Normal Emission Research Articles

Flexible control of excited state transition under pressure/temperature: distinct stimuli-responsive behaviours of two ESIPT polymorphs

The conversion between normal emission and ESIPT can be successfully achieved under pressure and temperature.

Investigation of thermoradiation properties of carbides of refractory metals at high temperatures by pulse electrical heating

Experimental study of thermoradiation properties of refractory metal carbides by the pulse heating method was performed. Quasi-stationary emission spectra of the eutectic system MoC0.82 at high temperatures are obtained, the normal spectral emissivity of this carbide material at two wavelengths is calculated. The efficiency of the chosen technique of spectral pyrometry for studying the thermoradiation properties of refractory carbides at high temperatures is demonstrated.

Assessment of protective effect of ascorbic acid in cisplatin ototoxicity on guinea pigs with electrophysiological tests and ultrastructural study: A Preliminary Study

Objective: It was aimed to display ascorbic acid’s protective efficiency in preventing ototoxicity caused by cisplatin use with electrophysiological tests (Transient Evoked Otoacoustic Emission and Auditory Brainstem Responses) and ultrastructural study (light and electron microscopic). Methods: As a result of electrophysiological tests, 30 ears of 15 guinea pigs with detected normal hearing threshold and emission have been taken into the scope of this survey and they have been randomly divided into 3 groups. One of these three groups have been planned as the control group (Group I), the other two (Group II and III) as working groups. The guinea pigs of the working group, Group II and Group III, have been intraperitoneally administered single dose of 1,5 mg/kg/day cisplatin and, additionally in Group III 300 mg/day Vitamin C administered intraperitoneally for a period of 8 days. Electrophysiological tests for 20 ears of 10 guinea pigs in Group II and III, who have been intraperitoneally drug administered, have been repeated. Internal and inter-group statistical comparisons of data acquired before and after intraperitoneal drug administration have been performed. Temporal bones have been prepared after the measurements, for ultrastructural examinations (for light and electron microscope). Results: No statistically significant differences in emission parameters (reproductibility, response and Signal/Noise rate) and auditory brainstem responses between the working group and control group before drug administration have been identified. The difference between otoacoustic emission parameters and auditory brainstem responses before and after drug administration in Group II (working group) have been identified as statistically significant (p0.05). In light and electron microscope findings of our works, normal cochlear structures have been observed in control group. After drug administration in working group II, clear dystrophic changes, hyper functions and activation of organelles have been observed both in light and electron microscopic images. No clear dystrophic changes have been identified in either light or electron microscopic images of receptor and support cells in Group III after drug administration. Conclusions: We may claim that use of ascorbic acid in preventing ototoxicity developing as a result of cisplatin use has a protective efficiency in line with electrophysiological and ultrastructural findings.

Application of pyrometer and standard sample to determine surface temperature of studied materials

Determining the surface temperature of materials with unknown emissivity is studied. A method for determining the surface temperature using a standard sample of average spectral normal emissivity in the wavelength range of 1,65–1,80 μm and an industrially produced Metis M322 pyrometer operating in the same wavelength range. The surface temperature of studied samples of the composite material and platinum was determined experimentally from the temperature of a standard sample located on the studied surfaces. The relative error in determining the surface temperature of the studied materials, introduced by the proposed method, was calculated taking into account the temperatures of the platinum and the composite material, determined from the temperature of the standard sample located on the studied surfaces, and from the temperature of the studied surfaces in the absence of the standard sample. The relative errors thus obtained did not exceed 1,7 % for the composite material and 0,5% for the platinum at surface temperatures of about 973 K. It was also found that: the inaccuracy of a priori data on the emissivity of the standard sample in the range (–0,01; 0,01) relative to the average emissivity increases the relative error in determining the temperature of the composite material by 0,68 %, and the installation of a standard sample on the studied materials leads to temperature changes on the periphery of the surface not exceeding 0,47 % for composite material and 0,05 % for platinum.

