bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of structure on the tissue dynamics of the human soleus muscle observed in MRI studies during isometric contractions
Authors: Hodgson John A. , Finni Taija , Lai Alex M. , Edgerton V. Reggie , Sinha Shantanu
Published: February 2006

This article investigates how the internal structure of muscle and its relationship with tendon and even skeletal structures influence the translation of muscle fiber contractions into movement of a limb. Reconstructions of the anatomy of the human soleus muscle from the Visible Human Dataset (available from the National Library of Medicine), magnetic resonance images (MRI), and cadaver studies revealed a complex 3D connective tissue structure populated with pennate muscle fibers. The posterior aponeurosis and the median septum of the soleus form the insertion of the muscle and are continuous with the Achilles tendon. The distal extremities of the pennate muscle fibers attach to these structures. The anterior aponeurosis is located intramuscularly, between the posterior aponeurosis and the median septum. It forms the origin of the muscle and contacts the proximal extremities of the soleus muscle fibers. MRI measurements of in vivo tissue velocities during isometric contractions (20% and 40% maximum voluntary contractions) revealed a similarly complex 3D distribution of tissue movements. The distribution of velocities was similar to the distribution of major connective tissue structures within the muscle. During an isometric contraction, muscle fiber contractions move the median septum and posterior aponeurosis proximally, relative to the anterior aponeurosis. The pennate arrangement of muscle fibers probably amplifies muscle fiber length changes but not sufficiently to account for the twofold difference in muscle fiber length changes relative to excursion of the calcaneus. The discrepancy may be accounted for by an additional gain mechanism operating directly on the Achilles tendon by constraining the posterior movement of the tendon, which would otherwise occur due to the increasingly posterior location of the calcaneus in plantarflexeion. J. Morphol. © 2006 Wiley‐Liss, Inc.
Application of the Weibull model to describe inactivation of Listeria monocytogenes and Escherichia coli by citric and lactic acid at different temperatures
Authors: Virto R , Sanz D , Álvarez I , Condón S , Raso J
Published: January 2006

Inactivation of Listeria monocytogenes and Escherichia coli by citric (10‐150 g L−1) and lactic (1‐60 mL L−1) acids at different temperatures (4, 20, 40 °C) has been investigated. Bactericidal effect of both acids was dependent on time and temperature of exposure and acid concentration. Survival curves of L. monocytogenes treated by lactic acid were concave downward and those treated by citric acid were linear. On the other hand, survival curves of E. coli treated by both organic acids were concave upward. Shape of survival curves depended on the type of acid but not on the treatment temperature. A mathematical model based on the Weibull distribution accurately described the kinetics of inactivation of both microorganisms by both acids. This model allowed quantification and comparison of the acid resistance of L. monocytogenes and E. coli. Lactic acid was more effective than citric acid and E. coli was more sensitive to both acids than L. monocytogenes. Copyright © 2006 Society of Chemical Industry
Bioavailability of zinc from infant foods by in vitro methods (solubility, dialyzability and uptake and transport by Caco‐2 cells)
Authors: Perales Sara , Barberá Reyes , Lagarda M Jesús , Farré Rosaura
Published: January 2006

The aim of this study was to evaluate the bioavailability of zinc from infant foods (adapted, follow‐up and toddler milk‐based formulas and fruit juices containing milk and cereals, FMC) using solubility, dialyzability and a model combining simulated gastrointestinal digestion and zinc uptake and transport by Caco‐2 cells. The greater solubility of zinc from infant formulas compared with fruit juices (FMC) could be due to the greater casein phosphopeptide content resulting from casein hydrolysis. The highest zinc dialysis percentage corresponded to FMC, which on the other hand had the lowest zinc contents of the analyzed samples. The presence of organic acids in samples of this kind favors the formation of soluble low molecular weight complexes with zinc, thereby increasing the solubility of the latter. Bifidobacterium addition exerted no effect upon zinc bioavailability. Transport and uptake efficiency in Caco‐2 cells were significantly greater for toddler formulas, which presented the highest casein contents. The greater efficiency in zinc transport and uptake from the powdered toddler formula compared with the liquid formulation could be explained by the effect of Maillard reaction products. Copyright © 2006 Society of Chemical Industry
Determination of Addition and Fragmentation Rate Coefficients in RAFT Polymerization via Time‐Resolved ESR Spectroscopy after Laser Pulse Initiation
Authors: Buback Michael , Hesse Pascal , Junkers Tanja , Vana Philipp
Published: January 2006

Summary: A method for simultaneous determination of both the addition and fragmentation rate coefficients of the RAFT equilibrium reactions is presented, which is based on laser single pulse initiation in conjunction with microsecond time‐resolved ESR spectroscopy. The build‐up and subsequent decay in concentration of the intermediate radical are measured and kad and kβ values are deduced from fitting the concentration versus time profiles to simple kinetic models.

