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In this paper, the impact of the strong Allee effect and ratio-dependent Holling–Tanner functional response on the dynamical behaviors of a predator–prey system is investigated. First, the positivity and boundedness of solutions of the system are proved. Then, stability and bifurcation analysis on equilibria is provided, with explicit conditions obtained for Hopf bifurcation. Moreover, global dynamics of the system is discussed. In particular, the degenerate singular point at the origin is proved to be globally asymptotically stable under various conditions. Further, a detailed bifurcation analysis is presented to show that the system undergoes a codimension- 1 Hopf bifurcation and a codimension- 2 cusp Bogdanov–Takens bifurcation. Simulations are given to illustrate the theoretical predictions. The results obtained in this paper indicate that the strong Allee effect and proportional dependence coefficient have significant impact on the fundamental change of predator–prey dynamics and the species persistence. [ABSTRACT FROM AUTHOR]

In this paper, we mainly investigate an infected-age structured HIV model with logistic growth for target cells, which simultaneously takes the latent factor and different transmission modes into consideration. On the basis of integrated semigroup theory and Hopf bifurcation theory for semilinear equations in a nondense domain, we reach a conclusion that the system undergoes a Hopf bifurcation around the positive equilibrium, which implies that there exists a nontrivial periodic oscillation phenomenon when the Hopf bifurcation parameter τ passes through some critical values. Namely, the HIV infection will periodically erupt when the mature period τ crosses the critical value τ k (k = 0 , 1 , 2 , ...), that is, HIV virus will always survive in the patient's body. In order to verify the fact that the biological maturation period τ does play an essential role in our system, we also offer the relevant numerical simulation results by selecting several decisive parameters. [ABSTRACT FROM AUTHOR]

In this work, we construct an age-structured HIV-1 infection model to investigate the interplay between T cells and viruses. In our model, we assume that the variations in the death rate of productively infected T cells and the production rate of virus in infected cells are all age-dependent, and the target cells follow logistic growth. We perform mathematical analysis and prove the persistence of the semi-flow of the system. We calculate the basic reproduction number and prove the local and global stability of the steady states. We show that if the basic reproduction number is less than one, the disease-free equilibrium is globally asymptotically stable, and if the basic reproduction number is greater than one, the infected steady state is locally asymptotically stable. [ABSTRACT FROM AUTHOR]

In this paper, we study a nonlinear coupled predator–prey diffusion system which widely exists in ecosystem. It is found that the self-diffusion and cross-diffusion do not change the stability of the semi-equilibrium point of the corresponding predator–prey system. However, the two kinds of diffusion play an important role on the positive equilibrium, in virtue of which Turing instability of the corresponding diffusion system either continues to exist or disappears and becomes stable. On the stationary patterns of the nonlinear coupled system, we find some interesting results which differ from the phenomenon found in corresponding diffusion system. Strong cross-diffusion can make the corresponding system generate stationary patterns. Finally, numerical simulation is also done to verify the existence of the effects of self-diffusion and cross-diffusion. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we studied a HIV latent infection model with two time delays, where one delay is the time between viral entry into a cell and establishment of HIV latency and the other delay is the time between cell infection and viral production. The infection usually considered is linear, but in this article we consider that the infection rate of modeling HIV infection is nonlinear, where the rate of infection is β T V 1 + b V , and logistic growth of the uninfected target cells T. We defined the basic reproductive number and showed the local and global stability of the disease-free equilibrium and the permanence of the infected equilibrium. Furthermore, we discussed the dynamics of system under the three conditions: (1) τ 1 = τ 2 = 0 , (2) τ 1 = 0 , τ 2 > 0 , (3) τ 1 > 0 , τ 2 ∈ [ 0 , τ 2 ∗). Highlights • A new HIV latent infection model with two time delays is introduced. • Numerical simulations are provided to support the theoretical analyses. • The basic reproduction number is obtained. • Our results show that the size of the delay can affect the infected equilibrium leading to a Hopf bifurcation. [ABSTRACT FROM AUTHOR]

This paper is concerned with a phytoplankton–zooplankton model with toxin delay. It is shown that the positive equilibrium of the system is stable when the toxin delay is not included. However, we find that the incorporation of a discrete toxin delay not only can destabilize the positive equilibrium of the system but also can cause a Hopf bifurcation at the positive equilibrium as it crosses some critical values. In particular, the normal form of the Hopf bifurcation arising in the system is determined to investigate the direction and the stability of periodic solutions bifurcating from these Hopf bifurcations. To verify the obtained conditions, a special numerical example is also included. These results in this work demonstrate that the toxin delay plays an important role on deriving the complex dynamics. [ABSTRACT FROM AUTHOR]

