bluuebunny/crossref_metadata_2025_split huggingface dataset:
Low viscous hydrophilic processing additives for extrusion of polyethylene at reduced temperatures
Authors: Kulikov Oleg , Hornung Klaus , Wagner Manfred 
Published: March 2010

AbstractIndustry is using fluorinated polymer processing additives (PPA) to delay the onset of sharkskin to higher rates of extrusion of PE resins. Yet it is necessary to keep elevated temperatures during extrusion to reduce apparent melt viscosity. We propose to use low viscous PPA made from reacting mixtures of polyethylene glycol with organic polyacids, phosphoric acid, and polyesters of oxiacids of Phosphorus. Surprisingly, extrusion pressures and apparent viscosity with the novel PPA at reduced temperatures are less, than at elevated temperatures. In total, extrusion pressures can be reduced 2–5 times for concentrations of PPA from 0.1 to 0.5 wt%, while sharkskin melt fracture can be eliminated for concentrations of PPA above 0.02 wt%. Extrusion with the novel PPA at reduced temperatures potentially increases productivity, reduces production cost, and allows processing of PE resins ofhigher MW and highly filled polymer composites. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers
Automatic velocity profile determination for uniform filling in injection molding
Authors: Chen Xi , Zhang Lei , Kong Xiangsong , Lu Junde , Gao Furong 
Published: March 2010

AbstractThe filling phase plays an important role in determining the quality of injection molded parts. Uniform melt‐front velocity has been recommended for minimizing the part non‐uniformity. On the basis of a capacitive transducer that has been developed for online measurement of melt front velocity, we propose an intelligent strategy for profiling injection velocity. The nonlinear response of melt development in a mold cavity is first acquired with a constant screw injection velocity. On the basis of this response, a stage division method is proposed to determine an appropriate stage number of a piecewise linear profile and the locations of the switch points. An optimization based on sequential simplex search is then conducted to search for the optimal profile of injection velocity. Online experimental tests on molds with different geometries show that the proposed method is effective in achieving a uniform mold filling. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers
Effect of applied voltage on surface and volume charge density of the jet in electrospinning of polyacrylonitrile solutions
Authors: Fallahi D. , Rafizadeh M. , Mohammadi N. , Vahidi B. 
Published: March 2010

AbstractTo investigate the effect of applied voltage on jet charge density, one must investigate its effect on the jet electric current and flow rate. However, there are some difficulties in measuring the jet flow rate. Here, the electrospinning jet flow rate is calculated by applying a new method and the effects of applied voltage and feed rate on jet charge density are investigated. The jet flow rate was independent of the feed rate and increased on increasing the applied voltage. By defining an experimental equation for dependence of jet flow rate on jet current, a relation between jet volume charge density and jet current could be defined. By measuring the electrospun fiber diameter, surface charge density of the jet could be estimated. On increasing the voltage, the jet volume charge density decreased whereas the jet surface charge density remained unchanged. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers
Design, selection, and characterization of a split chorismate mutase
Authors: Müller Manuel M. , Kries Hajo , Csuhai Eva , Kast Peter , Hilvert Donald 
Published: March 2010

AbstractSplit proteins are versatile tools for detecting protein–protein interactions and studying protein folding. Here, we report a new, particularly small split enzyme, engineered from a thermostable chorismate mutase (CM). Upon dissecting the helical‐bundle CM from Methanococcus jannaschii into a short N‐terminal helix and a 3‐helix segment and attaching an antiparallel leucine zipper dimerization domain to the individual fragments, we obtained a weakly active heterodimeric mutase. Using combinatorial mutagenesis and in vivo selection, we optimized the short linker sequences connecting the leucine zipper to the enzyme domain. One of the selected CMs was characterized in detail. It spontaneously assembles from the separately inactive fragments and exhibits wild‐type like CM activity. Owing to the availability of a well characterized selection system, the simple 4‐helix bundle topology, and the small size of the N‐terminal helix, the heterodimeric CM could be a valuable scaffold for enzyme engineering efforts and as a split sensor for specifically oriented protein–protein interactions.
Backbone additivity in the transfer model of protein solvation
Authors: Hu Char Y. , Kokubo Hironori , Lynch Gillian C. , Bolen D. Wayne , Pettitt B. Montgomery 
Published: March 2010

