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Theoretical approaches suggest that dynamic light scattering (DLS) signals from low-molecular-weight ternary mixtures are governed by fluctuations in temperature as well as two individual contributions from fluctuations in concentration that are related to the eigenvalues of the Fick diffusion matrix. Until now, this could not be proven experimentally in a conclusive way. In the present study, a detailed analysis of DLS signals in ternary mixtures consisting of n-dodecane (n-C12H26) and n-octacosane (n-C28H58) with dissolved hydrogen (H2), carbon monoxide (CO), or water (H2O) as well as of n-C12H26 or n-C28H58 with dissolved H2 and CO is given for temperatures up to 523 K and pressures up to 4.1 MPa. Thermal diffusivities of pure n-C12H26 and n-C28H58 as well as thermal and mutual diffusivities of their binary mixtures being the basis for the ternary mixtures with dissolved gas were studied for comparison purposes. For the investigated ternary mixtures, three individual signals could be distinguished in t...

The influence of fin structure and density on the condensation heat transfer of refrigerant 1,1,1,2-tetrafluoroethane (R134a) is investigated on single finned tubes and in corresponding bundles. Experiments have been performed on standard and enhanced finned tubes with 39, 48, and 56 fins per inch (FPI) and different fin heights. The enhanced finned tubes are based on the standard ones, and are characterized by a non-uniform fin structure. The condensation heat transfer coefficient (HTC) is determined for single tubes as well as for each row of the tube bundles and compared with predictions from analytical models. In the single tube measurements, the enhanced finned tubes showed distinctly higher HTCs than the standard finned tubes. Different condensation flow modes have been observed during the tube bundle experiments where the additional structures on the fin flank of the enhanced finned tubes promote sheet mode condensation. It has been demonstrated that the standard finned tubes show a lower decrease in the condensation HTC with increasing tube row number in the bundle than the enhanced finned tubes. Among the standard finned tubes, the one with 48 FPI and larger fin height exhibits the highest HTCs for single tube and tube bundle experiments. The increase in the fin height seems to delay the formation of sheet mode condensation and thus to increase the condensation HTC. Among the enhanced finned tubes, the tube with 39 FPI yields the highest HTCs for both single tube and tube bundle measurements. Low fin density and large fin height obviously tend to keep the insulating effect of retained condensate in the fin channels low.

In this study, a new analytical model for the effective thermal conductivity of liquids containing dispersed spherical and non-spherical nanometer particles was developed. In addition to heat conduction in the base fluid and the nanoparticles, we also consider convective heat transfer caused by the Brownian motion of the particles. For nanoparticle suspensions, the latter mechanism has significant influence on the effective thermal conductivity, which is reduced compared to a system in which only conduction is considered. The simple model developed allows for the prediction of the effective thermal conductivity of nanofluids as a function of volume fraction, diameter, and shape of the nanoparticles as well as temperature. Due to the inconsistency of experimental data in the literature, the model has been compared with the established Hamilton–Crosser model and other empirical models for the systems aluminum oxide (Al2O3) and titanium dioxide (TiO2) suspended in water and ethylene glycol. The theoretical estimates show no anomalous enhancement of the effective thermal conductivity and agree very well with the Hamilton–Crosser model within relative deviations of less than 8% for volume fractions of spherical particles up to 0.25. In accordance with the Hamilton–Crosser model for non-spherical particles, our model reveals that a more distinct increase in the enhancement of the effective thermal conductivity can be achieved using non-spherical nanoparticles having a larger volume-specific surface area.

The present work demonstrates that by the analysis of the dynamics of non-equilibrium fluctuations using the shadowgraph method, the thermal diffusivity, the Fick diffusion coefficient, the kinematic viscosity, and the Soret coefficient of a binary mixture can be determined from a single thermodiffusion experiment. The study was performed for a mixture consisting of equal masses of 1,2,3,4-tetrahydronaphthalene and n-dodecane in a newly developed shadowgraph apparatus at temperatures up to 373 K and pressures up to 40 MPa. The obtained results are mainly discussed in the light of their uncertainties at varying thermodynamic states for evaluating the benefits, drawbacks, and potentials of the apparatus. The Fick diffusion coefficient and the thermal diffusivity obtained with average expanded uncertainties of 2.8% and 6.6% agree with literature data and measurements for the same mixture taken by heterodyne dynamic light scattering. Current limitations of the method are reflected by the distinctly larger uncertainties of the kinematic viscosity and the Soret coefficient. Corresponding reasons and potential measures to overcome the limitations are discussed.

Ethnopharmacological relevance The haemorrhagic dengue fever affects up to 500 million patients, annually causing 20.000 deaths, with no chemotherapeutic agent available. The oleoresin labdanum of Cistus creticus L. has been established as an anti-infective agent since antiquity in Mediterranean ethnopharmacology. Materials and methods We tested several extracts and fractions of labdanum - standardised on labdane-type diterpenes via GC-MS - on their activity against the dengue virus (DENV-2 strain 00st-22A) in in vitro Vero cell cultures (96-well-plates, 5 days). Preliminary experiments with a labdanum diethyl ether raw-extract did not yield measureable results due to cytotoxic effects against Vero cells. In all following experiments, cell viability was constantly checked using the MTT-test. Fractionation of this raw-extract by liquid-liquid-extraction and column-chromatography on silica-gel (gradient elution with hexane, EtOAc, CHCl3, MeOH) succeeded in separating the anti-viral activity of labdanum from its cytotoxic effect. Results In the most active fraction GS5 at 30 μg/ml, the dengue virus proliferation was 100% suppressed and cell viability was over 90%. Structural elucidation of major constituents of GS5 is currently ongoing, but thin-layer chromatography showed that this fraction is manly dominated by manoyloxides, a class of labdane-type diterpenes with known antimicrobial activity. Claims concerning the antiviral activity of above ground parts of C. creticus have been made previously, but these generally ascribe this activity to hot water soluble polyphenols and propose an unspecific tanning effect of the viral surface proteins as the mechanism of action. However, the water soluble fraction enhanced viral proliferation. Conclusion We therefore describe a direct, pharmacological, antiviral activity of a dichloromethane extract of labdanum against a virulent haemorrhagic fever like dengue for the first time.

