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The surface plasmon resonance (SPR) technique has been widely applied to biosensing technologies for the rapid quantification of biomolecules without enzyme and fluorescent labeling. However, the conventional prism-coupling SPR method generally has a detection area of a few mm2, and the large contribution of the background signal forms a barrier to highly sensitive detection. Based on a highly spatially resolved SPR method, the present study constructed a scanning GC-SPR imaging instrument using an objective lens with a high numerical aperture and a plasmonic chip that could be used for grating-coupled SPR. Focusing light on the diffraction limit can suppress background signals and improve detection sensitivity. SPR imaging can also be performed by scanning a focal spot. Using this method, the refractive index of a mixture of water and dimethyl sulfoxide was measured with a detection accuracy of 2.43 × 10−3 RIU. Polydopamine films prepared with a thickness of <5 nm were also measured, and each film thickness was evaluated with high sensitivity from the effective refractive index detected in a small area of <1 µm2. [ABSTRACT FROM AUTHOR]

Light absorption enhancement in a 1.5 μm thick mercury–cadmium–telluride (Hg0.762Cd0.238Te, MCT) layer at room temperature utilizing 1D dielectric grating at mid-wave infrared (MWIR) wavelengths (3–5 μm) has been theoretically investigated. The optimized dielectric grating facilitates light diffraction and scattering into the MCT-absorbing waveguiding layer resulting in an increased lateral optical path. The light absorption was improved from ∼37.5% to ∼71% (TE) and ∼70% (TM) at normal incidence. With enhanced absorption, the photocarrier generation rate in the thin layer would be comparable to a bulk 5 μm thick MCT layer. A ∼3× reduction in the MCT layer thickness without compromising absorption has the potential for realizing infrared photodetectors with improved sensitivity at conventional operating temperatures and/or elevated operating temperatures. [ABSTRACT FROM AUTHOR]

As initiated Chemical Vapor Deposition (iCVD) finds increasing application in precision industries like electronics and optics, defect prevention will become critical. While studies of non-ideal morphology exist in the iCVD literature, no studies investigate the role of defects. To address this knowledge gap, we show that the buildup of short-chain polymers or oligomers during normal operation of an iCVD reactor can lead to defects that compromise film integrity. We used atomic force microscopy to show that oligomer aggregates selectively prevented film growth, causing these hole-like defects. X-ray diffraction and optical microscopy demonstrated the crystallinity of the aggregates, pointing to a flat-on lamellar or mono-lamellar structure. To understand the origin of the aggregates, spectroscopic ellipsometry showed that samples exposed to the reactor consistently accrued low-volatility contaminants. X-ray photoelectron spectroscopy revealed material derived from polymerization in the contamination, while scanning electron microscopy showed the presence of defect-causing aggregates. We directly linked oligomeric/polymeric contamination with defect formation by showing an increased defect rate when a contaminant polymer was heated alongside the sample. Most importantly, we showed that starting a deposition at a high sample temperature (e.g., 50 °C) before reducing it to the desired setpoint (e.g., 9 °C) unilaterally prevented defects, providing a simple method to prevent defects with minimal impact on operations. [ABSTRACT FROM AUTHOR]

Polarimetric infrared (IR) detection bolsters IR thermography by leveraging the polarization of light. Optical anisotropy, i.e., birefringence and dichroism, can be leveraged to achieve polarimetric detection. Recently, giant optical anisotropy is discovered in quasi‐1D narrow‐bandgap hexagonal perovskite sulfides, A1+xTiS3, specifically BaTiS3 and Sr9/8TiS3. In these materials, the critical role of atomic‐scale structure modulations in the unconventional electrical, optical, and thermal properties raises the broader question of the nature of other materials that belong to this family. To address this issue, for the first time, high‐quality single crystals of a largely unexplored member of the A1+xTiX3 (X = S, Se) family, BaTiSe3 are synthesized. Single‐crystal X‐ray diffraction determined the room‐temperature structure with the P31c space group, which is a superstructure of the earlier reported P63/mmc structure. The crystal structure of BaTiSe3 features antiparallel c‐axis displacements similar to but of lower symmetry than BaTiS3, verified by the polarization dependent Raman spectroscopy. Fourier transform infrared (FTIR) spectroscopy is used to characterize the optical anisotropy of BaTiSe3, whose refractive index along the ordinary (E ⊥ c) and extraordinary (E ‖ c) optical axes is quantitatively determined by combining ellipsometry studies with FTIR. With a giant birefringence Δn ∼ 0.9, BaTiSe3 emerges as a new candidate for miniaturized birefringent optics for mid‐wave infrared to long‐wave infrared imaging. [ABSTRACT FROM AUTHOR]

Red blood cell (RBC) aggregation as well as their deformation significantly affects blood microrheology. These processes depend on various factors, one of which is concentration of the nitric oxide, one of the main signaling molecule in the bloodstream. The purpose of this study was to investigate the effect of nitric oxide on the microrheological properties of red blood cells (RBCs) in RBC samples of various media after the addition of nitric oxide donor sodium nitroprusside in vitro. Microrheological properties were measured using laser aggregometer and ektacytometer based on diffuse light scattering and diffraction of laser light on a suspension of RBCs, respectively. The study found that heparin-stabilized blood showed increased RBC aggregation and deformation with sodium nitroprusside concentrations of 100, and 200 μ M, while EDTA-stabilized blood showed slightly decreased aggregation and unchanged deformation. With washed RBCs in dextran solution, the addition of sodium nitroprusside (in the concentrations of 100, and 200 μ M) resulted in decreased aggregation and increased deformation. These findings aid in our understanding of nitric oxide's effect on RBC microrheological properties. [ABSTRACT FROM AUTHOR]

Overlay (OVL) is one significant performance indicator for the lithography process control in semiconductor manufacturing. The accuracy of the OVL metrology is extremely critical for guarantee the lithography quality. Currently, diffraction-based overlay (DBO) is one of the mainstream OVL metrology techniques. Unfortunately, the accuracy of the DBO metrology is largely affected by the defect features of the OVL target. Therefore, there is a strong need to investigate the impacts of these target defects on the DBO metrology performance. However, efficiently investigating the statistical and interactive impacts of various DBO target defects remains challenging. This study aims to address this issue through proposing an intelligent sensitivity analysis approach. A cumulative distribution based global sensitivity analysis (GSA) method is utilized to assess the nonlinear influences of multiple defects in the OVL target on the DBO inaccuracy. The scenarios with both known and unknown distributions of the OVL target defects are considered. For the former, a neural network driven forward model is constructed for fast calculating the optical diffraction responses to accelerate the GSA process. For the latter, another neural network based inverse model are built for efficiently estimating the distribution of the target defects. Finally, a series of simulation experiments are conduct for typical DBO targets with multiple common defect features. The results demonstrate the effectiveness and robustness of the proposed approach as well as give valuable insights into the DBO defect analysis. Our study provides a strong tool to assist the practitioners in achieving intelligent and efficient DBO analysis and thus in enhancing OVL metrology performance. [ABSTRACT FROM AUTHOR]

