Stability Analysis of a Population Model with Maturation Delay and Ricker Birth Function

A single species population model is investigated, where the discrete maturation delay and the Ricker birth function are incorporated. The threshold determining the global stability of the trivial equilibrium and the existence of the positive equilibrium is obtained. The necessary and sufficient conditions ensuring the local asymptotical stability of the positive equilibrium are given by applying the Pontryagin's method. The effect of all the parameter values on the local stability of the positive equilibrium is analyzed. The obtained results show the existence of stability switch and provide a method of computing maturation times at which the stability switch occurs. Numerical simulations illustrate that chaos may occur for the model, and the associated parameter bifurcation diagrams are given for certain values of the parameters

Enhanced transmission of optically thick metallic films at infrared wavelengths

For an optically thick metallic film, the transmission for both s- and p-polarized waves is extremely low. If the metallic film is coated on both sides with a finite dielectric layer, light transmission for $p$-polarized waves can be enhanced considerably. This enhancement is not related to surface plasmon-polaritions. Instead, it is due to the interplay between Fabry-Perot interference in the coated dielectric layer and the existence of the Brewster angle at the dielectric/metallic interface. It is shown that the coated metallic films can act as excellent polarizers at infrared wavelengths.Comment: 3 pages, 4 figures. Submitted to Appl. Phys. Let

Association of dietary fatty acid intake with hypertension in children and adolescents: evidence from the NHANES 2005–2018

AimThis study aims to evaluate the association between dietary fatty acid intake and hypertension in children and adolescents.MethodsThis cross-sectional study used data of children and adolescents aged 8–17 years from the National Health and Nutrition Examination Survey (NHANES) 2005–2018. Dietary intake of total fat and fatty acid was evaluated via two 24-h dietary recall interviews. Multivariate logistic regression models were used to assess the association between fatty acid intake and hypertension, with odds ratios (ORs) and 95% confidence intervals (CIs) calculated. A subgroup analysis was conducted according to gender, age, and body mass index Z-score.ResultsThis study included 13,330 subjects, of which 11,614 were non-hypertensive and 1,716 were hypertensive. Higher intake of total polyunsaturated fatty acids (PUFAs) was associated with significantly lower odds of hypertension (OR = 0.85, 95% CI: 0.74–0.97, P = 0.018). No significant associations were found between the density of total saturated fatty acid, monounsaturated fatty acids, and PUFAs and the odds of hypertension (all P > 0.05). Increased intake of omega-3 (OR = 0.82, 95% CI: 0.72–0.93, P = 0.002) and omega-6 (OR = 0.86, 95% CI: 0.75–0.98, P = 0.025) PUFAs, octadecatrienoic acid (OR = 0.82, 95% CI: 0.72–0.93, P = 0.003), and octadecadienoic acid (OR = 0.86, 95% CI: 0.75–0.98, P = 0.025) was associated with significantly lower odds of hypertension, and individuals with higher omega-6/omega-3 ratio had significantly higher odds of hypertension (OR = 1.09, 95% CI: 1.02–1.17, P = 0.025). The density of omega-3 PUFAs (OR = 0.86, 95% CI: 0.78–0.95, P = 0.004) and octadecatrienoic acid (OR = 0.87, 95% CI: 0.78–0.96, P = 0.006) was inversely associated with the odds of hypertension, and the omega-6/omega-3 ratio was positively associated with the odds of hypertension (OR = 1.09, 95% CI: 1.02–1.17, P = 0.012).ConclusionTotal PUFA intake was negatively associated with the odds of hypertension in children and adolescents. Higher intake of omega-3 and omega-6 PUFAs, octadecatrienoic acid, and octadecadienoic acid, as well as density of omega-3 PUFAs and octadecatrienoic acid, was associated with lower odds of hypertension

Analysis of beauvericin in Isaria cicadae Miquel culture on different media

Objective To analyze beauvericin and enniatins concentrations in the culture complex after Isaria cicadae Miquel was inoculated on different media for certain time. Methods One strain of Isaria cicadae Miquel was inoculated on 4 kinds of liquid culture media and 4 kinds of solid culture media. After incubation for 1-7 weeks under 25 ℃, high performance liquid chromatography tandem mass spectrometry was employed to detect beauvericin and enniatins. Results The detection rates of beauvericin in Isaria cicadae Miquel culture on 4 kinds of liquid media ranged between 42.9%-100.0%, and the beauvericin concentrations varied from 1.0 to 94.6 μg/L. The positive rates of beauvericin in Isaria cicadae Miquel culture on 4 kinds of solid media were 100.0%, and the beauvericin concentrations ranged from 60.9 to 44 677.5 μg/kg. Enniatins were negative for Isaria cicadae Miquel on 8 kinds of culture media. Conclusion The strain of Isaria cicadae Miquel used in our study could produce beauvericin in 8 kinds of culture media after incubation for certain time, and the beauvericin concentrations in solid media were much higher than in liquid media. The strain of Isaria cicadae Miquel didn’t produce enniatins in 8 kinds of culture media after incubation for certain time

