Phase space localization of antisymmetric functions

Upper and lower bounds are written down for the minimum information entropy in phase space of an antisymmetric wave function in any number of dimensions. Similar bounds are given when the wave function is restricted to belong to any of the proper subspaces of the Fourier transform operator.Comment: 5 pages, REVTEX, no figure

Effects of Urbanization and Other Factors on Synthetic Unit Hydrographs

Paper by Albert H. Halff, Jose I. Novoa, and Louis M. Salced

Assessment of nutrient returns in a tropical dry forest after clear-cut without burning.

Tropical dry forests (TDFs) are being deforested at unprecedented rates. The slash/burn/ agriculture/fallow-extensive livestock sequence causes significant nutrient losses and soil degradation. Our aim is to assess nutrient inputs and outputs in a TDF area under an alternative management system, for exclusive wood production. The study involved clear-cutting a preserved caatinga TDF site without burning, quantifying nutrients exported in firewood/ timber and nutrients returned to the soil from the litter layer plus the slash debris, left to decompose unburned on the soil surface. Before clear-cut, the litter layer on the forest floor contained 6.1 t ha of dry matter (DM). After clear-cut, the aboveground biomass was 61.9 t DM ha-1 (consisting of 21.5 t DM ha-1 of commercial wood and 40.4 t DM ha-1 of clear-cut debris that did not include the underlying litter layer). The litter layer was composed of fine and coarse litter, with turnovers of 0.86 and 0.31 year-1, respectively, separately measured in uncut control plots during two rainy seasons (Dec-2007/June-2008 and Dec-2008/ June-2009). In a single season, its decomposition returned to the soil 48.4, 1.16 and 12.3 kg ha-1 of N, P and K. The clear-cut debris was mainly composed of branches, 33.4 t ha-1, bromeliads, 5.63 t ha-1 and green leaves, 1.32 t ha-1. In-situ decomposition rates for branches and bromeliads were 0.24 and 1.47 year-1, respectively. After two rainy seasons the clear-cut debris released 206, 6.5 and 106 kg ha-1 of N, P and K respectively. This input plus that of the underlying litter layer exceeded exports in the commercial wood, and replenished a soil nutrient stock (0?30 cm) of approximately the same magnitude

Nutrient dynamics in sugar cane. II. NO3-N and NH4-N lateral and vertical movement in the soil

Foi monitorado o deslocamento vertical e lateral de uréia aplicada em experimento com cana-de-açúcar em solo Podzólico Vermelho-Amarelo textura arenosa. Os tratamentos foram sem N. com 60 kg/ha de N no plantio e 20 kg/ha no plantio mais 40 kg/ha 90 dias após. Retiraram- se amostras de solo no sulco e a 30 e 62 cm do mesmo, em cinco profundidades (de 20 em 20cm) antes do plantio e 3, 6, 11 e 16 meses após. Nas amostras determinaram-se NO3-N e NH4-N extratável com KCl 2N. Em todas as amostras, NH4-N foi pouco variável, oscilando ao redor de 3 ppm. NO3-N variou significativamente com a profundidade, nas amostragens de zero, três e seis meses; aos três e seis meses houve também diferenças significativas em função da distância do furo no sulco, em amostras abaixo de 40 cm. A maior acumulação de NO3-N (17 ppm) ocorreu nos 40-60 cm abaixo do sulco, três meses após a aplicação de N em dose única. Após 11 e 16 meses do plantio, as concentrações de NO3 -N foram menores que 1 ppm em todas as amostras. As curvas de eluviação obtidas permitiram visualizar o rápido movimento vertical de NO3-N.Sugar cane plots in a Red-Yellow Podzolic sandy soil were monitored for vertical and lateral urea movement. Treatments were: no N, 60 kg/ha of N at planting time, and 20 kg/ha of N at planting time plus 40 kg/ha of N 90 days after. Soil samples were taken from five depths (20 cm each) before planting and 3, 6, 11 and 16 months after it. Each plot was sampled in the furrow and at distances of 30 and 62 cm from it. Samples were extracted with 2N KCl and analyzed for NH4-N and NO3-N concentrations. NH4-N concentrations oscillated around 3 ppm, with small variations among sample positions and sampling times. NO3-N concentrations varied significantly among depths in the first three sampling periods (zero, three and six months); at the third and sixth month the sampling distance to the furrow had also a significant effect upon NO3-N concentrations in samples bellow 40 cm. The maximum NO3-N accumulation (17 ppm) occurred at a depth of 40-60 cm, in the furrow line, three months after the single 60 kg/ha of N application. Independently of depth and location, samples collected 11 and 16 months (harvest) after planting showed less than 1 ppm NO3-N. The eluviation curves showed a fast vertical NO3-N movement down the profile

