Visible Source Research Articles

Infrared and visible image fusion using multi‐scale NSCT and rolling‐guidance filter

Image fusion is essential to produce a complementary and comprehensive image, with the source images derived from different sensors, captured from different illumination conditions. In this study, a novel multi-scale image fusion based on the combination of non-subsampled contourlet transform (NSCT) and rolling-guidance filter (RGF) is used to enhance the edges and texture details better than the conventional methods. Initially, infrared (IR) and visible (VIS) source images are multi-scale decomposed to low-frequency and high-frequency sub-band coefficients by NSCT for the best representation of edges and curves. Further, the low-frequency coefficients are decomposed into the base and detail layers by a combination of RGF and GF (Gaussian filter) to retain the features in multiple scales and to reduce halos near the edges. Base layers are fused by saliencybased fusion rule and detail layers are fused by Max absolute rule. High-frequency coefficients are fused by consistency verification based fusion rule to preserve visual details and to suppress noise from source images. Finally, the image is reconstructed by inverse NSCT with good visual perception. Experimental results are evaluated by different evaluation metrics and the results suggest that the proposed method results with better improved source information, clarity and contrast.

Synthesis and characterization of zinc-imidazolate coordination polymer and its use for photocatalytic degradation of methylene blue dye under visible light irradiation

Zinc-Imidazole coordination polymer (Zn-Im CP) was facilely synthesized by hydrothermal method from zinc acetate and imidazole as ligand. The structure of the synthesized Zn-Im CP was analyzed by using scanning electron microscopy (SEM), EDX, FTIR, and powder X-ray diffraction (PXRD). Surface area of Zn-Im CP was determined by BET analysis of N2 adsorption. The photocatalytic performance of Zn-Im CP using visible light irradiation source was investigated using UV–Vis spectrophotometer for the degradation of methylene blue. The pseudo first order reaction kinetic model was applied on the degradation data which gave the rate constant of 0.006 min−1. The results indicate that Zn-Im CP exhibits good photocatalytic performance for the photodegradation of methylene blue following indirect mechanism pathway.

Deep Red Tunability and Output Power Performances of Visible Laser Emission in a Pr:Ba(Y1-xLux)2F8 Single Crystal.

The demand for tunable visible laser sources with high power and high beam quality, for application ranging from metrology to remote sensing, is constantly increasing. In this work, we report on the details of crystal growth, via the Czochralski method, and laser characterization of a Pr-doped Ba(YLu)F (BYLF) single crystal, which is a promising candidate for fulfilling these requirements, both in terms of tunability and high-power capabilities. We measured for the first time the laser tunability curve in the deep red region obtaining a continuous range of 17 nm. The laser emission of the three main Pr lines in the visible (orange, red, and deep red) was tested under increased pump power with respect to previous studies on this material, demonstrating output powers of more than 360 mW and no thermal rolloff, up to 1.9 W of absorbed power.

Novel Norrish type I flavonoid photoinitiator for safe LED light with high activity and low toxicity by inhibiting the ESIPT process

In this study, flavonoid with N,N-diphenylamino group, 2-(4-(diphenylamino)phenyl)-3-hydroxy-4H-chromen-4-one (3HF–OH) was designed and synthesized as low-toxicity photoinitiator for photopolymerization under safe visible LED sources, however, low photoinitiation activity of 3HF–OH was found due to the excited state proton transfer (ESIPT) process. Hence, by replacing the 3-position hydroxyl group of 3HF–OH with benzoyl chloride and benzenesulfonyl chloride, flavonol carboxylate (3HF–C) and flavonol sulfonate (3HF–S) were synthesized, respectively. 3HF–C and 3HF–S showed not only one-component photoinitiating activity but also two-component photoinitiating activity when they were used with triethanolamine (TEOA) and iodonium salt (ONI) under safe, long-wavelength LED soft light sources. Photopolymerization kinetics reveals that photoinitiator 3HFs at low concentration exhibits the high polymerization rate and conversion. Results also showed that 3HF–S has much higher photoinitiation activity during photopolymerization compared with 3HF–OH and 3HF–C. The high extinction coefficient and aggregation-induced emission (AIE) characteristics of 3HF–S were observed, which proved that reducing the photoinitiator usage can effectively progress the photopolymerization activity. At the same time, the low usage of 3HF–S further reduces the toxicity of the cured material. Through electron spin resonance (ESR) experiment, the photoinitiation and sensitization mechanisms of these photoinitiators were observed. The school badge structure of hydrogels could be successfully 3D printed with 3HF–S and the stiffness of the structure was sufficient for further processing without breaking the structure. Moreover, the use of the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) method confirmed the lower toxicity for the final photopolymer provided.

