Minimum Spot Size Research Articles

Detection of Melamine in Soybean Meal Using Near-Infrared Microscopy Imaging with Pure Component Spectra as the Evaluation Criteria

Soybean meal was adulterated with melamine with the purpose of boosting the protein content for unlawful interests. In recent years, the near-infrared (NIR) spectroscopy technique has been widely used for guaranteeing food and feed security for its fast, nondestructive, and pollution-free characteristics. However, there are problems with using near-infrared (NIR) spectroscopy for detecting samples with low contaminant concentration because of instrument noise and sampling issues. In addition, methods based on NIR are indirect and depend on calibration models. NIR microscopy imaging offers the opportunity to investigate the chemical species present in food and feed at the microscale level (the minimum spot size is a few micrometers), thus avoiding the problem of the spectral features of contaminants being diluted by scanning. The aim of this work was to investigate the feasibility of using NIR microscopy imaging to identify melamine particles in soybean meal using only the pure component spectrum. The results presented indicate that using the classical least squares (CLS) algorithm with the nonnegative least squares (NNLS) algorithm, without needing first to develop a calibration model, could identify soybean meal that is both uncontaminated and contaminated with melamine particles at as low a level as 50 mg kg−1.

Tools for Defined Neural Networks on Multielectrode Arrays

Event Abstract Back to Event Tools for Defined Neural Networks on Multielectrode Arrays Serge Weydert1*, Greta Thompson-Steckel1, Harald Dermutz2, Hana Han1, Mathias Aebersold1, Csaba Forró1, Aline Renz1, Klas Tybrandt1, Tomaso Zambelli2 and Janos Voeroes1 1 ETH Zurich, Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, Switzerland 2 ETH Zürich, Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, Switzerland Motivation Deciphering the programming logic of the brain is one of the fundamental unsolved problems in neuroscience. In this work, we present a tool for approaching this challenge in a bottom-up manner. It represents a first step towards building topologically well-defined artificial neural networks on chips. Methods Using an atomic force microscope modified with a fluidic channel (FluidFM [1-4]) and a dynamic system of biomolecular coatings, we are able to perform living cell printing [7] and axon guidance [1] for forming unidirectional neuronal connections between network nodes. A hollow cantilever connected to a fluid chamber and a pressure reservoir deposits arbitrary solutions in the shape of confined spots (reliable minimum spot size of 3-5 µm), lines or any pattern on any flat surface. Using the FluidFM, it was possible to "write" adhesion promoting and growth signaling molecules in a highly dynamic and flexible manner and locally modify the adhesion properties in situ, i.e. by writing poly(L-lysine) to locally replace poly(L-lysine)-g-poly(ethylene glycol) [1,5]. In parallel, our aim is to also compare network activity at a single cell level to that at a population scale. As part of our approach, we have integrated structurally patterned neuronal circuits grown on a 3D scaffold with a custom-made MEA chip designed to improve the neuro-electronic interface [8,9] and to allow for high-throughput analysis. Results Once the adhesive landing spots are written and successfully occupied by cells after one day in vitro, the growth direction of interconnecting axons was successfully controlled by modifying the surface on the paths between the neurons sequentially in situ. We could confirm that the neurites growing on the controlled paths were mostly axons. Correlated activity of the neuron clusters was shown by a calcium indicator. Discussion and Conclusion The described system is a tool for neuroscientists who are interested in engineering simple well-defined neurologic circuits step-by-step and understanding functional activity by electrically stimulating and analyzing with multielectrode arrays. Despite its current limitations in scalability and usage complexity, it is a first and important step towards bottom-up neuroscience. Keywords: neural networks, Micoelectrode arrays Conference: MEA Meeting 2016 | 10th International Meeting on Substrate-Integrated Electrode Arrays, Reutlingen, Germany, 28 Jun - 1 Jul, 2016. Presentation Type: Poster Presentation Topic: MEA Meeting 2016 Citation: Weydert S, Thompson-Steckel G, Dermutz H, Han H, Aebersold M, Forró C, Renz A, Tybrandt K, Zambelli T and Voeroes J (2016). Tools for Defined Neural Networks on Multielectrode Arrays. Front. Neurosci. Conference Abstract: MEA Meeting 2016 | 10th International Meeting on Substrate-Integrated Electrode Arrays. doi: 10.3389/conf.fnins.2016.93.00115 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 22 Jun 2016; Published Online: 24 Jun 2016. * Correspondence: Dr. Serge Weydert, ETH Zurich, Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, Zurich, Switzerland, weydert@biomed.ee.ethz.ch Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Serge Weydert Greta Thompson-Steckel Harald Dermutz Hana Han Mathias Aebersold Csaba Forró Aline Renz Klas Tybrandt Tomaso Zambelli Janos Voeroes Google Serge Weydert Greta Thompson-Steckel Harald Dermutz Hana Han Mathias Aebersold Csaba Forró Aline Renz Klas Tybrandt Tomaso Zambelli Janos Voeroes Google Scholar Serge Weydert Greta Thompson-Steckel Harald Dermutz Hana Han Mathias Aebersold Csaba Forró Aline Renz Klas Tybrandt Tomaso Zambelli Janos Voeroes PubMed Serge Weydert Greta Thompson-Steckel Harald Dermutz Hana Han Mathias Aebersold Csaba Forró Aline Renz Klas Tybrandt Tomaso Zambelli Janos Voeroes Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Improvement of Filed Curvature Aberration in a Projector Lens by Using Hybrid Genetic Algorithm With Damped Least Square Optimization

