Fractographic analysis of fatigue damage in 7000 aluminium alloys

In this paper, an attempt is made to correlate the fatigue damage in 7000 aluminium alloys with different impurity contents to the microstructural features and to explain their interdependence through fractographic observations. The Paris constants of these alloys in the form of hot-forged plates subjected to the overaged T73 temper are evaluated and differences in the fatigue crack growth rate described by striation spacing measurements. Scanning electron microscopy analysis of fatigue fracture surfaces revealed that the type and morphological parameters of coarse intermetallic particles play a critical role in fatigue crack growth behaviour. The elemental distribution determined by means of energy-dispersive spectroscopy analysis showed that the fractured particles accelerating the crack advances are larger particles of Fe-rich phases. The fatigue crack growth rate increases considerably with increasing amounts of these particles. The smaller η, S and Mg2Si particles contribute beneficially to fatigue life

Influence of notch radius and microstructure on the fracture behavior of Al-Zn-Mg-Cu alloys of different purity

The influence of notch radius on the fracture behavior of two high-strength Al-Zn-Mg-Cu alloys with different Fe content in the T73 condition was investigated. The fracture toughness tests were performed on non-fatigue-precracked notched bending specimens with different notch radii ranged from 0.15 mm to 1.0 mm. The obtained data were interpreted using the concept of Notch Fracture Mechanics combined with finite-element method (FEM) calculations. It was found that both alloys are very sensitive to the notch radius. The fracture toughness increases with increasing notch radius. For a given notch radii, the increase in fracture toughness is more significant for the more pure alloy. The fracture behavior of investigated alloys with respect to microstructural features and their relation with the fracture micromechanisms were analyzed

Genetic diversity of the haemagglutinin (HA) of human influenza a (H1N1) virus in montenegro : Focus on its origin and evolution.

In 2009 an influenza A epidemic caused by a swine origin H1N1strain, unusual in human hosts, has been described. The present research is aimed to perform the first phylogenetic investigation on the influenza virus A (H1N1) strains circulating in Montenegro, from December 1, 2009, when the first case of death due to H1N1 was confirmed, and the epidemic began causing a total of four fatalities. The phylogenetic analysis of the strains circulating showed the absence of a pure Montenegrin cluster, suggesting the occurrence of multiple re-introductions in that population from different areas till as far as the early 2010. The time to most recent common ancestor (TMRCA) for the complete dataset has been dated in early 2008, pre-dating the first Montenegrin identification of H1N1 infection. These data suggest that virus was spreading undetected, may be as a consequence of unidentified infections in returning travelers. Anyhow, the estimated TMRCA of Montenegrin strains is fully consistent to that found in different areas. Compatibly with the time coverage of the study period here analyzed, molecular dynamic of Montenegrin strains follows similar trend as in other countries

Phylogeographic Reconstruction of HIV Type 1B in Montenegro and the Balkan Region

Human immunodeficiency virus (HIV) is one of the most genetically variable human viruses as it is characterized by high rates of mutation, viral replication, and recombination. Phylodynamics is a powerful means of describing the behavior of an infection as a combination of evolutionary and ecological processes. Only a few studies of HIV-1 molecular epidemiology have so far been carried out in the Balkans. In this study, we used Bayesian methods to reconstruct the phylogeography and phylodynamics of HIV-1B in Montenegro and some other Balkan countries on the basis of pol gene sequences retrieved from a public database. The phylogenetic analysis showed that 43% of the isolates grouped in accordance with their geographic area, whereas the majority were interspersed in the tree, thus confirming the multiple introductions of HIV-1B in the Balkans. The Bayesian phylogeographic analysis suggested that HIV-1B entered the Balkans in the early 1970s probably through Greece and other Mediterranean tourist/travel destinations (such as Slovenia). Other Balkan countries, such as Bulgaria and Serbia, may have played an important role in spreading the infection to the entire Eastern Mediterranean area, and possibly to Northeast Europe. This suggests that the Balkans may have played a role as a "gateway" between Western and Eastern Europe

Hepatitis B virus genotype and subgenotype prevalence and distribution in Montenegro

The Mediterranean area and the Balkans in particular show the highest level of genetic heterogeneity of HBV in Europe. Data about the circulation of HBV genotypes in Montenegro are lacking. It was studied the prevalence and distribution of HBV genot/subgenotypes in a total of 150 HBV infected patients living in Montenegro. Phylogenetic analysis of 136 successfully amplified P sequences showed a high degree of genetic heterogeneity of HBV in Montenegro. Subgenotype D2 (36.8%) and D3 (32.3%) were the most prevalent, followed by genotype A (subgenotype A2 in all of the cases-19.8%). Eight patients were infected with recombinant strains. HBV-D1 which is the most spread HBV subgenotype in the south-eastern Mediterranean countries, seems to be relatively rare in Montenegro, suggesting a penetration of HBV more probably from North-East or West than from Eastern Mediterranean countries. The relatively different prevalence of D3 and A2 among subjects infected through sexual route, seems to confirm the association of these subgenotypes with different route of transmissions (mainly parenteral for D3 and mainly sexual for A2) even in Montenegro. The low prevalence of D2 among children and its absence in perinatal transmission, suggests that this subgenotype circulated prevalently in the past. If this is due to changes in the most prevalent way of transmission and in the recent different contacts of Montenegro with other European countries, it remains to be established by other larger studies

