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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Co-Occurring Atmospheric Features and Their Contributions to Precipitation Extremes

Object-based identification algorithms for atmospheric features are commonly utilized to attribute global precipitation. This study employs a systematic approach to examine feature co-occurrences and their relationships to mean and extreme precipitation. Four features are identified using existing data sets for atmospheric rivers (ARs), mesoscale convective systems (MCSs), low-pressure systems (LPSs), and fronts (FTs). Often, a single atmospheric phenomenon satisfies the criteria set by multiple feature identification algorithms, yielding an association between precipitation and multiple features. Over the extra-tropics, the number of features attributed to a single event typically increases with precipitation intensity. Over two-thirds of the precipitation is from co-occurring features, with a considerable fraction related to AR-FT co-occurrences. Over the tropics, about one-quarter of precipitation is associated with co-occurring features, with LPS-MCS co-occurrences contributing substantially in monsoon regions. MCSs are the leading single-feature contributors over tropical land and oceans. In the extra-tropics, FTs, ARs, and their co-occurrences account for over half of the total precipitation over oceans. AR-FT-MCS and FT-MCS co-occurrences contribute to extremes (precipitation exceeding the 95th percentile) over both oceans (over 30%) and land (over 20%). Any combination of features involving MCSs shows a larger contribution to high percentiles of precipitation intensity. A case analysis indicates that AR-FT-MCS co-occurrences exhibit convective instability and deep vertical motion, suggesting that the feature trackers and reanalysis are capturing physics relevant to both convective and frontal systems. The results here emphasize the need for simultaneous identifications of multiple features when attributing precipitation to atmospheric phenomena.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Human-induced greening of the northern extratropical land surface

Significant land greening in the northern extratropical latitudes (NEL) has been documented from satellite observations during the past three decades. This enhanced vegetation growth has broad implications for surface energy, water and carbon budgets, and ecosystem services across multiple scales. Discernible human impacts on the Earth’s climate system have been revealed by using statistical frameworks of detection–attribution. These impacts, however, were not previously identified on the NEL greening signal, owing to the lack of long-term observational records, possible bias of satellite data, different algorithms used to calculate vegetation greenness, and the lack of suitable simulations from coupled Earth system models (ESMs). Here we have overcome these challenges to attribute recent changes in NEL vegetation activity. We have used two 30-year-long remote-sensing-based leaf area index (LAI) data sets, simulations from 19 coupled ESMs with interactive vegetation, and a formal detection and attribution algorithm. Our findings reveal that the observed greening record is consistent with an assumption of anthropogenic forcings, where greenhouse gases play a dominant role, but is not consistent with simulations that include only natural forcings and internal climate variability. These results provide the first clear evidence of a discernible human fingerprint on physiological vegetation changes other than phenology and range shifts.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Enhancing fatigue life by ductile-transformable multicomponent B2 precipitates in a high-entropy alloy

Catastrophic accidents caused by fatigue failures often occur in engineering structures. Thus, a fundamental understanding of cyclic-deformation and fatigue-failure mechanisms is critical for the development of fatigue-resistant structural materials. Here we report a high-entropy alloy with enhanced fatigue life by ductile-transformable multicomponent B2 precipitates. Its cyclic-deformation mechanisms are revealed by real-time in-situ neutron diffraction, transmission-electron microscopy, crystal-plasticity modeling, and Monte-Carlo simulations. Multiple cyclic-deformation mechanisms, including dislocation slips, precipitation strengthening, deformation twinning, and reversible martensitic phase transformation, are observed in the studied high-entropy alloy. Its improved fatigue performance at low strain amplitudes, i.e., the high fatigue-crack-initiation resistance, is attributed to the high elasticity, plastic deformability, and martensitic transformation of the B2-strengthening phase. This study shows that fatigue-resistant alloys can be developed by incorporating strengthening ductile-transformable multicomponent intermetallic phases.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Delineation of endorheic drainage basins in the MERIT-Plus dataset for 5 and 15 minute upscaled river networks

