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At least 757 records · Page 42

Development of One and Two Current Transition Amplitudes with Two Body Final States

One of the biggest challenges facing modern day nuclear physics is understanding the structure of states within the hadronic spectrum of Quantum Chromodynamics (QCD). We have shown this spectrum to be quite rich with hundreds of allowed states; however, if we wish to better grasp the dynamics of QCD, then it is necessary that we start investigating the internal structure of these states. This may be done by probing these states with external currents, but this requires a description of the intersection of QCD with the electroweak sector. This work acts as a stepping stone in this direction. Working to all orders in the strong interaction and to leading order in electroweak effects we present novel formalisms for transition amplitudes with one and two currents with two hadrons in the final state, namely the 2 + J ? 2 and 1 + J ? 2 + J amplitudes. Our results are valid for spinless hadrons with any number of open channels between two- and three-particle threshold, place no restrictions on the Lorentz structure or quantum numbers of the current, and are independent of any underlying model. We also show how this formalism may be used to rigorously access elastic form factors of resonances which has proven challenging to do experimentally. Finally, we present a toy calculation of elastic resonance form factors using the 2 + J ? 2 formalism in which we stress the importance of treating resonances rigorously as poles in the complex plane.

Sherman, Keegan↗

Comparison of Motion Analysis Systems in Tracking Upper Body Movement of Myoelectric Bypass Prosthesis Users

Current literature lacks a comparative analysis of different motion capture systems for tracking upper limb (UL) movement as individuals perform standard tasks. To better understand the performance of various motion capture systems in quantifying UL movement in the prosthesis user population, this study compares joint angles derived from three systems that vary in cost and motion capture mechanisms: a marker-based system (Vicon), an inertial measurement unit system (Xsens), and a markerless system (Kinect). Ten healthy participants (5F/5M; 29.6 ± 7.1 years) were trained with a TouchBionic i-Limb Ultra myoelectric terminal device mounted on a bypass prosthetic device. Participants were simultaneously recorded with all systems as they performed standardized tasks. Root mean square error and bias values for degrees of freedom in the right elbow, shoulder, neck, and torso were calculated. The IMU system yielded more accurate kinematics for shoulder, neck, and torso angles while the markerless system performed better for the elbow angles. By evaluating the ability of each system to capture kinematic changes of simulated upper limb prosthesis users during a variety of standardized tasks, this study provides insight into the advantages and limitations of using different motion capture technologies for upper limb functional assessment.

42 ENGINEERING↗

Equations of Motion for the Vertical Rigid-Body Rotor: Linear and Nonlinear Cases

Centuries ago, the prolific mathematician Leonhard Euler (1707–1783) wrote down the equations of motion (EOM) for the heavy symmetrical top with one point fixed. The resulting set of equations turned out to be nonlinear and had a limited number of closed-form solutions.Today, tools such as transfer matrix and finite elements enable the calculation of the rotordynamic properties for rotor-bearing systems. Some of these tools rely on the “linearized” version of the EOM to calculate the eigenvalues, unbalance response, or transients in these systems.In fact, industry standards mandate that rotors be precisely balanced to have safe operational characteristics. However, in some cases, the nonlinear aspect of the EOM should be considered.The purpose of this chapter is to show examples of how the linear vs. nonlinear formulations differ. This chapter also shows how excessive unbalance is capable of dramatically altering the behavior of the system and can produce chaotic motions associated with the “jump” phenomenon.

Laos, Hector↗

Analysis of Three Body Decays in Quasi-Real Photoproduction

This thesis presents preliminary measurements of the moments of angular distribution for the K?K+ mesonic final state using a quasi-real, linearly polarised photon. Two of the main points of focus for this analysis were the development of the formalism for photoproduced vector-pseudoscalar decay and the tools by which the analysis was carried out. The formalism described how the moments of angular distribution could be extracted from the angular decay variables, and how they related to resonance decays in terms of partial waves. In extracting the moments, it was found that adapted Markov Chain Monte Carlo (MCMC) methods proved to be more effective in terms of extracting results from the data compared to the sole use of gradient descent based fitting algorithms. These measurements are complementary to other decay channels and production mechanisms, with the global aim of probing the existence of exotic mesons. Data from this analysis was taken by the CLAS collaboration at the Thomas Jefferson National Accelerator Facility (JLab) by scattering from a liquid hydrogen target using a 10.6 GeV electron. This work was done within the MesonEx program at CLAS12 that aims to map the spectrum of mesons, and in doing so, gain a greater understanding of Quantum ChromoDynamics (QCD) and the strong force.

