Higher Wavenumbers Research Articles

A new electromagnetic probe array diagnostic for analyzing electrostatic and magnetic fluctuations in EAST plasmas

A novel electromagnetic probe array (EMPA) diagnostic, which consists of a magnetic probe array and an electrostatic probe array, has recently been developed on EAST. The EMPA is fixed near the first wall at horizontal port P. The magnetic probe array of the EMPA consists of 24 identical magnetic probes, each of them capable of measuring toroidal, poloidal and radial magnetic fluctuations simultaneously, providing additional toroidal magnetic fluctuation measurements compared with the regular magnetic probes on EAST. With a higher sampling rate and self-resonant frequency, the EMPA magnetic probes can provide higher frequency magnetic fluctuation measurements. The magnetic probe array of the EMPA is composed of two parallel layers of magnetic probes with a radial distance of 63 mm, and each layer of magnetic probes is arranged in four poloidal rows and three toroidal columns. The compact arrangement of the EMPA magnetic probe array largely improves the toroidal mode number measurement ability from to and also improves the high poloidal wave number measurement ability of magnetic fluctuations compared with the regular high frequency magnetic probes on EAST. The electrostatic probe array of the EMPA consists of two sets of four-tip probes and a single-tip probe array with three poloidal rows and four toroidal columns. It complements the electrostatic parameter measurements behind the main limiter and near the first wall in EAST. The engineering details of the EMPA diagnostic, including the mechanical system, the electrical system, the acquisition and control system, and the effective area calibration, are presented. The preliminary applications of the EMPA in L-mode and H-mode discharges on EAST have demonstrated that the EMPA works well for providing information on the magnetic and electrostatic fluctuations and can contribute to deeper physical analysis in future EAST experiments.

Preparation and Spectroscopic Characterization of Ternary Inclusion Complexes of Ascorbyl Palmitate and Urea with γ-Cyclodextrin

A three-component inclusion complex of ascorbyl palmitate (ASCP), urea (UR), and γ-cyclodextrin (γCD) with a molar ratio of 1/12 has been prepared for the first time using the evaporation method (EVP method) and the grinding and mixing method (GM method). Also, we investigated changes in the physicochemical properties of the three-component complexes. The powder X-ray diffraction (PXRD) measurements showed ASCP, UR, and γCD characteristic peaks in the physical mixture (PM) (AU (ASCP/UR = 1/12)/γCD = 1/2). In GM (AU (ASCP/UR = 1/12)/γCD = 1/1), new diffraction peaks were observed around 2θ = 7.5° and 16.6°, while characteristic peaks derived from EVP (ASCP/UR = 1/12) were observed at 2θ = 23.4° and 24.9°. On the other hand, new diffraction peaks at 2θ = 7.4° and 16.6° were observed in GM (1/2). In the differential scanning calorimeter (DSC) measurement, an endothermic peak at around 83 °C was observed in the GM (1/1) sample, which is thought to originate from the phase transition of urea from the hexagonal to the tetragonal form. An endothermic peak around 113.9 °C was also observed for EVP (ASCP/UR = 1/12). However, no characteristic phase transition-derived peak or EVP (ASCP/UR = 1/12)-derived endothermic peak was observed in GM (1/2). Near infrared (NIR) spectroscopy of GM (1/2) showed no shift in the peak derived from the CH group of ASCP. The peaks derived from the NH group of UR shifted to the high and low wavenumber sides at 5032 cm−1 and 5108 cm−1 in EVP (ASCP/UR = 1/12). The peak derived from the OH group of γCD shifted, and the peak derived from the OH group of ASCP broadened at GM (1/2). These results suggest that AU (ASCP/UR = 1/12)/γCD prepared by the mixed grinding method formed inclusion complexes at the molar ratio (1/2).

