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1
Nicolodi, Daniele, Bérengère Argence, Wei Zhang, Rodolphe Le Targat, Giorgio Santarelli, and Yann Le Coq. "Spectral purity transfer between optical wavelengths at the 10−18 level." Nature Photonics 8, no. 3 (January 19, 2014): 219–23. http://dx.doi.org/10.1038/nphoton.2013.361.
Повний текст джерела
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Xue, Hang, Yang Yang, Xiping Xu, Ning Zhang, and Yaowen Lv. "Application of Near Infrared Hyperspectral Imaging Technology in Purity Detection of Hybrid Maize." Applied Sciences 13, no. 6 (March 9, 2023): 3507. http://dx.doi.org/10.3390/app13063507.
Повний текст джерелаАнотація:
Seed purity has an important impact on the yield and quality of maize. Studying the spectral characteristics of hybrid maize and exploring the rapid and non-destructive detection method of seed purity are conducive to the development of maize seed breeding and planting industry. The near-infrared spectral data of five hybrid maize seeds were collected in the laboratory. After eliminating the obvious noises, the multiple scattering correction (MSC) was applied to pretreat the spectra. PLS-DA, KNN, NB, RF, SVM-Linear, SVM-Polynomial, SVM-RBF, and SVM-Sigmaid were used as pattern recognition methods to classify five different types of maize seeds. The recognition accuracy of the models established by different algorithms was 84.4%, 97.6, 100%, 96.4, 99.2%, 100%, 98.4%, and 91.2%, respectively. The results indicated that hyperspectral imaging technology could be used for variety classification and the purity detection of maize seeds. To improve the calculation speed, using the principal component analysis (PCA) to reduce the dimension of hyperspectral data, we then established classification models based on characteristic wavelengths. The recognition accuracy of the models established by different algorithms was 80.8%, 86.8%, 98%, 94%, 96.8%, 98.4%, 94.4%, and 88.2%, respectively. The results showed that the selected sensitive wavelengths could be used to detect the purity of maize seeds. The overall results indicated that it was feasible to use near-infrared hyperspectral imaging technology for the variety identification and purity detection of maize seeds. This study also provides a new method for rapid and non-destructive detection of seed purity.
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Park, Kyungdeuk, Dongjin Lee, and Heedeuk Shin. "Tunability of the Nonlinear Interferometer Method for Anchoring Constructive Interference Patterns on the ITU-T Grid." Applied Sciences 11, no. 4 (February 5, 2021): 1429. http://dx.doi.org/10.3390/app11041429.
Повний текст джерелаАнотація:
Recently, a method of engineering the quantum states with a nonlinear interferometer was proposed to achieve precise state engineering for near-ideal single-mode operation and near-unity efficiency (L. Cui et al., Phys. Rev. A 102, 033718 (2020)), and the high-purity bi-photon states can be created without degrading brightness and collection efficiency. Here, we study the coarse or fine tunability of the nonlinear interference method to match constructive interference patterns into a transmission window of standard 100-GHz DWDM channels. The joint spectral intensity spectrum is measured for various conditions of the nonlinear interference effects. We show that the method has coarse- and fine-tuning ability while maintaining its high spectral purity. We expect that our results expand the usefulness of the nonlinear interference method. The photon-pair generation engineered via this method will be an excellent practical source of the quantum information process.
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Barbieri, Piero, Cecilia Clivati, Marco Pizzocaro, Filippo Levi, and Davide Calonico. "Spectral purity transfer with 5 × 10−17 instability at 1 s using a multibranch Er:fiber frequency comb." Metrologia 56, no. 4 (July 5, 2019): 045008. http://dx.doi.org/10.1088/1681-7575/ab2b0f.
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Lin, Zhong-Ping, and Walter A. Aue. "Gas-phase luminescence of aromatic carbonyl compounds in excited nitrogen at atmospheric pressure." Canadian Journal of Chemistry 78, no. 1 (January 15, 2000): 95–117. http://dx.doi.org/10.1139/v99-203.
Повний текст джерелаАнотація:
Certain types of aroyl compounds such as benzaldehyde, acetophenone, benzophenone, and anthraquinone produce intense gas-phase luminescence in excited nitrogen at atmospheric pressure. This luminescence was measured in pressure ranges of 1.001.67 atm and temperature ranges of 343473 K. A novel, radioactively (Ni-63) stimulated, high-voltage( [Formula: see text]1750 V/mm), low-current ( [Formula: see text]35 nA) discharge in high-purity nitrogen was used for gas chromatographic detection and spectral excitation. The gas-phase luminescence spectra of about sixty aroyl compounds - introduced as gas chromatographic peaks - could thus be measured and compared with literature spectra obtained by conventional excitation in condensed phases. Only a few gas-phase spectra are available from the literature, and these did agree well with the spectra of this study. A speculative luminescence mechanism is proposed, in which ground-state N2 becomes excited by collision with fast electrons. This is followed by efficient triplet-triplet energy transfer from N2(A 3Σu+) to the n>π* excited aroyl compound. Key words: aroyl phosphorescence, excited-nitrogen excitation, aroyl triplet-triplet excitation, aroyl luminescence detection, gas-phase phosphorescence spectra, gas-phase aroyl detection.
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Kim, Ilhwan, Donghwa Lee, and Kwang Jo Lee. "Numerical Investigation of High-Purity Polarization-Entangled Photon-Pair Generation in Non-Poled KTP Isomorphs." Applied Sciences 11, no. 2 (January 8, 2021): 565. http://dx.doi.org/10.3390/app11020565.
Повний текст джерелаАнотація:
We investigated the high-purity entangled photon-pair generation in five kinds of “non-poled” potassium titanyl phosphate (KTP) isomorphs (i.e., KTiOPO4, RbTiOPO4, KTiOAsO4, RbTiOAsO4, and CsTiOAsO4). The technique is based on the spontaneous parametric down-conversion (SPDC) under Type II extended phase matching (EPM), where the phase matching and the group velocity matching are simultaneously achieved between the interacting photons in non-poled crystals rather than periodically poled (PP) KTPs that are widely used for quantum experiments. We discussed both theoretically and numerically all aspects required to generate photon pairs in non-poled KTP isomorphs, in terms of the range of the beam propagation direction (or the spectral range of photons) and the corresponding effective nonlinearities and beam walk-offs. We showed that the SPDC efficiency can be increased in non-poled KTP isomorphs by 29% to 77% compared to PPKTP cases. The joint spectral analyses showed that photon pairs can be generated with high purities of 0.995–0.997 with proper pump filtering. In contrast to the PPKTP case, where the EPM is achieved only at one specific wavelength, the spectral position of photon pairs in the non-poled KTP isomorphs can be chosen over the wide range of 1883.8–2068.1 nm.
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Zhang, Xiangyue, Yueming Wang, and Tianru Xue. "Quadratic Clustering-Based Simplex Volume Maximization for Hyperspectral Endmember Extraction." Applied Sciences 12, no. 14 (July 15, 2022): 7132. http://dx.doi.org/10.3390/app12147132.
Повний текст джерелаАнотація:
The existence of intra-class spectral variability caused by differential scene components and illumination conditions limits the improvement of endmember extraction accuracy, as most endmember extraction algorithms directly find pixels in the hyperspectral image as endmembers. This paper develops a quadratic clustering-based simplex volume maximization (CSVM) approach to effectively alleviate spectral variability and extract endmembers. CSVM first adopts spatial clustering based on simple linear iterative clustering to obtain a set of homogeneous partitions and uses spectral purity analysis to choose pure pixels. The average of the chosen pixels in each partition is taken as a representative endmember, which reduces the effect of local-scope spectral variability. Then an improved spectral clustering based on k-means is implemented to merge homologous representative endmembers to further reduce the effect of large-scope spectral variability, and final endmember collection is determined by the simplex with maximum volume. Experimental results show that CSVM reduces the average spectral angle distance on Samson, Jasper Ridge and Cuprite datasets to below 0.02, 0.06 and 0.09, respectively, provides the root mean square errors of abundance maps on Samson and Jasper Ridge datasets below 0.25 and 0.10, and exhibits good noise robustness. By contrast, CSVM provides better results than other state-of-the-art algorithms.
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Ou, Yiyi, Junyu Wei, and Hongbin Liang. "Tunable Luminescence and Energy Transfer of Sr3B2O6:Ce3+, Sm3+ Phosphors with Potential Anti-Counterfeiting Applications." Materials 15, no. 15 (July 26, 2022): 5189. http://dx.doi.org/10.3390/ma15155189.
Повний текст джерелаАнотація:
Sm3+ and Ce3+ singly doped and Sm3+ and Ce3+ co-doped Sr3B2O6 phosphors are prepared via a high-temperature solid-state reaction method. The crystal structure and phase purity are characterized by X-ray diffraction (XRD) analyses. The Sm3+-doped sample displays an emission in the orange-red region, with the strongest emission line at about 648 nm and possessing a good luminescence thermal stability between 78 and 500 K. With the increase in the Sm3+ content, the concentration quenching is observed due to the cross-relaxation (CR) processes among the Sm3+ ions. Upon 340 nm excitation, the Ce3+-doped phosphor presents a broad emission band in the blue region with a maximum at about 420 nm, which overlaps well with the 6H5/2 → 6P3/2 excitation line of Sm3+ and implies the possible energy transfer from Ce3+ to Sm3+. The spectral and decay measurements of the Ce3+ and Sm3+ co-doped samples are conducted and the Inokuti–Hirayama (I-H) model is adopted to analyze the luminescence decay dynamics of the donor Ce3+. Owing to the evident sensitization of the Sm3+ by the Ce3+ ions, the co-doped samples exhibit color variation under different wavelength excitations, endowing them with potential applications in optical anti-counterfeiting.
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Nejo, Adeola A., Gabriel A. Kolawole, Ayorinde O. Nejo, Tebogo V. Segapelo, and Christo J. Muller. "Synthesis, Structural, and Insulin-Enhancing Studies of Oxovanadium(IV) Complexes." Australian Journal of Chemistry 64, no. 12 (2011): 1574. http://dx.doi.org/10.1071/ch11291.