Abstract The MERIT-Hydro networks re-gridded by the Iterative Hydrography Upscaling (IHU) algorithm do not retain exo- or endorheic basin attributes from the original data. Here we developed methods to assign such attributes to those and any other digital river networks. The motivation is that endorheic inland drainage basins are essential for hydrologic modelling of global and regional water balances, land surface water storage, gravity anomalies, sea level rise, etc. First, we create basin attributes that explicitly label endorheic and exorheic catchments by the criteria of direct or hidden connectivity to the ocean without changing their flow direction grid. In the second step we alter the delineation of endorheic basins by the merging algorithm that eliminates small inland watersheds to the adjacent host basins. The resulting datasets have a significantly reduced number of endorheic basins while preserving the total land portion and topology of the inland basins. The data was validated using the Water Balance Model by comparing volume of endorheic inland depressions with modelled water accumulation in their inland lakes.

58 GEOSCIENCES↗
DOE OSTI2013

Ion effects in hydrogen-induced blistering of Mo/Si multilayers

The role that energetic (>800 eV) hydrogen ions play in inducing and modifying the formation of blisters in nanoscale Mo/Si multilayer samples is investigated. Such samples are confirmed to be susceptible to blistering by two separate mechanisms. The first is attributed to the segregation of H atoms to voids and vacancies associated with the outermost Mo layer, driving blister formation in the form of H{sub 2} filled bubbles. This process can occur in the absence of ions. A second blister distribution emerges when energetic ions are present in the irradiating flux. This is attributed to an ion-induced vacancy clustering mechanism that produces void blisters. The defects and strained states associated with the Mo-on-Si interfaces provide the preferred nucleation points for blistering in both cases. The effects of ions are ascribed to promotion of hydrogen uptake and mobility, in particular through the Si layers; to the generation of additional mobile species in the Si and Mo layers; and to the creation of new blister nucleation points. In addition to directly stimulating blistering via vacancy clustering, ions modify the development of H{sub 2}-filled blisters. This is most evident in the formation of multi-component structures due to overlapping delaminations at different layer interfaces. This affect is attributed to the introduction of active transport of hydrogen from the H{sub 2} filled blisters across the outermost Mo-on-Si interface to the underlying layers. Ion-induced variations in hydrogen uptake and distribution and in the rates of blister nucleation and growth produce lateral differences in blister size and areal number density that create a macroscopic concentric pattern across the surface.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Oxidation state of manganese in zinc pyrophosphate: Probed by luminescence and EPR studies

Zn{sub 2}P{sub 2}O{sub 7}: Mn was synthesized by wet chemical route and characterized by X-ray diffraction (XRD), photoluminescence (PL) and electron paramagnetic resonance (EPR) techniques. Photoluminescence spectrum shows two bands, one at 500 nm (green emission), which is attributed to the {sup 4}T{sub 1}({sup 4}G)-{sup 6}A{sub 1}({sup 6}S) transition of Mn{sup 2+} and other centered at 686 nm (red emission) is attributed to the electronic transition between {sup 2}E and {sup 4}A{sub 2} of Mn{sup 4+} accompanied with vibronic transitions. EPR spectroscopic studies also confirmed the presence of both Mn2+ and Mn4+ ions in zinc pyrophosphate with difference in the number of fine transitions and g values (Mn{sub 4+}, S=3/2, three fine transitions and g < 2.00; Mn{sup 2+} S=5/2, five fine transitions and g=2.00).Mn{sup 2+} is attributed to presence of Mn at 6-ccordinated Zn{sup 2+} site whereas Mn{sup 4+} is due to presence substitution of Mn{sup 4+} at Zn{sup 2+} site thereby invoking charge compensation by presence of interstitial oxygen ions around Mn{sup 4+} ion or due to substitution of manganese at distorted 5-coordinated zinc site.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Oxygen aggregation kinetics, thermal donors and carbon-oxygen defect formation in silicon containing carbon and tin

