bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multivariate monitoring of water quality: a case study of Lake Simpele, Finland
Authors: Heikka Riitta Aulikki 
Published: November 2008

AbstractLake Simpele is located in South‐east Finland. The surface area of the lake, which consists of its eastern and western parts, is 97 km2. The wastewater treatment plant of the Parikkala municipality is situated between the two parts in Särkisalmi. The eastern part of the lake is more under the influence of agriculture (discharges from fields). The rather polluted bay Siikalahti is also located in the eastern part of the lake. The data for this study was obtained through obligatory monitoring measurements during the period 1974–2006. The seven water quality variables used in the classifications were the dissolved oxygen saturation degree C2‐sat. %, chemical oxygen demand CODMn, total phosphorus concentration, total nitrogen concentration, pH, electrical conductivity and colour. All of the time series of the eight sampling sites were used in the first classification with PCA. The dissolved oxygen saturation degree was not used as a variable in this classification, because the depth of the sampling sites varied a great deal. The sampling sites were put in order according to the pooled t‐values of the years 2000–2005. The t‐values of the studied decades were also pooled in order to examine the history of water quality in the different sampling sites. The changes in water quality were studied during the past three decades. Measures to protect the environment during the past decades have improved the quality of the water in Lake Simpele. The water quality of the western part of the lake has been and still is better than that of the eastern part. The epilimnion and hypolimnion were classified in one sampling site. The low dissolved oxygen saturation degree and total phosphorus concentration had a strong negative correlation. It could be seen how the low oxygen saturation degree releases phosphorus in the hypolimnion. Copyright © 2008 John Wiley & Sons, Ltd.
High Catalytic Efficiency of Nanostructured Molybdenum Trioxide in the Benzylation of Arenes and an Investigation of the Reaction Mechanism
Authors: Wang Feng , Ueda Wataru 
Published: November 2008

AbstractThe synthesis and characterization of nanostructured MoO3 with a thickness of about 30 nm and a width of about 450 nm are reported. The composition formula of the MP (precipitation method) precursor was estimated to be [(NH4)2O]0.169⋅MoO3⋅ (H2O)0.239. The calcination of the precursor in air afforded nanostructured pellets of the α‐MoO3 phase. The nanostructured MoO3 catalyst exhibited high efficiency in catalyzing the benzylation of various arenes with substituted benzyl alcohols, which were strikingly different to common bulk MoO3. Most reactions offered >99 % conversion and >99 % selectivity to monoalkylated compounds. MoO3 is a typical acid catalyst. However, the benzylation reaction over nanostructured MoO3 does not belong to the acid‐catalyzed type or defect site‐catalyzed type, since the catalyst has no acidity and defect site on surface. Characterization with thermal, spectroscopic, and electronic techniques reveal that the catalyst contains fully oxygen‐coordinated MoO6 octahedrons on the surface but partially reduced species (Mo5+) within the bulk phase. The terminal oxygen atoms of MoO bonds on the (010) basal plane resemble oxygen anion radicals and act as active sites for the adsorption and activation of benzyl alcohols by electrophilic attack. Such sites are indispensable for catalytic reactions since the blocking of these sites by electron acceptors, such as tetracyanoethylene (TCNE), can greatly decrease catalytic activity. This work represents a successful example of combining a heterogeneous catalysis study with nanomaterial synthesis.
Template‐Controlled Assembly of Ditopic Catechol Phosphines: A Strategy for the Generation of Complexes of Bidentate Phosphines with Different Bite Angles
Authors: Chikkali Samir H. , Gudat Dietrich , Lissner Falk , Niemeyer Mark , Schleid Thomas , Nieger Martin 
Published: November 2008

AbstractA rational approach to the synthesis of heterobi‐ or ‐trimetallic complexes based upon self‐assembly of a flexible ditopic catechol‐phosphine ligand with [(cod)PdCl2] and simple metal halides such as GaCl3, BiCl3, SnCl4, or ZrCl4 is described. All products were characterized by spectroscopic and analytical data and single‐crystal X‐ray diffraction studies. The molecular structures can be described in terms of cis‐configured palladium complexes with supramolecular bisphosphine ligands that are formed by the assembly of two phosphine catecholate fragments on a main group/transition metal template. Of particular interest are the distinct decreases in P‐Pd‐P bite angles and P⋅⋅⋅P distances between the ligating atoms with increasing covalent radii of the templates. The range of these variations is of a magnitude similar to that of the geometrical changes in known families of complexes containing molecular bidentate ligands. Solution NMR studies give further evidence that in several cases the μ2‐bridging coordination of two of the catechol oxygen atoms in the template complexes is broken under the influence of donor solvents, thus allowing the supramolecular ligand to be switched between tetradentate ‐O2P2 and bidentate ‐P2 coordination modes.
Synthesis of Stable Aminoacyl‐tRNA Analogues Containing Triazole as a Bioisoster of Esters
Authors: Chemama Maryline , Fonvielle Matthieu , Arthur Michel , Valéry Jean‐Marc , Etheve‐Quelquejeu Mélanie 
Published: November 2008

