Bulk Damage Effects in Irradiated Silicon Detectors due to Clustered Divacancies

High resistivity silicon particle detectors will be used extensively in experiments at the future CERN Large Hadron Collider where the enormous particle fluences give rise to significant atomic displacement damage. A model has been developed to estimate the evolution of defect concentrations during irradiation and their electrical behaviour according to Shockley-Read-Hall (SRH) semiconductor statistics. The observed increases in leakage current and doping concentration changes can be described well after gamma irradiation but less well after fast neutron irradiation. A possible non-SRH mechanism is considered, based on the hypothesis of charge transfer between clustered divacancy defects in neutron damaged silicon detectors. This leads to a large enhancement over the SRH prediction for V2 acceptor state occupancy and carrier generation rate which may resolve the discrepancy

Attraction between DNA molecules mediated by multivalent ions

The effective force between two parallel DNA molecules is calculated as a function of their mutual separation for different valencies of counter- and salt ions and different salt concentrations. Computer simulations of the primitive model are used and the shape of the DNA molecules is accurately modelled using different geometrical shapes. We find that multivalent ions induce a significant attraction between the DNA molecules whose strength can be tuned by the averaged valency of the ions. The physical origin of the attraction is traced back either to electrostatics or to entropic contributions. For multivalent counter- and monovalent salt ions, we find a salt-induced stabilization effect: the force is first attractive but gets repulsive for increasing salt concentration. Furthermore, we show that the multivalent-ion-induced attraction does not necessarily correlate with DNA overcharging.Comment: 51 pages and 13 figure

CarniDIET 1.0: a database of terrestrial carnivorous mammal diets

Motivation A species’ diet is central to understanding many aspects of its biology, including its behaviour, movement, and ecological niche. The diets of terrestrial carnivorous mammals, defined here as species primarily consuming other mammals (hereafter, mammal‐consumers), have been extensively studied and can vary in the proportion of different food types, and species, consumed across their geographic ranges. Accessibility to data capturing such variation in diets of mammal‐consumers across the variety of ecosystems they occur in would provide valuable information for conservation, and open research avenues for macroevolution and macroecology. However, data on mammal‐consumer diets across their geographic ranges have not been systematically collated. Here, we present CarniDIET (version 1.0), an open‐access database containing quantitative data on the diets of terrestrial mammal‐consumers collated from the literature. Main types of variable contained Diet records capturing the percentage of mammalian prey, to the highest taxonomic resolution available, and non‐mammalian food types (e.g., birds, invertebrates) in the diets of mammal‐consumers at specific sites and times. Associated data with each diet record include, where available, age and sex of mammal‐consumer, sample size, sample origin, and quantification method as well as spatial and temporal variables including dates, season, study site, altitude and coordinates. Spatial location and grain Global, terrestrial. The spatial grain varies among sites from 0.03 to 100,000 km2, with a median of 170 km2. Study centroids are provided as latitude‐longitude coordinates. Time period and grain Original diet samples were collected between 1933 and 2017, with half of studies collected between 1994 and 2008. Studies summarize diets from 1 month to 66 years, with a median of 1 year. Major taxa and level of measurement Terrestrial carnivorous mammals that primarily consume other mammals (103 species). Studies generally represent species’ population averages, although can include demographic breakdowns

Investigating students’ mental models and knowledge construction of microscopic friction. I. Implications for curriculum design and development

In this paper, we discuss the first phase of a multiphase study aimed at investigating the dynamics of students’ knowledge construction in the context of unfamiliar physical phenomenon—microscopic friction. The first phase of this study involved the investigation of the variations in students’ mental models of microscopic friction. Clinical interviews were conducted with 11 students enrolled in conceptual modern physics to elicit their ideas and generate themes of explanations. A phenomenographic approach of data analysis was employed to establish the variations in students’ explanations. Results show that students’ mental models of friction at the atomic level are dominated by their macroscopic experiences. Friction at the atomic level according to most students is due to mechanical interactions (interlocking or rubbing of atoms)