bluuebunny/crossref_metadata_2025 huggingface dataset:
Voltammetric Determination of Methimazole Using a Carbon Paste Electrode Modified with a Schiff Base Complex of Cobalt
Authors: Shahrokhian Saeed , Ghalkhani Masoumeh
Published: April 2008

The electrochemical behavior of methimazole, as an antithyroid agent, is investigated on the surface of a carbon‐paste electrode modified with a newly synthesized Schiff base complex of cobalt. The prepared modified electrode showed an efficient catalytic role in the electrochemical oxidation of methimazole, leading to remarkable decrease in oxidation overpotential and enhancement of the kinetics of the electrode reaction. The mechanism of the electrocatalytic process on the surface of the modified electrode is analyzed by obtaining the cyclic voltammograms in various potential sweep rates and pHs of the buffer solutions. The differential pulse voltammetry is applied as a very sensitive analytical method for the determination of sub‐micromolar amounts of methimazole. A linear dynamic range of 1×10−6 to 1×10−4 M with a detection limit of 5×10−7 M is resulted for methimazole. The modified electrode is successfully applied for the accurate determination of methimazole in pharmaceutical and clinical preparations. The linear range in calibration curves remains constant in addition to tablet preparations of methimazole and also in spiking to the synthetic human serum samples. In comparison to calibration curves in background buffer solution, the slope of the curves showed a variation less than 3% in determinations in background solutions of tablet and human synthetic serum samples. These results showed high efficiency of the Voltammetric procedure for accurate determination of methimazole in drug and clinical preparations. The modified electrode can be prepared very easy and renewed in its surface by simple polishing. The reproducibility of the electrode response, based on ten measurements during two month, was 3.2% for the slope of the calibration curve.
A Novel Electrochemical DNA Biosensor Fabricated with Layer‐by‐Layer Covalent Attachment of Multiwalled Carbon Nanotubes and Gold Nanoparticles
Authors: Ma Haiyan , Zhang Liping , Pan Yan , Zhang Keying , Zhang Yuzhong
Published: April 2008

A novel DNA biosensor has been fabricated for the detection of DNA hybridization based on layer‐by‐layer (LBL) covalent assembly of gold nanoparticles (GNPs) and multiwalled carbon nanotubes (MWCNTs). The stepwise LBL assembly process was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The hybridization events were monitored by differential pulse voltammetry (DPV) measurement of the intercalated doxorubicin, and the factors influencing the performance of the DNA hybridization was investigated in detail. The signal was linearly changed with target DNA concentration increased from 0.5 to 0.01 nM, and had a detection limit of 7.5 pM (signal/noise ratio of 3). In addition, the DNA biosensor showed an excellent reproducibility and stability under the DNA‐hybridization conditions.
Simultaneous Determination of Nickel and Cadmium by Adsorptive Stripping Voltammetry
Authors: Gholivand M. B. , Bahrami S. , Abbasi S. , Sohrabi A.
Published: April 2008

A sensitive and fast method for the simultaneous determination of trace amounts of nickel and cadmium in real samples has been described using differential pulse adsorptive stripping voltammetry (DPASV) by adsorptive accumulation of the N,N′‐bis(salicylaldehydo)4‐carboxyphenylenediamine (BSCPDA)–complex on the hanging mercury drop electrode (HMDE). As supporting electrolyte 0.02 mol L−1 ammonia buffers containing ligand has been used. Optimal analytical conditions were found to be: BSCPDA concentration of 42 μM, pH 9.6 and adsorption potential at −50 mV versus Ag/AgCl. With an accumulation time of 20 s, the peaks current are proportional to the concentration of nickel and cadmium over the 1–180, and 0.5–200 ng mL−1 with detection limits of 0.06 and 0.03 ng mL−1 respectively. The sensitivity of method for determination of nickel and cadmium were obtained 0.54 and 0.98 nA mL ng−1, respectively. The procedure was applied to simultaneous determination of nickel and cadmium in some real and synthetic artificial samples with satisfactory results.
Simultaneous Determination of Acetaminophen and Ascorbic Acid at an Unmodified Boron‐Doped Diamond Electrode by Differential Pulse Voltammetry in Buffered Media
Authors: Radovan Ciprian , Cofan Codruta , Cinghita Dan
Published: April 2008

A boron‐doped diamond electrode (BDDE) was used for the simultaneous anodic determination of L‐ascorbic acid (AA) and acetaminophen (AC) in aqueous buffered media by differential pulse voltammetry (DPV). Linear calibration plots of anodic current peaks versus concentration were obtained for both analytes in the concentration range 0.01–0.1 mM with very high correlation coefficients. RSD of 2–3% and high sensitivities were obtained from DPV data in single and dicomponent systems. The potential applicability of the DPV technique associated with standard addition was illustrated by simultaneous determination of AA and AC in real sample solutions made up from pharmaceutical products.
Facilitated Transfer of Alkali Metal Ions by a Tetraester Derivative of Thiacalix[4]arene at the Liquid–Liquid Interface
Authors: Guler Akgemci Emine , Bingol Haluk , Ersoz Mustafa , Stibor Ivan
Published: April 2008

