Complete Spectral Characterization Research Articles

Multiparameter cascaded quantum interferometer

We theoretically propose a multiparameter cascaded quantum interferometer in which a two-input and two-output setup is obtained by concatenating 50:50 beam splitters with n independent and adjustable time delays. A general method for deriving the coincidence probability of such an interferometer is given based on the linear transformation of the matrix of beam splitters. As examples, we analyze the interference characteristics of one-, two-, and three-parameter cascaded quantum interferometers with different frequency correlations and input states. Some typical interferograms of such interferometers are provided to reveal richer and more complicated two-photon interference phenomena. This work offers a general theoretical framework for designing versatile quantum interferometers and provides a convenient method for deriving the coincidence probabilities involved. In principle, arbitrary two-input and two-output experimental setups can be designed with the framework. Potential applications can be found in the complete spectral characterization of two-photon states, multiparameter estimation, and quantum metrology.

Complete spectral characterization of biphotons by simultaneously determining their frequency sum and difference in a single quantum interferometer

Complete spectral characterization of biphotons by simultaneously determining their frequency sum and difference in a single quantum interferometer

Spin-orbit charge-transfer intersystem crossing in heavy-atom-free orthogonal covalent boron-dipyrromethene heterodimers.

Boron-dipyrromethene (BODIPY) derivatives are prospective organic-based triplet photosensitizers. Since the triplet generation yield of the parent BODIPY is low, heavy atoms are widely used to improve the triplet yield. However, the dimerization of BODIPYs can also significantly improve their ability to produce triplets. Through a comparative study of the triplet formation dynamics of two heavy-atom-free orthogonal covalent BODIPY heterodimers that differ in their dihedral angles, we have demonstrated that the mechanism of spin-orbit charge-transfer intersystem crossing (SOCT-ISC) promotes the triplet generation of BODIPY heterodimers in solution. Different from the general understanding of SOCT-ISC, the heterodimer with a smaller dihedral angle and low structural rigidity showed better triplet generation due to (a) the stronger inter-chromophoric interaction in the heterodimer, which promoted the formation of a solvent-stabilized charge-transfer (CT) state, (b) the more favorable energy level alignment with sizeable spin-orbit coupling strength, and (c) the balance between the stabilized singlet CT state and limited direct charge recombination to the ground state in a weakly polar solvent. The complete spectral characterization of the triplet formation dynamics clarified the SOCT-ISC mechanism and important factors affecting the triplet generation in BODIPY heterodimers.

On the stability of the compacton waves for the degenerate KdV and NLS models

In this paper, we consider the degenerate semi-linear Schrödinger and Korteweg-de Vries equations in one spatial dimension. We construct special solutions of the two models, namely standing wave solutions of NLS and traveling waves, which turn out to have compact support, compactons. We show that the compactons are unique bell-shaped solutions of the corresponding PDEs and for appropriate variational problems as well. We provide a complete spectral characterization of such waves, for all values of p p . Namely, we show that all waves are spectrally stable for 2 > p ≤ 8 2>p\leq 8 , while a single mode instability occurs for p > 8 p>8 . This extends previous work of Germain, Harrop-Griffiths and Marzuola [Quart. Appl. Math. 78 (2020), pp. 1–32] who have previously established orbital stability for some specific waves, in the range p > 8 p>8 .

On Koopman Operator Framework for Semi-explicit Differential-Algebraic Equations

Abstract The so-called Koopman operator framework has attracted a lot of interest in dynamical systems theory and control theory. In this note we extend the framework to systems described by nonlinear semi-explicit Differential-Algebraic Equations (DAEs). A complete spectral characterization of DAE systems with asymptotically stable equilibrium points is presented. A difficulty of the Koopman operator framework is also pointed out for a planar DAE system with forward impasse point.