This paper improves the filed curvature aberration (FCA) in a projector lens by using a hybrid genetic algorithm (GA) with damped least square (DLS) optimization. A modern projector lens still exposes its rays on a large flat screen to form the image, with the result that the FCA is one of the key aberrations dominating the image quality. Most commercial optical software applies the DLS optimization focus on the minimum spot size to optimize the lens, simultaneously making the FCA hard to improve. Merging the GA optimization can involve the FCA in the optimization process. As a result, using the hybrid GA with DLS optimization not only effectively suppresses the FCA but also remarkably enhances the image resolution in a projector lens design.

Experimental results on the irradiation of nuclear fusion relevant materials at the dense plasma focus ‘Bora’ device

Samples of materials counted as perspective ones for use in the first-wall and construction elements in nuclear fusion reactors (FRs) with magnetic and inertial plasma confinement (W, Ti, Al, low-activated ferritic steel ‘Eurofer’ and some alloys) were irradiated in the dense plasma focus (DPF) device ‘Bora’ having a bank energy of ⩽5 kJ. The device generates hot dense (T ∼ 1 keV, n ∼ 1019 cm−3) deuterium plasma, powerful plasma streams (v ∼ 3 × 107 cm s−1) and fast (E ∼ 0.1 … 1.0 MeV) deuterons of power flux densities q up to 1010 and 1012 W cm−2 correspondingly. ‘Damage factor’ F = q × τ0.5 ensures an opportunity to simulate radiation loads (predictable for both reactors types) by the plasma/ion streams, which have the same nature and namely those parameters as expected in the FR modules. Before and after irradiation we provided investigations of our samples by means of a number of analytical techniques. Among them we used optical and scanning electron microscopy to understand character and parameters of damageability of the surface layers of the samples. Atomic force microscopy was applied to measure roughness of the surface after irradiation. These characteristics are quite important for understanding mechanisms and values of dust production in FR that may relate to tritium retention and emergency situations in FR facilities. We also applied two new techniques. For the surface we elaborated the portable x-ray diffractometer that combines x-ray single photon detection with high spectroscopic and angular resolutions. For bulk damageability investigations we applied an x-ray microCT system where x-rays were produced by a Hamamatsu microfocus source (150 kV, 500 µA, 5 µm minimum focal spot size). The detector was a Hamamatsu CMOS flat panel coupled to a fibre optic plate under the GOS scintillator. The reconstruction of three-dimensional data was run with Cobra 7.4 and DIGIX CT software while VG Studio Max 2.1, and Amira 5.3 were used for segmentation and rendering. We have also provided numerical simulation of the fast ion beam action. The paper contains results on the investigations of modifications of the elemental contents, structure and properties of the materials.