The facilitated transfer of alkali metal ions (Na+, K+, Rb+, and Cs+) by 25,26,27,28‐tetraethoxycarbonylmethoxy‐thiacalix[4]arene across the water/1,2‐dichloroethane interface was investigated by cyclic voltammetry. The dependence of the half‐wave transfer potential on the metal and ligand concentrations was used to formulate the stoichiometric ratio and to evaluate the association constants of the complexes formed between ionophore and metal ions. While the facilitated transfer of Li+ ion was not observed across the water/1,2‐dichloroethane interface, the facilitated transfers were observed by formation of 1 : 1 (metal:ionophore) complex for Na+, K+, and Rb+ ions except for Cs+ ion. In the case of Cs+ a 1 : 2 (metal:ionophore) complex was obtained from its special electrochemical response to the variation of ligand concentrations in the organic phase. The logarithms of the complex association constants, for facilitated transfer of Na+, K+, Rb+, and Cs+, were estimated as 6.52, 7.75, 7.91 (log β1°), and 8.36 (log β2°), respectively.
Pseudo‐dynamic test of a full‐scale CFT/BRB frame—Part II: Seismic performance of buckling‐restrained braces and connections
Authors: Tsai Keh‐Chyuan , Hsiao Po‐Chien
Published: April 2008

This paper is Part II of a two‐part paper describing a full‐scale 3‐story 3‐bay concrete‐filled tube (CFT)/buckling‐restrained braced frame (BRBF) specimen tested using psuedo‐dynamic testing procedures. The first paper described the specimen design, experiment, and simulation, whereas this paper focuses on the experimental responses of BRBs and BRB‐to‐gusset connections. This paper first evaluates the design of the gusset connections and the effects of the added edge stiffeners in improving the seismic performance of gusset connections. Test results suggest that an effective length factor of 2.0 should be considered for the design of the gusset plate without edge stiffeners. Tests also confirm that the cumulative plastic deformation (CPD) capacity of the BRBs adopted in the CFT/BRBF was lower than that found in typical component tests. The tests performed suggest that the reduction in the BRB CPD capacities observed in this full‐scale frame specimen could be due to the significant rotational demands imposed on the BRB‐to‐gusset joints. A simple method of computing such rotational demands from the frame inter‐story drift response demand is proposed. This paper also discusses other key experimental responses of the BRBs, such as effective stiffness, energy dissipation, and ductility demands. Copyright © 2008 John Wiley & Sons, Ltd.
PKC‐dependent endocytosis of the GLT1 glutamate transporter depends on ubiquitylation of lysines located in a C‐terminal cluster
Authors: González‐gonzález Inmaculada M. , García‐tardón Noemí , Giménez Cecilio , Zafra Francisco
Published: April 2008

The activity of the main glutamate transporter in the CNS, GLT1, can be regulated by protein kinase C (PKC). It is known that activation of PKC by phorbol esters promotes the clathrin‐dependent internalization of the transporter, followed by its lysosomal degradation. However, the molecular mechanisms that link PKC activation and the internalization of GLT1 are not fully understood. In this article, we show that this internalization process is dependent on the ubiquitylation of lysine residues located in the C‐terminal tail of GLT1. Exposure to PMA increases the ubiquitylation of GLT1 in transfected cells and in the rat brain, and this ubiquitylated GLT1 accumulates in the intracellular compartment. However, internalization of ubiquitylated GLT1 was blocked with a dominant negative dynamin 2 mutant, indicating that the addition of ubiquitin moieties to the transporter in the membrane precedes its endocytosis. The elimination of lysines from the C‐terminus of the transporter (lysines 497, 517, 526, 550, 558, 570, and 573) blocked GLT1 ubiquitylation and endocytosis. However, reintroduction of lysine 517 alone into this mutant was sufficient to restore PMA dependent ubiquitylation and internalization of GLT1. Similarly, reintroduction of lysine 526 restored the endocytosis, while this was only partially recovered after the individual reintroduction of lysines 550 or 570. These data suggest that the activation of PKC induces the ubiquitylation of these C‐terminal lysine residues in GLT1 and that this modification mediates the interaction of the transporter with the endocytic machinery. © 2008 Wiley‐Liss, Inc.
Opioid addiction and pregnancy: Perinatal exposure to buprenorphine affects myelination in the developing brain
Authors: Sanchez Emilse S. , Bigbee John W. , Fobbs Wambura , Robinson Susan E. , Sato‐Bigbee Carmen
Published: April 2008

Buprenorphine is a μ‐opioid receptor partial agonist and κ‐opioid receptor antagonist currently on trials for the management of pregnant opioid‐dependent addicts. However, little is known about the effects of buprenorphine on brain development. Oligodendrocytes express opioid receptors in a developmentally regulated manner and thus, it is logical to hypothesize that perinatal exposure to buprenorphine could affect myelination. To investigate this possibility, pregnant rats were implanted with minipumps to deliver buprenorphine at 0.3 or 1 mg/kg/day. Analysis of their pups at different postnatal ages indicated that exposure to 0.3 mg/kg/day buprenorphine caused an accelerated and significant increase in the brain expression of all myelin basic protein (MBP) splicing isoforms. In contrast, treatment with the higher dose caused a developmental delay in MBP expression. Examination of corpus callosum at 26‐days of age indicated that both buprenorphine doses cause a significant increase in the caliber of the myelinated axons. Surprisingly, these axons have a disproportionately thinner myelin sheath, suggesting alterations at the level of axon‐glial interactions. Analysis of myelin associated glycoprotein (MAG) expression and glycosylation indicated that this molecule may play a crucial role in mediating these effects. Co‐immunoprecipitation studies also suggested a mechanism involving a MAG‐dependent activation of the Src‐family tyrosine kinase Fyn. These results support the idea that opioid signaling plays an important role in regulating myelinationin vivoand stress the need for further studies investigating potential effects of perinatal buprenorphine exposure on brain development. © 2008 Wiley‐Liss, Inc.
Adenosine induces hemeoxygenase‐1 expression in microglia through the activation of phosphatidylinositol 3‐kinase and nuclear factor E2‐related factor 2
Authors: Min Kyoung‐Jin , Kim Jong‐Hyeon , Jou Ilo , Joe Eun‐Hye
Published: April 2008

