bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two‐stage synthesis of sorbitan esters, and physical properties of the products
Authors: Smidrkal Jan , Cervenkova Radka , Filip Vladimir 
Published: December 2004

AbstractA series of sorbitan‐fatty acid esters with various fatty acid/sorbitol ratios was prepared using a 2‐stage process. In the first stage, sorbitol was dehydrated to sorbitan at 180 °C (using phosphoric acid as catalyst), and in the second stage, the sorbitan was esterified with the fatty acid at 220 °C (sodium hydroxide as catalyst). The course of the reaction was monitored and the composition of final products was determined by thin‐layer chromatography using a flame‐ionisation detector (TLC‐FID). The properties (surface tension, melting points, viscosity) of prepared sorbitan esters depend on the molecular ratio of fatty acid and sorbitol. The described method is suitable for the preparation of sorbitan esters at industrial scale.
Alcoholysis of waste fats with 2‐ethyl‐1‐hexanol using Candida antarctica lipase A in large‐scale tests
Authors: Brenneis Rudolf , Baeck Burkhard , Kley Gerd 
Published: December 2004

AbstractCommercial native lipase A from Candida antarctica was used to produce alkyl esters through the alcoholysis of (waste) fats with 2‐ethyl‐1‐hexanol. The process was carried out in batch stirred tank reactors (from 100 mL up to 3000 L).The content of alkyl esters in reaction mixtures was determined by gradient HPLC using an evaporative light scattering detector and the reaction progress was controlled by determining the ratio of the palmitic acid ester peak area to the oleic acid ester peak area in HPLC chromatograms.The results show that alcoholysis is the favoured reaction in presence of excess water and water‐insoluble alcohols in comparison with hydrolysis (fatty acid content <5%). The optimum amount of water for the alcoholysis was found to be 80–100% of the amount of fat. In the presence of low quantities of water both alcoholysis and hydrolysis are slow.Conversion rate increases with increasing temperature to 65–70 °C.Based on these results a large‐scale test to produce 3000 L of alkyl ester (to be used as lubricant coolant) was carried out. The experiments have proved that alcoholysis is completed after about 7–10 h depending on temperature.
Recent advances in microemulsion electrokinetic chromatography
Authors: Marsh Alex , Clark Brian , Broderick Margo , Power Joe , Donegan Sheila , Altria Kevin 
Published: December 2004

AbstractMicroemulsion electrokinetic chromatography (MEEKC) is an electrodriven separation technique. Separations are typically achieved using oil‐in‐water microemulsions, which are composed of nanometre‐sized droplets of oil suspended in aqueous buffer. The oil droplets are coated in surfactant molecules and the system is stabilised by the addition of a short‐chain alcohol cosurfactant. The novel use of water‐in‐oil microemulsions for MEEKC separations has also been investigated recently. This report summarises the different microemulsion types and compositions used to‐date and their applications with a focus on recent papers (2002–2004). The effects of key operating variables (pH, surfactant, cosurfactant, oil phase, buffer, additives, temperature, organic modifier) and methodology techniques are described.
The combination of flow injection with electrophoresis using capillaries and chips
Authors: Chen Xingguo , Fan Liuyin , Hu Zhide 
Published: December 2004

AbstractThe combined flow injection capillary electrophoresis (FI‐CE) system that integrates the essential favorable merits of FI and CE, can significantly expand the application scope of CE by exploring the various on‐line sample pretreatments and preconcentration of FI. The principle behind this technique, some innovative designs of the split‐flow interface, as well as novel applications to a variety of analytical problems, are reviewed and discussed. Some salient features and unique advantages of this technique are outlined.
Dual injection capillary electrophoresis: Foundations and applications
Authors: Priego‐Capote Feliciano , Luque de Castro Maria D. 
Published: December 2004

AbstractThe state of the art of capillary electrophoresis (CE) approaches based on dual injection is here reported. Dual injection strategies have been proposed with three main objectives: (i) to provide information about reaction kinetics and/or related parameters, (ii) to perform in‐capillary derivatization for improving separation and/or determination, (iii) to develop electrophoretic methods for the simultaneous analysis of anionic and cationic compounds. For the first two purposes, dual injection, which involves sample and reagent, can be realized either from the same end of the capillary (electrophoretically mediated microanalysis, EMMA) or from the two ends of the capillary (electroinjection analysis, EIA). The third objective, with dual injection of sample from the two ends of the capillary, takes advantage of moving cationic and anionic compounds with opposite directions. The foundations of each alternative, conditions necessary for working with them, restrictions, applications as well as perspectives are reviewed in order to establish the advantages, shortcomings, and convenience or no of their use in comparison to conventional CE.
The GEOTOP snow module
Authors: Zanotti Fabrizio , Endrizzi Stefano , Bertoldi Giacomo , Rigon Riccardo 
Published: December 2004

