Surveillance and Control Program
Synthesis and Characterization of Positive‐Charge Functionalized Mesoporous Silica Nanoparticles for Oral Drug Delivery of an Anti‐Inflammatory Drug
Authors: Lee Chia‐Hung , Lo Leu‐Wei , Mou Chung‐Yuan , Yang Chung‐Shi
Published: October 2008

We synthesized mesoporous silica nanoparticles (MSN) with different densities of surface positive charges. The positive surface charge was generated by incorporating trimethylammonium (TA) functional groups into the framework of MSN (MSN–TA) via direct co‐condensation of a TA‐silane and tetraethoxysilane (TEOS) in the presence of a base as a catalyst. These MSN–TA samples have well‐defined hexagonal structures with an average particle diameter of 100 nm, pore size of 2.7 nm, and surface area of about 1000 m2 g−1. Anionic drug molecules, Orange II (a fluorescent tracing molecule), and sulfasalazine (an anti‐inflammatory prodrug used for bowel disease), were effectively loaded into these MSN–TA samples and remained inside of the MSN–TA under acidic environment (pH 2–5). The amounts of loading of both Orange II and sulfasalazine were increased with increasing positive charge densities resulting from the increasing number of TA groups. When these drug‐loaded MSN–TA nanoparticles were placed in physiological buffer solution (pH 7.4), a partial negative surface charge on the MSN–TA was generated due to the deprotonation of silanol groups, and the strong electrostatic repulsion triggered a sustained release of the loaded molecules. MSN–TA as a nanovehicle for pH‐dependent loading and controllable release of anionic drug molecules can be used as an oral delivery drug systems targeting at intestine. These drugs can be remained trapped in the nanovehicle when passing through the stomach's acidic environment and be released in intestine where the environmental pH is close to neutral.
Asymmetric Carbonyl Reductions with Microbial Ketoreductases
Authors: Sorgedrager Menno J. , van Rantwijk Fred , Huisman Gjalt W. , Sheldon Roger A.
Published: October 2008

The biocatalytic reduction of β‐keto esters and some aromatic ketones in the presence of a variety of ketoreductases from different microbial origins was investigated. The prochiral selectivity was generally high and both product enantiomers could be obtained by a proper choice of enzyme. Aromatic ketones reacted slower than the esters but the prochiral selectivity was often high. The organic cosolvent tolerance of these enzymes was rather variable but useful activity could be maintained in a number of cases. Reduction of the oxidized cofactors NAD and NADP, employing 2‐propanol as a sacrificial reductant, was catalyzed by the ketoreductases from Rhodococcus erythropolis and Lactobacillus kefir, respectively.
Transfer Hydrogenation of Carbonyl Compounds Catalyzed by Ruthenium Nanoparticles Stabilized on Nanocrystalline Magnesium Oxide by Ionic Liquids
Authors: Kantam M. Lakshmi , Reddy R. Sudarshan , Pal Ujjwal , Sreedhar B. , Bhargava S.
Published: October 2008

Transfer hydrogenation of various carbonyl compounds was achieved in excellent yields by ruthenium nanoparticles stabilized on the nanocrystalline magnesium oxide by the incorporation of choline hydroxide, a basic ionic liquid. The procedure is simple, efficient and the catalyst can be recycled five times.
Novel Chemo‐Enzymatic Mimic of Hydrogen Peroxide‐Forming NAD(P)H Oxidase for Efficient Regeneration of NAD+ and NADP+
Authors: Pival Simone L. , Klimacek Mario , Nidetzky Bernd
Published: October 2008

The current methods for regeneration of NAD+ and NADP+ in dehydrogenase‐catalyzed organic synthesis are not technologically mature due to problems with operational stability, kinetic efficiency or thermodynamic equilibrium. We show here that Candida tenuis xylose reductase converts 9,10‐phenanthrenequinone with good turnover frequency when using NADH (12 s−1) or NADPH (1.6 s−1) as the coenzyme and exhibits high binding affinity for this quinone substrate (Km≤13 μM). Because chemical reaction of the hydroquinone product with dissolved molecular oxygen regenerates the quinone at a rate comparable to that of the enzymatic reduction, a chemo‐enzymatic process is established where the reductase, a catalytic concentration of 9,10‐phenanthrenequinone (25 μM) and molecular oxygen promote efficiently the production of NAD(P)+ from NAD(P)H. Oxidation of the hydroquinone occurs via a radical chain reaction that involves superoxide as the propagating species and yields a molar equivalent of hydrogen peroxide for each 9,10‐phenanthrenequinone recycled. Using the NAD+‐ or NADP+‐dependent transformation of D‐mannitol (25 mM) into D‐fructose as a model transformation, the total turnover numbers for 9,10‐phenanthrenequinone and the coenzyme obtained in a single batchwise conversion were 1000 and ≤125, respectively. The yields of ketose product were quantitative, indicating that molecular oxygen reduction drives the thermodynamically unfavourable synthetic reaction. Oxygen transfer to the liquid phase was shown to be rate‐limiting for the overall process under conditions of surface aeration and bubble‐free molecular oxygen supply. Xylose reductase was fully stable during the reaction (25 °C, pH 8.0). The novel chemo‐enzymatic system should therefore be broadly applicable to biocatalytic synthesis with isolated dehydrogenases utilizing NAD+ or NADP+.