Adenosine, a purine nucleoside, has been reported to suppress the inflammatory responses of microglia in the brain. However, the underlying mechanisms of its anti‐inflammatory action are unclear at present. Here we show that adenosine reduces the increase in intracellular reactive oxygen species (ROS) through expression of an antioxidant enzyme, hemeoxygenase‐1 (HO‐1). The H2O2‐induced intracellular ROS level was significantly low in microglia pretreated with adenosine for 3–6 h, compared with that in untreated cells. Adenosine induced HO‐1 mRNA and protein expression within 3 h, which was maintained for up to 12 h. Nuclear factor E2‐related factor 2 (Nrf2), a transcription factor, and phosphatidylinositol 3‐kinase (PI3K) and Akt pathways appear to mediate HO‐1 expression. In response to adenosine, Nrf2 translocated from the cytosol to nuclei, and bound to the antioxidant response element (ARE). Adenosine enhanced HO‐1 promoter activity in an ARE‐dependent manner. Moreover, the nucleoside stimulated Akt phosphorylation, and suppressors of PI3K (LY294002 and wortmannin) reduced adenosine‐induced HO‐1 expression. However, we propose that the effects of adenosine are independent of adenosine receptors, since agonists and antagonists of A1, A2a, and A3 had little effect on the regulation of intracellular ROS and HO‐1 expression. Our results collectively suggest that adenosine acts as an endogenous regulator of brain inflammation via modulation of microglial ROS production. © 2008 Wiley‐Liss, Inc.
Quantitative multifocal fMRI shows active suppression in human V1
Authors: Pihlaja Miika , Henriksson Linda , James Andrew C. , Vanni Simo
Published: April 2008

Multifocal functional magnetic resonance imaging has recently been introduced as an alternative method for retinotopic mapping, and it enables effective functional localization of multiple regions‐of‐interest in the visual cortex. In this study we characterized interactions in V1 with spatially and temporally identical stimuli presented alone, or as a part of a nine‐region multifocal stimulus. We compared stimuli at different contrasts, collinear and orthogonal orientations and spatial frequencies one octave apart. Results show clear attenuation of BOLD signal from the central region in the multifocal condition. The observed modulation in BOLD signal could be produced either by neural suppression resulting from stimulation of adjacent regions of visual field, or alternatively by hemodynamic saturation or stealing effects in V1. However, we find that attenuation of the central response persists through a range of contrasts, and that its strength varies with relative orientation and spatial frequency of the central and surrounding stimulus regions, indicating active suppression mechanisms of neural origin. Our results also demonstrate that the extent of the signal spreading is commensurate with the extent of the horizontal connections in primate V1. Hum Brain Mapp, 2008. © 2008 Wiley‐Liss, Inc.
Social cognition and the brain: A meta‐analysis
Authors: Van Overwalle Frank
Published: April 2008

This meta‐analysis explores the location and function of brain areas involved in social cognition, or the capacity to understand people's behavioral intentions, social beliefs, and personality traits. On the basis of over 200 fMRI studies, it tests alternative theoretical proposals that attempt to explain how several brain areas process information relevant for social cognition. The results suggest that inferring temporary states such as goals, intentions, and desires of other people—even when they are false and unjust from our own perspective—strongly engages the temporo‐parietal junction (TPJ). Inferring more enduring dispositions of others and the self, or interpersonal norms and scripts, engages the medial prefrontal cortex (mPFC), although temporal states can also activate the mPFC. Other candidate tasks reflecting general‐purpose brain processes that may potentially subserve social cognition are briefly reviewed, such as sequence learning, causality detection, emotion processing, and executive functioning (action monitoring, attention, dual task monitoring, episodic memory retrieval), but none of them overlaps uniquely with the regions activated during social cognition. Hence, it appears that social cognition particularly engages the TPJ and mPFC regions. The available evidence is consistent with the role of a TPJ‐related mirror system for inferring temporary goals and intentions at a relatively perceptual level of representation, and the mPFC as a module that integrates social information across time and allows reflection and representation of traits and norms, and presumably also of intentionality, at a more abstract cognitive level. Hum Brain Mapp, 2009. © 2008 Wiley‐Liss, Inc.
The cut‐off levels of CD23 expression in the differential diagnosis of MCL and CLL
Authors: Barna Gábor , Reiniger Lilla , Tátrai Péter , Kopper László , Matolcsy András
Published: April 2008

Flow cytometric analysis of CD23 expression in CD5‐positive B‐cells is a widely applied method in the differential diagnosis of chronic lymphocytic leukaemia (CLL) and mantle cell lymphoma (MCL). According to the most accepted criteria, the leukaemic cell population is CD19/CD5/CD23 triple positive in CLL but CD23‐negative in MCL. Recently, several groups have reported CD23‐positive MCL cases; however, these studies mostly analysed only CD23 positivity but not intensity. To determine the role and the cut‐off levels of CD23 positivity and intensity in the differential diagnosis of CLL and MCL, 26 cases of MCL and 84 cases of CLL were compared using flow cytometric analysis. Our results suggest that high values of CD23 positivity (>92.5%) and/or high fluorescence intensity (>44.5 mean fluorescence intensity (MFI)) of CD23 are related to CLL, whereas low CD23 positivity (<30%) is related to MCL. However, cases with intermediate CD23 positivity (between 30 and 92.5%) and lower intensity (<44.5 MFI) can either belong to CLL or MCL. In these cases, additional tests such as FISH analysis of the translocation t(11;14) or immunohistochemical detection of cyclin D1 overexpression are required to differentiate CLL from MCL. Copyright © 2008 John Wiley & Sons, Ltd.
Lung inflammation and thrombogenic responses in a time course study of Csb mice exposed to ozone
Authors: Kooter Ingeborg M. , Frederix Kim , Spronk Henri M. H. , Boere A. John F. , Leseman Daan L. A. C. , Steeg Harry van , Cate Hugo ten , Cassee Flemming R.
Published: April 2008

Ozone is a well‐known oxidant air pollutant, inhalation of which can result in oxidative stress, and lead to pulmonary inflammation.

