Theoretical Study Of Strain-induced Ordering In Cubic Inxga 1-xn Epitaxial Layers

Chemical ordering in cubic epitaxial InxGa1-xN layers is investigated by combining first-principles pseudo-potential plane-wave total-energy calculations, a local concentration-dependent cluster-based method, and Monte Carlo simulations. It is found that for the unstrained or fully relaxed layers there are no stable ordered structures, indicating the tendency of the alloy to undergo phase separation, in agreement with previous calculations and experiment. The energetics of the InxGal 1-xN layers pseudomorphycally grown on fully relaxed GaN (001) buffers shows that biaxial strain acts as the driving force for chemical ordering in the alloys. It is found that strained InxGa 1-xN alloy comprises stable ordered structures which are (210)-oriented super-lattices with composition in the range [0.5,0.63], the [AABB] alternation of planes (configuration "chalcopy-rite") being the most stable phase.69242453171-245317-10Nakamura, S., Fasol, G., (1997) The Blue Laser Diode, , Springer, BerlinAmbacher, O., (1998) J. Phys. D, 31, p. 2653Pearton, S.J., Zolper, J.C., Shul, R.J., Ren, F., (1999) J. Appl. Phys., 86, p. 1Kung, P., Razeghi, M., (2000) Opto-Electron. Rev., 8, p. 201(1991) Data in Science and Technology: Semiconductors, , edited by O. Madelung (Springer-Verlag, Berlin)Davydov, V.Yu., Klochikhin, A.A., Seisyan, R.P., Emtsev, V.V., Ivanov, S.V., Bechstedt, F., Furthmüller, J., Graul, J., (2002) Phys. Status Solidi B, 229, pp. R1Wu, J., Walukiewicz, W., Yu, K.M., Ager III, J.W., Haller, E.E., Lu, H., Schaff, W.J., Nanishi, Y., (2002) Appl. Phys. Lett., 80, p. 3967Chichibu, S., Azuhata, T., Sota, T., Nakamura, S., (1996) Appl. Phys. Lett., 69, p. 4188(1997) Appl. Phys. Lett., 70, p. 2822O'Donnell, K.P., Martin, R.W., Middleton, P.G., (1999) Phys. Rev. Lett., 82, p. 237Wetzel, C., Takeuchi, T., Amano, H., Akasaki, I., (1999) J. Appl. Phys., 85, p. 3786Chichibu, S.F., Abare, A.C., Mack, M.P., Minsky, M.S., Deguchi, T., Cohen, D., Kozodoy, P., Nakamura, S., (1999) Mater. Sci. Eng., B, 59, p. 298Lemos, V., Silveira, E., Leite, J.R., Tabata, A., Trentin, R., Scolfaro, L.M.R., Frey, T., Lischka, K., (2000) Phys. Rev. Lett., 84, p. 3666Krestnikov, I.L., Ledentsov, N.N., Hoffmann, A., Bimberg, D., Sakharov, A.V., Lundin, W.V., Tsatsul'Nikov, A.F., Gerthsen, D., (2002) Phys. Rev. B, 66, p. 155310Husberg, O., Khartchenko, A., As, D.J., Vogelsang, H., Frey, T., Schikora, D., Lischka, K., Leite, J.R., (2001) Appl. Phys. Lett., 79, p. 1243Behbehani, M.K., Piner, E.L., Liu, S.X., El-Masry, N.A., Bedair, S.M., (1999) Appl. Phys. Lett., 75, p. 2202Yamaguchi, S., Kariya, M., Nitta, S., Kato, H., Takeuchi, T., Wetzel, C., Amano, H., Akasaki, I., (1998) J. Cryst. Growth, 195, p. 309Teles, L.K., Furthmüller, J., Scolfaro, L.M.R., Leite, J.R., Bechstedt, F., (2000) Phys. Rev. B, 62, p. 