Low OH Research Articles

Efficient approach to designing low OH diffusion in the thermally shaped double-clad fibers

Hydroxyl groups (OH) penetrate the surface of the fiber preforms as a result of preform processing in the oxy-hydrogen flame. Designing double-clad fibers (DCFs) that have a complex noncircular inner-cladding shape with concave and convex edges are possible by shaping their optical preforms thermally with a CO2 laser. Unlike the mechanical technique, the thermal shaping via CO2 laser has paved the way for fabricating DCFs with various inner-cladding geometries that are not limited to the flat edge. However, due to the thermo-physical effects of the CO2 laser on the preform surface, the OH groups are still present in the drawn fibers as they were diffused in the preform while shaping. The OH groups cause attenuation on certain wavelengths that lay rather close to the commonly pumping wavelengths in DCFs. In this work, we have overcome this issue by approaching low OH diffusion in DCFs drawn of thermally shaped optical preforms. This approach was based on treating the preforms with hydrofluoric (HF) acid prior the CO2 laser shaping process in order to remove a thin layer soaked with OH groups. The OH penetration depth was estimated based on the optical attenuation measurement at water peak to be about ~600 µm from preform surface. By etching just 200 µm of the preform surface followed by laser shaping with ablation depth of 300 µm can reduce the attenuation attributed to OH groups by 43%. Surface scattering of the inner-clad shaped DCFs drawn of the etched preforms was shown to be low compared to the DCFs drawn of ground preforms. The measurements were carried out in multimode fibers drawn from pure silica Heraeus F300 rods and coated with low index material.

Attribution of the accelerating increase in atmospheric methane during 2010–2018 by inverse analysis of GOSAT observations

Abstract. We conduct a global inverse analysis of 2010–2018 GOSAT observations to better understand the factors controlling atmospheric methane and its accelerating increase over the 2010–2018 period. The inversion optimizes anthropogenic methane emissions and their 2010–2018 trends on a 4∘×5∘ grid, monthly regional wetland emissions, and annual hemispheric concentrations of tropospheric OH (the main sink of methane). We use an analytical solution to the Bayesian optimization problem that provides closed-form estimates of error covariances and information content for the solution. We verify our inversion results with independent methane observations from the TCCON and NOAA networks. Our inversion successfully reproduces the interannual variability of the methane growth rate inferred from NOAA background sites. We find that prior estimates of fuel-related emissions reported by individual countries to the United Nations are too high for China (coal) and Russia (oil and gas) and too low for Venezuela (oil and gas) and the US (oil and gas). We show large 2010–2018 increases in anthropogenic methane emissions over South Asia, tropical Africa, and Brazil, coincident with rapidly growing livestock populations in these regions. We do not find a significant trend in anthropogenic emissions over regions with high rates of production or use of fossil methane, including the US, Russia, and Europe. Our results indicate that the peak methane growth rates in 2014–2015 are driven by low OH concentrations (2014) and high fire emissions (2015), while strong emissions from tropical (Amazon and tropical Africa) and boreal (Eurasia) wetlands combined with increasing anthropogenic emissions drive high growth rates in 2016–2018. Our best estimate is that OH did not contribute significantly to the 2010–2018 methane trend other than the 2014 spike, though error correlation with global anthropogenic emissions limits confidence in this result.

Sonochemical dosimetry: A comparative study of Weissler, Fricke and terephthalic acid methods

