Direct Light Research Articles

Camphoric Acid in Nanomagnetic Photocatalyst Synthesis: Direct and Indirect Visible Light Photocatalytic Degradation of PCBs

Camphoric Acid in Nanomagnetic Photocatalyst Synthesis: Direct and Indirect Visible Light Photocatalytic Degradation of PCBs

Evaluation on Surface Characteristics, Accuracy, and Dimensional Stability of Tooth Preparation Dies Fabricated by Conventional Gypsum and 3D-Printed Workflows.

To evaluate the surface characteristics, accuracy (trueness and precision), and dimensional stability of tooth preparation dies fabricated using conventional gypsum and direct light processing (DLP), stereolithography (SLA), and polymer jetting printing (PJP) techniques. Gypsum preparation dies were replicated according to the reference data and imported into DLP, SLA, and PJP printers, and the test data were obtained by scanning after 0, 1, 3, 7, 14, 28, and 42 days. After analyzing the surface characteristics, a best-fit algorithm between the test and the reference data was used to evaluate the accuracy and dimensional stability of the preparation dies. The data were analyzed by one-way analysis of variance and Tukey test or Kruskal-Wallis H test (α = .05). Compared with the gypsum group (3.61 ± 0.59 μm), the root mean square error (RMSE) values of the SLA group (5.33 ± 0.48 μm) was rougher (P < .05), the PJP group (2.43 ± 0.37 μm) was smoother (P < .05), and the DLP group (2.92 ± 0.91 μm) had no significant difference (P > .05). For trueness, the RMSE was greater in the PJP (34.90 ± 4.91 μm) and SLA (19.01 ± 0.95 μm) groups than in the gypsum (16.47 ± 0.47 μm) group (P < .05), and no significant difference was found between the DLP (17.10 Å} 1.77 μm) and gypsum groups. Regarding precision, the RMSE ranking was gypsum = DLP = SLA < PJP group. The RMSE ranges in the gypsum, DLP, PJP, and SLA groups at different times were 6.79 to 8.86 μm, 5.44 to 10.17 μm, 10.16 to 11.28 μm, and 10.94 to 32.74 μm, respectively. Although gypsum and printed preparation dies showed statistically significant differences in surface characteristics, accuracy, and dimensional stability, all tooth preparation dies were clinically tolerated and used to produce fixed restorations.

Esketamine: Less Drowsiness, More Analgesia.

Racemic ketamine is a 1:1 mixture of 2 enantiomers that turn light in opposite direction: Dextrorotatory esketamine is approximately 4 times more affine for the N-methyl-D-aspartate (NMDA) receptor than levorotatory arketamine, which may explain why esketamine is about twice as potent as an analgesic and anesthetic as the racemate. Esketamine has attracted renewed interest in view of the opioid crisis, racemic ketamine's abuse, and esketamine's approval for expanded use. We evaluated the anesthesia literature concerning mental, cardiovascular, cerebral, and antinociceptive effects of esketamine published in English between 1980 and 2022. The review shows that esketamine and racemic ketamine are not "the same" at clinically equivalent analgesic and anesthetic dose: Psychomimetic effects seem to be essentially related to NMDA receptor blockade and esketamine is not devoid of unwanted mental impact. However, it probably involves less cholinergic inhibition. Cognitive disturbances during arousal, awakening, and recovery from the drug are less, and less pronounced with esketamine. The drug allows for an approximately 50% dose reduction in anesthesia and analgesia which goes along with a higher clearance and shorter recovery time as compared to racemic ketamine. In comparison of esketamine with placebo, esketamine shows cardiocirculatory stabilizing and neuroprotective effects which can be seen in anesthesia induction, cardiac surgery, and analgesia and sedation in brain injury. Evidence of esketamine's antinociceptive efficacy is inconsistent, although a recent meta-analysis reports improved pain relief after surgery in a study with short observation time. To better define esketamine's place, direct head-to-head comparison with the racemate at equi-analgesic/anesthetic dose is warranted.

Photophobotaxis in the filamentous cyanobacterium Phormidium lacuna: Mechanisms and implications for photosynthesis-based light direction sensing.

