Presence Of Emission Research Articles

Highlighting the operating regimes of microchannel electrodes under laminar flow: Mapping of photoluminescence and electrochemiluminescence through semi-transparent electrodes

Semi-transparent platinum electrodes were designed and optimized to implement photoluminescence (PL) and electrochemiluminescence (ECL) in microchannels under flow conditions. The luminescence properties of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)32+) were used to map steady-state emitted light through semi-transparent microchannel electrodes. Several diffusive-convective regimes were thus imposed in order to experimentally highlight the operating conditions of the electrodes, in particular the active zones at their upstream edges contributing to the Faradaic current. PL and ECL profiles were established on the electrode surfaces as a function of flow rate. The PL profiles confirmed the control of the process by mass transport. The data were validated by numerical simulations within the limits of experimental accuracy. ECL emission in presence of the co-reactant tri-n-propylamine (TPA) was also limited by mass transport. However, in comparison the characteristics of the ECL profiles demonstrated the complexity of the underlying mechanism involving Ru(bpy)32+ regeneration and TPA consumption.

Does entanglement enhance single-molecule pulsed biphoton spectroscopy?

Abstract It depends. For a single molecule interacting with one mode of a biphoton probe, we show that the spectroscopic information has three contributions, only one of which is a genuine two-photon contribution. When all the scattered light can be measured, solely this contribution exists and can be fully extracted using unentangled measurements. Furthermore, this two-photon contribution can, in principle, be matched by an optimised but unentangled single-photon probe. When the matter system spontaneously emits into inaccessible modes, an advantage due to entanglement can not be ruled out. In practice, time-frequency entanglement does enhance spectroscopic performance of the oft-studied weakly-pumped spontaneous parametric down conversion (PDC) probes. For two-level systems and coupled dimers, more entangled PDC probes yield more spectroscopic information, even in the presence of emission into inaccessible modes. Moreover, simple, unentangled measurements can capture between 60% and 90% of the spectroscopic information. We thus establish that biphoton spectroscopy using source-engineered PDC probes and unentangled measurements can provide tangible quantum enhancement. Our work underscores the intricate role of entanglement in single-molecule spectroscopy using quantum light.

A study of Be stars in the time domain – I. Spectral data and polarimetry

ABSTRACT We present the first part of a spectroscopic and polarimetric study on a sample of 58 Be stars that have been measured since 1998. The aim of the study is to understand the time-scales of disc variability, formation, and dissipation as a function of the properties (mass, luminosity, and rotational velocity) of the underlying B star. In this paper, we classified the sample based on the presence of emission or absorption of the Hα line, and the shape of the peak as single or double peak, as well as noting changes between emission and non-emission states. We find a probability of ∼0.75 per cent per year that an object in the sample will undergo such a change. We also present re-derived values of the projected rotational velocities for the sample. When we compare our polarization values with those from the literature, we find that most of the stars do not show a change in the value of the polarization angle; however, a small number show significant changes which could be attributed to either disc strength (optical depth) or geometry changes. Finally, we show how, by combining the (interstellar corrected) degree of polarization and the projected rotational velocity, we can construct an inclination angle-free parameter that includes the true equatorial velocity. Using this inclination angle-independent parameter, we show that the populations of single and double peak stars are indistinguishable, giving further evidence that Be star line profiles are essentially inclination angle driven.

A Practical Framework for Oil and Gas Operators to Estimate Methane Emission Duration Using Operational Data

Summary Methane management is a key greenhouse gas (GHG) reduction focus within the oil and gas industry. While there are a variety of techniques for methane detection and measurement, aircraft-mounted sensors have become popular for both academic studies and operators in onshore regions in North America due to their ability to screen many sites in a relatively short amount of time. Many traditional leak detection and repair (LDAR) techniques, like optical gas imaging (OGI), and emerging approaches, such as aircraft-based or satellite-based screenings, are periodic, which means that they can provide information about the presence of emissions and approximate rates during the observation period. Scaling periodic observations to annual emission estimates needed for regulatory and corporate reporting requires information on emission duration, which is not generally provided by the same screening techniques. In the literature to date, there have been several statistical approaches proposed for the annualization of basin-level methane observations, but these techniques may struggle to downscale to individual operators, across which methane emission intensities are expected to vary. In this paper, we propose a novel, conceptual framework for using other sources of data, such as records from operator inspections and parametric monitoring, to help define the duration of detected methane emissions. Such information may prove to be a useful input to measurement-informed methane emission protocols that are under development by multistakeholder groups, like GTI Energy Veritas and federal agencies in the United States.

