bluuebunny/crossref_metadata_2025 huggingface dataset:
Thymoquinone protects renal tubular cells against tubular injury
Authors: Sayed Ahmed Amir Radwan
Published: January 2008

In this work the effect of angiotensin II (AT II) on proximal tubular epithelial cells (pTECs) in vitro was studied. AT II was found to activate the nuclear factor κB (NF‐κB) and its controlled genes, for example, interleukin 6 (IL‐6) of pTECs in a time‐dependent manner. Two points with maximum NF‐κB activation were found, the first after 12 h and the second after 3.5 days. The first point may be due to activation of NF‐κB in pTECs in response to AT II while the second may be due to activation of the advanced glycation end product (AGE)/receptor of the AGE (RAGE) system. Thymoquinone (TQ) was found to decrease NF‐κB activation in a dose‐dependant manner with maximum inhibitory effect at a concentration of 500 nM. Also, pre‐incubation of pTECs with TQ leads to disappearance of the second peak of NF‐κB. These data are consistent with results obtained from IL‐6 enzyme‐linked immunosorbent assay (ELISA) and transient transfection experiments. The results explain the therapeutic value of TQ which can be used to delay end stage renal diseases in diabetics. Copyright © 2008 John Wiley & Sons, Ltd.
Solvent subset selection for polymorph screening
Authors: Allesø Morten , Rantanen Jukka , Aaltonen Jaakko , Cornett Claus , van den Berg Frans
Published: January 2008

In polymorph screening it is imperative to maximize the physicochemical diversity of solvents used in crystallization experiments. This is done in order to increase the probability of finding as many crystal forms of the compound as possible. When setting up a complete solid form screening scheme it is common practice to work with solvent subsets of varying sizes, adequately spanning the chemical space. There exists a wide array of algorithms to perform this pre‐experimental selection. Prior to the implementation of these methods, the impact on the physicochemical diversity observed in the selected subsets should be fully understood. In the current study subsets of 5, 10 and 20 solvents were selected from a database of 218 organic solvents times 24 property descriptors. For this purpose four mathematically different subset selection algorithms were tested and compared: Federov D‐optimal selection, Kennard‐Stone selection, Principal Properties selection and a Cluster‐Based selection. Federov D‐optimal, Kennard‐Stone and the Cluster‐Based selection primarily sampled in the outer regions of solvent space, whereas the Principal Properties approach represented more of a compromising solution selecting solvents closer to the centre. In conclusion, subset selection algorithms in crystallization experimental design should be used to guarantee physicochemical diversity, though it is recommended that the computed selection is supplemented with solvents selected based on chemical knowledge of the particular compound being screened. Copyright © 2008 John Wiley & Sons, Ltd.
Theoretical Studies of Damage to 3′‐Uridine Monophosphate Induced by Electron Attachment
Authors: Zhang Ru bo , Zhang Ke , Eriksson Leif A.
Published: January 2008

Low‐energy electrons (LEE) are well known to induce nucleic acid damage. However, the damage mechanisms related to charge state and structural features remain to be explored in detail. In the present work, we have investigated the N1‐glycosidic and C3′O(P) bond ruptures of 3′‐UMP (UMP=uridine monophosphate) and the protonated form 3′‐UMPH with −1 and zero charge, respectively, based on hybrid density functional theory (DFT) B3 LYP together with the 6‐31+G(d,p) basis set. The glycosidic bond breakage reactions of the 3′UMP and 3′UMPH electron adducts are exothermic in both cases, with barrier heights of 19–20 kcal mol−1 upon inclusion of bulk solvation. The effects of the charge state on the phosphate group are marginal, but the C2′OH group destabilizes the transition structure of glycosidic bond rupture of 3′‐UMPH in the gas phase by approximately 5.0 kcal mol−1. This is in contrast with the C3′O(P) bond ruptures induced by LEE in which the charge state on the phosphate influences the barrier heights and reaction energies considerably. The barrier towards C3′O(P) bond dissociation in the 3′UMP electron adduct is higher in the gas phase than the one corresponding to glycosidic bond rupture and is dramatically influenced by the C2′OH group and bulk salvation, which decreases the barrier to 14.7 kcal mol−1. For the C3′O(P) bond rupture of the 3′UMPH electron adduct, the reaction is exothermic and the barrier is even lower, 8.2 kcal mol−1, which is in agreement with recent results for 3′‐dTMPH and 5′‐dTMPH (dTMPH=deoxythymidine monophosphate). Both the Mulliken atomic charges and unpaired‐spin distribution play significant roles in the reactions.
Forecasting with panel data
Authors: Baltagi Badi H.
Published: January 2008

This paper gives a brief survey of forecasting with panel data. It begins with a simple error component regression model and surveys the best linear unbiased prediction under various assumptions of the disturbance term. This includes various ARMA models as well as spatial autoregressive models. The paper also surveys how these forecasts have been used in panel data applications, running horse races between heterogeneous and homogeneous panel data models using out‐of‐sample forecasts. Copyright © 2008 John Wiley & Sons, Ltd.
How children describe their shy/withdrawn peers
Authors: Younger Alastair J. , Schneider Barry H. , Guirguis‐Younger Manal
Published: January 2008

In individual interviews, 227 children from the first, third, fifth, and seventh grades described the behaviours that characterize shyness in their peers. The categories of behaviour most frequently described included the following: doesn't talk, stays by self, doesn't play, walks/runs away from others, hides, looks away/avoids eye contact, physical signs of anxiety, stays near familiar people, cries, blushes, and gets mixed up when talking/stutters. The number of children mentioning hides, stays near familiar people, and cries decreased significantly across grade level, whereas the number mentioning doesn't talk, stays by self, blushes, and gets mixed up when talking/stutters increased across grade level. The situations in which children described the shy behaviours as occurring were classified as entailing either fearful shyness or self‐conscious shyness. The number of children who mentioned contexts involving fearful shyness declined across grade level grade, whereas the number mentioning contexts involving self‐conscious shyness increased with increasing grade level. Copyright © 2008 John Wiley & Sons, Ltd.
Interference control in preschoolers: factors influencing performance on the day–night task
Authors: Montgomery Derek E. , Anderson Maren , Uhl Elizabeth
Published: January 2008

