bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spontaneous pulmonary interstitial emphysema in a term unventilated infant
Authors: Freysdottir Drifa , Olutoye Oluyinka , Langston Claire , Fernandes Caraciolo J. , Tatevian Nina 
Published: January 2006

AbstractPulmonary interstitial emphysema (PIE) is a form of air block most frequently seen in ventilated preterm infants with severe lung disease; it is rarely reported in spontaneously breathing term infants. We report on an infant previously diagnosed with laryngomalacia and congestive heart failure and with evidence of antenatal stroke before the onset of pulmonary disease. He presented at 6 weeks of age with spontaneous pneumothorax. Focal cystic changes were seen on imaging studies of the lungs. There was no prior history of mechanical ventilation. Prior chest X‐rays did not show cystic changes. He subsequently underwent resection of the affected lung areas. Pathologic examination revealed persistent PIE with cystic expansion, pleural blebs, and reactive pleuritis, as well as subpleural air‐space enlargement. The patient did well postoperatively and was discharged home without further problems. This case demonstrates that PIE can occur in an infant without any history of mechanical ventilation, suggesting the need for a high index of suspicion for PIE, even in nonventilated and spontaneously breathing term neonates. PIE should be included in the differential diagnosis of cystic lung lesions in all young infants. Pediatr Pulmonol. © 2006 Wiley‐Liss, Inc.
Native‐specific stabilization of flavodoxin by the FMN cofactor: Structural and thermodynamical explanation
Authors: Campos L. A. , Sancho J. 
Published: January 2006

AbstractFlavodoxins are useful models to investigate protein/cofactor interactions. The binding energy of the apoflavodoxin–FMN complex is high and therefore the holoflavodoxin is expected to be more stable than the apoprotein. This expectation has been challenged by reports on the stability of Desulfovibrio desulfuricans flavodoxin indicating that FMN binds to the unfolded polypeptide with similar affinity as to the native state, thus causing no net effect on protein stability. In previous work, we have analyzed in detail the stability of the apoflavodoxin from Anabaena PCC 7119 and the energetics of its functional complex with FMN. Here, we use the Anabaena holoprotein to directly investigate the contribution of the bound cofactor to protein stability through a detailed analysis of the chemical and thermal denaturation equilibria. Our data clearly shows that FMN binding largely stabilizes the protein towards both chemical and thermal denaturation, and that the stabilization observed at 25°C in low ionic strength conditions is precisely the one expected if full release of the cofactor takes place upon flavodoxin unfolding. On the other hand, the binding of FMN to the native polypeptide is shown to simplify the thermal unfolding so that, while apoflavodoxin follows a three‐state mechanism, the holoprotein unfolds in a two‐state fashion. Comparison of the X‐ray structure of native apoflavodoxin with the ϕ‐structure of the thermal intermediate indicates that the increase in cooperativity driven by the cofactor originates in its preferential binding to the native state, which is a consequence of the disorganization in the intermediate of the FMN binding loops and of an adjacent longer loop. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Hydrogen bonding is the prime determinant of carboxyl pKa values at the N‐termini of α‐helices
Authors: Porter Melissa A. , Hall Jordan R. , Locke James C. , Jensen Jan H. , Molina Pablo A. 
Published: January 2006

AbstractExperimentally determined mean pKa values of carboxyl residues located at the N‐termini of α‐helices are lower than their overall mean values. Here, we perform three types of analyses to account for this phenomenon. We estimate the magnitude of the helix macrodipole to determine its potential role in lowering carboxyl pKa values at the N‐termini. No correlation between the magnitude of the macrodipole and the pKa values is observed. Using the pKa program propKa we compare the molecular surroundings of 18 N‐termini carboxyl residues versus 233 protein carboxyl groups from a previously studied database. Although pKa lowering interactions at the N‐termini are similar in nature to those encountered in other protein regions, pKa lowering backbone and side‐chain hydrogen bonds appear in greater number at the N‐termini. For both Asp and Glu, there are about 0.5 more hydrogen bonds per residue at the N‐termini than in other protein regions, which can be used to explain their lower than average pKa values. Using a QM‐based pKa prediction model, we investigate the chemical environment of the two lowest Asp and the two lowest Glu pKa values at the N‐termini so as to quantify the effect of various pKa determinants. We show that local interactions suffice to account for the acidity of carboxyl residues at the N‐termini. The effect of the helix dipole on carboxyl pKa values, if any, is marginal. Backbone amide hydrogen bonds constitute the single biggest contributor to the lowest carboxyl pKa values at the N‐termini. Their estimated pKa lowering effects range from about 1.0 to 1.9 pKa units. Proteins 2006. © 2006 Wiley‐Liss, Inc.
In‐depth analysis of defects of an insulating sample by cathodoluminescence
Authors: Renoud R. , Papin F. , Ganachaud J.‐P. , Bigarré J. 
Published: January 2006

