325 research outputs found
Gli hedge fund: caratteristiche, impatto sui mercati e ruolo nelle crisi finanziarie
Gli hedge fund (HF) sono sempre pi`u diffusamente considerati responsabili
delle crisi finanziarie che si sono susseguite nel corso degli ultimi decenni. La loro natura
di segretezza e la fama di particolare propensione al rischio, unite ad un ampio ricorso alla leva
finanziaria, fanno si che questi operatori siano spesso indicati come principale causa dellaumento
della volatilit`a ed instabilit`a dei mercati o quantomeno in grado di accentuarne fortemente
le turbolenze. Per comprenderne correttamente il ruolo nelle situazioni di stress dei mercati, il
lavoro ne analizza dapprima la natura e le caratteristiche distintive: principali strategie di investimento
adottate, modalit`a di misurazione delle performance, struttura organizzativa tipica. Si
esaminano poi i vantaggi che tipicamente la dottrina e la prassi riconoscono alla loro operativit`
a: efficienza dei prezzi, liquidit`a dei mercati, innovazione innanzitutto. Si analizzano inoltre
gli aspetti critici connessi allattivit degli HF, soprattutto in relazione alle situazioni di turbolenza
dei mercati finanziari. Questa analisi `e essenziale per comprenderne il ruolo nellattuale crisi
globale. Lo studio si conclude con alcune riflessioni sul dibattito che divide la comunit finanziaria
circa lopportunit`a di introdurre misure specifiche di regolamentazione anche per lindustria
degli HF
Joint PDF modelling of turbulent flow and dispersion in an urban street canyon
The joint probability density function (PDF) of turbulent velocity and
concentration of a passive scalar in an urban street canyon is computed using a
newly developed particle-in-cell Monte Carlo method. Compared to moment
closures, the PDF methodology provides the full one-point one-time PDF of the
underlying fields containing all higher moments and correlations. The
small-scale mixing of the scalar released from a concentrated source at the
street level is modelled by the interaction by exchange with the conditional
mean (IECM) model, with a micro-mixing time scale designed for geometrically
complex settings. The boundary layer along no-slip walls (building sides and
tops) is fully resolved using an elliptic relaxation technique, which captures
the high anisotropy and inhomogeneity of the Reynolds stress tensor in these
regions. A less computationally intensive technique based on wall functions to
represent boundary layers and its effect on the solution are also explored. The
calculated statistics are compared to experimental data and large-eddy
simulation. The present work can be considered as the first example of
computation of the full joint PDF of velocity and a transported passive scalar
in an urban setting. The methodology proves successful in providing high level
statistical information on the turbulence and pollutant concentration fields in
complex urban scenarios.Comment: Accepted in Boundary-Layer Meteorology, Feb. 19, 200
Monitoring and modelling of soil–plant interactions: the joint use of ERT, sap flow and eddy covariance data to characterize the volume of an orange tree root zone
Abstract. Mass and energy exchanges between soil, plants and atmosphere control a number of key environmental processes involving hydrology, biota and climate. The understanding of these exchanges also play a critical role for practical purposes e.g. in precision agriculture. In this paper we present a methodology based on coupling innovative data collection and models in order to obtain quantitative estimates of the key parameters of such complex flow system. In particular we propose the use of hydro-geophysical monitoring via "time-lapse" electrical resistivity tomography (ERT) in conjunction with measurements of plant transpiration via sap flow and evapotranspiration (ET) from eddy covariance (EC). This abundance of data is fed to spatially distributed soil models in order to characterize the distribution of active roots. We conducted experiments in an orange orchard in eastern Sicily (Italy), characterized by the typical Mediterranean semi-arid climate. The subsoil dynamics, particularly influenced by irrigation and root uptake, were characterized mainly by the ERT set-up, consisting of 48 buried electrodes on 4 instrumented micro-boreholes (about 1.2 m deep) placed at the corners of a square (with about 1.3 m long sides) surrounding the orange tree, plus 24 mini-electrodes on the surface spaced 0.1 m on a square grid. During the monitoring, we collected repeated ERT and time domain reflectometry (TDR) soil moisture measurements, soil water sampling, sap flow measurements from the orange tree and EC data. We conducted a laboratory calibration of the soil electrical properties as a function of moisture content and porewater electrical conductivity. Irrigation, precipitation, sap flow and ET data are available allowing for knowledge of the system's long-term forcing conditions on the system. This information was used to calibrate a 1-D Richards' equation model representing the dynamics of the volume monitored via 3-D ERT. Information on the soil hydraulic properties was collected from laboratory and field experiments. The successful results of the calibrated modelling exercise allow for the quantification of the soil volume interested by root water uptake (RWU). This volume is much smaller (with a surface area less than 2 m2, and about 40 cm thick) than expected and assumed in the design of classical drip irrigation schemes that prove to be losing at least half of the irrigated water which is not taken up by the plants
