bluuebunny/crossref_metadata_2025 huggingface dataset:
The Pursuit of Palau'amine
Authors: Köck Matthias , Grube Achim , Seiple Ian B. , Baran Phil S.
Published: August 2007

Since 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

This 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

We 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

We 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

We 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

A 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

Reaction 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

The 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

The 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

A 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

Some 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

DNA 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

Gold 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

The 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

The 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

Chalcogenide 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

A 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.
Amperometric Glucose Biosensor Based on Glucose Oxidase Encapsulated in Carbon Nanotube–Titania–Nafion Composite Film on Platinized Glassy Carbon Electrode
Authors: Choi Han Nim , Han Jee Hoon , Park Ji Ae , Lee Joong Min , Lee Won‐Yong
Published: August 2007

A highly sensitive and selective glucose biosensor has been developed based on immobilization of glucose oxidase within mesoporous carbon nanotube–titania–Nafion composite film coated on a platinized glassy carbon electrode. Synergistic electrocatalytic activity of carbon nanotubes and electrodeposited platinum nanoparticles on electrode surface resulted in an efficient reduction of hydrogen peroxide, allowing the sensitive and selective quantitation of glucose by the direct reduction of enzymatically‐liberated hydrogen peroxide at −0.1 V versus Ag/AgCl (3 M NaCl) without a mediator. The present biosensor responded linearly to glucose in the wide concentration range from 5.0×10−5 to 5.0×10−3 M with a good sensitivity of 154 mA M−1cm−2. Due to the mesoporous nature of CNT–titania–Nafion composite film, the present biosensor exhibited very fast response time within 2 s. In addition, the present biosensor did not show any interference from large excess of ascorbic acid and uric acid.
Symptom severity and treatment course of bulimic patients with and without a borderline personality disorder
Authors: Zeeck A. , Birindelli E. , Sandholz A. , Joos A. , Herzog T. , Hartmann A.
Published: August 2007

There are contradictory results concerning the frequency of borderline personality disorder (BPD) in bulimic patients and its impact on eating pathology and treatment outcome. We evaluated 240 patients with bulimia nervosa using EDI‐2, SIAB and SCL‐90‐R. Only a minority of patients had a BPD (13.8%). There were no differences in binging or purging behaviour between patients with and without BPD, but borderline patients had significantly more feelings of ineffectiveness and more disturbances in interoceptive awareness. Bulimic patients with BPD showed significantly more general psychopathology. Although, BPD patients started with higher levels of pathology, there were similar reductions of symptoms over the course of treatment in both groups. Psychotherapy in bulimic patients with a BPD has to focus not only on eating pathology but also on aspects that are caused by the severe personality disturbance. Copyright © 2007 John Wiley & Sons, Ltd and Eating Disorders Association.
Gorilla society: What we know and don't know
Authors: Harcourt A. H. , Stewart K. J.
Published: August 2007

Science is fairly certain that the gorilla lineage separated from the remainder of the hominoid clade about eight million years ago,2, 4 and that the chimpanzee lineage and hominin clade did so about a million years after that.1, 2 However, just this year, 2007, it was discovered that although the human head louse separated from the congeneric chimpanzee body louse (Pediculus) around the same time as the chimpanzee and hominin lineages split,3 the human pubic louse apparently split from its sister species, the congeneric gorilla louse, Pthirus, 4.5 million years after their host lineages split.3 No tested explanations exist for the discrepancy. Much is known about hominin evolution, but much remains to be discovered. The same is true of primate socioecology in general and gorilla socioecology in particular.
Genetic changes in the evolution of multidrug resistance for cultured human ovarian cancer cells
Authors: Buys Timon P. H. , Chari Raj , Lee Eric H. L. , Zhang May , MacAulay Calum , Lam Stephen , Lam Wan L. , Ling Victor
Published: August 2007

