Small Ensembles Research Articles

Evolving Understanding of Antarctic Ice‐Sheet Physics and Ambiguity in Probabilistic Sea‐Level Projections

AbstractMechanisms such as ice‐shelf hydrofracturing and ice‐cliff collapse may rapidly increase discharge from marine‐based ice sheets. Here, we link a probabilistic framework for sea‐level projections to a small ensemble of Antarctic ice‐sheet (AIS) simulations incorporating these physical processes to explore their influence on global‐mean sea‐level (GMSL) and relative sea‐level (RSL). We compare the new projections to past results using expert assessment and structured expert elicitation about AIS changes. Under high greenhouse gas emissions (Representative Concentration Pathway [RCP] 8.5), median projected 21st century GMSL rise increases from 79 to 146 cm. Without protective measures, revised median RSL projections would by 2100 submerge land currently home to 153 million people, an increase of 44 million. The use of a physical model, rather than simple parameterizations assuming constant acceleration of ice loss, increases forcing sensitivity: overlap between the central 90% of simulations for 2100 for RCP 8.5 (93–243 cm) and RCP 2.6 (26–98 cm) is minimal. By 2300, the gap between median GMSL estimates for RCP 8.5 and RCP 2.6 reaches >10 m, with median RSL projections for RCP 8.5 jeopardizing land now occupied by 950 million people (versus 167 million for RCP 2.6). The minimal correlation between the contribution of AIS to GMSL by 2050 and that in 2100 and beyond implies current sea‐level observations cannot exclude future extreme outcomes. The sensitivity of post‐2050 projections to deeply uncertain physics highlights the need for robust decision and adaptive management frameworks.

Identifying heterogeneities in cooling and quality evolution for a pallet of packed fresh fruit by using virtual cold chains

Temperature control of fresh produce by forced convective cooling through ventilated packaging is essential to preserve quality in postharvest supply chains. The challenge is to achieve uniform cooling of fruit in the entire cargo. Most numerical research using computational fluid dynamics (CFD) focused on ventilated packaging with relatively small ensembles of fruit. This study aims to gain more insight into the thermal heterogeneity and the associated differences in quality evolution for large ensembles of packed fruit, by investigating the thermal behavior of an entire pallet of fruit throughout the entire cold chain. To this end, the virtual cold chain method is applied, which virtually tracks the temperature–time history of individual fruit using CFD and accordingly predicts fruit quality evolution using kinetic rate law models. The pallet includes 80 cartons, in which 5120 fruit are explicitly modelled as discrete spheres. Three cold chain scenarios are evaluated. For all the three unit operations in a cold chain (precooling, transport and storage), significant differences in the fruit cooling time are found along the airflow direction, where the blockage of local vent holes is found to increase the thermal heterogeneity. Cooling heterogeneity is the smallest for precooling and the largest for cold storage. Fruit in upstream cartons also show a higher cooling heterogeneity than those in downstream cartons. The difference in quality evolution between individual fruit is found to be very limited if proper precooling is applied in the cold chain. In the cold chain without precooling, about 23% more quality loss is found than in that with precooling. Ambient loading is promising to remove field heat during refrigerated transport.

Role of the Atlantic Multidecadal Variability in modulating the climate response to a Pinatubo-like volcanic eruption

The modulation by the Atlantic multidecadal variability (AMV) of the dynamical climate response to a Pinatubo-like eruption is investigated for the boreal winter season based on a suite of large ensemble experiments using the CNRM-CM5 Coupled Global Circulation Model. The volcanic eruption induces a strong reduction and retraction of the Hadley cell during 2 years following the eruption and independently of the phase of the AMV. The mean extratropical westerly circulation simultaneously weakens throughout the entire atmospheric column, except at polar Northern latitudes where the zonal circulation is slightly strengthened. Yet, there are no significant changes in the modes of variability of the surface atmospheric circulation, such as the North Atlantic Oscillation (NAO), in the first and the second winters after the eruption. Significant modifications over the North Atlantic sector are only found during the third winter. Using clustering techniques, we decompose the atmospheric circulation into weather regimes and provide evidence for inhibition of the occurrence of negative NAO-type circulation in response to volcanic forcing. This forced signal is amplified in cold AMV conditions and is related to sea ice/atmosphere feedbacks in the Arctic and to tropical-extratropical teleconnections. Finally, we demonstrate that large ensembles of simulations are required to make volcanic fingerprints emerge from climate noise at mid-latitudes. Using small size ensemble could easily lead to misleading conclusions especially those related to the extratropical dynamics, and specifically the NAO.

