Band Profiles Research Articles

Auger Suppression of Incandescence in Individual Suspended Carbon Nanotube pn-Junctions.

There are various mechanisms of light emission in carbon nanotubes (CNTs), which give rise to a wide range of spectral characteristics that provide important information. Here we report suppression of incandescence via Auger recombination in suspended carbon nanotube pn-junctions generated from dual-gate CNT field-effect transistor (FET) devices. By applying equal and opposite voltages to the gate electrodes (i.e., Vg1 = -Vg2), we create a pn-junction within the CNT. Under these gating conditions, we observe a sharp peak in the incandescence intensity around zero applied gate voltage, where the intrinsic region has the largest spatial extent. Here, the emission occurs under high electrical power densities of around 0.1 MW/cm2 (or 6 μW) and arises from thermal emission at elevated temperatures above 800 K (i.e., incandescence). It is somewhat surprising that this thermal emission intensity is so sensitive to the gating conditions, and we observe a 1000-fold suppression of light emission between Vg1 = 0 and 15 V, over a range in which the electrical power dissipated in the nanotube is roughly constant. This behavior is understood on the basis of Auger recombination, which suppresses light emission by the excitation of free carriers. Based on the calculated carrier density and band profiles, the length of the intrinsic region drops by a factor of 7-25× over the range from |Vg| = 0 to 15 V. We, therefore, conclude that the light emission intensity is significantly dependent on the free carrier density profile and the size of the intrinsic region in these CNT devices.

Anatomical features and SCoT profiles provide new insight into phenotypic plasticity in the halophyte Suaeda maritima in Thailand

Abstract. Rittirongsakul K, Srinual A, Vanijajiva O. 2020. Anatomical features and SCoT profiles provide new insight into phenotypic plasticity in the halophyte Suaeda maritima in Thailand. Biodiversitas 21: 1082-1090. Phenotypic plasticity is the variation in phenotypic traits of organisms to survive with fluctuating environments. Halophytes are plants that can naturally tolerate high concentrations of salt in the soil, and their tolerance to salt stress, which reflects the ability of the plants to produce different phenotypic traits in response to changing environmental conditions. Suaeda maritima (L.) Dumort is a polymorphic halophyte and prominent species complex from tropical to temperate regions due to diverse stressful saline habitats. Consequently, the identification of S. maritima based on morphological data is challenging due to high phenotypic plasticity. In Thailand, S. maritima, known as Seablite or Cha Khram, has only been reported for the genus Suaeda which frequently found in coastal salt marshes. The peculiarities of the prevalence of three distinctive color traits, green, green-reddish and reddish, were commonly observed in Thailand. This preliminary study aims to examine the morpho-anatomical characters and molecular analysis of S. maritima and to determine how their morphological and genetic characterizations are related to phenotypic traits, particularly in color variation within the population at Bang Khun Tien shoreline in Bangkok, Thailand. This combined investigation of anatomical characters and start codon targeted (SCoT) fingerprinting profiles provide first evidence of phenotypic variations and genetic characterizations of halophytic S. maritima in Thailand. Anatomical characters of leaf structures confirmed that the species is austrobassioid (C3) types. Meanwhile, molecular investigation of thirty SCoT primers found that only two SCoT primers (SCoT10 and SCoT27) failed to amplify the S. maritima genomic DNA. Thoroughly, twenty-eight SCoT primers produced 162 unambiguous and reproducible banding profiles with 140-1200 bp product size. Despite, there was no genetic variation detectable within the population, SCoT technique was considered a suitable tool to produces adequate characterization for DNA fingerprinting of halophyte S. maritima. However, further studies involving additional samples of S. maritima are needed to obtain a more general view of the conspicuous variation and colonization history in Thailand.

