Increased consumption, larger scale production and more efficient distribution of fresh produce over the past two decades have contributed to an increase in the number of illness outbreaks caused by ...this commodity. Pathogen contamination of fresh produce may originate before or after harvest, but once contaminated produce is difficult to sanitize. The prospect that some pathogens invade the vascular system of plants and establish “sub-clinical” infection needs to be better understood to enable estimation of its influence upon risk of human illness. Conventional surface sanitation methods can reduce the microbial load, but cannot eliminate pathogens if present. Chlorine dioxide, electrolyzed water, UV light, cold atmospheric plasma, hydrogen peroxide, organic acids and acidified sodium chlorite show promise, but irradiation at 1 kGy in high oxygen atmospheres may prove to be the most effective means to assure elimination of both surface and internal contamination of produce by pathogens. Pathogens of greatest current concern are Salmonella (tomatoes, seed sprouts and spices) and Escherichia coli O157:H7 on leafy greens (spinach and lettuce). This review considers new information on illness outbreaks caused by produce, identifies factors which influence their frequency and size and examines intervention effectiveness. Research needed to increase our understanding of the factors influencing microbial safety of fresh produce is addressed.
► Pre- and post-harvest environments are significant sources of pathogens. ► Pathogens of greatest current concern are Salmonella and Escherichiacoli O157:H7. ► E. coli O157:H7 and Salmonella can survive in soil and on produce for long periods. ► Bacterial harborage and biofilm formation complicate efforts to sanitize produce. ► Low dose irradiation at high O2 may control pathogens on produce.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A thermodynamic equilibrium analysis on the multi-reaction system for carbon dioxide reforming of methane in view of carbon formation was performed with Aspen plus based on direct minimization of ...Gibbs free energy method. The effects of CO2/CH4 ratio (0.5–3), reaction temperature (573–1473K) and pressure (1–25atm) on equilibrium conversions, product compositions and solid carbon were studied. Numerical analysis revealed that the optimal working conditions for syngas production in Fischer–Tropsch synthesis were at temperatures higher than 1173K for CO2/CH4 ratio being 1 at which about 4mol of syngas (H2/CO=1) could be produced from 2mol of reactants with negligible amount of carbon formation. Although temperatures above 973K had suppressed the carbon formation, the moles of water formed increased especially at higher CO2/CH4 ratios (being 2 and 3). The increment could be attributed to RWGS reaction attested by the enhanced number of CO moles, declined H2 moles and gradual increment of CO2 conversion. The simulated reactant conversions and product distribution were compared with experimental results in the literatures to study the differences between the real behavior and thermodynamic equilibrium profile of CO2 reforming of methane. The potential of producing decent yields of ethylene, ethane, methanol and dimethyl ether seemed to depend on active and selective catalysts. Higher pressures suppressed the effect of temperature on reactant conversion, augmented carbon deposition and decreased CO and H2 production due to methane decomposition and CO disproportionation reactions. Analysis of oxidative CO2 reforming of methane with equal amount of CH4 and CO2 revealed reactant conversions and syngas yields above 90% corresponded to the optimal operating temperature and feed ratio of 1073K and CO2:CH4:O2=1:1:0.1, respectively. The H2/CO ratio was maintained at unity while water formation was minimized and solid carbon eliminated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
► RD can has several advantages over conventional production of biodiesel. ► H3PW12O40·6H2O as a catalyst alleviates the neutralization problem. ► This process is environmentally friendly. ► RSM ...based on CCD was used to design the experiment and analyzed operating parameters.
