Storability of sweet potatoes (Ipomoea batatas (L.)) under tropical conditions: physiological and sensory aspects.

The shelf-life of the sweet potato storage root under tropical marketing conditions limits its potential for marketing. This research aimed to identify the physiological characteristics that affect the shelf-life of sweet potato cultivars when they are exposed to tropical marketing conditions. Weight loss was the key limiting factor in storability under the conditions studied. The range in weight loss was large amongst the 39 cultivars tested, and varied between 5 to 15% per week. Weight loss related to the marketable appearance. It consisted mainly of water loss and only 10% was due to respiratory metabolism. Sweet potatoes with high rates of water loss were more susceptible to rotting. The role of periderm characteristics (thickness and permeability), root-size, root surface area/mass ratio and shape were investigated. Although significant differences were observed among cultivars, these characteristics could not account for the variation in storability. The level of damage severely affected the rates of weight loss, with transpiration rate through damaged areas many times higher than through undamaged periderm. Breakage was found to be the most severe form of damage, having a great impact on weight loss for 14 days. Cultivars differed in susceptibility to damage after standardised damage treatments. Susceptibility to breaks was greater for long thin roots. Skinning injury was negatively related to the periderm thickness. Wound healing ability was a major factor for the shelf-life of sweet potato cultivars. It was demonstrated that lignification of wounds as measured by phloroglucinol staining, correlates with reduced susceptibility to weight loss, water loss and microbial attack. A lignin index was used to express the probability that lignification occurs. Cultivars differed significantly in their lignin indices under tropical marketing conditions. A high dry matter content generally coincided with a low lignin index. This relationship was consistent for 19 cultivars tested. Sensory evaluation of five sweet potato cultivars resulted in five distinct sensory profiles. During storage some of the cultivars lost some of their flavour but little changes were observed for textural properties. It was concluded that changes in sensory aspects are not a limiting factor for storage of sweet potato

Storability of sweet potatoes (Ipomoea batatas (L.)) under tropical conditions: physiological and sensory aspects.

The shelf-life of the sweet potato storage root under tropical marketing conditions limits its potential for marketing. This research aimed to identify the physiological characteristics that affect the shelf-life of sweet potato cultivars when they are exposed to tropical marketing conditions. Weight loss was the key limiting factor in storability under the conditions studied. The range in weight loss was large amongst the 39 cultivars tested, and varied between 5 to 15% per week. Weight loss related to the marketable appearance. It consisted mainly of water loss and only 10% was due to respiratory metabolism. Sweet potatoes with high rates of water loss were more susceptible to rotting. The role of periderm characteristics (thickness and permeability), root-size, root surface area/mass ratio and shape were investigated. Although significant differences were observed among cultivars, these characteristics could not account for the variation in storability. The level of damage severely affected the rates of weight loss, with transpiration rate through damaged areas many times higher than through undamaged periderm. Breakage was found to be the most severe form of damage, having a great impact on weight loss for 14 days. Cultivars differed in susceptibility to damage after standardised damage treatments. Susceptibility to breaks was greater for long thin roots. Skinning injury was negatively related to the periderm thickness. Wound healing ability was a major factor for the shelf-life of sweet potato cultivars. It was demonstrated that lignification of wounds as measured by phloroglucinol staining, correlates with reduced susceptibility to weight loss, water loss and microbial attack. A lignin index was used to express the probability that lignification occurs. Cultivars differed significantly in their lignin indices under tropical marketing conditions. A high dry matter content generally coincided with a low lignin index. This relationship was consistent for 19 cultivars tested. Sensory evaluation of five sweet potato cultivars resulted in five distinct sensory profiles. During storage some of the cultivars lost some of their flavour but little changes were observed for textural properties. It was concluded that changes in sensory aspects are not a limiting factor for storage of sweet potato

Through the Looking Glass: Why the "Cosmic Horizon" is not a horizon

The present standard model of cosmology, $\Lambda$CDM, contains some intriguing coincidences. Not only are the dominant contributions to the energy density approximately of the same order at the present epoch, but we note that contrary to the emergence of cosmic acceleration as a recent phenomenon, the time averaged value of the deceleration parameter over the age of the universe is nearly zero. Curious features like these in $\Lambda$CDM give rise to a number of alternate cosmologies being proposed to remove them, including models with an equation of state w = -1/3. In this paper, we examine the validity of some of these alternate models and we also address some persistent misconceptions about the Hubble sphere and the event horizon that lead to erroneous conclusions about cosmology.Comment: Accepted for publication by MNRAS, 6 pages, 3 figure

How does the Hubble Sphere limit our view of the Universe?