Two experiments investigated preschoolers' interference control in variants of the day–night task. The day–night task involves instructing children across 16 trials to say the word ‘day’ when viewing a card depicting a nighttime sky and to say ‘night’ when shown a picture of the daytime sky. The purpose of the experiments was to investigate whether the depiction on each card distracts children because it is semantically associated with the instructed response or because the depicted item cues the alternative (incorrect) response within the response set. The results in the first study (N=23, M=52.65 months) and second study (N=54, M=50.81 months) indicate that a close semantic relation between the picture and the target response does not pose substantial interference for preschoolers. In contrast, the pictured item poses a significant challenge for preschoolers when it depicts the interfering alternative in the response set. Theoretical implications of these results for the development of interference control are discussed. Copyright © 2008 John Wiley & Sons, Ltd.
Neighborhood hypergraphs of bipartite graphs
Authors: Boros Endre , Gurvich Vladimir , Zverovich Igor
Published: January 2008

Matrix symmetrization and several related problems have an extensive literature, with a recurring ambiguity regarding their complexity and relation to graph isomorphism. We present a short survey of these problems to clarify their status. In particular, we recall results from the literature showing that matrix symmetrization is in fact NP‐hard; furthermore, it is equivalent with the problem of recognizing whether a hypergraph can be realized as the neighborhood hypergraph of a graph. There are several variants of the latter problem corresponding to the concepts of open, closed, or mixed neighborhoods. While all these variants are NP‐hard in general, one of them restricted to the bipartite graphs is known to be equivalent with graph isomorphism. Extending this result, we consider several other variants of the bipartite neighborhood recognition problem and show that they all are either polynomial‐time solvable, or equivalent with graph isomorphism. Also, we study uniqueness of neighborhood realizations of hypergraphs and show that, in general, for all variants of the problem, a realization may be not unique. However, we prove uniqueness in two special cases: for the open and closed neighborhood hypergraphs of the bipartite graphs. © 2008 Wiley Periodicals, Inc. J Graph Theory 58: 69–95, 2008
Analytical characterization of microfabricated SU‐8 emitters for electrospray ionization mass spectrometry
Authors: Sikanen Tiina , Tuomikoski Santeri , Ketola Raimo A. , Kostiainen Risto , Franssila Sami , Kotiaho Tapio
Published: January 2008

We present a detailed optimization and characterization of the analytical performance of SU‐8‐based emitters for electrospray ionization mass spectrometry (ESI/MS). The improved SU‐8 fabrication process presented here enhances patterning accuracy and reduces the time and cost of fabrication. All emitters are freestanding and enable sample delivery by both pressure‐driven and spontaneous flows. The optimized emitter design incorporates a sharp, double‐cantilevered tip implemented to the outlet of an SU‐8 microchannel and provides highly sensitive ESI/MS detection. Moreover, the optimized design allows the use of relatively large microchannel dimensions (up to 200 × 50 µm2, w × h) without sacrificing the detection sensitivity. This is advantageous with a view of preventing emitter clogging and enabling reproducible analysis. The measured limits of detection for the optimized emitter design were 1 nM for verapamil and 4 nM for Glu‐fibrinopeptide B with good quantitative linearities between 1 nM and 10 µM (R2 = 0.9998) for verapamil and between 4 nM and 3 µM (R2 = 0.9992) for Glu‐fibrinopeptide B. The measured tip‐to‐tip repeatability for signal intensity was 14% relative standard deviation (RSD) (n = 3; 5 µM verapamil) and run‐to‐run repeatability 4–11% RSD (n = 4; 5 µM verapamil) for all individual emitters tested. In addition, long‐term stability of < 2% RSD was maintained for timescales of 30 min even under free flow conditions. SU‐8 polymer was also shown to be chemically stable against most of the tested electrospray solvents. Copyright © 2008 John Wiley & Sons, Ltd.
The effects of chromium(III) coordination on the dissociation of acidic peptides
Authors: Pu Dan , Vincent John B. , Cassady Carolyn J.
Published: January 2008

The complexes formed between chromium(III) and synthetic acidic peptides were studied by sustained off‐resonance irradiation collision‐induced dissociation (SORI‐CID) in a Fourier transform ion‐cyclotron resonance (FT‐ICR) mass spectrometer equipped with electrospray ionization (ESI). Neutral peptides and peptides containing one, two, and multiple acidic residues were studied. Formation of [M + Cr − 2H]+ occurred for all peptides. Three noteworthy features were found in the CID spectra of [M + Cr − 2H]+. The first is that fewer fragment ions were produced from [M + Cr − 2H]+ than from [M + H]+. The reason may be that multiple coordination between chromium(III) and carboxylate or carbonyl groups hinders the production of fragment ions by continuing to bind pieces of the peptide to chromium(III) after cleavage of bonds within the peptide. The second feature is loss of CO from [M + Cr − 2H]+ and [yn + Cr − H]+. A mechanism involving coordination of chromium(III) with carboxylate groups is proposed to rationalize elimination of CO. The third feature is that chromium(III) is retained in all fragment ions, indicating strong binding of the metal ion to the peptides. The complex [M + 2Cr − 5H]+ is formed as the peptide chain length and number of acidic residues increases. Longer peptides have more sites to coordinate with chromium(III) and more conformational flexibility. In addition, formation of [M + Cr − 2H]+ from AGGAAAA‐OCH3, which has no carboxylic acid groups, suggests that chromium(III) can coordinate with sites on the peptide backbone, albeit in low abundance. In the negative mode, [M + Cr − 4H]− was only found for peptides containing four or more carboxylic acid groups. This is consistent with deprotonated carboxylic acid groups being involved in chromium(III) coordination and with chromium existing in the 3 + state in the gas‐phase ions. Copyright © 2008 John Wiley & Sons, Ltd.
Isomerization of delta‐9‐THC to delta‐8‐THC when tested as trifluoroacetyl‐, pentafluoropropionyl‐, or heptafluorobutyryl‐ derivatives
Authors: Holler Justin M. , Smith Michael L. , Paul Shom N. , Past Marilyn R. , Paul Buddha D.
Published: January 2008