Multichannel Smartphone Spectrometer Using Combined Diffraction Orders

A robust multichannel smartphone spectrometer exploiting multiorder diffraction imaging on a smartphone camera is reported. The instrument utilizes a thin film diffractive element generating multiple orders of diffracted light from a broadband visible source (white LED, λ = 400-700 nm). The smartphone's CMOS camera captures all the diffraction orders simultaneously, producing a 2-D image. Each of these diffraction orders can be utilized as a single optical channel for dedicated samples enabling simultaneous multiple sample analysis. The wavelength distribution along the diffraction direction produces a tunable spectral resolution of δλ ~1.6 to 3.0 nm/pixel over the bandwidth of Δλ = 300 nm. A customized app processes each diffraction image into spectra. 3-D printing is used to create the entire instrument prototype. As an initial demonstration, simultaneous absorption measurements of reference and sample cells using the first diffraction orders (m = +1 and -1) is shown. Absorption spectra for a laser dye (Rhodamine B) and a pH-responsive buffer (bromothymol blue) are measured. This offers a low cost (<; $30) portable instrument layout comparable to conventional double beam benchtop instruments in performance but more rugged for field use.

ORAL FIBROUS PYOGENIC GRANULOMA: CASE REPORT

Pyogenic granuloma is a reactive tumor-like lesion commonly affecting the oral cavity. Histopathologically, pyogenic granuloma is classified into lobular capillary hemangioma (LCH) and non--LCH. The non-LCH type does not show any such organization and resembles granulation tissue. We report a patient, 41-year-old male, smoker and drinker, without systemic impairment that sought the stomatology center referred to evaluate a lesion in the mouth. Intraoral examination revealed a nodular, smooth, sessile lesion and painless, located on lower gingiva measuring 2.0 x 1.8 x 1.0 cm. Clinical hypothesis diagnostic was any reactive lesions of the oral cavity. Excisional biopsy was performed and the histopathological examination, and the immunohistochemical reaction for α-smooth muscle actin revealed oral fibrous pyogenic granuloma (OFPG). The OFPG treatment involved excision of gingival lesions up to periosteum with thorough scaling and root planning of adjacent teeth to remove all visible sources of irritation. Pyogenic granuloma is a reactive tumor-like lesion commonly affecting the oral cavity. Histopathologically, pyogenic granuloma is classified into lobular capillary hemangioma (LCH) and non--LCH. The non-LCH type does not show any such organization and resembles granulation tissue. We report a patient, 41-year-old male, smoker and drinker, without systemic impairment that sought the stomatology center referred to evaluate a lesion in the mouth. Intraoral examination revealed a nodular, smooth, sessile lesion and painless, located on lower gingiva measuring 2.0 x 1.8 x 1.0 cm. Clinical hypothesis diagnostic was any reactive lesions of the oral cavity. Excisional biopsy was performed and the histopathological examination, and the immunohistochemical reaction for α-smooth muscle actin revealed oral fibrous pyogenic granuloma (OFPG). The OFPG treatment involved excision of gingival lesions up to periosteum with thorough scaling and root planning of adjacent teeth to remove all visible sources of irritation.

