bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical functions of AlAsSb characterized by spectroscopic ellipsometry
Authors: Mozume T. , Tanaka M. , Yoshimi A. , Susaki W. 
Published: March 2008

AbstractNominally undoped AlAsx Sb1–x layers with a thickness of 200 nm to 370 nm and arsenic mole fraction x of 0.325–0.872 were grown on Fe‐doped (001) InP substrates by solid‐source molecular beam epitaxy. Their optical properties were investigated over a wide photon range of 0.7 eV to 5 eV at room temperature using variable angle spectroscopic ellipsometry. The obtained data were analyzed using standard multilayer calculation schemes. The determined thicknesses of these layers were in good agreement with the calibrated normal growth rate. For photon energies below the AlAsSb band gap, which is the transparency region of the AlAsSb layer, pronounced Fabry–Perot interference oscillations due to the multiple internal reflections in the AlAsSb layer were observed. A clear blue shift of the energy gap of AlAsSb was observed as the As concentration increased. The refractive index decreased with an increase of the bandgap energy in the energy range of 0.7 eV to 2.1 eV. This trend is the same as that observed in conventional III–V alloy semiconductors. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectroscopic ellipsometry study of Co‐doped TiO2 films
Authors: Águas H. , Popovici N. , Pereira L. , Conde O. , Branford W. R. , Cohen L. F. , Fortunato E. , Martins R. 
Published: March 2008

AbstractCo‐doped TiO2 films were characterized by spectroscopic ellipsometry to determine their thickness, deposition rate and optical properties as function of substrate temperature and background gas composition. To fit the data we used a combination of a single Tauc–Lorentz oscillator with the Drude free electron model to take in account the free electrons present in the film. The Co doping and the addition of H2 to the gas phase during film growth cause the formation of a titanium oxide which containsfree electrons that absorb the energy of the red part of the spectrum, causing k to increase. The n of the films at 1.5 eV is about 2.3 eV. The fittings also show that the n of films decreases and k increases at the surface. This can be related to a segregation of Co to the surface, which in some cases, of high substrate temperature and high H2 flow during deposition, can lead to an even higher concentration of free electrons at the surface. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ellipsometric measurements of quantum confinement effects on higher interband transitions of Ge nanocrystals
Authors: Alonso M. I. , Garriga M. , Bernardi A. , Goñi A. R. , Lopeandia A. F. , Garcia G. , Rodríguez‐Viejo J. , Lábár J. L. 
Published: March 2008

AbstractWe studied the dielectric functions of Ge nanocrystals obtained by crystallization of amorphous Ge thin films embedded in SiO2. Partial crystallization of films was induced by thermal annealing. Crystalline regions gave rise to clear spectral features due to interband transitions whose critical point parameters correlated with the initial a‐Ge thickness. These changes were clearly attributed to quantum confinement effects. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of O2 partial pressure and substrate temperature on the plasma emission spectra and ZnO growth behavior
Authors: Liu M. , Ma C. Y. , Zhang Q. Y. 
Published: March 2008

AbstractAn on‐line measurement of optical emission spectrum (OES) was used to study the variation of Zn and O components in the plasma of ZnO film growth with reactive radio‐frequency magnetron sputtering method. It was found that the decline of all the Zn emission lines shows three different stages with the increase of oxygen partial pressure (PO), corresponding to metal sputtering (PO < 6.0 × 10–3 Pa), the compound sputtering (PO > 5.0 × 10–2 Pa), and the transition range (6.0 × 10–3 Pa to 5.0 × 10–2 Pa), respectively. In the stage of compound sputtering, a critical oxygen pressure is found at about 1.5 × 10–1 Pa. At the oxygen pressures below and above the critical pressure, the film growth is found to be O‐controlled and Zn‐controlled, respectively. Similarly, a critical substrate temperature is found at about 550 °C. At the temperatures above the critical temperature, the variation of Zn472.6 intensity is more obvious, suggesting the deposited films is more close to the stoichiometric ratio than the films deposited at the lower temperatures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Antitumor effects of saponin extract from Patrinia villosa (Thunb.) Juss on mice bearing U14 cervical cancer
Authors: Zhang Tao , Li Qingwang , Li Kun , Li Yurong , Li Jian , Wang Guijie , Zhou Shaobo 
Published: March 2008