Acoustic cavitation and sonochemical reactions play a significant role in various applications of ultrasound. A number of dosimetry methods are in practice to quantify the amount of radicals generated by acoustic cavitation. In this study, hydroxyl radical (OH) yields measured by Weissler, Fricke and terephthalic acid dosimetry methods have been compared to evaluate the validities of these methods using a 490 kHz high frequency sonochemical reactor. The OH yields obtained after 5 min sonication at 490 kHz from Weissler and Fricke dosimetries were 200 µM and 289 µM, respectively. Whereas, the OH yield was found to be very low (8 µM) when terephthalic acid dosimetry was used under similar experimental conditions. While the results agree with those reported by Iida et al. (Microchem. J., 80 (2005) 159), further mechanistic details and interfering reactions have been discussed in this study. For example, the amount of OH determined by the Weissler and Fricke methods may have some uncertainty due to the formation of HO2 in the presence of oxygen. In order to account for the major discrepancy observed with the terephthalic acid dosimetry method, high performance liquid chromatography (HPLC) analysis was performed, where two additional products other than 2-hydroxy terephthalic acid were observed. Electrospray ionization mass spectrometry (ESI-MS) analysis showed the formation of 2,5-dihydroxyterephthalic acid as one of the by-products along with other unidentified by-products. Despite the formation of additional products consuming OH, the reason for a very low OH yield obtained by this dosimetry could not be justified, questioning the applicability of this method, which has been used to quantify OH yields generated not only by acoustic cavitation, but also by other processes such as γ-radiolysis. The authors are hoping that this Opinion Paper may initiate further discussion among researchers working in sonochemistry area that could help resolve the uncertainties around using these dosimetry methods.

Electrochemical Stability and Performance of Li2OHCl Substituted by F or Br as Solid-State Electrolyte

Abstract Li2(OH)0.9F0.1Cl, Li2(OH)0.9Br0.1Cl, and Li2OHCl0.8Br0.2 solid electrolytes were synthesized and compared with Li2OHCl to analyze the exact improvement mechanism for Li+ conductivity and electrochemical stability of Li2OHX-type solid electrolyte. The substituted materials exhibit improved electrochemical stability and Li+ conductivity Li2OHCl. Among these materials, Li(OH)0.9F0.1Cl has improved Li+ conductivity due to a reduction of the OH– concentration and the conductivity of Li2OHCl0.8Br0.2 was also increased compared with Li2OHCl due to the large interstitial site. In the case of Li2(OH)0.9Br0.1Cl, it had the highest Li+ conductivity and good Li+ migration by both effects because of a larger interstitial site and low OH− concentration. Furthermore, the electrochemical stability of four materials was compared due to the different structural stabilities and strengths of binary chemical bonds such as Li–X, H–X, and O–X. Comparing the Li+ conductivity of Li2(OH)0.9F0.1Cl and Li2OHCl0.8Br0.2, the Li+ conductivity is influenced by the OH− concentration unlike the other mechanisms.

Fluoride-free synthesis of mesoporous [Al]-[B]-ZSM-5 using cetyltrimethylammonium bromide and methanol-to-olefin activity with high propene selectivity

Large ZSM-5 crystals containing [B]-sites and mesopores with 2.5 nm pore sizes are synthesized in a fluoride-free, low OH− medium using cethyltrimethylammonium bromide as mesoporogen and 1,6-diaminohexane as structure directing agent. Absence of extra-framework Al sites and low concentrations of silanol sites are evidenced by 27Al MAS-NMR and in-situ FTIR analysis. The low-defect containing [Al]-[B]-ZSM-5 (Mes-[Al]-[B]-ZSM-5) is evaluated for catalyzing the methanol-to-olefins reaction and found to result in low coke formation (4.1 mg g-1 h-1) and very low alkane and aromatic formation rates. The propene to ethene ratio of 4.3 observed using Mes-[Al]-[B]-ZSM-5 is found to be superior to that (1.9) of a nano-sized [Al]-[B]-ZSM-5 (crystal sizes around 36 nm). Small particle sizes for nano-sized [Al]-[B]-ZSM-5 is found to be effective for supplying a higher coke tolerance, but insignificant for olefin product selectivity.

Compositional dependence of the apatite formation ability of Ti-Zr alloys designed for hard tissue reconstruction.

Ti-Zr alloys are expected to be novel biomaterials with low stress shielding owing to their lower Young's moduli than pure Ti. The drawback of metallic biomaterials is that their bone-bonding abilities are relatively low. NaOH and heat treatments have been performed to provide Ti-50Zr with apatite-forming ability in the body environment, which is essential for bone bonding. However, the systematic compositional dependence of apatite formation has not been revealed. In the present study, NaOH treatment of Ti-Zr alloys with various compositions and bone-bonding abilities was assessed in vitro by apatite formation in simulated body fluid (SBF). The corrosion current density in NaOH aqueous solution and the amount of Na incorporated into the surface tended to decrease with increasing Zr content. The apatite-forming ability of the treated alloy significantly decreased when the Zr content was ≥60 atom%. This phenomenon is attributed to the (1) low OH content on the surface, (2) low Na incorporation into the treated alloy surface, which enhances apatite formation, and (3) low ability of P adsorption to the Ti-Zr alloy in SBF following Ca adsorption to trigger apatite nucleation. Although the adhesion of the titanate/zirconate layer formed on the surfaces to the substrates increased as Zr content increased, the adhesion between the apatite and the substrate was still low.