AbstractThis study presents a novel interdisciplinary approach for characterizing the optical properties of nanostructured silver films, combining methodologies from polarized light spectroscopy (PLS) and mobile app-based spectroscopic image detection. Silver nanofilms were deposited using electron beam evaporation (EBE) and subsequently analyzed for their absorbance across the visible light spectrum through PLS spectroscopy. The innovative aspect of this study lies in the validation of PLS spectral data using a mobile application developed with MIT App Inventor, which analyzes the intensity of light beams captured in images taken by a smartphone. The findings indicate that the silver nanofilm exhibits peak absorbance at approximately 400 nm within the violet region, corroborated by the mobile app’s data, which shows the lowest light intensity. However, discrepancies were observed from 500 to 600 nm, likely due to ambient light interferences and inherent optical phenomena such as diffraction, reflection, and refraction. Despite these deviations, the app’s readings closely align with the PLS data, supporting the film’s selective absorption properties. This study demonstrates the potential of this multidisciplinary technique in nanomaterial research, highlighting the application of nanotechnology in material science and the transformative potential of integrating software engineering for in-depth material characterization. These findings open avenues for advancements in both academic and practical applications. [ABSTRACT FROM AUTHOR]

Developing high mass‐loading electrodes is crucial for enhancing the energy density of current batteries, yet challenges such as poor rate performance and cycling instability must be addressed. Spin charge storage on transition metal nanoparticle surfaces, characterized by rapid charging and the absence of phase transitions, offers an ideal storage behavior for high mass‐loading electrodes. In this study, electrospinning is utilized to fabricate free‐standing carbon nanofibers incorporating Co nanoparticles for high‐mass loading and high‐performance anodes. The resulting anode, with a maximum mass loading of 6.8 mg cm−2, exhibits remarkable cycle stability and high‐rate performance of 2 A g−1 at a capacity over 3 mAh cm−2, superior than reported results. Magnetometry and electron paramagnetic resonance spectroscopy are employed to monitor the charge storage mechanism of the Co@CNFs, involving both the reversible formation of a spin capacitance and the growth of radical anions in the solid electrolyte interface. Additionally, in situ X‐ray diffraction and optical microscopy provide direct evidence of the absence of mechanical stress‐induced phenomena within the spin charge process, attributed to high‐rate capable lithium storage under high mass loading. The strategic approach presented herein offers a reliable methodology for engineering high‐energy‐density lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

A lensless holographic microscope based on in-line holograms and optical diffraction tomography is an ideal imaging system for label-free 3D biological samples and can achieve large-volume imaging with single-cell resolution in a convenient way. However, due to the phase information loss and the missing cone problem, the imaging quality is significantly degraded by the reconstructed artifacts of twin images and out-of-focus images, which severely hinders the identification and interpretation of the objects. We propose an artifacts-free lensless on-chip tomography certified by three-dimensional deconvolution, which facilitates the extraction of real object morphology through straightforward yet effective computation. Initially, a globally valid systemic point spread function (PSF) is generated by simulating the imaging output of an ideal point light source positioned at the origin of the object space coordinate. Subsequently, an iterative three-dimensional deconvolution process is applied to the primitive imaging outcome of the lensless on-chip tomography using this PSF. Through rapid iterations, the optimized imaging result is swiftly obtained. Both the simulated and experimental results indicate that the artifacts-free lensless on-chip tomography can effectively circumvent the reconstructed artifacts and retrieve the real object morphology, which is critical for detailed observation and further quantitative analysis. In addition, we anticipate that the proposed approach has the potential to be transferred to other 3D imaging systems in systemic artifacts removal after corresponding modifications. [ABSTRACT FROM AUTHOR]

Macrophages are employed as targets for delivering genes, drugs, or lipid nanoparticles into tumors or other specific sites. Studying the interaction between solid lipid nanoparticles (SLNs) and macrophages is essential for assessing nanotoxicity and advancing the development of nanomedicines. However, limited data are currently available on the membrane microstructure and biochemical changes that occur when macrophages interact with SLNs. We conducted a label-free morphological and biochemical investigation of NR8383 macrophages using optical diffraction tomography (ODT), which validated the efficiency of the SLNs as a drug delivery system. ODT provided intracellular holotomography to characterize the macrophages and fluorescence imaging to analyze delivery efficiency. ODT analysis revealed the responses of phagocytic macrophages. Additionally, a quantitative analysis of lipid droplets using refractive indices revealed that, compared with incubation with normal cells, incubation with SLNs significantly increased the lipid droplet volume and surface area. The uptake of SLNs into macrophages resulted in increased cell volume, surface area, and concentration, which indicated greater morphological and biochemical variability in the treated cells than in the control cells. The results suggest that ODT imaging is promising for understanding the intracellular distribution of SLNs and useful for validating the efficacy of delivery of SLNs to macrophages. [Display omitted] • We conducted a label-free morphological and biochemical investigation of alveolar macrophages after treating with solid lipid nanoparticles (SLNs) using optical diffraction tomography (ODT). • Incubation with SLNs significantly increased the volume and surface area of lipid droplets as well as cell volume and surface area of the macrophages compared to normal cells. • The ODT imaging holds promise for understanding the intracellular distribution of SLNs and is valuable for validating the efficacy of SLNs delivery to macrophages. [ABSTRACT FROM AUTHOR]

We show that diffraction patterns can be directly simulated by a computer program implementing a lock-in algorithm. The two distinct physical topics, namely, single-slit diffraction and lock-in detection, are juxtaposed to highlight the common underlying physical principle in the context of the power spectrum of source signals arising from Fourier analysis. Editor's Note: Did you know that you could simulate a single-slit diffraction experiment using a lock-in amplifier? If not, you can read through this paper, which shows how using a rectangular time window when playing with a lock-in is the time-equivalent of the rectangular aperture in the optics experiment: The properties of Fourier transform guarantee that you will obtain a sinc function either in frequency for the lock-in experiment or in wave vector for the light diffraction experiment. Appropriate for undergraduate optics or instrumentation class. [ABSTRACT FROM AUTHOR]