Normalized ESR signal intensity vs. time after firing an initiating laser pulse in BMPT‐mediated butyl acrylate polymerization.

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Normalized ESR signal intensity vs. time after firing an initiating laser pulse in BMPT‐mediated butyl acrylate polymerization.
Control over the Wettability of Colloidal Crystal Films by Assembly Temperature
Authors: Wang Jingxia , Wen Yongqiang , Feng Xinjian , Song Yanlin , Jiang Lei
Published: January 2006

Summary: A facile method to fabricate colloidal crystal films with tunable wettability from an amphiphilic material polystyrene‐block‐poly(methyl methacrylate)‐block‐poly(acrylic acid) is presented. The wettability of the film can be tuned from superhydrophilic (CA, 0°) to superhydrophobic (CA, 150.2°) by varying the assembly temperature, while the position of the photonic bandgap of the colloidal crystal films remains virtually unchanged. The method could open new application fields of colloidal crystals in diverse environments.

The relationship of assembly temperature with water CA (inset is the water droplet profile of the relative water CA).

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The relationship of assembly temperature with water CA (inset is the water droplet profile of the relative water CA).
Cover Picture: Macromol. Rapid Commun. 3/2006
Authors: Godoy Lopez Ricardo , Boisson Christophe , D'Agosto Franck , Spitz Roger , Boisson Fernande , Gigmes Didier , Bertin Denis
Published: January 2006

Cover: The cover picture shows a strategy used to synthesize new functional polyethylenes (PE). A neodymium based complex catalyzes ethylene chain growth reaction on MgR2 producing Mg(PE)2. Those are excellent candidates to react with disulfides of thiocarbonylated compounds (RC(S)SSC‐(S)R). Further details can be found in the Communication by R. Godoy Lopez, C. Boisson, F. D'Agosto,* R. Spitz, F. Boisson, D. Gigmes, and D. Bertin on page 173.
Lymphatic microsurgery for the treatment of lymphedema
Authors: Campisi C. , Davini D. , Bellini C. , Taddei G. , Villa G. , Fulcheri E. , Zilli A. , Da Rin E. , Eretta C. , Boccardo F.
Published: January 2006

One of the main problems of microsurgery for lymphedema consists of the discrepancy between the excellent technical possibilities and the subsequently insufficient reduction of the lymphoedematous tissue fibrosis and sclerosis. Appropriate treatment based on pathologic study and surgical outcome have not been adequately documented. Over the past 25 years, more than 1000 patients with peripheral lymphedema have been treated with microsurgical techniques. Derivative lymphatic micro‐vascular procedures has today its most exemplary application in multiple lymphatic‐venous anastomoses (LVA). For those cases where a venous disease is associated to more or less latent or manifest lymphostatic pathology of such severity to contraindicate a lymphatic‐venous shunt, reconstructive lymphatic microsurgery techniques have been developed (autologous venous grafts or lymphatic‐venous‐Iymphatic‐plasty ‐ LVLA). Objective assessment was undertaken by water volumetry and lymphoscintigraphy. Subjective improvement was noted in 87% of patients. Objectively, volume changes showed a significant improvement in 83%, with an average reduction of 67% of the excess volume. Of those patients followed‐up, 85% have been able to discontinue the use of conservative measures, with an average follow‐up of more than 7 years and average reduction in excess volume of 69%. There was a 87% reduction in the incidence of cellulitis after microsurgery. Microsurgical lymphatic‐venous anastomoses have a place in the treatment of peripheral lymphedema and should be the therapy of choice in patients who are not sufficiently responsive to nonsurgical treatment. Improved results can be expected with operations performed earlier at the very first stages of lymphedema. © 2006 Wiley‐Liss, Inc. Microsurgery 26: 65–69, 2006.
New double quantum coherence filter for localized detection of glutathione in vivo
Authors: Zhao Tiejun , Heberlein Keith , Jonas Carolyn , Jones Dean P. , Hu Xiaoping
Published: January 2006

