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ABSTRACT: The aim of the present study was to evaluate the influence of a single corticosteroid application on stratum corneum hydration. Hydration of the skin was estimated by measuring the stratum corneum capacitance while colour measurements were employed for the estimation of the potency of die applied formulations. Two corticosteroids were tested: clobetasol-17-propionate and halcinonide. We used different halcinonide concentrations (ranging from 0.005% to 0.200%) to evaluate the influence of the active ingredient concentration. We also evaluated the influence of the quantity applied (3 and 10 mg/cm2), of the application time (2 and 12 h) and of a humectant in the formulation (5% urea). We found a significant drying effect after application of the clobetasol-17-propionate formulation, while the stratum corneum hydration remained unaffected after application of the different halcinonide formulations, irrespective of the concentration used, the applied quantity or die application time. The addition of urea to the formulation caused a significant increase in stratum corneum capacitance. The magnitude of the blanching response was only influenced by the application time.
07/2009; 8(3):193-197.
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ABSTRACT: The appearance of hair plays an important role in people's overall physical appearance and self-perception. Silicon (Si) has been suggested to have a role in the formation of connective tissue and is present at 1-10 ppm in hair. Choline-stabilized orthosilicic acid ("ch-OSA") is a bioavailable form of silicon which was found to improve skin microrelief and skin mechanical properties in women with photoaged skin. The effect of ch-OSA on hair was investigated in a randomized, double blind, placebo-controlled study. Forty-eight women with fine hair were given 10 mg Si/day in the form of ch-OSA beadlets (n = 24) or a placebo (n = 24), orally for 9 months. Hair morphology and tensile properties were evaluated before and after treatment. Urinary silicon concentration increased significantly in the ch-OSA supplemented group but not in the placebo group. The elastic gradient decreased in both groups but the change was significantly smaller in the ch-OSA group (-4.52%) compared to placebo group (-11.9%). Break load changed significantly in the placebo group (-10.8%) but not in the ch-OSA supplemented group (-2.20%). Break stress and elastic modulus decreased in both groups but the change was smaller in the ch-OSA group. The cross sectional area increased significantly after 9 months compared to baseline in ch-OSA supplemented subjects but not in the placebo group. The change in urinary silicon excretion was significantly correlated with the change in cross sectional area. Oral intake of ch-OSA had a positive effect on tensile strength including elasticity and break load and resulted in thicker hair.
Archives for Dermatological Research 01/2008; 299(10):499-505. · 2.28 Impact Factor
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ABSTRACT: Background/aims: Regional differences in percutaneous penetration and skin properties are well documented. However, only a few studies have investigated the relationship between substance penetration and specific skin characteristics in function of the body region. It was our aim to evaluate the physiological effect of topically applied substances in function of skin parameters determined at different body regions.Methods: The characterization of the blanching response to a topically applied corticosteroid and the characterization of the erythema response to topically applied nicotinates were used as two indicators for the percutaneous penetration at selected body regions. Stratum corneum hydration, skin temperature, TEWL, the amount of skin surface lipids and perfusion of the superficial microcirculation were determined at the same body regions.Results: Significant differences in pharmacodynamic response to the corticosteroids and the nicotinates were found in function of the body region. A strong correlation was detected between the parameters characterizing the pharmacodynamic response and the particular skin properties.Conclusion: The regional differences in pharmacological response to topically applied halcinonide and nicotinates may point to a body region dependent bioavailability of the vasoactive substances in the upper skin layers. The significant relationship between the parameters characterizing the physiological skin reaction and the determined skin parameters may be an indication of their involvement in the percutaneous penetration process. These regional differences in pharmacological response seem to be independent of the physicochemical properties of the topically applied substances.
