bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymerization of styrene using bis(β‐ketoamino)nickel(II)/methylaluminoxane catalytic systems
Authors: Yu Shuxian , He Xiaohui , Chen Yiwang , Liu Yongming , Hong Sanguo , Wu Qing 
Published: March 2007

AbstractStyrene (St) was polymerized in toluene solution by using bis(β‐ketoamino)nickel(II) complex as the catalyst precursor and methylaluminoxane (MAO) as the cocatalyst. The polymerization conditions, such as Al : Ni ratio, monomer concentration, reaction temperature, and polymerization time, were studied in detail. Both of the bis(β‐ketoamino)nickel(II)/MAO catalytic systems exhibited higher activity for polymerization of styrene, and polymerization gave moderate molecular weight of polystyrene with relatively narrow molecular weight distribution (Mw/Mn < 1.6). The obtained polymer was confirmed to be atactic polystyrene by analyzing the stereo‐triad distributions mm, mr, and rr of aromatic carbon C1 in NMR spectrum of the polymer. The mechanism of the polymerization was also discussed and a metal–carbon coordination mechanism was proposed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Competitive adsorption of uranyl ions in the presence of Pb(II) and Cd(II) ions by poly(glycidyl methacrylate) microbeads carrying amidoxime groups and polarographic determination
Authors: Çaykara Tuncer , Alaslan Şerife Şirin , İnam Recai 
Published: March 2007

AbstractThe adsorption capacity of UO in the presence of Pb(II) and Cd(II) ions was investigated with amidoximated poly(glycidyl methacrylate) (PGMA) microbeads with an average size of 135 μm packed in a glass column (0.5‐cm i.d. and 20‐cm length, flow rate = 3 mL/min) under competitive conditions. A differential pulse polarography technique was used for the determination of trace quantities of uptaken elements by the measurement of the reduction peak currents at −200/−950, −400, and −600 mV (vs a saturated calomel electrode) for UO, Pb(II), and Cd(II) ions, respectively. When only UO was found in the eluate, its adsorption was 85.3% from a 50 μM initial solution. However, when there was UO with binary systems of Pb(II) or Cd(II), it was 78.2 and 76.3%, respectively. On the other hand, in a ternary mixture of UO with Pb(II) and Cd(II), the adsorption was found to be 75.2% with the same initial concentration. According to the results, the competitive adsorption studies showed that these amidoximated PGMA microbeads had good adsorption selectivity for UO with the coexistence of Pb(II) and Cd(II) ions. The ionic strength of the solution also influenced the UO adsorption capacity of the amidoximated PGMA microbeads. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4168–4172, 2007
Novel tin‐coupled star‐shaped medium vinyl butadiene rubber. II. Vinyl content, molecular weight, and their effects on properties
Authors: Lu Jianmin , Zhang Xingying , Zhao Suhe , Yang Wantai 
Published: March 2007

AbstractOn the basis of our earlier work, extensive experiments were conducted to further investigate the regulating means of vinyl content, molecular weight, molecular weight distribution, and their effects on overall performance of star‐shaped medium vinyl butadiene rubber (S‐MVBR), which was prepared by “core‐first” method with novel multifunctional organolithium as initiator, tetrahydrofuran (THF) as structure regulator, and raffinate oil as solvent. The results showed that vinyl content and molecular weight for one arm were easily regulated from 30 to 55%, 6–10 ten thousand, respectively. The tensile strength and elongation at break increased with increasing vinyl content and the dynamic heating was the lowest at vinyl content of 43%. S‐MVBR had a relatively wide and symmetrical monomodal distribution, which was in favorable of good processing properties. S‐MVBR containing Sn atom, with arm number of 3.8, molecular weight for one arm of eight 10,000, vinyl content of 50%, and distribution of molecular weight of 1.54, had optimal overall properties. When compared with cis‐BR and linear MVBR, S‐MVBR had low rolling energy loss, high wet grip, good mechanical and processing properties. It was an ideal rubber for high performance tire tread. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3924–3930, 2007
Copper‐based reverse ATRP process for the controlled radical polymerization of methyl methacrylate
Authors: Pan Kai , Jiang Long , Zhang Juan , Dan Yi 
Published: March 2007