This paper is devoted to the study of spatiotemporal dynamics of a diffusive Leslie-Gower predator-prey system with ratio-dependent Holling type III functional response under homogeneous Neumann boundary conditions. It is shown that the model exhibits spatial patterns via Turing (diffusion-driven) instability and temporal patterns via Hopf bifurcation. Moreover, the existence of spatiotemporal patterns is established via Turing-Hopf bifurcation at the degenerate points where the Turing instability curve and the Hopf bifurcation curve intersect. Various numerical simulations are also presented to illustrate the theoretical results. [ABSTRACT FROM AUTHOR]

The dynamics of an amensalism system with strong generic delay kernel is considered. From a careful analysis of characteristic equation, the local asymptotic stability of the positive equilibrium and the existence of Hopf bifurcation from the positive equilibrium are investigated, where the time delay is used as the bifurcation parameter. Moreover, we apply the normal form theory and the center manifold theorem to study the direction of these Hopf bifurcations and the stability of bifurcated periodic orbits. Finally, numerical simulations supporting the theoretical analysis are also included. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A competitive Lotka-Volterra reaction-diffusion system with two delays subject to Neumann boundary conditions is considered. It is well known that the positive constant steady state of the system is globally asymptotically stable if the interspecies competition is weaker than the intraspecies one and is unstable if the interspecies competition dominates over the intraspecies one. If the latter holds, then we show that Hopf bifurcation can occur as the parameters (delays) in the system cross some critical values. In particular, we prove that these Hopf bifurcations are all spatially homogeneous if the diffusive rates are suitably large, which has the same properties as Hopf bifurcation of the corresponding delayed system without diffusion. However, if the diffusive rates are suitably small, then the system generates the spatially nonhomogeneous Hopf bifurcation. Furthermore, we derive conditions for determining the direction of spatially nonhomogeneous Hopf bifurcations and the stability of bifurcating periodic solutions. These results indicate that the diffusion plays an important role for deriving the complex spatiotemporal dynamics. [ABSTRACT FROM AUTHOR]

Abstract: The main purpose of this work is to investigate the effects of cross-diffusion in a strongly coupled predator–prey system. By a linear stability analysis we find the conditions which allow a homogeneous steady state (stable for the kinetics) to become unstable through a Turing mechanism. In particular, it is shown that Turing instability of the reaction–diffusion system can disappear due to the presence of the cross-diffusion, which implies that the cross-diffusion induced stability can be regarded as the cross-stability of the corresponding reaction–diffusion system. Furthermore, we consider the existence and non-existence results concerning non-constant positive steady states (patterns) of the system. We demonstrate that cross-diffusion can create non-constant positive steady-state solutions. These results exhibit interesting and very different roles of the cross-diffusion in the formation and the disappearance of the Turing instability. [Copyright &y& Elsevier]

Aims. To examine the dose-response relationship between self-reported alcohol consumption and levels of self-reported negative consequences of drinking. Design. Data from 10 general population random sample surveys over the years 1990-1997 were combined and responses were plotted and subjected to regression analysis. Setting. Auckland, a city of approximately 1 million people in the North Island of New Zealand. Participants were interviewed in their homes using a computer-assisted telephone interviewing system. Participants. General population sample of 11 817 aged 14-65 years, representative of the Auckland population. Measurements. Frequency of experience of 14 negative consequences; annual volume of alcohol consumed; frequency of drinking larger quantities of alcohol. Results. Three different patterns of relationship between consequences and consumption were found for different consequences. These differed between the prevalence and the frequency of consequences but were similar for two different measures of consumption, annual volume and larger quantity drinking. Analysis of the frequency of experienced consequences found that the risk curves for the most common consequences approximated a straight line and the effects at low volume intake were due to those drinking larger quantities. Three less common consequences clearly showed a concave curve suggesting a threshold effect, with effects beginning at about 20 litres per annum of absolute alcohol. Conclusion. The different relationships between consumption and consequences imply that some consequences occur only once a very heavy volume of drinking is reached, while others show a direct relationship with consumption, reflecting that volume of alcohol consumed is closely related to the quantities consumed. [ABSTRACT FROM AUTHOR]

