bluuebunny/crossref_metadata_2025_split huggingface dataset:
NAT2variation and idiopathic talipes equinovarus (clubfoot)
Authors: Hecht Jacqueline T. , Ester Audrey , Scott Allison , Wise Carol A. , Iovannisci David M. , Lammer Edward J. , Langlois Peter H. , Blanton Susan H. 
Published: August 2007

AbstractIdiopathic talipes equinovarus (ITEV), or isolated clubfoot, is a common developmental anomaly that is characterized by a rigid foot, adducted forefoot, cavus midfoot, equinovarus of the hindfoot, and hypoplastic calf musculature. The etiology of this common birth defect is largely unknown, but genetic factors have been implicated in population and family studies and maternal smoking during pregnancy has been identified as an environmental risk factor. The biotransformation of exogenous substances, such as tobacco smoke, is modulated by numerous genes includingN‐acetylation genes,NAT1andNAT2. Functional variants of these genes exist and can be distinguished by genotyping. We hypothesized that variation inNAT1andNAT2genes might be associated with ITEV. To test this hypothesis,NAT1andNAT2were genotyped in a sample of 56 multiplex ITEV families, 57 trios with a positive family history and 160 simplex trios with ITEV. The results detected a slight decrease in the expected number of homozygotes for theNAT2normal allele in the Hispanic simplex trios. In addition, in a pilot case–control study of ITEV, there were significantly more slowNAT2acetylators among the cases. This suggests that slow acetylation may be a risk factor for ITEV. This study is the first to find evidence suggesting a role for a biotransformation candidate gene in the etiology of ITEV and provides a scientific foundation to further explore the contributions of other tobacco metabolism genes in the etiology of clubfoot. © 2007 Wiley‐Liss, Inc.
Die Jagd auf Palau'amin
Authors: Köck Matthias , Grube Achim , Seiple Ian B. , Baran Phil S. 
Published: August 2007

AbstractSeit der Entdeckung im Jahr 1993 hat Palau'amin die Naturstoffchemiker fasziniert. Seine ungewöhnliche Molekülstruktur und die beschriebene biologische Aktivität machen diesen marinen Naturstoff zu einem lohnenden Ziel für die organische Synthese. Im Laufe der Jahre und im Zusammenhang mit der Isolierung verwandter mariner Alkaloide wurde die postulierte chemische Struktur von Palau'amin angezweifelt, und vor kurzem wurde die relative Konfiguration von Palau'amin schließlich revidiert. Dieser Kurzaufsatz gibt eine sorgfältige Übersicht über die Strukturrevision und deren Bedeutung für die Biosynthese sowie die Totalsynthese.
The Pursuit of Palau'amine
Authors: Köck Matthias , Grube Achim , Seiple Ian B. , Baran Phil S. 
Published: August 2007

AbstractSince its discovery in 1993, the marine natural product palau'amine has intrigued natural product chemists. Its exotic molecular architecture and purported bioactivity made it an ideal target for synthesis. However, as the years went by and related marine alkaloids were isolated, a skeptical eye was cast on the structure of palau'amine; recently these suspicions were confirmed and the structure of palau'amine revised. This Minireview gives a careful overview of the structural revision and its ramifications to both its biogenesis and total synthesis.
Stationary statistical properties of Rayleigh‐Bénard convection at large Prandtl number
Authors: Wang Xiaoming 
Published: August 2007

