Biexciton recombination rates in self-assembled quantum dots

The radiative recombination rates of interacting electron-hole pairs in a quantum dot are strongly affected by quantum correlations among electrons and holes in the dot. Recent measurements of the biexciton recombination rate in single self-assembled quantum dots have found values spanning from two times the single exciton recombination rate to values well below the exciton decay rate. In this paper, a Feynman path-integral formulation is developed to calculate recombination rates including thermal and many-body effects. Using real-space Monte Carlo integration, the path-integral expressions for realistic three-dimensional models of InGaAs/GaAs, CdSe/ZnSe, and InP/InGaP dots are evaluated, including anisotropic effective masses. Depending on size, radiative rates of typical dots lie in the regime between strong and intermediate confinement. The results compare favorably to recent experiments and calculations on related dot systems. Configuration interaction calculations using uncorrelated basis sets are found to be severely limited in calculating decay rates.Comment: 11 pages, 4 figure

Melhoria da qualidade ambiental de terras agricultáveis por meio da silvopastagem no sudeste dos Estados Unidos

Nossa hipótese é de que devido à habilidade das árvores seqüestrarem carbono (C) no perfil profundo do solo e remover o excesso de nutrientes dos solos, o sistema de silvopastagem agroflorestal poderia melhorar a qualidade ambiental de terras agricultáveis. Para testar esta hipótese, dois grupos de experimentos foram conduzidos em duas ordens de solos na Florida, Espodossolos e Ultissolos, com dois objetivos principais: i) determinar a acumulação de C do solo e investigar as fontes de C para as plantas nas frações dos solos, e ii) quantificar o fósforo solúvel em água (FSA) e estimar a capacidade de armazenamento de fósforo no solo (CAFS). O C total em ambos os solos foi maior sob o sistema de silvopastagem do que sob pastagens com menos árvores, particularmente nas profundidades mais baixas. A análise por assinatura de isótopo estável sugeriu que as plantas C3 (neste caso, slash pine, Pinis elliotti) contribuíram mais para a fração estável do carbono do que plantas C4 (neste caso, bahiagrass, Paspalum notatum) nas profundidades dos solos acima de 1 m. O FSA foi consistentemente maior em pastagens com poucas árvores, enquanto que a CAFS foi mais baixa neste sistema, sugerindo a grande probabilidade do fósforo ser mais facilmente movido do solo sob pastagens com poucas árvores do que nos sob silvopastagem. Deste modo, a presença de árvores em pastagens contribuiu para C mais estável nos perfis dos solos e o mais baixo FSA e a maior CAFS indicaram os grandes benefícios ambientais fornecidos pelos sistemas de silvopastagem comparados com as pastagens com poucas árvores em condições ecológicas similares.We hypothesized that, because of the ability of trees to sequester carbon (C) in the deep soil profile and remove excess nutrients from soils, the silvopastoral agroforestry system could enhance the environmental quality of the agricultural lands. To test this hypothesis, two sets of experiments were conducted in two soil orders in Florida, Spodosols and Ultisols, with two major objectives: i) determining the soil C accumulation and tracing the plant sources of C in soil fractions, and ii) quantifying water soluble phosphorus (WSP) and estimating the Soil P Storage Capacity (SPSC). Total C in both soil orders was greater under silvopasture than in treeless pastures, particularly at lower depths. Stable-isotope signature analysis suggested that C3 plants (in this case, slash pine, Pinus elliotii) contributed to a more stable C fraction than C4 plants (in this case, bahiagrass, Paspalum notatum) at soil depths up to 1 m. WSP was consistently higher in treeless pastures, while the remaining SPSC was lower in this land-use system, suggesting the greater likelihood of P moving out of the soil under treeless pasture than in silvopasture. Thus, the presence of trees in pastures contributed to more stable C within the soil profiles, lower WSP, and greater SPSC, indicating more environmental benefits provided by silvopastoral systems as compared to treeless pastures under similar ecological settings

Recursion Rules for Scattering Amplitudes in Non-Abelian Gauge Theories

We present a functional derivation of recursion rules for scattering amplitudes in a non-Abelian gauge theory in a form valid to arbitrary loop order. The tree-level and one-loop recursion rules are explicitly displayed.Comment: 18 pages, RevTeX, 2 postscript figures, a reference added, minor typographical errors correcte

Edges and Diffractive Effects in Casimir Energies

The prototypical Casimir effect arises when a scalar field is confined between parallel Dirichlet boundaries. We study corrections to this when the boundaries themselves have apertures and edges. We consider several geometries: a single plate with a slit in it, perpendicular plates separated by a gap, and two parallel plates, one of which has a long slit of large width, related to the case of one plate being semi-infinite. We develop a general formalism for studying such problems, based on the wavefunctional for the field in the gap between the plates. This formalism leads to a lower dimensional theory defined on the open regions of the plates or boundaries. The Casimir energy is then given in terms of the determinant of the nonlocal differential operator which defines the lower dimensional theory. We develop perturbative methods for computing these determinants. Our results are in good agreement with known results based on Monte Carlo simulations. The method is well suited to isolating the diffractive contributions to the Casimir energy.Comment: 32 pages, LaTeX, 9 figures. v2: additional discussion of renormalization procedure, version to appear in PRD. v3: corrected a sign error in (70

