Fine Spectrum Research Articles

Linear Modeling of Spectra of Fine Particulate Materials: Implications for Compositional Analyses of Primitive Asteroids

AbstractIn this study, we applied a sum to one constraint weighted least squares (STO WLS) model to thermal infrared (TIR) spectra of a suite of primitive asteroid analogs spectrally and volumetrically dominated by fine particulates (<38 μm). Since coarse particulate emissivity spectra combine linearly, deriving compositions from these are fairly straightforward. Across the TIR it is not as straightforward for fine particulate emissivity spectra due to the nonlinear behavior that arises from volumetric scattering between particles when the particle size becomes comparable to the wavelength of light. Using a WLS model, mixed spectra may be deconvolved into areal percentages of each end member which we assume corresponds to their volume percentages. We used a spectral library of pure mineral spectra to model TIR spectra of a suite of physical mixtures and meteorites obtained under ambient (Earth‐like) and simulated asteroid environment (SAE) conditions collected for the OSIRIS‐REx team (Donaldson Hanna et al., 2021, https://doi.org/10.1029/2020JE006624). The STO WLS model underestimated the modal abundances of the dominant mineral phases by ∼25.0 ± 0.1% on average over the full spectral range and ∼22.0 ± 0.4% over a limited spectral range in all of the ambient and SAE physical mixture and meteorite spectra. Minor phases present in the mixtures and meteorites (abundances ≤5%) were typically not modeled. Also, phases not present in the mixtures were commonly selected (∼2 phases on average with an average abundance of ∼25.2 ± 1.9%) to get the best mathematical fit.

Ro-vibrational spectral features and pressure broadening dynamics of dideutero-methane (12CH2D2) in the ν9(B2) fundamental band

Dideutero-methane 12CH2D2 is unique among all the methane isotopomers because of its asymmetric-top nature. Here, we first report the fine ro-vibrational gas-phase spectra of 12CH2D2 isotopomer in the a-type ν9 (B2-symmetry) fundamental band near 7.8 µm using ultra-sensitive cavity ring-down spectroscopy (CRDS) instrument in the mid-infrared spectral region. We utilized Gaussian 16 to calculate the relevant spectroscopic parameters of 12CH2D2 and subsequently performed the PGOPHER simulation for precise assignments of the fine ro-vibrational lines of 12CH2D2. Further, we conducted the pressure broadening dynamics of 12CH2D2 isotopomer with various foreign gases and accurately determined the pressure broadening coefficients, γi in cm−1 atm−1 [i = He, Ar, N2, Hydrogen mixture(H2 + N2) and zero air] of various transition lines of 12CH2D2.

Micro-size picosecond-duration fast neutron source driven by a laser–plasma wakefield electron accelerator

Abstract A pulsed fast neutron source is critical for applications of fast neutron resonance radiography and fast neutron absorption spectroscopy. However, due to the large transversal source size (of the order of mm) and long pulse duration (of the order of ns) of traditional pulsed fast neutron sources, it is difficult to realize high-contrast neutron imaging with high spatial resolution and a fine absorption spectrum. Here, we experimentally present a micro-size ultra-short pulsed neutron source by a table-top laser–plasma wakefield electron accelerator driving a photofission reaction in a thin metal converter. A fast neutron source with source size of approximately 500 μm and duration of approximately 36 ps has been driven by a tens of MeV, collimated, micro-size electron beam via a hundred TW laser facility. This micro-size ultra-short pulsed neutron source has the potential to improve the energy resolution of a fast neutron absorption spectrum dozens of times to, for example, approximately 100 eV at 1.65 MeV, which could be of benefit for high-quality fast neutron imaging and deep understanding of the theoretical model of neutron physics.