Two-Qubit Spectroscopy of Spatiotemporally Correlated Quantum Noise in Superconducting Qubits

Noise that exhibits significant temporal and spatial correlations across multiple qubits can be especially harmful to both fault-tolerant quantum computation and quantum-enhanced metrology. However, a complete spectral characterization of the noise environment of even a two-qubit system has not been reported thus far. We propose and experimentally validate a protocol for two-qubit dephasing noise spectroscopy based on continuous control modulation. By combining ideas from spin-locking relaxometry with a statistically motivated robust estimation approach, our protocol allows for the simultaneous reconstruction of all the single-qubit and two-qubit cross-correlation spectra, including access to their distinctive non-classical features. Only single-qubit control manipulations and state-tomography measurements are employed, with no need for entangled-state preparation or readout of two-qubit observables. While our experimental validation uses two superconducting qubits coupled to a shared engineered noise source, our methodology is portable to a variety of dephasing-dominated qubit architectures. By pushing quantum noise spectroscopy beyond the single-qubit setting, our work paves the way to characterizing spatiotemporal correlations in both engineered and naturally occurring noise environments.

Automatic detection and classification of sounds generated by ocean vehicles via cyclic demodulation and beamformed coherence

Narrow-band tonal signals generated by ocean vessels are a dominant source of underwater sound, occurring at discrete frequencies ranging from several Hertz to several kiloHertz and continuously over long time intervals. Here we develop a two-stage approach for the automated passive acoustic detection and classification of underwater vehicles. The first stage utilizes the commonly used cyclic demodulation to extract the low frequency tonal sound modulated into high frequency noisy signal from which the fundamental frequency and blade pass frequency of ship propeller can be determined. The second applies magnitude-squared coherence to beamformed signals to directly extract tonal sounds spanning a wide range of frequencies from low (∼10 Hz) up to the array cutoff frequency and to estimate their bearings. Both the modulated and unmodulated tonal signals generated by a ship can be simultaneously determined using this two-stage approach leading to a more complete spectral characterization of the underwater sound radiated by an ocean vessel. Here, the approach is applied to analyze and characterize the underwater sound generated by research vessel RV Knorr, received on a large-aperture densely populated coherent hydrophone array.Narrow-band tonal signals generated by ocean vessels are a dominant source of underwater sound, occurring at discrete frequencies ranging from several Hertz to several kiloHertz and continuously over long time intervals. Here we develop a two-stage approach for the automated passive acoustic detection and classification of underwater vehicles. The first stage utilizes the commonly used cyclic demodulation to extract the low frequency tonal sound modulated into high frequency noisy signal from which the fundamental frequency and blade pass frequency of ship propeller can be determined. The second applies magnitude-squared coherence to beamformed signals to directly extract tonal sounds spanning a wide range of frequencies from low (∼10 Hz) up to the array cutoff frequency and to estimate their bearings. Both the modulated and unmodulated tonal signals generated by a ship can be simultaneously determined using this two-stage approach leading to a more complete spectral characterization of the underwater sou...

Inclusion complex of β-cyclodextrin with tetrabutylammonium bromide: Synthesis, characterization and interaction with calf thymus DNA

Surfactant molecules are now become indispensible in drug formulations to reduce drug-drug interactions and most often to enhance the bioavailability of poorly water soluble life saving drugs. Recently, tetrabutylammonium bromide (TBAB) is the cationic surfactant of choice. A further advancement could be achieved by using mixed surfactant-cyclodextrin (CD) systems in drug delivery. A study on the inclusion behaviour of TBAB with β-CD host would therefore, have high scientific value for the development of novel TBAB based pharmaceutical formulations. We report herein the synthesis and complete physicochemical and spectral (UV, IR, NMR, ROESY, XRD, TGA, SEM etc.) characterization of the inclusion complex (IC) between TBAB and β-CD. The stoichiometry of the formed IC was evaluated as 1:1 by Job's plot. A comparison of 1H NMR spectra of TBAB, β-CD and IC and ROESY spectrum revealed that two out of four n-butyl chains were incorporated into CD cavity and the ammonium nitrogen atom stick out to the wider CD edge. The thermal stability of TBAB was found to increase after complexation. The experimental data were also correlated with the molecular docking study. In addition, the binding mode of the synthesized IC with Calf thymus DNA was also reported.

