Two-dimensional Spectra Research Articles

Façade Design Pattern Optimization Workflow Through Visual Spatial Frequency Analysis and Structural Safety Assessment

As the demand for highly efficient yet aesthetically pleasing, complex building envelope structures is rising worldwide, computational analysis and generative design tools are becoming ever so relevant. Previous methods for achieving a natural distribution of structural or shading elements in non-uniform façades are mostly based either on computer-generated pseudo-randomness or a literal biomorphic approach where a naturally occurring pattern is directly projected on the façade surface. As an alternative, this research introduces a novel technique for optimisation that utilises a two-dimensional Power Spectrum Analysis, suitable for numerically assessing the alignment of designed geometry with natural patterns. By integrating this optimisation method into the design process, the façade pattern generation can be automated and optimal design can be selected by evaluating multiple design solutions. Instead of using repetitive geometrical patterns or generated pseudo-randomness, patterns objectively similar to those occurring in nature can be created without directly copying natural structures. The distribution of the structural and shading elements controls the way natural light permeates the building and, considering the data gathered from images of natural scenes, this method can be used to design structures not only with optimal structural and energy performance but also with visual and psychological occupant comfort in mind.

In vitro spectroscopic analysis of the chemical interaction between calcium hypochlorite and chlorhexidine.

This study aimed to identify the chemical composition resulting from the chemical interaction between calcium hypochlorite [Ca(OCl)2] and chlorhexidine (CHX) using different 1H and 13C nuclear magnetic resonance spectrometry (NMR), correlated two-dimensional spectroscopy (2D COSY), heteronuclear single quantum coherence (HSQC), and Fourier Transform Infrared Spectroscopy (FTIR) experiments. The 5.25% Ca(OCl)2 was mixed with 2% CHX in a 1:1 ratio, obtaining an orange-brown precipitate that was filtered, washed in ultrapure water, dried and characterized by 1H and 13C NMR, 2D COSY, HSQC and FTIR. One-dimensional and two-dimensional NMR spectra demonstrated the chemical changes around the protons and carbon atoms of the initial CHX and after reacted with Ca(OCl)2. These techniques and FTIR show that the interaction generated two by-products from the degradation of CHX, none of which were parachloroaniline (PCA) despite both products obtained being substituted benzene compounds. Using NMR and FTIR data together with a previously proposed catalytic cleavage degradation mechanism for CHX, the products appear to be parachlorophenylurea (PCU) and parachlorophenylguanidyl-1,6-diguanidyl-hexane (PCGH). Therefore, this in vitro study demonstrated that the precipitate formed from the chemical interaction between Ca(OCl)₂ and CHX results in two by-products, PCU and PCGH, neither of which is PCA. Due to the absence of cytotoxicity studies on the products generated from the combination of Ca(OCl)₂ and CHX, an intermediate rinse with an inert solution is recommended to remove these compounds from the root canals.

Rapidly Screening the Correlation between the Rotational Mobility and the Hydrogen Bonding Strength of Confined Water.

Automated Deuterium Relaxation-Ordered SpectroscopY in solution (ADROSYS), an automated two-dimensional deuterium NMR methodology, discriminates between D2O populations (as well as deuterium-labeled alcohol groups) whose properties differ as a result of being confined inside nanoscale volumes. In this contribution, a proof-of-principle demonstration on reverse micelles (RMs) yields the insight that as the length scale of the confinement decreases from several nanometers down to less than a nanometer, the position of the signal peak migrates through the two-dimensional (2D) spectrum, tracing out a distinctive path in the 2D space (of relaxation time vs chemical shift). The signals typically follow a relatively gentle linear path for water confined on the scale of several nanometers, before curving once the surfactants confine the water molecules to length scales smaller than 1-2 nm. The qualitative shape of this path, especially in the regime of strong confinement, can change with different choices of surfactants, i.e., a different choice of chemistry at the edges of the confining environment. An important facet of this research was to demonstrate the relatively wide applicability of these techniques by showing that both: (1) Standard modern NMR instrumentation is capable of deploying an automated measurement, even though the choice of a deuterium nucleus is nonstandard and frequently requires companion proton spectra in order to reference the chemical shifts; and (2) well-established (though underutilized) modern techniques can process the resulting signal even though it involves the somewhat unusual combination of chemical shifts along one dimension and a distribution of relaxation times along another dimension. In addition to demonstrating that this technique can be deployed across many samples of interest, detailed facts pertaining to the broadening or shifting of resulting signals upon inclusion of various guest molecules are also discussed.