In this work, a new double quantum filter for glutathione (GSH) editing is introduced, combined with the point‐resolved spectroscopy localization sequence (PRESS), and demonstrated in vivo. Compared to the conventional double quantum coherence filter, the new filter has two major advantages. First, it eliminates the need for calibration scans for optimizing the signal yield, making it more efficient and convenient for routine use. Second, it removes the influence of water saturation pulses on the GSH yield, further improving its accuracy. With this method, GSH concentrations in the left and right parietal lobes of five healthy volunteers were determined to be 0.91 ± 0.16 mM and 0.89 ± 0.16 mM, respectively, in agreement with previous studies. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Development of the Vaccine Analytic Unit's research agenda for investigating potential adverse events associated with anthrax vaccine adsorbed
Authors: Payne Daniel C. , Franzke Laura H. , Stehr‐Green Paul A. , Schwartz Benjamin , McNeil Michael M.
Published: January 2006

Purpose

In 2002, the Centers for Disease Control and Prevention established the Vaccine Analytic Unit (VAU) in collaboration with the Department of Defense (DoD). The focus of this report is to describe the process by which the VAU's anthrax vaccine safety research plan was developed following a comprehensive review of these topics.

Methods

Public health literature, surveillance data, and clinical sources were reviewed to create a list of adverse events hypothesized to be potentially related to anthrax vaccine adsorbed (AVA). From this list, a consensus process was used to select 11 important research topics. Adverse event background papers were written for each of these topics, addressing predetermined criteria. These were independently reviewed and ranked by a National Vaccine Advisory Committee (NVAC) workgroup. The adverse events included in the final priority list will be the subject of observational or other post marketing surveillance studies using the Defense Medical Surveillance System (DMSS) database.

Results

A review of various information sources identified over 100 potential adverse events. The review process recommended 11 topics as potentially warranting further study. The NVAC workgroup identified the following adverse event topics for study: arthritis, optic neuritis, and Stevens–Johnson syndrome/Toxic epidermal necrolysis. Two additional topics (systemic lupus erythematosus (SLE) and multiple, near‐concurrent military vaccinations) were added in response to emerging public health and military concerns.

Conclusions

The experience described, while specific for establishing the VAU's research agenda for the safety of the current anthrax vaccine, may be useful and adapted for research planning in other areas of public health research. Copyright © 2006 John Wiley & Sons, Ltd.
Nanotechnologies in proteomics
Authors: Ivanov Yuri D. , Govorun Vadim M. , Bykov Victor A. , Archakov Alexander I.
Published: January 2006

Progress in proteomic researches is largely determined by development and implementation of new methods for the revelation and identification of proteins in biological material in a wide concentration range (from 10−3 M to single molecules). The most perspective approaches to address this problem involve (i) nanotechnological physicochemical procedures for the separation of multicomponent protein mixtures; among these of particular interest are biospecific nanotechnological procedures for selection of proteins from multicomponent protein mixtures with their subsequent concentration on solid support; (ii) identification and counting of single molecules by use of molecular detectors. The prototypes of biospecific nanotechnological procedures, based on the capture of ligand biomolecules by biomolecules of immobilized ligate and the concentration of the captured ligands on appropriate surfaces, are well known; these are affinity chromatography, magnetic biobeads technology, different biosensor methods, etc. Here, we review the most promising nanotechnological approaches for selection of proteins and kinetic characterization of their complexes based on these biospecific methods with subsequent MS/MS identification of proteins and protein complexes. Two major groups of methods for the analysis and identification of individual molecules and their complexes by use of molecular detectors will be reviewed: scanning probe microscopy (SPM) (including atomic‐force microscopy) and cryomassdetector technology.
SELDI‐TOF MS of quadruplicate urine and serum samples to evaluate changes related to storage conditions
Authors: Traum Avram Z. , Wells Meghan P. , Aivado Manuel , Libermann Towia A. , Ramoni Marco F. , Schachter Asher D.
Published: January 2006

Proteomic profiling with SELDI‐TOF MS has facilitated the discovery of disease‐specific protein profiles. However, multicenter studies are often hindered by the logistics required for prompt deep‐freezing of samples in liquid nitrogen or dry ice within the clinic setting prior to shipping. We report high concordance between MS profiles within sets of quadruplicate split urine and serum samples deep‐frozen at 0, 2, 6, and 24 h after sample collection. Gage R&R results confirm that deep‐freezing times are not a statistically significant source of SELDI‐TOF MS variability for either blood or urine.
Differential protein expression in brain capillary endothelial cells induced by hypoxia and posthypoxic reoxygenation
Authors: Haseloff Reiner F. , Krause Eberhard , Bigl Marina , Mikoteit Kerstin , Stanimirovic Danica , Blasig Ingolf E.
Published: January 2006