Impediments to mixing classical and quantum dynamics

The dynamics of systems composed of a classical sector plus a quantum sector is studied. We show that, even in the simplest cases, (i) the existence of a consistent canonical description for such mixed systems is incompatible with very basic requirements related to the time evolution of the two sectors when they are decoupled. (ii) The classical sector cannot inherit quantum fluctuations from the quantum sector. And, (iii) a coupling among the two sectors is incompatible with the requirement of physical positivity of the theory, i.e., there would be positive observables with a non positive expectation value.Comment: RevTex, 21 pages. Title slightly modified and summary section adde

Dinâmica de nutrientes em cana-de-açúcar. I. Eficiência na utilização de uréia (15N) em aplicação única ou parcelada

A fiel experiment was established, on a Podzolic Red-yellow soil in Goiana, PE, Brazil, with three tretments: 1) no nitrogen; 2) 60 kg/ha of 15N at planting time and, 3) 20 kg/ha of 15N at planting time plus 40 kg/ha of N three months later. Each plot had nine rows, 10 m long, and received liming plus 120 kg/ha of P2O5 and 100 kg/ha of K2O. In each plot receiving N, urea with 10,2% of 15N atom excess was added to two subplots, 1,25 by 1,25 m each. Nitrogen derived from fertilizer (Ndff) and total N in green and dry leaves, stalks and roots were determined 3, 6, 11 and 16 months after planting. Neither dry matter production nor N content in the different plant parts varied significantly among treatments, in any of the four sampling periods. At harvest time, cane production was 130 t/ha and N uptake was 250 kg/ha. Less than 10% of the N was derived from the fertilizer and absorved during the first three months of the growing period, Ndff percentages in the plants were proportional to 15N application rates, resulting in fertilizer efficiencies of about 40%. Different plant parts had different percentages of Nddf.  Instalou-se em Goiana, PE, em solo Podzólico Vermelho-Amarelo, um experimento de campo com três tratamentos: 1) sem nitrogênio; 2) 60 kg/ha de 15N no plantio; 3) 20 kg/ha de 15N no plantio e 40 kg/ha de N, três meses após. Cada parcela tinha nove sulcos de 10 m e recebeu calagem, 120 kg/ha de P2O5 e 100 kg/ha de K2O. Em cada parcela recebendo N, foram delimitadas duas subparcelas de 1,25 m x 1,25 m, às quais adicionou-se uréia com 10,2% átomos de excesso de 15N. Determinaram-se as quantidades de N, totais e provenientes do fertilizante (Nppf) nas folhas verdes e secas, colmos e raízes, aos 3, 6, 11 e 16 meses após o plantio. Em nenhuma época, houve diferenças significativas entre tratamentos, quanto às produções ou quantidades de N retiradas nas diferentes partes das plantas. Na colheita, a produção de cana foi de 130 t/ha; dos 250 kg/ha de N absorvidos pelas plantas, menos de 10% provieram do fertilizante e já haviam sido absorvidos até os três meses. As percentagens Nppf foram proporcionais às doses de 15N aplicadas, resultando em eficiências de utilização do fertilizante em torno de 40%. As percentagens de Nppf das várias partes diferiram entre si

Affine Toda model coupled to matter and the string tension in QCD2_{2}

The $sl(2)$ affine Toda model coupled to matter (ATM) is shown to describe various features, such as the spectrum and string tension, of the low-energy effective Lagrangian of QCD$_{2}$ (one flavor and $N$ colors). The corresponding string tension is computed when the dynamical quarks are in the {\sl fundamental} representation of SU(N) and in the {\sl adjoint} representation of SU(2).Comment: LaTex, 10 pages. Revised version to appear in Phys. Rev.