Abbreviations: CtXR: xylose reductase from Candida tenuis (E.C. 1.1.1.21); M2DH: D‐mannitol 2‐dehydrogenase (E.C. 1.1.1.67); OTR: O2 transfer rate; PQ: 9,10‐phenanthrenequinone; PQH2: 9,10‐phenanthrene hydroquinone; SOD: superoxide dismutase; STY: space‐time yield; TTN: total turnover number.
Palladium‐Catalyzed Desulfitative CC Cross‐Coupling Reaction of (Hetero)Aryl Thioesters and Thioethers with Arylsiloxanes
Authors: Mehta Vaibhav Pravinchandra , Sharma Anuj , Van der Eycken Erik
Published: October 2008

The first desulfitative Hiyama‐type cross‐coupling protocol is reported and exemplified by the synthesis of substituted 5‐chloro‐3‐arylpyrazinones. The method has also been successfully applied for the arylation of other (hetero)aryl thioethers and thioesters.
A Direct CC Cross‐Coupling of Alcohols at the β‐Position with Aldehydes under Co‐Promotion of Tris(triphenylphosphine)rhodium Chloride/Boron Trifuoride Etherate
Authors: Zhang Shu‐Yu , Tu Yong‐Qiang , Fan Chun‐An , Jiang Yi‐Jun , Shi Lei , Cao Ke
Published: October 2008

The novel tris(triphenylphosphine)rhodium chloride/boron trifuoride etherate [RhCl(PPh3)3/BF3⋅OEt2] co‐promoted the CC cross‐coupling of tertiary alcohols at the β‐position with aldehydes. This reaction provides an efficient synthesis of either structurally diverse 1,3‐diols or polysubstituted tetrahydropyrans by controlling the substrate structures, and it could be developed to a practical synthetic method for numerous natural products and medicinally important compounds.
Enantioselective Platinum‐Catalyzed Tandem Hydroarylation– Cycloisomerization of 1,6‐Enynes
Authors: Toullec Patrick Yves , Chao Chung‐Meng , Chen Qian , Gladiali Serafino , Genêt Jean‐Pierre , Michelet Véronique
Published: October 2008

The platinum(II) chloride/silver hexafluoroantimonate (PtCl2/AgSbF6) catalytic system associated with atropisomeric ligand Ph‐BINEPINE promotes a stereoselective tandem hydroarylation (Friedel–Crafts‐type addition) of electron‐rich aromatic and heteroaromatic derivatives to unactivated alkenes followed by a CC bond cyclization reaction (ee up to 96%). Some evidence shows that the catalytic species responsible for the highest enantiomeric excesses might reasonably be an L3Pt2+ species, L being a monodentate ligand.
[2.2]Paracyclophane in Polymerchemie und Materialwissenschaften
Authors: Hopf Henning
Published: October 2008

Nach einer langen Zeit als Modellverbindungen in der Grundlagenforschung werden [2.2]Paracyclophane immer wichtiger in der Anwendung. Sie lassen sich auf vielfältige Weise in polymere Systeme einbauen, wobei ihre Lagenstruktur entweder verloren geht (so genannte Parylene) oder beibehalten wird, und sie können zum Aufbau ungesättigter Molekülgerüste eingesetzt werden, die sich nicht nur durch konventionelle laterale π‐Elektronenwechselwirkungen auszeichnen, sondern auch durch cofaciale Überlappung zwischen den Ringen. Aus [2.2]Paracyclophanen hergestellte Oberflächen haben interessante biologische, photophysikalische und optoelektronische Eigenschaften.
Structural study of Ac‐Phe‐[Orn‐Pro‐dCha‐Trp‐Arg], a potent C5a receptor antagonist, by NMR
Authors: Zhang Li , Mallik Buddhadeb , Morikis Dimitrios
Published: October 2008

