bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrocatalytic Behavior of Glassy Carbon Electrodes Modified with Multiwalled Carbon Nanotubes and Cobalt Phthalocyanine for Selective Analysis of Dopamine in Presence of Ascorbic Acid
Authors: Cruz Moraes Fernando , Cabral Murilo F. , Machado Sergio A. S. , Mascaro Lucia H. 
Published: January 2008

AbstractThis work describes the development, electrochemical characterization and utilization of a cobalt phthalocyanine modified carbon nanotube electrode for the quantitative determination of dopamine in 0.2 mol L−1 phosphate buffer contaminated with high concentration of ascorbic acid. The electrode surface was analyzed by cyclic voltammetry and electrochemical impedance spectroscopy which showed a modified surface presenting a charge transfer resistance of 500 Ω, against the 16.46 kΩ value found for the bare glassy carbon surface. A pseudo rate constant value of 5.4×10−4 cm s−1 for dopamine oxidation was calculated. Voltammetric experiments showed a shift of the peak potential of DA oxidation to less positive value at 390 mV as compared with that of a bare GC electrode at 570 mV. The electrochemical determination of dopamine, in presence of ascorbic acid in concentrations up to 0.1 mol L−1 by differential pulse voltammetry, yielded a detection limit as low as 2.56×10−7 mol L−1.
Enhanced Sensitivity of 4‐Chlorophenol Detection by Use of Nitrobenzene as a Liquid Membrane over a Carbon Nanotube‐Modified Glassy Carbon Electrode
Authors: Phanthong Chatuporn , Somasundrum Mithran 
Published: January 2008

AbstractThe analytical utility of nitrobenzene as a liquid membrane for the detection of hydrophobic compounds was examined with a glassy carbon electrode, using 4‐chlorophenol as the model analyte. Electrochemical experiments indicated a large partition coefficient for the entry of 4‐chlorophenol into the nitrobenzene (7.6×102±1.5×102). This was combined with an increase in effective electrode area by coating with single‐walled nanotubes. Differential pulse voltammetry produced a linear response across the range 0.3 nM to 1.5 nM with a sensitivity of 1.1×10−5 A nM−1 cm−2. To the best of our knowledge, this limit of detection for phenol is lower than other nonenzymatic modifications of carbon.
High‐resolution computer simulation of the dynamics of isoelectric focusing: In quest of more realistic input parameters for carrier ampholytes
Authors: Mosher Richard A. , Thormann Wolfgang 
Published: January 2008

AbstractThe impact of the systematic variation of either ΔpKa or mobility of 140 biprotic carrier ampholytes on the conductivity profile of a pH 3–10 gradient was studied by dynamic computer simulation. A configuration with the greatest ΔpKa in the pH 6–7 range and uniform mobilities produced a conductivity profile consistent with that which is experimentally observed. A similar result was observed when the neutral (pI = 7) ampholyte is assigned the lowest mobility and mobilities of the other carriers are systematically increased as their pI's recede from 7. When equal ΔpKa values and mobilities are assigned to all ampholytes a conductivity plateau in the pH 5–9 region is produced which does not reflect what is seen experimentally. The variation in ΔpKa values is considered to most accurately reflect the electrochemical parameters of commercially available mixtures of carrier ampholytes. Simulations with unequal mobilities of the cationic and anionic species of the carrier ampholytes show either cathodic (greater mobility of the cationic species) or anodic (greater mobility of the anionic species) drifts of the pH gradient. The simulated cationic drifts compare well to those observed experimentally in a capillary in which the focusing of three dyes was followed by whole column optical imaging. The cathodic drift flattens the acidic portion of the gradient and steepens the basic part. This phenomenon is an additional argument against the notion that focused zones of carrier ampholytes have no electrophoretic flux.
Protein separations using polyelectrolyte multilayer coatings with molecular micelles in open tubular capillary electrochromatography
Authors: Luces Candace A. , Fakayode Sayo O. , Lowry Mark , Warner Isiah M. 
Published: January 2008