Skin Research and Technology 10/2006; 3(3):161 - 168. · 1.71 Impact Factor
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ABSTRACT: Large signal analyzers measure calibrated waves. Besides the classical linear SOLT-calibration, this requires two additional calibration steps: a power and a phase calibration over frequency. Nowadays phase relations can be calibrated with a frequency resolution of 2MHz. The aim of this paper is to obtain a fine frequency grid phase calibration for the large signal network analyser based on a coarse grid phase calibration. The approach uses a frequency conversion performed with a crystal detector
Microwave Symposium Digest, 2006. IEEE MTT-S International; 07/2006
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ABSTRACT: This paper presents a novel and low-cost analog front-end gain and phase mismatch calibration scheme for MIMO-OFDM TDD WLAN systems with transmit-processing, where the complete channel reciprocity and calibration of the access point hardware is needed. It is shown by analytical derivations that the novel scheme has similar performance to that of the older scheme. The new scheme also has the advantage of lower implementation cost by removing the necessity of having a calibration transceiver. In addition, it is demonstrated that the new scheme can easily be extended towards an arbitrary number of multi-antenna transceivers.
Radio and Wireless Symposium, 2006 IEEE; 02/2006
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ABSTRACT: A measurement based model for a microwave system operating in a power range up to several dB's of compression over its full operation frequency band is proposed. The measurements of the nonlinear behavior of the amplifier are performed with the large signal network analyzer. The model uses a limited amount of parameters, is easy to implement in an existing simulator, does not require the publishing of internal schematics, and predicts the response of the component over its whole working area. This model is hence a candidate for inclusion in data sheets.
Gallium Arsenide and Other Semiconductor Application Symposium, 2005. EGAAS 2005. European; 11/2005
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ABSTRACT: Chronic exposure of the skin to sunlight causes damage to the underlying connective tissue with a loss of elasticity and firmness. Silicon (Si) was suggested to have an important function in the formation and maintenance of connective tissue. Choline-stabilized orthosilicic acid ("ch-OSA") is a bioavailable form of silicon which was found to increase the hydroxyproline concentration in the dermis of animals. The effect of ch-OSA on skin, nails and hair was investigated in a randomized, double blind, placebo-controlled study. Fifty women with photodamaged facial skin were administered orally during 20 weeks, 10 mg Si/day in the form of ch-OSA pellets (n=25) or a placebo (n=25). Noninvasive methods were used to evaluate skin microrelief (forearm), hydration (forearm) and mechanical anisotropy (forehead). Volunteers evaluated on a virtual analog scale (VAS, "none=0, severe=3") brittleness of hair and nails. The serum Si concentration was significantly higher after a 20-week supplementation in subjects with ch-OSA compared to the placebo group. Skin roughness parameters increased in the placebo group (Rt:+8%; Rm: +11%; Rz: +6%) but decreased in the ch-OSA group (Rt: -16%; Rm: -19%; Rz: -8%). The change in roughness from baseline was significantly different between ch-OSA and placebo groups for Rt and Rm. The difference in longitudinal and lateral shear propagation time increased after 20 weeks in the placebo group but decreased in the ch-OSA group suggesting improvement in isotropy of the skin. VAS scores for nail and hair brittleness were significantly lower after 20 weeks in the ch-OSA group compared to baseline scores. Oral intake of ch-OSA during the 20 weeks results in a significant positive effect on skin surface and skin mechanical properties, and on brittleness of hair and nails.
Archives for Dermatological Research 11/2005; 297(4):147-53. · 2.28 Impact Factor
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ABSTRACT: Design and validation of an ESD protected ultra-wideband low noise amplifier is presented in this paper. It features an interstage matching network for gain roll-off compensation to achieve a flat gain over its passband. Evaluated with a chip-on-board approach, the amplifier demonstrates a gain of 11.8 ± 0.3 dB, minimum noise figure (NF) of 2.1 dB, and a group delay variation of ±30 ps from 3 to 5 GHz, even though using a less advanced 0.35-μm BiCMOS technology. Its input, output and power supply are all protected against HBM ESD stress up to 6.5 kV. Measured IIP3 at 4.5 GHz is -5.5 dBm. The core LNA draws 3 mA from a 3-V supply.