Fine spectra and compactness of generalized Cesàro operators in Banach lattices in [formula omitted

The generalized Cesàro operators Ct, for t∈[0,1), introduced in the 1980's by Rhaly, are natural analogues of the classical Cesàro averaging operator C1 and act in various Banach sequence spaces X⊆CN0. In this paper we concentrate on a certain class of Banach lattices for the coordinate-wise order, which includes all separable, rearrangement invariant sequence spaces, various weighted c0 and ℓp spaces and many others. In such Banach lattices X the operators Ct, for t∈[0,1), are always compact (unlike C1) and a full description of their point, continuous and residual spectrum is given. Estimates for the operator norm of Ct are also presented.

Innovative mass spectrometer for high-resolution ion spectroscopy.

Conventional ion spectroscopy is inapplicable for ions produced in low concentrations or with low spectral resolutions. Hence, we constructed a high-resolution vacuum ultraviolet mass-analyzed threshold ionization (HR VUV-MATI) spectrometer composed of a four-wave frequency mixing cell capable of generating long-lasting and intense VUV laser pulses of ∼1 × 1010 photons/pulse at wavelengths of 123.6-160.0nm, a space-focused linear time-of-flight photoionization chamber with a new ion-source assembly, and a compact molecular beam chamber with a temperature-controlled pulsed nozzle for ion spectroscopy. The ion-source assembly and pulsing schemes enabled an ∼15-μs-delayed but extremely weak pulsed-field-ionization of the molecules in the zero-kinetic-energy (ZEKE) states and first-order space focusing of the generated MATI ions. These ZEKE states were effectively generated by a minute electric jitter from the high-lying Rydberg states, which were initially prepared via VUV photoexcitation. The spectral and mass resolutions (∼5cm-1 and 2400, respectively) and the signal strength were simultaneously enhanced using this spectrometer. Moreover, it could be used to measure the fine vibrational spectrum from the zero-pointlevel of the cation and the exact adiabatic ionization energy of the neutral molecule. Additionally, it could be used to measure the appearance energies of the photoproducts and elucidate the vibrational structures of the cationic isotopomers, utilizing other pulsing schemes. Furthermore, this spectrometer could be used to analyze the congested vibrational spectrum of a cation with multiple conformations. Thus, the HR VUV-MATI spectrometer-a potential alternative to photoelectron spectrometers-can be used to analyze the conformational structure-dependent reactivities.

On the fine spectra of the Jacobi matrices on c_0,c,l_p (1≤p≤∞) and 〖bv〗_p (1≤p<∞)

The spectrum and spectral divisions of band matrices are very new and popular topics of studies. In this paper, our aims are to investigate boundedness of Jacobi matrix which is a band matrix has important role in physics and give subdivisions of the spectra, which are approximate point spectrum, defect spectrum and compression spectrum, for a special type Jacobi matrix. Moreover, we will find the fine division of spectrum which is given by Goldberg with the help of it.

Effect of Variation Substitution of Nd and Eu on the Crystal Structure of Y-124 Superconductor (Y1-x-yNdxEuyBa2Cu4O8??)

In this study, the substitution of elements Nd and Eu on the superconductor Y1-x-yNdxEuyBa2Cu4O8?? (Y-124) has been carried out using compounds Y2O3, BaCO3, CuO, Nd2O3 and Eu2O3 with molar variations of Nd (x) and Eu (y), respectively. 0, 0,05, 0,1, 0,15 and 0,2 respectively to determine the effect of Nd and Eu substitution on the volume fraction and crystal structure of the superconducting Y-124. Samples were synthesized using wet mixing method with HNO3 as solvent, followed by calcination process at 600 oC for 3 hours and sintering process at 900 oC for 10 hours. Analysis of the structure of the superconducting Y-124 was carried out by characterizing X-ray Diffraction (XRD) and Fourier-Transform Infrared Spectroscopy (FTIR). The results of XRD characterization showed a fine and sharp spectrum which indicated that crystallization had occurred completely. The resulting spectrum was dominated by the Y-124 phase and a small percentage of the impurities were detected. Substitution of Nd and Eu elements resulted in volume fractions of 82,7 %, 83,6 %, 84,4 %, 87,0 % and 85,9 %, respectively. The volume fraction value increased with the addition of Nd and Eu from 0 to 0,15, then decreased at 0,2. This indicates that the optimization of the addition of Nd and Eu is at a value of 0,15 in the molar ratio of compounds. The substitution of Nd and Eu elements also causes changes in the lattice parameters towards the a-axis with values between 3,7549 and 3,8323 , towards the b-axis with values between 3,8094 and 3,8425 , and towards the c-axis with values between 26,7390 and 26,8970. The FTIR results show the presence of an absorption band in the YBCO region, but the sample still contains impurities which are indicated to come from BaCO3 and HNO3.