Synthesis of NaLn(WO4)2 phosphors via a new phase-conversion protocol and investigation of up/down conversion photoluminescence

The two-dimensional (2D) crystallite morphology and low OH−/Ln3+ molar ratio of Ln2(OH)4SO4·2H2O (Ln = lanthanide) make it an ideal precursor for materials synthesis via phase conversion, which was manifested in this work by the direct generation of well-defined NaLn(WO4)2 phosphor particles via hydrothermal reaction with Na2WO4. Kinetics study showed that pure NaLn(WO4)2 can be produced by reaction at 180 °C for ~24 h or at 200 °C for ~6 h under WO42−/Ln3+ = 10 M ratio. Morphology analysis revealed that, though NaLn(WO4)2 evolved via re-precipitation, the layered crystal structure and 2D crystallite morphology of the precursor could have templated the nucleation/growth of NaLn(WO4)2, leading to uniform particles (~4–5 μm) of a unique microdisc-like morphology. Under 394 nm excitation, the Ln = La0.95Eu0.05 phosphor showed down-conversion luminescence having an absolute quantum yield of ~35.4%, a fluorescence lifetime of ~1.13 ms for its 616 nm main emission, and color coordinates of around (0.63, 0.37). Under 978 nm laser excitation, the Ln = La0.97Yb0.02Ho0.01 and Ln = La0.97Yb0.02Er0.01 phosphors exhibited the strongest up-conversion (UC) luminescence at ~660 nm (the 5F5 → 5I8 transition of Ho3+) and 551 nm (the 4S3/2 → 4I15/2 transition of Er3+), average fluorescence lifetimes of ~178.3 and 82.3 µs for the above emissions, and chromaticity coordinates of around (0.62, 0.38) and (0.25, 0.72), respectively. The two UC phosphors were also analyzed to exhibit UC luminescence through a two-photon mechanism.

Near blowout dynamics of a premixed, swirl stabilized flame

This paper analyzes the flame dynamics of near LBO (lean blowoff) swirl stabilized flames, using simultaneous OH and CH2O (formaldehyde) PLIF (planar laser induced fluorescence) measurements. Prior studies have shown that recirculation stabilized flames approach blowoff through two distinct stages – “stage 1” characterized by local extinction, where the overall flame and flow field remain largely unchanged, and “stage 2”, characterized by a fundamental change in the flow field, accompanied by violent flame flapping and wake disruption. This paper quantifies extinction spots along the flame edge, and entrained reactants within the combustion product region to analyze these stages in greater detail. Extinction spots were quantified by the overlapping regions of OH and CH2O – numerous such spots were found near blowoff. The entraining of unburnt reactants into the recirculation zone was quantified by detecting low intensity OH pockets that were not surrounded by CH2O. As expected, the flame near blowoff displayed significantly more entrained reactant pockets relative to a stable flame. Unexpectedly however, the volume of these pockets is tiny compared to the products, even on the edge of blowoff. Once they enter the wake, they are short-lived, suggesting that they are diluted and/or quickly react. This was surprising given the non-trivial baseflow and flame position disruption at these conditions, suggesting a striking similarity between the average composition of the wake, to that of a stable flame.

