bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wilcoxon–Mann–Whitney Test
Authors: Moses Lincoln E. 
Published: October 2008

AbstractThis 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

Abstract
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

AbstractIn 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

Abstract

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

AbstractWe 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

AbstractThe 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

AbstractTransfer 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractNach 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

AbstractThe 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

AbstractDevelopment 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

AbstractReactions 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

AbstractThe 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

AbstractIn 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

AbstractVor 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

AbstractTabak 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

AbstractDer 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

AbstractA 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.