Cyanobacterium Phormidium lacuna filaments move from dark to illuminated areas by twitching motility. Time-lapse recordings demonstrated that this photophobotaxis response was based on random movements with movement reversion at the light-dark border. The filaments in the illuminated area form a biofilm attached to the surface. The wild-type and the pixJ and cphA mutants were investigated for photophobotaxis at diverse wavelengths and intensities. CphA is a cyanobacterial phytochrome; PixJ is a biliprotein with a methyl-accepting chemotaxis domain and is regarded as a phototaxis photoreceptor in other species. The cphA mutant exhibited reduced biofilm surface binding. The pixJ mutant was characterized as a negative photophobotaxis regulator and not as a light direction sensor. 3-(3,4-dichlorophenyl)1,1-dimethylurea (DCMU) blocks electron transfer in PS II. At concentrations of 100 and 1000 μM DCMU, photophobotaxis was inhibited to a greater extent than motility, suggesting that PSII has a role in photophobotaxis. We argue that the intracellular concentrations of regular photoreceptors, including CphA or PixJ, are too small for a filament to sense rapid light intensity changes in very weak light. Three arguments, specific inhibition by DCMU, broad spectral sensitivity, and sensitivity against weak light, support photosynthesis pigments for use as photophobotaxis sensors.

Emergence of threefold symmetric helical photocurrents in epitaxial low twinned Bi2Se3

We present evidence of a strong circular photon drag effect (PDE) in topological insulators (TIs) through the observation of helicity-dependent topological photocurrents with threefold rotational symmetry using THz spectroscopy in epitaxially-grown Bi2Se3 with reduced crystallographic twinning. We establish how twinned domains introduce competing nonlinear optical (NLO) responses inherent to the crystal structure that obscure geometry-sensitive optical processes through the introduction of a spurious mirror symmetry. Minimizing the twinning defect reveals strong NLO response currents whose magnitude and direction depend on the alignment of the excitation to the crystal axes and follow the threefold rotational symmetry of the crystal. Notably, photocurrents arising from helical light reverse direction for left/right circular polarizations and maintain a strong azimuthal dependence-a result uniquely attributable to the circular PDE, where the photon momentum acts as an applied in-plane field stationary in the laboratory frame. Our results demonstrate new levels of control over the magnitude and direction of photocurrents in TIs and that the study of single-domain films is crucial to reveal hidden phenomena that couple topological order and crystal symmetries.

Proximity-Based Optical Camera Communication with Multiple Transmitters Using Deep Learning.

In recent years, optical camera communication (OCC) has garnered attention as a research focus. OCC uses optical light to transmit data by scattering the light in various directions. Although this can be advantageous with multiple transmitter scenarios, there are situations in which only a single transmitter is permitted to communicate. Therefore, this method is proposed to fulfill the latter requirement using 2D object size to calculate the proximity of the objects through an AI object detection model. This approach enables prioritization among transmitters based on the transmitter proximity to the receiver for communication, facilitating alternating communication with multiple transmitters. The image processing employed when receiving the signals from transmitters enables communication to be performed without the need to modify the camera parameters. During the implementation, the distance between the transmitter and receiver varied between 1.0 and 5.0 m, and the system demonstrated a maximum data rate of 3.945 kbps with a minimum BER of 4.2×10-3. Additionally, the system achieved high accuracy from the refined YOLOv8 detection algorithm, reaching 0.98 mAP at a 0.50 IoU.

A precise compensation algorithm for visual measurement in non-uniform refractive index environment based on Hamiltonian ray tracing method

In complex large-scale industrial environments, light rays no longer propagate in a straight line due to the influence of non-uniform refractive index, which will lead to large measurement errors in visual measurement. In order to accurately compensate the error, this paper firstly quantitatively analyzes the influence of non-uniform refractive index distribution on visual measurement. Then the symplectic matrix ray-tracing method of Hamiltonian optics is used to reconstruct spatial light in the reverse direction with known light propagation end point and spatial refractive index distribution. Thus the traditional model of light propagation along a straight line in visual measurement can be changed and the measurement error introduced by non-uniform refractive index field can be corrected. Finally, the proposed Hamiltonian ray tracing method was verified through the spatial non-uniform refractive index field reconstructed by Background Oriented Schlieren(BOS) method. The experimental results verified the effectiveness and feasibility of this method.

Rhodanine-Based Chromophores: Fast Access to Capable Photoswitches and Application in Light-Induced Apoptosis.

