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Ebihara, Ken, Hiroaki Takahashi i Isao Noda. "Nanosecond Two-Dimensional Resonance Raman Correlation Spectroscopy of Benzil Radical Anion". Applied Spectroscopy 47, nr 9 (wrzesień 1993): 1343–44. http://dx.doi.org/10.1366/0003702934067405.
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Nanosecond two-dimensional resonance Raman spectroscopy was used to investigate the photochemistry of the production and decay of the radical anion of benzil in various solvents. A newly developed correlation formalism was applied to a set of time-resolved resonance Raman spectra of the benzil radical anion to generate two-dimensional Raman spectra. Unlike the 2D correlation method previously developed for IR spectroscopy, which was based on signals induced by a sinusoidally varying external perturbation, the new correlation formalism is generally applicable to the studies of any transient spectroscopic signals having an arbitrary waveform. This makes it ideally suited for the analysis of time-resolved spectroscopic signals following photoexcitation. 2D Raman spectra effectively accentuate certain useful information which is sometimes obscured in the original time-resolved spectra. Spectral intensity changes and peak shifts arising from the photochemical reaction processes were clearly observed by the synchronous and asynchronous correlation.
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Johansson, Jonas, Staffan Folestad, Mats Josefson, Anders Sparén, Christoffer Abrahamsson, Stefan Andersson-Engels i Sune Svanberg. "Time-Resolved NIR/Vis Spectroscopy for Analysis of Solids: Pharmaceutical Tablets". Applied Spectroscopy 56, nr 6 (czerwiec 2002): 725–31. http://dx.doi.org/10.1366/000370202760077676.
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Time-resolved spectroscopy in the visible and near-infrared (NIR) regions was used in a feasibility study for analysis of solid pharmaceuticals. The objective of the experiments was to study the interaction of light with pharmaceutical solids and to investigate the usefulness of the method as an analytical tool for spectroscopic analysis. In these experiments, a pulsed Ti:sapphire laser and white light generation in water was utilized to form a pulsed light source in the visible/NIR region. The light was focused onto the surface of tablets, and the transmitted light was detected by a time-resolving streak camera. Two types of measurements were performed. First, a spectrometer was put in front of the streak camera for spectral resolution. Secondly, the signal originating from different locations of the sample was collected. Time-resolved and wavelength/spatially resolved data were generated and compared for a number of different samples. The most striking result from the experiments is that the typical optical path length through a 3.5-mm-thick tablet is about 20–25 cm. This indicates very strong multiple scattering in these samples. Monte Carlo simulations and comparison with experimental data support very high scattering coefficients on the order of 500 cm−1. Furthermore, the data evaluation shows that photons with a particular propagation time through the sample contain a higher chemical contrast than other propagation times or than steady-state information. In conclusion, time-resolved NIR spectroscopy yields more information about solid pharmaceutical samples than conventional steady-state spectroscopy.
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Arjmand, S., M. P. Anania, A. Biagioni, M. Ferrario, M. Galletti, V. Lollo, D. Pellegrini, R. Pompili i A. Zigler. "Different elements, same results: time-resolved temperature determination by oxygen and nitrogen elements". Journal of Instrumentation 18, nr 08 (1.08.2023): P08003. http://dx.doi.org/10.1088/1748-0221/18/08/p08003.
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Abstract The core purpose of this research is to use optical emission spectroscopy to determine the electron temperature (Te ) of a hydrogen plasma generated in a capillary discharge plasma, with a focus on its temporal variation. The plasma density (ne ) is first determined using the Stark broadening technique, which measures the broadening of spectral lines as a result of the electric field in the plasma. Subsequently, a passive spectroscopic technique is employed to estimate the electron plasma temperature by detecting the emitted light from the plasma. This spectral detection is performed using a visible range spectrometer. In this study, two elements, oxygen and nitrogen, are specifically selected based on the chemical composition of the capillary. The electron plasma temperature is estimated using the line ratio method, which involves comparing the intensities of two specific spectral lines emitted by the selected elements. By analyzing these line ratios, the electron plasma temperature can be inferred. The combination of the Stark broadening technique and line ratio method provides valuable insights into the plasma's physical characteristics, specifically its density and temperature.
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Trincao, Jose, Michelle L. Hamilton, Jeppe Christensen i Arwen R. Pearson. "Dynamic structural science: recent developments in time-resolved spectroscopy and X-ray crystallography". Biochemical Society Transactions 41, nr 5 (23.09.2013): 1260–64. http://dx.doi.org/10.1042/bst20130125.
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To understand the mechanism of biological processes, time-resolved methodologies are required to investigate how functionality is linked to changes in molecular structure. A number of spectroscopic techniques are available that probe local structural rearrangements with high temporal resolution. However, for macromolecules, these techniques do not yield an overall high-resolution description of the structure. Time-resolved X-ray crystallographic methods exist, but, due to both instrument availability and stringent sample requirements, they have not been widely applied to macromolecular systems, especially for time resolutions below 1 s. Recently, there has been a resurgent interest in time-resolved structural science, fuelled by the recognition that both chemical and life scientists face many of the same challenges. In the present article, we review the current state-of-the-art in dynamic structural science, highlighting applications to enzymes. We also look to the future and discuss current method developments with the potential to widen access to time-resolved studies across discipline boundaries.
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Radu, Liliana, Doina Gazdaru i B. Constantinescu. "Spectroscopic study of fast-neutron-irradiated chromatin". Canadian Journal of Physiology and Pharmacology 82, nr 2 (1.02.2004): 79–83. http://dx.doi.org/10.1139/y03-124.
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The effects produced by fast neutrons (0-100 Gy) on chromatin structure were analyzed by (i) [1H]-NMR spectroscopy, (ii) time resolved spectroscopy, and (iii) fluorescence resonance energy transfer (FRET). Two types of chromatin were tested: (i) a chromatin from a normal tissue (liver of Wistar rats) and (ii) a chromatin from a tumoral tissue (Guerin limphotrope epithelioma, a rat solid tumor). The fast-neutron action on chromatin determines greater values of the [1H]-NMR transverse relaxation time, indicating a more injured structure. Time-resolved fluorescence measurements show that the relative contribution of the excited state lifetime of bound ethidium bromide to chromatin DNA diminishes with increasing irradiation doses. This reflects the damage that occurs in DNA structure: production of single- and double-strand breaks due to sugar and base modifications. By the FRET method, the distance between dansyl chloride and acridine orange coupled at chromatin was determined. This distance increases upon fast-neutron action. The radiosensitivity of the tumor tissue chromatin seems higher than that of the normal tissue chromatin, probably because of its higher (loose) euchromatin/(compact) heterochromatin ratio. As the values of the physical parameters analyzed are specific for a determined dose, the establishment of these parameters may constitute a criterion for the microdosimetry of chromatin radiolesions produced by fast neutrons.Key words: chromatin, spectroscopic study, radiolesions, fast neutrons, microdosimetry.
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Silly, Mathieu G. "High resolution and time resolved photoemission spectroscopy for developing more efficient materials to reduce energy consumption and increase renewable energy production". EPJ Web of Conferences 273 (2022): 01013. http://dx.doi.org/10.1051/epjconf/202227301013.
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Due to the increase of energy consumption and the resulting ecological challenge, a collective awareness leads to the development of renewable energies and more efficient materials to increase the green energy production. Development of efficient photovoltaic materials is very closely related to their chemical and electronic properties. A better knowledge of these imbricated properties is needed, in addition to a better comprehension of their interplay with charge transport mechanisms. Exciton creation and recombination processes, charge transfer and charge collection processes take place at the surface and interface of the photoactive materials. Photoemission spectroscopy as chemical specific and surface sensitive spectroscopic technique is a method of choice on the study of physical phenomena at the origin of photoconversion efficiency. Time resolved photoemission spectroscopy has been recently renewed interest covering time scale from fs to more than seconds. It permits to probe the dynamics of relaxation of photoexcited charges and determine their lifetime. It finds application in various materials used in solar photovoltaics. In this paper, we define the physical and chemical properties determined by the combination of high resolution and time resolved photoemission spectroscopy. We show examples dealing with the development of renewable energy and energy consumption reduction in agreement with the current ecological trend for a better future.
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Takubo, Kou, Samiran Banu, Sichen Jin, Misaki Kaneko, Wataru Yajima, Makoto Kuwahara, Yasuhiko Hayashi i in. "Generation of sub-100 fs electron pulses for time-resolved electron diffraction using a direct synchronization method". Review of Scientific Instruments 93, nr 5 (1.05.2022): 053005. http://dx.doi.org/10.1063/5.0086008.
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To investigate photoinduced phenomena in various materials and molecules, ultrashort pulsed x-ray and electron sources with high brightness and high repetition rates are required. The x-ray and electron’s typical and de Broglie wavelengths are shorter than lattice constants of materials and molecules. Therefore, photoinduced structural dynamics on the femtosecond to picosecond timescales can be directly observed in a diffraction manner by using these pulses. This research created a tabletop ultrashort pulsed electron diffraction setup that used a femtosecond laser and electron pulse compression cavity that was directly synchronized to the microwave master oscillator (∼3 GHz). A compressed electron pulse with a 1 kHz repetition rate contained 228 000 electrons. The electron pulse duration was estimated to be less than 100 fs at the sample position by using photoinduced immediate lattice changes in an ultrathin silicon film (50 nm). The newly developed time-resolved electron diffraction setup has a pulse duration that is comparable to femtosecond laser pulse widths (35–100 fs). The pulse duration, in particular, fits within the timescale of photoinduced phenomena in quantum materials. Our developed ultrafast time-resolved electron diffraction setup with a sub-100 fs temporal resolution would be a powerful tool in material science with a combination of optical pump–probe, time-resolved photoemission spectroscopic, and pulsed x-ray measurements.