AbstractFrom the classical cathodoluminescence (CL) model, a new method is developed to carry out an in‐depth analysis of an insulating target luminescent defects. The depth profiling is performed using an electron beam energy variation and consequently a CL excitation range variation. The in‐depth distribution of defects is then obtained using numerical algorithms. Different ways are compared and the best method is evaluated by using the experimental results in the literature. The localization of defects is more realistic by using this algorithm compared to classical models. This new model is applied to the localization of subsurface defects in silica glass samples treated with different polishing processes. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Three prevalent properties of disordered systems and their common cause
Authors: Pollak M. 
Published: January 2006

AbstractThere are three properties very frequently observed in strongly disordered systems, an ac conductivity proportional to the frequency, resistance noise with a power spectrum inversely proportional to the frequency and a glassy relaxation logarithmic in time. It is proposed that a common cause produces these phenomena, namely transition rates between states being exponential functions of a random variable. It is shown how all three properties can be obtained from this exponential dependence. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theory of low‐field hopping mobility in organic solids with energetic and positional disorder
Authors: Fishchuk I. I. , Kadashchuk A. , Bässler H. 
Published: January 2006

AbstractThe influence of superimposed energetic and positional disorder on the field dependence of drift mobility in disordered organic solids is considered for the first time analytically by an Effective Medium theory. We find that the negative field dependence of the drift mobility at low fields is a genuine property of the nondispersive hopping transport in three‐dimensional disordered organic solids and caused by positional disorder. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A model for the electron glass
Authors: Pollak M. , Ovadyahu Z. 
Published: January 2006

AbstractA model for the glassy behavior of an electron glass is described and analyzed. The model is applied to conduction experiments where the electrons are excited by a change of the gate voltage. The predictions of the model are compatible with results of such experiments. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fano interference in mesoscopic rings with quantum dots
Authors: Moldoveanu V. , Aldea A. , Ţolea M. 
Published: January 2006

AbstractWe propose a general formalism for describing the coexistence of coherent and resonant transport in hybrid mesoscopic structures. The approach is based on Landauer‐Büttiker formula for the electronic transmittance and on an old formula of Feshbach. The latter gives the complete Green function of coupled subsystems in terms of effective Green functions of the disconnected parts and provides informations about the individual contributions of each subsystem to transport. Motivated by the experiments of Kobayashi et al.(Phys. Rev. Lett. 88, 256806 (2002)) and Holleitner et al. (Phys. Rev. Lett. 87, 256802 (2001)) we apply the formalism to study transport in Aharonov‐Bohm interferometers (ABI) containing one or two coupled two‐dimensional quantum dots (QD). In the single dot case, we reproduce and explain the magnetic field control of the Fano interference and investigate the interaction effects in a self‐consistent approach. In the double dot case, we obtain the charging diagrams and establish precise criteria for the observation of mesoscopic Fano effect and AB oscillations. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hopping magnetoresistance in two‐dimensional arrays of Ge/Si quantum dots
Authors: Yakimov A. I. , Dvurechenskii A. V. , Minkov G. M. , Sherstobitov A. A. , Nikiforov A. I. , Bloshkin A. A. , Stepina N. P. , Leitão J. P. , Sobolev N. A. , Pereira L. , do Carmo M. C. 
Published: January 2006

AbstractThe temperature and magnetic field dependences of the conductivity associated with hopping transport of holes over 2D arrays of Ge/Si quantum dots with various filling factors are studied experimentally. A transition from the Efros‐Shklovskii law for the temperature dependence of hopping conductivity to the Arrhenius law with an activation energy equal to 1.0‐1.2 meV is observed upon a decrease in temperature. The activation energy for the low‐temperature conductivity increases with the magnetic field and attains saturation in fields exceeding 4 T. It is found that the magnetoresistance in layers of quantum dots is essentially anisotropic: the conductivity decreases in magnetic fields oriented perpendicular to a dot layer and increases in a field whose vector lies in the plane of the sample. The absolute values of magnetoresistance for transverse and longitudinal field orientations differ by two orders of magnitude. Effect of spin correlations on the hopping magnetoresistance is discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Compressibility in the integer Quantum Hall Effect within Hartree‐Fock approximation
Authors: Sohrmann Christoph , Römer Rudolf A. 
Published: January 2006

