Density functional theory embedding for correlated wavefunctions: Improved methods for open-shell systems and transition metal complexes

Density functional theory (DFT) embedding provides a formally exact framework for interfacing correlated wave-function theory (WFT) methods with lower-level descriptions of electronic structure. Here, we report techniques to improve the accuracy and stability of WFT-in-DFT embedding calculations. In particular, we develop spin-dependent embedding potentials in both restricted and unrestricted orbital formulations to enable WFT-in-DFT embedding for open-shell systems, and we develop an orbital-occupation-freezing technique to improve the convergence of optimized effective potential (OEP) calculations that arise in the evaluation of the embedding potential. The new techniques are demonstrated in applications to the van-der-Waals-bound ethylene-propylene dimer and to the hexaaquairon(II) transition-metal cation. Calculation of the dissociation curve for the ethylene-propylene dimer reveals that WFT-in-DFT embedding reproduces full CCSD(T) energies to within 0.1 kcal/mol at all distances, eliminating errors in the dispersion interactions due to conventional exchange-correlation (XC) functionals while simultaneously avoiding errors due to subsystem partitioning across covalent bonds. Application of WFT-in-DFT embedding to the calculation of the low-spin/high-spin splitting energy in the hexaaquairon(II) cation reveals that the majority of the dependence on the DFT XC functional can be eliminated by treating only the single transition-metal atom at the WFT level; furthermore, these calculations demonstrate the substantial effects of open-shell contributions to the embedding potential, and they suggest that restricted open-shell WFT-in-DFT embedding provides better accuracy than unrestricted open-shell WFT-in-DFT embedding due to the removal of spin contamination.Comment: 11 pages, 5 figures, 2 table

The onsite manufacture of propellant oxygen from lunar resources

The Aerojet carbothermal process for the manufacture of oxygen from lunar materials has three essential steps: the reduction of silicate with methane to form carbon monoxide and hydrogen; the reduction of carbon monoxide with hydrogen to form methane and water; and the electrolysis of water to form hydrogen and oxygen. The reactions and the overall process are shown. It is shown with laboratory experimentation that the carbothermal process is feasible. Natural silicates can be reduced with carbon or methane. The important products are carbon monoxide, metal, and slag. The carbon monoxide can be completely reduced to form methane and water. The water can be electrolyzed to produce hydrogen and oxygen. A preliminary engineering study shows that the operation of plants using this process for the manufacture of propellant oxygen has a large economic advantage when the cost of the plant and its operation is compared to the cost of delivering oxygen from Earth

Density functional theory embedding for correlated wavefunctions: Improved methods for open-shell systems and transition metal complexes

Density functional theory (DFT) embedding provides a formally exact framework for interfacing correlated wave-function theory (WFT) methods with lower-level descriptions of electronic structure. Here, we report techniques to improve the accuracy and stability of WFT-in-DFT embedding calculations. In particular, we develop spin-dependent embedding potentials in both restricted and unrestricted orbital formulations to enable WFT-in-DFT embedding for open-shell systems, and develop an orbital-occupation-freezing technique to improve the convergence of optimized effective potential calculations that arise in the evaluation of the embedding potential. The new techniques are demonstrated in applications to the van-der-Waals-bound ethylene-propylene dimer and to the hexa-aquairon(II) transition-metal cation. Calculation of the dissociation curve for the ethylene-propylene dimer reveals that WFT-in-DFT embedding reproduces full CCSD(T) energies to within 0.1 kcal/mol at all distances, eliminating errors in the dispersion interactions due to conventional exchange-correlation (XC) functionals while simultaneously avoiding errors due to subsystem partitioning across covalent bonds. Application of WFT-in-DFT embedding to the calculation of the low-spin/high-spin splitting energy in the hexaaquairon(II) cation reveals that the majority of the dependence on the DFT XC functional can be eliminated by treating only the single transition-metal atom at the WFT level; furthermore, these calculations demonstrate the substantial effects of open-shell contributions to the embedding potential, and they suggest that restricted open-shell WFT-in-DFT embedding provides better accuracy than unrestricted open-shell WFT-in-DFT embedding due to the removal of spin contamination

Accurate basis set truncation for wavefunction embedding

Density functional theory (DFT) provides a formally exact framework for performing embedded subsystem electronic structure calculations, including DFT-in-DFT and wavefunction theory-in-DFT descriptions. In the interest of efficiency, it is desirable to truncate the atomic orbital basis set in which the subsystem calculation is performed, thus avoiding high-order scaling with respect to the size of the MO virtual space. In this study, we extend a recently introduced projection-based embedding method [F. R. Manby, M. Stella, J. D. Goodpaster, and T. F. Miller III, J. Chem. Theory Comput. 8, 2564 (2012)]10.1021/ct300544e to allow for the systematic and accurate truncation of the embedded subsystem basis set. The approach is applied to both covalently and non-covalently bound test cases, including water clusters and polypeptide chains, and it is demonstrated that errors associated with basis set truncation are controllable to well within chemical accuracy. Furthermore, we show that this approach allows for switching between accurate projection-based embedding and DFT embedding with approximate kinetic energy (KE) functionals; in this sense, the approach provides a means of systematically improving upon the use of approximate KE functionals in DFT embedding

Nucleo-cytoplasmic interactions that control nuclear envelope breakdown and entry into mitosis in the sea urchin zygote

