bluuebunny/crossref_metadata_2025 huggingface dataset:
Caracterización de dormancia, morfología y presencia de hongos endófitos en semillas de Morella pavonis (C.DC.) Parra-Os
Authors:   , Uvidia Calles Allison Camila
Published: March 2024

Morella pavonis es una especie nativa distribuida en el sur de Perú y en el norte de Chile, comúnmente conocida como pacama, denominada en la categoría de vulnerable. Existe escasa información sobre la germinación de semillas y hongos endófitos asociados en M. pavonis. Generar este conocimiento aportaría a desarrollar estrategias para ayudar a la preservación de esta especie. Se recolectaron frutos en cuatro localidades (Lotes) de las provincias de Arica y Tamarugal, el estudio de la morfología del fruto indicó que se compone por un endocarpio duro rodeado de cera que no inhibe el ingreso de agua, en su interior se encuentra una semilla exalbuminada, con un contenido de humedad del 22%, el test de tetrazolio evidenció la alta viabilidad en todos los lotes (75-88%). La máxima germinación se obtuvo en el Lote 4 alcanzando el 87% por la reducción del contenido de humedad, el segundo método más efectivo fue el uso de GA3 500 ppm maximizando la germinación ineficiente elevándola del 2% al 78% en el Lote 3, la estratificación fría a 4 °C incrementó la germinación en los Lotes 1 y 2 con valores finales del 28 y 33%, respectivamente, información que sugiere la existencia de dormancia fisiológica no profunda.Las semillas de Morella pavonis, además, revelaron albergar hongos endófitos, se encontró la presencia de 9 morfotipos presentes en los Lotes 3 y 4, la diversidad alfa mostró índices mayores en el Lote 4, casualmente semillas de este lote alcanzaron la máxima germinación.
Novel titanium complexes bearing two chelating phenoxy‐imine ligands and their catalytic performance for ethylene polymerization
Authors: Sun Junquan , Cheng Zhengzai , Nie Yujing , Schumann H. , Hummert M.
Published: March 2007

Three substituted salicylaldimine ligands (1a, 2a, 3a) and their titanium complexes bis[N‐(5‐nitrosalicylidene)‐2,6‐diisopropylanilinato]titanium(IV)dichloride (1), bis[N‐(5‐chlorosalicylidene)‐2,6‐diisopropylanilinato]titanium(IV)dichloride (2) and bis[N‐(5‐bromosalicylidene)‐2,6‐diisopropylanilinato]titanium(IV)dichloride (3) were synthesized and characterized by mass spectra, 1H NMR and elemental analyses, as well as complex 1 by X‐ray structure analysis. In the presence of methylaluminoxane (MAO), 1, 2 and 3 are efficient catalysts for ethylene polymerization in toluene. Under the conditions of T = 60 °C, p = 0.2 MPa, and n(MAO)/n(cat) = 1500, the activities of 1–3 reached 4.55–8.80 × 106 g of PE (mol of Ti h bar)−1, which is much higher than that of the unsubstituted complex bis[N‐(salicylidene)‐2,6‐diisopropylanilinato]titanium(IV)dichloride (4). The viscosity‐average molecular weight of polyethylene ranged from 24.8 × 104 to 44.9 × 104 g/mol for 1–3 and the molecular weight distribution Mw/Mn from 1.85 to 2.34. The effects of reaction conditions on the polymerization were examined in detail. The increase in ethylene pressure and rise in polymerization temperature are favorable for 1–3/MAO to rise the catalytic activity and the molecular weight of polyethylene. Copyright © 2007 John Wiley & Sons, Ltd.
Tetrahydroquinoline and tetrahydroisoquinoline mixed ligand rhenium complexes with the SNS/S donor atom set
Authors: Zablotskaya Alla , Segal Izolda , Lukevics Edmunds , Belyakov Sergey , Spies Hartmut
Published: March 2007

New oxorhenium complexes with 3‐methylazapentane‐1,5‐dithiolate (SNMeS) and thiol functionalized monodentate tetrahydroquinolyl and tetrahydroisoquinolyl derivatives have been synthesized by simultaneous reaction of [PPh3]2[Re(O)Cl3] with tridentate HSNMeSH and the corresponding N‐heterocycle containing thiol. The characterization of complexes involved elemental analysis, IR, 1H and 13C NMR spectroscopy and X‐ray crystallographic analysis. The nature of the heterocycle in monodentate ligand, even situated at the distance of two methylene group length, has been found to have a significant influence on the molecular conformation. Metal complexes were found to be active in psychotropic in vivo and cytotoxicity in vitro screening. Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis, characterization and cytotoxicity evaluation of new cerium(III), lanthanum(III) and neodymium(III) complexes
Authors: Kostova I. , Momekov G.
Published: March 2007

Complexes of cerium(III), lanthanum(III) and neodymium(III) with coumarin‐3‐carboxylic acid (HCCA) were synthesized by mixing of equimolar amounts of the respective metal nitrates and coumarin‐3‐carboxylic acid in ethanol. The complexes were characterized and identified by elemental analysis, IR and Raman spectroscopy. DTA and TGA were applied to study the compositions of the compounds. The vibrational study showed bidentate coordination of CCA− to Ln(III) ions through the carbonyl oxygen and the carboxylic oxygen atoms. The newly synthesized compounds were assayed for cytotoxicity against SKW‐3, HL‐60 and Reh cells. The complexes of cerium(III) and lanthanum(III) showed marginal cytotoxic activity against SKW‐3 and Reh cells as compared with the inorganic salts at concentration 200 µM. The complex of neodymium(III) induced approximately 50% reduction of the survival HL‐60 and SKW‐3 cells at concentration 200 µM. Copyright © 2007 John Wiley & Sons, Ltd.
The synthesis, crystal structures and SOD activities of a new ligand (Lse) and Co(Lse)2(SCN)2 complex [Lse = selenium ether bis‐(N‐1‐methyl‐ benzotriazole)]
Authors: Lu Yanchun , Tang Yu , Gao Hong , Zhang Zhihui , Wang Haifeng
Published: March 2007