Biomass and nutrient dynamics associated with slash fires in neotropical dry forests

Unprecedented rates of deforestation and biomass burning in tropical dry forests are dramatically influencing biogeochemical cycles, resulting in resource depletion, declines in biodiversity, and atmospheric pollution. We quantified the effects of defores- tation and varying levels of slash-fire severity on nutrient losses and redistribution in a second-growth tropical dry forest ("Caatinga") near Serra Talhada, Pernambuco, Brazil. Total aboveground biomass prior to burning was 74 Mg/ha. Nitrogen and phosphorus concentrations were highest in litter, leaves attached to slash, and fine wood debris (<0.64 cm diameter). While these components comprised only 30% of the prefire aboveground biomass, they accounted for -60% of the aboveground pools of N and P. Three experi- mental fires were conducted during the 1989 burning season. In these treatments con- sumption was 78, 88, and 95% of the total aboveground biomass. As much as 96% of the prefire aboveground N and C pools and 56% of the prefire aboveground P pool was lost during combustion processes. Nitrogen losses exceeded 500 kg/ha and P losses exceeded 20 kg/ha in the fires of the greatest severity. With increasing fire severity, the concentrations of N and P in ash decreased while the concentration of Ca increased. This indicates greater amounts of these nutrients were volatilized (i.e., greater ecosystem losses occurred) with increasing fire severity. Following fire, up to 47% of the residual aboveground N and 84% of the residual aboveground P were in the form of ash, which was quickly lost from the site via wind erosion. Fires appeared to have a minor immediate effect on total N, C, or P in the soils. However, soils in forests with no history of cultivation had significantly higher concentrations of C and P than second-growth forests. Based upon the measured losses of nutrients from these single slash-burning events, it would likely require a century or more of fallow for reaccumulation to occur. However, current fallow periods in this region are 15 yr or less

General Relativity and Weyl Geometry

We show that the general theory of relativity can be formulated in the language of Weyl geometry. We develop the concept of Weyl frames and point out that the new mathematical formalism may lead to different pictures of the same gravitational phenomena. We show that in an arbitrary Weyl frame general relativity, which takes the form of a scalar-tensor gravitational theory, is invariant with respect to Weyl tranformations. A kew point in the development of the formalism is to build an action that is manifestly invariant with respect to Weyl transformations. When this action is expressed in terms of Riemannian geometry we find that the theory has some similarities with Brans-Dicke gravitational theory. In this scenario, the gravitational field is not described by the metric tensor only, but by a combination of both the metric and a geometrical scalar field. We illustrate this point by, firstly, discussing the Newtonian limit in an arbitrary frame, and, secondly, by examining how distinct geometrical and physical pictures of the same phenomena may arise in different frames. To give an example, we discuss the gravitational spectral shift as viewed in a general Weyl frame. We further explore the analogy of general relativity with scalar-tensor theories and show how a known Brans-Dicke vacuum solution may appear as a solution of general relativity theory when reinterpreted in a particular Weyl frame. Finally, we show that the so-called WIST gravity theories are mathematically equivalent to Brans-Dicke theory when viewed in a particular frame.Comment: LATEX, 22 page

QCD equation of state in a virial expansion

We describe recent three-flavor QCD lattice data for the pressure, speed of soun d and interaction measure at nonzero temperature and vanishing chemical potentia l within a virial expansion. For the deconfined phase we use a phenomenological model which includes non-pert urbative effects from dimension two gluon condensates that reproduce the free en ergy of quenched QCD very well. The hadronic phase is parameterized by a generalized resonance-gas model. Furthermore, we extend this approach to finite quark densities introducing an ex plicit $\mu$-dependence of the interaction. We calculate pressure, quark-number density, entropy and energy density and compare to results of lattice calculatio ns. We, additionally, investigate the structure of the phase diagram by calculating the isobaric and isentropic lines as well as the critical endpoint in the ($T, \mu_q$)-plane.Comment: 9 pages, 11 figures. Submitted to Phys. Rev.