bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design of a drug delivery system based on poly(acrylamide‐co‐acrylic acid)/chitosan nanostructured hydrogels
Authors: Becerra‐Bracamontes Fausto , Sánchez‐Díaz Juan C. , González‐Álvarez Alejandro , Ortega‐Gudiño Pedro , Michel‐Valdivia Enrique , Martínez‐Ruvalcaba Agustín 
Published: September 2007

AbstractTo obtain biodegradable materials for biomedical applications, new biopolymeric hydrogels based on blends of polyacrylamide nanoparticles and chitosan have been prepared. In this work, we have studied the behavior of the diffusion of ascorbic acid (V‐C) from poly(acrylamide‐co‐acrylic acid)/chitosan nanostructured hydrogels. The process involves the synthesis of nanoparticles of polyacrylamide by inverse microemulsion polymerization and their complexation with chitosan dissolved in an acrylic acid aqueous solution. We have studied the effect of the concentration of the polyacrylamide nanoparticles, which are crosslinked with N,N′‐methylenebisacrylamide, in the delivery of V‐C. The results indicate that the drug delivery operates by a non‐Fickian mechanism. Also, we have obtained the diffusion coefficient for V‐C in gels for different nanoparticle concentrations, using a modified form of Fick's second law that takes into account dimensional changes in the hydrogels during drug release. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Synthesis and characterization of polycyanurate networks modified by oligo(ϵ‐caprolactone) as precursors of porous thermosets
Authors: Fainleib A. , Grigoryeva O. , Garda M. R. , Saiter J. M. , Lauprêtre F. , Lorthioir C. , Grande D. 
Published: September 2007

AbstractOligo(ϵ‐caprolactone)‐modified polycyanurate networks were synthesized by thermal polycyclotrimerization of dicyanate ester of bisphenol E in the presence of a dihydroxy‐telechelic poly(ϵ‐caprolactone) (PCL) oligomer with varying compositions. Using FTIR, gel fraction content and density measurements, it has been proved that the main part of the reactive modifier was chemically incorporated into the PCN network structure. According to the thermal behavior of the polymer networks as investigated by TGA, they can be divided into two groups. The first group of systems with low modifier content (i.e., up to 20 wt %) is characterized by one stage of decomposition under nitrogen, and two stages under oxygen. A second group of systems with higher modifier content is generally characterized by two stages of decomposition in nitrogen and three stages in oxygen. DSC and DMTA investigations have shown the occurrence of at least a two‐phase structure in all the samples. The PCN/PCL‐based hybrid networks can be effectively used as precursors for the generation of porous PCN thermosets, as evidenced by FTIR and SEM. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Influence of H+ and Cl− ions on inhibitive performance of poly(aniline) for iron corrosion in acid
Authors: Manivel P. , Sathiyanarayanan S. , Venkatachari G. 
Published: September 2007

AbstractThe inhibition effect of poly(aniline) on pure iron corrosion in 1M HCl and with various H+ ions and Cl− ions concentrations was investigated by the polarization and electrochemical impedance spectroscopy methods. The results showed that poly(aniline) suppressed both cathodic and anodic processes of iron dissolution in 1M HCl by its adsorption on the iron surface according to Langmuir's adsorption isotherm. The inhibition efficiency of poly(aniline) was found to increase with the inhibitor concentrations. Further, it was observed that, there was no significant variation in corrosion potential (Ecorr) values in the presence of inhibitors suggesting that, this polymer behaved as mixed type inhibitor. Similar studies for the inhibitor at 500 ppm in various concentrations of H+ and Cl− ions, have shown that the inhibition efficiency decreases with decrease in concentrations of H+ ions and Cl− ions in aqueous solution. It reveals that, the adsorption of inhibitor on iron surface is by more cationic form of inhibitor and higher efficiency at higher H+ and Cl− ions is due to enhanced adsorption of cat ionic form of inhibitor molecules. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Additives effects on the shrinkage behavior of PVC sheets
Authors: Hadi P. , Babaluo A. A. 
Published: September 2007

