bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparative separation and enrichment of four taxoids from Taxus chinensis needles extracts by macroporous resin column chromatography
Authors: Sun Rui , Fu Kusng , Fu Yujie , Zu Yuangang , Wang Ying , Luo Meng , Li Shuangming , Luo Hao , Li Zhengnan 
Published: April 2009

AbstractAn environment‐friendly method was established for the preparative separation and enrichment of four taxoids, namely 10‐deacetylbaccatin III (10‐DAB III), 7‐xylosyl‐10‐deacetyltaxol (7‐xyl‐10‐DAT), cephalomannine and paclitaxel from Taxus chinensis needles extracts. Characteristics of seven widely used macroporous resins for four taxoids were compared, AB‐8 resin offered better adsorption and desorption capacities than others. AB‐8 resin column chromatography was used to study the desorption process for four taxoids. The optimum parameters for desorption were 30% ethanol 5 RV for removing impurities, following 15 RV for 10‐DAB III, after the desorption of impurities with 35% ethanol 10 RV, 45% ethanol 30 RV for 7‐xyl‐10‐DAT, then 65% ethanol 10 RV for cephalomannine and paclitaxel, the flow rate was 6 RV/h. After separation on AB‐8 resin column chromatography, the contents of 10‐DAB III, 7‐xyl‐10‐DAT, cephalomannine and paclitaxel in the product reached 4.58, 13.17, 1.36 and 3.08%, respectively, which were 7.63‐, 3.68‐, 6.18‐ and 6.55‐fold to those in T. chinensis needles extracts. The recovery yields were 94.96, 77.32, 88.09 and 95.25%. In general, the AB‐8 resin column chromatography has the advantages of lower cost, high efficiency and simple procedure. Therefore, it may provide scientific references for the preparative separation and enrichment of taxoids from other T. species.
Separation of peptide isomers and conformers by ultra performance liquid chromatography
Authors: Winter Dominic , Pipkorn Rüdiger , Lehmann Wolf D. 
Published: April 2009

AbstractPeptide isomers are characterized by an identical brutto formula, so that their specific detection by LC‐MS/MS requires an individual LC retention time and/or an individual MS/MS spectrum. Mixtures of various classes of peptide isomers were analyzed by reversed phase nano ultra high performance liquid chromatography (UPLC)‐MS/MS. Gradient elution was performed with a water/acetonitrile/formic acid system. Using this solvent system and gradients of medium length (30 or 60 min), mixtures were analyzed composed of structural isomers of modified peptides, sequence isomers of unmodified peptides, peptide/isopeptide pairs, diastereomeric peptide pairs, and peptide conformers. The large majority of the peptide isomers analyzed could be completely separated due to the high resolving power of UPLC. For most isomers, the observed retention time differences significantly exceeded the corresponding baseline peak widths leading for several isomeric pairs to resolutions above 10. In addition, hints for a separation of peptide conformers were observed. Most of the peptides analyzed were of synthetic origin, so that their individual assignment in the UPLC‐MS/MS runs was straightforward. The relative elution order of numerous sets of peptide isomers is documented and discussed. The study highlights the important benefits of a high chromatographic separation power for the specificity of LC‐MS/MS in the field of analytical proteomics.
Rapid and efficient purification of naphthodianthrones from St. John's wort extract by using liquid–liquid extraction and SEC
Authors: Karioti Anastasia , Vincieri Franco F. , Bilia Anna R. 
Published: April 2009

AbstractHypericin and pseudohypericin, the main naphthodianthrones present in Hypericum species are among the most promising natural products, but the research concerning their biological activities is hindered by their low content in the plant. In this paper a method for the rapid isolation of hypericin and pseudohypericin from Hypericum perforatum hydro‐alcoholic dried extracts has been developed. Briefly, the method consists of a partition of the extract between organic and aqueous layers and further purification of the richest extract in naphthodianthrones with Sephadex LH‐20 column chromatography. A final separation of hypericin from pseudohypericin was achieved using Sephadex LH‐60 column chromatography. All partitions were carried out in triplicate and monitored by LC‐MS and NMR analyses. The best results were obtained by successive extraction with n‐hexane, Et2O and EtOAc. A three‐step fractionation resulted in 98% content in total naphthodianthrones. To the best of our knowledge this is the first report on the separation of hypericin from pseudohypericin using size exclusion chromatography.
Temperature and pH‐stability of commercial stationary phases
Authors: Teutenberg Thorsten , Hollebekkers Koen , Wiese Steffen , Boergers Andrea 
Published: April 2009