Image beam from a wire laser

We demonstrate the formation of a narrow beam from a long (L??) laser with subwavelength transverse dimensions (wire laser) as an image of the subwavelength laser waveguide formed by a spherical lens. The beam is linearly diverging with the angle determined by the ratio of the wavelength to the lens radius, while the minimum beam spot size is the same as that of the image of a point source. We realize such a beam experimentally using a terahertz quantum cascade wire laser.

A sample holder with integrated laser optics for an ELMITEC photoemission electron microscope.

We present a new sample holder compatible with ELMITEC Photoemission Electron Microscopes (PEEMs) containing an optical lens and a mirror. With the integrated optical elements, a laser beam is focused from the back side of the sample at normal incidence, yielding a minimum spot size of about 1 μm. This opens up new possibilities for local laser excitations in PEEM experiments such as imaging all-optical magnetization switching at a small length scale.

Subcellular-level resolution MALDI-MS imaging of maize leaf metabolites by MALDI-linear ion trap-Orbitrap mass spectrometer.

A significant limiting factor in achieving high spatial resolution for matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) imaging is the size of the laser spot at the sample surface. Here, we present modifications to the beam-delivery optics of a commercial MALDI-linear ion trap-Orbitrap instrument, incorporating an external Nd:YAG laser, beam-shaping optics, and an aspheric focusing lens, to reduce the minimum laser spot size from ~50μm for the commercial configuration down to ~9μm for the modified configuration. This improved system was applied for MALDI-MS imaging of cross sections of juvenile maize leaves at 5-μm spatial resolution using an oversampling method. A variety of different metabolites including amino acids, glycerolipids, and defense-related compounds were imaged at a spatial resolution well below the size of a single cell. Such images provide unprecedented insights into the metabolism associated with the different tissue types of the maize leaf, which is known to asymmetrically distribute the reactions of C4 photosynthesis among the mesophyll and bundle sheath cell types. The metabolite ion images correlate with the optical images that reveal the structures of the different tissues, and previously known and newly revealed asymmetric metabolic features are observed.

Performance predictions of a focused ion beam from a laser cooled and compressed atomic beam

Focused ion beams are indispensable tools in the semiconductor industry because of their ability to image and modify structures at the nanometer length scale. Here, we report on performance predictions of a new type of focused ion beam based on photo-ionization of a laser cooled and compressed atomic beam. Particle tracing simulations are performed to investigate the effects of disorder-induced heating after ionization in a large electric field. They lead to a constraint on this electric field strength which is used as input for an analytical model which predicts the minimum attainable spot size as a function of, amongst others, the flux density of the atomic beam, the temperature of this beam, and the total current. At low currents (I < 10 pA), the spot size will be limited by a combination of spherical aberration and brightness, while at higher currents, this is a combination of chromatic aberration and brightness. It is expected that a nanometer size spot is possible at a current of 1 pA. The analytical model was verified with particle tracing simulations of a complete focused ion beam setup. A genetic algorithm was used to find the optimum acceleration electric field as a function of the current. At low currents, the result agrees well with the analytical model, while at higher currents, the spot sizes found are even lower due to effects that are not taken into account in the analytical model.

Long-term follow-up of standard photodynamic therapy with standardized small spot size for diffuse retinal pigment epitheliopathy.