Reactive Molecular Dynamics Simulation of Kerogen Thermal Maturation and Cross-Linking Pathways

Molecular dynamics simulations were performed with a ReaxFF reactive force field to investigate bond breaking and bond formation mechanisms during the thermal maturation of three kerogens and potential cross-linking pathways toward the formation of three-dimensional (3D) quasi-infinite molecular networks (cross-linked kerogen macromolecules). Starting with small ensembles of high molecular mass models for immature type I Green River Shale kerogen (kerogen 1-I), top of the oil window type II kerogen (kerogen 2-L), and low maturity type III kerogen (kerogen 3-L), low molecular mass species including H2O, C2H4, and C3H6 were produced as the maturities of the remaining kerogens increased. Highly reactive fragments, which are not detected in pyrolysis experiments, were also produced. Further, the cross-linking mechanisms in the newly developed polymeric kerogen networks appear to be highly complex, and covalent —C–S—, —C–O—, and —C–C— bonds were the primary cross-links that structurally bond kerogen monomers t...

Tectonics Festival Glasgow

For those who, consciously or not, have come to associate today's exploratory music with small ensembles, electronics or performative physicality, the symphony orchestra can seem an unlikely source of new horizons. The orthodoxy of the concert hall, the uniforms, the absorption of human performers into an abstract whole, the stasis of musicians and audience: these aren't new anxieties but they persist in interesting ways.

Ensemble clustering for efficient robust optimization of naturally fractured reservoirs

In the development of naturally fractured reservoirs (NFRs), the existence of natural fractures induces severe fingering and breakthrough. To manage the flooding process and improve the ultimate recovery, we propose a numerical workflow to generate optimal production schedules for smart wells, in which the inflow control valve (ICV) settings can be controlled individually. To properly consider the uncertainty introduced by randomly distributed natural fractures, the robust optimization would require a large ensemble size and it would be computationally demanding. In this work, a hierarchical clustering method is proposed to select representative models for the robust optimization in order to avoid redundant simulation runs and improve the efficiency of the robust optimization. By reducing the full ensemble of models into a small subset ensemble, the efficiency of the robust optimization algorithm is significantly improved. The robust optimization is performed using the StoSAG scheme to find the optimal well controls that maximize the net-present-value (NPV) of the NFR’s development. Due to the discrete property of a natural fracture field, traditional feature extraction methods such as model-parameter-based clustering may not be directly applicable. Therefore, two different kinds of clustering-based optimization methods, a state-based (e.g., s w profiles) clustering and a response-based (e.g., production rates) clustering, are proposed and compared. The computational results show that the robust clustering optimization could increase the computational efficiency significantly without sacrificing much expected NPV of the robust optimization. Moreover, the performance of different clustering algorithms varies widely in correspondence to different selections of clustering features. By properly extracting model features, the clustered subset could adequately represent the uncertainty of the full ensemble.