Excitation and Relaxation Dynamics of the Photo-Perturbed Correlated Electron System 1T-TaS2

We investigate the perturbation and subsequent recovery of the correlated electronic ground state of the Mott insulator 1T-TaS 2 by means of femtosecond time-resolved photoemission spectroscopy in normal emission geometry. Upon an increase of near-infrared excitation strength, a considerable collapse of the occupied Hubbard band is observed, which reflects a quench of short-range correlations. It is furthermore found that these excitations are directly linked to the lifting of the periodic lattice distortion which provides the localization centers for the formation of the insulating Mott state. We discuss the observed dynamics in a localized real-space picture.

Determination of high-temperature radiative properties of porous silica by combined image analysis, infrared spectroscopy and numerical simulation

The influence of the texture of fused silica glasses − containing unconnected spherical bubbles − on their thermal radiative properties was investigated by combining experimental measurements and numerical simulations. Exact numerical replicas of the porous samples were obtained from X-ray microtomography and image analysis showed that their bubble populations include two lognormal distributions of radii. The complex refractive index of the silica matrix was extracted from emittance measurements acquired at 1200 K on two reference silica samples. The comparison between direct measurements of the normal spectral emittance of the porous samples and those generated by applying Monte-Carlo ray tracing, performed on the numerical replicas, validated the use of geometric optics. The OH content of the porous samples was evaluated to be around 210 ppm. Ray tracing simulations carried out on a set of virtual samples having a similar texture proved to be a flexible means to address experimental limits when characterizing semi-transparent materials. The simulations also provided a natural framework to test the ability of the modified two-flux approximation model to predict the thermal radiative response of the porous silica investigated.

Emission Factors for a Taxi Fleet Operating on Liquefied Petroleum Gas (LPG) as a Function of Speed and Road Slope

Real-driving emissions of NOx, CO and THC, as well as fuel consumption (FC) were studied from 18 liquefied petroleum gas (LPG) fueled taxis operating in a metropolitan road network. Euro 2 to Euro 5 technology vehicles were measured with the use of portable emission measurement systems (PEMS). Statistical processing was implemented to derive mean emission levels for the different technologies. The taxis were measured from 6 months to 2.5 years after their catalysts and lambda sensors were replaced. Τhe emission levels of Euro 4 taxis after catalyst replacement appear higher compared to pre-replacement levels, while pre-Euro 4 taxis emission levels were moderately reduced by the catalyst replacement. Overall, Euro 5 LPG taxis exhibit the lowest emissions, even below the respective regulated limits. The NH3 and N2O pollutant levels of a Euro 5 LPG taxi measured in the lab were found at about half its NOx emissions. Different integration methods of PEMS data were investigated towards the development of emission factors, including both time-based and distance-based approaches at different resolutions. Distance-based integration in sections of 500 m was considered suitable, as this provides a large dataset for statistical confidence and sufficient resolution for link-based modelling. Based on this, FC and emission factors of NOx, CO and THC as a function of speed and road slope are presented, separately for vehicles considered as normal and high emitters. Volatile organic compounds speciation of Euro 5 taxis showed that methane and butane are the most abundant hydrocarbon species in the exhaust.

Double Perovskite K3InF6 as an Upconversion Phosphor and Its Structural Transformation Through Rubidium Substitution

Luminescent properties including energy upconversion on rare‐earth doped cryolite (double perovskite) structured K3InF6 have been investigated by synthesizing samples (both pure and Eu3+, Tb3+, Er3+ doped and Yb3+/Er3+ co‐doped samples) solvothermally. Cryolite structure of K3InF6 was evident in its powder X‐ray diffraction (PXRD) pattern which could be refined successfully in Fd3 space group with a lattice constant of a = 17.718(3) Å. Three bands centred at 227, 311 and 496 cm–1 were present for K3InF6 in its Raman spectrum at room temperature confirming cryolite structure and phonon energy of it was estimated to be 367 cm–1 by Lorentz fitting procedure. Emissions in red and green regions were observed for Eu3+ and Tb3+ doped K3InF6 samples, respectively. The local site symmetry and nature of bonding in Eu3+ doped samples were analyzed by Judd–Ofelt (J–O) parameters. For Er3+ and Er3+–Yb3+ doped samples, upconversion emission with the laser of λ = 980 nm was carried out in addition to normal excitation and emission spectral measurements. Intra configurational f–f transitions of Er3+ ions were noticed both in normal and upconverted spectra. Emission in red region over the green dominated both in the normal and in upconverted emission spectra. These were reasoned to arise from cross relaxation (CR) energy transfer process between two nearby Er3+‐ions. Structural transformation of cryolite K3InF6 to elpasolite has also been examined by substituting K+ with Rb+.