BARYCENTRIC RATIONAL INTERPOLATION METHOD OF THE HELMHOLTZ EQUATION WITH IRREGULAR DOMAIN

In the work, a numerical method of the 2D Helmholtz equation with meshless interpolation collocation method is developed, which is defined in arbitrary domain with irregular shape. In our numerical method, based on the Chebyshev points, the partial derivatives and the spatial variables are discretized by the barycentric rational form basis function. After that the differential equations are simplified by employing differential matrix. To verify the the accuracy, effectiveness and stability in our method, some numerical tests based on the three types of different test points are adopted. Moreover, we can also verify that present method can be applied to both variable wave number problems and high wave number problems.

Simultaneous Dual-Wavelength Source Raman Spectroscopy with a Handheld Confocal Probe for Analysis of the Chemical Composition of In Vivo Human Skin.

Confocal Raman spectroscopy (CRS) is a powerful tool that has been widely used for biological tissue analysis because of its noninvasive nature, high specificity, and rich biochemical information. However, current commercial CRS systems suffer from limited detection regions (450-1750 cm-1), bulky sizes, nonflexibilities, slow acquisitions by consecutive excitations, and high costs if using a Fourier transform (FT) Raman spectroscopy with an InGaAs detector, which impede their adoption in clinics. In this study, we developed a portable CRS system with a simultaneous dual-wavelength source and a miniaturized handheld probe (120 mm × 60 mm × 50 mm) that can acquire spectra in both fingerprint (FP, 450-1750 cm-1) and high wavenumber (HW, 2800-3800 cm-1) regions simultaneously. An innovative design combining 671 and 785 nm lasers for simultaneous excitation through a compact and high-efficiency (>90%) wavelength combiner was implemented. Moreover, to decouple the fused FP and HW spectra, a first-of-its-kind precise Raman spectra separation algorithm (PRSSA) was developed based on the maximum a posteriori probability (MAP) estimate. The accuracy of spectra separation was greater than 99%, demonstrated in both phantom experiments and in vivo human skin measurements. The total data acquisition time was reduced by greater than 50% compared to other CRS systems. The results proved our proposed CRS system and PRSSA's superior capability in fast and ultrawideband spectra acquisition will significantly improve the integration of CRS in the clinical workflow.

Detection of Sub-20 μm Microplastic Particles by Attenuated Total Reflection Fourier Transform Infrared Spectroscopy and Comparison with Raman Spectroscopy.

Microplastics are particulate water contaminants that are raising concerns regarding their environmental and health impacts. Optical spectroscopy is the gold standard for their detection; however, it has severe limitations such as tens of hours of analysis time and spatial resolution of more than 10 μm, when targeting the production of a 2D map of the microparticle population. In this work, through a single spectrum acquisition, we aim at quickly getting information about the whole population of identical particles, their chemical nature, and their size in a range below 20 μm. To this end, we built a compact setup enabling both attenuated total reflection Fourier transform infrared (ATR-FTIR) and Raman spectroscopy measurement on the same sample for comparison purposes. We used monodisperse polystyrene and poly(methyl methacrylate) microplastic spheres of sizes ranging between 6 and 20 μm, also measured collectively using a bench-top FTIR spectrometer in ATR mode. The ATR-FTIR technique appears to be more sensitive for the smallest particles of 6 μm, while the opposite trend is observed using Raman spectroscopy. We use theoretical modeling to simulate and explain the ripples observed in the measured spectra at the shortest wavelength (higher wavenumber) region, which appears as an indicator of the microparticle dimension. The latter finding opens new perspectives for ATR-FTIR for the identification and classification of populations of nearly identical micro-scale bodies, such as bacteria and other micro-organisms, where the same measured spectrum embeds dual information about the chemical nature and the size.