Distinguishing Features and Identification Criteria for K-Dioctahedral 1M Micas (Illite-Aluminoceladonite and Illite-Glauconite-Celadonite Series) from Middle-Infrared Spectroscopy Data

A representative collection of K-dioctahedral 1M micas ranging in composition from (Mg, Fe)-poor illites to aluminoceladonites through Mg-rich illites (Fe-poor varieties) and from Fe-bearing, Mg-rich illites to celadonites through Fe-illites, Al-glauconites and glauconites (Fe-bearing varieties) was studied by Fourier-transform infrared (FTIR) spectroscopy in the middle-infrared region. Analysis and comparison of the relationships between the band positions and cation compositions of Fe-poor and Fe-bearing K-dioctahedral micas provided a generalized set of FTIR identification criteria that include the band positions and profiles in the regions of Si–O bending, Si–O stretching, and OH-stretching vibrations. FTIR data allow unambiguous identification of illites, aluminoceladonites, and celadonites, as well as distinction between Fe-illites and illites proper, as well as between Al-glauconites and glauconites. Specifically, a sharp maximum from the AlOHMg stretching vibration at ~3600 cm−1, the presence of a MgOHMg stretching vibration at 3583–3585 cm−1, as well as characteristic band positions in the Si–O bending (435–439, 468–472 and 509–520 cm−1) and stretching regions (985–1012 and 1090–1112 cm−1) are clearly indicative of aluminoceladonite. The distinction between Fe-illites and Al-glauconites, which have similar FTIR features, requires data on cation composition and unit-cell parameters.

Changes in essential oil composition, phenylalanine ammonia lyase gene expression and rosmarinic acid content during shoot organogenesis in cytokinin-treated Satureja spicigera (C. Koch) boiss. shoots

This study investigated the effects of different concentrations of zeatin and thidiazuron on the accumulation of phenolics and activity of phenylalanine ammonia lyase gene in the micropropagated Satureja spicigera shoots. S. spicigera clones were generated from cultured nodal segments on Murashige and Skoog including vitamins medium supported with zeatin and thidiazuron concentrations. Shoots were subcultured three times in the same medium and harvested at the end of the third month. The expression levels of phenylalanine ammonia lyase gene were conducted using semi-quantitative reverse transcription polymerase chain reaction technique. Rosmarinic acid contents were determined using reverse phase-high performance liquid chromatography with a diode array detector. Genetic stability of regenerants was performed using random amplified polymorphic DNA markers. Essential oils from shoots were identified by gas chromatography–mass spectrophotometry analysis. It has been detected that 0.1 mg/L thidiazuron is more effective on the node formation and shoot elongation. Contrarily, 4.0 mg/L thidiazuron caused a significant increase in shoot multiplication. The highest biomass accumulation was calculated from medium including 1.0 mg/L zeatin. According to random amplified polymorphic DNA analysis, all banding profiles from micropropagated plants were monomorphic. Gas chromatography–mass spectrophotometry analysis showed that rising concentrations of zeatin and thidiazuron increased the thymol and decreased the carvacrol content. It was also found that rosmarinic acid production increased significantly at 1.0 mg/L zeatin application. However, thidiazuron applications had no positive effect on rosmarinic acid accumulation. Comparing phenylalanine ammonia lyase gene expression and rosmarinic acid accumulation in in vitro shoots, it was found that they were correlated.