Thioxanthone Derivatives as a New Class of Organic Photocatalysts for Photopolymerisation Processes and the 3D Printing of Photocurable Resins under Visible Light

In the present paper, novel thioxanthone-based compounds were synthesised and evaluated as a component of photoredox catalysts/photoinitiating systems for the free-radical polymerisation (FRP) of acrylates and the ring-opening cationic polymerisation (CP) of epoxy monomers. The performance of the obtained thioxanthones in two- and three-component photoinitiating systems, in combination with amines, iodonium or sulphonium salt, as well as with alkyl halide, for photopolymerisation processes upon exposure to light emitting diodes (LEDs) with a maximum emission of 405 nm and 420 nm, was investigated. The studied compounds act also as one-component free-radical photoinitiators. Fourier transform real-time infrared spectroscopy was used to monitor the kinetics of disappearance of the functional groups of the monomers during photoinitiated polymerisation. Excellent photoinitiating efficiency and high final conversions of functional groups were observed. Moreover, the influence of thioxanthone skeleton substitution on photoinitiating efficiency was discussed. The photochemical mechanism was also investigated through cyclic voltammetry. It was discovered that thioxanthone derivatives can be used as a metal-free photoredox catalyst active for both oxidative and reductive cycles. Furthermore, a photopolymerizable system based on novel thioxanthone derivatives in a stereolithography three-dimensional (3D) printing technology under visible sources of light was used. The effects of photoinitiator type system and monomer type in photoresins during 3D printing processes were explored. The outcome of this research is the development of high-performance visible photosensitive resins with improved photosensitivity obtained thanks to the development of entirely novel photoinitiating systems specifically adapted for this application.

Multiple-graphene layer based p++–n–n−–n++ device on Si/3C-SiC (100) substrate: a highly sensitive visible photo-sensor

The current paper reports the prospects of a multiple-graphene-layer (MGL) based vertically doped p++–n–n––n++ avalanche photo-sensor in visible wavelength region (300 nm–800 nm). High carrier mobility, intrinsic optical and mechanical properties in graphene at room temperature, have made this material promising for various novel applications. The authors have used an indigenously developed and experimentally verified quantum-corrected field maximum classical drift-diffusion (QCFMCDD) mathematical model for studying the optical characteristics of MGL based p++–n–n––n++ avalanche photo-diode sensor. The validity of the simulator is established through a comparative study between the experimental and analytical observations under similar operating (structural/electrical/thermal) conditions. Additionally, the superiority of the QCFMCDD model over the conventional classical drift-diffusion model is established through this comprehensive study. The analysis reveals that the opto-electrical properties of the device-under-test improve significantly as a result of the incorporation of MGL in the low doped active region. The authors have compared the results with those of a Si/4H-SiC super-lattice avalanche photo-sensor at 500 nm wavelength of incident radiation. It is observed that graphene outperforms its Si/4H-SiC counterpart in terms of photo-responsivity (0.820 A W−1 vs. 0.650 A W−1) and quantum efficiency (84% vs. 62%) for optical irradiation with visible laser source. The opto-electrical performance of the 3 × 3 array type graphene photo-sensor is further analyzed and compared with those of its single array counterpart. The photo-responsivity as well as quantum efficiency increases by at least 30% in the case of the 3 × 3 photo-sensor array. In comparison to available photo detectors, reported so far in published literature, the designed photo-sensor shows overall performance betterment in the visible wavelength region. To the best of authors’ knowledge, this is the first report on MGL based 3 × 3 array type ultra fast highly sensitive visible avalanche diode photo-sensor.

Mapping Right to be Forgotten frames: Reflexivity and empirical payoffs at the intersection of network discourse and mixed network methods

Networks are almost ubiquitous in the social sciences, in terms of method and structure. Dominant discourses around networks–concerning their purported democratic, progressive values and capacities–also impact how they are approached in research. This article illustrates the potential of this impact by tracing the trajectory and findings of a project focused on networked discussion of an Internet privacy debate. Using mixed methods—hyperlink network mapping, textual analysis (qualitative and quantitative), and semi-structured interviews—I examine online framing of a controversial data protection concept, the Right to be Forgotten. Initial, more “traditional” research approaches allowed for insight only into the most central and visible frames and sources. This led to a reorientation of research approach. In attempt to diversify sources and framings, I began focusing on the margins and off the “networked public sphere.” This article thus also recounts the significant empirical findings that resulted from such reflexivity and reorientation.