Повний текст джерелаАнотація:
Oxovanadium(iv) complexes with Schiff bases derived from substituted salicylaldehyde and diamine have been prepared and characterized. 1H NMR and IR spectral data revealed that the symmetrical Schiff base was isolated, and elemental analysis confirmed the purity of all the compounds as formulated. The room-temperature magnetic moments of 1.6–1.8 Bohr magneton for the complexes confirmed that the complexes are VIV complexes, with d1 configuration. Cyclic voltammetry revealed only one quasi-reversible wave for each complex and they all showed redox couples with peak-to-peak separation values (ΔEp) ranging from 76 to 84 mV, indicating a single-step one-electron transfer process. An oral administration of these complexes supplied at a dose of 0.2 mmol kg–1 to streptozotocin-induced diabetic rats elicited a progressive reduction in plasma glucose over 6-h periods. Two of the complexes produced significant and consistent reduction in fasting blood glucose levels over a 6-h monitoring period.
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D. Lakshmijayasimha, Prajwal D., Prince M. Anandarajah, Pascal Landais, and Aleksandra Kaszubowska-Anandarajah. "Optical Frequency Comb Expansion Using Mutually Injection-Locked Gain-Switched Lasers." Applied Sciences 11, no. 15 (July 31, 2021): 7108. http://dx.doi.org/10.3390/app11157108.
Повний текст джерелаАнотація:
We propose a novel scheme for the expansion and comb densification of gain-switched optical frequency combs (GS-OFC). The technique entails mutual injection locking of two gain-switched lasers with a common master to generate a wider bandwidth OFC. Subsequently, the OFC is further expanded and/or densified using a phase modulator with optimum drive conditions. We experimentally demonstrate the generation of an OFC with 45 highly correlated lines separated by 6.25 GHz with an expansion factor ~3. In addition, operating in comb densification mode, the channel spacing of the OFC is tuned from 6.25 GHz to 390.625 MHz. Finally, a detailed characterization of the lines, across the entire expanded comb, is reported highlighting the excellent spectral purity with linewidths of ~40 kHz, a relative intensity noise better than –152 dB/Hz, and a high degree of phase correlation between the comb lines. The proposed method is simple, highly flexible and the architecture is suitable for photonic integration, all of which make such an OFC extremely attractive for the employment in a multitude of applications.
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Alyasseri, Zaid Abdi Alkareem, Ali H. Al-Timemy, Ammar Kamal Abasi, Alexandru Lavric, Husam Jasim Mohammed, Hidenori Takahashi, Jose Arthur Milhomens Filho, Mauro Campos, Rossen M. Hazarbassanov, and Siamak Yousefi. "A Hybrid Artificial Intelligence Model for Detecting Keratoconus." Applied Sciences 12, no. 24 (December 17, 2022): 12979. http://dx.doi.org/10.3390/app122412979.
Повний текст джерелаАнотація:
Machine learning models have recently provided great promise in diagnosis of several ophthalmic disorders, including keratoconus (KCN). Keratoconus, a noninflammatory ectatic corneal disorder characterized by progressive cornea thinning, is challenging to detect as signs may be subtle. Several machine learning models have been proposed to detect KCN, however most of the models are supervised and thus require large well-annotated data. This paper proposes a new unsupervised model to detect KCN, based on adapted flower pollination algorithm (FPA) and the k-means algorithm. We will evaluate the proposed models using corneal data collected from 5430 eyes at different stages of KCN severity (1520 healthy, 331 KCN1, 1319 KCN2, 1699 KCN3 and 579 KCN4) from Department of Ophthalmology and Visual Sciences, Paulista Medical School, Federal University of São Paulo, São Paulo in Brazil and 1531 eyes (Healthy = 400, KCN1 = 378, KCN2 = 285, KCN3 = 200, KCN4 = 88) from Department of Ophthalmology, Jichi Medical University, Tochigi in Japan and used several accuracy metrics including Precision, Recall, F-Score, and Purity. We compared the proposed method with three other standard unsupervised algorithms including k-means, Kmedoids, and Spectral cluster. Based on two independent datasets, the proposed model outperformed the other algorithms, and thus could provide improved identification of the corneal status of the patients with keratoconus.
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Depireux, Didier A., Jonathan Z. Simon, David J. Klein, and Shihab A. Shamma. "Spectro-Temporal Response Field Characterization With Dynamic Ripples in Ferret Primary Auditory Cortex." Journal of Neurophysiology 85, no. 3 (March 1, 2001): 1220–34. http://dx.doi.org/10.1152/jn.2001.85.3.1220.
Повний текст джерелаАнотація:
To understand the neural representation of broadband, dynamic sounds in primary auditory cortex (AI), we characterize responses using the spectro-temporal response field (STRF). The STRF describes, predicts, and fully characterizes the linear dynamics of neurons in response to sounds with rich spectro-temporal envelopes. It is computed from the responses to elementary “ripples,” a family of sounds with drifting sinusoidal spectral envelopes. The collection of responses to all elementary ripples is the spectro-temporal transfer function. The complex spectro-temporal envelope of any broadband, dynamic sound can expressed as the linear sum of individual ripples. Previous experiments using ripples with downward drifting spectra suggested that the transfer function is separable, i.e., it is reducible into a product of purely temporal and purely spectral functions. Here we measure the responses to upward and downward drifting ripples, assuming reparability within each direction, to determine if the total bidirectional transfer function is fully separable. In general, the combined transfer function for two directions is not symmetric, and hence units in AI are not, in general, fully separable. Consequently, many AI units have complex response properties such as sensitivity to direction of motion, though most inseparable units are not strongly directionally selective. We show that for most neurons, the lack of full separability stems from differences between the upward and downward spectral cross-sections but not from the temporal cross-sections; this places strong constraints on the neural inputs of these AI units.
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STARIKOV, E. B. "IMPORTANCE OF CHARGE TRANSFER EXCITATIONS IN DNA ELECTRON SPECTRUM: A ZINDO SEMIEMPIRICAL QUANTUM-CHEMICAL STUDY." Modern Physics Letters B 18, no. 16 (July 10, 2004): 825–31. http://dx.doi.org/10.1142/s0217984904007360.
Повний текст джерелаАнотація:
Electron spectra of DNA model compounds, adenosine-thymidine and guanosine-cytidine nucleoside base pairs, as well as the relevant homogeneous stacked base pair steps in A-DNA and B-DNA conformations, were investigated using ZINDO semiempirical quantum-chemical method. This work confirms that, in DNA with intact Watson–Crick hydrogen bonding and base stacking, the highest occupied molecular orbitals (HOMO) are residing on purine base residues, whereas the lowest unoccupied molecular orbitals (LUMO) — on pyrimidine base residues. In general, the present results are satisfactorily comparable with the available experimental data. The role of charge transfer excitations in the polymer DNA 260 nm spectral band is discussed.
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Liu, Yanxia, Guixia Liu, Jinxian Wang, Xiangting Dong, and Wensheng Yu. "Reddish-orange-emitting and paramagnetic properties of GdVO4:Sm3+/Eu3+ multifunctional nanomaterials." New Journal of Chemistry 39, no. 11 (2015): 8282–90. http://dx.doi.org/10.1039/c5nj01714a.
Повний текст джерелаАнотація:
The as-prepared samples are short and rod-like in shape with a diameter of about 10 nm and length of about 20–30 nm. The excitation spectra indicate that Sm3+ ions transfer energy to Eu3+ ions, which increases the color purity of Eu3+ ions in the GdVO4 system.
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Skalski, Bohdan, Stefan Paszyc, Ryszard W. Adamiak, Ronald P. Steer, and Ronald E. Verrall. "Photophysical properties of pyridinium salts derived from purine bases." Canadian Journal of Chemistry 68, no. 12 (December 1, 1990): 2164–70. http://dx.doi.org/10.1139/v90-332.
Повний текст джерелаАнотація:
The absorption spectra, fluorescence spectra, fluorescence lifetimes, fluorescence quenching, phosphorescence spectra, phosphorescence lifetimes, and picosecond transient absorption spectra of several purinyl-pyridinium salts have been measured in several solvents at room temperature and in ethanol glasses at 77 K. It is concluded that the previously observed photochemical transformation of N-[9-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)purin-6-yl]pyridinium chloride 1 into the highly fluorescent tri-O-acetylluminarosine 6 occurs via an excited triplet state. It is also shown that intersystem crossing in purinyl-pyridinium salts is induced by an intermolecular charge-transfer interaction with the counter ions. Keywords: purinyl-pyridinium salts, fluorescence, phosphorescence.
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Kowalski, N., D. A. Depireux, and S. A. Shamma. "Analysis of dynamic spectra in ferret primary auditory cortex. I. Characteristics of single-unit responses to moving ripple spectra." Journal of Neurophysiology 76, no. 5 (November 1, 1996): 3503–23. http://dx.doi.org/10.1152/jn.1996.76.5.3503.
Повний текст джерелаАнотація:
1. Auditory stimuli referred to as moving ripples are used to characterize the responses of both single and multiple units in the ferret primary auditory cortex. Moving ripples are broadband complex sounds with a sinusoidal spectral profile that drift along the logarithmic frequency axis at a constant velocity. 2. Neuronal responses to moving ripples are locked to the phase of the ripple, i.e., they exhibit the same periodicity as that of the moving ripple profile. Neural responses are characterized as a function of ripple velocity (temporal property) and ripple frequency (spectral property). Transfer functions describing the response to these temporal and spectral modulations are constructed. Temporal transfer functions are inverse Fourier transformed to obtain impulse response functions that reflect the cell's temporal characteristics. Ripple transfer functions are inverse Fourier transformed to obtain the response field, a measure analogous to the cell's response area. These operations assume linearity in the cell's response to moving ripples. 3. Transfer functions and other response functions are shown to be fairly independent on the overall level or depth of modulation of the ripple stimuli. Only downward moving ripples were used in this study. 4. The temporal and ripple transfer functions are found to be separable, in that their shapes remain unchanged for different test parameters. Thus ripple transfer functions and response fields remain statistically similar in shape (to within an overall scale factor) regardless of the ripple velocity or whether stationary or moving ripples are used in the measurement. The same stability in shape holds for the temporal transfer functions and the impulse response functions measured with different ripple frequencies. Separability implies that the combined spectrotemporal transfer function of a cell can be written as the product of a purely ripple and a purely temporal transfer functions, and thus that the neuron can be computationally modeled as processing spectral and temporal information in two separate and successive stages. 5. The ripple parameters that characterize cortical cells are distributed somewhat evenly, with the characteristic ripple frequencies ranging from 0.2 to > 2 cycles/octave and the characteristic angular frequency typically ranging from 2 to 20 Hz. 6. Many responses exhibit periodicities in the spectral envelope of the stimulus. These periodicities are of two types. Slow rebounds, not found in the spectral envelope, and with a period of approximately 150 ms, appear with various strengths in approximately 30% of the cells. Fast regular firings with interspike intervals of approximately 10 ms are much less common and appear to correspond to interactions between the component tones that make up a ripple.