Silicon determination via a SiO rotational line using high-resolution graphite furnace molecular absorption spectrometry: A straightforward approach for the analysis of solid samples prepared as suspensions

High-resolution graphite furnace molecular absorption spectrometry combined with samples prepared as suspensions were used for the quantification of Si in geological samples and in spent catalysts used for petrochemical processing. Measurements at the main Si resonance line at 251.6110 nm were proven unfeasible due to the formation of a quasi-continuous signal, which resulted in significant memory effect. An alternative was to monitor the fine rotational spectrum of SiO, which allowed memory effect-free measurements. A SiO rotational line centered at 231.9373 nm was selected to carry out quantitative analysis of Si at high percent concentrations in a variety of solid samples. Pyrolysis and vaporization temperatures were evaluated and optimized as 800 °C and 2400 °C, respectively, without the need to use a chemical modifier. Attempts to produce SiO molecules from acidified aqueous standards containing Si were unsuccessful, as the molecule could only be produced from solid samples, likely due to the formation mechanism that involves thermal decomposition of silicates. Hence, solid samples were prepared as suspensions in 0.14 mol L−1 HNO3. Calibration was performed using a series of suspensions prepared from a gabbro rock certified reference material (CRM), resulting in a limit of detection of 0.5% (m/m). The accuracy of the method was attested by the analysis of several CRM, including rocks, soils and sediments. Solid spent petrochemical catalyst samples were also analyzed and 97–114% recovery was obtained by spiking the catalyst suspensions with a CRM. The good accuracy demonstrated that the formation of SiO is free from matrix effects and highly efficient under the adopted conditions. Overall, the method was proven accurate and consists on a simple and fast alternative to determine Si in silicate-rich samples.

SOI-Based Multi-Channel AWG with Fiber Bragg Grating Sensing Interrogation System

For the development of minimized and high-rate photonic-integrated fiber Bragg grating interrogation (FBGI) systems, arrayed waveguide grating (AWG) has been widely used as one of the critical components. In this paper, we present an 8-channel SOI-based AWG for a photonic integrated FBG interrogation microsystem. The channel spacing of the AWG is designed to be 3 nm to meet a high-dynamic-range demodulation requirement. The core size of the fabricated AWG is about 335 × 335 μm2. The simulation results and experimental results are in high agreement, showing that AWG has a fine transmission spectrum with crosstalk below −16 dB, nonuniformity below 0.4 dB, insertion loss below −6.35 dB, 3 dB bandwidth about 1.3 nm and 10 dB bandwidth of 2.3 nm. The proposed AWG can be applied perfectly to the SOI-based AWG demodulation microsystem, exhibiting a large dynamic range of 1.2 nm, the resolution for measurements is 1.27 pm and a high accuracy of 20.6 pm.

Optomechanical Design and Application of Solar-Skylight Spectroradiometer.