Application of Two-Dimensional NMR for Quantitative Analysis of Viscosity in Medium–High-Porosity-and-Permeability Sandstones in North China Oilfields

The viscosity of crude oil plays a pivotal role in the exploration and development of oil fields. The predominant reliance on laboratory measurements, which are constrained by manual expertise, represents a significant limitation in terms of efficiency. Two-dimensional nuclear magnetic resonance (NMR) logging offers a number of advantages over traditional methods. It is capable of providing faster measurement rates, as well as insights into fluid properties, which can facilitate timely adjustments in oil and gas development strategies. This study focuses on the loose sandstone reservoirs with high porosity and permeability containing heavy oil in the Huabei oilfield. Two-dimensional nuclear magnetic resonance (NMR) measurements and analyses were conducted on saturated rocks with different-viscosity crude oils and varying oil saturation levels, in both natural and artificial rock samples. This study elucidates the distribution patterns of different-viscosity crude oils within the two-dimensional NMR spectra. Furthermore, the T1 and T2 peak values of the extracted oil signals were employed to establish a model correlating oil viscosity with NMR parameters. Consequently, a criterion for determining oil viscosity based on two-dimensional NMR was formulated, providing a novel approach for estimating oil viscosity. The application of this technique in the BQ well group of the Huabei oilfield region yielded an average relative error of 15% between the actual oil viscosity and the computed results. Furthermore, the consistency between the oil types and the oil discrimination chart confirms the reliability of the method. The final outcomes meet the precision requirements for practical log interpretation and demonstrate the excellent performance of two-dimensional nuclear magnetic resonance (NMR) logging in calculating oil viscosity. The findings of this study have significant implications for subsequent exploration and development endeavors in the research area’s oilfields.

Synthesis and Spatial Structure of 3-Phenylacrylic Acid Octahydroquinolizin-1-Ylmethyl Ester and 2-(Octahydroquinolizin-1-Ylmethyl)Isoindole-1,3-Dione

The reactions of lupinine alkaloid and its chlorine derivative with cinnamoyl chloride and 2-K-isoindole-1,3-dione were investigated to obtain 3-phenylacrylic acid octahydroquinolizin-1-ylmethyl ester and 2-(octahydroquinolizin-1-ylmethyl)isoindole-1,3-dione, respectively. The optimal conditions for carrying out the aforementioned reactions were determined, taking into account the nature of the solvent and medium. It was established that acylation of the molecule in a benzene medium, in the presence of trimethylamine, resulted in the formation of 3-phenylacrylic acid octahydroquinolizin-1-ylmethyl ester, with an 82% yield. It was demonstrated that the interaction of chlorolupinine with 2-K-isoindole-1,3-dione under Gabriel reaction conditions resulted in the formation of 2-(octahydroquinolizin-1-ylmethyl)isoindole-1,3-dione. The conformer with an axial orientation of the isoindole-1,3-dione substituent was observed to exhibit greater stability than the conformer with an equatorial orientation. The structure of the synthesized compounds was investigated by IR, 1H, and 13C NMR spectroscopy. The use of two-dimensional spectra in COSY (1H-1H) and HMQC (1H-13C) formats enabled the establishment of homo- and heteronuclear interactions, thereby confirming the structure of the compounds under investigation. The values of chemical shifts, multiplet and integrated intensity of 1H and 13C signals in one-dimensional NMR spectra of the novel compounds were determined. The crystal structures of 3-phenylacrylic acid octahydroquinolizin-1-ylmethyl ester and 2-(octahydroquinolizin-1-ylmethyl)isoindole-1,3-dione were elucidated through X-ray analysis.