AbstractIn this paper, the temperature and pH stability of silica‐based RP stationary phases were investigated. Furthermore, nonsiliceous phases like a polymeric column based on polystyrene divinylbenzene and a polybutadiene coated zirconium dioxide column were also included. The columns were heated up to 150°C at dynamic conditions, which means that the eluent consisting of water and methanol (90:10, v/v) was continuously purged through the packed bed. After every 5 h, the columns were cooled down to room temperature and the efficiency was measured by injecting a test sample based on the Neue test. It could be shown that some stationary phases exhibited a very good temperature stability at the test conditions specified above.
Tarnish and corrosion evaluation of a blue gold‐based alloy
Authors: Carvalho O. , Soares D. , Fonseca A. , Silva F. S. 
Published: April 2009

AbstractThe use of some coloured gold alloys is dependent on the physical stability of the material when subjected to a corrosion media. This paper is concerned with the effect of two common detrimental environments (sweat and sulphuric solutions) on the stability of a blue gold‐base alloy. Changes in physical properties, namely colour and brightness, were evaluated with time. It was observed that, for sulphuric solution, significant changes were obtained even for small immersion times. For the artificial sweat solution, changes occur, but the alloy is significantly more resistant. The alloy corrosion mechanisms are presented for both types of solutions. The products of corrosion were characterized by optical and SEM/EDS microscopy and by XPS spectroscopy. A comparison of the corrosion mechanisms, between the two immersion solutions, is also presented.
Electrochemical response of amorphous and devitrified Al‐Ni‐La‐X (X = Ag, Cu) alloys
Authors: Roy A. , Mandhyan A. K. , Sahoo K. L. , Banhart J. , Chattoraj I. 
Published: April 2009

AbstractThe electrochemical response of melt‐spun Al‐Ni‐La alloys with partial substitution of Ni after different stages of devitrification was studied. The base alloy was found to have the best corrosion resistance. It was observed that primary crystallization caused minimal deterioration in the corrosion resistance of the base alloy as compared to its amorphous state. The substitute alloys had different corrosion resistance dependent on the substituting element with the Ag containing alloy having the least resistance. This could be attributed to the operation of local galvanic cells, enhanced by chemical heterogeneities in the alloys. Secondary crystallization caused a reduction in the corrosion resistance of all the alloys due to the creation of intermetallic phases that increased the galvanic activity.
Analysis of electrochemical noise of X70 steel in Ku'erle soil by cluster analysis
Authors: Huang J.Y. , Qiu Y.B. , Guo X.P. 
Published: April 2009

AbstractElectrochemical noise (EN) technique was employed to study the corrosion behaviors of the X70 pipeline steel in the Xinjiang Ku'erle saline soil (moisture content 1.04%) during the initial corrosion period (0–7 days). The obtained EN data were analyzed by principal component analysis (PCA), hierarchical agglomerative cluster analysis (HACA) and wavelet analysis (WA). After the PCA applied, the potential standard deviation ($\sigma _E$) and mean value ($\overline E$) as well as current mean value ($\overline I$) were considered as the descriptors to characterize EN distribution. Then, using $\sigma _E$, $\overline E$, and $\overline I$ as variables, three different corrosion states of the local corrosion in the soil can be classified clearly by the HACA, including instable germination state, quick development state, and stable development state. According to the WA, the different characteristics of the three corrosion stages have been further proved. The results show that the PCA–HACA method should be successful for the analysis of EN signals from the soil corrosion system.
Influence of rare earth element Ce and La addition on corrosion behavior of AZ91 magnesium alloy
Authors: Liu W. , Cao F. , Zhong L. , Zheng L. , Jia B. , Zhang Z. , Zhang J. 
Published: April 2009

