3,850 research outputs found
Final state interaction in with I=1/2 and 3/2 channels
The final state interaction contribution to decays is computed for the
channel within a light-front relativistic three-body model for
the final state interaction. The rescattering process between the kaon and two
pions in the decay channel is considered. The off-shell decay amplitude is a
solution of a four-dimensional Bethe-Salpeter equation, which is decomposed in
a Faddeev form. The projection onto the light-front of the coupled set of
integral equations is performed via a quasi-potential approach. The S-wave
interaction is introduced in the resonant isospin and the
non-resonant isospin channels. The numerical solution of the light-front
tridimensional inhomogeneous integral equations for the Faddeev components of
the decay amplitude is performed perturbatively. The loop-expansion converges
fast, and the three-loop contribution can be neglected in respect to the
two-loop results for the practical application. The dependence on the model
parameters in respect to the input amplitude at the partonic level is exploited
and the phase found in the experimental analysis, is fitted with an appropriate
choice of the real weights of the isospin components of the partonic amplitude.
The data suggests a small mixture of total isospin to the dominant
one. The modulus of the unsymmetrized decay amplitude, which presents a deep
valley and a following increase for masses above GeV, is fairly
reproduced. This suggests the assignment of the quantum numbers to the
isospin 1/2 resonance
Evidence for entanglement at high temperatures in an engineered molecular magnet
The molecular compound
[Fe(-oxo)(CHN)(CO)]
was designed and synthesized for the first time and its structure was
determined using single-crystal X-ray diffraction. The magnetic susceptibility
of this compound was measured from 2 to 300 K. The analysis of the
susceptibility data using protocols developed for other spin singlet
ground-state systems indicates that the quantum entanglement would remain at
temperatures up to 732 K, significantly above the highest entanglement
temperature reported to date. The large gap between the ground state and the
first-excited state (282 K) suggests that the spin system may be somewhat
immune to decohering mechanisms. Our measurements strongly suggest that
molecular magnets are promising candidate platforms for quantum information
processing
Influence of the external pressure on the quantum correlations of molecular magnets
The study of quantum correlations in solid state systems is a large avenue
for research and their detection and manipulation are an actual challenge to
overcome. In this context, we show by using first-principles calculations on
the prototype material KNaCuSiO that the degree of quantum
correlations in this spin cluster system can be managed by external hydrostatic
pressure. Our results open the doors for research in detection and manipulation
of quantum correlations in magnetic systems with promising applications in
quantum information science
Avaliação do comportamento ecofisiológico e bioquímico de plantas de timbó (Derris urucu) em campo.
On the search for the chiral anomaly in Weyl semimetals: The negative longitudinal magnetoresistance
Recently, the existence of massless chiral (Weyl) fermions has been
postulated in a class of semi-metals with a non-trivial energy dispersion.These
materials are now commonly dubbed Weyl semi-metals (WSM).One predicted property
of Weyl fermions is the chiral or Adler-Bell-Jackiw anomaly, a chirality
imbalance in the presence of parallel magnetic and electric fields. In WSM, it
is expected to induce a negative longitudinal magnetoresistance (NMR), the
chiral magnetic effect.Here, we present experimental evidence that the
observation of the chiral magnetic effect can be hindered by an effect called
"current jetting". This effect also leads to a strong apparent NMR, but it is
characterized by a highly non-uniform current distribution inside the sample.
It appears in materials possessing a large field-induced anisotropy of the
resistivity tensor, such as almost compensated high-mobility semimetals due to
the orbital effect.In case of a non-homogeneous current injection, the
potential distribution is strongly distorted in the sample.As a consequence, an
experimentally measured potential difference is not proportional to the
intrinsic resistance.Our results on the MR of the WSM candidate materials NbP,
NbAs, TaAs, TaP exhibit distinct signatures of an inhomogeneous current
distribution, such as a field-induced "zero resistance' and a strong dependence
of the `measured resistance" on the position, shape, and type of the voltage
and current contacts on the sample. A misalignment between the current and the
magnetic-field directions can even induce a "negative resistance".
