bluuebunny/crossref_metadata_2025_split huggingface dataset:
The use of colloidal gas aphrons as novel downstream processing for the recovery of astaxanthin from cells ofPhaffia rhodozyma
Authors: Dermiki Maria , Gordon Mike H , Jauregi Paula 
Published: January 2008

AbstractBACKGROUND:There is an increasing interest in obtaining natural products with bioactive properties, using fermentation technology. However, the downstream processing consisting of multiple steps can be complicated, leading to increase in the final cost of the product. Therefore there is a need for integrated, cost‐effective and scalable separation processes.RESULTS:The present study investigates the use of colloidal gas aphrons (CGA), which are surfactant‐stabilized microbubbles, as a novel method for downstream processing. More particularly, their application for the recovery of astaxanthin from the cells ofPhaffia rhodozymais explored. Research carried out with standard solutions of astaxanthin and CGA generated from the cationic surfactant hexadecyl trimethyl ammonium bromide (CTAB) showed that up to 90% recovery can be achieved under optimum conditions, i.e., pH 11 with NaOH 0.2 mol L−1. In the case of the cells' suspension from the fermentation broth, three different approaches were investigated: (a) the conventional integrated approach where CGA were applied directly; (b) CGA were applied to the clarified suspension of cells; and finally (c) thein situapproach, where CGA are generated within the clarified suspension of cells. Interestingly, in the case of the whole suspension (approach a) highest recoveries (78%) were achieved under the same conditions found to be optimal for the standard solutions. In addition, up to 97% recovery of total carotenoids could be achieved from the clarified suspension after pretreatment with NaOH. This pretreatment led to maximum cell disruption as well as optimum conditioning for subsequent CGA separation.CONCLUSIONS:These results demonstrate the potential of CGA for the recovery of bioactive components from complex feedstock. Copyright © 2008 Society of Chemical Industry
Synthesis and Mechanical Properties of Polypropylene‐based Polymer Hybrids via Controlled Radical Polymerization
Authors: Kaneko Hideyuki , Matsuo Shingo , Kawahara Nobuo , Saito Junji , Matsugi Tomoaki , Kashiwa Norio 
Published: January 2008

AbstractIsotactic polypropylene‐based graft copolymers linking poly(methyl methacrylate), poly(n‐butyl acrylate) and polystyrene were successfully synthesized by a controlled radical polymerization with isotactic polypropylene (iPP) macroinitiator. The hydroxylated iPP, prepared by propylene/10‐undecen‐1‐ol copolymerization with a metallocene/methyl‐aluminoxane/triisobutylaluminum catalyst system, was treated with 2‐bromoisobutyryl bromide to produce a Br‐group containing iPP (PP‐g‐Br). The resulting PP‐g‐Br could initiate controlled radical polymerization of methyl methacrylate, n‐butyl acrylate and styrene by using a copper catalyst system, leading to a variety of iPP‐based graft copolymers with a different content of the corresponding polar segment. These graft copolymers demonstrated unique mechanical properties dependent upon the kind and content of the grafted polar segment.
Kinetic and Active Centre Studies on the Polymerization of Propylene using MgCl2 Supported Ziegler – Natta Catalysts and 1,3 Diether Donors
Authors: Yaluma Andrew K. , Chadwick John C. , Tait Peter J. T. 
Published: January 2008

AbstractAll polymerization experiments were carried out in a Büchi glass reactor capable of operating at propylene pressures of 1‐7 atmospheres. Two types of MgCl2 supported catalysts with controlled morphology were studied, viz., catalyst systems containing either a 1,3 diether (Catalysts A and D), 9,9‐bis (methoxymethyl) fluorene, or a simple diester (Catalysts B, C and E) such as diisobutylphthalate, used as reference systems. The kinetic behaviours of these catalysts were investigated for propylene polymerization. The 1,3‐diether based systems proved to be excellent catalyst systems for propylene polymerization showing high polymerization activities and stable rate‐time profiles and produced spherical polymer particles. Catalyst pre‐treatment was found to play an important role in controlling the morphology of the final polymer. A tritiated alcohol radio‐quenching technique was used to determine the concentrations active centres: values of 7.5 and 5.1 mol/mol % respectively were obtained for catalysts A and D and 3.5, 2.9 and 2.2 mol/mol % respectively were obtained for catalysts B, C and E. Catalysts A and D showed very high polymerization activities and also higher C0* values. All polymers produced were characterized by SEM, DSC, extraction and molecular weight determinations.
Experimental and Computational Approaches on the Isospecific Role of Monoester‐Type Internal Electron Donor for TiCl4/MgCl2 Ziegler‐Natta Catalysts
Authors: Liu Boping , Cheng Ruihua , Liu Zhen , Qiu Pengyuan , Zhang Shiliang , Taniike Toshiaki , Terano Minoru , Tashino Kunihiko , Fujita Takashi 
Published: January 2008