A new ligand containing selenium, Se (CH2‐N‐Btrzole)2 (Lse) (Btrzole = benzotriazole) and its cobalt(II) complex, Co(Lse)2(SCN)2, have been synthesized and the molecular structures of the title compounds have been determined by X‐ray techniques. The Lse is a meso‐configuration with a symmetric plane through the Se center, the intermolecular weak interactions of SeSe, SeN and ππ stacking between benzotriazole rings to extend the molecular structure to two‐dimensional network configuration. In the Co(II) complex, the metal center is in a six‐coordinated octahedral environment. Two Co(II) atoms are linked by two ligands to form a 20‐membered macrocycle; the adjacent macrocycles are linked by coordinated bond of CoNbentrozole to extend an infinite double strained chain. The SOD activity of the ligand and Co(II) complex have been studied by using the pyrogallol autoxidation method; thermal properties and luminescent properties of Co(II) complex have been tested, and the details of those properties have been discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Development of micropost force sensor array with culture experiments for determination of cell traction forces
Authors: Li Bin , Xie Luke , Starr Zane C. , Yang Zhaochun , Lin Jeen‐Shang , Wang James H‐C.
Published: March 2007

Cell traction forces (CTFs) are critical for cell motility and cell shape maintenance. As such, they play a fundamental role in many biological processes such as angiogenesis, embryogenesis, inflammation, and wound healing. To determine CTFs at the sub‐cellular level with high sensitivity, we have developed high density micropost force sensor array (MFSA), which consists of an array of vertically standing poly(dimethylsiloxane) (PDMS) microposts, 2 μm in diameter and 6 μm in height, with a center‐to‐center distance of 4 μm. In combination with new image analysis algorithms, the MFSA can achieve a spatial resolution of 40 nm and a force sensitivity of 0.5 nN. Culture experiments with various types of cells showed that this MFSA technology can effectively determine CTFs of cells with different sizes and traction force magnitudes. Cell Motil. Cytoskeleton 2007. © 2007 Wiley‐Liss, Inc.
A glucose derivative as natural alternative to the cyclohexane‐1,2‐diamine ligand in the anticancer drug oxaliplatin?
Authors: Berger Isabella , Nazarov Alexey A. , Hartinger Christian G. , Groessl Michael , Valiahdi Seied‐M. , Jakupec Michael A. , Keppler Bernhard K.
Published: March 2007

Having oxaliplatin as archetype, several platinum complexes with a carbohydrate moiety resembling the cyclohexane‐1,2‐diamine ligand of oxaliplatin have been prepared. As leaving groups, the anionic ligands iodide, oxalate, and malonate were utilized, and for comparison purposes the chloro complex was employed. All compounds were characterized by elemental analysis, nuclear magnetic resonance spectroscopy, and electrospray mass spectrometry. The crystal structure of (SP‐4‐3)‐diiodo(2,3‐diamino‐2,3‐dideoxy‐D‐glucose‐κ²N,N′)platinum(II) was determined by X‐ray diffraction. The affinity toward dGMP was assayed by capillary electrophoresis, revealing that the chloro complex shows the highest reactivity, followed by the iodo complex. In contrast, the binding kinetics of the dicarboxylato complexes are slower, with the malonato complex being the least reactive. Reactivity to dGMP in the cell‐free system correlates with cytotoxicity in two of four human cancer cell lines as determined by means of the MTT assay. In three of the four cell lines, the chloro and the malonato complex are the most and the least active of the carbohydrate‐Pt complexes, respectively, with IC50 values differing only by factors of up to 3.2. Cytotoxicity of the chloro complex is one to two orders of magnitude lower than that of oxaliplatin, but still comparable to that of carboplatin in two of the four cell lines.
Echoes—how to generate, recognize, use or avoid them in MR‐imaging sequences. Part II: Echoes in imaging sequences
Authors: Hennig Jürgen
Published: March 2007

Part I of this sequence of two papers on spin echoes introduced the echo phenomenon and presented the extended‐phase‐graph algorithm for the description of signals arising in the multi‐pulse sequences. In Part II, pulse sequences that are commonly used in MR imaging are discussed with the use of this algorithm. First, it is shown that phase graphs easily demonstrate how a proper multi‐echo imaging experiment should be designed. Then, they are used to shed some light on the signal behavior of gradient‐echo sequences. Finally, some hints are given about how to avoid or use spurious echoes in more general multi‐pulse sequences.
In‐plane spatial encoding in MRI and its central role in determining contrast and artifact with RF echo planar techniques
Authors: Mulkern Robert
Published: March 2007

Generating a magnetic resonance image requires that all three spatial dimensions of a spin system somehow get encoded into NMR signals. Although there are many ways this can be done, by far the most common is to restrict the excitation to a slice with the use of frequency‐selective radio frequency (rf) pulses in the presence of a magnetic field gradient and to encode the remaining two spatial dimensions into echo signals with two mutually orthogonal „in‐plane”︁ gradients. In the standard scheme, spins along one in‐plane dimension are localized by receiving the echo signal in the presence of a „read‐out”︁ gradient. Spins along the other in‐plane dimension are localized with the use of „phase‐encoding”︁ gradients of different amplitudes applied for short periods prior to each readout. Just how these processes yield a data set whose two‐dimensional (2D) Fourier transformation represents the spin density within the selected slice is a major topic of this discussion. A topical extension, to rf echo planar methods in which the usual phase‐encoding process is accelerated with the use of multiple echoes, is also presented. The effects on image contrast and artifact when different echoes are used for distinct phase‐encoding steps in the presence of T2 decay (the spin‐spin relaxation time) are analyzed and illustrated.
Creating multiple‐quantum coherences in solids
Authors: Gleason K. K.
Published: March 2007