Using a solar radiometer is an effective approach for improving the remote sensing of solar irradiance distribution and atmospheric composition. Long-term development of a solar scanning radiometer enables frequent and reliable measurement of atmospheric parameters such as the water vapor column and aerosol optical properties. However, the discrete wavelength radiometer has encountered a bottleneck with respect to its insufficient spectral resolution and limited observation waveband, and it has been unable to satisfy the needs of refined and intelligent on-site experiments. This study proposes a solar-skylight spectroradiometer for obtaining visible and near-IR fine spectrum with two types of measurement: direct-sun irradiance and diffuse-sky radiance. The instrument adopts distributed control architecture composed of the ARM-Linux embedded platform and sensor networks. The detailed design of the measuring light-path, two-axis turntable, and master control system will be addressed in this study. To determine all coefficients needed to convert instrument outputs to physical quantities, integrating sphere and Langley extrapolation methods are introduced for diffuse-sky and direct-sun calibration, respectively. Finally, the agreement of experimental results between spectroradiometers and measuring benchmarks (DTF sun-photometer, microwave radiometer, and Combined Atmospheric Radiative Transfer simulation) verifies the feasibility of the spectroradiometer system, and the radiation information of feature wavelengths can be used to retrieve the characteristics of atmospheric optics.

Ro-vibrational Distribution of NO+ Dissociated from NO2+ Ions in the a3B2 and b3A2 States: A Slow "Impulsive" Dissociation Example Revealed from Threshold Photoelectron-Photoion Coincidence Imaging.

To clarify the contentions about dissociative photoionization mechanism of nitrogen dioxide via the a3B2 and b3A2 ionic states, a new threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging has been conducted in the 12.8-14.0 eV energy range at the Hefei Light Source. The fine vibrational-resolved threshold photoelectron spectrum agrees well with the previous measurements. The ro-vibrational distributions of NO+, as the unique fragment ion in the dissociation of NO2+ in specific vibronic levels of a3B2 and b3A2 states, are derived from the recorded TPEPICO velocity images. A "cold" vibrational (v+ = 0) and "hot" rotational population is observed at the a3B2(0,3,0) and (0,4,0) vibronic levels, while the dissociation of NO2+ in b3A2(0,0,0) leads to the NO+ fragment with both hot vibrational and rotational populations. With the aid of the quantum chemical calculations at the time-dependent B3LYP level, minimum energy paths on the potential energy surfaces of the a3B2 and b3A2 states clarify their adiabatic dissociation mechanisms near the thresholds, and this study proposes reliable explanations for the observed internal energy distributions of fragment ions. Additionally, this study provides valuable insights into the application of the classical "impulsive" model on an overall slow dissociation process.

Simulation for measurement of lightning channel temperature using a dual-band high-precision lightning imaging spectrometer.

A dual-band high-precision lightning imaging spectrometer (DHLIS) is designed to capture the fine spectrum of transient lightning. DHLIS improves the theoretical spectral resolution limit to 10-3nm and broadens the spectral range to 30-40 nm by employing double echelle gratings in the arms of a spatial heterodyne spectrometer. Four strong and three fine spectral lines are selected to retrieve the temperature of the lightning channel using the Boltzmann plot method. The experimental results indicate that the inversion accuracy of the temperature obtained by inserting fine spectral lines is higher than that by implementation of four strong spectral lines.

Unusual photodegradation reactions of Asteraceae and Poaceae grass pollen enzymatic extracts on P25 photocatalyst.

In previous studies, it was demonstrated that photocatalysis by TiO2 nanoparticles can be effective for decomposition of pollen grains and pollen allergen extracts (PAEs) for Cupressus arizonica and Platanus hybrida species. In this work, the chemical and photochemical processes of five types of PAEs belonging to family Asteraceae, tribe Astereae, and family Poaceae, tribes Poeae and Triticea, were studied. It was confirmed that the PAEs suffered almost complete decomposition, which likely led to gaseous final products. For the species of Poeae tribe, i.e., Poa pratensis, Festuca pratensis, and Avena sativa, an unusual surface chemical modification of the photocatalyst consisting in the appearance of new bands on fine core level spectra of Ti 2p, C 1s, and O 1s was observed. These changes were associated with possible doping of TiO2 with C and N by pollen extracts. This was accompanied by a red shift of absorption spectra. The results suggest that some components of Poeae pollen can be grafted on TiO2 surface and they can activate the photocatalyst in the visible range. These findings can open a new pathway to eco-friendly chemical engineering of photocatalysts using organic biological compounds.

