We use molecular dynamics simulations to investigate the material properties of cubic zinc blende Si
0.5
Ge
0.5
alloy nanowire (NW). We elucidate the effect of nanowire size, crystal orientations, ...and temperature on the material properties. We found that the reduction in the NW cross-sectional area results in lower ultimate tensile strength (UTS) and Young’s modulus. The 111 and 110 oriented NWs exhibit the highest fracture strength and fracture toughness, respectively. The increased temperature degrades the strength of the material and facilitates failure. The vacancy defects introduced via removal of either Si or Ge atoms exhibit similar behavior, and linear reduction of UTS and Young’s modulus are realized with an increased vacancy concentration. We observed intrinsic failure characteristics of the NW as insensitive to the temperature. Overall, the new understanding of material properties and failure characteristics of Si
0.5
Ge
0.5
NW elicited in this study will be a guide for designing Si–Ge-based nanodevices.
Graphical abstract
Infectious bursal disease virus (IBDV) of chickens is a birnavirus with a bi-segmented double-stranded RNA genome, the segments designated as A and B. We performed phylogenetic analysis using a ...366-bp fragment of segment A (nt 785-1150) and a 508-bp fragment of segment B (nt 328-835) of IBDV. A total of 463 segment A and 434 segment B sequences from GenBank, including the sequences of eight recent Bangladeshi isolates, were used in the analysis. The analysis revealed eight genogroups of segment A under serotype 1, designated as A1 (classical), A2 (US antigenic variant), A3 (very virulent), A4 (dIBDV), A5 (atypical Mexican), A6 (atypical Italian), A7 (early Australian) and A8 (Australian variant), and a single genogroup under serotype 2, designated as A0. On the other hand, segment B could be categorized into five genogroups irrespective of serotype, these being B1 (classical-like), B2 (very virulent-like), B3 (early Australian-like), B4 (Polish & Tanzanian) and B5 (Nigerian). Segment B of serotype 2 strains clustered within genogroup B1. With the bi-segmented genome of IBDV, these differences would allow for a total of 45 possible assortments. Based on the combinations of segment A and segment B genogroups observed in 463 IBDV strains, a total of 15 genotypes could be recognized. Recent Bangladeshi IBDV strains, isolated in 2016, appeared to be segment reassortants having segment A of genogroup A3 (very virulent) and segment B of genogroup B3 (early Australian-like). An extended system of nomenclature of IBDV strains is proposed.
Almost the full range of 16 haemagglutinin (HA) and nine neuraminidase subtypes of avian influenza viruses (AIVs) has been detected either in waterfowl, land-based poultry or in the environment in ...Bangladesh. AIV infections in Bangladesh affected a wide range of host species of terrestrial poultry. The highly pathogenic avian influenza (AI) H5N1 and low pathogenic AI H9N2 were found to co-circulate and be well entrenched in the poultry population, which has caused serious damage to the poultry industry since 2007. By reviewing the available scientific literature, the overall situation of AIVs in Bangladesh is discussed. All Bangladeshi (BD) H5N1 and H9N2 AIV sequences available at GenBank were downloaded along with other representative sequences to analyse the genetic diversity among the circulating AIVs in Bangladesh and to compare with the global situation. Three different H5N1 clades, 2.2.2, 2.3.2.1 and 2.3.4.2, have been detected in Bangladesh. Only 2.3.2.1a is still present. The BD LP H9N2 viruses mostly belonged to the H9 G1 lineage but segregated into many branches, and some of these shared internal genes with HP viruses of subtypes H7N3 and H5N1. However, these reassortment events might have taken place before introduction to Bangladesh. Currently, H9N2 viruses continue to evolve their HA cleavage, receptor binding and glycosylation sites. Multiple mutations in the HA gene associated with adaptation to mammalian hosts were also observed. Strict biosecurity at farms and gradual phasing out of live-bird markets could be the key measures to better control AIVs, whereas stamping out is not a practicable option in Bangladesh. Vaccination also could be an additional tool, which however, requires careful planning. Continuous monitoring of AIVs through systematic surveillance and genetic characterisation of the viruses remains a hallmark of AI control.
Infectious bronchitis (IB) is a highly contagious respiratory disease caused by a gammacoronavirus that has been circulating for many years in chickens in Bangladesh, resulting in significant ...economic losses. The aim of this study was to detect and characterize infectious bronchitis virus (IBV) from clinical outbreaks and surveillance samples. Real-time RT-PCR was used to detect IBV in pooled lung and tracheal tissue samples (n = 78), oropharyngeal swabs (n = 19), and pooled fecal samples (n = 13) from live-bird markets. Both respiratory and nephropathogenic forms of IB were suspected at necropsy (n = 7) from clinical outbreaks. Sequencing of hypervariable regions (HVR1-2 and HVR3) of the region of the spike gene (S) encoding the S1 subunit of five isolates revealed circulation of the Mass-like, QX-like, and 4/91-like genotypes of IBV in Bangladesh. Each genotype was extremely variable, as shown by separate clustering of the viruses in a phylogenetic tree and high nucleotide (nt) sequence divergence (38.8–41.2% and 25.7–37.4% in the HVR1-2 and HVR3 sequence, respectively). The unique mutation G65E was observed in each Mass-like isolate, and Y328S was observed in each 4/91-like Bangladeshi isolate. Three neutralizing epitope sites were predicted within the HVRs that differed significantly among the three genotypes. In addition, one Bangladeshi isolate carried fixed mutations at 294F and 306Y, like other pathogenic QX-like IBVs, which could affect epitopes involved in neutralization, facilitating virus circulation among vaccinated flocks. Therefore, continuous screening and genotype characterization will be necessary to track the epidemiology of IBV and control IB infection in Bangladesh.