The observation that multiple‐quantum (MQ) coherence size will saturate in a finite network of strongly coupled nuclear dipoles has proved useful in characterizing such materials as semiconductors, catalysts, and polymers. However, even when the size of the coherence does not reach a plateau, the dynamics of MQ growth can provide insight about the distribution and motion of such nuclei as 1H and 19F in solids. This article builds a relatively simple physical picture of MQ‐NMR in terms of the angular momentum operators and eigenstates of individual nuclear spins. The predictive power of this framework is examined for interpreting the behavior of large numbers of dipole‐coupled nuclei. Some nuts‐and‐bolts aspects of implementing MQ spectroscopy in the laboratory also are discussed.
Low‐temperature NMR techniques
Authors: Conradi Mark S.
Published: March 2007

The techniques for NMR measurements at temperatures of 1‐120 K are discussed. Various cryogenic methods for attaining low temperatures are compared. Several designs and design criteria for the construction of low‐temperature NMR probes are presented. This article is intended to assist workers first entering the field of low‐temperature NMR.
Quantitative NMR imaging of flow
Authors: Pope J. M. , Yao S.
Published: March 2007

The principles of NMR imaging of flow are discussed in detail. Particular emphasis is given to basic concepts. The various methods are classified, and practical details of their implementation are explained. Quantitative flow‐imaging techniques are described and illustrated by examples obtained from a simple flow phantom.
An introduction to chemically induced dynamic nuclear polarization
Authors: Goez Martin
Published: March 2007

Measurements of chemically induced dynamic nuclear polarization (CIDNP) often yield valuable and otherwise unavailable information about the mechanisms of chemical reactions. The purposes of this article are to explain the fundamentals of this spectroscopic technique in elementary terms and to show what kind of information a chemist can get by using this method. After a description of a few introductory experiments, the radical‐pair mechanism is treated in detail. From an analysis of two simple systems, Kaptein's rules for CIDNP net and multiplet effects are derived. The advantages and limitations of CIDNP for the study of chemical reactions are discussed, and practical hints for CIDNP experiments are given.
Product operators, coherence pathways, and phase cycling. Part II. coherence pathways in multipulse sequences: spin echoes, stimulated echoes, and multiple‐quantum coherences
Authors: Kingsley Peter B.
Published: March 2007

The Compact Cartesian Coordinate Product‐Operator (C3PO) descriptions of an uncoupled spin I = ½ in one‐pulse, two‐pulse, and three‐pulse sequences are presented. The properties of free induction decays, spin echoes, double spin echoes, and stimulated echoes are discussed. Vector pictures of a 90°–90° spin echo and a stimulated echo are presented. The C3PO descriptions of IS and I3 S spin systems in multipulse sequences are also discussed, including polarization transfer and multiple‐quantum coherences. Suggestions for optimizing one coherence pathway and minimizing others are provided.
Density matrix theory for calculating magnetization transfer and dynamic lineshape effects
Authors: Johnston Eric R.
Published: March 2007

NMR is a powerful tool for the study of chemical rate processes and the mechanisms by which they occur. Dynamic processes give rise to characteristic changes in transverse and longitudinal relaxation, which manifest themselves in the NMR lineshape and in magnetization transfer phenomena, respectively. Analysis of these effects permits the extraction of kinetic data. The mathematical theory central to this analysis is illustrated using the formalism of the density matrix for a two‐spin system undergoing mutual intramolecular exchange in isotropic solution. The spin Hamiltonian and exchange operators are introduced, and the quantum mechanical equation of motion of the density matrix is presented, emphasizing those density matrix elements that correspond classically to longitudinal and transverse magnetization. The necessary Liouville and exchange superoperators are explicitly constructed from the corresponding Hamiltonian and exchange operators using tensor algebra. The equation of motion is then solved for the populations and single‐quantum coherences to illustrate the origin of magnetization transfer and dynamic lineshape effects. The extension of the theory to arbitrarily large exchanging spin systems is addressed and illustrated for two mutually exchanging spins scalar coupled to a third spin. Finally, the two‐spin lineshape calculation is fully worked out using a steady‐state method that reduces the problem to the solution of a set of simultaneous algebraic equations.
Reconstruction of dopaminergic neural network and locomotion function in planarian regenerates
Authors: Nishimura Kaneyasu , Kitamura Yoshihisa , Inoue Takeshi , Umesono Yoshihiko , Sano Shozo , Yoshimoto Kanji , Inden Masatoshi , Takata Kazuyuki , Taniguchi Takashi , Shimohama Shun , Agata Kiyokazu
Published: March 2007

Planarian, an invertebrate flatworm, has a high capacity for regeneration when compared with other worms and animals. We show here for the first time that the reconstructed dopamine (DA) neural network regulates locomotion and behavior in planarian regenerates. The gene encoding tyrosine hydroxylase in the planarian Dugesia japonica (DjTH) was identified. DjTH protein was coexpressed with aromatic amino acid decarboxylase‐like A (DjAADCA) in the planarian central nervous system (CNS). In addition, DjTH‐knockdown planarians lost the ability to synthesize DA, but showed no change in 5‐hydroxytryptamine synthesis. When the planarian body was amputated, DjTH‐positive neurons were regenerated in the brain newly rebuilt from the tail piece at Day 3, and the DjTH‐positive axonal and dendritic neural network in the CNS (dopaminergic tiara) was reconstructed at Days 5–7. At that time, autonomic locomotion and methamphetamine‐induced hyperkinesia were also suppressed in DjTH‐knockdown planarians. Planarian locomotion and behavior seem to be regulated in both cilia‐ and muscle‐dependent manners. In DjTH‐knockdown planarians, muscle‐mediated locomotion and behavior were significantly attenuated. These results suggest that DA neurons play a key role in the muscle‐mediated movement in planarians. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007.
Adult‐generated neurons exhibit diverse developmental fates
Authors: Whitman Mary C. , Greer Charles A.
Published: March 2007