Phosphorous incorporation in Pd2Sn alloys for electrocatalytic ethanol oxidation

Abstract Direct ethanol fuel cells (DEFCs) show a huge potential to power future electric vehicles and portable electronics, but their deployment is currently limited by the unavailability of proper electrocatalysis for the ethanol oxidation reaction (EOR). In this work, we engineer a new electrocatalyst by incorporating phosphorous into a palladium-tin alloy and demonstrate a significant performance improvement toward EOR. We first detail a synthetic method to produce Pd2Sn:P nanocrystals that incorporate 35% of phosphorus. These nanoparticles are supported on carbon black and tested for EOR. Pd2Sn:P/C catalysts exhibit mass current densities up to 5.03 A mgPd−1, well above those of Pd2Sn/C, PdP2/C and Pd/C reference catalysts. Furthermore, a twofold lower Tafel slope and a much longer durability are revealed for the Pd2Sn:P/C catalyst compared with Pd/C. The performance improvement is rationalized with the aid of density functional theory (DFT) calculations considering different phosphorous chemical environments. Depending on its oxidation state, surface phosphorus introduces sites with low energy OH− adsorption and/or strongly influences the electronic structure of palladium and tin to facilitate the oxidation of the acetyl to acetic acid, which is considered the EOR rate limiting step. DFT calculations also points out that the durability improvement of Pd2Sn:P/C catalyst is associated to the promotion of OH adsorption that accelerates the oxidation of intermediate poisoning COads, reactivating the catalyst surface.

NOx emission and thermal performances studies on premixed ammonia-oxygen combustion in a CO2-free micro-planar combustor

Unlike hydrocarbon fuel, ammonia is a carbon-free and renewable energy source. It is also regarded as one of the potential energy carriers. However, ammonia combustion for power generation is not well studied under micro-scale conditions, especially concerning nitrogen oxides (NOx) emission. For this, thermal performances and NO emission characteristics of premixed ammonia/oxygen combustion are numerically investigated on a micro-planar combustor. The effects of 1) the equivalence ratio ϕ, 2) inlet temperature Tin and 3) inlet pressure Pin are examined. The outer wall mean temperature (OWMT) is found to vary non-monotonically, as the mixture varies from lean to rich conditions, with the peak occurring at ϕ = 0.9 mainly due to the optimal heat transfer performance. However, a low ϕ could lead to the high nitric oxides (NO) concentrations because of the high flame temperature as well as O atom concentrations. Up to 75.5% of NO reduction could be achieved, as ϕ is optimized. Furthermore, increasing Tin is shown to be associated with a low OWMT and NO concentration. In addition, varying Pin is shown to lead to not only OWMT being changed but also NO formation being mitigated. The decrease in NO concentration for a high Pin is mostly attributable to the short residence time of a high flame temperature in the channel and low OH concentrations. This work reveals that optimizing the operating thermodynamic parameters is an effective means to reduce NO emissions and to improve thermal performances.

Differentiation Between Nitrate Aerosol Formation Pathways in a Southeast Chinese City by Dual Isotope and Modeling Studies

AbstractNitrate (NO3−), one of the most important inorganic aerosols in the atmosphere, is mainly formed by oxidation of NOx by the hydroxyl radical (OH) and ozone (O3) in urban atmospheres. However, the fractional contributions of its various oxidation pathways remain unclear. Here, we collected particulate matter with aerodynamic diameter less than 2.5 μm (PM2.5) samples in a second‐tier city in southeast China from 1 September to 31 December 2017 and measured the NO3− and nitrate isotopic compositions (δ15N and δ18O). The average concentration of NO3−, δ15N, and δ18O values were 14.7 ± 11.6 μg/m3, (+4.3 ± 4.3)‰, and (+71.8 ± 14.7)‰ with the ranges from 0.8 to 57.7 μg/m3, −10.5‰ to +12.5‰ and +34.5‰ to +91.9‰, respectively. All three species were significantly higher in winter than in summer. Based on a Bayesian mixing model with a dual isotope array for NO3−, contributions of (37.1 ± 33.4)%, (60.3 ± 32.2)%, and (2.6 ± 2.7)% to NO3− could be attributed to OH oxidation, N2O5 hydrolysis, and NO3 + hydrocarbon (HC) pathways, respectively. Higher OH radical concentrations with higher ratios of OH to O3 led to lower NO3− concentrations, while lower OH radical concentrations with higher ratios of O3 to OH led to higher contributions of N2O5 hydrolysis, forming higher NO3− concentrations in winter. Under low OH, an increased O3 to NOx ratio increased the contribution of the NO3 + HC pathway. The comprehensive analysis of the isotopic compositions of nitrate helped identify the importance of major oxidation pathways of NOx in this city.