The aim of this study was to evaluate the time‐course events after a single ozone exposure in transcription‐coupled repair defective Csb and wild type mice.

Mice were exposed for 3 h to 2 ppm ozone and biological parameters related to oxidative stress and inflammation were examined in the lungs at 0, 4, 9, 24 and 48 h after exposure. In addition the procoagulant and thrombomodulin activities were explored by a combination of assays for tissue factor and thrombin generation.

This study revealed a significant biological response to ozone, for both Csb and wild type mice. The onset of inflammation in Csb mice, as indicated by an increase in interleukin‐6, tumor necrosis factor‐α and total cell influx, occurred earlier compared with those seen in wild type mice. On the other hand, Csb mice showed a delayed antioxidant reaction compared with wild type mice. Both genotypes developed a procoagulant reaction characterized by a stably increased tissue factor activity and a progressive increase in thrombin generation after 2 days.

These experiments have shown that ozone, a well‐known toxic substance from the environment, induces not only inflammation, but also procoagulant reactions in the lungs of mice. These results have implications for understanding the systemic effects induced by oxidant air pollutants. Copyright © 2008 John Wiley & Sons, Ltd.
Are occupational exposure limits becoming more alike within the European Union?
Authors: Schenk Linda , Hansson Sven Ove , Rudén Christina , Gilek Michael
Published: April 2008

The occupational exposure limits (OELs) established by seven different national regulatory agencies of EU member states are compared with those of the European Commission (EC). The comparison concerned: (1) what chemicals have been selected, (2) the average level of exposure limits for all chemicals, and (3) the similarity between the OELs of different EU member states and the OELs recommended by the European Commission. The average level of the exposure limits has declined during the past 10 years in four of the five countries in our study for which historical data were available to us. Poland has not changed its level noticeably and Germany has increased it. Since the first list of indicative OELs was established by the EC, a few of the EU exposure limits have been lowered. The similarity index indicates that the exposure limits of EU member states are converging towards the European Commission's recommended OELs. Still, the average level of OELs differs between organizations – the Estonian OELs are on average 35% higher than the Polish OELs. Copyright © 2008 John Wiley & Sons, Ltd.
Informed consent to psychotherapy: Protecting the dignity and respecting the autonomy of patients
Authors: Fisher Celia B. , Oransky Matthew
Published: April 2008

Well‐implemented informed consent procedures demonstrate psychotherapists' respect for clients' right to self‐determination and can initiate meaningful contributions to treatment through enhancing mutual trust, building rapport, and facilitating a sense of ownership. This article details key components of informed consent to psychotherapy by placing them within real‐world psychotherapy scenarios. We provide information on client–therapist discussions of the nature and course of therapy, fees and payment policies, the involvement of third parties, confidentiality policies, and new and untested treatments. In addition, this article addresses informed consent procedures for individuals with impaired cognitive capacities and under the Health Insurance Portability and Accountability Act of 1996 (HIPAA) regulations. © 2008 Wiley Periodicals, Inc. J Clin Psychol:In Session 64: 1–13, 2008.
High doses of nicotinamide prevent oxidative mitochondrial dysfunction in a cellular model and improve motor deficit in a Drosophila model of Parkinson's disease
Authors: Jia Haiqun , Li Xin , Gao Hongxiang , Feng Zhihui , Li Xuesen , Zhao Lei , Jia Xu , Zhang Hongyu , Liu Jiankang
Published: April 2008

Nicotinamide, the principal form of niacin (vitamin B3), has been proposed to be neuroprotective in Parkinson's disease. However, the effects and mechanisms of nicotinamide on motor function in animals and on mitochondrial function in cellular systems have not been well studied. We hypothesized that niacin‐derived NAD(P)H as antioxidants and enzyme cofactors could inhibit oxidative damage and improve mitochondrial function and thus protect neurodegeneration and improve motor function. In the present study, the effects of nicotinamide on mitochondrial function and oxidative stress were studied in a 1‐methyl‐4‐phenylpyridinium (MPP+)–induced cellular model of Parkinson's disease, and the effects of improving motor dysfunction were studied in an α‐synuclein transgenic Drosophila Parkinson's model. Mitochondrial function was tested by measuring the activity of mitochondrial complex I and α‐ketoglutarate dehydrogenase, and oxidative damage was tested by measuring reactive oxygen species, DNA damage (8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine and Comet assay), and protein oxidation (protein carbonyls) levels. Nicotinamide at a relatively higher concentration, that is, 100‐fold of the level in the cell culture medium (101 mg/L), significantly protected SK‐N‐MC human neuroblastoma cells from an MPP+‐induced decrease in cell viability, complex I and α‐ketoglutarate dehydrogenase activity, and an increase in oxidant generation, DNA damage, and protein oxidation. In the Drosophila model, nicotinamide at 15 and 30 mg/100 g diet significantly improved climbing ability. These results suggest that nutritional supplementation of nicotinamide at high doses decreases oxidative stress and improves mitochondrial and motor function in cellular and/or Drosophila models and may be an effective strategy for preventing and ameliorating Parkinson's disease. © 2008 Wiley‐Liss, Inc.
Role for nitric oxide in permeability of hippocampal neuronal hemichannels during oxygen glucose deprivation
Authors: Zhang Le , Deng Tongle , Sun Yiguo , Liu Kezhou , Yang Yi , Zheng Xiaoxiang
Published: April 2008