In mammals, olfactory bulb (OB) interneurons, granule cells and periglomerular (PG) cells, are generated throughout adulthood. PG cells comprise a heterogeneous population in both morphology and molecular phenotypes. It is unknown whether adult genesis of PG cells occurs among all subtypes or is limited to a subpopulation. We show that within 2 weeks after retroviral labeling in the subventricular zone, two morphological populations of PG cells are found in the OB, one with large multi‐glomerular dendritic arbors, and one with dendritic arbors limited to one or two glomeruli. On both types, immature dendritic spines are first evident at 4 weeks and mature, pedunculated spines by 6 weeks. To differentiate PG subpopulations we used expression of calcium binding proteins, GAD67 and tyrosine hydroxylase as markers. Among adult‐born BrdU labeled cells, all molecular subtypes were represented, although GAD67 and tyrosine hydroxylase expressing cells were overrepresented proportional to their expression in the total PG cell population. During the time when spines are maturing, approximately half the PG cells are lost, in roughly equal proportions to their generation. Our data show the diverse developmental potential of SVZ neuroblasts and suggest that integration into synaptic circuits is necessary for survival. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007.
Correlation between the Stoichiometry and the Bistability of Electronic States in Valence‐Tautomeric RbxMn[Fe(CN)6]y·zH2O Complexes
Authors: Cobo Saioa , Fernández Raquel , Salmon Lionel , Molnár Gábor , Bousseksou Azzedine
Published: March 2007

A series of Prussian blue analogues, RbxMn[Fe(CN)6]y·zH2O with different stoichiometries have been synthesized. Elemental analyses reveal a quasilinear decrease in x and y when z increases. Some of these samples present a first‐order phase transition between the MnII–FeIII and MnIII–FeII electronic states with large thermal hysteresis loops observed in the magnetic susceptibility. The phase‐transition temperatures correlate with the stoichiometry, but quantitative predictions cannot be made because of the disordered nature of the compounds. Contrary to previous literature reports, calorimetric and Raman spectroscopic measurements reveal that the charge‐transfer phase transition is accompanied by a significant entropy change, ΔS = 48–59 J K–1 mol–1, of mainly vibrational origin. In addition to the thermal phase transition, Raman spectra also show that below ca. 120 K a photoinduced MnIII–FeII to MnII–FeIII conversion occurs in certain stoichiometries.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Rhodium(I) Complexes Containing β‐Amino Alcohol and 1,2‐Diamine Ligands: Syntheses, Structures, and Catalytic Applications
Authors: Dahlenburg Lutz , Treffert Harald , Farr Christian , Heinemann Frank W. , Zahl Achim
Published: March 2007

The bridge‐opening reaction of [(η4‐C8H12)2Rh2(μ‐Cl)2] with chiral and achiral β‐amino alcohol nucleophiles gave mononuclear complexes [(η4‐C8H12)RhCl{HN(R)∩OH‐κN}] containing the amino alcohol ligands in N‐monodentate coordination; HN(R)∩OH = ethanolamine (4), 2‐amino‐2‐methyl‐1‐propanol (5), and either enantiomer of (R)‐, (S)‐2‐amino‐3‐methyl‐1‐butanol (D‐, L‐valinol) [(R)‐6, (S)‐6], (R)‐, (S)‐2‐pyrrolidinemethanol (D‐, L‐prolinol) [(R)‐7, (S)‐7], (1S,2R)‐, (1R,2S)‐2‐amino‐1‐phenyl‐1‐propanol (D‐, L‐norephedrine) [(1S,2R)‐8, (1R,2S)‐8], and (1S,2R)‐, (1R,2S)‐cis‐1‐amino‐2‐indanol [(1S,2R)‐9, (1R,2S)‐9]. Coordination of the free hydroxy function of the N,O ligands was brought about by both dehydrochlorination, which furnished the neutral valinolato chelate complex [(η4‐C8H12)Rh{(S)‐H2NCH(CHMe2)CH2O‐κN,κO}], (S)‐10, and by precipitation of the metal‐bound chloride with TlO3SCF3 to produce ionic chelate complexes [(η4‐C8H12)Rh{HN(R)∩OH‐κN,κO}]O3SCF3; HN(R)∩OH = 2‐amino‐2‐methyl‐1‐propanol (11), (S)‐2‐amino‐3‐methyl‐1‐butanol [(S)‐12], (S)‐2‐pyrrolidinemethanol [(S)‐13], (1R,2S)‐2‐amino‐1‐phenyl‐1‐propanol [(1R,2S)‐14], and (1R,2S)‐cis‐1‐amino‐2‐indanol [(1R,2S)‐15]. Except for only two in situ characterized [{(R)‐binap}Rh(H2N∩OH‐κN,κO)]+ cations, where H2N∩OH = L‐valinol or L‐norephedrine, no compound containing the various N,O ligands in addition to mono‐ or bidentate phosphanes could be prepared. In contrast, theP2/N2‐coordinated chelate complexes [{(R)‐binap}Rh(H2N∩NH2)]BF4 with H2N∩NH2 = H2NCMe2CMe2NH2 [(R)‐(16)], (R,R)‐H2NCH(Ph)CH(Ph)NH2 [(R),(R,R)‐17], and (R,R)‐1,2‐(H2N)2C6H10 [(R),(R,R)‐18] were easily obtained from [(η4‐C8H12)Rh{(R)‐binap}]BF4 and 1,2‐diamines. Oxidative addition of HCl to (R),(R,R)‐17 produced trans‐[{(R)‐binap}Rh(H)(Cl){(R,R)‐H2NCH(Ph)CH(Ph)NH2}]BF4 [(R),(R,R)‐19]. If activated by strong base (KOH), (R),(R,R)‐17 and (R),(R,R)‐19 acted as moderately active and enantioselective catalysts for the reduction of acetophenone by both direct and transfer hydrogenation: eemax: 71 % (S). The crystal structures of 4, (S)‐6, (R)‐7, (1R,2S)‐8, (S)‐10, (1R,2S)‐14, (1R,2S)‐15, (R)‐16, (R),(R,R)‐17, and two alcohol/alcoholato addition compounds, [(η4‐C8H12)Rh(H2NCMe2CH2O‐κN,κO)][(η4‐C8H12)Rh(H2NCMe2CH2OH‐κN,κO)][(η4‐C8H12)RhCl2] [1·2], and [(η4‐C8H12)Rh(H2NCMe2CH2O‐κN,κO)][(η4‐C8H12)Rh(H2NCMe2CH2OH‐κN,κO)]Cl [1·3], were determined. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Effect of CyDye minimum labeling in differential gel electrophoresis on the reliability of protein identification
Authors: Hrebicek Thomas , Dürrschmid Karin , Auer Norbert , Bayer Karl , Rizzi Andreas
Published: March 2007

