Modes Of Illumination Research Articles

Petrographic Microscopy with Ray Tracing and Segmentation from Multi-Angle Polarisation Whole-Slide Images

‘Slide scanners’ are rapid optical microscopes equipped with automated and accurate x-y travel stages with virtual z-motion that cannot be rotated. In biomedical microscopic imaging, they are widely deployed to generate whole-slide images (WSI) of tissue samples in various modes of illumination. The availability of WSI has motivated the development of instrument-agnostic advanced image analysis software, helping drug development, pathology, and many other areas of research. Slide scanners are now being modified to enable polarised petrographic microscopy by simulating stage rotation with the acquisition of multiple rotation angles of the polariser–analyser pair for observing randomly oriented anisotropic materials. Here we report on the calibration strategy of one repurposed slide scanner and describe a pilot image analysis pipeline designed to introduce the wider audience to the complexity of performing computer-assisted feature recognition on mineral groups. The repurposed biological scanner produces transmitted light plane- and cross-polarised (TL-PPL and XPL) and unpolarised reflected light (RL) WSI from polished thin sections or slim epoxy mounts at various magnifications, yielding pixel dimensions from ca. 2.7 × 2.7 to 0.14 × 0.14 µm. A data tree of 14 WSI is regularly obtained, containing two RL and six of each PPL and XPL WSI (at 18° rotation increments). This pyramidal image stack is stitched and built into a local server database simultaneously with acquisition. The pyramids (multi-resolution ‘cubes’) can be viewed with freeware locally deployed for teaching petrography and collaborative research. The main progress reported here concerns image analysis with a pilot open-source software pipeline enabling semantic segmentation on petrographic imagery. For this purpose, all WSI are post-processed and aligned to a ‘fixed’ reflective surface (RL), and the PPL and XPL stacks are then summarised in one image, each with ray tracing that describes visible light reflection, absorption, and O- and E-wave interference phenomena. The maximum red-green-blue values were found to best overcome the limitation of refractive index anisotropy for segmentation based on pixel-neighbouring feature maps. This strongly reduces the variation in dichroism in PPL and interference colour in XPL. The synthetic ray trace WSI is then combined with one RL to estimate modal mineralogy with multi-scale algorithms originally designed for object-based cell segmentation in pathological tissues. This requires generating a small number of polygonal expert annotations that inform a training dataset, enabling on-the-fly machine learning classification into mineral classes. The accuracy of the approach was tested by comparison with modal mineralogy obtained by energy-dispersive spectroscopy scanning electron microscopy (SEM-EDX) for a suite of rocks of simple mineralogy (granulites and peridotite). The strengths and limitations of the pixel-based classification approach are described, and phenomena from sample preparation imperfections to semantic segmentation artefacts around fine-grained minerals and/or of indiscriminate optical properties are discussed. Finally, we provide an outlook on image analysis strategies that will improve the status quo by using the first-pass mineralogy identification from optical WSI to generate a location grid to obtain targeted chemical data (e.g., by SEM-EDX) and by considering the rock texture.

Dynamic Cell Imaging: application to the diatom Phaeodactylum tricornutum under environmental stresses

ABSTRACT The dynamic movement of cell organelles is an important and poorly understood component of cellular organization and metabolism. In this work we present a non-invasive non-destructive method (Dynamic Cell Imaging, DCI) based on light scattering and interferometry to monitor dynamic events within photosynthetic cells using the diatom Phaeodactylum tricornutum as a model system. For this monitoring we acquire for a few seconds movies of the signals that are related to the motion of dynamic structures within the cell (denoted scatterers), followed by a statistical analysis of each pixel time series. Illuminating P. tricornutum with LEDs of different wavelengths associated with short pulsed or continuous-wave modes of illumination revealed that dynamic movements depend on chloroplast activity, in agreement with the reduction in the number of pixels with dynamic behaviour after addition of photosystem II inhibitors. We studied P. tricornutum under two environmentally relevant stresses, iron and phosphate deficiency. The major dynamic sites were located within lipid droplets and chloroplast envelope membranes. By comparing standard deviation and cumulative sum analyses of the time series, we showed that within the droplets two types of scatterer movement could be observed: random motion (Brownian type) but also anomalous movements corresponding to a drift which may relate to molecular fluxes within a cell. The method appears to be valuable for studying the effects of various environments on microalgae in the laboratory as well as in natural aquatic environments. HIGHLIGHTS Light scattering is an alternative to fluorescence to rapidly evidence dynamic processes. Lipid droplets are the major metabolic active sites under stress. A non-destructive visualization method suitable for laboratory microalgae and aquatic samples.