Localized vibrational mode spectroscopy measurements on Czochralski silicon (Cz-Si) samples subjected to isothermal annealing at 450 °C are reported. First, we studied the effect of carbon (C) and tin (Sn) isovalent dopants on the aggregation kinetics of oxygen. It is determined that the reduction rate of oxygen is described by the Johnson-Mehl-Avrami equation in accordance with previous reports. The activation energy related with the reaction rate constant of the process is calculated to increase from Cz-Si, to C-doped Cz-Si (CCz-Si), to Sn-doped Cz-Si contained C (SnCz-Si). This is attributed to the presence of the isovalent dopants that may impact both the kinetics of the oxygen atoms and also may lead to the formation of other oxygen-related clusters. Second, we studied the effect of Sn on the formation and evolution of carbon-oxygen (C-O) defects. It was determined that the presence of Sn suppresses the formation of the C-O defects as indicated by the reduction in the strength of the 683, 626, and 586 cm{sup −1} well-known bands of C{sub s}O{sub i} defect. The phenomenon is attributed to the association of Sn with C atoms that may prevent the pairing of O with C. Third, we investigated the effect of C and Sn on the formation of thermal donors (TDs). Regarding carbon our results verified previous reports that carbon suppresses the formation of TDs. Interestingly, when both C and Sn are present in Si, very weak bands of TDs were observed, although it is known that Sn alone suppress their formation. This may be attributed to the competing strains of C and Sn in the Si lattice.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Optical and electron transport properties of rock-salt Sc{sub 1−x}Al{sub x}N

Epitaxial single-crystal Sc{sub 1−x}Al{sub x}N ternary alloy layers deposited by magnetron co-sputtering on MgO(001) substrates at 950 °C exhibit a solid solution rock-salt phase for x = 0–0.2 without decomposition. Optical absorption indicates a linear increase in the optical gap from 2.51 eV for ScN to 3.05 eV for Sc{sub 0.8}Al{sub 0.2}N and, after correction due to the Moss-Burstein shift, a direct X point interband transition energy E{sub g}(X) = 2.15 + 2.75 x (eV). Correspondingly, the direct transition at the zone center increases with Al concentration according to E{sub g}(Γ) = 3.80 + 1.45 x (eV), as determined from a feature in the reflection spectra. All layers are degenerate n-type semiconductors with a room temperature mobility that decreases from 22 to 6.7 to 0.83 cm{sup 2}/V s as x increases from 0 to 0.11 to 0.20. The corresponding carrier densities are 9.2 × 10{sup 20}, 7.9 × 10{sup 20}, and 0.95 × 10{sup 20 }cm{sup −3} as determined from Hall measurements and consistent with optical free carrier absorption below photon energies of 1 eV. Temperature dependent transport measurements indicate metallic conduction for ScN, but weak localization that leads to a resistivity minimum at 85 and 210 K for x = 0.051 and 0.15, respectively, and a negative temperature coefficient over the entire measured 4–300 K range for Sc{sub 0.8}Al{sub 0.2}N. The decreasing mobility is attributed to alloy scattering at randomly distributed Al atoms on cation sites, which also cause the weak localization. The carrier density is primarily due to unintentional F doping from the Sc target and decreases strongly for x > 0.15, which is attributed to trapping in defect states due to the deterioration of the crystalline quality, as evidenced by the x-ray diffraction peak width that exhibits a minimum of 0.14° for x = 0.11 but increases to 0.49° for x = 0.20. This is consistent with asymmetric x-ray diffraction analyses, indicating a relaxed lattice constant that decreases from 4.511 ± 0.005 to 4.411 ± 0.004 Å for x = 0–0.2, and a biaxial in-plane compressive strain that decreases from −1.1% to −0.2% as x increases from 0 to 0.11, which is attributed to the higher Al adatom mobility, but increases again to −1.8% for x = 0.20, as x approaches the critical composition for phase separation, which causes structural instability and a higher defect density.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Magnetically tunable alternating current electrical properties of x La{sub 0.7}Sr{sub 0.3}MnO{sub 3}–(1 − x) ErMnO{sub 3} (x = 0.1, 0.3, and 0.5) multiferroic nanocomposite