Plasmonic nano‐lasers possess enormous potential for miniaturization of on‐chip integrated light sources. However, achieving plasmonic lasing requires high‐quality plasmonic resonant cavities, which are currently limited by complex, small‐scale, and costly production methods. Here, a new type of external‐cavity free plasmonic nano‐lasers is first presented with ultra‐thin thickness, achieved through the facile spin‐coating of quasi‐2D perovskite films onto monocrystalline silver sheets. The external‐cavity free plasmonic nano‐lasers exhibit obvious lasing behaviors, evidenced by a well‐defined threshold, significant linewidth narrowing, and distinct polarization dependence. The internal lasing mechanism relies on the scattering loop of surface plasmon polaritons (SPPs) by the disordered grains of the polycrystalline perovskite film. Based on this loop, SPPs experience feedback and amplification at the interface between silver sheets and perovskite films, leading to the lasing. Compared to photonic mode lasers, plasmonic nano‐lasers exhibit a significantly reduced feature size (< 80 nm), a dramatically faster lasing dynamic process (17 ps), and enhanced feedback stability and efficiency. The external‐cavity free plasmonic nano‐lasers eliminate the strict requirements for plasmonic resonant cavities to overcome traditional optical diffraction limits, making them highly significant for future applications in on‐chip photoelectric or all‐optical integration. [ABSTRACT FROM AUTHOR]

Magnetic colloidal nanocrystalline clusters (MCNCs) exhibit a color‐changing response to a magnetic field due to their tunable assembly into photonic crystals demonstrating visible light diffraction. The use of this response to obtain a magnetically sensitive color micropattern on the surface of a solid substrate requires appropriate scalable technologies for deposition of MCNCs. Here, inkjet printing of MCNCs onto the surface of a solid substrate coated with uncured polydimethylsiloxane is addressed and demonstrate their capability to form desired patterns with structural colors from blue to red controlled by external magnetic field. The results, thereby, pave the way to semi‐commercial manufacture an anticounterfeiting imaging at a large scale. [ABSTRACT FROM AUTHOR]

Background: The emergence and spread of multidrug-resistant Staphylococcus aureus strains demonstrates the urgent need for new antimicrobials. Xanthorrhizol, a plant-derived sesquiterpenoid compound, has a rapid killing effect on methicillin-susceptible strains and methicillin-resistant strains of S. aureus achieving the complete killing of staphylococcal cells within 2 min using 64 µg/mL xanthorrhizol. However, the mechanism of its action is not yet fully understood. Methods: The S. aureus cells treated with xanthorrhizol were studied using optical diffraction tomography. Activity of xanthorrhizol against the wild-type and mscL null mutant of S. aureus ATCC 29213 strain was evaluated in the time-kill assay. Molecular docking was conducted to predict the binding of xanthorrhizol to the SaMscL protein. Results: Xanthorrhizol treatment of S. aureus cells revealed a decrease in cell volume, dry weight, and refractive index (RI), indicating efflux of the cell cytoplasm, which is consistent with the spontaneous activation of the mechanosensitive MscL channel. S. aureus ATCC 29213mscL was significantly more resistant to xanthorrhizol than was the wild-type strain. Xanthorrhizol had an enhanced inhibitory effect on the growth and viability of exponentially growing S. aureus ATCC 29213mscL cells overexpressing the SaMscL protein and led to a noticeable decrease in their viability in the stationary growth phase. The amino acid residues F5, V14, M23, A79, and V84 were predicted to be the residues of the binding pocket for xanthorrhizol. We also showed that xanthorrhizol increased the efflux of solutes such as K+ and glutamate from S. aureus ATCC 29213mscL cells overexpressing SaMscL. Xanthorrhizol enhanced the antibacterial activity of the antibiotic dihydrostreptomycin, which targets the MscL protein. Conclusion: Our findings indicate that xanthorrhizol targets the SaMscL protein in S. aureus cells and may have important implications for the development of a safe antimicrobial agent. [ABSTRACT FROM AUTHOR]

Structurally colored materials with a color mixing effect are developed using SiO2–ZrN core–shell particles, where ZrN nanoparticles used as shells exhibited localized surface plasmon resonances (LSPRs). ZrN nanoparticles (10–30 nm) are attached to monodispersed SiO2 particles by modifying SiO2 particles with polymers. The attached ZrN nanoparticles exhibited a plasmon resonance absorption band at 700 nm. These SiO2–ZrN core–shell particles have a highly monodisperse particle size and assemble into a particle‐stacked film with Bragg diffraction light in the visible spectrum. The particle‐stacked film of the SiO2–ZrN core–shell particles exhibited the maximum reflection depending on the particle size of the SiO2 core. The ratio of the reflection intensity in the long‐wavelength region corresponding to the ZrN absorption to that in the short‐wavelength region of the particle‐stacked film containing the ZrN shell is less than that of the ratio in only SiO2 particle‐stacked film. The results reveal that these particle‐stacked films exhibit a "color mixing effect" that combines specific wavelength absorption through plasmon resonance and specific wavelength diffraction owing to the periodic structure without using precious metals. [ABSTRACT FROM AUTHOR]

A growth cone is a highly motile tip of an extending axon that is crucial for neural network formation. Three‐dimensional‐structured illumination microscopy, a type of super‐resolution light microscopy with a resolution that overcomes the optical diffraction limitation (ca. 200 nm) of conventional light microscopy, is well suited for studying the molecular dynamics of intracellular events. Using this technique, we discovered a novel type of filopodia distributed along the z‐axis (“z‐filopodia”) within the growth cone. Z‐filopodia were typically oriented in the direction of axon growth, not attached to the substratum, protruded spontaneously without microtubule invasion, and had a lifetime that was considerably shorter than that of conventional filopodia. Z‐filopodia formation and dynamics were regulated by actin‐regulatory proteins, such as vasodilator‐stimulated phosphoprotein, fascin, and cofilin. Chromophore‐assisted laser inactivation of cofilin induced the rapid turnover of z‐filopodia. An axon guidance receptor, neuropilin‐1, was concentrated in z‐filopodia and was transported together with them, whereas its ligand, semaphorin‐3A, was selectively bound to them. Membrane domains associated with z‐filopodia were also specialized and resembled those of lipid rafts, and their behaviors were closely related to those of neuropilin‐1. The results suggest that z‐filopodia have unique turnover properties, and unlike xy‐filopodia, do not function as force‐generating structures for axon extension. [ABSTRACT FROM AUTHOR]