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Robert, H., i D. J. Pusiol. "Fast ρ-NQR Imaging with Slice Selection". Zeitschrift für Naturforschung A 51, nr 5-6 (1.06.1996): 353–56. http://dx.doi.org/10.1515/zna-1996-5-607.
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Abstract A combination of a new pulse sequence allowing fast data acquisition in the rotating frame version of NQR (ρ-NQRI) together with a method for slice selection, is reported. The procedure allows us to record the magnetization evolution during its motion in the rotating frame. At the same time a zero-crossing external magnetic field gradient is applied in order to select a determined slice of the object to be imaged. The experiments reported are the first steps toward a fast tridimensional ρ-NQRI; even more, as the spectroscopic information is preserved during the spatial encoding procedure, it could be considered as a 3D spatially resolved NQR spectroscopy technique.
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Fede, Letizia, Gregory Lefrere, Maroun Hjeij, Ronan Le Page, Luiz Poffo, Jean-Marc Goujon i Aymeric Le Gratiet. "Multiparametric Remote Investigation in the near-IR through Optical Fiber for In Situ Measurements". Sensors 23, nr 6 (7.03.2023): 2911. http://dx.doi.org/10.3390/s23062911.
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Diffuse reflectance spectroscopy (DRS) has proven to be a powerful, reliable, and non-invasive optical method for characterizing a specimen. Nevertheless, these methods are based on a rudimentary interpretation of the spectral response and can be irrelevant to understanding 3D structures. In this work, we proposed adding optical modalities into a customized handheld probe head in order to increase the number of parameters in DRS acquired from the light/matter interaction. It consists of (1) placing the sample in a reflectance manual rotation stage to collect spectral backscattered angularly resolved light and (2) illuminating it with two sequential linear polarization orientations. We demonstrate that this innovative approach leads to a compact instrument, capable of performing fast polarization-resolved spectroscopic analysis. Due to the significant amount of data available with this technique in a short time, we observe sensitive quantitative discrimination between two types of biological tissue provided by a raw rabbit leg. We believe that this technique can pave the way for rapid meat quality check or biomedical diagnosis of pathological tissues in situ at an early stage.
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Carden, Angela, Michael G. Yost i Richard A. Fenske. "Noninvasive Method for the Assessment of Dermal Uptake of Pesticides Using Attenuated Total Reflectance Infrared Spectroscopy". Applied Spectroscopy 59, nr 3 (marzec 2005): 293–99. http://dx.doi.org/10.1366/0003702053585372.
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Dermal absorption of pesticides is a primary exposure route for agricultural workers, but is not well characterized. Current measurement techniques are either invasive, such as tape-stripping, or require extensive sample preparation or analysis time, such as urinary metabolite monitoring or wipe sampling followed by gas chromatography analysis. We present the application of a noninvasive, spectroscopic approach for the measurement of pesticide absorption into skin. Attenuated total reflectance infrared spectroscopy (ATR-IR) was used to monitor directly the absorption of two pesticides—captan and azinphos-methyl—in ten volunteers over 20 min under occlusive conditions. We found substantial variability in absorption across subjects. Our results were comparable to those measured by the more traditional method of wipe-sampling followed by extraction and gas chromatography analysis. Multivariate data analysis, in the form of multivariate curve resolution (MCR), is a novel addition to this type of experiment, yielding time-resolved information unachievable by standard methods. These data are potentially more informative than the monitoring of blood or urinary metabolites because they can be acquired in essentially real-time, allowing observations of pesticide absorption on a rapid timescale rather than over hours or days.
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Yadav, R. S., Y. Dwivedi i S. B. Rai. "Structural and Optical Analysis of Eu3+ Doped BiVO4 Nanophosphor by Combustion Method". Applied Mechanics and Materials 752-753 (kwiecień 2015): 272–76. http://dx.doi.org/10.4028/www.scientific.net/amm.752-753.272.
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Present article report synthesis and spectroscopic analysis of BiVO4 nanophosphor doped with trivalent Eu ions. It was observed that BiVO4 nanocrystals shows higher yield in comparison with the as-made nanocrystals on 266 nm laser excitation. On 266 nm excitation, emission composed of red dominated wide spectrum in the range of 400-950 nm was reported. Emission intensity enhanced five times on annealed sample than the counterpart. Time resolved analysis explores significant alteration in excited state relaxation process due to annealing. Detailed photo physics involved to improve optical emissions has also been explained.
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Chaves, Otávio, Maurício Tavares, Micael Cunha, Roberto Parise-Filho, Carlos Sant’Anna i José Netto-Ferreira. "Multi-Spectroscopic and Theoretical Analysis on the Interaction between Human Serum Albumin and a Capsaicin Derivative—RPF101". Biomolecules 8, nr 3 (23.08.2018): 78. http://dx.doi.org/10.3390/biom8030078.
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The interaction between the main carrier of endogenous and exogenous compounds in the human bloodstream (human serum albumin, HSA) and a potential anticancer compound (the capsaicin analogue RPF101) was investigated by spectroscopic techniques (circular dichroism, steady-state, time-resolved, and synchronous fluorescence), zeta potential, and computational method (molecular docking). Steady-state and time-resolved fluorescence experiments indicated an association in the ground state between HSA:RPF101. The interaction is moderate, spontaneous (ΔG° < 0), and entropically driven (ΔS° = 0.573 ± 0.069 kJ/molK). This association does not perturb significantly the potential surface of the protein, as well as the secondary structure of the albumin and the microenvironment around tyrosine and tryptophan residues. Competitive binding studies indicated Sudlow’s site I as the main protein pocket and molecular docking results suggested hydrogen bonding and hydrophobic interactions as the main binding forces.
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Rooj, Bipin, Ankita Dutta, Debojyoti Mukherjee, Sahidul Islam i Ujjwal Mandal. "FRET Study Between Carbon Quantum Dots and Malachite Green by Steady-State and Time-Resolved Fluorescence Spectroscopy". Current Physical Chemistry 10, nr 3 (4.11.2020): 178–88. http://dx.doi.org/10.2174/1877946809666191114143123.
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Background: Understanding the interaction between different organic dyes and carbon quantum dots helps us to understand several photo physical processes like electron transfer, energy transfer, molecular sensing, drug delivery and dye degradation processes etc. Objective: The primary objective of this study is to whether the carbon quantum dots can act as an electron donor and can participate in the different photo physical processes. Methods: In this work, Carbon Quantum Dots (CQDLs) are synthesized in most economical and simple carbonization method where petals of Nelumbo nucifera L. are used as a carbon precursor. The synthesized CQDLs were characterized by using experimental techniques like UV−Vis absorption, FT-IR, Transmission Electron Microscopy (TEM), steadystate and time-resolved fluorescence spectroscopy. Results: The spectral analysis shows that the so synthesized CQDLs are spherical in shape and its diameter is around 4.2 nm. It shows the fluorescence emission maximum at 495 nm with a quantum yield of 4%. In this work the interaction between Carbon Quantum Dots (CQDLs) and an organic dye Malachite Green (MG) is studied using fluorescence spectroscopic technique under ambient pH condition (At pH 7). The quenching mechanism of CQDLs with MG was investigated using Stern-Volmer equation and time-resolved fluorescence lifetime studies. The results show that the dominant process of fluorescence quenching is attributed to Forster Resonance Energy Transfer (FRET) having a donor acceptor distance of 53 Å where CQDLs act as a donor and MG acts as an acceptor. Conclusion: This work has a consequence that CQDLs can be used as a donor species for different photo physical processes such as photovoltaic cell, dye sensitized solar cell, and also for antioxidant activity study.
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Webster, Richard D. "Electrochemical and Spectroscopic Characterization of Oxidized Intermediate Forms of Vitamin E". Molecules 27, nr 19 (21.09.2022): 6194. http://dx.doi.org/10.3390/molecules27196194.
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Vitamin E, a collection of lipophilic phenolic compounds based on chroman-6-ol, has a rich and fascinating oxidative chemistry involving a range of intermediate forms, some of which are proposed to be important in its biological functions. In this review, the available electrochemical and spectroscopic data on these oxidized intermediates are summarized, along with a discussion on how their lifetimes and chemical stability are either typical of similar phenolic and chroman-6-ol derived compounds, or atypical and unique to the specific oxidized isomeric form of vitamin E. The overall electrochemical oxidation mechanism for vitamin E can be summarized as involving the loss of two-electrons and one-proton, although the electron transfer and chemical steps can be controlled to progress along different pathways to prolong the lifetimes of discreet intermediates by modifying the experimental conditions (applied electrochemical potential, aqueous or non-aqueous solvent, and pH). Depending on the environment, the electrochemical reactions can involve single electron transfer (SET), proton-coupled electron transfer (PCET), as well as homogeneous disproportionation and comproportionation steps. The intermediate species produced via chemical or electrochemical oxidation include phenolates, phenol cation radicals, phenoxyl neutral radicals, dications, diamagnetic cations (phenoxeniums) and para–quinone methides. The cation radicals of all the tocopherols are atypically long-lived compared to the cation radicals of other phenols, due to their relatively weak acidity. The diamagnetic cation derived from α–tocopherol is exceptionally long-lived compared to the diamagnetic cations from the other β–, γ– and δ–isomers of vitamin E and compared with other phenoxenium cations derived from phenolic compounds. In contrast, the lifetime of the phenoxyl radical derived from α–tocopherol, which is considered to be critical in biological reactions, is typical for what is expected for a compound with its structural features. Over longer times via hydrolysis reactions, hydroxy para–quinone hemiketals and quinones can be formed from the oxidized intermediates, which can themselves undergo reduction processes to form intermediate anion radicals and dianions. Methods for generating the oxidized intermediates by chemical, photochemical and electrochemical methods are discussed, along with a summary of how the final products vary depending on the method used for oxidation. Since the intermediates mainly only survive in solution, they are most often monitored using UV-vis spectroscopy, FTIR or Raman spectroscopies, and EPR spectroscopy, with the spectroscopic techniques sometimes combined with fast photoinitiated excitation and time-resolved spectroscopy for detection of short-lived species.