Effect of movable insulation on performance of the Building integrated Semi-transparent Photovoltaic Thermal (BiSPVT) system for harsh cold climatic conditions: a case study

ABSTRACT Semi-transparent photovoltaic modules are integrated with the building’s rooftop with the provision of movable insulation during off-sunshine hours to reduce the heat losses from room to the ambient. A significant rise in room air temperature of about 6°C at desired hours for cold climatic conditions of Srinagar, India was noted in this study. Also, a metallic drum filled with water has been placed inside the room to reduce the room temperature fluctuations, thus reducing the thermal load leveling. The study is also focused to analyse the simultaneous impact of natural ventilation, direct gain and daylight savings through the south-facing window, thus leading to daylight savings and reducing the dependency on artificial modes of illumination. The effect of water mass and packing factor has also been studied on electrical energy and daylight savings. Analytical expressions for water, metallic drum/tank, room, floor and solar cell temperatures have been derived.

Editor’s Note: What We See Doth Lie

Editor’s Note: What We See Doth Lie

Pharmaceutical quantification with univariate analysis using transmission Raman spectroscopy

The purpose of this study was to investigate the quantification performance of transmission Raman spectroscopy with univariate analysis. Model dosage forms containing acetaminophen and an excipient, lactose monohydrate, were prepared. The Raman spectra of the tablets were obtained using the modes of transmission, backscattering micro-spectroscopy, and wide area illumination. Calibration curves for quantification of acetaminophen in the tablets were created using peak heights of the Raman spectra. Of the three modes of measurement, the quantitative results by transmission had the highest correlation with those by conventional UV–vis methods. In the validation of quantification by the transmission mode with univariate analysis, a certain degree of daily variation was confirmed. Additionally, quantitative results using peak heights were compared with those of partial least squares (PLSs) multivariate analysis. The root mean square error of prediction (RMSEP) suggested that quantification using PLS provided better precision than the peak height method as expected. However, content uniformity test using large sample sizes by the Raman spectra is not required to be very highly predictive because they usually employ non-parametric criteria and include wide specification ranges. Therefore, univariate analysis using transmission Raman spectroscopy was a suitable quantitative method for conducting content uniformity tests of large sample sizes.

Effect of Illumination on Ocular Status Modifications Induced by Short-Term 3D TV Viewing.

Objectives. This study aimed to compare changes in ocular status after 3D TV viewing under three modes of illumination and thereby identify optimal illumination for 3D TV viewing. Methods. The following measures of ocular status were assessed: the accommodative response, accommodative microfluctuation, accommodative facility, relative accommodation, gradient accommodative convergence/accommodation (AC/A) ratio, phoria, and fusional vergence. The observers watched 3D television for 90 minutes through 3D shutter glasses under three illumination modes: A, complete darkness; B, back illumination (50 lx); and C, front illumination (130 lx). The ocular status of the observers was assessed both before and after the viewing. Results. After 3D TV viewing, the accommodative response and accommodative microfluctuation were significantly changed under illumination Modes A and B. The near positive fusional vergence decreased significantly after the 90-minute 3D viewing session under each illumination mode, and this effect was not significantly different among the three modes. Conclusions. Short-term 3D viewing modified the ocular status of adults. The least amount of such change occurred with front illumination, suggesting that this type of illumination is an appropriate mode for 3D shutter TV viewing.