Spectro-Electrochemiluminescence Analysis of the Simultaneous Emission of Two Luminophores

Electrochemiluminescence (ECL) is a powerful technique that combines the best features of electrochemistry and chemiluminescence in a single experiment. Its versatility, simplified optical set-up, low background signal and high sensitivity [1] allows the increase of new analytical applications. ECL signals are usually obtained from the excited states of a luminophore generated at the electrode surface during an electrochemical reaction due to the presence of a co-reactant. Particularly, resonance energy transfer (RET) mechanism is produced when at least two luminophores are present in solution, one luminophore acts as donor and the other one as acceptor [2]. In the absence of an external light source, donor luminophore emits light as consequence of its electrochemical excitation, part of this emission is absorbed by the acceptor to be excited and re-emits light.Initially, ECL emission of two luminophores were separately analysed in this work: (1) luminol emission in presence of hydrogen peroxide as co-reactant shows one band from 350 to 600 nm (maximum at 420 nm) during its oxidation process at +0.20 V, while (2) ECL signal of Ru(bpy)3 2+ with tripropylamine as co-reactants displays one band at 620 nm at +0.95 V.Furthermore, the simultaneous emission of luminol and Ru(bpy)3 2 (RET-ECL system) was analysed using a microspectrometer detector [3]. ECL spectra display three emission bands at 420, 510 and 620 nm. According to the previous experiments, bands at 420 and 510 nm should be associated with luminol due to its band emission is located from 350 to 600 nm, while band at 620 nm corresponds to Ru(bpy)3 2+. Nevertheless, Ru(bpy)3 2+ shows a characteristic absorption band at 450 nm, so minimum observed at this wavelength in the spectra is related to the Ru(bpy)3 2+ absorption. It demonstrates that bands at 420 and 510 nm are not really two bands, they form the characteristic band of luminol at 350-600 nm but is separated due to the characteristic absorption of Ru(bpy)3 2+ at 450 nm. Then, it is clear than Ru(bpy)3 2+ absorbs part of ECL emission of luminol before producing their own emission at more positive potentials. Spectro-electrochemiluminescence results demonstrates that the interaction between luminol and Ru(bpy)3 2+ is an important effect to be considered when ECL system is formed by these two luminophores.

Exploring the effect of surfactants on the interactions of manganese dioxide nanoparticles with biomolecules

Interactions of manganese dioxide nanoparticles (MnO2 NPs) with vital biomolecules namely deoxyribonucleic acid (DNA) and serum albumin (BSA) have been studied in association with different surfactants by using fluorescence (steady state, synchronous and 3D), UV-visible, resonance light scattering (RLS), dynamic light scattering (DLS), and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The esterase activity of serum albumin was tested in associations with MnO2 NPs and surfactants. The antioxidant potential of prepared NPs was also evaluated (DPPH method). Gel electrophoresis was carried out to analyze the effect of MnO2 NPs and surfactants on DNA. Presence of CTAB, Tween 20, DTAB and Tween 80 enhanced nanoparticle-protein binding. Tween 20 based nanoparticle systems showed long-term stability and biocompatibility. The quenching of BSA fluorescence emission in presence of MnO2 NPs alone and along with Tween 20 revealed stronger association of nanoparticles with proteins. Enhancement in the esterase activity (BSA) was observed in the presence of Tween 20. Furthermore, radical scavenging activity showed highest antioxidant potential in presence of Tween 20. The enthalpy and entropy assessment for protein-NPs association showed the predominance of Vander Waals interactions and hydrogen bonding. The synchronous fluorescence analysis highlighted the involvement of tryptophan (Trp) in the MnO2 NPs-protein interactions. The study evaluates the influence of surfactant on the associations of MnO2 NPs with the essential biomolecules. The findings can be crucially utilized in designing biocompatible MnO2 formulations for long term applications. Communicated by Ramaswamy H. Sarma

Selective ion sensing in aqueous media with ESIPT active fluorescent probes – A particular case for hypochlorite detection

We report two ESIPT active novel fluorescent probes, 1 and 2, based on benzoxazole and benzimidazole units, respectively. Their sensing aptitude towards metal ions in aqueous media is reported. A specific response of 1 to Al3+ and, to a lesser extent, Zn2+, was found, while the emission of 2 is highly impacted by the Al3+, Cu2+, Fe2+ and Fe3+ metal ions by either a blue shift or a quenching of the emission. Emission of 2 also shows a relative sensitivity to the Ni2+ and Hg2+ cations. Anions sensing studies on 2 revealed a unique emission in presence of hypochlorite ions, while glyphosate and aminomethylphosphonic acid have the effect to decrease the emission intensity by 40% and 75%, respectively. Investigations on the recognition mechanism led to the conclusion that Al3+ was inhibiting the ESIPT process by deprotonation of the phenol group, and that a fast but weak interaction was taking place between the hypochlorite ion and 2.