For GC–MS analysis of delta‐9‐tetrahydrocannabinol (delta‐9‐THC), perfluoroacid anhydrides in combination with perfluoroalcohols are commonly used for derivatization. This reagent mixture is preferred because it allows simultaneous derivatization of delta‐9‐THC and its acid metabolite, 11‐nor‐delta‐9‐THC‐9‐carboxylic acid present in biological samples. When delta‐9‐THC was derivatized by trifluoroacetic anhydride/hexafluoroisopropanol (TFAA/HFIPOH) and analyzed by GC–MS using full scan mode (50–550 amu), two peaks (P1 and P2) with an identical molecular mass of 410 amu were observed. On the basis of the total ion chromatogram (TIC), P1 with a shorter retention time (RT) was the major peak (TIC 84%). To identify the peaks, delta‐8‐THC was also tested under the same conditions. The RT and spectra of the major peak (TIC 95%) were identical with that of P1 for delta‐9‐THC. A minor peak (5%) present also correlated well with the latter peak (P2) for the delta‐9‐THC derivative. The fragmentation pathway of P1 was primarily demethylation followed by retro Diels‐Alder fragmentation (M − 15–68, base peak 100%) indicating P1 as a delta‐8‐THC‐trifluoroacetyl compound. This indicated that delta‐9‐THC isomerized to delta‐8‐THC during derivatization with TFAA/HFIPOH. Similar results were also observed when delta‐9‐THC was derivatized with pentafluoropropionic anhydride/pentafluoropropanol or heptafluorobutyric anhydride/heptafluorobutanol. No isomerization was observed when chloroform was used in derivatization with TFAA. In this reaction, the peaks of delta‐8‐THC‐TFA and delta‐9‐THC‐TFA had retention times and mass spectra matching with P1 and P2, respectively. Because of isomerization, perfluoroacid anhydrides/perfluoroalcohols are not suitable derivatizing agents for analysis of delta‐9‐THC; whereas the TFAA in chloroform is suitable for the analysis. Published in 2008 by John Wiley & Sons, Ltd.
Reduction and adduct formation from electrosprayed solutions of porphyrin salts
Authors: Ramos Catarina I. V. , Santana‐Marques M. Graça , Ferrer Correia A. J. , Tomé João P. C. , Alonso Cristina M. , Tomé Augusto C. , Neves M. Graça P. M. S. , Cavaleiro J. A. S.
Published: January 2008

The solutions of four meso‐tetrakis(N‐alkylpyridinium‐4‐yl)porphyrin salts and of the p‐toluenesulfonate salt of meso‐tetrakis(4‐trimethylammoniumphenyl)porphyrin, in methanol, were studied by electrospray mass spectrometry, in order to investigate the influence of the type of counter ion, the length of the substituent N‐alkyl groups of the four (N‐alkylpyridinium‐4‐yl)porphyrins and the presence of an aromatic (alkylpyridinium) or aliphatic (trimethylammonium) nitrogen, in ion formation.

In our experimental conditions, adducts with the counter ions were formed only for the meso‐tetrakis(4‐trimethylammoniumphenyl)porphyrin and were not observed for the other porphyrins, even when the counter ion was the same. In contrast, formation of reduced species, such as the [M4+ + e−]3+, [M4+ + 2e−]2+, [M4+ + 4e− + 2H+]2+, and [M4+ + 5e− + 2H+]+ ions was observed only for the (N‐alkylpyridinium‐4‐yl)porphyrins and the appearance of these species is apparently solvent related and may occur via counter ion/solvent adducts. Copyright © 2008 John Wiley & Sons, Ltd.
Sea surface temperature patterns in the Gulf of Guinea: their implications for the spatio‐temporal variability of precipitation in West Africa
Authors: Odekunle Theophilus O. , Eludoyin A. O.
Published: January 2008

This study examined the sea surface temperature (SST) patterns in the Gulf of Guinea (GOG) and discussed their implications for the spatio‐temporal variability of precipitation in West Africa. The SST data spanning over 49 years (1950–1998) at 2° × 2° resolutions were sourced from the archive of the International Research Institute for climate prediction. The specific locations where data were collected to represent the GOG are longitudes 10°W, 8°W, 6°W, 4°W, 2°W, 0° , 2°E, 4°E, 6°E, and 8°E, and latitudes 5°N, 3°N, 1°N, 1°S, 3°S, and 5°S. The results obtained show that the SST in the GOG generally decreases westward and southward, while the reverse of the case holds for its variability values. Detailed observations show that the SST is generally below the latitudinal average and its variability values, above the latitudinal average mainly between longitudes 8°W and 2°E. The results also show that during the period of July‐August‐September, the SST is anomalously colder between longitudes 8°W and 2°E and the West African coastal border and latitude 3°N. This area was observed as constituting the area of the coastal upwelling. The intra‐annual distribution of the SST, as evident along latitudes 3°N and 5°N, shows two main regimes and two transitional periods in between the regimes. The first regime is November to May, and the second, July to September. The first regime transits to the second during the month of June and the second back to the first, during the month of October. The comparative analysis of the first and second half of the period of study indicates that the SST of the GOG has undergone some warming over time. The comparison also shows that although the SST has generally risen, an area of relatively cool SST near the Guinea coast has expanded from longitudes 7°W–0°W to 8°W–3°E. Copyright © 2008 Royal Meteorological Society
An automated sea breeze selection technique based on regional sea‐level pressure difference: WeMOi
Authors: Azorin‐Molina Cesar , Lopez‐Bustins Joan‐Albert
Published: January 2008

