Timo Karppinen

Daylight photodynamic therapy for actinic keratoses: a randomized double-blinded nonsponsored prospective study comparing 5-aminolaevulinic acid nanoemulsion (BF-200) with methyl-5-aminolaevulinate

Daylight‐mediated photodynamic therapy (DL‐PDT) using methyl‐5‐aminolaevulinate (MAL) is effective for thin, grade I, actinic keratoses (AK). There are no published studies of other photosensitizers used in DL‐PDT.

The stiffness modulus in Norway spruce as a function of year ring

Abstract The elastic properties of Norway spruce were studied by means of ultrasound. Samples were from stems that were grown either at a medium- or a high-fertility site in Finland. The stiffness modulus was determined in the longitudinal, radial, and tangential directions as a function of the distance from the pith using 1-mm-thick samples. Tangentially cut samples contained only earlywood, while radially and longitudinally cut samples contained both earlywood and latewood. The stiffness modulus in the longitudinal direction for Norway spruce grown at a medium-fertility site increased with distance from the pith from 6±1 to 8.5±1 GPa. This parameter increased as the mean microfibril angle decreased. In the radial and tangential directions, the stiffness modulus was nearly constant, at 1±0.15 and 0.35±0.04 GPa, respectively. The longitudinal stiffness modulus of fast-growing clonal trees, which contained a large share of juvenile wood and were growing on a fertile site, was ca. 30% smaller (4±1 GPa near the pith and 6±1 GPa at the age of 12 years) than that of trees on a medium-fertility site. No difference was found in the radial and tangential stiffness modulus between stems grown at the two sites.

Phase-delayed laser diode array allows ultrasonic guided wave mode selection and tuning

Selecting and tuning modes are useful in ultrasonic guided wave non-destructive testing (NDT) since certain modes at various center frequencies are sensitive to specific types of defects. Ideally one should be able to select both the mode and the center frequency of the launched waves. We demonstrated that an affordable laser diode array can selectively launch either the S0 or A0 ultrasonic wave mode at a chosen center frequency into a polymer plate. A fiber-coupled diode array (4 elements) illuminated a 2 mm thick acrylic plate. A predetermined time delay matching the selected mode and frequency was employed between the output of the elements. The generated ultrasound was detected by a 215 kHz piezo receiver. Our results imply that this array permits non-contacting guided wave ultrasonic NDT. The solution is small, affordable, and robust in comparison to conventional pulsed lasers. In addition, it does not require experienced operators.

Measuring paper wetting processes with laser transmission

We introduce a method to measure paper wetting based on the measurement of monochromatic (670 nm) light transmission through paper. The samples were 49.8–51.7 g m−2 handsheets, the hydrophobicity of which was tuned by the fibre content of the furnish. In addition, one of the samples was internally sized. Impact wetting with isopropanol and water mist pulses was applied. The duration of a pulse was 100 ms, and the amount of liquid per pulse was 12.6 ± 1.2 g m−2. Optical changes in a paper sample were detected by measuring the average intensity of transmitted light through a selected area. The results showed that different wetting processes (pure capillary and combined capillary and diffusion wetting) could be distinguished from each other. With the presented method, differences in the individual behaviour of the samples during wetting could also be seen.

Air-coupled ultrasonic measurement of the change in roughness of paper during wetting

We investigated the change in surface roughness of paper during wetting. Four kinds of paper were examined by time-dependent attenuation of focused 1.2 MHz airborne ultrasound reflected from a paper sample. The samples were wetted with fog from mixtures of water and isopropanol and the transmitted ultrasonic signal was measured at 15 ms intervals for 16 s after the application of the mixture. The results showed that the attenuation of the reflected sound by time differs for various kinds of paper, indicating that there are differences in the development of wetting.

Photo-acoustic excitation and detection of guided ultrasonic waves in bone samples covered by a soft coating layer