AbstractElectron‐electron interactions seem to play a surprisingly small role in the description of the integer quantum Hall effect, considering that for just slightly different filling factors the interactions are of utmost importance causing the interaction‐mediated fractional quantum Hall effect. However, recent imaging experiments by Cobden et al. (Phys. Rev. Lett. 82, 4695 (1999)) [1] and Ilani et al. (Nature 427, 328 (2004)) [2] constitute strong evidence for the importance of electron‐electron interactions even in the integer effect. The experiments report on measurements of the conductance and electronic compressibility of mesoscopic MOSFET devices that show disagreement with predictions from the single particle model. By diagonalising a random distribution of Gaussian scatterers and treating the interactions in Hartree‐Fock approximation we investigate the role of electron‐electron interactions for the integer quantum Hall effect and find good agreement with the experimental results. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
1/f noise near the “metal‐to‐insulator transition” in the 2DEG in a Si‐MOSFET
Authors: Kretinin A. V. , Roshko S. H. , Savchenko A. K. , Mayorov A. S. , Kvon Z. D. 
Published: January 2006

AbstractContrary to some recent observations of a gradual increase of 1/f ‐noise with decreasing carrier density in a 2DEG in Si and a 2DHG in GaAs, we have observed a non‐monotonic variation of noise power in a 2DEG in Si. We discuss the role of the following effects in the noise near the carrier density where ∂R /∂T changes its sign: i) formation of an electron glass; ii) percolation transition; iii) existence of a narrow impurity band at the Si‐SiO2 interface. We also analyse the effect of temperature fluctuations in the observed non‐monotonic behaviour of the noise power. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Accelerated on‐column lysine derivatization and cysteine methylation by imidazole reaction in a deuterated environment for enhanced product ion analysis
Authors: Cindrić Mario , Čepo Tina , Škrlin Ana , Vuletić Marko , Bindila Laura 
Published: January 2006

AbstractThe combination of separation techniques and mass spectrometry (MS) for peptide investigation allows superior sensitivity of detection and richer fragmentation data than available by direct MS analysis of a complex mixture. In this regard, liquid chromatography (LC) coupled to electrospray ionization (ESI) and matrix‐assisted laser desorption/ionization (MALDI) MS have evolved as versatile analytical tools in proteomics. Very often, however, the product ion mass spectrum is either incomplete or overfilled with ions, thus making sequence analysis difficult. Here we report overall ion intensity improvement of C‐terminal lysine‐containing peptides from Lys‐C digest by on‐column derivatization of lysines with 2‐methoxy‐4,5‐dihydro‐1H‐imidazole. The method is simple, fast and exhibits 100% efficiency of the reaction. Additionally, post‐source decay carried out on derivatized peptides gave rise almost exclusively to y‐series ion formation, at 100% sequence coverage and high intensity. The novelty of the method resides in the side reaction of this derivatization process, namely the methylation of cysteines. This facilitates the estimation of the disulfide bridge position in a protein and the fragmentation of cysteine‐containing peptide fragments. Additionally, by using this derivatization procedure, the loss of peptides, their degradation and/or oxidation, usually occurring in digest alkylation procedures, is greatly minimized. The new on‐column derivatization protocol is designed to be carried out on C18 Spin Tubes or Cleanup C18 Pipette Tips. We observed that use of buffered D2O solvent prevented unwanted oxidation and degradation reactions with respect to the stationary phase. This may be due to the fact that a deuteron is less polar than a proton, and thus the bonded silica stationary phase saturated with deuterons does not affect the reaction between ε‐amino or cysteine thiol groups and 2‐methoxy‐4,5‐dihydro‐1H‐imidazole. Complete tagging of the peptides by on‐column reaction could be obtained when using D2O, as compared to water‐based reaction. Methylation of cysteine residues was enhanced when β‐mercaptoethanol was added in the reactant solution. Copyright © 2006 John Wiley & Sons, Ltd.
N‐(2‐Hydroxyethyl)‐N‐methyldithiocarbamato Complexes of Nickel(II) with Phosphorus Donor Ligands
Authors: Manohar A. , Ramalingam K. , Thiruneelakandan R. , Bocelli G. , Righi L. 
Published: January 2006

