Shell Spectra Research Articles

Enhancing Traceability of Italian Almonds through IR Spectroscopy and Chemometric Classifiers

Almonds are the seeds of the almond (Prunus Amygdalus) tree and are a nut consumed worldwide. The present study utilized the ATR FT-IR technique followed by a chemometric analysis to develop predictive models for determining the geographical origin of almonds from three regions in Southern Italy (Apulia, Calabria, and Sicily). IR spectra were collected on both the almond shell and the edible kernel to accurately characterize the three different geographical origins. The spectroscopic data obtained were processed using Soft Independent Modeling of Class Analogies (SIMCA) and Partial Least Squares Discriminant Analysis (PLS-DA). Both SIMCA and PLS-DA revealed that the shell spectra are more useful for assessing the geographical origin of samples. In particular, the PLS-DA model applied to these data achieved a 100% correct classification rate (on the external test set of individuals) for all the investigated classes.

Unified view of the hydrogen-bond structure of water in the hydration shell of metal ions (Li+, Mg2+, La3+, Dy3+) as observed in the entire 100–3800 cm−1 regions

Hydrogen-bond (H-bond) structure of water in the hydration shell of an anion is fairly well understood, but the corresponding knowledge for cation hydration shell is sparse, mainly because of the overwhelming effect of anion on water that easily masks the subtle effect of cation. Moreover, most of the hydration shell investigations are confined to the OH stretch band of water. Using Raman difference spectroscopy with simultaneous curve fitting (Raman-DS-SCF), we have retrieved the spectrum of water pertaining to the hydration shell of different metal ions (Li+, Mg2+, La3+, Dy3+) in the entire spectral region of 100–3800 cm−1, encompassing the intermolecular H-bond stretch (HOH---OH2; 200 cm−1), librational (300–1000 cm−1), HOH bend (1640 cm−1), bend-librational combination (2120 cm−1) and intramolecular O–H stretch (3000–3700 cm−1) of water. The hydration shell spectra and their polarization dependence (Polarized Raman) are compared for different metal ions and with the hydration shell of Cl− anion and also the high temperature water component (80 °C; extracted by Raman-DS-SCF). These results reveal that the hydration shells of high charge density metal ions have “enhanced” as well as “reduced” H-bond structure. The intermolecular H-bonds become stiffer and the librational freedom of the water gets restricted in the hydration shell. The bend-librational combination band blue-shifts to a large extent and appears toward the tail of the OH stretch, which is expected to facilitate the ultrafast energy dissipation of higher vibrational modes of water.

Experimental determination of the Ag L -subshell x-ray-production cross sections by electron impact through two bulk target methods

The experimental determination of x-ray-production cross sections by electron impact on thick samples is faced in this work, especially focusing on the $L$ subshells of Ag. The integrodifferential method used by An et al. is compared with a recently implemented approach involving the ionization distribution function. The first method has shown good results under suitable conditions, namely, when multiple scattering, bremsstrahlung enhancement, and other secondary effects are negligible. Monte Carlo simulations were performed in order to analyze the influence of these conditions and therefore to extend the validity range of the method by adding a correction factor. The second approach uses the ionization distribution function $\ensuremath{\phi}(\ensuremath{\rho}z)$ to predict the intensity of the emitted photons; this magnitude is assessed by the poema software, previously developed, and it is used to determine correction factors to the cross sections included in the software database. Both approaches were tested by fitting several $L$-shell spectra measured in a wide interval of incident electron energies, ranging from 4.0 to 25 keV, with an electron microprobe equipped with a wavelength-dispersive spectrometer. The x-ray-production cross sections obtained for each $L$ subshell and the total $L$ x-ray-production cross section were compared with theoretical predictions based on the distorted-wave approach theory and with experimental determinations when available.

Origin of the spectacular tidal shells of galaxy NGC 474

Context.The lenticular galaxy NGC 474 hosts a rich system of tidal shells and streams, some of which are exceptionally bright. Two teams recently presented spectroscopic observations of the brightest shells. These were the first shell spectra ever observed in integrated starlight. The authors studied the stellar populations of the shell, of the center of the galaxy, and of its globular clusters. The precise formation scenario for the tidal features of this prominent galaxy still remained unclear, however.Aims.Here, we add further clues on their formation from the radii of the shells, and we present a scenario for the formation of the tidal features that seems to be unique and can explain all available data.Methods.Shell radii were analyzed with the shell identification method, and we ran self-consistent simulations of the formation of the tidal features. We considered Newtonian as well as MOND gravity.Results.Observations suggest that the tidal features originate from the accretion of a spiral galaxy. According to the shell identification method, the merging galaxies first collided 1.3 Gyr ago and then again 0.9 Gyr ago, thereby forming the shells in two generations. This would also explain the young ages of stellar populations in the center of the galaxy and the young age of the globular clusters. The analytic models of shell propagation that underlie the shell identification method are verified by a simulation. The simulations reproduce the observed morphology of the tidal features well. The accreted spiral likely reached NGC 474 on the plane of the sky nearly radially from the south, its rotation axis pointing toward us. It probably had a stellar mass of about one-sixth of NGC 474, that is, 109.8 M⊙. Apparently, all tidal features in the galaxy originate from one merger.