Detailed magnetically tunable ac electrical properties of x La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO)–(1 − x) ErMnO{sub 3} (EMO) (x = 0.1, 0.3, and 0.5) multiferroic nanocomposites have been studied at 300 K in presence of varying magnetic field (H{sub appl}), applied both in parallel and perpendicular configuration with respect to the measuring electric field. AC electrical properties have exhibited significant variation with H{sub appl} for all composites, whereas for parallel configuration of H{sub appl} such effect is very feeble for x = 0.3 composite. We have attributed this anisotropic behavior to the demagnetization effect in the sample. In contrast, for x = 0.1 and 0.5 composites, no such anisotropy effect is experimentally evidenced. Impedance and real part of impedance have been found to decrease with H{sub appl} at low frequency (f) region. We attribute this observation to the depinning of the magnetic domain walls from the grain boundaries pinning centers and thereby enhancing the spin dependent transport in the composite. For x = 0.3 composite, Nyquist plots have been fitted considering dominant contributions of LSMO and EMO grain boundaries and the interface region between them. However, for x = 0.1 composite, it corresponds to EMO grain boundaries and grain boundary interface region. The relaxation frequency (f{sub R}) is observed to shift at higher/lower f region in perpendicular/parallel configuration of H{sub appl} for x = 0.3 composite. This opposite variation of f{sub R}s with H{sub appl} for perpendicular and parallel configurations has been attributed to two competing factors of H{sub appl} induced enhancement of inductive part and H{sub appl} enhanced spin dependent transport causing fast relaxation processes in the sample. For x = 0.1 composite, in both configurations of H{sub appl}, f{sub R}s is shifting towards high f region, which has been discussed in terms of dominant role of spin dependent transport.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

The role of the substrate on the dispersion in accumulation in III-V compound semiconductor based metal-oxide-semiconductor gate stacks

Dispersion in accumulation is a widely observed phenomenon in metal-oxide-semiconductor gate stacks based on III-V compound semiconductors. The physical origin of this phenomenon is attributed to border traps located in the dielectric material adjacent to the semiconductor. Here, we study the role of the semiconductor substrate on the electrical quality of the first layers at atomic layer deposited (ALD) dielectrics. For this purpose, either Al{sub 2}O{sub 3} or HfO{sub 2} dielectrics with variable thicknesses were deposited simultaneously on two technology important semiconductors—InGaAs and InP. Significantly larger dispersion was observed in InP based gate stacks compared to those based on InGaAs. The observed difference is attributed to a higher border trap density in dielectrics deposited on InP compared to those deposited on InGaAs. We therefore conclude that the substrate plays an important role in the determination of the electrical quality of the first dielectric monolayers deposited by ALD. An additional observation is that larger dispersion was obtained in HfO{sub 2} based capacitors compared to Al{sub 2}O{sub 3} based capacitors, deposited on the same semiconductor. This phenomenon is attributed to the lower conduction band offset rather than to a higher border trap density.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Ultra-wide bandgap β-Ga 2 O 3 films: Optical, phonon, and temperature response properties

Optical and phonon interactions of Ga 2 O 3 thin films with nanocrystalline morphology were studied at extreme temperatures. The films were grown using a sputtering technique and analyzed via temperature response transmission, Raman scattering, and high-resolution deep-UV photoluminescence (PL). Raman modes indicated that the structure corresponds to the β-phase. The optical-gap at the range of 77–620 K exhibited a redshift of ~200 meV, with a temperature coefficient of ~0.4 meV/K. The optical-gap at room-temperature is 4.85 eV. The electron–phonon interaction model at that temperature range pointed to a low energy phonon, ~31 meV, that is involved in the thermal properties of the optical-gap. Detailed Urbach energy analysis indicated that defects are the dominant mechanism controlling the band-edge characteristics even at an elevated temperature regime where phonon dominance is usually expected. Defects are attributed to the disordered forms of graphite that were detected via Raman scattering and to the granular morphology of the film. A deep-UV laser with an above bandgap exaction line of 5.1 eV was employed to map the PL of the films. The highly resolved spectra, even at room-temperature, show a strong emission of ~3.56 eV attributed to self-trapped holes (STHs). The STH is discussed and modeled in terms of the self-trapped exciton. Moreover, a very distinct but low-intensity emission was found at 4.85 eV that agrees with the value of the optical-gap and is attributed to bandgap recombination. The intensity ratio between the STH and that of the bandgap was found to be 6:1.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Quantifying the influence of global warming on unprecedented extreme climate events