This study aims to develop an optimal continuous process to produce fatty acid methyl esters (biodiesel) from waste cooking oil in a reactive distillation column catalyzed by a heteropolyacid, H3PW12O40·6H2O. The conventional production of biodiesel in the batch reactor has some disadvantage such as excessive alcohol demand, short catalyst life and high production cost. Reactive distillation combines reaction and separation to simplify the process operation. The reaction catalyzed by H3PW12O40·6H2O overcomes the neutralization problem that occurs in conventional transesterification of waste cooking oil with high free fatty acid (FFAs) and water content. Response surface methodology (RSM) based on central composite design (CCD) was used to design the experiment and analyzed four operating parameters: total feed flow, feed temperature, reboiler duty and methanol/oil ratio. The optimum conditions were determined to be 116.23 (mol/h) total feed flow, 29.9°C feed temperature, 1.3kW reboiler duty, and 67.9 methanol/oil ratio. The optimum and actual free fatty acid methyl ester (FAME) yield was 93.98% and 93.94%, respectively, which demonstrates that RSM is an accurate method for the current procedure.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Screening of modified ZSM-5 catalysts for conversion of glycerol to light olefins has been investigated. In this study HZSM-5, Al/ZSM-5, Ca/ZSM-5, Cr/ZSM-5, Cu/ZSM-5, Li/ZSM-5, Mg/ZSM-5 and Ni/ZSM-5 ...zeolite catalysts were prepared, tested and screened. The catalysts were characterized to relate their properties with catalyst activity. XRD and FTIR characterization results demonstrated that the structure of the catalysts remained intact while BET revealed the surface and micropore areas decreased after metal loading. TPR data exhibited the reduction phenomenon of the catalysts. NH₃-TPD analysis indicated that Cu/ZSM-5 catalyst has relatively more moderate and strong active acid sites compared to others. GC TCD/FID analysis detected light olefins and paraffins; methane, CO and CO₂ in the gaseous product stream. The acidity of the catalyst affected olefin production, but no direct correlation between surface area and olefin yield was observed. The turnover frequency (TOF) for Cu/ZSM-5 and Cr/ZSM-5 catalysts were significantly high comparatively. Cu/ZSM-5 produced the highest light olefins selectivity and yield due to the synergistic effect of the physico-chemical properties between the parent ZSM-5 and the metals.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Effects due to magnetic field and the inner core size on the opto-electronic characters of impurity in the CdS/ZnS core/shell quantum dot are investigated. The magnetic field dependent ground state ...energies and the transition energies of donor impurity in the CdS/ZnS core/shell quantum dot are computed. The oscillator strength, linear, nonlinear and total absorption coefficient and the changes of refractive index are investigated for various values of magnetic field. The results show that the energy difference due to the ground and first excited states is much more sensitive to the strong confinement and the magnetic field. The maximum of absorption peak and the changes due to refractive index are found to enhance with the inclusion of impurity. These properties can be applied in different potential applications based on the intraband optical transitions.
•Effects due to magnetic field and the inner core size on the opto-electronic characters of impurity in the CdS/ZnS core/shell quantum dot are investigated.•The magnetic field dependent ground state energies and the transition energies of donor impurity in the CdS/ZnS core/shell quantum dot are computed.•Linear, nonlinear and total absorption coefficient and the changes of refractive index are investigated for various values of magnetic field.•The results show that the energy difference due to the ground and first excited states is much more sensitive to the strong confinement and the magnetic field.•These properties can be applied in different potential applications based on the intraband.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Foodborne illness outbreaks caused by the consumption of food contaminated with harmful bacteria has drastically increased in the past decades. Therefore, detection of harmful bacteria in the food ...has become an important factor for the recognition and prevention of problems associated with food safety and public health. Staphylococcus aureus is one of the most commonly isolated foodborne pathogen and it is considered as a major cause of foodborne illnesses worldwide. A number of different methods have been developed for the detection and identification of S. aureus in food samples. However, some of these methods are laborious and time-consuming and are not suitable for on-site applications. Therefore, it is highly important to develop rapid and more approachable detection methods. In the last decade, biosensors have gained popularity as an attractive alternative method and now considered as one of most rapid and on-site applicable methods. An overview of the biosensor based methods used for the detection of S. aureus is presented herein. This review focuses on the state-of-the-art biosensor methods towards the detection and quantification of S. aureus, and discusses the most commonly used biosensor methods based on the transducing mode, such as electrochemical, optical, and mass-based biosensors.
•Recent advances in development of biosensors for detection of S. aureus are discussed.•An overview of biosensors based on transducing mode is presented.•Electrochemical, optical, and mass-based biosensors are mainly discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The coronavirus disease 2019 (COVID-19) is a clinical syndrome caused by severe acute respiratory syndrome corona virus-2 (SARS-CoV-2). COVID-19 was declared a pandemic by the World Health ...Organization (WHO) on March 11, 2020 due to its rapid and extensive spread among many countries through its very contagious nature and its high mortality among the elderly and infirm. Recently, data on the survival of SARS-CoV-2 on contact surfaces has been reported, but there is none on the survival of COVID-19 on food surfaces and packages. The potential survival and transmission of SARS-CoV-2 on/via food and packages are discussed based on data available for other respiratory viruses such as SARS-CoV and MERS-CoV. However, studies are needed to explore its transmission via food and survival on food packaging materials. The implementation of food safety management systems such as Hazard Analysis and Critical Control Points (HACCP), and Good Manufacturing Practices (GMP) are important to reduce the risk of COVID-19 infection. Cleaning, sanitation, good hygienic practices, and active packaging are also needed from farm to fork.