Raman spectroscopy study for the systems (LiCl-H2O and LiCl-MgCl2-H2O): Excess spectra and hydration shell spectra

The micro-structure of hydration shell of solute in water is significant for understanding the properties of aqueous solutions. Raman spectroscopy has been employed for studying the hydration shell structure of the solute for decades, however, Raman imaging data is still seriously overlapped, making it challenging to obtain information on the spectrum of hydrated water molecules. In this paper, Raman spectroscopy was employed to study the O-H vibration peaks of LiCl aqueous solution and LiCl-MgCl2-H2O mixed aqueous solution. The changes of stretching vibration peak of 2800 ∼ 3800 cm-1O-H and hydrogen bond network structure in aqueous solution were analyzed at room temperature and ion association. With the increase of magnesium salt ratio, the damage of solute to the bulk water gradually decreases in the mixed solution, which indicated that LiCl has a more significant influence on the bulk water molecules. It is mainly due to the intense hydration of Li+, which can not only affect the water molecules in the first hydration shell but also affect the water molecules in the second hydration shell. The number of water molecules in the first hydration shell were obtained by extracting the spectra of different solute first hydration shells from the solution spectra. Those spectra of the hydration shell were employed to study the micro-structures of the first hydration shells of anions, and the aggregation behavior of ions in the the mixed solution.

Kosmotropic Electrolyte (Na2CO3, NaF) Perturbs the Air/Water Interface through Anion Hydration Shell without Forming a Well-Defined Electric Double Layer.

The ion-driven electric double layer (EDL) and the structural transformation of interfacial water are implicated in unusual reaction kinetics at the air/water interface. By combining heterodyne-detected vibrational sum frequency generation (HD-VSFG) with differential spectroscopy involving simultaneous curve fitting (DS-SCF) analysis, we retrieve electrolyte (Na2CO3 and NaF)-correlated OH-stretch spectra of water at the air/water interface. Vibrational mapping of the perturbed interfacial water with the hydration shell spectra (obtained by DS-SCF analysis of Raman spectra) of the corresponding anion discloses that the kosmotropic electrolytes do not form well-defined EDL at the air/water interface. Instead, the interfacial water forms a stronger hydrogen-bond with the surface-expelled anions (CO32- and F-) and becomes more inhomogeneous than the pristine air/water interface. Together, the results reveal that the perturbation of interfacial water by the kosmotropic electrolyte is a "local phenomenon" confined within the hydration shell of the surface-expelled anion.

Shedding light on the formation mechanism of shell galaxy NGC 474 with MUSE

Stellar shells around galaxies could provide precious insights into their assembly history. However, their formation mechanism remains poorly empirically constrained, regarding in particular the type of galaxy collisions at their origin. We present MUSE at VLT data of the most prominent outer shell of NGC 474, to constrain its formation history. The stellar shell spectrum is clearly detected, with a signal-to-noise ratio of ∼65 pix−1. We used a full spectral fitting method to determine the line-of-sight velocity and the age and metallicity of the shell and associated point-like sources within the MUSE field of view. We detect six globular cluster (GC) candidates and eight planetary nebula (PN) candidates that are all kinematically associated with the stellar shell. We show that the shell has an intermediate metallicity, [M/H] = −0.83−0.12+0.12, and a possible α-enrichment, [α/Fe] ∼ 0.3. Assuming the material of the shell comes from a lower mass companion, and that the latter had no initial metallicity gradient, such a stellar metallicity would constrain the mass of the progenitor at around 7.4 × 108 M⊙, implying a merger mass ratio of about 1:100. However, our census of PNe and earlier photometry of the shell would suggest a much higher ratio, around 1:20. Given the uncertainties, this difference is only significant at the ≃1σ level. We discuss the characteristics of the progenitor, and in particular whether the progenitor could also be composed of stars from the low-metallicity outskirts of a more massive galaxy. Ultimately, the presented data do not allow us to put a firm constraint on the progenitor mass. We show that at least two GC candidates possibly associated with the shell are quite young, with ages below 1.5 Gyr. We also note the presence of a young (∼1 Gyr) stellar population in the center of NGC 474. The two may have resulted from the same event.