An efficient adaptive algorithm for robust control optimization using StoSAG

There is significant geological uncertainty in the reservoir description due to the limited knowledge about the underground formation. The common approach is to use multiple plausible geostatistical realizations of the reservoir model in order to quantify the uncertainty, however, usually a small ensemble of realizations is utilized in the robust optimization due to the computational cost. This may results in erroneous estimation of uncertainty in the predicted optimal reservoir production performance. We propose an efficient algorithm for robust optimization where a large number of representative realizations are considered. The algorithm proposed in this work assumes confidence in a subset of realizations for representing the full-set of realizations in the neighbourhood of the current control estimate. The subset is chosen based on a ranking method and modified adaptively throughout the optimization iterations. The optimizer in this paper is the steepest ascent method using the Stochastic Simplex Approximate Gradient (StoSAG), but the proposed algorithm is suitable to be combined with other optimization algorithms. Three synthetic reservoir examples generated with different geostatistical modelling methods are tested to validate the proposed algorithm. All three examples show that compared with a full-set robust optimization, the proposed adaptive robust optimization algorithm not only improves the optimization convergence rate, but also find a higher optimal NPV when the optimization is terminated at a maximum affordable simulation cost using the stochastic simplex gradient.

Propagation of Input Uncertainty in Presence of Model-Form Uncertainty: A Multifidelity Approach for Computational Fluid Dynamics Applications

Proper quantification and propagation of uncertainties in computational simulations are of critical importance. This issue is especially challenging for computational fluid dynamics (CFD) applications. A particular obstacle for uncertainty quantifications in CFD problems is the large model discrepancies associated with the CFD models used for uncertainty propagation. Neglecting or improperly representing the model discrepancies leads to inaccurate and distorted uncertainty distribution for the quantities of interest (QoI). High-fidelity models, being accurate yet expensive, can accommodate only a small ensemble of simulations and thus lead to large interpolation errors and/or sampling errors; low-fidelity models can propagate a large ensemble, but can introduce large modeling errors. In this work, we propose a multimodel strategy to account for the influences of model discrepancies in uncertainty propagation and to reduce their impact on the predictions. Specifically, we take advantage of CFD models of multiple fidelities to estimate the model discrepancies associated with the lower-fidelity model in the parameter space. A Gaussian process (GP) is adopted to construct the model discrepancy function, and a Bayesian approach is used to infer the discrepancies and corresponding uncertainties in the regions of the parameter space where the high-fidelity simulations are not performed. Several examples of relevance to CFD applications are performed to demonstrate the merits of the proposed strategy. Simulation results suggest that, by combining low- and high-fidelity models, the proposed approach produces better results than what either model can achieve individually.

Coating Pd/Al2O3 catalysts with FeOx enhances both activity and selectivity in 1,3-butadiene hydrogenation

Pd-based catalysts are widely used in hydrogenation reactions, and it is essential to improve the selectivity of these catalysts to give the desired products, especially at high conversions. However, improvements in selectivity have generally been achieved at the expense of catalytic activity. Here, we report that deposition of FeOx onto a Pd/Al2O3 catalyst using atomic layer deposition with precise, near atomic control provides a remarkable improvement in both activity and butene selectivity in the selective hydrogenation of 1,3-butadiene under mild conditions. Diffuse reflectance infrared Fourier transform spectroscopy for CO chemisorption measurements illustrate that FeOx preferentially nucleates on Pd (111) facets and divides the Pd surface atoms into small ensembles. X-ray photoelectron spectroscopy measurements revealed that the Pd became electron deficient after FeOx deposition owing to the strong Pd–FeOx interaction. Our results suggest that a geometric effect, that is, the formation of small Pd ensembles, is the main contributor to the improvement in butene selectivity, whereas the enhancement in hydrogenation activity may be attributed to both electronic effects and the newly generated Pd–FeOx interface.