Specific temperature-related features of photoconductivity relaxation in PbSnTe:In films under interband excitation

The time dependences of variations in the photoconductivity of PbSnTe:In films in the range of T ≈ 19—25 K upon interband excitation are studied. It is found that the character of conductivity relaxation after switch-off of illumination depends on the duration and intensity of the preceding illumination. In this case, the characteristic times of relaxation for various modes of illumination can differ by more than an order of magnitude. The obtained results are discussed in the context of a model assuming the presence of a quasicontinuous spectrum of capture levels in the band gap of PbSnTe:In and also a possible effect on the parameters of these levels of the ferroelectric phase transition, the temperature of which is found to be in the temperature range under study

Flexible ultrathin-body single-photon avalanche diode sensors and CMOS integration.

We proposed the world's first flexible ultrathin-body single-photon avalanche diode (SPAD) as photon counting device providing a suitable solution to advanced implantable bio-compatible chronic medical monitoring, diagnostics and other applications. In this paper, we investigate the Geiger-mode performance of this flexible ultrathin-body SPAD comprehensively and we extend this work to the first flexible SPAD image sensor with in-pixel and off-pixel electronics integrated in CMOS. Experimental results show that dark count rate (DCR) by band-to-band tunneling can be reduced by optimizing multiplication doping. DCR by trap-assisted avalanche, which is believed to be originated from the trench etching process, could be further reduced, resulting in a DCR density of tens to hundreds of Hertz per micrometer square at cryogenic temperature. The influence of the trench etching process onto DCR is also proved by comparison with planar ultrathin-body SPAD structures without trench. Photon detection probability (PDP) can be achieved by wider depletion and drift regions and by carefully optimizing body thickness. PDP in frontside- (FSI) and backside-illumination (BSI) are comparable, thus making this technology suitable for both modes of illumination. Afterpulsing and crosstalk are negligible at 2µs dead time, while it has been proved, for the first time, that a CMOS SPAD pixel of this kind could work in a cryogenic environment. By appropriate choice of substrate, this technology is amenable to implantation for biocompatible photon-counting applications and wherever bended imaging sensors are essential.

Growing of sterlet Acipenser ruthenus in pool conditions at various modes of illumination

Growing of sterlet Acipenser ruthenus in pool conditions at various modes of illumination

Green bioprinting: Viability and growth analysis of microalgae immobilized in 3D‐plotted hydrogels versus suspension cultures

In this study, microalgae were cultivated in the form of suspension cultures and a new structurally organized immobilization technique called “Green Bioprinting.” This technique allows the cocultivation of microorganisms in close vicinity to, but without direct contact with microalgae, to improve the oxygen supply of different cell types by photosynthetic oxygen evolution. However, more research on the optimum culture conditions for immobilized microalgae is necessary. Therefore, Chlamydomonas reinhardtii 11.32b and Chlorella sorokiniana UTEX1230 were suspended in culture medium or embedded in hydrogels by the 3D‐bioprinting process followed by cultivation under different temperatures (26°C, 30°C, or 37°C) and modes of illumination (continuous illumination or a 14/10 h light/dark cycle). The viability was monitored by either flow cytometry (suspension cultures) analysis of DiBAC4(3)‐stained cells or fluorescence image analysis (hydrogel‐embedded cultures). Suspended microalgae subjected to continuous illumination exhibited an increased number of membrane‐depolarized cells compared to those cultivated at a 14/10 h light/dark cycle. Hydrogel immobilization resulted in a facilitated viability and stable growth rates between 0.4 and 0.7 d−1 for both microalgae strains. Concluding, the 3D‐bioprinting immobilization represents a technique to cultivate microalgae at a high viability and growth rate even under nonoptimal temperature conditions.