Significance Extreme climate events have increased in many regions. Efforts to test the influence of global warming on individual events have also increased, raising the possibility of operational, real-time, single-event attribution. We apply four attribution metrics to four climate variables at each available point on a global grid. We find that historical global warming has increased the severity and probability of the hottest monthly and daily events at more than 80% of the observed area and has increased the probability of the driest and wettest events at approximately half of the observed area. Our results suggest that scientifically durable operational attribution is possible but they also highlight the importance of carefully diagnosing and testing the physical causes of individual events.

Diffenbaugh, Noah S.↗
DOE OSTI2013

THE CARRIERS OF THE INTERSTELLAR UNIDENTIFIED INFRARED EMISSION FEATURES: CONSTRAINTS FROM THE INTERSTELLAR C-H STRETCHING FEATURES AT 3.2-3.5 μm

The unidentified infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 μm, commonly attributed to polycyclic aromatic hydrocarbon (PAH) molecules, have recently been ascribed to mixed aromatic/aliphatic organic nanoparticles. More recently, an upper limit of <9% was placed on the aliphatic fraction (i.e., the fraction of carbon atoms in aliphatic form) of the UIE carriers based on the observed intensities of the 3.4 μm and 3.3 μm emission features by attributing them to aliphatic and aromatic C-H stretching modes, respectively, and assuming A{sub 3.4}/A{sub 3.3} ≈ 0.68 derived from a small set of aliphatic and aromatic compounds, where A{sub 3.4} and A{sub 3.3} are, respectively, the band strengths of the 3.4 μm aliphatic and 3.3 μm aromatic C-H bonds. To improve the estimate of the aliphatic fraction of the UIE carriers, here we analyze 35 UIE sources exhibiting both the 3.3 μm and 3.4 μm C-H features and determine I{sub 3.4}/I{sub 3.3}, the ratio of the power emitted from the 3.4 μm feature to that from the 3.3 μm feature. We derive the median ratio to be (I{sub 3.4}/I{sub 3.3}) ≈ 0.12. We employ density functional theory to compute A{sub 3.4}/A{sub 3.3} for a range of methyl-substituted PAHs. The resulting A{sub 3.4}/A{sub 3.3} ratio well exceeds ∼1.4, with an average ratio of A{sub 3.4}/A{sub 3.3} ≈ 1.76. By attributing the 3.4 μm feature exclusively to aliphatic C-H stretch (i.e., neglecting anharmonicity and superhydrogenation), we derive the fraction of C atoms in aliphatic form from I{sub 3.4}/I{sub 3.3} ≈ 0.12 and A{sub 3.4}/A{sub 3.3} ≈ 1.76 to be ∼2%. We therefore conclude that the UIE emitters are predominantly aromatic.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