Constraining 1-D inner core attenuation through measurements of strongly coupled normal mode pairs

SUMMARYWe measured inner core normal mode pair 10S2–11S2, which cross-couples strongly for 1-D structure and is sensitive to shear wave velocity, and find that our measurements agree with a strongly attenuating inner core. In the past, this mode pair has been used to try to resolve the debate on whether the inner core is strongly or weakly attenuating. Its large spectral amplitude in observed data, possible through the apparent low attenuation of 10S2, has been explained as evidence of a weakly attenuating inner core. However, this contradicted body waves and other normal modes studies, which resulted in this pair of modes being excluded from inner core modelling. Modes 10S2 and 11S2 are difficult to measure and interpret because they depend strongly on the underlying 1-D model used. This strong dependence makes these modes change both their oscillation characteristics and attenuation values under a small 1-D perturbation to the inner core model. Here, we include this effect by allowing the pair of modes to cross-couple or resonate through 1-D structure and treat them as one hybrid mode. We find that, unlike previously thought, the source of 10S2 visibility is its strong cross-coupling to 11S2 for both 1-D elastic and anelastic structure. We also observe that the required 1-D perturbation is much smaller than the 2 per cent vs perturbation previously suggested, because we simultaneously measure 3-D structure in addition to 1-D structure. Only a 0.5 per cent increase in inner core vs or a 0.5 per cent decrease in inner core radius is required to explain 10S2–11S2 observations and a weakly attenuating inner core is not needed. In addition, the 3-D structure measurements of mode 10S2 and its cross-coupling to 11S2 show the typical strong zonal splitting pattern attributed to inner core cylindrical anisotropy, allowing us to add further constrains to deeper regions of the inner core.

Calculating luminous flux radiated to a camera lens via high dynamic range photogrammetry

A camera-aided method of using high dynamic range photogrammetry was developed to calculate luminous flux radiated to the camera lens from an environment or its subareas, with per-pixel contributions from visible light-emitting sources, objects, and reflective surfaces. A series of equations were derived to calculate the luminous flux with valid sub-divisibility and additivity. A pilot study was first conducted, followed by a laboratory experiment using an integrating sphere to improve and validate this high dynamic range imaging method with a measurement error of 5.6%. This method was then tested in a real office space to estimate ‘visible’ luminous flux arriving at the camera lens simulating a typical view of 30 office users under four different test scenarios (fluorescent vs. LED lighting, with vs. without access to lighting controls). The luminous flux retrieved from each of a total of 120 high dynamic range images was checked with the illuminance measured at the camera lens. This camera-aided method for remote measurement of luminous flux was proven valid and useful for lighting practice and research. Further investigations on this method are necessary to overcome several limitations and issues of the present study.

Enhanced photocatalytic hydrogen evolution from band-gap tunable Ag2S:X (X = Ni, Co, Zn, Mn) nanocrystals: Effect of transition metal ions

In the present work, Ni, Co, Zn and Mn doped Ag2S nanocrystal catalysts were prepared via the hot-injection technique which is one of the top-down approach. The nanocrystals were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), diffuse reflectance spectroscopy (DRS), UV−vis spectroscopy (UV) and cyclic voltammetry (CV) to illuminate the crystal properties and the photocatalytic mechanism. The presence of doping each of the transition metals on Ag2S nanocrystals were tested for their performance in the photocatalytic hydrogen evolution from water containing TEOA and EY as a hole scavenger and photoabsorber, respectively. The results demonstrated that Ni, Co, Zn and Mn doped Ag2S nanocrystals were showed higher photocatalytic activity as compared with the Ag2S under visible light irradiation source. In addition, transition metal consisting Ag2S catalysts, which in view of the limited literatures, provides new insights for expanding the application of chalcogenide catalysts.

Formation of an amorphous carbon nitride/titania composite for photocatalytic degradation of RR4 dye