Enhanced Performance of White Light Generation from ZnS/ZnO Core/Shell Nanocrystals

Zinc sulfide (ZnS) and zinc oxide (ZnO) nanocrystals (NCs) were synthesized to arrangement the ZnS / ZnO core / shell NCs via chemical reaction afterward produced from nanocomposite. The modified development of ZnS / ZnO NCs and the sulfurization and oxidation ecosystems could detect many external appearance and colors. Photoluminescence (PL) was analyzed to determine the properties and optical features of such nanostructures, as well as the energy gap between chemical bands. In addition, material characterizations verified, take in electron microscopy scanning and X-ray diffraction a first rising ZnS/ZnO core / shell nanocrystals. An absorption spectrum of ZnO shells on ZnS cores NCs was limited to development technique. The prepared nanocomposites seemed to have the results of scanning electron microscopy (SEM) and uniform in size limited within 3-4 nm radius. The core / shell nanocomposites ZnS / ZnO NCs are capable of generating white light uses. The white light emission was accomplished by illumination the UV-LED (GaN) nanocomposites of the core ZnS and ZnO cover NC.

Counter Cations Affect Transport in Aqueous Hydroxide Solutions with Ion Specificity.

The anomalously high mobility of hydroxide and hydronium ions in aqueous solutions is related to proton transfer and structural diffusion. The role of counterions in these solutions, however, is often considered to be negligible. Herein, we explore the impact of alkali metal counter cations on hydroxide solvation and mobility. Impedance measurements demonstrate that hydroxide mobility is attenuated by lithium relative to sodium and potassium. These results are explained by ab initio molecular dynamics simulations and experimental vibrational hydration shell spectroscopy, which reveal substantially stronger ion pairing between OH- and Li+ than with other cations. Hydration shell spectra and theoretical vibrational frequency calculations together imply that lithium and sodium cations have different effects on the delocalization of water protons donating a hydrogen bond to hydroxide. Specifically, lithium leads to enhanced proton delocalization compared with sodium. However, proton delocalization and the overall diffusion process are not necessarily correlated.

Manganese speciation in Mn-rich CaCO3: A density functional theory study

The manganese content of aragonitic bivalve shells is a potential archival indicator of temporal Mn bioavailability in aquatic environments. The Mn speciation mechanism in biogenic aragonite minerals remains elusive because the analog is challenging to synthesize, and the metastable phase has yet to be fully resolved experimentally. In this study, we performed density functional theory (DFT) computations of hypothetical Mn-doped aragonite to examine its local coordination structure and thermodynamic and electronic properties. Our DFT calculations reproduced the experimental crystal structures and solubility product constants (Ksp) of Mn-doped calcite. The magnetic moment of Mn was close to 5 μB in both Mn-doped calcite and Mn-doped aragonite (Ca1−xMnxCO3). The calculated Ksp of Mn-doped aragonite was higher than that of Mn-doped calcite and increased with Mn content, indicative of the unfavorable coprecipitation of Mn with the aragonite phase. We found that the incorporation of a small mole fraction of Mn into aragonite created significant structural distortion around the Mn site, resulting in mixed coordination numbers of Mn (mainly five and seven). Valence-to-core X-ray emission spectroscopy (XES) measurements are useful in determining the coordination environment of Mn complexes. We calculated theoretical XES spectra, with a 1s core hole in Mn, for Mn-doped calcite and four versions of Mn-doped aragonite. The Boltzmann-averaged spectrum for different coordination numbers in Mn-doped aragonite was akin to an experimental XES spectrum of aragonitic bivalve shells. The energy position of the Kβ2,5 band was calculated to be insensitive to Mn speciation in CaCO3; however, the band intensity was relatively sensitive to Mn speciation. The XES spectrum intensity decreased exponentially with increasing Mn–O distance. This quantitative XES relationship we report can reduce uncertainties in the spectral interpretation due to the absence of an Mn-doped aragonite reference spectrum.

Possible Areas of Splitting the Flexural Frequency Spectrum of Shells with Asymmetric Shape Imperfections

The influence of initial deviations from the ideal circular shape on the dynamic characteristics of the thin circular cylindrical shell is investigated. The emergence of new zones of splitting the flexural frequency spectrum of imperfect shells is detected.