A recently defined regional teleconnection pattern for the western Mediterranean basin (western Mediterranean Oscillation, WeMO) has allowed an objective quantification of the synoptic circulation factor on the occurrence of sea breezes. The associated WeMO index (WeMOi) can be used as an initial objective filter for selecting ideal surface pressure conditions for sea breeze development. Applying this filter to the sea breeze database created for Alicante (reference synoptic station) and performing a manual selection method for the 2‐year period (1999–2000), we confirmed the potential use of this objective primary criterion. We used wind speed (WS) and direction (WD) data from 9 coastline meteorological stations to assess the WeMOi applicability to the Iberian Mediterranean coast and the Balearic Isles. The [−1, 1] threshold interval of the daily WeMOi was seen to be a good proxy for detecting weak pressure gradients at surface level. Observational and numerical sea breeze studies require quality databases in order to analyse in depth the main characteristics and physical processes controlling sea breezes. This automated selection technique enabled us to improve the accuracy and processing time of the filter methods for finding sea breeze days by adding a new objective criterion. This new threshold technique [−1, 1], based on regional sea‐level pressure (SLP) difference, is adaptable to any coastal region at mid‐latitudes where a regional barometric dipole can be defined. A regional teleconnection pattern, such as the WeMOi, could be used as a suitable tool for forecasting sea breeze occurrence. Copyright © 2008 Royal Meteorological Society
Micro‐Raman and particle‐induced X‐ray emission spectroscopy for the study of pigments and degradation products present in 17th century coloured maps
Authors: Mendes Nuno , Lofrumento C. , Migliori A. , Castellucci E. M.
Published: January 2008

Three different maps of the 17th century, two of them of Portugal and the third of the Iberian Peninsula, all of them hand coloured and of Dutch manufacture (copper engraving), were studied in this work. The study was carried out by using particle‐induced X‐ray emission (PIXE) and micro‐Raman spectroscopy. These are two non‐destructive techniques that provide complementary information on the composition of the materials: PIXE giving elemental information and Raman providing information at a molecular level. By means of the two techniques it has been possible to identify the inorganic pigments used in the three maps, as well as some products of degradation whose causes are not completely understood yet. This article contributes to a better knowledge of the techniques and palettes used for the colouring of maps of this period as well as the degradations of the pigments. Particular attention is given to the presence of a copper oxalate found in two different maps, its presence being associated with green coloured areas and indicating a degradation of a copper‐based green pigment. Copyright © 2008 John Wiley & Sons, Ltd.
Micro‐Raman and fluorescence spectroscopy for the assessment of the effects of the exposure to light on films of egg white and egg yolk
Authors: Osticioli Iacopo , Nevin Austin , Anglos Demetrios , Burnstock Aviva , Cather Sharon , Becucci Maurizio , Fotakis Costas , Castellucci Emilio
Published: January 2008

In this work, non‐destructive techniques were employed for the spectrofluorimetric and micro‐Raman differentiation of solid films of egg yolk and egg white as a function of exposure to light. Using both techniques it is possible to discriminate between the samples on the basis of composition and follow some chemical changes involved during the light‐ageing of egg proteins and fatty acid esters. In egg white, fluorescence emission spectra highlighted the presence of multiple fluorophores, with an effective broadening of the fluorescence emissions following light exposure, ascribed to the partial oxidation and depletion of tryptophan; in the Raman spectrum of dark‐aged egg white a peak at 758 cm−1 is ascribed to the vibrational mode of tryptophan, which is completely absent in the spectrum of samples exposed to light. Changes in the fluorescence of egg yolk following exposure to light are ascribed to the degradation of amino acids, cross‐linking between amino acids and the formation of oxygenated triacylglycerides. These results are corroborated with Raman spectra of the light‐exposed samples, which are associated with wavenumber shifts with respect to the dark‐aged sample for the Amide I and for the characteristic carbonyl vibration at 1744 cm−1 ascribed to the oxidation of fatty acid esters. Copyright © 2008 John Wiley & Sons, Ltd.
New Polyolefin‐Nanocomposites by In Situ Polymerization with Metallocene Catalysts
Authors: Scharlach Katrin , Kaminsky Walter
Published: January 2008

Summary: Polypropylene‐nanocomposites were prepared by in‐situ polymerization with the catalysts systems rac[Et(IndH4)2]ZrCl2, Me2Si(Flu)(Ind)ZrCl2 and rac[Me2Si(2‐Me‐4‐(1‐Naph)Ind)2]ZrCl2. The type and size of the nanoparticles and the concentration of the propene were varied. The activity is independent of the type and the size of the filler. It was observed that the filler contents in the polypropylene‐nanocomposites depend on the catalysts system used. The morphology results using TEM revealed that the nanoparticles are uniformly distributed in the isotactic polypropylene matrix. Additionally, the melting points, glass temperatures and crystallization temperatures changed with the amount of the fillers.
Applications of Calixarenes in Polymer Synthesis
Authors: Zhu Weipu , Gou Pengfei , Shen Zhiquan
Published: January 2008

Summary: The applications of calixarenes in polymer synthesis have been reviewed. Calixarenes have been used as ligands to prepare rare earth calixarene complexes. A series of rare earth calixarene complexes have been synthesized and employed as efficient catalysts for the polymerization of ethylene, styrene, butadiene, propylene oxide, styrene oxide, trimethylene carbonate, and 5,5‐dimethyl trimethylene carbonate. On the other hand, the synthesis and characterization of star‐shaped polymers with calixarene as core molecules are also described.
Preparation of Poly(amic acid) and Polyimide via Microwave‐Assisted Polycondensation of Aromatic Dianhydrides and Diamines
Authors: Li Quantao , Yang Xiaojin , Chen Wenqiu , Yi Changfeng , Xu Zushun
Published: January 2008