AbstractNovel polyelectrolyte multilayer (PEM) coatings for enhanced protein separations in open tubular CEC (OT‐CEC) are reported. Use of four cationic polymers (poly‐L‐lysine, poly‐L‐ornithine, poly‐L‐lysine‐serine, and poly‐L‐glutamic acid‐lysine), and three anionic molecular micelles, sodium poly(N‐undecanoyl‐L‐leucyl‐alaninate) (poly‐L‐SULA), sodium poly(N‐undecanoyl‐L‐leucyl‐valinate) (poly‐L‐SULV), and sodium poly(undecylenic sulfate) (poly‐SUS) were investigated in PEM coatings for protein separations. The simultaneous effects of cationic polymer concentration, number of bilayers, temperature, applied voltage, and pH of the BGE on the separation of four basic proteins (α‐chymotrypsinogen A, lysozyme, ribonuclease A, and cytochrome c) were analyzed using a Box Behnken experimental design. The influence of NaCl on the run‐to‐run reproducibility was investigated for PEM coatings containing each cationic polymer. All coatings exhibited excellent reproducibilities with a %RSD of the EOF less than 1% in the presence of NaCl. Optimal conditions were dependent on both the cationic and anionic polymers used in the PEM coatings. Poly‐L‐glutamic acid‐lysine produced the highest resolution and longest migration time. The use of molecular micelles to form PEM coatings resulted in better separations than single cationic coatings. Chiral poly‐L‐SULA and poly‐L‐SULV resulted in higher protein resolutions as compared to the achiral, poly‐SUS. Furthermore, the use of poly‐L‐SULV reversed the elution order of lysozyme and cytochrome c when compared to poly‐L‐SULA and poly‐SUS.
An advanced application of the quantitative structure–activity relationship concept in electrokinetic chromatography of metal complexes
Authors: Oszwałdowski Sławomir , Timerbaev Andrei R. 
Published: January 2008

AbstractThe relevance of the quantitative structure–activity relationship (QSAR) principle in MEKC and microemulsion EKC (MEEKC) of metal–ligand complexes was evaluated for a better understanding of analyte migration mechanism. A series of gallium chelates were applied as test solutes with available experimental migration data in order to reveal the molecular properties that govern the separation. The QSAR models operating with n‐octanol–water partition coefficients or van der Waals volumes were found to be valid for estimation of the retention factors (log k′) of neutral compounds when using only an aqueous MEEKC electrolyte. On the other hand, consistent approximations of log k′ for both uncharged and charged complexes in either EKC mode (and also with hydro‐organic BGEs) were achievable with two‐parametric QSARs in which the dipole moment is additionally incorporated as a structural descriptor, reflecting the electrostatic solute–pseudostationary phase interaction. The theoretical analysis of significant molecular parameters in MEKC systems, in which the micellar BGE is modified with an organic solvent, confirmed that concomitant consideration of hydrophobic, electrostatic, and solvation factors is essential for explaining the migration behavior of neutral metal complexes.
Regular properties of simple electrophoretic BGEs with multiprotic weak acids: Discovery of complex hybrid system boundaries
Authors: Gebauer Petr , Malá Zdena , Šlampová Andrea , Boček Petr 
Published: January 2008

AbstractIn electrophoresis, the introduction of a sample into the BGE creates two new zone boundaries, the front and rear boundary of the sample zone which is sandwiched between the BGE. During an electrophoresis run, these boundaries move and split into other new boundaries demarcating the zones of analytes. Besides the analyte zones migrating out of the original sample location, system zones may be also formed. Such zones are formed by the BGE components and differ from the BGE only in their concentrations. The front and rear boundaries of such system zones evolve during electromigration and may show sharp (S), dispersed (D), and/or hybrid character. This contribution brings the results of theoretical and experimental investigation of system properties of very simple BGEs formed by one weak acid and one weak or strong base provided that the acid is polyprotic. It is shown that system boundaries of the hybrid type occur even in these simple systems represented, e.g., by the very common phosphate buffer. Theory reveals that a phosphate buffer system (formed by phosphoric acid and a strong cation) may exhibit a very unusual complex shape of the electromigration dispersion velocity curve showing three turns. This leads to the formation of complex hybrid boundaries having D–S–D, S–D–S, or even S–D–S–D or D–S–D–S concentration profile types that have not been reported so far. The velocity diagram method allows theoretical analysis of such complicated profiles and the results are in good accordance with both computer simulation and experiments.
Changes in regional cerebral blood flow following antidepressant treatment in late‐life depression
Authors: Ishizaki Junko , Yamamoto Hideki , Takahashi Taro , Takeda Maki , Yano Madoka , Mimura Masaru 
Published: January 2008

