The maximum weighted independent set (MWIS) problem is important since it occurs in various applications, such as facility location, selection of non-overlapping time slots, labeling of digital maps, ...etc. However, in real-life situations, input parameters within those models are often loosely defined or subject to change. For such reasons, this paper studies robust variants of the MWIS problem. The study is restricted to cases where the involved graph is a tree. Uncertainty of vertex weights is represented by intervals. First, it is observed that the max–min variant of the problem can be solved in linear time. Next, as the most important original contribution, it is proved that the min–max regret variant is NP-hard. Finally, two mutually related approximation algorithms for the min–max regret variant are proposed. The first of them is already known, but adjusted to the considered situation, while the second one is completely new. Both algorithms are analyzed and evaluated experimentally.
This work deals with the robust maximum weighted independent set problem, i.e. finding a subset of graph vertices that are not adjacent to each other and whose sum of weights is as large as possible. ...Uncertainty in problem formulation is restricted to vertex weights and expressed explicitly by a finite set of scenarios. Three criteria of robustness are considered: absolute robustness (max-min), robust deviation (min-max regret), and relative robustness (relative min-max regret). Since the conventional maximum weighted independent set problem is already NP-hard, finding the exact solution of its robust counterpart should obviously have a prohibitive computational complexity. Therefore, we propose an approximate algorithm for solving the considered robust problem, which is based on evolutionary computing and on various crossover and mutation operators. The algorithm is experimentally evaluated on appropriate problem instances. It is shown that satisfactory solutions can be obtained for any of the three robustness criteria in reasonable time.
Usutu virus (USUV) is an emerging arbovirus isolated in 1959 (Usutu River, Swaziland). Previously restricted to sub-Saharan Africa, the virus was introduced in Europe in 1996. While the USUV has ...received little attention in Africa, the virus emergence has prompted numerous studies with robust epidemiological surveillance programs in Europe. The natural transmission cycle of USUV involves mosquitoes (vectors) and birds (amplifying hosts) with humans and other mammals considered incidental (“dead-end”) hosts. In Africa, the virus was isolated in mosquitoes, rodents and birds and serologically detected in horses and dogs. In Europe, USUV was detected in bats, whereas antibodies were found in different animal species (horses, dogs, squirrels, wild boar, deer and lizards). While bird mortalities were not reported in Africa, in Europe USUV was shown to be highly pathogenic for several bird species, especially blackbirds (Turdus merula) and great gray owls (Strix nebulosa). Furthermore, neurotropism of USUV for humans was reported for the first time in both immunocompromised and immunocompetent patients. Epizootics and genetic diversity of USUV in different bird species as well as detection of the virus in mosquitoes suggest repeated USUV introductions into Europe with endemization in some countries. The zoonotic potential of USUV has been reported in a growing number of human cases. Clinical cases of neuroinvasive disease and USUV fever, as well as seroconversion in blood donors were reported in Europe since 2009. While most USUV strains detected in humans, birds and mosquitoes belong to European USUV lineages, several reports indicate the presence of African lineages as well. Since spreading trends of USUV are likely to continue, continuous multidisciplinary interventions (“One Health” concept) should be conducted for monitoring and prevention of this emerging arboviral infection.
In this paper, we determine the upper and lower bound for the total domination number and exact values and the upper bound for the double-total domination number on hexagonal grid H m , n with m ...hexagons in a row and n hexagons in a column. Further, we explore the ratio between the total domination number and the number of vertices of H m , n when m and n tend to infinity.
While it is clear that SARS CoV-2 coronavirus is the primary respiratory virus, there are no entirely clarified ways of transmission. Foodborne transmission has remained an unexplained path. ...Therefore, the goals of this paper are to examine and present an assessment of the most appropriate of the four selected kits for RNA extraction for the testing and detection of SARS-CoV-2 on food packaging surfaces, food surfaces, and in food. This will enable to indicate the possibility of infection through contact or direct food consumption.
Finding the best technique is vital as RNA extraction is one of the essential elements in detecting SARS-CoV-2. This was achieved through an experiment with four commercial kits following the original manufacturers' protocols, and with a modification of the original protocols that included the use of ethanol and isopropanol. The selected kit was used for RNA extraction from the swabs of packaging surfaces, food surface, and ready-to-eat food samples. The coronavirus was then identified using real-time reverse transcription-polymerase chain reaction (RT-PCR) assays to determine whether the SARS-CoV-2 virus or viral particles are present in the food chain with the overall purpose of demonstrating the possibility that food can contribute as a vehicle for the transmission of the virus.
The findings of this investigation made the most effective extraction kit and protocol stand out. The results of the applicability of the kit indicated a significant share of positive samples of viral SARS-CoV-2 virus particles on surfaces from the environment where infected persons with 'silent' COVID-19 infection, with mild symptoms or no symptoms, were present. However, according to the findings of the second part of the study, the virus was not detected on the examined samples of food packaging surfaces, food surfaces, and food.
The presented results distinguished one of the most suitable protocols for isolating RNA from environmental surface samples. The main contribution of the study is in the presentation of the results, that is, the examination of samples that are primarily related to the food chain, food packaging, food surfaces, and ready-to-eat food. The results of this study could also be helpful for further determination of the potential of food as a vector for the transmission of coronaviruses.