Molecular photoswitches are highly desirable in all chemistry-related areas of research. They provide effective outside control over geometric and electronic changes at the nanoscale using an easy to apply, waste-free stimulus. However, simple and effective access to such molecular tools is typically not granted, and elaborate syntheses and substitution schemes are needed in order to obtain efficient photoswitching properties. Here we present a series of rhodanine-based photoswitches that can be prepared in one simple synthetic step without requiring elaborate purification. Photoswitching is induced by UV and visible light in both switching directions, and thermal stabilities of the metastable states as well as quantum yields are very high. An additional benefit is the hydrogen-bonding capacity of the rhodanine fragment, which enables applications in supramolecular or medicinal chemistry. We further show that the known rhodanine-based inhibitor SMI-16a is a photoswitchable apoptosis inducer. The biological activity of SMI-16a can effectively be switched ON or OFF by reversible photoisomerization between the inactive E and the active Z isomer. Rhodanine-based photoswitches therefore represent an easy to access and highly valuable molecular toolbox for implementing light responsiveness to the breadth of functional molecular systems.

Generation of nearly pure and highly directional magnetic light in fluorescence of rare-earth ions

Generation of nearly pure and highly directional magnetic light in fluorescence of rare-earth ions

A directionally illuminated pixel-selective flickering-free autostereoscopic display

A directionally illuminated pixel-selective flickering-free autostereoscopic display is proposed and demonstrated. The system consists of the U-shaped backlight, the mix-grooves cylindrical Fresnel lens array, a light shaping diffuser film, and a liquid crystal display with a directional light splitting element. Simulation is applied to obtain the crosstalk and the illuminance distribution at each viewpoint, which serves as design guideline for system structure and component parameters. The simulation and experimental results indicate that directional projection of parallax images is achieved for a high-quality flickering-free autostereoscopic display with a large viewing angle and continuous viewing volume. The crosstalk between left- and right-channels can be controlled down to 5.49%, while the resolution for each eye is more than a full HD. Furthermore, the alternative flickering in high refresh rate directional backlight autostereoscopic displays is removed by the proposed system, resulting in a high-quality and flickering-free viewing experience for multiple users.

Effects of polarizing film arrangement on the viewing angle of polymer-dispersed liquid crystal films

Polymer-dispersed liquid crystal (PDLC) film is an electrically controlled dimming film in which the orientation of the liquid crystal molecules can be changed by applying an electric field. When the liquid crystals are perpendicular to the PDLC film, the film is transparent. Birefringence occurs after light passes through the liquid crystal molecules, resulting in two beams of light with perpendicular vibration directions. Therefore, PDLC film appears hazy when viewed from the side. In this study, a polarizing film was introduced to reduce the side-view haze, and its influence on the haze at different angles and positions was investigated. Experiment results revealed that aligning the PDLC film along the polarizing film’s absorption axis reduced the haze at all angles. When the polarizing film was attached to each side of the PDLC film and the absorption axis angle of the films was 0∘, a wide-viewing-angle PDLC film was obtained; at a 45∘ tilt, the haze only increased by 0.33%, and at 60∘ it maintained a clear field of view. This may be because only light in the same direction as the absorption axis passed through the film, reducing the amount of light that did not match the polymer refractive index.

Topographic correction of visible near‐infrared reflectance spectra for horizon‐scale soil organic carbon mapping

AbstractUnderstanding soil organic carbon (SOC) response to global change has been hindered by an inability to map SOC at horizon scales relevant to coupled hydrologic and biogeochemical processes. Standard SOC measurements rely on homogenized samples taken from distinct depth intervals. Such sampling prevents an examination of fine‐scale SOC distribution within a soil horizon. Visible near‐infrared hyperspectral imaging (HSI) has been applied to intact monoliths and split cores surfaces to overcome this limitation. However, the roughness of these surfaces can influence HSI spectra by scattering reflected light in different directions posing challenges to fine‐scale SOC mapping. Here, we examine the influence of prescribed surface orientation on reflected spectra, develop a method for correcting topographic effects, and calibrate a partial least squares regression (PLSR) model for SOC prediction. Two empirical models that account for surface slope, aspect, and wavelength and two theoretical models that account for the geometry of the spectrometer were compared using 681 homogenized soil samples from across the United States that were packed into sample wells and presented to the spectrometer at 91 orientations. The empirical approach outperformed the more complex geometric models in correcting spectra taken at non‐flat configurations. Topographically corrected spectra reduced bias and error in SOC predicted by PLSR, particularly at slope angles greater than 30°. Our approach clears the way for investigating the spatial distributions of multiple soil properties on rough intact soil samples.