Increased hemichannel opening induced by oxygen glucose deprivation (OGD) was reported in the hippocampal pyramidal neuron. It was suggested that the pannexin1 hemichannel opening could mediate ionic flux dysregulation, anoxic depolarization, and energy‐depleting efflux of glucose and ATP for ischemic neurons. However, the regulatory mechanisms of pannexin1 hemichannel opening have been poorly understood. Here we showed that excessive generation of nitric oxide (NO) during ischemia could induce the calcein leakage from neurons, which was markedly reduced by NO synthase inhibitor. The calcein leakage from neurons during OGD was also attenuated by the application of N‐ethylmaleimide (NEM), an SH‐alkylating agent, and dithiothreitol (DTT), a reducer of oxidized sulfhydryl groups. However, the soluble guanylyl cyclase (sGC) inhibitor had a minor effect on the calcein leakage during OGD. Furthermore, the elevated intracellular but not extracellular levels of glutathione could also inhibit the calcein leakage during OGD. Similar results were observed in metabolic inhibition (MI), which is another ischemic‐like condition. Finally, immunocytochemical and immunoblotting analysis revealed that, after 1 hr of OGD stimulation, the distribution and expression of pannexin1 showed no significant difference compared with control. However, the pannexin1 mRNA expression was elevated after 1 hr of OGD and a sustained increase was maintained during reperfusion. These results implied that the reactive oxygen species (ROS), especially NO, might be involved in the enhanced pannexin1 hemichannel opening and that the S‐nitrosylation but not the NO/cGMP pathway played a more important role in this event. © 2008 Wiley‐Liss, Inc.
Volatile compounds from the integument of White Leghorn Chickens (Gallus gallus domesticus L.): Candidate attractants of ornithophilic mosquito species*
Authors: Bernier Ulrich R. , Allan Sandra A. , Quinn Brian P. , Kline Daniel L. , Barnard Donald R. , Clark Gary G.
Published: April 2008

Candidate kairomones of ornithophilic mosquito species are reported from GC/MS analysis of compounds from the skin on the back, the feet, and feathers from the back of White Leghorn chickens (Gallus gallus domesticus). Hexane and ether extracts of chicken feathers differ significantly in attractiveness of Culex spp. mosquitoes. The active (hexane) extracts contained an abundance of alcohols, ketones, and diones. The inactive (ether) extracts contained aldehydes, which also were in the hexane extracts. Analysis of hexane extracts from chicken feet, skin, and feathers demonstrated the qualitative similarity in the compounds collected with subtle differences observed in the quantitative amounts of these compounds. Aldehydes and carboxylic acids were detected in a concentrated ether extract of feathers in quantitatively similar ratios within each compound class for the corresponding series of C6–C9 aldehydes and acids.
6‐Oxy‐(acetyl ethylenediamine) fluorescein, a novel fluorescent derivatization reagent for carboxylic acids and its application in HPLC
Authors: Du Xiao‐Lan , Wang Hong , Ma Ming , Deng Ying‐Hua , Zhang Hua‐Shan
Published: April 2008

A novel fluorescent derivatization reagent for carboxylic acids, 6‐oxy‐(acetyl ethylenediamine) fluorescein (AEF), was well designed, synthesized, and applied to HPLC. The derivatization reaction with 12 fatty acids, including n‐valeric acid (C5), n‐hexanoic acid (C6), n‐heptanoic acid (C7), n‐octanoic acid (C8), n‐nonanoic acid (C9), n‐decanoic acid (C10), lauric acid (C12), myristic acid (C14), palmitic acid (C16), stearic acid (C18), oleic acid (C18:1), and linoleic acid (C18:2), was completed at 55°C within 40 min. The derivatives of fatty acids were separated on a C18 RP column and detected by fluorescence detection. The LODs attained were 0.4–1.2 nM (S/N of 3). It has been demonstrated that AEF is a prominent derivatization reagent for carboxylic acids which is suitable for HPLC.
Effect of temperature on the chromatographic retention of ionizable compounds. III. Modeling retention of pharmaceuticals as a function of eluent pH and column temperature in RPLC
Authors: Gagliardi Leonardo G. , Castells Cecilia B. , Ràfols Clara , Rosés Martí , Bosch Elisabeth
Published: April 2008

We propose a general simple equation for accurately predicting the retention factors of ionizable compounds upon simultaneous changes in mobile phase pH and column temperature at a given hydroorganic solvent composition. Only four independent experiments provide the input data: retention factors measured in two pH buffered mobile phases at extreme acidic and basic pH values (e. g., at least ± 2 pH units far from the analyte pKa) and at two column temperatures. The equations, derived from the basic thermodynamics of the acid–base equilibria, additionally require the knowledge of the solute pKa and enthalpies of acid–base dissociation of both the solute and the buffer components in the hydroorganic solvent mixture. The performance of the predictive model is corroborated with the comparison between theoretical and experimental retention factors of several weak acids and bases of important pharmacological activity, in mobile phases containing different buffer solutions prepared in 25% w/w ACN in water and at several temperatures.
Screening of anti‐platelet aggregation agents from Panax notoginseng using human platelet extraction and HPLC–DAD–ESI‐MS/MS
Authors: Wang Jing , Huang Zhao‐gang , Cao Hui , Wang Yi‐tao , Hui Ping , Hoo Chai , Li Shao‐ping
Published: April 2008