Cadmium (Cd) is a pollutant that poses a health risk for humans and animals. Coral fossil (CF) acts as an adsorbent, yet limited knowledge is available on impacts of CF on Cd toxicities. The work was ...performed to figure out the effects of CF on hematobiochemical details and specific organs in Cd exposed broilers. The experiment was carried out with 45 broilers and were divided into three groups (15 in each). Group A was served as control. The birds in group B received Cd (75 mg /kg b. w.) orally. Whereas group C was orally supplemented with Cd (75 mg /kg b. w.) and CF (1 gm/kg b. w.). The trial was lasted for 30 days. For hematobiochemical analysis, blood samples were drawn, and sera were separated. Liver, kidney and muscle were collected to assess accumulation concentration. Brain, liver and kidney samples were also collected for histopathological study. The results showed that hematological parameters (TEC, Hb, PCV, MCV, MCH, MCHC and DLC) were altered by Cd but restored with CF supplementation. Liver (AST, ALT and ALP) and kidney (total protein and creatinine) biomarkers were increased significantly in Cd treated broilers while decreased significantly after CF supplementation. CF reduced accumulation concentration of Cd in liver, kidney and muscle. Cd intoxicated broilers showed degenerative changes in brain, hyperplastic bile duct and proliferation of renal tubular epithelium with focal degeneration and necrosis; and these were improved after CF supplementation. Therefore, it can be concluded that CF is a potential adsorbent against Cd toxicities.
Poultry production in Bangladesh has been experiencing H5N1 highly pathogenic avian influenza (HPAI) and H9N2 low pathogenic avian influenza (LPAI) for the last 14 years. Vaccination of chickens ...against H5 HPAI is in practice since the end of 2012. Subsequently, the official reporting of HPAI outbreaks gradually decreased. However, the true extent of circulation of avian influenza virus (AIV) in commercial poultry production is not clear. To explore this, we conducted active surveillance in 422 small‐scale commercial layer farms in 20 villages of Mymensingh and Tangail districts of Bangladesh during 2017 and 2018 for the presence of diseases with respiratory signs. A total of 88 farms with respiratory disease problems were identified and investigated during the surveillance. In addition, 22 small‐scale commercial layer farms in the neighbouring areas with respiratory disease problem were also investigated on request from the farmers. Pooled samples of oropharyngeal swabs from live birds or respiratory tissues from dead birds of the farm suffering from respiratory disease problem were tested for molecular detection of avian influenza virus (AIV), Newcastle disease virus (NDV), infectious bronchitis virus (IBV), infectious laryngotracheitis virus (ILTV), Mycoplasma gallisepticum and Avibacterium paragallinarum. A total of 110 farms (88 in the surveillance site and 22 in the neighbouring region) were investigated, and one or more respiratory pathogens were detected from 89 farms. AIV was detected in 57 farms often concurrently with other pathogens. Among these 57 farms, H5, H9, both H5 and H9 or non‐H5 and non‐H9 AIV were detected in 28, 9, 13 or 7 farms, respectively. Birds of most of the H5 AIV‐positive farms did not present typical clinical signs or high mortality. Twenty such farms were observed longitudinally, which had only 1.05%–5.50% mortality but a marked drop in egg production. This widespread circulation of H5 AIV along with H9 AIV and other pathogens in small‐scale commercial layer farms, often with low mortality, reaffirms the enzootic circulation of AIV in Bangladesh, which may escape syndromic surveillance focused on unusual mortality only. To reduce public health risks, strengthening of the control programme with comprehensive vaccination, enhanced biosecurity, improved surveillance and outbreak response is suggested.
Display omitted
•MD is used to study the tensile, and fracture mechanics of NC 2D SiC.•Effects of grain size on the stress–strain profile of the NC-SiC have been investigated.•The NC-SiC encounters a ...substantial degradation in mechanical properties relative to its single-crystal counterpart.•Fracture strength as a function of grain size can be characterized by the inverse pseudo Hall-Petch relation.•Increasing grain size brings about more elasticity in the structure, albeit at the price of fracture strain.
