THE OPTIMAL SYSTEM FOR SERIES SYSTEMS WITH WARM STANDBY COMPONENTS AND A REPAIRABLE SERVICE STATION

This paper deals with the reliability and availability characteristics of three different series system configurations with warm standby components and a repairable service station. The failure time of the primary and warm standby are assumed to be exponentially distributed with parameters and respectively. The repair time distribution of each server is also exponentially distributed with parameter . The breakdown time and the repair time of the service station are also assumed exponentially distributed with parameters and respectively. We derive the reliability dependent on time, availability dependent on time, the mean time to failure, , and the steady-state availability for three configurations and perform comparisons. Comparisons are made for specific values of distribution parameters and of the cost of the components. The three configurations are ranked based on: , and where is either or

Antimicrobial, and antibiofilm activities of silver doped hydroxyapatite: a novel bioceramic material for dental filling

Even though hydroxyapatite (HA) is the most common biocompatible material; it has limited antibacterial resistance. HA experiences a tailor-made structure depending on the desired applications. In this regard, silver (Ag) is of particular interest to inhibit wide spectrum of pathogenic bacteria and other microorganisms. Silver doped hydroxyapatite (Ag-HA) was developed via wet co-precipitation with subsequent hydrothermal processing to hinder the growth and multiplication of pathogenic microbes. Ag-HA demonstrated mono-dispersed nano-rods of 70 nm length and 7 nm diameters. Even though silver dopant induced stresses within the crystal lattice; Ag-HA maintained the crystallographic structure of HA with no change. Ag-HA nanocomposite demonstrated Ca/P value of 1.238 compared with 1.402 for virgin HA via XPS spectroscopy. The reduction of Ca/P value was correlated to the partial replacement of Ca+2 with Ag+1; Silver content was reported to be of 1 atomic %. Elemental mapping using EDAX confrmed uniform dispersion of silver ion within HA lattice. Antimicrobial results indicated that, Ag-HA nanocomposite demonstrated the most potent zone of inhibition (ZOI) against Staphylococcus aureus, and Candida albicans. Antibioflm results indicated that Ag-HA nanocomposite at 10.0 µg/mL, experienced the highest percentage for S. aureus and C. albicans of 96.09%, and 77.77%, respectively. Ag-HA nanocomposite demonstrated an excellent disinfectant agent once it had excited by UV light. In growth curve assay, the OD600 value of Ag- HA were lower, showing the repression impact on the growth of S. aureus. It was observed that the quantity of cellular protein discharged from S. aureus is directly proportional to the concentration of Ag-HA, which proves the antibacterial characteristics of the Ag-HA nanocomposite, and explains the creation of holes in the bacterial membrane producing the oozing out of the proteins from the S. aureus cytoplasm. Ag-HA nanocomposite achieved the complete lysis of the bacterial cell and cell malformation, decreasing the total viable number, so the outstanding antimicrobial results encouraged the tooth flling biomedical applications

Evaluation of the role of glutathione in the lead-induced toxicity in Saccharomyces cerevisiae

The effect of intracellular reduced glutathione (GSH) in the lead stress response of Saccharomyces cerevisiae was investigated. Yeast cells exposed to Pb, for 3 h, lost the cell proliferation capacity (viability) and decreased intracellular GSH level. The Pb-induced loss of cell viability was compared among yeast cells deficient in GSH1 (∆gsh1) or GSH2 (∆gsh2) genes and wild-type (WT) cells. When exposed to Pb, ∆gsh1 and ∆gsh2 cells did not display an increased loss of viability, compared with WT cells. However, the depletion of cellular thiols, including GSH, by treatment of WT cells with iodoacetamide (an alkylating agent, which binds covalently to thiol group), increased the loss of viability in Pb-treated cells. In contrast, GSH enrichment, due to the incubation of WT cells with amino acids mixture constituting GSH (l-glutamic acid, l-cysteine and glycine), reduced the Pb-induced loss of proliferation capacity. The obtained results suggest that intracellular GSH is involved in the defence against the Pb-induced toxicity; however, at physiological concentration, GSH seems not to be sufficient to prevent the Pb-induced loss of cell viability

Potential impact of iron oxide conjugated nano-fertilizer on growth, flowering and isozyme expression in Gardenia jasminoides

Nano-fertilizers protect the soil from the excessive addition of traditional fertilizers, enhancing the efficiency of the elements and diminishing the number of additive fertilizers. The effect of Fe2O3NPs-Boron (Fe2O3NPs-B), and Fe2O3 NP-Humic Acid (Fe2O3NPs-HA) at 100, 150 and 250 ppm, Fe2O3, and control (without any iron fertilizers) on the vegetative growth, flowering, photosynthetic pigments, nutrient element content and isozymes activity (peroxidase, superoxide dismutase and polyphenol oxide) of Gardenia jasminoides plants was investigated. Gamma-rays at 25 kGy were conducted for the promising synthesis of Fe2O3NPs-B, and Fe2O3NPs-HA. The experiment was carried out under greenhouse conditions during two successive seasons. The results stated that Fe2O3NPs-B and Fe2O3NPs-HA at the highest concentration (250 ppm) had a significant positive effect in all vegetative characteristics, photosynthetic pigments, nutrient element content and isozymes activity. Fe2O3NPs-HA showed the optimal result in all morphological and biochemical characteristics. The highest activity of enzymes appeared in the treated plants with Fe2O3 NPs-B followed by Fe2O3 NPs-HA at 250 ppm. The advantage nano-fertilizer usage may be summarized as saving the soil from the unreasonable accumulation of classic fertilizers, improving the use efficiency of parts and reducing the number of different fertilizers as a consequence of their increased surface area and their nano-size