Synthesis and Anti-Inflammatory Activity of New Nicotinoyl Amides

The article presents the results of a study of the amination reaction of nicotinic acid chlorohydride with amines morpholine, cytisine, and 1-aminoadamantane, which are often used in the search and creation of drugs for respiratory and circulatory stimulants. The study was conducted to search for new biologically active compounds with anti-inflammatory activity. The synthesis of new aminoamides was carried out by the interaction of nicotinic acid with molecules of morpholine, cytisine, and adamantane in anhydrous ethanol. As a result of the conducted studies, new amides of nicotinic acid with high yields (90.7–93.1%) were obtained. The structures of the new compounds were determined using NMR 1H and 13C spectroscopy methods, as well as data from two-dimensional spectra of COSY (1H-1H), HMQC (1H-13C), HMBC (1H-13C) and mass spectrometry. The results of an experimental study of the anti-inflammatory activity of synthesized new amides are presented. The anti-inflammatory effect of nicotinic acid N-adamantylamide was established, other new amides were ineffective compared with ibuprofen (p2 < 0.05).

Single-pulse Emissions of PSRs J1611–0114 and J1617+1123

In this paper, the emissions from two pulsars, PSRs J1611−0114 and J1617+1123, were investigated using the Five-hundred-meter Aperture Spherical radio Telescope operating at a central frequency of 1250 MHz. The average pulse profile of PSR J1611−0114 shows two components, the first of which is relatively weak in intensity. The two-dimensional pulse stack exhibits an obvious nulling phenomenon, with an estimated nulling fraction of 40.1% ± 5.4%. The durations of the nulls and bursts are consistent with power-law distributions, and no periodic nulling phenomenon is found. The results from PSR J1617+1123 demonstrate that the average pulse profile is composed of four components. The peak intensity of the fourth component varies significantly, causing an unstable integrated profile. In addition, the modulation characteristics of J1611−0114 and J1617+1123 were studied by analyzing the modulation index, longitude resolved fluctuation spectrum and two-dimensional fluctuation spectrum using the software PSRSALSA. It was found that the two pulsars exhibit intensity modulation. In particular, J1611−0114 displays even–odd modulation, with the modulation period of approximately two pulses. The modulation period of J1617+1123 is relatively broad. There is an obvious subpulse drift phenomenon, and the value of P 2 is ∼0.125c/P 0, corresponding to 12 pulse longitude bins, and the drift rate (P 2/P 3) is about 0.29.

Spectral broadening and vibronic dynamics of the S2 state of canthaxanthin in the orange carotenoid protein

We have performed a series of broadband multidimensional electronic spectroscopy experiments to probe the electronic and vibrational dynamics of the canthaxanthin chromophore of the Orange Carotenoid Protein (OCP) from Synechocystis sp. PCC 6803 in its photoactivated red state, OCPR. Cross-peaks observed below the diagonal of the two-dimensional electronic spectrum indicate that absorption transitions prepare the bright S2 state of the ketocarotenoid canthaxanthin near to a sequence of conical intersections, allowing passage to the dark S1 state via the Sx intermediate in <50 fs. Rapid damping of excited-state coherent wavepacket motions suggests that the branching coordinates of the conical intersections include out-of-plane deformation and C=C stretching coordinates of the π-conjugated isoprenoid backbone. The unusual proximity of the Franck–Condon S2 state structure to the conical intersections with Sx and S1 suggests that the protein surroundings of canthaxanthin prepare it to function as an excitation energy trap in the OCPR–phycobilisome complex. Numerical simulations using the multimode Brownian oscillator model demonstrate that the ground-state absorption spectrum of OCPR overlaps with the fluorescence emission spectrum of allophycocyanin due to spectral broadening derived especially from the intramolecular motions of the canthaxanthin chromophore in its binding site.