The normal spectral emittance of the real surface from worked aero-engine nozzle

The radiative properties of the surfaces of aero-engine components have significant impact on inner heat transfer. It is necessary to research the radiative properties of surfaces which have experienced real working conditions. In this paper, samples were cut from an aero-engine exhaust nozzle which was in operation in the engine and have complex surface properties. Some samples were further processed by grinding or scrubbing to produce a substrate alloy sample and a sample without contaminants. The normal spectral emittances of each sample have been measured for wavelengths ranging in 2.5–20 μm at different temperatures (400–1200 K) using Fourier Transform Infrared (FT-IR) spectrometer. The emittance of the substrate alloy increases as temperature increases and wavelength decreases. By comparing different measurement results of samples, it can be inferred that there are three main factors affecting the radiative properties, including oxidation, surface roughness and contaminants. Oxidation can elevate the normal spectral emittance of sample surfaces and give more weight to short-wavelength range. Roughness would mainly affect radiative properties in long-wavelength range. It seems that contaminants change the radiative properties in the whole wavelength range. In reality, these factors usually exist simultaneously and are related to each other. Though the radiative properties of realistic alloy surfaces are relatively complex, it can be analyzed by different factors.

Study of normal spectral emissivity of copper during thermal oxidation at different temperatures and heating times

The normal spectral emissivity of oxidized copper is measured by an experimental setup based on a Fourier transform infrared spectrometer (Bruker 70V) in the wavelength range of 3–20 μm at four temperatures (573 K, 673 K, 773 K, 873 K) during thermal oxidation. Normal spectral emissivity of the samples is obtained every ten minutes for 60 min while the samples are heated at each temperature. The influence of wavelength, temperature, and heating time on the normal spectral emissivity of pure copper during the oxidation process is analyzed. It was found that the spectral emissivity at 12 μm, 15 μm, and 17 μm remained constant for different heating times at 673 K. At the other three temperatures, the normal spectral emissivity demonstrated only a marginal increase with the increase of the heating time at the same wavelength. The oscillation of normal spectral emissivity of pure copper during oxidation was also found. At shorter wavelengths, the theory of radiation interference between the oxide layer and substrate is introduced to explain the spectral emissivity oscillation. In the long wavelength band, the lattice oscillation of the oxide film is used to explain the spectral emissivity oscillation. To better understand these phenomena and the radiative properties of pure copper during thermal oxidation process, the X-ray diffraction, scanning electron microscope and evaluation of surface roughness were performed to describe the compositions and surface micromorphology of the oxide film.

Hydrogen-induced metallization on the ZnO(0001) surface

The formation of hydrogen overlayers on the Zn-terminated $\mathrm{ZnO}(0001)$ surface has been reexamined by angle-resolved photoemission spectroscopy (ARPES). While low-energy electron diffraction patterns display the same (1 \ifmmode\times\else\texttimes\fi{} 1) symmetry for different surface preparations, the electronic structure feature close to the Fermi level shows the formation of electron pockets, compatible with hydrogen-induced metallic states. Using ARPES and density functional theory (DFT) calculations, we show that hydrogen adspecies can also lead to metallization of this zinc-oxide surface in a similar manner as observed previously on $\mathrm{ZnO}(10\overline{1}0)$ and O-terminated $\mathrm{ZnO}(000\overline{1})$. Importantly, our DFT calculations indicate that these electron pockets are formed by $sp$ hybridized states and therefore the angular distribution of the emitted photoelectron is significantly suppressed at the normal emission.

Research on the normal spectral band emissivity of tungsten between 150 and 500 °C.