Ultra-Wideband, 2005. ICU 2005. 2005 IEEE International Conference on; 10/2005
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ABSTRACT: The work presents the impact of analog front-end effects on the BER performance of MIMO/SDMA-OFDM downlink transmission using minimum mean-squared error transmit processing at the access point. The implementation loss due to gain and phase mismatch, analog filtering, clipping and quantization, phase noise, and I/Q mismatch in the front-ends is given.
Radio and Wireless Conference, 2004 IEEE; 10/2004
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ABSTRACT: The work presents a front-end gain and phase mismatch calibration scheme for OFDM-MIMO/TDD WLAN systems using transmit-processing, where complete channel reciprocity and calibration of the access point (AP) hardware is needed. Simulation results for a single-user 2×2 OFDM-MIMO system with QAM-64 modulation show that our calibration method can reduce the implementation loss to as little as 0.2 dB at a coded BER of 10<sup>-5</sup> The calibration scheme has been implemented and demonstrated by IMEC.
Radio and Wireless Conference, 2004 IEEE; 10/2004
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ABSTRACT: A balance is made between accuracy and cost in the wideband (45 MHz-18 GHz) determination of the permittivity of a polymerised elastic coating. It is shown that the combination of S-parameters measurements of 2 coplanar wave guides (CPW) before and after coating with a thick layer of the material under test (MUT) and the use of an analytical expression for the calculation of the permittivity of the lines, can lead to a 'best bargain' solution. Expensive narrow-banded methods fall out of the scope for this application.
Instrumentation and Measurement Technology Conference, 2004. IMTC 04. Proceedings of the 21st IEEE; 06/2004
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ABSTRACT: Analog and RF circuit performance in single-chip transceivers can severely suffer from coupling of digital switching noise to the silicon substrate. To predict this performance degradation, a deeper understanding of the impact of substrate noise is absolutely necessary. Using measurements, this impact is studied as the cascade of attenuation through the substrate from the source of substrate noise to the RF circuit and the propagation through the RF circuit to its output. This approach has been validated with measurements on a 0.25 μm and a 0.18 μm CMOS low-noise amplifier (LNA) and reveals insight in the mechanisms of impact of substrate noise on RF circuits. In addition, impact of a real digital circuit is measured on a 0.18 μm differential CMOS LNA.
Instrumentation and Measurement Technology Conference, 2003. IMTC '03. Proceedings of the 20th IEEE; 06/2003
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ABSTRACT: Coupling of digital switching noise to the silicon substrate can severely degrade the analog and RF performance in single-chip transceivers. To predict the degradation of the performance of RF circuits, modeling of the impact of substrate noise is absolutely necessary. Using measurements, this impact is modeled by the cascade of an attenuation through the substrate from the source of substrate noise to the RF circuit and the propagation through the RF circuit to its output. This approach has been validated with measurements on a 0.25 μm CMOS low-noise amplifier (LNA) and reveals insight in the mechanism of impact of substrate noise on RF circuits. In addition, impact of a real digital circuit is measured on a 0.18 μm differential CMOS LNA.
Mixed-Signal Design, 2003. Southwest Symposium on; 03/2003
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ABSTRACT: Analog integrated circuit designs are often differential and require differential-to-single-ended hybrids for spectral measurements. This paper describes a broadband, high-frequency hybrid, whose output signal is proportional to the difference of two input ports, i.e., proportional to the differential signal. The main novelty of this hybrid is its high bandwidth (two to three decades). Such high bandwidth is obtained through combining broadband structures: a pair of broadband impedances are used to scale the two incoming signals; a symmetric structure of two identical broadband directional couplers and a power combiner are used afterwards to obtain the differential signal. The high bandwidths of both the impedances, the directional couplers, and the power combiner make it possible to obtain a differential coupling factor and a common-mode rejection ratio which is frequency insensitive over several decades in frequency. Measurements support the statement that bandwidths of more than three decades can be obtained using the proposed hybrid.