AbstractIn this work, a combination of experimental and computational approaches on the isospecific role of monoester‐type internal electron donors (ED) such as phenylpropionate (PhP), ethylheptanoate (EH), methylbenzoate (MB), ethylbenzoate (EB) for TiCl4/ED/MgCl2 Ziegler‐Natta catalysts had been performed. The propylene polymerization results revealed that the isospecificity of catalysts increases in the following order: PhP < EH < MB < EB. The subsequent molecular modeling on the electronic properties of the donors and two kinds of cluster model catalysts: TiCl4/ED/MgCl2 and TiCl4/ED/(MgCl2)4 based on density functional theory (DFT) method was carried out. Two kinds of ED coordination on MgCl2 clusters through either O or O within the monoester‐type ED had been disclosed. A perfect correlation between the dipole moment of ED, the coordination bond length of O … Mg, the competitive coordination from O with Mg ion and the isospecificity of the catalysts had been established.
Density Functional Calculations for Electronic and Steric Effects of Ethyl Benzoate on Various Ti Species in MgCl2‐Supported Ziegler‐Natta Catalysts
Authors: Taniike Toshiaki , Terano Minoru 
Published: January 2008

AbstractPossible coadsorption states of Ti mononuclear species and ethyl benzoate (EB) and their interaction on MgCl2 (110) and (100) surfaces were investigated with periodic density functional calculations in order to obtain the microscopic understanding about how EB affects the steric and electronic natures of the Ti species. EB was unlikely to be attached to the TiCl4 species on both the MgCl2 (110) and (100) surfaces. The coadsorption of EB at Mg2+ ions near the Ti species was as favorable as the separate adsorption, which implied the random placement of these adsorbants in the final catalyst. The charge redistributions upon coadsorption among the Ti species, EB and the support were found to be dependent on the surface structures: the electron density of the Ti speceies was rather decreased by the coadsorption on the (100) surface, while that of the Ti species was enhanced due to the support‐mediated electron transfer from EB on the (110) surface. It was suggested that the presence of EB close to the Ti species should generate donor‐related active sites selectively on the (110) surface.
Supported Zr‐and Hf‐cene Catalysts for Propylene Polymerization
Authors: Novokshonova L. A. , Ushakova T. M. , Lysova M. V. , Kudinova O. I. , Krasheninnikov V. G. , Lyubimtsev A. L. 
Published: January 2008

AbstractThe supported metallocene catalysts were obtained on the layered silicate montmorillonite (MMT), using AlMe3 and AliBu3 for synthesis of alkylaluminoxane directly on a support surface, followed by metallocene supporting. It was shown that the MMT‐H2O/AliBu3 forms with ansa‐Zr‐cenes of C1 and C2‐symmetry the significantly more active supported metal‐alkyl complexes in propene polymerization, than MMT‐H2O/AlMe3. The MMT‐H2O/AliBu3 is the effective activator of the ansa‐Hf‐cenes, in contrast to MAO and MMT‐H2O/AlMe3, giving the high active supported catalysts for synthesis of isotactic and elastic polypropene. The character of influence of metallocene fixation on support on the isotactic pentad [mmmm] content in polymer, compared to homogeneous analogues, depends on the metallocene nature. The introduction of borate Ph3CB(C6F5)4 in the case of both Zr‐cene and Hf‐cene catalysts increases significantly the activity at the reduced ratio of Al/Zr, Hf (100–500 instead of 2000–3000) and stabilizes the catalytic complexes.
Improvement of Structure and Properties of Polypropylene/Poly(ethylene‐co‐propylene) In‐reactor Alloy by Modifying the Cocatalyst
Authors: Dong Qi , Fan Zhiqiang , Fu Zhisheng , Xu Junting 
Published: January 2008