AbstractThis is the third in a series of our study of Rayleigh‐Bénard convection at large Prandtl number. Here we investigate whether stationary statistical properties of the Boussinesq system for Rayleigh‐Bénard convection at large Prandtl number are related to those of the infinite Prandtl number model for convection that is formally derived from the Boussinesq system via setting the Prandtl number to infinity. We study asymptotic behavior of stationary statistical solutions, or invariant measures, to the Boussinesq system for Rayleigh‐Bénard convection at large Prandtl number. In particular, we show that the invariant measures of the Boussinesq system for Rayleigh‐Bénard convection converge to those of the infinite Prandtl number model for convection as the Prandtl number approaches infinity. We also show that the Nusselt number for the Boussinesq system (a specific statistical property of the system) is asymptotically bounded by the Nusselt number of the infinite Prandtl number model for convection at large Prandtl number. We discover that the Nusselt numbers are saturated by ergodic invariant measures. Moreover, we derive a new upper bound on the Nusselt number for the Boussinesq system at large Prandtl number of the form

which asymptotically agrees with the (optimal) upper bound on Nusselt number for the infinite Prandtl number model for convection. © 2007 Wiley Periodicals, Inc.
Obtaining upper bounds of heat kernels from lower bounds
Authors: Grigor′yan Alexander , Hu Jiaxin , Lau Ka‐Sing 
Published: August 2007

AbstractWe show that a near‐diagonal lower bound of the heat kernel of a Dirichlet form on a metric measure space with a regular measure implies an on‐diagonal upper bound. If in addition the Dirichlet form is local and regular, then we obtain a full off‐diagonal upper bound of the heat kernel provided the Dirichlet heat kernel on any ball satisfies a near‐diagonal lower estimate. This reveals a new phenomenon in the relationship between the lower and upper bounds of the heat kernel. © 2007 Wiley Periodicals, Inc.
A nondisplaceable Lagrangian torus in T*S2
Authors: Albers Peter , Frauenfelder Urs 
Published: August 2007

AbstractWe show that the Lagrangian torus in the cotangent bundles of the 2‐sphere obtained by applying the geodesic flow to the unit circle in a fiber is not displaceable by computing its Lagrangian Floer homology. The computation is based on a symmetry argument. © 2007 Wiley Periodicals, Inc.
Sofic groups and diophantine approximation
Authors: Thom Andreas 
Published: August 2007

AbstractWe prove the algebraic eigenvalue conjecture of J. Dodziuk, P. Linnell, V. Mathai, T. Schick, and S. Yates (see [2]) for sofic groups. Moreover, we give restrictions on the spectral measure of elements in the integral group ring. Finally, we define integer operators and prove a quantization of the operator norm below 2. To the knowledge of the author, there is no group known that is not sofic. © 2007 Wiley Periodicals, Inc.
Synthesis, Structure and Magnetic Properties of a Novel Hexanuclear Copper Methylsiloxane Complex
Authors: Zherlitsyna Larissa , Auner Norbert , Bolte Michael , Pozdniakova Yulia , Shchegolikhina Olga , Lyssenko Konstantin , Pashchenko Vladimir , Wolf Bernd , Lang Michael , Schütz Florian , Kollar Marcus , Sauli Francesca , Kopietz Peter 
Published: August 2007

AbstractA new hexanuclear copper(II) sandwich complex based on two 12‐membered macrocyclic methylsiloxanolate ligands, [Cu6{(MeSiO2)6}2]·6DMF, was synthesized and characterized by single‐crystal X‐ray diffraction analysis and magnetic measurements. The cluster compound crystallizes in the monoclinic system, space group P21/n (No. 14), with a = 13.3728(5) Å, b = 15.4281(7) Å, c = 17.4335(7) Å, β = 98.932(3)° and Z = 2. The unit cell contains two identical molecular clusters, each consisting of six interacting Cu2+ (S = ${1 \over 2}$) ions. Within the cluster the six oxygen‐bridged Cu2+ ions are arranged in an almost regular hexagon. An analysis of the high‐temperature part of the magnetic susceptibility reveals that the complex has a strong average ferromagnetic Cu–Cu exchange interaction of |Jav/kB| = (50.4 ± 1) K with a high‐spin S = 3 ground state. A satisfactory fit for the magnetic susceptibility and the magnetization in the whole accessible temperature range is obtained from a Heisenberg model with nonuniform exchange couplings within a ring, corresponding to a system of two weakly coupled trimers with a ferromagnetic intratrimer exchange coupling of |J/kB| = 72.5 K and a ferromagnetic intertrimer exchange coupling of |J′/kB| = 7 K. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Synthesis and Structure of Self‐Complementary {2}‐Metallacryptates and Their Linear or Meandering Infinite Arrangements in the Solid State
Authors: Saalfrank Rolf W. , Mooren Nicolai , Scheurer Andreas , Maid Harald , Heinemann Frank W. , Hampel Frank , Bauer Walter 
Published: August 2007