Standardization of container type, substrate and nutrition for potted plant production of China aster [Callistephus chinensis (L.) Ness.] var. Arka Archana

A study was conducted at the ICAR-Indian Institute of Horticultural Research, Hesaraghatta, Bengaluru for three consecutive seasons during 2019-20, to standardize the container type, substrate combination and nutrition for potted plant production of China aster var. Arka Archana. The treatments comprised of two type of containers (plastic and coir), three substrates {Red soil + FYM + Sand (1:1:1 v/v), Arka Fermented cocopeat (AFC), AFC + Vermicompost (1:1 v/v)} and four nutrition concentration (160:30:180 ppm N:P: K, 128:24:144 ppm N:P: K, 96:18:108 ppm N:P: K and Jeevamrutha @ 3%) laid out in factorial completely randomized design with three replications. Plant height at flowering (33.12 cm), number of primary branches (12.4), plant spread (536.64 cm2), number of flowers/plant (26.47), flower size (5.26 cm) and uptake of major, secondary and minor nutrients were maximum in the plants grown in 6" plastic pots using the substrate combination of soil +sand +FYM (1:1:1 v/v/v) along with the weekly application of nutrient solution of 96:18:108 ppm NPK/plant. This production protocol resulted in a dense canopy and highly floriferous potted plants. The benefit cost ratio of potted China aster production was 1.70. This technology can be adopted by the nurserymen for large-scale commercial potted plant production

Noncommutative gravity: fuzzy sphere and others

Gravity on noncommutative analogues of compact spaces can give a finite mode truncation of ordinary commutative gravity. We obtain the actions for gravity on the noncommutative two-sphere and on the noncommutative ${\bf CP}^2$ in terms of finite dimensional $(N\times N)$-matrices. The commutative large $N$ limit is also discussed.Comment: LaTeX, 13 pages, section on CP^2 added + minor change

Schlieren textures in biaxial nematic liquid crystals

The optical textures exhibited by the mesophases of three compounds, all of which are reported to show the biaxial nematic phase, have been examined. The textures are of the usual nematic schlieren type, except that they consist entirely of disclinations of strength |s| = 1/2. It is suggested that the absence of disclinations of unit strength is diagnostic of biaxiality

Biochemical correlates of cardiac hypertrophy. IV. Observations on the cellular organization of growth during myocardial hypertrophy in the rat

The mechanisms by which the DNA content of the heart increases following acutely induced cardiac hypertrophy were investigated in mature Sprague-Dawley rats. Special attention was given to the cellular organization of the growth process. Autoradiographic studies provided conclusive evidence that the uptake of tritiated thymidine is completely limited to nonmuscular cellular elements, chiefly connective tissue cells. The frequency of labeled nuclei was increased by sixfold during hypertrophy. The thymidine pool was not appreciably different in the hypertrophied hearts. Connective tissue nuclei formed a larger proportion of the total nuclear population in hypertrophied hearts, and their distribution was less uniform than in the normal heart. Quantitative histologic studies also showed that the total number of left ventricular muscle cell nuclei did not increase during hypertrophy but rather may have decreased slightly. Both the concentration and the total amount of hydroxyproline increased in parallel with the proliferative changes in the connective tissue and provide further supportive evidence to the autoradiographic and histologic studies

Antiproliferative effects of total alkaloid extract of roots of Chassalia curviflora (Wall.) Thwaites on cancer cell lines

389-395Chassalia curviflora is used in folklore medicines for treating several ailments and infections owing to its anti-inflammatory properties. Though the plant has been reported to possess anti-inflammatory antihepatotoxic and analgesic activities, its anticancer potential has not been studied so far. In the present study, we investigated the antiproliferative effects of the total alkaloids isolated from the roots of C. curviflora. The total alkaloid was validated by MTT assay in three cancer cell lines, such as liver cancer cell line-A549, breast cancer cell line-MCF-7 and ovarian cancer cell line -HeLa. Significant antiproliferative effect (IC50 value 3.59±0.14*** µg/mL) was observed in A549 cells, and was taken for further studies. Cell cycle analysis showed that the cells got arrested in sub G0 phase and annexin V-FITC assay revealed that 27.4% cells were in early apoptosis and 7% cells in late apoptosis. The study revealed that the total alkaloids of Chassalia curviflora roots possess significant antiproliferative and apoptotic activity