Enhanced decision tree ensembles for land-cover mapping from fully polarimetric SAR data

ABSTRACTFully polarimetric synthetic aperture radar (PolSAR) Earth Observations showed great potential for mapping and monitoring agro-environmental systems. Numerous polarimetric features can be extracted from these complex observations which may lead to improve accuracy of land-cover classification and object characterization. This article employed two well-known decision tree ensembles, i.e. bagged tree (BT) and random forest (RF), for land-cover mapping from PolSAR imagery. Moreover, two fast modified decision tree ensembles were proposed in this article, namely balanced filter-based forest (BFF) and cost-sensitive filter-based forest (CFF). These algorithms, designed based on the idea of RF, use a fast filter feature selection algorithms and two extended majority voting. They are also able to embed some solutions of imbalanced data problem into their structures. Three different PolSAR datasets, with imbalanced data, were used for evaluating efficiency of the proposed algorithms. The results indicated that all the tree ensembles have higher efficiency and reliability than the individual DT. Moreover, both proposed tree ensembles obtained higher mean overall accuracy (0.5–14% higher), producer’s accuracy (0.5–10% higher), and user’s accuracy (0.5–9% higher) than the classical tree ensembles, i.e. BT and RF. They were also much faster (e.g. 2–10 times) and more stable than their competitors for classification of these three datasets. In addition, unlike BT and RF, which obtained higher accuracy in large ensembles (i.e. the high number of DT), BFF and CFF can also be more efficient and reliable in smaller ensembles. Furthermore, the extended majority voting techniques could outperform the classical majority voting for decision fusion.

A comparison of resampling schemes for estimating model observer performance with small ensembles

In objective assessment of image quality, an ensemble of images is used to compute the 1st and 2nd order statistics of the data. Often, only a finite number of images is available, leading to the issue of statistical variability in numerical observer performance. Resampling-based strategies can help overcome this issue. In this paper, we compared different combinations of resampling schemes (the leave-one-out (LOO) and the half-train/half-test (HT/HT)) and model observers (the conventional channelized Hotelling observer (CHO), channelized linear discriminant (CLD) and channelized quadratic discriminant). Observer performance was quantified by the area under the ROC curve (AUC). For a binary classification task and for each observer, the AUC value for an ensemble size of 2000 samples per class served as a gold standard for that observer. Results indicated that each observer yielded a different performance depending on the ensemble size and the resampling scheme. For a small ensemble size, the combination [CHO, HT/HT] had more accurate rankings than the combination [CHO, LOO]. Using the LOO scheme, the CLD and CHO had similar performance for large ensembles. However, the CLD outperformed the CHO and gave more accurate rankings for smaller ensembles. As the ensemble size decreased, the performance of the [CHO, LOO] combination seriously deteriorated as opposed to the [CLD, LOO] combination. Thus, it might be desirable to use the CLD with the LOO scheme when smaller ensemble size is available.

Ultracold bosonic scattering dynamics off a repulsive barrier: Coherence loss at the dimensional crossover

We explore the impact of dimensionality on the scattering of a small bosonic ensemble in an elongated harmonic trap off a centered repulsive barrier, thereby taking particle correlations into account. The loss of coherence as well as the oscillation of the center of mass are studied and we analyze the influence of both particle and spatial correlations. Two different mechanisms of coherence losses in dependence of the aspect ratio are found. For small aspect ratios, loss of coherence between the region close to the barrier and outer regions occurs, due to spatial correlations, and for large aspect ratios, incoherence between the two density fragments of the left and right side of the barrier arises, due to particle correlations. Apart form the decay of the center of mass motion induced by the reflection and transmission, further effects due to the particle and spatial correlations are explored. For tight transversal traps, the amplitude of the center of mass oscillation experiences a weaker damping, which can be traced back to the population of a second natural orbital, and for a weaker transversal confinement, we detect a strong decay, due to the possibility of transferring energy to transversal excited modes. These effects are enhanced if the aspect ratio is integer valued.

Pt Nanoparticle Collisions Detected by Electrocatalytic Amplification and Atomic Force Microscopy Imaging: Nanoparticle Collision Frequency, Adsorption, and Random Distribution at an Ultramicroelectrode Surface.