The multidrug resistant (MDR) phenotype is often attributed to the activity of ATP‐binding cassette (ABC) transporters such as P‐glycoprotein (ABCB1). Previous work has suggested that modulation of MDR may not necessarily be a single gene trait. To identify factors that contribute to the emergence of MDR, we undertook integrative genomics analysis of the ovarian carcinoma cell line SKOV3 and a series of MDR derivatives of this line (SKVCRs). As resistance increased, comparative analysis of gene expression showed conspicuous activation of a network of genes in addition to ABCB1. Functional annotation and pathway analysis revealed that many of these genes were associated with the extracellular matrix and had previously been implicated in tumor invasion and cell proliferation. Further investigation by whole genome tiling‐path array CGH suggested that changes in gene dosage were key to the activation of several of these overexpressed genes. Remarkably, alignment of whole genome profiles for SKVCR lines revealed the emergence and decline of specific segmental DNA alterations. The most prominent alteration was a novel amplicon residing at 16p13 that encompassed the ABC transporter genes ABCC1 and ABCC6. Loss of this amplicon in highly resistant SKVCR lines coincided with the emergence of a different amplicon at 7q21.12, which harbors ABCB1. Integrative analysis suggests that multiple genes are activated during escalation of drug resistance, including a succession of ABC transporter genes and genes that may act synergistically with ABCB1. These results suggest that evolution of the MDR phenotype is a dynamic, multi‐genic process in the genomes of cancer cells. © 2007 Wiley‐Liss, Inc.
The putative tumor suppressor AIM2 is frequently affected by different genetic alterations in microsatellite unstable colon cancers
Authors: Woerner Stefan M. , Kloor Matthias , Schwitalle Yvette , Youmans Hanni , Doeberitz Magnus von Knebel , Gebert Johannes , Dihlmann Susanne
Published: August 2007

Mismatch repair (MMR) deficiency is a major mechanism of colorectal tumorigenesis that is observed in 10–15% of sporadic colorectal cancers and those associated with the hereditary nonpolyposis colorectal cancer (HNPCC) syndrome. MMR deficiency leads to the accumulation of mutations mainly at short repetitive sequences termed microsatellites, constituting the high level microsatellite instability (MSI‐H) phenotype. In recent years, several genes have been described that harbor microsatellites in their coding region (coding microsatellites, cMS) and are frequently affected by mutations in MMR‐deficient cancers. However, evidence for a functional role of most of the known cMS‐containing genes is missing, and further analyses are needed for a better understanding of MSI tumorigenesis. Here, we examined in detail alterations of the absent in melanoma 2 (AIM2) gene that shows a high frequency of cMS frameshift mutations in MSI‐H colorectal, gastric, and endometrial tumors. AIM2 belongs to the HIN‐200 family of interferon (IFN)‐inducible proteins, its role in colon carcinogenesis, however, is unknown. Sequencing of the entire coding region of AIM2 revealed a high frequency of frameshift and missense mutations in primary MSI‐H colon cancers (9/20) and cell lines (9/15). Biallelic AIM2 alterations were detected in 8 MSI‐H colon tumors and cell lines. In addition, AIM2 promoter hypermethylation conferred insensitivity to IFN‐γ‐induced AIM2 expression of three MSI‐H colon cancer cell lines. These results demonstrate that inactivation of AIM2 by genetic and epigenetic mechanisms is frequent in MMR‐deficient colorectal cancers, thus suggesting that AIM2 is a mutational target relevant for the progression of MSI‐H colorectal cancers. © 2007 Wiley‐Liss, Inc.
Simple procedure to simulate karstic aquifers
Authors: Padilla Alberto , Pulido‐Bosch Antonio
Published: August 2007

A procedure to simulate karstic aquifers is presented. It is based on a simulation of spring discharge using precipitation and, where necessary, temperature as input data. The karstic aquifer system is considered to be divided into three zones: the surface zone, the unsaturated zone (UZ) and the saturated zone (SZ). Each of these is described by a transfer function that determines the water supplied from the overlying zone. Water loss through evapotranspiration is calculated empirically and subtracted from the total precipitation in order to obtain the effective infiltration into the UZ. The transfer function characterizing the UZ can be expressed as a convolution function. The UZ acts as a buffer, delaying effective infiltration into the SZ. Water discharge from the SZ is described by the recession function of the spring, and this becomes the transfer function that characterizes the emergence of water from the SZ. The model permits the simulation of the influence of pumped abstractions from the system by a simple modification of the transfer functions involved. Copyright © 2007 John Wiley & Sons, Ltd.
Understanding hydrological processes with scarce data in a mountain environment
Authors: Chaponnière A. , Boulet G. , Chehbouni A. , Aresmouk M.
Published: August 2007