Magnetic field measurement based on a fiber laser oscillation circuit merged with a polarization-maintaining fiber Sagnac interference structure.

A compact optical magnetic field sensor based on a fiber laser oscillator circuit merged with a Sagnac loop that contains a polarization-maintaining fiber (PMF) and a magnetostrictive rod is proposed. The combination of the PMF-Sagnac loop and fiber laser oscillation circuit significantly increases the signal-to-noise ratio of the reflection spectrum in the system, which is a mixed spectrum that includes interference fringes and lasers. For the proposed system, an erbium-doped fiber amplifier is used to provide gain, a dispersion compensating fiber is used to compensate for dispersion in the system, a PMF is inserted in the Sagnac loop as a microwave filter, while a section of the PMF is bonded to a magnetostrictive rod to achieve magnetic field sensing. The proposed system is shown experimentally to produce a fine reflection interference spectrum. The highest intensity reflection interference peak (from the laser) is over 40 dB with a -3 dB line-width of about 0.03 nm. The system can provide magnetic field sensitivities of 0.07 nm/mT and 0.076 nm/mT for sensor head lengths of 1 m and 2 m, respectively, and exhibits a stability of ±0.029 nm over 1 h. The proposed sensing system has advantages of low cost, high sensitivity, compact structure, and can produce a fine and stable reflection spectrum.

A survey on the spectra of the difference operators over the Banach space c

Recently, due to its numerous applications, the spectra of the bounded operators over Banach spaces have been studied extensively. This work aims to collect some of the investigations on the spectra of difference operators or matrices on the Banach space c in the literature and provide a foundation for related problems. To the best of our investigations, the problem has been solved over the sequence space c so far up to maximum order 2. In the present work, the fine spectra of the difference operator $$\Delta ^m, m\in \mathbb {N}$$ on c have been computed. The generalized difference operator $$\Delta ^m$$ on the Banach space c is defined by $$(\Delta ^mx)_k= \sum _{i=0}^m(-1)^i\left( {\begin{array}{c}m\\ i\end{array}}\right) x_{k-i},\;k=0,1,2,3,\dots $$ with $$ x_{k} = 0$$ for $$k<0$$ . Indeed, the operator $$\Delta ^m$$ is represented by an $$(m+1)$$ -th band matrix which generalizes several difference operators such as $$\Delta ,\Delta ^2,B(r,s)$$ and B(r, s, t) etc, under different limiting conditions. Initially, we provide some essential background results on the linearity and boundedness of the backward difference operator $$\Delta ^m$$ . Finally, the sets for the spectrum and fine spectra such as the point spectrum, the continuous spectrum and the residual spectrum of the defined operator on the space c have been computed. The geometrical interpretation for the spectral subdivisions of the above difference operator is also incorporated.

New Method for Spectral Leakage Reduction in the FFT of Stator Currents: Application to the Diagnosis of Bar Breakages in Cage Motors Working at Very Low Slip

Motor current signature analysis has become a widespread fault diagnosis technique for induction machines (IMs), because it is noninvasive and requires low resources of hardware (a current sensor) and software (a fast Fourier transform). Nevertheless, its industrial application faces practical problems. One of its most challenging scenarios is the detection of broken bars in IMs working at very low slip, like large machines with a very small rated slip, or unloaded induction motors in off-line tests. In these cases, the leakage of the main supply component can hide the fault harmonics, even with a severe fault. Diverse solutions to this problem have been proposed, such as the use of smoothing windows, advanced spectral estimators, or the removal of the supply component. Nevertheless, these methods modify the spectral content of the current signal or add a high computational burden. In this work, a new approach is proposed, based on the analysis of the current with a very fine spectrum, obtained via simple zero padding, followed by the extraction of a practically leakage-free conventional, coarse spectrum. The method is experimentally validated by the diagnosis of a broken bar fault in a 3.15-MW induction motor.