Optical detection of ensonified capillary-gravity waves using polarimetric imaging

The optical detection of surface capillary-gravity waves induced by underwater sound has many potential applications that range from the detection of sound-generating underwater objects to airborne bathymetric surveys. While multiple lab-based efforts have measured acoustically generated surface capillary-gravity waves, we report on a recent field-based measurement using polarimetric imaging. A controlled acoustic source was placed 10 m below a lake surface and emitted sound in the 500 Hz to 10000Hz frequency range. The lake surface was imaged using a polarimetric camera mounted 7 m above the lake surface. Measurable short-lived surface capillary-gravity waves (∼3 mm wavelength) were observed in the polarimetric camera images during ensonification of the lake surface. Changes were observed in both the omnidirectional and directional wave spectra. In the omni-directional wavenumber spectrum, enhanced capillary wave activity at high wavenumbers was observed for acoustic source frequencies in the 2–5 kHz range. Additionally, ensonification was observed to result in the amplitude and wavenumber modulation (enhancement/diminution) of existing wind-generated surface gravity-capillary waves. In the directional spectra, while ambient gravity-capillary waves showed a spreading function with stronger downwind versus upwind propagation, the acoustically generated gravity-capillary waves showed minimal impact on the directionality of the wave spectra.

Gamma-ray induced effect on the structural and optical properties and durability of neodymium-doped zinc–bismuth–borotellurite glasses and glass ceramics

This study explores the effect of gamma rays on a new glass and glass–ceramic 10ZnO–34.5B2O3–34.5TeO2–20Bi2O3–1Nd2O3. The samples were exposed to different gamma-ray doses of 2.5, 10, and 50 kGy. The impact of gamma-ray irradiation was investigated using different physicochemical methods. The X-ray diffraction (XRD) results for glass samples show that the amorphous nature did not change before and after irradiation, and a shift in the main peak along with a change in the unit cell volume with increasing doses was observed in glass-ceramic matrix. The Fourier transform infrared (FTIR) and Raman spectra (IR) for the glass samples show change in intensity without variation in the band position. The 50 kGy dose hid a high wavenumber peak in the FTIR and Raman spectra for the glass–ceramic sample, indicating a significant change in the glass–ceramic matrix. The reduction in the band gap energy for the glass samples confirms the FTIR results. The durability of the glass samples was gradually enhanced by increasing the dose up to 10 kGy. The up-conversion photoluminescence in the glass samples exhibits an emission peak at 525 nm that decreases in intensity as the dose increases. The mean free path results confirm the shielding features of the glass when compared to other reference glass materials. The results show that the glass is excellently stable and can withstand high gamma-ray doses, making it suitable for radiation applications.

Bactericide gold decorated mulberry fibers for therapeutic and non-therapeutic tenacities

In this study an approach was made to efficaciously synthesize gold decorated mulberry fibers by a facetious dip coating procedure. Assortments of inorganic compounds are being employed to impart antimicrobial properties to fabrics and textiles. Earlier workers have used gold as coloring agent for cotton and yarn etc. Herein, for the first time an attempt was made to liftoff a progressive textile conjured of gold and mulberry fibers which will be exploited for fabrication of antimicrobial stuffs for diverse medical and non-medical uses. The morphology, physicochemical and antibacterial characteristics of gold decorated mulberry fibers were scanned via X-ray diffraction (XRD), Scanning electron microscope (SEM), Electron probe microanalysis (EPMA), Fourier transform infrared (FTIR) and antibacterial testing. The average size of gold particles was between 1.9 and 3 μm. The even distribution of Au on mulberry fibers was corroborated by SEM, and the results of XRD and FTIR analysis confirmed integration of nanogold in mulberry. The XRD data of Au blended fibers revealed no change in peak location, implying that gold coating has no effect on mulberry fiber structure. Gold decorated mulberry has a little higher intensity and a slight change in peak position toward higher wavenumber, which could be related to functionalization or interaction of gold particles with mulberry fibers. These gold incapacitated mulberry fibers shown out antibacterial activity against illustrative bacterium E. coli. Thus our study provides optimistic indications to pick up mulberry fibers decked with nanogold as prime material for fabrication of forthcoming antimicrobial materials for therapeutic and non-therapeutic tenacities.