AbstractTwo types of AZ91 magnesium alloys containing rare earth element Ce or La were fabricated. Hydrogen evolution and electrochemical tests were carried out to evaluate the corrosion behavior of new AZRE (RE = Ce or La) and AZ91 alloys in 3.5% NaCl solutions (pH 6.50). Various corrosion rate tests indicated that addition of RE obviously enhanced corrosion resistance of AZ91 magnesium alloy. The optimal content of RE was 0.92% for Ce and 0.66% for La. Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and low‐angle X‐ray diffraction (XRD) were used to characterize the effect of RE addition on microstructure and corrosion product film of AZ91 magnesium alloy. The refined β phase and formation of γ phase in AZRE alloy were observed by SEM, which resulted in the improvement of corrosion resistance due to the depression of microgalvanic couples. Moreover, the enhanced protective effectiveness of corrosion products was another reason for the improved corrosion resistance.
Electrochemical corrosion response of a low carbon heat treated steel in a NaCl solution
Authors: Osório W. R. , Peixoto L. C. , Garcia L. R. , Garcia A. 
Published: April 2009

AbstractDual‐phase (DP) steels are produced from a specific heat treatment procedure and have recently emerged as a potential class of engineering materials for a number of structural and automobile applications. Such steels have high strength‐to‐weight ratio and reasonable formability. The present study aims to investigate the effects of four different and conventional heat treatments (i.e., hot rolling, normalizing, annealing, and intercritical annealing) on the resulting microstructural patterns and on the electrochemical corrosion behavior. Electrochemical impedance spectroscopy (EIS) and Tafel plots were carried out on heat treated steel samples in a 0.5 M NaCl solution at 25 °C with neutral pH. An equivalent circuit analysis was also used to provide quantitative support for the discussions. The normalizing and the annealing heat treatments have provided the highest and the lowest corrosion resistances, respectively. The intercritical annealing and as‐received (hot rolled) low carbon steel samples have shown similar corrosion behavior. Although a deleterious effect on the corrosion resistance has been verified for DP steel due to the residual stress from the martensite formation, it combines good mechanical properties with intermediate electrochemical corrosion resistance.
Corrosion characteristics of electroless Ni–P coating in sulfur‐bearing solution
Authors: Wu Y. H. , Liu T. M. , Luo S. X. 
Published: April 2009

AbstractThe corrosion behaviors of electroless Ni–P coatings deposited on carbon steel in sulfur‐bearing solutions were investigated by weight gain test and scanning electron microscopy. The results indicate that the corrosion rate of electroless Ni–P coating was directly related to the sulfur content, immersion time, and test temperature. The corrosion rate increased with the prolonged immersion time. Increasing the temperature can markedly increase the corrosion rate of electroless Ni–P coating. The electroless Ni–P coating had a better corrosion resistance than 316L stainless steel against Cl− corrosion in sulfur‐bearing solution.
Molecular Shapes of Monosubstituted Polyacetylenes in their Liquid Crystalline Phases
Authors: Liu Kai‐Peng , Yu Zhen‐Qiang , Liu Jia‐Hao , Chen Er‐Qiang 
Published: April 2009

AbstractIn this short review, we discuss the molecular shapes of monosubstituted polyacetylenes (MSPAs) in their liquid crystalline (LC) phases. Their rigid backbone with high stereoregularity can endow MSPAs with significant shape persistency, which largely determines their LC structures. Helical cis‐cisoidal and cis‐transoidal MSPAs render rod‐like shapes and can form columnar LC (Φ) phases. In the smectic LC (Sm) phases of MSPAs with mesogenic side‐chains, the main chain, with trans‐cisoidal, trans‐transoidal or extended cis‐transoidal conformation, is in fact largely coplanar with the side‐chains, resulting in a sheet‐like molecular shape. From a simple geometric point of view, the rod‐ or sheet‐like MSPA molecules serve as the building block of their LC phases.magnified image
HMGB1: The jack‐of‐all‐trades protein is a master DNA repair mechanic
Authors: Lange Sabine S. , Vasquez Karen M. 
Published: April 2009