2475Tabata, A., Teles, L.K., Scolfaro, L.M.R., Leite, J.R., Kharchenko, A., Frey, T., As, D.J., Bechstedt, F., (2002) Appl. Phys. Lett., 80, p. 769Singh, R., Doppalapudi, D., Moustakas, T.D., Romano, L.T., (1997) Appl. Phys. Lett., 70, p. 1089Doppalapudi, D., Basu, S.N., Ludwig Jr., K.F., Moustakas, T.D., (1998) J. Appl. Phys., 84, p. 1389Ruterana, P., Nouet, G., Van Der Stricht, W., Moerman, I., Considine, L., (1998) Appl. Phys. Lett., 72, p. 1742Northrup, E., Romano, L.T., Neugebauer, J., (1999) Appl. Phys. Lett., 74, p. 2319Srivastava, G.P., Martins, J.L., Zunger, A., (1985) Phys. Rev. B, 31, pp. R2561Ferreira, L.G., Wei, S.-H., Zunger, A., (1991) Int. J. Supercomput. Appl., 5, p. 34Wei, S.-H., Ferreira, L.G., Zunger, A., (1992) Phys. Rev. B, 45, p. 2533Zunger, A., (1994) Handbook of Crystal Growth, 3, p. 998. , D. T. J. Hurle, Elsevier, AmsterdamTeles, L.K., Ferreira, L.G., Leite, J.R., Scolfaro, L.M.R., Kharchenko, A., Husberg, O., As, D.J., Lischka, K., (2003) Appl. Phys. Lett., 82, p. 4274Sanchez, J.M., Ducastelle, F., Gratias, D., (1984) Physica A, 128, p. 334Ozoliņš, V., Wolverton, C., Zunger, A., (1998) Phys. Rev. B, 57, p. 6427Lu, Z.W., Wei, S.-H., Zunger, A., Frota-Pessoa, S., Ferreira, L.G., (1991) Phys. Rev. B, 44, p. 512De Fontaine, D., (1979) Solid State Physics, 34, p. 73. , edited by H. Ehrenreich, F. Seitz, and D. Turnbull (Academic, New York)Connolly, J.W.D., Williams, A.R., (1983) Phys. Rev. B, 27, p. 5169Ferreira, L.G., Wei, S.-H., Zunger, A., (1989) Phys. Rev. B, 40, p. 3197Mbaye, A.A., Ferreira, L.G., Zunger, A., (1987) Phys. Rev. Lett., 58, p. 49Ferreira, L.G., Mbaye, A.A., Zunger, A., (1988) Phys. Rev. B, 37, pp. 10 547Ferreira, L.G., Ozoliņš, V., Zunger, A., (1999) Phys. Rev. B, 60, p. 1687Hohenberg, P., Kohn, W., (1964) Phys. Rev., 136, pp. B864Kohn, W., Sham, L.J., (1965) Phys. Rev., 140, pp. A1133Vanderbilt, D., (1990) Phys. Rev. B, 41, p. 7892Großner, U., Furthmüller, J., Bechstedt, F., (1998) Phys. Rev. B, 58, pp. R1722Großner, U., Furthmüller, J., Bechstedt, F., (1999) Appl. Phys. Lett., 74, p. 3851Perdew, J.P., Zunger, A., (1981) Phys. Rev. B, 23, p. 5048Monkhorst, H.J., Pack, J.D., (1976) Phys. Rev. B, 13, p. 5188Kresse, G., Furthmüller, J., (1996) Phys. Rev. B, 54, pp. 11 169Kresse, G., Furthmüller, J., (1996) Comput. Mater. Sci., 6, p. 15Metropolis, N., Rosenbluth, A.W., Rosenbluth, M.N., Teller, A.H., Teller, E., (1953) J. Chem. Phys., 21, p. 1087Zunger, A., (1987) Appl. Phys. Lett., 50, p. 164Neugebauer, J., Van De Walle, C.G., (1995) Phys. Rev. B, 51, pp. 10 568Scolfaro, L.M.R., (2002) Phys. Status Solidi A, 190, p. 15Silveira, E., Tabata, A., Leite, J.R., Trentin, R., Lemos, V., Frey, T., As, D.J., Lischka, K., (1999) Appl. Phys. Lett., 75, p. 3602Saito, T., Arakawa, Y., (1999) Phys. Rev. B, 60, p. 1701Takayama, T., Yuri, M., Itoh, K., Baba, T., Harris Jr., J.S., (2000) J. Appl. Phys., 88, p. 1104Karpov, Yu.S., (1998) MRS Internet J. Nitride Semicond. Res., 3, p. 16Shimotomai, M., Yoshikawa, A., (1998) Appl. Phys. Lett., 73, p. 325

