Freeform concentrator design for IR wireless-to-fiber link communications.

Airplanes use heavy wired harnesses to provide multimedia services to the seats. Optical wireless communications (OWC) are a natural choice to reduce the amount of weight, reduce the wiring complexity, and avoid possible spurious electromagnetic radiation that risks affecting the airplane's navigation systems. The light's dual use as lighting and optical communications functionalities allows for providing light and multimedia content through the reading lamp. Thus, an optical system using optical fibers to replace wires and a reading lamp can provide a cabin seat with lighting and onboard connectivity. However, changing shielded harnesses by optical fibers is-from an optical design point of view-a challenging task as the reading lamp must also meet the stringent requirements to link the optical wireless transmissions to the optical fiber. The difficulty up to now lies in injecting the light emitted from the passenger's device into the optical fiber using the reading lamp as the receiving antenna and light injector. Here, we describe a proof-of-concept device that experimentally allowed for establishing a link between a transmitter and a photodetector coupled to an optical fiber-end, i.e., the link consisted of an optical wireless communication and the launching of the light modulated signal into an optical fiber. Additionally, from the experimental experience, we will describe the optical design strategies permitting designing a compound freeform concentrator to allow optical free space-to-fiber links.

General formula to design a freeform singlet free of spherical aberration and astigmatism: comment.

In their paper [Appl. Opt.58, 1010 (2019)APOPAI0003-693510.1364/AO.58.001010] González-Acuña et al. claimed: "an analytical closed-form formula for the design of freeform lenses free of spherical aberration and astigmatism." However, as we show here, their formula can only be applied when the object and image are both real, and the image is inversed; additionally, the refractive index in the object and image media is the same. Here, we present the complete solution of this particular formula.

Microbiota composition and intestinal integrity remain unaltered after the inclusion of hydrolysed Nannochloropsis gaditana in Sparus aurata diet.

The use of lysed microalgae in the diet of carnivorous fish can increase the bioavailability of proteins and bioactive compounds, such as unsaturated fatty acids or vitamins in the digestive tract. These are essential molecules for the proper physiological development of fish in aquaculture. However, some antinutritional components and other undesirable molecules can be released from an excess of microalgae supplied, compromising the integrity of the intestine. The inclusion of small amounts of hydrolized microalgae in the fish diet can be a good strategy to avoid negative effects, improving the availability of beneficial compounds. Nannochloropsis gaditana is an interesting microalgae as it contains nutraceuticals. Previous studies reported beneficial effects after its inclusion in the diet of Sparus aurata, a widely cultured species in Europe and in all Mediterranean countries. However, administration of raw microalgae can produce intestinal inflammation, increased intestinal permeability, bacterial translocation and disturbance of digestion and absorption processes. The aim of this study was to evaluate changes in the intestinal microbiota and barrier stability of S. aurata fed with low inclusion (5%) hydrolysed N. gaditana. Intestinal microbiota was analyzed using Illumina MiSeq technology and libraries were constructed using variable regions V3-V4 of 16S rDNA molecules. Analysis were based in the identification, quantification and comparison of sequences. The predictive intestinal microbial functionality was analyzed with PICRUSt software. The results determined that the intestinal microbiota bacterial composition and the predictive intestinal microbiota functionality did not change statistically after the inclusion of N. gaditana on the diet. The study of gene expression showed that genes involved in intestinal permeability and integrity were not altered in fish treated with the experimental diet. The potential functionality and bacterial taxonomic composition of the intestinal microbiota, and the expression of integrity and permeability genes in the intestine of the carnivorous fish S. aurata were not affected by the inclusion of hydrolysed 5% N. gaditana microalgae.

Analysis of interferograms with a spatial radial carrier or closed fringes and its holographic analogy.

It is well known that an interferogram can be demodulated to find the wave-front shape if a linear carrier is introduced. We show that it can also be demodulated if it has many closed fringes or a circular carrier appears. A basic assumption is that the carrier fringes are of a bandwidth adequate to contain the wave-front distortion. This phase determination, called here demodulation, is made in the space domain, as opposed to demodulation in Fourier space, but the low-pass filter characteristics must be properly chosen. For academic purposes a holographic analogy of this demodulation process is also presented, which shows that the common technique of multiplying by a sine function and a cosine function is equivalent to holographically reconstructing with a tilted-flat wave front. Alternatively, a defocused (spherical) wave front can be used as a reference to perform the reconstruction or demodulation of some closed-fringe interferograms.