AbstractReaction of bis(1,3‐diketone) H2L1 in the presence of cesium acetate with magnesium acetate yielded crystalline one‐dimensional coordination polymer rac‐(2)n. The {2}‐metallacryptand core [Mg2(L1)3]2– is composed of two magnesium centres linked through three bis(1,3‐diketo) dianions (L1)2–. These {2}‐metallacryptands are homochiral with either (Δ,Δ)‐fac or (Λ,Λ)‐fac stereochemistry at the magnesium centres, and they are capable to host a cesium ion in the cavity. Charge compensation of the thus formed {2}‐metallacryptates {Cs⊂[Mg2(L1)3]}– is achieved through extra external cesium ions to give the neutral self‐complementary building blocks [{Cs⊂[(Δ,Δ)/(Λ,Λ)‐Mg2(L1)3]}Cs], which aggregate end‐on across the external cesium ions to give the homochiral one‐dimensional strings [{Cs⊂[(Δ,Δ)‐Mg2(L1)3]}Cs]n [Δ‐(2)n] and [{Cs⊂[(Λ,Λ)‐Mg2(L1)3]}Cs]n [Λ‐(2)n], which are packed in the crystal in alternating homochiral layers. However, reaction of bulkier phenyl‐substituted bis(1,3‐diketone) H2L2 instead of methyl‐substituted H2L1 with cesium or rubidium acetate and magnesium, cobalt or zinc acetate yielded the meandering polymer meso‐{[({M1⊂[(Δ,Δ)‐M22(L2)3]}M1end)({M1⊂[(Λ,Λ)‐M22(L2)3]}M1side)][({M1⊂[(Λ,Λ)‐M22(L2)3]}M1end)({M1⊂[(Δ,Δ)‐M22(L2)3]}M1side)]}n [meso‐(3)n] (M1 = Cs+, Rb+; M2 = Mg2+, Co2+, Zn2+). In this case, the {2}‐metallacryptates {M1⊂[(Δ,Δ/Λ,Λ)‐M22(L2)3]}– are linked by only one cesium ion end‐on to give the fragments meso‐[({M1⊂[(Δ,Δ)‐M22(L2)3]}M1end)({M1⊂[(Λ,Λ)‐M22(L2)3]}M1side)], which are connected by the second cesium ions side‐on. The one‐dimensional meander strands of isostructural meso‐(3)n are packed in the crystal in parallel. Reaction of 4 equiv. of zinc acetate and 1 equiv. of cesium or rubidium acetate with 2 equiv. of H2L2 afforded the {M1⊂[Zn2(L2)2OAc]} cryptates 4a,b (M1 = Cs+, Rb+). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Radical Cations in Electrospray Mass Spectrometry: Formation of Open‐Shell Species, Examination of the Fragmentation Behaviour in ESI‐MSn and Reaction Mechanism Studies by Detection of Transient Radical Cations
Authors: Schäfer Mathias , Drayß Miriam , Springer Andreas , Zacharias Philipp , Meerholz Klaus 
Published: August 2007