Local and regional species extirpations may become more common as changing climate and disturbance regimes accelerate species’ in situ range contractions. Identifying locations that function as both climate and disturbance refugia is critical for biodiversity conservation. Here, we investigate the persistence of a disjunct, fire-sensitive conifer population, yellow-cedar (Callitropsis nootkatensis), in the historically frequent-fire landscape of the Blue Mountains in eastern Oregon, USA. We used tree rings to reconstruct multi-century fire histories, which were then used to compare historical mean fire return intervals (MFRIs) inside of the cedar grove to the surrounding dry forest matrix, as well as to examine relationships between historical fire occurrence and reconstructed climate. We also examined trends in post-fire yellow-cedar mortality and regeneration between 2006, when the grove burned in a wildfire, through 2017. Results indicated that fire was less frequent in the cedar grove (MFRI = 35.8 years) than in the surrounding dry mixed-conifer forest (MFRI = 14.4 years). Historical fire occurrence was associated with hotter and drier conditions. Following the 2006 fire, cedar mortality was high (>90%), but by 2017 post-fire regeneration was abundant (median = 8125 seedlings ha-1). The eastern Oregon cedar grove appears to occupy a fire refugium historically decoupled from the frequent-fire regime of the broader landscape. The topographic position of the grove suggests it is also a climate refugium. Despite high mortality following fire in 2006, yellow-cedar is regenerating in the grove. Managing for climate and disturbance refugia has been identified as an important option for conservation in the context of rapid global change, and this study provides evidence that locations where climate and disturbance refugia overlap may be disproportionately important for the maintenance of regional biodiversity. However, active management may be required for populations to persist in some of these locations as anthropogenic change is capable of overwhelming the underlying buffering capacity of refugia.

Binary diffusion coefficients D12 for the molecular gas systems propane–methane (C3H8–CH4) and propane–carbon dioxide (C3H8–CO2) have been measured with a Loschmidt cell combined with holographic interferometry at (293 and 313) K, between (0.05 and 0.5) MPa, and for different mixture compositions. Improved experimental and evaluation procedures already validated for the noble-gas system helium–krypton have been successfully adapted for the molecular gas systems. For the investigated mixtures, adsorption–desorption processes are superimposed on the diffusion process and increase the achievable uncertainties. This hinders reliable conclusions regarding a concentration dependency of the diffusion coefficient. D12 clearly increases with increasing temperature and decreasing pressure. At the same pressure, temperature, and C3H8 mole fraction, the diffusion coefficient is larger for C3H8–CH4 than for C3H8–CO2. For both systems, the presented diffusion coefficients are in reasonable agreement with available literature data. In particular, the pressure-dependent trend and the absolute values of D12 at a given temperature match with recent theoretical data based on ab initio calculations in the zero-density limit for both systems.

The present work represents a continuation of a former study where the simultaneous determination of thermal and mutual diffusivity for binary mixtures of n-octacosane (n-C28H58) with dissolved carbon monoxide (CO), hydrogen (H2), or water (H2O) by using dynamic light scattering (DLS) was demonstrated. Here, the same properties are studied for binary mixtures of the n-alkanes n-dodecane (n-C12H26) or n-tetracontane (n-C40H82) with dissolved CO, H2, or H2O. In most cases, expanded relative uncertainties (k = 2) ranging from 2 to 12 % and 3 to 25 % for the thermal and mutual diffusivities could be obtained. The experimental mutual diffusivities for mixtures of n-C12H26 with CO, H2, or H2O measured at temperatures from 398 to 524 K and pressures from 0.2 to 4.2 MPa at saturation conditions agree well with molecular dynamics (MD) simulations using atomistic models and with experimental data from literature. Binary mixtures of n-C40H82 with dissolved CO, H2, or H2O were investigated in a temperature range from...

The viscosity of pure n-alkanes and n-alkane mixtures was studied by molecular dynamics (MD) simulations using the Green–Kubo method. n-Alkane molecules were modeled based on the Transferable Potential for Phase Equilibria (TraPPE) united atom force field. MD simulations at constant number of molecules or particles, volume and temperature (NVT) were performed for n-C8 up to n-C96 at different temperatures as well as for binary and six-component n-alkane mixtures which are considered as prototypes for the hydrocarbon wax produced during the Gas-To-Liquid (GTL) Fischer–Tropsch process. For the pure n-alkanes, good agreement between our simulated viscosities and existing experimental data was observed. In the case of the n-alkane mixtures, the composition dependence of viscosity was examined. The simulated viscosity results were compared with literature empirical correlations. Moreover, a new macroscopic empirical correlation for the calculation of self-diffusion coefficients of hydrogen, carbon monoxide, and water in n-alkanes and mixtures of n-alkanes was developed by combining viscosity and self-diffusion coefficient values in n-alkanes. The correlation was compared with the simulation data and an average absolute deviation (AAD) of 11.3% for pure n-alkanes and 14.3% for n-alkane mixtures was obtained.

