198 research outputs found
Sinkhole genesis and evolution in Apulia, and their interrelations with the anthropogenic environment
Sinkhole development occurs in many areas of the world where soluble rocks crop out. Sinkholes are generally the surface expression of the presence of caves and other groundwater flow conduits in carbonate rocks, which are solutionally enlarged secondary permeability features. Their formation may be either natural or caused by man's activities. In both cases, heavy consequences have to be registered on the anthropogenic environment and related infrastructures. Knowledge of the mechanism of formation of this subtle geohazard is therefore necessary to planners and decision makers for performing the most appropriate and suitable programs of land use and development. <P style='line-height: 20px;'> The Apulia region of southern Italy is characterized for most of its extension by carbonate rocks, which makes it one of the most remarkable example of karst in the Mediterranean Basin. Based on analysis of literature and in situ surveys, including caving explorations, we have identified in Apulia three main types of possible mechanisms for sinkhole formation: 1) collapse of a chamber in a natural cave or in man-made cavities; 2) slow and gradual enlargement of doline through dissolution; 3) settlement and internal erosion of filling deposits of pre-existing dolines. Since sinkhole formation very often affects directly the human settlements in Apulia, and have recently produced severe damage, some considerations are eventually presented as regards the interrelationships between sinkholes and the anthropogenic environment
The recent floods in the Asso Torrent basin (Apulia, Italy): An investigation to improve the stormwater management
Stormwater management is of concern to public institutions and academies. In the Asso Torrent endorheic basin (Salento peninsula, Southern Italy), a network of natural and artificial channels crossing urban and rural areas and flowing towards six swallow karst holes, several floods occurred in the last six years, after the end of extensive hydraulic works. In this paper, the results of an observational study on the meteorological and hydrological factors concurring to these floods are reported. It was inferred that soil saturation, cumulative precipitation anticipating the events, and clogging of the swallow holes are of relevance and must be considered in the definition of new criteria in decision-making procedure. The adoption of both innovative modeling techniques and real-time control should be an efficient solution to properly regulate the flow control devices before and during the precipitation events. With a view to providing solutions for a sustainable management of the water resources, easy-to-implement measures are suggested, such as the selection of flood-tolerant crops and construction of harvesting systems for alternative water uses
Be Decay Anomaly and Light
In this proceedings, we discuss a light (17 MeV) solution to the anomaly
observed in the decay of Beryllium-8 by the Atomki collaboration. We detail an
anomaly free model with minimal particle content which can satisfy all other
experimental constraints with gauge couplings .Comment: Prepared for the 2019 EW session of the 54th Rencontres de Moriond,
talk presented by Simon Kin
Comments on Anomaly Cancellations by Pole Subtractions and Ghost Instabilities with Gravity
We investigate some aspects of anomaly cancellation realized by the
subtraction of an anomaly pole, stressing on some of its properties in
superspace. In a local formulation these subtractions can be described in terms
of a physical scalar, an axion and related ghosts. They appear to be necessary
for the unitarization of the theory in the ultraviolet, but they may generate
an infrared instability of the corresponding effective action, signalled by
ghost condensation. In particular the subtraction of the superanomaly multiplet
by a pole in superspace is of dubious significance, due to the different nature
of the chiral and conformal anomalies. In turn, this may set more stringent
constraints on the coupling of supersymmetric theories to gravity.Comment: 18 pages. Revised version. To appear in "Classical and Quantum
Gravity
Do radiolucent lines and stress shielding of the humeral shaft really matter in shoulder arthroplasty?