AbstractDespite the unique applications of heat shrinkable PVC sheets in food packaging industry, a few works have been carried out on the shrinkage behavior of this kind of sheets. So, in our work, investigation of the shrinkability of PVC sheets and influence of different parameters on the above‐mentioned property has been focused, intensively. This paper presents the results of research aimed at characterizing the shrinkage behavior of PVC sheets, accompanied by the effect of different additives and their weight fractions on the shrinkability of the prepared sheets using experimental design Taguchi method. Also, shrinkage behavior of PVC sheets at optimum conditions has been studied and the stretching and shrinking temperature effects have been investigated. It was found that, among seven investigated variables, plasticizer has the most significant effect on the shrinkability of PVC sheets. Also, at optimum conditions, an increase in the stretching temperature can extensively influence the crystalline structure of the polymer and subsequently, shrinking temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Preparation and properties of dough‐modeling compound/fly ash/reclaim powder composites
Authors: Wu Weili 
Published: September 2007

AbstractA novel composite was prepared with reclaim powder (RP) matrix, dough‐modeling compound (DMC) reinforcement and fly ash (FA) filler in this article. The compatibility and crosslinking construction of the FA/RP composites were respectively, studied by the polarizing microscope and IR, the optimal formulation and experimental process were determined by measuring the mechanical properties such as shore A hardness, tensile strength, elongation at break, wear resistance and the thermal stability. The results showed that DMC/FA/RP composites exhibited extremely high mechanical and thermal properties when the mass ratio of the DMC/FA/RP composites was 45/25/100, and the cure condition is at 145°C for 30 min under 9 MPa. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Germanates of 1D Chains, 2D Layers, and 3D Frameworks Built from Ge–O Clusters by Using Metal‐Complex Templates: Host–Guest Symmetry and Chirality Transfer
Authors: Liu Guang‐Zhen , Zhang Hong‐Xia , Lin Zhi‐En , Zheng Shou‐Tian , Zhang Jie , Zhao Jing‐Tai , Wang Guo‐Ming , Yang Guo‐Yu 
Published: September 2007

AbstractThe self‐assembly of Ge–O polyhedra by metal‐complex templates leads to initial examples of open germanate structures under mild solvothermal conditions. These materials are constructed from Ge–O cluster building bocks (Ge7X19 (X=O, OH, or F) or Ni@Ge14O24(OH)3) and span the full range of dimensionalities from 1D chains of Ge7O13(OH)2F3⋅Cl⋅2[Ni(dien)2] (FJ‐6) to 2D layers of Ge7O14F3⋅0.5[In(dien)2]⋅0.5H3dien⋅ 2H2O (1) and 3D frameworks of Ni@ Ge14O24(OH)3⋅2[Ni(L)3] (FJ‐1 a/FJ‐1 b) (dien=diethylenetriamine, L=ethylenediamine (en) or 1,2‐diaminopropane (enMe)). The Ge7X19 cluster in FJ‐6 and 1 is formed by condensation of four GeX4 tetrahedra, two GeX5 trigonal bipyramids, and one GeX6 octahedron with a μ3‐O atom at the center of the cluster, whereas the Ni@ Ge14O24(OH)3 cluster in FJ‐1 a/FJ‐1 b is formed by condensation of nine peripheral GeO4 tetrahedra and five interior GeO3Ni units with one μ5‐Ni atom at the center of the cluster. FJ‐6 is characterized by a pair of racemic Ge7O14(OH)2F3 cluster chains and represents only one example of 1D germanates; 1 exhibits unique germanate layers with uniform 10‐membered‐ring apertures encapsulating an unknown indium complex, and the framework structure of FJ‐1 a/FJ‐1 b with large 24‐membered‐ring channels is the first example of porous materials that contain metal–metal bonds (Ge2+Ni+). These initial examples of germanates from metal‐complex templates provide a useful model system for understanding the mechanisms of host–guest interactions, which may further facilitate the design and development of new porous materials “on demand”. It is shown that the symmetry and configuration of the guest metal complex can be imprinted onto the host inorganic framework through hydrogen bonding between host and guest.
Finite‐Elemente‐Methode für geotechnische Nachweise nach neuer Normung?
Authors: Heibaum Michael , Herten Markus 
Published: September 2007

AbstractFür geotechnische Berechnungen nimmt der Einsatz der Finite‐Elemente‐Methode (FEM) dank immer leistungsfähigerer Rechner zu, weshalb untersucht werden muss, inwieweit dieses Berechnungsverfahren für geotechnische Nachweise entsprechend den europäischen und deutschen Normen geeignet ist. Die nach Norm geforderten Sicherheiten basieren auf bestimmten Modellen und den damit vorliegenden Erfahrungen, die nicht ungeprüft auf andere Ansätze übertragen werden können. Für die Nachweise gemäß DIN 1054 bzw. dem Verfahren 2* nach EN 1997‐1 wird unter Verwendung von Berechnungsbeispielen gezeigt, dass Einwirkungen und Beanspruchungen gut mit der FEM ermittelt werden können. Auch Widerstände können durchaus berechnet werden. Die Erfahrungsgrundlage zur Beurteilung ihrer Verlässlichkeit ist jedoch zu gering, so dass zum gegenwärtigen Zeitpunkt die bestehende Vorgehensweise beibehalten werden sollte. Ebenso kann eine Abweichung von den festgelegten Sicherheiten nicht ausreichend abgesichert werden.
Zusammenführung von europäischen und deutschen Normen Eurocode 7, DIN 1054 und DIN 4020
Authors: Schuppener Bernd , Ruppert Franz‐Reinhard 
Published: September 2007

