Augmented Reality Based on SLAM to Assess Spatial Short-Term Memory

Spatial short-term memory is defined as the limited ability of people to retain and remember the location of elements for short periods of time. In this paper, we present the first AR app based on SLAM (Simultaneous Localization and Mapping) to assess spatial short-term memory. A total of 55 participants were involved in a study for remembering the real place where four virtual objects were located in the real environment. The participants were divided into two groups: the ARGroup (the participants learned the location of the virtual objects in the real environment in an adaptation phase using AR) and the NoARGroup (the participants learned the location of the objects by looking at photographs). The results indicated that the performance outcomes in remembering objects and their location for the participants in the ARGroup were statistically significantly greater than those obtained by the participants in the NoARGroup. From this result and our observations, we can conclude that touring the augmented environment helped the participants to better remember the location of virtual objects added to the real scene compared to looking at photographs of the environment. Furthermore, statistically significant differences were not found in relation to gender or age. Finally, our app has several advantages: 1) Our app works in any environment and does not require adding real elements to the environment; 2) the evaluators can select any real environment and place the virtual elements where they want and even change them between sessions; and 3) our app could work similar to the way spatial memory does in everyday life

SLAM-based augmented reality for the assessment of short-Term spatial memory. A comparative study of visual versus tactile stimuli

The assessment of human spatial short-Term memory has mainly been performed using visual stimuli and less frequently using auditory stimuli. This paper presents a framework for the development of SLAM-based Augmented Reality applications for the assessment of spatial memory. An AR mobile application was developed for this type of assessment involving visual and tactile stimuli by using our framework. The task to be carried out with the AR application is divided into two phases: 1) a learning phase, in which participants physically walk around a room and have to remember the location of simple geometrical shapes; and 2) an evaluation phase, in which the participants are asked to recall the location of the shapes. A study for comparing the performance outcomes using visual and tactile stimuli was carried out. Fifty-Three participants performed the task using the two conditions (Tactile vs Visual), but with more than two months of difference (within-subject design). The number of shapes placed correctly was similar for both conditions. However, the group that used the tactile stimulus spent significantly more time completing the task and required significantly more attempts. The performance outcomes were independent of gender. Some significant correlations among variables related to the performance outcomes and other tests were found. The following significant correlations among variables related to the performance outcomes using visual stimuli and the participants subjective variables were also found: 1) the greater the number of correctly placed shapes, the greater the perceived competence; 2) the more attempts required, the less the perceived competence. We also found that perceived enjoyment was higher when a higher sense of presence was induced. Our results suggest that tactile stimuli are valid stimuli to exploit for the assessment of the ability to memorize spatial-Tactile associations, but that the ability to memorize spatial-visual associations is dominant. Our results also show that gender does not affect these types of memory tasks

Activities of methionine-γ-lyase in the acidophilic archaeon “Ferroplasma acidarmanus” strain fer1

Biogeochemical processes on exposed pyrite ores result in extremely high levels of sulfuric acid at these locations. Acidophiles that thrive in these conditions must overcome significant challenges, including an environment with proton concentrations at pH 3 or below. The role of sulfur metabolism in the archaeon “Ferroplasma acidarmanus” strain fer1’s ability to thrive in this environment was investigated due to its growth-dependent production of methanethiol, a volatile organic sulfur compound. Two putative sequences for methionine- γ-lyase (EC 4.4.1.11), an enzyme known to carry out α,γ-elimination on L-methionine to produce methanethiol, were identified in fer1. Bioinformatic analyses identified a conserved pyridoxal-5′-phosphate (PLP) binding domain and a partially conserved catalytic domain in both putative sequences. Detection of PLP-dependent and L-methionine-dependent production of α-keto compounds and thiol groups in fer1 confirmed the presence of methionine-γ-lyase activity. Further, fer1 lysate was capable of processing related substrates, including D-methionine, L-cysteine, L-cystathionine, and L/D-homocysteine. When the two putative fer1 methionine-γ- lyase gene-coded proteins were expressed in Escherichia coli cells, one sequence demonstrated an ability to carry out α, γ-elimination activity, while the other exhibited γ-replacement activity. These fer1 methionine-γ-lyases also exhibited optimum pH, substrate specificity, and catalytic preferences that are different from methionine-γ-lyases from other organisms. These differences are discussed in the context of molecular phylogeny constructed using a maximum likelihood algorithm based on methionine-γ-lyase sequences from a diverse selection of organisms

Activities of methionine-γ-lyase in the acidophilic archaeon “Ferroplasma acidarmanus” strain fer1

