Influence of Temperature and Impact Velocity on the Coefficient of Restitution

Tests were performed on a variety of material combinations to understand the effects of temperature and impact velocity on the coefficient of restitution (COR). The tests, performed in a vacuum at room and liquid nitrogen temperatures, consisted of dropping a ball onto a target plate and recording the impact time history of the ball's bounce-down. Time intervals between successive impacts were measured from the time history and used to calculate the coefficient of restitution and impact velocity for each impact. Maximum impact velocities ranged from approximately 33 (0.84) to 52 in./s (1.32 m/s). Five ball-target plate combinations were evaluated: type 316 stainless steel (316 SS) on 316 SS; M50 tool steel on Armalon; M50 on 4340 steel; 410C steel on Armalon; and copper on copper. The coefficient of restitution for the 316 SS-316 SS, M50-Armalon, 410C-Armalon, and copper-copper combinations increased as the temperature and impact velocity decreased. The coefficient for the hard steel combination, M50-4340, was not greatly influenced by temperature or variations in impact velocity

Situated Learning with Bebras Tasklets

A Bebras short task, a tasklet, is designed to provide a source for exploring a computational thinking concept: at the end of the contest it could be used as a starting point to delve deeper into a computing topic. In this paper we report an experience which aims at taking full advantage of the potential of Bebras tasklets. A math teacher asked her pupils to act as Bebras \u201ctrainers\u201d for younger mates. The pupils, in pairs, were assigned to design and prepare a tangible game inspired by a Bebras tasklet, devised for the younger pupils to practice. They also had to explain the game to the younger pupils, make them play and support them in solving it. In carrying out this assignment the pupils acting as trainers had to deeply explore the Bebras tasklet and face its computational thinking challenge, and also practiced soft skills as collaborating with peers towards a common goal, adapting language and communicative style to engage with younger mates, devising and designing a tangible object, and planning its creation. The experience proved that using Bebras tasklets as the social and cultural context for situated learning of computational thinking competencies is indeed quite productive

Novel insights into the transport mechanism of the human amino acid transporter LAT1 (SLC7A5) : probing critical residues for substrate translocation

BACKGROUND: LAT1 (SLC7A5) is the transport competent unit of the heterodimer formed with the glycoprotein CD98 (SLC3A2). It catalyzes antiport of His and some neutral amino acids such as Ile, Leu, Val, Cys, Met, Gln and Phe thus being involved in amino acid metabolism. Interestingly, LAT1 is over-expressed in many human cancers that are characterized by increased demand of amino acids. Therefore LAT1 was recently acknowledged as a novel target for cancer therapy. However, knowledge on molecular mechanism of LAT1 transport is still scarce. METHODS: Combined approaches of bioinformatics, site-directed mutagenesis, chemical modification, and transport assay in proteoliposomes, have been adopted to unravel dark sides of human LAT1 structure/function relationships. RESULTS: It has been demonstrated that residues F252, S342, C335 are crucial for substrate recognition and C407 plays a minor role. C335 and C407 cannot be targeted by SH reagents. The transporter has a preferential dimeric structure and catalyzes an antiport reaction which follows a simultaneous random mechanism. CONCLUSIONS: Critical residues of the substrate binding site of LAT1 have been probed. This site is not freely accessible by molecules other than substrate. Similarly to LeuT, K+ has some regulatory properties on LAT1. GENERAL SIGNIFICANCE: The collected data represent a solid basis for deciphering molecular mechanism underlying LAT1 function

Improving spatial landslide prediction with 3d slope stability analysis and genetic algorithm optimization: Application to the oltrepò pavese

In this study, we compare infinite slope and the three-dimensional stability analysis performed by SCOOPS 3D (software to analyze three-dimensional slope stability throughout a digital landscape). SCOOPS 3D is a model proposed by the U. S. Geological Survey (USGS), the potentialities of which have still not been investigated sufficiently. The comparison between infinite slope and 3D slope stability analysis is carried out using the same hydrological analysis, which is performed with TRIGRS (transient rainfall infiltration and grid-based regional slope-stability model)—another model proposed by USGS. The SCOOPS 3D model requires definition of a series of numerical parameters that can have a significant impact on its own performance, for a given set of physical properties. In the study, we calibrate these numerical parameters through a multi-objective optimization based on genetic algorithms to maximize the model predictability performance in terms of statistics of the receiver operating characteristics (ROC) confusion matrix. This comparison is carried out through an application on a real case study, a catchment in the Oltrepò Pavese (Italy), in which the areas of triggered landslides were accurately monitored during an extreme rainfall on 27–28 April 2009. Results show that the SCOOPS 3D model performs better than the 1D infinite slope stability analysis, as the ROC True Skill Statistic increases from 0.09 to 0.37. In comparison to other studies, we find the 1D model performs worse, likely for the availability of less detailed geological data. On the other side, for the 3D model we find even better results than the two other studies present to date in the scientific literature. This is to be attributed to the optimization process we proposed, which allows to have a greater gain of performance passing from the 1D to the 3D simulation, in comparison to the above-mentioned studies, where no optimization has been applied. Thus, our study contributes to improving the performances of landslide models, which still remain subject to many uncertainty factors

Pomological, sensorial, nutritional and nutraceutical profile of seven cultivars of Cherimoya (Annona cherimola Mill)

In this work, the food quality of four international (Campas, Chaffey, Fino de Jete and White) and three local (Daniela, Torre1 and Torre2) cultivars of Cherimoya (Annona cherimola Mill) was investigated. With this aim, pomological traits, sensorial attributes, physiochemical parameters (pH, total soluble content and total acidity), nutritional composition (macro- and micro-nutrients) and nutraceutical values (bioactive compounds, radical scavenging and antioxidant properties) were evaluated. Among the seven observed cultivars, Fino de Jete was identified as the best, not only for its commercial attributes such as pomological traits and physiochemical values, but also for its nutritional composition. On the other hand, Chaffey and Daniela were the cultivars with the highest content of polyphenols, proanthocyanidins, and with the strongest antioxidant capacity. Concerning the two local ecotypes, Torre1 and Torre2, they displayed a balanced nutritional profile that, if combined with their discrete nutraceutical, physicochemical and pomological values, may result in a reassessment of their commercial impact. In conclusion, our data provide interesting information about the pomological, nutritional, and nutraceutical properties of cherimoya fruits. Our results, in addition to promoting the commercial impact of local cultivars, may increase the use of individual cultivars in breeding programs

What if? Mouse proteomics after gene inactivation

The complex interactions among proteins and of proteins with small molecular weight protein ligands are overturned every time one of the components of the network is missing. For study purposes, animal models lacking one protein are obtained by experimental manipulation of the genome: in the knocking out approach, a gene is altered through the insertion of an artificial DNA sequence, which halts the transcription-translation sequence of events. In this review we have compiled the research papers that analyze the effects of knocking out individual genes on the proteomes of various tissues/organs throughout the body. We have gathered and organized all the available evidence and then compared the proteomic data in order to stress the context-specificity of the outcome every time two or more organs were investigated in the same KO mice. Finally, in a symmetrical approach to the above, we surveyed whether there is any obvious overlap among the effects of different KO on the same organ, marking affection of general pathways or lacking specificity of the gene targeting. Specific attention was put on the possible involvement of cellular stress markers