AbstractDer Eurocode 7, “Entwurf, Berechnung und Bemessung in der Geotechnik”, liegt mit seinen beiden Teil en: DIN EN 1997‐1 “Allgemeine Regeln” und DIN EN 1997‐2 “Erkundung und Untersuchung des Baugrunds” seit September 2007 vollständig in deutscher Sprache vor. Der Inhalt dieser beiden Teil e des Eurocode deckt sich zum Teil mit zwei fundamentalen deutschen Normen der Geotechnik, DIN 1054:2005‐1 “Baugrund – Sicherheitsnachweise im Erd‐ und Grundbau” und DIN 4020:2003‐09 “Geotechnische Untersuchungen für bautechnische Zwecke”. Die Regeln der Europäischen Union verlangen, dass nach einer Kalibrierungsperiode von zwei Jahren und einer Koexistenzperiode von weiteren drei Jahren alle deutschen Normen zurückgezogen werden müssen, die Regelungen der Eurocodes enthalten. In etwa drei bzw. fünf Jahren werden daher DIN 1054 und DIN 4020 in der jetzigen Form nicht mehr gültig sein und durch überarbeitete Fassungen abgelöst werden. Es wird dargestellt, welche inhaltlichen und formalen Anpassungen für die zukünftigen deutschen geotechnischen Normen erforderlich werden und wie die in den deutschen Normen enthaltenen speziellen deutschen Erfahrungen im Erd‐ und Grundbau in das neue Normenwerk integriert werden.
Ein Ansatz zur versuchstechnischen Simulation und Übertragbarkeit der Hydroabrasion strömungsbeanspruchter Betonoberflächen im Wasserbau
Authors: Helbig Ulf , Horlacher Hans‐B. 
Published: September 2007

AbstractAn strömungsbeanspruchten Bauwerksoberflächen des konstruktiven Wasserbaus oder auch des Siedlungswasserbaus werden regelmäßig Schäden unterschiedlichster Art, insbesondere durch Hydroabrasion, beobachtet und in der Fachliteratur dargestellt und dokumentiert. Das im Folgenden beschriebene Verfahren stellt auf der Basis des Einsatzes von Abrasionstrommeln einen Ansatz zur versuchstechnischen Simulation und Übertragbarkeit verschiedener praktisch auftretender Abrasionsregimes dar. Hierbei ist wesentlich zu beachten, dass natürliche Fließgewässer unterschiedliche Einflussgrößen bezüglich vorhandener Fließgeschwindigkeiten, Geschiebezusammensetzungen und resultierender Feststofftransportraten aufweisen. Dies ist sowohl bei der Bemessung von Bauwerksoberflächen als auch bei der versuchstechnischen Replikation zu beachten.
The effect of mobile phone electromagnetic fields on the alpha rhythm of human electroencephalogram
Authors: Croft R.J. , Hamblin D.L. , Spong J. , Wood A.W. , McKenzie R.J. , Stough C. 
Published: September 2007

AbstractMobile phones (MP) emit low‐level electromagnetic fields that have been reported to affect neural function in humans; however, demonstrations of such effects have not been conclusive. The purpose of the present study was to test one of the strongest findings in the literature; that of increased “alpha” power in response to MP‐type radiation. Healthy participants (N = 120) were tested using a double‐blind counterbalanced crossover design, with each receiving a 30‐min Active and a 30‐min Sham Exposure 1 week apart, while electroencephalogram (EEG) data were recorded. Resting alpha power (8–12 Hz) was then derived as a function of time, for periods both during and following exposure. Non‐parametric analyses were employed as data could not be normalized. Previous reports of an overall alpha power enhancement during the MP exposure were confirmed (relative to Sham), with this effect larger at ipsilateral than contralateral sites over posterior regions. No overall change to alpha power was observed following exposure cessation; however, there was less alpha power contralateral to the exposure source during this period (relative to ipsilateral). Employing a strong methodology, the current findings support previous research that has reported an effect of MP exposure on EEG alpha power. Bioelectromagnetics 29:1–10, 2008. © 2007 Wiley‐Liss, Inc.
Some effects of a buried electricity transmission cable on bulk soil
Authors: Scalenghe Riccardo 
Published: September 2007