Biogeochemical processes on exposed pyrite ores result in extremely high levels of sulfuric acid at these locations. Acidophiles that thrive in these conditions must overcome significant challenges, including an environment with proton concentrations at pH 3 or below. The role of sulfur metabolism in the archaeon “Ferroplasma acidarmanus” strain fer1’s ability to thrive in this environment was investigated due to its growth-dependent production of methanethiol, a volatile organic sulfur compound. Two putative sequences for methionine- γ-lyase (EC 4.4.1.11), an enzyme known to carry out α,γ-elimination on L-methionine to produce methanethiol, were identified in fer1. Bioinformatic analyses identified a conserved pyridoxal-5′-phosphate (PLP) binding domain and a partially conserved catalytic domain in both putative sequences. Detection of PLP-dependent and L-methionine-dependent production of α-keto compounds and thiol groups in fer1 confirmed the presence of methionine-γ-lyase activity. Further, fer1 lysate was capable of processing related substrates, including D-methionine, L-cysteine, L-cystathionine, and L/D-homocysteine. When the two putative fer1 methionine-γ- lyase gene-coded proteins were expressed in Escherichia coli cells, one sequence demonstrated an ability to carry out α, γ-elimination activity, while the other exhibited γ-replacement activity. These fer1 methionine-γ-lyases also exhibited optimum pH, substrate specificity, and catalytic preferences that are different from methionine-γ-lyases from other organisms. These differences are discussed in the context of molecular phylogeny constructed using a maximum likelihood algorithm based on methionine-γ-lyase sequences from a diverse selection of organisms

An X-ray study of the SNR G344.7-0.1 and the central object CXOU J170357.8-414302

Aims. We report results of an X-ray study of the supernova remnant (SNR) G344.7-0.1 and the point-like X-ray source located at the geometrical center of the SNR radio structure. Methods. The morphology and spectral properties of the remnant and the central X-ray point-like source were studied using data from the XMM-Newton and Chandra satellites. Archival radio data and infrared Spitzer observations at 8 and 24 $\mu$m were used to compare and study its multi-band properties at different wavelengths. Results. The XMM-Newton and Chandra observations reveal that the overall X-ray emission of G344.7-0.1 is extended and correlates very well with regions of bright radio and infrared emission. The X-ray spectrum is dominated by prominent atomic emission lines. These characteristics suggest that the X-ray emission originated in a thin thermal plasma, whose radiation is represented well by a plane-parallel shock plasma model (PSHOCK). Our study favors the scenario in which G344.7-0.1 is a 6 x 10^3 year old SNR expanding in a medium with a high density gradient and is most likely encountering a molecular cloud on the western side. In addition, we report the discovery of a soft point-like X-ray source located at the geometrical center of the radio SNR structure. The object presents some characteristics of the so-called compact central objects (CCO). However, its neutral hydrogen absorption column (N_{H}) is inconsistent with that of the SNR. Coincident with the position of the source, we found infrared and optical objects with typical early-K star characteristics. The X-ray source may be a foreground star or the CCO associated with the SNR. If this latter possibility were confirmed, the point-like source would be the farthest CCO detected so far and the eighth member of the new population of isolated and weakly magnetized neutron stars.Comment: 9 pages, 8 figures, accepted for publication in Astronomy and Astrophysics. Higher resolution figures can be seen on A&

Natural genetic diversity of nutritive value traits in the genus Cynodon

The Cynodon spp. collection maintained by United States Department of Agriculture National Plant Germplasm System (USDA-NPGS) has limited information on nutritive value (NV) traits. In this study, crude protein (CP), phosphorous concentration (P), in vitro digestible organic matter (IVDOM), and neutral detergent fiber (NDF) were determined to (i) estimate genetic parameters for NV, (ii) obtain genetic values for the whole population across two harvests, (iii) estimate genotype by harvest interaction (GHI) for NV traits, and (iv) select accessions exhibiting improved NV traits compared to ‘Tifton 850 . The experiment was setup as a row-column design with two replicates and augmented representation of controls: Tifton 85, ‘Jiggs’, and ‘Coastal’. The whole-population was harvested twice, and data were analyzed using linear mixed models with repeated measures. In addition, a selected population of 15 genotypes were evaluated across 11 harvests to determine the extent of GHI. Genetic parameters revealed the presence of significant genetic variability, indicating potential improvements for NV through breeding. Specifically, P and IVDOM presented large variation, while NDF had lower diversity but some accessions exhibited lower NDF than Tifton 85. Low GHI, except for IVDOM, indicated genotypic stability and potential for selecting improved accessions under fewer harvests. Breeding line 240, PI-316510, and PI-3166536 presented superior NV than Tifton 85

A Novel Communication Platform to Enable the Collaboration of Autonomous Underwater Vehicles

Abstract -A novel communication platform is introduced to enable the collaboration of a set of Autonomous Underwater Vehicles (AUV´