We demonstrate good agreement between the theoretical and experimental collision frequency of individual Pt nanoparticles (NPs) undergoing collisions at a Au ultramicroelectrode (UME) (5 μm radius) using electrocatalytic amplification provided by 15 mM hydrazine in 5 mM phosphate buffer (PB; pH 7) over 100 to 300 s. Dynamic light scattering (DLS) measurements demonstrated that Pt NP aggregation in this solution had the least impact on NP diffusion coefficient and concentration values, which are directly proportional to collision frequency. We show that the smaller, uniform current steps are indicative of NPs of metallic radii in agreement with those determined by transmission electron microscopy (TEM), with corresponding larger NP diffusion coefficient and concentration, in agreement with DLS results. These contribute to the larger NP collision frequency observed experimentally. Using atomic force microscopy (AFM) imaging, we show good agreement between the number of NPs imaged on the UME surface and the number of NP collisions that led to their adsorption, a spherical NP shape with a metallic radius size distribution comparable to that determined by TEM, and a random NP distribution on the UME surface. Through the Pt NP electroactive surface area, we show that all NPs on the UME surface after collision are attached and electrochemically active. Collectively, these results demonstrate for the first time that, within experimental error, every NP collision is successful and occurs through a sticking mechanism. Thus, collision experiments can be used to prepare small NP ensembles on a UME (i.e., UME-NPEs). In electrocatalysis, such UME-NPEs bridge the gap between classical ensemble studies on large platforms and isolated single NP investigations.

Work-related floors as injury hazards \u2013 a nationwide pilot project analyzing floors in theatres and education establishments in Germany

BackgroundAn adequate dance floor is said to prevent injuries. On the basis of scientific research, numerous recommendations regarding an adequate dance floor have been developed. Up to the present, however, studies have still been lacking into how far these recommendations have already been implemented in theatres with regular dance productions and/or in-house dance ensembles. The aim of this study is to analyze a nationwide survey on dance floors of theatres and education establishments in Germany.MethodsA questionnaire-based survey on existence and type of floors in the various dance-related working areas was carried out at theatres and education establishments institutions (n = 86 institutions (n = 76 theatres, n = 10 education establishments). References as to region, size of dance ensembles and dance styles performed were created.ResultsOf all education establishments, 75.3% were equipped with a sprung sub-floor in the ballet studios. In contrast, sprung sub-floors were only found in 29.7% of the working areas, the stage AND ballet studios in theatres. The percentage of theatres providing sprung sub-floors in all rooms used by dancers is even lower. Considering all dance-related work areas, larger ensembles (>30 dancers) were offered better conditions regarding floors than smaller ensembles (p > 0.001). No significant tendencies were found regarding regions or dance styles.ConclusionRecommendations concerning an appropriate dance floor have only partly been realized. Besides secured finances for reinstallation, further education of responsible officials and artists is essential. However, accrediting dance as own genre in theatres is the indispensable prerequisite.

An inhibitory gate for state transition in cortex.

Large scale transitions between active (up) and silent (down) states during quiet wakefulness or NREM sleep regulate fundamental cortical functions and are known to involve both excitatory and inhibitory cells. However, if and how inhibition regulates these activity transitions is unclear. Using fluorescence-targeted electrophysiological recording and cell-specific optogenetic manipulation in both anesthetized and non-anesthetized mice, we found that two major classes of interneurons, the parvalbumin and the somatostatin positive cells, tightly control both up-to-down and down-to-up state transitions. Inhibitory regulation of state transition was observed under both natural and optogenetically-evoked conditions. Moreover, perturbative optogenetic experiments revealed that the inhibitory control of state transition was interneuron-type specific. Finally, local manipulation of small ensembles of interneurons affected cortical populations millimetres away from the modulated region. Together, these results demonstrate that inhibition potently gates transitions between cortical activity states, and reveal the cellular mechanisms by which local inhibitory microcircuits regulate state transitions at the mesoscale.