Antimicrobial Resistance, Virulence, and Genetic Characterization of Methicillin-Resistant Staphylococcus aureus Recovered from Ready-to-Eat (RTE) Food in China: A New Challenge for Food Safety

The objective of the present study was to determine the prevalence, antimicrobial resistance, virulence profiles, and molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) obtained from ready-to-eat (RTE) foods in China. Two hundred seventy-six RTE food-associated S. aureus isolates were collected from 25 provinces across China in 2018, then characterized by antimicrobial susceptibility testing, virulence factors detecting, multilocus sequence typing (MLST), spa typing, SCC mec typing and pulsed-field gel electrophoresis (PFGE). Two hundred fifty isolates (90.6%) were resistant to at least one antimicrobial agent; 73 (26.4%) isolates were multi-drug resistant (MDR). Thirty MRSA isolates were identified, among which nine toxin genes ( sea, seb, sec, sed, seh, selk, sell, selq , and tsst-1 ) were detected. Sixty percent (18/30) of the MRSA isolates harbored multiple toxin genes. Four virulence gene patterns were identified, with seb-selk-selq (30/30) being the most common pattern. Thirteen sequence types, as well as 13 spa and 4 SCC mec types were found among 30 MRSA isolates. The most prevalent MRSA lineages were CC59-t437-SCC mec IV/V (23.3% [7/30]), CC398-t011-SCC mec V (23.3% [7/30]), and CC1-t114-SCC mec IV (16.7% [5/30]). Our findings highlight the importance for the identification of prevalent clones, assessment of drug-resistance and virulence, and formulation of food safety measures for public health

Foaming behaviour of primary, secondary and tertiary aqueous solution of amine for the removal of carbon dioxide

This study is focusing on the effect by the usage of different amine in order to remove acid gases that is foaming. Foam is made up of thousands of gas filled bubbles. Bubbles are formed when a liquid film encapsulates gas. This research is to investigate the foaming behaviour on the different cases for the primary (monoethanolamine, MEA), secondary (diethanolamine, DEA) and tertiary (methyldiethanolamine, MDEA) amine on the effect of concentration, temperature and impurities. Effect of all this parameters will be evaluated based on height of foam and collapse time of foam. Nitrogen gas (N2) will be used in this experiments as bubble gas. For this work several hypothesis has been set according to respectively cases. The hypothesis of this study is a higher solution concentration of MEA will reduce the foaminess. Other hypothesis is a higher solution temperature of MEA and DEA will reduce the foaminess also. Effects of impurities toward foaming formation are classified as following: iron sulphide, for MDEA solution foaming decrease; sodium chloride, for MDEA solution tendency for formation of foam decrease; methanol, foaming decrease in MDEA solution. It is apparently iron sulphide meet the most influential contaminants to the foam formation at the same concentrations of all impurities studie

Klebsiella , a Hitherto Underappreciated Zoonotic Pathogen of Importance to One Health: A Short Review

Members of the genus, Klebsiella , are becoming increasingly challenging to control due to the recent convergence of multidrug resistant (MDR) and hypervirulent (hv) phenotypes in some species of concern to One Health . This short review will provide an introduction to this bacterial genus in the hospital and other settings, update Klebsiella taxonomy, and comment on recent findings describing the prevalence of Klebsiella species in the food chain, a hitherto infrequently recognised ecologic niche. The paper will also consider this bacterium in the context of the One Health paradigm and its importance to food safety and security

Thermoluminescence (TL) analysis for otoliths of the wild carps (cyprinoid) from Baiyangdian Lake and Miyun Reservoir: Some implications for monitoring water environment

Otolith is a typical biomineral carrier growing on insides of fish skull with prominent zoning structure formed by alternating layers of protein and calcium carbonate growing around the nucleus. Even though thermoluminescence (TL) analysis on biomineral has been widely used to measure the radiation exposure in the recent twenty years, the TL characteristics of the fish otolith have not yet been reported in literature. TL characteristics of otoliths from the wild carps (cyprinoid) living in the Baiyangdian Lake, Hebei Province and Miyun Reservoir, Beijing City was first studied, and the differences of energy gap (E) between the fish otoliths in the two waters have also been discussed in this paper. The experimental results indicated that TL curve parameters: peak temperature (Tp), luminous intensity (I), integrated intensity (S) and middle width (Wm) for the glow curves of the cyprinoid otoliths from Baiyangdian Lake are greater than those from Miyun reservoir, and the stability of the formers’ TL curve parameters value and energy gap (E) was weaker than the latter. In comparison to the Miyun Reservoir, the analysis manifested that the electrons and vacancies trapped in the otoliths from Baiyangdian Lake are more likely to escape. According to the investigation, the contaminative degree and eutrophication in the water of Baiyangdian Lake was heavier than that of Miyun Reservoir. Therefore, the characteristics of TL growth curves of the cyprinoid otoliths is quite sensitive to heavier contaminated and less contaminated water, and this could be regarded as an important typomorphic biomineral for monitoring the contaminative degree and environment change of the water.Keywords: Cyprinoid otoliths, thermoluminescence, water environment, typomorphic minera