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Krutskii, Yuri, Evgeny Maksimovskii, Roman Petrov, Olga Netskina, Arina Ukhina, Tatiana Krutskaya, and Tatiana Gudyma. "Synthesis of titanium carbide and titanium diboride for metal processing and ceramics production." Metal Working and Material Science 23, no. 4 (December 13, 2021): 155–66. http://dx.doi.org/10.17212/1994-6309-2021-23.4-155-166.
Повний текст джерелаАнотація:
Introduction. Titanium carbide and diboride are characterized by high values of hardness, chemical inertness and for this reason are widely used in modern technology. This paper provides information on the synthesis of titanium carbide and diboride by carbothermal and carbide-boron methods, respectively, on the use of titanium carbide as an abrasive and in the manufacture of tungsten-free hard alloys, carbide steels, wear-resistant coatings, as well as titanium diboride in the production of cutting tools and ceramics based on boron carbide The aim of this work is to study the processes of synthesis of highly dispersed powders of titanium carbide and diboride, which are promising for the manufacture of cutting tools, wear-resistant coatings, abrasives and ceramics. Research methods. Titanium oxide TiO2, nanofibrous carbon (NFC), and highly dispersed boron carbide were used as reagents for the synthesis of titanium carbide and diboride. Experiments to obtain titanium carbide were carried out in a resistance furnace, and titanium diboride in an induction furnace. X-ray studies of the phase composition of titanium carbide and diboride samples were carried out on an ARL X-TRA diffractometer (Thermo Electron SA). The determination of the content of titanium and impurities in the samples of titanium carbide and diboride was carried out by the X-ray spectral fluorescence method on an ARL-Advant'x analyzer. The total carbon content in the titanium carbide samples was determined on an S-144 device from LECO. The content of boron and other elements for titanium diboride samples was determined by inductively coupled plasma atomic emission spectrometry (ICP AES) on an IRIS Advantage spectrometer (Thermo Jarrell Ash Corporation). The surface morphology and particle sizes of the samples were studied using a Carl Zeiss Sigma scanning electron microscope (Carl Zeiss). The determination of the particle/aggregate size distribution was performed on a MicroSizer 201 laser analyzer (BA Instruments). Results. The paper proposes technological processes for obtaining highly dispersed powders of titanium carbide and diboride. The optimum synthesis temperature for titanium carbide is 2,000…2,100 oC, and for titanium diboride 1,600…1,700 oC. The content of the basic substance is at the level of 97.5…98.0 wt. %. Discussion. A possible mechanism for the formation of titanium carbide and diboride is proposed, which consists in the transfer of vapors of titanium oxides to the surface of solid carbon (synthesis of titanium carbide) and vapors of boron and titanium oxides to the surface of solid carbon (synthesis of titanium diboride). Due to the high purity and dispersion values, the resulting titanium carbide powder can be used as an abrasive material and for the manufacture of tungsten-free hard alloys, carbide steels, wear-resistant coatings, and titanium diboride powder can be used for the preparation of cutting tools and ceramics based on boron carbide.
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Weng, Wenle, Aleksandra Kaszubowska-Anandarajah, Junqiu Liu, Prince M. Anandarajah, and Tobias J. Kippenberg. "Frequency division using a soliton-injected semiconductor gain-switched frequency comb." Science Advances 6, no. 39 (September 2020): eaba2807. http://dx.doi.org/10.1126/sciadv.aba2807.
Повний текст джерелаАнотація:
With optical spectral marks equally spaced by a frequency in the microwave or the radio frequency domain, optical frequency combs have been used not only to synthesize optical frequencies from microwave references but also to generate ultralow-noise microwaves via optical frequency division. Here, we combine two compact frequency combs, namely, a soliton microcomb and a semiconductor gain-switched comb, to demonstrate low-noise microwave generation based on a novel frequency division technique. Using a semiconductor laser that is driven by a sinusoidal current and injection-locked to microresonator solitons, our scheme transfers the spectral purity of a dissipative soliton oscillator into the subharmonic frequencies of the microcomb repetition rate. In addition, the gain-switched comb provides dense optical spectral emissions that divide the line spacing of the soliton microcomb. With the potential to be fully integrated, the merger of the two chipscale devices may profoundly facilitate the wide application of frequency comb technology.
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Jalilov, Almaz S., Sameer Patwardhan, Arunoday Singh, Tomekia Simeon, Amy A. Sarjeant, George C. Schatz, and Frederick D. Lewis. "Structure and Electronic Spectra of Purine–Methyl Viologen Charge Transfer Complexes." Journal of Physical Chemistry B 118, no. 1 (December 23, 2013): 125–33. http://dx.doi.org/10.1021/jp410348b.
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Flores, Enrique, Ernesto Rivera-Avalos, Braulio Rodríguez-Molina, Carlos Frontana, Lluvia López, and Denisse de Loera. "Study of Organic Radicals Generated upon Naphthoquinone-Hydantoins Reactions in Basic Aqueous Solution." Chemistry Proceedings 3, no. 1 (November 14, 2020): 58. http://dx.doi.org/10.3390/ecsoc-24-08415.
Повний текст джерелаАнотація:
In this work, the synthesis of thiohydantoins from l-amino acids and isothiocyanates was studied, using a high purity method based on the Edman cycle. This process, expected to occur through the Michael addition to a series of 1,4-naphthoquinone derivatives did not lead to the expected final product, rather leading to a colored mixture of compounds, where EPR spectra showed that some of them presented unpaired electrons, indicating that an electron transfer pathway was also involved in the reaction mixture. Detected organic radicals proved to be stable albeit with the use of different experimental conditions. Voltammetric results indicated that the reactions led to the formation of electroactive species, probably derived by homogeneous electron transfer between the reactive quinone moieties and the oxidizable urea functions within the hydantoin species.
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Rangari, V. V., Vijay Singh, and S. J. Dhoble. "Photoluminescence Properties of YAl3(BO3)4:RE3+ (RE=Ce/Dy/Tb) Phosphors." Defect and Diffusion Forum 361 (January 2015): 195–213. http://dx.doi.org/10.4028/www.scientific.net/ddf.361.195.
Повний текст джерелаАнотація:
YAl3(BO3)4 doped with three rare earth (RE) ions namely Ce3 +, Dy3+ and Tb3+ were prepared by the conventional solid state diffusion method. The phosphors were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) techniques. PL spectra of Ce-doped samples showed the Ce3+ emission characteristic due to the 5d-4f transition. Dy-doped sample upon excitation at 351 nm, showed peaks corresponding to the 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions. PL spectra of Tb-doped sample showed peaks corresponding to the 5D3→7FJ transition. Upon excitation at 364 nm, the enhanced luminescence observed in Ce3+ co-doped YAl3(BO3)4:Tb3+/Dy3+ phosphors is understood as due to energy transfer from Ce3+ to Tb3+/Dy3. The color purity has also been verified by using the chromaticity diagram.
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Lin, Hui Hong, Yan Ru Lin, and Gui Po Fang. "The Luminescence Properties of Ca3(BO3)2 Doped with Ce3+, Tb3+." Advanced Materials Research 941-944 (June 2014): 647–52. http://dx.doi.org/10.4028/www.scientific.net/amr.941-944.647.
Повний текст джерелаАнотація:
The phosphors Ca3(BO3)2: Ce3+, Ca3(BO3)2: Tb3+ and Ca3(BO3)2: Ce3+, Tb3+ were synthesized by the solid-state reaction method at high temperature. The phase purity was characterized by the powder x-ray diffraction (XRD). The luminescence properties were investigated by ultraviolet (UV)-Vis spectra. For the phosphor Ca3(BO3)2: Ce3+, the lowest 5d levels, the emission and the Stokes shifts of Ce3+ in the host lattice are identified. For the phosphor Ca3(BO3)2: Tb3+, the f-d transitions of Tb3+ in the host lattice are assigned and discussed. Moreover, the energy transfer phenomenon between Ce3+ and Tb3+ in Ca3(BO3)2: Ce3+, Tb3+ has been discussed. The emission of Tb3+ is remarkably enhanced due to energy transfer from Ce3+ to Tb3+ when Ce3+, Tb3+ doped together in Ca3(BO3)2.
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Park, Hyeong-Ho, Xin Zhang, Yong-June Choi, Hyung-Ho Park, and Ross H. Hill. "Synthesis of Ag Nanostructures by Photochemical Reduction Using Citrate-Capped Pt Seeds." Journal of Nanomaterials 2011 (2011): 1–7. http://dx.doi.org/10.1155/2011/265287.
Повний текст джерелаАнотація:
A simple synthesis of Ag nanostructures such as nanorods and nanowires has been demonstrated with citrate-capped Pt seeds. UV-visible spectra and photographs of the synthesized solutions at different UV exposure times showed that the citrate-capped Pt seed played a crucial role in the growth of Ag nanostructures. After UV exposure of the colloidal solution for 60 min, the average diameter, length, and aspect ratio of the Ag nanostructures were about 95 nm, 2.1 μm, and 22, respectively. The photochemical reduction is hypothesized to result from photoelectron transfer from adsorbed citrate to Pt nanoparticle seed allowing Ag ions to form Ag nanostructures. Based on X-ray diffraction spectra and transmission electron microscope images, the synthesized Ag nanostructures were a face-centered cubic single crystal with good purity. These results suggest that the photochemical reduction method can provide Ag nanostructures in the presence of citrate-capped Pt seeds at room temperature for anisotropic Ag products.
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Welchinska, Elena. "ANTI-TUMOR ACTIVITY OF BACTERIAL LECTIN AND 5-METHYLURACIL ADDUCT." CBU International Conference Proceedings 2 (July 1, 2014): 307–12. http://dx.doi.org/10.12955/cbup.v2.476.