AN OUTFLOW PERPENDICULAR TO THE RADIO JET IN THE SEYFERT NUCLEUS OF NGC 5929

We report the observation of an outflow perpendicular to the radio jet in near-infrared integral field spectra of the inner 250 pc of the Seyfert 2 galaxy NGC 5929. The observations were obtained with the Gemini Near-infrared Integral Field Spectrograph at a spatial resolution of ∼20 pc and spectral resolution of R ≈ 5300 and reveal a region ∼50 pc wide crossing the nucleus and extending by ∼300 pc perpendicularly to the known radio jet in this galaxy. Along this structure—which we call the south-east-north-west (SE-NW) strip—the emission line profiles show two velocity components, one blueshifted and the other redshifted by –150 km s{sup –1} and 150 km s{sup –1}, respectively, relative to the systemic velocity. We interpret these two components as being due to an outflow perpendicular to the radio jet, which is supported by low-frequency radio emission observed along the same region. We attribute this feature to the interaction of ambient gas with an ''equatorial outflow'' predicted in recent accretion disk and torus wind models. Perpendicularly to the SE-NW strip, thus approximately along the radio jet, single-component profiles show blueshifts of ≈ – 150 km s{sup –1} to the north-east and similar redshifts to the south-west, which can be attributed to gas counter-rotating relative to the stellar kinematics. More double-peaked profiles are observed in association with the two radio hot spots, attributed to interaction of the radio jet with the surrounding gas.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Observing pre-edge K -shell resonances in Kr, Xe, and XeF 2

The 1s→np Rydberg transitions below the 1s ionization thresholds of Kr and Xe are obscured in x-ray absorption spectra due to core-hole lifetime broadening. However, the np spectator electrons associated with those resonances can affect the core-hole decay spectra. We report on ion charge-state distributions of Kr and Xe measured in coincidence with KL 2,3 (K α1,2 ), KM 2,3 (Kβ 1,3 ), and KN 2,3 (Kβ 2 ) x-ray fluorescence as the incident x-ray energy is scanned through pre-edge resonances and ionization thresholds. The coincidence measurements select vacancy cascades that begin with a radiative transition that transfers 1s holes to the 2p, 3p, and 4p shells followed by emission of Auger electrons. We observe shifts of ion yields from higher to lower charge states that we attribute to np spectator electrons. For the special case of Kr 1+ that is produced in coincidence with Kβ 2 x rays, the ion yield decreases in the pre-edge region. This is attributed to production of neutral, metastable Kr 4p –1 np states that reduce the Kr 1+ yield. Model fits to the x-ray absorption spectra are presented to show the lifetime broadened pre-edge resonances and ionization thresholds. High-level relativistic coupled-cluster calculations that treat relativistic, electron correlation, and wave function relaxation effects on the same footing obtain agreement with the experimental 1s ionization energies of Kr and Xe to <2 eV. The Xe K-edge x-ray absorption spectrum and ion charge-state distributions of XeF2 were also recorded. Excitation of the 7σ u lowest unoccupied molecular orbital (LUMO) in XeF 2 is observed in the pre-edge region. Our ab initio calculations find that the 6p z Rydberg state is strongly perturbed by the presence of the 7σu LUMO. A fit to the measured LUMO, 6p x , 6p y , 6p z Rydberg states, and ionization threshold is guided by the relativistic coupled-cluster calculations. The F ligands modify the valence electron charge distribution and result in a ~2.3 eV chemical shift of the Xe 1s ionization energy relative to atomic Xe. Xe 1s –1 core-hole decay in XeF 2 results in ionization of the F ligands and energetic fragmentation into atomic ions. Ion charge-state spectra of XeF 2 were recorded in coincidence with x-ray fluorescence for excitation on the LUMO resonance and above the Xe 1s ionization threshold. For the ion time of flight spectra recorded on the LUMO resonance, the F q+ (q = 1–4) peaks are split into two peaks along the linear polarization direction of the incident x-ray beam. This effect is attributed to spatial alignment of XeF 2 molecules by resonant x-ray absorption, and the peak splittings are used to measure the F ion fragmentation energies following Kα 1,2 , Kβ 1,3 , and Kβ 2 x-ray fluorescence. Here, we observe variations of the F ion charge state yields and fragmentation energies for the three fluorescence pathways that leave the molecule in different outer-shell hole states.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2014