Tuning the Aggregation of GHG by Changing Sample Concentration and pH

Self-assembly of peptides is an important issue explored in biomedical, biophysical, and biomaterial research. Small peptides have been heavily researched due to their inherent biodegradability. Low molecular weight di- and tripeptides with aromatic residues and terminal groups have been found to self-assemble into gels. However, despite their aromatic character, short histidine-containing peptides were predicted to exhibit a low aggregation propensity. Contrary to this expectation, we discovered that unblocked GHG forms a hydrogel upon deprotonation of the imidazole side chain. Concomitantly, its apparent pK decreases due to a gelation induced stabilization of its deprotonated state. The apparent pK decreases further with increasing concentration. The sub-millimeter fibril length differs significantly from those of other hydrogel-forming peptides, which are generally on the sub-micrometer scale. We utilized rheology, circular dichroism, and vibrational spectroscopy to study the gelation process and the thermal stability of the gel. Rheology measurements yielded G’ values on the order of 105 kPa. As we increase the pH past the initial point of gelation, the rate of formation and the final G’ value increase. The enhanced circular dichroism of the amide I’ band is diagnostic of long and stable fibrils. The circular dichroism signal indicates anisotropy of the sample. Corresponding IR band profiles indicate a complex mixture of β-sheet and amorphous aggregate structures. Our results show that histidine can be used as a switch for the formation of large supramolecular structures even in very short peptides and that the properties of the gel can be tuned by altering the concentration and pH of the sample.

Identification and Characterization of Novel Thermophilic Bacteria from Hot Springs, Erzurum, Turkey.

The aim of present study was the isolation and characterization of thermophilic bacteria from three different hot springs in Erzurum, Turkey. For this purpose, 85 bacteria were isolated and characterized by ERIC-PCR genomic fingerprinting and classical identification methods such as morphological, physiological and biochemical characteristics. According to the results, 29 bacterial isolates with different band profiles were analyzed by 16S rRNA gene sequencing and identified as belonging to the genus of Bacillus, Pseudomonas, Silanimonas, Thermomonas and Thauera. This is the first report on the isolation of Silanimonas lenta, Thauera sp. and Thermomonas haemolytica from Turkey Hot Springs. The amylase, lipase and protease enzyme production potentials of the isolates were 80%, 91.25% and 81.25%, respectively. Moreover, 56.47% of the isolates (48) were able to produce all of these enzymes. Therefore, the results of the study indicated that these bacteria and their enzymes can be used as a source of industrial enzymes.

Liquid culture for efficient in vitro propagation of adventitious shoots in wild Vaccinium vitis-idaea ssp. minus (lingonberry) using temporary immersion and stationary bioreactors

Efficient systems to multiply adventitious shoots regenerated from excised leaves of greenhouse-grown wild Vaccinium vitis-idaea L. ssp. minus (Lodd.) Hult. (lingonberry) clones were developed in vitro. Shoot regeneration took place when the leaf explants were cultured on a semi-solid gelled medium, positioned with the adaxial or abaxial side touching the culture medium and maintained in darkness for 2 weeks followed by culturing for another 6 weeks under light. Although zeatin (9.1 μM) or TDZ (1.8 μM) were efficient to induce adventitious shoots from leaf explants, shoot elongation was better on a medium with zeatin. Nodal segments of regenerated shoots were evaluated for shoot proliferation on a semi-solid and in a liquid medium using stationary (SB) and temporary immersion bioreactors (TIB). After 8 weeks of culture, shoot multiplication was 2–3 times more in liquid medium than on a semi-solid medium. Although shoots proliferated in a liquid medium containing 9.1 μM zeatin or 1.8 μM TDZ showed 10 % and 25 % hyperhydricity in SB and TIB respectively, rooting was not affected when regenerated shoots were dipped into 39.4 mM indole-3-butyric acid powder and planted in a 2:1 of peat: perlite medium. Liquid culture-derived plants when transferred to a greenhouse for acclimatization, 90–95 % plants survived. Micropropagated plants were phenotypically similar to the donor mother plants although the contents of chlorophyll a and b were more in the leaves of cutting propagated plants compared to micropropagated ones. Expressed sequence tag - simple sequence repeat (EST-SSR), EST- polymerase chain reaction (PCR) and inter simple sequence repeat (ISSR) banding profiles of the regenerated plants were monomorphic like those of the donor plants that confirmed clonal fidelity of tissue culture plants derived from in vitro leaf culture in V. vitis-idaea ssp. minus.