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Chu, S. S., i C. P. Grigoropoulos. "Determination of Kinetic Energy Distribution in a Laser-Ablated Titanium Plume by Emission and Laser-Induced Fluorescence Spectroscopy". Journal of Heat Transfer 122, nr 4 (2.06.2000): 771–75. http://dx.doi.org/10.1115/1.1318214.
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Pulsed laser deposition (PLD) of thin films has become a viable technique for a wide range of applications over the last few decades. As kinetic energy of the ablated plume is an important parameter in determining the quality of the film; consequently there is great interest in nonintrusive evaluation of the plume kinetic energy. Spectroscopic techniques such as optical time-of-flight (TOF) utilizes emission spectroscopy or laser-induced-fluorescence (LIF) and is an excellent method for this purpose since they offer temporal and spatial resolution as well as the capability of distinguishing different species. In this paper, the effects of laser fluence and background gas pressure on the kinetic energies of the ablated species are found by the optical time-of flight technique and by emission imaging. Laser-induced-fluorescence is employed for spectrally resolved imaging. The axial velocity of neutral titanium is found to be as high as 2×104 m/s. The distribution of species within the plume is also determined. [S0022-1481(00)01704-7]
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Olvera Cano, Lilia I., Guadalupe C. Villanueva Lopez, Evelyn Romero Mateos i Alfredo Cruz Orea. "Photoacoustic Spectroscopy and Hyperglycemia in Experimental Type 1 Diabetes". Applied Spectroscopy 75, nr 12 (1.10.2021): 1465–74. http://dx.doi.org/10.1177/00037028211047257.
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According to the World Health Organization, diabetes was the seventh leading cause of death in 2016. Long-term diabetes complications are associated with hyperglycemia. It is difficult to predict the beginning and evolution of those complications. The goal of the study was to evaluate the relationship between glycemia and blood spectroscopic variables in an experimental model of type 1 diabetes (streptozotocin model). Blood samples were taken weekly (10 weeks) from the tail of male Wistar rats with or without diabetes. Blood optical absorption spectra were obtained by means of photoacoustic spectroscopy. It was possible to estimate the time-course of blood characteristic peak ratios. The area under the curve of those peaks correlated with hyperglycemia. The evolution of the optical absorption at 450 nm, related to cytochrome p450, was obtained by using the phase-resolved method. The area under the curve of p450 correlated also with hyperglycemia. It is concluded that photoacoustic spectroscopy is a reliable technology to detect the effects of hyperglycemia on blood with possible applications in the study of long-term diabetes complications.
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Hooijschuur, J. H., M. F. C. Verkaaik, G. R. Davies i F. Ariese. "Will Raman meet bacteria on Mars? An overview of the optimal Raman spectroscopic techniques for carotenoid biomarkers detection on mineral backgrounds". Netherlands Journal of Geosciences - Geologie en Mijnbouw 95, nr 2 (12.02.2015): 141–51. http://dx.doi.org/10.1017/njg.2015.3.
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AbstractRaman spectroscopy appears to be an ideal technique for the initial detection of biomarkers, molecules that are potentially indicative of life on planetary bodies elsewhere in our solar system. Carotenoids are particularly useful biomarkers as they are used widely across the species, relatively resistant to breakdown and no inorganic source is known. They are used by microorganisms in their cell membranes for protection against UV radiation. In this paper we focus on the detection of carotenoids in microorganisms within a mineral matrix. We compare the Raman signatures of pure compounds with those of laboratory-made mixtures of β-carotene and minerals. Carotenoids covered by 2.5 mm of translucent calcite or 40 mm of transparent halite were detected using a conventional confocal Raman microscope. To improve sensitivity and hence detection levels, Raman measurements were successfully performed under resonant conditions. Raman analysis can be compromised by fluorescence interference. Data are presented to show how the contribution from the fluorescent background in the Raman spectra can be reduced when making use of gated detection in time-resolved Raman spectroscopy. Overall, this study demonstrates some of the potential of Raman spectroscopy as a method for the detection of (past) life signatures during future planetary missions without taking current technical limitations such as instrumental size into account as recent rapid technical developments suggest these limitations will be resolved in time.
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Jabbar, Abdul, Mahmood Akhtar, Shaukat Mehmood, Koo Hendrick Kurniawan, Rinda Hedwig i Muhammad Aslam Baig. "Analytical Approach of Laser-Induced Breakdown Spectroscopy to Detect Elemental Profile of Medicinal Plants Leaves". Indonesian Journal of Chemistry 19, nr 2 (9.04.2019): 430. http://dx.doi.org/10.22146/ijc.38263.
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Laser ablation chemical and spectroscopic studies of Calotropis procera, Chenopodium ambrosioides, and Nerium indicum leaves was performed using 1064 nm Nd: YAG laser in air at different pressure and time delay. These medicinal plant’s leaves are used by local people for different diseases. The knowledge of medicinal and toxic metals in these plants is very important. We have presented time-resolved studies of different elements and how their lives change with different delay time. C, H, Si, Al, Fe, Cu, Ca, Mg, Na, K, N, O, Sr and Ba have been detected in all the three samples with a molecular form of Carbon and Nitrogen band. We have detected C, H, N, and O as a major element while, Fe, Cu, Mg, K and Ca as essential medicinal metals with other trace elements such as Si, Sr, Al and Ba in all the three plants leaves. We present 1 µs delay time is the best time for elements lifetime in time resolved studies. The behaviour of intensity with different pressures was also studied and it was concluded that 7 torr was the best pressure for the maximum value of intensity. In particular, the electron density and the temperatures of the plasma were reported. The temperature was calculated from the well-known Boltzmann plot method and electron density was estimated from the stark broadened profile of the Hα line.
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Ray, Sudeshna, Sergio Fabián León-Luis, Francisco Javier Manjón, Miguel Alfonso Mollar, Óscar Gomis, Ulises Ruymán Rodríguez-Mendoza, Said Agouram, Alfonso Muñoz i Victor Lavín. "Broadband, site selective and time resolved photoluminescence spectroscopic studies of finely size-modulated Y2O3:Eu3+ phosphors synthesized by a complex based precursor solution method". Current Applied Physics 14, nr 1 (styczeń 2014): 72–81. http://dx.doi.org/10.1016/j.cap.2013.07.027.
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Uemura, Yohei, Toshihiko Yokoyama, Tetsuo Katayama, Shunsuke Nozawa i Kiyotaka Asakura. "Tracking the Local Structure Change during the Photoabsorption Processes of Photocatalysts by the Ultrafast Pump-Probe XAFS Method". Applied Sciences 10, nr 21 (4.11.2020): 7818. http://dx.doi.org/10.3390/app10217818.
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The birth of synchrotron radiation (SR) facilities and X-ray free electron lasers (XFELs) has led to the development of new characterization tools that use X-rays and opened frontiers in science and technology. Ultrafast X-ray absorption fine structure (XAFS) spectroscopy for photocatalysts is one such significant research technique. Although carrier behavior in photocatalysts has been discussed in terms of the band theory and their energy levels in reciprocal space (k-space) based on optical spectroscopic results, it has rarely been discussed where photocarriers are located in real-space (r-space) based on direct observation of the excited states. XAFS provides information on the local electronic and geometrical structures around an X-ray-absorbing atom and can address photocarrier dynamics in the r-space observed from the X-ray-absorbing atom. In this article, we discuss the time dependent structure change of tungsten trioxide (WO3) and bismuth vanadate (BiVO4) photocatalysts studied by the ultrafast pump-probe XAFS method in the femtosecond to nanosecond time scale with the Photon Factory Advanced Ring (PF-AR) and the SPring-8 Angstrom Compact free-electron LAser (SACLA). WO3 shows a femtosecond decay process of photoexcited electrons followed by a structural change to a metastable state with a hundred picosecond speed, which is relaxed to the ground-state structure with a nanosecond time constant. The Bi L3 edge of BiVO4 shows little contribution of the Bi 6s electron to the photoabsorption process; however, it is sensitive to the structural change induced by the photoexcited electron. Time-resolved XAFS measurements in a wide range time domain and with varied wavelengths of the excitation pump laser facilitate understanding of the overall details regarding the photocarrier dynamics that have a significant influence on the photocatalytic performance.
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Ohtani, Masataka, i Shunichi Fukuzumi. "Photoelectrochemical properties of donor-acceptor nanocomposite films composed of porphyrin-functionalized cup-shaped nanocarbon materials". Journal of Porphyrins and Phthalocyanines 14, nr 05 (maj 2010): 452–58. http://dx.doi.org/10.1142/s1088424610002264.