Integrated comprehensive two-dimensional gas-chromatographic and spectroscopic characterization of vetiveryl acetates: Molecular identifications, quantification of constituents, regulatory and olfactory considerations

Vetiveryl acetate is a common ingredient of the perfume industry highly prized by perfumers for its crisp vetiver note and thus often used in high-end perfume compositions. Vetiveryl acetate is currently manufactured from vetiver oil by means of various industrial processes that result in the conversion of the main vetiver alcohols into their corresponding acetates. Despite being used for decades as perfume ingredient, vetiveryl acetate has barely been studied in the past, therefore its chemical composition is poorly documented. While vetiveryl acetate is currently under investigation by regulation authorities, it was crucial to fill this gap of knowledge. We report here the first detailed investigation of different types of vetiveryl acetates, covering analytical, regulatory, and olfactory aspects. This study is based upon an integrated analytical methodology involving a full array of gas chromatographic techniques and spectroscopic/spectrometric methods. The principal objective was the identification of the main ester constituents contained in different samples of vetiveryl acetate, as well as linking their chemical composition with their manufacture process. Among the major esters detected in all samples, 23 ester constituents were either isolated by capillary preparative-gas chromatography or synthesized in order to provide their complete spectral characterization. The quantification of constituents in both commercial and laboratory-made vetiveryl acetates was carried out by internal calibration using comprehensive two-dimensional-gas chromatography and predicted relative response factors. The generated set of analytical data permitted to explore both the regulatory aspects and the olfactory properties associated with the substance. The manufacture of vetiveryl acetate modulates the initial scent of vetiver essential oil by suppressing the notes brought by the main fragrant alcohols. While the impact of undesired odorant molecules such as phenol derivatives and geosmin is lowered, the major odour-active ketones such as khusimone, ziza-6(13)-en-3-ones, and the two vetivones develop their own odor characters in vetiveryl acetate.

Synthesis and Characterization of Potential Impurities of Canagliflozin

Multiple sources of anticipated process and degradation impurities of canagliflozin drug has been identified during its laboratory optimization and later in commercial scale manufacturing process. The structure of these impurities were confirmed by their independent synthesis as well as by their complete spectral characterization including 2D NMR, 19F NMR, and their chromatographic retention time profile. As a part of these investigations, three new impurities such as Hydroperoxide (Impurity-D), Sulfone (impurity-F) and Dimer (impurity-C) were characterized. The present work describe our detailed investigations on the structural characterization of canagliflozin impurities, and further their independent synthesis.

Tapered optical fiber sensor for chemical pollutants detection in seawater

Three tapered silica optical fibers, uncoated and coated with metallic (Al or Cu) and dielectric layers (TiO2), are employed to determine the presence of oil and Hazardous and Noxious Substances (HNS from now on) in water, by means of the measurement of their spectral transmittance. With our experimental assembly, the presence of oil and HNS spills can be detected employing the three different kinds of tapers, since the complete range of refractive indices of the pollutants (1.329–1.501) is covered with these tapers. The most suitable spectral range to detect the presence of a chemical pollutant in seawater has been identified and a complete spectral characterization of the three types of optical fiber tapers has been carried out. The results obtained show that, in general terms, these devices working together can be employed for the early detection of oil and HNS spills in seawater in a marine industrial environment. These sensors have many advantages, such as its low cost, its simplicity and versatility (with interesting properties as quick response and repeatability), and especially that they can be self-cleaned with seawater in motion.