Effective Schottky Barrier Height Model for N‐Polar and Ga‐Polar GaN by Polarization‐Induced Surface Charges with Finite Thickness

The nitrogen‐polar GaN material system is a promising candidate for high‐frequency applications, such as those in the millimeter‐wave range. Schottky barrier height is one of fundamental parameters necessary for device applications of N‐polar GaN. Herein, vertical Schottky diodes for both N‐polar and Ga‐polar GaN are prepared, and it is found through experiments that the barrier height of N‐polar GaN is smaller than that of Ga‐polar GaN by 0.21 V. This difference in the barrier height stems from the polarization‐induced surface charge layer of a few angstroms thickness under the surface. Numerical calculation of band profiles suggests that a significant band bending caused by the large amount of polarization charges pushes the conduction band energy downward (upward) in the N‐polar (Ga‐polar) surface depending on the sign of the polarization charges, which results in two different effective Schottky barrier heights. This difference is explained by assuming the polarization‐charge layer thickness of about 5 Å. A simple analytical model to estimate the difference in barrier heights between the two polarities is also proposed.

A reproducible protocol for adventitious shoot regeneration from leaves of apple rootstock Merton793 and assessment of genetic stability

The present studies were aimed to develop an efficient and reproducible method for shoot regenerationfrom leaf explants of apple rootstock Merton793. The influence of two cytokinins BA and TDZ with three auxinsIAA, IBA and NAA in different combinations were evaluated for shoot induction using light and dark incubation.Direct and healthy shoots were obtained from leaves on MS medium with BA-NAA and BA-IAA combinations inlight incubation and 100% regeneration was achieved on medium with 4 mg/l BA and 1 mg/l NAA. Both directand indirect shoot regeneration was obtained on TDZ-NAA and TDZ-IBA. Maximum shoot regeneration waspromoted on 0.8 & 0.6 mg/l TDZ with 1 mg/l NAA, however, it showed abnormal, vitrified, small and rosettetype of shoots. Dark treated leaf explants showed low rates of shoot induction with TDZ combinations. Healthyadventitious shoots regenerated directly from leaves were multiplied, rooted and hardened successfully. RAPD analysis of regenerants revealed that all the banding profiles from directly originated shoots were monomorphicand similar to those of the mother plant, while shoots originated through intervening callus revealed 61.2%polymorphism. The results show that genetic fidelity of directly produced adventitious shoots was maintained,and thus, our regeneration protocol can be an useful method in transformation research in Merton793 withoutthe induction of variation.

Characteristics of Blue GaN/InGaN Quantum-Well Light-Emitting Transistor

We demonstrate simultaneous electrical and optical modulations of the first GaN/InGaN quantum-well light-emitting transistor (QW-LET) which contains an In0.15 Ga0.85N QW in the heavily p-doped In0.05 Ga0.95N base. Unlike GaAs/InGaAs counterparts, the GaN/InGaN QW- LET has a current gain (up to 5) and optical power which increases linearly with the base current. Its emission spectra are centered at a wavelength of 420 nm and barely shift with the current injection, in contrast to the behavior of typical nitride-based LEDs. The unusual features of this device may be related to the tilted band profile induced by the polarization field in the QW and issue of p-type doping.

Doping-induced energy barriers to improve the current spreading effect for AlGaN-based ultraviolet-B light-emitting diodes

Current crowding effect for AlGaN based ultraviolet-B light-emitting diodes (UVB LEDs) is normally observed at high injection current levels, which can cause non-uniform optical emission and generate very high local heat. In this work, UVB LED with a PNP-AlGaN current spreading layer is fabricated and studied. The PNP-AlGaN current spreading layer is obtained by sandwiching the n-AlGaN layer into the p-AlGaN layer. Owing to the modulated energy band profiles by the different doing types, the formed energy barriers for holes in PNP-AlGaN layer can make the current more uniformly distributed laterally and therefore the hole injection efficiency at the mesa edges can be enhanced. As a result, the measured external quantum efficiency (EQE) and optical output power for the proposed UVB LED is increased. Moreover, thanks to the enhanced current spreading effect, the thermal droop for the optical output power is suppressed and the forward voltage decreases for the proposed architecture.