AbstractSaponin extracted from Patrinia villosa (Thunb.) Juss (SPVJ) is a Chinese medicine which is used widely by traditional medicine doctors. In this study, the antitumor effects and the possible mechanisms of SPVJ were investigated in mice bearing U14 cervical cancer. The results showed that SPVJ (50 mg/kg and 100 mg/kg) effectively reduced the weight of U14 cervical tumor (35.1% and 57.1%, respectively). Compared with the control group, SPVJ (100 mg/kg) significantly increased tumor cells in the G0/G1 phase (38.1% vs 68.5%), increased the number of cells in apoptosis (9.4% vs 28.9%) and G0/G1 phase and decreased the number of cells in S phase (41% vs 26.2%) and G2/M (20.9% vs 5.3%), inhibited proliferating cell nuclear antigen (PCNA) of tumor cell (80.6% vs 21.8%), decreased the expression of mutant p53 (66.4% vs 33.5%) and bcl‐2 protein (78.2% vs 20.3%). The mechanism of the SPVJ antitumor effect might be associated with inhibition of tumor cells in G0/G1 phase, inducing apoptosis and inhibiting the expression of PCNA, mutant P53 and Bcl‐2 protein. Copyright © 2008 John Wiley & Sons, Ltd.
Effect of green tea and (‐)‐epigallocatechin gallate on ethanol‐induced toxicity in HepG2 cells
Authors: Lee Sang Il , Kim Hyo Jung , Boo Yong Chool 
Published: March 2008

AbstractDespite the continuing reports supporting the hepatoprotective effects of green tea against ethanol intoxication, there remain controversies regarding the active compound(s) and molecular mechanism. These issues were addressed in the present study using cultured HepG2 cells exposed to a lethal dose of ethanol. Gamma‐glutamyl transferase (GGT) was chosen as a marker of ethanol toxicity because it is widely used in clinics. When the cells were treated with ethanol at various concentrations, there was a dose‐dependent increase of GGT activity in the culture media and loss of cell viability. Pretreatment of the cells with green tea extract attenuated the changes significantly. Among the green tea constituents, (‐)‐epigallocatechin gallate (EGCG) attenuated the ethanol cytotoxicity effectively, whereas l‐theanine and caffeine had no effects. The ethanol cytotoxicity was also attenuated by alcohol dehydrogenase inhibitor 4‐methyl pyrazol and GGT inhibitor acivicin as well as by thiol modulators such as S‐adenosyl‐l‐methionine, N‐acetyl‐l‐cysteine and glutathione. EGCG failed to prevent the intracellular glutathione loss caused by ethanol, but it appeared to be a strong GGT inhibitor. Therefore the cytoprotective effects of green tea could be attributed to the inhibition of GGT activity by EGCG. This study suggests that GGT inhibitors including EGCG may provide a novel strategy for attenuating ethanol‐induced liver damage. Copyright © 2008 John Wiley & Sons, Ltd.
A novel function of bamboo extract in relieving lipotoxicity
Authors: Panee Jun , Liu Wanyu , Lin Yanling , Gilman Christy , Berry Marla J. 
Published: March 2008

AbstractLipotoxicity is closely related to the etiology and complications of type 2 diabetes mellitus. This study investigated the protective effect of an extract from bamboo Phyllostachys edulis against palmitic acid (PA)‐induced lipoapoptosis. The lipo‐detoxification function of the bamboo extract (BEX) was evaluated using cell culture models. Cell viability was measured by MTT assay and cell apoptosis was monitored by Annexin V staining. Cellular uptake of fluorescent free fatty acid (FFA) analog was measured by flow cytometry. Protein levels of total protein kinase B (Akt) and phosphorylated Akt (p‐Akt) were measured by western blotting. The results show that co‐incubating BEX with mouse myoblast C2C12 cells had no effect on the cellular uptake of FFA, but dramatically decreased PA‐induced cell apoptosis and protected cell viability. A similar antilipotoxicity effect of BEX was observed in other mammalian cells. BEX significantly decreased the protein levels of both Akt and p‐Akt in C2C12 cells under normal cell culture conditions but not under lipotoxic conditions, indicating the regulatory effect of BEX on cell signaling pathways and its response to a high FFA environment. This study demonstrated a novel function of bamboo extract in preventing lipotoxicity in mammalian cells, implicating a promising phytotherapeutic approach for lipo‐detoxification. Copyright © 2008 John Wiley & Sons, Ltd.
Antimicrobial activity of some medicinal plants of the Cerrado, Brazil
Authors: Costa E. S. , Hiruma‐Lima C. A. , Lima E. O. , Sucupira G. C. , Bertolin A. O. , Lolis S. F. , Andrade F. D. P. , Vilegas W. , Souza‐Brito A. R. M. 
Published: March 2008