Evidence-based characterization of the diagnostic and prognostic value of the hematological and immunological markers related to the epidemic of Coronavirus Disease 2019 (COVID-19) is critical to ...understand the clinical course of the infection and to assess in development and validation of biomarkers.
Based on systematic search in Web of Science, PubMed, Scopus, and Science Direct up to April 22, 2020, a total of 52 eligible articles with 6,320 laboratory-confirmed COVID-19 cohorts were included. Pairwise comparison between severe versus mild disease, Intensive Care Unit (ICU) versus general ward admission and expired versus survivors were performed for 36 laboratory parameters. The pooled standardized mean difference (SMD) and 95% confidence intervals (CI) were calculated using the DerSimonian Laird method/random effects model and converted to the Odds ratio (OR). The decision tree algorithm was employed to identify the key risk factor(s) attributed to severe COVID-19 disease.
Cohorts with elevated levels of white blood cells (WBCs) (OR = 1.75), neutrophil count (OR = 2.62), D-dimer (OR = 3.97), prolonged prothrombin time (PT) (OR = 1.82), fibrinogen (OR = 3.14), erythrocyte sedimentation rate (OR = 1.60), procalcitonin (OR = 4.76), IL-6 (OR = 2.10), and IL-10 (OR = 4.93) had higher odds of progression to severe phenotype. Decision tree model (sensitivity = 100%, specificity = 81%) showed the high performance of neutrophil count at a cut-off value of more than 3.74x109/L for identifying patients at high risk of severe COVID-19. Likewise, ICU admission was associated with higher levels of WBCs (OR = 5.21), neutrophils (OR = 6.25), D-dimer (OR = 4.19), and prolonged PT (OR = 2.18). Patients with high IL-6 (OR = 13.87), CRP (OR = 7.09), D-dimer (OR = 6.36), and neutrophils (OR = 6.25) had the highest likelihood of mortality.
Several hematological and immunological markers, in particular neutrophilic count, could be helpful to be included within the routine panel for COVID-19 infection evaluation to ensure risk stratification and effective management.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•PCM encapsulated in a sphere was experimentally investigated.•Experimental results were validated with simulations for both freezing and melting.•Effective thermal conductivity of the PCM relates as ...a function of Rayleigh number.•The correlation represents the natural convection in the liquid PCM during melting.
Heat transfer in phase change materials (PCMs) contained in spherical encapsulations can be modelled more simply if an effective thermal conductivity can be determined to represent the natural convection occurring within the PCMs. Previous research has shown that natural convection in PCM can be characterised by a constant effective thermal conductivity during the melting process. However, this research did not consider the impact of the increased buoyancy forces with increased temperature difference between the heat transfer fluid flowing around the encapsulation and the PCM. An experimental study was conducted on the heat transfer through a single sphere subject to varying temperature differences. A computational fluid dynamics (CFD) model which ignored buoyancy of the PCM in a sphere was developed. Using this CFD model, the effective thermal conductivity of the liquid portion of the PCM was determined by correlating data from the model against experimental data at various temperature differences with water as the PCM. A suitable relationship for the effective thermal conductivity was developed as a function of the Rayleigh number. This empirical correlation applies to the geometry and PCM used in this study. The study demonstrates the applicability of determining effective thermal conductivity relationships to represent natural convection in PCM thermal storage systems. This correlation can be directly applied to numerical models of PCM storage systems with spheres.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Exopolysaccharides (EPSs) are metabolites synthesized and excreted by a variety of microorganisms, including lactic acid bacteria (LAB). EPS serve several biological functions such as interactions ...between bacteria and their environments, protection against hostile conditions including dehydration, the alleviation of the action of toxic compounds (bile salts, hydrolyzing enzymes, lysozyme, gastric, and pancreatic enzymes, metal ions, antibiotics), and stresses (changing pH, osmolarity), and evasion of the immune response and phage attack. Bacterial EPSs are considered valuable by the food, pharmaceutical, and nutraceutical industries, owing to their health-promoting benefits and rheological impacts. Numerous studies have reported the unusual antimicrobial activities of various EPS against a wide variety of pathogenic microbes (bacteria, virus, and fungi). This review aims to provide a comprehensive examination of the
in vitro
and
in vivo
antimicrobial activities of different EPSs, mainly against foodborne bacterial, fungal, and viral pathogens. The mechanism of EPS action against these pathogens as well as the methods used to measure antimicrobial activities are critically reviewed.
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