Photoacoustic spectroscopy of thermal relaxation processes of solar energy in the photosynthetic apparatus of plants

The time and energy characteristics of light energy dissipation in plant leaves have been studied by photoacoustic spectroscopy. We have considered the frequency dependences of a photoacoustic signal as a whole and its components in different modes of illumination. In this article, we analyzed the generation conditions of the “photothermal” and “photobarometric” signal component and also obtained formulas describing their frequency dependences. It is shown that at high-intensity irradiation of plant leaves adapted to different levels of light intensity, induction curves of the “photothermal” and “photobarometric” components of a signal in “photophilous” and “shade-loving” plant samples allow us to reveal the characteristic features of energy transformation processes. We discuss the characteristics of photoinactivation and photoreduction processes in leaves caused by their adaptation to different levels of solar radiation.

Microscopic techniques to study Roman renders and mural paintings from various sites

Based on recent research on mural paintings from a number of ancient Roman sites, i.e. Ostia, Ephesos, Carnuntum and Saalfelden, the contribution presents the results obtained by microscopic techniques used to study similar paints from different sites as well as paints of different artistic quality, style and date from one and the same site. It is shown that careful microscope investigations are capable of detecting the stratigraphic sequence of plaster layers, the way of preparing and applying the mortars, the raw materials used, and the means to produce the desired surface in terms of colour and texture. The analyses focus on petrographic thin-sections observed in different modes of illumination. Pseudocoloured images produced from characteristic sample micrographs are presented in order to better illustrate the relevant features. The preparatory — arriccio-plaster layers always contain aggregate from local sources, preferentially unwashed river sands with enhanced amounts of silt. For the finish — intonaco-plaster layers, the aggregate was produced by crushing selected stone material of light colour; when available or appropriate, marble was employed, but other stones can be found as well. For high quality paints, a number of intonaco layers were applied always using the same raw materials at reduced grain sizes and eventually admixing pigments. While this was the usual way to produce a smooth surface, a few examples were found which indicate grinding of the hardened intonaco prior to painting. The microscopic aspect of the paint layers clearly point to the application of a lime-pigment colour onto a dry or semi-dry surface, i.e. no true fresco technique was used.

Dynamic modes of illumination in productions terms

The method of dynamic change of illumination is considered in productions terms. The variant of change of intensity of illumination is offered during a working day, and also variant of change of spectrum of radiation of artificial source of light on the certain scenario of discoloration in the colorimetery system of RGB in accordance with the change of spectrum of radiation of a Sun.

Methods and Modes of Romanesque Manuscript Illumination at the Scriptorium of S. Frediano in Lucca

Methods and Modes of Romanesque Manuscript Illumination at the Scriptorium of S. Frediano in Lucca

Infrared imaging of subcutaneous veins

Imaging of subcutaneous veins is important in many applications, such as gaining venous access and vascular surgery. Despite a long history of medical infrared (IR) photography and imaging, this technique is not widely used for this purpose. Here we revisited and explored the capability of near-IR imaging to visualize subcutaneous structures, with a focus on diagnostics of superficial veins. An IR device comprising a head-mounted IR LED array (880 nm), a small conventional CCD camera (Toshiba Ik-mui, Tokyo, Japan), virtual-reality optics, polarizers, filters, and diffusers was used in vivo to obtain images of different subcutaneous structures. The same device was used to estimate the IR image quality as a function of wavelength produced by a tunable xenon lamp-based monochrometer in the range of 500-1,000 nm and continuous-wave Nd:YAG (1.06 microm) and diode (805 nm) lasers. The various modes of optical illumination were compared in vivo. Contrast of the IR images in the reflectance mode was measured in the near-IR spectral range of 650-1,060 nm. Using the LED array, various IR images were obtained in vivo, including images of vein structure in a pigmented, fatty forearm, varicose leg veins, and vascular lesions of the tongue. Imaging in the near-IR range (880-930 nm) provides relatively good contrast of subcutaneous veins, underscoring its value for diagnosis. This technique has the potential for the diagnosis of varicose veins with a diameter of 0.5-2 mm at a depth of 1-3 mm, guidance of venous access, podiatry, phlebotomy, injection sclerotherapy, and control of laser interstitial therapy.