AbstractStable analogues: An effective synthetic route involving cycloaddition between alkynes and azidonucleosides to afford a new class of stable aminoacyl‐tRNA analogues such as depicted is presented. Biological evaluation showed that theses new compounds act as potent inhibitors of FemXWv aminoacyl transferase, a novel drug target.magnified imageAminoacyl‐tRNAs have important roles in a variety of biological processes, including protein synthesis by ribosomes, targeting of proteins for degradation by the proteasome, and bacterial cell wall synthesis. Here we describe the synthesis of stable aminoacyl‐tRNA analogues containing 1,4‐ and 1,5‐substituted 1,2,3‐triazole rings. The procedure involves i) Cu‐ and Ru‐catalysed cycloadditions of 3′‐azidoadenosine and alkynes, which produced the 1,4 and 1,5 regioisomers of the triazoles, respectively, ii) coupling between the resulting triazole‐deoxyadenosine derivatives and a deoxycytidine phosphoramidite, and iii) the enzymatic ligation of the substituted dinucleotides with a 22 nt RNA microhelix that mimics the acceptor arm of tRNA. Nucleoside and nucleotide compounds were characterized by MS spectrometry and 1H, 31P and 13C NMR spectroscopy and were assayed for inhibition of FemXWv, an alanyltransferase essential for the formation of the peptidoglycan network of Gram‐positive bacterial pathogens. The low IC50 values obtained (2 to 4 μM) indicate that the five‐membered triazole rings acted as bioisosters of esters and can be used for the design of stable aminoacyl‐tRNA analogues.
Anion–π Slides for Transmembrane Transport
Authors: Mareda Jiri , Matile Stefan 
Published: November 2008

AbstractThe recognition and transport of anions is usually accomplished by hydrogen bonding, ion pairing, metal coordination, and anion–dipole interactions. Here, we elaborate on the concept to use anion–π interactions for this purpose. Different to the popular cation–π interactions, applications of the complementary π‐acidic surfaces do not exist. This is understandable because the inversion of the aromatic quadrupole moment to produce π‐acidity is a rare phenomenon. Here, we suggest that π‐acidic aromatics can be linked together to produce an unbendable scaffold with multiple binding sites for anions to move along across a lipid bilayer membrane. The alignment of multiple anion–π sites is needed to introduce a cooperative multi‐ion hopping mechanism. Experimental support for the validity of the concept comes from preliminary results with oligonaphthalenediimide (O‐NDI) rods. Predicted by strongly positive facial quadrupole moments, the cooperativity and chloride selectivity found for anion transport by O‐NDI rods were consistent with the existence of anion–π slides. The proposed mechanism for anion transport is supported by DFT results for model systems, as well as MD simulations of rigid O‐NDI rods. Applicability of anion–π slides to achieve electroneutral photosynthesis is elaborated with the readily colorizable oligoperylenediimide (O‐PDI) rods. To clarify validity, scope and limitations of these concepts, a collaborative research effort will be needed to address by computer modeling and experimental observations the basic questions in simple model systems and to design advanced multifunctional anion–π architectures.
Salt Effects on the Structure of Water Probed by Attenuated Total Reflection Infrared Spectroscopy and Molecular Dynamics Simulations
Authors: Riemenschneider Julian , Holzmann Jörg , Ludwig Ralf 
Published: November 2008