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Porphyrin-functionalized cup-shaped nanocarbons (CNC-H2P) have been assembled onto nanostructured SnO2 films using an electrophoretic deposition method to examine the photoelectrochemical properties. The obtained CNC-H2P nanohybrid films were examined by a series of steady-state and time-resolved spectroscopic measurements and photoelectrochemical measurements. The resulting nanohybrid film afforded drastic enhancement in the photoelectrochemical performance as well as broader photoresponse in the visible region as compared with the reference CNC system without porphyrins. The enhancement of photocurrent generation may be caused by the efficient electron injection from the long-lived charge-separated state of CNC-H2P upon photoexcitation. This feature makes cup-shaped nanocarbon materials a useful candidate for developing efficient photoelectrochemical and photovoltaic cells.
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Finkenzeller, Henning, Denis Pöhler, Martin Horbanski, Johannes Lampel i Ulrich Platt. "New methods for the calibration of optical resonators: integrated calibration by means of optical modulation (ICOM) and narrow-band cavity ring-down (NB-CRD)". Atmospheric Measurement Techniques 16, nr 5 (14.03.2023): 1343–56. http://dx.doi.org/10.5194/amt-16-1343-2023.
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Abstract. Optical resonators are used in spectroscopic measurements of atmospheric trace gases to establish long optical path lengths L with enhanced absorption in compact instruments. In cavity-enhanced broad-band methods, the exact knowledge of both the magnitude of L and its spectral dependency on the wavelength λ is fundamental for the correct retrieval of trace gas concentrations. L(λ) is connected to the spectral mirror reflectivity R(λ), which is often referred to instead. L(λ) is also influenced by other quantities like broad-band absorbers or alignment of the optical resonator. The established calibration techniques to determine L(λ), e.g. introducing gases with known optical properties or measuring the ring-down time, all have limitations: limited spectral resolution, insufficient absolute accuracy and precision, inconvenience for field deployment, or high cost of implementation. Here, we present two new methods that aim to overcome these limitations: (1) the narrow-band cavity ring-down (NB-CRD) method uses cavity ring-down spectroscopy and a tunable filter to retrieve spectrally resolved path lengths L(λ); (2) integrated calibration by means of optical modulation (ICOM) allows the determination of the optical path length at the spectrometer resolution with high accuracy in a relatively simple setup. In a prototype setup we demonstrate the high accuracy and precision of the new approaches. The methods facilitate and improve the determination of L(λ), thereby simplifying the use of cavity-enhanced absorption spectroscopy.
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Ibrahim, Ahmad, Bandar El Fouhaili, Aurélie Chan Yong, Christian Ley, Xavier Allonas i Christiane Carré. "Optimization of a Safranine O three-component photoinitiating system for use in holographic recording". Canadian Journal of Chemistry 93, nr 12 (grudzień 2015): 1345–53. http://dx.doi.org/10.1139/cjc-2014-0606.
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The coupling between a holographic resin, combining multiple monomers and additives, with photoinitiating systems (PIS) is not straightforward. In this paper, a classic PIS based on Safranine O (SFH+) as dye, an amine (ethyl-4-(dimethylamino)benzoate) as electron donor, and a triazine derivative (2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine) as electron acceptor for holographic recording was studied using time-resolved spectroscopic experiments. By taking into account the viscosity of the matrix, a method to evaluate the overall quantum yield of radicals released is proposed and the contribution of singlet and triplet excited states of SFH+ in the formation of radicals is evaluated. Then the corresponding photopolymerization efficiencies of the PIS, studied by real-time FTIR, are compared with holographic recording experiments: this system allows the formation of a hologram with high diffraction efficiency (0.9) in 3 s of irradiation time. It is shown that besides holographic resin formulation, the photochemistry of PIS also impacts the hologram formation.
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Alizadehfanaloo, Saba, Jan Garrevoet, Martin Seyrich, Vadim Murzin, Johannes Becher, Dmitry E. Doronkin, Thomas L. Sheppard, Jan-Dierk Grunwaldt, Christian G. Schroer i Andreas Schropp. "Tracking dynamic structural changes in catalysis by rapid 2D-XANES microscopy". Journal of Synchrotron Radiation 28, nr 5 (12.08.2021): 1518–27. http://dx.doi.org/10.1107/s1600577521007074.
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Many processes and materials in heterogeneous catalysis undergo dynamic structural changes depending on their chemical environment. Monitoring such dynamic changes can be challenging using conventional spectroscopic characterization tools, due to the high time resolution required. Here, a high-resolution 2D X-ray camera operating at 50 Hz full-frame rate was synchronized with a QEXAFS monochromator, enabling rapid spectro-microscopic imaging with chemical contrast over individual pixels. This was used to monitor chemical gradients within a model Pt/Al2O3 catalyst during catalytic partial oxidation of methane to synthesis gas. The transition from methane combustion (partly oxidized Pt) to combustion-reforming and partial oxidation (fully reduced Pt) was observed by a characteristic reduction front, which progressed from the end of the catalyst bed towards its beginning on the second time scale. The full-field QEXAFS imaging method applied here allows acquisition of entire XANES spectra `on the fly' in a rapid and spatially resolved manner. The combination of high spatial and temporal resolution with spectroscopic data offers new opportunities for observing dynamic processes in catalysts and other functional materials at work. The methodology is flexible and can be applied at beamlines equipped with a QEXAFS or other fast-scanning monochromators and a suitable sample environment for gas phase analytics to allow for catalytic studies at the same time.
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Pavlovski, K., C. A. Hummel, A. Tkachenko, A. Dervişoğlu, C. Kayhan, R. T. Zavala, D. J. Hutter i in. "Dynamical parallax, physical parameters, and evolutionary status of the components of the bright eclipsing binary α Draconis". Astronomy & Astrophysics 658 (luty 2022): A92. http://dx.doi.org/10.1051/0004-6361/202142292.
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Aims. Both components of the bright eclipsing binary α Dra have been resolved using long baseline interferometry and the secondary component has been shown to contribute approximately 15% of the total flux; however, a spectroscopic detection of the companion star has so far been unsuccessful. We aim for a firm spectroscopic detection of the secondary component of α Dra using state-of-the-art spectroscopic analysis methods for very high-quality spectroscopic observations. This will allow the determination of fundamental and atmospheric properties of the components in the system with high precision and accuracy. Methods. To achieve our goals, we use a combined data set from interferometry with the Navy Precision Optical Interferometer (NPOI), photometry with the TESS space observatory, and high-resolution spectroscopy with the HERMES fibre-fed spectrograph at the La Palma observatory. We use the method of spectral disentangling to search for the contribution of a companion star in the observed composite HERMES spectra, to separate the spectral contributions of both components, and to determine orbital elements of the α Dra system. TESS light curves are analysed in an iterative fashion with spectroscopic inference of stellar atmospheric parameters to determine fundamental stellar properties and their uncertainties. Finally, NPOI interferometric measurements are used for determination of the orbital parameters of the system and angular diameters of both binary components. Results. We report the first firm spectroscopic detection of the secondary component in α Dra and deliver disentangled spectra of both binary components. The components’ masses and radii are inferred with high precision and accuracy, and are MA = 3.186 ± 0.044 M⊙, RA = 4.932 ± 0.036 R⊙, and MB = 2.431 ± 0.019 M⊙, RB = 2.326 ± 0.052 R⊙ for the primary and secondary components, respectively. Combined astrometric and spectroscopic analysis yields the semi-major axis of the system, which is ultimately used to derive the dynamical parallax of π = 11.48 ± 0.13 mas, and the distance d = 87.07 ± 1.03 pc to the α Dra system. Evolutionary analysis of both binary components with MESA stellar structure and evolution models suggests the primary is an evolved post-TAMS A-type star, while the companion is a main-sequence A-type star with a convective core mass of Mcc = 0.337 ± 0.011 M⊙. Positions of both binary components in the Kiel- and HR-diagrams suggest a value of the convective core overshooting parameter fov well below 0.010 Hp, and we infer the age of the system to be 310 ± 25 Myr. Conclusions. The inferred near-core mixing properties of both components do not support a dependence of the convective core overshooting on the stellar mass. At the same time, the α Dra system provides extra support to hypothesise that the mass discrepancy in eclipsing spectroscopic double-lined binaries is associated with inferior atmospheric modelling of intermediate- and high-mass stars, and less so with the predictive powerof stellar structure and evolution models as to the amount of near-core mixing and mass of the convective core.
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Kagawa, K., K. Kawai, M. Tani i T. Kobayashi. "XeCl Excimer Laser-Induced Shock Wave Plasma and its Application to Emission Spectrochemical Analysis". Applied Spectroscopy 48, nr 2 (luty 1994): 198–205. http://dx.doi.org/10.1366/0003702944028551.
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A XeCl excimer laser (20 ns, 15–70 mJ) has been focused on a Zn plate in surrounding gas at low pressures (100–1500 Pa). The characteristics of the resultant plasma are examined with the use of a unique time-resolved spectroscopic method. A density jump in the distribution of Zn atoms is clearly observed, which indicates the generation of a shock wave. Furthermore, it is proved that the relationships among the displacement length of the front of the emission of the Zn neutral emission line, the pressure of the ambient gas, and the energy of the laser pulse are in good agreement with the theoretical result for a blast wave explosion. An application is also presented to show that the plasma induced by a blast wave is excellent as a light source for emission spectrochemical analysis because of its very low background emission intensity.
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Zheng, Yaxin, Bahareh Sadeghimakki, Navid M. S. Jahed i Siva Sivoththaman. "Scalable Non-injection Synthesis of Cd-Free Copper Indium Sulfide/Zinc Sulfide Quantum Dots for Third-Gen Photovoltaic Application". MRS Advances 1, nr 30 (2016): 2193–98. http://dx.doi.org/10.1557/adv.2016.536.