In sea urchin zygotes and mammalian cells nuclear envelope breakdown (NEB) is not driven simply by a rise in cytoplasmic cyclin dependent kinase 1-cyclin B (Cdk1-B) activity; the checkpoint monitoring DNA synthesis can prevent NEB in the face of mitotic levels of Cdk1-B. Using sea urchin zygotes we investigated whether this checkpoint prevents NEB by restricting import of regulatory proteins into the nucleus. We find that cyclin B1-GFP accumulates in nuclei that cannot complete DNA synthesis and do not break down. Thus, this checkpoint limits NEB downstream of both the cytoplasmic activation and nuclear accumulation of Cdk1-B1. In separate experiments we fertilize sea urchin eggs with sperm whose DNA has been covalently cross-linked to inhibit replication. When the pronuclei fuse, the resulting zygote nucleus does not break down for \u3e180 minutes (equivalent to three cell cycles), even though Cdk1-B activity rises to greater than mitotic levels. If pronuclear fusion is prevented, then the female pronucleus breaks down at the normal time (average 68 minutes) and the male pronucleus with cross-linked DNA breaks down 16 minutes later. This male pronucleus has a functional checkpoint because it does not break down for \u3e120 minutes if the female pronucleus is removed just prior to NEB. These results reveal the existence of an activity released by the female pronucleus upon its breakdown, that overrides the checkpoint in the male pronucleus and induces NEB. Microinjecting wheat germ agglutinin into binucleate zygotes reveals that this activity involves molecules that must be actively translocated into the male pronucleus

Technical assistance to the Uganda AIDS Commission for operationallisation of the performance monitoring and management plan

The Uganda AIDS Commission (UAC) has committed to rolling out and making operational a new National Performance Monitoring and Management Plan (PMMP) to monitor and evaluate the national response to the HIV/AIDS epidemic. The PMMP has at its core the collection and processing of 58 national indicators, 47 district output indicators, and 22 outcome indicators covering prevention, care, treatment, and social support. The rollout is challenging because at least seven organizations must collaborate at the national level, and appropriate staff at the district level need to be in place and trained in new procedures of data collection. In addition, these data are to be supplied to district planning organizations that may or may not be functioning and the cooperation of civil society organizations is necessary even though their participation is voluntary. The Population Council and Makerere University School of Public Health were funded by USAID/Uganda to assist the UAC in assessing these challenges and determining appropriate procedures for creating a successful rollout of the new PMMP system. This final report focuses on recommendations for successful completion of the rollout

Long‐lived Snell dwarf mice display increased proteostatic mechanisms that are not dependent on decreased mTORC1 activity

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111144/1/acel12329.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/111144/2/acel12329-sup-0001-SuppInfo.pd

The Little Paint Site: A Classic Toyah Camp on the South Llano River, Kimble County, Texas

On behalf of the Texas Department of Transportation (TxDOT), SWCA Environmental Consultants (SWCA) conducted testing and data recovery investigations at the Little Paint site (41KM226), a prehistoric multi-component site in the US 377 right-of-way along the South Llano River in Kimble County, Texas. While the site revealed Archaic and Late Prehistoric components, the earlier components were stratigraphically intermixed. Consequently, data recovery focused almost entirely on a discrete Toyah component, which, based on earlier test excavations conducted in August and September 2006, had previously been determined to be eligible for listing on the National Register of Historic Places and as a State Archeological Landmark. SWCA performed the investigations under Texas Antiquities Permits 4184 and 4318. Kevin A. Miller served as Principal Investigator. The excavations recovered approximately 102 m2 of a stratigraphically-discrete Toyah component consisting of rock-lined hearths, Perdiz points, Cliffton points, a bird-bone bead, bone-tempered ceramics, bifaces, scrapers (notably end scrapers on blade-flakes), various informal lithic tools, drills, awls, debitage, and faunal remains. Based on the assemblage, the site is interpreted as a Toyah basecamp as indicated by a diversity of tool forms and site furniture. The component has good integrity, is vertically and horizontally discrete, and contains a substantial amount of archaeological materials. The suite of 16 radiometric dates indicates intermittent Toyah occupations between 240 and 570 years ago, a time range that is generally consistent with recognized span of the Toyah assemblage. The archaeological assemblage and site structure, however, suggests a possible single Toyah occupation. While not a focal point of the data recovery investigations, the excavations also recovered mixed Archaic components below the Toyah component. Artifacts include diagnostic point styles that indicate Late Archaic to early Late Prehistoric occupations, representing 1,000 to 2,000 years of the regional cultural chronology compressed within a thin stratum. Based on the findings, the depositional conditions below the Toyah component, as was previously determined by the testing data, were found to be generally not conducive to the formation of stratigraphic separation of the successive occupations. This compression resulted in intermixing of components and poor integrity. Below the mixed Archaic zone, deeply buried Middle to Early Archaic deposits were identified. These retained a better potential for significant isolable strata, but these deeper deposits were beyond the project impacts and therefore were not the subject of mitigative efforts. The deeper deposits are preserved by avoidance. As previously determined and further substantiated by the data recovery investigations, the Little Paint site, because of the Toyah component and perhaps earlier deposits, is eligible for National Register of Historic Places listing under Criterion D, 36 CFR 60.4, and eligible for State Archeological Landmark designation under Criteria 1 and 2 of the Rules of Practice and Procedure for the Antiquities Code of Texas, 13 TAC 26.8. The excavations have mitigated the adverse effects of the US 377 bridge replacement by recovering the vast majority of the Toyah component within the area of potential effect of the roadway undertaking. No further archaeological work is recommended. Portions of the site outside of the right-of-way have not been fully evaluated. The artifacts and records from the project are curated at the Center for Archaeological Studies, Texas State University