Variations of OH defects and chemical impurities in natural quartz within igneous bodies

In this study, we present the first systematic dataset on natural variations of OH defect and trace element contents in quartz within igneous bodies. Samples were derived from bore holes of two plutonic bodies from the Krušné Hory/Erzgebirge (German–Czech border), representing typical A-type (Cínovec/Zinnwald granite cupola) and S-type (Podlesí Stock) granite intrusions. Fourier Transform Infrared spectroscopy of quartz was used to investigate the sample set with regard to its OH defect speciation and content. For Zinnwald quartz, IR absorption spectra reveal different lithologies due to changes of the OH defect inventory, enabling a subdivision of the granitic body: (1) hydrothermal greisen quartz of the uppermost part of the intrusion have low OH defect contents (average of 15 µg/g H2O); (2) zinnwaldite granite quartz vary strongly in defect content and show the highest content of the dataset (10–70 µg/g H2O); (3) quartz from an underlying biotite granite have slightly lower, but very uniform contents down to the bottom of the borehole at 1600 m (average 20 µg/g H2O). Infrared spectra of Podlesí quartz reveal a gradual increase in total defect water content with increasing depth over 350 m (30–55 µg/g H2O). Lithium contents in quartz samples from the uppermost part of the Zinnwald intrusion correlate with the occurrence of Li-specific OH defects, while cathodoluminescence (CL) images do not show specific differences. Our findings evidence the potential of OH defects in quartz as a tool to decipher differentiation trends in igneous bodies, and the application of their eroded material for provenance analyses.

Abstract P306: Racial/Ethnic Differences In Self-reported Sedentary Time Are Related To Differential Risk For Prevalent Hypertension: NHANES 2011-2016

Introduction: Evidence suggests there are racial/ethnic differences in lifestyle behaviors that may affect cardiovascular health outcomes such as physical activity engagement, diet, and sleep duration. However, the literature on racial/ethnic differences in sedentary time (ST) and whether these differences may be related differentially to cardiovascular health is limited. The goals of this study are to investigate racial/ethnic differences in self-reported ST, and examine if the modifying effect of ST with race/ethnicity will be associated with hypertension (HTN) prevalence. Methods: Adults (N=15903, age ≥20 yrs) from the National Health and Nutrition Examination Survey (NHANES) 2011-2016 reported their race/ethnicity (Mexican American [MA], Other Hispanic [OH], non-Hispanic White [NHW], non-Hispanic Black [NHB], non-Hispanic Asian, Other or mixed race [OM]), ST on a typical day (median split at 6 hrs: Low vs. High ST), and history of physician diagnosed HTN (yes/no). Weighted logistic regression models were conducted to examine the association between race/ethnic groups and ST, and combined racial/ethnic-ST groups (reference group: NHW with Low ST) on HTN prevalence while controlling for age, sex, education, body mass index, smoking status, moderate-vigorous physical activity min/wk, and history of diabetes, cardiovascular (i.e., heart failure, myocardial infarction, stroke, coronary heart disease) and kidney conditions. Results: There was a significant association between race/ethnic groups and ST (Wald F [5,43]=23.4, p <0.001) such that compared to NHW, MA (OR=.43, 95%CI:.36,.51) OH (OR=.51, 95%CI:.42,.62), and OM (OR=.71, 95%CI:.55,.91) had lower odds for High ST. Weighted percent of the sample with HTN was 32.6%. There was a significant effect of combined race by ST groups on HTN (Wald F [11,37] = 9.8, p <0.001). Compared to NHW with Low ST, MA (OR=.70, 95%CI: .54,.90) and OH (OR=.79, 95%CI: .64,.97) with Low ST had lower odds for HTN, whereas NHB with Low ST (OR=1.58, 95%CI: 1.34,1.87) and High ST (OR=1.76, 95%CI: 1.50,2.07) had increased odds of HTN. Conclusion: In a large national cohort, daily ST differed by race/ethnicity, and ST modified the association between race/ethnicity and odds for HTN such that compared to more active NHW, more active Hispanic groups had decreased odds for HTN, but NHB regardless of ST had increased risk for HTN. ST may be a key modifiable risk factor in addressing race/ethnic disparities in cardiovascular health.