To evaluate the long-term efficacy and safety of standard-fluence photodynamic therapy (PDT) with verteporfin using the minimum PDT spot size in patients with diffuse retinal pigment epitheliopathy (DRPE). This is a retrospective study of 67 DRPE cases treated with PDT using a standardized minimum spot size of 850 μm. Indocyanine green angiography (ICGA) was used to guide and determine the outcome of PDT treatment. Best-corrected visual acuity (BCVA), central retinal thickness (CRT), recurrences, and adverse events were recorded and analyzed. The mean follow-up period of the study was 35.8 ± 16.6 months. There was a statistically significant difference in BCVA between baseline and the end of the follow-up (p<0.001). The BCVA improved in 41 eyes (61.2%), remained stable in 20 eyes (29.9%), and deteriorated in 6 eyes (9%). Accordingly, there was a statistically significant difference in CRT between the baseline and the last follow-up visit (p<0.001). The recurrence rate was 13.4% and only one eye presented a recurrence at the same site as the laser treatment. No adverse events were noted. Application of ICGA-guided standard PDT, with a laser spot size of minimum diameter, on the site of active leakage seems to be effective and safe in a long-term follow-up period, presenting improvement in BCVA, decrease in CRT, and low rate of recurrence.

Determination of spot size and acid diffusion length in positive chemically amplified resist for e-beam lithography at 100 and 5 kV

An experimental method to determine the beam spot size and the acid diffusion length of a positive chemically amplified electron-beam resist (p-CAR) is proposed. This method is applied to a reference p-CAR with a Vistec VB6 electron beam at 100 kV and with a MAPPER tool at 5 kV. Beam spot size characterization is based on the width measurement of a single line exposure. This procedure is applied to two specific dose ranges. In the first one, the chemical mechanism occurring in the exposed resist is dominated by acid catalytic deprotection of a partially protected polymer (standard process). In the second dose range, the chemistry is governed by the cross-linking mechanism due to the intentional overdose of the p-CAR, leading to a polarity inversion. The authors assume that comparing the results obtained with the standard and the cross-linked p-CAR enables the determination of the acid diffusion length of the p-CAR process. This hypothesis was verified with measurements performed with a nonchemically amplified process. A relationship between the best exposure latitudes achieved at 5 and 100 kV and the minimum spot sizes determined with the present method is observed with very high resolution grating exposures. In this work, a suitable method is proposed for fine resist process characterization.

Constraints on a charge in the Reissner-Nordström metric for the black hole at the Galactic Center

Using an algebraic condition of vanishing discriminant for multiple roots of fourth degree polynomials we derive an analytical expression of a shadow size as a function of a charge in the Reissner -- Nordstr\"om (RN) metric \cite{Reissner_16,Nordstrom_18}. We consider shadows for negative tidal charges and charges corresponding to naked singularities $q=\mathcal{Q}^2/M^2 > 1$, where $\mathcal{Q}$ and $M$ are black hole charge and mass, respectively, with the derived expression. An introduction of a negative tidal charge $q$ can describe black hole solutions in theories with extra dimensions, so following the approach we consider an opportunity to extend RN metric to negative $\mathcal{Q}^2$, while for the standard RN metric $\mathcal{Q}^2$ is always non-negative. We found that for $q > 9/8$ black hole shadows disappear. Significant tidal charges $q=-6.4$ (suggested by Bin-Nun (2010)) are not consistent with observations of a minimal spot size at the Galactic Center observed in mm-band, moreover, these observations demonstrate that a Reissner -- Nordstr\"om black hole with a significant charge $q \approx 1$ provides a better fit of recent observational data for the black hole at the Galactic Center in comparison with the Schwarzschild black hole.

Multi-image acquisition-based distance sensor using agile laser spot beam.