This paper deals with the maximum weighted independent set (MWIS) problem. We consider several robust variants of the MWIS problem on trees and prove that most of them are NP-hard. We propose a ...heuristic for solving the considered robust MWIS variants, which is customized for trees. We demonstrate by experiments that our algorithm produces high-quality solutions and runs much faster than a general-purpose optimization software.
The epidemiology of West Nile (WNV) and Usutu virus (USUV) has changed dramatically over the past two decades. Since 1999, there have been regular reports of WNV outbreaks and the virus has expanded ...its area of circulation in many Southern European countries. After emerging in Italy in 1996, USUV has spread to other countries causing mortality in several bird species. In 2009, USUV seroconversion in horses was reported in Italy. Co-circulation of both viruses was detected in humans, horses and birds. The main vector of WNV and USUV in Europe is
, however, both viruses were found in native
mosquito species (
). Experimental competence to transmit the WNV was also proven for native and invasive mosquitoes of
and
genera (
). Recently,
and
naturally-infected with USUV were reported. While neuroinvasive human WNV infections are well-documented, USUV infections are sporadically detected. However, there is increasing evidence of a role of USUV in human disease. Seroepidemiological studies showed that USUV circulation is more common than WNV in some endemic regions. Recent data showed that WNV strains detected in humans, horses, birds, and mosquitoes mainly belong to lineage 2. In addition to European USUV lineages, some reports indicate the presence of African USUV lineages as well. The trends in WNV/USUV range and vector expansion are likely to continue in future years. This mini-review provides an update on the epidemiology of WNV and USUV infections in Southern Europe within a multidisciplinary "One Health" context.
Molecular methods are increasingly being utilized for accurate identification of ticks (Acari: Ixodidae), especially in cases of morphologically highly similar species. In this study, we performed ...molecular research of the tick fauna in Croatia using DNA barcoding method. Ticks were sampled in three biogeographical regions and thirteen species were recorded: Dermacentor marginatus, Dermacentor reticulatus, Haemaphysalis concinna, Haemaphysalis inermis, Haemaphysalis punctata, Hyalomma marginatum, Ixodes frontalis, Ixodes hexagonus, Ixodes kaiseri, Ixodes ricinus, Rhipicephalus bursa, Rhipicephalus sanguineus s.l. and Rhipicephalus turanicus. Ixodes kaiseri is for the first time recorded in the fauna of Croatia. Of the thirteen hard tick species analyzed in this study, pathogens from different groups (bacteria, protozoa and viruses) have been detected in eight species in Croatia so far. For the important vector species R. sanguineus s.s., new distributional data for Croatia are given. The standard COI barcoding region was amplified, and the sequences were analyzed by species delimitation methods together with the sequences of conspecific and congeneric species from the public BOLD database. Our specimens of H. punctata represent a new, genetically distinct MOTU. A brief overview of the available public DNA barcoding data for Ixodidae is presented, highlighting the need for an integrative approach for the clarification of the taxonomic status of problematic Ixodid taxa. The results provide a basis for the establishment of a molecular data platform for the Ixodidae of the Croatian fauna.
In the period from 2015 to 2020, an entomological survey for the presence of West Nile virus (WNV) and Usutu virus (USUV) in mosquitoes was performed in northwestern Croatia. A total of 20,363 ...mosquitoes were sampled in the City of Zagreb and Međimurje county, grouped in 899 pools and tested by real-time RT-PCR for WNV and USUV RNA. All pools were negative for WNV while one pool each from 2016 (
), 2017 (
complex), 2018 (
complex), and 2019 (
complex), respectively, was positive for USUV. The 2018 and 2019 positive pools shared 99.31% nucleotide homology within the USUV NS5 gene and both clustered within USUV Europe 2 lineage. The next-generation sequencing of one mosquito pool (
complex) collected in 2018 in Zagreb confirmed the presence of USUV and revealed several dsDNA and ssRNA viruses of insect, bacterial and mammalian origin.
Background: Tahyna orthobunyavirus (TAHV) is a neglected mosquito-borne bunyavirus. Although the virus is widespread in continental Europe, TAHV infections are rarely reported. We analyzed the ...prevalence of TAHV in humans and different animal species as well as mosquitoes collected in urban areas of Zagreb and its surroundings in the period from 2020 to 2022. Methods: The study included 32 patients with neuroinvasive disease (NID), 218 asymptomatic individuals, 98 horses, 94 pet animals (dogs and cats), and 4456 Aedes vexans mosquitoes. Cerebrospinal fluid (CSF) and urine samples of patients with NID were tested for the TAHV RNA using a real-time reverse transcription-polymerase chain reaction (RT-qPCR). Human and animal serum samples were tested for TAHV-neutralizing (NT) antibodies using a virus-neutralization test (VNT). Mosquito pools were tested for TAHV RNA using an RT-qPCR. Results: TAHV NT antibodies were detected in 3/9.4% of patients with NID, 8/3.7% of asymptomatic individuals, 29/29.6% of horses, and 11/11.7% of pet animals. There was no difference in the seroprevalence according to age, sex, and area of residence in asymptomatic individuals. In addition, TAHV seropositivity did not differ according to age and sex in pet animals. None of the tested mosquito pools was TAHV RNA-positive. Conclusions: The presented results highlight the importance of interdisciplinary surveillance ("One Health") of this neglected viral zoonosis.
PDF