The cyclic hexapeptide Ac0‐Phe1‐[Orn2‐Pro3‐dCha4‐Trp5‐Arg6] (the square brackets denote cyclization) is a potent antagonist against C5a (the a‐fragment of complement protein C5) binding to C5a receptor (C5aR) and an excellent candidate to become a therapeutic agent against diseases that involve unregulated activation of the complement system. We present the solution structure determination of this cyclic C5aR peptide antagonist (cC5aR‐pa), using nuclear magnetic resonance (NMR) data and restrained molecular dynamics‐based simulated annealing in torsion angle space with NMR‐derived distance and torsion angle restraints. The calculated NMR ensemble of structures demonstrates the presence of a predominant conformation of a distorted type II′ β‐turn in the segment Pro3‐dCha4‐Trp5‐Arg6. We critically examine the calculated structure with measured NMR parameters, such as nuclear Overhauser enhancement (NOE) connectivity patterns and intensities characteristic of specific structures, 3J(HN‐Hα) scalar coupling constants, temperature coefficients for NH groups, and differences between observed chemical shifts and their random coil values. The raw NMR data are consistent with the presence of the type II′ β‐turn, but also indicate the presence of conformational inter‐conversion. The calculated three‐dimensional coordinates for cC5aR‐pa will form the basis for further computational studies and for the development of pharmacophore models. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 90: 803–815, 2008.

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Artificial collagen gels via self‐assembly of de novo designed peptides
Authors: Yamazaki Chisato M. , Asada Shinichi , Kitagawa Kouki , Koide Takaki
Published: October 2008

Development of artificial collagens to replace the animal‐derived collagens presents a challenge in the formation of safer and functional biomaterials. We report here the development of collagen‐like gels by means of the self‐assembly of chemically synthesized peptides. The peptides are disulfide‐linked trimers of collagenous Gly‐X‐Y triplet repeats with self‐complementary shapes. Upon cooling the peptide solutions, hydrogels of peptide supramolecules are formed by spontaneous intermolecular triple helix formation. The thermal gel–sol transition appeared to be reversible, and the transition temperatures were found to be tunable by the design of the peptides. Our systems for the formation of artificial collagen‐like gels will offer possibilities for novel types of biomaterials. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 90: 816–823, 2008.

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Head‐to‐Head Right‐Handed Cross‐Links of the Antitumor‐Active Bis(μ‐N,N′‐di‐p‐tolylformamidinato)dirhodium(II,II) Unit with the Dinucleotides d(GpA) and d(ApG)
Authors: Chifotides Helen T. , Dunbar Kim R.
Published: October 2008

Reactions of cis‐[Rh2(DTolF)2(NCCH3)6](BF4)2 with the dinucleotides d(GpA) and d(ApG) proceed to form [Rh2(DTolF)2{d(GpA)}] and [Rh2(DTolF)2{d(ApG)}], respectively, with bridging purine bases spanning the Rh–Rh unit in the equatorial positions. Both dirhodium adducts exhibit head‐to‐head (HH) arrangement of the bases, as indicated by the presence of H8/H8 NOE cross‐peaks in the 2D ROESY NMR spectra. The guanine bases bind to the dirhodium core at positions N7 and O6, a conclusion that is supported by the absence of N7 protonation at low pH values and the notable increase in the acidity of the guanine N1H sites (pKa≈7.4 in 4:1 CD3CN/D2O), inferred from the pH‐dependence titrations of the guanine H8 proton resonances. In both dirhodium adducts, the adenine bases coordinate to the metal atoms through N6 and N7, which induces stabilization of the rare imino tautomer of the bases with a concomitant substantial decrease in the basicity of the N1H adenine sites (pKa≈7.0–7.1 in 4:1 CD3CN/D2O), as compared to the imino form of free adenosine. The presence of the adenine bases in the rare imino form is further corroborated by the observation of DQF‐COSY H2/N1H and ROE N1H/N6H cross‐peaks in the 2D NMR spectra of [Rh2(DTolF)2{d(GpA)}] and [Rh2(DTolF)2{d(ApG)}] in CD3CN at −38 °C. The 2D NMR spectroscopic data and the molecular modeling results suggest the presence of right‐handed variants, HH1R, in solution for both adducts (HH1R refers to the relative base canting and the direction of propagation of the phosphodiester backbone with respect to the 5′ base). Complete characterization of [Rh2(DTolF)2{d(GpA)}] and [Rh2(DTolF)2{d(ApG)}] by 2D NMR spectroscopy and molecular modeling supports anti‐orientation of the sugar residues for both adducts about the glycosyl bonds as well as N‐ and S‐type conformations for the 5′‐ and 3′‐deoxyribose residues, respectively.
Computational NMR Spectroscopy of Organoarsenicals and the Natural Polyarsenic Compound Arsenicin A
Authors: Tähtinen Petri , Saielli Giacomo , Guella Graziano , Mancini Ines , Bagno Alessandro
Published: October 2008