The purpose of this study is to evaluate at a mid-term follow up, the radiological survival of an
uncemented humeral stem in shoulder arthroplasty. One hundred and twenty-six replacements
including hemi (HA), total (TSA) and reverse (RSA) implanted from 1999 to 2008 were reviewed at
a mean follow up of 7.2 years (48-144 months). The same uncemented triconical stem (SMR, Lima
Corporate) was implanted. There were: 23 HSA, 43 TSA, 60 RSA. An independent observer evaluated
all the patients with Constant Score. A radiologic analysis by an expert radiologist and an orthopaedic
surgeon was performed: humeral component-bone interface was divided in seven zones. They judged
a mobilisation if a migration or tilt of the humeral implant or if≥ 2 mm radiolucent line in at least
three zones was present. Chi-squared test, Fisher test and analysis of variance were performed and
a p<0.05 was considered statistically significant. No major radiological signs of loosening and no tilt
or migration of the humeral component were found. Only 23 (18.2%) patients had no RL around the
humeral implant. In the remaining 103 (81.7%) implants: 96 (76.1%) presented RL less than 2 mm,
particularly 75 (59.5%) in less than 3 zones and 21 (16.6%) in more than 3 zones. Of the remaining 7
(5.5%) implants the presence of RL of 2 mm or greater in only one zone was seen. Apart from sepsis
no revision was performed for humeral component loosening. Although a high rate of RL, uncemented
humeral stem has an excellent survivorship at a mid-term follow up. Relationship between presence,
position and depth of RL and internal stress shielding is commonly observed but does not appear t
Meccanica quantistica e "lensing" gravitazionale
La deflessione della luce in un campo gravitazionale è una delle prove sperimentali più rilevanti della relatività generale. In questo contesto si discutono alcuni effetti della meccanica quantistica sulla propagazione dei fotoni in uno spazio-tempo curvo. In particolare si presentano le correzioni quantistiche del Modello Standard delle particelle elementari alla diffusione del fotone da una sorgente gravitazionale
Risk factors for recurrence in patients with Clostridium difficile infection due to 027 and non-027 ribotypes
Objectives: Our objective was to evaluate factors associated with recurrence in patients with 027+ and 027– Clostridium difficile infection (CDI). Methods: Patients with CDI observed between January and December 2014 in six hospitals were consecutively included in the study. The 027 ribotype was deduced by the presence of tcdB, tcdB, cdt genes and the deletion Δ117 in tcdC (Xpert® C. difficile/Epi). Recurrence was defined as a positive laboratory test result for C. difficile more than 14 days but within 8 weeks after the initial diagnosis date with reappearance of symptoms. To identify factors associated with recurrence in 027+ and 027– CDI, a multivariate analysis was performed in each patient group. Subdistributional hazard ratios (sHRs) and 95% confidence intervals (95%CIs) were calculated. Results: Overall, 238 patients with 027+ CDI and 267 with 027– CDI were analysed. On multivariate analysis metronidazole monotherapy (sHR 2.380, 95%CI 1.549–3.60, p <0.001) and immunosuppressive treatment (sHR 3.116, 95%CI 1.906–5.090, p <0.001) were factors associated with recurrence in patients with 027+ CDI. In this patient group, metronidazole monotherapy was independently associated with recurrence in both mild/moderate (sHR 1.894, 95%CI 1.051–3.410, p 0.033) and severe CDI (sHR 2.476, 95%CI 1.281–4.790, p 0.007). Conversely, non-severe disease (sHR 3.704, 95%CI 1.437–9.524, p 0.007) and absence of chronic renal failure (sHR 16.129, 95%CI 2.155–125.000, p 0.007) were associated with recurrence in 027– CDI. Conclusions: Compared to vancomycin, metronidazole monotherapy appears less effective in curing CDI without relapse in the 027+ patient group, independently of disease severity
Dilaton Interactions and the Anomalous Breaking of Scale Invariance of the Standard Model
We discuss the main features of dilaton interactions for fundamental and
effective dilaton fields. In particular, we elaborate on the various ways in
which dilatons can couple to the Standard Model and on the role played by the
conformal anomaly as a way to characterize their interactions. In the case of a
dilaton derived from a metric compactification (graviscalar), we present the
structure of the radiative corrections to its decay into two photons, a photon
and a , two gauge bosons and two gluons, together with their
renormalization properties. We prove that, in the electroweak sector, the
renormalization of the theory is guaranteed only if the Higgs is conformally
coupled. For such a dilaton, its coupling to the trace anomaly is quite
general, and determines, for instance, an enhancement of its decay rates into
two photons and two gluons. We then turn our attention to theories containing a
non-gravitational (effective) dilaton, which, in our perturbative analysis,
manifests as a pseudo-Nambu Goldstone mode of the dilatation current ().
The infrared coupling of such a state to the two-photons and to the two-gluons
sector, and the corresponding anomaly enhancements of its decay rates in these
channels, is critically analyzed.Comment: Revised version, 42 pages, 5 figure
Anomalous U(1) Models in Four and Five Dimensions and their Anomaly Poles
We analyze the role played by anomaly poles in an anomalous gauge theory by
discussing their signature in the corresponding off-shell effective action. The
origin of these contributions, in the most general kinematical case, is
elucidated by performing a complete analysis of the anomaly vertex at
perturbative level. We use two independent (but equivalent) representations:
the Rosenberg representation and the longitudinal/transverse (L/T)
parameterization, used in recent studies of of the muon and in the proof
of non-renormalization theorems of the anomaly vertex. The poles extracted from
the L/T parameterization do not couple in the infrared for generic anomalous
vertices, as in Rosenberg, but we show that they are responsible for the
violations of unitarity in the UV region, using a class of pole-dominated
amplitudes. We conclude that consistent formulations of anomalous models
require necessarily the cancellation of these polar contributions. Establishing
the UV significance of these terms provides a natural bridge between the
anomalous effective action and its completion by a nonlocal theory. Some
additional difficulties with unitarity of the mechanism of inflow in extra
dimensional models with an anomalous theory on the brane, due to the presence
of anomaly poles, are also pointed out.Comment: Revised final version, to appear on JHE
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