Entropy generation and CO2 emission in presence of pulsating oscillations in a bifurcating thermoacoustic combustor with a Helmholtz resonator at off-design conditions

In this work, we develop a 2D numerical model of a Y-shaped bifurcating combustor with a Helmholtz resonator attached. Propane (C3H8) is fueled and burnt with air by applying single-step eddy dissipation combustion model and k−ϵ−RNG turbulence model for simplicity. To validate the numerical findings, experimental measurements are conducted on a bifurcating Y-shaped thermoacoustic combustor with an off-design Helmholtz resonator implemented. It is found that the frequency and amplitude of the dominant mode as experimentally measured agree well with the numerical results. Further agreement is obtained between numerically and theoretically predicted mode-shapes. With the model validated, it is applied to gain insights on the entropy generation and nonlinearity of the pulsating oscillations and the flow fluctuations across the resonator neck. It is found that the nonlinearities are originated in the unsteady heat release rate of the premixed propane flame, and the mass flow rate across the resonator neck. In addition, the rate of the entropy production depends strongly on the temperature fluctuations. Approximately 99% of the entropy production rate involves with the temperature oscillations. Furthermore, it is non-uniformly distributed along the combustor. In addition, the energy conversion rate between total heat release rate and the acoustical energy production rate is less than 0.0001%. Finally, the production of CO2 is increased exponentially, and then reduced gradually in the axial flow direction. In general, the present work provides a low-cost numerical tool of a bifurcating thermoaocustic system. It could be applied to predict the acoustic signature of the combustor and to examine and evaluate the performance of the Helmholtz resonator on attenuating self-sustained thermoacoustic oscillations.

Modeling of spontaneous emission in presence of cylindrical nanoobjects: the scattering matrix approach

We propose a method of analysis of spontaneous emission of a quantum emitter (an atom, a luminescence center, a quantum dot) inside or in vicinity of a cylinder. At the focus of our method are analytical expressions for the scattering matrix of the cylindrical nanoobject. We propose the approach to electromagnetic field quantization based of eigenvalues and eigenvectors of the scattering matrix. The method is applicable for calculation and analysis of spontaneous emission rates and angular dependences of radiation for a set of different systems: semiconductor nanowires with quantum dots, plasmonic nanowires, cylindrical hollows in dielectrics and metals. Relative simplicity of the method allows obtaining analytical and semi-analytical expressions for both cases of radiation into external medium and into guided modes.

Expeditious fluorimetric detection of bilirubin by simple imidazole derived luminophore and it's pragmatic applicability in spiked biological fluids

Bilirubin is an indispensable biomarker for liver diseases. Utilizing organic molecules as sensor platform for effective detection of bilirubin are little. In addition, the reported fluorophores required longer incubation time for detection. Hence, herein we have attempted to design an imidazole derivative 4-(3H-imidazo[4,5-b]pyridin-2-yl)-N,N-diphenylaniline (IMI) from triphenylamine and pyridine units which could detect bilirubin swiftly without any incubation period. IMI manifested an instant quenching of emission in presence of bilirubin with limit of detection (LOD) 11.74 × 10−6 mol L−1. The mechanistic aspect of detection involves coexistence of both static and dynamic quenching which was suitably justified. Finally, the pragmatic application of IMI was performed in bio-fluids.

Examining the effect of information and communication technology, innovations, and renewable energy consumption on CO2 emission: evidence from BRICS countries.

The increasing use of information and communication technology (ICT) in this digital era and its interlinkage with other economic and environmental factors have gotten considerable attention from researchers. ICT tools are considered very important in economic activities such as international trade, the financial sector, and foreign direct investment. ICT is also interlinked with innovation and energy consumption. However, ICT with these activities influences ecological footprint, especially in emerging economies such as BRICS (Brazil, Russia, India, China, and South Africa) countries. Therefore, this topic has got considerable attention from researchers and policy makers on the impact of ICT and economic growth activities on environmental quality. Consequently, this study investigates the impact of information and communication technology, renewable energy consumption and innovation on carbon dioxide emission in BRICS countries from 1990 to 2019 using cointegration, generalized least square, and panel corrected standard errors models. The findings show that two ICT indicators, mobile cellular subscription and fixed broadband subscription, negatively affect carbon emission along with economic growth and financial development. Innovation and renewable energy consumption also significantly reduce emission in presence of ICT indicators, while trade openness and fixed telephone subscriptions increase it. In the case of the ICT index model, all variables are positively associated with carbon emission except renewable energy consumption, however, the square and interaction term of all indicators significantly reduce carbon emission and evidence the environmental Kuznets curve hypothesis except trade openness. ICT growth should be considered in the energy sector, innovation, and financial development to enhance environmental quality. The findings of the study have considerable policy implications for the sample countries.