This article introduces a novel hole edge inspection and metrology technology by edge diffractometry, which occurs when light interacts with the hole edge. The proposed method allows for simultaneous characterization of hole part error and edge roughness conditions. Edge diffraction occurs as light bends at a sharp edge. Such a diffractive fringe pattern, the so-called interferogram, is directly related to edge geometry and roughness. Image-based diffractometry inspection technology was developed to capture the diffractive fringe patterns. The collected fringe patterns were analyzed through statistical feature extraction methods, and numerical results such as roundness index, concentricity, and via edge roughness (VER) were obtained. The results indicated that hole 1 had an average VER of 0.665 µm and a roundness index of 0.95, while hole 2 was measured an average VER of 0.753 µm and a roundness index of 0.96. Through-focus scanning optical microscopy (TSOM) was also utilized to perform three-dimensional characterization of hole features along the depth direction. As a result, the proposed method could characterize hole part error and evaluate its roughness conditions. This study showed the potential to be adapted for automatic optical inspection for advancing microelectronics and semiconductor packaging technology. [ABSTRACT FROM AUTHOR]

In situ linear optical diffraction is a new method for studies of surface mass transport in electrochemical environments that is based on the equilibration of coverage gratings in an adlayer on the electrode surface. We, here, discuss the temporal evolution of the diffraction intensity on the basis of experimental data for sulfur adsorbates on Pt(111) electrodes in 0.1M H2SO4 and simulations of the time-dependent diffusion profiles. At low and medium sulfur coverage, the decay of the signal exhibits two time scales, which can be explained by the influence of coverage-dependent diffusion rates on the evolution of gratings with large coverage modulation. At high coverage, a further ultra-slow decay process or even a complete termination of the decay is observed, which we attribute to the presence of high-density, ordered, adlayer phases with low sulfur mobility. These results provide insight into the approaches required for extracting quantitative surface transport rates from linear optical diffraction measurements. [ABSTRACT FROM AUTHOR]

We present a design strategy for fabricating ultrastable phase-pure films of formamidinium lead iodide (FAPbI3) by lattice templating using specific two-dimensional (2D) perovskites with FA as the cage cation. When a pure FAPbI3 precursor solution is brought in contact with the 2D perovskite, the black phase forms preferentially at 100°C, much lower than the standard FAPbI3 annealing temperature of 150°C. X-ray diffraction and optical spectroscopy suggest that the resulting FAPbI3 film compresses slightly to acquire the (011) interplanar distances of the 2D perovskite seed. The 2D-templated bulk FAPbI3 films exhibited an efficiency of 24.1% in a p-i-n architecture with 0.5-square centimeter active area and an exceptional durability, retaining 97% of their initial efficiency after 1000 hours under 85°C and maximum power point tracking. [ABSTRACT FROM AUTHOR]

Hollow beam is a peculiar structure beam, which has been widely used in various areas. Here, we propose a novel diffraction optical element to generate tunable hollow beams. This element is composed of periodic concentric rings. The phase of each ring is periodically distributed between -n and n and satisfies a complex variable function. By tuning the parameters of the structure, we can flexibly manipulate the size and length of the hollow beam. The length of the beam can be increased from 98 X to 248 X, and the full width at half maximum varies from 0.43 X to 0.61 X. Moreover, the light intensity and side lobe of the hollow beam can also be regulated using the designed diffraction optical element. The potential applications of this highly tunable hollow beam include optical nanomanipulation, microscopic imaging, and nanolithography. [ABSTRACT FROM AUTHOR]

It has been shown for the first time that the electric field can enhance the acousto-optic (AO) figure of merit due to the induced ellipticity of eigenwaves through the electro-gyration effect. As a result of the analysis, we have revealed that for the isotropic types of interaction, the increasing of the strength of the electric field results in the broadening of the full width at half maximum (FWHM) of the peak of the AO figure of merit, while almost does not affect the maximal value of this peak. The FWHM of the peak of the AO figure of merit tends to saturation with increasing electric field strength. For anisotropic types of diffraction, the peak of the AO figure of merit is not observed, but with increasing the electric field strength, the surface of the AO figure of merit is expanded. [ABSTRACT FROM AUTHOR]

This paper explores the development of pottery technology in the Trieste Karst region (North-East Italy) from the Neolithic to the Early Bronze Age (EBA). It also seeks to identify cultural links with other areas by examining potentially imported vessels. Archaeometric analyses (X-ray diffraction and optical microscopy) reveal significant differences between Neolithic ceramics (Danilo–Vlaška Group) and the majority of Late Copper Age (LCA)/Early Bronze Age (EBA) pottery (primarily associated with the Ljubljana Culture and a few with the Cetina Culture). Neolithic pottery displays consistent characteristics across all vessel types, including coarse grain, prevalent sparry calcite temper, and the absence of grog. In contrast, most LCA and EBA vessels exhibit distinct features such as very fine-grained paste, no sparry calcite, notable use of grog temper, higher quartz, muscovite, and flint content. Notably, from a technological perspective, the analyzed Cetina vessels bear a strong resemblance to the majority of LCA ceramics. The differences between Neolithic and LCA/EBA vessels clearly suggest the use of new raw materials, recipes, and techniques, likely reflecting changes in cultural and social contexts and potential connections with the core area of the Ljubljana Culture. [ABSTRACT FROM AUTHOR]

Mitochondria are complex organelles with an outer membrane enveloping a second inner membrane that creates a vast matrix space partitioned by pockets or cristae that join the peripheral inner membrane with several thin junctions. Several micrometres long, mitochondria are generally close to 300 nm in diameter, with membrane layers separated by a few tens of nanometres. Ultrastructural data from electron microscopy revealed the structure of these mitochondria, while conventional optical microscopy revealed their extraordinary dynamics through fusion, fission, and migration processes but its limited resolution power restricted the possibility to go further. By overcoming the limits of light diffraction, Super-Resolution Microscopy (SRM) now offers the potential to establish the links between the ultrastructure and remodelling of mitochondrial membranes, leading to major advances in our understanding of mitochondria's structure-function. Here we review the contributions of SRM imaging to our understanding of the relationship between mitochondrial structure and function. What are the hopes for these new imaging approaches which are particularly important for mitochondrial pathologies? [ABSTRACT FROM AUTHOR]