The 1H and 13C NMR chemical shifts and coupling constants of a series of organoarsenic compounds were calculated with DFT methods and compared with available experimental spectra. We show that non‐relativistic methods successfully model the NMR spectra of these molecules; relativistic spin–orbit effects are small but appreciable for 13C shifts, and their inclusion is beneficial. Application of the same methods of calculation to the intriguing natural polyarsenic compound arsenicin A allowed several viable alternative structures to be ruled out and thereby confirmed the previously suggested adamantane‐like structure of arsenicin A. These results not only reinforce the known predictive power of DFT NMR calculations, but also open the way for the investigation of other naturally occurring molecules with unusual structures outside the scope of empirical methods.
Methan im Gashydrat. Gefangen im Wasserkäfig
Authors: Schicks Judith
Published: October 2008

In diesem Artikel wird die Vielfalt der Gashydrate hinsichtlich ihres Vorkommens, ihrer Zusammensetzung, ihrer Charakterisierung und ihrer potenziellen Nutzbarkeit beschrieben. Neben den Hydraten, die in Natur vorkommen, wird auch auf die synthetisierten Clathrathydrate eingegangen. Verschiedene Methoden, von der Laboranalytik bis zum Feldeinsatz, werden beschrieben.
Friedrich Theodor Althoffs Beziehungen zur Chemie
Authors: Zott Regine
Published: October 2008

Vor 100 Jahren verstarb Friedrich Theodor Althoff, der über 25 Jahre lang als vortragender Rat im “Preußischen Ministerium der Geistlichen, Unterrichts‐ und Medicinalangelegenheiten” (Kultusministerium) wirkte. Nachhaltig beeinflusste er das deutsche Hochschulwesen und dessen Beziehungen zur Industrie sowie die internationalen Wissenschaftsbeziehungen. Sein Zuständigkeitsbereich umfasste sowohl Hochschulen und Universitäten, Denkmalpflege, Bibliotheken und die medizinischen Forschungseinrichtungen, als auch die universitäre Berufungspolitik und die Förderung sowie Gründung wissenschaftlicher Einrichtungen. Er führte neuartige Organisationsformen ein wie beispielsweise die jährliche “Konferenz deutscher Universitätsverwaltungen in Hochschulangelegenheiten” (die späteren Kultusministerkonferenzen). Mit Menschenkenntnis und vielseitiger Kommunikation (“System Althoff”) veranlasste er den leistungsgerechten Einsatz besonders begabter Gelehrter. Hoch geehrt und auch viel geschmäht galt er als der “heimliche Kultusminister”.
Nicotin
Authors: Schäfer Bernd
Published: October 2008

Tabak und sein Hauptalkaloid Nicotin haben eine große kulturgeschichtliche Bedeutung. In erster Linie diente er dem menschlichen Konsum. Nicotin war aber auch eines der ersten Insektizide, das in der Landwirtschaft schon seit Ende des 19. Jahrhunderts mit großem Erfolg eingesetzt wurde. Die Biogenese des hoch toxischen Alkaloids leitet sich von verschiedenen Aminosäuren ab. Mit Nicotin sind eine Reihe anderer Naturstoffe, wie Anabasin, Epibatidin, Cytisin und Anatoxin A verwandt, die eine vergleichbare Pharmakologie besitzen. Seit der Strukturaufklärung von Nicotin durch Adolf Pinner und Paul Karrer wurden mehrere elegante Synthesen des racemischen und enantiomerenreinen Naturstoffs publiziert.
Zehn Jahre “Chemie entdecken”
Authors: Schumacher Elke
Published: October 2008

Der Experimentalwettbewerb “Chemie entdecken” für Schülerinnen und Schüler der Klassenstufen 5 bis 10 aller Schulformen in Nordrhein‐Westfalen besteht nunmehr seit zehn Jahren. In diesem Zeitraum nahmen 56.312 Schülerinnen und Schüler teil, es fanden 10 Jahresfeiern mit insgesamt 2.726 Preisträgern und mehr als 70.000 Gästen statt – ein Anlass, kurz zurück zu blicken und eine Zwischenbilanz zu ziehen.
Kinetic Study of Humic Acid Ozonation in Aqueous Media
Authors: Miao Hengfeng , Tao Wenyi , Cui Fengjie , Xu Zhenghong , Ao Zonghua
Published: October 2008