Leaf and fine root economics spectrum across 49 woody plant species in Wuyi Mountains

Leaf and fine root economics spectrum across 49 woody plant species in Wuyi Mountains

Fine needle aspiration cytology-based spectrum of salivary gland lesions at a teaching institute in north India

Introduction: Salivary gland swellings can occur because of inflammation, cyst or neoplastic process. Neoplasms of salivary glands are relatively rare comprising less than 2% of all human tumors. Prevalence of salivary of gland lesions differ from place to place. There are more than 30 morphologically different types of salivary gland neoplasms; majority of which can be diagnosed on fine needle aspiration cytology with expertise. Material and methods: This was a retrospective observational study spanning over 5 years carried out in the department of Pathology, Shaheed Hasan Khan Mewati Government Medical College, Nalhar. Hundred and forty-seven patients with salivary gland swelling were included in the study. Result: Benign salivary gland neoplasm was the most common lesion (54.42%) followed by inflammatory lesions (20.40%). Pleomorphic adenoma (90%) was the most common benign tumor affecting predominantly female patient and mostly involving the parotid gland. Mucoepidermoid carcinoma was the most common malignant tumor (36.85%) followed by poorly differentiated carcinoma (26.31%). Benign tumors were more common in females, whereas malignant tumors occurred more frequently in males. Conclusion: Fine needle aspiration cytology is fast, reliable and relatively accurate method to give tissue-based diagnosis of salivary gland swellings. It helps the clinician to plan the treatment modality for the patients in short time.

Root trait-microbial relationships across tundra plant species.

Summary Fine roots, and their functional traits, influence associated rhizosphere microorganisms via root exudation and root litter quality. However, little information is known about their relationship with rhizosphere microbial taxa and functional guilds.We investigated the relationships of 11 fine root traits of 20 sub‐arctic tundra meadow plant species and soil microbial community composition, using phospholipid fatty acids (PLFAs) and high‐throughput sequencing. We primarily focused on the root economics spectrum, as it provides a useful framework to examine plant strategies by integrating the co‐ordination of belowground root traits along a resource acquisition–conservation trade‐off axis.We found that the chemical axis of the fine root economics spectrum was positively related to fungal to bacterial ratios, but negatively to Gram‐positive to Gram‐negative bacterial ratios. However, this spectrum was unrelated to the relative abundance of functional guilds of soil fungi. Nevertheless, the relative abundance of arbuscular mycorrhizal fungi was positively correlated to root carbon content, but negatively to the numbers of root forks per root length.Our results suggest that the fine root economics spectrum is important for predicting broader groups of soil microorganisms (i.e. fungi and bacteria), while individual root traits may be more important for predicting soil microbial taxa and functional guilds.

Random Fiber Grating Characterization Based on OFDR and Transfer Matrix Method.

Random fiber gratings (RFGs) have shown great potential applications in fiber sensing and random fiber lasers. However, a quantitative relationship between the degree of randomness of the RFG and its spectral response has never been analyzed. In this paper, two RFGs with different degrees of randomness are first characterized experimentally by optical frequency domain reflectometry (OFDR). Experimental results show that the high degree of randomness leads to low backscattering strength of the grating and strong strength fluctuations in the spatial domain. The local spectral response of the grating exhibits multiple peaks and a large peak wavelength variation range when its degree of randomness is high. The linewidth of its fine spectrum structures shows scaling behavior with the grating length. In order to find a quantitative relationship between the degree of randomness and spectrum property of RFG, entropy was introduced to describe the degree of randomness induced by period variation of the sub-grating. Simulation results showed that the average reflectivity of the RFG in dB scale decreased linearly with increased sub-grating entropy, when the measured wavelength range was smaller than the peak wavelength variation range of the sub-grating. The peak reflectivity of the RFG was determined by (where is the coupling coefficient, is the grating length, is period variation range of the sub-grating) rather than when is larger than 8 nm in the spatial domain. The experimental results agree well with the simulation results, which helps to optimize the RFG manufacturing processes for future applications in random fiber lasers and sensors.