Interannual variability in mesoscale distribution of Dinophysis acuminata and D. acuta in Northwestern Patagonian fjords.

Dinophysis acuminata and D. acuta, which produce diarrheogenic toxins and pectenotoxins in southern Chile, display site-specific differences in interannual variability (2006 - 2018) in Reloncaví, Pitipalena and Puyuhuapi fjords (41 - 46 °S), Chilean Patagonia. Linear Models show decreasing trends in rainfall and river discharge.

Exploring the destiny and distribution of thiocyanate in the water-soil-plant system and the potential impacts on human health.

Endocrine disruptors like thiocyanate are some of the principal causes of chronic disorders worldwide. Prenatal and postnatal exposure to thiocyanate can interfere with normal neurological development in both fetuses and newborns. Currently, little information regarding thiocyanate levels and potential sources of exposure is available.

Lack of Synergy Between β-Agonist Treatment and a Blockage of Sarcoplasmic Calcium Flow in a Rat Cancer Cachexia Model.

Background: During cancer cachexia, both skeletal muscle and adipose tissue losses take place. The use of β2-agonists, formoterol in particular, has proven to be very successful in the treatment of the syndrome in pre-clinical models. The object of the present research was to study the effects of a combination of formoterol and dantrolene, an inhibitor of the ryanodine receptor 1 (RyR1), on body weight loss and cachexia in tumour-bearing animals.

Beam width of highly-focused radially-polarized fields.

On the basis of a formal analogy with the irradiance moments, analytical definitions are proposed for the width of both the transverse and the longitudinal component of rotationally-symmetric radially-polarized fields at the focal plane of a high-focusing optical system. The beam width of the whole field is also introduced. The transverse beam size is thus associated with the overall spatial structure of the field.

Angular momentum decomposition of nonparaxial light beams.

The total angular momentum per unit length of a general non-paraxial beam is decomposed into an orbital component associated with the spiral spectrum at the far field and a component concerning the balance between right- and left-handed circular-polarization content of the angular spectrum. Expressions for the linear momentum and energy per unit length are also provided. The well-known division into orbital and spin components is shown to be recovered in the paraxial limit.

Cross-correlation between spiral modesand its influence on the overall spatial characteristics of partially coherent beams.

The overall spatial structure of a general partially coherent field is shown to be connected with the cross-correlation between the so-called spiral modes, understood as the terms of the spiral-harmonics series expansion of the field. The formalism based on the beam irradiance-moments is used, and the light field is globally described by the beam width, the far-field divergence, the beam quality factor, the orientation of the beam profile and the angular orbital momentum, given as the sum of its asymmetrical and vortex parts. This overall spatial description is expressed in terms of the intermodal coherence features (cross-correlation between spiral modes).

Elementary-field expansions of genuine cross-spectral density matrices.

A necessary and sufficient nonnegative definiteness condition for the cross-spectral density matrix (CDM) is derived. It is also shown that this realizability condition allows the expansion of genuine CDMs in terms of recently introduced elementary fields, namely, mean-square coherent beams, and fields with position-independent stochastic behavior. The special case of uniformly polarized electromagnetic Schell-model sources is also analyzed.

Genuine cross-spectral densities and pseudo-modal expansions.

A necessary and sufficient non-negative definiteness condition for the cross-spectral density (CSD) is provided. It is also shown that any genuine CSD can be expanded in terms of the so-called pseudo-modes of the source, understood as coherent contributions, not orthogonal to one another, that, superposed in an uncorrelated way, give rise to the CSD. Their evaluation is analyzed by means of an illustrative example.

Maximizing Young's fringe visibility under unitary transformations for mean-square coherent light.

Given the values of the degree of polarization of the fields at the pinholes in a Young interferometer, the maximum attainable visibility under unitary transformations is determined when the illuminating beam is mean-square light. Analytical expressions are also obtained for both the field vector (in the mean-square sense) and the cross-spectral density matrix associated with this kind of beams. A comparative summary is also provided of the main characteristics of well-known types of random electromagnetic fields frequently handled in the literature.

Equivalence between optimum Young's fringe visibility and position-independent stochastic behavior of electromagnetic fields.

Stochastic electromagnetic fields characterized by optimized fringe visibility in a Young interferometric arrangement are shown to be those whose random character is position independent. The optimization procedure involves local unitary transformations, which can be implemented by using reversible anisotropic polarization devices placed at the two pinholes. It is also shown that the local degree of polarization in the optimized interferometer is constant across the superposition region and coincides with the degree of polarization at the two pinholes.

Propagation of light fields with radial or azimuthal polarization distribution at a transverse plane.

In terms of the angular spectrum representation, general expressions are given to describe the free-space propagation of electromagnetic fields with radial or azimuthal polarization structure at a transverse plane. The transverse distributions of the radial, azimuthal and longitudinal components of these fields are also analysed. In particular, the on-axis behavior upon free propagation is studied.