AbstractThe transfer model implying additivity of the peptide backbone free energy of transfer is computationally tested. Molecular dynamics simulations are used to determine the extent of change in transfer free energy (ΔGtr) with increase in chain length of oligoglycine with capped end groups. Solvation free energies of oligoglycine models of varying lengths in pure water and in the osmolyte solutions, 2Murea and 2MtrimethylamineN‐oxide (TMAO), were calculated from simulations of all atom models, and ΔGtrvalues for peptide backbone transfer from water to the osmolyte solutions were determined. The results show that the transfer free energies change linearly with increasing chain length, demonstrating the principle of additivity, and provide values in reasonable agreement with experiment. The peptide backbone transfer free energy contributions arise from van der Waals interactions in the case of transfer to urea, but from electrostatics on transfer to TMAO solution. The simulations used here allow for the calculation of the solvation and transfer free energy of longer oligoglycine models to be evaluated than is currently possible through experiment. The peptide backbone unit computed transfer free energy of −54 cal/mol/M compares quite favorably with −43 cal/mol/M determined experimentally.
Dimer–monomer equilibrium of human thymidylate synthase monitored by fluorescence resonance energy transfer
Authors: Genovese Filippo , Ferrari Stefania , Guaitoli Giambattista , Caselli Monica , Costi M. Paola , Ponterini Glauco 
Published: March 2010

AbstractAn ad hoc bioconjugation/fluorescence resonance energy transfer (FRET) assay has been designed to spectroscopically monitor the quaternary state of human thymidylate synthase dimeric protein. The approach enables the chemoselective engineering of allosteric residues while preserving the native protein functions through reversible masking of residues within the catalytic site, and is therefore suitable for activity/oligomerization dual assay screenings. It is applied to tag the two subunits of human thymidylate synthase at cysteines 43 and 43′ with an excitation energy donor/acceptor pair. The dimer–monomer equilibrium of the enzyme is then characterized through steady‐state fluorescence determination of the intersubunit resonance energy transfer efficiency.
Chronic systemic hypoxia promotes LNCaP prostate cancer growth in vivo
Authors: Terraneo Laura , Bianciardi Paola , Caretti Anna , Ronchi Raffaella , Samaja Michele 
Published: March 2010

AbstractOBJECTIVESolid tumors contain underperfused regions where hypoxia‐inducible factor‐1α (HIF‐1α) over‐expression induces hypoxia adaptation and cell proliferation. We test the hypothesis that systemic hypoxia promotes prostate cancer growth in vivo and examine HIF‐1α centrality in this effect.METHODSMale athymic mice were xenografted with 3 × 106 LNCaP cells per each flank and exposed for 28 days to either chronic hypoxia (CH, 10% O2) or CH with reoxygenation (CHReox, 3 times/week for 1 hr), with normoxia as control (n = 17, 9, and 20, respectively). At the end of the observation, mice were euthanized and tumors harvested for analyses.RESULTSThe successful xenografts grew faster in CH and CHReox than in normoxia (first‐order rate constants 0.15 ± 0.01, 0.18 ± 0.03, and 0.09 ± 0.01 day−1, P < 0.05, n = 18, 15, and 25, respectively). Furthermore, the tumor masses at the end were 4.09 ± 0.58, 3.42 ± 0.55, and 1.86 ± 0.25 mg/g bw (P < 0.05), respectively. HIF‐1α, assayed by Western blot and immunofluorescence, was slightly increased in CH with respect to normoxia, but markedly over‐expressed (5–10 times) in CHReox (P < 0.001). The tumor hemoglobin content, higher in CH and CHReox than in normoxia, reflected the higher blood hemoglobin concentration, not neovascularization, as supported by similar expression levels of vascular endothelial growth factor (VEGF) in the three groups. By contrast, protein kinase B (Akt) was more phosphorylated in both hypoxic groups than in normoxia (P < 0.01).CONCLUSIONIn vivo systemic hypoxia promotes prostate cancer growth regardless of HIF‐1α expression level and neovascularization, suggesting an important role for hypoxia‐dependent pathways that do not involve HIF‐1α, as the phosphatidyl inositol‐3‐phosphate signaling cascade. Prostate 70: 1243–1254, 2010. © 2010 Wiley‐Liss, Inc.
ToF‐SIMS investigations of adsorbed proteins on dental titanium
Authors: Wald J. , Müller C. , Wahl M. , Hoth‐Hannig W. , Hannig M. , Kopnarski M. , Ziegler C. 
Published: March 2010