Liquid organic hydrogen carrier (LOHC) systems constitute a very promising concept for future hydrogen storage and logistics. The concept builds on the conversion of excess renewable energy to hydrogen via electrolysis followed by reversible catalytic hydrogenation/dehydrogenation of a diesel-like organic carrier molecule. For an ideal design of the catalytic process, insight into reaction mechanisms and kinetics but also precise knowledge on mass transport properties are necessary. In the present study, binary diffusion coefficients in selected binary LOHC mixtures with five different compositions of perhydrodibenzyltoluene (H18-LOHC) and dibenzyltoluene (LOHC) were measured by dynamic light scattering (DLS). The compositions were defined by mixing appropriate amounts of LOHC and H18-LOHC to realize different hydrogenation degrees of the LOHC. Binary diffusion coefficients were investigated over a temperature range from (264 to 571) K with an absolute uncertainty of (3 to 25) %. Moreover, an empirical eq...

The liquid density, liquid kinematic viscosity, and surface tension of the segregated hydrofluoroethers (HFEs) HFE-7000 (1,1,1,2,2,3,3-heptafluoro-3-methoxy-propane), HFE-7100 (mixture of the isomers 1,1,1,2,2,3,3,4,4-nonafluoro-4-methoxy-butane and 1,1,1,2,3,3-hexafluoro-3-methoxy-2-(trifluoromethyl)propane), HFE-7200 (mixture of the isomers 1-ethoxy-1,1,2,2,3,3,4,4,4-nonafluorobutane and 1-ethoxy-1,1,2,3,3,3-hexafluoro-2-(trifluoromethyl)propane), HFE-7300 (1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)pentane), and HFE-7500 (3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-(trifluoromethyl)hexane) were studied in dependence on temperature under saturation conditions. A vibrating-tube densimeter was used for the measurement of the saturated-liquid density at temperatures from (273.15 to 363.15) K with a relative expanded uncertainty (k = 2) of 0.02 %. The kinematic viscosity of the liquid phase and surface tension were obtained on the basis of surface light scattering (SLS) measurements for...

The paper reports on binary diffusion coefficient data for the gaseous systems argon–neon, krypton–helium, ammonia–helium, nitrous oxide–nitrogen, and propane–helium measured using a Loschmidt cell combined with holographic interferometry between (293.15 and 353.15) K as well as between (1 and 10) bar. The investigations on the noble gas systems aimed to validate the measurement apparatus by comparing the binary diffusion coefficients measured as a function of temperature and pressure with theoretical data. In previous studies, it was already shown that the raw concentration-dependent data measured with the applied setup are affected by systematic effects if pure gases are used prior to the diffusion process. Hence, the concentration-dependent measurement data were processed to obtain averaged binary diffusion coefficients at a mean mole fraction of 0.5. The data for the molecular gas systems complete literature data on little investigated systems of technical interest and point out the capabilities of the applied measurement apparatus. Further experimental data are reported for the systems argon–helium, krypton–argon, krypton–neon, xenon–helium, xenon–krypton, nitrous oxide–carbon dioxide, and propane–carbon dioxide at 293.15 K, 2 bar, and a mean mole fraction of 0.5.

The present paper reports on efforts to explain discrepancies which were found in concentration-dependent binary diffusion coefficient data determined with a Loschmidt cell combined with holographic interferometry using pure gases prior to the diffusion process. While the binary diffusion coefficient data which are determined in the upper half-cell decrease with the mole fraction of the heavier component, those determined in the lower half-cell increase. The reason for such discrepancies, which can also be found in other literature data obtained with interferometric gas analysis methods, is not clear. Therefore, systematic experimental and theoretical investigations on the Loschmidt experiment and the applied evaluation procedure were performed. Furthermore, the influence of different driving forces on the particle flux was examined. Although the reason for the discrepancies between the measurement data determined in each half-cell could not been clarified, various reasons that have been debated in the literature could be excluded. Moreover, experiments using a gas mixture in one of the half-cells suggested that the evaluation procedure is most likely to be the reason for the observed discrepancies.

The surface tension of nine tricyanomethanide ([C(CN)3]−)- and tetracyanoborate ([B(CN)4]−)-based ionic liquids (ILs) carrying a homologous series of the 1-alkyl-3-methylimidazolium ([alkyl-MIM]+) cations [EMIM]+ (ethyl), [BMIM]+ (butyl), [HMIM]+ (hexyl), [OMIM]+ (octyl), and [DMIM]+ (decyl) was measured with the pendant drop method in the temperature range between (283 and 353) K at atmospheric pressure with an estimated uncertainty of 2 % (k = 2). For the probed ILs, the surface tension decreases with increasing temperature and increasing alkyl chain length of the cation. Smaller values for the [B(CN)4]−-based ILs compared to the [C(CN)3]−-based ILs having the same cation were observed. The measured surface tensions agree with the limited number of experimental data found in the literature for the two IL families. A simple prediction based on the surface tension measured at 293 K and the temperature dependence of density showed good agreement with the measured temperature-dependent data. In comparison t...