Повний текст джерелаАнотація:
The synthesis was performed using 5-methyluracil mono-and bis-derivatives with the halogen-containing pharmacophore groups in the composition of molecules; their physiochemical and biological properties were studied. These reactions are a typical example of substitution reactions on heteroatom N(1) of uracil molecule using as the second component the reaction of halothane—the known inhaled anesthetic. The reactions were carried out in a solvent system: benzene-dimethyl formamide and diethyl ether, under conditions of phase transfer catalysis DB-18-crown-6-complex (alkaline medium), by heating from 2 to 11 hours, followed by purification, and drying of the resulting products. The structure of the synthesized compounds was confirmed by elemental analysis, IR and 1HNMR spectra. The purity was controlled by the methods of thin-layer and gas-liquid chromatography. Chromatography, IR and 1HNMR spectra of the final products were identified in comparison with the chromatograms, IR and 1HNMR spectra of the initial compounds. Variation of the reaction conditions and changes in methods of synthesis enabled to receive the synthesized compounds of high purity and to increase their practical output up to 43-80%. Molecular complex of Bacterial lectin and 5-methyluracil bis-derivative was obtained. The toxicity and anti-tumor activity of some of the synthesized compounds were investigated. We have found that the new molecular complex of Bacterial lectin and 5-methyluracil bis-derivative has high anti-tumor activity in Limphosarcoma Plissa—62.8% (activity criterion >50%), which allows us to consider the synthesized compound as a physiologically active compound with the prospect for further study as a potential vehicle for anti-tumoral treatment in patients.
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Grella, Konstantin, and Christoph Schwab. "Sparse Discrete Ordinates Method in Radiative Transfer." Computational Methods in Applied Mathematics 11, no. 3 (2011): 305–26. http://dx.doi.org/10.2478/cmam-2011-0017.
Повний текст джерелаАнотація:
AbstractThe stationary monochromatic radiative transfer equation (RTE) is a partial differential transport equation stated on a five-dimensional phase space, the Cartesian product of physical and angular domain. We solve the RTE with a Galerkin FEM in physical space and collocation in angle, corresponding to a discrete ordinates method (DOM). To reduce the complexity of the problem and to avoid the "curse of dimension", we adapt the sparse grid combination technique to the solution space of the RTE and show that we obtain a sparse DOM which uses essentially only as many degrees of freedom as required for a purely spatial transport problem. For smooth solutions, the convergence rates deteriorate only by a logarithmic factor. We compare the sparse DOM to the standard full DOM and a sparse tensor product approach developed earlier with Galerkin FEM in physical space and a spectral method in angle. Numerical experiments confirm our findings.
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Zhang, Zhen Ming, Run Lai Li, Shuan Li, Pei Liu, and Kai Kai Song. "Synthesis of 2-Pyridyl Tribromomethyl Sulfone." Advanced Materials Research 781-784 (September 2013): 272–75. http://dx.doi.org/10.4028/www.scientific.net/amr.781-784.272.
Повний текст джерелаАнотація:
Polyethylene glycol-400 was used as phase transfer catalyst in reaction of dichloropyridine and sodium thiomethoxide to form 2-methylthiopyridine with a yield of 97.8%. Then 2-methylthiopyridine and sodium hypochlorite were added respectively to oxidize and bromize it to synthesis 2-Pyridyl tribromomethyl sulfone, with the purity of 99.6% and yield of 93.3%. Mass ratio of dichloropyridine versus polyethylene glycol-400 is 1:0.18, and molar ratio of dichloropyridine versus sodium thiomethoxide is 1:1.2. The optimum conditions to prepare sodium hypochlorite are a temperature at-5 to 0 °C, a molar ratio of bromine versus sodium hydroxide being 1:4. Proved optimum conditions to synthesis 2-pyridyl tribromomethyl sulfone are a temperature at (80±1)°C, reaction time for 5 hours and the molar ratio of 2-methylthiopyridine versus bromine being 1:6.58. Probable mechanism of synthetizing 2-methylthiopyridine was speculated, properties with structure of resultant substances were characterized by melting point apparatus, IR spectra and magnetic resonance spectrum.
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Ahn, Yu-Hwan. "Development of an Inverse Model from Ocean Reflectance." Marine Technology Society Journal 33, no. 1 (January 1, 1999): 69–80. http://dx.doi.org/10.4031/mtsj.33.1.9.
Повний текст джерелаАнотація:
An inverse ocean color model with three components—chlorophyll, suspended sediment and dissolved organic matter—is developed to extract the constituents of seawater from the surface reflectance (400‐700 nm) in oligotrophic, eutrophic and turbid waters. Ocean reflectance obtained from just beneath the sea surface by a spectral radiometer (with 61 bands) is associated with four specific absorption and backscattering coefficients of seawater constituents, including heterotrophic organisms and seawater itself. Although many semi-analytical methods have been used before, this is the first time to apply a purely analytical technique to the inverse model. A known radiative transfer theory was applied to extract the constituents. The model results showed good agreement between the measured values in seawaters and simulated values.
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Xiang, Gang, Na Li, Guang-Hui Chen, Qiao-Hong Li, Shu-Mei Chen, Yan-Ping He, and Jian Zhang. "Enhancing Third-Order Nonlinear Optical Property by Regulating Interaction between Zr4(embonate)6 Cage and N, N-Chelated Transition-Metal Cation." Molecules 28, no. 5 (March 1, 2023): 2301. http://dx.doi.org/10.3390/molecules28052301.
Повний текст джерелаАнотація:
Herein, the combination of anionic Zr4L6 (L = embonate) cages and N, N-chelated transition-metal cations leads to a series of new cage-based architectures, including ion pair structures (PTC-355 and PTC-356), dimer (PTC-357), and 3D frameworks (PTC-358 and PTC-359). Structural analyses show that PTC-358 exhibits a 2-fold interpenetrating framework with a 3,4-connected topology, and PTC-359 shows a 2-fold interpenetrating framework with a 4-connected dia network. Both PTC-358 and PTC-359 can be stable in air and other common solvents at room temperature. The investigations of third-order nonlinear optical (NLO) properties indicate that these materials show different degrees of optical limiting effects. It is surprising that increasing coordination interactions between anion and cation moieties can effectively enhance their third-order NLO properties, which can be attributed to the formation of coordination bonds that facilitate charge transfer. In addition, the phase purity, UV-vis spectra, and photocurrent properties of these materials were also studied. This work provides new ideas for the construction of third-order NLO materials.
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Shi, Hui, Xi-Yan Zhang, Neng-Li Wang, Wei-Li Dong, and Xiao-Yun Mi. "Preparation of Y2O3:Eu3+, Tb3+ nanopowders with tunable luminescence by ammonium bicarbonate co-precipitation method." Functional Materials Letters 08, no. 01 (February 2015): 1550006. http://dx.doi.org/10.1142/s179360471550006x.
Повний текст джерелаАнотація:
Y 2 O 3: Eu 3+, Tb 3+ nanopowders were prepared by co-precipitation method with NH 4 HCO 3 as precipitant. The nanopowders with different calcined temperatures and Eu 3+/ Tb 3+ doped ratio were characterized by X-ray Diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrophotometer. The results showed that the nanopowders calcined at 1100°C for 2 h had a uniform distribution, high purity and good dispersibility. The particle size was in the range of 60–80 nm. The excitation spectra of Eu 3+/ Tb 3+ co-doped phosphors were wide. The phosphors could emit the green light at the peak of 543 nm and the red light at the peak of 611 nm simultaneously under 276 nm or 300 nm excited. Because of the energy transfer between Tb 3+ and Eu 3+, the 543 nm emission of Tb 3+ ion was weakened while the 611 nm emission of Eu 3+ enhanced. The emissive colors of Y 2 O 3: Eu 3+, Tb 3+ nanopowders could be adjusted from yellow-green to orange-red by changing the Eu 3+/ Tb 3+ doping ratio.
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Ruan, Chunkao, Yongyi Chen, Li Qin, Peng Jia, Yugang Zeng, Yue Song, Yuxin Lei, Zhijun Zhang, Nan Zhang, and Zaijin Li. "Purely Gain-Coupled Distributed-Feedback Bragg Semiconductor Laser Diode Emitting at 770 nm." Applied Sciences 11, no. 4 (February 8, 2021): 1531. http://dx.doi.org/10.3390/app11041531.
Повний текст джерелаАнотація:
The transition lines of Mg, K, Fe, Ni, and other atoms lie near 770 nm, therefore, this spectral region is important for helioseismology, solar atmospheric studies, the pumping of atomic clocks, and laser gyroscopes. However, there is little research on distributed-feedback (DFB) semiconductor lasing at 770 nm. In addition, the traditional DFB semiconductor laser requires secondary epitaxy or precision grating preparation technologies. In this study, we demonstrate an easily manufactured, gain-coupled DFB semiconductor laser emitting at 770 nm. Only micrometer scale periodic current injection windows were used, instead of nanoscale grating fabrication or secondary epitaxy. The periodically injected current assures the device maintains single longitudinal mode working in the unetched Fabry–Perot cavity under gain coupled mechanism. The maximum continuous-wave output power reached was 116.3 mW at 20 °C, the maximum side-mode-suppression ratio (SMSR) was 33.25 dB, and the 3 dB linewidth was 1.78 pm.
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Srinivasa, Rao. "Study of Compton broadening due to electron-photon scattering." Serbian Astronomical Journal, no. 180 (2010): 11–18. http://dx.doi.org/10.2298/saj1080011s.
Повний текст джерелаАнотація:
We have investigated the effects of Compton broadening due to electron-photon scattering in hot stellar atmospheres. A purely electron-photon scattering media is assumed to have plane parallel geometry with an input radia?tion field localized on one side of the slab. The method is based on the discrete space theory of radiative transfer for the intensity of emitted radiation. The solution is developed to study the importance of scattering of radiation by free electrons in high temperature stellar atmospheres which produces a brodening and shift in spectral lines because of the Compton effect and the Doppler effect arising from mass and thermal motions of scattering electrons. It is noticed that the Comptonized spectrum depends on three parameters: the optical depth of the medium, the temperature of the thermal electrons and the viewing angle. We also showed that the Compton effect produces red shift and asymmetry in the line. These two effects increase as the optical depth increases. It is also noticed that the emergent specific intensities become completely asymmetric for higher optical depths.
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Yang, Chaoqing, Dimitrije Mara, Joydeb Goura, Flavia Artizzu, and Rik Van Deun. "Photophysical and Primary Self-Referencing Thermometric Properties of Europium Hydrogen-Bonded Triazine Frameworks." Molecules 27, no. 19 (October 8, 2022): 6687. http://dx.doi.org/10.3390/molecules27196687.