AbstractTwo model proteins, bovine serum albumin (BSA) and lysozyme (LSZ), were used to study adsorption behavior on dental titanium by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). Protein films were prepared as single component layers and as mixtures of the two proteins. Additionally, the behavior of consecutive adsorption of both proteins was investigated. The obtained data were analyzed by means of principal component analysis (PCA). Dental titanium samples with a layer consisting of simply one protein could be separated from each other by selecting amino acid related peaks and using PCA or samples coated with a mixture of both proteins, the differentiation was also possible. The partial displacement of LSZ molecules by BSA was shown in the case of simultaneous adsorption. The consecutive adsorption of BSA and subsequently LSZ resulted in layers with a bigger amount of LSZ than of BSA compared to the layers obtained by simultaneous adsorption.
Application of segmented flow for quality control of food using microfluidic tools
Authors: Schemberg Jörg , Grodrian Andreas , Römer Robert , Cahill Brian P. , Gastrock Gunter , Lemke Karen 
Published: March 2010

AbstractThe integration of segmented flow into the development of a new rapid detection method for food‐borne pathogens is presented. The workflow is subdivided into different steps. The selective part is to catch contaminants from the food matrix. Afterward, the fluorescently labeled target cells converted from the cell suspension into droplets (nl‐scale). For this, microfluidic tools like glass or polydimethylsiloxane (PDMS) chips are necessary. It is the main step to determine the amount of contaminants (target cells) fluorescently inside one droplet. Therefore the number of target cells was detected by means of a microscope or by generating one droplet with one fluorescent target cell spectroscopically based on a yes‐ or no‐decision. For a competitive platform, PDMS as a cost‐effective chip‐module was integrated into an automatic microscopic detection system. For quality control during routine analysis a commercial spectroscopic detection system was used to measure the fluorescence signal. Based on these efforts a prototype design for spectroscopic detection was developed.
Fabrication and application of a microfluidic‐embedded silicon nanowire biosensor chip
Authors: Vu Xuan Thang , Stockmann Regina , Wolfrum Bernhard , Offenhäusser Andreas , Ingebrandt Sven 
Published: March 2010

AbstractWe report the fabrication of a silicon nanowire (SiNW) transistor array realized in a top‐down process on 4′′ silicon‐on‐insulator (SOI) wafers. This process is a second, optimized version combining thermal nanoimprint lithography and wet chemical etching to define planar nanowires and contact lines out of the top silicon layer in one etching step. We used ion implantation to reduce series resistance of source and drain contact lines. In total 56 individually addressable SiNWs were aligned in two lines. Wires dimensions were down to 60 nm in width and 40 nm in height having lengths up to 40 µm. Due to an improved processing we obtained almost identical wire structures and electronic properties throughout the 4′′ wafer enabling direct comparison of signals from one chip. The wires were capped by a microfuidic structure, which was used to administer different analyte solutions. First pH characterization measurements and molecular detection experiments using charged polyelectrolytes (PEs) and poly(D)lysine were successful. In future these devices could be used to observe diffusion of analytes in a time‐dependent, spatially‐ and quantitatively‐resolved readout.
GaAs nanowires grown by MOVPE
Authors: Bauer Jens , Paetzelt Hendrik , Gottschalch Volker , Wagner Gerald 
Published: March 2010

AbstractGaAs nanowire (NW) growth was studied by metal‐organic vapour phase epitaxy (MOVPE). The vapour–liquid–solid (VLS) mechanism with gold‐based alloy particles and the selective‐area growth (SAG) mechanism on electron beam lithographically prepared SiNx/GaAs mask structures were applied. A special focus is set on thermodynamic aspects of the VLS process. The alloy particle formation and the influence of MOVPE growth parameters on the growth rate and the GaAs NW morphology are examined. Furthermore, the improvement of the real structure with particular interest on the twin formation is studied. Besides the commonly used continuous VLS growth mode also a pulsed VLS growth mode with alternating precursor supply is reported. Based on photoluminescence measurements the effect of strain in core/shell NW structures is confirmed. For the SAG mechanism the MOVPE growth parameters are determined and the real structure is described. magnified image
Picosecond kinetics of the electron‐hole layers formation in wide‐bandgap II‐VI type‐II heterostructures
Authors: Filatov E.V. , Zaitsev S.V. , Tartakovskii I.I. , Maksimov A.A. , Yakovlev D.R. , Waag A. 
Published: March 2010