Time-series analysis of alcohol consumption data has shown an impact of real price on alcohol consumption in NZ in the decade 1984-96. Beer consumption was reduced by real price increases and wine consumption was increased by real price decreases. By contrast, during this period spirits were price inelastic. A further influence on alcohol consumption was the introduction of wine into grocery stores, which led to a sudden permanent increase in wine consumption 3 months after the legislation came into force. Beer and spirits were not introduced into supermarkets at this time and while there was no effect on beer consumption there was a significant decrease in spirits consumption. [ABSTRACT FROM AUTHOR]

Presents a longitudinal study which evaluated the impact of televised alcohol advertising and beer-brand allegiance, on alcohol consumption and related aggressive behavior in New Zealand. Methods employed to make this assessment; Relationships between alcohol advertising, consumption and alcohol-related violence; What findings suggests; Conclusions reached by authors.

Presents a study which examined the association of responses to alcohol advertisements, drinking behavior and related problems within New Zealand, while focusing on the role of positive and negative beliefs concerning drinking as intervening variables. Measurement of response to specific alcohol advertisements; What the structural equation modelling (SEM) offers; Requirements of the use of structural equation models.

Presents a study on the relationships between 10 to 17-year-old New Zealander's responses to alcohol televised advertisements, their drinking behavior and future drinking expectations. Consideration given to the role of positive and negative beliefs relating to drinking; Details on the subjects used in the study; Method in which the study was conducted; Examination of the results; Discussion based on the findings.

Details on the longitudinal study of young New Zealanders access to alcohol from license premises. Study of youthful use of alcohol in New Zealand; Methodology of the study; Impact of access via licensed premises on drinking and related problems; Results of the study.

Examines the data from the national sample of some New Zealanders that allowed the comparison of six different alcohol consumption measures. Alcohol consumption measures; Variation of Finnish period estimate; Data collection based on random sampling; Statistics of alcohol consumption by sex and age; Results of the analysis; Discussion.

People's self report of a variety of alcohol-related problems was collected as part of a national survey carried out in New Zealand in 1988. These problems included self perception of adverse effects of drinking on a number of life areas such as health, friendships and financial position; items covering tangible consequences of alcohol use and items suggestive of alcohol dependence. The experience of these problems was predicted from a number of socio-demographic variables and respondent's reports of their typical drinking behaviour. Of the Socio-demographic variables only age was found to relate strongly to experience of problems. The overall frequency of drinking relatively large amounts and the typical quantity drunk in certain licensed premises (hotels, taverns and clubs) and the typical quantity drunk in others' homes predicted the experience of problems. These findings are similar to research from other countries using different methodologies and support the likely effectiveness of prevention strategies which reduce the access of young people to alcohol and which aim to influence the amounts consumed in drinking sessions on licensed premises. [ABSTRACT FROM AUTHOR]

The main purpose of this work is to investigate the effects of nonlinear diffusion on positive steady states in a Beddington-DeAngelis model. By the energy method and Leray-Schauder degree theory, we consider the non-existence and existence of concerning non-constant positive steady states of the model. We demonstrate that nonlinear diffusion can create non-constant positive steady-state solutions even when the random diffusion fails to do so. [ABSTRACT FROM AUTHOR]

Aim: To develop the 17-item Asthenopia Survey Questionnaire (ASQ)-17 by Rasch analysis, and to generate a predictiveness score., Methods: Totally 739 participants were recruited and 680 were involved in the result analysis in this prospective, cross-sectional study. Three rounds of Rasch analysis were used to analyze the psychometric characteristics of items and options., Results: Phase 1 assessed the original ASQ-19, adjusted the item scoring mode to a four-point Likert response rating scale and combined the 18 th and 19 th items into a new item. Phase 2 deleted the 11 th item. Phases 3 and 4 assessed the new ASQ-17. All the evaluation indexes of ASQ-17 were acceptable. The Infit and Outfit MnSq values of items were 0.67-1.48, the variance explained by the principal component and the unexplained variance explained by the first contrast were 53.90%-59.40% and 1.50-1.80 in three dimensions. The curve peaks of scores in each dimension were separated and in the same order. The PSR and PSI values were 2.80 and 0.89, respectively. The mean scores of dimensions A (9.5±4.1 vs 3.5±3.2), B (7.3±3.3 vs 2.5±2.7), C (4.3±2.2 vs 1.4±2.0) and total (21.1±8.1 vs 7.4±7.0) in asthenopia participants were significantly higher than those without asthenopia (all P <0.001). The area under the curve in two groups was 0.899 ( P <0.001). Youden's index was up to the maximum value of 0.784 when the cut-off value was 12.5., Conclusion: ASQ-17 has stronger option sorting and suitability than ASQ-19. It is an effective assessment tool for asthenopia with an optimal cut-off threshold value of 12.5, which is suitable for diagnosis and curative effect evaluation., (International Journal of Ophthalmology Press.)

