Response of porous SMA: a micromechanical study

Lately porous shape memory alloys (SMA) have attracted great interest as low weight materials characterized by high energy dissipation capability. In the present contribution a micromechanical study of porous SMA is proposed, introducing the simplifying hypothesis of periodic distribution of voids. The mechanical response of the heterogeneous porous medium is derived by performing nonlinear finite element micromechanical analyses considering a typical repetitive unit cell made of a circular hole in a dense SMA matrix and prescribing suitable periodicity and continuity conditions. The constitutive behavior and the dissipation energy capability of the porous Nitinol are examined for several porosity levels. Numerical applications are performed in order to test the ability of the proposed procedure to well capture the overall behavior and the key features of the special heterogeneous material

Subsidence due to crack closure and depressurization of hydrothermal systems: a case study from Mt Epomeo (Ischia Island, Italy)

Levelling surveys carried out between 1990 and 2003 on the Mt Epomeo resurgent block (Ischia Island) record negative dislocations on its northern and southern flanks with a maximum subsidence rate of 1.27 cm yr)1. This deformation is not associated with the cooling, crystallization or lateral drainage of magma and cannot be explained by a pressure point or prolate ellipsoid source. Results from dislocation models and the available structural and geochemical information indicate that the subsidence is due to crack closure processes along two main ENE–WSW and E–W preexisting faults, which represent the preferred pathway of CO2 degassing from the hydrothermal system located beneath Mt Epomeo. The monitoring of the dislocations and CO2 flux along these faults could give useful information on the dynamics of the hydrothermal system

Acoustic neuroma surgery and delayed facial palsy

Delayed onset of facial palsy is possibly an underestimated but distressing complication of acoustic neuroma surgery. The incidence of this complication reported in the literature has varied from 11.7 to 41%. This study reviewed retrospectively 60 primary acoustic neuroma surgeries performed by a single neurotologist. The dee-layed onset of facial dysfunction was defined according to the guidelines described by of Lalwani Butt, Jackler, Pitts and Jingling in 1995. They considered either a deterioration of facial function from normal to abnormal or an increased severity of the degree of facial paralysis, which was grouped using the House-Brackmann scale system. Fifteen of the 60 patients (25%) were found to have a deterioration of facial function. The incidence of delayed facial palsy was not influenced by age, sex or tumor size. The majority of the patients had a favorable prognosis. Only three patients had a grade III-IV facial function at 1 year. It is possible that these latter cases might have benefited from intraoperative meatal facial nerve decompression, as advocated by Sargent, Kartush and Graham

Ionospheric error analysis in gps measurements

The results of an experiment aimed at evaluating the effects of the ionosphere on GPS positioning applications are presented in this paper. Specifically, the study, based upon a differential approach, was conducted utilizing GPS measurements acquired by various receivers located at increasing inter-distances. The experimental research was developed upon the basis of two groups of baselines: the first group is comprised of "short" baselines (less than 10 km); the second group is characterized by greater distances (up to 90 km). The obtained results were compared either upon the basis of the geometric characteristics, for six different baseline lengths, using 24 hours of data, or upon temporal variations, by examining two periods of varying intensity in ionospheric activity respectively coinciding with the maximum of the 23 solar cycle and in conditions of low ionospheric activity. The analysis revealed variations in terms of inter-distance as well as different performances primarily owing to temporal modifications in the state of the ionosphere

Roles of Cholesteryl--Glucoside Transferase and Cholesteryl Glucosides in Maintenance of Helicobacter pylori Morphology, Cell Wall Integrity, and Resistance to Antibiotics

ABSTRACT Infection of the human stomach caused by Helicobacter pylori is very common, as the pathogen colonizes more than half of the world’s population. It is associated with varied outcomes of infection, such as peptic ulcer disease, gastric ulcers, and mucosa-associated lymphoid tissue lymphoma, and is generally considered a risk factor for the development of gastric adenocarcinoma. Cholesteryl glucosides (CGs) constitute a vital component of the cell wall of H. pylori and contribute to its pathogenicity and virulence. The hp0421 gene, which encodes cholesteryl-α-glucoside transferase (CGT), appears critical for the enzymatic function of integrating unique CGs into the cell wall of H. pylori, and deletion of this gene leads to depletion of CGs and their variants. Herein, we report that the deletion of hp0421 and consequent deficiency of cholesterol alter the morphology, shape, and cell wall composition of H. pylori cells, as demonstrated by high-resolution confocal microscopy and flow cytometry analyses of two different type strains of H. pylori, their isogenic knockouts as well as a reconstituted strain. Moreover, measurement of ethidium bromide (EtBr) influx by flow cytometry showed that lack of CGs increased cell wall permeability. Antimicrobial susceptibility testing revealed that the hp0421 isogenic knockout strains (Hp26695Δ421 and Hp76Δ421) were sensitive to antibiotics, such as fosfomycin, polymyxin B, colistin, tetracycline, and ciprofloxacin, in contrast to the wild-type strains that were resistant to the above antibiotics and tended to form denser biofilms. Lipid profile analysis of both Hp76 and Hp76Δ421 strains showed an aberrant profile of lipopolysaccharides (LPS) in the Hp76Δ421 strain. Taken together, we herein provide a set of mechanistic evidences to demonstrate that CGs play critical roles in the maintenance of the typical spiral morphology of H. pylori and its cell wall integrity, and any alteration in CG content affects the characteristic morphological features and renders the H. pylori susceptible to various antibiotics. IMPORTANCE Helicobacter pylori is an important cause of chronic gastritis leading to peptic ulcer and is a major risk factor for gastric malignancies. Failure in the eradication of H. pylori infection and increasing antibiotic resistance are two major problems in preventing H. pylori colonization. Hence, a deeper understanding of the bacterial survival strategies is needed to tackle the increasing burden of H. pylori infection by an appropriate intervention. Our study demonstrated that the lack of cholesteryl glucosides (CGs) remarkably altered the morphology of H. pylori and increased permeability of the bacterial cell wall. Further, this study highlighted the substantial role of CGs in maintaining the typical H. pylori morphology that is essential for retaining its pathogenic potential. We also demonstrated that the loss of CGs in H. pylori renders the bacterium susceptible to different antibiotics