We present a novel laser-based distance measurement technique that uses multiple-image-based spatial processing to enable distance measurements. Compared with the first-generation distance sensor using spatial processing, the modified sensor is no longer hindered by the classic Rayleigh axial resolution limit for the propagating laser beam at its minimum beam waist location. The proposed high-resolution distance sensor design uses an electronically controlled variable focus lens (ECVFL) in combination with an optical imaging device, such as a charged-coupled device (CCD), to produce and capture different laser spot size images on a target with these beam spot sizes different from the minimal spot size possible at this target distance. By exploiting the unique relationship of the target located spot sizes with the varying ECVFL focal length for each target distance, the proposed distance sensor can compute the target distance with a distance measurement resolution better than the axial resolution via the Rayleigh resolution criterion. Using a 30mW 633nm He-Ne laser coupled with an electromagnetically actuated liquid ECVFL, along with a 20cm focal length bias lens, and using five spot images captured per target position by a CCD-based Nikon camera, a proof-of-concept proposed distance sensor is successfully implemented in the laboratory over target ranges from 10 to 100cm with a demonstrated sub-cm axial resolution, which is better than the axial Rayleigh resolution limit at these target distances. Applications for the proposed potentially cost-effective distance sensor are diverse and include industrial inspection and measurement and 3D object shape mapping and imaging.

Simulation Study on Optically Designed Refractive Beam Expander for Nd: YAG Laser Harmonics for 7 Km Detection Range

The simulation study has been conducted for the harmonics of Nd: YAG laser, namely the second harmonic generation SHG, the third harmonic generation THG, and the fourth harmonic generation FHG. Determination of beam expander's expansion ratio for specific wavelength and given detection range is the key in beam expander design for determining minimum laser spot size at the target. Knowing optimum expansion ratio decreases receiving unit dimensions and increases its performance efficiency. Simulation of the above mentioned parameters is conducted for the two types of refractive beam expander, Keplerian and Galilean. Ideal refractive indices for the lenses are chosen adequately for Nd: YAG laser harmonics wavelengths, so that increasing transmission of laser beam, consequently the received power to the detector for practical convenience.

Simulation Study on Optically Designed Refractive Beam Expander for Nd: YAG Laser Harmonics for 7 Km Detection Range

The simulation study has been conducted for the harmonics of Nd: YAG laser, namely the second harmonic generation SHG, the third harmonic generation THG, and the fourth harmonic generation FHG. Determination of beam expander's expansion ratio for specific wavelength and given detection range is the key in beam expander design for determining minimum laser spot size at the target. Knowing optimum expansion ratio decreases receiving unit dimensions and increases its performance efficiency. Simulation of the above mentioned parameters is conducted for the two types of refractive beam expander, Keplerian and Galilean. Ideal refractive indices for the lenses are chosen adequately for Nd: YAG laser harmonics wavelengths, so that increasing transmission of laser beam, consequently the received power to the detector for practical convenience.

Effect of electron focusing in x-ray sources using LiTaO3 crystals excited by neodymium-doped yttrium lithium fluoride laser light

The intensity of x-rays from a 15 mm-diameter metal target bombarded by electrons emitted from a LiTaO3 crystal is found to depend upon the distance, h, between the crystal and the target. The electron emission of the LiTaO3 crystal is generated by being excited with light from a neodymium-doped yttrium lithium fluoride laser. The x-ray intensity is highest for h = 6 mm, coinciding also with a minimum electron spot size. The coincidence of the minimum electron spot size and maximum x-ray intensity with the 15 mm-diameter target is a result of self-focusing of the electrons by the higher electric field at the edge of the cylindrical crystal. The maximum electron energy at h = 6 mm with 120 s of laser irradiation is 47 keV, which is estimated from the maximum energy of bremsstrahlung x-rays.

Supermassive black hole at the galactic center

We derive an analytical expression of a shadow size as a function of a charge in the Reissner - Nordstr?m (RN) metric. Using the derived expression we consider shadows for negative tidal charges and charges corresponding to naked singularities q=Q2/M2>1, where Q and M are black hole charge and mass, respectively. An introduction of a negative tidal charge q can describes black hole solutions in theories with extra dimensions, so following the approach we consider an opportunity to extend RN metric to negative Q2, while for the standard RN metric Q2 is always non-negative. We found that for q > 9=8 black hole shadows disappear. Significant tidal charges q=-6.4 are not consistent with observations of a minimal spot size at the Galactic Center observed in mm-band, moreover, these observations demonstrate that in comparison with the Schwarzschild black hole a Reissner-Nordstr?m black hole with a significant charge q ? 1 provides a better fit of recent observational data for the black hole at the Galactic Center.

