Spectral Match Research Articles

LkHα 225 (V1318 Cyg) South in Outburst

Abstract Magakian et al. called attention to the current bright state of LkHα 225 South, a well-known highly embedded, intermediate-mass young stellar object that over the past two decades has brightened visually from >20 m to <13 m . We present recent optical photometric monitoring showing colorless, nonsinusoidal, periodic brightness oscillations occurring every 43 days with amplitude ∼0.7 mag. We also present new flux-calibrated optical and near-infrared spectroscopy, which we model in terms of a Keplerian accretion disk, and high-dispersion spectra that demonstrate similarity to some categories of “mixed-temperature” accretion-outburst objects. At blue wavelengths, LkHα 225 South has a pure absorption spectrum and is a good spectral match to the FU Ori stars V1515 Cyg and V1057 Cyg. At red optical and infrared wavelengths, however, the spectrum is more similar to Gaia 19ajj, showing emission in TiO, CO, and metals. Sr ii absorption indicates a low-surface-gravity atmosphere. There are also signatures of a strong wind/outflow. LkHα 225 South was moderately bright in the early 1950s as well as in the late 1980s, with evidence for deep fades during intervening epochs. The body of evidence suggests that LkHα 225 South is another case of a source with episodically enhanced accretion that causes brightening by orders of magnitude, and development of a hot absorption spectrum and warm wind. It is similar to Gaia 19ajj, but also reminiscent in its long brightening time and brightness oscillation near peak to the embedded sources L1634 IRS7 and ESO Ha 99.

Toward Class AAA LED Large Scale Solar Simulator With Active Cooling System for PV Module Tests

Solar simulators are significant in testing solar cells and photovoltaic (PV) modules since they provide spectrum and optic characteristics close to natural sunlight. This research introduces two fundamental novelties to the literature on light-emitting diode (LED) light source solar simulators. One of these innovations is designing and developing a solar simulator to achieve <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I-V</i> characterization on a PV module basis instead of cell-based contrary to the previous studies. For this purpose, a unique board with a modular structure is designed on which the LEDs are positioned. In the research, LEDs of at six different wavelengths are used. Spectral match, spatial nonuniformity, and temporal instability performance criteria tests conducted on the illuminated area is performed based on IEC 60904-9 and ASTM 927E-10 standards. Class AAA was obtained according to the large-scale solar simulator standard specified in ASTM 927E-10. The second novelty the study introduces is developing an active cooling system that can prevent an increase in LED junction temperature when the number of LEDs increases in an LED solar simulator with a wide illuminated area. In addition to the fans, this solution is suggested to prevent any damage to the LEDs during the test, as well as high temperatures from affecting the wavelengths and at the same time achieve 25 °C, one of the standard test conditions. Also, the device dimensions are optimized ergonomically for ease of use. With this system designed and devised, it becomes possible to test commercially available PV modules successfully. The active cooling system minimizes the heating problem and the impact of wavelengths that might invalidate performance criteria classes.

Random Telegraph Noise of a 28-nm Cryogenic MOSFET in the Coulomb Blockade Regime

We observe rich phenomena of two-level random telegraph noise (RTN) from a commercial bulk 28-nm p-MOSFET (PMOS) near threshold at 14 K, where a Coulomb blockade (CB) hump arises from a quantum dot (QD) formed in the channel. Minimum RTN is observed at the CB hump where the high-current RTN level dramatically switches to the low-current level. The gate-voltage dependence of the RTN amplitude and power spectral density match well with the transconductance from the DC transfer curve in the CB hump region. Our work unequivocally captures these QD transport signatures in both current and noise, revealing quantum confinement effects in commercial short-channel PMOS even at 14 K, over 100 times higher than the typical dilution refrigerator temperatures of QD experiments (<100 mK). We envision that our reported RTN characteristics rooted from the QD and a defect trap would be more prominent for smaller technology nodes, where the quantum effect should be carefully examined in cryogenic CMOS circuit designs.