Correlation between real geometry and tensile mechanical behaviour for Ti6Al4V electron beam melted thin specimens

The Electron Beam Melting (EBM) is an Additive Layer Manufacturing (ALM) technique used to directly manufacture 3D functional parts from metal powder, selectively melted, layer by layer, by an electron beam according to a geometry defined by a CAD model. The EBM technology allows benefitting from countless advantages: material waste reduction, easy manufacturing of complex shapes, lead time reduction, etc; on the other hand the EBM process is typically associated with lower resolutions and higher surface roughness (Ra = 25–30 μm) compared to similar laser based powder bed metal processes. Therefore the surface morphology may be a critical issue for the structural integrity of components made in EBM and used in-service in their “as built” condition, i.e. with the characteristic surface released by the process. This study evaluates surface morphology and tensile properties of Ti6Al4V specimens of varying nominal thickness (1–5.0 mm), made by using EBM process with a layer thickness of 50 μm. The aim is therefore to investigate how the surface morphology and the tensile properties are affected by the nominal thickness of the component

Investigating post-processing impact on fatigue performance of LPBF Ti6Al4V with heat treatment, high pressure heat treatment, and dry electropolishing strategies

This study investigates the impact of post-processing techniques on the fatigue behaviour of specimens in Ti6Al4V made by laser powder bed fusion (LPBF) for relevant applications, such as motorsport. Despite the LPBF advantages in terms of complex design and weight reduction, challenges such as reduced fatigue performance persist. Therefore, the application of post-processing treatments can play a critical role. In addition to traditional sandblasting (SB), three post-processing conditions were investigated to enhance mechanical properties under quasi-static and fatigue loading conditions: heat treatment (HT) and the innovative High Pressure Heat Treatment (HPHT) along with dry electropolishing (EP) treatment. The results indicate that both the HT and HPHT treatments produced a macrostructure with equiaxial grains composed of fine α + β lamellae. Mechanical analyses demonstrated that the HPHT-SB-EP condition exhibits properties comparable to those of forged Ti6Al4V used in the automotive field, with a good balance between strength and ductility. The EP treatment effectively reduced surface roughness and inherent surface irregularities caused by the LPBF process. The best fatigue results were achieved with the HPHT-SB-EP condition, despite data scattering. An increase in fatigue resistance was observed by using SB at a higher pressure

Metabolic Flexibility in Canine Mammary Tumors: Implications of Carnitine System

Deregulation of fatty acid catabolism provides an alternative energy source to glycolysis for cancer cell survival and proliferation. The regulator enzymes of the carnitine system (CS), responsible for the transport of fatty acids across mitochondrial membranes for β-oxidation are deregulated in tumorigenesis. Recently, we found that Carnitine Palmitoyl Transferase 1 (CPT1), a crucial regulator of CS components, is expressed and dysregulated in canine mammary tumor (CMT) tissues and cells. In this study, we examined the protein expression of the three remaining enzymes of CS (Carnitine Acylcarnitine Translocase (CACT), Carnitine Palmitoyl Transferase 2 (CPT2), Carnitine O-acetyltransferase (CrAT), in canine mammary cells and tissues by Western blot and immunohistochemistry. Protein expression of the components of CS was found in normal mammary glands and a concomitant deregulation of expression in CMT tissues that inversely correlated with the degree of tumor differentiation. Moreover, the expression and a different deregulation of CS-related proteins was also observed in CF33, CMT-U27, CMT-U309, and P114 cell lines used as in vitro model. These results demonstrate for the first time the expression of CS components in CMT tissues and cancer cells; however, further studies are needed to elucidate their roles in dogs as well

Hijacking SARS-CoV-2/ACE2 Receptor Interaction by Natural and Semi-synthetic Steroidal Agents Acting on Functional Pockets on the Receptor Binding Domain

The coronavirus disease 2019 (COVID-19) is a respiratory tract infection caused by the severe acute respiratory syndrome coronavirus (SARS)-CoV-2. In light of the urgent need to identify novel approaches to be used in the emergency phase, we have embarked on an exploratory campaign aimed at repurposing natural substances and clinically available drugs as potential anti-SARS-CoV2-2 agents by targeting viral proteins. Here we report on a strategy based on the virtual screening of druggable pockets located in the central β-sheet core of the SARS-CoV-2 Spike's protein receptor binding domain (RBD). By combining an in silico approach and molecular in vitro testing we have been able to identify several triterpenoid/steroidal agents that inhibit interaction of the Spike RBD with the carboxypeptidase domain of the Angiotensin Converting Enzyme (ACE2). In detail, we provide evidence that potential binding sites exist in the RBD of the SARS CoV-2 Spike protein and that occupancy of these pockets reduces the ability of the RBD to bind to the ACE2 consensus in vitro. Naturally occurring and clinically available triterpenoids such as glycyrrhetinic and oleanolic acids, as well as primary and secondary bile acids and their amidated derivatives such as glyco-ursodeoxycholic acid and semi-synthetic derivatives such as obeticholic acid reduces the RBD/ACE2 binding. In aggregate, these results might help to define novel approaches to COVID-19 based on SARS-CoV-2 entry inhibitors