Повний текст джерелаАнотація:
Lanthanide hydrogen-bonded organic frameworks (LnHOFs) are recently emerging as a novel versatile class of multicomponent luminescent materials with promising potential applications in optics and photonics. Trivalent europium (Eu3+) incorporated polymeric hydrogen-bonded triazine frameworks (PHTF:Eu) have been successfully obtained via a facile and low-cost thermal pyrolysis route. The PHTF:Eu material shows a porous frame structure principally composed of isocyanuric acid and ammelide as a minor constituent. Intense red luminescence with high colour-purity from Eu3+ is obtained by exciting over a broad absorption band peaked at 300 nm either at room or low temperature. The triazine-based host works as excellent optical antenna towards Eu3+, yielding ~42% sensitization efficiency (ηsens) and an intrinsic quantum yield of Eu3+ emission (ΦEu) as high as ~46%. Temperature-dependent emission studies show that PHTF:Eu displays relatively high optical stability at elevated temperatures in comparison to traditional inorganic phosphors. The retrieved activation energy of 89 meV indicates that thermal quenching mechanisms are attributed to the intrinsic energy level structure of the metal-triazine assembly, possibly via a thermally activated back transfer to ligand triplet or CT states. Finally, by using an innovative approach based on excitation spectra, we demonstrate that PHTF:Eu can work as a universal primary self-referencing thermometer based on a single-emitting center with excellent relative sensitivity in the cryogenic temperature range.
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CIMARELLI, A., and E. DE ANGELIS. "Analysis of the Kolmogorov equation for filtered wall-turbulent flows." Journal of Fluid Mechanics 676 (April 4, 2011): 376–95. http://dx.doi.org/10.1017/s0022112011000565.
Повний текст джерелаАнотація:
The analysis of the energy transfer mechanisms in a filtered wall-turbulent flow is traditionally accomplished via the turbulent kinetic energy balance, as in Härtel et al. (Phys. Fluids, vol. 6, 1994, p. 3130) or via the analysis of the energy spectra, as in Domaradzki et al. (Phys. Fluids, vol. 6, 1994, p. 1583). However, a generalized Kolmogorov equation for channel flow has recently been proven successful in accounting for both spatial fluxes and energy transfer across the scales in a single framework by Marati, Casciola & Piva (J. Fluid Mech., vol. 521, 2004, p. 191). In this context, the same machinery is applied for the first time to a filtered velocity field. The results will show what effects the subgrid scales have on the resolved motion in both physical and scale space, singling out the prominent role of the filter scale compared to the cross-over scale between production-dominated scales and inertial range, lc, and the reverse energy cascade region ΩB. Finally, we will briefly discuss how the filtered Kolmogorov equation can be used as a new tool for the assessment of large eddy simulation (LES) models. Classical purely dissipative eddy viscosity models will be analysed via an a priori procedure.
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LEE, Ho Joon, Lu-Yun LIAN, and S. Nigel SCRUTTON. "Recombinant two-iron rubredoxin of Pseudomonas oleovorans: overexpression, purification and characterization by optical, CD and 113Cd NMR spectroscopies." Biochemical Journal 328, no. 1 (November 15, 1997): 131–36. http://dx.doi.org/10.1042/bj3280131.
Повний текст джерелаАнотація:
The gene (alk G) encoding the two-iron rubredoxin of Pseudomonas oleovorans was amplified from genomic DNA by PCR and subcloned into the expression vector pKK223-3. The vector directed the high-level production of rubredoxin in Escherichia coli. A simple three-step procedure was used to purify recombinant rubredoxin in the 1Fe form. 1Fe-rubredoxin was readily converted to the 2Fe, apoprotein and cadmium forms after precipitation with trichloroacetic acid and resolubilization in the presence or absence of ferrous ammonium sulphate or CdCl2 respectively. Recombinant 1Fe and 2Fe rubredoxins are redox-active and able to transfer electrons from reduced spinach ferredoxin reductase to cytochrome c. The absorption spectrum and dichroic features of the CD spectrum for the cadmium-substituted protein are similar to those reported for cadmium-substituted Desulfovibrio gigas rubredoxin [Henehan, Poutney, Zerbe and Vasak (1993) Protein Sci. 2, 1756-1764]. Difference absorption spectroscopy of cadmium-substituted rubredoxin revealed the presence of four Gaussian-resolved maxima at 207, 228, 241 and 280 nm; the 241 nm band is attributable, from J⊘rgensen's electronegativity theory, to a CysS-CdII charge-transfer excitation. The 113Cd NMR spectrum of the 113Cd-substituted rubredoxin contains two 113Cd resonances with chemical shifts located at 732.3 and 730 p.p.m. The broader linewidth and high frequency shift of the resonance at 730 p.p.m. indicates that the Cd2+ ion is undergoing chemical exchange and, consistent with the difference absorption spectra, is bound less tightly than the Cd2+ ion, giving rise to the chemical shift at 732.3 p.p.m.
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Shamsutdinov, Artyom Sh, and Anatoliy B. Shein. "CATHODIC HYDROGEN EVOLUTION ON COBALT MONOSILICIDE IN POTASSIUM HYDROXIDE SOLUTION." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 60, no. 10 (November 16, 2017): 9. http://dx.doi.org/10.6060/tcct.20176010.5581.
Повний текст джерелаАнотація:
The kinetics of hydrogen evolution reaction on cobalt monosilicide CoSi in potassium hydroxide solution was studied using methods of polarization and impedance measurements. Electrochemical impedance of CoSi was studied in 1 M KOH at 21-22 °C in the range of potentials of hydrogen evolution. Solutions were prepared from high-purity reagents and de-ionized water (Milli-Q). The working solutions were de-aerated with hydrogen (purity 99.999 %). Cobalt silicide was prepared from silicon (99.99 % purity) and electrolytic cobalt (99.98 % purity) by Czochralski method (pulling from the melt at speed of 0.4 mm/min). Electrodes were cut using electric-spark method. The working electrode surface was 0.4 – 0.6 cm2. Before measurements, the working electrode surface was abraded with emery papers of 1000 and 2000, cleaned with ethanol and washed in the working solution. Electrochemical measurements were carried out in three-electrode electrochemical cell with cathodic and anodic compartments separated with a porous glass diaphragm. Potentials Е were changed from low to high cathodic polarisations and vice versa. Before recording an impedance spectrum at each potential value, the electrode was polarised under potentiostatic conditions until constant value of current was reached. The electrode potentials are given with respect to the SHE. Impedance measurements were carried out using FRA Solartron and potentiostat Solartron 1280 (Solartron Analytical) in the frequency range from 10 kHz to 0.01 Hz (10 points per decade). The alternating signal amplitude was 10 mV. The CorrWare2, ZPlot2 and ZView2 software (Scribner Associates, Inc.) was used for measuring and processing the impedance data. In 1 М KOH polarization curve for CoSi-electrode has Tafel plot with the slope bk = 0.113 V. Earlier it was established that b for Со2Ѕі and CoSi2 at these conditions were 0.123 and 0.105 V, respectively, while b for Co was equal to 0.144 V. Tafel slope for cobalt monosilicide is less than Co, i.e. the difference between the current densities on the silicide and cobalt increases with increasing in cathodic polarization. At a constant electrode potential E, the current density i for CoSi is higher than for Co (at E = -1.2 V the value of i for CoSi is equal to 1.58 mA/cm2, and for Co i = 0.32 mA/cm2). Nyquist diagrams consist of the combination of capacitive semicircle at high frequencies and an inductive arc at low frequencies. Impedance spectra of cobalt silicide can not be accurately described by a simple equivalent circuit consisting of parallel-connected charge transfer resistance and the double layer capacitance. In order to describe the behavior of CoSi - electrode in 1 M KOH solution in the range of investigated potentials the equivalent circuit was used which was obtained in several works as a model of two-stage process with the adsorption of intermediate substances, in particular for hydrogen evolution reaction. In order to analyze the impedance data we used the diagnostic criteria for hydrogen evolution reaction mechanisms, based on the dependence of equivalent circuit elements on the overvoltage and OH- ions concentration, which were previously proposed. Determination of the kinetic parameters (rate constants and transfer coefficients) of hydrogen evolution reaction steps on the basis of the impedance data has been considered. Hydrogen evolution reaction on CoSi electrode in alkaline solution is discussed using the proposed criteria. It has been shown that hydrogen evolution reaction on CoSi in potassium hydroxide solution proceeds through the Volmer-Heyrovsky route with Heyrovsky reaction as the rate-determining and with the Langmuir isotherm for hydrogen adsorption. Forcitation:Shamsutdinov A.Sh., Shein A.B. Cathodic hydrogen evolution on cobalt monosilicide in potassium hydroxide solution. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 10. P. 9-15
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Schewe, Hanns Christian, Eva Muchová, Michal Belina, Tillmann Buttersack, Dominik Stemer, Robert Seidel, Stephan Thürmer, Petr Slavíček, and Bernd Winter. "Observation of intermolecular Coulombic decay and shake-up satellites in liquid ammonia." Structural Dynamics 9, no. 4 (July 2022): 044901. http://dx.doi.org/10.1063/4.0000151.
Повний текст джерелаАнотація:
We report the first nitrogen 1s Auger–Meitner electron spectrum from a liquid ammonia microjet at a temperature of ∼223 K (–50 °C) and compare it with the simultaneously measured spectrum for gas-phase ammonia. The spectra from both phases are interpreted with the assistance of high-level electronic structure and ab initio molecular dynamics calculations. In addition to the regular Auger–Meitner-electron features, we observe electron emission at kinetic energies of 374–388 eV, above the leading Auger–Meitner peak (3a12). Based on the electronic structure calculations, we assign this peak to a shake-up satellite in the gas phase, i.e., Auger–Meitner emission from an intermediate state with additional valence excitation present. The high-energy contribution is significantly enhanced in the liquid phase. We consider various mechanisms contributing to this feature. First, in analogy with other hydrogen-bonded liquids (noticeably water), the high-energy signal may be a signature for an ultrafast proton transfer taking place before the electronic decay (proton transfer mediated charge separation). The ab initio dynamical calculations show, however, that such a process is much slower than electronic decay and is, thus, very unlikely. Next, we consider a non-local version of the Auger–Meitner decay, the Intermolecular Coulombic Decay. The electronic structure calculations support an important contribution of this purely electronic mechanism. Finally, we discuss a non-local enhancement of the shake-up processes.