Root of Panax notoginseng (Sanqi in Chinese) is a highly valued and commonly used Chinese medicine. It has been widely used for treatment of cardio‐ and cerebro‐vascular diseases. In this study, a method involving human platelet extraction and HPLC–DAD–ESI‐MS/MS was developed for screening potential anti‐platelet aggregation agents in Sanqi. Five compounds which could interact with human platelets were found, and four were identified as adenosine, guanosine, ginsenoside Rh1, and ginsenoside F1, respectively. The effects on rabbit platelet aggregation induced by arachidonic acid, adenosine diphosphate, and thrombin were also investigated in vitro. The results showed that the nucleosides adenosine and guanosine mainly contributed to the anti‐platelet aggregation of Sanqi. The data suggest that human platelet extraction combined with HPLC–DAD–ESI‐MS/MS is a useful method for screening anti‐platelet aggregation agents from Chinese medicines.
Preparation of nitrocellulose (NC) immuno‐affinity membrane for purification of rAPC antibody
Authors: Sun Haixiang , Ge Baosheng , Liu Shengnan , Chen Huanlin
Published: April 2008

In this study, recombinant allophycocyanin (rAPC) with a purity of 98% was transferred from a gel to a nitrocellulose (NC) membrane to develop a simple and efficient immuno‐affinity membrane. Atomic force microscopy (AFM) was used to investigate the surface topography of the affinity membrane and its characterization indicated that rAPC easily forms trimers or hexamers on the membrane surface on use of the given transfer method. The hydrodynamic radius (Rh) of the rAPC aggregation was equal to 103 nm or 365 nm according to dynamic light scattering (DLS), which was in agreement with the result obtained by AFM. Based on the specific immunological reaction of antigen and antibody, anti‐APC antibodies were purified from rabbit polyclonal serum in a single step. The amount of absorbed antibody was 5.79 mg/g membrane according to analysis by ELISA methods. The purity of antibodies was up to 98% according to SDS‐PAGE. The adsorption‐desorption cycle of rAPC was repeated six times using the same immuno‐affinity membrane, and there was no significant loss in adsorption capacity. The method provides a novel and efficient immunological affinity membrane for the purification of antibodies.
Instability of hexane–acetonitrile mobile phases used for the chromatographic analysis of triacylglycerides
Authors: Harfmann Robert G. , Julka Samir , Cortes Hernan J.
Published: April 2008

Comprehensive 2‐D LC is an emerging separation technique that has seen a rapid increase in applications in the last decade. The technique has been applied for the separation of numerous complex mixtures including triacylglycerides (TAG). Determination of TAG in food products such as rice, palm, and canola oils have been previously described and the technique of choice utilizes a silver‐modified silica column with hexane–ACN as the mobile phase. Repeated retention time inconsistencies were experienced in our studies when this mobile phase was applied to the separation of natural and synthetic mixtures containing TAG. The present report summarizes a study performed to determine the relative stability of ACN, propionitrile (PCN), and butyronitrile (BCN) at concentrations ranging from 0.43 to 2.8% in hexane and heptane. The data obtained suggest that unless evaporative loss of the mobile phase is prevented, TAG retention time irreproducibility can be significant when using mobile‐phase mixtures prepared with ACN or PCN. BCN should be used as the solvent modifier in cases where evaporation cannot be prevented.
Coatings for Solderable Wires for the Modern Electric Industry
Authors: Rost Simon
Published: April 2008

The scientific and industrial history of polyurethane wire enamels during the previous six decades is reviewed. Their main use is as coatings for wires in miniature electrical devices and in electronics, where fast solderability at low temperatures is crucial. Market trends for polyurethane enamels are discussed, and an outlook is provided as to how future developments might influence the industrial use of polyurethane wire enamels.

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Supramolecular Materials Comprising Nucleic Acid Biopolymers
Authors: Smitthipong Wirasak , Neumann Thorsten , Chworos Arkadiusz , Jaeger Luc , Tirrell Matthew
Published: April 2008

We have generated a supramolecular self‐assembling film by exchanging the counter‐ions of the phosphate moieties in nucleic acid with those of cationic amphiphiles as didodecyldimethylammonium bromide (or DDAB). SAXS and WAXS data for all film samples showed similar harmonic peaks suggesting a lamellar multilayer structure with layers of nucleic acids being separated by lipid bilayers of DDAB. AFM height images also showed that double stranded nucleic acid film can form the step or plateau type of structure and shorter nucleic acid film showed shorter step feature. Moreover, the length and the molecular structure of DNA and RNA can be used to manipulate the mechanical properties of these self‐assembled films.
Effects of Modified MMT on Mechanical Properties of EVA/MMT Nanocomposites and Their Foams
Authors: Xu Zheng Run , Park Hae Youn , Kim Ho Young , Seo Kwan Ho
Published: April 2008