Influence of the chemical structure of additives poly(ethylene‐co‐vinyl acetate)‐based on the pour point of crude oils

ABSTRACTOne of the methods to prevent wax precipitation, during petroleum production, transport, and refining, is the use of polymer additives that can reduce the oil pour point. However, no single additive work for all types of crude oil and this relation is not yet well known. In this study, a family of polymers based on poly(ethylene‐co‐vinyl acetate), containing hydroxyl groups and long pendant hydrocarbon chains (from C6 to C18), were synthesized and characterized by H1 nuclear magnetic resonance and solubility test. Four crude oil samples containing different amounts and size distribution of the wax were used. The additive's action is favored by higher contents of iso + cycloalkanes and lower contents of n‐paraffins with larger chain sizes. The presence of the CH3COO group in the copolymers promoted the lowering of the pour point, supported by a low OH concentration and the presence of a long pendant hydrocarbon chain: the best results were obtained with C10 and C12 chain lengths. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48969.

Enhanced mid-infrared emission by energy transfer in Er3+/Yb3+ co-doped zirconium fluoride-chloride transparent glass

Transparent Er3+/Yb3+ co-doped zirconium fluoride-chloride (ZFC) glass are firstly prepared for mid-infrared emission. The stronger 2750 nm emission from Er3+: ZFC glass is owing to a stronger covalence and local asymmetry of the crystal field around the Er3+ ions. The low phonon energy (600 cm−1) of ZFC glass are calculated from FTIR spectra and confirmed by Raman spectra. The low OH− concentration (9.75 × 10−17 cm−3) and high transmittance (1300-4000 cm−1) of ZFC glass are beneficial to mid-infrared emission. Co-doping rare earth ions Yb3+ enhances the 2750 nm emission. The energy transfer process between Yb3+ and Er3+ are identified based on luminescence spectra and decay curves. The role of Yb3+ plays the sensitizer on Er3+: 4I11/2 and enhances the excited state absorption of Er3+: 4I13/2 → 4F9/2, which is good for transition Er3+: 4I11/2 → 4F13/2. Thus, Er3+/Yb3+: ZFC glass with large emission cross section (1.06 × 10−20 cm2) is a potential laser application material.

Ex vivo testing of air-cooled CW/modulated 30 W thulium fiber laser for lithotripsy.

A diode-pumped, air-cooled, all-fiber, quasi-continuous-wave thulium laser at an operating wavelength of 1.94μm has been designed to study the performance of the laser parameter on the rate of fragmentation and its dependence on stone composition, fragmented particle size, as well as the retropulsion effect. The optimized laser cavity with an active fiber core/cladding diameter of 10/130μm under a counter-propagating pump provides a stable laser power of 30W at a slope efficiency of 50% and wall plug efficiency of 17%. The rate of fragmentation along with the retropulsion effect has been studied with human calcium oxalate monohydrate (COM) urinary stones (N=36) of different composition by using the designed laser and 200-μm-core low OH silica delivery fiber. The thulium fiber laser setting of 2.7J pulse energy at the pulse rate of 10Hz, pulse width of 90ms, and peak power of 30W is successful in breaking human COM stones in a controlled manner at a fragmentation rate of 0.8±0.4 mg/s, with almost uniform fragments of particle size less than 1.6mm. During the stone fragmentation, the stone displacement (retropulsion effect) is less than 15mm, even for the fragmented stone mass of 15±5 mg.

An experiment analysis of MILD combustion with liquid fuel spray in a combustion vessel