AbstractSummary: A series of polypropylene/poly(ethylene‐co‐propylene) in‐reactor alloy were synthesized by a TiCl4/MgCl2/SiO2/diester type Ziegler‐Natta catalyst, using triethylaluminium (TEA), triisobutylaluminium (TIBA) or TEA/TIBA mixtures of different molar ratio as cocatalyst. Mechanical properties of the alloy are strongly influenced by the cocatalyst. Toughness‐stiffness balance of the alloy synthesized using a 50/50 TEA/TIBA mixture as cocatalyst is much better than that of the alloy based on pure TEA cocatalyst. Changes in copolymer chain structure and composition distribution are thought to be the main reason for this improvement of properties.
A Flat Model Approach to Ziegler‐Natta Catalysts for Propylene Polymerization and a Preparation Method of Well‐defined Crystallites of MgCl2‐supported Catalysts
Authors: Andoni Adelaida , Chadwick John C. , Niemantsverdriet Hans (J.W.) , Thune Peter C. 
Published: January 2008

AbstractSummary: An active model for a Ziegler‐Natta propylene polymerization catalyst has been prepared by spin‐coating of a MgCl2/diether donor solution in ethanol on a flat silica wafer, followed by crystal growth by Ostwald ripening to give well‐defined MgCl2 · diether · nEtOH crystallites. The flat model approach facilitates detailed characterization of the catalyst and polymer using surface spectroscopy and microscopy techniques. The growth of the crystallites on the flat silica indicates formation of only 120° edge angles, suggesting the preference for the formation of one particular crystallite face for the MgCl2. Subsequent treatment with TiCl4 generates the catalyst and in propylene polymerization polymer forms on the lateral face of each crystallite.
Ultrahigh Molecular Weight Ethene Copolymers from Metallocene and Ziegler Catalysts
Authors: Hasebe Koichi , Fujiwara Akio , Nozaki Takashi , Miyamoto Koichi 
Published: January 2008

AbstractIn this study, ultrahigh molecular weight polyethene homopolymer and copolymer were successfully produced with the metallocene and the Ziegler catalyst system. In case with the metallocene catalyst system, viscosity average molecular weight of the homopolymer was controlled from 2 million to 10 million. Also, the molecular weight of the copolymer was reached up to 6 million. In case with the Ziegler catalyst system, the molecular weight of the copolymer was reached up to 4 million. The transparency of the copolymer by the Ziegler catalyst, with which the copolymer with better uniformity was produced, could be comparable with that by the metallocene catalyst.
Chromium Catalysts for Butadiene and Norbornene Polymerization
Authors: Ricci Giovanni , Boglia Aldo , Boccia Antonella Caterina , Zetta Lucia 
Published: January 2008

AbstractA new class of chromium catalysts were obtained by combining bidentate phosphine chromium(II) complexes with methylaluminoxanes. These systems were found to be very active in the polymerization of butadiene giving 1,2 polymers having different tacticity (iso or syndio) depending on the type of phosphine bonded to the chromium atom. Moreover, they were also able to polymerize norbornene, giving crystalline all exo‐enchained vinyl addition polymers, exhibiting a rather unusual structure in the field of olefin stereospecific polymerization, namely diheterotactic structure, characterized by regular sequences of (mr) atactic triads.
Dynamic Monte Carlo Simulation of Olefin Polymerization in Stopped‐Flow Reactors
Authors: Soares João B. P. , Nguyen Tuan 
Published: January 2008

AbstractStopped‐flow reactors are very useful to estimate olefin polymerization rate constants and to investigate particle morphology development. Because the residence time in these reactors is comparable to the life time of the polymer chains, very narrow molecular weight distributions are obtained and the number average molecular weight is proportional to reactor residence time. In this case, traditional models for olefin polymerization in industrial reactors can not be applied. In this contribution, we derived analytical solutions and performed Monte Carlo simulations to describe the time evolution of the molecular weight distribution of polyolefins made with single‐ and multiple‐site catalysts in stopped‐flow reactors.
Bilateral pedunculopontine nuclei strokes presenting as freezing of gait
Authors: Kuo Sheng‐Han , Kenney Christopher , Jankovic Joseph 
Published: January 2008