Wishart, Robert↗

Double-sided cooling cold plates with overhanging heat sinks and through body busbar for high-power density power electronics

A double-sided cold plate includes a manifold comprising openings extending from a first surface of the manifold through the manifold to a second surface of the manifold forming recesses within the manifold and an inlet channel and an outlet channel fluidly coupled to the recesses within the manifold, a plurality of first heat sinks coupled to the first surface of the manifold enclosing the openings on the first surface, and a plurality of second heat sinks positioned adjacent each other along a length of the manifold and coupled to the second surface of the manifold, enclosing the openings on the second surface, a width of the plurality of second heat sinks is greater than a width of the manifold thereby forming an overhanging portion on each lengthwise side of the manifold, the overhanging portion configured to mechanically support a plurality of electrical components positioned around a perimeter of the manifold.

Zhou, Feng↗

Impact of Two-Body Currents on Semi-Exclusive Lepton-Nucleus Reactions

We generalize the spectral-function formalism to describe two-nucleon knockout processes in exclusive kinematics. Significant improvements are introduced both in the treatment of the current operators entering the $Δ$-current contribution and in the modeling of correlations between the two struck nucleons, including a consistent treatment of isospin dependence and the explicit incorporation of angular correlations. The framework is validated through comparisons with relativistic Fermi-gas calculations and with semi-exclusive electron-nucleus scattering data. Our results demonstrate that an accurate description of nuclear dynamics plays a crucial role in modeling this reaction mechanism. We further present a study of selected electroweak observables relevant to neutrino-scattering experiments.

Rocco, N. [Fermilab; Valencia U., IFIC] (ORCID:000↗

Impact of Two-Body Currents on Semi-Exclusive Lepton-Nucleus Reactions

We generalize the spectral-function formalism to describe two-nucleon knockout processes in exclusive kinematics. Significant improvements are introduced both in the treatment of the current operators entering the $Δ$-current contribution and in the modeling of correlations between the two struck nucleons, including a consistent treatment of isospin dependence and the explicit incorporation of angular correlations. The framework is validated through comparisons with relativistic Fermi-gas calculations and with semi-exclusive electron-nucleus scattering data. Our results demonstrate that an accurate description of nuclear dynamics plays a crucial role in modeling this reaction mechanism. We further present a study of selected electroweak observables relevant to neutrino-scattering experiments.

Rocco, N. [Fermilab; Valencia U., IFIC] (ORCID:000↗

Impact of Two-Body Currents on Semi-Exclusive Lepton-Nucleus Reactions

We generalize the spectral-function formalism to describe two-nucleon knockout processes in exclusive kinematics. Significant improvements are introduced both in the treatment of the current operators entering the $Δ$-current contribution and in the modeling of correlations between the two struck nucleons, including a consistent treatment of isospin dependence and the explicit incorporation of angular correlations. The framework is validated through comparisons with relativistic Fermi-gas calculations and with semi-exclusive electron-nucleus scattering data. Our results demonstrate that an accurate description of nuclear dynamics plays a crucial role in modeling this reaction mechanism. We further present a study of selected electroweak observables relevant to neutrino-scattering experiments.

Rocco, N. [Fermilab; Valencia U., IFIC] (ORCID:000↗

Impact of Two-Body Currents on Semi-Exclusive Lepton-Nucleus Reactions

We generalize the spectral-function formalism to describe two-nucleon knockout processes in exclusive kinematics. Significant improvements are introduced both in the treatment of the current operators entering the $Δ$-current contribution and in the modeling of correlations between the two struck nucleons, including a consistent treatment of isospin dependence and the explicit incorporation of angular correlations. The framework is validated through comparisons with relativistic Fermi-gas calculations and with semi-exclusive electron-nucleus scattering data. Our results demonstrate that an accurate description of nuclear dynamics plays a crucial role in modeling this reaction mechanism. We further present a study of selected electroweak observables relevant to neutrino-scattering experiments.

