1,241 research outputs found
Alternative approach to electromagnetic field quantization in nonlinear and inhomogeneous media
A simple approach is proposed for the quantization of the electromagnetic
field in nonlinear and inhomogeneous media. Given the dielectric function and
nonlinear susceptibilities, the Hamiltonian of the electromagnetic field is
determined completely by this quantization method. From Heisenberg's equations
we derive Maxwell's equations for the field operators. When the nonlinearity
goes to zero, this quantization method returns to the generalized canonical
quantization procedure for linear inhomogeneous media [Phys. Rev. A, 43, 467,
1991]. The explicit Hamiltonians for the second-order and third-order nonlinear
quasi-steady-state processes are obtained based on this quantization procedure.Comment: Corrections in references and introductio
Identification of Potential Diesel Oil-degrading Bacteria Isolated From Manado Sea Port Based on 16s Rrna Gene
Petroleum contamination and its derivate in ecosystem are considered as environmental threat all over the world. Some microorganisms exhibit potential to degrade hydrocarbon in contaminated environments. This study aims at identifying potential diesel oil-degrading bacteria grown on artificial media. Bacteria isolated from Manado Sea port were grown in nutrient agar containing artificial diesel oil plus salt water and diesel oil only, respectively. The growing bacteria were isolated and each of them was grown separately to obtain pure isolate. Three bacterial isolates namely AO2, OA3 and OA4 were identified using 16S rRNA gene as Pseudomonas aeroginosa, Klebsiella oxytoca, and Citrobacter sp, respectively
Exploring the psychological rewards of a familiar semirural landscape: connecting to local nature through a mindful approach
This study analyses a 53,000 word diary of a year engaging with nature through over 200 trips to a semi-rural landscape. Thematic analysis revealed two themes; the transition from observer to nature connectedness and the ways in which the natural environment was experienced once a connection was made. These themes are discussed in relation to theories that seek to explain the positive effect of nature and nature connectedness. The findings are important as they suggest that repeated engagement with local semi-rural countryside can lead to a mindful approach and psychological rewards that do not require travel into the wilderness. The work informs further research into outcomes and processes of nature based interventions such as: trip frequency, duration and diary keeping
Interaction of the quantized electromagnetic field with atoms in the presence of dispersing and absorbing dielectric bodies
A general theory of the interaction of the quantized electromagnetic field
with atoms in the presence of dispersing and absorbing dielectric bodies of
given Kramers--Kronig consistent permittivities is developed. It is based on a
source-quantity representation of the electromagnetic field, in which the
electromagnetic-field operators are expressed in terms of a continuous set of
fundamental bosonic fields via the Green tensor of the classical problem.
Introducing scalar and vector potentials, the formalism is extended in order to
include in the theory the interaction of the quantized electromagnetic field
with additional atoms. Both the minimal-coupling scheme and the
multipolar-coupling scheme are considered. The theory replaces the standard
concept of mode decomposition which fails for complex permittivities. It
enables us to treat the effects of dispersion and absorption in a consistent
way and to give a unified approach to the atom-field interaction, without any
restriction to a particular interaction regime in a particular frequency range.
All relevant information about the dielectric bodies such as form and intrinsic
dispersion and absorption is contained in the Green tensor. The application of
the theory to the spontaneous decay of an excited atom in the presence of
dispersing and absorbing bodies is addressed.Comment: Paper presented at the International Conference on Quantum Optics and
VIII Seminar on Quantum Optics, Raubichi, Belarus, May 28-31, 2000, 14 pages,
LaTeX2e, no figure
Synergies for Improving Oil Palm Production and Forest Conservation in Floodplain Landscapes
Lowland tropical forests are increasingly threatened with conversion to oil palm as global demand and high profit drives crop expansion throughout the world’s tropical regions. Yet, landscapes are not homogeneous and regional constraints dictate land suitability for this crop. We conducted a regional study to investigate spatial and economic components of forest conversion to oil palm within a tropical floodplain in the Lower Kinabatangan, Sabah, Malaysian Borneo. The Kinabatangan ecosystem harbours significant biodiversity with globally threatened species but has suffered forest loss and fragmentation. We mapped the oil palm and forested landscapes (using object-based-image analysis, classification and regression tree analysis and on-screen digitising of high-resolution imagery) and undertook economic modelling. Within the study region (520,269 ha), 250,617 ha is cultivated with oil palm with 77% having high Net-Present-Value (NPV) estimates (637/ha?yr); but 20.5% is under-producing. In fact 6.3% (15,810 ha) of oil palm is commercially redundant (with negative NPV of -65/ha?yr) due to palm mortality from flood inundation. These areas would have been important riparian or flooded forest types. Moreover, 30,173 ha of unprotected forest remain and despite its value for connectivity and biodiversity 64% is allocated for future oil palm. However, we estimate that at minimum 54% of these forests are unsuitable for this crop due to inundation events. If conversion to oil palm occurs, we predict a further 16,207 ha will become commercially redundant. This means that over 32,000 ha of forest within the floodplain would have been converted for little or no financial gain yet with significant cost to the ecosystem. Our findings have globally relevant implications for similar floodplain landscapes undergoing forest transformation to agriculture such as oil palm. Understanding landscape level constraints to this crop, and transferring these into policy and practice, may provide conservation and economic opportunities within these seemingly high opportunity cost landscapes
Three-dimensional quantization of the electromagnetic field in dispersive and absorbing inhomogeneous dielectrics
A quantization scheme for the phenomenological Maxwell theory of the full
electromagnetic field in an inhomogeneous three-dimensional, dispersive and
absorbing dielectric medium is developed. The classical Maxwell equations with
spatially varying and Kramers-Kronig consistent permittivity are regarded as
operator-valued field equations, introducing additional current- and
charge-density operator fields in order to take into account the noise
associated with the dissipation in the medium. It is shown that the equal-time
commutation relations between the fundamental electromagnetic fields
and and the potentials and in the Coulomb gauge
can be expressed in terms of the Green tensor of the classical problem. From
the Green tensors for bulk material and an inhomogeneous medium consisting of
two bulk dielectrics with a common planar interface it is explicitly proven
that the well-known equal-time commutation relations of QED are preserved
Cumulant expansion for studying damped quantum solitons
The quantum statistics of damped optical solitons is studied using
cumulant-expansion techniques. The effect of absorption is described in terms
of ordinary Markovian relaxation theory, by coupling the optical field to a
continuum of reservoir modes. After introduction of local bosonic field
operators and spatial discretization pseudo-Fokker-Planck equations for
multidimensional s-parameterized phase-space functions are derived. These
partial differential equations are equivalent to an infinite set of ordinary
differential equations for the cumulants of the phase-space functions.
Introducing an appropriate truncation condition, the resulting finite set of
cumulant evolution equations can be solved numerically. Solutions are presented
in Gaussian approximation and the quantum noise is calculated, with special
emphasis on squeezing and the recently measured spectral photon-number
correlations [Spaelter et al., Phys. Rev. Lett. 81, 786 (1998)].Comment: 17 pages, 13 figures, revtex, psfig, multicols, published in
Phys.Rev.
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