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ABSTRACTCopper Indium Sulfide (CIS)-based quantum dots (QDs) are considered as a safer alternative compared to carcinogenic cadmium- and lead-based QDs. Here, we present a facile, high throughput, and non-injection method of synthesizing CIS-based QDs. The structure, shape, size, and crystalline structure of the synthesized QDs were studied using high resolution transmission electron microscopy (HRTEM). The effects of temperature and compositional dependency on the structure and optical properties of the resulting QDs were investigated using elemental, absorption, photoluminescence (PL), and time-resolved spectroscopic analyses. We observed that a gradient increase of temperature during the core growth, as well as addition of excess indium (In) and zinc (Zn) precursors during core and core/shell synthesis, at low growth temperatures, resulted in QDs with improved PL and lifetime. The large Stokes shift, broad emission spectra, and long-lived emission of the synthesized QDs reveal their potential applicability to third generation photovoltaic and optoelectronic devices.
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Quinet, Pascal, i Patrick Palmeri. "Current Status and Developments of the Atomic Database on Rare-Earths at Mons University (DREAM)". Atoms 8, nr 2 (2.05.2020): 18. http://dx.doi.org/10.3390/atoms8020018.
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The main purpose of the Database on Rare Earths At Mons University (DREAM) is to provide the scientific community with updated spectroscopic parameters related to lanthanide atoms (Z = 57–71) in their lowest ionization stages. The radiative parameters (oscillator strengths and transitions probabilities) listed in the database have been obtained over the past 20 years by the Atomic Physics and Astrophysics group of Mons University, Belgium, thanks to a systematic and extensive use of the pseudo-relativistic Hartree-Fock (HFR) method modified for taking core-polarization and core-penetration effects into account. Most of these theoretical results have been validated by the good agreement obtained when comparing computed radiative lifetimes and accurate experimental values measured by the time-resolved laser-induced fluorescence technique. In the present paper, we report on the current status and developments of the database that gathers radiative parameters for more than 72,000 spectral lines in neutral, singly-, doubly-, and triply-ionized lanthanides.
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STEVENS, NATHAN, i DANIEL L. AKINS. "COUMARIN DYE AS A FLUORESCENCE SENSOR FOR METHANOL VAPOR". International Journal of High Speed Electronics and Systems 18, nr 01 (marzec 2008): 195–203. http://dx.doi.org/10.1142/s0129156408005278.
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The sol-gel method has been employed in the fabrication of mesoporous composite films consisting of a nonionic surfactant, Pluronic P123, as the organic component, and silica as the inorganic component. The hybrid nature of these films resulted in their having an internal structure consisting of nanometer size self-assembled organic mesostructures surrounded by a silica framework. These films served as the host matrix for the laser dye coumarin 481 (C481) and an energy transfer complex formed between C481 and J-aggregated meso-tetra(4-sulfonatophenyl)porphyrin (TSPP). Upon exposure to methanol vapor, a rapid and reversible decrease in fluorescence intensity occurs for films containing C481 alone as well as containing both C481 and TSPP. Steady-state and time-resolved spectroscopic studies suggest that the decrease in fluorescence intensity is primarily due to an excited state interaction between methanol and C481; while, additionally, morphological changes within the film appear to play a role for films containing both C481 and TSPP.
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Tong, William G., i Dennis A. Chen. "Doppler-Free Spectroscopy Based on Phase Conjugation by Degenerate Four-Wave Mixing in Hollow Cathode Discharge". Applied Spectroscopy 41, nr 4 (maj 1987): 586–90. http://dx.doi.org/10.1366/0003702874448599.
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Optical phase conjugation in the hollow cathode lamp by degnerate four-wave mixing is a novel analytical laser spectroscopic method in which a laser beam is generated as the signal beam. With the use of a demountable hollow cathode discharge cell and a continuous-wave dye laser, the signal beam is clearly visible to the naked eye when 1 µg of sodium is placed inside the cathode cavity. Since the signal beam is a time-reversed replica of the probe laser beam, highly efficient optical signal detection can be performed with minimum optical background noise. Since the signal is Doppler-free with negligible Lorentzian broadening (30 Torr discharge pressure), it provides excellent spectral resolution. Sodium D2 hyperfine lines of 3s 2S1/2 ( F' = 2) → 3p 2P3/2 ( F = 3) and 3s 2S1/2 ( F' = 1) → 3p 2P3/2 ( F = 0) were resolved. In addition to excellent spectral resolution and ease of signal detection, the technique also offers unique properties of optical phase conjugation.
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Farkas, József, i István Dalmadi. "Near infrared and fluorescence spectroscopic methods and electronic nose technology for monitoring foods". Progress in Agricultural Engineering Sciences 5, nr 1 (1.12.2009): 1–29. http://dx.doi.org/10.1556/progress.5.2009.1.
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There is a clear need for application of proper methods for measuring food quality and safety in the globalized food-webs. Numerous instrumental methods have been established in the course of the 20th century and are developing further, together with data analysis techniques, for such purposes. Among them, near-infrared and fluorescence spectroscopic methods and chemical sensor arrays called electronic noses show particular promise for rapid, non-destructive, non-invasive and cost-effective ways for assessing changes and enhancing control during processing and storage of foods. Their key advantages as analytical tools are 1) their relatively high speed of analysis, 2) the lack of a need to carry out complex sample preparation or processing, 3) their relatively low cost, and 4) their suitability for on-line monitoring or quality control. The present survey attempts to demonstrate examples from the above areas, limiting itself mainly to monitoring some quality indices which contribute to the functionality or acceptability of foods as affected by alternative processing technologies, or loss of freshness/microbial safety, or developing spoilage during storage and marketing. These instrumental methods are correlative techniques: they must be calibrated first against (traditional) reference properties, and the instrumental data are evaluated with the help of chemometric methods. Near-infrared (NIR) spectroscopy can be used in either the reflectance or the transmittance mode. NIR spectra transformed to mathematical derivatives allows subtle spectrum changes to be resolved. Selected examples from the extensive NIRS literature relate to assessment of the quality of frozen fish, predicting cooking loss of chicken patties, detecting complex physico-chemical changes of minced meat as a function of the intensity of high hydrostatic pressure treatment, comparing changes of NIR spectrometric “fingerprints” caused by gamma radiation or high pressure pasteurization of liquid egg white. Changes of NIR spectra reflect several parameters which suit the evaluation of loss of freshness, and onset of spoilage of various foods. NIR spectroscopy shows an application potential for rapid detection of bacterial or mould contamination. It may serve as a tool for detecting initial stages of mobilization processes during germination of cereal grains, or even for GMO screening. Spectrofluorometic measurements have shown potential, e.g. to monitor lipid oxidation and development of meat rancidity, to differentiate between raw and processed milks, and to monitor fish and egg freshness. Electronic noses containing chemical sensor arrays offer a rapid method for evaluation of head-space volatiles of food samples, important for characterizing quality and safety. Such gas sensors may be able to classify storage time, and determine spoilage, either earlier or at the same time as the human senses, or “sniffing out” bacterial pathogens or (toxigenic) fungal growth on certain foods. Electronic nose sensing is also a promising method for detecting quality changes of fruit- and vegetable products non-destructively. In relation to some examples to be presented in the paper, certain software developments as qualitative classification tools made by Hungarian scientists will be pointed out.
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RAO, C. N. R., K. S. SUBRAHMANYAM, H. S. S. RAMAKRISHNA MATTE i A. GOVINDARAJ. "GRAPHENE: SYNTHESIS, FUNCTIONALIZATION AND PROPERTIES". Modern Physics Letters B 25, nr 07 (20.03.2011): 427–51. http://dx.doi.org/10.1142/s0217984911025961.
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Graphenes with varying number of layers can be synthesized by different strategies. Thus, single-layer graphene is obtained by the reduction of single layer graphene oxide, CVD and other methods besides micromechanical cleavage. Few-layer graphenes are prepared by the conversion of nanodiamond, arc-discharge of graphite and other means. We briefly present the various methods of synthesis and the nature of graphenes obtained. We then discuss the various properties of graphenes. The remarkable property of graphene of quenching fluorescence of aromatic molecules is shown to be associated with photo-induced electron transfer, on the basis of fluorescence decay and time-resolved transient absorption spectroscopic measurements. The interaction of electron donor and acceptor molecules with few-layer graphene samples has been discussed. Decoration of metal nano-particles on graphene sheets and the resulting changes in electronic structure are examined. Few-layer graphenes exhibit ferromagnetic features along with antiferromagnetic properties, independent of the method of preparation. Graphene-like MoS 2 and WS 2 have been prepared by chemical methods, and the materials are characterized by electron microscopy, atomic force microscopy (AFM) and other methods. Boron nitride analogues of graphene have been obtained by a simple chemical procedure starting with boric acid and urea and have been characterized by various techniques.
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RAO, C. N. R., K. S. SUBRAHMANYAM, H. S. S. RAMAKRISHNA MATTE, URMIMALA MAITRA, KOTA MOSES i A. GOVINDARAJ. "GRAPHENE: SYNTHESIS, FUNCTIONALIZATION AND PROPERTIES". International Journal of Modern Physics B 25, nr 30 (10.12.2011): 4107–43. http://dx.doi.org/10.1142/s0217979211059358.