Recent developments in the Thomson Parabola Spectrometer diagnostic for laser-driven multi-species ion sources

Ongoing developments in laser-driven ion acceleration warrant appropriate modifications to the standard Thomson Parabola Spectrometer (TPS) arrangement in order to match the diagnostic requirements associated to the particular and distinctive properties of laser-accelerated beams. Here we present an overview of recent developments by our group of the TPS diagnostic aimed to enhance the capability of diagnosing multi-species high-energy ion beams. In order to facilitate discrimination between ions with same Z/A, a recursive differential filtering technique was implemented at the TPS detector in order to allow only one of the overlapping ion species to reach the detector, across the entire energy range detectable by the TPS. In order to mitigate the issue of overlapping ion traces towards the higher energy part of the spectrum, an extended, trapezoidal electric plates design was envisaged, followed by its experimental demonstration. The design allows achieving high energy-resolution at high energies without sacrificing the lower energy part of the spectrum. Finally, a novel multi-pinhole TPS design is discussed, that would allow angularly resolved, complete spectral characterization of the high-energy, multi-species ion beams.

Synthesis, Single Crystal Structure and Spectroscopic Aspects of Benzo[b]thiophene-3-carbaldehyde Based Chalcones

The present study highlights the synthesis, single crystal structure and complete spectral characterization of two heteroaryl chalcones, namely (i) (E)-3-(benzo[b]thiophen-3-yl)-1-(2-hydroxyphenyl)prop-2-en-1-one (C17H12O2S) and (ii) (E)-1-(2-aminophenyl)-3-(benzo[b]thio phen-3-yl)prop-2-en-1-one (C17H13NOS). In both of these compounds, the molecules show weak intermolecular C–H···O interactions utilizing the keto group in addition to hydrogen bonding including hydroxyl and amino groups. In the case of compound (ii) water molecules are trapped in voids of the crystal lattice. π–π stacking interactions between phenyl and benzothiazole rings are observed in the crystal packing. In addition to crystallographic data, both the structures are also described for the first time with 1H NMR, H–H Cosy, 13C NMR, DEPT-135, HR-MS, TGA-DTG, DSC, IR and UV spectral data. The synthesis, single crystal structure and complete spectral characterization of benzo[b]thiophene-3-carbaldehyde based novel heteroaryl chalcones.

Optical attosecond pulses and tracking the nonlinear response of bound electrons.

The time it takes a bound electron to respond to the electromagnetic force of light sets a fundamental speed limit on the dynamic control of matter and electromagnetic signal processing. Time-integrated measurements of the nonlinear refractive index of matter indicate that the nonlinear response of bound electrons to optical fields is not instantaneous; however, a complete spectral characterization of the nonlinear susceptibility tensors--which is essential to deduce the temporal response of a medium to arbitrary driving forces using spectral measurements--has not yet been achieved. With the establishment of attosecond chronoscopy, the impulsive response of positive-energy electrons to electromagnetic fields has been explored through ionization of atoms and solids by an extreme-ultraviolet attosecond pulse or by strong near-infrared fields. However, none of the attosecond studies carried out so far have provided direct access to the nonlinear response of bound electrons. Here we demonstrate that intense optical attosecond pulses synthesized in the visible and nearby spectral ranges allow sub-femtosecond control and metrology of bound-electron dynamics. Vacuum ultraviolet spectra emanating from krypton atoms, exposed to intense waveform-controlled optical attosecond pulses, reveal a finite nonlinear response time of bound electrons of up to 115 attoseconds, which is sensitive to and controllable by the super-octave optical field. Our study could enable new spectroscopies of bound electrons in atomic, molecular or lattice potentials of solids, as well as light-based electronics operating on sub-femtosecond timescales and at petahertz rates.

Synthesis of Derivatized Chitooligomers using Transglycosidases Engineered from the Fungal GH20 β‐N‐Acetylhexosaminidase

AbstractThe synthesis of oligosaccharides using mutant glycosidases has been dynamically developing due to the need for novel carbohydrate‐based materials. Chitooligomers (β‐1→4‐linked oligomers of N‐acetylglucosamine) are bioactive compounds applicable in many industrial and pharmacological areas; however, their accessibility is still rather low. In this work, GH20 β‐N‐acetylhexosaminidase from the fungus Talaromyces flavus was engineered by site‐directed mutagenesis to obtain three efficiently transglycosylating variants with ca. 200‐times suppressed hydrolytic activity. Thus, we have prepared the first GH20 transglycosidases. In the reactions catalyzed by these mutant β‐N‐acetylhexosaminidases we were able to easily prepare and isolate both natural and modified chitooligomers in sufficient amounts for their complete spectral characterization and possible further application. The presented method for the synthesis of chitooligomers with aglycones suitable for linking to other biological structures is simple and robust enough to be easily scaled up.magnified image