In this study, nanocomposites of poly(ethylene‐co‐vinyl acetate) with two kinds of organically modified montmorillonite (OMMT) were prepared by melt intercalation. Their structures and mechanical properties were characterized by X‐ray diffraction (XRD) and tensile test respectively. Especially, foaming of these nanocomposites mixed with chemical blowing agent was carried out through compression molding. Influences of OMMT on foaming ratio and mechanical properties were investigated by density test, tensile test and tear test. Results revealed that both kinds of OMMT with proper content increased tensile strength and Young's modulus of nanocomposites without a compromise of elongation at break. For foaming, OMMTs apparently improved foaming ratio and in particular, one of them can improve tear strength, tensile strength, Young's modulus and elongation although the density was decreased.
Polypropylene Composites for Polymer Electrolyte Membrane Fuel Cell Bipolar Plates
Authors: Yeetsorn Rungsima , Fowler Michael , Tzoganakis Costas , Yuhua Wang , Taylor Mali
Published: April 2008

The polymer electrolyte membrane fuel cell (PEMFC) holds tremendous promise for a variety of mobile and stationary power generation applications and is the cornerstone of the anticipated hydrogen economy. One of the major factors limiting fuel cell commercialization is the development of bipolar plates since bipolar plates account for approximately 70% of the PEMFC weight, and 60% of the stack manufacturing and materials cost. The objective of this research is to investigate a feasibility of a conductive composite family to be used as bipolar plates in a PEMFC, in order to get the highly conductive, light weight, and low cost bipolar plates. This work utilized a combination of a polypropylene and low cost conductive filler materials: graphite, conductive carbon black, and carbon fibers. The components were combined in a batch mixer and injection molded into samples for testing with loadings up to 65%wt of fillers. The novel blends were tested for electrical conductivity, hydrophobicity, rheology, and actual plates (16 cm2) were tested in fuel cell testing trials. The impact of different types of fillers on the composite properties was evaluated, as well as the synergetic effect of mixtures of fill types within a polypropylene matrix. From the results, the highest conductivity, 1900 S/m (in‐plane) and 156 S/m (through plane), was obtained with the 65% composite. Moreover, the effects of additives such as coupling agents, and intrinsically conductive polymer (polypyrrole) were observed in this work. The electrical conductivity was influenced by polypyrrole added to the polypropylene composite.
Effect of Blending Factors on Eri Silk and Cotton Blended Yarn and Fabric Characteristics
Authors: Chollakup Rungsima , Suesat Jantip , Ujjin Suchada
Published: April 2008

Eri cocoons were prepared into short fibers and subsequently blended with cotton fiber in order to develop the new fiber blended yarn in the short spinning system. The Eri and cotton fibers were blended using the drawframe blending with varying blending factors, viz. blending composition (0–100%) and yarn counts (30 and 50 tex). The results showed that Eri fiber which was longer and stronger than cotton fiber, affected the fiber distribution in the yarn cross‐section. The mechanical properties of the blended fibers and yarns increased with increasing silk content. Longer fibers of Eri silk tended to move towards the yarn core, especially at silk content higher than 50%. Moreover, stronger and more extensible Eri silk fiber gave an advantage to the improvement of mechanical properties of those blended yarns with silk content higher than 50%. However, with increasing silk content, the blended yarns were more irregular as shown in %CV. Concerning the yarn count effect, the higher yarn count of 50 tex resulted in a more regular yarn with higher yarn strength than that of 30 tex. The plain‐woven fabrics were prepared using the blended yarns as a weft yarn and the cotton yarn or silk yarn as a warp yarn. The mechanical properties of those woven fabrics were characterized in order to study the influence of silk contents. The results showed that tensile strength, %elongation and tear strength of woven fabrics using the blended yarn were increased with an increase in silk content. This is an advantage of Eri silk in the aspect of rendering the strength to the blended yarns and fabrics.
Isotactic Poly(propylene)/Wood Sawdust Composite: Effects of Natural Weathering, Water Immersion, and Gamma‐Ray Irradiation on Mechanical Properties
Authors: Phiriyawirut Manisara , Saenpong Puriphat , Chalermboon Suradet , Sooksakoolrut Ruangdet , Pochanajit Nikorn , Vuttikit Leartprakit , Thongchai Apichate , Supaphol Pitt
Published: April 2008

Isotactic poly(propylene) (iPP)/wood sawdust composite containing 30 wt.% of the natural fibers was first prepared by melt‐mixing in a twin screw extruder and later molded into various shaped specimens by injection molding machine. The effect of natural weathering, water immersion, and gamma‐ray irradiation on mechanical properties of the specimens were studied. All of the tensile properties were improved with initial increase in the exposure time of natural weathering of up to 30 days and decreased afterwards. Similarly, the tensile strength and the Young's modulus of the composite increased with initial increase in the radiation dosage and decreased afterwards. On the contrary, the tensile strength and the elongation at break of the composite were unchanged after having been immersed in water for the first 15 days, but increased slightly afterwards. The alteration in these properties were postulated to be a result of the interplay between the cross‐linking and the chain scission reactions that occurred during natural weathering and gamma‐ray irradiation and the plasticizing effect of the absorbed water molecules during water immersion.
Effect of Silane Coupling Agent and Compatibilizer on Properties of Short Rossells Fiber/Poly(propylene) Composites
Authors: Jarukumjorn Kasama , Sutapun Wimonlak , Ruksakulpiwat Yupaporn , Kluengsamrong Jongrak
Published: April 2008