Finite-element simulations of the potential distribution inside the sample,
using typical resistance anisotropies, are in good agreement with the
experimental findings. Our study demonstrates that great care must be taken
before interpreting measurements of a NMR as evidence for the chiral anomaly in
putative Weyl semimetals.Comment: 13 pages, 6 figure
Thermopower and thermal conductivity in the Weyl semimetal NbP
The Weyl semimetal NbP exhibits an extremely large magnetoresistance (MR) and
an ultra-high mobility. The large MR originates from a combination of the
nearly perfect compensation between electron- and hole-type charge carriers and
the high mobility, which is relevant to the topological band structure. In this
work we report on temperature- and field-dependent thermopower and thermal
conductivity experiments on NbP. Additionally, we carried out complementary
heat capacity, magnetization, and electrical resistivity measurements. We found
a giant adiabatic magnetothermopower with a maximum of 800 V/K at 50 K in
a field of 9 T. Such large effects have been observed rarely in bulk materials.
We suggest that the origin of this effect might be related to the high
charge-carrier mobility. We further observe pronounced quantum oscillations in
both thermal conductivity and thermopower. The obtained frequencies compare
well with our heat capacity and magnetization data.Comment: 6 pages, 3 figure
Ising-type Magnetic Anisotropy in CePdAs
We investigated the anisotropic magnetic properties of CePdAs by
magnetic, thermal and electrical transport studies. X-ray diffraction confirmed
the tetragonal ThCrSi-type structure and the high-quality of the single
crystals. Magnetisation and magnetic susceptibility data taken along the
different crystallographic directions evidence a huge crystalline electric
field (CEF) induced Ising-type magneto-crystalline anisotropy with a large
-axis moment and a small in-plane moment at low temperature. A detailed CEF
analysis based on the magnetic susceptibility data indicates an almost pure
CEF ground-state doublet with the dominantly
and the doublets at 290 K and 330
K, respectively. At low temperature, we observe a uniaxial antiferromagnetic
(AFM) transition at K with the crystallographic -direction being
the magnetic easy-axis. The magnetic entropy gain up to reaches almost
indicating localised -electron magnetism without significant
Kondo-type interactions. Below , the application of a magnetic field along
the -axis induces a metamagnetic transition from the AFM to a
field-polarised phase at T, exhibiting a text-book example
of a spin-flip transition as anticipated for an Ising-type AFM.Comment: 9 Pages, 8 figure
Tecnologia de produção de vinagre de mel.
Com a perspectiva de diversificação dos produtos derivados do mel, este trabalho teve como finalidade avaliar a produção de vinagre de mel de abelhas africanizadas (Apis mellifera L.). A produção do vinagre foi realizada através da fermentação acética de hidromel com teor alcoólico de 8% (v/v), obtido a partir de um mosto com 17,11% (m/v) de açúcares totais. A fermentação acética foi realizada pelo método rápido, em fermentador vertical com capacidade de 15 litros, utilizando vinagre forte não pasteurizado como inóculo, por 72 horas. Durante esta fermentação foram monitoradas as temperaturas interna (fermentador) e ambiente. O vinagre obtido apresentou acidez em torno de 9% e teor alcoólico em torno de 1% (v/v). O rendimento da fermentação acética foi entre 91,2 e 97,17%. O produto final foi diluído de acordo com a legislação brasileira (4,0% de acidez) e analisado sensorialmente, demonstrando ser de boa aceitabilidade Os teores de álcool etílico, ácido acético, resíduo mineral fixo e resíduo seco a 105oC foram de 0,32%; 4,2%; 0,05% e 1,76%, respectivamente. A análise microscópica revelou ausência de sujidades, larvas e parasitas.bitstream/CPAP-2009-09/57063/1/BP86.pd
Desenvolvimento de planilha para a escrituração zootécnica de colmeias povoadas com colônias de abelhas africanizadas.
Apresenta uma planilha que pode contribuir para ampliar e, possivelmente consolidar, o uso da escrituração zootécnica de colmeias povoadas com colônias de abelhas africanizadas no Pantanal e nas outras situações em que a apicultura é desenvolvida no Brasil.bitstream/item/219976/1/DOC-169-Escrituracao-Colmeias-abelhas.pd
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