Properties of laser-produced GaAs plasmas measured from highly resolved X-ray line shapes and ratios

The properties of hot, dense plasmas generated by the irradiation of GaAs targets by the Titan laser at Lawrence Livermore National Laboratory were determined by the analysis of high resolution K shell spectra in the 9 keV to 11 keV range. The laser parameters, such as relatively long pulse duration and large focal spot, were chosen to produce a steady-state plasma with minimal edge gradients, and the time-integrated spectra were compared to non-LTE steady state spectrum simulations using the FLYCHK and NOMAD codes. The bulk plasma streaming velocity was measured from the energy shifts of the Ga He-like transitions and Li-like dielectronic satellites. The electron density and the electron energy distribution, both the thermal and the hot non-thermal components, were determined from the spectral line ratios. After accounting for the spectral line broadening contributions, the plasma turbulent motion was measured from the residual line widths. The ionization balance was determined from the ratios of the He-like through F-like spectral features. The detailed comparison of the experimental Ga spectrum and the spectrum simulated by the FLYCHK code indicates two significant discrepancies, the transition energy of a Li-like dielectronic satellite (designated t) and the calculated intensity of a He-like line (x), that should lead to improvements in the kinetics codes used to simulate the X-ray spectra from highly-charged ions.

Influence of Local Environment on Inner Shell Excitation Spectra, Studied by Electron and X-ray Spectroscopy and Spectromicroscopy

Abstract Inner shell excitation spectroscopy is a local probe of the unoccupied electronic structure in the immediate vicinity of the core excited atom. As such, one might expect the inner shell spectrum of a given unit (a molecular fragment or a repeat unit of a solid) to be largely independent of where that unit is located. This is often an implicit assumption in spectral analysis and analytical applications. However, there are situations where inner shell excitation spectra exhibit significant sensitivity to their local environment. Here I categorize the ways in which inner shell spectra are affected by their local environment, and give examples from a career dedicated to developing a better understanding of inner shell excitation spectroscopy, its experimental techniques, and applications.

Majorana states in prismatic core-shell nanowires

We consider core-shell nanowires with conductive shell and insulating core and with polygonal cross section. We investigate the implications of this geometry on Majorana states expected in the presence of proximity-induced superconductivity and an external magnetic field. A typical prismatic nanowire has a hexagonal profile, but square and triangular shapes can also be obtained. The low-energy states are localized at the corners of the cross section, i.e., along the prism edges, and are separated by a gap from higher energy states localized on the sides. The corner localization depends on the details of the shell geometry, i.e., thickness, diameter, and sharpness of the corners. We study systematically the low-energy spectrum of prismatic shells using numerical methods and derive the topological phase diagram as a function of magnetic field and chemical potential for triangular, square, and hexagonal geometries. A strong corner localization enhances the stability of Majorana modes to various perturbations, including the orbital effect of the magnetic field, whereas a weaker localization favorizes orbital effects and reduces the critical magnetic field. The prismatic geometry allows the Majorana zero-energy modes to be accompanied by low-energy states, which we call pseudo Majorana, and which converge to real Majoranas in the limit of small shell thickness. We include the Rashba spin-orbit coupling in a phenomenological manner, assuming a radial electric field across the shell.

A Note on Possible Healing Effects of Conch Shell Frequencies

The conch shell as a music tool with its innumerable uses has occupied a singular place in almost all ancient traditions and cultures across the globe. It could be considered as the sole musical instrument designed by Nature herself into a fascinating piece of art. However, studies aimed at understanding the acoustical attributes of a conch shell received very less attention in modern times. None of the previous studies on conch shell aimed at looking into a few aspects for which it is usually adored and considered sacred. In general, the sound radiated from a conch shell is believed to hold a healing aspect, and that is the underlying reason why different cultures used it during ritual practices, special ceremonies and at acoustically designed sacred sites. The present concept seminates from the observation that we have an additional ultrasonic component in the sound spectrum of a conch shell along with other harmonic frequencies. Since the low-range ultrasonic frequencies are known for their beneficial and healing effects, it’s obvious to relate them to such component existing in the conch shell spectrum. In this respect, the present note serves as a starting step in analyzing the fundamental grounds for its healing aspect.

Modelling K shell spectra from short pulse heated buried microdot targets

K shell X-ray emission measurements have been used to diagnose plasma conditions in short-pulse heated buried microdot targets on the Orion high power laser. These experiments have been used to validate simulations of short pulse laser-solid interaction that combine hybrid PIC modelling of the laser absorption with radiation-hydrodynamics simulations including an electron transport model. Comparison of these simulations with streaked K shell spectroscopy show the importance of including radial gradients in fitting the spectra. An example is presented of the emission of sulphur from a 50µm diameter microdot sample buried in a plastic foil. Previously agreement between simulation and experiment was obtained only by treating the absorbed energy, electron temperature and beam divergence as fitting parameters. The good agreement obtained in this work used the measured laser energy and laser pulse length and calculated the laser-solid target interaction from first principles.