AbstractPlanar nickel(II) complexes involving N‐(2‐Hydroxyethyl)‐N‐methyldithiocarbamate, such as [NiX(nmedtc)(PPh3)] (X = Cl, NCS; PPh3 = triphenylphosphine), and [Ni(nmedtc)(P‐P)]ClO4(P‐P = 1,1‐bis(diphenylphosphino)methane(dppm); 1,3‐bis(diphenylphosphino)propane (1,3‐dppp); 1,4‐bis(diphenylphosphino)butane(1,4‐dppb) have been synthesized. The complexes have been characterized by elemental analyses, IR and electronic spectroscopies. The increased νC–N value in all the complexes is due to the mesomeric drift of electrons from the dithiocarbamate ligands to the metal atom. Single crystal X‐ray structure of [Ni(nmedtc)(1,3‐dppp)]ClO4·H2O is reported. In the present 1,3‐dppp chelate, the P–Ni–P angle is higher than that found in 1,2‐bis(diphenylphosphino)ethane‐nickel chelates and lower than 1,4‐bis(diphenylphosphino)butane‐nickel chelates, as a result of presence of the flexible propyl back bone connecting the two phosphorus atoms of the complex.
Tethering versus Non‐Coordination of Hydroxy and Methoxy Side Chains in Arene Half Sandwich Dichloro Ruthenium Complexes
Authors: Čubrilo Jadranka , Hartenbach Ingo , Schleid Thomas , Winter Rainer F. 
Published: January 2006

AbstractWe are reporting on the hydroxyalkyl appended arene ruthenium half sandwich complexes [{η6‐C6H5(CH2)nOH}RuCl2] (n = 2, 3) and the methyl ether of the hydroxypropyl derivative. Most significantly, a structural comparison between the hydroxypropyl complex 1a and its methyl ether 2a reveals, that the latter adopts the conventional dichloro bridged dimeric structure while 1a is a monomer. Coordinative saturation of the ruthenium centre is achieved by intramolecular coordination of the appended hydroxy function, thus rendering the functionalized arene an eight electron donor chelate ligand. The structure is further stabilized by intermolecular OH···Cl hydrogen bridges between a terminal chloride ligand of one and the coordinated hydroxy group of a neighbour molecule, resulting in a sheet structure. These intermolecular interactions appear to be even stronger in the hydroxyethyl analogue. Several phosphine adducts have been prepared from the hydroxy or alkoxy functionalized [(η6‐arene)RuCl2]n precursors, including water soluble P(CH2OH)3 adducts. Electrochemical properties of the phosphine adducts and of the dichloro bridged aryl ether complex 2a are also discussed.
Hydrothermal Synthesis, Solid State Structure, and Thermal Properties of a Family of Isomorphous 1‐D Coordination Polymers Aggregated by Extensive Hydrogen Bonding: {[M(3,3′‐bpy)(H2O)4](SO4)·2H2O} (M = Co, Ni, Zn)
Authors: LaDuca Robert L. , Desciak Matthew P. , Rarig Randy S. , Zubieta Jon A. 
Published: January 2006

AbstractHydrothermal synthesis has afforded a family of new coordination polymers incorporating 3,3′‐bipyridine (3,3′‐bpy), {[M(3,3′‐bpy)(H2O)4](SO4)·2H2O} (M = Co, Ni, Zn). The crystal structures revealed 1‐D undulating cationic ribbons of formulation {[M(3,3′‐bpy)(H2O)4]}n2n+ with both unligated charge‐balancing sulfate anions and water molecules of crystallization entrapped by hydrogen bonding. The 1‐D ribbons run along the (101) crystal direction and further aggregate via extensive hydrogen bonding patterns. Thermal decomposition data were consistent with stepwise loss of water molecules of crystallization and aquo ligands followed by decomposition due to ligand removal.
Synthesis and Crystal Structure Analysis of KAg11(VO4)4
Authors: Kovalevskiy Anton , Jansen Martin 
Published: January 2006

AbstractNew potassium silver vanadate KAg11(VO4)4 was obtained by reacting the stoichiometric mixture of Ag2O and V2O5 at elevated oxygen pressure, adding a small portion of aqueous KOH. The synthesis was done at 573 K and 430 MPa of oxygen pressure. The crystal structure was solved by direct methods basing on single crystal diffraction data (Pbca, Z = 4, a = 16.533(1), b = 10.6286(7), c = 10.5452(7) Å, 3983 independent reflections, R1 = 5.4 %). The optical band gap for KAg11(VO4)4 was determined as 2.0 eV. According to magnetic measurements, KAg11(VO4)4 is diamagnetic.
Splitting the Phosphorus Bridge of 7‐Phosphanorbornadiene Complexes by Fluoride Ion
Authors: Compain Carine , Mathey François 
Published: January 2006