Differential 2‐DE (DIGE) is a widely applied tool for the quantitative analysis of differentially represented proteins. The method involves covalent minimal labeling of proteins prior to their electrophoretic separation using CyDye™ DIGE Fluor minimal dyes. This methodology creates two different species per protein, the labeled (approx. 1–2%) and unlabeled (approx. 98–99%) ones, which differ in their molecular masses by 434–464 Da, depending on the attached dye. DIGE followed by automated spot picking according to the CyDye coordinates misses in many instances the exact positions where the maximum amounts of the considered proteins are located. This fact leads to a loss in sensitivity of the subsequent MALDI‐MS analyses and results in a reduced reliability of protein identification and sequence coverage. In this paper, the migration differences of labeled and unlabeled species are quantified together with the impact of this effect on the certainty of protein identification and sequence coverage investigating proteins up to 90 kDa.
Probabilistic estimation of maximum inelastic displacement demands for performance‐based design
Authors: Ruiz‐García Jorge , Miranda Eduardo
Published: March 2007

A probabilistic approach to estimate maximum inelastic displacement demands of single‐degree‐of‐freedom (SDOF) systems is presented. By making use of the probability of exceedance of maximum inelastic displacement demands for given maximum elastic spectral displacement and the mean annual frequency of exceedance of elastic spectral ordinates, a simplified procedure is proposed to estimate mean annual frequencies of exceedance of maximum inelastic displacement demands. Simplifying assumptions are thoroughly examined and discussed. Using readily available elastic seismic hazard curves the procedure can be used to compute maximum inelastic displacement seismic hazard curves and uniform hazard spectra of maximum inelastic displacement demands. The resulting maximum inelastic displacement demand spectra provide a more rational way of establishing seismic demands for new and existing structures when performance‐based approaches are used. The proposed procedure is illustrated for elastoplastic SDOF systems having known‐lateral strength located in a region of high seismicity in California. Copyright © 2007 John Wiley & Sons, Ltd.
On dichotomizing phenotypes in family‐based association tests: quantitative phenotypes are not always the optimal choice
Authors: Fardo David , Celedón Juan C. , Raby Benjamin A. , Weiss Scott T. , Lange Christoph
Published: March 2007

In family‐based association studies, quantitative traits are thought to provide higher statistical power than dichotomous traits. Consequently, it is standard practice to collect quantitative traits and to analyze them as such. However, in many situations, continuous measurements are more difficult to obtain and/or need to be adjusted for other factors/confounding variables which also have to be measured. In such scenarios, it can be advantageous to record and analyze a “simplified/dichotomized” version of the original trait. Under fairly general circumstances, we derive here rules for the dichotomization of quantitative traits that maintain power levels that are comparable to the analysis of the original quantitative trait. Using simulation studies, we show that the proposed rules are robust against phenotypic misclassification, making them an ideal tool for inexpensive phenotyping in large‐scale studies. The guidelines are illustrated by an application to an asthma study. Genet. Epidemiol. 2007. © 2007 Wiley‐Liss, Inc.
An open trial of aripiprazole augmentation for SSRI non‐remitters with late‐life depression
Authors: Rutherford Bret , Sneed Joel , Miyazaki Marissa , Eisenstadt Rachel , Devanand Devangere , Sackeim Harold , Roose Steven
Published: March 2007

Objective

To evaluate the efficacy and tolerability of aripiprazole augmentation in elderly depressed patients who did not reach remission after treatment with an SSRI.

Method

Outpatients 50 years and older with major depressive disorder not remitting after adequate treatment with an SSRI were eligible for the study. In the 6‐week long augmentation phase, antidepressants were continued without change and aripiprazole was titrated if needed to a maximum dose of 15 mg per day. Patients were evaluated at the study endpoint on an intent to treat basis, and the primary outcome measure was remission of depression as measured by Hamilton Rating Scale for Depression (HRSD) ≤ 10.