Evaluation of photocatalytic activity of Cu3(PO4)2/MgO nanocomposite for the efficient removal of amaranth dye under solar light irradiation

The amaranth dye was removed using photocatalysis on a Cu3(PO4)2/MgO nanocomposite synthesized by co-precipitation method. The crystalline component and the nanostructure of the samples were analyzed by XRD, FTIR, UV–vis-DRS, SEM, EDS, HR-TEM and EIS confirming the successful formation of the nanocomposite. In powder XRD, the average crystallite size is found to be ∼ 26–37 nm. Electrochemical impedance spectroscopy, Nyquist plots represents the charge-transfer resistance at contact interface and the arc diameter of Cu3(PO4)2/MgO is much smaller than that of pure MgO and Thermo gravimetric analysis (TGA), from TGA curve the weight-loss of Cu3(PO4)2 and Cu3(PO4)2/MgO nanocomposite was calculated as 14.18 % and 18.16 % which gives the more contribution to the large enhancement of photocatalytic activity. The photocatalytic degradation efficiency of Cu3(PO4)2/MgO nanocomposite (0.1 g/L, 10 μM and 150 min) was investigated under natural direct solar light irradiation against the dyes. The rate of degradation of amaranth with Cu3(PO4)2/MgO followed pseudo–first order kinetics in the dye concentration. Degradation efficiency (99 %) and degradation rates of amaranth were increases with increasing Cu3(PO4)2/MgO concentration. Generally, this research work advances the possible utilization of Cu3(PO4)2/MgO as an efficient catalyst for taking away of dye from aqueous solution and improvement the catalyst to be used for a numerous cycles. The Cu3(PO4)2/MgO nanocomposites showed good activity against bacteria of Staphylococcus aureus, Staphylococcus pyogenes and Klebsilla pneumoniae.

Decorrelating ReSTIR Samplers via MCMC Mutations

Monte Carlo rendering algorithms often utilize correlations between pixels to improve efficiency and enhance image quality. For real-time applications in particular, repeated reservoir resampling offers a powerful framework to reuse samples both spatially in an image and temporally across multiple frames. While such techniques achieve equal-error up to 100× faster for real-time direct lighting [Bitterli et al. 2020 ] and global illumination [Ouyang et al. 2021 ; Lin et al. 2021 ], they are still far from optimal. For instance, spatiotemporal resampling often introduces noticeable correlation artifacts, while reservoirs holding more than one sample suffer from impoverishment in the form of duplicate samples. We demonstrate how interleaving Markov Chain Monte Carlo (MCMC) mutations with reservoir resampling helps alleviate these issues, especially in scenes with glossy materials and difficult-to-sample lighting. Moreover, our approach does not introduce any bias, and in practice, we find considerable improvement in image quality with just a single mutation per reservoir sample in each frame.

Impact of illumination technique on the detectability of irregularities in high-resolution images of visual in-situ process monitoring in Laser Powder Bed Fusion

The layerwise geometry build-up of additive manufacturing (AM) enables the possibility of in-situ process monitoring. The objective is the detection of irregularities during the build cycle, ensuring component quality and process stability. Focus of this work is the visual in-situ monitoring of the process of powder bed fusion with laser beam of metals (PBF-LB/M). Current state of the art visual monitoring systems for PBF-LB/M are limited by low resolution, allowing the detection of gross flaws. In this work a 65 Mpixel high-resolution monochrome camera is integrated into a commercial PBF-LB/M machine enabling a spatial resolution of approx. 17.2 µm/Pixel. The observed inhomogeneities are clustered into directly detectable irregularities, and indirectly detectable irregularities that can be inferred from the surface. In parallel, two different illumination techniques are realized in the process chamber and compared. The impact of the distinct illumination technique, direct light and dark field, on the identification of irregularities is evaluated.

Evaluation of Grain Size Distribution by Digital Image Processing

Sieve analysis tests are frequently used to determine the grain size distribution of granular materials. This project proposes an ImageJbased image analysis approach for evaluating aggregate particle size distribution. Grain size in image analysis should be estimated to compare the graduation curves between the two methods.. Black sheets were more effective than white sheets for particle placement, perhaps due to light effects. This technology may be utilized for in-suit testing, as it requires a camera and computer. The study used monochromatic light and a highdefinition camera to capture grain photos while controlling for background, light direction, and intensity. A ground truth was established to evaluate errors in determining grain areas. All grain shape parameters are obtained using the ImageJ program. The grain size distribution curve is generated using image analysis.

