136 research outputs found
Magnus and Dyson Series for Master Integrals
We elaborate on the method of differential equations for evaluating Feynman
integrals. We focus on systems of equations for master integrals having a
linear dependence on the dimensional parameter. For these systems we identify
the criteria to bring them in a canonical form, recently identified by Henn,
where the dependence of the dimensional parameter is disentangled from the
kinematics. The determination of the transformation and the computation of the
solution are obtained by using Magnus and Dyson series expansion. We apply the
method to planar and non-planar two-loop QED vertex diagrams for massive
fermions, and to non-planar two-loop integrals contributing to 2 -> 2
scattering of massless particles. The extension to systems which are polynomial
in the dimensional parameter is discussed as well.Comment: 32 pages, 6 figures, 2 ancillary files. v2: references added, typos
corrected in the text and in the ancillary file
Soil conditions under a Fagus sylvatica CONECOFOR stand in Central Italy: an integrated assessment through combined solid phase and solution studies.
As soil solution represents the major phase of soil chemical reactions, its study is a powerful tool for ecological investigations. Soil solution chemical composition gives a realistic idea about the soil chemical components immediately available in the environment, mainly in relation to the soil ecosystem reaction to the disturbance due to acidifying loads. Within the CONECOFOR Program, the monitoring of forest soil conditions was performed in a level II plot (ABR I), under a Fagus sylvatica (European beech) stand, through the study of throughfall and soil solutions collected from depths ranging between the base of the litter layers and 90 cm. To be able to investigate solution contents of nutrients, acidifying agents and DOC throughout the profile, both zero tension and tension lysimeters were used. The first ones were inserted below the organic horizons, while tension lysimeters were placed within the mineral horizons at 15, 25, 55 and 90 cm depth. Sampled solutions were analyzed for Na, K, Ca, Mg, NH4, Cl, F, NO3, SO4, and DOC. The results evidence a clear seasonal pattern, mainly for macronutrients and inorganic N components. Acidic pulses were mostly evident below the organic horizons, in relation to strong nitric N releases from litter; these last were not always immediately neutralized by basic cations. Acid solutions leaving the organic horizons were invariably neutralized in the surface mineral horizons, within 15 cm depth. Temporal patterns of sulphate retention and release suggest that the soil has low retention capability for this anion. Such behaviour can be explained by the composition of the solid phase, where potential anion adsorbants appear strongly linked with organic matter in long residence time complexes. Sulphate and nitrate loading of this soil appear, anyway, to be mostly non-anthropogenic, but rather linked to natural mineralization pulses and, for sulphate, to aeolian solid transport from the south
Discharge variations of springs induced by strong earthquakes: the case of the mw 6.5 Norcia event (Italy, October 30 th 2016)
Earthquakes, dynamic strain, groundwater circulation, structural permeability
Outcome of liver transplantation with grafts from brain-dead donors treated with dual hypothermic oxygenated machine perfusion, with particular reference to elderly donors
Prompted by the utilization of extended criteria donors, dual hypothermic oxygenated machine perfusion (DâHOPE) was introduced in liver transplantation to improve preservation. When donors after neurological determination of death (DBD) are used, DâHOPE effect on graft outcomes is unclear. To assess DâHOPE value in this setting and to identify ideal scenarios for its use, data on primary adult liver transplant recipients from January 2014 to April 2021 were analyzed using inverse probability of treatment weighting, comparing outcomes of DâHOPEâtreated grafts (n = 121) with those preserved by static cold storage (n = 723). Endâischemic DâHOPE was systematically applied since November 2017 based on donor and recipient characteristics and transplant logistics. DâHOPE use was associated with a significant reduction of early allograft failure (OR: 0.24; 0.83; p = .024), grade â„3 complications (OR: 0.57; p = .046), comprehensive complication index (â7.20 points; p = .003), and improved patient and graft survival. These results were confirmed in the subset of elderly donors (>75âyearâold). Although DâHOPE did not reduce the incidence of biliary complications, its use was associated with a reduced severity of ischemic cholangiopathy. In conclusion, DâHOPE improves postoperative outcomes and reduces early allograft loss in extended criteria DBD grafts
The Alto Tiberina Near Fault Observatory (northern Apennines, Italy)
The availability of multidisciplinary and high-resolution data is a fundamental requirement to understand the physics of earthquakes and faulting. We present the Alto Tiberina Near Fault Observatory (TABOO), a research infrastructure devoted to studying preparatory processes, slow and fast deformation along a fault system located in the upper Tiber Valley (northern Apennines), dominated by a 60 km long low-angle normal fault (Alto Tiberina, ATF) active since the Quaternary. TABOO consists of 50 permanent seismic stations covering an area of 120 à 120 km2. The surface seismic stations are equipped with 3-components seismometers, one third of them hosting accelerometers. We instrumented three shallow (250 m) boreholes with seismometers, creating a 3-dimensional antenna for studying micro-earthquakes sources (detection threshold is ML 0.5) and detecting transient signals. 24 of these sites are equipped with continuous geodetic GPS, forming two transects across the fault system. Geochemical and electromagnetic stations have been also deployed in the study area. In 36 months TABOO recorded 19,422 events with ML †3.8 corresponding to 23.36e-04 events per day per squared kilometres; one of the highest seismicity rate value observed in Italy. Seismicity distribution images the geometry of the ATF and its antithetic/synthetic structures located in the hanging-wall. TABOO can allow us to understand the seismogenic potential of the ATF and therefore contribute to the seismic hazard assessment of the area. The collected information on the geometry and deformation style of the fault will be used to elaborate ground shaking scenarios adopting diverse slip distributions and rupture directivity models.PublishedS03275T. Sismologia, geofisica e geologia per l'ingegneria sismicaJCR Journa
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