Process parameters investigation of a laser-generated single clad for minimum size using design of experiments

Purpose – This paper aims to investigate the effect of four important process parameters (i.e. laser focal distance, travel speed, feeding gas flow rate and standoff distance) on the size of single clad geometry created by coaxial nozzle-based powder deposition by high power laser. Design/methodology/approach – Design of experiments (DOE) and statistical analysis methods were both used to find optimum parameter combinations to get minimum sized clad, i.e. clad width and clad height. Factorial experiment arrays were used to design parameter combinations for creating experimental runs. Taguchi optimization methodology was used to find out optimum parameter levels to get minimum sized clad geometry. Response surface method was used to investigate the nonlinearity among parameters and variance analysis was used to assess the effectiveness level of each problem parameters. Findings – The overall results show that wisely selected four problem parameters have the most prominent effects on the final clad geometry. Generally, minimum clad size was achieved at higher levels of gas flow rate, travel speed and standoff distance and at minimum spot size level of the laser focal distance. Originality/value – This study presents considerable contributions in assessing the importance level of problems parameters on the optimum single clad geometry created laser-assisted direct metal part fabrication method. This procedure is somewhat complicated in understanding the effects of the selected problem parameters on the outcome. Therefore, DOE methodologies are utilized so that this operation can be better modeled/understood and automated for real life applications. The study also gives future direction for research based on the presented results.

Production of 70-nm Cr dots by laser-induced forward transfer

The effect of donor film thickness and laser beam fluence on the size of laser-induced forward transfer (LIFT) spots is studied to achieve sub-100 nm features. A 130 fs, 800 nm laser is focused on ultrathin Cr films, and the transfer and ablation thresholds of these films at various thicknesses are determined. The minimum transfer spot size decreases with decreasing donor film thickness and incident laser fluence. Minimum LIFT spots of 70-450 nm diameter are obtained from films of 20-80 nm thickness, respectively. The 70 nm diameter transfer spots obtained from sputtered continuous films are the smallest to date.

An adjustable focusing system for a 2 MeV H− ion beam line based on permanent magnet quadrupoles

A compact adjustable focusing system for a 2 MeV H− RFQ Linac is designed, constructed and tested based on four permanent magnet quadrupoles (PMQ). A PMQ model is realised using finite element simulations, providing an integrated field gradient of 2.35 T with a maximal field gradient of 57 T m−1. A prototype is constructed and the magnetic field is measured, demonstrating good agreement with the simulation. Particle track simulations provide initial values for the quadrupole positions. Accordingly, four PMQs are constructed and assembled on the beam line, their positions are then tuned to obtain a minimal beam spot size of (1.2 × 2.2) mm2 on target. This paper describes an adjustable PMQ beam line for an external ion beam. The novel compact design based on commercially available NdFeB magnets allows high flexibility for ion beam applications.

Effects of Tube Voltage on Phase-Contrast Imaging for Different Microfocus X-Ray Tubes

In the past decade, phase-contrast imaging (PCI) has become a hot research with an increased improvement of the image contrast with respect to conventional absorption radiography. In this paper, effects of tube voltage (kVp) on propagation-based phase-contrast imaging have been investigated with two types of microfocus x-ray tubes, a conventional sealed x-ray tube with the focal spot size of 13 - 20 μm and an open x-ray tube with minimum focal spot size less than 2 μm. A cooled x-ray CCD detector with the pixel size of 24 μm was used to acquire digital images. Two thin plastic sheets with different thickness were used as radiography phantoms. Two different phenomena were observed for the two x-ray tubes. For the open tube, phase-contrast effect has a slight drop with the increasing of tube voltage, however, it is opposite for the sealed tube. A further investigation indicates that the variation of focal spot size causes the abnormal result for the sealed tube. It also shows that phase-contrast effect is more sensitive to focal spot size than tube voltage.