Temperature-Irradiance Matrix and Determination of Temperature Coefficients of a Monocrystalline PV Module

Photovoltaic (PV) modules performance testing and energy rating as described in IEC 61853-1 standard depend on electrical performance parameters (short-circuit current, open-circuit voltage, maximum-power) of PV modules as a function of temperature and irradiance. In this work, in order to precisely determine the effects of temperature on the electrical parameters of a monocrystalline PV module, the temperature controlled, xenon light based solar simulator system with irradiance attenuating masks was used. This solar simulator, according to the IEC 60904-9 standard in terms of spectral match, spatial non-uniformity and temporal instability has A+A+A+ classes which are two times better than the standard requirements for a solar simulator to be used in PV module measurements. Moreover, the thermal chamber used in this work is a closed type chamber with fast opening door for not allowing the distortion of temperature uniformity over the surface of PV modules under test. Within about 2 m × 2 m area within 15°C to 75°C temperature interval, the temperature uniformity obtained for this system is less than 1.0°C which is almost two times better than the IEC 60891 standard requirements (±2.0°C). The temperature and irradiance dependent measurements of the electrical performance parameters of a mono-crystalline PV module at various irradiance levels and the evaluation of its temperature coefficients [α (% °C-1), β (% °C-1) and δ (% °C-1)] were done by implementing the interpolation method described in IEC 60891 standard.

Characterization of Simulator and Relative Spectral Responsivity Measurements of Photovoltaic Modules with Band Pass Filter Technique

One of the most important parameter used for the evaluation of the energy rating of PV modules is, their spectral responsivities which are the measure of electrical performance parameters per incident solar radiation. In this work, spectral responsivity measurements of a mono-crystalline, a poly-crystalline, a CIGS thin film and a bifacial module were measured using xenon-based flash type solar simulator system and a set of band pass filters. For the comprehensive characterization of parameters that may influence the spectral responsivity measurements, initially the simulator system was characterized both optically and thermally according to the IEC60904-9 and IEC60891 standard requirements. The optical characterizations in terms of spectral match, spatial non-uniformity and temporal instability indicate that the measured results (~3.0%, ~0.30% and ~0.20%) according to the IEC 60904-9 standard’s classification requirements correspond to A+A+A+ classes. Moreover, thermal characterizations in terms of the temperature uniformity show that over the 2 × 2 m area temperature uniformity of simulator system’s light distribution (1ºC) is almost two times better than the IEC 60891 standard requirements (±2ºC). Next, PV modules were electrically stabilized according to the IEC 61215-2 standard requirement’s (stability test) to reduce the fluctuations in their electrical performance parameters. Then, using the band pass filters, temperature controlled xenon-based solar simulator system and a reference PV module of the spectral responsivity of PV modules were measured from 400 nm to 1100 nm with 50 nm steps with relative uncertainty of 10-3 level.

Multitarget Multiple-Instance Learning for Hyperspectral Target Detection

In remote sensing, it is often challenging to acquire or collect a large data set that is accurately labeled. This difficulty is usually due to several issues, including but not limited to the study site’s spatial area and accessibility, errors in the global positioning system (GPS), and mixed pixels caused by an image’s spatial resolution. We propose an approach, with two variations, that estimates multiple-target signatures from training samples with imprecise labels: multitarget multiple-instance adaptive cosine estimator (MTMI-ACE) and multitarget multiple-instance spectral match filter (MTMI-SMF). The proposed methods address the abovementioned problems by directly considering the multiple-instance, imprecisely labeled data set. They learn a dictionary of target signatures that optimizes detection against a background using the adaptive cosine estimator (ACE) and spectral match filter (SMF). Experiments were conducted to test the proposed algorithms using a simulated hyperspectral data set, the MUUFL Gulfport hyperspectral data set collected over the University of Southern Mississippi–Gulfpark Campus, and the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) hyperspectral data set collected over Santa Barbara County, CA, USA. Both simulated and real hyperspectral target detection experiments show that the proposed algorithms are effective at learning target signatures and performing target detection.

Highly-efficient radiative thermal rectifiers based on near-field gap variations.