AbstractConsiderable slowdown of luminescence kinetics of the direct optical transition was discovered in ZnSe/BeTe type‐II heterostructures under high levels of optical pumping. The effect is attributed to forming of a potential barrier for holes in the ZnSe layer due to band bending at high densities of spatially separated carriers. That results in a longer time of the photoexcited holes energy relaxation to their ground state in the BeTe layer.The decrease of overlapping of electron and hole wavefunctions in the ZnSe layer in thick ZnSe/BeTe structures at high levels of optical excitation reveals an additional important effect, that leads to sufficient retardation of radiative recombination time for photoexcited carriers (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of elemental compositions by gas chromatography/time‐of‐flight mass spectrometry using chemical and electron ionization
Authors: Abate Salvatore , Ahn Yun Gyong , Kind Tobias , Cataldi Tommaso R. I. , Fiehn Oliver 
Published: March 2010

AbstractMany metabolomic applications use gas chromatography/mass spectrometry (GC/MS) under standard 70 eV electron ionization (EI) parameters. However, the abundance of molecular ions is often extremely low, impeding the calculation of elemental compositions for the identification of unknown compounds. On changing the beam‐steering voltage of the ion source, the relative abundances of molecular ions at 70 eV EI were increased up to ten‐fold for alkanes, fatty acid methyl esters and trimethylsilylated metabolites, concomitant with 2‐fold absolute increases in ion intensities. We have compared the abundance, mass accuracy and isotope ratio accuracy of molecular species in EI with those in chemical ionization (CI) with methane as reagent gas under high‐mass tuning. Thirty‐three peaks of a diverse set of trimethylsilylated metabolites were analyzed in triplicate, resulting in 342 ion species ([M+H]+, [M–CH3]+ for CI and [M]+., [M–CH3]+. for EI). On average, CI yielded 8‐fold more intense molecular species than EI. Using internal recalibration, average mass errors of 1.8 ± 1.6 mm/z units and isotope ratio errors of 2.3 ± 2.0% (A+1/A ratio) and 1.7 ± 1.8% (A+2/A ratio) were obtained. When constraining lists of calculated elemental compositions by chemical and heuristic rules using the Seven Golden Rules algorithm and PubChem queries, the correct formula was retrieved as top hit in 60% of the cases and within the top‐3 hits in 80% of the cases. Copyright © 2010 John Wiley & Sons, Ltd.
Evaluation of tetracationic salts as gas‐phase ion‐pairing agents for the detection of trivalent anions in positive mode electrospray ionization mass spectrometry
Authors: Zhang Xiaotong , Wanigasekara Eranda , Breitbach Zachary S. , Dodbiba Edra , Armstrong Daniel W. 
Published: March 2010

AbstractIn previous studies, new electrospray ionization mass spectrometry (ESI‐MS) approaches were developed for the highly sensitive detection of singly and doubly charged anions in positive mode ESI‐MS by using specially synthesized dicationic and tricationic ion‐pairing agents, respectively. By detecting the positively charged ion complex in the positive mode, limits of detection (LODs) for the anions can be lowered by several magnitudes. In this work, we used eighteen newly synthesized tetracationic ion‐pairing agents, constructed with different geometries, linkages and cation moieties, for the detection of eighteen triply charged anions of different structural motifs. The LODs for these anions were from ten to several thousand times lower in the positive selective ion monitoring (SIM) mode than in the negative mode. These tetracationic agents also were shown to be useful for the detection of −1 and −2 anions. In addition, the LODs for −3 anions can be further lowered by monitoring the product fragments of the ion‐pairing complexes in the single reaction monitoring (SRM) mode. Copyright © 2010 John Wiley & Sons, Ltd.
In situ probing of cholesterol in astrocytes at the single‐cell level using laser desorption ionization mass spectrometric imaging with colloidal silver
Authors: Perdian D. C. , Cha Sangwon , Oh Jisun , Sakaguchi Donald S. , Yeung Edward S. , Lee Young Jin 
Published: March 2010