Ionic liquids (ILs) are possible working fluids for the separation of carbon dioxide (CO2) from flue gases. For evaluating their performance in such processes, reliable mutual-diffusivity data are required for mixtures of ILs with relevant flue gas components. In the present study, dynamic light scattering (DLS) and molecular dynamics (MD) simulations were used for the investigation of the molecular diffusion in binary mixtures of the IL 1-ethyl-3-methylimidazolium tetracyanoborate ([EMIM][B(CN)4]) with the dissolved gases carbon dioxide, nitrogen, carbon monoxide, hydrogen, methane, oxygen, and hydrogen sulfide at temperatures from 298.15 to 363.15 K and pressures up to 63 bar. At conditions approaching infinite dilution of a gas, the Fick mutual diffusivity of the mixture measured by DLS and the self-diffusivity of the corresponding gas calculated by MD simulations match, which could be generally found within combined uncertainties. The obtained diffusivities are in agreement with literature data for the same or comparable systems as well as with the general trend of increasing diffusivities for decreasing IL viscosities. The DLS and MD results reveal distinctly larger molecular diffusivities for [EMIM][B(CN)4]-hydrogen mixtures compared to mixtures with all other gases. This behavior results in the failure of an empirical correlation with the molar volumes of the gases at their normal boiling points. The DLS experiments also showed that there is no noticeable influence of the dissolved gas and temperature on the thermal diffusivity of the studied systems.

We present a collections-based checklist for bryophyte and lichen species known or expected to occur within the boundaries of Malheur National Forest, an administrative unit spanning several climatic zones and vegetation types in the semi-arid Blue Mountains of eastern Oregon. A synthesis of survey, literature and herbarium records yielded 2 hornwort species, 51 liverworts, 219 mosses and 276 lichens. Notable bryophytes included: Anoectangium aestivum, Bruchia bolanderi, Bryum calobryoides, Calliergonella lindbergii, Racomitrium depressum, Fontinalis hypnoides, Preissia quadrata and Schistidium cinclidodonteum. Notable lichens included: Lecanora pringlei, Peccania arizonica, Placidiopsis cinerascens, Schaereria dolodes and 6 calicioid lichens. We also provide conservation notes and conclude with a brief synopsis of collecting history in the region.

ZusammenfassungDie regulatorische Situation pflanzlicher Arzneimittel (einschließlich der Formulierungen der traditionellen japanischen ­Kampo-Medizin) und verwandter Produktkategorien in Japan ist deutlich komplexer als das entsprechende europäische ­Pendant. Um eine gemeinsame Basis für das Verständnis von japanischer Kampo-Medizin und westlicher Phytotherapie zu schaffen, erklärt der vorliegende Artikel die grundlegenden gesetzlichen Kategorien von Phytopharmaka in Japan für ein deutsches Publikum. Die folgenden Seiten konzentrieren sich auf Übersetzungen der ­wesentlichen Fachbegriffe sowie eine ­Erklärung der zum Verständnis jeweils ­notwendigen Hintergrundinformationen.

In the present study, dynamic light scattering (DLS) experiments and molecular dynamics (MD) simulations were used for the investigation of the molecular diffusion in binary mixtures of liquids with dissolved gases at macroscopic thermodynamic equilibrium. Model systems based on the n-alkane n-hexane or n-decane with dissolved hydrogen, helium, nitrogen, or carbon monoxide were studied at temperatures between 303 and 423 K and at gas mole fractions below 0.06. With DLS, the relaxation behavior of microscopic equilibrium fluctuations in concentration and temperature is analyzed to determine simultaneously mutual and thermal diffusivity in an absolute way. The present measurements document that even for mole gas fractions of 0.007 and Lewis numbers close to 1, reliable mutual diffusivities with an average expanded uncertainty ( k = 2) of 13% can be obtained. By use of suitable molecular models for the mixture components, the self-diffusion coefficient of the gases was determined by MD simulations with an averaged expanded uncertainty ( k = 2) of 7%. The DLS experiments showed that the thermal diffusivity of the studied systems is not affected by the dissolved gas and agrees with the reference data for the pure n-alkanes. In agreement with theory, mutual diffusivities and self-diffusivities were found to be equal mostly within combined uncertainties at conditions approaching infinite dilution of the gas. Our DLS and MD results, representing the first available data for the present systems, reveal distinctly larger mass diffusivities for mixtures containing hydrogen or helium compared to mixtures containing nitrogen or carbon monoxide. On the basis of the broad range of mass diffusivities of the studied gas-liquid systems covering about 2 orders of magnitude from about 10

Low-viscosity ionic liquids (ILs) based on the anions [B(CN)4]− (tetracyanoborate) and [C(CN)3]− (tricyanomethanide) are currently discussed as alternative working fluids for various applications. The dynamic viscosity of such ILs carrying [1-alkyl-MIM]+ (1-alkyl-3-methylimidazolium) cations was investigated via determination of the translational particle diffusion coefficient by dynamic light scattering (DLS). The long-term stability of suspensions of different particles in the ILs, their particle diameters, and the influence of laser power on the measured particle diffusion coefficient for semitransparent ILs were studied. For temperatures from 283 to 353 K at atmospheric pressure, the dynamic viscosity of the four pure ILs forming stable suspensions was obtained with an uncertainty of less than 5% (k = 2) and agrees with literature. Absorption of CO2 at pressures up to 0.87 MPa induced a distinct decrease in the dynamic viscosity. Differences between the viscosities of the different systems can be expl...

In this study, we demonstrate the ability of polarization-difference Raman spectroscopy (PDRS) to detect dissolved free water molecules in a n-octacosane (n-C28H58) liquid-rich phase, and thus to determine its solubility, at temperatures and pressures relevant to the Fischer–Tropsch synthesis. Our results for the pure alkane reveal thermal decomposition above a temperature of 500 K as well as an increase of gauche conformers of the alkane chains with an increase in temperature. For binary homogeneous mixtures, raw spectra obtained from two different polarization scattering geometries did not show a relevant signal in the OH stretching frequency range. In contrast, isotropic spectra obtained from the PDRS technique reveal a narrow and tiny peak associated with the dangling OH bonds. Over the complete range of temperatures and pressures, no signature of hydrogen-bonded water molecules was observed in the isotropic Raman scattering intensities. A thorough investigation covering a large range of temperatures ...

