A study of postponed replacement in a delay time model

We develop a delay time model for a one component system with postponed replacement to analyze situations in which maintenance might not be executed immediately upon discovery of a defect in the system. Reasons for postponement are numerous: to avoid production disruption or unnecessary or ineffective replacement; to prepare for replacement; to extend component life; to wait for an opportunity. This paper explores conditions that make postponement cost-effective. We are interested in modelling the reality in which a maintainer either prioritizes functional continuity or is not confident of the inspection test indicating a defective state. In some cases more frequent inspection and a longer time limit for postponement are recommended to take advantage of maintenance opportunities, characterized by their low cost, arising after a positive inspection. However, when the cost of failure increases, a significant reduction in the time limit of postponement interval is observed. The examples reveal that both the time to defect arrival and delay time have a significant effect upon the cost-effectiveness of maintenance at the limit of postponement. Also, more simply, we find that opportunities must occur frequently enough and inspection should be a high quality procedure to risk postponement

Imperfect inspection of a system with unrevealed failure and an unrevealed defective state

This paper proposes a model of inspection of a protection system in which the inspection outcome provides imperfect information of the state of the system. The system itself is required to operate on demand typically in emergency situations. The purpose of inspection is to determine the functional state of the system and consequently whether the system requires replacement. The system state is modeled using the delay time concept in which the failed state is preceded by a defective state. Imperfect inspection is quantified by a set of probabilities that relate the system state to the outcome of the inspection. The paper studies the effect of these probabilities on the efficacy of inspection. The analysis indicates that preventive replacement mitigates low quality inspection and that inspection is cost-effective provided the imperfect-inspection probabilities are not too large. Some derivative policies in which replacement is “postponed” following a positive inspection are also studied. An isolation valve in a utility network motivates the modeling

Conditional inspection and maintenance of a system with two interacting components

In this paper we consider the inspection and maintenance of a two-component system with stochastic dependence. A failure of component 1 may induce the defective state in component 2 which in turn leads to its failure. A failure of component 1 and a defect in component 2 are detected by inspection. Our model considers a conditional inspection policy: when component 1 is found to have failed, inspection of component 2 is triggered. This opportunistic inspection policy is a natural one to use given this stochastic dependence between the components. The long-run cost per unit time (cost-rate) of the conditional inspection policy is determined generally. A real system that cuts rebar mesh motivates the model development. The numerical examples reveal that when the ratio of the cost of corrective system replacement, that is on failure, to the cost of preventive system replacement is large there exists a finite optimum policy in most cases. Moreover, for the studied system wherein inspections of component 2 are expensive relative to those of component 1, having a reliable indicator of the defective state in component 2 is a good strategy to avoid costly failures of component 2, particularly when its time to failure is short

Evaluation of the postharvest quality of Cagaita fruits (Eugenia dysenterica DC.) coated with chitosan and associated with refrigeration

Cagaita fruits are subject to seasonality and perishability. This work aims to use scanning electron microscopy (SEM) to evaluate the physicochemical characteristics, texture, color and physical structure of cagaita fruits coated with different chitosan concentrations. The fruits were divided as follows: T0 (uncoated fruits), T1 (fruits coated with 1% (v/v) chitosan), T2 (fruits coated with 2% (v/v) chitosan) and T3 (fruits coated with 3% (v/v) chitosan). They were analyzed at 0, 10, 20 and 30 days of storage. Titratable acidity and soluble solids content showed no conservation of fruit characteristics; they showed better results for uncoated fruits, as well as weight loss, vitamin C and peak strain. The color of cagaita fruits confirmed ripening during storage regardless of treatment. Scanning electron microscopy showed that the film solution did not adhere, as desired, to the cell wall of fruits. As the results of fruits coated with 3% pectin were close to control, further studies should be carried out with higher coating percentages so that the fruit quality is maintained during storage.Keywords: Physical structure, film solution, quality, shelf life