Mild combustion is characterized by its distinguished features, such as suppressed pollutant emission, homogeneous temperature distribution, reduced noise, and thermal stress. Recently, many studies have revealed the potential of MILD combustion in various power systems but most studies have been focused on gas phase fuel MILD combustion. Therefore, further study on MILD combustion using liquid fuel is needed for the application to a liquid-fueled gas turbine especially. In this work, we studied experimentally on the formation of liquid fuel MILD combustion under the condition of high dilution by burnt gas generated from a first premixed flame in two stages combustor which consists of the first premixed burner and secondary combustor. In particular, the effects of burnt gas velocity and oxygen level of burnt gas on the formation of liquid fuel MILD combustion were investigated. The results show that as the burnt gas velocity through the nozzle becomes higher, the color of flames was changed from yellow to pale blue and flames became very short. The OH radical measured by ICCD camera was uniformly distributed on the pale blue flame surface and its intensity was very low compared to conventional liquid diffusion flame. As burnt gas velocity is increased, local high-temperature region appeared to be diminished and the flame temperature became spatially uniform. And CO emission was sampled around 1 ppm and NOx emission was measured around 10 ppm under the overall equivalence ratio of 0.8 to 0.98 for 40 mm or less diameter of velocity control nozzle. This low NOx emission seems to be attributed to maintaining the average temperature in secondary combustor below the threshold temperature of thermal NOx formation. In view of the uniform temperature distribution, low OH radical intensity and low NOx emission data in the secondary combustor, formation of stable MILD combustion using kerosene liquid fuel could be verified at high burnt gas velocity.

OH defects in quartz as a provenance tool: Application to fluvial and deep marine sediments from SW Japan

Hydrogen-related point defects (OH defects) in the crystal lattice of detrital, monocrystalline quartz have been proposed as an indicator to distinguish different sediment sources, making it a potential tool for provenance analysis. This study tests this novel technique on samples from SW Japan by comparing the results of OH defect analyses with those of “classical” provenance studies. OH defects of 188 detrital, monocrystalline quartz grains from five rivers (Fuji, Tenryu, Nagara, Yoshino, and Shimanto) and four offshore wells drilled in the Nankai Trough area (ODP site 1177; IODP sites C0002, C0007, C0012) are characterized using Fourier-transform infrared (FTIR) spectroscopy. Considerable differences in OH defect concentrations are identified between individual river samples. A general increase of values from east to west is observed. Possible links to the respective source geology are established. Very low OH defect contents (<1 wt. ppm water) of sediment from the Fuji and Tenryu rivers may be a result of high deformation and exhumation in the Izu-Honshu collision zone. Moderate to high OH defect contents of Nagara and Yoshino river samples (up to 50 wt. ppm water) are similar to the values of the global average in continental crust, possibly due to a mixing of various source lithologies. High and very diverse OH defect contents of Shimanto River sediments (up to 211 wt. ppm water) are likely an effect of extensive sediment reworking and mixing in the Nankai accretionary wedge. The OH defect signal is shown to be traceable through the offshore sedimentary record. In the western Shikoku Basin (ODP site 1177), turbidite deposits at 15 Ma and 7 Ma show a very similar signal as recent Shimanto river sediment, whereas eastern Shikoku Basin sediments (IODP Site C0012), at 15 Ma and 6 Ma strongly resemble present day Nagara and Yoshino river sediments. Sediments deposited in the Nankai trench wedge at 1 Ma (IODP Site C0007) indicate a shift towards lower OH defect concentrations. This may be due to increased, trench parallel sediment flux from the low-OH defect Fuji and Tenryu river sources, as proposed by previous studies. This study presents the first OH defect dataset in detrital quartz from rivers and offshore drill sites in a subduction zone environment, introducing OH defects as a new useful tool for sediment provenance analysis in active convergent margin settings.

Metallic state two-dimensional holey-structured Co3FeN nanosheets as stable and bifunctional electrocatalysts for zinc–air batteries

Two-dimensional holey-structured metallic-state Co3FeN nanosheets exhibit enhanced catalytic properties owing to the complete exposure of atoms and low OH* adsorption energy.

Dispersion-Engineered Step-Index Tellurite Fibers for Mid-Infrared Coherent Supercontinuum Generation from 1.5 to 4.5 μm with Sub-Nanojoule Femtosecond Pump Pulses

Mid-infrared supercontinuum generation from 1.5 to 4.5 µm with sub-nanojoule femtosecond pump pulses is demonstrated by using a short segment of dispersion-engineered step-index tellurite fiber with very low OH content. Distinct group-velocity dispersion regimes in a simple design of step-index tellurite fiber are also reported, which allows to choose the nonlinear pulse propagation regime according to the required tailoring of the supercontinuum source. Numerical simulations based on the generalized nonlinear Schrödinger equation are used to determine optimized fiber parameters before experimental demonstrations. We also analyse the coherence properties of the resulting supercontinuum sources.