Optical amplification enhancement in photonic crystals

Improving and controlling the efficiency of a gain medium is one of the most challenging problems of laser research. By measuring the gain length in an opal based photonic crystal doped with laser dye, we demonstrate that optical amplification is more than twenty-fold enhanced along the Gamma-K symmetry directions of the face centered cubic photonic crystal. These results are theoretically explained by directional variations of the density of states, providing a quantitative connection between density of the states and light amplification

Nonlinear Interaction of Transversal Modes in a CO2 Laser

We show the possibility of achieving experimentally a Takens-Bogdanov bifurcation for the nonlinear interaction of two transverse modes ($l = \pm 1$) in a $CO_2$ laser. The system has a basic O(2) symmetry which is perturbed by some symmetry-breaking effects that still preserve the $Z_2$ symmetry. The pattern dynamics near this codimension two bifurcation under such symmetries is described. This dynamics changes drastically when the laser properties are modified.Comment: 16 pages, 0 figure

Influence of Ceramic Recycled Aggregates on the Properties of Prestressed Precast Concrete Elements

This work presents the results of an experimental study performed on the mechanical behavior of concrete manufactured with ceramic recycled aggregates (CRA), from precast ventilation ducts, that once made have been rejected by defective. The ultimate objective is to use these wastes to manufacture prestressed concrete joists used in building floors. The coarse fraction and the fine fraction have been considered. The work has been carried out in three phases: characterization of the material, characterization of concrete with CRA and manufacturing and testing of prestressed joists. With the results obtained it is determined the influence of the ceramic recycled aggregate on the properties analyzed. There are not enough studies about prestressed elements that include the replacement of the aggregate in the fine fraction. In view of the results obtained could both of fine and coarse fraction can be used in these applications

Orthogonal basis with a conicoid first mode for shape specification of optical surfaces: Reply

We present some comments to the paper “Orthogonal basis with a conicoid first mode for shape specification of optical surfaces: comment.

A multidimensional approach to the resilience in older adults despite COVID-19.

Researchers have mainly focused on aging risk factors and COVID-19 consequences. However, older adults have proved their ability to overcome adversities along their life. Resilience is a protective variable that dampens the impact of stress. Based on MacLeod’s et al. (2016) approach, we aimed to analyze the relationship between older adults’ resilience and COVID-19 related-stressors as well as their physical, mental, and social characteristics. Eight hundred eighty-nine people aged 60 and over participated in this study. Older participants, women, having better perceived health and not losing a loved one because of the virus were associated with more resilience. Moreover, higher levels of gratitude, personal growth, life purpose and lower levels of depression were associated with greater scores in resilience. This study offers a change of perspective in which aging is perceived from a positive viewpoint by focusing on easily accessible resources that may help older adults to cope with adverse situations.post-print913 K

Characterization of plant growth promoting bacteria (PGPR) isolated from the rhizosphere of Arthrocnemum macrostachyum.

Motivation: The recent boom in organic agriculture has awakened the need to find alternative methods to chemical products. PGPRs (plant growth-promoting rhizobacteria) are rhizospheric bacteria that contribute in a favourable way for the plant development through different mechanisms like exudates production (that enhance plant rooting), nutrient solubilization or resistance to pathogenic agents (1). The study of these microorganisms and its subsequent use for different agriculture requirements is a viable option in order to get good results in a more sustainable way. In addition, it is an interesting approach to promote the soil regenerative abilities of some plants, like the halophyte Arthrocnemum macrostachyum (2).Methods: Bacteria from the rhizosphere of A. macrostachyum were isolated from plants grown in different areas at the Lebrija marshes. 5 µl of exponentially bacterial cultures were dropped onto Petri dishes containing different media: CAS to test siderophores production (3), PVK for phosphate solubilization (3), nutrient broth supplemented with NaCl for testing tolerance to sodium chloride and nutrient broth with 0,5mM and 1mM Zn concentrations to test heavy metal resistance. All of them were incubated at 28ºC for 72h. Acyl-homoserine lactone and indolacetic acid (IAA) production tests (3) were also performed. In addition, 5 µl droplets of each bacterial suspension were spotted on Petri dishes together with a disk of active Macrophomina phaseolina culture to test antifungal activity.Results: A total of 203 strains were isolated from the rhizosphere of A.macrostachyum plants. In CAS medium, 40% of them formed an orange-yellowish halo, denoting siderophore production. In PVK medium, 7% shown a transparent halo, indicating phosphate solubilization ability. 30% of the strains were auxin producers, while only a 13% exhibited the quorum sensing mechanism. 3% of all the strains displayed high halotolerance, showed positive growth in 24 % (p/v) NaCl. 5% and 3% of the strains were able to grow in the presence of 0,5 and 1 mM Zn, respectively. Taking into account fungicide activity, 11% of the bacterial isolates are able to inhibit the growth of the pathogenic fungus M. phaseolina.Conclusions: An earlier conclusion of this incipient study is that the rhizosphere of halophyte plants living in natural stressing areas is a good source for isolating bacteria with desirable properties to be used as PGPR and also for the control of pathogenic fungus