Spatial orientation of CdS nanowiresbased on second harmonic generation spectroscopy and microscopic Imaging

The second harmonic generation (SHG), as a nonlinear optical effect, has a wide range of applications in obtaining information such as material composition, structure, and properties due to its good polarization sensitivity. Although SHG spectroscopy or SHG microscopy has been used to explore the precise positioning or tracking of nanowires, there are few reports on the combination of SHG spectroscopy and SHG microscopy to study the structure of nanomaterials and the spatial orientation of crystal axes. In this work, we investigate the spatial orientation and crystal axis orientation of cadmium sulfide (CdS) nanowires by combining SHG spectroscopy and microscopic imaging. Firstly, we experimentally and theoretically study the spectral intensity of the SHG of CdS nanowires with the polarization direction of the incident light based on the all-optical analysis method proposed by the predecessors. We also analyze the influence of the azimuth angle of the crystal axis γ, ω and φ on the pattern of the SHG of CdS nanowires in detail. Secondly, through the mutual verification of theoretical calculations and experimental measurement results, we successfully determine the three axial orientations of a single CdS nanowire. Finally, we also investigate the spatial orientation of a single CdS nanowire by using the polarization-dependent SHG microscopic imaging method. It is shown that different parts of the CdS nanowire have different SHG responses when the polarization is changed. These results provide a new idea and an important reference for studying the application of SHG spectroscopy and microscopic imaging in the research of high-precision spatial positioning of nanomaterials. This study provides important enlightenment for realizing the potential applications of nanomaterials in biomedicine.

Analysis on the improvement direction of display cabinets and lighting in the display of art works in art museums

Analysis on the improvement direction of display cabinets and lighting in the display of art works in art museums

Preserving Vision and Preventing Complications: A Case Report on the Diagnosis and Management of Chronic Angle Closure Glaucoma

ABSTRACT This case report presents the clinical presentation and management of a 68-year-old male with chronic angle closure glaucoma. Upon examination, the right eye (OD) exhibited a significant decline in visual acuity to 1/300. Findings included conjunctival congestion (CVI +) and absence of posterior conjunctival vessel congestion (PCVI -), corneal opacification and edema, shallow anterior chamber, midriasis of the pupil, and absence of direct and consensual light reflexes (−). Additionally, lens opacification and chemosis (+) were observed. Conversely, the left eye (OS) had a visual acuity of 6/30 with an intraocular pressure (IOP) of 6/15. Similar to the right eye, it displayed corneal opacification and edema, a shallow anterior chamber, midriasis of the pupil, absence of light reflexes (direct and consensual), lens opacification, and chemosis (+). This case underscores the importance of early diagnosis of chronic angle closure glaucoma to prevent adverse prognostic outcomes. Keywords: Chronic Angle Closure Glaucoma, Vision, Preventing Adverse Outcomes

Improving mixed-reality neuronavigation with blue-green light: a comparative multimodal laboratory study.

This study aimed to rigorously assess the accuracy of mixed-reality neuronavigation (MRN) in comparison with magnetic neuronavigation (MN) through a comprehensive phantom-based experiment. It introduces a novel dimension by examining the influence of blue-green light (BGL) on MRN accuracy, a previously unexplored avenue in this domain. Twenty-nine phantoms, each meticulously marked with 5-6 fiducials, underwent CT scans as part of the navigation protocol. A 3D model was then superimposed onto a 3D-printed plaster skull using a semiautomatic registration process. The study meticulously evaluated the accuracy of both navigation techniques by pinpointing specific markers on the plaster surface. Precise measurements were then taken using digital calipers, with navigation conducted under three distinct lighting conditions: indirect white light (referred to as no light [NL]), direct white light (WL), and BGL. The research enlisted two operators with distinct levels of experience, one senior and one junior, to ensure a comprehensive analysis. The study was structured into two distinct experiments (experiment 1 [MN] and experiment 2 [MRN]) conducted by the two operators. Data analysis focused on calculating average and median values within subgroups, considering variables such as the type of lighting, precision, and recording time. In experiment 1, no statistically significant differences emerged between the two operators. However, in experiment 2, notable disparities became apparent, with the senior operator recording longer times but achieving higher precision. Most significantly, BGL consistently demonstrated a capacity to enhance accuracy in MRN across both experiments. This study demonstrated the substantial positive influence of BGL on MRN accuracy, providing profound implications for the design and implementation of mixed-reality systems. It also emphasized that integrating BGL into mixed-reality environments could profoundly improve user experience and performance. Further research is essential to validate these findings in real-world settings and explore the broader potential of BGL in a variety of mixed-reality applications.