Functionalized platinum nanoparticles with surface charge trigged by pH: synthesis, characterization and stability studies

In this work, the synthesis and characterization of functionalized platinum nanoparticles (PtNPs) have been investigated. PtNPs were obtained by a wet redox procedure using 2-diethylaminoethanethiol hydrochloride (DEA) as capping agent. By varying the Pt/thiol molar ratio, monodispersed and stable particles with diameters in the range of 3-40 nm were isolated. The amino functionality allows neutral particles to be obtained in basic water solution and positive charged nanoparticles in neutral or acidic water solution (pH 7-2), as confirmed by DLS and ζ-potential measurements. FTIR spectroscopy, FE-SEM, DLS and ζ-potential measurements confirmed the size and showed long term water stability (up to three months) of the colloidal system

High School Students’ Performances in Transitions between Different Representations of Linear Relationships in Mathematics and Physics

This study involved 643 high school students to assess their performance in using different representations of linear functions—graphs, tables, and algebraic relationships—in mathematics and kinematics. The results show that students encounter greater difficulties when they have to interpret representations involving algebraic relations in mathematics. Furthermore, it is shown how the ability to switch from one type of representation to another is influenced by spatial reasoning skills, orientation toward physics, and self-confidence in the field of mathematics and physics. Implications for teaching kinematics and linear functions are briefly discussed

Magnetic dipoles and electric currents

We discuss several similarities and differences between the concepts of electric and magnetic dipoles. We then consider the relation between the magnetic dipole and a current loop and show that in the limit of a pointlike circuit, their magnetic fields coincide. The presentation is accessible to undergraduate students with a knowledge of the basic ideas of classical electromagnetism.Comment: 7 pages, 1 figur

Dynamic images to address conceptual nodes about mechanical waves: Example materials and preliminary results of the experimentation of the teacher training module IMAGONDE

In the framework of the 2002-03 project “Fisica per la Formazione Culturale - FORMazione Insegnanti” funded by Italy ministry of Education, a set of training materials, focused on mechanical waves, has been developed. The core of the materials is represented by animated images purposely designed in order to: 1) address intrinsically dynamic aspects of one-dimensional impulses/waves propagation on a string; 2) have the trainees reflect upon students’ difficulties in reading/interpreting static images (as the ones which are featured in common textbooks) and animations. In this paper we discuss example materials concerning transversal impulses on strings to address conceptual nodes such as: 1) configuration of the string at a given time and its abstract representation; 2) displacement vs. time graph of a string element and its abstract representation; 3) relationships between the two abstract representations; 4) modelization of mechanical wave propagation in one dimension. Moreover the results of the experimentation of the training materials in the framework of the Post Graduate School to Became Physics Teacher in Secondary Schools are presented and commented

Formation and evolution of clumpy tidal tails around globular clusters

We present some results of numerical simulations of a globular cluster orbiting in the central region of a triaxial galaxy on a set of 'loop' orbits. Tails start forming after about a quarter of the globular cluster orbital period and develop, in most cases, along the cluster orbit, showing clumpy substructures as observed, for example, in Palomar 5. If completely detectable, clumps can contain about 7,000 solar masses each, i.e. about 10% of the cluster mass at that epoch. The morphology of tails and clumps and the kinematical properties of stars in the tails are studied and compared with available observational data. Our finding is that the stellar velocity dispersion tends to level off at large radii, in agreement to that found for M15 and Omega Centauri.Comment: LaTeX 2e, uses AASTeX v5.x, 40 pages with 18 figures. Submitted to The Astronomical Journa

The Supersymmetric Ward-Takahashi Identity in 1-Loop Lattice Perturbation Theory. I. General Procedure

The one-loop corrections to the lattice supersymmetric Ward-Takahashi identity (WTi) are investigated in the off-shell regime. In the Wilson formulation of the N=1 supersymmetric Yang-Mills (SYM) theory, supersymmetry (SUSY) is broken by the lattice, by the Wilson term and is softly broken by the presence of the gluino mass. However, the renormalization of the supercurrent can be realized in a scheme that restores the continuum supersymmetric WTi (once the on-shell condition is imposed). The general procedure used to calculate the renormalization constants and mixing coefficients for the local supercurrent is presented. The supercurrent not only mixes with the gauge invariant operator $T_\mu$. An extra mixing with other operators coming from the WTi appears. This extra mixing survives in the continuum limit in the off-shell regime and cancels out when the on-shell condition is imposed and the renormalized gluino mass is set to zero. Comparison with numerical results are also presented.Comment: 16 pages, 2 figures. Typos error correcte