• Microstructure, hardness, corrosion rate evolution under solution treatment tracked. • Accelerated characterization via XRD, microscopy, hardness, immersion studies. • Physics-based Machine Learning decodes structure-property correlation. • Grain size and ternary precipitate control crucial for strength-corrosion optimization. [Display omitted] Magnesium alloys are emerging as promising alternatives to traditional orthopedic implant materials thanks to their biodegradability, biocompatibility, and impressive mechanical characteristics. However, their rapid in-vivo degradation presents challenges, notably in upholding mechanical integrity over time. This study investigates the impact of high-temperature thermal processing on the mechanical and degradation attributes of a lean Mg-Zn-Ca-Mn alloy, ZX10. Utilizing rapid, cost-efficient characterization methods like X-ray diffraction and optical microscopy, we swiftly examine microstructural changes post-thermal treatment. Employing Pearson correlation coefficient analysis, we unveil the relationship between microstructural properties and critical targets (properties): hardness and corrosion resistance. Additionally, leveraging the least absolute shrinkage and selection operator (LASSO), we pinpoint the dominant microstructural factors among closely correlated variables. Our findings underscore the significant role of grain size refinement in strengthening and the predominance of the ternary Ca 2 Mg 6 Zn 3 phase in corrosion behavior. This suggests that achieving an optimal blend of strength and corrosion resistance is attainable through fine grains and reduced concentration of ternary phases. This thorough investigation furnishes valuable insights into the intricate interplay of processing, structure, and properties in magnesium alloys, thereby advancing the development of superior biodegradable implant materials. [ABSTRACT FROM AUTHOR]

Diffractive neural networks (DNNs) are emerging as a new machine learning hardware based on optical diffraction with parallel and high‐throughput information processing. The optical inputs to DNNs are spatially modulated by propagating through passive diffractive layers that work in succession to achieve an inference. Herein, visible wavelength classification using single‐ and two‐layer DNNs fabricated using direct laser writing is demonstrated. The proposed DNN approach accepts the point spread function of two different wavelengths modeled after a microscope objective as the input and modulates the input field toward the target detector for classification. Of the three models trained to classify different wavelength pairs, the highest performance observed is for the classification of 561 and 785 nm, achieving over 90% accuracy. This work demonstrates the potential of all‐optical artificial neural networks for applications requiring visible wavelengths, from visible light beam shaping to spectral analysis and optical imaging. [ABSTRACT FROM AUTHOR]

Six different commercial powders, finer than 45 μm, were used for examining the effects of particle characteristics on mean particle size and specific surface area. The measurements were carried out using the most commonly used air permeability- and laser light diffraction (scattering) techniques. As the air permeability method has been used as a benchmark for decades in the powder metallurgy (P/M) industry, the physical phenomena that govern the passage of gas through the powder bed under laminar flow conditions were also presented. The experimental data indicate that both methods give similar results for spherical powders. The advantage of laser light systems over gas permeameters is the ability to provide additional information on particle size distribution. Irregularly shaped powders should be analyzed by both techniques, relying on gas permeametry for surface area measurements and on laser light diffraction for the estimation of mean particle size and size distribution. Application of scanning electron microscopy as a complementary technique was found very helpful in the interpretation of data through visualization of individual particles. [ABSTRACT FROM AUTHOR]

The photorefractive properties of triphenylamine polymer-based composites with various composition ratios were investigated via optical diffraction, response time, asymmetric energy transfer, and transient photocurrent. The composite consisted of a photoconductive polymer of poly((4-diphenylamino)benzyl acrylate), a photoconductive plasticizer of (4-diphenylamino)phenyl)methanol, a sensitizer of [6,6]-phenyl-C61-butyric acid methyl ester, and a nonlinear optical dye of (4-(azepan-1-yl)-benzylidene)malononitrile. The photorefractive properties and related quantities were dependent on the composition, which was related to the glass transition temperature of the photorefractive polymers. The quantum efficiency (QE) of photocarrier generation was evaluated from the initial slope of the transient photocurrent. Transient photocurrents were measured and showed two unique peaks: one in the range of 10−4 to 10−3 s and the other in the range of 10−1 to 1 s. The transient photocurrents was well simulated (or reproduced) by the expanded two-trapping site model with two kinds of photocarrier generation and recombination processes and two different trapping sites. The obtained photorefractive quantity of trap density was significantly related to the photoconductive parameters of QE. [ABSTRACT FROM AUTHOR]

[Display omitted] Photonic crystals (PCs) have attracted great interest and wide applications in displays, printing, anti-counterfeiting, etc. However, two main challenges significantly hinder their applications: 1) the tradeoff between high optical transparency across the whole visible range and brilliant colors requiring a large refractive index contrast (Δn), and 2) the way of regulating structural colors by altering tens of different sizes. To address these issues, a new type of metal–organic framework (MOF)-based transparent photonic crystal (TPC) has been fabricated through self-assembling MOF particles into three-dimensional ordered structures which were then infiltrated by polydimethylsiloxane (PDMS). Compared to conventional PCs, these TPCs exhibit 1) both brilliant forward iridescent structural colors and high transmittance (>75 %) across the whole visible spectra range, and 2) conveniently adjustable colors based on bidisperse particles. The unique color-generating mechanism of the light diffraction by each plane lattice and the small Δn between MOF particles and PDMS are the keys to TPCs' characteristics. Moreover, the prepared invisible anti-counterfeit labels can reversibly hide-reveal patterns with elaborate and exchangeable color contrast in a non-destructive way, showing potential applications in anti-counterfeiting, information encryption, and optical devices. [ABSTRACT FROM AUTHOR]