Near-field radiative thermal rectifiers (NFRTRs) enabling directional heat transport hold great promise for various applications, including thermal logic computing, thermal management, and energy conversion. Current NFRTR designs rely on dissimilar terminal materials with high contrasts in their temperature-dependent dielectric properties, which in turn hinders the spectral match for radiative heat transfer and thus limits the device's efficiency. Herein, this dilemma is solved by designing heterostructures where a pair of polaritonic layers are separately stacked on a thermally-expanding layer and a rigid substrate, spaced by a vacuum gap. In this scheme, the symmetric polaritonic layers can provide stable near-field radiative channels for heat transfer, while the thermally-expanding layer can modulate the gap size with flipped temperature bias to allow high contrasts in heat flux. In exemplified implementations, the hBN-based design has achieved a record-high thermal rectification factor (TRF, ∼104) even under small thermal gradients (∼20 K), which can be further boosted by polaritonic hybridizations in the graphene/hBN-based design. This study paves the way to design novel NFRTRs with 2D materials, thus providing enriched polaritons to realize higher TRFs.

μATR-FTIR Spectral Libraries of Plastic Particles (FLOPP and FLOPP-e) for the Analysis of Microplastics

Raman spectral libraries specific to microplastics demonstrated improved spectral matching results when weathered plastics and a variety of particle colors and morphologies were included. Here, we explore if this is true for Fourier transform infrared (FTIR) spectroscopy as well. We present two novel databases specific to microplastics using attenuated total reflection (μATR-FTIR): (1) an FTIR library of plastic particles (FLOPP), containing 186 spectra from common plastic items, across 14 polymer types and (2) an FTIR library of plastic particles sourced from the environment (FLOPP-e), containing 195 spectra across 15 polymer types. Both libraries include particles from a variety of sources, morphologies, and colors. We demonstrate the applicability of these libraries for microplastics research by comparing spectral match results from two microplastic datasets. For this, we use different combinations of libraries including: commercially available reference libraries, an open-access polymer library, and FLOPP and FLOPP-e. Among tests, the greatest mean HQI result was achieved when the greatest number of libraries was included. This work demonstrates that spectral libraries specific to plastic particles found in the environment improve the accuracy of spectral matching and are best used in combination with commercial libraries containing chemical components that are commonly found within plastics and other anthropogenic particles. Multivariate principal component analyses of FLOPP and FLOPP-e spectra confirmed differences among polymer types and higher variation in principal component scores among weathered particles, but no patterns were observed among particle colors or morphologies. These results demonstrate that ATR-FTIR analyses are sensitive to weathering of plastics but not to particle color and morphology.

Metabolomics of the wild mushroom Gymnopilus imperialis (Agaricomycetes, Basidiomycota) by UHPLC-HRMS/MS analysis and molecular network

Gymnopilus consists in a widely distributed genus of mushroom-forming fungi, especially in tropical regions of the world. Literature on Gymnopilus representatives reports the presence of oligoisoprenoids, and styrylpyrones. Considering the large number of secondary metabolites that basidiomycetes might contain, dereplication tools such as GNPS (Global Natural Products Social Molecular Networking), has become important in prospecting metabolites, saving time and work on isolation and characterization of natural products. Thus, this work identified the wild mushroom Gymnopilus imperialis and dereplicated their extracts with the aid of GNPS to annotate oligoisoprenoids. It was possible to annotate 24 oligoisoprenoids from methanol, dichloromethaneand ethyl acetate extracts of G. imperialis, 4 of them from GNPS spectral library match, and 20 from prediction based on molecular network. Moreover HRMS-ESI-(+) dereplication of the acetate extract annotated bisnoryangonin and hispidin. To the best of our knowledge, this is the first report on the annotation of a series of gymnopilins analogues based on GNPS molecular network. Our findings suggest that GNPS might be an effective, rapid, and open-source device to identify compounds and predict analogues.

The worldsheet dual of free super Yang-Mills in 4D

The worldsheet string theory dual to free 4d mathcal{N} = 4 super Yang-Mills theory was recently proposed in [1]. It is described by a free field sigma model on the twistor space of AdS5 × S5, and is a direct generalisation of the corresponding model for tensionless string theory on AdS3 × S3. As in the case of AdS3, the worldsheet theory contains spectrally flowed representations. We proposed in [1] that in each such sector only a finite set of generalised zero modes (‘wedge modes’) are physical. Here we show that after imposing the appropriate residual gauge conditions, this worldsheet description reproduces precisely the spectrum of the planar gauge theory. Specifically, the states in the sector with w units of spectral flow match with single trace operators built out of w super Yang-Mills fields (‘letters’). The resulting physical picture is a covariant version of the BMN light-cone string, now with a finite number of twistorial string bit constituents of an essentially topological worldsheet.

