Analytical profiling, modeling and transdermal/transmucosal characteristics of bioactive N-alkylamides

N-alkylamides are a group of bioactive molecules found in several plants. Extracts and formulations derived from these plants are not only used orally, but are applied on the skin and buccal mucosa as well. However, there is no specific information available about the intrinsic local pharmacokinetics of N-alkylamides after topical application, questioning the role of this mode of administration. Therefore, we investigated the transdermal and transmucosal behaviour of spilanthol, a prominent N-alkylamide, in a commercial Spilanthes extract, two mouth gels and different propylene glycol (PG)/H20 solutions

Jet-flap interaction noise in model scale and full scale - and the implications for evaluating noise reduction technologies

Jet-flap interaction (JFI) noise consists of both broadband effects and tonal components. The frequency range of the tonal components can be characterized with a cut-on and cut-off frequency [1]. The JFI tones are well-audible and significant for the model scale engines. In addition to this, for very large commercial jet engines (e.g. UHBR class), the (in model scale) high-frequent broadband-like JFI-noise becomes very relevant in full scale. It can be shown that JFI noise spectra of different model size experiments collapse as expected: Two geometrically similar JFI-experiments were conducted at AWB (large scale) and JEXTRA (small scale) where the model geometries differ by a relevant factor (2.5). These results indicate, that it is safe to derive full scale spectra from experimental model scale spectra. In order to account for the human hearing, weighting functions can be applied. A sensitivity study wrt. height gives hints about the relevance of two different frequency ranges of JFI noise, JFI noise below and above the tonal cut-off frequency

Porous flap trailing edges for the reduction of jet-flap interaction noise

This presentation defines jet-flap interaction in terms of a general problem statement, geometry, aerodynamics and acoustic effects. The jet-flap interaction noise delta defines the noise reduction potential. Noise reduction is achieved with the help of a porous flap with and without cover mesh. The noise reduction performance is shown for jet speeds between Mj=0.45 and 0.76, for the full spectrum as well as its decomposition into broadband-like and tonal parts. The additional cover mesh shows an exceptional performance and is recommended for future use

Drivers of Jet-flap interaction noise: The thrust vs. shear layer difference velocity experiment

The fundamentals of jet-flap interaction (JFI) are not fully known. One of the open questions is the search for the velocity scaling similarity parameter. While the scaling exponent is known to be n=5...6 from static JFI experiments (single-phase), the two-phase flight ops JFI problem produces more than one suitable flow parameter candidate. Promising scaling parameters are thrust velocity and shear layer (S/L) difference velocity. These two velocity parameters are played out against one another in order to force a definitive experimental result. The changes in build length due to using different operational parameters are calculated. The experimental parameter room is limited by max velocity limits of wind tunnel air and pressurized air (volumetric limit or sonic jet velocity), by quasi-static velocity ratio (for closed-circuit wind tunnel) and either upper limit of JFI effect or velocity profile type (here strong normal velocity profiles). The derived experiment is tailored to force a definite result wrt. thrust or S/L velocity. If this experiment does not give a clear result, JFI scaling cannot be easily modelled. A next step could be for example the measurement of downwash-velocities, i.e. flow properties which are more complex to determine and may require a build-dependent model

Acoustic Mach number, jet Mach number or jet speed – what is the optimal control property for jet noise experiments at AWB

Some experimental facilities are planned energy-lean, but this comes typically with slightly imperfect test conditions. Especially temperature control systems are often slow, demand energy and increase operational cost. Contrary to this, low-cost experimental pressurized air test rigs, such as the one at AWB (Acoustic Wind tunnel Braunschweig), respond to control commands much faster, but do not meet norm conditions. Therefore, the question needs to be answered which flow parameter should be used for operation control, the acoustic Mach number Mac, jet Mach number Mj or jet velocity Uj. This study starts with the definition of ideal ISA norm conditions and a re-writing of the FfowcsWilliams jet noise analogy without any temperature terms. Using a rough assumption for the mixed (shear layer) density, the jet noise scales according to I ~ Mj2 Uj Mac5. The derivation will be used in order to judge the three control options at a test rig with a constant total temperature for the jet. As a result, this study will recommend the testing of jet velocities for jet noise experiments at AWB

Steady aerodynamics flow analysis for determining the necessary build space of an isolated jet shear layer

It is rather difficult to characterize the geometry of multi-body multi-flow problems, such as jet-flap interaction. Even the 1D similarities are not obvious. Therefore, a clear measurement hypothesis cannot be formulated and measurement results are harder to interpret. The solution to this problem is the study of the near field geometry of the isolated jet shear layer. Its geometry can be modelled with the help of the virtual shear layer origin, mixed jet radius and half-jet opening angle. This information is very practical when introducing a second body to the problem. Even though the flow might change a lot, the theoretically necessary space for isolated jet flow can be determined. This superposition allows to make a qualitative guess on possible interaction scenarios, and theoretical jet impingement areas. It is also easier to track deviations from the superposition. The experimental measurement with a spanwise oriented rake in the streamwise plane is cost-effect for symmetric problems: A small streamwise resolution allows for fast measurement times while significant data properties are gathered