Characterization of inpaint residuals in interferometric measurements of the epoch of reionization

ABSTRACTTo mitigate the effects of Radio Frequency Interference (RFI) on the data analysis pipelines of 21 cm interferometric instruments, numerous inpaint techniques have been developed. In this paper, we examine the qualitative and quantitative errors introduced into the visibilities and power spectrum due to inpainting. We perform our analysis on simulated data as well as real data from the Hydrogen Epoch of Reionization Array (HERA) Phase 1 upper limits. We also introduce a convolutional neural network that is capable of inpainting RFI corrupted data. We train our network on simulated data and show that our network is capable of inpainting real data without requiring to be retrained. We find that techniques that incorporate high wavenumbers in delay space in their modelling are best suited for inpainting over narrowband RFI. We show that with our fiducial parameters discrete prolate spheroidal sequences (dpss) and clean provide the best performance for intermittent RFI while Gaussian progress regression (gpr) and least squares spectral analysis (lssa) provide the best performance for larger RFI gaps. However, we caution that these qualitative conclusions are sensitive to the chosen hyperparameters of each inpainting technique. We show that all inpainting techniques reliably reproduce foreground dominated modes in the power spectrum. Since the inpainting techniques should not be capable of reproducing noise realizations, we find that the largest errors occur in the noise dominated delay modes. We show that as the noise level of the data comes down, clean and dpss are most capable of reproducing the fine frequency structure in the visibilities.

Toward high-fidelity imaging: Dynamic matching FWI and its applications

Full-waveform inversion (FWI) is firmly established within our industry as a powerful velocity model building tool. FWI carries significant theoretical advantages over conventional velocity model building methods such as refraction and reflection tomography. Specifically, by solving a nonlinear inverse problem through the wave equation, FWI is able to recover a broadband velocity model containing both high and low spatial wavenumbers, thus extending the approximation of residual moveout correction inherent in traditional velocity model building approaches. Moreover, FWI is capable of inverting information from the entire wavefield (i.e., early arrivals, reflections, refractions, and multiple energy) rather than from a subset as in conventional approaches (i.e., first break and primary reflections), thereby availing itself of more information to better constrain its model estimate. However, these theoretical benefits cannot be realized easily in practice because various complexities of real seismic data often conspire to violate algorithmic assumptions, leading to unsatisfactory results. Dynamic matching FWI (DMFWI) is a newly developed algorithm that solves an inversion problem that maximizes the cross correlation of two dynamically matched data sets — one recorded and the other synthetic. Dynamic matching of the two data sets de-emphasizes the amplitude impact, which allows the algorithm to focus on minimizing their kinematic differences rather than amplitude in the data-fitting process. The multichannel correlation makes the algorithm robust for data with low signal-to-noise ratio. Applications of DMFWI across different types of acquisition and geologic settings demonstrate that this novel FWI approach can resolve complex velocity errors and provide high-quality migrated images that exhibit a high degree of geologic plausibility. Additionally, reflectivity images can be obtained in a straightforward manner as natural byproducts through computation of the directional derivative of the inverted FWI velocity models.

Tracking and Understanding Dynamics of Atoms and Clusters of Late Transition Metals with In-Situ DRIFT and XAS Spectroscopy Assisted by DFT

Dynamic structural changes of single-atom catalysts (SACs) are key to many reactions that were reported to be catalyzed by supported single atoms. To understand these changes, systematic in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and X-ray absorption spectroscopy (XAS) experiments were performed under reducing (1% CO) and oxidizing (1% CO + 1% O2) reaction atmospheres at room temperature over CeO2-supported late transition metals (Ru, Rh, Pd, Ir, and Pt) synthesized via two different methods (wet impregnation and precipitation) to account for the influence of surface properties. As a general trend, the CO vibrational frequencies downshifted under the CO atmosphere, which we assigned to the formation of clusters. Upon changing the gas mixture to more oxidizing (1% CO + 1% O2), single sites are retained as evidenced by the CO vibrational frequencies at higher wavenumbers. Among the investigated metals, Pt2+ and Pd2+ are more prone to cluster formation, and Rh3+ and Ru4+ are found to be stable as single sites following the order Rh > Ru > Ir > Pt > Pd. In combination with the density functional theory (DFT) calculations of CO vibrational frequencies, we were able to assign shifts to changes in the oxidation state of the metals. These findings thus serve as a benchmark for ceria-supported Pd, Pt, Ru, Ir, and Rh SACs.