Performance of process‐based hydrological models is usually assessed through comparison between simulated and measured streamflow. Although necessary, this analysis is not sufficient to estimate the quality and realism of the modelling since streamflow integrates all processes of the water cycle, including intermediate production or redistribution processes such as snowmelt or groundwater flow. Assessing the performance of hydrological models in simulating accurately intermediate processes is often difficult and requires heavy experimental investments. In this study, conceptual hydrological modelling (using SWAT) of a semi‐arid mountainous watershed in the High Atlas in Morocco is attempted. Our objective is to analyse whether good intermediate processes simulation is reached when global‐satisfying streamflow simulation is possible. First, parameters presenting intercorrelation issues are identified: from the soil, the groundwater and, to a lesser extent, from the snow. Second, methodologies are developed to retrieve information from accessible intermediate hydrological processes. A geochemical method is used to quantify the contribution of a superficial and a deep reservoir to streamflow. It is shown that, for this specific process, the model formalism is not adapted to our study area and thus leads to poor simulation results. A remote‐sensing methodology is proposed to retrieve the snow surfaces. Comparison with the simulation shows that this process can be satisfyingly simulated by the model. The multidisciplinary approach adopted in this study, although supported by the hydrological community, is still uncommon. Copyright © 2007 John Wiley & Sons, Ltd.
Modelling canopy interception loss from a Madrean pine‐oak stand, northeastern Mexico
Authors: Carlyle‐Moses D. E. , Price A. G.
Published: August 2007

Throughfall associated with 34 rainfall events was measured from Year Day 1, 1999 to Year Day 184, 2001 within a pine‐oak stand of the central Sierra Madre Oriental mountain range of northeastern Mexico. Throughfall and canopy interception loss accounted for 83·6 ± 2·1% and 15·8 ± 1·8% (significance level, α, = 0·05) of the 691·8 mm cumulative rainfall input, respectively. A reformulated Gash analytical interception loss model and the Liu analytical model run with predetermined model parameters derived from the literature underestimated cumulative interception loss by 34·4%, and 37·1%, respectively. When the models were run with study period derived parameters the reformulated Gash model overestimated the observed interception by 3·0%, while the Liu model underestimated observed cumulative interception by 0·8%. Although good agreement between observed and estimated cumulative canopy interception loss was found using the analytical models with study period derived parameters, relatively poor agreement was found at the rainfall event scale. Although the analytical versions of the reformulated Gash and Liu models provided similar results, the Liu model is recommended for further application in the study area since it requires less data input and follows an exponential wetting of the canopy approach, something that the data collected during the study supports. Future work regarding the Liu model is discussed. Copyright © 2007 John Wiley & Sons, Ltd.
The role of waves in ice‐jam flooding of the Peace‐Athabasca Delta
Authors: Beltaos Spyros
Published: August 2007

Since the late 1960s, a paucity of ice‐jam flooding in the lower Peace River has resulted in prolonged dry periods and considerable reduction in the area covered by lakes and ponds that provide habitat for aquatic life in the Peace‐Athabasca Delta (PAD) region. To identify the causes of this trend, and to develop mitigation or adaptation strategies under present and future climatic conditions, it is necessary to understand the mechanisms that lead to breakup of the ice cover and jamming within the delta reach of Peace River. Because the lower Peace is extremely flat, the long‐period waves caused by spring snowmelt are not generally capable of dislodging the winter ice cover, even under conditions of very high flow. The ice cover decays in place and rubble generation, an essential condition for ice jamming, does not occur. However, major jams do, on occasion, form in the middle section of the river and make their way to the delta via repeated releases and stalls. Each release generates a steep wave which can greatly amplify the hydrodynamic forces that are applied on the ice cover and bring about its dislodgment. This is quantified for the lower Peace River by applying recently developed methodology to local hydrometric data. Detailed in situ observations in the spring of 2003, and additional data from 1997 and 2002, fully corroborate this conclusion. Implications to other flat rivers of northern Canada are discussed. Copyright © 2007 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.
Estimating sub‐canopy shortwave irradiance to melting snow on forested slopes
Authors: Ellis Chad R. , Pomeroy John W.
Published: August 2007