Results

Twenty patients having mean age 63.0 ± 9.6 years old, HRSD 20.0 ± 4.2, Beck Depression Inventory (BDI) 21.0 ± 9.8, Clinical Global Impression—Severity (CGI—S) 3.7 ± 0.9, and Mini Mental State Examination (MMSE) 29.2 ± 1.0 entered the study. At the study endpoint, mean HRSD was 7.6 ± 5.9, BDI 9.1 ± 9.3, and CGI—S 1.9 ± 1.1. A 50% remission rate of depression was observed after six weeks of augmentation with aripiprazole. Twenty five percent of subjects did not complete the study. The most frequent side effects observed were dry mouth (25%), agitation/anxiety (20%), and drowsiness (15%).

Conclusion

In this study 50% of depressed patients not remitting after an adequate trial of an SSRI achieved a final HRSD ≤ 10 when given aripiprazole augmentation. Open trials such as this require follow up in a randomized, placebo‐controlled trial. Copyright © 2007 John Wiley & Sons, Ltd.
Northern Lights, Canada's version of the UNCITRAL Model Law on Cross‐Border Insolvency
Authors: Sarra Janis
Published: March 2007

Statute of Canada Chapter 47, when it is proclaimed in force, will largely adopt the UNCITRAL Model Law on Cross‐border Insolvency. The current and proposed cross‐border provisions could be considered Canada's “Northern Lights”, evolving constantly, but aligning with the objectives and scope of the UNCITRAL Model Law. While Chapter 47 is a modified version of the Model Law, it continues Canada's regime as one of modified universalism, with a strong commitment to comity and coordination. There are likely to be contests for control over the scope of foreign proceedings, although arguably, no more so than under the language of the Model Law. The most critical issues to resolve in the short term are definitions of COMI where corporate groups are involved, and the issue of the scope and extent of possible concurrent main proceedings, both areas left to the discretion of the courts in their interpretation of the legislation's domestic, as well as cross‐border, provisions. Copyright © 2007 John Wiley & Sons, Ltd.
Origin of intrinsic 310‐helix versus strand stability in homopolypeptides and its implications for the accuracy of the Amber force field
Authors: Jagielska Anna , Skolnick Jeffrey
Published: March 2007

Current all‐atom force fields often fail to recognize the native structure of a protein as the lowest free energy minimum. One possible cause could be the mathematical form of the potential based on the assumption that the conformation of a residue is independent of its neighbors. Here, using quantum mechanical (QM) methods (MP2/6‐31g**//HF/6‐31g** and MP2/cc‐pVDZ//cc‐pVDZ//HF/cc‐pVDZ), the intrinsic correctness of the gas phase terms (without solvation) of the Amber ff03 and ff99 potentials are examined by testing their ability to reproduce the relative 310‐helix versus extended structure stabilities in the gas phase for 1–7‐residue alanine, valine, leucine, and isoleucine homopolypeptides. The 310‐helix versus extended state stability strongly depends on chain length and less on the amino acid identity. The helical conformation becomes lower in energy than the extended conformation for all tested peptides longer than two residues, and its stability increases with the increase of chain length. The ff03 potential better describes the 310‐helix versus extended state energy than ff99 and also reproduces the curvature of the relative helix‐extended state energies. Therefore, the mathematical form of the Amber potential is sufficient to describe the local effect of 310‐helix versus extended structure stabilization in the gas phase. However, the energy curves are shifted and the backbone geometries differ compared with the QM results. This may cause significant geometric discrepancies between native and predicted structures. Therefore, extant molecular mechanics force fields, such as Amber, need refinement of their parameters to correctly describe helix‐extended state energetics and geometry of major conformations. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
A parallel distributed data CPHF algorithm for analytic Hessians
Authors: Alexeev Yuri , Schmidt Michael W. , Windus Theresa L. , Gordon Mark S.
Published: March 2007

One of the most commonly used means to characterize potential energy surfaces of reactions and chemical systems is the Hessian calculation, whose analytic evaluation is computationally and memory demanding. A new scalable distributed data analytic Hessian algorithm is presented. Features of the distributed data parallel coupled perturbed Hartree‐Fock (CPHF) are (a) columns of density‐like and Fock‐like matrices are distributed among processors, (b) an efficient static load balancing scheme achieves good work load distribution among the processors, (c) network communication time is minimized, and (d) numerous performance improvements in analytic Hessian steps are made. As a result, the new code has good performance which is demonstrated on large biological systems. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Chemical graph theory andn‐center electron delocalization indices: A study on polycyclic aromatic hydrocarbons
Authors: Mandado Marcos , González‐Moa María J. , Mosquera Ricardo A.
Published: March 2007

Relations between aromaticity indices derived from chemical graph theory and those based on 6‐center electron delocalization are investigated for a series of polybenzenoid hydrocarbons. Aromatic stabilization obtained by means of the effective scaled electron delocalization is highly correlated to the resonance energy, RE, obtained both from SCF MO calculations and conjugated ring circuits model. Local aromaticity of benzene rings is discussed using two different criteria, in one of them aromaticity is just given by the cyclicπ‐electron conjugation of the ring, whereas terms involving more than one ring are also considered in the other one. Indices derived from chemical graph theory and those obtained from the 6‐center electron delocalization give rise to the same local aromaticity. Moreover, 6‐center electron delocalization provides more quantitative information. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Characterization of conformational equilibria through Hamiltonian and temperature replica‐exchange simulations: Assessing entropic and environmental effects
Authors: Faraldo‐Gómez José D. , Roux Benoît
Published: March 2007