Characterization of tamarind biomass to substantiate the feasibility towards alternative fuel

Sustainable energy resources development from every possible route is the utmost priority in today’s modern scenario around the globe. This situation reaches highly alarming rate after the pandemic situation due to the shortcomings on ease transportation viability among all the countries. Therefore, the present work aims at developing a sustainable biofuel from Tamarind seed biomass samples and to evaluate its suitability for various power generation applications. The proposed work consists of three samples: tamarind shell (TAN1), tamarind nut with peel (TAN2) and tamarind nut without peel (TAN3) undergoing physicochemical and thermal analyses to analyse their feasibility as a biofuel. Fourier transform infrared spectroscopy (FTIR) concluded high oxygenated compounds mainly alcohols, esters and carboxylic acids were determined at higher wave numbers. Ultimate and proximate analyses gave high amounts of carbon, volatile matter and low nitrogen and ash content. Thermogravimetric (TG) analyses showed the maximum mass loss in the temperature range of 150 °C–400 °C and confirm the presence of volatile compounds. It was mainly due to the degradation of hemicellulose. Calorimetry test gave high heating value (HHV) results and those compared with the empirical values calculated using the ultimate analysis equation. TAN3 is selected as a promising feedstock for pyrolysis and the characterization results signify the presence of organic compounds and infer high energetic value and bio refining potential. The bio oil obtained was characterized and analysed using GC–MS, FTIR, and H NMR to assess the bio oil potential as alternative fuel and presented in this paper.

A new method to retrieve rainfall intensity level from rain-contaminated X-band marine radar image

ABSTRACT In this study, a new methodcombining wave-number energy spectrum (WES) and Genetic algorithm-back propagation neural network (GA-BPNN) isproposed to retrieve the rainfall intensity level from rain-contaminated X-bandmarine radar image. Since the intensity of spatialrainfall can be reflected by the distribution of energy in the wavenumberfrequency domain, the obtained WES is divided into three wavenumber segments(low, medium and high wavenumber segments), and the ratio of the wavenumber ineach wavenumber segment to the total wavenumber is calculated separately as the characteristicparameters. Based on the excellent networkconvergence speed and data prediction accuracy of the GA-BPNN, these calculatedparameters are input into the constructed GA-BPNN for training to complete thetask of rainfall intensity level retrieval. The proposed method is tested usingdata collected at the ocean observation station of Haitan Island in PingtanCounty. Referring to the actual rainfallintensity synchronously recorded by the rain gauge, the retrieval accuracy ofthe proposed method is 97.4%, which is 4.3% higher than that of back propagation neural network (BPNN) not optimizedby Geneticalgorithm(GA). In addition, compared with theretrieval performance of the ratio of zero intensity to echo (RZE) method basedon the occlusion area of radar image, the retrievalaccuracy of the proposed method is improved by about 12.9%.

Evolution of dissipative fluid flows with imposed helicity conservation

We propose the helicity-conserved Navier–Stokes (HCNS) equation by modifying the non-ideal force term in the Navier–Stokes (NS) equation. The corresponding HCNS flow has strict helicity conservation, and retains major NS dynamics with finite dissipation. Using the helical wave decomposition, we show that the pentadic interaction of Fourier helical modes in the HCNS dynamics is more complex than the triadic interaction in the NS dynamics, and enhanced variations for left- and right-handed helicity components cancel each other in the HCNS flow to keep the invariant helicity. A comparative study of HCNS and NS flow evolutions with direct numerical simulation elucidates the influence of the helicity conservation on flow structures and statistics in the vortex reconnection and isotropic turbulence. First, the HCNS flow evolves towards a Beltrami state with a $-4$ scaling law of the energy spectrum at high wavenumbers at long times. Second, large-scale flow structures are almost identical during the viscous reconnection of vortex tubes in the two flows, whereas many more small-scale helical structures are generated via the pentadic mode interaction in the HCNS flow than in the NS flow. Moreover, we demonstrate that parity breaking at small scales can trigger a notable helicity variation in the NS flow. These findings hint that the helicity may not be conserved in the inviscid limit of the NS flow.