AbstractWe study aqueous solutions of alkaline chlorides (NaCl, KCl, RbCl and CsCl) with a combination of attenuated total reflection infrared (ATR‐IR) spectroscopy and molecular dynamics (MD) simulations using the TIP4P‐Ew water model (Horn et al.,J. Chem. Phys.2004,120, 9665), covering concentration ranges between 0.1 and 6 M. Spectral modifications in the OH stretch region are evaluated and correlated to the various salts and salt concentrations. By taking the difference spectra between the spectral line shapes of aqueous salt solutions and those of pure water, we specifically focus on the small quasi‐“free OH“ band appearing at the highest wavenumbers in the spectra. This free‐OH feature is found constantly at 3650 cm−1for all salts and salt concentrations, but it shows a characteristic intensity depending on the chosen cation. In the order from Na+to Cs+, the free OH intensity decreases compared to that of pure water. To interpret the experimental results, we performed MD simulations for similar salt solutions. The experimentally observed effects can be correlated with structural alterations indicated by differences between the site–site pair correlation functions of water in aqueous salt solutions and those of pure water.
Freezing and Melting of Water Confined in Silica Nanopores
Authors: Findenegg Gerhard H. , Jähnert Susanne , Akcakayiran Dilek , Schreiber Andreas 
Published: November 2008

AbstractIn nanosized pores, liquid water can be thermodynamically stable down to temperatures well below the limit of homogeneous nucleation of bulk water (∼235 K). Studies of water in such pores therefore offer an opportunity to reveal the anomalous behavior of deeply supercooled water. Herein we focus on recent studies of the limits of freezing and melting of water in the cylindrical pores of ordered mesoporous silicas with pore diameters in the range of 2–10 nm, based on vapor sorption measurements, calorimetric studies, NMR spectroscopy and cryoporometry, and neutron diffraction studies.
Induction of an antigen specific humoral immune response by immunization with the aggregate‐free human TGFα‐P64k fusion protein
Authors: Capote Ailem Rabasa , Gómez Pérez José A. , Hidalgo Greta Garrido , Hernández Liliet Matech , Gómez Iván Piñera , Ramírez Belinda Sánchez , Rodríguez Rolando Pérez , Vitlloch Adolfo Castillo , Molina Luis E. Fernández 
Published: November 2008

AbstractTransforming growth factor alpha (TGFα) is an important epidermal growth factor receptor (EGFR) ligand. Over‐expression of both molecules in epithelial tumors has been correlated with poor prognosis and disease progression. Due to the importance of TGFα in tumorigenesis, this molecule has great potential for cancer immunotherapy. We previously designed a TGFα‐based vaccine consisting of a fusion protein between human TGFα (hTGFα) and P64k protein from Neisseria meningitidis expressed in Escherichia coli. However, this protein was obtained highly aggregated, which hampered its introduction into clinical use. In this study, we demonstrate that this aggregation state is not a consequence of IMAC purification, but is formed after bacterial disruption. To obtain this protein as a monomer, we designed a procedure that included an unfolding/refolding step at the end of purification. We verified that hTGFα in the refolded fusion protein (hTGFα‐P64k‐r) is immunogenic in mice. The latter was capable of inducing a humoral immune response against hTGFα identical to that generated with the aggregated fusion protein, demonstrating that the aggregation level has no influence on hTGFα immunogenicity. We also showed that TGFα‐directed antibodies induced apoptosis in A431 cells. The present results also validated the potential use of this vaccine in cancer patients with tumors overexpressing TGFα. Drug Dev Res 69 2008. © 2008 Wiley‐Liss, Inc.
Forest floor carbon dioxide fluxes within an upland‐peatland complex in the Western Boreal Plain, Canada
Authors: Solondz Danielle S. , Petrone Richard M. , Devito Kevin J. 
Published: November 2008

AbstractThis study examined the midday (10:00 to 16:00) growing season (April to October) surface cover CO2 relationships with different canopy closures in a forested upland–peatland–pond complex in the Western Boreal Plain (WBP), north‐central Alberta, Canada. Large differences were observed among the forest floors of landscape units with different canopy covers with respect to midday total respiration [(Rtot) = vegetation respiration (Rveg) + soil respiration (Rsoil)] and gross ecosystem production (GEP), and the seasonal pattern of GEP and Rtot. Highest rates of Rtot followed the general progression of riparian > upland > open peatland > covered peatland, with high Rsoil contributions. Strong correlations were observed between C:N, soil temperature, moisture and Rtot. Photosynthetic active radiation (PAR) controlled the GEP, which was highest in the open and covered peatland. GEP and Rtot were highest in the middle of the growing season when soil and air temperatures were warmest; in addition Rveg contributed more to Rtot during this time. However, Rsoil dominated the flux.This study demonstrated that controlling environmental factors on CO2 exchange cannot necessarily be extrapolated among land cover units within a sub‐humid region, such as Canada's WBP. In addition, forest floors of different land cover units, and microtopography should be taken into account when discussing understory contributions to CO2 exchange. Copyright © 2008 John Wiley & Sons, Ltd.
The hydraulic structure of a raised bog and its implications for ecohydrological modelling of bog development
Authors: Baird Andrew J. , Eades Phil A. , Surridge Ben W. J. 
Published: November 2008