AbstractObjectiveReversible/irreversible abnormalities of regional cerebral blood flow (rCBF) are seen in patients with depression. However, in late‐life depression there is little evidence of a longitudinal change in rCBF through remission. We examined whether the decreased rCBF in individuals with late‐life depression resolves following treatment.MethodsTwenty‐five depressed patients older than 55 years completed the Hamilton Rating Scale for Depression and single photon emission computed tomography before and after a mean of 13.7 weeks of pharmacotherapy. Quantitative analyses were performed using the Statistical Parametric Mapping procedure.ResultsPatients with depression demonstrated decreased rCBF in the anterior ventral and dorsal medial prefrontal cortex (PFC), including anterior cingulate cortices, bilateral ventrolateral PFC to temporal cortices, and bilateral medial to lateral parieto‐occipital lobes relative to healthy controls. No particular areas showed increased rCBF. Following pharmacotherapy, rCBF significantly increased in the left dorsolateral PFC to precentral areas and the right parieto‐occipital regions. However, decreased rCBF at baseline in the anterior ventral/dorsal medial PFC, bilateral ventrolateral PFC, bilateral temporal lobes, and bilateral parietal lobes did not show significant improvement after treatment.ConclusionsRemarkable improvements in rCBF in the left dorsolateral PFC to precentral regions are consistent with the hypothesis that neuronetworks including the left frontal cortex may be functionally and reversibly involved in late‐life unipolar major depression (state‐dependent). In contrast, neural circuits including bilateral medial, dorsolateral, and parietal areas may reflect underlying and continuous pathognomonic brain dysfunction of depression (trait‐dependent). Copyright © 2008 John Wiley & Sons, Ltd.
Self‐organized criticality and the development of EEG phase reset
Authors: Thatcher Robert Wayne , North Duane Michael , Biver Carl John 
Published: January 2008

AbstractObjectives: The purpose of this study was to explore human development of self‐organized criticality as measured by EEG phase reset from infancy to 16 years of age. Methods: The electroencephalogram (EEG) was recorded from 19 scalp locations from 458 subjects ranging in age from 2 months to 16.67 years. Complex demodulation was used to compute instantaneous phase differences between pairs of electrodes and the 1st and 2nd derivatives were used to detect the sudden onset and offset times of a phase shift followed by an extended period of phase locking. Mean phase shift duration and phase locking intervals were computed for two symmetrical electrode arrays in the posterior‐to‐anterior locations and the anterior‐to‐posterior directions in the α frequency band (8–13 Hz). Results: Log–log spectral plots demonstrated 1/f α distributions (α ≈ 1) with longer slopes during periods of phase shifting than during periods of phase locking. The mean duration of phase locking (150–450 msec) and phase shift (45–67 msec) generally increased as a function of age. The mean duration of phase shift declined over age in the local frontal regions but increased in distant electrode pairs. Oscillations and growth spurts from mean age 0.4–16 years were consistently present. Conclusions: The development of increased phase stability in local systems is paralleled by lengthened periods of unstable phase in distant connections. Development of the number and/or density of synaptic connections is a likely order parameter to explain oscillations and growth spurts in self‐organized criticality during human brain maturation. Hum Brain Mapp, 2009. © 2008 Wiley‐Liss, Inc.
Altered small‐world brain functional networks in children with attention‐deficit/hyperactivity disorder
Authors: Wang Liang , Zhu Chaozhe , He Yong , Zang Yufeng , Cao QingJiu , Zhang Han , Zhong Qiuhai , Wang Yufeng 
Published: January 2008

AbstractIn this study, we investigated the changes in topological architectures of brain functional networks in attention‐deficit/hyperactivity disorder (ADHD). Functional magnetic resonance images (fMRI) were obtained from 19 children with ADHD and 20 healthy controls during resting state. Brain functional networks were constructed by thresholding the correlation matrix between 90 cortical and subcortical regions and further analyzed by applying graph theoretical approaches. Experimental results showed that, although brain networks of both groups exhibited economical small‐world topology, altered functional networks were demonstrated in the brain of ADHD when compared with the normal controls. In particular, increased local efficiencies combined with a decreasing tendency in global efficiencies found in ADHD suggested a disorder‐related shift of the topology toward regular networks. Additionally, significant alterations in nodal efficiency were also found in ADHD, involving prefrontal, temporal, and occipital cortex regions, which were compatible with previous ADHD studies. The present study provided the first evidence for brain dysfunction in ADHD from the viewpoint of global organization of brain functional networks by using resting‐state fMRI. Hum Brain Mapp, 2009. © 2008 Wiley‐Liss, Inc.
Functional connectivity of default mode network components: Correlation, anticorrelation, and causality
Authors: Uddin Lucina Q. , Clare Kelly A.M. , Biswal Bharat B. , Xavier Castellanos F. , Milham Michael P. 
Published: January 2008

