502 research outputs found
The structural life of a Cathedral and the worksites of the Duomo di Milano
The life of Milan Cathedral is described with the evolution of the structural system and the restorations carried out throughout the centuries. The organization of the Veneranda Fabbrica del Duomo di Milano is outlined, with the latest restoration interventions. The case study of the construction and restorations of the Tiburio with its supporting pillars is analyzed, from the initial design to the dramatic damage in the 20th century. The rebirth of the Cathedral was the fruit of restorations preserving the structural identity of the monument up to the present. The conclusions address the study of damage and maintenance and repair operations of mon-umental heritage buildings within a life cycle perspective, in relation to the underlying socie-tal values
A note on reaction to novel stimulus and restraint by therapeutic riding horses
Little research has been done to measure reactivity objectively in therapeutic riding horses (TRH). As individual reactivity and chronic stress could be assessed by exposing animals to acute, novel stressors, the authors of this work aimed at comparing reactions of TRHs and jumping horses (JH) to two challenges. Four TRHs and four JHs were exposed to a restraint covering their head with a hood for I h and to a startling stimulus (a 40 cm long, red and white synthetic holiday garland shaken with a rustling noise inside the box). Heart rate (HR) and heart rate variability (HRV) were recorded continuously and telemetrically, the reaction was video-recorded and analysed with a software for behavioural analysis. Blood samples were collected before and after each challenge to determine lymphocyte proliferation and other biochemical parameters. Horses spent most of the time immobile, during the challenges (p < 0.05). TRHs had a significantly higher average basal HR than JH (p < 0.05), probably due to their better condition. HR varied among different behaviours during the restraint (p < 0.05): the average HR during "pawing" was higher than during other behaviours (p < 0.005). A significant decrease in the proliferation of lymphocytes in samples taken after the removal of the hood (p < 0.05) was found, while the other stress related parameters did not vary significantly after the challenges. The authors conclude that TRHs did not react less than JHs to the new stimuli and this should be taken into consideration while planning their daily work and management
Large Magnetoresistance in Co/Ni/Co Ferromagnetic Single Electron Transistors
We report on magnetotransport investigations of nano-scaled ferromagnetic
Co/Ni/Co single electron transistors. As a result of reduced size, the devices
exhibit single electron transistor characteristics at 4.2K. Magnetotransport
measurements carried out at 1.8K reveal tunneling magnetoresistance (TMR)
traces with negative coercive fields, which we interpret in terms of a
switching mechanism driven by the shape anisotropy of the central wire-like Ni
island. A large TMR of about 18% is observed within a finite source-drain bias
regime. The TMR decreases rapidly with increasing bias, which we tentatively
attribute to excitation of magnons in the central island.Comment: 12 pages (including 4 figures). Accepted for publishing on AP
Theory of Tunneling Spectroscopy in a Mn Single-Electron Transistor by Density-Functional Theory Methods
We consider tunneling transport through a Mn molecular magnet using
spin density functional theory. A tractable methodology for constructing
many-body wavefunctions from Kohn-Sham orbitals allows for the determination of
spin-dependent matrix elements for use in transport calculations. The tunneling
conductance at finite bias is characterized by peaks representing transitions
between spin multiplets, separated by an energy on the order of the magnetic
anisotropy. The energy splitting of the spin multiplets and the spatial part of
their many-body wave functions, describing the orbital degrees of freedom of
the excess charge, strongly affect the electronic transport, and can lead to
negative differential conductance.Comment: 4 pages, 3 figures, a revised version with minor change
Spectral properties of a generalized chGUE
We consider a generalized chiral Gaussian Unitary Ensemble (chGUE) based on a
weak confining potential. We study the spectral correlations close to the
origin in the thermodynamic limit. We show that for eigenvalues separated up to
the mean level spacing the spectral correlations coincide with those of chGUE.
Beyond this point, the spectrum is described by an oscillating number variance
centered around a constant value. We argue that the origin of such a rigid
spectrum is due to the breakdown of the translational invariance of the
spectral kernel in the bulk of the spectrum. Finally, we compare our results
with the ones obtained from a critical chGUE recently reported in the
literature. We conclude that our generalized chGUE does not belong to the same
class of universality as the above mentioned model.Comment: 12 pages, 3 figure
Instability of antiferromagnetic magnons in strong fields
We predict that spin-waves in an ordered quantum antiferromagnet (AFM) in a
strong magnetic field become unstable with respect to spontaneous two-magnon
decays. At zero temperature, the instability occurs between the threshold field
and the saturation field . As an example, we investigate the
high-field dynamics of a Heisenberg antiferromagnet on a square lattice and
show that the single-magnon branch of the spectrum disappears in the most part
of the Brillouin zone.Comment: RevTeX, 4 pages, 3 figures, accepted to PR
Influence of cover crop termination on ground dwelling arthropods in organic vegetable systems
open7noA key aspect in cover crop management is termination before the cash crop is planted. The aim of this study was to assess the effects of termination methods on ground-dwelling arthropods. The conventional mechanical termination methodâi.e., green manuring by means of a disc harrowâwas compared to flattening using a roller crimper. Two different crop systems were investigated for two growing seasons; cauliflower was grown in autumn after the termination of a mixture of cowpea, pearl millet, and radish, and tomato was cropped in spring and summer after the termination of a mixture of barley and vetch. Ground beetles (Coleoptera: Carabidae), rove beetles (Coleoptera: Staphylinidae), and spiders (Araneae) were sampled by means of standard pitfall traps throughout the growing season of both cash crops. The roller crimper increased the overall abundance of ground beetles in the first growing season of both cash crops, whereas in the second year, no significant effect could be detected. Rove beetles were more abundant in plots where the cover crops were terminated by the roller crimper. Finally, green manuring increased the abundance of spiders, especially on the first sampling date after cover crop termination. Albeit different taxa showed different responses, the termination of cover crops by a roller crimper generally increased the abundance of ground dwelling arthropods. Given that most of the sampled species were generalist predators, their increased abundance could possibly improve biological control.openDepalo L.; Burgio G.; Magagnoli S.; Sommaggio D.; Montemurro F.; Canali S.; Masetti A.Depalo L.; Burgio G.; Magagnoli S.; Sommaggio D.; Montemurro F.; Canali S.; Masetti A
Forecasting in the light of Big Data
Predicting the future state of a system has always been a natural motivation
for science and practical applications. Such a topic, beyond its obvious
technical and societal relevance, is also interesting from a conceptual point
of view. This owes to the fact that forecasting lends itself to two equally
radical, yet opposite methodologies. A reductionist one, based on the first
principles, and the naive inductivist one, based only on data. This latter view
has recently gained some attention in response to the availability of
unprecedented amounts of data and increasingly sophisticated algorithmic
analytic techniques. The purpose of this note is to assess critically the role
of big data in reshaping the key aspects of forecasting and in particular the
claim that bigger data leads to better predictions. Drawing on the
representative example of weather forecasts we argue that this is not generally
the case. We conclude by suggesting that a clever and context-dependent
compromise between modelling and quantitative analysis stands out as the best
forecasting strategy, as anticipated nearly a century ago by Richardson and von
Neumann
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