Single-beam Technique Research Articles

Radiosensitization of Allogenic Subcutaneous C6 Glioma Model with Focused Ultrasound-Induced Mild Hyperthermia.

The radiosensitization potential of focused ultrasound (FUS)-induced mild hyperthermia was assessed in an allogenic subcutaneous C6 glioma tumor model in rats. Mild hyperthermia at 42 °C was induced in tumors using a single-element 350 kHz FUS transducer. Radiation was delivered with a small animal radiation research platform using a single-beam irradiation technique. The combined treatment involved 20 min of FUS hyperthermia immediately before radiation. Tumor growth changes were observed one week post-treatment. A radiation dose of 2 Gy alone showed limited tumor control (30% reduction). However, when combined with FUS hyperthermia, there was a significant reduction in tumor growth compared to other treatments (tumor volumes: control-1174 ± 554 mm3, FUS-HT-1483 ± 702 mm3, 2 Gy-609 ± 300 mm3, FUS-HT + 2 Gy-259 ± 186 mm3; ANOVA p < 0.00001). Immunohistological analysis suggested increased DNA damage as a short-term mechanism for tumor control in the combined treatment. In conclusion, FUS-induced mild hyperthermia can enhance the effectiveness of radiation in a glioma tumor model, potentially improving the outcome of standard radiation treatments for better tumor control.

Single-beam technique for ultrashort pulse characterization based on the nonlinear ellipse rotation signal

We present a single-beam method based on the third-order nonlinear-ellipse-rotation (NER) measurement in thick samples to determine the pulse properties, including the duration and linear chirp. Our approach exploits the influence of the intrinsic second-order dispersions of the nonlinear materials, which affect the NER signal as a function of propagation. Two advantages can be highlighted: no delay line is required, and there are no phase-matching issues. To test our method, we characterized ultrafast chirped pulses from a Ti:sapphire amplified laser system and tunable pulses from an optical parametric amplifier using two samples with high dispersions and nonlinearities: SF6 and LaSF-N30 optical glasses.

Novel time-resolved CARS implementation for application in microscopy

Vibrational dephasing times for benzene and carbon disulfide are measured using a custom single-beam Coherent Anti-Stokes Raman Spectroscopy (CARS) setup. A femtosecond oscillator is used to pump a polarization maintaining all normal dispersion photonic crystal fibre (PM-ANDi-PCF) to generate a broad band supercontinuum, covering a spectral region from 680 to 900 nm. The dispersion properties of the PM-ANDi-PCF ensures the supercontinuum is stable and there exists a fixed phase relationship between the spectral components of the supercontinuum. This enables its temporal compression using i2PIE, implemented using a liquid crystal spatial light modulator (SLM) in a 4f geometry. This SLM is also used to shape the pulse spectrally and temporally. With this setup we could demonstrate time-resolved CARS, measuring the vibrational relaxation times of a carbon disulfide (CS2)/benzene mixture, and eliminate the non-resonant background completely. The main advantage of this setup is the fact that it is a single beam technique, eliminating the requirement for aligning the overlap of the pump and probe, both spatially and temporally, in the focal plane of the microscope. The strengths and limitations of the technique are highlighted and the route to time-resolved/background free vibrational microscopy is proposed.

Improving side-pumped solar lasers using ring-array concentrators

ABSTRACT We report here a significant enhancement in side-pumped solar laser collection efficiency and solar-to-laser conversion efficiency by a ring-array primary concentrator. A single and a dual-rod side-pumping configuration were numerically investigated. In the former, a thick laser rod was pumped with the full collection area of the ring-array solar concentrator. In the latter, two thin laser rods were pumped simultaneously. 49.70 W continuous-wave multimode solar laser power, corresponding to 29.06 W/m2 collection efficiency, and 3.06% solar-to-laser power conversion efficiency were numerically attained for the dual-rod side-pumping scheme, being 1.65 and 1.26 times higher than the previous experimental records with Nd:YAG side-pumping configurations. A three-folding-scheme single laser beam technique is presented, enabling a significant improvement of laser beam quality factors.

High-resolution quantitative phase imaging based on a spatial light modulator and incremental binary random sampling.