AbstractMass spectrometric imaging has been utilized to localize individual astrocytes and to obtain cholesterol populations at the single‐cell level in laser desorption ionization (LDI) with colloidal silver. The silver ion adduct of membrane‐bound cholesterol was monitored to detect individual cells. Good correlation between mass spectrometric and optical images at different cell densities indicates the ability to perform single‐cell studies of cholesterol abundance. The feasibility of quantification is confirmed by the agreement between the LDI‐MS ion signals and the results from a traditional enzymatic fluorometric assay. We propose that this approach could be an effective tool to study chemical populations at the cellular level. Published in 2010 by John Wiley & Sons, Ltd.
Release kinetics of actives from chewing gums into saliva monitored by direct analysis in real time mass spectrometry
Authors: Jeckelmann Nicolas , Haefliger Olivier P. 
Published: March 2010

AbstractDirect analysis in real time mass spectrometry (DART‐MS) was used to monitor the release kinetics of a taste‐refreshing compound from chewing gums into the saliva of subjects. A new DART‐MS sample probe was designed which was about four times more sensitive than the current benchmark probe. This decreased the impact of the dilution of the saliva samples that was required to minimize ion suppression effects and make quantitative analyses without an internal standard possible. The new probe was also about three times more reproducible, which allowed quantitative measurements to be conducted manually without requiring the enhanced precision provided by an automatic sample positioner. The accuracy of analyses performed by DART‐MS was verified by comparing the results obtained from saliva samples analyzed both by DART‐MS and by a more classical liquid chromatography/mass spectrometry (LC/MS) method. This investigation showed good agreement between the two techniques. DART‐MS could then be used to objectively demonstrate the efficiency of a granular carbohydrate‐based delivery system to boost for a few minutes the release of a lipophilic flavor raw material with a high octanol/water partition coefficient, cyclohexanecarboxamide, N‐ethyl‐5‐methyl‐2‐(1‐methylethyl) (WS‐3), from chewing gum into saliva. Copyright © 2010 John Wiley & Sons, Ltd.
Elevation moment of inertia: A new feature for Monte Carlo localization in outdoor environment with elevation map
Authors: Kwon Tae‐Bum , Song Jae‐Bok , Joo Sang‐Hyun 
Published: March 2010

AbstractThe elevation map is one of the most popular maps for outdoor navigation. We propose the elevation moment of inertia (EMOI), which represents the distribution of elevation around a robot in an elevation map, for use in the matching of elevation maps. Using this feature, outdoor localization can be performed with an elevation map without external positioning systems. In this research, the Monte Carlo localization (MCL) method is used for outdoor localization, and the conventional method is based on range matching, which compares range sensor data with the range data predicted from an elevation map. Our proposed method is based on EMOI matching. The EMOI around a robot is compared with the EMOIs for all cells of the pregiven reference elevation map to find a robot pose with respect to the reference map. MCL based on EMOI matching is very fast, although its accuracy is slightly lower than that of conventional range matching. To deal with the disadvantage of EMOI matching, an adaptive switching scheme between EMOI matching and range matching was also proposed. Various outdoor experiments indicated that the proposed EMOI significantly reduced the convergence time of MCL. Therefore, the proposed feature is considered to be useful when an elevation map is used for outdoor localization. © 2010 Wiley Periodicals, Inc.
Atomic force microscopy study on chlorpromazine‐induced morphological changes of living HeLa cells In Vitro
Authors: Li Yongjun , Zhang Jing , Zhang Bailin 
Published: March 2010

AbstractChlorpromazine (CPZ)‐induced morphological changes of living human cervical carcinoma cells were investigated by atomic force microscopy in near physiological condition. The results showed that the cell morphology changed visibly with time in the presence of CPZ (>21 µM). The cell membrane shrank gradually and detached finally from the substrate. After being treated with CPZ for 50 min, the cell volume increased by about 27.6% while its projective area (cell adhered to the substrate) decreased by about 12%. The mechanism was also discussed. SCANNING 31: 259–265, 2009. © 2010 Wiley Periodicals, Inc.