A pseudo first‐order kinetic model that describes the ozonation of two sources of humic acid (HA) in aqueous media is developed and investigated in a semi‐batch system. Further investigation shows that the degradation rates of the two HAs are highly dependent on the initial pH, temperature of the ozonation, the source of HA, and the overall kinetic rate constant, which is mainly composed of two parts, i. e., direct oxidation by molecular ozone and indirect oxidation by hydroxyl radicals (•OH). The contributions of the two pathways to HA ozonation can be traced using tert‐butanol as the radical scavenger at different pH values (3, 7, and 11), temperatures (283–303 K), and the results show that •OH oxidation is more sensitive to the operating variables than molecular ozone oxidation and exerts a contribution of ca. 50 to 60% on the overall reaction at the different operating parameters. Furthermore, the direct molecular ozone oxidation rate constant is correlated with temperature by a modified Arrhenius equation with an activation energy, Ea, of 33.57 kJ mol–1.
A parallel adaptive finite element method for the simulation of photon migration with the radiative‐transfer‐based model
Authors: Lu Yujie , Chatziioannou Arion F.
Published: October 2008

Whole‐body optical molecular imaging of mouse models in preclinical research is rapidly developing in recent years. In this context, it is essential and necessary to develop novel simulation methods of light propagation for optical imaging, especially when a priori knowledge, large‐volume domain and a wide‐range of optical properties need to be considered in the reconstruction algorithm. In this paper, we propose a 3D parallel adaptive finite element method with simplified spherical harmonics (SPN) approximation to simulate optical photon propagation in large volumes of heterogeneous tissues. The simulation speed is significantly improved by a posteriori parallel adaptive mesh refinement and dynamic mesh repartitioning. Compared with the diffusion equation and the Monte Carlo methods, the SPN method shows improved performance and the necessity of high‐order approximation in heterogeneous domains. Optimal solver selection and time‐costing analysis in real mouse geometry further improve the performance of the proposed algorithm and show the superiority of the proposed parallel adaptive framework for whole‐body optical molecular imaging in murine models. Copyright © 2008 John Wiley & Sons, Ltd.
Ordered Polyelectrolyte Multilayers: Unidirectional FRET Cascade in Nanocompartmentalized Polyelectrolyte Multilayers
Authors: Peralta Sébastien , Habib‐Jiwan Jean‐Louis , Jonas Alain M.
Published: October 2008

Multifunctional polyelectrolyte (or layer‐by‐layer, LbL) multilayers consisting of a set of nanocompartments separated by impermeable ultrathin barriers, whereby the thickness of the compartments is tuned in the range 1–10 nm, are synthesized. Each compartment contains a different dye, introduced by co‐adsorption during multilayer deposition. Different LbL barriers are tested for impermeability towards dye diffusion while simultaneously allowing energy transfer to occur between the compartmentalized dyes. Cross‐linked LbL multilayers based on poly(acrylic acid) and poly(allyl amine) are shown to provide the desired impermeability for thicknesses as small as about 2.5 nm. A proof‐of‐concept system is then realized involving a cascade of two FRET processes, whereby the light energy is collected in a first nanocompartment containing pyranine, sent to a second nanocompartment loaded with fluorescein, before finally being transferred to a third, Nile blue‐filled compartment located at the external surface of the film. This demonstrates the possibility to fabricate complex light‐harvesting antenna systems by LbL assembly while controlling the architecture of the antenna down to a few nanometers.
Determining the impact of internet channel use on a customer's lifetime
Authors: Boehm Martin
Published: October 2008

In light of mature markets and increasing competitive pressure, retaining the existing customer base becomes crucial for the future success of a firm. As a consequence, firms are increasingly interested in understanding the factors influencing and driving customer retention. One factor that is hypothesized to have an impact on customer retention is the growing use of the Internet channel. Firms are interested in understanding whether and how the Internet use induces a change in customer retention.

The aim of this paper is to empirically quantify the impact of Internet use on customer retention when accounting for potentially present self-selection. Furthermore, the paper will derive managerial implications on how to use customer channel migration to improve overall customer retention. The results of the empirical study indicate a strong positive impact of Internet use on customer retention. Hence, migrating customers to the Internet channel has the potential to increase overall retention rates.
Influence of Cultural Dimensions on Online Interactive Review Feature Implementations: A Comparison of Korean and U.S. Retail Web Sites
Authors: Yun Gi Woong , Park Sung-Yeon , Ha Louisa
Published: October 2008

This study examines the nature of online consumer-generated communications, focusing especially on consumer reviews of leading retail Web sites in South Korea and the U.S. The current investigation adopts a two-pronged approach that utilizes both the user control concept and a cross-cultural perspective. The active implementations of consumer review features in Korean Web sites found in this study indicate that people in high power distance countries can adopt information technology rapidly to facilitate horizontal communication. As a result, we were able to support and expand the traditional view looking at the differences between Northeast Asian business culture and Western business culture.
Improving predictive scoring models through model aggregation
Authors: Malthouse Edward C. , Derenthal Kirstin M.
Published: October 2008