We propose a single-beam high-resolution quantitative phase imaging method based on a spatial light modulator (SLM) and an incremental binary random sampling (IBRS) algorithm. In this method, the image of the test object presents on the image sensor through an optical microscopy system composed of an objective lens and a collimating lens. A transmittance SLM displaying a group of well-designed IBRS patterns is inserted in the optical microscopy system to modulate the object wavefront. The phase information of the object image can be quantitatively retrieved from the recorded intensities using the IBRS algorithm and the amplitude obtained directly from the diffraction intensity. The IBRS algorithm employed in our method has higher accuracy for phase retrieval compared with our previously proposed complementary random sampling algorithm, which is confirmed by simulations. Further, we demonstrate experimentally the feasibility of our method through several examples: phase imaging of immersion oil droplets with a diffraction-limited lateral resolution of 1.54 µm and a few microbiological specimens with 0.70 µm. Experimental results reveal that our proposed method provides a feasible single-beam technique for quantitative phase imaging with a high spatial resolution.

Toward sustainable performance of reservoir sedimentation in aquatic environment of Katery lake, Tamil Nadu, India

In present study, a detailed analysis on the rate of sedimentation of Katery lake (Tamil Nadu, India) was performed by using Differential Global Positioning System-based single-beam dual-frequency echo sounder bathymetry technique to find out the amount of sediment deposited over the years and reasons behind the water scarcity to local population. The collected bathymetry data during survey were processed with MATLAB and Surfer software for lake bed surface profile generation to find out the depth of water and deposited sediments, while the volume estimation was carried out by Extended Simpson 3/8 method. Sedimentation analysis was performed over the time interval of 10 years during 2003 and 2013. Herein, it was observed that rate of sedimentation was 3224.8 m3/year and the estimated quantity of deposited silt was 156,327 m3 which are 69% of total water storage capacity of the lake. Therefore, in order to curtail the after-effects of fast sedimentation, the rejuvenation program was executed in the years 2014–2015, to maintain long-term sustainability and performance of the lake. Sediment estimation was validated using numerical analysis and practical dredged volume, which helped in regaining 239% water storage capacity of lake. Thus, the lake rejuvenation program was successfully executed using bathymetry survey analysis for all three phases.

Environmental Influence on Module Delamination Rate

This study begins to investigate the role of environmental factors, such as temperature and humidity, on the delamination kinetics of the ethylene vinyl acetate (EVA)/silicon–photovoltaic (Si–PV) cell interface. A fracture mechanics approach based on a single cantilever beam technique is employed to measure the delamination rate as a function of applied driving force. To glean insight into the mechanisms of bonding and degradation at this interface, and the effect of manufacturing variability and quality, we consider a high-quality pristine EVA and two EVAs formulated with reduced amounts of its adhesion promoter, silane. Results indicate that a bulk change in the viscoelastic properties of the EVA dominates the delamination kinetics at high driving forces and low humidity and the effect of a chemical reaction only becomes apparent at higher humidity and lower driving forces. These findings suggest that only interfacial phenomenon of susceptible, degraded material may have to be considered to adequately model PV module delamination failure.

Elemental analysis of Brazilian coffee with ion beam techniques: From ground coffee to the final beverage

Brazilian coffee is well known worldwide due to its quality and richness in taste. The aim of the present study is to provide the elemental characterization of Brazilian coffee along different stages of the drip brewing process. To that end, samples from roasted ground coffee, spent coffee, paper filters and the final beverage were analyzed with one single ion beam technique, namely particle-induced X-ray emission (PIXE). In total, over 140 samples from 8 different Brazilian brands of ground coffee were analyzed. Large differences in some elemental concentrations were observed among different brands and among different batches of a single brand, which leads to high variances in the data. Concerning the beverage preparation, the analysis of the spent coffee shows that the transfer ratio from the ground coffee to the beverage differs for each element. Our results indicate that potassium and chlorine have the highest transfer ratio. Moreover, the concentration of rubidium is relatively high in drinking coffee. Finally, there is no influence of the elemental composition of paper filter in the preparation of drinking coffee.

Exclusive-OR Encryption by Photoconduction and Two-Photon Absorption in Carbon Nanotubes.