Geometric and electronic effects of bimetallic Ni–Re catalysts for selective deoxygenation of m-cresol to toluene

Ni–Re/SiO2 bimetallic catalysts were prepared using a co-impregnation method and tested in vapor phase hydrodeoxygenation of m-cresol at 300°C and 1atm H2. In contrast to the use of unselective monometallic Ni/SiO2 for catalyzing deoxygenation, hydrogenation, and CC hydrogenolysis reactions, bimetallic 5%Ni–2.5%Re/SiO2 improved the intrinsic reaction rate of the hydrodeoxygenation reaction by a factor of 6, with the turnover frequency for selective deoxygenation to toluene increased by four times, while that for CC hydrogenolysis to methane was reduced by one-half. Characterization results from X-ray diffraction, Raman, transmission electron microscopy, X-ray photoelectron spectroscopy, infrared spectroscopy of CO adsorption, H2 temperature-programmed reduction, and CO chemisorption indicate that adding Re increased Ni dispersion and resulted in Ni–Re surface alloy formation after reduction. The presence of Re in the surface alloy breaks the continuous Ni surface into smaller ensembles (geometric effect) and reduces the d-band electron density of Ni (electronic effect). Results from density functional theory calculations indicate that the Ni–Re neighboring site is the active site for breaking the CO bond by adsorbing the O atom on Re and the phenyl ring on the neighboring Ni atoms, which facilitates deoxygenation to toluene. The reduced Ni ensemble size inhibits the hydrogenolysis of the CC bond by destabilizing the transition state, whereas the reduction of the electronic density in d states of Ni weakens the adsorption of the phenyl ring, and both contribute to the greatly reduced methane production from successive CC hydrogenolysis.

Quasi-chemical model of self-assembly and the formation of kinetically controlled structures

A quasi-chemical model of self-assembly among identical objects is proposed. The model rests on two main premises: (a) larger ensembles are more stable and (b) have slower rates of transformation, growth, and decomposition. These statements result from all paired interactions in the considered ensemble. This formulation of self-assembly is shown to be conducive to the formation of large ensembles with sizes distributed normally in a fairly narrow range, and with the concentrations of smaller ensembles being negligible. The existence of two critical points follows from the model. One is a critical concentration that initiates self-assembly in the system when exceeded. The other is a critical ensemble size that sets a threshold for the self-driven growth of ensembles in the system. The growth of ensembles nearly ceases at a point far from equilibrium, and the mean ensemble size and the ensemble’s size distribution are under kinetic control. Stable structures of this kind (with kinetic control of their organization) can serve as models for many natural self-organized systems.

Quench-induced resonant tunneling mechanisms of bosons in an optical lattice with harmonic confinement

The non-equilibrium dynamics of small boson ensembles in a one-dimensional optical lattice is explored upon a sudden quench of an additional harmonic trap from strong to weak confinement. We find that the competition between the initial localization and the repulsive interaction leads to a resonant response of the system for intermediate quench amplitudes, corresponding to avoided crossings in the many-body eigenspectrum with varying final trap frequency. In particular, we show that these avoided crossings can be utilized to prepare the system in a desired state. The dynamical response is shown to depend on both the interaction strength as well as the number of atoms manifesting the many-body nature of the tunneling dynamics.

Improving ensemble covariances in hybrid variational data assimilation without increasing ensemble size

Increasing the size of the ensemble used in hybrid‐variational assimilation methods has been shown to be beneficial, but is computationally expensive. This work sets out to see whether similar improvements can be obtained from a smaller ensemble by better estimation of ensemble covariances. Methods for improving these are described and illustrated using a toy model. The optimal settings depend on the ensemble size, the criterion used to measure error and the errors in ensemble generation. A hybrid covariance, filtered by spectral localization using wavebands and scale‐dependent spatial localization, is shown to perform well and robustly.In the cycled ensemble data‐assimilation scheme used for numerical weather prediction (NWP), another method of increasing the effective ensemble size in covariance estimates is the use of time‐lagged and time‐shifted perturbations. This is demonstrated to be effective in the Met Office's hybrid‐4DEnVar system, both on its own and with waveband and scale‐dependent localization. The best such combination performs nearly as well as an increase in ensemble size from 44 to 200.