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Horník, Štěpán, Lenka Michálková, Jan Sýkora, Vladimír Ždímal, Štěpánka Vlčková, Štěpánka Dvořáčková, and Daniela Pelclová. "Effects of Workers Exposure to Nanoparticles Studied by NMR Metabolomics." Applied Sciences 11, no. 14 (July 18, 2021): 6601. http://dx.doi.org/10.3390/app11146601.
Повний текст джерелаАнотація:
In this study, the effects of occupational exposure to nanoparticles (NPs) were studied by NMR metabolomics. Exhaled breath condensate (EBC) and blood plasma samples were obtained from a research nanoparticles-processing unit at a national research university. The samples were taken from three groups of subjects: samples from workers exposed to nanoparticles collected before and after shift, and from controls not exposed to NPs. Altogether, 60 1H NMR spectra of exhaled breath condensate (EBC) samples and 60 1H NMR spectra of blood plasma samples were analysed, 20 in each group. The metabolites identified together with binning data were subjected to multivariate statistical analysis, which provided clear discrimination of the groups studied. Statistically significant metabolites responsible for group separation served as a foundation for analysis of impaired metabolic pathways. It was found that the acute effect of NPs exposure is mainly reflected in the pathways related to the production of antioxidants and other protective species, while the chronic effect is manifested mainly in the alteration of glutamine and glutamate metabolism, and the purine metabolism pathway.
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Allen, John F., and Thomas Pfannschmidt. "Balancing the two photosystems: photosynthetic electron transfer governs transcription of reaction centre genes in chloroplasts." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 355, no. 1402 (October 29, 2000): 1351–59. http://dx.doi.org/10.1098/rstb.2000.0697.
Повний текст джерелаАнотація:
Chloroplasts are cytoplasmic organelles whose primary function is photosynthesis, but which also contain small, specialized and quasi–autonomous genetic systems. In photosynthesis, two energy converting photosystems are connected, electrochemically, in series. The connecting electron carriers are oxidized by photosystem I (PS I) and reduced by photosystem II (PS II). It has recently been shown that the oxidation–reduction state of one connecting electron carrier, plastoquinone, controls transcription of chloroplast genes for reaction centre proteins of the two photosystems. The control counteracts the imbalance in electron transport that causes it: oxidized plastoquinone induces PS II and represses PS I; reduced plastoquinone induces PS I and represses PS II. This complementarity is observed both in vivo , using light favouring one or other photosystem, and in vitro , when site–specific electron transport inhibitors are added to transcriptionally and photosynthetically active chloroplasts. There is thus a transcriptional level of control that has a regulatory function similar to that of purely post–translational ‘state transitions’ in which the redistribution of absorbed excitation energy between photosystems is mediated by thylakoid membrane protein phosphorylation. The changes in rates of transcription that are induced by spectral changes in vivo can be detected even before the corresponding state transitions are complete, suggesting the operation of a branched pathway of redox signal transduction. These findings suggest a mechanism for adjustment of photosystem stoichiometry in which initial events involve a sensor of the redox state of plastoquinone, and may thus be the same as the initial events of state transitions. Redox control of chloroplast transcription is also consistent with the proposal that a direct regulatory coupling between electron transport and gene expression determines the function and composition of the chloroplast's extra–nuclear genetic system.
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PERRY, Ashlee, Lu-Yun LIAN, and Nigel S. SCRUTTON. "Two-iron rubredoxin of Pseudomonas oleovorans: production, stability and characterization of the individual iron-binding domains by optical, CD and NMR spectroscopies." Biochemical Journal 354, no. 1 (February 8, 2001): 89–98. http://dx.doi.org/10.1042/bj3540089.
Повний текст джерелаАнотація:
A minigene encoding the C-terminal domain of the 2Fe rubredoxin of Pseudomonas oleovorans was created from the parental alk G gene contained in the expression plasmid pKK223-3. The vector directed the high-level production of the C-terminal domain of this rubredoxin; a simple procedure was used to purify the recombinant domain in the 1Fe form. The 1Fe form of the C-terminal domain was readily converted into the apoprotein and cadmium forms after precipitation with trichloroacetic acid and resolubilization in the presence or absence of cadmium chloride respectively. In steady-state assays, the recombinant 1Fe C-terminal domain is redox-active and able to transfer electrons from reduced rubredoxin reductase to cytochrome c. The absorption spectrum and dichroic features of the CD spectrum for the iron- and cadmium-substituted C-terminal domain are similar to those reported for the iron- and cadmium-substituted Desulfovibrio gigas rubredoxin [Henehen, Pountney, Zerbe and Vasak (1993) Protein Sci. 2, 1756–1764]. Difference absorption spectroscopy of the cadmium-substituted C-terminal domain revealed the presence of four Gaussian-resolved maxima at 202, 225, 240 and 276nm; from J⊘rgensen's electronegativity theory, the 240nm band is attributable to a CysS-Cd(II) charge-transfer excitation. Attempts to express the N-terminal domain of the 2Fe rubredoxin directly from a minigene were unsuccessful. However, the N-terminal domain was isolated through cleavage of an engineered 2Fe rubredoxin in which a factor Xa proteolysis site had been introduced into the putative interdomain linker. The N-terminal domain is characterized by absorption spectra typical of the 1Fe rubredoxins. The domain is folded as determined by CD and NMR spectroscopies and is redox-active. However, the N-terminal domain is less stable than the isolated C-terminal domain, a finding consistent with the known properties of the full-length 2Fe and cadmium-substituted Ps. oleovorans rubredoxin.
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Liu, Yong, Liangqi Zhang, Hao Liu, Linmao Yin, Yao Xiao, Yue Wang, and Zhong Zeng. "Convective instabilities in the Czochralski model with different radii ratios." Physics of Fluids 34, no. 11 (November 2022): 114108. http://dx.doi.org/10.1063/5.0117206.
Повний текст джерелаАнотація:
In this work, we explore the instability of the complex convection in the Czochralski model concerning the effects of the radii ratio, melt materials, and crystal rotation. Particularly, linear stability analysis is conducted based on the spectral element method for three groups of cases with the same interval for the variation of the radii ratio ( Λ) but different material Prandtl number ( Pr) and dimensionless crystal rotation velocity ωs. We observe that, for both ωs = 0 and ωs = 300, the mixed convection of silicon melt ( Pr = 0.011) becomes less stable with the increase in radii ratio and the instability is of purely inertial mechanism. In contrast, as for the LiCaAlF6 melt ( Pr = 1.4), a larger radii ratio would improve the stability and the instability is dominated by buoyancy mechanism for ωs = 300. Moreover, two times of critical wavenumber transitions occur in the critical stability curve for silicon melt ( Pr = 0.011). Each transition associates with a convex turning point of the critical stability curve for ωs = 0, while only one turning point remains when ωs shifts to 300.
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Delgutte, Bertrand, Philip X. Joris, Ruth Y. Litovsky, and Tom C. T. Yin. "Receptive Fields and Binaural Interactions for Virtual-Space Stimuli in the Cat Inferior Colliculus." Journal of Neurophysiology 81, no. 6 (June 1, 1999): 2833–51. http://dx.doi.org/10.1152/jn.1999.81.6.2833.
Повний текст джерелаАнотація:
Receptive fields and binaural interactions for virtual-space stimuli in the cat inferior colliculus. Sound localization depends on multiple acoustic cues such as interaural differences in time (ITD) and level (ILD) and spectral features introduced by the pinnae. Although many neurons in the inferior colliculus (IC) are sensitive to the direction of sound sources in free field, the acoustic cues underlying this sensitivity are unknown. To approach this question, we recorded the responses of IC cells in anesthetized cats to virtual space (VS) stimuli synthesized by filtering noise through head-related transfer functions measured in one cat. These stimuli not only possess natural combinations of ITD, ILD, and spectral cues as in free field but also allow precise control over each cue. VS receptive fields were measured in the horizontal and median vertical planes. The vast majority of cells were sensitive to the azimuth of VS stimuli in the horizontal plane for low to moderate stimulus levels. Two-thirds showed a “contra-preference” receptive field, with a vigorous response on the contralateral side of an edge azimuth. The other third of receptive fields were tuned around a best azimuth. Although edge azimuths of contra-preference cells had a broad distribution, best azimuths of tuned cells were near the midline. About half the cells tested were sensitive to the elevation of VS stimuli along the median sagittal plane by showing either a peak or a trough at a particular elevation. In general receptive fields for VS stimuli were similar to those found in free-field studies of IC neurons, suggesting that VS stimulation provided the essential cues for sound localization. Binaural interactions for VS stimuli were studied by comparing responses to binaural stimulation with responses to monaural stimulation of the contralateral ear. A majority of cells showed either purely inhibitory (BI) or mixed facilitatory/inhibitory (BF&I) interactions. Others showed purely facilitatory (BF) or no interactions (monaural). Binaural interactions were correlated with azimuth sensitivity: most contra-preference cells had either BI or BF&I interactions, whereas tuned cells were usually BF. These correlations demonstrate the importance of binaural interactions for azimuth sensitivity. Nevertheless most monaural cells were azimuth-sensitive, suggesting that monaural cues also play a role. These results suggest that the azimuth of a high-frequency sound source is coded primarily by edges in azimuth receptive fields of a population of ILD-sensitive cells.
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Solomonidou, A., C. Neish, A. Coustenis, M. Malaska, A. Le Gall, R. M. C. Lopes, A. Werynski, et al. "The chemical composition of impact craters on Titan." Astronomy & Astrophysics 641 (September 2020): A16. http://dx.doi.org/10.1051/0004-6361/202037866.