AbstractThe reaction of fluoride ion with 7‐phosphanorbornadiene P–W(CO)5 complexes yields fluorophosphido complexes which, in turn, can attack a second molecule of 7‐phosphanorbornadiene to give a fluorobiphosphine complex. The corresponding anion displays a huge P–P coupling. The structure of the anionic chromium analogue has been investigated by DFT calculations. The P–P bond is relatively short at 2.20 Å and displays a huge polarity suggesting an interesting chemistry. When the 7‐phosphanorbornadiene P‐substituent is 2‐chloroethyl, the attack of the fluoride ion is followed by a cyclization and a reductive dimerization leading to the first known biphosphirane complex.
Polymeric [{Cd(en)}3{Fe(CN)6}2]·4H2O: Preparation, Crystal Structure and Characterization (en = 1,2–diaminoethane)
Authors: Mal'arováa Miroslava , Černák Juraj , Kuchár Juraj , Varret François , Massa Werner 
Published: January 2006

AbstractA new polymeric coordination compound [{Cd(en)}3{Fe(CN)6}2]·4H2O (1; en = 1,2–diaminoethane) was isolated from a reaction mixture containing CdCl2·2.5H2O, en, K3[Fe(CN)6] and [R4N]+ (R = propyl (Pr), butyl (Bu)) and was characterized by chemical analysis, X‐ray diffraction, IR and Mössbauer spectroscopy, and magnetic studies. Its crystal structure is 3D, where the cyanometallate framework is electrically neutral and four water molecules per formula unit are placed in the octahedral cavities of the formed structure. The framework is built up of hexacyanoferrate(3‐) anions exhibiting connectivity 6 and two crystallographically independent [Cd(en)]2+ cations with connectivities 4. Both CdII atoms are hexacoordinated by six nitrogen atoms from one chelate bound en molecule and four bridging cyano groups. The water molecules are connected by hydrogen bonds to form a four‐membered ring. The Mössbauer spectra confirm FeIII to be in the low spin state (S = 1/2). The magnetic properties are well described by the Curie law down to 5 K.
Spectroscopic and Crystal Structure of Europium(III) Picrate Complexes with Novel BINOL Derivatives
Authors: Wang Ya‐Wen , Liu Wei‐Sheng , Yu Kai‐Bei 
Published: January 2006

AbstractTwo novel ligands N‐Benzyl‐2‐{2′‐[(benzyl‐phenyl‐carbamoyl)‐methoxy]‐[1,1′]binaphthalenyl‐2‐yloxy}‐N‐phenyl‐acetamide (L1) and N‐Methyl‐2‐{2′‐[(methyl‐phenyl‐carbamoyl)‐methoxy]‐[1,1′]binaphthalenyl‐2‐yloxy}‐N‐phenyl‐acetamide (L2), and their europium(III) complexes with picrate, [Eu(pic)3(L1)] and [Eu(pic)3(L2)], were synthesized and characterized by elemental analysis, IR, UV‐Vis and fluorescence spectroscopy. The crystal structure of [Eu(pic)3(L1)]·2CHCl3 was determined by single crystal X‐ray diffraction. The europium atom is coordinated by nine oxygen atoms of four from the L1 and five from two bidentate and one unidentate picrates. The fluorescent intensity of [Eu(pic)3(L2)] is about 2.6 times that of [Eu(pic)3(L1)] in solid states. But in CHCl3 solution, the fluorescent intensity of [Eu(pic)3(L1)] is stronger slightly than [Eu(pic)3(L2)].
An Aqua‐Bridged Helical‐Chain Copper(II)‐Saccharinato Polymer Linked into a Two‐Dimensional Supramolecular Framework
Authors: Yilmaz Veysel T. , Kars Vecdi , Kazak Canan 
Published: January 2006

AbstractA new assembly [Cu2(sac)2(μ‐dmea)2(μ‐H2O)]n (sac = saccharinate and Hdmea = 2‐dimethylaminoethanol) has been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis and single crystal X‐ray diffraction. The complex crystallizes in the monoclinic space group C2/c and consists of dinuclear modules of [Cu2(sac)2(dmea)2]. The sac ligand is N‐coordinated, while the dmea ligand is in the deprotanated form by losing the ethanol hydrogen atom and acts as a bidentate donor through the alkoxo group and N atom. The alkoxo group also serves as a bridge between two copper(II) ions, leading to an intra‐dimer Cu···Cu separation of 3.0229(7) Å. The dimeric units are bridged by aqua ligands to generate a one‐dimensional water‐bridged helical chain, in which the copper(II) ions exhibit a distorted square‐pyramidal CuN2O3 coordination. The Cu–Cu distance in the chain separated by the bridging aqua ligands is 5.297Å. The polymeric chains are further linked by π(sac)···π(sac) and C–H···π(sac) interactions into a two‐dimensional supramolecular network.