AbstractA series of copper‐based reverse atom transfer radical polymerizations (ATRP) were carried out for methyl methacrylate (MMA) at same conditions (in xylene, at 80°C) using N,N,N′,N′‐teramethylethylendiamine (TMEDA), N,N,N′,N′,N′‐pentamethyldiethylentriamine (PMDETA), 2‐2′‐bipyridine, and 4,4′‐Di(5‐nonyl)‐2,2′‐bipyridine as ligand, respectively. 2,2′‐azobis(isobutyronitrile) (AIBN) was used as initiator. In CuBr2/bpy system, the polymerization is uncontrolled, because of the poor solubility of CuBr2/bpy complex in organic phase. But in other three systems, the polymerizations represent controlled. Especially in CuBr2/dNbpy system, the number‐average molecular weight increases linearly with monomer conversion from 4280 up to 14,700. During the whole polymerization, the polydispersities are quite low (in the range 1.07–1.10). The different results obtained from the four systems are due to the differences of ligands. From the point of molecular structure of ligands, it is very important to analyze deeply the two relations between (1) ligand and complex and (2) complex and polymerization. The different results obtained were discussed based on the steric effect and valence bond theory. The results can help us deep to understand the mechanism of ATRP. The presence of the bromine atoms as end groups of the poly(methyl methacrylate) (PMMA) obtained was determined by 1H‐NMR spectroscopy. PMMA obtained could be used as macroinitiator to process chain‐extension reaction or block copolymerization reaction via a conventional ATRP process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Absorption and release of zinc and copper ions by chitosan fibers
Authors: Qin Yimin , Zhu Changjun , Chen Jie , Liang Di , Wo Gaofeng 
Published: March 2007

AbstractChitosan fibers were treated with aqueous solutions of ZnCl2and CuSO4·5H2O to prepare zinc and copper containing fibers, respectively. Significant weight gains were obtained as the zinc and copper ions were absorbed onto the fibers through chelation with the primary amine groups. The fibers were then placed in contact with aqueous solutions containing NaCl and water soluble proteins, respectively, to assess the release of zinc and copper ions. Results showed that the release of zinc and copper ions were affected by the treatment temperature, time, and the composition of the contacting media. More metal ions were released when the fibers were in contact with aqueous protein solutions than in NaCl solution, indicating the binding abilities of the protein molecules for zinc and copper ions. The zinc and copper containing fibers were tested for their antimicrobial effects against several species of bacteria commonly found in wound and skin. Results showed that these metal containing chitosan fibers had much stronger antimicrobial properties than the original chitosan fiber. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Online medium‐throughput respirometry‐based OTR measurements in magnetically stirred cultures
Authors: Brethauer Simone , Held Martin , Panke Sven 
Published: March 2007

AbstractIntensified bioprocess development requires parallelized medium‐ to high‐throughput experimentation with high on‐ and offline data density across all early scales of the development trajectory from microtiter plate via shake flask to lab‐scale reactor. We developed a widespread measurement principle for intermediate scales, respirometry, into a parallelized oxygen transfer rate measurement device that could accurately record common process development‐relevant effects such as acetate formation, diauxic growth, and nutrient limitations. The device was further equipped with dissolved oxygen measurement capability and sampling ports that allowed repetitive monoseptic sample withdrawal without disturbing the cultivation. Optimization of the operating parameters lead to kL a values of up to 160 h−1 and corresponding oxygen transfer rates of 1 g L−1 h−1 for cultivation volumes of 50 mL. Biotechnol. Bioeng. 2007;98: 356–367. © 2007 Wiley Periodicals, Inc.
Process development for the electroenzymatic synthesis of (R)‐methylphenylsulfoxide by use of a 3‐dimensional electrode
Authors: Lütz S. , Vuorilehto K. , Liese A. 
Published: March 2007

AbstractThe electrogeneration of hydrogen peroxide via reduction of dissolved oxygen was carried out in a three‐dimensional electrochemical cell using graphite grains as cathode material and combined with the enantioselective oxidation of thioanisole to (R)‐methylphenylsulfoxide catalyzed by Chloroperoxidase from Caldariomyces fumago. The relevant parameters for process development (e.g., conductivity of the biotransformation medium) were identified and optimized, leading to an efficient electroenzymatic process with a space‐time yield of 104 g · L−1 · d−1. The isolated product was produced on gram scale (1.2 g, purity >98%, ee > 98.5%). Biotechnol. Bioeng. 2007;98: 525–534. © 2007 Wiley Periodicals, Inc.
Control of hepatic differentiation via cellular aggregation in an alginate microenvironment
Authors: Maguire Tim , Davidovich Alexander E. , Wallenstein Eric J. , Novik Eric , Sharma Nripen , Pedersen Henrik , Androulakis Ioannis P. , Schloss Rene , Yarmush Martin 
Published: March 2007