In the present study, dynamic light scattering (DLS) experiments and molecular dynamics (MD) simulations were used for the investigation of the molecular diffusion in binary mixtures of liquids with dissolved gases at macroscopic thermodynamic equilibrium. Model systems based on the n-alkane n-hexane or n-decane with dissolved hydrogen, helium, nitrogen, or carbon monoxide were studied at temperatures between 303 and 423 K and at gas mole fractions below 0.06. With DLS, the relaxation behavior of microscopic equilibrium fluctuations in concentration and temperature is analyzed to determine simultaneously mutual and thermal diffusivity in an absolute way. The present measurements document that even for mole gas fractions of 0.007 and Lewis numbers close to 1, reliable mutual diffusivities with an average expanded uncertainty ( k = 2) of 13% can be obtained. By use of suitable molecular models for the mixture components, the self-diffusion coefficient of the gases was determined by MD simulations with an averaged expanded uncertainty ( k = 2) of 7%. The DLS experiments showed that the thermal diffusivity of the studied systems is not affected by the dissolved gas and agrees with the reference data for the pure n-alkanes. In agreement with theory, mutual diffusivities and self-diffusivities were found to be equal mostly within combined uncertainties at conditions approaching infinite dilution of the gas. Our DLS and MD results, representing the first available data for the present systems, reveal distinctly larger mass diffusivities for mixtures containing hydrogen or helium compared to mixtures containing nitrogen or carbon monoxide. On the basis of the broad range of mass diffusivities of the studied gas-liquid systems covering about 2 orders of magnitude from about 10-9 to 10-7 m2·s-1, effects of the solvent and solute properties on the temperature-dependent mass diffusivities are discussed. This contributed to the development of a simple semiempirical correlation for the mass diffusivity of the studied gases dissolved in n-alkanes of varying chain length at infinite dilution as a function of temperature. The generalized expression requiring only information on the kinematic viscosity and molar mass of the pure solvent as well as the molar mass and acentric factor of the solute represents the database from this work and further literature with an absolute average deviation of about 11%.

The thermal conductivity of ten ionic liquids (ILs) based on the anions $$[\mathrm{C(CN)}_{3}]^{-}$$ (tricyanomethanide) and $$[\mathrm{B(CN)}_{4}]^{-}$$ (tetracyanoborate) carrying a homologous series of the [alkyl-MIM] $$^{+}$$ (1-alkyl-3-methylimidazolium) cations [EMIM] $$^{+}$$ (ethyl), [BMIM] $$^{+}$$ (butyl) [HMIM] $$^{+}$$ (hexyl), [OMIM] $$^{+}$$ (octyl), [DMIM] $$^{+}$$ (decyl) was measured by a steady-state guarded parallel-plate instrument in the temperature range between (283.15 and 353.15) K at atmospheric pressure with a total uncertainty of 5 % ( $$k\,=\,2$$ ). Furthermore, the refractive index required for data evaluation and the density, which is an important property in the developed prediction method for the thermal conductivity, were determined. In general, the measured thermal conductivities of the probed ILs decrease with increasing temperature and increasing alkyl-chain length of the cation. Regarding the influence of the anion, somewhat smaller values for the $$[\mathrm{B(CN)}_{4}]^{-}$$ -based ILs compared to the $$[\mathrm{C(CN)}_{3}]^{-}$$ -based ILs carrying the same cation are observed. Our previously developed simple prediction method for the thermal conductivity of ILs at 293.15 K using only information on the molar mass and the density could be improved. By the combination of this approach with the temperature dependence of the density, an extended empirical correlation additionally describing the temperature dependence of the thermal conductivity of ILs is recommended. This correlation represents all experimental thermal-conductivity data in the literature with a standard deviation of less than 7 %.

The applicability of dynamic light scattering (DLS) for the characterization of the size of supercritical carbon dioxide (sc-CO2)-swollen micelles in a polyester polyol-based multicomponent microemulsion with nonionic surfactant has been thoroughly proved for the first time in this work. Systematic experiments confirming that a hydrodynamic mode is observable in either a homodyne or a heterodyne detection scheme as well as the evaluation of the influence of the laser power applied to the slightly colored microemulsion have ensured an accurate implementation of this technique for a technically relevant system. The correlation times associated with the translational diffusion coefficient of the swollen micelles in a continuous liquid phase were measured for temperatures from (298.15 to 338.15)K at pressures of (90 and 100)bar. While there was no significant effect of pressure, it was found that the translational diffusion coefficient increases with increasing temperature as expected. We postulate this is primarily related to the effect of decreasing viscosity of the continuous phase. An estimation of the hydrodynamic diameter of the sc-CO2-swollen micelles is in good agreement with values for similar systems reported in the literature. For the derivation of absolute sizes for corresponding systems, also dynamic viscosity and refractive index data will be determined simultaneously in a currently developed closed experimental loop.