Tungsten is the baseline divertor material for a tokamak. Due to the effect of the interaction of plasma and the first wall, the first wall accumulates a large amount of heat flux and suffers irreversible damages. Therefore, the diagnosis of the first wall temperature of the tokamak by using a radiation thermometer is the premise to ensure the safe and stable operation of the whole facility. However, in order to achieve high precision of temperature measurement, the emissivity of tungsten must be measured accurately. In this paper, we built a set of emissivity measurement system and a method for accurate calculation of emissivity is proposed. This method effectively eliminated the interference of background radiation and improves the accuracy of emissivity measurement. By using this method, the author measured the emissivity of tungsten under the conditions of different surface roughness in the range of 150 °C-500 °C and discussed the uncertainty of the measurement at the end.

Anatomically and functionally relevant coronary stenoses in patients with normal single-photon emission computed tomography but persistent stable angina.

Single-photon emission computed tomography (SPECT) is widely used for the assessment of coronary artery disease and for decision making regarding revascularization. Concerns about possible false negative findings exist. Our aim was to assess the prevalence of stenoses which are both functionally and anatomically significant in patients referred for invasive fractional flow reserve (FFR) measurements following a normal SPECT, because of persistent complaints. One hundred and thirty-three consecutive patients with normal SPECT were included, with a total of 180 FFR measurements. Luminal narrowing of ≥70% (≥50% for left main) together with a FFR ≤0.80 denoted an anatomically and functionally significant coronary artery stenosis. Separate analyses were performed for FFR <0.75. Mean age of the patients was 65, 40% were women. Sixteen percent of the study population had both anatomically and functionally significant stenoses. Besides the use of nitrate, no differences in baseline characteristics, symptoms, coronary history, or pre-test likelihood could be identified for the prediction of functionally relevant obstructive coronary disease. If FFR <0.75 was used, only 7.5% of the patients had both anatomically and functionally significant stenoses. In patients with normal SPECT who undergo FFR measurements because of persistent complaints, the prevalence of stenoses which are both anatomically and functionally significant is low. This suggests that the prevalence of false-negative SPECT is (very) low.

Optical property evaluation of thoria doped with heavier rare‐earth oxides LnO1.5 (Ln = Er3+, Ho3+, Tm3+, and Yb3+)

AbstractTo address the existing gap in the literature of upconversion studies involving thoria, samples of thoria doped with Ho3+‐Yb3+, Er3+‐Yb3+, and Tm3+‐Yb3+ were synthesized following epoxide gel method and were characterized. Fluorite structure of the doped samples was evident for the calcined samples from the corresponding xerogels as noticed in their powder X‐ray diffraction patterns. The presence of a sharp band near 460 cm−1 in the Raman spectra of all these samples supported the results from diffraction experiments. Intraconfigurational f‐f transitions of Ho3+, Er3+, and Tm3+ were present in the UV‐visible absorbance spectra of these samples. Both normal emission and upconversion emission from these samples have been studied. Emissions in all three basic colors were observed in the upconversion emission spectra. Two‐photon process was found to be responsible for the upconversion in these systems. Decay time measurements for these emissions were analyzed. This synthetic process was further extended to determine the extent of dissolution of heavier lanthanides and found that up to 50 mol% of Ho3+, Er3+ and 60 mol% of Tm3+, Yb3+ could be dissolved retaining fluorite structure. Creation of oxygen vacancies for these heavily doped specimens was quite encouraging and it could be useful as solid electrolytes in fuel cells.