Optimal design and experimental test of a solar simulator for solar photovoltaic modules

AbstractSolar simulators have been widely used to characterize the performance of solar photovoltaics cells, which typically have a size of 156 × 156 mm2. In order to amplify the testing area, a flexible optimal design method for solar simulators is presented in this study. In this work, 20 quartz tungsten halogen lamps are used with a light filter composed of a mixture of distilled water and cyan ink. The methodology includes the measurements of the irradiance nonuniformities, spectral profile, and explores the effects of light filters on the primary light source used. During this stage, the power source of the lights should be selected, where direct current is usually assumed. As soon as the primary light source is characterized by its corresponding model, a layout is defined by optimizing the nonuniformity of the irradiance. The constructed solar simulator presents a spectral match of 1.69%, a spatial nonuniformity of irradiance of 1.66%, and a temporal instability of irradiance lower than 0.1%. In addition, the current‐voltage curves are compared under indoor and outdoor test showing a root‐mean‐squared error lower than 3%. A class CAA solar simulator is achieved according to the International Electrotechnical Commission and American Society for Testing and Materials standards over an area of 270 × 270 mm2, suitable for testing small size solar photovoltaic modules.

A complete search of combinatorial peptide library greatly benefited from probabilistic incorporation of prior knowledge

The core of peptide detection in tandem mass spectrometry lies in associating fragment spectra with promising peptide candidates. We examined such detection in a synthetic combinatorial peptide library using four scoring metrics, against all theoretical peptides, and with a varying level of probabilistic prior knowledge—analyzing more than a trillion peptide-spectrum matches in total. Even after adjusting for peptide-length scoring bias, most MS/MS spectra had multiple at-least-as-good candidates as the correct peptide, showing that the highest spectral match was not a guarantee of correctness. As a remedy, we probabilistically integrated prior knowledge about expected cleavage behavior and expected peptide sequences into peptide scoring, reaching and even overcoming the performance of state-of-the-art de novo sequencing algorithms. Overall, we found that even partial and weak beliefs considerably improved peptide detection and are, in principle, generally applicable to any detection approach. Detection of peptides in a complete search thus often resulted in multiple admissible candidates near the maximal score, and the use of probabilistic prior knowledge substantially improved their discrimination.

(INVITED) Ultraviolet cross-luminescence in ternary chlorides of alkali and alkaline-earth metals

After the discovery of a cross-luminescence (CL) in BaF2 in 1982, a large number of CL scintillators were investigated. However, no CL scintillator superior to BaF2 has been discovered, and the research of CL scintillators has subsided. Recent technological development in medical imaging and high-energy physics created a new demand for ultra-fast scintillators further supported by the development of UV-sensitive semiconductor photodetectors. As a consequence, renewed interest in CL scintillators appeared. To satisfy the requirements of fast timing applications high photo-detection efficiency, e. i. a good spectral match between the scintillator and photodetector must be achieved. Cesium-based ternary chlorides could provide a red-shift (∼1.5 eV) of CL towards the sensitive region of the photodetector (PMT or SiPM) while keeping light output and timing characteristics comparable to BaF2.

Physical Characterization of Metal-rich Near-Earth Asteroids 6178 (1986 DA) and 2016 ED85

Abstract Metal-rich near-Earth asteroids (NEAs) represent a small fraction of the NEA population that is mostly dominated by S- and C-type asteroids. Because of this, their identification and study provide us with a unique opportunity to learn more about the formation and evolution of this particular type of bodies, as well as their relationship with meteorites found on Earth. We present near-infrared (NIR) spectroscopic data of NEAs 6178 (1986 DA) and 2016 ED85. We found that the spectral characteristics of these objects are consistent with those of metal-rich asteroids, showing red slopes, convex shapes, and a weak pyroxene absorption band at ∼0.93 μm. The compositional analysis showed that they have a pyroxene chemistry of Fs40.6±3.3Wo8.9±1.1 and a mineral abundance of ∼15% pyroxene and 85% metal. We determined that these objects were likely transported to the near-Earth space via the 5:2 mean motion resonance with Jupiter. Asteroid spectra were compared with the spectra of mesosiderites and bencubbinites. Differences in the NIR spectra and pyroxene chemistry suggest that bencubbinites are not good meteorite analogs. Mesosiderites were found to have a similar pyroxene chemistry and produced a good spectral match when metal was added to the silicate component. We estimated that the amounts of Fe, Ni, Co, and the platinum group metals present in 1986 DA could exceed the reserves worldwide.

