2,669 research outputs found
Avaliação de cultivares de canola em Dourados, MS.
bitstream/item/66168/1/CPAO-PESQ.-AND.-23-93.pd
Adubos verdes de outono/inverno no Mato Grosso do sul.
Aspectos gerais de manejo da materia organica; Resultados obtidos entre 1986-1989, na regiao de Dourados; Resultados obtidos no periodo 1990-1992, na regiao de Dourados; Resultados obtidos em 1993, na regiao centro-norte do Mato Grosso do Sul; Conclusoes e sugestoes de pesquisa; Caracterizacao das principais especies selecionadas; Centeio; Nabo forrageiro; Aveia; Aveia-preta; Aveia-branca; Canola; Triticalebitstream/item/38988/1/DOC4-1995.pd
Rotational spectroscopy of the HCCO and DCCO radicals in the millimeter and submillimeter range
The ketenyl radical, HCCO, has recently been detected in the ISM for the
first time. Further astronomical detections of HCCO will help us understand its
gas-grain chemistry, and subsequently revise the oxygen-bearing chemistry
towards dark clouds. Moreover, its deuterated counterpart, DCCO, has never been
observed in the ISM. HCCO and DCCO still lack a broad spectroscopic
investigation, although they exhibit a significant astrophysical relevance. In
this work we aim to measure the pure rotational spectra of the ground state of
HCCO and DCCO in the millimeter and submillimeter region, considerably
extending the frequency range covered by previous studies. The spectral
acquisition was performed using a frequency-modulation absorption spectrometer
between 170 and 650 GHz. The radicals were produced in a low-density plasma
generated from a select mixture of gaseous precursors. For each isotopologue we
were able to detect and assign more than 100 rotational lines. The new lines
have significantly enhanced the previous data set allowing the determination of
highly precise rotational and centrifugal distortion parameters. In our
analysis we have taken into account the interaction between the ground
electronic state and a low-lying excited state (Renner-Teller pair) which
enables the prediction and assignment of rotational transitions with up
to 4. The present set of spectroscopic parameters provides highly accurate,
millimeter and submillimeter rest-frequencies of HCCO and DCCO for future
astronomical observations. We also show that towards the pre-stellar core
L1544, ketenyl peaks in the region where - peaks,
suggesting that HCCO follows a predominant hydrocarbon chemistry, as already
proposed by recent gas-grain chemical models
Spectral determinants and zeta functions of Schr\"odinger operators on metric graphs
A derivation of the spectral determinant of the Schr\"odinger operator on a
metric graph is presented where the local matching conditions at the vertices
are of the general form classified according to the scheme of Kostrykin and
Schrader. To formulate the spectral determinant we first derive the spectral
zeta function of the Schr\"odinger operator using an appropriate secular
equation. The result obtained for the spectral determinant is along the lines
of the recent conjecture.Comment: 16 pages, 2 figure
Zeta functions of quantum graphs
In this article we construct zeta functions of quantum graphs using a contour
integral technique based on the argument principle. We start by considering the
special case of the star graph with Neumann matching conditions at the center
of the star. We then extend the technique to allow any matching conditions at
the center for which the Laplace operator is self-adjoint and finally obtain an
expression for the zeta function of any graph with general vertex matching
conditions. In the process it is convenient to work with new forms for the
secular equation of a quantum graph that extend the well known secular equation
of the Neumann star graph. In the second half of the article we apply the zeta
function to obtain new results for the spectral determinant, vacuum energy and
heat kernel coefficients of quantum graphs. These have all been topics of
current research in their own right and in each case this unified approach
significantly expands results in the literature.Comment: 32 pages, typos corrected, references adde
The Berry-Keating operator on L^2(\rz_>, x) and on compact quantum graphs with general self-adjoint realizations
The Berry-Keating operator H_{\mathrm{BK}}:=
-\ui\hbar(x\frac{
\phantom{x}}{
x}+{1/2}) [M. V. Berry and J. P. Keating,
SIAM Rev. 41 (1999) 236] governing the Schr\"odinger dynamics is discussed in
the Hilbert space L^2(\rz_>,
x) and on compact quantum graphs. It is
proved that the spectrum of defined on L^2(\rz_>,
x) is
purely continuous and thus this quantization of cannot yield
the hypothetical Hilbert-Polya operator possessing as eigenvalues the
nontrivial zeros of the Riemann zeta function. A complete classification of all
self-adjoint extensions of acting on compact quantum graphs
is given together with the corresponding secular equation in form of a
determinant whose zeros determine the discrete spectrum of .