CANAL DISH (CD), THE NEW ANTIMICROBIAL TESTING APPARATUS

Objective: This writing aims to introduce new antimicrobial test apparatus called Canal Dish (CD), theoretically.Methods: We have designed two types of CD such as Circular CD (CCD) and Square CD (SCD). Internally, the CCD is a 80 mm diameter circular while the SCD is a 80×80 mm square CD plate. Both of them contain 2(40×2) mm parallel travelling canals from the each CD-centre having radius of 3 mm. Canals are 6 mm in depth.Results: The features of CCD and SCD indicate possible allowance of various size, low media consuming, the inclusion of multiple microorganisms and/or test samples/doses, ease of handling; therefore, understanding, rapidity, and economy.Conclusion: CD may replace currently used Petri dishes due to its cost-effectiveness, rapidity, ease of handling and a wider range of applicability.Keywords: Antimicrobial assay, Canal dish, Circular, Square, New apparatu

MACERATION-VORTEX-TECHNIQUE (MVT), A RAPID AND NEW EXTRACTION METHOD IN PHYTO-PHARMACOLOGICAL SCREENING

Extraction is a process of preparation of extracts from biological materials (plant/animal/microorganism) in the essence of drug discovery and development scienticism. This writing is aimed at proposing a new, rapid, economical and easy extraction method, Maceration-Vortex-Technique (MVT). For this 2-5 g of powdered materials is sucked into 5-10 ml of solvent recommended for extraction. A cleaned, small amber-colored glass bottle of 20-25 ml capacity is needed for this purpose. Powdered materials are mixed with the solvent, then followed by shaking vigorously; shaken for 1.5-2 h and vortexed for 5 min. The extract is collected by immediate filtration through filter paper (Whatmann no. 1) and allowed for concentration and/or solvent partitioning. The MVT allows a 3 h extraction of plant materials. A small amount of extraction material is needed along with a small quantity of solvent which is a marker for the economy of this extraction process. In conclusion, rapidity in the extraction process is the rapidity in the screening process of biological materials. The MVT may be one of the speediest and most economical extraction processes.Keywords: Extraction, Maceration-Vortex-Technique, New method, Phyto-pharmacological screenin

COFFEE: A HEALTH FUEL-BLOT POPULAR DRINKING

Now, the days begin with cups of coffee worldwide. Caffeine is the main component of coffee, which is vastly consumed as a psychoactive agent, and in varieties of dietary supplements. Day by day coffee and caffeinated-consumption areas are expanding. Only a single cup of coffee contains thousands of biochemical. Otherwise, during roasting, some of which turn to convert other chemicals moieties. Thus, the coffee is an interesting item to the drug scientists. Upon this jackpot, a number of researches have been done on coffee and its chemical components; in which many postulations are still in contentious and some are unclear to the coffee users. Upon going through the stand-point, this study has been snapshot to sketch a complete overview on coffee and its components. Our finding depicts constituents of coffee to have antioxidant, anti-inflammatory, anti-Alzheimer's disease, anti-Parkinson's disease, and cardioprotective activities. But the anti-cancerous effect of coffee components is not clear yet. In conclusion, coffee, and its constituents are in important in phytopharmacological research.Keywords: Coffee, Coffee components, Health-effect

Possible oxidative effects of isotretinoin and modulatory effects of vitamins A and C in Saccharomyces cerevisiae

Isotretinoin (ITN), chemically known as 13-cis-retinoic acid, is a part of the broad group of compounds related to vitamin A. It is particularly employed in the treatment of nodular cystic acne and as an inhibitor of proliferation of neoplastic cells, by exerting a regulatory effect on the cell differentiation. This study aimed at investigating the possible oxidative effects of ITN and modulatory effects of vitamins A and C in mutant and non-mutant Saccharomyces cerevisiae strains. In addition, to reconfirm the oxidative effects, five in vitro antioxidant assays were also prepared taking the alpha-tocopherol analogue, trolox as a standard. In vivo study conducted on S. cerevisiae cells was carried out with ITN 20 μg/ml taking hydrogen peroxide (H2O2) as stressor (STR), whereas ITN 5 to 50 μg/ml was considered for in vitro assays taking similar dose of trolox (TRO). Results show ITN to have oxidative effect in both in vitro and in vivo tests. In conclusion, ITN produced oxidative effects and there may be an hypervitaminosis effect with vitamins A and C, thus insinuation to genetic material.Key words: Assay, isotretinoin, vitamin A, vitamin C, oxidative stress