A versatile guarded parallel-plate instrument for the measurement of the thermal conductivity in steady state is presented. The instrument stands out due to its applicability for fluids as well as solid bodies, bulk solids, and compressible solids. Besides flexibility regarding sample material and thickness, the instrument design is aimed at the minimization of parasitic heat flows due to convection, radiation, or heat leakages. Remaining effects of radiative heat transfer can be taken into account by appropriate calculation methods. A precise and automated measurement and control system for temperature and heat flow including objective criteria for identifying steady-state conditions allows convenient and accurate measurements. A comparison of results obtained for water, toluene, air, and a PTFE disk at temperatures between 308.15 K and 368.15 K with reference data confirms that uncertainties of less than 3% can be achieved by choosing adequate sample thicknesses and temperature differences between the plates. For compressible materials, the accessibility of the equivalent quantities overall heat transfer coefficient, overall thermal resistance, and apparent thermal conductivity in dependence on the degree of compression is demonstrated.

Fur Argon/Neon-Gemische wurden uber den gesamten Zusammensetzungsbereich binare Diffusionskoeffizienten Dij mittels einer Loschmidt-Zelle bei 293,15 – 333,15 K und 1 – 10 bar bestimmt. Die beiden Halbzellen der Loschmidt-Zelle wurden vor Beginn der Messungen mit den unterschiedlichen Reingasen befullt. Nach Verbindung der beiden Halbzellen wurde die Veranderung der partiellen Moldichte bzw. des Brechungsindex als Funktion von Ort und Zeit mittels holografischer Interferometrie detektiert. Die hieraus erhaltenen Daten fur Dij zeigen im Vergleich zu Literaturdaten in der oberen Halbzelle systematische Abweichungen. Fur die entsprechenden Werte der unteren Halbzelle kann dagegen eine sehr gute Ubereinstimmung mit der Literatur gefunden werden. Das Produkt aus molarer Mischungsdichte und Dij weist im Rahmen der Messunsicherheit keine signifikante Abhangigkeit vom Druck auf. Binary diffusion coefficients Dij were determined for mixtures of argon and neon over the entire composition range using a Loschmidt cell at 293.15 – 333.15 K and 1 – 10 bar. Before the measurements, the different pure gases were added into the two half-cells of the Loschmidt cell. After connecting both half-cells, the change in partial molar density, or rather in the refractive index has been detected simultaneously as a function of position and time within each half-cell using holographic interferometry. The binary diffusion coefficients obtained for the upper half-cell show systematic deviations from literature data. In contrast, the data measured in the lower half-cell are in excellent agreement with literature. Within the measurement uncertainty, the product of the molar density of the mixture and Dij is not affected by the pressure.

The paper reports on experimental binary diffusion coefficient data of neon–argon gas mixtures. Measurements were performed in the temperature range between 293.15 K and 333.15 K and for pressures between 1 bar and 10 bar over almost the whole composition range using a Loschmidt diffusion cell combined with holographic interferometry. The thermostated Loschmidt cell is divided into two half-cells, which can be separated and connected by a sliding plate. Prior to the measurements, two different pure gases are filled into the two half-cells. After starting the diffusion process, the temporal change of the partial molar densities, or rather of the refractive index of the gases, is detected in both half-cells using two holographic interferometers. With this apparatus, the temperature, pressure, and concentration dependence of the binary diffusion coefficient can be determined. The relative uncertainty of a diffusion measurement is between 0.4 % and 1.4 % depending on the pressure. The experimental data are compared with data from the literature and with new theoretical data based on quantum-mechanical ab initio calculations combined with the kinetic theory of gases. Due to a systematic error, the concentration dependence determined in the upper half-cell shows deviations from the theoretical values and from most of the literature data. The concentration, temperature, and pressure dependence obtained from the data from the lower half-cell, however, are in very good agreement with available data. The product of the binary gas diffusion coefficient and the molar density of the gas mixture shows no significant dependence on pressure for the studied neon–argon noble gas system.

Dynamic light scattering (DLS) has been used for the measurement of several thermophysical properties of the refrigerant mixtures R410A and R407C. Thermal diffusivity and sound speed have been obtained by light scattering from bulk fluids for both the liquid and vapor phases under saturation conditions over a temperature range from about 290 K up to the liquid-vapor critical point. By applying the method of DLS to a liquid-vapor interface, also called surface light scattering (SLS), the saturated liquid kinematic viscosity and surface tension can be determined simultaneously. These properties have been measured for R410A and R407C from about 240 to 330 K and 240 to 350 K, respectively. The results are discussed in detail in comparison with literature data and with a simple prediction method based on the mass-weighted properties of the pure components expressed as functions of the reduced temperature.

Thermophysical properties of the ionic liquid (IL) [EMIM][B(CN)4] (1-ethyl-3-methylimidazolium tetracyanoborate) were investigated both by conventional techniques and by surface light scattering (SLS) at atmospheric pressure. The density was measured between (283.15 and 363.15) K with a vibrating U-tube densimeter. An Abbe refractometer was used for the measurement of the refractive index in the range from (283.15 to 313.15) K. Self-diffusion coefficients for the cation and anion were measured by nuclear magnetic resonance (NMR) spectroscopy from (273.15 to 318.15) K. The interfacial tension was obtained from the pendant drop technique at 297.04 K. Based on this datum and the temperature dependence of density, the interfacial tension for all relevant temperatures was estimated via an appropriate prediction model. For the IL studied within the present work, the quantity directly accessible by SLS at low temperatures was the ratio of dynamic viscosity to interfacial tension. Combining the results from SLS w...