Scoring models predict responses to some contact that will be made in the future, helping an organization decide which customers to target. They are usually built from a single “proxy” contact from the past, for which responses have already been observed. This approach is risky because there could be differences between the proxy and future contact, and other exogenous factors could have changed. We propose averaging predictions from multiple scoring models and develop a rationale for this approach by showing under certain assumptions that the expected squared difference between the true responses to the future contact and the predicted values from the averaged model is less than or equal to the expected squared difference from a single previous contact. The improvement of the aggregated model over the single model increases as (1) the variation in effect sizes across contacts increases, (2) the number of averaged contacts increases, and (3) the variance of the effect estimates increases. We incorporate the effects of external factors in our model by weighting the coefficients with a general linear model (GLM). Using data from a retail catalog company and a nonprofit organization, we evaluate our model empirically by testing whether our assumptions hold, examine the extent of variation in slopes and predicted values across models build from various previous contacts, evaluate the amount of improvement over extant models in terms of prediction error and performance as measured by a gains table, and study how improvement depends on the number of averaged contacts. Conservative estimates suggest that our method could increase annual profits for the nonprofit organization by over a half-million dollars and tens of thousands of dollars for the small catalog company.
Nature conservation and urban development control in the Portuguese planning system: a new impetus against old praxis?
Authors: Fidelis Teresa , Sumares David
Published: October 2008

Natura 2000 areas bring a new incentive to assess the performance of land‐use planning in protecting environmental values from the impacts of development pressures. In the last decades, urban growth and consequent environmental impacts on natural areas have been a major concern for the Portuguese land‐use planning system. Sprawl around sensitive areas has been revealed to be a persistent phenomenon in spite of the increasing challenges underlying land‐use plans. This article critically analyses the content of three main documents recently adopted by the Portuguese government – the ‘National Strategy for Sustainable Development’, the ‘National Policy Programme for Spatial Planning’ and the ‘Sector Plan for Natura 2000’ – seeking prospects to innovate future plans at lower levels in order to prevent additional pressures on natural areas. First, the article reviews the recent theoretical debate on planning for the protection of natural areas. Results evidenced by recent EU evaluation reports are used to propose a set of guidelines to evaluate planning guidance at national level. Second, it critically analyses the three planning documents, bearing in mind the main features of the planning system and the proposed guidelines. The article is concluded with a discussion of their potential, exploring whether they bring a new impetus to the role of land‐use planning against an outdated and persistent praxis, or whether, on the contrary, further efforts to strengthen planning guidance remain to be formulated. Copyright © 2008 John Wiley & Sons, Ltd and ERP Environment.
Effect of membrane filtration on the flavor of virgin olive oil
Authors: Bottino Aldo , Capannelli Gustavo , Mattei Alissa , Rovellini Pierangela , Zunin Paola
Published: October 2008

Cross‐flow microfiltration (MF) and ultrafiltration (UF) with different commercial membranes were applied to virgin olive oil (VOO) in order to remove some compounds that are responsible for oil unpleasant flavor without altering the oil composition. Experimental tests were carried out using a Spanish VOO from Andalusia, which had the typical eucalyptus aroma. Several classical analytical parameters (acidity, peroxide number, UV absorbance) were determined. Moreover, the contents of total chlorophyll and minor polar compounds were detected. The effect of filtration on oil aroma was evaluated by detecting carbonyl compounds and by a panel of trained tasters. The UF Carbosep M1 membrane was the most suitable for softening the oil organoleptic features. Carbosep UF M1 and MF M14 membranes also induced a reduction of the content of total chlorophyll, which certainly slowed down the oil oxidation processes. It should be considered, however, that the observed decrease in the content of phenolic compounds with Carbosep M1 might have an adverse affect on the oil's stability to oxidation, but the observed decrease in total chlorophyll content should oppose it.
Effect of Citrus essential oil addition upon growth and cellular lipids of Yarrowia lipolytica yeast
Authors: Papanikolaou Seraphim , Gortzi Olga , Margeli Eleni , Chinou Ioanna , Galiotou‐Panayotou Maria , Lalas Stavros
Published: October 2008