Engine integration of high aspect ratio rectangular jet nozzle (unheated subsonic flow)

Jet noise is a crucial component in the entire mix of aircraft-relevant noise sources. A quiet aircraft requires a low noise engine integration. Compared to the conventional round jet engine, the jet potential core length is shorter for a rectangular jet engine with same nozzle outlet area. This is especially true for high aspect ratio rectangular jets (here AR 13.3). Hence, the engine integration of the rectangular nozzle onto a wing could be conducted in a way where jet noise is shielded from an observer at the ground. Yet, the question is how such a low noise engine integration should be designed. Therefore, an experimental setup was built at the Aeroacoustic Wind tunnel Braunschweig (AWB) where rather large engine integration lengths and heights between engine lip and plate trailing edge can be studied. This allows to test shielding effects of embedded engine systems, e.g. short and long aft-decks, backward-facing steps as well as non-embedded/poled engines. The contributions of this paper are made in terms of the aero-geometric characterization of the problem physics, the evaluation of the installation effect for observers on the ground (along flyover arc or overhead position) as well as the evaluation of the shielding effect. The aero-geometric analysis helps to predict acoustical effects which occur for three general installation problems: the asymmetric nozzle, jet-surface interaction as well as wide-angle installations. Shielding benefits due to the installation of a plate can be determined by a shielding frequency criterion. Unfortunately, the high-frequent noise reduction comes with a lowfrequent installation penalty, thereby making noise reduction a diffcult design mission: All in all, only one tested configuration shows an overall installation noise benefit. The general results of rather achieving design penalties for long bevel/aft-deck design and step configurations is in agreement with previous studies conducted by NASA and Georgia Tech. Future low noise rectangular engine integrations may therefore consist of rather small engine integration lengths

Acoustic Mach number, jet Mach number or jet velocity: Choosing the optimal control property for jet noise experiments at different test rigs

Wind tunnel experiments are great in order to study jet noise. Yet, the heat demand even for ISA cold engine thrust conditions is rather high. The additional heating and/or cooling of air in order to meet atmospheric norm conditions increases both energy demand, test time and test cost. Some energy lean experimental pressureized air test rigs make compromises on the temperature control system. Hence, norm conditions cannot be met and a way must be found how to optimally deal with the shortcomings of the test rig. This paper starts with an ideal test rig and the implications of testing especially subsonic jets under ISA norm conditions. Then, the shortcomings due to low-energy designs will be investigated by examining two factors: The jet temperature as well as the temperature of the acoustic chamber (below or above ISA norm temperature). The Ffowcs-Williams analogy for jet noise will be rewritten without any temperature terms. This will show that jet noise scales approximately with I ~ Mj^2 Uj^1 Mac^5. The derivation will be used in order to evaluate measurement strategies on two different pressureized air test rigs: (case 1) the remotely located compressor which is characterized by a constant total jet temperature, but - if unheated - is typically too cold for ISA norm conditions, and (case 2) a closely located compressor, where the compression heat is preserved, yet causes runaway temperatures within the jet and possibly within the acoustic test room. The aim of this paper is to show a solution to the discussion on which operational parameter is optimal for any test facility: the acoustic Mach number Mac, jet Mach number Mj or jet velocity Uj. A suitable test parameter produces a small error (e.g. less than 12% or 0.5dB) in comparison to ISA norm conditions over a wide range of any subsonic operation. Assuming that the test room is warmer than ISA, unheated (too cold) jet test rigs like AWB make small errors when using the jet velocity whereas slightly too hot jet test rigs like JExTRA are better of using jet Mach number or acoustic Mach number for the definition of their jet operations. The latter case is demonstrated using a data example from JExTRA

Transdermal evaluation of caffeine in different formulations and excipients

Background: The stratum corneum(SC) forms adifficultphysical barrier fordrugs to pass through the skin. Several strategieswere developed to overcome this barrier.Optimization of topical drug formulations by selected excipients may facilitate the penetration of drugs through the SC into the viable skin cells and ultimately into the systemic circulation. Methods: Here, both the influence of two formulations (a classic carbomer-based gel and a novel Pluronic® lecithin organo gel (PLO gel)) and selected excipients (ethanol, propylene glycol, diethylene glycol monoethyl ether, isopropyl myristate (IPM), and water) with or without the penetration enhancer miconazole nitrate on the transdermal penetration characteristics of caffeine were determined using an in vitro Franz diffusion cell setup. Results: Higher fluxes were observed for the carbomer-based gel compared to the PLO gel. Among the commonly used excipients, IPM showed the best penetration enhancing properties, while the presence of the penetration enhancer miconazole nitrate did not significantly alter the apparent skin permeation characteristics for caffeine. Conclusion: The high ethanol percentage in the carbomer-based gel could explain the results as supported by our excipient data.Moreover, IPMcould play a beneficial role in topical formulations as this excipient was responsible for a significant increase in the amount of caffeine penetrated through the skin. No overall statistical significant effect of the presence of miconazole nitrate as a penetration enhancer was observed