Genetic diversity of HIV type 1 in Montenegro

Human immunodeficiency virus type 1 (HIV-1) is characterized by high genetic variability due to its high replication rate and the lack of proofreading activity of the reverse transcriptase enzyme. On the basis of phylogenetic analysis performed on numerous isolates from all over the world, HIV-1 is subdivided into types, subtypes, subsubtypes, circulating recombinant forms, and unique recombinant forms. No data are currently available about the circulation of HIV-1 types in Montenegro. Here, we describe the genetic variability of HIV-1 strains identified in plasma samples of patients from Montenegro. Phylogenetic analysis on 32 HIV-1 sequences was carried out. The prevalent circulating HIV-1 subtype is B. The strains were interspersed within the tree. Two main clades (I and II) may suggest independent introductions of HIV-1 subtype B into Montenegro, although other epidemiological evidence will be needed to assume a small number of introductions. No obvious evidence of clustering by residence, age, or sex was found (data not shown). Nelfinavir resistance was found, though lopinavir is the only PI administered. Continuous monitoring of HIV-1-infected individuals is crucial to a better understand of the epidemiology of the B subtype in Montenegro

Hepatitis C virus genotype 3A in a population of injecting drug users in Montenegro: Bayesian and evolutionary analysis

Few reports are available on HCV molecular epidemiology among IDUs in Eastern Europe, and none in Montenegro. The aim of this study was to investigate the HCV genotype distribution in Montenegro among IDUs and to perform Bayesian and evolutionary analysis of the most prevalent HCV genotype circulating in this population. Sixty-four HCV-positive IDUs in Montenegro were enrolled between 2013 and 2014, and the NS5B gene was sequenced. The Bayesian analysis showed that the most prevalent subtype was HCV-3a. Phylogenetic data showed that HCV-3a reached Montenegro in the late 1990s, causing an epidemic that exponentially grew between the 1995 and 2005. In the dated tree, four different entries, from 1990 (clade D), 1994 (clade A) to 1999 (clade B) and 2001 (clade C), were identified. In the NS5B protein model, the amino acids variations were located mainly in the palm domain, which contains most of the conserved structural elements of the active site. This study provides an analysis of the virus transmission pathway and the evolution of HCV genotype 3a among IDUs in Montenegro. These data could represent the basis for further strategies aimed to improve disease management and surveillance program development in high-risk populations. © 2017 Springer-Verlag Wie

Reconstruction of the evolutionary dynamics of hepatitis C virus subtypes in Montenegro and the Balkan region

More than 20million hepatitis C virus (HCV) carriers live in the countries of the Eastern Mediterranean. We determined HCV genotype distribution among chronically infected patients in Montenegro and investigated the phylodynamics and phylogeography of the most represented HCV subtypes. The HCV-NS5b sequences of the Montenegrin patients were compared with sequences isolated in different known localities of the Mediterranean area, Europe and Asia. A Bayesian approach was used in order to allow the simultaneous estimate of the evolutionary rate, time-scaled phylogeny, demography and ancestral spatial status. The most frequent HCV subtypes among the Montenegrin patients, were 1b (34.7%) and 3a (24.7%), but there was also a significant prevalence of 1a and 4d (19.5%). Subtype 3a was significantly more frequent among younger patients and intravenous drug users (IDUs), whereas subtype 1b was more frequently associated with iatrogenic exposure and older ages. The spatio-temporal analysis of the epidemic suggested that HCV-1b penetrated Europe at the beginning of the XX century, probably through Greece and Cyprus and in the 1920s reached Montenegro, where there was an exponential increase in the effective number of infections between the 1950s and 1970s. The phylogeographic and phylodynamic analysis of HCV 3a showed that its most probable origin was in the Indian sub-continent (Pakistan in our reconstruction) about 300years ago. The evolutionary dynamics analysis showed that HCV-3a reached Montenegro more recently in the late 1970s and underwent multi-phasic growth still persisting. Our data suggest multiple introduction of HCV subtypes in the area, supported by different causes of dispersion: adverse social conditions and unsafe medical practices for HCV-1b and i.v. drug use for HCV-3a