Notes and News

Notes and News Dr. Ken Hoppmann Call for Papers The fifty-second annual Western Literature Association conference will be held October 25–28, 2017, in Minneapolis. The conference theme is Sweet Land, Mighty Waters: Myth and Storytelling West of the Mississippi. The conference’s theme grew from the short story collection Sweet Land by Minnesota writer Will Weaver and Minnesota’s long heritage of nature and regional writing. The state is also known for its mythic figures and master storytellers. Innovative proposals are encouraged on the following topics: myth, storytelling, and storytellers; nature writing and literature of place; plays, theater, and performance; Native American and other ethnic writers and writing; borders and border crossing; Minnesota/midwestern writers and literature; food writing. The conference organizers are open to sessions on teaching, workshops, and roundtable discussions. Submissions must include a 250-word abstract, name, affiliation, contact information, and audiovisual requests. Proposals for panels and roundtable discussions should include an abstract for each paper or presentation. Deadline: June 15, 2017. Please submit abstracts, proposals, or questions to Florence Amamoto <amamoto@gac.edu> or Susan Maher <smaher@d.umn.edu>. For more information see <http://www.westernlit.org/wla-conference-2017/>. Editor’s Note We would like to call attention to a unique musical event that occurred in honor of Chief Standing Bear (Ponca). A special performance of a new composition was introduced in 2016. Below, the artistic director of the Standing Bear Project describes this innovative event. Standing Bear: A Ponca Indian Cantata in Eight Tableaux The Hildegard Center for the Arts in Lincoln, Nebraska, recently presented a newly commissioned chamber work by American composer Jerod Impichchaachaaha’ Tate, a self-described Chickasaw classical composer. In his piece Standing Bear: A Ponca Indian Cantata in Eight Tableaux, Tate has set one of the most important Native American stories of all time. His musical rendering employs a traditionally classical setting for solo baritone, piano, and string sextet. His musical ideas convey the drama and strength of the nineteenth-century Ponca chief while incorporating European compositional techniques from the twentieth century and beyond. It is understandable that American Indians would fiercely protect their indigenous cultures and stories. It is also understandable that there could be resentment toward non-Native people, ancestors of their first oppressors, who attempt to co-opt important and sacred stories that hold deep cultural significance for a tribe. Hildegard Center for the Arts is honored to be entrusted with the story of Chief Standing Bear. We acknowledge that we are among those who need to learn from and experience the rich culture of our Ponca friends. It has been a challenge for us to authentically and accurately represent Standing Bear with our European art and music, yet we believe that it is vitally important to do so. [End Page 75] In his cantata, Jerod Tate sets the story of Standing Bear in a manner consistent with his classical training. He uses traditional compositional techniques and western European instrumentation. His harmonic language is based primarily on accepted European quartal and quintal intervals, while he combines shifting accents and unexpected metric groupings to create a Stravinsky-like rhythmic drive. The story unfolds within a compositional framework consisting of eight tableaux, or movements. This formal structure allows Jerod Tate ample space to move about and develop the dramatic pull necessary for such a weighty story. Tate’s experience as an operatic and ballet composer is evident in his use of dramatic techniques even within the confines of a small ensemble. He succeeds in filling the smaller compositional space with the mastery of a Baroque painter, making certain that every square inch is effectively and powerfully utilized. There is no shortage of western Europe in Tate’s Standing Bear cantata. But what about Native America? Throughout the Indianist era, western composers attempted to “Indianize” compositions simply by creating Native-sounding titles, incorporating a few Native rhythms, or by using an established Native story as the basis for a piece. In Tate’s piece, however, we are presented with many substantial and authentic Indian qualities. The story is one of Ponca strength and resilience. In telling it, the composer extends his Chickasaw hand of friendship to the...