Mineralogical and Spectral (Near-Infrared) Characterization of Fe-Rich Vermiculite-Bearing Terrestrial Deposits and Constraints for Mineralogy of Oxia Planum, ExoMars 2022 Landing Site.

Oxia Planum is a Noachian plain on Mars. It was chosen as the final landing site for in situ studies by ExoMars 2022 rover. The main scientific objectives of the mission are to understand the mineralogy and aqueous evolution of ancient Mars with relevance to habitability. Oxia is covered by vast deposits of Fe,Mg-phyllosilicates, but the exact nature of these deposits is not yet fully understood. We performed a survey of potential terrestrial analog rocks, and here we show combined mineralogical characterization of these rocks with their near-infrared spectral analysis. Samples from two terrestrial sites were studied: (1) vermiculitized chlorite-schists from Otago, New Zealand, which underwent an alteration process without significant oxidation; and (2) basaltic tuffs from Granby, Massachusetts, USA, with Fe-rich clays filling amygdales of supposedly hydrothermal origin. Both analogues are incorporated into the newly built Planetary Terrestrial Analogue Library (PTAL) collection. Oxia bedrock clay-rich deposits are spectrally matched best by a well-crystallized trioctahedral vermiculite/saponite mixture from the basaltic tuff, although the contribution of saponite must be minor. Otago vermiculite is a good analogue to Oxia vermiculite in terms of overall mineralogy and Fe content. However, spectral inconsistencies related to the Al content in the Otago clays indicate that illitization of vermiculite, which results from postalteration oxidation, did not occur at Oxia. This implies limited water/rock interactions and reducing conditions during deposition of sediments now constituting the bedrock at Oxia. Whereas the spectral match does not conclusively imply the mineralogy, trioctahedral vermiculite should be considered a likely mineral component of the bedrock unit at Oxia Planum. Vermiculite has great potential to store organic matter, and the postdeposition geological context of Oxia Planum derived from understanding of environmental conditions in analog sites is promising for organic matter preservation.

A method to measure the spectral responsivity of a photometer using optical excitations with arbitrary spectral distributions

The spectral responsivity of a photometer is usually measured using very narrow optical excitations, provided by a monochromator or a tuneable laser. This article describes a technique to measure the spectral responsivity using an arbitrary number of optical excitations having any type of spectral distribution. The problem is formulated as an inverse problem which is solved using a probabilistic approach based on Bayes’ theorem. The method requires a prior knowledge of the spectral responsivity, which can be proportional to the standard photopic function, with an uncertainty level related to the spectral match index of the photometer. Using this method, the estimation can be performed from data provided by a simple experimental set-up. The numerical application provides a stable and unique solution to the inverse problem, along with the estimation uncertainties. Using a tuneable LED source, the method was applied to an illuminance measurement head, giving an estimation of its spectral responsivity from 380 to 780 nm with a step of 1 nm. The results were in good agreement with data obtained by a monochromator-based technique. Our measurement had larger uncertainties towards the red and blue limits of the spectrum as the light source provided very little light at these wavelengths.

Topological Cavity Based on Slow-Light Topological Edge Mode for Broadband Purcell Enhancement

Slow light in topological valley photonic crystal structures offers possibilities to enhance light-matter interaction. We report a topological cavity based on slow-light topological edge modes for broadband Purcell enhancement. The topological edge modes with large group indices over 100 can be realized with a bearded interface between two topologically distinct valley photonic crystals, featuring the greatly enhanced Purcell factor because of the increased local density of states. In the slow-light regime, the topological cavity supports much more cavity modes with a higher quality factor than that in the fast-light regime, which is both demonstrated theoretically and experimentally. We demonstrate the cavity enables the broadband Purcell enhancement together with substantial Purcell factor, benefiting from dense cavity modes with a high quality factor in a wide spectral range. It has great benefit for the realization of high-efficiency quantum-dot-based single-photon sources and entangled-photon sources with less restriction on spectral match. Such a topological cavity could serve as a significant building block toward the development of photonic integrated circuits with embedded quantum emitters.