AbstractA case study in NW Italy investigating an underground electric line (1 m depth triple cable at operative voltages 220–380 kV) measured electric fields in the surrounding soil virtually close to zero but magnetic fields (µTs) 20 times the background level. After 6 months, the influence radius around the cable on microbial activity (estimated by soil ATP), organic carbon, and total nitrogen follows exactly the inverse trend of the MF, shifting the biological activity with a lag distance of 5 m from the 220 kV cable. Bioelectromagnetics 28:667–671, 2007. © 2007 Wiley‐Liss, Inc.
An elementary metabolite unit (EMU) based method of isotopically nonstationary flux analysis
Authors: Young Jamey D. , Walther Jason L. , Antoniewicz Maciek R. , Yoo Hyuntae , Stephanopoulos Gregory 
Published: September 2007

AbstractNonstationary metabolic flux analysis (NMFA) is at present a very computationally intensive exercise, especially for large reaction networks. We applied elementary metabolite unit (EMU) theory to NMFA, dramatically reducing computational difficulty. We also introduced block decoupling, a new method that systematically and comprehensively divides EMU systems of equations into smaller subproblems to further reduce computational difficulty. These improvements led to a 5000‐fold reduction in simulation times, enabling an entirely new and more complicated set of problems to be analyzed with NMFA. We simulated a series of nonstationary and stationary GC/MS measurements for a large E. coli network that was then used to estimate parameters and their associated confidence intervals. We found that fluxes could be successfully estimated using only nonstationary labeling data and external flux measurements. Addition of near‐stationary and stationary time points increased the precision of most parameters. Contrary to prior reports, the precision of nonstationary estimates proved to be comparable to the precision of estimates based solely on stationary data. Finally, we applied EMU‐based NMFA to experimental nonstationary measurements taken from brown adipocytes and successfully estimated fluxes and some metabolite concentrations. By using NFMA instead of traditional MFA, the experiment required only 6 h instead of 50 (the time necessary for most metabolite labeling to reach 99% of isotopic steady state). Biotechnol. Bioeng. 2008;99: 686–699. © 2007 Wiley Periodicals, Inc.
Identification of age‐structured models: Cell cycle phase transitions
Authors: Sherer E. , Tocce E. , Hannemann R.E. , Rundell A.E. , Ramkrishna D. 
Published: September 2007

AbstractA methodology is developed that determines age‐specific transition rates between cell cycle phases during balanced growth by utilizing age‐structured population balance equations. Age‐distributed models are the simplest way to account for varied behavior of individual cells. However, this simplicity is offset by difficulties in making observations of age distributions, so age‐distributed models are difficult to fit to experimental data. Herein, the proposed methodology is implemented to identify an age‐structured model for human leukemia cells (Jurkat) based only on measurements of the total number density after the addition of bromodeoxyuridine partitions the total cell population into two subpopulations. Each of the subpopulations will temporarily undergo a period of unbalanced growth, which provides sufficient information to extract age‐dependent transition rates, while the total cell population remains in balanced growth. The stipulation of initial balanced growth permits the derivation of age densities based on only age‐dependent transition rates. In fitting the experimental data, a flexible transition rate representation, utilizing a series of cubic spline nodes, finds a bimodal G0/G1 transition age probability distribution best fits the experimental data. This resolution may be unnecessary as convex combinations of more restricted transition rates derived from normalized Gaussian, lognormal, or skewed lognormal transition‐age probability distributions corroborate the spline predictions, but require fewer parameters. The fit of data with a single log normal distribution is somewhat inferior suggesting the bimodal result as more likely. Regardless of the choice of basis functions, this methodology can identify age distributions, age‐specific transition rates, and transition‐age distributions during balanced growth conditions. Biotechnol. Bioeng. 2008;99: 960–974. © 2007 Wiley Periodicals, Inc.
Purification of an acidic recombinant protein from transgenic tobacco
Authors: Holler Chris , Zhang Chenming 
Published: September 2007