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Graphenes with varying number of layers can be synthesized by different strategies. Thus, single-layer graphene is obtained by the reduction of single layer graphene oxide, CVD and other methods besides micromechanical cleavage. Few-layer graphenes are prepared by the conversion of nanodiamond, arcdischarge of graphite and other means. We briefly present the various methods of synthesis and the nature of graphenes obtained. We then discuss the various properties of graphenes. The remarkable property of graphene of quenching fluorescence of aromatic molecules is shown to be associated with photo-induced electron transfer, on the basis of fluorescence decay and time-resolved transient absorption spectroscopic measurements. The interaction of electron donor and acceptor molecules with few-layer graphene samples has been discussed. Decoration of metal nano-particles on graphene sheets and the resulting changes in electronic structure are examined. Few-layer graphenes exhibit ferromagnetic features along with antiferromagnetic properties, independent of the method of preparation. Graphene-like MoS 2 and WS 2 have been prepared by chemical methods, and the materials are characterized by electron microscopy, atomic force microscopy (AFM) and other methods. Boron nitride analogues of graphene have been obtained by a simple chemical procedure starting with boric acid and urea and have been characterized by various techniques.
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Kimura, Tetsunari, Takehiko Tosha, Yoshitsugu Shiro i Minoru Kubo. "1P097 Development of micro-channel flow-flash method for time-resolved spectroscopic study of enzymatic reactions(02.Heme proteins,Poster,The 51st Annual Meeting of the Biophysical Society of Japan)". Seibutsu Butsuri 53, supplement1-2 (2013): S122. http://dx.doi.org/10.2142/biophys.53.s122_1.
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Kakkad, D., E. Sani, A. F. Rojas, Nicolas D. Mallmann, S. Veilleux, Franz E. Bauer, F. Ricci i in. "BASS XXXI: Outflow scaling relations in low redshift X-ray AGN host galaxies with MUSE". Monthly Notices of the Royal Astronomical Society 511, nr 2 (17.01.2022): 2105–24. http://dx.doi.org/10.1093/mnras/stac103.
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ABSTRACT Ionized gas kinematics provide crucial evidence of the impact that active galactic nuclei (AGNs) have in regulating star formation in their host galaxies. Although the presence of outflows in AGN host galaxies has been firmly established, the calculation of outflow properties such as mass outflow rates and kinetic energy remains challenging. We present the [O iii]λ5007 ionized gas outflow properties of 22 z<0.1 X-ray AGN, derived from the BAT AGN Spectroscopic Survey using MUSE/VLT. With an average spatial resolution of 1 arcsec (0.1–1.2 kpc), the observations resolve the ionized gas clouds down to sub-kiloparsec scales. Resolved maps show that the [O iii] velocity dispersion is, on average, higher in regions ionized by the AGN, compared to star formation. We calculate the instantaneous outflow rates in individual MUSE spaxels by constructing resolved mass outflow rate maps, incorporating variable outflow density and velocity. We compare the instantaneous values with time-averaged outflow rates by placing mock fibres and slits on the MUSE field-of-view, a method often used in the literature. The instantaneous outflow rates (0.2–275 M⊙ yr−1) tend to be two orders of magnitude higher than the time-averaged outflow rates (0.001–40 M⊙ yr−1). The outflow rates correlate with the AGN bolometric luminosity (Lbol ∼ 1042.71–1045.62 erg s−1) but we find no correlations with black hole mass (106.1–108.9 M⊙), Eddington ratio (0.002–1.1), and radio luminosity (1021–1026 W Hz−1). We find the median coupling between the kinetic energy and Lbol to be 1 per cent, consistent with the theoretical predictions for an AGN-driven outflow.
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GROSS, KEVIN C., i GLEN P. PERRAM. "THE PHENOMENOLOGY OF HIGH EXPLOSIVE FIREBALLS FROM FIELDED SPECTROSCOPIC AND IMAGING SENSORS FOR EVENT CLASSIFICATION". International Journal of High Speed Electronics and Systems 18, nr 01 (marzec 2008): 19–29. http://dx.doi.org/10.1142/s0129156408005102.
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Conventional munitions emit intense radiation upon detonation which spans much of the electromagnetic spectrum. The phenomenology of time-resolved visible, near- and mid-IR spectra from these fast transient events is poorly understood. The observed spectrum is driven by many factors including the type, size and age of the chemical explosive, method of detonation, interaction with the environment, and the casing used to enclose the explosive. Midwave infrared emissions (1800–6000 cm -1, 1.67–5.56 μm) from a variety of conventional military munitions were collected with a Fourier transform spectrometer (16 cm-1, 21 Hz) to assess the possibility of event classification via remotely sensed spectra. Conventional munitions fireballs appear to be graybodies in the midwave. Modeling the spectra as a single-temperature Planckian (appropriately modified by atmospheric transmittance) provided key features for classification and substantially reduced the dimensionality of the data. The temperature cools from ~1800 K to ambient conditions in 3–5 s, often following an exponential decay with a rate near 1 s-1 second. A systematic, large residual spanning 2050–2250 cm -1 was consistently observed shortly after detonation and may be attributable to hot CO 2 emission at the periphery of the fireball. For two different explosive types detonated under similar conditions, features based on the temperature, area and fit residuals could be used to distinguish between them. This paper will present the phenomenology of detonation fireballs and explore the utility of physics-based features for explosive classification.
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Bashmakova, Nataliia V., Yevgeniy O. Shaydyuk, Andriy M. Dmytruk, Tomasz Świergosz, Olexiy D. Kachkovsky, Kevin D. Belfield, Mykhailo V. Bondar i Wiktor Kasprzyk. "Nature of Linear Spectral Properties and Fast Electronic Relaxations in Green Fluorescent Pyrrolo[3,4-c]Pyridine Derivative". International Journal of Molecular Sciences 22, nr 11 (25.05.2021): 5592. http://dx.doi.org/10.3390/ijms22115592.
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The electronic nature of 4-hydroxy-1H-pyrrolo[3,4-c]pyridine-1,3,6(2H,5H)-trione (HPPT) was comprehensively investigated in liquid media at room temperature using steady-state and time-resolved femtosecond transient absorption spectroscopic techniques. The analysis of the linear photophysical and photochemical parameters of HPPT, including steady-state absorption, fluorescence and excitation anisotropy spectra, along with the lifetimes of fluorescence emission and photodecomposition quantum yields, revealed the nature of its large Stokes shift, specific changes in the permanent dipole moments under electronic excitation, weak dipole transitions with partially anisotropic character, and high photostability. Transient absorption spectra of HPPT were obtained with femtosecond resolution and no characteristic solvate relaxation processes in protic (methanol) solvent were revealed. Efficient light amplification (gain) was observed in the fluorescence spectral range of HPPT, but no super-luminescence and lasing phenomena were detected. The electronic structure of HPPT was also analyzed with quantum-chemical calculations using a DFT/B3LYP method and good agreement with experimental data was shown. The development and investigation of new pyrrolo[3,4-c]pyridine derivatives are important due to their promising fluorescent properties and potential for use in physiological applications.
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Weng, Wubin, Jim Larsson, Joakim Bood, Marcus Aldén i Zhongshan Li. "Quantitative Hydrogen Chloride Detection in Combustion Environments Using Tunable Diode Laser Absorption Spectroscopy with Comprehensive Investigation of Hot Water Interference". Applied Spectroscopy 76, nr 2 (4.01.2022): 207–15. http://dx.doi.org/10.1177/00037028211060866.
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Hydrogen chloride (HCl) monitoring during combustion/gasification of biomass fuels and municipal solid waste, such as polyvinyl chloride (PVC) and food residues, is demanded to avoid the adverse effect of HCl to furnace operation and to improve the quality of the gas products. Infrared tunable diode laser absorption spectroscopy (IR-TDLAS) is a feasible nonintrusive in-situ method for HCl measurements in harsh environments. In the present work, the measurement was performed using the R(3) line of the ν2 vibrational band of HCl at 5739.25 cm–1 (1742.4 nm). Water vapor is ubiquitous in combustion/gasification environments, and its spectral interference is one of the most common challenges for IR-TDLAS. Spectral analysis based on the current well-known databases was found to be insufficient to achieve an accurate measurement. The lack of accurate temperature-dependent water spectra can introduce thousands parts per million (ppm) HCl overestimation. For the first time, accurate spectroscopic data of temperature-dependent water spectra near 5739.3 cm–1 were obtained based on a systematic experimental investigation of the hot water lines in a well-controlled, hot flue gas with a temperature varying from 1100 to 1950 K. With the accurate knowledge of hot water interference, the HCl TDLAS system can achieve a detection limit of about 100 ppm⋅m at around 1500 K, and simultaneously the gas temperature can be derived. The technique was applied to measure the temporally resolved HCl release and local temperature over burning PVC particles in hot flue gas at 1790 K.
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Kára, J., S. Zharikov, M. Wolf, H. Kučáková, P. Cagaš, A. L. Medina Rodriguez i M. Mašek. "The period-gap cataclysmic variable CzeV404 Her: A link between SW Sex and SU UMa systems". Astronomy & Astrophysics 652 (sierpień 2021): A49. http://dx.doi.org/10.1051/0004-6361/202140958.