AbstractIntegral to the development of embryonic stem cell therapeutic strategies for hepatic disorders is the identification and establishment of a controllable hepatic differentiation strategy. In order to address this issue we have established an alginate microencapsulation approach which provides a means to modulate the differentiation process through changes in key encapsulation parameters. We report that a wide array of hepatocyte specific markers is expressed by cells differentiated during a 23‐day period within an alginate bead microenvironment. These include urea and albumin secretion, glycogen storage, and cytochrome P450 transcription factor activity. In addition, we demonstrate that cellular aggregation is integral to the control of differentiation within the bead environment and this process is mediated by the E‐cadherin protein. The temporal expression of surface E‐cadherin and hepatocyte functional expression occur concomitantly and both cellular aggregation and albumin synthesis are blocked in the presence of anti E‐cadherin immunoglobulin. Furthermore, by establishing a compartmental model of differentiation, which incorporates this aggregation phenomenon, we can optimize key encapsulation parameters. Biotechnol. Bioeng. 2007;98: 631–644. © 2007 Wiley Periodicals, Inc.
Determination of catecholamines and serotonin by micellar electrokinetic chromatography with laser‐induced fluorescence detection
Authors: Cao Li‐Wei 
Published: March 2007

Abstract6‐Oxy‐(N‐succinimidyl acetate)‐9‐(2′‐methoxycarbonyl) fluorescein, a new synthesized fluorescent reagent, was established for the first time as a label for the sensitive analysis of catecholamines (CAs) and serotonin (5‐HT) by micellar electrokinetic chromatography (MEKC) with laser‐induced fluorescence detection. After careful study on the derivatization conditions such as pH value, reagent concentration, temperature and reaction time, the labeling reaction was accomplished as quickly as 7 min with stable yield. The separation parameters for the CAs and 5‐HT were also optimized in detail. The derivatives were baseline separated in a running buffer containing 30 mm boric acid and 15 mm sodium dodeculsulfate at pH 9.0. The detection limits ranged from 5 × 10−10 to 2 × 10−9 m (signal‐to‐noise ratio = 3). The rapid and sensitive method was also applied to the determination of the CAs and 5‐HT of urine samples. Copyright © 2007 John Wiley & Sons, Ltd.
HPLC determination of andrographolide in rat whole blood: study on the pharmacokinetics of andrographolide incorporated in liposomes and tablets
Authors: Suo Xu‐Bin , Zhang Han , Wang Yu‐Qiang 
Published: March 2007

AbstractA sensitive and simple high‐performance liquid chromatographic method with UV detection was developed and validated for the determination of andrographolide in rat whole blood. Carbamazepine was employed as internal standard and the blood sample was extracted with chloroform. Chromatographic separations were achieved on a Chromasil ODS column (250 × 4.6 mm, 5 µm). The mobile phase was consisted of methanol–water (52:48, v/v) and delivered at 0.8 mL/min. The detection wavelength was set at 225 nm. The calibration curve had a good linearity in the range 0.053–530 µg/mL in rat whole blood with its correlation coefficient being 0.996. The extraction recovery of andrographolide was ranged from 65.7 to 72.6%. The intra‐day and inter‐days repeatabilities were below 4.2% in terms of the percentage of relative standard deviation (RSD). The method was used to provide data on the pharmacokinetics of the drug in rats. The data obtained was processed using the 3P87 pharmacokinetic program. The results showed that the disposition of andrographolide after intravenous administration of liposomal andrographolide conformed to a two‐compartment open model with α = 4.75 × 10−2 ± 2.41 × 10−3 min−1, β = 3.16 × 10−3 ± 1.58 × 10−4 min−1, Vc = 174.67 ± 13.97 mL, k21 = 1.60 × 10−2 ± 8.12 × 10−4 min−1, k10 = 9.38 × 10−3 ± 5.62 × 10−4 min−1, k12 = 2.53 × 10−2 ± 1.27 × 10−3 min−1 and AUC0‐∞ = 1525.47 ± 92.35 µg min/mL. For the intragastric administration of andrographolide tablets, the disposition of andrographolide followed a one‐compartment open model with ke = 6.78 × 10−3 ± 3.53 × 10−4 min−1, ka = 3.69 × 10−2 ± 4.68 × 10−3 min−1, Tmax = 59.69 ± 3.61 min, Cmax = 1.62 ± 0.11 µg/mL, Vc = 1056.90 ± 83.42 mL, AUC0‐∞ = 348.75 ± 24.41 µg min/mL. Copyright © 2007 John Wiley & Sons, Ltd.
Determination of oleanolic acid, ursolic acid and amygdalin in the flower ofEriobotrya japonicaLindl. by HPLC
Authors: Zhou Chunhua , Chen Kunsong , Sun Chongde , Chen Qingjun , Zhang Wangshu , Li Xian 
Published: March 2007