Photo-acoustic (PA) excitation was combined with skeletal quantitative ultrasound (QUS) for multi-mode ultrasonic assessment of human long bones. This approach permits tailoring of the ultrasonic excitation and detection so as to efficiently detect the fundamental flexural guided wave (FFGW) through a coating of soft tissue. FFGW is a clinically relevant indicator of cortical thickness. An OPO laser with tunable optical wavelength, was used to excite a photo-acoustic source in the shaft of a porcine femur. Ultrasonic signals were detected by a piezoelectric transducer, scanning along the long axis of the bone, 20-50 mm away from the source. Five femurs were measured without and with a soft coating. The coating was made of an aqueous gelatin-intralipid suspension that optically and acoustically mimicked real soft tissue. An even coating thickness was ensured by using a specific mold. The optical wave length of the source (1250 nm) was tuned to maximize the amplitude of FFGW excitation at 50 kHz frequency. The experimentally determined FFGW phase velocity in the uncoated samples was consistent with that of the fundamental antisymmetric Lamb mode (A0). Using appropriate signal processing, FFGW was also identified in the coated bone samples, this time with a phase velocity consistent with that theoretically predicted for the first mode of a fluid-solid bilayer waveguide (BL1). Our results suggest that photo-acoustic quantitative ultrasound enables assessment of the thickness-sensitive FFGW in bone through a layer of soft tissue. Photo-acoustic characterization of the cortical bone thickness may thus become possible.

Crystallization and shear modulus of a forming biopolymer film determined by in situ x-ray diffraction and ultrasound reflection methods

The structure and the rigidity of a forming biopolymer film were determined using concurrent x-ray diffraction and ultrasonic reflection measurements. Film formation of a xylan solution (de-ionized water, 10g∕l xylan, 4g∕l glycerol) was studied during water evaporation at 24(±2)°C, 37(±5)%RH. X-ray diffraction (XRD) data showed the crystallization and ultrasonic data the increase of the shear modulus (G) during water evaporation. Xylan crystallized into small xylan dihydrate crystallites, the number of which increased as water evaporated. Crystallization began earlier than the increase in G during film formation. The increase in G also continued after the crystallites were fully formed, indicating still ongoing structural changes in the amorphous parts. The maximum value of G was 0.1–0.5GPa. XRD measurements performed ex situ showed a crystallinity of 16%–19% (±5%) and a fairly isotropic crystallite orientation in the surface plane of the films.

Changes in Nanostructure of Wood Cell Wall during Deformation

The excellent mechanical properties of wood arise from its cellular and cell wall structure. X-ray scattering, ultrasound, and mechanical testing is combined to study the effects of strain on crystalline cellulose in wood. Results for dry and re-moistened softwood samples are reviewed and new results are presented for native, never-dried samples of Silver birch. When softwood is stretched parallel to the cell axis, the mean microfibril angle diminishes significantly in compression wood, but only slightly in clear wood. The cellulose chains in the crystallites elongate and their distance diminishes. In the never-dried Silver birch samples, axial strain caused the mode of the microfibril angle distribution to slightly decrease from the initial value of 14 degrees to 12 degrees. Unlike in softwood, in never-dried birch crystalline cellulose showed auxetic tensile behaviour. The distance of the chains increased and the X-ray Poisson ratio νca was negative, -0.3 ± 0.2. Dehydration of never-dried Silver birch caused no difference to the microfibril angle distribution.

Photo-acoustic excitation and detection of fundamental antisymmetric Lamb mode in coated bone phantoms

Photo-acoustic (PA) imaging was combined with skeletal quantitative ultrasound (QUS) for multi-mode ultrasonic assessment of human long bones. This approach permits tailoring the ultrasonic excitation and detection to efficiently receive the fundamental antisymmetric Lamb mode (A0) through a coating of soft tissue. The method was tested on five axisymmetric bone phantoms of individualized wall thickness (1-5 mm) made of a composite material and coated with a layer (2.5 mm) of soft material that mimics the soft tissue. Signals were excited with a pulsed Nd:Yag laser at 532 nm wavelength and detected on the same side of the coated phantom with (i) a laser Doppler vibrometer (LDV) and for comparison also with (ii) a piezoelectric contact ultrasound receiver, scanning a source-receiver distance of 20-50 mm along the phantom. At a centre frequency of 50 kHz, a phase velocity consistent with that of the theoretically predicted A0 mode was identified in the recorded signals. Our results thus suggest that photo-a...

Concurrent structural and mechanical characterization of forming colloidal film by ultrasound and light

We combined noninvasive ultrasonic and optical measurements to estimate the mechanical properties of forming colloidal films. Light reflection measurements determined the stage of drying and film structure. A concurrent ultrasound measurement quantified the film stiffness. The main finding was that compressing capillary forces induced a temporal peak in film stiffness when air began to enter the pores in the film. We believe that empirically observing such a stiffening event has not been reported before. This finding advances the understanding of the physics of consolidating suspensions.