Повний текст джерелаАнотація:
We investigate the spectral behavior of nine Titan impact craters in order to constrain their composition. Past studies that have examined the chemical composition of impact craters on Titan have either used qualitative comparisons between craters or combined all craters into a single unit, rather than separating them by geographic location and/or degradation state. Here, we use Visual and Infrared Mapping Spectrometer (VIMS) data and a radiative transfer code to estimate the atmospheric contribution to the data, extract the surface albedos of the impact craters, and constrain their composition by using a library of candidate Titan materials, including essentially water ice, tholin, a dark component, and other possible ices at different grain sizes. Following a general characterization of the impact craters, we study two impact crater subunits, the “crater floor” and the “ejecta blanket”. The results show that the equatorial dune craters – Selk, Ksa, Guabonito, and the crater on Santorini Facula – appear to be purely composed of organic material (mainly an unknown dark component). Titan’s midlatitude plain craters – Afekan, Soi, and Forseti – along with Menrva and Sinlap, are enriched in water ice within an organic-based mixture. This follows the geographic pattern observed in our previous work with VIMS data, where the uppermost layers of the midlatitude alluvial fans, undifferentiated plains, and labyrinth terrains were found to consist of a mixture of organics and water ice, while the equatorial plains, hummocky terrains, and dunes were found to consist of a mixture of dark material and tholins. Furthermore, we found that the addition of some form of ice improves the fit in the ejecta spectra of Afekan and Sinlap craters. We find no indication for the presence of either NH3 or CO2 ice. Our main results agree with an existing Titan surface evolution scenario, wherein the impact cratering process produces a mixture of organic material and water ice, which is later “cleaned” through fluvial erosion in the midlatitude plains. This cleaning process does not appear to operate in the equatorial regions, which are quickly covered by a thin layer of sand sediment (with the exception of the freshest crater on Titan, Sinlap). Thus, it appears that active processes are working to shape the surface of Titan, and it remains a dynamic world in the present day.
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Zhukov, Ivan V., Alexey S. Kiryutin, Mikhail S. Panov, Natalya N. Fishman, Olga B. Morozova, Nikita N. Lukzen, Konstantin L. Ivanov, Hans-Martin Vieth, Renad Z. Sagdeev, and Alexandra V. Yurkovskaya. "Exchange interaction in short-lived flavine adenine dinucleotide biradical in aqueous solution revisited by CIDNP (chemically induced dynamic nuclear polarization) and nuclear magnetic relaxation dispersion." Magnetic Resonance 2, no. 1 (April 13, 2021): 139–48. http://dx.doi.org/10.5194/mr-2-139-2021.
Повний текст джерелаАнотація:
Abstract. Flavin adenine dinucleotide (FAD) is an important cofactor in many light-sensitive enzymes. The role of the adenine moiety of FAD in light-induced electron transfer was obscured, because it involves an adenine radical, which is short-lived with a weak chromophore. However, an intramolecular electron transfer from adenine to flavin was revealed several years ago by Robert Kaptein by using chemically induced dynamic nuclear polarization (CIDNP). The question of whether one or two types of biradicals of FAD in aqueous solution are formed stays unresolved so far. In the present work, we revisited the CIDNP study of FAD using a robust mechanical sample shuttling setup covering a wide magnetic field range with sample illumination by a light-emitting diode. Also, a cost efficient fast field cycling apparatus with high spectral resolution detection up to 16.4 T for nuclear magnetic relaxation dispersion studies was built based on a 700 MHz NMR spectrometer. Site-specific proton relaxation dispersion data for FAD show a strong restriction of the relative motion of its isoalloxazine and adenine rings with coincident correlation times for adenine, flavin, and their ribityl phosphate linker. This finding is consistent with the assumption that the molecular structure of FAD is rigid and compact. The structure with close proximity of the isoalloxazine and purine moieties is favorable for reversible light-induced intramolecular electron transfer from adenine to triplet excited flavin with formation of a transient spin-correlated triplet biradical F⚫−-A⚫+. Spin-selective recombination of the biradical leads to the formation of CIDNP with a common emissive maximum at 4.0 mT detected for adenine and flavin protons. Careful correction of the CIDNP data for relaxation losses during sample shuttling shows that only a single maximum of CIDNP is formed in the magnetic field range from 0.1 mT to 9 T; thus, only one type of FAD biradical is detectable. Modeling of the CIDNP field dependence provides good agreement with the experimental data for a normal distance distribution between the two radical centers around 0.89 nm and an effective electron exchange interaction of −2.0 mT.
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Suurs, Frans V., Alexander Kristian, Gebregziabher Petros, Yuan Zeng Feng, Karianne G. Fleten, Roger M. Bjerke, Alan Cuthbertson, and Kjersti Flatmark. "Abstract 2467: SPECT-imaging guided development and evaluation of targeted alpha therapy (TAT) for colorectal liver metastasis." Cancer Research 82, no. 12_Supplement (June 15, 2022): 2467. http://dx.doi.org/10.1158/1538-7445.am2022-2467.
Повний текст джерелаАнотація:
Abstract BACKGROUND: Only a small fraction of patients with colorectal liver metastases (CLM) is eligible for curative resection, and novel treatment options are highly needed. The high linear-energy transfer of short-ranged alpha particles can induce complex double-stranded DNA breaks, leading to cell death. With no known resistance mechanism, alpha-particle emitting isotopes represent a promising tool in cancer management. In targeted alpha therapy (TAT), an alpha-particle emitting isotope is attached to a tumor-targeting antibody (hereafter TAT antibody), ensuring specific delivery to the tumor. By substituting the alpha-particle emitting isotope (Actinium-225, 225Ac) with a diagnostic isotope (Zirconium-89, 89Zr), the in-vivo distribution of the TAT antibody can be monitored using PET/SPECT/CT. The aim of this work was to set up robust labeling and PET/SPECT protocols to evaluate TAT in CLM using novel experimental models. METHODS: For SPECT-imaging of 225Ac daughter isotopes, the combined gamma emission spectra were gated at 218 keV ± 20% and 440 keV ± 20% for Francium-221 and Bismuth-213, respectively. 89Zr was labeled to a desferrioxamine* (DFO*) conjugated TAT antibody, which recognizes both the murine and human antigen. Indium-111 (111In) labeling was performed through diethylenetriaminepentaacetic acid (DTPA) conjugated to an isotype antibody. Radiochemical purity and protein integrity were assessed by size exclusion HPLC, iTLC and SDS-PAGE. For orthotopic CLM model development, 106 cells of human colorectal cancer cell lines HT-55 or LS1034 were injected in the spleen of female Rj:NMRI-Foxn1nu mice, followed by splenectomy. Tumor growth was monitored by T2-weighted MR-imaging. Non-tumor bearing mice (n = 12, 3 per group) were injected with 4 MBq of 10, 20, 50 or 100 µg 89Zr-TAT antibody to evaluate biodistribution and the mice scanned on day 2, 4 and 6 after iv injection. RESULTS: Francium-221 and Bismuth-213 could be separately visualized after free Actinium-225 administration (i.v.). 89Zr and 111In were routinely labeled to their respective antibody with up to 500 MBq/mg with >95% radiochemical purity. 89Zr-DFO*-TAT antibody showed >95% radiochemical purity and >95% protein integrity after 7 days stability test in serum, shown by iTLC and SDS-PAGE. SPECT/CT of 89Zr-DFO*-TAT antibody in non-tumor bearing mice showed little uptake in healthy tissues apart from the liver due to hepatic antibody clearance. Orthotopic models of CLM show reproducible development of metastases for HT-55 and LS1034 within 3 weeks. CONCLUSION: Robust labeling methods, PET/SPECT imaging protocols and suitable animal models of CLM were established. Results of our dual-isotope SPECT/CT imaging of our 89Zr-DFO*-TAT antibody in comparison with an 111In-labeled isotype antibody, together with efficacy data of the TAT, will be presented at the meeting. Citation Format: Frans V. Suurs, Alexander Kristian, Gebregziabher Petros, Yuan Zeng Feng, Karianne G. Fleten, Roger M. Bjerke, Alan Cuthbertson, Kjersti Flatmark. SPECT-imaging guided development and evaluation of targeted alpha therapy (TAT) for colorectal liver metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2467.
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Shenar, T., D. P. Sablowski, R. Hainich, H. Todt, A. F. J. Moffat, L. M. Oskinova, V. Ramachandran, et al. "The Wolf–Rayet binaries of the nitrogen sequence in the Large Magellanic Cloud." Astronomy & Astrophysics 627 (July 2019): A151. http://dx.doi.org/10.1051/0004-6361/201935684.
Повний текст джерелаАнотація:
Context. Massive Wolf–Rayet (WR) stars dominate the radiative and mechanical energy budget of galaxies and probe a critical phase in the evolution of massive stars prior to core collapse. It is not known whether core He-burning WR stars (classical WR; cWR) form predominantly through wind stripping (w-WR) or binary stripping (b-WR). Whereas spectroscopy of WR binaries has so-far largely been avoided because of its complexity, our study focuses on the 44 WR binaries and binary candidates of the Large Magellanic Cloud (LMC; metallicity Z ≈ 0.5 Z⊙), which were identified on the basis of radial velocity variations, composite spectra, or high X-ray luminosities. Aims. Relying on a diverse spectroscopic database, we aim to derive the physical and orbital parameters of our targets, confronting evolution models of evolved massive stars at subsolar metallicity and constraining the impact of binary interaction in forming these stars. Methods. Spectroscopy was performed using the Potsdam Wolf–Rayet (PoWR) code and cross-correlation techniques. Disentanglement was performed using the code Spectangular or the shift-and-add algorithm. Evolutionary status was interpreted using the Binary Population and Spectral Synthesis (BPASS) code, exploring binary interaction and chemically homogeneous evolution. Results. Among our sample, 28/44 objects show composite spectra and are analyzed as such. An additional five targets show periodically moving WR primaries but no detected companions (SB1); two (BAT99 99 and 112) are potential WR + compact-object candidates owing to their high X-ray luminosities. We cannot confirm the binary nature of the remaining 11 candidates. About two-thirds of the WN components in binaries are identified as cWR, and one-third as hydrogen-burning WR stars. We establish metallicity-dependent mass-loss recipes, which broadly agree with those recently derived for single WN stars, and in which so-called WN3/O3 stars are clear outliers. We estimate that 45 ± 30% of the cWR stars in our sample have interacted with a companion via mass transfer. However, only ≈12 ± 7% of the cWR stars in our sample naively appear to have formed purely owing to stripping via a companion (12% b-WR). Assuming that apparently single WR stars truly formed as single stars, this comprises ≈4% of the whole LMC WN population, which is about ten times less than expected. No obvious differences in the properties of single and binary WN stars, whose luminosities extend down to log L ≈ 5.2 [L⊙], are apparent. With the exception of a few systems (BAT99 19, 49, and 103), the equatorial rotational velocities of the OB-type companions are moderate (veq ≲ 250 km s−1) and challenge standard formalisms of angular-momentum accretion. For most objects, chemically homogeneous evolution can be rejected for the secondary, but not for the WR progenitor. Conclusions. No obvious dichotomy in the locations of apparently single and binary WN stars on the Hertzsprung-Russell diagram is apparent. According to commonly used stellar evolution models (BPASS, Geneva), most apparently single WN stars could not have formed as single stars, implying that they were stripped by an undetected companion. Otherwise, it must follow that pre-WR mass-loss/mixing (e.g., during the red supergiant phase) are strongly underestimated in standard stellar evolution models.