Analysis of aroma and polyphenolic compounds in Saperavi red wine vinified in Qvevri
The purpose of this study is to analyze and characterize a Georgian red wine from Saperavi grape, obtained in Qvevri (Georgian traditional winemaking method), by using innovative techniques for the determination of the polyphenolic content, aroma, and its correlation to the sensory characteristics. This peculiar red wine, after high‐performance liquid chromatography with diode‐array detection and mass spectrometry (HPLC‐DAD‐MS), headspace solid‐phase microextraction–gas chromatography–mass spectrometry (HS‐SPME‐GC‐MS), and HS‐SPME‐GCxGC‐MS/TOF (two‐dimensional gas chromatography) chemical characterization showed a high polyphenol content (19.6 × 10(2) mg/L, 38.4% anthocyanins) and a wide range of volatile compounds, among which terpenes were associated with the aroma of flowers, lemongrass, and wood. Analyses were also conducted to determine the total polyphenol content correlated to antioxidant activity with the Folin–Ciocalteu spectrophotometric in vitro method (4.650 g GAE/L). In conclusion, for the first time on Saperavi wine, innovative techniques such as HPLC‐DAD‐MS, GC‐MS, and GCxGC‐MS/TOF were simultaneously applied in association with the traditional analytic techniques to perform a complete chemical characterization. These activities are part of a project about circular viticulture in the Georgian territory that will lead the production of traced quality wines and the valorization of the Georgian wine sector
2016 Central Italy Earthquakes: comparison between GPS signals and low-cost distributed MEMS arrays
Abstract. Modern seismic ground-motion sensors have reached an excellent
performance quality in terms of dynamic range and bandwidth resolution. The
weakest point in the recording of seismic events remains spatial sampling
and spatial resolution, due to the limited number of installed sensors. A
significant improvement in spatial resolution can be achieved by the use of
non-conventional motion sensors, such as low-cost distributed sensors arrays
or positioning systems, capable of increasing the density of classical
seismic recording networks. In this perspective, we adopted micro-electro
mechanical system (MEMS) sensors to integrate the use of standard
accelerometers for moderate-to-strong seismic events. In addition, we
analyse high-rate distributed positioning system data that also record soil
motion. In this paper, we present data from the 2016 Central Italy
earthquakes as recorded by a spatially dense prototype MEMS array installed
in the proximity of the epicentral area, and we compare the results to the
signal of local 1s GPS stations. We discuss advantages and limitations of
this joint approach, reaching the conclusion that such low-cost sensors and
the use of high rate GPS signal could be an effective choice for integrate
the spatial density of stations providing strong-motion parameters
Combining Models of Root-Zone Hydrology and Geoelectrical Measurements: Recent Advances and Future Prospects
Recent advances in measuring and modeling root water uptake along with refined electrical petrophysical models may help fill the existing gap in hydrological root model parametrization. In this paper, we discuss the choices to be made to combine root-zone hydrology and geoelectrical data with the aim of characterizing the active root zone. For each model and observation type we discuss sources of uncertainty and how they are commonly addressed in a stochastic inversion framework. We point out different degrees of integration in the existing hydrogeophysical approaches to parametrize models of root-zone hydrology. This paper aims at giving emphasis to stochastic approaches, in particular to Data Assimilation (DA) schemes, that are generally identified as the best way to combine geoelectrical data with Root Water Uptake (RWU) models. In addition, the study points out a more suitable objective function taken from the optimal transport theory that better captures complex geometry of root systems. Another pathway for improvement of geoelectrical data integration into RWU models using DA relies on the use of stem based methods as a leverage to introduce more extensive root knowledge into RWU macroscopic hydrological models
Understanding the dynamics of enhanced light non-aqueous phase liquids (LNAPL) remediation at a polluted site: Insights from hydrogeophysical findings and chemical evidence