Estimates of shortwave irradiance energy beneath needle‐leaf forests over complex terrain are needed to drive energy balance snowmelt models and to evaluate the potential hydrological impacts of forest‐cover change in mountain regions. This paper outlines and evaluates a physically‐based model designed to estimate sub‐canopy shortwave irradiance to snowcover under needle‐leaf forest‐cover with respect to surface slope and azimuth. Transmission of above‐canopy irradiance was estimated using forest‐surveys and hemispherical photographs to determine the fractions of forest‐cover occupied by non‐transmitting trunks, partially‐transmitting crowns and fully‐transmitting gaps with respect to above‐canopy diffuse and direct beam shortwave irradiance. Simulations were conducted for continuous, uniform lodgepole pine forests on level site and a north facing slope and a discontinuous, non‐uniform forest on a southeast facing slope during snowmelt at the Marmot Creek Research Basin, Alberta, Canada. Mean observed daily transmissivity values of irradiance were 0·09 at the north‐facing forest, 0·21 at the level forest and 0·36 at the southeast‐facing forest. Modelled and observed results indicate that potential snowmelt energy from sub‐canopy shortwave irradiance is likely to exhibit the greatest variation with change in cloudiness and forest‐cover density under south‐facing forests and the least variation under north‐facing forests. Comparisons of simulations to observations indicate that the model can explain much of the difference in daily shortwave transmission amongst sites, performing relatively poorest at the north‐facing forest where fluxes were small and relatively best at the south‐east facing forest where fluxes were large. However, simulation errors in terms of absolute irradiance were greatest at the southeast‐facing forest, having a root mean square error (RMSE) 0·64 MJ m−2d−1 compared to 0·44 MJ m−2d−1 at the level forest and 0·27 MJ m−2d−1 at the north‐facing forest. Copyright © 2007 John Wiley & Sons, Ltd.
Snowmelt runoff sensitivity analysis to drought on the Canadian prairies
Authors: Fang Xing , Pomeroy John W.
Published: August 2007

The Canadian prairies are subject to severe extended droughts that are characterized by warmer temperatures, lower precipitation, lower soil moisture and sparser vegetation than normal conditions. The physically based cold regions hydrological modelling platform (CRHM) provides a possible means to analyse the sensitivity of prairie snowmelt processes to drought. The model was tested against detailed observations from Creighton Tributary of the Bad Lake Research Basin, Saskatchewan for the 1974–1975 and 1981–1982 hydrological years and found to perform satisfactorily in reproducing snow accumulation and streamflow without parameter calibration. By lowering winter precipitation and raising winter air temperature from actual meteorological observations and by lowering fall soil moisture and vegetation height parameters, the resulting drought condition sensitivity of snow accumulation, snow cover duration, sublimation of blowing snow, evaporation, infiltration into frozen soils, soil moisture storage change, snowmelt runoff and streamflow discharge was estimated. Snow accumulation and snow cover duration were relatively insensitive to meteorological changes associated with drought because the suppression of blowing snow sublimation moderated reduced snowfall. Infiltration, soil moisture storage change and evaporation were also relatively insensitive to drought conditions. However, lower precipitation, higher air temperature and lower initial soil moisture caused a marked reduction in snowmelt runoff. Similarly, large reductions in streamflow discharge were caused by diminished winter precipitation, increased winter air temperature and decreased fall soil moisture content. A scenario showed that a combination of these factors could cause complete cessation of spring streamflow even under moderate drought of 15% reduction in winter precipitation and 2·5 °C increase in winter mean air temperature. Results show that spring runoff and streamflow discharge are inherently unstable in the Canadian prairie environment, and so, magnify the impacts of drought, and through multi‐season storage and vegetation change can cause the impacts of hydrological drought to persist for several seasons after meteorological drought has ended. Copyright © 2007 John Wiley & Sons, Ltd.
Chemical pollution, respiratory allergy and asthma: a perspective
Authors: Evans Gareth S. , Cadogan David , Flueckiger Andreas , Hennes Christa , Kimber Ian
Published: August 2007