Rocco, N. [Fermilab; Valencia U., IFIC] (ORCID:000↗

Functional Data Analysis in Wearable Body Sensor Networks

Improving response time of indirect room-size calorimeters is still an outstanding problem in metabolic research. Accurate estimates of instantaneous rates of gaseous exchange require numerical differentiation of measured gaseousgas concentrations. We propose a new method to estimate the instantaneous gaseousgas exchange rates in indirect calorimetry. In contrast to the previously developed techniques, the method addresses the problem of differentiation of gaseous concentrations as an ill-posed problem. By applying the method of regularization, the problem of differentiation is converted into a well-posed problem resulting in smooth and consistent gaseous exchange rates. The validity of the method is tested on a large dataset of calorimeter experiments which included 313 human experiments along with 231 alcohol combustion experiments. It is demonstrated that the method is able to reliably differentiate between the “unphysiological” process of alcohol combustion and physiological variations produced by human metabolism. The method also allowed unraveling the previously unreported relative kinetics of O2 consumption and Respiratory Quotient (RQ) in humans. It was found that the kinetics of oxidative fuel selection lags behind the energy expenditure in humans exhibiting some sort of oxidative inertia. The time lag varies from 2-3 min up to 30 min, depending on particular individual. No such lag was found in alcohol combustion experiments. In addition to the relative kinetics of substrate oxidation, two statistical indexes reflecting variability of minute-by-minute RQ were estimated. The indexes were the RQ’s standard deviation and RQ’s first-order derivative. Both indexes showed statistically significant difference between human experiments and alcohol combustion experiments. We conclude that the proposed method can consistently extract physiologically-relevant information from noisy calorimetry data and the aforesaid information can provide additional insights into the mechanism of metabolic fuel selection in humans.

60 - APPLIED LIFE SCIENCES↗

RidgeAlloy: A high pressure die casting alloy that captures the approaching wave of automotive body sheet scrap

Oak Ridge National Laboratory (ORNL) has recently launched an effort to economically expand the North American aluminum supply chain by designing and developing a new family of Al-Mg-Si-Fe-Mn structural die cast aluminum alloys that can be made from up to 100% mixed 5xxx and 6xxx series automotive post-consumer sheet scrap and do not require heat treatment. The goal is to develop an alloy capable of capturing the approaching scrap wave of aluminum sheet intensive vehicles (in the 2030’s) into integrated structural high pressure die castings, rather than down-cycling these high-grade sheet alloys into non-structural castings. ORNL discovered a significant gap in the commercial thermodynamic databases that were unable to predict the trends of a key primary intermetallic phase as a function of composition. Experiments were performed to correct this gap and to create a unique, corrected quaternary database for Al-Mg-Si-Fe. High throughput computational methods, including solidification simulations, were used to identify a composition volume capable of avoiding this embrittling primary intermetallic phase, even at higher Fe + Si contents. Laboratory scale castings validated the thermodynamic and solidification predictions and resulted in lab-cast alloys with little primary intermetallic, and which met or exceeded structural casting properties requirements for yield strength and ductility. An accelerated demonstration of an HPDC automotive part was conducted in collaboration with two U.S. small businesses. Ingots made from 100% recycled 5xxx and 6xxx series scrap (plus Fe) were used to die cast one variant of this new family of Al-Mg-Si-Fe-Mn alloys (with high Si + Fe content) into a mid-sized HPDC structural-type automotive component. The HPDC alloy demonstration part showed good properties (especially ductility) and good castability for a complex component.