Summary: A copolycondesation‐type poly (amic acid) (PAA) was synthesized using pyromellitic dianhydride (PMDA) and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) as dianhydride monomers, and 4,4′‐oxydianiline (ODA) as a diamine monomer under microwave irradiation in dimethylformamide (DMF). PAA was then converted into a polyimide (PI) by an imidization. The structure and performance of the polymer were characterized by Fourier‐transform infrared (FT‐IR) spectroscopy, Proton nuclear magnetic resonance (1H NMR) spectrometry, viscosity, X‐ray diffraction (XRD), and thermogravimetric (TG) analyses. The results showed that under microwave irradiation, the intrinsic viscosity and the yield of PAA were increases, and the reaction time was shortened. The FT‐IR spectra of the polymer revealed characteristic peaks for PI around 1778– and 1723 cm–1. TG curves indicated that the obtained PI began to lose weight at 535 °C, and its 10% thermal decomposition temperature under N2 was 587 °C.
Tuning Macromolecular Structures of Synthetic Vectors for Gene Therapy
Authors: Cheradame H. , Sassatelli M. , Pomel C. , Sanh A. , Gau‐Racine J. , Bacri L. , Auvray L. , Guégan P.
Published: January 2008

Summary: The synthesis of triblocks poly(2‐methyl‐2‐oxazoline‐b‐tetrahydrofurane‐b‐2‐methyl‐2‐oxazoline) has been developed. It was shown that the technique of polymerization of the second block from the living species created on the two chain ends of poly(THF) is successful but makes the control of the size of the poly(THF) block difficult due a fast depolymerization upon the introduction of the second monomer. A purification technique was used to get rid of the possible homopoly(2‐methyl‐2‐oxazoline) formed. Various analytical techniques were used to characterize the behavior of the triblock and more particularly in the presence of DNA. Electrophoresis on agarose gels and neutron scattering, demonstrated that the neutral triblock does not appreciably interact with DNA. It was also shown that the triblock for which approximately half (47%) of the methyloxazoline units were transformed into ethylenimine units by hydrolysis gives only loose interactions with DNA. This result is assigned to the fact that charge density plays a major role in the interactions of positive polyelectrolytes with the negatively charged DNA. The triblock was shown being able to interact with bilayer lipid membranes mimicking cell membranes. The efficiency of the hydrolysed triblock was much higher, while the size of holes created in the membranes is not large enough to give passage to DNA.
Numerical stabilization of Biot's consolidation model by a perturbation on the flow equation
Authors: Aguilar G. , Gaspar F. , Lisbona F. , Rodrigo C.
Published: January 2008

In this paper a stabilized finite element scheme for the poroelasticity equations is proposed. This method, based on the perturbation of the flow equation, allows us to use continuous piecewise linear approximation spaces for both displacements and pressure, obtaining solutions without oscillations independently of the chosen discretization parameters. The perturbation term depends on a parameter which is established in terms of the mesh size and the properties of the material. In the one‐dimensional case, this parameter is shown to be optimal. Some numerical experiments are presented indicating the efficiency of the proposed stabilization technique. Copyright © 2008 John Wiley & Sons, Ltd.
Recent advances in plant cell wall proteomics
Authors: Jamet Elisabeth , Albenne Cécile , Boudart Georges , Irshad Muhammad , Canut Hervé , Pont‐Lezica Rafael
Published: January 2008

The plant extracellular matrix contains typical polysaccharides such as cellulose, hemicelluloses, and pectins that interact to form dense interwoven networks. Plant cell walls play crucial roles during development and constitute the first barrier of defense against invading pathogens. Cell wall proteomics has greatly contributed to the description of the protein content of a compartment specific to plants. Around 400 cell wall proteins (CWPs) of Arabidopsis, representing about one fourth of its estimated cell wall proteome, have been described. The main points to note are that: (i) the diversity of enzymes acting on polysaccharides suggests a great plasticity of cell walls; (ii) CWPs such as proteases, polysaccharide hydrolytic enzymes, and lipases may contribute to the generation of signals; (iii) proteins of unknown functions were identified, suggesting new roles for cell walls. Recently, the characterization of PTMs such as N‐ and O‐glycosylations improved our knowledge of CWP structure. The presence of many glycoside hydrolases and proteases suggests a complex regulation of CWPs involving various types of post‐translational events. The first 3‐D structures to be resolved gave clues about the interactions between CWPs, or between CWPs and polysaccharides. Future work should include: extracting and identifying CWPs still recalcitrant to proteomics, describing the cell wall interactome, improving quantification, and unraveling the roles of each of the CWPs.
Characteristics of thermo‐ and photo‐stimulated electron emission from silicon wafers
Authors: Momose Yoshihiro , Satou Arata , Sakurai Takao , Nakayama Keiji
Published: January 2008

The temperature dependence of photoelectric emission and its spectral yield has been studied for Si (100) wafer surfaces with a native oxide film. The emission measurement was performed using a gas‐flow Geiger counter developed for examining real surfaces. The saturation emission observed as a function of temperatures between 26 and 350 °C under illumination with far ultraviolet rays had the average activation energy of 0.27 eV in the Arrhenius plot. The analysis of the spectral yield observed after the preillumination gave two almost temperature independent photoelectric thresholds of 4.84 ± 0.11 and 5.57 ± 0.15 eV. The difference between the former value and the indirect optical excitation threshold for a clean, cleaved silicon surface reported by Gobeli and Allen approximately agrees with the activation energy. This energy is interpreted as being due to a thermal process for electron transport from the silicon substrate to the SiO2/Si interface states. A new emitting center with optical activation energy of about 5.7 eV was also found for the preilluminated surfaces. Copyright © 2008 John Wiley & Sons, Ltd.
Ce 3d XPS investigation of cerium oxides and mixed cerium oxide (CexTiyOz)
Authors: Bêche Eric , Charvin Patrice , Perarnau Danielle , Abanades Stéphane , Flamant Gilles
Published: January 2008

This article presents an XPS study of Ce 3d emission spectra dominated by atomic multiplet effects in core level spectroscopy of rare earth compounds (Ce oxides). Core level spectroscopy has been used to study the electronic states of Ce 3d5/2 and Ce 3d3/2 levels in Ce4+ and Ce3+ states. The well‐resolved components of Ce 3d5/2 and Ce 3d3/2 spin‐orbit components, due to various final states (4f0, 4f1, 4f2 configurations), were determined on 3d XPS spectra from commercial powders (CeO2, CePO4).