Switching to electric vehicles can lead to significant reductions of PM2.5 and NO2 across China

Switching to electric vehicles can lead to significant reductions of PM2.5 and NO2 across China

Geomagnetic data recovery approach based on the concept of digital twins

There is no ground-based magnetic station or observatory that guarantees the quality of information received and transmitted to it. Data gaps, outliers, and anomalies are a common problem affecting virtually any ground-based magnetometer network, creating additional obstacles to efficient processing and analysis of experimental data. It is possible to monitor the reliability and improve the quality of the hardware and soft- ware modules included in magnetic stations by develop- ing their virtual models or so-called digital twins.
 In this paper, using a network of high-latitude IMAGE magnetometers as an example, we consider one of the possible approaches to creating such models. It has been substantiated that the use of digital twins of magnetic stations can minimize a number of problems and limitations associated with the presence of emissions and missing values in time series of geomagnetic data, and also provides the possibility of retrospective forecasting of geomagnetic field parameters with a mean square error (MSE) in the auroral zone up to 11.5 nT. Integration of digital twins into the processes of collecting and registering geomagnetic data makes the automatic identification and replacement of missing and abnormal values possible, thus increasing, due to the redundancy effect, the fault tolerance of the magnetic station as a data source object.
 By the example of the digital twin of the station “Kilpisjärvi” (Finland), it is shown that the proposed approach implements recovery of 99.55 % of annual information, while 86.73 % with M not exceeding 12 nT.

Подход к восстановлению геомагнитных данных на базе концепции цифровых двойников

There is no ground-based magnetic station or observatory that guarantees the quality of information received and transmitted to it. Data gaps, outliers, and anomalies are a common problem affecting virtually any ground-based magnetometer network, creating additional obstacles to efficient processing and analysis of experimental data. It is possible to monitor the reliability and improve the quality of the hardware and soft- ware modules included in magnetic stations by develop- ing their virtual models or so-called digital twins.
 In this paper, using a network of high-latitude IMAGE magnetometers as an example, we consider one of the possible approaches to creating such models. It has been substantiated that the use of digital twins of magnetic stations can minimize a number of problems and limitations associated with the presence of emissions and missing values in time series of geomagnetic data, and also provides the possibility of retrospective forecasting of geomagnetic field parameters with a mean square error (MSE) in the auroral zone up to 11.5 nT. Integration of digital twins into the processes of collecting and registering geomagnetic data makes the automatic identification and replacement of missing and abnormal values possible, thus increasing, due to the redundancy effect, the fault tolerance of the magnetic station as a data source object.
 By the example of the digital twin of the station “Kilpisjärvi” (Finland), it is shown that the proposed approach implements recovery of 99.55 % of annual information, while 86.73 % with M not exceeding 12 nT.

Development of inorganic-organic hybrid nanostructured material for H2O2 sensing application

An organic-inorganic hybrid nanoparticle (HNPs) composed of Sm(TTA)3Phen, a coordination compound, and NaY0.78Er0.02Yb0.20F4, an upconversion nanoparticles (UCNPs), has been developed and used for H2O2 sensing application. Herein, Sm(TTA)3Phen absorbs ultraviolet (UV) light and gives fluorescence in yellow-red-near infrared (NIR) region. Whereas, the UCNPs absorb NIR radiations (980 nm) and consequently emit in green-red region through photon upconversion process. Two important optical phenomena are observed when HNPs are simultaneously excited with UV (266 nm) and NIR (980 nm) laser radiation- (i) an energy transfer from Sm3+ to Er3+ ions, and (ii) color tunable emission from red to green, if the power of 980 nm laser is varied. Further, the material is highly competent to sense H2O2 through fluorescence quenching of Sm3+ emission in presence of H2O2. The nature of quenching is conspicuously different for different concentration/volume range of H2O2. For lower volume range, the rate of decrease of emission/excitation intensity is linear, while for higher volume range the decay in intensity is exponential. The attained minimum detection limit for H2O2 is 2 μl, which is significant for sensing applications.