A composite of amorphous carbon nitride and titanium dioxide (a-C3N4/TiO2) has been successfully synthesized using urea and P25-TiO2 under microwave irradiation. The characterizations suggested that the carbon nitride component of the a-C3N4/TiO2 composite prepared sample is the best described as amorphous like structure containing carbonyl and amine functionality. This amorphous carbon nitrite (a-C3N4) is coated on TiO2 surface with 2.5–3.9 nm of thin thickness layer detected by HRTEM. The low bandgap energy of a-C3N4 in a-C3N4/TiO2 induce this amorphous acted as electron injector. The a-C3N4/TiO2 provide a lower electron-hole recombination as compared with P25-TiO2 base PL intensity. The photocatalytic activities of a-C3N4/TiO2 and P25-TiO2 were compared for the photodegradation of the dye reactive red 4 (RR4) under low intensity visible light irradiation source (273 W m−2). The photocatalytic degradation of RR4 for a-C3N4/TiO2 was degrade completely within 60 min under visible light irradiation, approximately 5.3 times faster than P25-TiO2. This almost equivalent to their electron-hole recombination rate based on PL intensity. The hybridization of these two semiconductors have shown some improvement photocatalytic activity under visible light irradiation that influenced from the low bandgap energy of a-C3N4, which can act as an electron injector and electron hole recombination inhibitor.

One-component cationic photoinitiators based on coumarin scaffold iodonium salts as highly sensitive photoacid generators for 3D printing IPN photopolymers under visible LED sources

This paper describes the development of new coumarin chromophore-based iodonium salts as efficient one-component cationic photoinitiators upon LEDs irradiation with maximum emission under the UV-A region at 365 nm and under visible light at 405 nm.

Naphthochromenones: Organic Bimodal Photocatalysts Engaging in Both Oxidative and Reductive Quenching Processes

AbstractTwelve naphthochromenone photocatalysts (PCs) were synthesized on gram scale. They absorb across the UV/Vis range and feature an extremely wide redox window (up to 3.22 eV) that is accessible using simple visible light irradiation sources (CFL or LED). Their excited‐state redox potentials, PC*/PC.− (up to 1.65 V) and PC.+/PC* (up to −1.77 V vs. SCE), are such that these novel PCs can engage in both oxidative and reductive quenching mechanisms with strong thermodynamic requirements. The potential of these bimodal PCs was benchmarked in synthetically relevant photocatalytic processes with extreme thermodynamic requirements. Their ability to efficiently catalyze mechanistically opposite oxidative/reductive photoreactions is a unique feature of these organic photocatalysts, thus representing a decisive advance towards generality, sustainability, and cost efficiency in photocatalysis.

Naphthochromenones: Organic Bimodal Photocatalysts Engaging in Both Oxidative and Reductive Quenching Processes.

Twelve naphthochromenone photocatalysts (PCs) were synthesized on gram scale. They absorb across the UV/Vis range and feature an extremely wide redox window (up to 3.22 eV) that is accessible using simple visible light irradiation sources (CFL or LED). Their excited-state redox potentials, PC*/PC.- (up to 1.65 V) and PC.+ /PC* (up to -1.77 V vs. SCE), are such that these novel PCs can engage in both oxidative and reductive quenching mechanisms with strong thermodynamic requirements. The potential of these bimodal PCs was benchmarked in synthetically relevant photocatalytic processes with extreme thermodynamic requirements. Their ability to efficiently catalyze mechanistically opposite oxidative/reductive photoreactions is a unique feature of these organic photocatalysts, thus representing a decisive advance towards generality, sustainability, and cost efficiency in photocatalysis.

Transfusion Medicine Equations Made Internet Accessible.

Multiple mathematical equations inform the practice of transfusion medicine. These equations apply to a wide range of topics: dosage of blood products, calculation of fluid volumes, and even specific treatment decisions (e.g. corrected count increment for determination of platelet refractoriness). The calculation of these equations can be complicated, prone to error, and time-consuming. A trusted source is needed to accurately perform these calculations 24 hours a day without error and without monetary cost. We sought to build internet-enabled calculators relevant to the practice of transfusion medicine. We partnered with MDCalc, an online host of medical calculators with 1 million monthly users in 196 countries, to design and host the calculators. The calculators guide users in the application of transfusion medicine equations by providing indications for use, inputs for the equations variables, error-checking, warnings for bad inputs, and interpretive guidance of the result. The following calculators were built: blood volume, corrected count increment (CCI), plasma dosage, cryoprecipitated antihemophilic factor dosage, approximate number of units for compatibility testing, maternal-fetal hemorrhage Rh(D) immune globulin dosage, intrauterine RBC transfusion dosage, neonatal polycythemia partial exchange, theoretical removal of a substance by plasmapheresis, sickle cell RBC exchange volume, peripheral blood stem cell collection, and a calculator relevant to donor lymphocyte infusion. Clinicians can now utilize this reputable and highly visible online source to access these common transfusion medicine equations at any time with an internet-enabled device (https://www.mdcalc.com/search?filter=transfusion+medicine).