A Spectral Characterization of Controllability for Linear Discrete-Time Systems with Conic Constraints

In this paper, we generalize all previously known results on the controllability of discrete-time linear systems with conic input and/or state constraints. In addition, we single out two cases of the problem which did not appear in the literature before. We provide a characterization for the first one of these new cases. For the second newly introduced case, we show that it is rare and pathological. Moreover, we show that the classical results cannot be extended to this last pathological case. These results altogether lead to an almost complete spectral characterization of controllability for discrete-time linear systems with conic input and/or state constraints.

Synthesis and conformational analysis of phosphorylated β-(1→2) linked mannosides

Phosphorylated β-(1→2)-oligomannosides are found on the cell surface of several Candida species, including Candida albicans (an opportunistic pathogen). These molecules are believed to take part in the invasion process of fungal infections, which in the case of C. albicans can lead to severe bloodstream infections and death, and can therefore be considered important from a biological standpoint. Understanding the mechanism of their action requires access to the corresponding oligosaccharide model compounds in pure form. In the present work, synthesis of the model core structures involved in the invasion process of C. albicans, consisting of phosphorylated β-(1→2)-linked mannotriose and tetraose, is reported. In order to elucidate the nature of these molecules in more detail, an extensive NMR-spectroscopic study encompassing complete spectral characterization, conformational analysis and molecular modelling was performed. The obtained results were also compared to similar chemical entities devoid of the charged phosphate group.

High Resolution Energy-Angle Correlation Measurement of Hard X Rays from Laser-Thomson Backscattering

Thomson backscattering of intense laser pulses from relativistic electrons not only allows for the generation of bright x-ray pulses but also for the investigation of the complex particle dynamics at the interaction point. For this purpose a complete spectral characterization of a Thomson source powered by a compact linear electron accelerator is performed with unprecedented angular and energy resolution. A rigorous statistical analysis comparing experimental data to 3D simulations enables, e.g., the extraction of the angular distribution of electrons with 1.5% accuracy and, in total, provides predictive capability for the future high brightness hard x-ray source PHOENIX (photon electron collider for narrow bandwidth intense x rays) and potential gamma-ray sources.

Improved Extraction and Complete Mass Spectral Characterization of Steroidal Alkaloids from Veratrum Californicum

Four steroidal alkaloids extracted from the roots and rhizomes of Veratrum californicum were separated by high performance liquid chromatography (HPLC) and identified using high resolution electrospray ionization time of flight tandem mass spectrometry (ESI-TOF-MS/MS) as veratrosine, cycloposine, veratramine, and cyclopamine. This paper compares ethanol and benzene as extraction solvents, HPLC solvent conditions leading to good separation of steroidal alkaloids, and MS/MS fragmentation patterns for the four steroidal alkaloids which have been released to the public database MassBank.jp. The reported Soxhlet extraction method nearly triples the recovery of steroidal alkaloids from V. californicum.

Femtosecond filamentation in sapphire with diffractive lenses

In this paper, we demonstrate novel properties in the phenomenology of supercontinuum generation in sapphire with diffractive lenses and provide a complete spatial, spectral, and temporal characterization of the so-generated pulses. Filament formation inside the sample is analyzed and related to the measured spectra, finding that clipping of the filament results in blueshifted spectra. For comparison, filament formation with refractive lenses is also examined, and the roles of diffraction and extension of the focusing region are inspected. The tunability achieved in the anti-Stokes side of the spectrum is also extended to the ultraviolet by frequency mixing with infrared femtosecond pulses. © 2013 Optical Society of America OCIS codes: (050.0050) Diffraction and gratings; (320.6629) Supercontinuum generation; (320.7110) Ultrafast nonlinear optics.