Effect of the rate and duration of forced air cooling on the quality of Imperial apricots and Pioneer and Songold plums

The original publication is available at http://www.actahort.org/books/682/682_218.htmGel breakdown (GB) and overripeness (OR) remain the biggest internal Problems with Prunus armeniaca L. ‘Imperial’, which makes the biggest contribution to the total volume of apricots exported from South Africa per annum. Prunus salicina L. ‘Pioneer’, an early season South African plum cultivar, ripens quickly on and off the tree which results in rejections for soft fruit at packing and on arrival overseas. ‘Songold’, a yellow, midseason plum cultivar tends to develop GB and OR during cold-storage in some seasons, which renders the fruit inedible and results in high rejection rates. Prompt cooling and good temperature management are essential to lower the rate of physiological deterioration of stone fruit. In some commercial depots in South Africa, forced air cooling (FAC) of stone fruit can take as long as 48 to 72 h, depending on the type of packaging. Consequently, the objective of this study was to determine the effect of the rate and duration of FAC on the fruit quality of different stone fruit cultivars. Fruit was subjected to the following FAC rates at a delivery air temperature of -1.0°C to a pulp temperature of 0°C for 6 h, 12 h, 24 h stepwise cooling and 48 h stepwise cooling for the apricot, and 12 h, 24 h, 48 h stepwise cooling, and 72 h stepwise cooling for the two plum cultivars. The fruit was evaluated after cold-storage and a simulated shelf-life period. The trial was conducted in two consecutive seasons. ‘Imperial’ apricots had the best internal quality after 6 h of FAC, ‘Pioneer’ plums were not affected by FAC rate or duration, and ‘Songold’ plums had the best internal quality when FAC was applied for 12 h and longer. These results on plums demonstrate that cultivar differences must be considered when drawing up handling protocols for stone fruit, as a blanket recommendation may lead to the induction of quality defects

On the Computation of Blow-up Solutions for Semilinear ODEs and Parabolic PDEs

We introduce an adaptive numerical method for computing blow-up solutions for ODEs and well-known reaction-diffusion equations. The method is based on the implicit midpoint method and the implicit Euler method. We demonstrate that the method produces superior results to the adaptive PECE-implicit method and the MATLAB solver of comparable order

On the numerical solution of Fisher’s equation with coefficient of diffusion term much smaller than coefficient of reaction term

Abstract Li et al. (SIAM J. Sci. Comput. 20:719–738, 1998) used the moving mesh partial differential equation (MMPDE) to solve a scaled Fisher’s equation and the initial condition consisting of an exponential function. The results obtained are not accurate because MMPDE is based on a familiar arc-length or curvature monitor function. Qiu and Sloan (J. Comput. Phys. 146:726–746, 1998) constructed a suitable monitor function called modified monitor function and used it with the moving mesh differential algebraic equation (MMDAE) method to solve the same problem of scaled Fisher’s equation and obtained better results. In this work, we use the forward in time central space (FTCS) scheme and the nonstandard finite difference (NSFD) scheme, and we find that the temporal step size must be very small to obtain accurate results. This causes the computational time to be long if the domain is large. We use two techniques to modify these two schemes either by introducing artificial viscosity or using the approach of Ruxun et al. (Int. J. Numer. Methods Fluids 31:523–533, 1999). These techniques are efficient and give accurate results with a larger temporal step size. We prove that these four methods are consistent for partial differential equations, and we also obtain the region of stability

Higher Order Compact Finite Difference Schemes for Unsteady Boundary Layer Flow Problems

We investigate the applicability of the compact finite difference relaxation method (CFDRM) in solving unsteady boundary layer flow problems modelled by nonlinear partial differential equations. The CFDRM utilizes the Gauss-Seidel approach of decoupling algebraic equations to linearize the governing equations and solve the resulting system of ordinary differential equations using compact finite difference schemes. The CFDRM has only been used to solve ordinary differential equations modelling boundary layer problems. This work extends its applications to nonlinear partial differential equations modelling unsteady boundary layer flows. The CFDRM is validated on two examples and the results are compared to results of the Keller-box method

Nonlinear nanofluid flow over heated vertical surface with sinusoidal wall temperature variations

The nonlinear density temperature variations in two-dimensional nanofluid flow over heated vertical surface with a sinusoidal wall temperature are investigated. The model includes the effects of Brownian motion and thermophoresis. Using the boundary layer approximation, the two-dimensional momentum, heat, and mass transfer equations are transferred to nonlinear partial differential equations form and solved numerically using a new method called spectral local linearisation method.The effects of the governing parameters on the fluid properties and on the heat and nanomass transfer coefficients are determined and shown graphically

Thermal, viscoelastic and mechanical behavior of polypropylene with synthetic boehmite alumina nanoparticles