In addition, an exact trace formula and the Weyl asymptotics of the eigenvalue
counting function are derived. Furthermore, we introduce the "squared"
Berry-Keating operator which is a special case of the
Black-Scholes operator used in financial theory of option pricing. Again, all
self-adjoint extensions, the corresponding secular equation, the trace formula
and the Weyl asymptotics are derived for on compact quantum
graphs. While the spectra of both and on
any compact quantum graph are discrete, their Weyl asymptotics demonstrate that
neither nor can yield as eigenvalues the
nontrivial Riemann zeros. Some simple examples are worked out in detail.Comment: 33p
Fragmentation and systematics of the Pygmy Dipole Resonance in the stable N=82 isotones
The low-lying electric dipole (E1) strength in the semi-magic nucleus 136Xe
has been measured which finalizes the systematic survey to investigate the
so-called pygmy dipole resonance (PDR) in all stable even N=82 isotones with
the method of nuclear resonance fluorescence using real photons in the entrance
channel. In all cases, a fragmented resonance-like structure of E1 strength is
observed in the energy region 5 MeV to 8 MeV. An analysis of the fragmentation
of the strength reveals that the degree of fragmentation decreases towards the
proton-deficient isotones while the total integrated strength increases
indicating a dependence of the total strength on the neutron-to-proton ratio.
The experimental results are compared to microscopic calculations within the
quasi-particle phonon model (QPM). The calculation includes complex
configurations of up to three phonons and is able to reproduce also the
fragmentation of the E1 strength which allows to draw conclusions on the
damping of the PDR. Calculations and experimental data are in good agreement in
the degree of fragmentation and also in the integrated strength if the
sensitivity limit of the experiments is taken into account
Multiscale Monte Carlo equilibration: Pure Yang-Mills theory
We present a multiscale thermalization algorithm for lattice gauge theory, which enables efficient parallel generation of uncorrelated gauge field configurations. The algorithm combines standard Monte Carlo techniques with ideas drawn from real space renormalization group and multigrid methods. We demonstrate the viability of the algorithm for pure Yang-Mills gauge theory for both heat bath and hybrid Monte Carlo evolution, and show that it ameliorates the problem of topological freezing up to controllable lattice spacing artifacts
Topological phases for bound states moving in a finite volume
We show that bound states moving in a finite periodic volume have an energy
correction which is topological in origin and universal in character. The
topological volume corrections contain information about the number and mass of
the constituents of the bound states. These results have broad applications to
lattice calculations involving nucleons, nuclei, hadronic molecules, and cold
atoms. We illustrate and verify the analytical results with several numerical
lattice calculations.Comment: 4 pages, 1 figure, version to appear in Phys. Rev. D Rapid
Communication
Investigation of octupole vibrational states in 150Nd via inelastic proton scattering (p,p'g)
Octupole vibrational states were studied in the nucleus
via inelastic proton scattering with \unit[10.9]{MeV} protons which are an
excellent probe to excite natural parity states. For the first time in
, both the scattered protons and the rays were
detected in coincidence giving the possibility to measure branching ratios in
detail. Using the coincidence technique, the ratios of the decaying
transitions for 10 octupole vibrational states and other negative-parity states
to the yrast band were determined and compared to the Alaga rule. The positive
and negative-parity states revealed by this experiment are compared with
Interacting Boson Approximation (IBA) calculations performed in the (spdf)
boson space. The calculations are found to be in good agreement with the
experimental data, both for positive and negative-parity states
- …