The European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) convened a workshop in June 2005 to address the speculation that exposure to specific chemicals, and/or chemical pollutants in general, may play an important role in the increased prevalence of allergy and asthma in ‘westernised’ societies. This paper summarises one perspective arrived at during this workshop. It was acknowledged that certain chemicals and certain types of pollution might trigger or exacerbate asthmatic reactions in sensitised subjects. However, overall levels of pollution appear not to have had a major impact upon the prevalence of atopic allergy. Epidemiological studies suggest that pollution may in some circumstances protect from acquisition of sensitisation. Increasing exposure to household chemicals may enhance pre‐existing allergies, but evidence for their causation of allergy is lacking. Other risk factors considered included societal dietary changes and exposure to endotoxins.

Future research needs were identified which included epidemiological studies employing exposure and biomonitoring data, studies on domestic exposure to chemicals and their association with the incidence of allergy and asthma, and prospective birth cohort studies employing well‐defined aspects of lifestyle, diet, chemical and endotoxin exposure as factors that may drive susceptibility to allergy and asthma. Copyright © 2007 John Wiley & Sons, Ltd.
Nanoscale surface electrical properties of zinc oxide films investigated by conducting atomic force microscopy
Authors: Yu Chang‐Feng , Chen Sy‐Hann , Xie Wen‐Jia , Lin Yung‐Shao , Shen Cheng‐Yu , Tsai Sheng‐Jhong , Sung Che‐Wei , Ay Chyung
Published: August 2007

In this study, conducting atomic force microscopy was employed to investigate the nanoscale surface electrical properties of zinc oxide (ZnO) films prepared by pulsed laser deposition (PLD) at different substrate temperatures for use as anode materials in polymer light‐emitting diodes. The results show that the surface conductivity distribution of ZnO is related to its surface structure. At substrate temperatures of 150–200°C, the conducting regions may cover over 90% of the ZnO thin‐film surface, thus providing the best local conductivity. Moreover, heating at substrate temperatures of above 250°C can effectively make the conductivity on the ZnO surface uniform. In particular, at substrate temperatures of around 300°C, the conducting regions where currents are between 1 and 2 μA may cover as much as 83% of the surface, and furthermore, the transmission ratio in the visible range is higher than 80%. This is a rather ideal production temperature for the PLD for ZnO films. Microsc. Res. Tech., 2008. © 2007 Wiley‐Liss, Inc.
What is the biological relevance of the specific bond properties revealed by single‐molecule studies?
Authors: Robert Philippe , Benoliel Anne‐Marie , Pierres Anne , Bongrand Pierre
Published: August 2007

During the last decade, many authors took advantage of new methodologies based on atomic force microscopy (AFM), biomembrane force probes (BFPs), laminar flow chambers or optical traps to study at the single‐molecule level the formation and dissociation of bonds between receptors and ligands attached to surfaces. Experiments provided a wealth of data revealing the complexity of bond response to mechanical forces and the dependence of bond rupture on bond history. These results supported the existence of multiple binding states and/or reaction pathways. Also, single bond studies allowed us to monitor attachments mediated by a few bonds. The aim of this review is to discuss the impact of this new information on our understanding of biological molecules and phenomena. The following points are discussed: (i) which parameters do we need to know in order to predict the behaviour of an encounter between receptors and ligands, (ii) which information is actually yielded by single‐molecule studies and (iii) is it possible to relate this information to molecular structure? Copyright © 2007 John Wiley & Sons, Ltd.
Cooking activities during the Middle Ages: organic residues in ceramic vessels from the Sant'Antimo Church (Piombino–Central Italy)
Authors: Salvini Laura , Pecci Alessandra , Giorgi Gianluca
Published: August 2007