This study intricately unfolds a pioneering methodology for remediating contaminants in a persistent light non-aqueous phase liquids (LNAPL)-contaminated site. The remediation strategy seamlessly integrates enhanced desorption and in-situ chemical oxidation (ISCO), orchestrating the injection of PetroCleanze® (a desorbent) and RegenOx® (an oxidizer) through meticulously designed wells. These injections, based on detailed geological and hydrogeological assessments, aim at mobilizing residual contaminants for subsequent extraction. Real-time subsurface dynamics are investigated through geophysical monitoring, employing electrical resistivity tomography (ERT) to trace reagent migration pathways via their effect on bulk electrical conductivity. The integration of groundwater sampling data aims at providing additional insights into the transformations of contaminants in the spatiotemporal context. Vivid two-dimensional time-lapse ERT sections showcase the evolution of resistivity anomalies, providing high-resolution evidence of the heterogeneity, dispersion pathways of desorbent and oxidant, and residual LNAPL mobilization. Hydrochemical analyses complement this, revealing effective mobilization processes with increasing aqueous concentrations of total petroleum hydrocarbons (TPH) over time. Speciation analysis unveils the intricate interplay of desorption and oxidation, portraying the dynamic fractionation of hydrocarbon components. The hydrogeophysical and data-driven framework not only delivers qualitative and quantitative insights into reagent and contaminant distribution but also enhances understanding of spatial and temporal physio-chemical changes during the remediation process. Time-lapse ERT visually narrates the reagent's journey through time, while chemical analyses depict the unfolding processes of desorption and oxidation across space and time. The coupling of hydrogeophysical and chemical findings pictures the transformations of pollutants following the sequence of product injection and the push and pull activities, capturing the removal of mobilized contaminants through hydraulic barrier wells. This enhanced understanding proves instrumental towards optimizing and tailoring remediation efforts, especially in heterogeneous environmental settings. This study establishes a new standard for a sophisticated and innovative contaminant remediation approach, advancing environmental practices through the harmonized analysis of geophysical and chemical data
Site adverse reactions after intramuscular injections in adults: review of literature
Trata-se de um “survey” descritivo, com o objetivo de verificar os estudos das áreas médica e de enfermagem, que tratam da temática: complicações pós-injeções intramusculares, publicados no período de janeiro de 1970 a agosto de 1997. Foi realizado levantamento bibliográfico, através dos bancos de dados MEDLINE E LILACS. Os artigos foram catalogados em fichas individuais e analisados de acordo com complicações relatadas, causas apontadas, número de casos e tipo de medicação utilizada. Foram encontrados dezoito artigos abordando a temática. A reação adversa mais relatada foi a dor, embora dos seiscentos e setenta (670) casos de pacientes investigados, 61 (sessenta e um) apresentaram os tipos mais diversos de complicações, tais como manchas avermelhadas no local, hipertemia, edema e outros. Na amostra investigada, não houve artigos descrevendo complicações na região ventroglútea, o que permite sugerir que isso deve ser a região prioritária de aplicação de injeções intramusculares. A técnica de aplicação das injeções é importante e exige atenção e cuidados de todos os profissionais, não devendo ser utilizada por pessoas sem orientação técnica e científica.This study was a descriptive survey. The objetive was to verify the medical and nursing literature published between January, 1970 and August, 1997 about adverse reactions afterintramuscular injections. The MEDLINE and LILACS databases were used. The articles were classified into individual bases and analyzed following the complications cited, causes, number of cases and the medication used. It was found eighteen articles. The adverse reaction more cited was pain, although others reactions were cited as dermatitis, fever and others. In the investigated sample there were not articles describing adverse reactions in the ventro-glútea site. This confirms that it isthe best site of intramuscular injections. The technique of the intramuscular injections is very important and it is necessary attention, responsibility, scientific and technical knowledge of the professionals
Intramuscular site complications after sodium diclofenac injections
O uso da injeção intramuscular na terapêutica medicamentosa envolve, na atualidade, uma série de aspectos como: desvantagens quanto ao local, reações adversas e complicações surgidas após as injeções. Este estudo tem o objetivo de relatar o caso de uma paciente com complicações pós-aplicação de dezoito injeções de Diclofenaco de Sódio. As complicações apresentadas foram dermatológicas e musculares. Ao final, são discutidos cuidados a serem tomados na aplicação de injeções intramusculares, em especial, no uso de Diclofenaco de Sódio, a fim de se evitarem mais casos de complicações, após administração de medicações por via intramuscular.The use of intramuscular injections involves some disadvantages in the site of the injectons as adverse reactions and complications after the injections. This study aims to report a case of a patient with complications after eighteen injections of Diclofenac Sodium. The complications presented were of dermatological level and in the muscles. Authors discussed technical procedures to the administration of injections, specially in the use of the Diclofenac Sodium in order, to minimize cases with complications after intramuscular injections
- …