High performance graphene-like thinly layered graphite based visible light photodetector

In this work, the drop casting method is utilized to obtain a thin graphene-like graphite layer as a photodetection layer on a SiO2/Si substrate, and its performance is characterized to determine its potential use in commercial applications. The thin layer is formed by first synthesizing graphite soot from a butane flame before being turned into a liquid solution and drop-casted onto the substrate to form a thin graphene-like graphite film. Field emission scanning electron microscope and Raman vibrational mode analyses indicate that the fabricated graphene-like graphite layer has characteristics similar to the graphene. The graphene-like graphite photodetector demonstrates a narrow photoresponse from 530 to 680 nm, covering visible sources from green to red. The responsivity and external quantum efficiency of the device under the illumination of red laser 660 nm is found to be around 148 mA W−1 and 27.8% respectively and is faster than that reported for similar systems using graphene and reduced graphene oxide previously. A fast response time of 83.7 and 28 µs at a modulation frequency of 1.0 and 10000 Hz respectively from the graphene-like thinly layered graphite photodetector shows potential application for the development of low-cost carbon-based photodetectors in near future.

First imaging spectroscopy observations of solar drift pair bursts

Drift pairs are an unusual and puzzling type of fine structure sometimes observed in dynamic spectra of solar radio emission. They appear as two identical short narrowband drifting stripes separated in time; both positive and negative frequency drifts are observed. Currently, due to the lack of imaging observations, there is no satisfactory explanation for this phenomenon. Using the Low Frequency Array (LOFAR), we report unique observations of a cluster of drift pair bursts in the frequency range of 30−70 MHz made on 12 July 2017. Spectral imaging capabilities of the instrument have allowed us for the first time to resolve the temporal and frequency evolution of the source locations and sizes at a fixed frequency and along the drifting pair components. Sources of two components of a drift pair have been imaged and found to propagate in the same direction along nearly the same trajectories. Motion of the second component source is seen to be delayed in time with respect to that of the first one. The source trajectories can be complicated and non-radial; positive and negative frequency drifts correspond to opposite propagation directions. The drift pair bursts with positive and negative frequency drifts, as well as the associated broadband type-III-like bursts, are produced in the same regions. The visible source velocities are variable from zero to a few 104 (up to ∼105) km s−1, which often exceeds the velocities inferred from the drift rate (∼104 km s−1). The visible source sizes are of about 10′−18′; they are more compact than typical type III sources at the same frequencies. The existing models of drift pair bursts cannot adequately explain the observed features. We discuss the key issues that need to be addressed, and in particular the anisotropic scattering of the radio waves. The broadband bursts observed simultaneously with the drift pairs differ in some aspects from common type III bursts and may represent a separate type of emission.

In situ spectroelectrochemical ellipsometry using super continuum white laser: Study of the anodization of magnesium alloy

This work shows the interest to use a real time, white laser-based ellipsometer to characterize a complex electrolyte|electrode interface during an electrochemical process in an aqueous-based medium. This method is proposed to probe electrochemical interfaces that are usually not suitable to the full extent application of ellipsometry due to great disturbance of the reflected light flux provoked by gas evolution or roughness. In situ spectroelectrochemical ellipsometry combining such a visible super continuum fiber laser-band source was not previously reported to the best of the authors’ knowledge. The setup was employed to monitor an electrochemical process whose mechanism was previously incompletely described: the prespark anodization regime of the plasma electrolytic oxidation process of the Mg alloy AZ91D in the 3M KOH electrolyte. Above the anodization voltage of 4 V, the side water oxidation reaction induced light diffusion that reduces reflected light beam intensity. The process is monitored in an extended voltage range from 4 to 40 V and in an extended spectral range (495–800 nm). In the presented case, the use of a visible super continuum fiber laser-band source enhanced the signal-to-noise ratio giving access to a deeper picture of the triplex layer structure during surface repassivation by monitoring the evolution of the outer, inner, and interfacial layers.