Detection of serum alterations in polysubstance use patients by FT-Raman spectroscopy

Substance use disorders pose significant health risks and treatment challenges due to the diverse interactions between substances and their impact on physical and mental health. The chemical effects of multiple substance use on bodily fluids are not yet fully understood. Therefore, this study aimed to investigate the chemical changes induced by a combination of substances compared to a control group. Analysis of FT-Raman spectra revealed structural alterations in the amide III, I, and C = O functional groups of lipids in subjects treated with opioids, alcohol and cannabis (polysubstance group). These changes were evident in the form of peak shifts compared to the control group. Additionally, an imbalance in the amide-lipid ratio was observed, indicating perturbations in serum protein and lipid levels. Furthermore, a 2D plot of two-track two-dimensional correlation spectra (2T2D-COS) demonstrated a shift towards dominance of lipid vibrations in the polysubstance use groups, contrasting with the predominance of the amide fraction in the control group. This observation suggests distinct molecular changes induced by multiple substance use, potentially contributing to the pathophysiology of substance use disorders. Principal Component Analysis (PCA) was utilized to visualize the data structure and identify outliers. Subsequently, Partial Least Squares Discriminant Analysis (PLS-DA) was employed to classify the polysubstance use and control groups. The PLS-DA model demonstrated high classification accuracy, achieving 100.00 % in the training dataset and 94.74 % in the test dataset. Furthermore, receiver operating characteristic (ROC) analysis yielded perfect AUC values of 1.00 for both the training and test sets, underscoring the robustness of the classification model.This study highlights the quantitative and qualitative changes in serum protein and lipid levels induced by polysubstance use groups, as evidenced by FT-Raman spectroscopy. The findings underscore the importance of understanding the chemical effects of polysubstance use on bodily fluids for improved diagnosis and treatment of substance use disorders. Moreover, the successful classification of spectral data using machine learning techniques emphasizes the potential of these approaches in clinical applications for substance abuse monitoring and management.

Accuracy verification of the 2D spectral AIS method by the hull monitoring data

Accuracy validation of the 2D spectral AIS method (AIS method using two-dimensional wave spectrum; 2D-AIS method) using hull monitoring data of a large ore carrier is discussed. The AIS method predicts the response of actual ships using AIS-based ship position data, hindcast wave data, and response characteristics data. The conventional AIS method uses representative parameters(H, T, θ) from wave spectrum modeling. The modeling involves many uncertainties. By using the 2D wave spectrum as it is, the effect of uncertainties associated with wave spectrum modeling is investigated. Compared to the analysis of the monitoring data conducted in this study, it was found that the 2D-AIS method improves the accuracy to about 15 %, while the conventional AIS method shows an error of up to about 35 % compared to the actual measurements in the long-term maximum expected values. This enhancement is attributed to the inability of the modeled wave spectrum to accurately represent the two-peak wave spectrum observed in extreme sea states, leading to a deficiency in reproducing wave frequency components corresponding to peak frequencies of the response. The findings underscore the effectiveness of the 2D-AIS method in refining long-term hull stress estimations, thus offering valuable insights for enhancing the safety and performance of hull structures.

Automated system for classifying images of video streams for timely detection of fires

ABSTRACT Early detection of a fire during its development stage is highly desired to minimize human and material losses. The improvement of the efficiency of these monitoring systems through the analysis of fire video data drawn from unmanned aerial vehicles is considered . Classification of video images when monitoring a fire event on the territory is used based on their segmentation into identical rectangular segments of a given size and then assigning them to one of three classes: Smoke, Flame, and Indifferent classes. The Walsh-Hadamard transform was used to form descriptors for the Weak classifiers. Descriptors were calculated for three Weak classifiers; first, the Walsh-Hadamard transform was calculated for the window of the entire segment, and its spectral coefficients were used for the first Weak classifier. Next, the descriptors were calculated in windows whose sizes were half and a quarter of the original window size. The classifier consisted of three independently-trained neural networks. A simple ensemble averaging block was used to combine the outputs of those networks. A special software code has been developed to classify video images. The code allows us to create a database of segments of the ‘Smoke’ and ‘Flame’ classes, determine the two-dimensional Walsh-Hadamard spectrum of video image segments, train fully connected neural networks, conduct exploratory analysis and evaluate the relevance of the calculated two-dimensional spectral coefficients. For validation we used real data from Сlosed Circuit Television cameras presented in open databases. The experimental studies on the classification of video data containing flames and smoke showed that the proposed method has an average smoke detection accuracy of 86% and an average flame detection accuracy of 89.5%. Errors II in smoke detection and flame detection had the averages of 13% and 4.5%, respectively.

