**7. References**

298 Acoustic Waves – From Microdevices to Helioseismology

The experimental results obtained (average values for each parameter of the fitting curve) are summarized in Table 3; interpretation of such results must consider that the initial amplitude (A1) of the PA signal corresponds to the system formed by the applied drug+skin, while the final amplitude (A2) corresponds to the skin only, with the product having penetrated beyond the layer responsible for the generation of the PA signal (about 30µm, in

Application Method A1 (u.a) A2 (u.a) t0 Dt ts (t0 + dt) Massage 0,66 ± 0,04 0,70 ± 0,02 7 ± 2 4 ± 2 11 ± 2 Phonophoresis 0,65 ± 0,03 0,72 ± 0,04 5 ± 1 1,3 ± 0,3 7 ± 1 Table 3. Average values (± standard error) for A1 and A2 (in arbitrary units), t0 and dt (in

In order to understand if penetration was effective, first of all, it is imperative to evaluate if the difference between A1 and A2 is statistically significant. Therefore, initially a paired t-test was carried on to verify if there was significant difference between A1 and A2 for each application method employed (indicating significant penetration of the applied product). This was verified for both application methods; however, this difference is more evident for phonophoresis application, in which the difference between the initial and the final signal

Statistical tests were also employed in the comparison between the two application methods (massage and phonophoresis); no statistical significance was found for t0 and dt. Considering tS = (t0 + dt) as the total effective penetration time for the epidermal layer under study, the results obtained (average ± error, N=10) are 11(±2) minutes (for massage application) and 7(±1) minutes (for phonophoresis application). The paired t-test for this

Experiments performed at FASBio/UNIVAP show that the form of application can influence the kinetics of transdermal drug delivery, depending on the applied product. In the experiment presented here, significant penetration has been reported for both forms of administration (massage and phonophoresis); PA measurements showed that effective penetration is at least more evident after phonophoresis application, when compared to

The possibility of performing *in vivo* studies brings great value to the use of the PA technique in experimental skin research. The potential and relevance of PA measurements in this field have been shown by a large range of experiments being performed by different research groups around the world – actually, the examples here presented must be seen as a

PA measurements *in vivo* are able to detect alterations in skin pigmentation. Even in skin regions normally protected from sun exposure, the PA signal level tends to follow clinical classification; actually, the use of the PA technique goes one step ahead, allowing

Topical drug application has been employed in the treatment of many pathological processes; its efficiency is associated to the efficiency of transdermal drug delivery. PA

comparative and quantitative research through simple, direct measurements.

the present case).

parameter shows p=0,073.

massage application.

**5. Conclusion and perspectives** 

sample of what has been done.

minutes), for each of the application methods (N=10)

presents p=0,011 (p=0,066 was found for massage application).


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**14** 

*Czech Republic* 

**Acoustic–Gravity Waves in the Ionosphere** 

Terrestrial atmosphere shows a high variability over a broad range of periodicities, which mostly consists of wave-like perturbations characterized by various spatial and temporal scales. The interest for short time variability in ionospheric attributes is related to the role that ionosphere plays in the Earth's environment and space weather. Acoustic-gravity waves (AGWs), waves in the period range from sub-seconds to several hours, are sources of most of the short-time ionospheric variability and play an important role in the dynamics and energetics of atmosphere and ionosphere systems. Many different mechanisms are likely to contribute to the acoustic-gravity wave generation: for instance, excitation at high latitudes induced by geomagnetic and consequent auroral activity, meteorological phenomena, excitation in situ by the solar terminator passages and by the occurrence of solar eclipses. During solar eclipse, the lunar shadow creates a cool spot in the atmosphere that sweeps at supersonic speed across the Earth's atmosphere. The atmosphere strongly responds to the decrease in ionization flux and heating. The very sharp border between sunlit and eclipsed region, characterized by strong gradients in temperature and ionization flux, moves throughout the atmosphere and drives it into a non-equilibrium state. Acoustic-gravity waves contribute to the return to equilibrium. At thermospheric heights, the reduction in temperature causes a decrease in pressure over the totality footprint to which the neutral winds respond. Thermal cooling and downward transport of gases lead to neutral composition changes in the thermosphere that have significant influence on the resulting electron density distribution. Although the mechanisms are not well understood, several studies show direct evidence that solar eclipses induce wave-like oscillations in the acoustic-

Many different mechanisms are likely to contribute to wave generation and enhancement at ionospheric heights. Hence, it is difficult to clearly separate or differentiate each contributing agent and to decide which part of wave field belongs to the in situ generated and which part comes from distant regions. First experimental evidence of the existence of gravity waves in the ionosphere during solar eclipse was reported by Walker et al. (1991), where waves with

As the solar radiation penetrates Earth's atmosphere it forms pairs of charged particles. Under a normal day-time conditions the ionization solar flux increases immediately after

periods of 30–33 min were observed on ionosonde sounding virtual heights.

**1. Introduction** 

gravity wave domain.

**1.1 Ionospheric sounding** 

**During Solar Eclipse Events** 

Petra Koucká Knížová and Zbyšek Mošna

*Institute of Atmospheric Physic, Czech Academy of Sciences* 