Evanescent field of vectorial highly non-paraxial beams.

In terms of the Fourier spectrum, a simple but general analytical expression is given for the evanescent field associated to a certain kind of non-paraxial exact solutions of the Maxwell equations. This expression enables one to compare the relative weight of the evanescent wave with regard to the propagating field. In addition, in those cases in which the evanescent term is significant, the magnitude of the field components across the transverse profile (including the evanescent features) can be determined.

Quality improvement of partially polarized beams.

Improvement of the beam-quality parameter of partially polarized beams is investigated. We focus on the use of a Mach-Zehnder-type interferometric arrangement with crossed polarizers. The analysis has been carried out within the framework of the intensity moment formalism.

On the vectorial fields with position-independent stochastic behavior.

Vectorial fields with position-independent stochastic behavior within a certain region are analyzed. More specifically, we deal with the transverse components of this class of beamlike fields (the longitudinal component assumed to be negligible). The general form of the cross-spectral density tensor (CDT) of these fields is shown.

Relation between degrees of coherence for electromagnetic fields.

In terms of the electric spectral density tensors associated with a random electromagnetic field, it is shown that, under certain conditions, a link can be established between two definitions of the degree of coherence for electromagnetic beams introduced not long ago by Wolf [Phys. Lett. A312, 263 (2003)] and by Setälä [Opt.

Maximum visibility under unitary transformations in two-pinhole interference for electromagnetic fields.

In terms of the spectral density tensors associated with the electric field vector, the maximum visibility one can obtain in a two-point interference arrangement by using local (i.e., position-dependent) unitary transformations applied at such points is determined.

On the spatial orientation of the transverse irradiance profile of partially coherent beams.

On the basis of the irradiance-moments formalism, four matrices are proposed whose elements, defined for any partially coherent field, are closely related with the second-order measurable parameters handled in the ISO standard 11146. These matrices are shown to exhibit a number of properties concerning the orientation of the transverse profile of a partially coherent beam. This behavior is described by the rotation of the principal axes of the field around its propagation axis.

On the control of the spatial orientation of the transverse profile of a light beam.

A first-order optical system (represented by its 4x4 ABCD matrix) is given in order to obtain a beam that preserves its spatial orientation of the transverse profile under free propagation from a beam with rotating irradiance distribution in free space. Within the formalism of the second-order irradiance moments, this transverse orientation is analyzed in terms of the evolution of the principal axes of the field irradiance distribution. It is shown that the spatial profile of the beam emerging from the proposed optical system does not rotate when light freely propagates.

Beam-quality optimization of partially polarized fields.

For light fields propagating through rotationally symmetric first-order optical systems, the possibility of improvement of the beam-propagation factor is shown to arise when the vectorial behavior is taken into account. For partially polarized beams, we find the optimized value of the beam-quality parameter that can be attained by using this kind of system. This value is given in terms of the beam qualities associated with the transverse polarization components of the vector field.

Anisotropic pure-phase plates for quality improvement of partially coherent, partially polarized beams.

From a theoretical point of view, the use of anisotropic pure-phase plates (APP) is considered in order to improve the quality parameter of certain partially coherent, partially polarized beams. It is shown that, to optimize the beam-quality parameter, the phases of the two Cartesian components of the field at the output of the APP plate should be identical and should exhibit a quadratic dependence on the radial polar coordinate.

Spatial width and power-content ratio of hard-edge diffracted beams.

On the basis of the intensity-moment formalism, certain analytical relationships are obtained for both the angular domain and the size of a transverse region of the beam that ensure a power content of at least 75% of the total power. As an illustrative application, the analytical results are compared with the exact values (numerically computed) of the amplitude of a lowest-order Gaussian beam diffracted by slits.

Beam propagation through uniaxial anisotropic media: global changes in the spatial profile.

The propagation of electromagnetic beams through uniaxial anisotropic media is investigated. The Maxwell equations are solved in the paraxial limit in terms of the plane-wave spectrum associated with each Cartesian field component. Attention is focused on the global changes in the spatial structure of the beam, which are described by means of the second-order intensity moment formalism.

Time-resolved spatial profile of TEA CO2 laser pulses: influence of the gas mixture and intracavity apertures.

The evolution of the intensity profile of transversely excited atmospheric CO2 laser pulses is investigated within the intensity moment formalism. The beam quality factor M2 is used to study the mode evolution. Attention is focused on the influence of both the gas mixture (N2 :CO2 :He) and the diameter of an intracavity diaphragm placed to attenuate higher-order modes.

Vectorial structure of nonparaxial electromagnetic beams.

A representation of the general solution of the Maxwell equations is proposed in terms of the plane-wave spectrum of the electromagnetic field. In this representation the electric field solution is written as a sum of two terms that are orthogonal to each other at the far field: One is transverse to the propagation axis, and the magnetic field associated with the other is also transverse. The concept of the so-called closest field to a given beam is introduced and applied to the well-known linearly polarized Gaussian beam.