AbstractTobacco has proven to be a promising alternative for the production of recombinant therapeutic proteins and offers numerous advantages over other plants as a host system. However, the recovery and purification steps needed to obtain a protein at high recovery and purity have not been well investigated. In this study, a process was developed to purify a model acidic protein, recombinant β‐glucuronidase (rGUS) from transgenic tobacco leaf tissue, in three main steps after extraction: polyelectrolyte precipitation, hydrophobic interaction chromatography (HIC), and hydroxyapatite chromatography (HAC). Using this three‐step process, up to 40% of the initial rGUS activity could be recovered to near homogeneity as judged by SDS–PAGE. This work demonstrates that acidic recombinant proteins expressed in tobacco may be purified to high yield with high purity in a minimal amount of steps that are suitable for scale‐up. Furthermore, the general steps used in this process may suggest that a wide variety of acidic recombinant proteins may be purified in a similar manner from transgenic tobacco or other leafy crops. Biotechnol. Bioeng. 2008;99: 902–909. © 2007 Wiley Periodicals, Inc.
Electrooptical measurements for monitoring metabolite fluxes in acetone–butanol–ethanol fermentations
Authors: Junne Stefan , Klein Eva , Angersbach Alexander , Goetz Peter 
Published: September 2007

AbstractAnisotropy of electrical polarizability in Clostridium acetobutylicum cells during pH 5 controlled acetone butanol ethanol fermentations was observed. Cell length was determined from the electrooptical data. Mean length was determined as being 2.5 μm in the growth phase and 3.5 μm in the early stationary phase. Based on the obtained frequency dispersion of polarizability anisotropy (FDPA) in the range of 190 to 2,100 kHz, the switch from the acidogenic to the solventogenic phase could be monitored. The slope of polarizability versus the frequency made it possible to differentiate between phases of dominating acid and solvent production. Metabolite fluxes determined from concentration measurements correlated well to the polarizability. A partial least‐squares (PLS) model was established and validated by applying data from several fermentations. The root mean square error of calibration (RMSEC) was 0.09 for the acid fluxes and 0.11 for the solvent fluxes. The root mean square error of prediction (RMSEP) was 0.20 for acid fluxes and 0.24 for solvent fluxes. The ratio of polarizability at high and low frequencies correlated to the ongoing sporulation process. At ratios below 0.25, spore formation in the cells became visible under the microscope. The advantage of using electrooptical measurements is the ability to observe metabolite fluxes rather than concentrations, which provides useful information on productivity during a bioprocess. Biotechnol. Bioeng. 2008;99: 862–869. © 2007 Wiley Periodicals, Inc.
Silicon Analogues of the Retinoid Agonists TTNPB and 3‐Methyl‐TTNPB, Disila‐TTNPB and Disila‐3‐methyl‐TTNPB: Chemistry and Biology
Authors: Büttner Matthias W. , Burschka Christian , Daiss Jürgen O. , Ivanova Diana , Rochel Natacha , Kammerer Sabrina , Peluso‐Iltis Carole , Bindler Audrey , Gaudon Claudine , Germain Pierre , Moras Dino , Gronemeyer Hinrich , Tacke Reinhold 
Published: September 2007

AbstractTwofold sila‐substitution (C/Si exchange) in the saturated ring of the tetrahydronaphthalene skeleton of the retinoid agonists TTNPB (1 a) and 3‐methyl‐TTNPB (2 a) leads to disila‐TTNPB (1 b) and disila‐3‐methyl‐TTNPB (2 b), respectively. The silicon compounds 1 b and 2 b were synthesized in multiple steps, and their identities were established by elemental analyses, multinuclear NMR experiments, and single‐crystal X‐ray diffraction studies. Like TTNPB (1 a) and 3‐methyl‐TTNPB (2 a), the analogous silicon‐based arotinoids 1 b and 2 b are strong pan‐RAR agonists and display the same strong differentiation and apoptosis‐inducing activity in NB4 promyelocytic leukemia cells as the parent carbon compounds. These results are in keeping with the nearly isomorphous structures of 1 a and 1 b bound to the complex of the RARβ ligand‐binding domain with the nuclear receptor (NR) box 2 peptide of the SRC‐1 coactivator. The contacts within the ligand‐binding pocket are identical except for helix H11, for which two turns are shifted in the disila‐TTNPB (1 b) complex. This study represents the first comprehensive structure–function analysis of a carbon/silicon switch in a signaling molecule and demonstrates that silicon analogues can have the same biological functionalities and conserved structures as their parent carbon compounds, and it illustrates at the same time that silicon analogues of biologically active compounds have the potential to induce alternative allosteric effects, as in the case of helix H11, which might allow for novel options in drug design.