Multivariate volume visualization through dynamic projections

We propose a multivariate volume visualization framework that tightly couples dynamic projections with a high-dimensional transfer function design for interactive volume visualization. We assume that the complex, high-dimensional data in the attribute space can be well-represented through a collection of low-dimensional linear subspaces, and embed the data points in a variety of 2D views created as projections onto these subspaces. Through dynamic projections, we present animated transitions between different views to help the user navigate and explore the attribute space for effective transfer function design. Our framework not only provides a more intuitive understanding of the attribute space but also allows the design of the transfer function under multiple dynamic views, which is more flexible than being restricted to a single static view of the data. For large volumetric datasets, we maintain interactivity during the transfer function design via intelligent sampling and scalable clustering. As a result, using examples in combustion and climate simulations, we demonstrate how our framework can be used to visualize interesting structures in the volumetric space.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2015

Sensory interaction between 3-mercaptohexan-1-ol, 3-isobutyl-2-methoxypyrazine and oxidation-related compounds: Sauvignon Blanc sensory interaction studies

Wine aroma is influenced by complex interactions between various wine constituents. This study investigated the sensorial interactive effects of Sauvignon Blanc impact compounds, 3-mercaptohexan-1-ol,3-isobutyl-2-methoxypyrazine with aldehydes typically originating from oxidation of white wines, methional and phenylacetaldehyde. Spiked model wines were subjected to sensory descriptive analysis using a trained panel.The concentration of each compound varied from below aroma threshold value to high values reported inwine. Combinations of the four compounds were also evaluated sensorially. Depending on the concentrationof the compounds, methional had a strong suppressive effect on the intensity of attributes contributed by3-mercaptohexan-1-ol, such as grapefruit and guava, whereas methional and 3-isobutyl-2-methoxypyrazine enhanced the intensity of certain attributes, which included cooked beans and cooked potato. Complex sensory interactions may occur between Sauvignon Blanc impact compounds and compounds related to oxidation depending on concentration of the compounds. Oxidation-derived compounds such asmethional can suppress pleasant aroma attributes linked to volatile thiols, while contributing negative attributesespecially in the presence of 3-isobutyl-2-methoxypyrazine. This paper highlights the importance of preserving fresh and fruity flavours while preventing the formation of unwanted aldehydes due to interactions that can influence the overall aroma profile of the wine. This study may also contribute to the sensory characterisation of oxidised Sauvignon Blanc wine.

3-isobutyl-2-methoxypyrazine↗
DOE OSTI2016

Sensory effect of acetaldehyde on the perception of 3-mercaptohexan-1-ol and 3-isobutyl-2-methoxypyrazine: Role of acetaldehyde in sensory interactions

Background and Aims-Wine aroma is influenced by complex interactions between various wine constituents. This study investigated the sensory interactive effects of Sauvignon Blanc impact compounds, 3-mercaptohexan-1-ol and 3-isobutyl-2-methoxypyrazine, with acetaldehyde that typically forms during the oxidation of wine. Methods and Results-Spiked model wines were subjected to sensory descriptive analysis using a trained sensory panel. Additionally, the concentration of each compound varied from below aroma threshold values to high values as reported for wine. Depending on the concentration, acetaldehyde enhanced fruity attributes at a lower concentration, whereas suppression occurred at a higher concentration. Acetaldehyde effectively suppressed the green pepper aroma attribute at certain concentration values, whereas 3-mercaptohexan-1-ol suppressed oxidised green apple associated with acetaldehyde. Changes in attributes used for aroma description also occurred because of change in concentration. Conclusions-Complex sensory interactions may occur between Sauvignon Blanc impact compounds and one of the main oxidation-derived compounds, acetaldehyde. Acetaldehyde can enhance or suppress pleasant fruity characters depending on the concentration. Significance of the Study-This study showed the potential positive effect of acetaldehyde on white wine aroma when present at a low concentration. Formation of this compound during winemaking and ageing should, however, be controlled because of negative sensory interactions occurring at a higher concentration. In conclusion, this study may also contribute to the sensory characterisation of Sauvignon Blanc wine undergoing oxidation.

3-isobutyl-2-methoxypyrazine↗