834 research outputs found

    Evaluation and Selection of Gel Base for the Formulation of Dexpanthenol Products

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    Purpose: To formulate dexpanthenol gels with enhanced in vivo absorption properties via skin.Methods: Carboxyvinyl derivatives (Carbopol 980 and Ultrez 10) and poloxamer (Lutrol F 127) were used as the hydrogel base in the formulations. Changes in rheological properties (apparent viscosity and penetration values) during the storage period were examined by Rheotest RN rotational viscometer and PNR12 penetrometer. In vitro release study using Franz diffusion cell was employed to compare the release  characteristics of the formulated hydrogels with those of a reference cream.Results: The flow curves of the gels with Carbopol 980 and Ultrez 10 showed pseudoplastic flow. Lutrol F 127 gels presented thixotropic  behaviour. The consistency of the studied gels was in the following rank order: Lutrol F 127 > Ultrez 10 > Carbopol 980. In vitro results showed that dexpanthenol was released in lower amounts from the reference cream than from the three test gels. No significant differences were observed in the amount of active substance released from the gels due probably to the fact that Carbopol 980 and Ultrez 10 are both carboxyvinyl polymers. The highest amount of dexpanthenol was released from Lutrol F 127 gel.Conclusion: The hydrogel made with Lutrol F 127 gel base possesses the best properties of all the gels and is recommended for the formulation of a suitable dexpanthenol gel.Keywords: Hydrogel, Dexpanthenol, Carboxyvinyl polymers, Gels,  Carbopol, Poloxamer, Rheology, Drug release, Penetromete

    Biomass potential assessment for locating biorefinery plant in Hungary

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    To find a suitable site for a 150,000 metric ton dry material per year (t dm/yr) input capacity biorefinery plant in Hungary is a challenging task. Not only biomass potentials have to be assessed, competing uses, sustainability aspects, public opinion and future threats to feedstock availability should be also taken into account. As a result of our calculations, currently there is enough feedstock available for the targeted input capacity to operate in an ecologically sustainable way. However, several factors may threaten the future of feedstock availability. In the long run enhanced price competition is anticipated for biomass among biorefinery, livestock keeping, timber industry and biomass based renewable energy production. The majority of stakeholders accept in general biorefinery as a promising solution for substituting fossil based plastics, still local interests give priority to a balanced agricultural production including higher shares of husbandry

    Mid-infrared interferometric variability of DG Tau: implications for the inner-disk structure

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    Context. DG Tau is a low-mass pre-main sequence star, whose strongly accreting protoplanetary disk exhibits a so-far enigmatic behavior: its mid-infrared thermal emission is strongly time-variable, even turning the 10 μ\mum silicate feature from emission to absorption temporarily. Aims. We look for the reason for the spectral variability at high spatial resolution and at multiple epochs. Methods. We study the temporal variability of the mid-infrared interferometric signal, observed with the VLTI/MIDI instrument at six epochs between 2011 and 2014. We fit a geometric disk model to the observed interferometric signal to obtain spatial information about the disk. We also model the mid-infrared spectra by template fitting to characterize the profile and time dependence of the silicate emission. We use physically motivated radiative transfer modeling to interpret the mid-infrared interferometric spectra. Results. The inner disk (r<1-3 au) spectra exhibit a 10 μ\mum absorption feature related to amorphous silicate grains. The outer disk (r>1-3 au) spectra show a crystalline silicate feature in emission, similar to the spectra of comet Hale-Bopp. The striking difference between the inner and outer disk spectral feature is highly unusual among T Tauri stars. The mid-infrared variability is dominated by the outer disk. The strength of the silicate feature changed by more than a factor of two. Between 2011 and 2014 the half-light radius of the mid-infrared-emitting region decreased from 1.15 to 0.7 au. Conclusions. For the origin of the absorption we discuss four possible explanations: a cold obscuring envelope, an accretion heated inner disk, a temperature inversion on the disk surface and a misaligned inner geometry. The silicate emission in the outer disk can be explained by dusty material high above the disk plane, whose mass can change with time, possibly due to turbulence in the disk.Comment: 16 pages, 13 figure

    Matthiessen's rule in MgB2: Resistivity and T-c as a function of point defect concentration

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    We present the results of a systematic study of the temperature-dependent resistivity and of T-c of a single crystal MgB2 sample as a function of point defect concentration. We have found linear, albeit weak, correlation between the decreasing superconducting critical temperature and the residual resistivity and no variation of the slope of the rho(T) curve at high temperature. These findings reinforce the already existing picture of s-wave pairing for the superconductivity. The interband scattering is low despite increasing disorder. Somewhat surprisingly, Matthiessen's rule is followed even in this two-band metal
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