Charge Generation in a Dye-Sensitized Solid-State Cell under Different Modes of Illumination

A dye-sensitized solid-state cell was fabricated by sandwiching ruthenium bypridyl complex in between porous TiO2 and CuI films. Cis-dithiocyanate-bis(2,2′-bipyridyl -4-4′-dicarboxylate) ruthenium (II) exhibited excellent performance among the dyes tested for TiO2∣dye∣CuI cell. Different mechanisms are proposed for charge generation of the cell under different modes of illumination. A high incident photon to current conversion efficiency was observed under back wall illumination compared to that of front wall illumination. Dye molecules exhibited a relay effect under back wall mode illumination at wavelengths shorter than 400 nm.

Aesthetic laser marking assessment

In this paper, the CIE color difference formula was applied to evaluate four types of material surfaces; anodized aluminium, stainless steel, poly-butylene tetra-phthalate (PBT), and phenol formaldehyde, marked using a Nd:YAG laser, and viewed under three common modes of illumination; tungsten, fluorescent and daylight. The color difference values were based on the spectral reflectance readings obtained from a spectrophotometer. Each material exhibited different color difference trends in relation to marking speed for the different modes of illumination. Nevertheless, general comparisons could be made in terms of operational marking speeds and the maximal color difference values for each material.

Near-field optical microscopy with a phase-conjugating mirror

To increase the contrast in near-field optical imaging of small objects, we suggest using a phase-conjugating mirror (PCM) as substrate. The expected contrast enhancement is related to the evanescent coupling of scattered light to the PCM. Preliminary experimental results on near-field optical imaging of complicated structures of latex spheres on the PCM surface are presented. The PCM is established by degenerate four-wave mixing in a Fe:LiNbO 3 0.04 wt% photorefractive crystal. Temporal evolution of the near-field optical images is investigated for both external and internal modes of illumination of the surface structures. Possibilities and limitations of the proposed technique are discussed on the basis of the results obtained.

Quantum efficiency and spectral response of compositionally graded HgCdTe P-n heterojunction photodiodes

Results are presented of a study of the quantum efficiency of HgCdTe heterojunction photodiodes. All heterojunctions considered in the study consist of a wide-band-gap P-type layer and a narrow-band-gap n-type layer, and are illuminated from the backside. The n-type layer is compositionally graded and therefore contains a built-in electric field. Due to the difference in band gaps photons are absorbed in the active n-type layer only and are collected by both drift and diffusion mechanisms. The one-dimensional continuity equation is first solved in the linearly graded n-type region under illumination conditions, and then the dependence of the quantum efficiency on the resulting built-in electric field is presented. Two different modes of illumination are compared: In the first mode, associated with n-on-P HgCdTe diodes, the light reaches the transparent P layer first; in the second mode, associated with P-on-n diodes, the light reaches the transparent P side after it passes through the opaque n-type layer. The superiority of the first mode is demonstrated: It consistently renders higher quantum efficiencies, and is also less sensitive to several properties of the diode such as the width of the absorbing layer and the quality of the backside interface.

Sensitivity of biphotonic systems to light intensity fluctuations: Experimental evidence in the thermoluminescence of fluoresceine in boric acid glass

We study the response of biphotonic systems to fluctuations of the incident light intensity. A convenient experimental model for such a system is the thermoluminescence of fluoresceine in boric acid glass. The location of the steady states of this system as a function of the incident light intensity is determined for constant and fluctuating modes of illumination. A comparison of the results for these two modes reveals that the light intensity fluctuations can significantly modify the curve of the steady states. For low values of the average intensity the efficiency of the photoionization is lowered, whereas for high values of the average light intensity the efficiency is enhanced.