AbstractThe ion formation mechanism in electrospray MS is reviewed, with special focus on the electrochemical red/ox reactions responsible for the formation of radical molecular ions. Prerequisites influencing the likelihood of formation and observation of a particular compound as an open‐shell molecular species in ESI‐MS (i.e., the structure and the oxidation potential of the analyte, the solvent and additives) are evaluated. For illustration of the ESI phenomena governing radical cation formation, an ESI‐MS study of tetra(aryl)benzidine compounds is presented. The facile formation of abundant radical molecular cations in ESI‐MS demonstrates imposingly that the basicity of the analyte's nitrogen atoms is strongly overcompensated by the ability to stabilize unpaired electrons. ESI‐MSn spectra of the tetra(aryl)benzidine molecular ions exhibit a characteristic feature in the loss of radicals. This process is the major fragmentation pathway of open‐shell molecular precursor ions in their MS2 spectra, and also that of even‐electron ions in sequential MSn spectra. The collision‐induced dissociation (CID) behaviour suggests a general assumption: easily oxidizable compounds (e.g., hydrocarbon polyenes, polycyclic aromatic hydrocarbons, porphyrins etc.) generating predominantly molecular radical cations in ESI‐MS contradict the even electron rule in ESI‐MSn experiments. The strong ability to stabilize unpaired electrons is preserved in product ions and makes the formation of open‐shell species energetically less demanding. A selection of solution‐phase reaction mechanistic studies in which open‐shell intermediates were detected and structurally characterized by ESI‐MS and ESI‐MS/MS, respectively, is presented. The merits of ESI‐MS and ESI‐MSn for mechanistic studies of chemical reaction are critically discussed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Synthesis of the Carbon Framework of the Stephaoxocanes Employing a Sequential RCM/Pomeranz–Fritsch Approach
Authors: Bracca Andrea B. J. , Kaufman Teodoro S. 
Published: August 2007

AbstractThe syntheses of two cyclodeca[ij]isoquinoline derivatives, which embody the carbon framework of stephaoxocanidine, excentricine and the recently isolated stephalonganines A, B and C, are reported. The target tricyclic compounds were prepared from isovanillin, employing a ring‐closing metathesis approach towards the synthesis of a benzocyclodecane‐type common intermediate; different modifications of thePomeranz–Fritsch protocol allowed the installation of the heterocyclic ring.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Hydrophobically Directed Aldol Reactions: Polystyrene‐Supported L‐Proline as a Recyclable Catalyst for Direct Asymmetric Aldol Reactions in the Presence of Water
Authors: Gruttadauria Michelangelo , Giacalone Francesco , Mossuto Marculescu Adriana , Lo Meo Paolo , Riela Serena , Noto Renato 
Published: August 2007

AbstractA simple synthetic methodology for the preparation of a polystyrene‐supported L‐proline material is reported, and this material has been used as catalyst in direct asymmetric aldol reactions between several ketones and arylaldehydes to furnish aldol products in high yields and stereoselectivities. Screening of solvents showed that these reactions take place only in the presence of water or methanol, at lower levels of conversion in the latter case. This solvent effect, coupled with the observed high stereoselectivities, has been explained in terms of the formation of a hydrophobic core in the inner surface of the resin, whereas the hydrophilic proline moiety lies at the resin/water interface. Such a microenvironment both promotes the aldol reaction and increases the stereoselectivity. Recycling investigations have shown that this material can be reused, without loss in levels of conversion and stereoselectivity, for at least five cycles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Automatic Voltammetric System for Continuous Trace Metal Monitoring in Various Environmental Samples
Authors: Mikkelsen Øyvind , Strasunskiene Kristina , Skogvold Silje , Schrøder Knut H. , Johnsen Camilla Constance , Rydningen Marion , Jonsson Patrik , Jonsson Anders 
Published: August 2007

