Fretting fatigue damage is a typical material damage arising in mechanical components. In such a damage condition, surface cracks can initiate at the surface contact zone, and under a fluctuating ...loading they can grow up to the complete failure of the component, resulting in a catastrophic failure.
In order to prevent/mitigate fretting fatigue damage, shot peening is widely used in mechanical components. The improvement due to shot peening is related to different factors, but the main one is the compressive residual stress field produced by such a treatment in a region near the contact surface. Unfortunately, both the uncertainty in measurements and stability (relaxation) of residual stress field, make shot peening effects difficult to be included in models aimed to the estimation of fatigue life. Due to this lack in the literature, especially relatively to the fretting fatigue field, in the present paper a new fretting fatigue model, that is able to consider shot peening residual stress and its relaxation, is presented. A 3D elastic-plastic finite element model, which incorporates the shot peening residual stress and its relaxations, is employed. The results obtained, in terms of stress field, are used as input data of a multiaxial stress-based criterion to estimate both fatigue lifetime and crack initiation direction.
•A new fretting fatigue model able to consider shot peening residual stress is presented.•The residual stability of the shot peening residual stress during fretting fatigue life is considered.•Results are compared with those coming from an experimental campaign performed on Al 7075-T651 specimens.•The model estimates well the fatigue life and crack initiation direction.
•Research on sustainable buildings is devoted to lightweight construction materials.•A cement-based mortar reinforced with date-palm mesh fibres is experimentally analysed.•Physical, mechanical and ...fracture properties are examined.•Effectiveness of fibres on the ductility/weight mortar performance is proved.
Nowadays, research on sustainable buildings is devoted to materials which offer advantages in terms of recyclability, low cost, environmentally-friendly features, no toxicity, biodegradability and good mechanical performance. The lightweight construction materials composed by a cement-based matrix reinforced with vegetal fibres are able to satisfy the above statements. In the present paper, the physical, mechanical and fracture properties of a cement-based mortar reinforced with date-palm mesh (DPM) fibres is experimentally analysed. The results obtained show that the positive effect of such fibres on the ductility/weight mortar performance increases by increasing the fibre content.
C1 inhibitor (C1-INH, also known as SERPING1) can be deficient in plasma as a result of genetic or acquired conditions, and this causes an episodic, local increase in vascular permeability in the ...subcutaneous and submucosal layers, identified as angioedema (hereditary or acquired). Bradykinin, the mediator of the increase in vascular permeability, is released on inappropriate activation of the contact system, which is controlled by C1 inhibitor. Therapy aims to reverse or prevent angioedema. Advances in understanding the complex effects of C1-INH deficiency at the molecular level have led to new molecular-targeted approaches. Three new treatments, an inhibitor of kallikrein to prevent bradykinin release, an antagonist of the bradykinin receptor to prevent its action and a recombinant human C1-INH produced in transgenic animals, are under clinical evaluation currently. Here, we review the molecular mechanisms underlying angioedema due to C1-inhibitor deficiency and clinical progress using molecular-targeted interventions.
Abstract
Carbapenem-resistant Enterobacteriaceae (CRE), Acinetobacter baumannii (CRAB), and Pseudomonas aeruginosa (CRPsA) are a serious cause of healthcare-associated infections, although the ...evidence for their control remains uncertain. We conducted a systematic review and reanalysis to assess infection prevention and control (IPC) interventions on CRE-CRAB-CRPsA in inpatient healthcare facilities to inform World Health Organization guidelines. Six major databases and conference abstracts were searched. Before-and-after studies were reanalyzed as interrupted time series if possible. Effective practice and organization of care (EPOC) quality criteria were used. Seventy-six studies were identified, of which 17 (22%) were EPOC-compatible and interrupted time series analyses, assessing CRE (n = 11; 65%), CRAB (n = 5; 29%) and CRPsA (n = 3; 18%). IPC measures were often implemented using a multimodal approach (CRE: 10/11; CRAB: 4/5; CRPsA: 3/3). Among all CRE-CRAB-CRPsA EPOC studies, the most frequent intervention components included contact precautions (90%), active surveillance cultures (80%), monitoring, audit and feedback of measures (80%), patient isolation or cohorting (70%), hand hygiene (50%), and environmental cleaning (40%); nearly all studies with these interventions reported a significant reduction in slope and/or level. The quality of EPOC studies was very low to low.
A systematic review and reanalysis found that infection prevention and control strategies including contact precautions, active surveillance cultures, monitoring, audit and feedback, patient isolation or cohorting, hand hygiene, and environmental cleaning were critical to the control of nosocomial carbapenem-resistant Enterobacteriaceae, Acinetobacter baumannii, and Pseudomonas aeruginosa.