AbstractThe penduculopontine nucleus (PPN) has been suggested to play an important role in locomotion, based on animal studies, but its function in humans has not been well defined. Autopsy studies have suggested that PPN pathology correlates with gait dysfunction in Parkinson's disease and in progressive supranuclear palsy but direct clinical evidence is lacking. We report a patient with bilateral PPN infarcts whose dominant clinical feature was freezing of gait, thus providing evidence that PPN is involved in human locomotion and that damage to the PPN may lead to abnormal gait. © 2008 Movement Disorder Society
The long‐term impact of adolescent gestational weight gain
Authors: Groth Susan W. 
Published: January 2008

AbstractThis study involved 330 primiparous Black adolescents. The purpose of the study was to examine predictors of body mass index (BMI) change in Black adolescents 6 and 9 years after they gave birth. Predictors were gestational weight gain, pre‐pregnant BMI, and age (p < .001). For older adolescents (ages 18–19), gestational weight gain was the only predictor of BMI change (p = .008). Regardless of pre‐pregnant BMI category, adolescents whose gestational weight gain exceeded Institute of Medicine (IOM) recommendations were 4.6 times more likely to be obese than those whose weight gain was within recommendations. Excessive gestational weight gain and pre‐pregnant overweight contribute to adolescent obesity. These findings have implications from both a clinical and public health perspective. © 2008 Wiley Periodicals, Inc. Res Nurs Health 31:108–118, 2008
Analysis of the hysteretic behavior of silicon nanowire transistors
Authors: Fahem Z. , Csaba G. , Erlen C. M. , Lugli P. , Weber W. M. , Geelhaar L. , Riechert H. 
Published: January 2008

AbstractWe present a combined experimental and theoretical analysis of the transport properties of silicon nanowire (NW) transistors. The NWs are grown by catalytic chemical vapour deposition and are later deposited on pre‐patterned oxidized silicon substrates that provide the device source and drain electrodes. A back gate configuration is used for our study. Through a controlled nickel diffusion, parts of the nominally undoped NWs are turned into nickel silicide NWs, thus pro‐ viding a direct metallic nanolead to the semiconducting wire. The transistors obtained with NWs of 10‐30 nm diameters display p‐type behaviour, current densities up to 0.8 MA/cm2, and on/off current ratios of up to 107. The subthreshold characteristics show a strong hysteresis. The simulation based on a drift‐diffusion approach indicates that traps at the interface between the NWs and SiO2 are responsible for such behaviour. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Full counting statistics for electron number in quantum dots
Authors: Utsumi Yasuhiro , Golubev Dmitri S. , Schön Gerd 
Published: January 2008

AbstractMeasurements of the average current and its fluctuations (noise) have been powerful tools to study the quantumtransport in mesoscopic systems. Recently it became possible to measure the probability distribution of current, ‘full counting statistics’ (FCS), by using quantum point‐contact charge‐detectors. Motivated by recent experiments, we developed the FCS theory for the joint probability distribution of the current and the electron number inside quantum dots (QDs).We show that a non‐Gaussian exponential distribution appears when there is no dot state close to the lead chemical potentials. We show that the measurement of the joint probability distribution of current and electron number would reveal nontrivial correlations, which reflect the asymmetry of tunnel barriers.We also show that for increasing strength of tunneling, the quantum fluctuations of charge qualitatively change the probability distribution of the electron number. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Editorial: phys. stat. sol. (c) 5/1
Authors: Stutzmann Martin 
Published: January 2008

AbstractHow do you find the scientific information and the manuscript reference you need? The answer to this basic but very important question for every active scientist has changed significantly over the last 30 years. When I was a Ph.D. student or a young postdoc, I would venture regularly to a strange and quiet place called a “library”, where all important journals in my field could be easily identified already from the amount of the shelve space they filled. To find a spe‐cific reference and to preserve it for future use was limited by the physical exercise to carry a stack of heavy volumes to the copy machine and to press a “copy” button for each page I really wanted to keep. On the way, sometimes I actually found another interesting paper just by browsing through the latest issue of Journal X, and I copied this one, too. And in most cases, I even read what I copied.Today, things are much better! All relevant information is available online in electronic form, so I do not have to leave my office anymore to find out what's new. The impact factors of journals and the h ‐factors of authors help me to distinguish good from bad, or at least that is the hope. Whenever I search for a specific topic, anyhow I will get more hits than I can digest in a realistic time. Fortunately, printers by now are so fast and powerful that I can transfer the rest to a printout which I will, most likely, never use again in the foreseeable future.But seriously, although the way to make use of and to deal with scientific information has changed drastically in the last couple of decades, the basic needs of active scientists for reliable, up‐to‐date, and easily accessible information exchange with their international colleagues worldwide has basically remained the same. We at physica status solidi, therefore, for more than 45 years have been and are dedicated to provide exactly that service to our authors and readers, whether they make use of the pss hard‐copies in the library or whether they browse the online files of physica status solidi. Last year, more than 2500 articles have been published after strict peer review and careful editing, which makes physica status solidi (nomen est omen) the second largest journal series in solid state physics. The journal has more than doubled in volume since the year 2000, but the Impact Factor also has increased by a factor of two since 1995, showing that we did not trade in quantity for quality. And, last but not least, the visibility of the journal series as meas‐ured by the number of full text downloads has in‐creased by a similar factor of two in the last 24 months alone.In October 2007, more than 40000 full text downloads of physica status solidi articles have been registered by the Wiley Interscience data base. Unfortunately, we have no idea how many of these articles have actually been read …In the name of the entire pss‐team, I thank all of you for your continued support of and interest in physica status solidi and wish you a successful year 2008!
Ring signatures for benzenoids with up to seven rings, Part 2: Pericondensed systems
Authors: Balaban Alexandru T. , Randić Milan 
Published: January 2008