Cerebral ischemia causes functional alteration of the blood–brain barrier, formed by brain capillary endothelial cells (BCEC). Changes in protein expression and activity of selected differentially expressed enzymes were investigated in BCEC subjected to hypoxia (24 h) alone or followed by a 24‐h reoxygenation. BCEC proteins were isolated, separated by 2‐DE, and identified by MALDI‐MS. Computer‐based 2‐D gel analysis identified 21 up‐regulated proteins and 4 down‐regulated proteins after hypoxia alone and 9 proteins that were further up‐regulated after posthypoxic reoxygenation. The expression of the majority of hypoxia‐induced proteins was reduced toward control levels during reoxygenation. The most prominent changes were identified for glycolytic enzymes (e.g., phosphoglycerate kinase), proteins of the ER (e.g., calreticulin), and cytoskeletal (e.g., vimentin) proteins. The results indicate that BCEC respond to hypoxia/reoxygenation by adaptive up‐regulation of proteins involved in the glycolysis, protein synthesis, and stress response.
Vinyl‐terminated side‐chain liquid‐crystalline polyethers containing mesogenic benzylideneaniline moieties
Authors: Callau Lourdes , Giamberini Marta , Reina José Antonio , Mantecón Ana
Published: January 2006

The synthesis of two vinyl‐terminated side‐chain liquid‐crystalline polyethers containing benzylideneaniline moieties as mesogenic cores was approached in two different ways: by chemically modifying poly(epichlorohydrin) with suitable mesogenic acids or by polymerizing analogous glycidyl ester or glycidyl ether derivatives. In all the conditions tested, the first approach led to materials in which the imine group was hydrolyzed. The second approach led to the desired polymers PG2a and PG2b, but only from the glycidyl ether derivatives and when the initiator was the system that combined polyiminophosphazene base t‐Bu‐P4 and 3,5‐di‐t‐butylphenol. These polymers were chemically characterized by IR and 1H and 13C NMR spectroscopies. The estimated degrees of polymerization ranged from 30 to 36. The liquid crystalline behavior of the synthesized polymers was studied by differential scanning calorimetry, polarized optical microscopy (POM) and X‐ray diffraction. Both polymers behave like liquid crystals and exhibited a single mesophase, which was recognized as a smectic C mesophase, probably with a bilayer arrangement, i.e., a smectic C2 mesophase. The crosslinking of both polymers was performed with dicumyl peroxide as initiator, which led to liquid crystalline thermosets. POM and X‐ray diffraction confirmed that the mesophase organization mantained on the crosslinked materials. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1877–1889, 2006
Copolymerization of ethylene with styrene catalyzed by a linked bis(phenolato) titanium catalyst
Authors: Capacchione Carmine , Proto Antonio , Ebeling Henner , Mülhaupt Rolf , Okuda Jun
Published: January 2006

Copolymerization of ethylene with styrene, catalyzed by 1,4‐dithiabutanediyl‐linked bis(phenolato) titanium complex and methylaluminoxane, produced exclusively ethylene–styrene copolymers with high activity. Copolymerization parameters were calculated to be rE = 1.2 for ethylene and rS = 0.031 for styrene, with rE rS = 0.037 indicating preference for alternating copolymerization. The copolymer microstructure can be varied by changing the ratio between the monomers in the copolymerization feed, affording copolymers with styrene content up to 68%. The copolymer microstructure was fully elucidated by 13C NMR spectroscopy revealing, in the copolymers with styrene content higher than 50%, the presence of long styrene–styrene homosequences, occasionally interrupted by isolated ethylene units. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1908–1913, 2006
Spontaneous pulmonary interstitial emphysema in a term unventilated infant
Authors: Freysdottir Drifa , Olutoye Oluyinka , Langston Claire , Fernandes Caraciolo J. , Tatevian Nina
Published: January 2006

Pulmonary 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

Flavodoxins 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

Experimentally 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

From 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

There 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

The 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

A 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

We 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

The 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

Electron‐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

Contrary 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

The 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

Planar 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

We 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

Hydrothermal 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

New 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

The 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

A 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

Two 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

A 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.
Crystal Structure and Thermal Behaviour of K2[CrF5·H2O]
Authors: Sassoye Capucine , de Kozak Ariel
Published: January 2006