AbstractA snow accumulation and melt module implemented in the GEOTOP model is presented and tested. GEOTOP, a distributed model of the hydrological cycle, based on digital elevation models (DEMs), calculates the discharge at the basin outlet and estimates the local and distributed values of several hydro‐meteorological quantities. It solves the energy and the mass balance jointly and deals accurately with the effects of topography on the interactions among radiation physics, energy balance and the hydrological cycle. Soil properties are considered to depend on soil temperature and moisture, and the heat and water transfer in the soil is modelled using a multilayer approach. The snow module solves for the soil–snow energy and mass exchanges, and, together with a runoff production module, is embedded in a more general energy balance model that provides all the boundary conditions required. The snowpack is schematized as a single snow layer where a limited number of physical processes are described. The module can be seen essentially as a parameter‐free model. The application to an alpine catchment (Rio Valbiolo, Trentino, Italy), monitored by an in situ snow‐depth sensor, is discussed and shown to give results comparable to those of more complex models. Copyright © 2004 John Wiley & Sons, Ltd.
Effects of LDL‐immunoapheresis on plasma concentrations of vitamin E and carotenoids in patients with familial hypercholesterolemia
Authors: Cauza Edmund , Jansen Martin , Resch Ulrike , Dunky Attila , Derfler Kurt , Winklhofer‐Roob Brigitte M. , Kostner Karam 
Published: December 2004

AbstractRecently very potent extracorporeal cholesterol‐lowering treatment options have become available for patients with hypercholesterolemia. LDL immunoapheresis treatment selectively removes LDL and lipoprotein(a) from the circulation. Since LDL is the major carrier of lipophilic antioxidants in plasma, the purpose of the present study was to assess the effects of a single LDL apheresis treatment on plasma concentrations of tocopherols (α‐ and γ‐tocopherol) and carotenoids (α‐ and β‐carotene, zeaxanthin, cryptoxanthin, canthaxanthin, lycopene, and retinol). Plasma antioxidant concentrations were determined by HPLC in 7 patients with familial hypercholesterolemia before and after LDL immunoapheresis treatment. Plasma concentrations of both α‐ and γ‐tocopherol and the different carotenoids were significantly reduced by LDL apheresis. However, when standardized for cholesterol to adjust for cholesterol removal, α‐ and γ‐tocopherol, retinol, and the more polar carotenoids lutein and zeaxanthin increased in response to apheresis treatment, while the more unpolar carotenoids such as β‐carotene and lycopene did not change. These data demonstrate that a single LDL immunoapheresis treatment affects tocopherols and individual carotenoids differently. This may be explained by differences in chemical structure and preferential association with different lipoproteins. These results further imply that tocopherols, lutein, zeaxanthin, and retinol, are associated in part with lipoproteins and other carriers such as retinol‐binding protein that are not removed during apheresis treatment. J. Clin. Apheresis 19:174–179, 2004. © 2004 Wiley‐Liss, Inc.
New Fluorinated Thermoplastic Elastomers, 4
Authors: Andre Sébastian , Guida‐Pietrasanta Francine , Rousseau Alain , Boutevin Bernard , Caporiccio Gérardo 
Published: December 2004