Die Warmeleitfahigkeiten von sieben ionischen Flussigkeiten (ILs) mit dem Kation [EMIM] (1-Ethyl-3-methylimidazolium) und vier ILs mit dem Anion [NTf2] (Bis(trifluoromethylsulfonyl)imid) wurden mithilfe einer stationaren Plattenapparatur im Temperaturbereich zwischen 0 und 80 °C gemessen. Auf dieser Grundlage wurde eine einfache Beziehung zwischen der Warmeleitfahigkeit, der molaren Masse und der Dichte der ILs bei konstanter Temperatur gefunden, die als nutzliches Hilfsmittel zur Abschatzung der Warmeleitfahigkeit von beliebigen ILs dienen kann. Thermal conductivities of seven ionic liquids (ILs) based on the cation [EMIM] (1-ethyl-3-methylimidazolium) and four ILs based on the anion [NTf2] (bis(trifluoromethylsulfonyl)imide) were measured for temperatures between 0 and 80 °C using a guarded parallel plate instrument. With the corresponding data, a simple relation between thermal conductivity, molar mass, and density of the ILs at constant temperature was found, representing a convenient tool for the estimation of the thermal conductivities of arbitrary ILs.

This study reports thermal-conductivity data for a series of [EMIM] (1-ethyl-3-methylimidazolium)-based ionic liquids (ILs) having the anions [NTf2] (bis(trifluoromethylsulfonyl)imide), [OAc] (acetate), [N(CN)2] (dicyanimide), [C(CN)3] (tricyanomethide), [MeOHPO2] (methylphosphonate), [EtSO4] (ethylsulfate), or [OcSO4] (octylsulfate), and in addition for ILs with the [NTf2]-anion having the cations [HMIM] (1-hexyl-3-methylimidazolium), [OMA] (methyltrioctylammonium), or [BBIM] (1,3-dibutylimidazolium). Measurements were performed in the temperature range between (273.15 and 333.15) K by a stationary guarded parallel-plate instrument with a total measurement uncertainty of 3 % (k = 2). For all ILs, the temperature dependence of the thermal conductivity can well be represented by a linear equation. While for the [NTf2]-based ILs, a slight increase of the thermal conductivity with increasing molar mass of the cation is found at a given temperature, the [EMIM]-based ILs show a pronounced, approximately linear decrease with increasing molar mass of the different probed anions. Based on the experimental data obtained in this study, a simple relationship between the thermal conductivity, molar mass, and density is proposed for the prediction of the thermal-conductivity data of ILs. For this, also densities were measured for [EMIM][OAc], [EMIM][C(CN)3], and [HMIM][NTf2]. The mean absolute percentage deviation of all thermal-conductivity data for ILs found in the literature from the proposed prediction is about 7 %. This result represents a convenient simplification in the acquisition of thermal conductivity information for the enormous amount of structurally different IL cation/anion combinations available.

Stable dropwise condensation of saturated steam was achieved on stainless-steel tube bundles implanted with nitrogen ions by plasma ion implantation. For the investigation of the condensation heat transfer enhancement by plasma ion implantation, a condenser was constructed in order to measure the heat flow and the overall heat transfer coefficient for the condensation of steam on the outside surface of tube bundles. For a horizontal tube bundle of nine tubes implanted with a nitrogen ion dose of 1016 cm− 2, the enhancement ratio, which represents the ratio of the overall heat transfer coefficient of the implanted tube bundle to that of the unimplanted one, was found to be 1.12 for a cooling-water Reynolds number of about 21,000. The heat flow and the overall heat transfer coefficient were increased by increasing the steam pressure. The maximum overall heat transfer coefficient of 2.22 kW · m−2· K−1 was measured at a steam pressure of 2 bar and a cooling-water Reynolds number of about 2,000. At these condi...

In this work density data for binary mixtures of the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO4]) with acetone, acetonitrile, propylene carbonate, dichloromethane, methanol, ethanol, and water are presented. Measurements were performed in dependence on composition for temperatures from (278.15 to 308.15) K using the vibrating-tube method with an expanded relative uncertainty (k = 2) of less than ± 0.02 %. All calculated excess molar volumes are negative, indicating denser molecular packing than in the pure liquids. The size and the structure of the solvent molecules as well as the nature of interaction between all mixture components seem to affect the extent of the observed compression effect.

Stable dropwise condensation of steam was achieved by ion beam implantation of N+ on titanium surfaces stabilized by a preoxidation procedure. It is pointed out that dropwise condensation can be adjusted by ion implantation in spite of increased wettability indicated by contact angle and surface free energy measurements. Our results suggest a nucleation mechanism possibly caused by interactions of nano-scale surface roughness and surface chemistry effects connected with precipitation of nitrides. Measured heat transfer coefficients for dropwise condensation were up to 5.5 times larger than values calculated by Nuselt film theory. No significant influence of the applied ion implantation parameters was found.

There are only a few models for studying epidermal migration in vitro, and their interpretation is made difficult by reliance on cell monolayers and the choice of a specific substrate. In this study, the process of keratinocyte migration and epiboly were investigated by using a bilayered bioengineered skin construct, consisting of human neonatal foreskin keratinocytes and dermal fibroblasts (Apligraf, Organogenesis, Canton, MA). At baseline, 6-mm punch biopsies of the construct were placed in serum-free media (AIM-V) or DMEM with or without 10% FBS. At varying time points the bioengineered skin samples were processed and analyzed by histology and immunostaining. By 72 hours, in a time-dependent manner, the epidermis had migrated over and enveloped the entire dermis (full epiboly). Full epiboly was partially inhibited by serum and was maximal in serum-free medium. Epiboly was preserved 5 days after stated expiration date and was equivalent to that seen in unexpired construct when stored at room temperature. The process of epiboly was downregulated in a dose-dependent manner by neutralizing antibodies to EGF and TGF-beta 1. The migrating epithelium was characterized by decreased keratinocyte proliferation (as per Ki67 immunostaining) and increased expression of vitronectin (epibolin). Increasing concentrations of antibodies of vitronectin blocked the process of epiboly, as did antibodies to the alpha5-betaV integrin receptor, which mediates vitronectin-driven keratinocyte locomotion. Interesting, epiboly was also blocked by preseeding human dermal fibroblasts on the dermal side of the construct. We propose that the process of epiboly in this model can be used to better understand and assess the mechanisms involved in keratinocyte migration and may be used as an assay for establishing construct functional viability.