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Context. We present a new study of the eclipsing cataclysmic variable CzeV404 Her (Porb = 0.098 d) that is located in the period gap. Aims. This report determines the origin of the object and the system parameters and probes the accretion flow structure of the system. Methods. We conducted simultaneous time-resolved photometric and spectroscopic observations of CzeV404 Her. We applied our light-curve modelling techniques and the Doppler tomography method to determine the system parameters and analyse the structure of the accretion disk. Results. We found that the system has a massive white dwarf MWD = 1.00(2) M⊙, a mass ratio of q = 0.16, and a relatively hot secondary with an effective temperature T2 = 4100(50) K. The system inclination is i = 78.8°. The accretion disk spreads out to the tidal limitation radius and has an extended hot spot or line region. The hot spot or line is hotter than the remaining outer part of the disk in quiescence or in intermediate state, but does not stand out completely from the disk flux in (super)outbursts. Conclusions. We claim that this object represents a link between two distinct classes of SU UMa-type and SW Sex-type cataclysmic variables. The accretion flow structure in the disk corresponds to the SW Sex systems, but the physical conditions inside the disk fit the behaviour of SU UMa-type objects.
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Li, D., X. Yang, X. Y. Bai, J. T. Su, Z. J. Ning, W. Cao i Y. Y. Deng. "Doppler shift oscillations of a sunspot detected by CYRA and IRIS". Astronomy & Astrophysics 642 (październik 2020): A231. http://dx.doi.org/10.1051/0004-6361/202039007.
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Context. The carbon monoxide (CO) molecular line at around 46655 Å in solar infrared spectra is often used to investigate the dynamic behavior of the cold heart of the solar atmosphere, i.e., sunspot oscillation, especially at the sunspot umbra. Aims. We investigated sunspot oscillation at Doppler velocities of the CO 7-6 R67 and 3-2 R14 lines that were measured by the Cryogenic Infrared Spectrograph (CYRA), as well as the line profile of Mg II k line that was detected by the Interface Region Imaging Spectrograph (IRIS). Methods. A single Gaussian function is applied to each CO line profile to extract the line shift, while the moment analysis method is used for the Mg II k line. Then the sunspot oscillation can be found in the time–distance image of Doppler velocities, and the quasi-periodicity at the sunspot umbra are determined from the wavelet power spectrum. Finally, the cross-correlation method is used to analyze the phase relation between different atmospheric levels. Results. At the sunspot umbra, a periodicity of roughly 5 min is detected at the Doppler velocity range of the CO 7-6 R67 line that formed in the photosphere, while a periodicity of around 3 min is discovered at the Doppler velocities of CO 3-2 R14 and Mg II k lines that formed in the upper photosphere or the temperature minimum region and the chromosphere. A time delay of about 2 min is measured between the strong CO 3-2 R14 line and the Mg II k line. Conclusions. Based on the spectroscopic observations from the CYRA and IRIS, the 3 min sunspot oscillation can be spatially resolved in the Doppler shifts. It may come from the upper photosphere or the temperature minimum region and then propagate to the chromosphere, which might be regarded as a propagating slow magnetoacoustic wave.
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BIBI, SAJIDA, SHAHAB ALI, SHAHI DIN, IKRAM ULLAH, ABDUR RAUF, MUHAMMAD ARIF, MUHAMMAD UMAR i in. "Chemical composition and anti-microbial analysis of Mentha arvensis L. and Thymus linearis Benth. essential oils of leaves". Romanian Biotechnological Letters 26, nr 5 (20.09.2021): 2893–900. http://dx.doi.org/10.25083/rbl/26.5/2893.2900.
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This study was performed to evaluate the chemical composition of the essential oils of Mentha arvensis and Thymus linearis and their antimicrobial activities. The complexity of the essential oils is a basic challenge for determining their reliable and accurate compositional data. Rapid advances in spectroscopic and chromatographic techniques have resolved this challenge to a large extent by examining essential oils. Essential oils were analyzed through Gas Chromatography-Mass Spectrometry (GC-MS) following extraction through steam distillation from their leaves for the first time in Miandam, District Swat, KP, Pakistan. The GC-MS analysis revealed 26 and 25 components in the essential oil of Mentha arvensis and Thymus linearis respectively. The major components were carvone (23.53%), P-Cymen-2-ol (20.35%), and caryophyllene oxide (18.81%) in Mentha arvensis but Thymus linearis has Thymol (2-isopropyl-5-methyl phenol) (40%), O-Cymene (2-Isopropyltoluene) (14.95%) and beta-bisbolene (12.54%). The essential oils of both plants showed bactericidal activities against five different bacterial strains (i.e. Escherichia coli, Staphylococcus aureus, Klesiella pneumonia, Bacillus subtilis, and Pseudomonas aeruginosa) during disc diffusion method and therefore it is suggested that they may be used as a natural antiseptic and could play important roles in food and pharmaceutical industry.
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Liu, Wen, Liping Wang, Bin Wang, Yanchao Xu, Guoliang Zhu, Mengmeng Lan, Weiming Zhu i Kunlai Sun. "Diketopiperazine and Diphenylether Derivatives from Marine Algae-Derived Aspergillus versicolor OUCMDZ-2738 by Epigenetic Activation". Marine Drugs 17, nr 1 (22.12.2018): 6. http://dx.doi.org/10.3390/md17010006.
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A chemical-epigenetic method was used to enhance the chemodiversity of a marine algicolous fungus. Apart from thirteen known compounds, (+)-brevianamide R ((+)-3), (‒)-brevianamide R ((‒)-3), (+)-brevianamide Q ((+)-4), (‒)-brevianamide Q ((‒)-4), brevianamide V ((+)-5), brevianamide W ((‒)-5), brevianamide K (6), diorcinol B (7), diorcinol C (8), diorcinol E (9), diorcinol J (10), diorcinol (11), 4-methoxycarbonyldiorcinol (12), two new compounds, (+)- and (‒)-brevianamide X ((+)- and (‒)- 2)), as well as a new naturally occurring one, 3-[6-(2-methylpropyl)-2-oxo-1H-pyrazin-3-yl]propanamide (1), were isolated from chemical-epigenetic cultures of Aspergillus versicolor OUCMDZ-2738 with 10 µM vorinostat (SAHA). Compared to cultures in the same medium without SAHA, compounds 1–4, 8, 9, 11, and 12 were solely observed under SAHA condition. The structures of these compounds were elucidated based on spectroscopic analysis, specific rotation analysis, ECD, and X-ray crystallographic analysis. (±)-3, (±)-4, and (±)-5 were further resolved into the corresponding optically pure enantiomers and their absolute configurations were determined for the first time. Compounds 11 and 12 showed selective antibacterial against Pseudomonas aeruginosa with a minimum inhibitory concentration (MIC) of 17.4 and 13.9 μM, respectively. Compound 10 exhibited better α-glucosidase inhibitory activity than the assay control acarbose with IC50 values of 117.3 and 255.3 μM, respectively.
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Abbene, Leonardo, Gaetano Gerardi, Fabio Principato, Manuele Bettelli, Paul Seller, Matthew C. Veale, Oliver Fox i in. "Dual-polarity pulse processing and analysis for charge-loss correction in cadmium–zinc–telluride pixel detectors". Journal of Synchrotron Radiation 25, nr 4 (26.06.2018): 1078–92. http://dx.doi.org/10.1107/s1600577518006422.
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Charge losses at the inter-pixel gap are typical drawbacks in cadmium–zinc–telluride (CZT) pixel detectors. In this work, an original technique able to correct charge losses occurring after the application of charge-sharing addition (CSA) is presented. The method, exploiting the strong relation between the energy after CSA and the beam position at the inter-pixel gap, allows the recovery of charge losses and improvements in energy resolution. Sub-millimetre CZT pixel detectors were investigated with both uncollimated radiation sources and collimated synchrotron X-rays, at energies below and above the K-shell absorption energy of the CZT material. The detectors are DC coupled to fast and low-noise charge-sensitive preamplifiers (PIXIE ASIC) and followed by a 16-channel digital readout electronics, performing multi-parameter analysis (event arrival time, pulse shape, pulse height). Induced-charge pulses with negative polarity were also observed in the waveforms from the charge-sensitive preamplifiers (CSPs) at energies >60 keV. The shape and the height of these pulses were analysed, and their role in the mitigation of charge losses in CZT pixel detectors. These activities are in the framework of an international collaboration on the development of energy-resolved photon-counting systems for spectroscopic X-ray imaging (5–140 keV).
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Maklygina, Yu S., I. D. Romanishkin, A. S. Skobeltsin, T. A. Savelyeva, A. A. Potapov, G. V. Pavlova, I. V. Chekhonin, O. I. Gurina i V. B. Loschenov. "Time-resolved fluorescence imaging technique for rat brain tumors analysis". Journal of Physics: Conference Series 2058, nr 1 (1.10.2021): 012028. http://dx.doi.org/10.1088/1742-6596/2058/1/012028.
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Abstract The paper presents a new approach to assessing the state of tissues that differ in phenotype and in the degree of immunocompetent cells activity using photosensitizers (PS) and time-resolved fluorescence analysis methods. The main attention is paid to the detection of differences between tumor cells and tumor-associated macrophages (TAM) using spectroscopic and microscopic methods by the fluorescent kinetics signal and the difference in the accumulation of PS (the accumulation is several times greater in macrophages). The results of the PS photoluminescence study were obtained using two different techniques: time-resolved spectroscopy and time-resolved fluorescence microscopy (FLIM). Time-resolved spectroscopic analysis of the PS fluorescence lifetime was performed on adult female rats with induced C6 glioma in vivo. 5-ALA-induced Pp IX, which is widely used in clinical practice for carrying out effective conduction photodiagnostics and PDT, was used as the PS.
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Masutani, Koji, Hisashi Sugisawa, Akira Yokota, Yukio Furukawa i Mitsuo Tasumi. "Asynchronous Time-Resolved Fourier Transform Infrared Spectroscopy". Applied Spectroscopy 46, nr 4 (kwiecień 1992): 560–67. http://dx.doi.org/10.1366/0003702924124871.