A fast-filament eruption observed in the Hα spectral line

Context. Solar filament eruptions usually appear to occur in association with the sudden explosive release of magnetic energy accumulated in long-lived arched magnetic structures. The released energy occasionally drives fast-filament eruptions that can be the source regions of coronal mass ejections. A quantitative analysis of high-speed filament eruptions is thus essential to help elucidate the formation and early acceleration of coronal mass ejections. Aims. The goal of this paper is to investigate the dynamic processes of a fast-filament eruption by using unprecedented high-resolution full-disk Hα imaging spectroscopy observations. Methods. The whole process of the eruption was captured in a wide spectral window of the Hα line (±9.0 Å), which allowed for the detection of highly Doppler-shifted plasma. By applying the “cloud model” and obtaining two-dimensional optical thickness spectra, we derived the Doppler velocity; the true eruption profiles (height, velocity, and acceleration); and the trajectory of the filament eruption in 3D space. Results. The Doppler velocity maps show that the filament was predominantly blueshifted. During the main and final process of the eruption, strongly blueshifted materials manifest, traveling with velocities exceeding 250 km s−1. The spectral analysis further revealed that the erupting filament is made of multiple components, some of which were Doppler-shifted approximately to −300 km s−1. We found that the filament eruption attains a maximum true velocity and acceleration of about 600 km s−1 and 2.5 km s−2, respectively, and its propagation direction deviates from the radial direction. On the other hand, downflows manifested as redshifted plasma close to the footpoints of the erupting filament move with velocities of 45–125 km s−1. We interpret these redshifted signatures as draining material and therefore as mass loss of the filament, which has implications for the dynamic and the acceleration process of the eruption. Furthermore, we have estimated the total mass of the Hα filament, resulting in ∼5.4 × 1015 g.

Higher Order Structure Differences Among Insulin Crystalline Drugs Revealed by 2D heteronuclear NMR.

During therapeutic protein development, two-dimensional (2D) heteronuclear NMR spectra can be a powerful analytical method for measuring protein higher order structure (HOS) in solution since the spectra exhibit much higher resolution than homonuclear 1H spectra. However, 2D NMR capabilities for characterizing protein HOS in crystalline states remain to be assessed, given the low 13C natural abundance and intrinsically broader lines in solid-state NMR (SSNMR). Herein, high-resolution heteronuclear correlation (HETCOR) SSNMR was utilized to directly measure intact crystal drug products of insulin human, insulin analogs of insulin lispro and insulin aspart. The fingerprint regions in 2D 1H-13C HETCOR spectra were identified, which distinguished the insulin crystals in their primary structure, HOS heterogeneity and dynamics, as well as the manufacturing processes. The HOS heterogeneity in insulin analogs is consistent with their therapeutic effect of rapid action; while insulin human crystals showed more structural homogeneity, consistent with their slower pharmacokinetics (PK)peak time than insulin analogs. Therefore, heteronuclear NMR could be broadly applicable to study protein drug dosage forms from liquid to solid, yielding improved molecular level structure data for assessing drug HOS in biosimilar drug development.

An evaluation of source-blending impact on the calibration of SKA EoR experiments