A two-wave photoconductive system dependent on the nonlinear optical absorption in carbon nano-tubes is presented. Optical irradiation at 532 nm wavelength and 1 nanosecond pulse duration was employed for performing the experiments. A vectorial two-wave mixing configuration was used in order to measure the absorptive and refractive nonlinearities. A single-beam transmittance technique was carried out to evaluate the photoconductivity and also it allows us to confirm the participation of the nonlinear optical absorption displayed by the samples. A two-photon absorption effect was identified as the main physical mechanism associated to the third order absorptive nonlinearity. The exclusive disjunctive logic function was achieved by the optoelectronic response of an interferometric configuration. An ultrasonic spray pyrolysis processing route was utilized for the preparation of the samples. The morphology of the nanotubes was estimated by using scanning electronic microscopy. By combining the photoconductive response of two different carbon nanotubes thin film samples, a straightforward XOR encryption was performed.

Nonlinear optical properties of bulk cuprous oxide using single beam Z-scan at 790 nm

The two-photon absorption (TPA) coefficient β and the nonlinear index of refraction n2 for bulk cuprous oxide (Cu2O) direct gap semiconductor single crystal have been measured by using a balance-detection Z-scan single beam technique, with an excellent signal to noise ratio. Both coefficients were measured at 790 nm using a 65 fs laser pulse at a repetition rate of 90.9 MHz, generated by a Ti:Sapphire laser oscillator. The experimental values for β were explained by using a model that includes allowed-allowed, forbidden-allowed, and forbidden-forbidden transitions. It was found that the forbidden-forbidden transition is the dominant mechanism, which is consistent with the band structure of Cu2O. The low value for β found in bulk, as compared with respect to thin film, is explained in terms of the structural change in thin films that result in opposite parities of the conduction and valence band. The n2 is also theoretically calculated by using the TPA dispersion curve and the Kramers-Kronig relations for nonlinear optics.

Influence of diamond particles content on the critical load for crack initiation and fracture toughness of SiOC glass–diamond composites

The crack initiation load and fracture toughness were characterized as a function of diamond particle content, up to 25 vol%, in silicon oxycarbide glass matrix by means of Vickers indentation and single edge notch beam (SENB) technique, respectively. The larger fracture toughness value of 3.21 ± 0.3 MPa m1/2 was reached for 20 vol% diamond content composites and the value was 4 times higher than that of the unreinforced glass. The addition of diamond particles greatly influenced the crack initiation load, which increased from 2.9 to 49.0 N. The enhancement in the fracture toughness and crack initiation load can be explained by both the intrinsic mechanical properties of diamond (especially the elastic properties; E ∼ 1100 GPa) and the diamond/SiOC glass interfacial bonding. A clear correlation was found between the fracture energy, the reinforced interparticle spacing and the residual stress arising upon cooling due to thermal expansion mismatch between the matrix and the diamond particles.

Periodic and aperiodic liquid crystal-polymer composite structures realized via spatial light modulator direct holography

In this work we present the first realization and characterization of two-dimensional periodic and aperiodic POLICRYPS (Polymer Liquid Crystal Polymer Slices) structures, obtained by means of a single-beam holographic technique exploiting a high resolution spatial light modulator (SLM). A first investigation shows that the gratings, operating in the Raman Nath regime, exhibit a morphology and a electro-optical behavior that are typical of the POLICRYPS gratings realized by two-beam interference holography.

High-resolution quantitative phase microscopic imaging in deep UV with phase retrieval

High-resolution three-dimensional (3D) microscopic imaging requires the use of short wavelengths. Quantitative 3D imaging techniques, such as digital holographic microscopy, require interference between the object beam and a known reference background for the extraction of phase information. At shorter wavelengths, due to short coherence lengths, it may be difficult to implement a two-beam off-axis setup. Thus, a single-beam technique, which provides complete phase information, may be better suited for short wavelengths. This Letter describes the development of a quantitative microscopy technique at 193 nm using multiple intensity samplings and phase retrieval.

Pulse train fluorescence technique for measuring triplet state dynamics

We report on a method to study the dynamics of triplet formation based on the fluorescence signal produced by a pulse train. Basically, the pulse train acts as sequential pump-probe pulses that precisely map the excited-state dynamics in the long time scale. This allows characterizing those processes that affect the population evolution of the first excited singlet state, whose decay gives rise to the fluorescence. The technique was proven to be valuable to measure parameters of triplet formation in organic molecules. Additionally, this single beam technique has the advantages of simplicity, low noise and background-free signal detection.