In 3D microsphere tracking, unlike in-plane motion that can be measured directly by a microscope, axial displacements are resolved by optical interference or a diffraction model. As a result, the axial results are affected by the environmental noise. The immunity to environmental noise increases with measurement accuracy and the signal-to-noise ratio (SNR). In compound digital holography microscopy (CDHM)-based measurements, precise identification of the tracking marker is critical to ensuring measurement precision. The reconstruction centering method (RCM) was proposed to suppress the drawbacks caused by installation errors and, at the same time, improve the correct identification of the tracking marker. The reconstructed center is considered to be the center of the microsphere, rather than the center of imaging in conventional digital holographic microscopy. This method was verified by simulation of rays tracing through microspheres and axial moving experiments. The axial displacements of silica microspheres with diameters of 5 μm and 10 μm were tested by CDHM in combination with the RCM. As a result, the SNR of the proposed method was improved by around 30%. In addition, the method was successfully applied to axial displacement measurements of overlapped microspheres with a resolution of 2 nm. [ABSTRACT FROM AUTHOR]

[Display omitted] Lanthanide complexes [CpXLnCl 2 (Me 3 tach)] n (Ln = Tb, Gd; CpX = Cp, Cp Ph 2 , Cp Ph 4 ; Me 3 tach = 1,3,5-trimethyl-1,3,5- triazacyclohexane; n = 1, 2), containing cyclopentadienyl (Cp), 1,3-diphenylcyclopentadienyl (Cp Ph 2) and tetraphenyl- cyclopentadienyl (Cp Ph 4) anions as ν-bonded antenna ligands, have been synthesized. A combined analysis of quantum chemical, optical and X-ray diffraction data has shown that the introduction of phenyl groups into the Cp ring leads to the inevitable appearance of intraligand charge transfer states due to the nonequivalence of the phenyl rings. [ABSTRACT FROM AUTHOR]

Optical diffraction tomography can be performed with low phototoxicity and photobleaching to analyze 3D cells and tissues. It is desired to develop high throughput and powerful data processing capabilities. We propose high bandwidth holographic microscopy (HBHM). Based on the analyticity of complex amplitudes, the unified holographic multiplexing transfer function is established. A high bandwidth scattering field is achieved via the k-space optical origami of two 2D wavefronts from one interferogram. Scanning illumination modulates the high-horizontal and axial k-space to endow synthetic-aperture from 2D high space-bandwidth product (SBP) scattering fields. The bright-field counterpart SBP of a single scattering field from HBHM is 14.6 megapixels, while the number of pixels is only 13.7 megapixels. It achieves an eight-fold SBP enhancement under the same number of pixels and diffraction limit. The HBHM paves the way toward the performance of high throughput, large-scale, and non-invasive histopathology, cell biology, and industrial inspection. [ABSTRACT FROM AUTHOR]

We describe a method that can be used to produce ruthenium/ruthenium oxide patterns starting from a ruthenium thin film. The method is based on highly localized oxidation of a small surface area of a ruthenium film by means of exposure to a pulsed laser under ambient conditions. Laser exposure is followed by dissolution of the un-exposed ruthenium in a NaClO solution, which leaves the conductive, partially oxidized ruthenium area on the substrate. Spatially selective oxidation, material removal, and, by implication, patterning, are, therefore, achieved without the need for a photoresist layer. Varying the exposure laser parameters, such as fluence, focus diameter, and repetition rate, allows us to optimize the process. In particular, it enables us to obtain circular Ru/RuO2 islands with a sub-diffraction-limited diameter of about 500 nm, for laser exposure times as short as 50 ms. The capability to obtain such small islands suggests that heat-diffusion is not a limiting factor to pattern Ru by laser heating on a (sub-)micron scale. In fact, heat diffusion helps in that it limits the area where a sufficiently high temperature is reached and maintained for a sufficiently long time for oxidation to occur. Our method provides an easy way to produce metallic Ru/RuO2 (sub-)micron structures and has possible applications in semiconductor manufacturing. [ABSTRACT FROM AUTHOR]

Conventional optical microscopes are only able to resolve objects down to a size of approximately 200 nm due to optical diffraction limits. The rapid development of nanotechnology has increased the demand for greater imaging resolution, with a need to break through those diffraction limits. Among super-resolution techniques, microsphere imaging has emerged as a strong contender, offering low cost, simple operation, and high resolution, especially in the fields of nanodevices, biomedicine, and semiconductors. However, this technology is still in its infancy, with an inadequate understanding of the underlying principles and the technology's limited field of view. This paper comprehensively summarizes the status of current research, the advantages and disadvantages of the basic principles and methods of microsphere imaging, the materials and preparation processes, microsphere manipulation methods, and applications. The paper also summarizes future development trends. [ABSTRACT FROM AUTHOR]

Expansion microscopy (ExM) is a revolutionary novel approach to increase resolution in light microscopy. In contrast to super-resolution microscopymethods that rely on sophisticated technological advances, including novel instrumentation, ExM instead is entirely based on sample preparation. In ExM, labeled target molecules in fixed cells are anchored in a hydrogel, which is then physically enlarged by osmotic swelling. The isotropic swelling of the hydrogel pulls the labels apart from one another, and their relative organization can thus be resolved using conventionalmicroscopes even if it was below the diffraction limit of light beforehand. As ExM can additionally benefit from the technical resolution enhancements achieved by super-resolution microscopy, it can reach into the nanometer range of resolution with an astoundingly lowdegree of error induced by distortion during the physical expansion process. Because the underlying chemistry is well understood and the technique is based on a relatively simple procedure, ExM is easily reproducible in non-expert laboratories and has quickly been adopted to address an ever-expanding spectrum of problems across the life sciences. In this Review, we provide an overview of this rapidly expanding new field, summarize the most important insights gained so far and attempt to offer an outlook on future developments. [ABSTRACT FROM AUTHOR]

High spatial resolution imaging over the entire volume for intravital imaging of biological specimens has long been vital. However, the depth‐of‐field (DOF) and spatial resolution are intrinsically interdependent. Here, a new extended DOF (EDOF) microscopy technique based on partially coherent annular illumination is proposed, termed AI‐EDOF, by combining an electrically tunable lens with a conventional microscope with modified illumination, for motion‐free, high spatial resolution real‐time all‐in‐focus imaging over thick volumes. EDOF imaging is obtained with spatial resolution up to near the incoherent diffraction limit (∼$\sim $388 nm, 20×$\times$/ 0.8NA) and temporal resolution ∼$\sim $30 fps. Moreover, it is demonstrated that the coupled phase and absorption components of the complex refractive index in optical diffraction tomography microscopy can be solved by focus scanning. The Richardson‐Lucy deconvolution with total variation regularization is adopted for deblurring and suppressing noise under low light efficiency high‐speed exposure. To demonstrate the capabilities of the proposed method, experiments are conducted using fixed transgenic zebrafish larvae, Drosophila larvae and dynamic Caenorhabditis elegans under both transmissive and fluorescent imaging modalities, revealing the proposed approach is prospective to be adopted by broad applications such as pharmacokinetics and tumor immunology. [ABSTRACT FROM AUTHOR]