IEEE Transactions on Instrumentation and Measurement 01/2003; · 1.21 Impact Factor
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ABSTRACT: Temperature influences the stratum corneum adsorption of several topically applied compounds. This study was designed to evaluate the influence of the temperature on the stratum corneum adsorption of 3 UV filters. The UV filters were solubilized in two vehicles, an emulsion gel and petroleum jelly and applied at respectively, 31 and 40 degrees C during 30 min. In vivo stratum corneum UV filter content was measured using the tape stripping method. Similar amounts of UV filter were detected in the stratum corneum when comparing applications at the different temperatures. Application of the UV filters in the emulsion gel resulted in higher stratum corneum UV filter concentrations compared with application in the petroleum jelly. The application temperature did not influence the stratum corneum adsorption of the tested UV filters while the nature of the vehicle significantly influenced the amount of UV filters recovered from the stratum corneum.
Journal of Dermatological Science 11/2001; 27(2):77-81. · 3.72 Impact Factor
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ABSTRACT: This paper describes the design methodology of a broadband, high
frequency differential coupler. The output signal of this differential
coupler is proportional to the difference of 2 input ports, i.e.
proportional to the differential signal of the 2 inputs. This signal is
made using a hybrid structure. The overall performance of this
differential coupler and the hybrid structure is characterized by the
differential coupling factor and by the common mode rejection ratio. A
pair of broadband impedances are used to scale the 2 incoming signals
with 2 complex coefficients. A symmetric structure of two identical
broadband directional couplers and a symmetric power combiner are used
afterwards to obtain the differential signal. The high bandwidth of both
the terminations, the directional couplers and the power combiner make
it possible to obtain a differential coupling factor and a common mode
rejection ratio which is frequency insensitive over several decades.
Measurements demonstrate a differential coupler with a bandwidth of more
than 3 decades
Instrumentation and Measurement Technology Conference, 2001. IMTC 2001. Proceedings of the 18th IEEE; 02/2001
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ABSTRACT: This paper proposes a method to measure the amplitude and the
phase of the spectral tones present in both sidebands of a microwave
amplitude modulated RF signal. The method exploits once more the phase
conservation property inherent to the frequency down conversion
operation performed by an envelope detection circuit while a pair of
filters bring the needed discrimination on the side-tones
Microwave Symposium Digest. 2000 IEEE MTT-S International; 02/2000
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ABSTRACT: A validation of the low-band microwave multitone (multisine)
signal is presented. This signal consists of a grid of microwave
spectral lines with a known phase relation between the spectral lines.
Such signals will prove their utility for the calibration of the next
generation nonlinear vectorial network analysers operating in narrowband
measurement mode
Microwave Symposium Digest, 1999 IEEE MTT-S International; 02/1999
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ABSTRACT: Theoretically, a positive relation is expected between skin temperature and the percutaneous penetration of topically applied substances. The aim of the present study was to evaluate the influence of the temperature on the in vitro percutaneous penetration of dihydrotestosterone. Hairless rat skin was mounted in static diffusion cells placed in a water bath at different temperatures (28.6, 35.1 and 38.2 degrees C, respectively). Different vehicles were tested as well as the addition of penetration promoting molecules such as oleic acid and limonene. A saline buffer was used as the receptor phase. Penetration through the skin was evaluated by means of scintillation counting of the radiolabelled dihydrotestosterone. Experiments were followed for a period of 29 h. The total amount of penetrant, dihydrotestosterone, as well as the flux, were calculated from these kinetics. Our results demonstrate a temperature effect with the highest penetration at 38.2 degrees C. The vehicle was also found to influence the penetration of dihydrotestosterone in a significant way. Furthermore, limonene presented better penetration promoting properties compared with oleic acid.
European Journal of Pharmaceutics and Biopharmaceutics 12/1998; 46(3):279-83. · 4.27 Impact Factor
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Sportverletzung · Sportschaden 10/1998; 12(3):XXIV-XXVI. · 0.61 Impact Factor