Molecular dynamics simulations based on the replica‐exchange framework (REMD) are emerging as a useful tool to characterize the conformational variability that is intrinsic to most chemical and biological systems. In this work, it is shown that a simple extension of the replica‐exchange method, known as Hamiltonian REMD, greatly facilitates the characterization of conformational equilibria across large energetic barriers, or in the presence of substantial entropic effects, overcoming some of the difficulties of REMD based on temperature alone. In particular, a comparative assessment of the HREMD and TREMD approaches was made, through computation of the gas‐phase free‐energy difference between the so‐called D2d and S4 states of tetrabutylammonium (TBA), an ionic compound of frequently used in biophysical studies of ion channels. Taking advantage of the greater efficiency of the HREMD scheme, the conformational equilibrium of TBA was characterized in a variety of conditions. Simulation of the gas‐phase equilibrium in the 100–300 K range allowed us to compute the entropy difference between these states as well as to describe its temperature dependence. Through HREMD simulations of TBA in a water droplet, the effect of solvation on the conformational equilibrium was determined. Finally, the equilibrium of TBA in the context of a simplified model of the binding cavity of the KcsA potassium channel was simulated, and density maps for D2d and S4 states analogous to those derived from X‐ray crystallography were constructed. Overall, this work illustrates the potential of the HREMD approach in the context of computational drug design, ligand‐receptor structural prediction and more generally, molecular recognition, where one of the most challenging issues remains to account for conformational flexibility as well for the solvation and entropic effects thereon. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Maximization of contrast‐to‐noise ratio to distinguish diffusion and microcirculatory flow
Authors: Maki Jeffrey H. , Benveniste Helene , MacFall James R. , Johnson G. Allan
Published: March 2007

Optimization of the contrast‐to‐noise ratio (CNR) is described for microcirculation magnetic resonance (MR) imaging techniques based on flow‐compensated/flow‐dephased sequences, both with and without even‐echo rephasing. The authors present the most advantageous manner of applying flow‐dephased gradients, such that de‐phasing is maximal while diffusion losses are minimal. The theoretical considerations include phase, diffusion, echo time, and bandwidth in the determination of the optimal parameters for microcirculation imaging. Studies in phantoms consisting of stationary and flowing copper sul‐fate in Sephadex columns demonstrate the validity of the calculations. Optimized in vivo images of a rat stroke model demonstrate the potential of the flow‐compensated/flow‐dephased technique and the importance of optimizing CNR.
Phase III clinical evaluation of Gd‐HP‐DO3A in head and spine disease
Authors: Runge Val M. , Dean Bruce , Lee Charles , Carolan Fred , Heard Gene
Published: March 2007

As part of a phase III clinical trial, 25 patients with suspected intracranial or spinal disease underwent magnetic resonance (MR) imaging before and after intravenous injection of 0.1 mmol/ kg Gd‐HP‐DO3A (1,4,7‐tris[carboxymethy1]‐10‐[2′hydroxypropy1]‐1,4,7,10‐tetraazacyclodode‐cane), a neutral (nonionic) gadolinium chelate. Laboratory analysis included a complete blood count; blood chemistry; measurement of electrolyte levels; hepatic function, clotting function, and iron metabolism panels; and urinalysis both before and 24 hours after contrast agent administration. No statistically significant changes related to contrast agent administration were noted in laboratory values after administration of the contrast agent. In this selected group of patients, the contrast agent‐enhanced study provided greater diagnostic information than did the precontrast study in 69% of head cases and 67% of spine cases. These initial clinical trials demonstrate that Gd‐HP‐DO3A is a safe, efficacious agent for head and spine examinations.
Meningeal mesenchymal chondrosarcoma of the spine: A case report
Authors: Huckabee Rife E.
Published: March 2007

Primary soft‐tissue chondro‐sarcomas are most often of the mesenchymal variety. When affecting the central nervous system, these tumors usually arise from the intracranial meninges. Intraspinal meningeal lesions are much less common but may be considered, especially in the pediatric age group, when clinical or radiologic presentation is atypical. The author presents a case report including MR imaging studies of a 7‐year‐old girl with intraspinal dural chon‐drosarcoma.
Policies, guidelines, and recommendations for MR imaging safety and patient management
Authors: Shellock Frank G. ,   SMRI Safety Committee
Published: March 2007

The following are policies, guidelines, and recommendations from the Safety Committee of the Society for Magnetic Resonance Imaging (SMRI) concerning various issues related to magnetic resonance (MR) imaging safety and patient management. These policies, guidelines, and recommendations were developed to provide standardized and consistent information for use by health practitioners involved in clinical MR imaging.
Comparing the FAISE method with conventional dual‐echo sequences
Authors: Melki Philippe S. , Mulkern Robert V. , Panych Lawrence P. , Jolesz Ferenc A.
Published: March 2007

The FAISE (fast‐acquisition interleaved spin‐echo) technique consists of a hybrid rapid‐acquisition relaxation‐enhanced (RARE) sequence combined with a specific phase‐encode reordering method. Implemented on a 1.5‐T unit, this multisection, high‐resolution technique permits convenient contrast manipulation similar to that of spin‐echo imaging, with selection of a pseudo‐echo‐time parameter and a TR interval. With a TR of 2 seconds, eight 256 × 256 images are obtained in 34 seconds with either T2 or proton‐density weighting. A direct comparison between FAISE and spin echo for obtaining T2‐weighted head images in healthy subjects indicates that FAISE and spin‐echo images are qualitatively and quantitatively similar. Image artifacts are more pronounced on “proton‐density” FAISE images than on the T2‐weighted FAISE images. T1 contrast can be obtained with inversion recovery and short TR FAISE images. Preliminary temperature measurements in saline phantoms do not indicate excessive temperature increases with extended FAISE acquisitions. However, extensive studies of radio‐frequency power deposition effects should be performed if the FAISE technique is to be fully exploited.
Electrocardiograph‐independent, “wireless” cardiovascular cine MR imaging
Authors: White Richard D. , Paschal Cynthia B. , Clampitt Mark E. , Spraggins Thomas A. , Lenz Gerald W.
Published: March 2007