Molecular Typing of Different Salmonella Serotypes by Multiple-Locus Analysis of Tandem Repeats.

Salmonella enterica subspecies enterica causes salmonellosis in humans and animals and is an important cause of food infections worldwide. In recent years, the multiple-locus variable-number of tandem repeat (VNTR) analysis (MLVA), a fast molecular typing method with strong epidemiological discrimination, has facilitated the effective control of diverse infections. This study aimed at the typing of 28 human origined Salmonella enteritidis, Salmonella infantis, and Salmonella typhimurium strains by using a single MLVA protocol. Previously these strains have been identified by pulsed field gel electrophoresis (PFGE) method and it has been shown that each strain produced a distinct PFGE banding profile. One MLVA protocol was tested on 3 serotypes simultaneously and it produced three banding patterns specific to each of the three common Salmonella serotypes. MLVA also constitute a relatively more cost-effective and faster method than PFGE.

Impact of Digital Alloy Capping Layers on Bilayer InAs Quantum Dot Heterostructures

The influence of digital alloy capping technique on the strain-coupled bilayer InAs quantum dots (QDs) has been presented. Multiple capping layers of different composition have been utilized instead of a single thick capping layer to reduce the overall strain inside the heterostructure. In bilayer QDs, the propagation of residual strain from the lower QD layer to the top QD layer introduces defects and dislocations. By using the digital alloy technique over the conventional or analog alloy capping technique, the surface defects could be minimized and the crystallinity could be improved. In this study, four different capping materials have been considered, viz. two ternary materials (InxGa1-xAs and GaAs1-xSbx) and two quaternary materials (InxAlyGa1-x-yAs and InxGa1-xAs1-ySby) for analysis of both analog alloy and digital alloy techniques. The strain and energy band profile has been computed for all the heterostructures using Nextnano software. The biaxial and hydrostatic strain have been computed and compared to understand the strain distribution within the heterostructures. The ground state emission wavelength was found red shifted for the InAs bilayer QD heterostructure with digital alloy capping layers as compared to that of the analog alloy capping. Moreover, the choice of capping materials exhibits both type-I and type-II energy band alignment which is suitable for different optoelectronic applications. This comparative study of analog and digital alloy capping layer for the bilayer QDs would definitely help in optimization of the device heterostructures with minimal strain and defects.

The absorption and fluorescence spectra of 4-(3-methoxybenzylidene)-2-methyl-oxazalone interpreted by Franck-Condon simulation in various pH solvent environments.

The absorption and fluorescence spectra of 4-(3-methoxybenzylidene)-2-methyl-oxazalone (m-MeOBDI) dissolved in neutral, acidic, and basic solvent environments have been investigated and assigned by using Franck-Condon (FC) simulations at the quantum TDDFT level. Four different structures of m-MeOBDI in the ground and excited states are optimized and are found to be responsible for the observed absorption and fluorescence spectra. The (absorption) fluorescence of m-MeOBDI in pure methanol and neutral/basic methanol/water (1/9 vol) mixed solvent is found to arise from the (ground neutral N-I) excited neutral N-I* and cationic C-III* species, respectively. In acidic solvent, the absorption is found to arise from ground acidic C-II species, and the excited divalent cation DC-IV* is found to be formed in its excited state due to the excess H+ in the solution, and then it emits ∼560 nm fluorescence. FC simulations have also been employed to confirm our assignments as well as interpret the vibronic band profiles. As expected, the simulated emission spectrum of the divalent cationic species is in good agreement with the experimental observation. Therefore, within the present FC simulation, the observed absorption and fluorescence spectra have been reasonably interpreted and novel fluorescence mechanisms of m-MeOBDI in various pH solvent environments have been proposed.