AbstractSummary: The synthesis of fluorinated polyimide‐polyhybridsiloxane block copolymers (FPI‐HPHSX) was performed by polycondensation of α,ω‐dichlorosilane fluorinated polyimides (SiCl‐FPI) and α,ω‐disilanol‐polyhybridsiloxanes (SiOH‐HPHSX). The α,ω‐disilanol polyhybridsiloxanes were synthesized by polyhydrosilylation between 1,7‐octadiene and hexamethyltrisiloxane (HMTS). The resulting siloxanes exhibit a glass transition temperature close to −98 °C. The α,ω‐dichlorosilane fluorinated polyimide was prepared by hydrosilylation of α,ω‐diallyl fluorinated polyimide and dimethylchlorosilane in the presence of Karstedt's catalyst. Then a series of four FPI‐HPHSX was synthesized by polycondensation and, with tuning of the number average molecular weight ($\overline M _{\rm n}$) of the soft polyhybridsiloxane and the hard polyimide groups, they were characterized. The influence of the segment lengths on the behavior (surface tension and thermal stability) of the thermoplastic elastomer (TPE) material was studied. The FPI‐HPHSX block copolymers' thermomechanical properties are also reported and discussed.General procedure for the synthesis of alternating block copolymers FPI‐HPHSX by polycondensation.magnified imageGeneral procedure for the synthesis of alternating block copolymers FPI‐HPHSX by polycondensation.
1H and 13C spectral assignments of 7β‐(cinnamoyl‐substituted)amino‐3‐acetoxymethyl‐cephalosporins
Authors: López Miguel A. , Rodríguez Zalua , González Maritza , Tolón Blanca , Avila Rizette , Mamposo Taimirys , Vélez Hermán , Fini Adamo 
Published: December 2004

AbstractThe 1H and 13C spectroscopic data for 7β‐(cinnamoyl‐substituted)amino‐3‐acetoxymethyl‐cephalosporins were fully assigned by a combination of one‐ and two‐dimensional experiments. Substitution on the aromatic ring and on the double‐bond α‐position of the cinnamoyl moiety has little influence on the spectroscopic properties of the 7β‐aminocephalosporanic acid parent moiety. Copyright © 2004 John Wiley & Sons, Ltd.
The (3,4) Mode Interaction in the GeoFlow Framework
Authors: Beltrame Philippe , Egbers Christoph 
Published: December 2004

AbstractThe problem of convection in a self‐gravitating spherical shell of fluid is commonly encountered in sciences like astrophysics and geophysics (earth's liquid core). The GEOFLOW‐experiment is a project of the European Space Agency in order to perform the spherical Rayleigh‐Bénard convection problem on the International Space Station in a micro‐gravity environment: the central force field is simulated by a dielectrophoretic one. Beyond a critical Rayleigh number Rac, generically an unique spherical ℓ mode becomes unstable and only stationary or travelling waves solutions are expected near the onset. But, for a critical aspect ratio ηc two consecutive modes (ℓ, ℓ + 1) are unstable. The (1,2) and (2,3) interactions have showed a rich bifurcation diagram, in particular, we have found heteroclinic cycles predicted by the theoretical study. Because of the experiment requirements, only the (3,4) one is possible. So, this paper purposes to analyse this bifurcation in non‐rotating case in the GEOFLOWframework using the theory of bifurcation with the spherical symmetry.
Numerical simulation of 1‐D incompressible laminar micro‐flow convection behaviour with temperature dependent fluid properties
Authors: Mahulikar S. P. , Herwig H. , Hausner O. , Kock F. 
Published: December 2004

AbstractThis paper investigates the qualitative behaviour of single‐phase laminar convection for microchannels and conventionallysized channels formed between two parallel plates, captured by a numerical simulation on water flow. The convection parameters are obtained by separate numerical calculations on a series of parallel plates at constant temperatures. The pairs of parallel plates are maintained at progressively greater temperatures, to simulate the condition of increasing fluid temperature in a channel. The governing one‐dimensional (1‐D) momentum and energy equations are formulated to incorporate the dependence on temperature of both fluid viscosity (μ) and thermal conductivity (k). The qualitative behaviour of Nusselt number (Nu) decreasing with increasing Reynolds number (Re), exhibited by reported experimental data in literature, is simulated. Results show that it is practically dif_cult to observe this behaviour in the conventionally‐sized channels, but the effect easily surfaces in microchannels for practical lengths of flow and allowable high heat flux (q″W). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Isotropic models for a heat transfer in periodic composites
Authors: Wierzbicki Ewaryst , Siedlecka Urszula 
Published: December 2004

AbstractA macroscopic model for the non – stationary heat transfer processes in a periodic honeycomb – type anisotropic rigid conductor is formulated. The main aim of this contribution is to show that the macroscopic properties of this conductor are isotropic. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experiments on baroclinic instabilities
Authors: von Larcher Th. , Beyer W. , Egbers C. 
Published: December 2004