To date the pathophysiology of COVID-19 remains unclear: this represents a factor determining the current lack of effective treatments. In this paper, we hypothesized a complex host response to ...SARS-CoV-2, with the Contact System (CS) playing a pivotal role in innate immune response. CS is linked with different proteolytic defense systems operating in human vasculature: the Kallikrein-Kinin (KKS), the Coagulation/Fibrinolysis and the Renin-Angiotensin (RAS) Systems. We investigated the role of the mediators involved. CS consists of Factor XII (FXII) and plasma prekallikrein (complexed to high-molecular-weight kininogen-HK). Autoactivation of FXII by contact with SARS-CoV-2 could lead to activation of intrinsic coagulation, with fibrin formation (microthrombosis), and fibrinolysis, resulting in increased D-dimer levels. Activation of kallikrein by activated FXII leads to production of bradykinin (BK) from HK. BK binds to B2-receptors, mediating vascular permeability, vasodilation and edema. B1-receptors, binding the metabolite des-Arg
-BK (DABK), are up-regulated during infections and mediate lung inflammatory responses. BK could play a relevant role in COVID-19 as already described for other viral models. Angiotensin-Converting-Enzyme (ACE) 2 displays lung protective effects: it inactivates DABK and converts Angiotensin II (Ang II) into Angiotensin-(1-7) and Angiotensin I into Angiotensin-(1-9). SARS-CoV-2 binds to ACE2 for cell entry, downregulating it: an impaired DABK inactivation could lead to an enhanced activity of B1-receptors, and the accumulation of Ang II, through a negative feedback loop, may result in decreased ACE activity, with consequent increase of BK. Therapies targeting the CS, the KKS and action of BK could be effective for the treatment of COVID-19.
Intestinal carriage with extended spectrum β-lactamase Enterobacteriaceae (ESBL-E) and carbapenemase-producing Enterobacteriaceae (CPE) can persist for months. We aimed to evaluate whether oral ...antibiotics followed by faecal microbiota transplantation (FMT) can eradicate intestinal carriage with ESBL-E/CPE.
Randomized, open-label, superiority trial in four tertiary-care centres (Geneva (G), Paris (P), Utrecht (U), Tel Aviv (T)). Non-immunocompromised adult patients were randomized 1: 1 to either no intervention (control) or a 5-day course of oral antibiotics (colistin sulphate 2 × 106 IU 4×/day; neomycin sulphate 500 mg 4×/day) followed by frozen FMT obtained from unrelated healthy donors. The primary outcome was detectable intestinal carriage of ESBL-E/CPE by stool culture 35–48 days after randomization (V4). ClinicalTrials.govNCT02472600. The trial was funded by the European Commission (FP7).
Thirty-nine patients (G = 14; P = 16; U = 7; T = 2) colonized by ESBL-E (n = 36) and/or CPE (n = 11) were enrolled between February 2016 and June 2017. In the intention-to-treat analysis 9/22 (41%) patients assigned to the intervention arm were negative for ESBL-E/CPE at V4 (1/22 not receiving the intervention imputed as positive) whereas in the control arm 5/17 (29%) patients were negative (one lost to follow up imputed as negative) resulting in an OR for decolonization success of 1.7 (95% CI 0.4–6.4). Study drugs were well tolerated overall but three patients in the intervention group prematurely stopped the study antibiotics because of diarrhoea (all received FMT).
Non-absorbable antibiotics followed by FMT slightly decreased ESBL-E/CPE carriage compared with controls; this difference was not statistically significant, potentially due to early trial termination. Further clinical investigations seem warranted.
•A fatigue strength assessment procedure for steels with inclusions is proposed.•Such a procedure implements a defect content analysis and the area-parameter model.•The multiaxial critical ...plane-based criterion by Carpinteri at al. is also implemented.•A return period optimisation, in terms of fatigue strength estimations, is performed.•An experimental campaign is analysed to evaluate the accuracy of the above procedure.
In the present paper, a procedure for fatigue strength assessment of high strength steel (AISI 4140) containing non-metallic inclusions (NMIs) is proposed. Such a procedure implements: (i) a defect content analysis, (ii) the area-parameter model, and (iii) the multiaxial critical plane-based criterion by Carpinteri at al. According to the defect content analysis, the distribution of NMIs is determined in two cross-sections perpendicular to the maximum principal stress directions under normal and shear uniaxial cyclic loadings. The return periods, obtained optimising the accuracy of the procedure in terms of fatigue strength estimation, are determined by taking into account five different prediction volumes. The results achieved through the proposed procedure are compared with both the experimental data and the results obtained employing the Carpinteri et al. criterion without optimisation.
The present research work deals with the fatigue assessment of an Al 7075-T651 subjected to fretting fatigue testing characterised by cylindrical contact. A small rolling of the pads is ...experimentally observed and, consequently, the contact surface stresses are different to the hertzian one. Therefore, the methodology, recently proposed by some of the present authors for the fatigue assessment of fretting-affected metallic components, is here employed for the first time in conjunction with a FE numerical model able to take into account the effect of the rolling of the pads, in order to find out both the crack nucleation orientation and the lifetime for each specimen of the experimental campaign analysed.
•Fretting fatigue-affected specimens made of Al 7075-T651 aluminium alloy are examined.•The specimens are subjected to cylindrical contact in partial slip regime.•FE models, either neglecting or incorporating the rolling, are employed.•The effect of the rolling of the pads on crack orientation and lifetime is analysed.
•The fatigue behaviour of Ductile Cast Iron specimens is theoretically investigated The critical plane-based multiaxial fatigue criterion by Carpinteri et al. is applied.•Both infinite and finite ...life fatigue tests, found in the literature, are simulated.•The fatigue endurance is estimated for both types of the examined tests.•The fatigue life assessment is carried out for finite life tests.
In the present paper, the fatigue behaviour of two Ductile Cast Irons (DCIs) is analyzed. Both infinite and finite life fatigue tests are simulated by employing the Carpinteri et al. criterion. Such tests, found in the literature, are related to DCI smooth specimens subjected to proportional and non-proportional constant amplitude cyclic loadings. The theoretical results are compared with the experimental ones in terms of both fatigue endurance and fatigue life.
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