Genetic Characterization of Maize Kisar Var. Kuning Genjah and Maize Var. Bisi-II-Hibrida Based On Molekular RAPD Marker

The variety of maize in Southwest Maluku (MBD) has an ability to grow in the extremely dry land, especially at Kisar island, because those areas were dominated by dry land. Dry resistance very useful to be used for genetical characterization in order to provide accurate data about the character of local maize Kisar var. Kuning Genjah. To identify the characteristics at the genome level of this local maize variety, one of the molecular methods that can be applied was RAPD molecular method. The advantage of the RAPD marker is it's technically simpler and fast in testing, does not require DNA sequence information, hence this marker becomes widely used, it only requires a small sample of DNA, the primary is commercially available and does not use radioactive compounds. The aim of this study was to find out the bands profile that has the potential to be used as a marker of dry resistance. The method applied was RAPD (Random Amplified Polymorphic DNA) using OPA-02, OPA-07, and OPC-12 primers and produces 22 DNA bands. The measurement of bands by estimating the molecular weight based on marker exponential regression. The polymorphic percentage was 90.9% between var. Kuning genjah and var. BIZI-II-Hybrid. The percentage of polymorphism showed the potential of bands that can be used as molecular markers for markers of dry resistance that can be utilized in plant breeding

Band Variations Caused by Strain Effects for Quantum Wires With Arbitrary Orientations

We develop a 2-D continuum elasticity model to study semiconductor band variations caused by strain effects for quantum wires (QWRs) with arbitrary orientations on the (001) plane. The model is implemented by the finite-element method, considering the anisotropic properties of semiconductor crystals and the geometric shapes of QWRs. Using this model, we systematically investigate the changes of band profiles and band gaps as the orientation of an InAs/GaAs QWR varies. We find that band energy deformations due to hydrostatic strain, biaxial strain, and piezoelectric effects are all orientation dependent. In particular, the piezoelectric energy changed dramatically with the orientation. These effects, in turn, cause the bandgap to be orientation dependent. The QWR along [100] or [010] has the minimum bandgap; and the QWR along the [110] or $[{1}{\overline {{{1}}}}{0}]$ direction has the largest bandgap. For some cases, such as the triangle-based QWR, the bandgap change can be significant; and the heavy-hole and light-hole bands may cross or even flip at certain orientations. We also observe that the bandgap profile or pattern inside the QWRs is not sensitive to the orientation. For cylindrical QWRs, the bandgap is uniform, but for the triangle-based QWR, the bandgap has strong location dependence.

Thermal and IR-Fourier transform spectroscopic study of water-soluble carbohydrate-arylamine condensation products in neutral media

Production of synthetic analogues of natural compounds, including high-molecular ones, as well as study of processes of their structure formation, is a pressing task of organic substances technology. To a large extent, this applies to synthetic humic substances, important products characterized by plant growth effect, chelating and other important properties. Simple carbohydrates and aromatic amines as oxygen and nitrogen-containing constituents during condensation in ethanol media produce water-fractionated products, the soluble fractions of which are studied herein by thermal degradation in combination with IR-Fourier transform spectroscopy. Spectral band profile is confirmed mainly by aliphatic structure with high degree of functionalization by carboxyl, hydroxyl and amine groups. As the isolated water-soluble solid products are thermally decomposed in the range of 100-180 °С temperatures in an inert atmosphere, the intensity of bands at 1030 and 1090 cm-1 decreases, and the intensity of the first band drops to almost zero at 180 °С. This experimental fact indicates the progress of thermal dehydration processes, indicating the presence of hydroxyl functions in the structure of the products. The latter are both OH-groups of carbohydrate residue and groups, formed during condensation processes. Additionally, the intensity of the absorption band in the region of 1600 cm-1 corresponding to the fluctuations of double bonds resulting from dehydration is increased. It can be assumed that unlike products of insoluble fractions, as well as products of acid-catalyzed condensations, water-soluble products are formed in neutral ethanol media, the main processes of formation of which are processes of direct retro-aldol cleavage of N-glycosylamines with subsequent condensation of decomposition products. Such a set of processes is an alternative to the experimental difficulty of Amadori rearrangement and lead to formation of products structure differ from one for acid catalyzed condensation products.