Floristic Checklist From An Atlantic Forest Vegetation Mosaic In Reserva Particular Do Patrimônio Natural Fazenda Tabatinga, Pernambuco, Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)A floristic inventory was made in the Reserva Particular do Patrimônio Natural Fazenda Tabatinga to show the importance of small forest fragments for conservation of the biodiversity of the Atlantic Forest. The reserve protects a vegetation mosaic typical of coastal habitats in an area of ​ca. 20 ha, located in the northern part of the Brazilian Atlantic Forest. Samples of vascular plants were collected between January 2010 and November 2011, and altogether 329 species were recorded. These are classified in 230 genera and 79 families of angiosperms and two genera and two families of ferns. Among the species found, 28 are endemic to the Atlantic Forest, while others are rare and restricted to the Pernambuco Endemism Center. In addition, three threatened species were detected. The presence of endemic, rare, and threatened species, along with floristic patterns typical of coastal areas of Brazil, reinforce the importance of the area for the conservation. © 2016 Check List and Authors.126BMBF, Bundesministerium für Bildung und ForschungCNPq, Conselho Nacional de Desenvolvimento Científico e TecnológicoDEB-0946618, NSF, National Science FoundationConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Regulation of primary production in the Gulf of California through interaction of large-scale and local ocean processes [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The suppression of primary productivity observed in eastern boundary ecosystems of the Pacific during El Nino episodes does not occur throughout the Gulf of California. On the contrary, analysis of the modern siliceous phytoplankton record from annually layered sediments and compilation of available primary productivity measurements indicate that production is significantly increased in the central Gulf during El Nino years compared to anti-El Nino years. Integrated observations of biological and physical variability during the spring of 1983, under the influence of the strong El Nino, show that very high primary productivity occurred along the eastern margin of the central Gulf. This resulted from the upwelling of a nutrient rich source provided by the locally formed Gulf water mass originating in the northern Gulf. Lower productivity and phytoplankton biomass were associated with the anomalous penetration of Tropical Surface Water along the western side of the Gulf

Fast, exact CMB power spectrum estimation for a certain class of observational strategies

We describe a class of observational strategies for probing the anisotropies in the cosmic microwave background (CMB) where the instrument scans on rings which can be combined into an n-torus, the {\em ring torus}. This class has the remarkable property that it allows exact maximum likelihood power spectrum estimation in of order $N^2$ operations (if the size of the data set is $N$) under circumstances which would previously have made this analysis intractable: correlated receiver noise, arbitrary asymmetric beam shapes and far side lobes, non-uniform distribution of integration time on the sky and partial sky coverage. This ease of computation gives us an important theoretical tool for understanding the impact of instrumental effects on CMB observables and hence for the design and analysis of the CMB observations of the future. There are members of this class which closely approximate the MAP and Planck satellite missions. We present a numerical example where we apply our ring torus methods to a simulated data set from a CMB mission covering a 20 degree patch on the sky to compute the maximum likelihood estimate of the power spectrum $C_\ell$ with unprecedented efficiency.Comment: RevTeX, 14 pages, 5 figures. A full resolution version of Figure 1 and additional materials are at http://feynman.princeton.edu/~bwandelt/RT