AbstractWe study experiments on baroclinic instabilities in a different heated rotating annulus cooled from within. Characteristic time series of the flow velocity are measured with the Laser–Doppler–Velocimetry (LDV) technique. The surface flow is observed with a co–rotating camera. Steady waves as well as complex flow states are observed. Hysteresis is also found. The drift rate of stable baroclinic waves is determined. The methods of non–linear time series analysis are used to investigate the dynamics of baroclinic waves, particulary in transition zones between different flow regimes. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Taylor‐Couette Strömung von Nichtnewtonschen Fluiden
Authors: Smieszek M. , Farnik J. , Egbers C. 
Published: December 2004

AbstractEs wird das Strömungsverhalten von einem Newtonschen und einem Nichtnewtonschen Fluid im Taylor‐Couette System untersucht. Für beide Fluide werden Stabilitätsdiagramme aufgenommen. Das Nichtnewtonsche Fluid basiert auf einer Saccharoselösung und einem Polyacrylamid. Als Newtonsches Fluid wird ein Silikonöl (Baysilone M3) eingesetzt. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A ray‐integral solution for the wave‐field in the Sommerfeld model
Authors: Borejko Piotr 
Published: December 2004

AbstractA ray‐integral solution is presented for the wave‐field in the Sommerfeld model (liquid half‐space over solid half‐space), where a point source is placed in the fluid and the two media (fluid and solid) of contrasting densities and wave speeds are homogeneous. This exact closed form solution is then used to evaluate complete time records of the acoustic pressure (at a point receiver located in the fluid in the vicinity of the penetrable fluid‐solid interface) for two Sommerfeld models: one where the shear wave speed in the solid bottom is lower than the sound speed in the fluid and the other where the shear wave speed is higher. These pressure response curves indicate the relative importance of the various wave‐forms (the critically refracted longitudinal and shear waves, the pseudo‐Rayleigh and Stoneley interface waves, the direct wave, and the totally reflected wave) contributing to the solution and the possibility of utilizing the arrival times of the refracted and interface waves to determine the bottom rigidity. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sound Insulation of Porous Plates
Authors: Busse Anke , Schanz Martin 
Published: December 2004

AbstractBecause of the still increasing noise pollution the numerical simulation of acoustic problems becomes more and more important. One essential aspect is the numerical treatment of noise insulation of solid walls. The main noise source is the bending vibration of separating components. In general, they consist of porous material, e.g., concrete or bricks. To take into account the porous structure as well as the damping effect of the porosity of these components a poroelastic plate theory is developed. The Finite Element implementation of this plate theory shows the importance of taking porous materials into account. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FEM–BEM–Kopplung und strukturakustische Sensitivitätsanalyse f ür Schalengeometrien
Authors: Fritze Denny , Marburg Steffen , Hardtke Hans‐Jürgen 
Published: December 2004

AbstractDurch lokale Veränderungen der Geometrie kann bei Schalen direkt in die Steifigkeit und somit in das Schwingungsverhalten bzw. die Schallemission eingegriffen werden. In der gradientenbasierten strukturakustischen Optimierung stellt allerdings die Sensitivitätsanalyse den zeitaufwendigsten Teil dar. Es wird ein Konzept vorgestellt, welches die Schalengeometrie parametrisiert, die Fluid‐Struktur‐Kopplung vereinfacht und strukturelle Sensitivitäten effizient bestimmt. Dabei wird für die Strukturanalyse die Finite‐Elemente‐Methode und für die akustische Simulation die Randelementemethode verwendet. Beide Verfahren werden dann so gekoppelt, daß an der Schnittsteile nichtidentische Diskretisierungen beider Modelle zugelassen werden. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Composite beams with shape memory alloy fibres
Authors: Kuczma Mieczysław S. 
Published: December 2004

AbstractWe are concerned with the bending problem of fibrous composite beams in which fibres are made of shape memory alloys. These are alloys that may undergo a stress‐induced martensitic phase transformation. The matrix is treated as an elastic medium, and perfect bonding between matrix and fibres is supposed. In our model, the beam is decomposed into layers and the hysteretic behaviour of the shape memory fibres is taken into account. The boundary value problem is formulated in the form of an evolution variational inequality which, after finite element discretization, can be solved incrementally as a sequence of linear complementarity problems. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of filler size and heat treatment on the crystallization behavior of glass bead‐filled polypropylene
Authors: Yuan Qiang , Jiang Wei , An Lijia , Li R. K. Y. 
Published: December 2004