Two-dimensional Silicon Carbide (SiC) has opened the route to a cornucopia of advanced functionalities in the realm of quantum condensed matter. It holds great promise for highly efficient nanoelectronic, optoelectronic, renewable energy, and spintronic applications thanks to the confluence of a wide spectrum of mesmerizing physical properties like a wide direct bandgap with high exciton binding energy, robust spin–orbit-coupling, excellent photoluminescence, suitable mechanical strength, and thermodynamic stability. Nonetheless, it is still a daunting challenge to incorporate SiC in functional systems since extensive analyses of the mechanical properties, and fracture mechanism of nanocrystalline (NC)-SiC is still obscure. In this light, this work is an attempt to report detailed information concerning the room-temperature tensile mechanical properties and fracture phenomena of NC-SiC executing Molecular Dynamics (MD) simulations. In particular, effects of grain size on the stress–strain profile, fracture strength, fracture strain, and Young’s modulus of the NC-SiC have been thoroughly investigated. It has been found that the strength as a function of grain size can be characterized by the inverse pseudo Hall-Petch relation. Increasing grain size brings about more elasticity in the structure, albeit at the price of fracture strain. The NC-SiC encounters a substantial degradation in mechanical properties relative to its single-crystal counterpart. Afterward, we performed an exhaustive fracture analysis on two NC-SiC samples of different grain sizes. The single-crystal SiC can endure more tensile strain before rupture compared to that of the NC-SiC. At last, the nanosheet exhibits more immunity to fracture with decreasing grain size. This study would lay the groundwork for NC-SiC to be successfully realized in functional systems as well as serving as a solid roadmap for engineering the mechanical properties of nanocrystalline materials.
Growth kinetics of a Vero cells adapted Bangladeshi strain of
peste des petits ruminants
virus was studied in Vero cells to determine maximum virus yield. One-step growth curve was formulated after ...determining virus in both supernatant (CFV) and cell lysate (CAV) at different time categories by microtitre plate titration in Vero cells and the viral presence was confirmed by real-time RT-PCR. The virus was first detected in both the supernatants and cell pellets at 12 hpi. The virus titre reached its plateau at 72 hpi. Maximum virus titre of CAV was 6.2 log
10
TCID
50
/ml and that of CFV was 5.2 log
10
TCID
50
/ml at 72 hpi. After that, the titer gradually declined, but maintained at 4.5 log
10
TCID
50
/ml in case of CAV and 4.2 log
10
TCID
50
/ml in case of CFV at 96 hpi. It was concluded that the optimum time point for harvesting Vero cell culture is 72 hpi.
Domestic waterfowl play an important role in the perpetuation and transmission of avian pathogens including avian influenza viruses (AIV) of low and high pathogenicity, which pose severe economic and ...public health concerns in Bangladesh. This study focused on active surveillance of several avian viral pathogens with a special reference to AIV in selected backyard duck populations in Bangladesh. A total of 500 pooled oropharyngeal and cloacal samples from individual ducks of four districts were tested by real time PCRs for the presence of AIV, avian avulavirus-1, anatid herpesvirus-1, avian parvovirus, avian bornavirus and avian coronavirus. The investigation identified 27 (5.4%) ducks positive for AIV and 12 (2.4%) positive for avian coronavirus. In 13 samples, RNA specific for AIV H4N6 was detected. Phylogenetic analysis of the AIV haemagglutinin H4 and neuraminidase N6 genes suggested a clustering of Bangladeshi AIV H4N6 in Eurasian lineage group 2. Other AIV positive samples had very low virus loads (Cq > 36) and were not subtyped. Coronaviral sequences of a fragment of the polymerase gene were related to Eurasian-Australian duck gamma-coronaviruses. Our current active surveillance in free-range domestic backyard ducks in Bangladesh failed to detect highly pathogenic (HP) AIV in contrast to our previous passive monitoring study. Nevertheless, active monitoring of domestic duck populations may be important to highlight presence and transmission dynamics of economically less important AIV that still may serve as reassortment partners for the generation of new HP and zoonotic AIV.
RESEARCH HIGHLIGHTS
Active surveillance for viral pathogens in domestic free-range backyard ducks.
Detection of avian influenza virus subtype H4N6.
First identification of avian gammacoronavirus in ducks in Bangladesh.
Avian influenza virus (AIV) remains a huge challenge for poultry production with negative repercussions for micro- and macro-economy and public health in Bangladesh. High (HP) H5N1 and low ...pathogenicity (LP) H9N2 AIV are currently endemic in poultry, and both have been reported to infect humans sporadically. Multiple virus introductions of different clades of HPAIV H5N1, reassorted genotypes, and on-going diversification of LPAIV H9N2 create a highly volatile virological environment which potentially implicates increased virulence, adaptation to new host species, and subsequent zoonotic transmission. Allotropy of poultry rearing systems and supply chains further increase the risk of virus spreading, which leads to human exposure and fosters the emergence of new potentially pre-pandemic virus strains. Here, we review the epidemiology, focusing on (i) risk factors for virus spreading, (ii) viral genetic evolution, and (iii) options for AIV control in Bangladesh. It is concluded that improved control strategies would profit from the integration of various intervention tools, including effective vaccination, enhanced biosecurity practice, and improved awareness of producers and traders, although widespread household poultry rearing significantly interferes with any such strategies. Nevertheless, continuous surveillance associated with rapid diagnosis and thorough virus characterization is the basis of such strategies.
PDF