The differences between the macroscopic and microscopic magnetic properties of granular, rod, and tubular nano-maghemites were studied. The macroscopic magnetic properties of the different nano-maghemites were all ferrimagnetic by using a superconducting quantum interference device (SQUID). However, the coercive magnetic field and magnetization per unit volume were both in the orders of grain > tube > rod, which indicated that the crystal shape influenced macroscopic magnetic properties. A magnetic force microscope (MFM) was used to observe the microscopic magnetic structures; the samples were all magnetic in multiple domains, but the form and distribution of these domains were different. However, the domain information of nano-maghemites calculated from SQUID results suggested that all specimens were pseudo-single domains. The MFM results suggested that the crystal morphology had a significant effect on magnetic properties of these nano-maghemites owing to their different magnetic domain structures. Therefore, MFM can be used to detect minute magnetic-properties that are imperceptible to macroscopic measurements. Thus, it is a tool with potential development in earth science.

Study Design: An in vitro laboratory study., Objective: (i) To evaluate the effect of osteoporotic degree in determining the strength of sacral screw fixation and (ii) to compare the strength of unaugmented bicortical pedicle screw and polymethylmethacrylate (PMMA) augmented unicortical pedicle screw in sacral fixation., Summary of Background Data: Screw loosening is a clinical problem in lumbosacral fusions, especially in osteoporotic patients. To improve the screw anchoring strength of sacrum, bicortical and PMMA augmented sacral pedicle screw fixation techniques are widely used in clinical practice. However, the biomechanical strength of the bicortical and PMMA augmented sacral screw fixations remains undetermined in different degrees of osteoporosis., Methods: Twenty-five fresh osteoporotic cadavers were used in this study. According to the value of lumbar bone mineral density (BMD) assessed by DEXA, specimens were divided into 3 groups: group A (N=9): BMD=0.7 to 0.8 g/cm, group B (N=8): BMD=0.6 to 0.7 g/cm, and group C (N=8): BMD<0.6 g/cm. In each specimen, S1 pedicle screw was inserted bicortically on the left side, and S1 pedicle screw with PMMA augmentation was inserted unicortically on the right side of the sacrum. Following a dynamic cyclic loading from 30 to 250 N on the screw head for 2000 cycles, the subsidence displacement and axial pull-out strength of each screw were measured., Results: No anchoring failure (defined as the subsidence displacement exceeding 2 mm within 2000 loading cycles) occurred in group A and B. However, in group C, 6 cases (75%) in bicortical fixation and 5 cases (63%) in PMMA augmented fixation failed during cyclic loading. In group A, no significant difference between the bicortical and PMMA augmented fixations was detected in terms of the subsidence and maximal pull-out strength. In group B, significantly less subsidence and higher maximal pull-out strength were demonstrated in the PMMA augmented technique than that in the bicortical fixation. Both techniques exhibited lower subsidence of the screw in group A than in group B. The bicortical technique exhibited higher maximum pull-out strength in group A than that in group B. However, statistical difference in terms of PMMA augmentation was not detected between group A and B., Conclusion: For BMD value more than 0.70 g/cm, bicortical sacral pedicle screw fixation could obtain sufficient anchoring strength comparable with the PMMA augmented technique. When BMD value is within 0.6 to 0.7 g/cm, the PMMA augmented technique would be more beneficial in improving the fixation strength than the bicortical fixation. For BMD values less than 0.6 g/cm, early screw loosening may occur in both bicortical and PMMA augmented fixations.

Objective: To study the relationship between drinking environment, attitudes and situation and alcohol-related health problems., Methods: A sample of 2327 respondents was randomly collected from Wuhan, Hubei Province in China by a face-to-face interview. The structural equation modeling analysis was performed for the data collected., Results: Both parents' drinking behaviors and respondents' drinking situation strongly impacted the alcohol-related problems and diseases. Friends' or peers' drinking behaviors influenced the respondents' drinking attitudes and behaviors. Males experienced more alcohol-related problems and diseases than females., Conclusions: Comparatively, parents' drinking behaviors exert the most significant influence on drinkers. Therefore, it is beneficial to restrict parents' drinking behaviors for the offsprings and the whole society, and an intensive professional education in early motherhood is also necessary for Chinese women.