AbstractThe high mobility group protein B1 (HMGB1) is a highly abundant protein with roles in several cellular processes, including chromatin structure and transcriptional regulation, as well as an extracellular role in inflammation. HMGB1's most thoroughly defined function is as a protein capable of binding specifically to distorted and damaged DNA, and its ability to induce further bending in the DNA once it is bound. This characteristic in part mediates its function in chromatin structure (binding to the linker region of nucleosomal DNA and increasing the instability of the nucleosome structure) as well as transcription (bending promoter DNA to enhance the interaction of transcription factors), but the functional consequences of HMGB1's binding to damaged DNA is still an area of active investigation. In this review we describe HMGB1's actions in the nucleotide excision repair (NER) pathway, and we discuss aspects of both the “repair shielding” and “repair enhancing” hypotheses that have been suggested. We also report information regarding HMGB1's roles in the mismatch repair (MMR), nonhomologous end‐joining (NHEJ), and V(D)J recombination pathways, as well as its newly‐discovered involvement in the base excision repair (BER) pathway. We further explore the potential of HMGB1 in DNA repair in the context of chromatin. The elucidation of HMGB1's role in DNA repair is critical for the complete understanding of HMGB1's intracellular functions, which is particularly relevant in the context of anti‐HMGB1 therapies that are being developed to treat inflammatory diseases. © 2009 Wiley‐Liss, Inc.
The traffic problem: Modeling of the overtaking
Authors: Buřič Lubor , Janovský Vladimír 
Published: April 2009

AbstractThe classical microscopic single line follow‐the‐leader model of a road traffic may collapse in finite time due to a car collision. In order to avoid the collision, the natural action of a driver would be to overtake the slower car. We propose a simple model of overtaking assuming a circular road. The model is a dynamical system with discontinuous right‐hand side (the Filippov system). As a case study, we assumed that the system consists of N =3 identical cars. We studied a particular periodic solution (oscillatory pattern). We explored the possibility to use the standard software (AUTO97) to continue the pattern with respect to a parameter. Copyright © 2009 John Wiley & Sons, Ltd.
Review on sample preparation strategies and methods used for the analysis of aflatoxins in food and feed
Authors: Reiter Elisabeth , Zentek Jürgen , Razzazi Ebrahim 
Published: April 2009

AbstractMycotoxins are of toxicological relevance and consequently important contaminants in food and feed. The most common mycotoxins with the highest toxicity are the aflatoxins (AFs), which cause liver cirrhosis or primary liver carcinomas and have been shown to be the immunosuppressive. The European Union has set the maximum levels as low as reasonably achievable to protect consumers. To perform appropriate risk assessment for AFs robust analytical methods are required to provide reliable results. Different steps in the analysis of AFs in food and feed are necessary such as sampling, extraction, sample purification and detection. Throughout the analysis chain, methods have to be precise and reproducible. The sensitivity of an analysis, especially if the detection is not selective enough depends strongly on the sample clean up. However, techniques in sample preparation and analytical methods are improving continuously. This manuscript gives an overview on different analytical methods with emphasize on sample preparation strategies used in the analysis of AFs in food and feed.
The Fusarium toxin enniatin B exerts no genotoxic activity, but pronounced cytotoxicity in vitro
Authors: Behm Claudia , Degen Gisela H. , Föllmann Wolfram 
Published: April 2009

AbstractEnniatin B, a fungal metabolite produced by various Fusarium strains, is a frequent contaminant in cereals used for human foods and animal feeds, but, so far very limited data are available on its toxicity. The aim of this study was to investigate the effects of enniatin B in a battery of short‐term tests to evaluate its genotoxic potential. In Salmonella typhimurium assays (Ames assay) with the strains TA 98, TA 100, TA 102, and TA 104, both in the presence and absence of an external metabolizing enzyme system (rat liver S9), no mutagenicity was detected up to toxic levels (100 μM) of enniatin B. Likewise, mutagenicity tests in mammalian cells, i. e., the hypoxanthin‐guanin‐phosphoribosyl‐transferase (HPRT) assay with V79 cells performed with and without S9 mix, did not reveal a significant increase in mutant frequency for enniatin B up to 30 μM, a cytotoxic concentration. Additional tests on other types of genotoxicity, i. e., clastogenicity and chromosomal damage, were conducted in V79 cells, applying the alkaline single cell gel electrophoresis (Comet assay with and without FPG, formamidopyrimidine DNA glycosylase, enzyme) and the micronucleus assay. None of these assays revealed a significant genotoxic potential of enniatin B. However, enniatin B exerts pronounced cytotoxic effects in V79 cells as determined by neutral red uptake assay for 48 h exposure: The IC20 and IC50 values of 1.5 and 4 μM, are higher than those of the more potent Fusarium toxin deoxynivalenol (IC20 0.6 μM, IC50 of 0.8 μM), but in a similar range as values reported for cytotoxicity of enniatin B in various tumor cell lines. In summary, despite an apparent lack of genotoxic activity, enniatin B can exert biological activity at low micromolar concentrations in mammalian cells.
Potential of deoxynivalenol to induce transcription factors in human hepatoma cells
Authors: Nielsen Carina , Lippke Harald , Didier Andrea , Dietrich Richard , Märtlbauer Erwin 
Published: April 2009