AbstractSome recent developments and results in the field of automatic monitoring of electrolabile concentration of zinc and iron in the low μg/L range in river water, drainage water, and waste water by use of solid dental amalgam electrode (DAM) as a working electrode are reviewed for three different geographical sites representing the mentioned matrixes. At all sites, voltammetric measurements were carried out continuously every 30 or 60 minutes for periods up to 4 months, and compared with total amounts of the metals found by ICP‐MS on manually collected samples. In total, the observed concentration ranges analyzed was in the ranges of sub‐μg/L to approximately 30 μg/L for zinc, and from approximately 1 μg/L to 150 μg/L. for iron. Results shows good calibration curves for the metals in the different matrixes (r2avg=0.99) with standard deviation within 5%. The voltammetric system showed good stability and gave reliable results which were in a reasonable agreement with ICP‐MS measurements for all analyses when comparing the concentration trends. The frequency of maintenance varied from once a week in waste water samples to once a month in river water.
Electrochemical Sensing of Chromium‐Induced DNA Damage: DNA Strand Breakage by Intermediates of Chromium(VI) Electrochemical Reduction
Authors: Vacek Jan , Mozga Tomáš , Cahová Kateřina , Pivoňková Hana , Fojta Miroslav 
Published: August 2007

AbstractDNA damage by CrV and/or CrIV intermediates of CrVI electrochemical reduction was detected using a supercoiled DNA‐modified mercury electrode. A signal sensitive to formation of DNA strand breaks, AC voltammetric DNA peak 3, increased due to incubation of the DNA‐modified electrode in micromolar solutions of CrVI at potentials sufficiently negative for CrVI reduction. Damage to DNA in solutions containing CrVI and a chemical reductant (ascorbic acid, AA) was observed only at relatively high chromium concentrations (hundreds of μM). To eliminate interferences of excess CrVI in measurements of guanine electrochemical signals, a magnetoseparation double surface electrochemical technique was introduced. Using this approach, DNA damage in solution was detected for 50–250 μM CrVI upon addition of 1 mM AA. Our results suggest a more efficient DNA damage at the electrode surface due to continuous production of the reactive chromium species, compared to DNA exposure to chromium being reduced chemically in solution.
Synthesis of Polyoxometalate‐Protected Gold Nanoparticles by a Ligand‐Exchange Method: Application to the Electrocatalytic Reduction of Bromate
Authors: Ernst Andrzej Z. , Sun Laisheng , Wiaderek Kamila , Kolary Aneta , Zoladek S. , Kulesza Pawel J. , Cox James A. 
Published: August 2007

AbstractGold nanoparticles (AuNPs) protected by an alkanethiol in nonaqueous solvent are converted to AuNPs with a surrounding layer of a polyoxometalate, AuNP‐POM, by ligand exchange and liquid–liquid extraction into aqueous solution without changing the size of the metal core. With glassy carbon electrodes modified with PMo12‐AuNP (PMo12=H3PMo12O40), the reduction of bromate was mediated by the first redox process of the MoVI centers; the reduction occurred at a lower overpotential and yielded a higher cathodic current than that observed with PMo12 alone as the mediator. This synergistic electrocatalysis, which approached a linear diffusion‐controlled process, was used to demonstrate the feasibility of the determination of bromate. A detection limit of 3 μM (k=3 criterion) was achieved by pulse voltammetry.
Electrochemical Analysis of D‐Penicillamine Using a Carbon Paste Electrode Modified with Ferrocene Carboxylic Acid
Authors: Raoof Jahan‐Bakhsh , Ojani Reza , Chekin Freshteh 
Published: August 2007

AbstractThe electrochemical behavior of D‐penicillamine (D‐PA) studied at the surface of ferrocene carboxylic acid modified carbon paste electrode (FCAMCPE) in aqueous media using cyclic voltammetry and double step potential chronoamperometry. It has been found that under optimum condition (pH 7.00), the oxidation of D‐PA at surface of such an electrode is occurred about 420 mV less positive than that an unmodified carbon paste electrode (CPE). The catalytic oxidation peak current was linearly dependent on the D‐PA concentration and a linear calibration curve was obtained in the ranges 7.5×10−5 M – 1.0×10−3 M and 6.5×10−6 M−1.0×10−4 M of D‐PA with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods respectively. The detection limits (3σ) were determined as 6.04×10−5 M and 6.15×10−6 M. This method was also used for the determination of D‐PA in pharmaceutical preparation (capsules) by standard addition method.
Comparative Studies of Quercetin Interactions with Monophosphate Nucleotides Using UV‐Vis Spectroscopy and Electrochemical Techniques
Authors: Kikandi Samuel N. , Musah Samira , Lee Kyoungyun , Hassani John , Rajan Shawn , Zhou Ailing , Sadik Omowunmi. A. 
Published: August 2007