These results were used to study the 3d spin‐orbit component of mixed cerium‐titanium oxide.

This compound was prepared by co‐melting commercial powders of CeO2 and TiO2 at 1800 K under air using a solar furnace with a flux density of 16 MW.m−2 at the focal point of the parabolic concentrator. The mixed oxide Ce2Ti2O7 was produced and contained Ce(III) species which may be reactive with water to give back the initial metal oxides and generate hydrogen, a valuable product considered as a promising energy carrier in the future in replacement of oil.

The 3d photoemission spectra revealed the presence of mixed components attributed to mainly Ce(III) and Ce(IV) species. Copyright © 2008 John Wiley & Sons, Ltd.
On the development of long‐range order in ultra‐thin amorphous Al2O3 films upon their transformation into crystalline γ‐Al2O3
Authors: Jeurgens L. P. H. , Reichel F. , Frank S. , Richter G. , Mittemeijer E. J.
Published: January 2008

The changes in the local chemical environments of Al and O ions in ultra‐thin (<1 nm) amorphous Al2O3 films on Al{111} and Al{100} substrates during their transformation into γ‐like‐Al2O3 have been deduced from the corresponding changes in the so‐called Auger parameters for Al and O (as measured using XPS), in combination with structural analysis by high resolution transmission electron microscopy and low‐energy electron diffraction. It is demonstrated that the difference between the O and Al Auger parameters can be employed to monitor the change in polarisation state of the O anions in the oxide film during the amorphous‐to‐crystalline transition. It follows that (i) the amorphous‐to‐crystalline transition occurs at higher temperatures (starting at T > 425 K) for the oxide films grown on Al{111} than for the oxide films formed on Al{100} (starting at T < 400 K) and (ii) the low‐mismatch (epitaxial) crystalline oxide films on Al{111} possess a higher degree of crystalline order as compared to the high‐mismatch oxide films formed on Al{100}. Copyright © 2008 John Wiley & Sons, Ltd.
REEL spectra from aluminium: experiment and Monte Carlo simulation using two different dielectric functions
Authors: Dapor Maurizio , Calliari Lucia , Filippi Massimiliano
Published: January 2008

Within the framework of the dielectric theory, the spectral response of a solid irradiated by an electron beam is described by the energy loss function.

In the limit of zero momentum transfer, the dielectric function is generally known from optical data for many materials. The main problem, when electron beams are involved, concerns the extension of the dielectric function from the optical limit to non‐zero momentum transfer.

This extension requires introducing a dielectric function, which depends on both energy loss and momentum transfer.

Using Al–representative of a dilute gas of free electrons–as a case study, the present work compares two Monte Carlo (MC) simulations with experimental reflection electron energy loss (REEL) spectra excited by 2 keV electrons. To obtain the two MC simulated spectra, the dielectric function was modelled, respectively, according to Ashley (1988) and according to an early suggestion by Ritchie and Howie (1977), later reconsidered by Yubero and Tougaard (1992).

MC simulated REEL spectra obtained according to the latter model reproduce the experimental REEL spectra better than those obtained using the Ashley dielectric function. The comparison involves not only the single scattering plasmon peak (bulk and surface) but also multiple scattering peaks. Copyright © 2008 John Wiley & Sons, Ltd.
Imputation‐based strategies for clinical trial longitudinal data with nonignorable missing values
Authors: Yang Xiaowei , Li Jinhui , Shoptaw Steven
Published: January 2008

Biomedical research is plagued with problems of missing data, especially in clinical trials of medical and behavioral therapies adopting longitudinal design. After a literature review on modeling incomplete longitudinal data based on full‐likelihood functions, this paper proposes a set of imputation‐based strategies for implementing selection, pattern‐mixture, and shared‐parameter models for handling intermittent missing values and dropouts that are potentially nonignorable according to various criteria. Within the framework of multiple partial imputation, intermittent missing values are first imputed several times; then, each partially imputed data set is analyzed to deal with dropouts with or without further imputation. Depending on the choice of imputation model or measurement model, there exist various strategies that can be jointly applied to the same set of data to study the effect of treatment or intervention from multi‐faceted perspectives. For illustration, the strategies were applied to a data set with continuous repeated measures from a smoking cessation clinical trial. Copyright © 2008 John Wiley & Sons, Ltd.
[{μ‐Cy8Si8O13}2Ca(DME)Ca(THF)2] – The First Metallasilsesquioxane Derivative of a Heavier Alkaline Earth Metal
Authors: Lorenz Volker , Blaurock Steffen , Edelmann Frank T.
Published: January 2008

[{μ‐Cy8Si8O13}2Ca(DME)Ca(THF)2] (2), the first metallasilsesquioxane derivative of a heavier alkaline earth metal, has been prepared by a reaction of Cy7Si7O9(OH)3 (1) with metallic Ca in liquid ammonia / THF followed by recrystallization from DME. In the course of the reaction ligand rearrangement under formation of the (Cy8Si8O13)− dianion takes place. In the dinuclear calcium complex 2 the anionic silsesquioxane cages act as bridging ligands. The Ca2+ ions are unsymmetrically coordinated by THF and DME molecules.
[Cp2TiNi(S2N2)2] – The First Organometallic Derivative of [Ni(S2N2H)2]
Authors: Edelmann Frank T. , Blaurock Steffen , Lorenz Volker , Chivers Tristram
Published: January 2008

