Search results for "Wren"
showing 10 items of 46 documents
Il pedone, dal viadotto alle greenway. Figure architettoniche del suolo per camminare in città, 1960-2015
2022
L’articolo traccia un quadro nel quale le fasi successive dell’architettura della città europea del Novecento si leggono attraverso il rapporto fra il pedone e la strada, e pone l’ipotesi che la condizione contemporanea di tale rapporto sia l’aggiornamento di un tema indicatore dell’evoluzione del ruolo della maglia viaria. Come ogni strada, la via pedonale è un’infrastruttura, in cui interagiscono l’idea di progresso, i modi di fabbricazione e consumo degli spazi urbani, nuovi orizzonti politici e di investimento economico, e che rinvia ad immaginari collettivi. A partire dall’inizio della pedonalizzazione, nei primi anni Sessanta, l’articolo discute in un’ottica comparativa e genealogica …
Exploiting transport properties for the detection of optical pumping in heavy ions
2020
We present a kinetic model for optical pumping in Lu$^+$ and Lr$^+$ ions as well as a theoretical approach to calculate the transport properties of Lu$^+$ in its ground $^1S_0$ and metastable $^3D_1$ states in helium background gas. Calculations of the initial ion state populations, the field and temperature dependence of the mobilities and diffusion coefficients, and the ion arrival time distributions demonstrate that the ground- and metastable-state ions can be collected and discriminated efficiently under realistic macroscopic conditions.
Atom-at-a-time laser resonance ionization spectroscopy of nobelium
2016
Resonance ionization spectroscopy of nobelium (atomic number 102) reveals its ground-state transition and an upper limit for its ionization potential, paving the way to characterizing even heavier elements via optical spectroscopy. Characterizing the heaviest elements in the periodic table is a gruelling task because they are radioactive, exist only for split seconds at a time and need to be artificially produced in sufficient quantities by complicated procedures. The heaviest element that has been characterized by optical spectroscopy is fermium, which has an atomic number of 100. Mustapha Laatiaoui et al. extend the methods used for fermium to perform optical spectroscopy on nobelium (ato…
Direct Mapping of Nuclear Shell Effects in the Heaviest Elements
2014
Quantum-mechanical shell effects are expected to strongly enhance nuclear binding on an "island of stability" of superheavy elements. The predicted center at proton number $Z=114,120$, or $126$ and neutron number $N=184$ has been substantiated by the recent synthesis of new elements up to $Z=118$. However the location of the center and the extension of the island of stability remain vague. High-precision mass spectrometry allows the direct measurement of nuclear binding energies and thus the determination of the strength of shell effects. Here, we present such measurements for nobelium and lawrencium isotopes, which also pin down the deformed shell gap at $N=152$.
Direct mass measurements of the heaviest elements with Penning traps
2013
Abstract Penning-trap mass spectrometry (PTMS) is a mature technique to provide atomic masses with highest precision. Applied to radionuclides it enables us to investigate their nuclear structure via binding energies and derived quantities such as nucleon separation energies. Recent progress in slowing down radioactive ion beams in buffer gas cells in combination with advanced ion-manipulation techniques has opened the door to access even the elements above fermium by PTMS. Such elements are produced in complete fusion–evaporation reactions of heavy ions with lead, bismuth, and actinide targets at very low rates. Pioneering high-precision mass measurements of nobelium and lawrencium isotope…
First ionization potential of the heaviest actinide lawrencium, element 103
2016
The first ionization potential (IP1 ) of element 103, lawrencium (Lr), has been successfully determined for the first time by using a newly developed method based on a surface ionization process. The measured IP 1 value is 4.9630.08 0.07 eV. This value is the smallest among those of actinide elements and is in excellent agreement with the value of 4.963(15) eV predicted by state-of-the-art relativistic calculations also performed in this work. Our results strongly support that the Lr atom has an electronic configuration of [Rn]7s 2 5f 14 7p 1 1/2 , which is influenced by strong relativistic effects. The present work provides a reliable benchmark for theoretical calculations and also opens t…
High-precision ab initio calculations of the spectrum of Lr$^+$
2019
The planned measurement of optical resonances in singly-ionised lawrencium (Z = 103) requires accurate theoretical predictions to narrow the search window. We present high-precision, ab initio calculations of the electronic spectra of Lr$^+$ and its lighter homologue lutetium (Z = 71). We have employed the state-of-the-art relativistic Fock space coupled cluster approach and the AMBiT CI+MBPT code to calculate atomic energy levels, g-factors, and transition amplitudes and branching-ratios. Our calculations are in close agreement with experimentally measured energy levels and transition strengths for the homologue Lu$^+$ , and are well-converged for Lr$^+$ , where we expect a similar level o…
Ethics and economics, friends or foes? An educational debate
2004
This paper reviews an ongoing debate about moral standards for vocational education in German speaking countries. At the centre of the controversy is the question of universalistic versus domain‐specific moral orientations, namely the question of whether business people ought to develop different moral points of view in different situations (such as ‘private’ versus ‘professional’). Of pivotal importance in this context is also a prominent ethical approach (by Karl Homann, a philosopher in the tradition of liberal economists) which serves as a foundation for those who advocate domain specificity and which is strongly criticized by their counterparts. This approach is also presented, since t…
BIOLOGY OF THE WREN, TROGLODYTES TROGLODYTES, IN A MEDITERRANEAN INSULAR AGROECOSYSTEM
2009
In the last years many species of birds have exploited urban and suburban habitats, taking opportunistically advantage of human presence for their niche parameters. The Wren is one of them and shows a high variability in the choice of nesting sites in the gardens of the outskirts of Palermo (Sicily). For many years the authors studied the breeding habits of this small bird, and thanks to the video-tape recordings on the nests, they were able to gather new information on its feeding habits and parental care. They could establish the role played by both parents, the different prey types carried to the chicks, and other data, scarcely known in the southern part of distribution of this passerin…
DIO SALVI IL RESTAURO. L’apporto inglese alla cultura della conservazione dei monumenti
2020
Sebbene già riuscissimo a percepire quanto rilevante fosse l’apporto inglese per aver contribuito alla definizione del restauro modernamente inteso, sino ad oggi mancavano ancora sia una chiara visione d’insieme delle articolate vicende connesse all'affermazione dei princìpi conservativi, sia una più approfondita conoscenza delle fonti documentarie, necessarie al fine di tracciare i profili culturali dei protagonisti e scandagliarne i contributi teorici. La ricostruzione delle vicende è sviluppata entro margini temporali estesi all'incirca per tre secoli, dalla fine del Seicento al principio del Nove-cento, e strutturata attraverso la traduzione e lo studio di testi perlopiù mai circolati i…