ABSTRACT Twenty-one-centimetre signals from the Epoch of Reionization (EoR) are expected to be detected in the low-frequency radio window by the next-generation interferometers, particularly the Square Kilometre Array (SKA). However, precision data analysis pipelines are required to minimize the systematics within an infinitesimal error budget. Consequently, there is a growing need to characterize the sources of errors in EoR analysis. In this study, we identify one such error origin, namely source blending, which is introduced by the overlap of objects in the densely populated observing sky under SKA1-Low’s unprecedented sensitivity and resolution, and evaluate its two-fold impact in both the spatial and frequency domains using a novel hybrid evaluation (HEVAL) pipeline combining end-to-end simulation with an analytic method to mimic EoR analysis pipelines. Sky models corrupted by source blending induce small but severe frequency-dependent calibration errors when coupled with astronomical foregrounds, impeding EoR parameter inference with strong additive residuals in the two-dimensional power spectrum space. We report that additive residuals from poor calibration against sky models with blending ratios of 5 and 0.5 per cent significantly contaminate the EoR window. In contrast, the sky model with a 0.05 per cent blending ratio leaves little residual imprint within the EoR window, therefore identifying a blending tolerance at approximately 0.05 per cent. Given that the SKA observing sky is estimated to suffer from an extended level of blending, strategies involving de-blending, frequency-dependent error mitigation, or a combination of both, are required to effectively attenuate the calibration impact of source-blending defects.

Ultrafast and Coherent Dynamics in a Solvent Switchable "Pink Box" Perylene Diimide Dimer.

Perylene diimide (PDI) dimers and higher aggregates are key components in organic molecular photonics and photovoltaic devices, supporting singlet fission and symmetry breaking charge separation. Detailed understanding of their excited states is thus important. This has proven challenging because interchromophoric coupling is a strong function of dimer architecture. Recently, a macrocyclic PDI dimer was reported in which excitonic coupling could be turned on and off simply by changing the solvent. This presents a useful case where coupling is modified without synthetic changes to tune supramolecular structure. Here we present a detailed study of solvent dependent excited state dynamics in this dimer by means of coherent multidimensional spectroscopy. Spectral analysis resolves the different coupling strengths, which are consistent with solvent dependent changes in dimer conformation. The strongly coupled conformer forms an excimer within 300 fs. The low-frequency Raman active modes recovered from two-dimensional electronic spectra reveal frequencies characteristic of exciton coupling. These are assigned to modes modulating the coupling from the corresponding DFT calculations. Further analysis reveals a time dependent frequency during excimer formation. Analysis of two-dimensional "beatmaps" reveals features in the coupled dimer which are not predicted by the displaced harmonic oscillator model and are assigned to vibronic coupling.

Evaluation of the water state and protein characteristics of Tibetan pork under the storage conditions of modified atmosphere packaging: Effect of oxygen concentration

To explore the changes in water status and protein characteristics of Tibetan pork (TP) under modified atmosphere packaging (MAP) with different oxygen concentrations compared to Duroc×Landrace×Yorkshire pork (DLY), the water holding capacity (WHC), water distribution, protein oxidation, and conformation of both types were determined. Results indicate that under MAP, TP pork and DLY pork exhibited higher water retention and lower protein oxidation compared to air packaging. However, with increased oxygen concentration in the MAP, protein oxidation intensified, leading to reduced WHC in the pork. Compared to DLY pork, TP pork in different packaging conditions maintained the integrity of protein secondary and tertiary structures, reducing protein cross-linking aggregation. The lower content of P3 in the two-dimensional relaxation spectra, shorter T1 and T2 relaxation times, and higher proton density suggest better water retention properties in Tibetan pork. These findings support the development of long-distance preservation and transportation technologies for TP pork.

UV/Visible Diffusion-Ordered Spectroscopy: A Simultaneous Probe of Molecular Size and Electronic Absorption.

Based on concepts from nuclear magnetic resonance, we have developed UV/vis diffusion-ordered spectroscopy, which simultaneously probes the size and electronic absorption spectrum of molecules and particles. We use simple flow technology to create a step-function concentration profile inside an optical sample cell, and by measuring the time-dependent absorption spectrum in an initially solvent-filled part of the sample volume, we obtain the diffusion coefficients and UV/vis spectra of the species present in the sample solution. From these data, we construct a two-dimensional spectrum with absorption wavelength on one axis and diffusion coefficient (or equivalently, size) on the other, in which the UV/vis spectrum of a mixture with different molecular sizes is separated into the spectra of the different species, sorted by size. We demonstrate this method on mixed solutions of fluorescent dyes, biomolecules, and the UV-absorbing components of coffee, caffeine, and chlorogenic acid, all with concentrations in the μM range.