Do dense molecular cores with broad emission spectra at |l| ≈ 5.4°, |b| ≈ 0.4° trace the Galactic bar? A multimolecular line study from HOPS

ABSTRACT We used NH$\rm _3$(1,1) data from the H$\rm _2$O Southern Galactic Plane Survey (HOPS) between −60° < l < −2.7° and 3.9° < l < 30° and |b| < 0.5° to identify dense molecular regions/clumps of the Milky Way Galaxy that are likely to form high-mass stars. We identified ∼500 such clumps and in this paper we report on 14 of these clumps near the Central Molecular Zone that show broad emission spectral lines (with observed velocity widths between 19.8 and 47.6 km s−1 corresponding to intrinsic velocity widths between 7.1 and 25.2 km s−1). We find that these clumps are grouped into three clusters of dense molecular cores centred at l ≈ 5.4°, −5.4°, and −10°. We name them ‘Cluster-1’, ‘Cluster-2’ (also known as ‘Bania’s Clump 1’), and ‘Cluster-3’. We find that the same clumps exhibit broad emission spectra for other molecular lines – NH$\rm _3$(2,2), (3,3), and HC3N(3 − 2). The antisymmetry of Cluster-1 and Cluster-2 in the l − b plane, and the large velocity dispersion of each clump in these two clusters suggest that clusters 1 and 2 may be associated with the Galactic bar potential x−1 orbits. Our assessments show that the clumps of these three clusters host hot gases and their emission-line broadening are associated with shock heating. We find that Cluster-3 is likely to be undergoing high-mass star formation, as suggested by the presence of emission from H$\rm _2$O maser and radio recombination line (H69α) from HOPS.

New Probability Distributions in Astrophysics: IV. The Relativistic Maxwell-Boltzmann Distribution

Two relativistic distributions which generalizes the Maxwell Boltzman (MB) distribution are analyzed: the relativistic MB and the Maxwell-J{\"u}ttner (MJ) distribution. For the two distributions we derived in terms of special functions the constant of normalization, the average value, the second moment about the origin, the variance, the mode, the asymptotic behavior, approximate expressions for the average value as function of the temperature and the connected inverted expressions for the temperature as function of the average value. Two astrophysical applications to the synchrotron emission in presence of the magnetic field and the relativistic electrons are presented.

Education, methane emission and poverty in developing countries

ABSTRACT In developing world, poor people are forced to overuse environmental resources to survive daily, and their impoverishment of the environment is expected to further impoverish them. With poverty and environmental degradation are the primary attribute of most developing countries, this study aims to show the implication of education on poverty-environmental issue in developing countries using panel data of 22 developing countries for the period of 1990–2016. Adopting autoregressive distributed lag (ARDL) approach, the paper finds evidence substantiating the presence of emission which discharged from poverty. There is also evidence to indicate that the positive impact of poverty can be reduced if education has attained a certain high threshold level. The marginal effect displays that the impact of poverty on environmental degradation depends on education, with improvement in education helps to minimize the destruction potentially offered by the poor. Hence, policy focuses on improving various aspects of education, especially those relevant to combat poverty, can mitigate the adverse effect of poverty on emission.

ДОСЛІДЖЕННЯ ТЕПЛОВОГО ВПЛИВУ ВОГНИЩА ПОЖЕЖІ ЧЕРЕЗ ВІКОННИЙ ПРОРІЗ БУДІВЛІ НА ЕЛЕМЕНТИ СУМІЖНИХ ОБ’ЄКТІВ

Наведено результати експериментального визначення зміни температури на елементах суміжних об’єктів від теплового впливу вогнища пожежі через віконний проріз будівлі. Проведено обробку отриманих експериментальних даних за статистичними показниками (абсолютними, відносними та середньоквадратичними відхиленнями, дисперсіями, а також критеріями Граббса та Фішера). Побудована залежність температури на поверхні елементів суміжної будівлі від відстані розташування такої будівлі від осередку горіння та тривалості теплового впливу.

Exploring Bikaverin as Metal Ion Biosensor: A Computational Approach

A computational exploration of fungi produced pigment bikaverin as a biosensor towards bioavailable metal ions is presented. Systematic studies of the optimized ground and excited state geometries were attempted for exploring metal ion binding pocket, comparative binding propensity and optical properties of the bikaverin and its adducts with studied metal ions. The screening of thirteen (13) bioavailable metal ions, revealed a range of binding strength towards bikaverin receptor with Ca2+, Mg2+ and Al3+as the strongest binders. Besides, upon binding to bikaverin receptor an enhancement in its fluorescence intensity was observed in the order Ca2+> Al3+> Mg2+. The computationally predicted selectivity of bikaverin receptor towards Ca2+was experimentally corroborated through the preliminary fluorescence studies. The bikaverin probe showed an enhancement of fluorescence emission in presence of Ca2+ ions in buffered aqueous medium.