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A novel asynchronous time-resolved FT-IR spectrophotometer based on a conventional continuous-scan interferometer has been developed. In contrast to the existing methods, this method does not require the synchronization between the signal for time resolving and that for the sampling of the A/D converter. The signal-processing assembly for time-resolved measurements consists of a pulse generator, a pulse delay circuit, a gate circuit, and a low-pass filter. This assembly can be attached to any conventional FT-IR spectrophotometer. By this method, time-resolved spectra without any spectral distortion or artifacts can be obtained for repetitive fast phenomena. As an application of this method, time-resolved FT-IR measurements have been carried out for the reorientation process in a ferroelectric liquid crystal induced by the reversal of external electric field, and a time resolution of 0.5 μs or less has been achieved. The present system is best suited for observing repetitive transient phenomena with lifetimes in the range from approximately 1 μs to 1 ms.
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Yuzawa, Tetsuro, Chihiro Kato, Michael W. George i Hiro-O. Hamaguchi. "Nanosecond Time-Resolved Infrared Spectroscopy with a Dispersive Scanning Spectrometer". Applied Spectroscopy 48, nr 6 (czerwiec 1994): 684–90. http://dx.doi.org/10.1366/000370294774368947.
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A nanosecond time-resolved infrared spectroscopic system based on a dispersive scanning spectrometer has been constructed. This is an advanced version of a similar system reported in a previous paper; the time resolution has been improved from 1 μs to 50 ns and the sensitivity from 10−4 in intensity changes to 10−6. These have been achieved by the use of a high-temperature ceramic infrared light source, a photovoltaic MCT detector, and a low-noise, wide-band preamplifier developed specifically for the present purpose. Time-resolved infrared spectra of a few samples of photochemical and photobiological interests are presented to show the capability of the system. The origin of the thermal artifacts, which have been found to hamper the time-resolved infrared measurements seriously, is shown to be due to the transient reflectance change induced by a small temperature jump. The future prospect of time-resolved infrared spectroscopy is discussed with reference to other methods including infrared laser spectroscopy and Fourier transform infrared spectroscopy.
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Cañameras, R., S. Schuldt, S. H. Suyu, S. Taubenberger, T. Meinhardt, L. Leal-Taixé, C. Lemon, K. Rojas i E. Savary. "HOLISMOKES". Astronomy & Astrophysics 644 (grudzień 2020): A163. http://dx.doi.org/10.1051/0004-6361/202038219.
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We present a systematic search for wide-separation (with Einstein radius θE ≳ 1.5″), galaxy-scale strong lenses in the 30 000 deg2 of the Pan-STARRS 3π survey on the Northern sky. With long time delays of a few days to weeks, these types of systems are particularly well-suited for catching strongly lensed supernovae with spatially-resolved multiple images and offer new insights on early-phase supernova spectroscopy and cosmography. We produced a set of realistic simulations by painting lensed COSMOS sources on Pan-STARRS image cutouts of lens luminous red galaxies (LRGs) with redshift and velocity dispersion known from the sloan digital sky survey (SDSS). First, we computed the photometry of mock lenses in gri bands and applied a simple catalog-level neural network to identify a sample of 1 050 207 galaxies with similar colors and magnitudes as the mocks. Second, we trained a convolutional neural network (CNN) on Pan-STARRS gri image cutouts to classify this sample and obtain sets of 105 760 and 12 382 lens candidates with scores of pCNN > 0.5 and > 0.9, respectively. Extensive tests showed that CNN performances rely heavily on the design of lens simulations and the choice of negative examples for training, but little on the network architecture. The CNN correctly classified 14 out of 16 test lenses, which are previously confirmed lens systems above the detection limit of Pan-STARRS. Finally, we visually inspected all galaxies with pCNN > 0.9 to assemble a final set of 330 high-quality newly-discovered lens candidates while recovering 23 published systems. For a subset, SDSS spectroscopy on the lens central regions proves that our method correctly identifies lens LRGs at z ∼ 0.1–0.7. Five spectra also show robust signatures of high-redshift background sources, and Pan-STARRS imaging confirms one of them as a quadruply-imaged red source at zs = 1.185, which is likely a recently quenched galaxy strongly lensed by a foreground LRG at zd = 0.3155. In the future, high-resolution imaging and spectroscopic follow-up will be required to validate Pan-STARRS lens candidates and derive strong lensing models. We also expect that the efficient and automated two-step classification method presented in this paper will be applicable to the ∼4 mag deeper gri stacks from the Rubin Observatory Legacy Survey of Space and Time (LSST) with minor adjustments.
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Weidner, H., i R. E. Peale. "Event-Locked Time-Resolved Fourier Spectroscopy". Applied Spectroscopy 51, nr 8 (sierpień 1997): 1106–12. http://dx.doi.org/10.1366/0003702971941917.
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A low-cost method of adding time-resolving capability to commercial Fourier transform spectrometers with a continuously scanning Michelson interferometer has been developed. This method is specifically designed to eliminate noise and artifacts caused by mirror-speed variations in the interferometer. The method exists of two parts: (1) a novel timing scheme for synchronizing the transient events under study and the digitizing of the interferogram and (2) a mathematical algorithm for extracting the spectral information from the recorded data. The novel timing scheme is a modification of the well-known interleaved, or stroboscopic, method. It achieves the same timing accuracy, signal-to-noise ratio, and freedom from artifacts as step-scan time-resolving Fourier spectrometers by locking the sampling of the interferogram to a stable time base rather than to the occurrences of the HeNe fringes. The necessary pathlength-difference information at which samples are taken is obtained from a record of the mirror speed. The resulting interferograms with uneven pathlength-difference spacings are transformed into wavenumber space by least-squares fits of periodic functions. Spectra from the far-infrared to the upper visible at resolutions up to 0.2 cm−1 are used to demonstrate the utility of this method.
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Raspollini, Piera, Enrico Arnone, Flavio Barbara, Massimo Bianchini, Bruno Carli, Simone Ceccherini, Martyn P. Chipperfield i in. "Level 2 processor and auxiliary data for ESA Version 8 final full mission analysis of MIPAS measurements on ENVISAT". Atmospheric Measurement Techniques 15, nr 6 (28.03.2022): 1871–901. http://dx.doi.org/10.5194/amt-15-1871-2022.
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Abstract. High quality long-term data sets of altitude-resolved measurements of the atmospheric composition are important because they can be used both to study the evolution of the atmosphere and as a benchmark for future missions. For the final ESA reprocessing of MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) on ENVISAT (ENViromental SATellite) data, numerous improvements were implemented in the Level 2 (L2) processor Optimised Retrieval Model (ORM) version 8.22 (V8) and its auxiliary data. The implemented changes involve all aspects of the processing chain, from the modelling of the measurements with the handling of the horizontal inhomogeneities along the line of sight to the use of the optimal estimation technique to retrieve the minor species, from a more sensitive approach to detecting the spectra affected by clouds to a refined method for identifying low quality products. Improvements in the modelling of the measurements were also obtained with an update of the used spectroscopic data and of the databases providing the a priori knowledge of the atmosphere. The HITRAN_mipas_pf4.45 spectroscopic database was finalised with new spectroscopic data verified with MIPAS measurements themselves, while recently measured cross-sections were used for the heavy molecules. The Level 2 Initial Guess (IG2) data set, containing the climatology used by the MIPAS L2 processor to generate the initial guess and interfering species profiles when the retrieved profiles from previous scans are not available, was improved taking into account the diurnal variation of the profiles defined using climatologies from both measurements and models. Horizontal gradients were generated using the ECMWF ERA-Interim data closest in time and space to the MIPAS data. Further improvements in the L2 V8 products derived from the use of the L1b V8 products, which were upgraded to reduce the instrumental temporal drift and to handle the abrupt changes in the calibration gain. The improvements introduced into the ORM V8 L2 processor and its upgraded auxiliary data, together with the use of the L1b V8 products, lead to the generation of the MIPAS L2 V8 products, which are characterised by an increased accuracy, better temporal stability and a greater number of retrieved species.
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Maíz Apellániz, J., R. H. Barbá, S. Simón-Díaz, A. Sota, E. Trigueros Páez, J. A. Caballero i E. J. Alfaro. "Lucky Spectroscopy, an equivalent technique to Lucky Imaging". Astronomy & Astrophysics 615 (lipiec 2018): A161. http://dx.doi.org/10.1051/0004-6361/201832885.
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Context. Many massive stars have nearby companions whose presence hamper their characterization through spectroscopy. Aims. We want to obtain spatially resolved spectroscopy of close massive visual binaries to derive their spectral types. Methods. We obtained a large number of short long-slit spectroscopic exposures of five close binaries under good seeing conditions. We selected those with the best characteristics, extracted the spectra using multiple-profile fitting, and combined the results to derive spatially separated spectra. Results. We demonstrate the usefulness of Lucky Spectroscopy by presenting the spatially resolved spectra of the components of each system, in two cases with separations of only ~0.′′3. Those are δ Ori Aa+Ab (resolved in the optical for the first time) and σ Ori AaAb+B (first time ever resolved). We also spatially resolve 15 Mon AaAb+B, ζ Ori AaAb+B (both previously resolved with GOSSS, the Galactic O-Star Spectroscopic Survey), and η Ori AaAb+B, a system with two spectroscopic B+B binaries and a fifth visual component. The systems have in common that they are composed of an inner pair of slow rotators orbited by one or more fast rotators, a characteristic that could have consequences for the theories of massive star formation.