AbstractAn array of integers pij indicate in how many of the K resonance structures one finds 6 > i > 0 π‐electrons in the corresponding ring (which is labeled with capital letters A through a subsequent letter up to G). The index j for the rows indicates the ring type, denoted by capital letters (that is, j = 1 stands for A, j = 2 stands for B, etc.). Row sums lead to π‐electron ring partitions after division by the number K of resonance structures. Column sums lead to a sequence of seven integers (Ri sequence) which after division by K affords the ri sequence; this is finally converted into the signature of the benzenoid si sequence). The analysis of signatures for pericondensed benzenoids with h = 4 through 7 benzenoid rings has revealed interesting regularities and correlations with structure, and has also allowed a confirmation of Clar's theory by investigating five isomeric dibenzopyrenes. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Au/N‐type Si Schottky‐barrier contact and oxidation kinetics in Au‐contaminated and thermally oxidized N‐type Si (001) surfaces
Authors: Shimizu H. , Wakashima H. , Shimada S. , Ishikawa T. , Ikeda M. 
Published: January 2008

AbstractAnomalous Au locations in SiO2/Si system of Au‐contaminated and thermally oxidized n‐type Si(001) have been investigated using XPS and alternating current surface photovoltage (AC SPV) techniques. On the basis of XPS analyses, in Au‐contaminated (2 × 1015 atoms/cm2) and thermally oxidized Si surfaces between 823 and 973 K, the Au existed both on the top of the SiO2 and the SiO2/Si interface as a cluster that did not make bonds with other elements such as O and H. The resulting Au/n‐type Si Schottky barrier causes an occurrence of frequency‐dependent AC SPV, demonstrating that the Si surface was depleted and/or weakly inverted. This result indicates that the Au/n‐type Si Schottky barrier (calculated to be 0.70 eV) survived at the SiO2/Si interface even after the thermal oxidation. As the temperature increased higher than 1023 K, the Au at the SiO2/Si interface diffused into bulk Si, resulting in drastic reduction of AC SPV. On oxidation kinetics between 1023 and 1173 K, Au is thought to act as a catalyst and to promote the SiO2 growth at the Si surface, resulting in enhanced oxidation. Copyright © 2008 John Wiley & Sons, Ltd.
Transmission power and duration‐aware playout control for packetized media streaming over wireless links
Authors: Li Yan , Bambos Nicholas 
Published: January 2008

AbstractWe investigate joint transmission power control and playout buffer control for packetized media streaming over wireless links. We propose a novel model formulation that tracks the play/freeze duration and play/freeze switch jitter to control the transmission power and playout rate (1 or 0, i.e., play or rebuffer). The model is especially appropriate for audio/music streaming. The optimal joint control is obtained using a Dynamic Programming approach to balance the average power used against achieved quality of service (QoS), reflecting play/freeze duration and jitter frequency. We also investigate two key special cases, where either only power control or rebuffer control is exercised; we obtain certain useful provable structural properties of these individual side controls. Based on those, we also design a low‐complexity heuristic control that ‘mimics’ the obtained structural properties of the optimal ones. Through simulation we see that the developed controls can achieve substantially higher performance over standard benchmark schemes. Copyright © 2008 John Wiley & Sons, Ltd.