Acquired angioedema

Acquired angioedema (AAE) is characterized by acquired deficiency of C1 inhibitor (C1-INH), hyperactivation of the classical pathway of human complement and angioedema symptoms mediated by bradykinin released by inappropriate activation of the contact-kinin system. Angioedema recurs at unpredictable intervals, lasts from two to five days and presents with edema of the skin (face, limbs, genitals), severe abdominal pain with edema of the gastrointestinal mucosa, life-threateing edema of the upper respiratory tract and edema of the oral mucosa and of the tongue. AAE recurs in association with various conditions and particularly with different forms of lymphoproliferative disorders. Neutralizing autoantibodies to C1-INH are present in the majority of patients. The therapeutic approach to a patient with AAE should first be aimed to avoid fatalities due to angioedema and then to avoid the disability caused be angioedema recurrences. Acute attacks can be treated with plasma-derived C1-INH, but some patients become non-responsive and in these patients the kallikrein inhibitor ecallantide and the bradykinin receptor antagonist icatibant can be effective. Angioedema prophylaxis is performed using antifibrinolytic agents and attenuated androgens with antifibrinolytic agents providing somewhat better results. Treatment of the associated disease can resolve AAE in some patients

Mechanical behaviour and phase transition mechanisms of a shape memory alloy by means of a novel analytical model

The aim of the present paper is to examine both the fatigue behaviour and the phase transition mechanisms of an equiatomic pseudo-elastic NiTi Shape Memory Alloy through cyclic tests (up to 100 loading cycles). More precisely, miniaturised dog-bone specimens are tested by using a customised testing machine and the contents of both austenite and martensite phase are experimentally measured by means of X-Ray diffraction (XRD) analyses. On the basis of such experimental results in terms of martensite content, an analytical model is here formulated to correlate the stress-strain relationship to the phase transition mechanisms. Finally, a validation of the present model by means of experimental data pertaining the stress-strain relationship is performed

contribution of date palm fibres reinforcement to mortar fracture toughness

Abstract The present paper aims to analyse the fracture behaviour of date-palm fibre-reinforced mortar. The vegetable fibres have been valorized over the last few years as a suitable reinforcement of cement-based matrixes used in non-structural applications. As a matter of fact, the desirable characteristics of such fibres (for instance, low environmental impact, biodegradability, low cost and density, and equitable stiffness and toughness) have led many designers to employ vegetable fibres in building composite materials. To the best knowledge of the authors, there are no studies in the literature related to the fracture behaviour of a cement-based mortar reinforced by a date-palm fibre mesh. In the present paper, the fracture behavior of a cement mortar reinforced by short fibres extracted from date-palm mesh is analysed. An experimental campaign is carried out on single edge-notched specimens, by examining five different values of fibre content. The experimental tests are performed under three-point bending loading and crack mouth opening displacement control. The Modified Two-Parameter Model proposed by the authors is herein adopted in order to compute the fracture toughness. Such a method is able to take into account the possible crack kinking occurring during the stable crack propagation, which is typical of quasi-brittle materials

A nonlocal elasticity theory to model the static behaviour of edge-cracked nanobeams

In the present paper, the mechanical behaviour of edge-cracked nanobeams under Mixed-Mode loading is analytically investigated by means of the Stress-Driven nonlocal model.  Firstly, the proposed formulation is outlined, and then applied to the case of a cantilever edge-cracked nanobeam.  A parametric study is performed by varying both the crack depth and the crack position along the beam axis.  Finally, the above formulation is applied to simulate some experimental tests available in the literature

A New Model to Derive the Transport Parameters in CZT Detectors with a Liner Decreasing Internal Electric Field

Charge collection efficiency and material transport properties in CdTe and CZT planar devices for X and gamma ray detection are commonly determined by means of the Hecht equation, under the limiting approximation of a uniform internal electric field. As an alternative, the Manys theory is helpful when surface recombination velocity of carriers has to be taken into account. Experiments carried out on planar detectors have shown a non constant, linearly decreasing profiles of the internal electric field and, in several cases, the electric field does not decrease down to zero but to a fixed value different and afterwards it result to be constant. A similar non-uniform electric field could be also expected when a high radiation flux hits the surface near the detector contacts. This fact could explains as photoconductivity measurements on these kinds of devices are often not so easy described by means of the Hecht theory. Last of all, the use of the Hecht or Manys equations to fit photoconductivity curves could lead to wrong conclusionsin the determination of μτ product. Starting from the Ramo-Shockley theorem, the authors calculate a new relation between charge collection efficiency and applied bias in the case of an electric field decreasing linearly along the detector thickness, being satisfied all the other Hecht hypotheses. The new functional dependence of charge collection efficiency on applied bias contains the slope of the electric field as a parameter and provides for the Hecht model as the special solution when the electric field is uniform. Moreover this model allows to fit with a very good accuracy experimental results on several our CZT detectors. The authors believe that this shape of field should be widespread in presence of diffused spatial charge and think that this model could be an important instrument for interpreting the data arising from pulsed photocurrent measures not only for CdTe and CZT detectors but also for other materials