AbstractIn order to determine the potential of Cerrado plants as sources of antimicrobial activity, the phytochemical screening of ethanol extracts from Virola surinamensis, Qualea grandiflora, Alchornea castaneifolia, Hancornia speciosa and Curatella americana traditionally used in folk medicine are reported. Copyright © 2008 John Wiley & Sons, Ltd.
Cancer chemoprotective effects of Curcuma xanthorrhiza
Authors: Park Jae Hee , Park Kwang Kyun , Kim Mi Jeong , Hwang Jae Kwan , Park Sun Kyu , Chung Won Yoon 
Published: March 2008

AbstractCurcuma xanthorrhiza Roxb. (Zingiberaceae) is a medicinal plant widely spread in South East Asia. In particular, it is commonly used not only for food and medicinal purposes in Indonesia, but also for the topical treatment of acne and skin inflammations as Thai traditional medicine. It was found that the methanol extract of C. xanthorrhiza inhibited significantly 7,12‐dimethylbenz[a]anthracene (DMBA)‐induced bacterial mutagenesis of Salmonella typhimurium TA98 and TA100 in the presence of S9, and the mutagenesis induced by H2O2 and tert‐butylhydroperoxide in S. typhimurium TA102, respectively. In addition, 12‐O‐tetradecanolyphorbol‐13‐acetate(TPA)‐induced mouse ear edema was markedly inhibited by pretreatment with C. xanthorrhiza extract. C. xanthorrhiza extract dose‐dependently reduced ODC expression in mouse skin with TPA‐induced acute inflammation. Furthermore, repeated treatment with 0.1% C. xanthorrhiza extract reduced the average number of tumors per mouse and the percentage of tumor‐bearing mice in a multistage mouse skin carcinogenesis induced by DMBA and TPA. These results demonstrate that the methanol extract of C. xanthorrhiza possesses cancer chemopreventive potential. Copyright © 2008 John Wiley & Sons, Ltd.
Hypericum perforatum and substance dependence: a review
Authors: Uzbay Tayfun I. 
Published: March 2008

AbstractSubstance abuse and dependence is a serious problem throughout the world. The development of several types of dependence remedies has medical, social and economical significance. In particular, alcohol and tobacco are the most commonly abused substances worldwide. An extract of Hypericum perforatum L. (HPE) displayed a clear antidepressant action and it has been used for the treatment of mild to moderate depression. Recent reports imply that HPE may be effective in the treatment of substance abuse. Studies have focused on alcohol and nicotine dependence. In this review, the effects of HPE on substance dependence and its possible benefit have been discussed in the light of current literature. Copyright © 2008 John Wiley & Sons, Ltd.
Carbon isotope determination for separate components of heterogeneous materials using coupled thermogravimetric analysis/isotope ratio mass spectrometry
Authors: Manning David A. C. , Lopez‐Capel Elisa , White Maggie L. , Barker Sam 
Published: March 2008

AbstractA gas‐tight thermal analysis system (Netzsch STA 449C Jupiter) has been connected to an isotope ratio mass spectrometer (PDZ Europa 20‐20) via an interface containing an oxidizing furnace, water trap, and gas‐sampling valve. Using this system, δ13C has been measured for CO2 derived from the thermal decomposition of carbonate and oxalate minerals and organic materials at temperatures that correspond to different decomposition events. There is close agreement between measured and published δ13C values for carbonate and oxalate minerals, which have simple decarbonation reactions on heating. Cellulose and lignin‐rich materials show much more complex thermal decomposition, reflecting differences in their purity and structure, and measured δ13C values vary with the temperature of gas sampling. Provided that measurements are made at temperatures that correspond to the decomposition of cellulose and lignin (indicated by maximum weight loss), internally consistent data can be obtained. However, measurements for cellulose and lignin are systematically enriched in δ13C (by up to 1.4‰) with respect to those reported for reference materials, possibly due to the slower combustion kinetics (compared with EA‐IRMS). Thermogravimetric analysis/isotope ratio mass spectrometry (TG‐IRMS) is ideal for materials and samples for which it is not possible to use other isotopic measurement techniques, for example because of sample heterogeneity. Copyright © 2008 John Wiley & Sons, Ltd.
On‐line measurements of δ15N in biological fluids by a modified continuous‐flow elemental analyzer with an isotope‐ratio mass spectrometer
Authors: Wang Xu , Feng Lianjun , Zhang Fusong , Ding Zhongli 
Published: March 2008