AbstractRaised bogs are important ecohydrological systems in which there are strong two‐way links between plant succession, litter and peat decay, and hydrological functioning. Using recently established protocols, we measured the hydraulic structure of a raised bog in West Wales. We tested two hypotheses: (i) that the hydraulic conductivity (K) of the peat shows depth dependency such that lower layers of peat are effectively impermeable, and (ii) that the K of the marginal peat of the bog dome is lower than that in central areas. From 107 piezometer measurements we found there was depth dependency of K but that lower peat layers were not poorly permeable or impermeable. We also found that the K of the peat on the margin of the bog dome was generally significantly lower than that in central areas. Our results suggest that, for some bogs at least, it is important to simulate water flow through deeper peats when simulating peatland development or growth. They also raise the intriguing possibility that the low K of marginal peat is important in maintaining wet conditions in central bog areas, allowing bogs to reach greater thicknesses than they would do in the absence of the low‐K margin; an idea first proposed for blanket bogs by Lapen et al. (2005). Copyright © 2008 John Wiley & Sons, Ltd.
Voltammetric Sensing of Mercury and Copper Cations at Poly(EDTA‐like) Film Modified Electrode
Authors: Buica George O. , Bucher Christophe , Moutet Jean‐Claude , Royal Guy , Saint‐Aman Eric , Ungureanu Eleonora M. 
Published: November 2008

AbstractComplexing polymer‐coated electrodes have been synthesized by oxidative electropolymerization of ethylenediamine tetra‐N‐(3‐pyrrole‐1‐yl)propylacetamide (monomer L). The presence of four polymerizable pyrrole fragments on the same EDTA skeleton was thought to confer enhanced rigidity and controlled dimensionality to the resulting complexing materials, which were used for the electrochemical detection of Hg(II), Cu(II), Pb(II) and Cd(II) ions by means of the chemical preconcentration‐anodic stripping technique. The polyamide electrode material showed particularly a significant selectivity towards mercury ions, even in the presence of a large excess of other metal cations. Moreover, the use of imprinted polymer‐coated electrodes prepared by electropolymerization of L in the presence of metal cations turned out to significantly improve the detection limits, down to 5×10−10 mol L−1 for Hg(II) and Cu(II) species.
Microfluidics: Applications for analytical purposes in chemistry and biochemistry
Authors: Ohno Ken‐ichi , Tachikawa Kaoru , Manz Andreas 
Published: November 2008

AbstractIn this review, we present recent advancements and novel developments in fluidic systems for applied analytical purposes in chemistry, biochemistry, and life science in general that employ and reflect the full benefits of microfluidics. A staggering rise in publications related to integrated, all‐in‐one microfluidic chips capable of separation, reaction, and detection have been observed, all of which realise the principal of micro total analysis systems or lab‐on‐a‐chip. These integrated chips actively adopt the scaling law concepts, utilising the highly developed fabrication techniques. Their aim is to multi‐functionalise and fully automate devices believed to assist the future advancements of point‐of‐care, clinical, and medical diagnostics.
Improved workup for glycosaminoglycan disaccharide analysis using CE with LIF detection
Authors: Hitchcock Alicia M. , Bowman Michael J. , Staples Gregory O. , Zaia Joseph 
Published: November 2008