Spitsbergen volume : Frontiers of Rationality

This volume contains 20 papers related to the workshop Frontiers of Rationality that was held in Longyearbyen, Spitsbergen, in July 2014

Geometry Diagnostics of a Stellar Flare from Fluorescent X-rays

We present evidence of Fe fluorescent emission in the Chandra HETGS spectrum of the single G-type giant HR 9024 during a large flare. In analogy to solar X-ray observations, we interpret the observed Fe K$\alpha$ line as being produced by illumination of the photosphere by ionizing coronal X-rays, in which case, for a given Fe photospheric abundance, its intensity depends on the height of the X-ray source. The HETGS observations, together with 3D Monte Carlo calculations to model the fluorescence emission, are used to obtain a direct geometric constraint on the scale height of the flaring coronal plasma. We compute the Fe fluorescent emission induced by the emission of a single flaring coronal loop which well reproduces the observed X-ray temporal and spectral properties according to a detailed hydrodynamic modeling. The predicted Fe fluorescent emission is in good agreement with the observed value within observational uncertainties, pointing to a scale height $\lesssim 0.3$\rstar. Comparison of the HR 9024 flare with that recently observed on II Peg by Swift indicates the latter is consistent with excitation by X-ray photoionization.Comment: accepted for publication on the Astrophysical Journal Letter

A detailed study of the rise phase of a long duration X-ray flare in the young star TWA 11B

We analyzed a long duration flare observed in a serendipitous XMM-Newton detection of the M star CD-39 7717B (TWA 11B), member of the young stellar association TW Hya (~ 8 Myr). Only the rise phase (with a duration of ~ 35 ks) and possibly the flare peak were observed. We took advantage of the high count-rate of the X-ray source to carry out a detailed analysis of its spectrum during the whole exposure. After a careful analysis, we interpreted the rise phase as resulting from the ignition of a first group of loops (event A) which triggered a subsequent two-ribbon flare (event B). Event A was analyzed using a single-loop model, while a two-ribbon model was applied for event B. Loop semi-lengths of ~ 4 R* were obtained. Such large structures had been previously observed in very young stellar objects (~ 1 - 4 Myr). This is the first time that they have been inferred in a slightly more evolved star. The fluorescent iron emission line at 6.4 keV was detected during event B. Since TWA 11B seems to have no disk, the most plausible explanation found for its presence in the X-ray spectrum of this star is collisional - or photo- ionization. As far as we are concerned, this is only the third clear detection of Fe photospheric fluorescence in stars other than the Sun.Comment: Accepted for publication in ApJ. 15 pages, 9 figure

Chemical–Physical, sensory analyses and consumers’ quality perception of local vs. imported loquat fruits: a sustainable development perspective

Local products and their distribution through short supply chains play a key role in the sustainable development of many rural areas, as affirmed by the 2030 Food and Agriculture Organization of the United Nations (FAO) Agenda. Moreover, in the last years, more and more consumers have shown a specific interest towards local production, pushed by the need for healthy eating, protecting the environment, and boosting the local economy. However, the cultivation of local fruit varieties or ecotypes has considerably decreased in the last decades because of their low production potential. As a result, many farmers have been forced to replace local orchards with few worldwide grown cultivars, causing a loss of genetic agrobiodiversity. For instance, in Italy, the loquat market is composed of imported cultivars and local grown autochthonous fruits (ecotype). Therefore, the aim of this study is to analyze the chemical–physical and sensory qualities, as well as the determinants of Italian consumer preference towards local ecotype of loquat fruit compared to imported varieties. Results show that local ecotypes result in excellent physico-chemical and sensory attributes, and that place of purchase and taste are the most important factors influencing consumers’ preference towards local loquats. Therefore, the cultivation of loquat ecotypes, together with effective marketing strategies, could increase the competitiveness of certain Italian rural areas, where this crop has always played a significant role in the economy