Plotkowski, Alex [ORNL] (ORCID:0000000154718681)↗

Materials Data on Y2Zr24O51 by Materials Project

Y2Zr24O51 crystallizes in the orthorhombic Pmm2 space group. The structure is three-dimensional. there are two inequivalent Y3+ sites. In the first Y3+ site, Y3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Y–O bond distances ranging from 2.16–2.42 Å. In the second Y3+ site, Y3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are two shorter (2.09 Å) and four longer (2.37 Å) Y–O bond lengths. There are twenty-four inequivalent Zr4+ sites. In the first Zr4+ site, Zr4+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.17–2.33 Å. In the second Zr4+ site, Zr4+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.11–2.42 Å. In the third Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are four shorter (2.10 Å) and four longer (2.44 Å) Zr–O bond lengths. In the fourth Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.09–2.46 Å. In the fifth Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.09–2.46 Å. In the sixth Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are four shorter (2.09 Å) and four longer (2.45 Å) Zr–O bond lengths. In the seventh Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.09–2.45 Å. In the eighth Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.09–2.45 Å. In the ninth Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.09–2.45 Å. In the tenth Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.09–2.45 Å. In the eleventh Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.10–2.45 Å. In the twelfth Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.10–2.43 Å. In the thirteenth Zr4+ site, Zr4+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.20–2.27 Å. In the fourteenth Zr4+ site, Zr4+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.13–2.39 Å. In the fifteenth Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.10–2.44 Å. In the sixteenth Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.09–2.45 Å. In the seventeenth Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.09–2.45 Å. In the eighteenth Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.09–2.45 Å. In the nineteenth Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.09–2.45 Å. In the twentieth Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.09–2.45 Å. In the twenty-first Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.09–2.45 Å. In the twenty-second Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.09–2.44 Å. In the twenty-third Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.09–2.44 Å. In the twenty-fourth Zr4+ site, Zr4+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Zr–O bond distances ranging from 2.10–2.43 Å. There are fifty-one inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Y3+ and two equivalent Zr4+ atoms to form OY2Zr2 tetrahedra that share corners with fourteen OZr4 tetrahedra and edges with five OY2Zr2 tetrahedra. In the second O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of corner and edge-sharing OZr4 tetrahedra. In the third O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of corner and edge-sharing OZr4 tetrahedra. In the fourth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the fifth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the sixth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the seventh O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the eighth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the ninth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the tenth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the eleventh O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the twelfth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the thirteenth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the fourteenth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the fifteenth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the sixteenth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the seventeenth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the eighteenth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the nineteenth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the twentieth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the twenty-first O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the twenty-second O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the twenty-third O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the twenty-fourth O2- site, O2- is bonded to four Zr4+ atoms to form distorted OZr4 tetrahedra that share corners with sixteen OY2Zr2 tetrahedra and edges with six OZr4 tetrahedra. In the twenty-fifth O2- site, O2- is bonded to two equivalent Y3+ and two equivalent Zr4+ atoms to form distorted OY2Zr2 tetrahedra that share corners with fourteen OZr4 tetrahedra and edges with five OY2Zr2 tetrahedra. In the twenty-sixth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of corner and edge-sharing OZr4 tetrahedra. In the twenty-seventh O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the twenty-eighth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the twenty-ninth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the thirtieth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the thirty-first O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the thirty-second O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the thirty-third O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the thirty-fourth O2- site, O2- is bonded to four Zr4+ atoms to form OZr4 tetrahedra that share corners with sixteen OY2Zr2 tetrahedra and edges with six OZr4 tetrahedra. In the thirty-fifth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the thirty-sixth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the thirty-seventh O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the thirty-eighth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the thirty-ninth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the fortieth O2- site, O2- is bonded to two equivalent Y3+ and two equivalent Zr4+ atoms to form a mixture of distorted corner and edge-sharing OY2Zr2 tetrahedra. In the forty-first O2- site, O2- is bonded to two equivalent Y3+ and two equivalent Zr4+ atoms to form OY2Zr2 tetrahedra that share corners with twelve OZr4 tetrahedra and edges with six OY4 tetrahedra. In the forty-second O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the forty-third O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the forty-fourth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the forty-fifth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the forty-sixth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the forty-seventh O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the forty-eighth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the forty-ninth O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra. In the fiftieth O2- site, O2- is bonded to four Y3+ atoms to form a mixture of corner and edge-sharing OY4 tetrahedra. In the fifty-first O2- site, O2- is bonded to four Zr4+ atoms to form a mixture of distorted corner and edge-sharing OZr4 tetrahedra.

36 MATERIALS SCIENCE↗