Tracking of Intentionally Inoculated Lactic Acid Bacteria Strains in Yogurt and Probiotic Powder.

The present work aimed at tracking intentionally inoculated lactic acid bacteria (LAB) strains in yogurt and probiotic powder. Leuconostoc (Leu.) mesenteroides (11251), Lactobacillus (L.) brevis (B151), and Lactobacillus plantarum (LB41K) strains were tracked in yogurt, and L. plantarum (LB41P) was tracked in a commercial probiotic powder. The yogurt was intentionally inoculated with the selected bacterial strains. Two types of yogurt with known and unknown bacterial pools were utilized. The standard 16S rRNA gene sequencing was used to evaluate the initial screening. The molecular typing tools, random amplified polymorphic DNA (RAPD), repetitive element palindromic PCR (rep-PCR), and comparative gene sequence analysis of selected housekeeping loci were used to track the inoculated dubious strains. Out of 30 random selections for each inoculation, the developed method identified seven (11251), nine (B151), and five (LB41K) colonies in the yogurt. The validation was performed by identifying 7 colonies (LB41P) out of 30 in the probiotic powder. The DNA banding profiles and the gene sequence alignments led to the identification of the correct inoculated strains. Overall, the study summarizes the use of molecular tools to identify the deliberately inoculated LAB strains. In conclusion, the proposed polyphasic approach effectively tracked the intentionally inoculated strains: Leu. mesenteroides, L. brevis, and L. plantarum (LB41K) in yogurt and L. plantarum (LB41P) in probiotic powder. The study demonstrates how to track industrially relevant misused LAB strains in marketable food products.

Revision of the 60-GHz atmospheric oxygen absorption band models for practical use

Two models for millimeter-wave absorption by molecular oxygen in the air are updated. To derive the updated parameter set, earlier resonator spectrometer data are refined and recent data on the collisional parameters’ temperature behavior are taken into account. The updated models provide significantly better agreement between laboratory measurements and calculated absorption band profiles than their earlier versions. The predictive ability of the models is confirmed by new experimental data. The covariance matrix of empirical parameter uncertainties, together with absorption-calculation uncertainty, are evaluated for both updated models. Contributions of the various sources to the total calculation uncertainty are discussed.

Impacts of N2 and CO2 diluent gas composition on flame emission spectroscopy for fuel concentration measurements in flames

Flame emission spectroscopy (FES) is used to determine methane fuel concentration in a premixed flat-flame burner with varying diluent composition. Spectral profiles of the molecular emission bands of OH* (306.4 nm), CH* (431.5 nm), and C2* (520 nm) in the UV-to-visible range are recorded and analyzed for various equivalence ratios (0.72 < ∅ < 1.25), oxygen concentration (0.19 < XO2 < 0.35), and diluent gas species (N2, CO2). The importance of flame radiation, which is strong and reliable in the UV spectrum, is confirmed particularly for quantitative measurement purposes. In air-methane flames, the band intensity ratios of OH*/CH* and C2*/CH* are shown to be highly sensitive to fuel stoichiometry, and can thus serve as accurate indicators of ∅. In addition, the impact of diluent gas composition on flame radiation characteristics and FES utilizing band intensity ratios is investigated for potential applications such as clean combustion utilizing exhaust gas recirculation (EGR), and oxy-combustion in supercritical CO2 power plants. It is shown that the strength of the underlying broadband emission is strongly dependent on the diluent gas composition, and influences the sensitivity and accuracy of the FES-based ∅ measurement.