The chemical composition of the essential oil from fruits of the Greek citrus hybrid Citrus sinensis cv New Hall – Citrus aurantium was investigated by GC and GC‐MS. Forty‐four compounds were identified, representing 92.83% of the total oil. Limonene, myrcene, β‐pinene, α‐pinene and α‐terpineol constituted the major components of the oil. The effect of the addition of this oil upon the behavior of Yarrowia lipolytica yeast was also investigated. The microorganism was aerobically grown on glucose and oil was added to the culture medium in various initial quantities (from 0.0 to 1.5 mL/L). The strain underwent significant inhibition exerted by the added essential oil; a decrease of the highest achieved biomass concentration, even if the oil was added to the culture medium at small concentrations (e.g. 0.3 mL/L), was observed. The more oil was added, the more the lag phase of the growth increased, while the biomass yield on glucose consumed decreased with the addition of the oil. When the essential oil was added to the medium, even at small concentrations, a significant increase of cellular medium‐chain saturated fatty acids (12:0 and 14:0) resulting in an increase of saturated fatty acid content in the cellular lipids, was observed.
Client‐driven load balancing through association control in IEEE 802.11 WLANs
Authors: Garcia Eduard , Ferrer Josep L. , Lopez‐Aguilera Elena , Vidal Rafael , Paradells Josep
Published: October 2008

The growth of IEEE 802.11 wireless local area networks (WLANs) (Wi‐Fi) brings new possibilities of getting connected in public spaces, known as Hot Spots. Current client‐access point associations are an interesting research topic because in these scenarios, users tend to be ‘gregarious’ and essentially static. Under IEEE 802.11 standards, association and roaming decisions are made by client devices and most implementations are based on signal strength measurements; i.e. a client station selects the access point (AP) that provides the strongest signal, which leads to an uneven distribution of clients and load between neighbouring APs. As it can be observed in practical scenarios, the default AP‐client association scheme followed in IEEE WLANs, produces unfair situations. This work provides means to effectively alleviate this performance issue and also gives details for a feasible implementation. In this paper we analyse how new IEEE 802.11 standards will allow new radio measurements to provide more efficient association decisions. We propose a new load metric that will produce client‐driven associations that ensure greater fairness and throughput. Copyright © 2008 John Wiley & Sons, Ltd.
Der Komponist mit dem Januskopf
Authors: Konrad Ulrich
Published: October 2008

Das Schaffen Winfried Zilligs und anderer namhafter Musiker nach 1933 war von kaum begreifbaren Widersprüchen geprägt: Die künstlerisch‐ambitionierte Moderne stand neben der anspruchslosen Anbiederung an Ideologie und Propaganda
Zürcher Zuteilung
Authors: Pukelsheim Friedrich
Published: October 2008

Wie die Stochastik einer alten Demokratie ein neues Wahlsystem beschert
A reach‐scale biogeochemical model for temporary rivers
Authors: Tzoraki Ourania , Nikolaidis Nikolaos P. , Trancoso Anna Rosa , Braunschweig Frank , Neves Ramiro
Published: October 2008

The RS‐tempQ Model (reach–scale temporary flow biogeochemical model) is a conceptual model that can describe the hydrologic, sediment transport and biogeochemical processes of temporary rivers at the reach scale. The model takes into account the expansion–contraction of the inundated area of the river. It simulates the sediment transport and the nutrient fluxes that are transferred to the coastal area due to the first flash flood and during extreme rain events. The RS‐tempQ Model simulates the in‐stream processes during the wet and dry cycles as the river corridor expands and contracts. The model was used to assess and quantify the hydrologic and geochemical processes occurring in a temporary river reach (Krathis River) in Greece. Since the conventional gauging techniques cannot measure the flow in rivers that are split into small braided streams, discharge measurements could not be obtained in order to calibrate and verify the model. Other field measurements such as infiltration losses and sediment accumulation were used for model calibration. Copyright © 2008 John Wiley & Sons, Ltd.
Measuring snow accumulation and ablation dynamics during rain‐on‐snow events: innovative measurement techniques
Authors: Floyd William , Weiler Markus
Published: October 2008

Rain‐on‐snow (ROS) is the primary generator of peak flow events in mountainous coastal regions of North America. Uncertainty remains as to the role of forest canopy interception leading up to and during ROS events. Much of this uncertainty can be attributed to a lack of suitable techniques to collect data during ROS, due in part to the dynamic nature of climatic conditions, particularly related to snow accumulation and melt. We supplemented a meteorological network with non‐weighing snow melt lysimeters, suspended spring scales to measure snow throughfall and an automated time lapse photography network to monitor state of precipitation (rain vs. snow), snow accumulation/ablation, canopy interception and unloading of snow from the canopy. Image analysis software allowed for the extraction of data from images. Rapid loading and unloading of snow from the canopy, closely linked to changes in temperature, was observed using this approach. We were also able to continuously monitor throughfall snow water equivalent using low cost suspended spring scales. This experimental design allowed us to capture information previously unavailable without direct observation. Copyright © 2008 John Wiley & Sons, Ltd.
Dynamics of the Conformal‐Cubic Atmospheric Model projected climate‐change signal over southern Africa
Authors: Engelbrecht F. A. , McGregor J. L. , Engelbrecht C. J.
Published: October 2008

The projected climate‐change signal in simulations by the Conformal‐Cubic Atmospheric Model (CCAM) over southern Africa is presented, with particular emphasis on the projected changes in circulation over the region. Current (1975–2005) and future (2070–2100; A2 scenario) climate simulations are used for this purpose.