A new electrocardiograph (ECG)‐independent, “wireless” gating technique for cine magnetic resonance (MR) imaging was evaluated in 23 cases of cardiovascular disease; in each case, standard ECG‐dependent image loops were available for comparison. The ECG‐independent strategy references cine MR imaging data retrospectively to inherent periodic changes in MR signal related to the cardiac cycle. With a “double‐section” method, both timing data reflecting such changes and imaging data can be acquired simultaneously. “Artificial R waves” are extracted from the timing data acquired with a projection approach. The ECG‐independent image loops were diagnostic in 91 % of cases. Their overall image quality was at least equal to that of available ECG‐dependent versions in only 39% of cases, but this proportion increased to 53% if cases with suboptimal imaging orientations for monitoring of the motion‐dependent signal changes were excluded. Orientation appeared to be the primary technical limitation associated with this ECG‐independent technique; however, poor ventricular function also significantly impaired performance. Improvement in the performance of the ECG‐independent strategy is anticipated with technical advances.
Application of a connected‐voxel algorithm to MR angiographic data
Authors: Saloner David , Hanson William A. , Tsuruda Jay S. , van Tyen Rem , Anderson Charles M. , Lee Ralph E.
Published: March 2007

A connected‐voxel algorithm (CVA) that improves the contrast and conspicuity of blood vessels in maximum‐intensity‐projection (MIP) magnetic resonance (MR) angiography is described. Images from a variety of anatomic regions in healthy volunteers were calculated with either an MIP procedure alone or with data that had first been processed with the CVA. A low‐signal‐intensity threshold is first applied to separate groups of voxels associated with different vessels from one another and to eliminate the contribution from low‐intensity stationary material. The remaining voxels are grouped by a connectivity criterion into discrete “objects.” Vessels are represented by extended objects, and small objects are discarded. The CVA, therefore, reduces the full three‐dimensional data set into a small number of discrete objects. It is a powerful technique that can be used to remove signal from vessels overlying the vessel of interest, to separate objects representing arterial flow from those representing venous flow, to eliminate flow artifact from projection images, and to more completely retain signal within the vascular lumen. This technique has been successfully demonstrated with MR angiography in healthy volunteers.
Use of magnetic particles for sensitizing MR images to blood flow
Authors: Hardy Peter A. , Bronskill Michael J. , Belanger Marie‐Jose , Henkelman R. Mark
Published: March 2007

Magnetic resonance (MR) images made with the IVIM (intravoxel incoherent motion) technique for demonstrating tissue microcirculation are limited in sensitivity because of the small volume of blood involved. This limitation may be overcome by incorporating magnetic particles into the flow. The magnetic perturbation caused by the particles extends beyond the walls of the capillary and affects a much larger volume than that of the flowing material. Imaging experiments conducted with an artificial capillary system for renal dialysis, containing large magnetic particles, showed that signal intensity decreased with increasing flow rate through the dialysis bundle and with increasing particle concentration. Predictions of the effect based on a theoretical model of spin dephasing in the field of a magnetic dipole agreed with the experimental data. The results hold promise for development of the technique in vivo.
Muscle edema in musculoskeletal tumors: MR imaging characteristics and clinical significance
Authors: Hanna Soheil L. , Fletcher Barry D. , Parham David M. , Bugg Michael F.
Published: March 2007

To determine the frequency and clinical significance of tumor‐associated muscle edema, magnetic resonance (MR) imaging findings in 46 consecutive patients with benign or malignant musculoskeletal lesions were reviewed. Increased muscle signal intensity on T2‐weighted, STIR (short‐inversion‐time inversion‐recovery), and gadopentetate dimeglumine‐enhanced TI‐weighted images was present in 41 cases, with the clearest delineation of tumor margins seen on T2‐weighted images. Typical peri/paratu‐moral edema (PTE) was present in equal proportions of malignant (25 of 37) and benign lesions (six of nine). Massive edema involving the entirety of at least one contiguous muscle‐to the authors' knowledge, a previously undescribed finding‐was identified on MR images of eight malignant and two benign lesions (22% of both groups). All cases of massive edema had a substantial soft‐tissue component and involved muscles disrupted by tumor at the point of attachment to bone. Malignant tumors associated with massive edema were larger than those with typical or no PTE, showed a poorer response to initial chemotherapy, and had a higher frequency of metastases at diagnosis. Thus, the presence of massive muscle edema appears to be an ominous clinical finding in patients with malignant musculoskeletal lesions.
Phase‐offset multiplanar (POMP) volume imaging: A new technique
Authors: Glover Gary H.
Published: March 2007

Phase‐offset multiplanar (POMP) imaging is a technique that excites several sections simultaneously for improved imaging efficiency. The centers of the reconstructed images from each of the POMP sections are offset from each other in the phase‐encoding direction by means of view‐dependent phase modulation of the radio‐frequency (RF) excitation pulses and are placed adjacent to each other in the reconstruction. With a suitable reconstruction matrix size, the images can be made nonoverlapping and stored separately. At constant imaging time, signal‐to‐noise ratio (S/N), and resolution, POMP imaging produces a factor In: Book of abstracts: Society of Magnetic Resonance in Medicine In: Book of abstracts: Society of Magnetic Resonance in Medicine Np more sections than a conventinal sequence but with a reduced field of view. Alternatively, imaging time may be invreased by the factor Np to retain the same field of view but with the expected S/N advantage. The average RF power deposited by the 90° composite RF pulse is greater by the factor Np, but the power for the 180° pulse is unchanged. The POMP method is discussed and compared with three‐dimensional and Hadamard techniques.