Optical superresolution microscopy is an important field, where nonlinear optical processes or prior information is used to defeat the classical diffraction limit of light. Quantum correlation microscopy uses photon arrival statistics from single photon emitters to aid in the determination of properties including the number of emitters and their relative brightness. Here we model quantum correlation microscopy in the few emitter regime, i.e. around four single photon emitters below the diffraction limit. We use the Akaike Information Criterion to determine the number of emitters and we vary the relative contributions of intensity to quantum correlation information to determine contribution that provides optimal imaging. Our results show diffraction unlimited performance and a change in localisation scaling behaviour dependent on emitter closeness. [ABSTRACT FROM AUTHOR]

Analytical expressions for the nonparaxial mode diffraction of a terahertz laser metal waveguide resonator are obtained. The study assumes interaction between the modes and a spiral phase plate, considering different topological charges (n). Also, using numerical modeling, the physical features of the emerging vortex beams as they propagate in free space are studied. The Rayleigh-Sommerfeld vector theory is employed to investigate the propagation of vortex laser beams in the Fresnel zone, excited by the modes of a metal waveguide quasi-optical resonator upon incidence on a spiral phase plate. In free space, the spiral phase plate for exciting TE11 mode from the profile with the intensity maximum in the center (n = 0) forms an asymmetric ring one with two maxima (n = 1, 2). For the exciting TE01 mode, the initial ring (n = 0) structure of the field intensity is transformed into a structure with a maximum radiation intensity in the center (n = 1), and later again into a ring (n = 2). The phase front of the beam for the Ey component of the linearly polarized along the y axis TE11 mode changes from spherical to spiral with one on-axis singularity point. In the phase profile of the transverse components of the azimuthally polarized TE01 mode, a region with two and three off-axis phase singularity points appears. [ABSTRACT FROM AUTHOR]

Recently, multifunctional metasurface has showcased its powerful functionality to integrate nanoprinting and holography, and display ultracompact meta-images in near- and far-field simultaneously. Herein, we propose a tri-channel metasurface which can further extend the meta-imaging ranges, with three independent images located at the interface, Fresnel and Fourier domains, respectively. Specifically, a structural-color nanoprinting image is decoded right at the interface of the metasurface, enabled by varying the dimensions of nanostructures; a Fresnel holographic image and another Fourier holographic image are present at the Fresnel and Fourier (far-field) domains, respectively, enabled by geometric phase. The spectral and phase manipulation capabilities of nanostructures have been maximized, and the spatial multiplexing capabilities for diffraction in metasurfaces have also been fully exploited. By leveraging the design freedom enabled through the tuning of the geometric size and orientation of nanostructures, as well as optimizing the diffraction spatial light wave transformation, the encoding of multiple images on the single-celled metasurface is achieved. More interestingly, due to the spatial separation of images across different channels, crosstalk is virtually eliminated, effectively enhancing imaging quality. The proposed metasurface offers several advantages, including a compact design, easiness of fabrication, minimal crosstalk, and high storage density. Consequently, it holds promising applications in image display, data storage, information encryption, anti-counterfeiting, and various other fields. [ABSTRACT FROM AUTHOR]

In this research, copper nanoparticles were synthesized via laser ablation in liquid using a nanosecond Nd:YAG laser. First, the effect of wavelengths of 532 nm and 1064 nm on the synthesis of copper nanoparticles in acetone and distilled water was investigated. After finding the appropriate wavelength, the effect of synthesis media in the presence of surfactants containing cetyltrimethylammonium chloride, sodium dodecyl sulfate, and polyvinyl pyrrolidone on copper nanoparticles was studied. Visible-ultraviolet optical spectroscopy, atomic absorption spectroscopy, dynamic light diffraction, and field emission scanning electron microscopy were employed to investigate the optical properties, synthesis efficiency, size, and morphology of copper nanoparticles prepared by the laser ablation in liquid method, respectively. The results showed that copper nanoparticles could be successfully synthesized in an acetone medium at 1064 nm wavelength. Also, due to the formation of copper oxides instead of copper nanoparticles, there is a slight possibility of preparing copper nanoparticles in aqueous environments. [ABSTRACT FROM AUTHOR]

The control of laser emission angles in laser devices is essential for many optoelectronic and photonic applications such as optical sensing and displays. In this context, we studied the light diffraction pattern of laser beams in a one-dimensional sampled distributed feedback resonator having organic gain media. The gratings consist of the repetition of supercells having a mixed-order sampled grating in which 1st-order gratings surround a 2nd-order grating. The experimental results showed that the diffraction angles of the laser beams are quite diverse depending on the supercell structures. We demonstrate that the interval of the diffraction angle (θ) of the laser beams is inversely proportional to the length of the supercell experimentally and theoretically. By tuning the length of supercells as well as the length of 1st-order and 2nd-order regions, the interval θ was tuned from 0.1° to 43° with the different arc emission patterns. With the reduction of θ, i.e., the longer 1st-order region, a significant decrease in the laser threshold was obtained, resulting in the lowest lasing threshold of 2.5 ± 0.1 μJ/cm2 with ∼3.5 ns of a long pulse width excitation source. [ABSTRACT FROM AUTHOR]

Photothermal spectroscopy, a remarkable detection method that can analyze microscale objects in a noninvasive and nondestructive manner, has been successfully coupled with micro/nanofluidic devices. Specifically, methods that employ a thermal lens microscope (TLM), including a photothermal optical phase shift and photothermal optical diffraction, are a powerful tool for the sensitive detection of nonfluorescent or nonlabeled molecules in micro/nanofluidic channels. This review focuses on the family of TLMs in terms of their historical development. Their recent applications, ranging from separation, particle, biomedical, energy, and environmental analyses, are summarized, and future perspectives in nanoscale liquid science, system integration, and biological studies, such as single-cell analyses, are also discussed. [ABSTRACT FROM AUTHOR]