AbstractThe default mode network (DMN), based in ventromedial prefrontal cortex (vmPFC) and posterior cingulate cortex (PCC), exhibits higher metabolic activity at rest than during performance of externally oriented cognitive tasks. Recent studies have suggested that competitive relationships between the DMN and various task‐positive networks involved in task performance are intrinsically represented in the brain in the form of strong negative correlations (anticorrelations) between spontaneous fluctuations in these networks. Most neuroimaging studies characterize the DMN as a homogenous network, thus few have examined the differential contributions of DMN components to such competitive relationships. Here, we examined functional differentiation within the DMN, with an emphasis on understanding competitive relationships between this and other networks. We used a seed correlation approach on resting‐state data to assess differences in functional connectivity between these two regions and their anticorrelated networks. While the positively correlated networks for the vmPFC and PCC seeds largely overlapped, the anticorrelated networks for each showed striking differences. Activity in vmPFC negatively predicted activity in parietal visual spatial and temporal attention networks, whereas activity in PCC negatively predicted activity in prefrontal‐based motor control circuits. Granger causality analyses suggest that vmPFC and PCC exert greater influence on their anticorrelated networks than the other way around, suggesting that these two default mode nodes may directly modulate activity in task‐positive networks. Thus, the two major nodes comprising the DMN are differentiated with respect to the specific brain systems with which they interact, suggesting greater heterogeneity within this network than is commonly appreciated. Hum Brain Mapp 30:625–637, 2009. © 2008 Wiley‐Liss, Inc.
Diarylheptanoids from the Rhizomes of Alpinia officinarum
Authors: Sun Yi , Matsubara Hideki , Kitanaka Susumu , Yasukawa Ken 
Published: January 2008

AbstractA novel dimeric diarylheptanoid, (5R,5′R)‐7,7′‐(6,6′‐dihydroxy‐5,5′‐dimethoxy[1,1′‐biphenyl]‐3,3′‐diyl)bis[5‐methoxy‐1‐phenylheptan‐3‐one] (1), and two new diarylheptanoids, (4E,6R)‐6‐hydroxy‐7‐(4‐hydroxy‐3‐methoxyphenyl)‐1‐phenylhept‐4‐en‐3‐one (2) and (4E,6R)‐6‐hydroxy‐1,7‐diphenylhept‐4‐en‐3‐one (3), together with seven known diarylheptanoids, were isolated from the rhizomes of Alpinia officinarum. Their structures were elucidated by application of extensive spectroscopic analyses and the modified Mosher method.
Two New Benzophenanthridine Alkaloids from Zanthoxylum nitidum
Authors: Cui Xin‐Gang , Zhao Qing‐Jie , Chen Qiao‐Ling , Xu Lei , Song Yan , Jin Yong‐Sheng , Xu Dan‐Feng 
Published: January 2008

AbstractTwo new benzophenanthridine alkaloids, named 8‐methoxysanguinarine (1) and 8‐methoxyisodecarine (2), were isolated from the EtOH extract of the rhizoma of Zanthoxylum nitidum. Their structures were determined on the basis of spectroscopic analysis.
A Novel One‐Pot Conversion of Allyl Alcohols into Primary Allyl Halides Mediated by Acetyl Halide
Authors: Kishali Nurhan , Polat M. Fatih , Altundas Ramazan , Kara Yunus 
Published: January 2008

AbstractA new and simple method for the synthesis of the primary allyl chlorides and bromides 9–16 from the secondary or tertiary allyl alcohols 3–8 and acyl halide was developed (Scheme 2, Table 1). Non‐commercially available secondary and tertiary allyl alcohols were synthesized from the related ketones and aldehydes via the addition of vinylmagnesium chloride. Mechanistic studies indicate that the alcohols were first acetylated by the acetyl halide and then protonated prior to substitution by the halide, Cl− or Br−, via an SN2′ reaction, to yield the primary halides (Scheme 5).
Laminins and their roles in mammals
Authors: Miner Jeffrey H. 
Published: January 2008

AbstractLaminins are α‐β‐γ heterotrimeric components of all basement membranes. Laminins are now known to play the central role in organizing and establishing the basement membrane. The diversity of laminins allows them to impart special structural and signaling properties to the basement membrane. Of the 12 known laminin chain genes, 10 have been either found to be mutated in humans or experimentally mutated in mice. This has led to great progress over the last several years towards understanding both the functions of laminins and the reasons for their great diversity. In this review, I will summarize the in vivo studies in mice and humans that have contributed to this new knowledge. Microsc. Res. Tech., 2008. © 2008 Wiley‐Liss, Inc.
Myocardial fibrosis of left ventricle: Magnetic resonance imaging in noncompaction
Authors: Alsaileek Ahmed A. , Syed Imran , Seward James B. , Julsrud Paul 
Published: January 2008