AbstractThe nature and extent of the interactions of phytoestrogens such as quercetin (Q) with monophosphate nucleotides have implications in cell cycle arrest, DNA damage, and inhibition of intracellular enzymes involved with cell proliferation. We have studied the interactions of quercetin with individual RNA/DNA monophosphate nucleotides using UV‐vis spectroscopy, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) under physiological conditions. The monophosphate nucleotides studied included: guanosine 5‐monophosphate (GMP), adenosine 5‐monophosphate (AMP), deoxythymidine 5‐monophosphate (TMP), and cytidine 5‐monophosphate (CMP). Based on the characteristic absorption spectra isobestic points, hypochromism phenomenon, electrochemical shifts in peak potential and the changes in forward‐to reverse peak currents (Δ Ipc/Ipa), the order of the affinity recorded was GMP>AMP>TMP>CMP respectively. The % Δ Ipc/Ipa recorded were 42.8, 78.6, 57.1, and 21.4 for Q:AMP, Q:GMP, Q:TMP, and Q:CMP respectively, indicating an overall higher affinity for the purine nucleotides which is consistent with UV‐vis results. The DPV data showed that the peak potentials shifted more positive with a simultaneous decrease in peak currents with increasing nucleotide concentrations, which were attributed to the Q‐nucleotide adduct formation.
About 20 Years of Silicon‐Based Thin‐Film Sensors with Chalcogenide Glass Materials for Heavy Metal Analysis: Technological Aspects of Fabrication and Miniaturization
Authors: Schöning Michael J. , Kloock Joachim P. 
Published: August 2007

AbstractChalcogenide glass materials as membranes for potentiometric sensors for chemical analysis in solutions, e.g., ion‐selective electrodes, have been studied for more than three decades. Already in the 1970's, first papers dealt with the ion‐sensing properties of chalcogenide glasses, followed by systematic investigations of their solid‐state chemistry, the sensing mechanism and their analytical characteristics. Combining the analytical performance of chalcogenide glass membranes with techniques originally invented for semiconductor processing, a new generation of silicon‐based thin‐film sensors with chalcogenide glass materials for heavy metal detection has been created. In the beginning, co‐sputtering of Cu and As2Se3 resulted in a Cu2+‐selective field‐effect sensor, while in recent years, a variety of chalcogenide glass materials have been stoichiometrically deposited onto ISFETs (ion‐sensitive field‐effect transistor), EIS (electrolyte‐insulator‐semiconductor), LAPS (light‐addressable potentiometric sensor) and μISE structures, respectively, serving as miniaturized chemical sensors. The present review paper is devoted to research and development in the field of silicon‐based thin‐film sensors with chalcogenide glass materials and emphasizes technological aspects of fabrication and miniaturization within the last 20 years.
Stripping Chronopotentiometry in Environmental Analysis
Authors: Serrano Núria , Díaz‐Cruz José Manuel , Ariño Cristina , Esteban Miquel 
Published: August 2007

AbstractA review with 101 references on the applications of stripping chronopotentiometry (SCP) to environmental analysis since its development in 1976 is presented. The references are classified into three categories: i) determination of total concentrations of elements, ii) element speciation analyses and iii) theoretical and experimental methods for the study of heavy metal complexation/speciation in the environment. Additionally, some concluding remarks are given and future perspectives of environmental SCP are discussed.