Holographically Recorded Low Spatial Frequency Volume Bragg Gratings and Holographic Optical Elements

Low spatial frequency volume gratings (a few hundred lines per millimetre) are near the borderline of what can be considered Bragg gratings. Nevertheless, in some applications, their very low selectivity can be a benefit because it increases the angular and spectral working range of the holographic optical element. This chapter presents work carried out using an instantaneously selfdeveloping photopolymer recording material and examines holographic optical elements with spatial frequencies below 500 lines/mm. The advantages of volume photopolymer holographic gratings are discussed in the context of existing research. Specific examples explored include a combination of off‐axis cylindrical lenses used to direct light from a solar simulator onto a c‐Si solar cell, producing increases of up to 60% in the energy collected. A study of the microstructure of such elements is also presented. A good fit is obtained between the experimental and theoretical Bragg curves and the microstructure of the element is examined directly using microscopy. This is followed by a discussion of an unusual holographic recording approach that uses the nonlinearities inherent in low spatial frequency grating profiles to record gratings using a single beam. In conclusion, the properties of low spatial frequency volume gratings are summarized and future development discussed

Illinois Cave Amphipod ( Gammarus acherondytes ) Recovery Plan

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Characterization of Dynamic Behaviour of MCF7 and MCF10A Cells in Ultrasonic Field Using Modal and Harmonic Analyses

<div><p>Treatment options specifically targeting tumour cells are urgently needed in order to reduce the side effects accompanied by chemo- or radiotherapy. Differences in subcellular structure between tumour and normal cells determine their specific elasticity. These structural differences can be utilised by low-frequency ultrasound in order to specifically induce cytotoxicity of tumour cells. For further evaluation, we combined <i>in silico</i> FEM (finite element method) analyses and <i>in vitro</i> assays to bolster the significance of low-frequency ultrasound for tumour treatment. FEM simulations were able to calculate the first resonance frequency of MCF7 breast tumour cells at 21 kHz in contrast to 34 kHz for the MCF10A normal breast cells, which was due to the higher elasticity and larger size of MCF7 cells. For experimental validation of the <i>in silico</i>-determined resonance frequencies, equipment for ultrasonic irradiation with distinct frequencies was constructed. Differences for both cell lines in their response to low-frequent ultrasonic treatment were corroborated in 2D and in 3D cell culture assays. Treatment with ~ 24.5 kHz induced the death of MCF7 cells and MDA-MB-231 metastases cells possessing a similar elasticity; frequencies of > 29 kHz resulted in cytotoxicity of MCF10A. Fractionated treatments by ultrasonic irradiation of suspension myeloid HL60 cells resulted in a significant decrease of viable cells, mostly significant after threefold irradiation in intervals of 3 h. Most importantly in regard to a clinical application, combined ultrasonic treatment and chemotherapy with paclitaxel showed a significantly increased killing of MCF7 cells compared to both monotherapies. In summary, we were able to determine for the first time for different tumour cell lines a specific frequency of low-intensity ultrasound for induction of cell ablation. The cytotoxic effect of ultrasonic irradiation could be increased by either fractionated treatment or in combination with chemotherapy. Thus, our results will open new perspectives in tumour treatment.</p></div

Decreased survival of HL60 cells after fractionated irradiation.

<p>HL60 suspension cells were treated by ultrasonic irradiation once, twice or three times at intervals of 3h (2x 3 h, 3x 3 h) or 6 h (2x 6 h). The number of vital cells was determined by FACS 1 h after each irradiation. (The number of vital cells of the untreated control was set as 100%.) Results represent the means of data from three independent experiments; the error bars represent the standard errors; p-values were calculated by the two-sided, paired Student’s t-test with * p<0.05, ** p<0.01, *** p<0.001.</p

Harmonic vibration analysis of (A) MCF7 and (B) MCF10A cells (minimal sizes for both cell types) with external hydrostatic pressure in a frequency range of 20 kHz up to 60 kHz showing the displacement amplitudes.

<p>The red horizontal lines depict the maximum cell size which allows the amplitudes with the cell dimension to be compared.</p

Influence of (A) material properties (Young’s modulus for cytoplasm and nucleus are as first and second value in parenthesis), (B) cell dimensions, (C) thickness of the actin cortex in percent of the cell radius, and (D) cell embedding (Young’s modulus for agar in parenthesis) on natural frequencies of MCF10A cells (A) or MCF7 cells (A-D).

<p>Influence of (A) material properties (Young’s modulus for cytoplasm and nucleus are as first and second value in parenthesis), (B) cell dimensions, (C) thickness of the actin cortex in percent of the cell radius, and (D) cell embedding (Young’s modulus for agar in parenthesis) on natural frequencies of MCF10A cells (A) or MCF7 cells (A-D).</p

Decreased survival of MCF7 cells after irradiation with an ultrasonic frequency of 24.5 kHz as determined by XCelligence (Roche).

<p>Decreased survival of MCF7 cells after irradiation with an ultrasonic frequency of 24.5 kHz as determined by XCelligence (Roche).</p

Increased death of MCF7 and MDA-MB-231 cells after irradiation with an ultrasonic frequency of 24.5 kHz.

<p>(A) Cells either cultivated in 2D culture or (B) growing in 3D culture on alginate beads (gems) were treated with 24.5 kHz and four different intensities for 4 min; 1 h later the proportion of dead cells (propidium iodide (PI) positive cells) was determined by FACS analysis. Results represent the means of data from eight (A) or three (B) independent experiments; the error bars represent the standard errors; p-values were calculated by the two-sided, paired Student’s t-test with * p<0.05, ** p<0.01.</p

Treatment of MCF7 cells with either (A) ultrasonic irradiation with 23.22 kHz and two different intensities (0.3 W/cm² or 1 W/cm², dark grey bars), (B) paclitaxel with 100 nM or 200 nM (light grey bars) or (C) combinations of both treatments (ultrasonic irradiation followed by paclitaxel treatment; white bars) with a) constant concentration of paclitaxel and different intensities of ultrasonic irradiation, and b) constant intensity and different concentrations of paclitaxel.

<p>Results represent the means of data from eight independent experiments; the error bars represent the standard errors; p-values were calculated by the two-sided, paired Student’s t- test with * p<0.05, ** p<0.01, *** p<0.001.</p