Signal and System Approximation from General Measurements

In this paper we analyze the behavior of system approximation processes for stable linear time-invariant (LTI) systems and signals in the Paley-Wiener space PW_\pi^1. We consider approximation processes, where the input signal is not directly used to generate the system output, but instead a sequence of numbers is used that is generated from the input signal by measurement functionals. We consider classical sampling which corresponds to a pointwise evaluation of the signal, as well as several more general measurement functionals. We show that a stable system approximation is not possible for pointwise sampling, because there exist signals and systems such that the approximation process diverges. This remains true even with oversampling. However, if more general measurement functionals are considered, a stable approximation is possible if oversampling is used. Further, we show that without oversampling we have divergence for a large class of practically relevant measurement procedures.Comment: This paper will be published as part of the book "New Perspectives on Approximation and Sampling Theory - Festschrift in honor of Paul Butzer's 85th birthday" in the Applied and Numerical Harmonic Analysis Series, Birkhauser (Springer-Verlag). Parts of this work have been presented at the IEEE International Conference on Acoustics, Speech, and Signal Processing 2014 (ICASSP 2014

Microscopic Description Of The Phase Separation Process In Al Xgayin1-x-yn Quaternary Alloys

Ab initio total energy electronic structure calculations are combined with Monte Carlo simulations to study the thermodynamic properties of Al xGayIn1-x-yN quaternary alloys. We provide a microscopic description of the phase separation process by analyzing the thermodynamic behavior of the different atoms with respect to the temperature and cation contents. We obtained, at growth temperatures, the range of compositions for the stable and unstable phases. The presence of Al in InGaN is proven to "catalyze" the phase separation process for the formation of the In-rich phase. Based on our results, we propose that the ultraviolet emission currently seen in samples containing AlInGaN quaternaries arises from the matrix of a random alloy, in which composition fluctuations toward InGaN- and AlGaN-like alloys formation may be present, and that a coexisting emission in the green-blue region results from the In-rich segregated clusters.707732021-073202-4Lemos, V., Silveira, E., Leite, J.R., Tabata, A., Trentin, R., Scolfaro, L.M.R., Frey, T., Lischka, K., (2000) Phys. Rev. Lett., 84, p. 3666. , and references thereinKung, P., Razegui, M., (2000) Opto-Electron. Rev., 8, p. 201Kneissl, M., Treat, D.W., Teepe, M., Miyashita, N., Johnson, N.M., (2003) Appl. Phys. Lett., 82, p. 2386Adivarahan, V., Chitnis, A., Zhang, J.P., Shatalov, M., Yang, J.W., Simin, G., Khan, M.A., Shur, M.S., (2001) Appl. Phys. Lett., 79, p. 4240Yasan, A., McClintock, R., Mayes, K., Darvish, S.R., Zhang, H., Kung, P., Razeghi, M., Han, J.Y., (2002) Appl. Phys. Lett., 81, p. 2151Nagahama, S., Yanamoto, T., Sano, M., Mukai, T., (2001) Jpn. J. Appl. Phys., Part 2, 40, pp. L778Teles, L.K., Furthmüller, J., Scolfaro, L.M.R., Leite, J.R., Bechstedt, F., (2000) Phys. Rev. B, 62, p. 2475Teles, L.K., Scolfaro, L.M.R., Leite, J.R., Furthmüller, J., Bechstedt, F., (2002) J. Appl. Phys., 92, p. 7109Tamulaitis, G., Kazlauskas, K., Jursenas, S., Zukauskas, A., Khan, M.A., Yang, J.W., Zhang, J., Gaska, R., (2000) Appl. Phys. Lett., 77, p. 2136Hirayama, H., Kinoshita, A., Yamabi, T., Enomoto, Y., Hirata, A., Araki, T., Nanishi, Y., Aoyagi, Y., (2002) Appl. Phys. Lett., 80, p. 207Chen, C.H., Chen, Y.F., Lan, Z.H., Chen, L.C., Chen, K.H., Jiang, H.X., Lin, J.Y., (2004) Appl. Phys. Lett., 84, p. 1480Feng, S.W., Cheng, Y.C., Chung, Y.Y., Yang, C.C., Ma, K.J., Yan, C.C., Hsu, C., Jiang, H.X., (2003) Appl. Phys. Lett., 82, p. 1377Yamaguchi, S., Kariya, M., Nitta, S., Kato, H., Takeuchi, T., Wetzel, C., Amano, H., Akasaki, I., (1998) J. Cryst. Growth, 195, p. 309Takayama, T., Yuri, M., Itoh, K., Harris Jr., J.S., (2001) J. Appl. Phys., 90, p. 2358Matsuoka, T., (1998) MRS Internet J. Nitride Semicond. Res., 3, p. 54Marques, M., Teles, L.K., Ferreira, L.G., Scolfaro, L.M.R., Leite, J.R., unpublishedKresse, G., Furthmüller, J., (1996) Comput. Mater. Sci., 6, p. 15Marques, M., Teles, L.K., Scolfaro, L.M.R., Leite, J.R., Furthmüller, J., Bechstedt, F., (2003) Appl. Phys. Lett., 83, p. 890Ferreira, L.G., Wei, S.-H., Zunger, A., (1991) Int. J. Opt. Sens., 5, p. 34Metropolis, N., Rosenbluth, A.W., Rosenbluth, M.N., Teller, A.H., Teller, E., (1953) J. Chem. Phys., 21, p. 1087Cowley, J.M., (1950) J. Appl. Phys., 21, p. 2