The synthesis and structural characterization of the first organometallic derivative of [Ni(S2N2H)2] (1) are reported. Treatment of K2[Ni(S2N2)2] (2) with stoichiometric amounts of [Cp2TiCl2] in boiling toluene afforded black, crystalline [Cp2TiNi(S2N2)2] (3) in 50 % yield. According to a single‐crystal X‐ray diffraction study, the novel heterobimetallic complex 3 comprises a nearly planar TiNi(S2N2)2 arrangement. The Ti···Ni separation in 3 is 2.8348(5) Å, a value that is typical for bridged early‐late heterobimetallic complexes.
Synthesen, Kristallstrukturen und Drillingsbildung der Cluster‐Trimere Bi2[PtBi6Br12]3 und Bi2[PtBi6I12]3
Authors: Günther Anja , Steden Folker , Ruck Michael
Published: January 2008

Syntheses, Crystal Structures, and Triple Twinning of the Cluster Trimers Bi2[PtBi6Br12]3 and Bi2[PtBi6I12]3

Melting reactions of Bi with Pt and BiX3 (X = Br, I) yield shiny black, air insensitive crystals of the subhalides Bi2[PtBi6X12]. Bi2[PtBi6Br12]3 crystallizes in the monoclinic space group C2/m with lattice parameters a = 1617.6(2) pm, b = 1488.5(1) pm, c = 1752.4(2) pm, and β = 110.85(4)°. Bi2[PtBi6I12]3 adopts the triclinic space group $C{\bar 1}$ with pseudo‐monoclinic lattice parameters a = 1711.2(2) pm, b = 1585.1(1) pm, c = 1865.7(2) pm, and α = 90°, β = 111.15(4)°, γ = 90°. The two homoeotypic compounds consist of cuboctahedral [Pt−IIBiII6X−I12]2− clusters that are concatenated into linear trimers by BiIII atoms. The ordered distribution of BiIII atoms destroys the inherent threefold rotation axes in the packing of cluster anions. As a consequence of the pseudosymmetry the crystals are triple twinned along [201]. Due to different orientations of the cluster trimers there are two BiII···X inter‐cluster bridges per BiII atom in Bi2[PtBi6Br12]3 but only one bridge in Bi2[PtBi6I12]3. The structure of the iodine compound can be deduced from the NaCl structure type, leaving 37 of 96 atomic positions unoccupied. The arrangement of the cuboctahedral clusters follows the motif of a body‐centered cubic packing.
Hexachloroplatinates of the Lanthanides: Syntheses and Thermal Decomposition of [M(NO3)2(H2O)6]2[PtCl6]·2H2O (M = La, Pr) and [M(NO3)(H2O)7][PtCl6]·4H2O (M = Gd, Dy)
Authors: Arndt Annika , Posavec Damir , Schwarzer Stefan , Wickleder Mathias S.
Published: January 2008

The reaction of the nitrates M(NO3)3·6H2O (M = La, Pr) and (H3O)2PtCl6 led to yellow single crystals of [M(NO3)2(H2O)6]2[PtCl6]·2H2O (M = La, Pr) (monoclinic, P21/c, Z = 2, La/Pr: a = 697.4(3)/695.5(1), b = 1654.5(1)/1652.5(2), c = 1317.7(6)/1318.5(3) pm, β = 93.97°(7)/93.93°(2), Rall = 0.0169/0.0659) while the reaction of M(NO3)3·5H2O (M = Gd, Dy) and (H3O)2PtCl6 yielded yellow single crystals of [M(NO3)(H2O)7][PtCl6]·4H2O (monoclinic, P21/n, Z = 4, Gd/Dy: a = 838.72(3)/838.40(2), b = 2131.98(6)/2139.50(7), c = 1142.63(3)/1143.10(3) pm, β = 95.670(4)/95.698(3), Rall = 0.0475/0.0337). The crystal structures consist of octahedral [PtCl6]2− anions and complex [M(NO3)2(H2O)6]2+ and [M(NO3)(H2O)7]2+ cations, respectively. The thermal decomposition of both types of compounds leads via various steps to elemental platinum and the oxide chlorides MOCl (M = La, Pr, Gd, Dy).
Synthesis, Crystal Structure and Magnetism Characterization of Two Coordination Polymers based on Ni(2‐mpac)2(H2O)2 as Molecular Building Block
Authors: Chen San‐Ping , Fan Guang , Gao Sheng‐Li
Published: January 2008

Taking Ni(2‐mpac)2(H2O)2 as molecular building block, two novel coordination polymers with the formula of [Ni(2‐mpac)2(4,4′‐bpy)·(4,4′‐bpy)]n (1) and [Ni(2‐mpac)2(py)·4H2O]n (2) (2‐mpac = 5‐methyl‐2‐pyrazinecarboxylic acid; 4,4′‐bpy = 4,4′‐bipyridine; py = pyrazine) have been synthesized and structurally characterized by X‐ray single crystal diffraction method. In addition, elemental analysis, IR and magnetism characterization are presented.
[{Er(NC5H4COOH)(H2O)2}2(H5O2)(HgCl5)(HgCl4)2(H2O)2]n – Synthesis, Crystal Structure and Properties
Authors: Chen Wen‐Tong , Xu Ya‐Ping , Luo Qiu‐Yan , Fang Xiao‐Niu , Chen Hua‐Long
Published: January 2008

The first heterometallic 4f‐5d inorganic‐organic metal‐isonicotinic acid hybrid [{Er(NC5H4COOH)(H2O)2}2(H5O2)(HgCl5)(HgCl4)2(H2O)2]n (1) has been synthesized via hydrothermal reaction and structurally characterized. Complex 1 crystallizes in the space group C2/c of the monoclinic system with four formula units per unit cell: a = 24.194(3), b = 20.792(3), c = 15.289(4) Å, β = 128.39(2)°, V = 6028(2) Å3, C36H47Cl13Er2Hg3N6O20, Mr = 2280.94, Dc = 2.513 g/cm3, S = 0.929, μ(MoKα) = 11.017 mm−1, F(000) = 4248, R = 0.0425 and wR = 0.0739. The crystal structure analysis reveals that the title complex is characteristic of a one‐dimensional chain‐like structure. Photoluminescent investigation reveals that the title complex displays interesting emissions. Optical absorption spectra of 1 reveal the presence of an optical gap of 3.45 eV. The magnetic properties show that complex 1 exhibits antiferromagnetic interactions.
Preparation and Structure of Melemium Melem Perchlorate HC6N7(NH2)3ClO4·C6N7(NH2)3
Authors: Sattler Andreas , Schnick Wolfgang
Published: January 2008