AbstractSimple and accurate HPLC methods were developed for the determination of oleanolic acid (OA), ursolic acid (UA) and amygdalin in loquat (Eriobotrya japonicaLindl.) flower, which is commonly used for the treatment of various diseases as a traditional Chinese medicine. HPLC assay was performed on a reversed‐phase C18column and all three compounds were detected at 210 nm with a flow rate of 1.0 mL/min. The mobile phase consisted of methanol (A) and 0.03 mol/L phosphate buffer (pH 2.8) (B) with a ratio of 88:12 (A:B, v/v) for simultaneous detection of OA and UA, and 25:75 (A:B, v/v) for detection of amygdalin. The established methods showed good precision and accuracy with overall intra‐day and inter‐day variation of 0.99–3.55 and 1.05–4.05%, respectively, and overall recoveries of 97.37–99.32% for the three compounds. Application of these methods to determine the OA, UA and amygdalin contents in loquat flower showed that cultivar had a minor effect on the contents of all three compounds, with average amounts of 0.38–0.51 mg OA/g dry weight (DW), 2.15–2.68 mg UA/g DW and 1.23–1.56 mg amygdalin/g DW among five loquat cultivars tested. However, developmental stages and flower tissues showed significant effect on the contents of all three bioactive components. Copyright © 2007 John Wiley & Sons, Ltd.
Surface Change of Ras Enabling Effector Binding Monitored in Real Time at Atomic Resolution
Authors: Kötting Carsten , Kallenbach Angela , Suveyzdis Yan , Eichholz Carolin , Gerwert Klaus 
Published: March 2007

AbstractRas, the prototype of the Ras superfamily, acts as a molecular switch for cell growth. External growth signals induce a GDP‐to‐GTP exchange. This modifies the Ras surface (RasonGTP) and enables effector binding, which then activates signal‐transduction pathways. GTP hydrolysis, catalysed by Ras and GAP, returns the signal to “off” (RasoffGDP). Oncogenic mutations in Ras prevent this hydrolysis, and thereby cause uncontrolled cell growth. In the Rasoff‐to‐Rason transition, the Ras surface is changed by a movement of the switch I loop that controls effector binding. We monitored this surface change at atomic resolution in real time by time‐resolved FTIR (trFTIR) spectroscopy. In the transition from Rasoff to Rason a GTP‐bound intermediate is now identified, in which effector binding is still prevented (RasoffGTP). The loop movement from RasoffGTP to RasonGTP was directly monitored by the CO vibration of Thr35. The structural change creates a binding site with a rate constant of 5 s−1 at 260 K. A small molecule that shifted the equilibrium from the RasonGTP state towards the RasoffGTP state would prevent effector binding, even if hydrolysis were blocked by oncogenic mutations. We present a spectroscopic fingerprint of both states that can be used as an assay in drug screening for such small molecules.
Differences in right and left ventricular remodeling after transcatheter closure of atrial septal defect among adults
Authors: Wu En‐Ting , Akagi Teiji , Taniguchi Manabu , Maruo Takeshi , Sakuragi Satoru , Otsuki Shinichi , Okamoto Yoshio , Sano Shunji 
Published: March 2007

AbstractObjectives: To evaluate acute cardiac remodeling after transcatheter closure of atrial septal defect (ASD) in adult patients. Background: In adult patients with ASD, longer periods of cardiac adaptation should be expected after the procedure due to long‐standing RV volume overload and subsequent changes in the pulmonary vasculature. There are limited reports about this remodeling in adult patients. Methods: We prospectively enrolled 17 adults (mean age 58.4 ± 17.3 years) who underwent successful transcatheter closure of their ASDs from August 2005 to July 2006. We performed routine transthoracic echocardiographic studies, including LV and RV myocardial performance indices, or Tei indices, and plasma brain natriuretic peptide (BNP) sampling before closure of the ASD, and 1 day, 1 month, and 3 months after closure. Results: We found (1) LV end diastolic diameter increased, and RVEDD decreased markedly after the closure; (2) differences existed in LV and RV adaptation. While LV Tei index improved soon after the procedure, RV Tei index worsened until 1 month after the procedure, then recovered by the 3 month follow‐up visit; and (3) BNP elevated 1 day after closure of the ASD and declined by the 1‐month follow‐up visit. Conclusion: “Shrinkage” of the RV and “expansion” of the LV occurred soon after the procedure, even in elderly patients. Device closure of ASDs caused rapid improvement of LV function, but RV function underwent transient deterioration, probably due to delayed changes in RV ventricular mass in the face of acute volume reduction in this aged cohort. © 2007 Wiley‐Liss, Inc.
Medical device development: Managing conflicts of interest encountered by physicians
Authors: Baim Donald S. , Donovan Aine , J. Smith John , Briefs Nancy , Geoffrion Richard , Feigal David , Kaplan Aaron V. 
Published: March 2007