AbstractA modified continuous‐flow elemental analyzer coupled to an isotope‐ratio mass spectrometer (modified EA‐IRMS) was tested for on‐line δ15N measurement on urea solution and biological fluids (e.g. urine). The elemental analyzer configuration was adapted by adding a U‐shaped cold trap and an X‐pattern four‐way valve for on‐line trapping/venting of water from the liquid samples. Results indicate that the δ15N ratios show little variation (standard deviation (SD) = 0.05‰) with a sample size above the equivalent N yield of 0.2 mg urea (0.092 mg N) when the mass spectrometer conditions were carefully optimized. By contrast, a significant logarithmic decrease in δ15N with sample size was observed but this can be offset by applying a linearity correction or blank correction when the sample size is between equivalent N yields of 0.05 and 0.2 mg urea. The blank corrected δ15N ratios give an overall precision of ∼0.16‰ whereas the average precision for δ15N corrected using combined linearity and shift correction is 0.05‰. The relatively large variation in blank corrected δ15N values may be attributed to the variability of the blank δ15N in the sequence. Therefore, the blank correction should be carefully performed in routine measurements. As a result, the linearity range of a modified EA‐IRMS can be extended to a minimum sample size of 0.023 mg N. In addition, the reproducibility of the new system is good, as indicated by the precision (<0.2‰) for a set of standards and unknowns. The data show that fluids containing nitrogen can be successfully analyzed in the modified EA‐IRMS. Copyright © 2008 John Wiley & Sons, Ltd.
Spiking of serum specimens with exogenous reporter peptides for mass spectrometry based protease profiling as diagnostic tool
Authors: Findeisen Peter , Peccerella Teresa , Post Stefan , Wenz Frederik , Neumaier Michael 
Published: March 2008

AbstractSerum is a difficult matrix for the identification of biomarkers by mass spectrometry (MS). This is due to high‐abundance proteins and their complex processing by a multitude of endogenous proteases making rigorous standardisation difficult. Here, we have investigated the use of defined exogenous reporter peptides as substrates for disease‐specific proteases with respect to improved standardisation and disease classification accuracy. A recombinant N‐terminal fragment of the Adenomatous Polyposis Coli (APC) protein was digested with trypsin to yield a peptide mixture for subsequent Reporter Peptide Spiking (RPS) of serum. Different preanalytical handling of serum samples was simulated by storage of serum samples for up to 6 h at ambient temperature, followed by RPS, further incubation under standardised conditions and testing for stability of protease‐generated MS profiles. To demonstrate the superior classification accuracy achieved by RPS, a pilot profiling experiment was performed using serum specimens from pancreatic cancer patients (n = 50) and healthy controls (n = 50). After RPS six different peak categories could be defined, two of which (categories C and D) are modulated by endogenous proteases. These latter are relevant for improved classification accuracy as shown by enhanced disease‐specific classification from 78% to 87% in unspiked and spiked samples, respectively. Peaks of these categories presented with unchanged signal intensities regardless of preanalytical conditions. The use of RPS generally improved the signal intensities of protease‐generated peptide peaks. RPS circumvents preanalytical variabilities and improves classification accuracies. Our approach will be helpful to introduce MS‐based proteomic profiling into routine laboratory testing. Copyright © 2008 John Wiley & Sons, Ltd.
Strategic networks and entrepreneurial ventures
Authors: Stuart Toby E. , Sorenson Olav 
Published: March 2008

AbstractMuch research suggests that social networks shape the emergence and development of nascent ventures. Scholars have argued that founders' and firms' networks influence innovation and the identification of entrepreneurial opportunities, as well as facilitate the mobilization of resources for growth and the harvesting of value from fledgling firms. It is not an exaggeration to claim that existing empirical findings point to the centrality of networks in every aspect of the entrepreneurial process. However, with exceptions so few they may be counted on one hand, this research untenably treats network structures as exogenous—in other words, as if entrepreneurs and enterprises do not pursue valuable connections. In this article, we review the literature on networks in entrepreneurial contexts, argue that it disproportionately focuses on the consequences of networks at the expense of research on their origins, and consider the implications for the literature of the fact that most entrepreneurs and young ventures are strategic in their formation of relations. We then articulate a research agenda composed of five areas of inquiry we consider critical to a better understanding of networks and entrepreneurship. Copyright © 2008 Strategic Management Society.
Entrepreneurship, growth, and Adam Smith
Authors: Michael Steven C. 
Published: March 2008