Stable dropwise condensation (DWC) of saturated steam has been achieved on an aluminum alloy Al 6951 disc with an average surface finish of about 0.15 μm by means of ion beam implantation technology with an ion dose of 1016 N+ cm−2 and an implantation energy of 20 keV. Measurements of the condensation heat transfer coefficient at steam pressures of 1200 and 1400 mbar were carried out as a function of surface subcooling on vertical plates of the same material which is commonly used for heat transfer equipment. Probably due to alloy inhomogeneities, only on about 50% of the plate surface DWC could be achieved, resulting in a maximum enhancement factor of 2.0 for DWC in comparison with theoretical values calculated by a corrected form of the Nusselt film theory. The heat transfer coefficient increases with increasing steam pressure and decreases with increasing surface subcooling. Furthermore, it was shown that condensation heat transfer cannot be enhanced if the ion implantation does not induce DWC. For the investigations, two different condensers have been used, one for the stability tests on discs and one for the heat transfer measurements on plates.

In order to find evidence of effective optimization of motivation enhancement within a task culture, a content analysis method is applied. This method takes the nature and extent of motivation-enhancing features into account. Based on the results of motivational research (e.g. the self-determination theory of motivation), an ordered category system of indicators has been developed. In the same manner as content analysis, a manual containing examples and operational descriptions was developed in order to analyze tasks using a combined theory-based deductive and inductive tasks-based approach. The main categories were expanded along with the motivation-enhancing features (e.g. task format, required cognitive operation, didactic intent). At present, written work orders in a select subject (Arbeit-Wirtschaft-Technik, a subject taught at Bavarian secondary schools) are coded and analyzed descriptively. This paper describes a systematic approach, the main categories and their selected indicators, selected results and their objectivity. Finally, methodological problems and limitations are discussed.

Zur Optimierung des Warmeubergangs und der damit verbundenen Wasserabscheidung aus stromender feuchter Luft in Klimatisierungssystemen wurde die Verringerung der Benetzbarkeit relevanter Aluminiumlegierungen durch Oberflachenmodifikation mittels Ionenimplantation erprobt. Ein Mas fur eine deutliche Reduzierung der Benetzbarkeit ist die Einstellung von Tropfenkondensation unter Sattdampfbedingungen, was an der Legierung Al 6951 erstmals durch die Implantation von Stickstoffionen reproduzierbar gelang. Warmetechnische Untersuchungen unter Sattdampfbedingungen zeigten, dass selbst beim Auftreten von Tropfenkondensation auf nur etwa 50 % einer Kondensatoroberflache mehr als eine Verdopplung des Warmeubergangskoeffizienten fur die Kondensation moglich ist. Anschliesend wurden Untersuchungen mit dem Arbeitsmedium feuchte Luft in einer Laborklimaanlage durchgefuhrt, in der einzelne in technischen Kondensatoren eingesetzte Finschichten unter realistischen Betriebsbedingungen hinsichtlich der Wasserabscheidung visuell und warmetechnisch analysiert werden konnen. Vergleichende Versuche mit unbehandelten und durch Ionenimplantation modifizierten Fins unter identischen Randbedingungen zeigten keine Unterschiede in der auftretenden Kondensationsform. Am implantierten Fin wurden leicht verbesserte Wasserabscheidungswirkungsgrade ermittelt.

Plasma-ion implantation was used to achieve stable dropwise condensation of saturated steam on stainless steel tubes. For the investigation of the efficiency of plasma-ion implantation regarding the condensation process a condenser was constructed in order to measure the heat flux density q ˙ and the heat transfer coefficient hc for the condensation of steam on the outside surface of a single horizontal tube. For tubes implanted with a nitrogen ion dose of 1016 cm−2, the heat transfer coefficient hc was found to be larger, by a factor of 3.2, in comparison to values theoretically calculated by the corrected Nusselt film theory. The heat flux density q ˙ and the heat transfer coefficient hc were found to increase with increasing ion dose and steam pressure. The heat transfer coefficient decreases with increasing surface subcooling as it has been found in former work for dropwise condensation on ion implanted vertical plates.

The capabilities of prompt gamma neutron activation analysis (PGAA) are examined for fullerene samples. As shown PGAA is a promising instrumental technique for the determination of the light elements of the periodic table. These elements (C, H, O, N and B) were inaccessible by instrumental neutron activation analysis (INAA) as done by the authors in previous publications.

The minority cytotype exclusion principle describes how random mating between diploid and autotetraploid cytotypes hinders establishment of the rare cytotype. We present deterministic and stochastic models to ascertain how selfing, inbreeding depression, unreduced gamete production, and finite population size affect minority cytotype exclusion and the establishment of autotetraploids. Results demonstrate that higher selfing rates and lower inbreeding depression in autotetraploids facilitate establishment of autotetraploid populations. Stochastic effects due to finite population size increase the probability of polyploid establishment and decrease the mean time to tetraploid fixation. Our results extend the minority cytotype exclusion principle to include important features of plant reproduction and demonstrate that variation in mating system parameters significantly influences the conditions necessary for polyploid establishment.