Effects Of The Coulomb Correlation On The Calculated Results For Atoms With And Without Spin Polarization

In this paper we present the results of some atomic calculations as affected by the Coulomb correlation. We deal with atoms and ions with and without spin polarization. Thus we are able to compare calculated energy eigenvalues and hyperfine fields of contact with the experimental ionization energies and fields. Our approximation for the mass operator (exchange plus correlation) can thus be compared with the approximations proposed by Slater, Gaspar, Kohn and Sham, and Liberman. A broad evaluation of the results implies that our approximation for exchange and correlation is correct. Furthermore, when neglecting the correlation effects, we noticed that the results become poorer. Thus, this paper favors a single-particle description of many-body systems based on an effective-wave equation with the mass operator instead of the simpler exchange operator of the Hartree-Fock theory. © 1971 The American Physical Society.341224123

Residual Biomass: A Comprehensive Review on the Importance, Uses and Potential in a Circular Bioeconomy Approach

ReviewThe paradigm shift towards sustainable growth is urgent, and biomass, which is the oldest energy source that humans have used since the discovery of fire, might play an important role. Biomass waste from forestry and agriculture is expected to fuel part of the increasing demand for biomass, and its valorization allows for more the efficient use of nutrients and resources. In this study, we carried out an extensive literature review on the valorization of residual agroforestry biomass since the 1970s to understand the leading research focuses on the subject over the last few decades, identify the most recent trends, and establish a possible solution path for the future of biomass. It was observed that most studies focused on biomass as being capable of replacing fossil energy sources. According to the literature, biomass has the most significant potential to meet requirements and ensure fuel supplies in the future. The developments of the last decades have significantly improved the conversion processes, leading to greener solutions, but there is still much to be studied and put into practice. Closing the loop into biomass waste recovery will be essential for a genuinely circular bioeconomyinfo:eu-repo/semantics/publishedVersio

Assessment of Woody Residual Biomass Generation Capacity in the Central Region of Portugal: Analysis of the Power Production Potential

Biomass is an alternative energy source with high potential to contribute to the global energy mix and to countries’ energetic independence. The case of Portugal is particularly relevant, given its biomass availability. Thus, the quantification of woody residual biomass is assumed to be urgent. To achieve the objective of quantifying residual woody biomass, various available data were used, namely the Land Cover and Soil Use Map (COS 2018), from which areas occupied by different categories were selected as being the most relevant. Then, based on coefficients previously established, the amounts of residual woody biomass were determined, namely for maritime pine forests, eucalyptus forests, scrubland, vineyards, olive groves, and orchards. Then, the potential for generating electricity was estimated. It was found that for the hypothetical scenario of the total conversion of the recently closed Pêgo coal power plant to biomass, the available amounts of residual woody biomass in the country would not be sufficient to ensure the operation. On the other hand, if the power plant only worked as a backup unit, the available quantities could ensure its operation and contribute to creating a value chain for residual woody biomass of forest and agricultural origin within a circular economy and sustainable development approachinfo:eu-repo/semantics/publishedVersio