Identification of malachite and alteration minerals using airborne AVIRIS-NG hyperspectral data

Hyperspectral remote sensing technique is a robust technique for the delineation and mapping of hydrothermally altered and weathered mineral deposits. The purpose of present study is to identify, delineate and map the altered zones by AVIRIS-NG Airborne hyperspectral data and validate the output by field survey and analysis of lab spectra. Major lithologies of the study area includes the presence of dolomite, banded iron formation, orthoquartzite, grey phyllite, granites and carbonaceous phyllite. Hydrothermal altered zones are delineated in the study area based on Airborne Visible Infrared Imaging Spectrometer-Next Generation (AVIRIS-NG) hyperspectral data. FLAASH atmospheric correction was applied to hyperspectral data followed by minimum noise fraction, pixel purity index, n-dimensional visualisation and spectral angle mapper (SAM). SAM classified image was used for identification of altered minerals such as kaolinite, talc, kaosmec, sensitive to the shortwave infrared, whereas iron oxides such as goethite and limonite were distinguished in Visible and Near Infrared region. With the help of alteration minerals, Malachite mineral stains in the study area were identified. Representative rock samples are collected from field and lab spectra generated between wavelength region of 350–2500 nm. ASD spectra and image spectra compared with the USGS spectral library minerals which shows good spectral match with the collected samples. Therefore, it can be concluded that AVIRIS-NG hyperspectral data is useful in identification, delineation and mapping of altered and weathered minerals.

Chemical composition analysis of carbohydrate fragmentation products

Fragmentation of simple sugars, using fluidized thermal bed cracking, results in a mixture that contains a variety of polar oxygenated compounds, some yet unknown to the industries. This lack of understanding of the product composition, hinders the downstream processes in conversion of sugars to useful chemicals. The aim of this study was fourfold: to develop a GC–MS identification workflow for carbohydrate fragmentation compounds, to build a library of compounds detected by five GC–MS methods including liquid injection, liquid-liquid extraction, static headspace, solid-phase microextraction and derivatization, to investigate and compare the compound coverage of the five methods, and finally investigate possible reaction pathways for some of the analytes in the mixture. The analysis was done on a mixture of seven representative sugar fragmentation samples. The identification workflow was based on mass spectral match factors (>80 %), retention indices and analytical standards. A total of 389 compounds were detected, out of which, 46 compounds were fully identified (through confirmatory analysis of analytical standards), 87 were tentatively identified (spectral match factors above 80 %), 71 were un-identified with spectral match factors of below 80 % and 185 were discarded (contaminants in blanks etc.). The production pathway for some of the identified compounds in the sugar conversion mixtures were also discussed. In conclusion, solid-phase microextraction detected the highest number of analytes (93), mostly volatile organic compounds and the derivatization GC–MS technique detected the lowest number of analytes (19) but was the only method to detect the largest molecules (C6-C12) in size. This library of CF products can be used as a suspect-screening database for other biomass fragmentation mixtures.

Identification and implication of organic compounds of Viola odorata: a potential source for bio-fabrication of nickel oxide nanoparticles

Due to the vast application of nano-materials in different fields, there is a need for their safety and cost-effective synthesis routes. The traditional synthesis methods are not environmentally safe and mostly require high cost thus, the focus on green synthesis has arisen. The present study was conducted to synthesize nickel oxide nanoparticles (NiO Nps) while using leaf extract of Viola odorata: a medicinal plant common as an anti-inflammatory agent. The major identified phyto-compounds with high spectral purity and similarity match in Viola odorata were decanoic acid, benzenemethanol and 6-Hexadecen-4-yne which provide fuel for the synthesis of NiO nanoparticles. The optimized nickel oxide nanoparticles were delineated by Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX), Field emission-scanning electron microscopy (FESEM) and Gas Chromatography-Mass Spectroscopy (GC–MS). XRD confirmed the formation of pure NiO nanoparticles with an average crystallite size of 8.002 nm as calculated by Debye Scherer formula in good agreement with SEM and EDX results.