Charge Correction in X and Gamma Ray Detectors Based on CZT

CZT, show some prerogatives as materials for X and gamma ray detection because of its properties, as high stopping power, good transport properties, and low leakage current even at room temperature. Nevertheless, despite the improvement in the grown techniques, its transport properties are limited, if compared with those of traditional materials for radiation detection. This fact leads to a reduction of spectroscopic properties especially when increases the penetration length of gamma-rays at high energies. Several methods have been proposed to link the interaction depth and the charge losses achieving good improvements in the spectroscopy but, in most cases, they produce only heuristic corrections without any clearly visible relation with some physical models. Bargholtz et al. have improved the spectroscopy digitizing the signals and fitting them with a model, but this method is very expensive in term of computing power because of the high number of fitting paramiters. In this work, we propose an hybrid approach to the problem. Once known the read-out electronic transfer function, the detector signal could be corrected using the photon impact depth (extracted from the discontinuity in the current signal) and the material transport parameters, obtained from two simple fitting procedure with only four free parameters for each fit. This method, based on the Zanio model, is not only useful to correct the charge losses but also to achieve the characteristic properties of CZT, because takes into account also the detrapping contribution. In the last year we have presented the results obtained with a simplified model, now we show those obtained with the complete model, with a more accurate fit that lead to a more precise measure of detrapping time. The transfer function used in the calculations is the one measured in our system; nevertheless the procedure employed and the calculation of the integral terms are immediately extendable to many other transfer function

fracture toughness of fibre reinforced concrete determined by means of numerical analysis

Abstract As is well-known, the addition of fibres to concrete mix (Fibre Reinforced Concrete, FRC) produces a positive effect on cracking behaviour. In this work, the results of an experimental campaign on FRC specimens with randomly distributed micro-synthetic polypropylene fibrillated fibres are examined. The tests concern single-notched beams under three-point bending, where the fibre content varies. Such an experimental testing is numerically analysed through a non-linear finite element model, named 2D-PARC, where a proper constitutive law for fibre-reinforced concrete is implemented. The load-crack mouth opening displacement (CMOD) curves numerically obtained are employed to determine the critical stress-intensity factor (fracture toughness) for different values of fibre content, according to the two-parameter model. The comparison between such numerical results and those obtained by applying the two-parameter model to the experimental load-CMOD curves is performed

Study of the interface shape of CdZnTe crystals grown by Vertical Bridgman for X-ray detector applications

CdZnTe crystals are currently used for the preparation of X-ray detectors. However, the large-scale exploitation of CdZnTe-based detectors is limited by the low single crystalline yield of the available growth techniques. In particular, two problems connected with the growth process seem to be critical. The first one concerns with the first part of the growth: due to the presence of tellurium structures in the melt above the melting point, superheating is necessary, causing difficulties to standard seeding procedures. For this reason, unseeded growth is usually preferred, with the consequence that at least the first part of the growth is characterized by polycrystalline material. The second problem is connected with the difficulty to obtain a convex growth interface, basically because of the low thermal conductivity of CdZnTe crystals. This fact favors the development of spurious nuclei at the crucible walls. Some of the authors have recently proposed a modification of the vertical Bridgman technique that makes use of a boron oxide layer covering the melt during the growth. In this work, the growth interface of several CdZnTe crystals grown by the vertical Bridgman technique, with and without the use of boron oxide to cover the charge, has been studied mainly by means of pholuminescence mapping, optical microscopy, and EDS microanalysis. The results show that, even in the presence of a vertical thermal gradient of about 10?C/cm, considered ideal for achieving a good crystallization of CdZnTe crystals, nucleation often starts not from the lower tip of the crucible, but rather from lateral crucible walls. This seems to be due to a local modification of the thermal gradient due to the presence of the molten charge, the crucible, and the crucible support. Moreover, while the first part of the main body of the crystal is characterized by a convex interface, the second half is characterized by a concave interface in the case of crystals grown without encapsulant. On the contrary, if the melt is covered by boron oxide, the interface is convex up to the end of the growth. The explanation of this experimental evidence can be found in the different thermal conductivity of boron oxide and vapor and in the fact that boron oxide separates the melt from the convective flows in the vapor

Lifetime estimation for 316 stainless steel specimens by using a critical plane approach

Abstract The lifetimes of 316 stainless steel specimens are herein evaluated using the multiaxial critical plane-based criterion by Carpinteri et al. for high-cycle fatigue (HCF) loading with constant amplitude. In the present paper, the stress-based version of such a criterion is applied to assess the results of experimental tests under HCF triaxial loading, the hollow cylindrical dog-bone specimens being subjected to a quenching heat treatment. The analytical results of fatigue life and initial crack plane orientation are compared with the experimental data