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Bendiak, Brad, Tammy T. Fang, and David NM Jones. "An effective strategy for structural elucidation of oligosaccharides through NMR spectroscopy combined with peracetylation using doubly 13C-labeled acetyl groups." Canadian Journal of Chemistry 80, no. 8 (August 1, 2002): 1032–50. http://dx.doi.org/10.1139/v02-132.
Повний текст джерелаАнотація:
The use of NMR spectroscopy for the elucidation of larger carbohydrate structures isolated from natural sources is principally limited by severe overlap of 1H signals, poor sensitivity when experiments involve 13C nuclei, and difficulties in conclusively establishing linkage positions. Peracetylation of oligosaccharides with doubly 13C-labeled acetyl groups provides several major advantages for their structural elucidation when combined with specifically tailored NMR pulse sequences. The 2.54.7 Hz J-coupling constants between acetyl carbonyl-13C nuclei and protons of the sugar ring at the sites of acetylation enables these sites to be readily assigned. By inference, glycosidic linkage positions on monosaccharides can be unambiguously determined. This can be used in lieu of permethylation analysis, yet does not require degradation of oligosaccharides. Spectral dispersion in the directly detected (1H) dimension is increased ~2.62.7-fold due to the downfield shifting of sugar-ring protons at the positions of acetylation. Peracetylation also introduces three new frequency dimensions for NMR studies, namely the 13CO, 13CMe, and 1HMe frequencies of the acetyl groups. These frequencies can be correlated to sugar protons, either independently or in combination, in alternative 2-, 3-, or 4-D experiments. The use of HartmannHahn coherence transfer combined with zero-quantum dephasing periods permits purely absorptive in-phase multiplets to be extracted and enables accurate scalar couplings between ring protons to be measured, even in multidimensional experiments. Results are illustrated on a nonasaccharide-alditol derived from N-linked glycoproteins and on some smaller structures containing sialic acids and N-acetylhexosamines. Methods for small-scale sample acetylation using the superacylation catalyst, 4-dimethylamino pyridine, are described. A brief historical perspective pertinent to the fundamental contributions of Dr. R.U. Lemieux to the field of carbohydrate NMR is also presented.Key words: NMR, oligosaccharides, peracetylation, doubly 13C-labeled acetyl groups, tailored pulse sequences, heteronuclear HartmannHahn.
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De Grazia, Gemma, Lorenzo Cucinotta, Archimede Rotondo, Paola Donato, Luigi Mondello, and Danilo Sciarrone. "Expanding the Knowledge Related to Flavors and Fragrances by Means of Three-Dimensional Preparative Gas Chromatography and Molecular Spectroscopy." Separations 9, no. 8 (August 4, 2022): 202. http://dx.doi.org/10.3390/separations9080202.
Повний текст джерелаАнотація:
As universally known, gas chromatography (GC) coupled with mass spectrometry (MS) allows us to acquire spectra that can be searched in specific databases to attain qualitative information on a peak of interest. When not present in databases, structure elucidation is required before including a new component in a library: from that moment, scientists all around the world will be able to identify the new molecule with analytical confidence after GC-MS analysis. Conversely, if data are not shared in commercial databases, even if a molecule is studied and elucidated, it appears to be unknown or only identifiable on the basis of third-party data taken from the literature, which is a serious limitation. The present paper deals with a case that confirms this assumption. A component of Myrtus communis L. volatile fraction was tentatively identified based on literature data. Despite this, reliable identification could not be achieved due to the lack of a corresponding spectrum in commercial MS databases. Afterwards, the target component was isolated in a reasonable quantity and with a high degree of purity for downstream characterization by spectroscopic techniques. For this purpose, preparative (prep) GC may appear insufficient for the isolation of volatile components from highly complex samples. In this study, a prep-MDGC system was implemented for the isolation of the compound of interest from myrtle oil, consisting of three wide-bore columns of different selectivity coupled by means of Deans switch transfer devices. Based on the NMR and GC-FTIR data acquired, the unknown compound was identified as 2,2,5,5,7,7-hexamethyl-3,7-dihydro-1-benzofuran-4,6(2H,5H)-dione. Noticeably, this is a known molecule, yet its mass spectrum had never been registered into MS databases and thus was not available to the scientific community. Finally, the spectrum was included for the first time in a commercial library, namely the FFNSC 5.0 MS database. The aim of the present study was to highlight the opportunity to make analytical data quickly available in a reliable way by registering them in searchable MS databases to improve the identification means for researchers all over the world.
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Colanera, Antonio, Alessandro Della Pia, and Matteo Chiatto. "Data-driven global stability of vertical planar liquid jets by dynamic mode decomposition on random perturbations." Physics of Fluids 34, no. 12 (December 2022): 122101. http://dx.doi.org/10.1063/5.0123550.
Повний текст джерелаАнотація:
A data-driven approach to estimate the global spectrum of gravitational planar liquid jets (sheet or curtain flows) is presented in this work. The investigation is carried out by means of two-dimensional numerical simulations performed through the solver BASILISK, based on the one-fluid formulation and the volume-of-fluid approach. The dynamic mode decomposition technique is applied to extract the underlying linear operator, considering random perturbations of the base flow. The effectiveness of this procedure is first evaluated comparing results with those of a simplified one-dimensional curtain model in terms of spectrum and eigenfunctions. The methodology is then applied to a two-dimensional configuration obtaining the BiGlobal spectra for both supercritical (Weber number We > 1) and subcritical ( We < 1) regimes. Results highlight that in supercritical regime, the spectrum presents three branches: the upper and lower ones exhibit a purely sinuous behavior with frequencies quite close to those predicted by the one-dimensional model; the middle branch presents a predominant varicose component, increasing with the frequency. The subcritical spectrum, instead, shows that the first two less stable eigenvalues, sorted by increasing frequency, exhibit, respectively, a sinuous and a varicose behavior, while their growth rate is almost the same. As expected, the subcritical regime does not reveal the slow branch. The effect of the density ratio, [Formula: see text], between the two phases is investigated, revealing that the flow system is unstable for [Formula: see text]. Topological inspections of the leading modes in this unstable configuration show that the predominance of a varicose behavior is related to the rupture of the curtain.
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Tavora, Juliana, Emmanuel Boss, David Doxaran, and Paul Hill. "An Algorithm to Estimate Suspended Particulate Matter Concentrations and Associated Uncertainties from Remote Sensing Reflectance in Coastal Environments." Remote Sensing 12, no. 13 (July 7, 2020): 2172. http://dx.doi.org/10.3390/rs12132172.
Повний текст джерелаАнотація:
Suspended Particulate Matter (SPM) is a major constituent in coastal waters, involved in processes such as light attenuation, pollutant propagation, and waterways blockage. The spatial distribution of SPM is an indicator of deposition and erosion patterns in estuaries and coastal zones and a necessary input to estimate the material fluxes from the land through rivers to the sea. In-situ methods to estimate SPM provide limited spatial data in comparison to the coverage that can be obtained remotely. Ocean color remote sensing complements field measurements by providing estimates of the spatial distributions of surface SPM concentration in natural waters, with high spatial and temporal resolution. Existing methods to obtain SPM from remote sensing vary between purely empirical ones to those that are based on radiative transfer theory together with empirical inputs regarding the optical properties of SPM. Most algorithms use a single satellite band that is switched to other bands for different ranges of turbidity. The necessity to switch bands is due to the saturation of reflectance as SPM concentration increases. Here we propose a multi-band approach for SPM retrievals that also provides an estimate of uncertainty, where the latter is based on both uncertainties in reflectance and in the assumed optical properties of SPM. The approach proposed is general and can be applied to any ocean color sensor or in-situ radiometer system with red and near-infra-red bands. We apply it to six globally distributed in-situ datasets of spectral water reflectance and SPM measurements over a wide range of SPM concentrations collected in estuaries and coastal environments (the focus regions of our study). Results show good performance for SPM retrieval at all ranges of concentration. As with all algorithms, better performance may be achieved by constraining empirical assumptions to specific environments. To demonstrate the flexibility of the algorithm we apply it to a remote sensing scene from an environment with highly variable sediment concentrations.
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Briard, Antoine, and Thomas Gomez. "Dynamics of helicity in homogeneous skew-isotropic turbulence." Journal of Fluid Mechanics 821 (May 25, 2017): 539–81. http://dx.doi.org/10.1017/jfm.2017.260.
Повний текст джерелаАнотація:
The dynamics of helicity in homogeneous skew-isotropic freely decaying turbulence is investigated, at very high Reynolds numbers, thanks to a classical eddy-damped quasi-normal Markovian (EDQNM) closure. In agreement with previous direct numerical simulations, a $k^{-5/3}$ inertial range is obtained for both the kinetic energy and helical spectra. In the early stage of the decay, when kinetic energy, initially only present at large scales cascades towards small scales, it is found that helicity slightly slows down the nonlinear transfers. Then, when the turbulence is fully developed, theoretical decay exponents are derived and assessed numerically for helicity. Furthermore, it is found that the presence of helicity does not modify the decay rate of the kinetic energy with respect to purely isotropic turbulence, except in Batchelor turbulence where the kinetic energy decays slightly more rapidly. In this case, non-local expansions are used to show analytically that the permanence of the large eddies hypothesis is verified for the helical spectrum, unlike the kinetic energy one. Moreover, the $4/3$ law for the two-point helical structure function is assessed numerically at very large Reynolds numbers. Afterwards, the evolution equation of the helicity dissipation rate is investigated analytically, which provides significant simplifications and leads notably to the definition of a helical derivative skewness and of a helical Taylor scale, which is numerically very close to the classical Taylor longitudinal scale at large Reynolds numbers. Finally, when both a mean scalar gradient and helicity are combined, the quadrature spectrum, linked to the antisymmetric part of the scalar flux, appears and scales like $k^{-7/3}$ and then like $k^{-5/3}$ in the inertial range.