K2[CrF5·H2O] is monoclinic: a = 9.6835(3) Å, b = 7.7359(2) Å, c = 7.9564(3) Å, β = 95.94(1)°, Z = 4, space group C2/c (no 15). Its crystal structure was solved from its X‐ray powder pattern recorded on a powder diffractometer, using for the refinement the Rietveld method. It is built up from isolated octahedral [CrF5·OH2]2− anions separated by potassium cations. The dehydration of K2[CrF5·H2O] leads to anhydrous orthorhombic K2CrF5: a = 7.334(2) Å, b = 12.804(4) Å, c = 20.151(5) Å, Z = 16, space group Pbcn (no 60), isostructural with K2FeF5.
Diseases of gadoid fish in cultivation: a review
Authors: Bricknell Ian R. , Bron James E. , Bowden Tim J.
Published: January 2006

Given the rapid development of intensive culture systems for cold-water marine gadoids such as cod (Gadus morhua), haddock (Melanogrammus aeglefinus), hake (Merluccius spp.), and ling (Molva molva), an urgent need exists to examine likely threats posed by disease in intensive gadoid culture. While little is known about diseases that may affect or be introduced by cold-water marine gadoid fish once the animals are brought into intensive commercial culture systems, certain risks can be inferred both from an examination of disease problems experienced during the introduction of intensive culture systems for other cold-water marine species and from an examination of the existing literature on gadoid pathogens. This paper provides an overview of the potential disease risks associated with the development of intensive gadoid aquaculture and focuses on previously characterized diseases that the authors consider as posing the greatest threat to intensive gadoid culture. In addition to disease risk, this paper discusses risk reduction, including vaccination strategies and the risk of inter-species infection. Specific viral, bacterial, fungal, protoctistan, and metazoan pathogens are discussed in light of their previous implication in the causation of disease in cultured gadoids or other cold-water species, their occurrence and pathogenicity in wild gadoids, and with respect to life strategies and biology that may favour their propagation within intensive aquaculture systems.
Prevalence of selected infectious disease agents in cats from Arizona
Authors: Eberhardt Jason M , Neal Karter , Shackelford Tom , Lappin Michael R
Published: January 2006

The objective of this study was to use polymerase chain reaction (PCR) assays to determine the prevalence of Ehrlichia species, Anaplasma phagocytophilum, Mycoplasma haemofelis, ‘ Candidatus Mycoplasma haemominutum’ and Bartonella species from feral and relinquished cats in Phoenix and Nogales, Arizona. DNA from one or more of the organisms was amplified from 31 of 112 blood samples (27.7%). DNA consistent with Bartonella clarridgeiae 15 (13.4%), Bartonella henselae 14 (12.5%), ‘ Candidatus M haemominutum’ 9 (8.0%), and M haemofelis 5 (4.5%) were detected. DNA of Ehrlichia species, Neorickettsia risticii, or A phagocytophilum was not amplified. Failure to amplify DNA of A phagocytophilum may relate to the absence of appropriate tick vectors. Failure to amplify Ehrlichia species DNA suggests that cats were not exposed, exposed but not infected, or infected but the DNA was not detected by the PCR assay used in this study. The Bartonella species and hemoplasma results suggest flea control should be maintained.
Litter production, decomposition and nutrient release in cleared and uncleared pasture systems of central Queensland, Australia
Authors: Sangha Kamaljit K. , Jalota Rajesh K. , Midmore David J.
Published: February 2006

The temporal impact of clearing trees on litter production, litter decomposition and on C, N and P release through decomposition of litter was examined in the pasture systems of a semi-arid zone of central Queensland. Paired sites for cleared pastures (developed from clearing woodlands) and uncleared (intact woodland) pastures were selected to represent three dominant tree communities of the region i.e. Eucalyptus populnea, E. melanophloia and Acacia harpophylla, with three different time-since-clearing (5, 11–13 and 33 y) treatments. Yearly litter production was greater at uncleared sites (1732–1948 kg ha−1 y−1 for eucalypt and 2596 kg ha−1 y−1 for acacia communities) compared with cleared sites (1038–1282 kg ha−1 y−1 for eucalypt and 1100 kg ha−1 y−1 for acacia communities averaged over three time-since-clearing treatments). Rates of litter decomposition and of release of C, N and P from decomposing litter were higher at cleared than uncleared sites for all three tree communities. The cleared and uncleared sites did not differ significantly in total amount of C and N released per year since the concentrations of C and N were greater in litter from uncleared sites but the rate of release was less than that at cleared sites. Slow but continuous release of nutrients in eucalypt and acacia woodlands may be an adaptation of these communities to maintain the nutrient cycle and to avoid leaching of nutrients in the nutrient-poor soils of the region.