Similar to the optical diffraction of light passing through a material grating, the Kapitza-Dirac effect occurs when an electron is diffracted by a standing light wave. In its original description, the effect is time independent. Here, we extended the Kapitza-Dirac effect to the time domain. By tracking the spatiotemporal evolution of a pulsed electron wave packet diffracted by a 60-femtosecond (where one femtosecond = 10−15 seconds) standing wave pulse in a pump-probe scheme, we observed time-dependent diffraction patterns. The fringe spacing in the observed pattern differs from that generated by the conventional Kapitza-Dirac effect. By exploiting this time-resolved diffraction scheme, we can access the time evolution of the phase properties of a free electron and potentially image ionic potentials and electronic decoherences. [ABSTRACT FROM AUTHOR]

Bacterial chromosomes are folded into tightly regulated three-dimensional structures to ensure proper transcription, replication, and segregation of the genetic information. Direct visualization of chromosomal shape within bacterial cells is hampered by cell-wall confinement and the optical diffraction limit. Here, we combine cell-shape manipulation strategies, high-resolution fluorescence microscopy techniques, and genetic engineering to visualize the shape of unconfined bacterial chromosome in real-time in live Bacillus subtilis cells that are expanded in volume. We show that the chromosomes predominantly exhibit crescent shapes with a non-uniform DNA density that is increased near the origin of replication (oriC). Additionally, we localized ParB and BsSMC proteins – the key drivers of chromosomal organization – along the contour of the crescent chromosome, showing the highest density near oriC. Opening of the BsSMC ring complex disrupted the crescent chromosome shape and instead yielded a torus shape. These findings help to understand the threedimensional organization of the chromosome and the main protein complexes that underlie its structure. The spatial structure of the bacterial chromosome is resolved in the absence of confinement by the cell boundary. Size-expanded cells reveal a crescent-shaped Bacillussubtilis chromosome and the effects of ParB and SMC proteins on chromosome shape. [ABSTRACT FROM AUTHOR]

Label-free thermometry is a pivotal tool for many disciplines. However, most current approaches are only suitable for planar heat sources in steady state, thereby restricting the range of systems that can be reliably studied. Here, we introduce pump probe-based optical diffraction tomography (ODT) as a method to map temperature precisely and accurately in three dimensions (3D) at the single-particle level. To do so, we first systematically characterize the thermal landscape in a model system consisting of gold nanorods in a microchamber and then benchmark the results against simulations and quantitative phase imaging thermometry. We then apply ODT thermometry to resolve thermal landscapes inaccessible to other label-free approaches in the form of nonplanar heat sources embedded in complex environments and freely diffusing gold nanorods in a microchamber. Last, we foresee that our approach will find many applications where routine thermal characterization of heterogeneous nanoparticles samples in 3D or in non-steady state is required. [ABSTRACT FROM AUTHOR]

The transmission of viral diseases is highly unstable and highly contagious. As the carrier of virus transmission, cell is an important factor to explore the mechanism of virus transmission and disease. However, there is still a lack of effective means to continuously monitor the process of viral infection in cells, and there is no rapid, highthroughput method to assess the status of viral infection. On the basis of the virus light diffraction fingerprint of cells, we applied the gray co-occurrence matrix, set the two parameters effectively to distinguish the virus status and infection time of cells, and visualized the virus infection process of cells in high throughput. We provide an effcient and nondestructive testing method for the selection of excellent livestock and poultry breeds at the cellular level. Meanwhile, our work provides detection methods for the recessive transmission of human-to-human, animal-to-animal, and zoonotic diseases and to inhibit and block their further development. [ABSTRACT FROM AUTHOR]

Mask-free multi-photon lithography enables the fabrication of arbitrary nanostructures low cost and more accessible than conventional lithography. A major challenge for multi-photon lithography is to achieve ultra-high precision and desirable lateral resolution due to the inevitable optical diffraction barrier and proximity effect. Here, we show a strategy, light and matter co-confined multi-photon lithography, to overcome the issues via combining photo-inhibition and chemical quenchers. We deeply explore the quenching mechanism and photoinhibition mechanism for light and matter co-confined multiphoton lithography. Besides, mathematical modeling helps us better understand that the synergy of quencher and photo-inhibition can gain a narrowest distribution of free radicals. By using light and matter co-confined multiphoton lithography, we gain a 30 nm critical dimension and 100 nm lateral resolution, which further decrease the gap with conventional lithography. Mask-free multi-photon lithography allows the straightforward fabrication of nanostructures, but high precision and good resolution can be challenging to achieve. Here, the authors report a combination of photo-inhibition and chemical quenchers for improved lithography performance. [ABSTRACT FROM AUTHOR]

It is challenging for traditional smart windows to possess both high optical transparency (90%, 380–780 nm) and brilliant colors since they are usually contradictory to each other. Here, novel liquid thermal‐responsive smart windows (TSWs) exhibiting high optical transparency (94%), bright iridescent forward scattering structural color, and extremely weak reflective structural colors are fabricated by constructing a refractive index (RI)‐matched non‐close‐packing ordered structure with large lattice distances and thus unique light diffraction mechanisms. The transmittance (24‐94%) and dual‐mode structural color saturation (1–55 times) can be dynamically regulated by simply altering temperatures (20–100 °C), which can be attributed to the temperature‐dependent light diffraction and scattering efficiency. A new information encryption‐decryption technique is developed by combining TSWs with outstanding shapeability, recyclability, and flowability. The information is hidden under normal conditions, while 76 different pieces of information can be decrypted in programmable ways under different stimuli, showing their potential in anti‐counterfeiting and information encryption. [ABSTRACT FROM AUTHOR]

The method of common lines is a well-established reconstruction technique in cryogenic electron microscopy (cryo-EM), which can be used to extract the relative orientations of an object given tomographic projection images from different directions. In this paper, we deal with an analogous problem in optical diffraction tomography. Based on the Fourier diffraction theorem, we show that rigid motions of the object, i.e., rotations and translations, can be determined by detecting common circles in the Fourier-transformed data. We introduce two methods to identify common circles. The first one is motivated by the common line approach for projection images and detects the relative orientation by parameterizing the common circles in the two images. The second one assumes a smooth motion over time and calculates the angular velocity of the rotational motion via an infinitesimal version of the common circle method. Interestingly, using the stereographic projection, both methods can be reformulated as common line methods, but these lines are, in contrast to those used in cryo-EM, not confined to pass through the origin and allow for a full reconstruction of the relative orientations. Numerical proof-of-the-concept examples demonstrate the performance of our reconstruction methods. [ABSTRACT FROM AUTHOR]