The Efficacy of Na-Butyrate Encapsulated in Palm Fat on Experimentally Induced Necrotic Enteritis and Enumeration of intestinal resident Clostridium perfringens in Broiler Chickens

Abstract: Experimental induction of necrotic enteritis (NE) successfully achieved by daily oral inoculation o

Influence of some industrial wastes as a heavy aggregate on durability of concrete upon utilization in the special constructions

The aim of this study is to investigate the effect of some industrial wastes as a heavy aggregate on durability of the concrete after exposure to different effects. The coarse aggregates used to perform the concrete were dolomite (control) and lead slag, while fine aggregate were sand and lead slag aggregate. The physical and mechanical properties of use draw aggregates were determined also the physical and mechanical properties of different types of concrete were studied. The linear attenuation coefficients (μ) and half value layer (HVL) of gamma rays measurements have been carried out using γ-rays sources of Cs173 and Co60. Effect of sea water on the mechanical properties of high performance concrete; in addition, corrosion behavior of reinforcing steel embedded in concrete incorporating different aggregates upon exposure to sea water were studied. It was found that, the compressive strength for all concrete mixes made with dolomite and lead slag coarse aggregates satisfy the requirements of compressive strength for high performance concrete (grade-M60) after 28 days of curing in tap water. The results indicate that, the compressive strength values and gamma radiation shielding properties of concrete mix containing lead slag aggregate enhances upon replacing sand by fine portion of lead slag aggregate. The concrete mixes made with lead slag coarse aggregate proved their high endurance and could sustain sea water exposure, achieving compressive strength values exceeding grade M-60 concrete even after 6 months exposure. Lead slag concrete- in spite of its efficient durability-requires the incorporation of a corrosion inhibitor to counteract the hostile effect of the high sulfate concrete in the aggregate

Infection, colonization and shedding of Campylobacter and Salmonella in animals and their contribution to human disease: A review

Livestock meat and offal contribute significantly to human nutrition as sources of high‐quality protein and micronutrients. Livestock products are increasingly in demand, particularly in low‐ and middle‐income settings where economies are growing and meat is increasingly seen as an affordable and desirable food item. Demand is also driving intensification of livestock keeping and processing. An unintended consequence of intensification is increased exposure to zoonotic agents, and a contemporary emerging problem is infection with Campylobacter and Salmonella spp. from livestock (avian and mammalian), which can lead to disease, malabsorption and undernutrition through acute and chronic diarrhoea. This can occur at the farm, in households or through the food chain. Direct infection occurs when handling livestock and through bacteria shed into the environment, on food preparation surfaces or around the house and surroundings. This manuscript critically reviews Campylobacter and Salmonella infections in animals, examines the factors affecting colonization and faecal shedding of bacteria of these two genera as well as risk factors for human acquisition of the infection from infected animals or environment and analyses priority areas for preventive actions with a focus on resource‐poor settings

Oxalic acid, versatile peroxidase secretion and chelating ability of Bjerkandera fumosa in rich and limited culture conditions

Efficient ligninolytic systems of wood-degrading fungi include not only oxidizing enzymes, but also low-molecular-weight effectors. The ability of Bjerkandera fumosa to secrete oxalic acid and versatile peroxidase (VP) in nitrogen-rich and nitrogen-limited media was studied. Higher activity of VP was determined in the nitrogen-limited media but greater concentration of oxalic acid was observed in the cultures of B. fumosa without nitrogen limitation. Ferric ions chelating ability of Bjerkandera fumosa studied in ferric ions limited media was correlated with the increased level of oxalic acid. The presence of hydroxamate-type siderophores in B. fumosa media were also detected. Oxalate decarboxylase was found to be responsible for regulation of oxalic acid concentration in the tested B. fumosa cultures

Second asymptomatic carotid surgery trial (ACST-2): a randomised comparison of carotid artery stenting versus carotid endarterectomy

Background: Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence. Methods: ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligible if they had severe unilateral or bilateral carotid artery stenosis and both doctor and patient agreed that a carotid procedure should be undertaken, but they were substantially uncertain which one to choose. Patients were randomly allocated to CAS or CEA and followed up at 1 month and then annually, for a mean 5 years. Procedural events were those within 30 days of the intervention. Intention-to-treat analyses are provided. Analyses including procedural hazards use tabular methods. Analyses and meta-analyses of non-procedural strokes use Kaplan-Meier and log-rank methods. The trial is registered with the ISRCTN registry, ISRCTN21144362. Findings: Between Jan 15, 2008, and Dec 31, 2020, 3625 patients in 130 centres were randomly allocated, 1811 to CAS and 1814 to CEA, with good compliance, good medical therapy and a mean 5 years of follow-up. Overall, 1% had disabling stroke or death procedurally (15 allocated to CAS and 18 to CEA) and 2% had non-disabling procedural stroke (48 allocated to CAS and 29 to CEA). Kaplan-Meier estimates of 5-year non-procedural stroke were 2·5% in each group for fatal or disabling stroke, and 5·3% with CAS versus 4·5% with CEA for any stroke (rate ratio [RR] 1·16, 95% CI 0·86–1·57; p=0·33). Combining RRs for any non-procedural stroke in all CAS versus CEA trials, the RR was similar in symptomatic and asymptomatic patients (overall RR 1·11, 95% CI 0·91–1·32; p=0·21). Interpretation: Serious complications are similarly uncommon after competent CAS and CEA, and the long-term effects of these two carotid artery procedures on fatal or disabling stroke are comparable. Funding: UK Medical Research Council and Health Technology Assessment Programme