AbstractNew technologies introduced over the past three decades have transformed medical diagnosis and treatment, and significantly improved patient outcomes. These changes have been mediated by the introduction of new medical devices, particularly for the treatment of cardiovascular, orthopedic, and ophthalmic disorders. These devices, in turn, have created large markets and spawned a burgeoning medical device industry, including six Fortune 500 companies whose combined market capitalization now exceeds 400 billion dollars. This success story, which has unquestionably benefited patients and society alike, has been dependent upon an intense collaboration among industry, clinicians, and regulatory authorities. However, when physicians actively involve in patient care participate in such collaborations, they are increasingly vulnerable to creating potential conflicts between these two (clinical and device development) roles. Such conflicts, which may ultimately erode public trust, have important consequences not only for the individual physicians, but also for their parent institutions, their patients, sponsoring companies, and the entire clinical research enterprise that makes the development and introduction of new devices possible. The third Dartmouth Device Development Symposium held in October 2005 brought together thought leaders within the medical device community, including academicians, clinical investigators, regulators from the Food and Drug Administration and Centers for Medicare and Medicaid Services (CMS), large and small device manufacturers and the financial (venture capital and investment banks) community. The Symposium examined the conflicts of interest encountered during the early development and commercialization of a medical device. The goal of these discussions was to (1) identify and characterize the conflicts that arise and (2) provide strategies to address these conflicts. This manuscript was prepared by a writing committee to provide a summary report of those discussions. © 2007 Wiley‐Liss, Inc.
Automated alignment of chromatographic data
Authors: Skov Thomas , van den Berg Frans , Tomasi Giorgio , Bro Rasmus 
Published: March 2007

AbstractThis paper focuses on the practical aspects and implications of preprocessing chromatographic data to correct for undesirable time‐shifts. An approach to automate the alignment of chromatographic data based on peak alignment or warping is proposed. This approach deals with selection of the required parameters including selection of reference sample to warp towards, and chooses warping settings based on a new evaluation criterion for goodness of correction. The new criterion aims at quantifying goodness of alignment while at the same time penalising significant shape or area‐changes in the warped peaks. The entire selection procedure is automated using a discrete‐coordinates simplex‐like optimisation routine. Examples with simulated chromatographic data, GC‐FID and HPLC‐Fluorescence measurement series illustrate the potential of using this automated alignment tool. Copyright © 2007 John Wiley & Sons, Ltd.
Unique Ligand‐Based Oxidative DNA Cleavage by Zinc(II) Complexes of Hpyramol and Hpyrimol
Authors: Maheswari Palanisamy Uma , Barends Sharief , Özalp‐Yaman Seniz , de Hoog Paul , Casellas Hélène , Teat Simon J. , Massera Chiara , Lutz Martin , Spek Anthony L. , van Wezel Gilles P. , Gamez Patrick , Reedijk Jan 
Published: March 2007

AbstractThe zinc(II) complexes reported here have been synthesised from the ligand 4‐methyl‐2‐N‐(2‐pyridylmethyl)aminophenol (Hpyramol) with chloride or acetate counterions. All the five complexes have been structurally characterised, and the crystal structures reveal that the ligand Hpyramol gradually undergoes an oxidative dehydrogenation to form the ligand 4‐methyl‐2‐N‐(2‐pyridylmethylene)aminophenol (Hpyrimol), upon coordination to ZnII. All the five complexes cleave the ϕX174 phage DNA oxidatively and the complexes with fully dehydrogenated pyrimol ligands were found to be more efficient than the complexes with non‐dehydrogenated Hpyramol ligands. The DNA cleavage is suggested to be ligand‐based, whereas the pure ligands alone do not cleave DNA. The DNA cleavage is strongly suggested to be oxidative, possibly due to the involvement of a non‐diffusible phenoxyl radical mechanism. The enzymatic religation experiments and DNA cleavage in the presence of different radical scavengers further support the oxidative DNA cleavage by the zinc(II) complexes.