Heterologous Biosynthesis of New Lanthipeptides Nocardiopeptins with an Unprecedented Bridging Pattern of Lanthionine and Labionin.

The class III lanthipeptide synthetase (LanKC) installs unusual amino acids, such as lanthionine and labionin, in lanthipeptides. Through genome mining, we discovered a new class III lanthipeptide synthetase coding gene (nptKC) and precursor peptide coding genes (nptA1, nptA2, and nptA3) in the genome of the actinobacterium Nocardiopsis alba. Coexpression experiments of the biosynthetic genes in Escherichia coli resulted in the production of new lanthipeptides named nocardiopeptins A1-A3. Analysis of two-dimensional NMR spectra after enzymatic degradation and partial basic hydrolysis of nocardiopeptin A2 revealed that labionin was located in lanthionine with opposite orientations, forming a nesting structure in nocardiopeptin A2. To the best of our knowledge, this bridging pattern in the lanthipeptides was unprecedented, indicating a novel reaction characteristic of the class III lanthipeptide synthetase NptKC.

Signatures of exciton-exciton annihilation in 2DES spectra including up to six-wave mixing processes.

Two-dimensional electronic spectroscopy (2DES) is a powerful spectroscopic tool that allows us to study the dynamics of excited states. Exciton-exciton annihilation is at least a fifth order process, which corresponds to intrachromophoric internal conversion from the double-excited high-energy chromophoric state into the single-excited state of the same chromophore. At high excitation intensities, this effect becomes apparent in standard 2DES and can be inspected via high order nK1⃗-nK2⃗+K3⃗ nonlinear processes. We calculate 2DES based on K1⃗-K2⃗+K3⃗ and 2K1⃗-2K2⃗+K3⃗ wave mixing processes to reveal exciton-exciton annihilation (EEA) induced exciton symmetry breaking, which occurs at high excitation intensities. We present the general theory that captures all these processes for bosonic and paulionic quasiparticles in a unified way and demonstrate that the NEEs can be easily utilized for highly nonlinear two-dimensional spectra calculations by employing phase cycling for separating various phase matching conditions. The approach predicts various excitonic third- to fifth-order features; however, due to high excitation intensities, contributions of different order processes become comparable and overlap, i.e., the signals no longer can be associated with well-defined order-to-the-field contributions. In addition, EEA leads to breaking of the exciton symmetries, thus enabling population of dark excitons. Such effects are due to the local nature of the EEA process.

Simultaneous Measurement of Two-Trace Two-Dimensional (2T2D) Near-Infrared (NIR) Asynchronous Correlation Spectra and Small-Angle X-ray Scattering (SAXS) to Characterize Thermally Aged Polypropylene (PP).

In this study, a new system was developed to carry out simultaneous near-infrared (NIR) and small-angle X-ray scattering (SAXS) measurements. Aged polypropylene (PP) was examined with the NIR-SAXS system to demonstrate how it can be utilized to derive pertinent information about the polymer structure. Pairs of SAXS profiles and NIR spectra of PP in its initial state and after aging were measured to derive an in-depth understanding of the aging phenomenon. The SAXS profiles of the PP samples showed a clear shift of the SAXS peak to the lower q direction induced by the thermal aging, indicating an increase in the length of the long-period structure. Two-trace two-dimensional (2T2D) asynchronous correlation spectra derived from NIR spectra clearly revealed that the aging treatment leads to a substantial increase in the spectral intensity of the regularity bands representing the longer helix present in a folded lamellar structure. In other words, it suggests that the long helix structure is more abundantly present than the short helix structure in the aged PP than in the initial PP. By combining the information derived from the SAXS profiles and NIR spectra, the details of the aging-induced variation were clearly determined. Namely, aging causes additional crystallization of the PP by developing more helical structures, which involves an increase in the lamellar thickness as well as a decrease in the amorphous region. The growth of the rigid crystalline phase restricts the elastic deformation in the amorphous structure, which eventually induces the deterioration of PP by making the polymer hard but brittle. Such observation, in turn, implies that retarding or accelerating the crystallized structure of PP substantially works to control the progress of aging.