AbstractThe effects of glass bead (GB) size and annealing temperature on the formation of β‐crystals of glass bead‐filled polypropylene (PP) are studied in this articles. Differential scanning calorimetry (DSC) measurements indicated that the amount of β‐form in PP crystals was a function of the glass bead content and size. For a fixed glass bead content, it was found that the smaller the diameter of the glass bead, the higher was the content of β‐crystals formed in the PP. On the other hand, wide‐angle X‐ray diffraction (WAXD) measurements revealed that the annealing temperature was also a major factor that affected the crystallization behavior of glass bead‐filled PP. It seemed that the blends with different glass bead contents had their own optimal annealing temperatures for β‐crystal formation. As an example, when the glass bead content was 48 wt %, the optimal annealing temperature for β‐crystal formation was about 108 °C, whereas it shifted to 100 °C for 14 wt % glass bead‐filled polypropylene. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 306–313, 2005
Pseudospin Hamiltonian parameters evaluated with regard to alkali metal ions in K3(H/D)(SO4)2 materials
Authors: Dolin S. P. , Levin A. A. , Mikhailova T. Yu. , Solin M. V. , Gavriluyk A. B. , Polyakov E. V. 
Published: December 2004

AbstractAn analysis of ferroelectric behavior of K3(H/D)(SO4)2 as members of the M3(H/D)(AO4)2 family is examined quantum chemically in the cluster approach using the structural models extended through the incorporation of K ions in an explicit form. We apply several structural models that describe the different types of (H/D)(SO4)2‐dimer surrounded by K ions, the geometry of the dimer being borrowed from the corrected diffraction data of the K3D(SO4)2 crystal in its ordered phase at the temperature below critical point Tc = 85 K. The calculations of the pseudospin Hamiltonian parameters—the Ising coupling parameters Jij and tunneling integrals Ω—were performed on the Hartree–Fock and second‐order Møller–Plesset perturbation theory levels with the 6‐31G–type basis sets. It is demonstrated that an effect of the K ions incorporation on the Jij values is minor (about several Kelvins). At the same time an influence of these ions on the double‐well potential characteristics (particularly, on the barrier heights) and thus on the tunneling integral value is more pronounced for both D‐ and H‐containing species. Despite the changes of the Hamiltonian parameters found, the major conclusion obtained earlier, referring to the suppression of the structural phase transition in H‐containing specimens due to proton quantum fluctuations, remains valid. The numerical estimations of the critical temperature Tc for completely deuterated materials that are obtained with and without regard to alkali metal ions are discussed. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Initial velocity distributions of ions generated by in‐flight laser desorption/ionization of individual polystyrene latex microparticles as studied by the delayed ion extraction method
Authors: Vera César Costa , Trimborn Achim , Hinz Klaus‐Peter , Spengler Bernhard 
Published: December 2004

AbstractThe delayed ion extraction method has been used to study characteristics of the initial velocity distributions of positive and negative ions produced simultaneously by laser desorption/ionization (LDI) from non‐impacted single aerosol polymeric particles, using a bipolar time‐of‐flight (TOF) instrument (LAMPAS 2). Due to the geometry of the setup and the characteristics of the ablation process, only the projections of the velocities on the axis of the mass spectrometer can be directly studied. Additionally, since the mean initial velocity under these conditions should be close to zero, it was necessary to extend the method by taking into account higher order contributions of the velocity distribution. Theoretical expressions for these higher order terms are presented and discussed. The bipolar characteristics of the instrument permit evaluation and treatment of a possible instrumental artifact caused by small inclinations of the ionizing laser with respect to the ideal incidence direction. Results of a number of experiments are presented and discussed in relation to the theoretical expressions presented, and to possible ablation scenarios. Evidence pointing out that, under our experimental conditions, only partial ablation of the latex particles occurs was obtained. The variance of the distribution of the projection of the initial velocities can be directly estimated from these results. By assuming that the total initial velocities of the ions are developed completely according to a single‐temperature adiabatic expansion mechanism, temperatures of approximately 50  K/Da can be assigned to the ion clouds from the variance estimations. If a two‐temperature model is used, a radial temperature of about 100 K/Da results. These values are in reasonable agreement with results for polymer ablation from the literature. Copyright © 2004 John Wiley & Sons, Ltd.