Corrosion Inhibition of Steel (St 44-2) by Pomegranate Shells in Acidic Medium

Pomegranate shells were investigated as green inhibitors for steel 44-2 in 0.1M HCl at various temperatures (30, 40, 50, and 60) °C using electrochemical technique. Five concentrations of inhibitor were added 4, 8, 12, and 16 ppm. Corrosion tests were performed by Potentiostat at 5 mV.sec-1 scan rate and the data measured by Tafel extrapolation method such as Tafel slopes, corrosion current density and corrosion potential. Inhibition efficiencies were calculated and indicated that 8 ppm was the best concentration for inhibition especially at 60oC, where was 96.47%. Pomegranate Shells behaves as anodic inhibitor type and obeys Langmuir adsorption isotherm. The equilibrium constant of the adsorption-desorption process and the apparent free energy of adsorption confirm the physicsorption of Pomegranate shells. FTIR spectroscopy was used to test film formed on steel surface compared with FTIR spectrum of Pomegranate Shells. These spectra confirm the formation of Fe2+Pomegranate shells complex.

Solvation Shell Structure of Small Molecules and Proteins by IR-MCR Spectroscopy.

The flexibility of the hydrogen-bonded network of water is the basis for its excellent solvation properties. Accordingly, it is valuable to understand the properties of water in the solvation shell surrounding small molecules and biomolecules. Recent high-quality Raman spectra analyzed with Self-Modeling Curve Resolution (SMCR) have provided Raman spectra of small-molecule solvation shells. Here we apply SMCR to the complementary technique of Fourier transform infrared (FTIR) spectroscopy in the attenuated total reflection (ATR) configuration to extract the IR spectra of solvation shells. We first illustrate the method by obtaining the IR-MCR solvation shell spectra of tert-butanol (TBA), before applying it to antifreeze protein type III. Our results show that IR-SMCR spectroscopy is a powerful method for studying the solvation shell structure of small molecules and biomolecules. Given the wide availability of FTIR-ATR instruments, the method could prove to be an impactful tool for studying solvation and solvent-mediated interactions.

Near isotropic behavior of turbulent thermal convection

We investigate the anisotropy in turbulent convection in a 3D box using direct numerical simulation. We compute the anisotropic parameter $A = u_\perp^{2}/(2u_{\parallel}^{2})$, where $u_{\perp}$ and $u_{\parallel}$ are the components of velocity perpendicular and parallel to the buoyancy direction, the shell and ring spectra, and shell-to-shell energy transfers. We observe that the flow is nearly isotropic for the Prandtl number $\mathrm{Pr} \approx 1$, but the anisotropy increases with the Prandtl number. For $\mathrm{Pr}=\infty$, $A \approx 0.3$, thus anisotropy is not very significant even in extreme cases. We also observe that $u_{\parallel}$ feeds energy to $u_{\perp}$ via pressure. The computation of shell-to-shell energy transfers reveals that the energy transfer in turbulent convection is local and forward, similar to hydrodynamic turbulence. These results are consistent with the Kolmogorov's spectrum observed by Kumar et al.~[Phys. Rev. E {\bf 90}, 023016 (2014)] for turbulent convection.

Ratiometric detection of Raman hydration shell spectra

The micro-structure of hydration shell of solute in water is significant for understanding the properties of aqueous solutions. However the spectra of hydration shell are difficult to be obtained. Herein, a novel Raman ratio spectra, which is obtained through dividing the Raman spectra of aqueous solutions from the spectrum of water, was applied to deduce the spectra of hydration shell of organic (acetone-D6) and inorganic compounds (NaNO3, NaSCN, NaClO4, Na2SO4, NaCl) in water. Those spectra of the hydration shell were employed to study the micro-structures of the first hydration shells of anions, the number of water molecules in the first hydration shell of free anions and acetone-D6, and the aggregation behavior of ions in the concentrated aqueous NaNO3. The number of water molecules in the hydration shell was supported by our molecular dynamic simulations. The Raman ratio spectra can be widely employed to obtain the spectra of the first hydration shell, and it is helpful to understand the micro-structure of aqueous solutions. Copyright © 2016 John Wiley & Sons, Ltd.