Dynamical Instability of Self-Gravitating Membranes.

We show that a generic relativistic membrane with in-plane pressure and surface density having the same sign is unstable with respect to a series of warping mode instabilities with high wave numbers. We also examine the criteria of instability for commonly studied exotic compact objects with membranes, such as gravastars, anti-de Sitter bubbles, and thin-shell wormholes. For example, a gravastar which satisfies the weak energy condition turns out to be dynamically unstable. A thin-layer black hole mimicker is stable only if it has positive pressure and negative surface density (such as a wormhole), or vice versa.

Evaluating the Skin Interactions and Permeation of Alginate/Fucoidan Hydrogels Per Se and Associated with Different Essential Oils

Marine polysaccharides are recognized for their biological properties and their application in the drug delivery field, favoring hydrogel-forming capacities for cutaneous application towards several dermatological conditions. Essential oils have been widely used in skin, not only for their remarkable biological properties, but also for their capacity to enhance permeation through the skin layers and to confer a pleasant scent to the formulation. In this study, menthol, L-linalool, bergamot oil, and β-pinene were incorporated in alginate/fucoidan hydrogels to evaluate their skin permeation enhancement profile and assess their influence on the skin organization. The combinations of different essential oils with the marine-based fucoidan/alginate hydrogel matrix were characterized, resulting in formulations with pseudoplastic rheological properties favorable for a uniform application in the skin. The ex vivo Franz diffusion permeation assays revealed that calcein loaded in bergamot-alginate/fucoidan hydrogel permeated more than 15 mg out of the initial 75 mg than when in linalool-alginate/fucoidan, alginate/fucoidan or hydrogel without any incorporated oil. Skin calcein retention for menthol- and pinene-alginate/fucoidan hydrogels was 15% higher than in the other conditions. Infrared micro-spectroscopic analysis through synchrotron-based Fourier Transform Infrared Microspectroscopy evidenced a symmetric shift in CH3 groups towards higher wavenumber, indicating lipids' fluidization and less lateral packing, characterized by a band at 1468 cm-1, with the bergamot-alginate/fucoidan, which contributes to enhancing skin permeation. The study highlights the effect of the composition in the design of formulations for topical or transdermal delivery systems.

Latent heat thermal energy storage in a shell-tube: A wavy partial layer of metal foam over tubes

The melting thermal energy storage and heat transfer of paraffin wax in a storage unit was modeled in the presence of a wavy copper foam. The phase-change energy and natural convection effects were modeled using the enthalpy porosity approach. The control equations were solved using the finite element method over a structured mesh. The energy storage was simulated for the wavenumber and amplitude of the foam layer. It was found that the higher wavenumber, the shorter the charging time and better energy storage power. A lower wave magnitude was also better than a longer wave magnitude. The shortest melting time was obtained for a flat foam layer, which was 20 % better than a low wave long amplitude foam layer. The current work intends to reduce the weight of applied metal foams in thermal energy storage applications by enhancing the geometry design. Here, a wavy form layer of metal foam was used to guide the natural convection flows and also boost the heat transfer mechanism. The phase change heat transfer has not been investigated in a wavy form metal foam layer.