In the austral winter of the future climate, frontal rain bands are displaced to the south as a result of the subtropical high‐pressure belt intensifying to the south of the subcontinent. In spring and autumn, mid‐ and upper‐level highs are simulated to become more prominent over the eastern and central parts of southern Africa. The enhanced subsidence associated with these systems results in generally lower rainfall totals over much of the south‐eastern subcontinent. To the north of these highs, enhanced westward moisture advection contributes to increased rainfall totals over northern Mozambique, whilst along the western periphery of the anomalously strong highs, enhanced southward moisture advection results in higher rainfall totals over Namibia, Botswana and the central and western interior of South Africa. In mid‐summer, the Indian Ocean High (IOH) is simulated to intensify most over the south‐western Indian Ocean (IO). This seemingly results in the more frequent occurrence of the cloud bands that constitute the South Indian Convergence Zone (SICZ) over the south‐eastern subcontinent—resulting in generally wetter conditions over this region. Copyright © 2008 Royal Meteorological Society
The transpatellar approach for the knee in the laboratory
Authors: Merican Azhar M. , Ghosh Kanishka M. , Deehan David J. , Amis Andrew A.
Published: October 2008

This paper describes a longitudinal patellar‐splitting approach to the knee that includes provision for accurate reconstruction. Our in vitro experiments showed that patellofemoral kinematics and length‐change patterns of specific bands of the peripatellar retinacula were not changed significantly by opening and closing the knee via the transpatellar approach. This surgical approach will be useful for in vitro experiments on the knee, when effects due to alterations of internal structures such as cruciate ligament reconstructions or joint replacement are to be studied, avoiding confounding effects caused by changes to the retinacula. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:330–334, 2009
Contributions of different intraarticular tissues to the acute phase elevation of synovial fluid MMP‐2 following rat ACL rupture
Authors: Tang Zhenyu , Yang Li , Wang Yequan , Xue Ruyue , Zhang Jin , Huang Wei , Chen Peter C. , Sung K.‐L. Paul
Published: October 2008

Inflammation and accumulation of matrix metalloproteinases (MMPs) in synovial fluids may be involved in the poor healing ability of the anterior cruciate ligament (ACL) after injury. With a rat ACL rotating injury model, we found that levels of IL‐1β, IL‐6, and TNF‐α were significantly higher in synovial fluids after ACL injury. MMP‐2 activity and global MMP activity in synovial fluids also increased significantly in a time‐dependent manner. Ex vivo studies showed that all tissues contributed to the elevation of MMP‐2 in synovial fluids, especially synovium and the injured ACL. We concluded that although the regular wound‐healing mechanism also occurs after ACL injury, accumulation of MMP activity in the synovial fluids, due to all of the intraarticular tissues, may be at least one of the important reasons why an injured ACL cannot be repaired. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:243–248, 2009
Shear fatigue micromechanics of the cement–bone interface: An in vitro study using digital image correlation techniques
Authors: Mann Kenneth A. , Miller Mark A. , Race Amos , Verdonschot Nico
Published: October 2008

Loss of fixation at the cement–bone interface is known to contribute to aseptic loosening, but little is known about the mechanical damage response of this interface. An in vitro study using cement–bone specimens subjected to shear fatigue loading was performed, and the progression of stiffness changes and creep damage at the interface was measured using digital image correlation techniques. Stiffness changes and creep damage were localized to the contact interface between cement and bone. Interface creep damage followed a three‐phase response with an initial rapid increase in creep, followed by a steady‐state increase, concluding in a final rapid increase in creep. The initial creep phase was accompanied by an increase in interface stiffness, suggesting an initial locking‐in effect at the interface. Interface stiffness decreased as creep damage progressed. Power law models were reasonably successful in describing the creep and stiffness damage response and were a function of loading magnitude, number of loading cycles, and contact area at the interface. More microcrack damage occurred to the cement when compared to the bone, and the damage was localized along the interface. These findings indicate that damage to the cement–bone interface could be minimized by improving cement–bone contact and by strengthening the fatigue resistance of the cement. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:340–346, 2009