Colour holography: the ultimate 3D imaging technique

An overview of the colour holographic recording technique is presented. Colour holography is the most accurate imaging technology known to science. It is now possible to produce three-dimensional (3D) holographic images for display that are almost indistinguishable from the original object or scene. The current status of colour holography based on Denisyuk’s single-beam technique is presented including the rendition of colour in a hologram. The demand on the recording materials for such holograms is explained. The applications of display holography have increased when it is now possible to record artefacts in full colour for museums and for other display purposes, e.g. in advertising, art and documentation. The major advantages of holographic reproduction are discussed together with its limitations.

Reconstrução anatômica do LCA com duplo feixe: primeiros 40 casos

OBJETIVO: Discutir a técnica de reconstrução anatômica do ligamento cruzado anterior (LCA) com duplo feixe, a curva de aprendizado e os resultados preliminares. MÉTODOS: Quarenta pacientes com lesão do LCA foram submetidos à reconstrução anatômica com duplo feixe, utilizando-se do tendão semitendinoso para refazer a banda anteromedial (AM) e gracilis para refazer a banda posterolateral (PL) do joelho. RESULTADOS: Tivemos dois casos de limitação de extensão, sendo que em um deles foi necessária a realização de artrólise artroscópica, e um caso de trombose venosa profunda. CONCLUSÃO: A reconstrução do LCA com duplo feixe se mostrou factível, apesar de apresentar uma maior curva de aprendizado; e as vantagens da técnica proposta ainda deverão ser comprovadas se comparada com a técnica de feixe único.

FDTD analysis of photonic quasicrystals with different tiling geometries and fabrication by single-beam computer-generated holography

Multiple-beam holography has been widely used for the realization of photonic quasicrystals with high rotational symmetries not achievable by the conventional periodic crystals. Accurate control of the properties of the interfering beams is necessary to provide photonic band-gap structures. Here we show, by FDTD simulations of the transmission spectra of 8-fold quasiperiodic structures, how the geometric tiling of the structure affects the presence and properties of the photonic band-gap for low refractive index contrasts. Hence, we show an interesting approach to the fabrication of photonic quasicrystals based on the use of a programmable Spatial Light Modulator encoding Computer-Generated Holograms, that permits an accurate control of the writing pattern with almost no limitations in the pattern design. Using this single-beam technique we fabricated quasiperiodic structures with high rotational symmetries and different geometries of the tiling, demonstrating the great versatility of our technique.

Two-dimensional photonic quasicrystals by single beam computer-generated holography

Recently important efforts have been dedicated to the realization of a new kind of photonic crystals, known as photonic quasicrystals, in which the lack of the translational symmetry is compensated by rotational symmetries not achievable by the conventional periodic crystals. Here we show a novel approach to their fabrication based on the use of a programmable Spatial Light Modulator encoding Computer-Generated Holograms. Using this single beam technique we fabricated Penrose-tiled structures possessing rotational symmetry up to 23-fold, and a two-dimensional Thue-Morse structure, which is an aperiodic structure not achievable by multiple beam holography.

Nonlinear change in refractive index of Co2+:ZnSe at short-pulse single-beam 1.54-μm Z-scan probing

An experimental study and theoretical modeling of the nonlinear change in refractive index of a Co2 +: ZnSe crystal at the short-pulse single-beam probing at the wavelength 1.54 μm is reported. In the experimental conditions of negligible contributions in the index non-linearity stemming from the Kerr-effect and inhomogeneous heating, the nonlinear change in refractive index in Co2 +:ZnSe is shown to be caused by the resonant Co2 + population-perturbation effect (i.e., by the Co2 + ground-state absorption saturation). The Z-scan single-beam technique and novel theoretical approach addressing the resonant nonlinear refraction in a saturable doped medium are used, respectively, for an experimental and theoretical inspection of the phenomenon. For a set of Co2 +:ZnSe samples with different concentrations of Co2 + ions at the short-pulse (200 ns) mJ-range probing, we show that the maximal nonlinear change in refractive index is about of units of 10− 4 at the chosen wavelength.

Metal nanoparticles-embedded three-dimensional microstructures created by single-beam holography

Silver nanoparticles-embedded three-dimensional (3D) dielectric microstructures are demonstrated with a single-beam holographic technique. By using a top-cut triangular prism to split an incident plane wave into four umbrellalike beams and then to automatically combine the four beams in Ag+-doped dielectric matrices, a 3D microstructure with periodically embedded Ag nanoparticles is encoded. Our method can be used to create any 3D microstructures in various materials and hence provide a robust way for photonic crystal fabrications, label-free 3D biological imaging, and optical integration etc.