Rossells fiber reinforced polypropylene composites were prepared by melt mixing. The fiber content was 20 wt%. Octadecyltrimethoxysilane (OTMS) and maleic anhydride grafted polypropylene (MAPP) were used to improve the adhesion between poly(propylene) (PP) and the fiber. The mechanical, rheological, and morphological properties, and heat distortion temperature (HDT) of the composites were investigated. Tensile strength, impact strength, flexural strength and HDT of MAPP modified PP composites increased with an increase in MAPP content. However, no remarkable effect of MAPP content on the Young's modulus of the composites was found. OTMS resulted in small decreases of tensile strength and Young's modulus, and increase in impact strength. Scanning electron micrographs revealed that MAPP enhanced surface adhesion between the fiber surface and PP matrix.
Preparation and Properties of Pyrene‐Modified Multi‐ Walled Carbon Nanotube/Epoxy Resin Nanocomposites
Authors: Choi Deok‐Kyu , Jin Sung‐Hun , Lee Dai‐Soo
Published: April 2008

Nanocomposites of multi‐walled carbon nanotube (MWCNT)/bis‐phenol A type epoxy resin were prepared and physical properties of the nanocomposites were investigated. For the fine dispersion of MWCNT in the epoxy resin, MWCNT was modified with pyrene butyric acid (PBA) in the supercritical carbon dioxide (CO2). The physical adsorption of PBA on the surface of MWCNTs was studied with a thermogravimetric analyzer and a transmission electron microscopy. The electrical surface resistivities of the nanocomposites showed threshold decreases due to percolations above the critical concentration of the MWCNT. The resistivities showed maximum depending on the concentration and the modification of the surface of the MWCNT with PBA. It is postulated that the dispersion of the MWCNT in epoxy resins resulted in dispersion systems which exhibit rheological properties similar to lyotropic liquid crystalline polymers. The surface resistivities of the MWCNT/epoxy systems reflected the morphological characteristics of the systems which also determined rheological properties of the systems.
Synthesis and Characterization of Amino Acid Modified Chitooligosaccharides
Authors: Ngamviriyavong Patcharee , Uppanan Paweena , Janvikul Wanida
Published: April 2008

Amino acid modified chitooligosaccharides were synthesized by the new synthetic route. The chloroacetyl‐chitooliogosaccharide intermediates were prepared under a mild condition via a reaction between chitooligosaccharide (COS) and chloroacetic anhydride. The intermediates were subsequently reacted with a variety of amino acids, e.g., glycine, aspartic acid, alanine, arginine, and serine, under a basic condition, yielding amino acid modified COS products. The degree of chloroacetylation was calculated based on new 1H NMR absorption peaks at 3.80 and 3.94 ppm, corresponding to NHCOCH2Cl and OCOCH2Cl, respectively. The degrees of chloroacetylation determined were 0.40, 0.44, 0.62, and 0.93 when the mole ratios of chloroacetic anhydride to COS were 0.5, 1, 2, and 4, respectively. The chemical structures of the COS derivatives were also determined using 1H NMR spectroscopy. The biological properties of the derivatives were evaluated. Cytotoxicity of the derivatives was assessed by a direct contact, using L929 cells. An MTT assay was a method of choice to evaluate the efficacy of the derivatives to enhance the proliferation of L929 cells.
Effect of Soxhlet Extraction and Surfactant System on Morphology and Properties of Poly(DVB)PolyHIPE
Authors: Pakeyangkoon Pornsri , Magaraphan Rathanawan , Malakul Pomthong , Nithitanakul Manit
Published: April 2008

Poly(Divinylbenzene)PolyHIPE (Poly(DVB)PolyHIPE) was successfully prepared by using two different systems of three‐component surfactants (S20M and S80M) and toluene as porogenic solvent. Phase morphology, mechanical properties and surface area measurements of the obtained Poly(DVB)Poly HIPE were investigated. After polymerization of continuous phase followed by extraction process, the porous materials (open cellular structure with interconnections) were obtained. The cell size and surface area were found to be improved: this is due to the ability of porogenic solvent and mixture of the surfactants to prevent the Ostwald ripening (coalescence) of the emulsion droplet system. Moreover, the surface area and mechanical properties of the resulting materials were found to be depended on the Soxhlet extraction time. It was demonstrated that the usage of Soxhlet extraction technique for Poly(DVB)PolyHIPE improved surface area of the obtained materials by 107% as compared with the unextracted PolyHIPE. However, when the extraction time was longer than 12 hours, the properties of the obtained materials became poor. It was concluded that the suitable Soxhlet extraction time for Poly(DVB)PolyHIPE was 6–12 hours and at this condition, high surface area with the highest mechanical properties of the porous material were obtained.
Role of timing in assessment of nerve regeneration
Authors: Brenner Michael J. , Moradzadeh Arash , Myckatyn Terence M. , Tung Thomas H. H. , Mendez Allen B. , Hunter Daniel A. , Mackinnon Susan E.
Published: April 2008

Small animal models are indispensable for research on nerve injury and reconstruction, but their superlative regenerative potential may confound experimental interpretation. This study investigated time‐dependent neuroregenerative phenomena in rodents. Forty‐six Lewis rats were randomized to three nerve allograft groups treated with 2 mg/(kg day) tacrolimus; 5 mg/(kg day) Cyclosporine A; or placebo injection. Nerves were subjected to histomorphometric and walking track analysis at serial time points. Tacrolimus increased fiber density, percent neural tissue, and nerve fiber count and accelerated functional recovery at 40 days, but these differences were undetectable by 70 days. Serial walking track analysis showed a similar pattern of recovery. A “blow‐through” effect is observed in rodents whereby an advancing nerve front overcomes an experimental defect given sufficient time, rendering experimental groups indistinguishable at late time points. Selection of validated time points and corroboration in higher animal models are essential prerequisites for the clinical application of basic research on nerve regeneration. © 2008 Wiley‐Liss, Inc. Microsurgery, 2008.