AbstractTo assess the hepatotoxicity of deoxynivalenol (DON), human hepatoma cells (Hep‐G2) were used as an in vitro model. After exposing Hep‐G2 cells to low (1 μM) and high dose (10 μM), gene expression profiles were analysed by microarray. More than 5% of genes were up‐regulated, most of them being involved in transcriptional regulation. By real‐time RT‐PCR, elevated expression of transcription factors, commonly induced by activation of MAPK‐pathway, was demonstrated for Hep‐G2 cells on mRNA and protein level. Further studies, involving U937 human monocytes, showed that effects of DON treatment on mRNA and protein level were concentration‐dependent and cell‐specific. An inverse relation was noticed for the level of DON induced expression of transcription factors (JUN, FOS, EGR1 and ATF3) and the susceptibility of the cell lines towards the mycotoxin. This is the first report giving evidence that on a molecular level the mild hepatotoxic effects of DON are probably caused by the induction of transcription factors which are known to be associated with injury‐induced liver regeneration processes. With ATF3, a novel downstream target gene was identified in DON‐related cell signalling suggesting a potential linkage between molecular action and biological effects like reduction of glycogen storage in liver tissue.
Palaeopathology in Britain: a critical analysis of publications with the aim of exploring recent trends (1997–2006)
Authors: Park V. M. , Roberts C. A. , Jakob T. 
Published: April 2009

AbstractThis study collects data from three major journals and analyses them in order to assess the recent (1997–2006) nature of the study of palaeopathology within Britain. It considers the types of study published (case, population or method), whether findings are integrated with other data, the particular ‘theme’ that is considered (diet, activity patterns, etc) and the particular pathological condition focused upon (metabolic, dental, etc). The findings show there is a move away from the traditional case study and an increase in the acknowledgement of the value of integrating data with wider information. There is also a bias towards certain ‘themes’ and pathologies, reasons for which are discussed. Copyright © 2009 John Wiley & Sons, Ltd.
An efficient microwave‐assisted extraction process of stevioside and rebaudioside‐A from Stevia rebaudiana (Bertoni)
Authors: Jaitak Vikas , Bandna Bikram Singh , Kaul V. K. 
Published: April 2009

AbstractIntroductionStevioside and rebaudioside‐A are major low‐calorie diterpene steviol glycosides in the leaves of Stevia rebaudiana. They are widely used as natural sweeteners for diabetic patients, but the long extraction procedures required and the optimisation of product yield present challenging problems.ObjectiveTo develop a rapid and effective methodology for the extraction of stevioside and rebaudioside‐A from S. rebaudiana leaves and to compare yields using different extraction techniques.MethodologyDried and powdered leaves of S. rebaudiana were extracted by conventional, ultrasound and microwave‐assisted extraction techniques using methanol, ethanol and water as single solvents as well as in binary mixtures. Conventional cold extraction was performed at 25°C for 12 h while ultrasound extraction was carried out at temperature of 35 ± 5°C for 30 min. Microwave‐assisted extraction (MAE) was carried out at a power level of 80 W for 1 min at 50°C.ResultsMAE yielded 8.64 and 2.34% of stevioside and rebaudioside‐A, respectively, while conventional and ultrasound techniques yielded 6.54 and 1.20%, and 4.20 and 1.98% of stevioside and rebaudioside‐A, respectively.ConclusionA rapid and efficient method has been developed for the extraction of stevioside and rebaudioside‐A in optimum yields using MAE procedure. This method has the advantage of rapid extraction and fast screening of a large number of S. rebaudiana samples for assessment of planting material. MAE saves considerable time, energy and has implications in the quality assessment of stevioside and rebaudioside‐A prior to their industrial production from the leaves of S. rebaudiana. Copyright © 2009 John Wiley & Sons, Ltd.