Isogeometric indirect BEM solution based on virtual continuous sources placed directly on the boundary of 2D Helmholtz acoustic problems

An indirect boundary element method (BEM) based on isogeometric analysis (IGA) is proposed for 2D Helmholtz acoustic problems using virtual continuous sources placed directly on the problem boundary. The virtual sources form a virtual boundary identical to the main problem boundary. The proposed solution couples the CAD model with the analysis model by approximating both the CAD model and the virtual continuous sources with the same non-uniform rational B-spline functions (NURBS). Moreover, neither domain discretization nor truncation boundaries at the far-field are required. This solution creates only one coefficient matrix by directly arranging the linear system of equations.The solution follows a collocation scheme on the boundaries based on Greville abscissae with offsets wherever C0 continuity is encountered to permit an easy prediction for the normal directions and the free-terms at the collocation points required in the cases of Neumann and Robin boundary conditions. It allows us also to treat all integrals with standard Gauss quadrature points.Several numerical examples for exterior and interior acoustic problems are discussed to verify the proposed solution with comparisons to analytical solutions and previously published numerical results. These examples prove the robustness of the proposed solution even for high wavenumbers, in contrast to the previous attempts which implemented extensive investigations to find out the optimum place of the sources outside the domain producing minimum errors. Furthermore, no fictitious eigenfrequency problem is observed for exterior acoustic problems.

High wavenumber Raman spectroscopy for intraoperative assessment of breast tumour margins.

Optimal oncological results and patient outcomes are achieved in surgery for early breast cancer with breast conserving surgery (BCS) where this is appropriate. A limitation of BCS occurs when cancer is present at, or close, to the resection margin - termed a 'positive' margin - and re-excision is recommended to reduce recurrence rate. This is occurs in 17% of BCS in the UK and there is therefore a critical need for a way to assess margin status intraoperatively to ensure complete excision with adequate margins at the first operation. This study presents the potential of high wavenumber (HWN) Raman spectroscopy to address this. Freshly excised specimens from thirty patients undergoing surgery for breast cancer were measured using a surface Raman probe, and a multivariate classification model to predict normal versus tumour was developed from the data. This model achieved 77.1% sensitivity and 90.8% specificity following leave one patient out cross validation, with the defining features being differences in water content and lipid versus protein content. This demonstrates the feasibility of HWN Raman spectroscopy to facilitate future intraoperative margin assessment at specific locations. Clinical utility of the approach will require further research.

The search for a band of a defect predicted above 4000 cm-1 in diamond through infrared vibrational spectra: a quantum mechanical investigation.

For many years, the atomic structures of several defects in diamond with high wavenumber (>4000 cm-1), including "amber centers", H1b, and H1c, have been investigated, but a conclusive explanation is still lacking. In this paper, we propose a novel model for the N-H bond under repulsion, with an expected vibrational frequency exceeding 4000 cm-1. Additionally, potential defects called NVH4 are proposed to investigate their correlation with these defects. Three NVH4 defects are considered, denoting a charge of e = +1, e = 0, and e = -1 for NVH4+, NVH04, and NVH4-, respectively. Subsequently, the geometry, charge, energy, band structure, and spectroscopic characterization of the three defects NVH4+, NVH04, and NVH4- are analysed. Then, the calculated harmonic modes of N3VH defects are used as a benchmark for studying NVH4. The simulations indicate that, with the use of scaling factors, the highest NVH4+ harmonic infrared peaks are 4072 cm-1, 4096 cm-1, and 4095 cm-1 with PBE, PBE0, and B3LYP, respectively, along with a calculated anharmonic infrared peak at 4146 cm-1. These calculated characteristic peaks closely match those observed in "amber centers" (4065 cm-1 and 4165 cm-1). However, based on the additional simulated anharmonic infrared peak at 3792 cm-1, NVH4+ cannot be assigned to the 4165 cm-1 band. It is possible to assign the 4065 cm-1 band to NVH4+; even though it can remain stable in diamond at 1973 K, establishing and measuring this benchmark could be challenging. Although NVH4+ is uncertain as a structure in "amber centers", a model of the N-H bond under repulsion stretching is proposed, which can generate a vibrational frequency surpassing 4000 cm-1. It may provide a useful avenue for investigating high wavenumber defect structures in diamond.