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Laser Speckle Contrast Analysis (LASCA) has been proven to be a highly useful tool for the full-field determination of the blood perfusion of a variety of tissues. Some of the major advantages of this technique are its relatively high spatial and temporal resolution as well as its good or excellent accordance to Doppler systems. However, traditionally it is only able to report a single characteristic speed regarding to the actual range of interest. This might be misleading if multiple characteristic speeds are present (e. g. tremor and perfusion in skin) or if several kinds of tissues are mixed (e. g. parenchyma and vessels in brain). Here we present two relatively simple extensions of LASCA for these problems. The application of multiple autocorrelation functions (combined with the usage of multiple exposure times) can help in the separation of multiple characteristic speeds. We also present a useful method for the separation of information those originate from a mixture of different tissues. The latter method can be also implemented to single-exposure systems.

Laser Speckle Contrast Analysis (LASCA) was introduced in 1981. Since then, several enhancements were applied to it. Nowadays, the technique can provide relatively high accuracy as well as high temporal and spatial resolution during the examination of ocular or cerebral tissues. However, in the case of skin, the results are highly affected by the intensive scattering on the skin surface, as the scattering on the non-moving parts of the sample lead to the detrimental decrease of the accuracy. We present a LASCA method based on the use of multiple exposure times, combined with the switching-mode control of the light intensity and a special sampling technique to achieve near to real-time measurement of the skin perfusion. The system based on our method is able to automatically handle the destructive effect of the skin surface and re-tune itself according to the changes of the sample, while it provides full-field perfusion maps with high accuracy, without the need of any precalibrations.

An atomic force microscopic method to study the incubation states of UV laser irradiated polymer samples is presented. Targets were illuminated by different number of pulses at 5.8 and 8.9 mJ/cm2 fluences. The induced adhesive and morphological changes were investigated simultaneously by an atomic force microscope equipped with a pulsed force mode extension. Importantly, below 100 pulses morphological changes were not observable while significant changes in the adhesion were found as a result of the incubation at 8.9 mJ/cm2 fluence. This method allows the imaging and detection of the whole laser modified area with nanometer resolution. [ABSTRACT FROM AUTHOR]

We present an investigation on absorbing film assisted laser induced forward transfer (AFA-LIFT) of fungus (Trichoderma) conidia. A KrF excimer laser beam [λ=248 nm,FWHM=30 ns (FWHM, full width at half maximum)] was directed through a quartz plate and focused onto its silver coated surface where conidia of the Trichoderma strain were uniformly spread. The laser fluence was varied in the range of 0–2600 mJ/cm2 and each laser pulse transferred a pixel of target material. The average irradiated area was 8×10-2 mm2. After the transfer procedure, the yeast extract medium covered glass slide and the transferred conidia patterns were incubated for 20 h and then observed using an optical microscope. The transferred conidia pixels were germinated and the areas of the culture medium surfaces covered by the pixels were evaluated as a function of laser fluence. As the laser fluence was increased from 0 to 355 mJ/cm2 the transferred and germinated pixel area increased from 0 to 0.25 mm2. Further increase in fluence resulted in a drastic decrease down to an approximately constant value of 0.06 mm2. The yield of successful transfer by AFA-LIFT and germination was as much as 75% at 355 mJ/cm2. The results prove that AFA-LIFT can successfully be applied for the controlled transfer of biological objects. [ABSTRACT FROM AUTHOR]

ArF excimer laser ablation of micrometer size smoke grains was investigated. It was demonstrated that this procedure is suitable for destruction of these particulates in consequence of very fast heating, oxidation, burning, and evaporation. The time-resolved investigations revealed that the destruction process takes place between 0 and 7 ns after the maximum of the excimer pulse. The efficiency of breaking into small pieces was found to be dependent on the excimer laser fluence. Atomic force microscopic investigations of the sedimented smoke particles proved that the size of the grains significantly decreased by the excimer laser radiation. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Highlights: [•] A method for determining fractal dimension of cauliflower-like layers is presented. [•] An objective thresholding routine for SEM micrographs is introduced. [•] A fractal dimension of 1.83 for TiO x films grown at 5–50Pa pressures was found. [•] The fractal structure of inverse pulsed laser deposited TiO x films was confirmed. [•] The obtained fractal dimension suggests that aggregation of plasma species has only limited contribution to the deposition. [Copyright &y& Elsevier]

Significance: Application of multiexposure speckle contrast imaging (MESI) methods for perfusion measurements can correct for the contribution of static scattering of the skin, at the expense of reduced temporal resolution as compared to classical single-exposure methods. Persistence of tissue scattering properties during the measurements could allow for an initial calibration and enhancement of the temporal resolution of the measurements., Aim: We aim to study the influence of the perfusion on the light scattering of the forearm skin and to use the obtained data for the enhancement of the temporal resolution., Approach: A wide range of skin perfusion states was induced while monitoring the changes in the dynamic range of the exposure-dependent contrast. Different measurement and evaluation methods were tested based on an initial MESI calibration followed by image recording with reduced number of exposure time values., Results: The changes in the skin perfusion can alter not only the contribution of the static scattering to the speckle images but also the short-exposure time contrast limit., Conclusions: The perfusion-dependent scattering of the skin can invalidate the precalibrations (e.g., β calibration) characterizing the combination of the given tissue and the measurement system., (© 2023 The Authors.)

The increasing prevalence of water insoluble or poorly soluble drugs calls for the development of new formulation methods. Common approaches include the reduction of particle size and degree of crystallinity. Pulsed laser ablation is a clean technique for producing sub-micrometre sized drug particles and has the potential to induce amorphization. We studied the effect of femtosecond pulsed laser ablation (ELI ALPS THz pump laser system: λ c  = 781 nm, τ = 135 fs) on meloxicam in distilled water and in air. The ablated particles were characterized chemically, morphologically and in terms of crystallinity. We demonstrated that femtosecond laser ablation can induce partial amorphization of the particles in addition to a reduction in particle size. In the case of femtosecond pulsed laser ablation in air, the formation of pure meloxicam spheres showed that this technique can produce amorphous meloxicam without the use of excipients, which is a unique result. We also aimed to describe the ablation processes in both investigated media., (© 2023. The Author(s).)