A new perchlorate salt of melem (2,6,10‐triamino‐s‐heptazine, C6N7(NH2)3) was obtained from an aqueous solution of HClO4 at lower concentration than the ones reported for the synthesis of melemium perchlorate monohydrate (HC6N7(NH2)3)ClO4·H2O. The new salt was identified as melemium melem perchlorate (HC6N7(NH2)3)ClO4·C6N7(NH2)3 representing a melem adduct of water free melemium perchlorate. The crystal structure was solved by single‐crystal X‐ray methods ($P{\bar 1}$, no. 2, Z = 2, a = 892.1(2), b = 992.7(2), c = 1201.5(2) pm, α = 112.30(3), β = 96.96(3), γ = 95.38(3)°, V = 965.8(4)·106 pm3, 4340 data, 387 parameters, R1 = 0.039). Melemium melem perchlorate crystallizes in a layer‐like structure containing both protonated HC6N7(NH2)3 and non protonated C6N7(NH2)3 moieties in the coplanar layers as well as perchlorate ions between them, all of which being interconnected by hydrogen bonds. Vibrational spectroscopic investigations (FTIR and Raman) of the salt were conducted.
Synthesis and Structure of the Cerium Schiff‐Base Complexes [Ce(Salen′)2] and [(THF)2KCe(Salen′)2]
Authors: Gottfriedsen Jochen , Spoida Marlies , Blaurock Steffen
Published: January 2008

The synthesis of [Ce(Salen′)2] (1) (H2Salen′ = N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)ethylenediamine) was performed using two different approaches. CeCl3 reacts with two equivalents of K2Salen′ in THF under the formation of [(THF)2KCe(Salen′)2] (2). Complex 2 could be converted to the CeIV complex 1 via oxidation with p‐benzoquinone and air, respectively. The reversible reduction process was realized using elemental potassium in boiling THF. Furthermore, the reaction of the CeIV starting material [(tBuO)4Ce(THF)2] with the “free” ligand H2Salen′ in boiling toluene lead in the formation of 1 as well.
Solvothermal Synthesis, Crystal Structure and Properties of a New Organic Templated Lanthanum Sulfate [C4N3H16][La(SO4)3(H2O)]
Authors: Zhu Yalin , Zhou Guangpeng , Xu Yan , Zhu Dunru , Zheng Xuefang
Published: January 2008

A new organic templated lanthanum sulfate [C4N3H16][La(SO4)3(H2O)] (1) has been solvothermally synthesized by using n‐butanol as solvent. The colorless block crystals were characterized by IR, TGA, ICP, and XRD. The structure was determined by single‐crystal X‐ray diffraction: Monoclinic, P21/c, a = 10.8878(19), b = 15.478(3), c = 9.9639(18) Å, β = 114.062(2)°, V=1533.2(5) Å3, Z = 4]. Crystal structure analysis shows that the one dimensional chain of 1 consists of the LaO9 polyhedra and the sulfate groups. Coordination water molecules link adjacent chains by using hydrogen bonds to generate 2D layers, whereas the organic amines are inserted between the layers. The formation of 1 demonstrates that solvents play an important role during the synthesis.
Syntheses and X‐Ray Structures of Zinc Amidinate Complexes
Authors: Eisenmann Tamara , Khanderi Jayaprakash , Schulz Stephan , Flörke Ulrich
Published: January 2008

Reactions of ZnX2 (X = Cl, Br) with equimolar amounts of Li[t‐BuC(NR)2] (R = i‐Pr, Cy) yielded mono‐amidinate complexes [{t‐BuC(NR)2}ZnX]2 (X = Cl, R = i‐Pr 1, Cy 2; X = Br, R = i‐Pr 3, Cy 4), whereas reactions with two equivalents of Li‐amidinate resulted in the formation of the corresponding bis‐amidinate complexes [t‐BuC(NR)2]2Zn (R = i‐Pr 5, Cy 6). 1 ‐ 6 were characterized by elemental analyses, IR, mass and multinuclear NMR spectroscopy (1H, 13C), and single crystal X‐ray analysis (1, 2, 3, 6). In addition, the single crystal X‐ray structure of [t‐BuC(NCy)2]ZnBr·LiBr(OEt2)2 7, which was obtained as a byproduct in low yield from re‐crystallization experiments of 4 in Et2O, is reported.
A One‐Dimensional Pyrazine Bridged Copper(II)‐Saccharinato Coordination Polymer
Authors: Senel Evrim , Yilmaz Veysel T. , Kazak Canan
Published: January 2008

A one‐dimensional copper(II) complex {[Cu(sac)2(μ‐pyz)(H2O)]·H2O}n (1) (pyz = pyrazine, and sac = saccharinate) has been synthesized and characterized by elemental analysis, IR spectroscopy, thermal and single crystal X‐ray analyses. Complex 1 crystallizes in the triclinic space group $P{\bar 1}$. The [Cu(sac)2(H2O)] units are bridged by pyz leading to a one‐dimensional alternating chain in which the copper(II) ions exhibit a distorted square–pyramidal coordination of CuN4O. The intradimer Cu···Cu distance is 6.881Å, while interdimer Cu···Cu distance is 7.066Å. The supramolecular interactions are mainly controlled by the sac anion and water molecules. The individual chains are linked by strong OW–H···O(sac) hydrogen bonds into a two‐dimensional layers, which are further arranged in a three‐dimensional supramolecular network by aromatic π(sac)···π(sac) stacking interactions and CH···π(pyz) interactions. Thermal analysis of complex 1 shows that the decompositions of the aqua, pyz and sac ligands are observed as distinct steps on the DTA and TG curves.