Effects of nanofiller concentration and surface treatments on the morphology, thermal, viscoelastic and mechanical behaviors of polypropylene copolymer (PP)/boehmite alumina (BA) nanocomposites were investigated. Both untreated and treated BA particles with octylsilane (OS) and with sulphonic acid compound (OS2) were added up to 10 wt% to produce nanocomposites by melt mixing followed by film blow molding and hot pressing. Dispersion of BA was studied by scanning electron microscopy. Differential scanning calorimetry and wide-angle X-ray scattering were adopted to detect changes in the crystalline structure of PP. Thermooxidative degradation of the nanocomposites was assessed by thermogravimetrical analysis. Dynamic mechanical analysis served for studying the viscoelastic, whereas quasi-static tensile, creep and Elmendorf tear tests were used to detect changes in the mechanical performance. BA nanoparticles were finely dispersed in PP up to 10 wt%, even when they were not surface modified. The resistance to thermal degradation was markedly improved by BA nanomodification. Changes observed in the mechanical properties were attributed to BA dispersion, filler/matrix interactions and related effects because the crystalline characteristics of the PP matrix practically did not change with BA modification

Pathways From Food Insecurity to Intimate Partner Violence Perpetration Among Peri-Urban Men in South Africa.

INTRODUCTION: Although poverty is sometimes seen as a driver of intimate partner violence victimization, less is known about how it intersects with men's violence perpetration. Food insecurity is a sensitive marker of poverty that may have unique mechanisms leading to men's intimate partner violence perpetration given its association with gender roles and men "providing for the family." METHODS: Using cluster-based sampling, the team conducted an audio-assisted questionnaire in 2016 among men living in a peri-urban settlement near Johannesburg, South Africa. The aim was to examine the relationship between men's food insecurity and their use of past-year intimate partner violence, and to explore the pathways linking these two conditions. RESULTS: Among 2,006 currently partnered men, nearly half (48.4%) perpetrated intimate partner violence and more than half (61.4%) were food insecure. Food insecurity was associated with doubled odds of intimate partner violence (OR=2.15, 95% CI=1.73, 2.66). This association persisted after controlling for sociodemographics, relationship characteristics, and neighborhood clustering. In a structural equation model, food insecurity retained a direct relationship with men's violence perpetration and worked through indirect pathways of mental health and relationship quality. CONCLUSIONS: Addressing men's perpetration of intimate partner violence may require examination of broader structural challenges, such as food insecurity. Future interventions should consider livelihood strategies alongside relationship and mental health approaches

On the Computation of Blow-Up Solutions for Nonlinear Volterra Integrodifferential Equations

We make use of an adaptive numerical method to compute blow-up solutions for nonlinear ordinary Volterra integrodifferential equations (VIDEs). The method is based on the implicit midpoint method and the implicit Euler method and is named the implicit midpoint-implicit Euler (IMIE) method and was used to compute blow-up solutions in semilinear ODEs and parabolic PDEs in our earlier work. We demonstrate that the method produces superior results to the adaptive PECE-implicit Euler (PECE-IE) method and the MATLAB solver of comparable order just as it did in our previous contribution. We use quadrature rules to approximate the integral in the VIDE and demonstrate that the choice of quadrature rule has a significant effect on the blow-up time computed. In cases where the problem contains a convolution kernel with a singularity we use convolution quadrature

Investigating hair zinc concentrations in children with and without atopic dermatitis

Background. Atopic dermatitis (AD) is a common chronic inflammatory skin condition that disproportionately affects children and is associated with reduced quality of life. Zinc deficiency may contribute to the pathogenesis of AD because zinc plays a role in epidermal barrier integrity and the immune system. Systematic review evidence suggests that low zinc is associated with AD, but limitations of included studies support further investigation.Objectives. To investigate hair zinc concentrations in children with AD v. healthy controls in a low- to middle-income country setting.Methods. One hundred and five children aged 1 - 12 yea­rs participated in a frequency-matched for age case-control study. The outcome variable, AD, was confirmed by a clinician and corroborated using the UK Working Party criteria. The primary predictor, long-term average zinc concentration, was determined by measuring hair zinc using inductively coupled mass spectrometry. Baseline demographic characteristics, anthropometry and measures of socioeconomic status were included in our logistic regression analysis. Subgroup analysis was performed where interaction terms suggested effect modification.Results. Using data from the overall sample, population median hair zinc was not significantly different between children with AD and healthy controls. However, subgroup analysis suggested a clinically and statistically significant difference in median zinc between children with AD (175.35 µg/g) and healthy controls (206.4 µg/g) in the older age group (5 - 12 years) (p=0.01). In this age group, multivariable logistic regression analysis also found significantly decreased hair zinc concentrations in AD (odds ratio 0.83; 95% confidence interval 0.66 - 0.96; p=0.046).Conclusions. The inverse association between zinc status and AD in children aged 5 - 12 years in our setting is consistent with the international literature. The clinical importance of decreased zinc levels in AD is not yet known. Further investigation into relevant underlying mechanisms seems warranted given the global reach of AD, its effect on quality of life, and the low cost of potential zinc-based interventions.