It has recently been claimed that the Hubble Sphere represents a previously unknown limit to our view of the universe, with light we detect today coming from a proper distance less than this "Cosmic Horizon" at the present time. By considering the paths of light rays in several cosmologies, we show that this claim is not generally true. In particular, in cosmologies dominated by phantom energy (with an equation of state of \omega < -1) the proper distance to the Hubble Sphere decreases, and light rays can cross it more than once in both directions; such behaviour further diminishes the claim that the Hubble Sphere is a fundamental, but unrecognised, horizon in the universe.Comment: 4 pages, 4 figures: Accepted for publication in Monthly Notices of the Royal Astronomical Society Letter

Guidelines for the design of haptic widgets

Haptic feedback has been shown to improve user performance in Graphical User Interface (GUI) targeting tasks in a number of studies. These studies have typically focused on interactions with individual targets, and it is unclear whether the performance increases reported will generalise to the more realistic situation where multiple targets are presented simultaneously. This paper addresses this issue in two ways. Firstly two empirical studies dealing with groups of haptically augmented widgets are presented. These reveal that haptic augmentations of complex widgets can reduce performance, although carefully designed feedback can result in performance improvements. The results of these studies are then used in conjunction with the previous literature to generate general design guidelines for the creation of haptic widgets

Sweetpotato post-harvest assessment

For any crop cultivar to be successful it must not only have good production characteristics but also characteristics that ensure the harvested crop is acceptable and suitable for its intended use. Sweetpotato Post-harvest Assessment summarizes work carried out on postharvest aspects of sweetpotato between 1994 and 2002 within collaborative projects involving the Natural Resources Institute (UK), the International Potato Center and the Tanzanian Ministry of Agriculture, with input from the Kenyan Agricultural Research Institute and the National Agricultural Research Organization of Uganda. Methods are discussed for assessing different quality aspects of sweetpotato cultivars within breeding programmes. The book is expected to be of particular interest to sweetpotato breeding organizations and those involved in research on sweetpotato, but will also be useful to those working on other crops

Impact of aeration on the removal of organic matter and nitrogen compounds in constructed wetlands treating the liquid fraction of piggery manure

The increasing demand for sustainable, robust and cost-efficient wastewater treatment techniques strengthen the implementation of constructed wetlands (CWs) in the agricultural sector. In countries like Belgium (Flanders), the compliance of strict water quality standards and surface area requirements have hindered considerably their application. New wetland designs such as aerated CWs, could help to overcome these challenges. This study evaluated the capacity of artificially aerated mesocosm systems to decrease chemical oxygen demand (COD) concentrations below the 125 mgO(2)/L limit imposed on installations treating animal manure. The treatment of this high-strength wastewater has been slightly studied via aerated CWs. A three-stage experiment investigated the effect of constant, intermittent and non-aeration regimes on: ammonium volatilisation, the evolution of organic and nitrogen compounds concentrations, and denitrification. The results were assessed through a mixed modelling procedure using SAS 9.4 software. A COD removal between 65% and 58% in constantly and intermittent aerated systems, versus 27% COD removal in the non-aerated system indicated the effectiveness of aeration. However, a dissimilarity was encountered in the removal of nitrogen compounds, resulting in an 82% decrease of nitrate concentrations in the non-aerated system, versus 0.5% and 11% in the aerated ones. Based on the results, this experimental set-up adjusted to field operational conditions can prove that aerated CWs can treat the liquid fraction of piggery manure