AbstractThis work describes improved workup and instrumental conditions to enable robust, sensitive glycosaminoglycan (GAG) disaccharide analysis from complex biological samples. In the process of applying CE with LIF to GAG disaccharide analysis in biological samples, we have made improvements to existing methods. These include (i) optimization of reductive amination conditions, (ii) improvement in sensitivity through the use of a cellulose cleanup procedure for the derivatization, and (iii) optimization of separation conditions for robustness and reproducibility. The improved method enables analysis of disaccharide quantities as low as 1 pmol prior to derivatization. Biological GAG samples were exhaustively digested using lyase enzymes, the disaccharide products and standards were derivatized with the fluorophore 2‐aminoacridone and subjected to reversed polarity CE‐LIF detection. These conditions resolved all known chondroitin sulfate (CS) disaccharides or 11 of 12 standard heparin/heparan sulfate disaccharides, using 50 mM phosphate buffer, pH 3.5, and reversed polarity at 30 kV with 0.3 psi pressure. Relative standard deviation in migration times of CS ranged from 0.1 to 2.0% over 60 days, and the relative standard deviations of peak areas were less than 3.2%, suggesting that the method is reproducible and precise. The CS disaccharide compositions are similar to those obtained by our group using tandem MS. The reversed polarity CE‐LIF disaccharide analysis protocol yields baseline resolution and quantification of heparin/heparan sulfate and CS/dermatan sulfate disaccharides from both standard preparations and biologically relevant proteoglycan samples. The improved CE‐LIF method enables disaccharide quantification of biologically relevant proteoglycans from small samples of intact tissue.
Topology optimization of microfluidic mixers
Authors: Andreasen Casper Schousboe , Gersborg Allan Roulund , Sigmund Ole 
Published: November 2008

AbstractThis paper demonstrates the application of the topology optimization method as a general and systematic approach for microfluidic mixer design. The mixing process is modeled as convection dominated transport in low Reynolds number incompressible flow. The mixer performance is maximized by altering the layout of flow/non‐flow regions subject to a constraint on the pressure drop between inlet and outlet. For a square cross‐sectioned pipe the mixing is increased by 70% compared with a straight pipe at the cost of a 2.5 fold increase in pressure drop. Another example where only the bottom profile of the channel is a design domain results in intricate herring bone patterns that confirm findings from the literature. Copyright © 2008 John Wiley & Sons, Ltd.
Isolation and X‐Ray Structures of Reactive Intermediates of Organocatalysis with Diphenylprolinol Ethers and with Imidazolidinones
Authors: Seebach Dieter , Grošelj Uroš , Badine D. Michael , Schweizer W. Bernd , Beck Albert K. 
Published: November 2008

AbstractReaction of 2‐phenylacetaldehyde with the Me3Si ether of diphenyl‐prolinol, with removal of H2O, gives a crystalline enamine (1). The HBF4 salts of the MePh2Si ether of diphenyl‐prolinol and of 2‐(tert‐butyl)‐3‐methyl‐ and 5‐benzyl‐2,2,3‐trimethyl‐1,3‐imidazolidin‐4‐one react with cinnamaldehyde to give crystalline iminium salts 2, 3, and 4. Single crystals of the enamine and of two iminium salts, 2 and 3, were subjected to X‐ray structure analysis (Figs. 1, 2, and 6), and a 2D‐NMR spectrum of the third iminium salt was recorded (Fig. 7). The crystal and NMR structures confirm the commonly accepted, general structures of the two types of reactive intermediates in organocatalysis with the five‐membered heterocycles, i.e., D, E (Scheme 2). Fine details of the crystal structures are discussed in view of the observed stereoselectivities of the corresponding reactions with electrophiles and nucleophiles. The structures 1 and 2 are compared with those of other diphenyl‐prolinol derivatives (from the Cambridge File CSD; Table 1) and discussed in connection with other reagents and ligands, containing geminal diaryl groups and being used in enantioselective synthesis (Fig. 4). The iminium ions 3 and 4 are compared with N‐acylated imidazolidinones F and G (Figs. 9, 12, and 13, and Table 3), and common structural aspects such as minimalization of 1,5‐repulsion (the ‘A1,3‐effect’), are discussed. The crystal structures of the simple diphenyl‐prolinol⋅HBF4 salt (Fig. 3) and of Boc‐ and benzoyl‐(tert‐butyl)methyl‐imidazolidinone (Boc‐BMI and Bz‐BMI, resp.; Figs. 10 and 11) are also reported. Finally, the crystal structures are compared with previously published theoretical structures, which were obtained from high‐level‐of‐theory DFT calculations (Figs. 5 and 8, and Table 2). Delicate details including pyramidalization of trigonal N‐atoms, distortions around iminium CN bonds, shielding of diastereotopic faces, and the π‐interaction between a benzene ring and a Me group match so well with, and were actually predicting the experimental results that the question may seem appropriate, whether one will soon start considering to carry out such calculations before going to the laboratory for experimental optimizations.