AbstractIn the canonical work of economics, Adam Smith's Wealth of Nations, he explained that nations grow wealthy through changes in the division of labor. Using Smith's insight, entrepreneurship can be defined as the study of human actions that lead to changes in the division of labor. This definition gives theoretical and empirical meaning to studies examining new venture formation and economic growth, and can be used by scholars for intellectual profit, as illustrated by Baumol and Strom, Casson and Wadeson, and Agarwal, Audretsch, and Sarkar. Copyright © 2008 Strategic Management Society.
Entrepreneurial pursuits of self‐ and collective interests
Authors: Van de Ven Andrew H. , Sapienza Harry J. , Villanueva Jaume 
Published: March 2008

AbstractEntrepreneurs are often portrayed as rugged individualists who go it alone to build new organizations and programs that maximize their self‐interests. This portrayal is incomplete, because it does not account for the fact that entrepreneurs also pursue collective interests. It fails to recognize a basic paradox in human beings of simultaneously seeking individual and collective interests. We argue that an appreciation of the dialectical nature of human beings leads to fundamentally different conceptions of entrepreneurship than those commonly found in literature on entrepreneurship theory and practice. To illustrate our central premise, we focus on entrepreneurial opportunity realization, resource mobilization, and running in packs. Copyright © 2008 Strategic Management Society.
Zinc Porphyrin‐Driven Assembly of Gold Nanofingers
Authors: Arima Valentina , Blyth Robert I. R. , Matino Francesca , Chiodo Letizia , Sala Fabio Della , Thompson Julie , Regier Tom , Del Sole Roberta , Mele Giuseppe , Vasapollo Giuseppe , Cingolani Roberto , Rinaldi Ross 
Published: March 2008

AbstractNanofingers of gold covered by porphyrins are prepared by a combination of atomic manipulation and surface self‐organization. A submonolayer of zinc(II) 5,10,15,20‐tetrakis(4‐tert‐butylphenyl)‐porphyrin (ZnTBPP) axially ligated to a self‐assembled monolayer of 4‐aminothiophenol (4‐ATP) on Au(111) is prepared and studied using a combination of ultrahigh vacuum techniques. Under the electric field produced by the STM tip, the relatively weakly bound Au surface atoms along the discommensuration lines become mobile due to the strong bond to 4‐ATP, while the tendency of the porphyrins towards self‐assembly result in a collective motion of gold clusters. The clusters diffuse onto the surface following well‐defined pathways along the $[{\rm 11}\overline {\rm 2}]$ direction and then reach the step edges where they assembled, thus forming nanofingers. First‐principles density functional theory calculations demonstrate the reduction of the binding energies between the surface gold clusters and the substrate induced by adsorption of thiols. Scanning tunneling microscopy images show assemblies across three adjacent discommensuration lines of the Au(111)‐(22 × √3) reconstruction, which collectively diffuse along these lines to form islands nucleated at step edges.
A vector system for efficient and economical switching of C‐terminal epitope tags in Saccharomyces cerevisiae
Authors: Sung Min‐Kyung , Ha Cheol Woong , Huh Won‐Ki 
Published: March 2008

AbstractIn Saccharomyces cerevisiae, one‐step PCR‐mediated modification of chromosomal genes allows fast and efficient tagging of yeast proteins with various epitopes at the C‐ or N‐terminus. For many purposes, C‐terminal tagging is advantageous in that the expression pattern of epitope tag is comparable to that of the authentic protein and the possibility for the tag to affect normal folding of polypeptide chain during translation is minimized. As experiments are getting complicated, it is often necessary to construct several fusion proteins tagged with various kinds of epitopes. Here, we describe development of a series of plasmids that allow efficient and economical switching of C‐terminally tagged epitopes, using just one set of universal oligonucleotide primers. Containing a variety of epitopes (GFP, TAP, GST, Myc, HA and FLAG tag) and Kluyveromyces lactis URA3 gene as a selectable marker, the plasmids can be used to replace any MX6 module‐based C‐terminal epitope tag with one of the six epitopes. Furthermore, the plasmids also allow additional C‐terminal epitope tagging of proteins in yeast cells that already carry MX6 module‐based gene deletion or C‐terminal epitope tag. Copyright © 2008 John Wiley & Sons, Ltd.