Stress-dependence of generalized stacking fault energies

The energy associated with shearing of planes of atoms in a crystal is the generalized stacking fault energy (GSFE). It is a crucial material property for describing nanoscale plasticity phenomena in crystalline materials, such as dislocation dissociation, nucleation, and twinning. The dependence of the GSFE on applied stress normal to the stacking fault has been suggested to influence such phenomena. Here, the stacking fault stress dependence is analyzed through (i) the generalized stacking fault potential energy (GSFE) and (ii) the generalized stacking fault enthalpy (GSFH). At an imposed shear displacement, there is also an associated inelastic inter-planar normal displacement around the fault. Extensive molecular statics simulations with interatomic potentials and/or first principle calculations in Ni, Cu, Al and Mg reveal that GSFE and inelastic normal displacement both increase with tensile stress. An increasing GSFE contradicts long-standing wisdom and previous studies. Positive inelastic normal displacement coupled to the applied normal stress decreases the GSFH, but is not useful for general mechanics problems. The existence of the inelastic displacement can lead to incorrect measurements of the GSFE and GSFH in finite systems loaded by an applied strain. Application of the GSFE and the inelastic normal displacement to both fcc dissociation distance versus applied normal stress and crack tip dislocation emission under mixed Mode II/I loading show very good agreement with direct simulations. In general, “opening softening” effects are not universal, and so the analysis of any particular nanomechanics problem requires precise implementation of the combination of GSFE and inelastic normal displacement rather than the GSFH.

The normal spectral emission characteristics of Ni-based alloys during oxidation at high temperatures

The emissivity change due to oxidation of the Ni-based alloys that are used for turbine blades in severe environment will cause large errors in radiation thermometry. In this paper, the normal spectral emissivity of three Ni-based alloys DZ125, DD6 and K465 is experimentally measured during oxidation at about 810, 914 and 998 °C in air. And the measurement wavelength varies from 1.35 to 2.35 μm. The combined standard uncertainties of the normal spectral emissivity are less than 3%. The oscillations of the emissivity are observed, and the effects of oxidation temperature, heating time and wavelength on the emissivity are investigated. The oscillations of the emissivity are produced with growth of the oxidation film by the interference effect between the direct transmission radiation and the transmission radiation after reflections by the substrate and air/film interface emitted by of the substrate. The oscillation extremums of the emissivity shift towards larger wavelengths as the oxidation process proceeds. The results show that the normal spectral emissivity increases basically with increasing temperature and decreasing wavelength except for the occurrence of the oscillations of the emissivity. The normal spectral emissivity increases rapidly at the initial heating time, and the change of emissivity becomes slow when the oxidation tends to be saturated gradually. Furthermore, the emissivity models versus heating time and wavelength are established, which fit the experimental results very well. The relative errors of the fitting models for emissivity are less than 4%.

Correlation among Hydrogen Bond, Excited-State Intramolecular Proton-Transfer Kinetics and Thermodynamics for −OH Type Proton-Donor Molecules

A series of new molecules bearing alkyl-substitutes on the parent molecule 1-hydroxy-11H-benzo[b]fluoren-11-one (HBF) has been designed and synthesized, which possesses an intramolecular hydrogen bond (H-bond) between −OH proton donor and carbonyl proton acceptor. All studied molecules present an equilibrium type of excited-state intramolecular proton transfer (ESIPT) at 298 K. The alkyl-substitutions at various positions subtly alter the intramolecular H-bond strength, which then fine-tune the excited-state equilibrium and hence thermodynamics between normal and tautomer species. These, in combination with finite rates of ESIPT resolved by femtosecond fluorescence upconversion techniques, lead to the establishment of an empirical relationship among H-bond strengths, ESIPT kinetics, and thermodynamics for HBF series of molecules, in which the stronger H-bond is, the faster and more exergonic ESIPT is. The intensity ratio for normal versus proton-transfer tautomer emission can be systematically tuned, demo...

Density of Liquid Tantalum and Estimation of Critical Point Data

In order to determine the density of tantalum over the entire liquid phase (at the pressure applied) and several hundred K into the super-heated region, the method of ohmic pulse-heating was applied. For this purpose, images of the thermal radial expansion of the resistively heated sample wires were taken with an adapted CCD system. A newly integrated high-power photoflash and improved triggering of the experiment allowed the acquisition of high-contrast shadow images of the expanding wires. To reduce the uncertainty arising from simultaneous pyrometric temperature measurement, the change in normal spectral emissivity as a function of temperature was additionally taken into account. In this work, the density versus temperature relationship of tantalum is reported and compared to existing literature data. From the newly obtained liquid-phase density, critical point data of tantalum, such as critical temperature and critical density, were estimated via an extrapolation procedure. Furthermore, an estimate of the phase diagram in the density versus temperature plane is given. The work is concluded by a rigorous density uncertainty estimation according to the guide to the expression of uncertainty in measurement (GUM).