AbstractThis report describes a 24‐year‐old female with left ventricular noncompaction. Cardiovascular magnetic resonance (CMR) imaging demonstrated the characteristic features of noncompaction. We were also able to noninvasively document the presence and extent of myocardial fibrosis depicted on myocardial delayed enhancement (MDE). Magnetic resonance imaging can be performed simply and give much information about the morphologic and tissue characteristics of left ventricular wall in noncompaction. In particular, MDE imaging is useful to demonstrate the associated myocardial scaring that may result in heart failure and arrhythmia. J. Magn. Reson. Imaging 2008. © 2008 Wiley‐Liss, Inc.
Enhanced tumor MR imaging with gadolinium‐loaded polychelating polymer‐containing tumor‐targeted liposomes
Authors: Erdogan Suna , Medarova Zdravka O. , Roby Aruna , Moore Anna , Torchilin Vladimir P. 
Published: January 2008

AbstractPurposeTo significantly enhance tumor MR imaging by using a contrast agent combining three components—a long‐circulating liposome, liposomal membrane‐incorporated polychelating amphiphilic polymer heavily loaded with gadolinium, and cancer‐specific monoclonal antibody 2C5 attached to the liposome surface.Materials and MethodsTumor‐bearing animals were imaged prior and 4, 24, and 48 hours after i.v. injection of 2C5‐modified and unmodified Gd‐PAP‐containing PEGylated liposomes. The faster and more specific accumulation of the novel contrast nanoparticles in tumors was also confirmed by 3D angiograms and by direct visualization of Gd‐immunoliposomes in tumor sections by confocal microscopy.Results2C5‐modified Gd‐PAP‐containing PEGylated liposomes allowed for fast and specific tumor imaging as early as 4 hours postinjection. T1 inversion recovery maps demonstrated a significant increase in tumor‐associated R1 in animals injected with antibody‐modified Gd‐loaded liposomes 4 hours postinjection, followed by a gradual decrease consistent with clearance of the agent from the tumor region. In control animals injected with antibody‐free liposomes the corresponding R1 values at all investigated timepoints were significantly smaller.ConclusionThe results support the feasibility of using such multifunctional nanoparticular liposome‐based agents simultaneously providing prolonged circulation, heavy Gd load, and specific cancer cell recognition as a superior contrast for MR tumor imaging. J. Magn. Reson. Imaging 2008. © 2008 Wiley‐Liss, Inc.
CBF, BOLD, CBV, and CMRO2 fMRI signal temporal dynamics at 500‐msec resolution
Authors: Shen Qiang , Ren Hongxia , Duong Timothy Q. 
Published: January 2008

AbstractPurposeTo investigate the temporal dynamics of blood oxygenation level‐dependent (BOLD), cerebral blood flow (CBF), cerebral blood volume (CBV), and cerebral metabolic rate of oxygen (CMRO2) changes due to forepaw stimulation with 500‐msec resolution in a single setting.Materials and MethodsForepaw stimulation and hypercapnic challenge on rats were studied. CBF and BOLD functional MRI (fMRI) were measured using the pseudo‐continuous arterial spin‐labeling technique at 500‐msec resolution. CBV fMRI was measured using monocrystalline iron‐oxide particles following CBF and BOLD measurements in the same animals. CMRO2 change was estimated via the biophysical BOLD model with hypercapnic calibration. Percent changes and onset times were analyzed for the entire forepaw somatosensory cortices and three operationally defined cortical segments, denoted Layers I–III, IV–V, and VI.ResultsBOLD change was largest in Layers I–III, whereas CBF, CBV, and CMRO2 changes were largest in Layers IV–V. Among all fMRI signals in all layers, only the BOLD signal in Layers I–III showed a poststimulus undershoot. CBF and CBV dynamics were similar. Closer inspection showed that CBV increased slightly first (P < 0.05), but was slow to peak. CBF increased second, but peaked first. BOLD significantly lagged both CBF and CBV (P < 0.05).ConclusionThis study provides important temporal dynamics of multiple fMRI signals at high temporal resolution in a single setting. J. Magn. Reson. Imaging 2008. © 2008 Wiley‐Liss, Inc.