A combined gas chromatography‐electron ionization (GC‐EI), atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) and MS/MS approach has been used for characterizing organic residues of ceramic vessels of different forms and dimensions recovered from a vault of the apse of the 13th century church of Sant'Antimo in Piombino (Central Italy). The artifacts studied in this investigation are pots, jugs, colanders and pans probably used for cooking meals or as food containers. GC‐MS has shown the presence of different fatty acids and other nonpolar markers, while APCI ionization proved to be particularly useful in the detection of diterpenoids and diacylglycerols. The data show that some organic markers may be of animal origin, while others are typical constituents or biodegradation products of vegetables. This allows one to propose the main use of these articles as vessels for cooking meat and maybe vegetable broths and soups. As there is no strict correlation between organic markers and shape, form and dimension of the ceramic vessel, it appears that the different objects probably served the same function. Chemical characterization of the organic residues of ceramic vessels, together with all the other archaeological data, contributes to a better understanding of their uses and the customs of people in the Middle Ages in Central Italy. Copyright © 2007 John Wiley & Sons, Ltd.
Gas‐phase basicity of methionine
Authors: Desaphy Sylvain , Malosse Christian , Bouchoux Guy
Published: August 2007

Proton affinity and protonation entropy of methionine (Met) were determined by the extended kinetic method from ESI‐Q‐TOF tandem mass spectrometry experiments. The values, PA(Met) = 937.5 ± 2.9 kJ mol−1 and ΔpS°(Met) = − 22 ± 5 J mol−1 K−1, lead to gas‐phase basicity GB(Met) = 898.2 ± 3.2 kJ.mol−1. Quantum chemical calculations using density functional theory confirm that the proton affinity of Met is indeed in the 940 kJ mol−1 range and that a significant entropy loss, of at least − 25 J mol−1 K−1, occurs upon protonation. This last point is evidenced here for the first time and suggests revision of the tabulated protonation thermochemistry of Met. A comparison with previous experimental data allows us to propose the following evaluated thermochemical values: PA(Met) = 943 ± 4 kJ mol−1 and ΔpS°(Met) = − 35 ± 15 J mol−1 K−1 and GB(Met) = 900 ± 2 kJ mol−1. Copyright © 2007 John Wiley & Sons, Ltd.
The relationships of the North Atlantic Oscillation to water temperature along the southern Baltic Sea coast
Authors: Girjatowicz Józef Piotr
Published: August 2007

The present paper focuses on the relationships between the North Atlantic oscillation (NAO) index and surface water temperature along the southern Baltic Sea coast. Monthly water temperature values from the period of 1951–2000 were measured in Świnoujście, Miȩdzyzdroje, Kołobrzeg, Mielno, Ustka, Władysławowo, Hel and Gdynia: sites which are located along the Polish coast. Correlation and regression methods were applied to calculate and analyse the relationships between the NAO index and water temperature.

A statistically significant positive correlation between NAO index and the water temperature occurred in winter from December to March with the strongest relationships observed in January followed by February and March. The relationships between the NAO index and water temperature are usually statistically insignificant in the remaining part of the year (April–November).

Various kinds of relationships were tested in this study. Our research revealed that asynchronous relationships are rather weak, although in winter they are also statistically significant. They are strongest for the January value of the NAO index combined with February water temperature. However, after three to four months they become statistically insignificant. They regain statistical significance only in late Autumn.

It has also been shown that during the cold season, local factors, especially solar ones, weaken the NAO index relationships with the water temperature. This is clearly visible especially towards the turn of winter when insolation increases. During very mild winters the influence of the local factors may be significant beginning from mid‐winter. Copyright © 2007 Royal Meteorological Society