Tinnitus and Auditory Perception After a History of Noise Exposure: Relationship to Auditory Brainstem Response Measures.

To determine whether auditory brainstem response (ABR) wave I amplitude is associated with measures of auditory perception in young people with normal distortion product otoacoustic emissions (DPOAEs) and varying levels of noise exposure history. Tinnitus, loudness tolerance, and speech perception ability were measured in 31 young military Veterans and 43 non-Veterans (19 to 35 years of age) with normal pure-tone thresholds and DPOAEs. Speech perception was evaluated in quiet using Northwestern University Auditory Test (NU-6) word lists and in background noise using the words in noise (WIN) test. Loudness discomfort levels were measured using 1-, 3-, 4-, and 6-kHz pulsed pure tones. DPOAEs and ABRs were collected in each participant to assess outer hair cell and auditory nerve function. The probability of reporting tinnitus in this sample increased by a factor of 2.0 per 0.1 µV decrease in ABR wave I amplitude (95% Bayesian confidence interval, 1.1 to 5.0) for males and by a factor of 2.2 (95% confidence interval, 1.0 to 6.4) for females after adjusting for sex and DPOAE levels. Similar results were obtained in an alternate model adjusted for pure-tone thresholds in addition to sex and DPOAE levels. No apparent relationship was found between wave I amplitude and either loudness tolerance or speech perception in quiet or noise. Reduced ABR wave I amplitude was associated with an increased risk of tinnitus, even after adjusting for DPOAEs and sex. In contrast, wave III and V amplitudes had little effect on tinnitus risk. This suggests that changes in peripheral input at the level of the inner hair cell or auditory nerve may lead to increases in central gain that give rise to the perception of tinnitus. Although the extent of synaptopathy in the study participants cannot be measured directly, these findings are consistent with the prediction that tinnitus may be a perceptual consequence of cochlear synaptopathy.

Fine-tuning the photophysical properties of the five quinolin based nanophotoswitches in the gas phase, polar and nonpolar solvents: A TD-DFT approach

Fluorophores exhibiting excited state intramolecular proton transfer (ESIPT) have received increasing attention during the last decades. The swiftness of ESIPT process often avoids its inspection with only experimental methods, and theoretical explorations are often necessary to achieve a full justification of the observations and fine-tuning the ESIPT fluorescence properties. In this work, photo-switching in five novel red light emitting molecules 11hydroxy-indeno[1,2-b]quinolin-4ol (11HIQO), 4hydroxy-11H-indeno[1,2-b]quinolin-11one (4HIQO), 10H-indolo[3,2-b]quinolin-6-ol (10HIQO), benzofuro[3,2-b]quinolin-6-ol (BFQO) and benzothieno[3,2-b]quinolin-6-ol (BTQO) was comprehensively investigated using a robust protocol based on Time-Dependent Density Functional Theory (TD-DFT) at PBE0/6-311++G(2d,2p) level of theory. The interplay between π-conjugation and aromaticity was observed in all five photo-switching molecules in which are able to render both normal and keto fluorescence emissions with wavelengths longer than 610 nm and large Stokes shifts in gas phase (242–472 nm) and solvent media (187–385 nm). The normal and tautomer emissions were assigned to the relaxation of the initially excited Franck-Condon (FC) state to normal (S1-E) and tautomer (S1-K) states, respectively. The full photo-switching cycle and potential energy surfaces in the ground and excited states and structural parameters, H-bonding energy, absorption and emission wavelengths, vertical excitation and emission energies, oscillator strength, fluorescence rate constant, dipole moment, atomic charges and electron density at critical points for five new photochromic ESIPT switches were explored. The potential of these molecules as emissive switches in designing and generation of new displays and light sources in the molecular photo-devices were predicted based on their high red Stokes shifts.