Contextualizing transport infrastructure and services in Ghanaian peri-urbanism

This study interrogates the demand and supply of transport infrastructure and services in peri-urban areas of Sunyani Municipality in Ghana. Structured one-on-one interviews were conducted with 100 households across three peri-urban communities in Sunyani (Abesim-Kyidom, Asuakwaa and Adomako). Findings revealed that a majority of peri-urban households (84%) in the study communities who commute daily to and from the city centre are faced with poor transport infrastructure (e.g. poor conditions of road) and unreliable services (e.g. unregulated public transport). Inadequate investment in transport infrastructure and services by the Ghanaian government, the limited activity locations in peri-urban areas, and the concentration of activity locations at the city centre were identified to be contributing to the poor state of transport infrastructure and services in the case study communities. Policy recommendations to improve the situation are further proffered.     

Optimisation of the microencapsulation conditions and physicochemical properties of enteric‐coated lactase microcapsules

Enteric double‐coated lactase microcapsules were developed, and the encapsulation conditions were optimised using response surface methodology. The optimum concentration of the enteric coating material was 4.85 g/100 mL, and the amount of core material was 1.85 mL. The particle size of the zein‐coated microcapsules was 2.868 μm, which was smaller than that of the other microcapsules. All microcapsules showed high zeta‐potential values between pH 6 and 8. The in vitro release rates of hydroxypropyl methyl cellulose phthalate (HPMCP)‐ and shellac‐coated microcapsules were superior to that of the zein‐coated microcapsules. Finally, the microcapsules were barely hydrolysed in simulated gastric fluid; however, almost all the microcapsules coated with HPMCP or shellac released their contents in simulated intestinal fluid within 2 h (93.23 and 97.27%, respectively).     

Steady state inferential modeling of temperature and pressure in an air-swept coal pulverizing ball mill

Mill discharge temperature and differential pressure have a strong effect on efficiency and safety of a coal fired power plant. Therefore, it is imperative that they are closely monitored and controlled during mill operation to keep their levels within a predetermined safe and efficient operating range regardless of the rate at which the raw coal is fed to the mill. One way to achieve this is through a control schedule that compares the value obtained from the process to the stored set-point value to determine if there is any deviation that requires correction. This paper describes a steady state model that could be used alongside conventional controllers as an on-line shadow that provides inferential estimates of desired temperatures and pressure drops in the mill circuit which can be continuously compared with the actual values for adjustment. This would not only help to avoid the difficulties associated with direct measurement but also provide a means for early detection of drifts and failing sensors and serve as a temporal back-up for the out-of-order sensors. The model was tested using industrial data collected from four ball mills at a coal fired power plant in South Africa and the results show a reasonable agreement between the measured data and model predictions both qualitatively and quantitatively within a 5% error margin. The model outputs were found to be highly sensitive to the variation in mill loading, the primary air (PA) flow and the mill channel dimensions. Therefore, for validity of this model, accurate determination of all significant parameters is essential. For now, the model is only valid for the ball mills involved in the current study, but with availability of data it can be reproduced elsewhere.     

An Unexpected Pressure Effect in the Catalytic Hydrogenolysis of a Complex Benzyl Amine

The selective hydrogenolysis of a complex benzylamine containing a pyridone ring and aryl fluorides was investigated. The aim of the research was to find a catalyst and reaction conditions under which the complete hydrogenolysis of the benzylamine could be accomplished with no aryl fluoride cleavage nor pyridone hydrogenation observed. This objective was accomplished by use of a specific 10 % Pd/C catalyst in a THF/EtOH solvent at 40 °C. It was found that as the H₂ pressure decreased the amount of debenzylated amine increased because of the decrease in pyridone hydrogenation. Unexpectedly, though, the rate of hydrogenolysis also increased with decreasing H₂ pressure. A rationale for this observation is presented.     

Toxicological housekeeping genes: do they really keep the house?

It is assumed that the expression of housekeeping genes is constant regardless of experimental conditions. In toxicology, this assumption has indeed become a misconception of reasonable concern, as these so-called housekeeping genes vary considerably across different experimental conditions and thereby lead to an erroneous interpretation of the expression profile of a target gene. Given that the choice of reference gene will ultimately influence statistical interpretation of toxicological data, it is essential to validate potential reference genes prior to their use, to establish their suitability for a specific experimental purpose. Therefore, the aim of this study is to quantitatively evaluate the most commonly used housekeeping genes in toxicology research for their suitability as reference endpoints, and thus provide toxicology researchers who have little experience in molecular biology but find themselves interested or involved with gene expression analysis with a summary of information necessary for re-evaluating their procedures. We show that the expression pattern of beta-actin, beta-tubulin, 18S ribosomal RNA (18S rRNA), and elongation factor-lalpha (EF-lalpha), representing commonly used housekeeping genes in toxicology, was modulated on the basis of random exposure condition and time, in both in vivo and in vitro test systems of Atlantic salmon (Salmo salar). Based on the data presented herein and several other reports by other researchers, there are very few biological justifications to refer to anything as a housekeeping gene in real-time PCR assays for toxicological research. However, given the absolute need for normalization genes to correct for sample-to-sample variations, the choice of internal control gene should be determined empirically on the basis of the individual exposure condition and by the individual researcher.     

Influence of particle size fractions on the physicochemical properties of maize flour and textural characteristics of a maize-based nonfermented food gel

The physicochemical properties of fractionated maize flour and the textural characteristics of a maize-based nonfermented food gel (maize tuwo ) prepared from the respective fractionated flours were evaluated. The maize flour was fractionated into four fractions: <75 μm, 75–150 μm, 150–300 μm, 300–425 μm and whole meal (<425 μm). There were variations in the selected chemical constituents of fractionated maize flour including protein (2.9–4%), ash (0.80–0.97%), crude fibre (0.73–0.91%) and damaged starch (10.1–17.4%). The fractionated maize flour gave variable bulk density (0.80–0.93 g cm⁻³), water absorption capacity (1.9–2.1 g g⁻¹) and oil absorption capacity (1.7–2.1 g g⁻¹). The colour characteristics of the fractionated maize flour and the pasting properties were all affected by the fractionation. The cohesiveness index (strain at peak compressive force) of the food gel from the flour fractions ranged between 15% and 19.5% while the softness index of the food gel ranged between 16.7 and 17.5 mm. The relative high cohesiveness and softness indexes (i.e. 19.5% and 17.4 mm respectively) of maize tuwo prepared from the flour fraction of 75–150 μm can predispose the food gel towards easier hand-mouldability and swallowability respectively; being important quality indicators for its acceptability.     

液体弹珠的微流体操作及工程应用

微流体技术是一种精确操控和检测微量流体的新兴技术,广泛应用于生物、化学、材料等领域的实验及工程中.液体弹珠作为一种新兴的数字微流体平台在近几年快速发展.它是一种将疏水的微纳米级颗粒包裹在液滴表面形成的软物质,体积通常在几微升到几百微升之间.区别于构建特殊表面微结构或化学改性制备的超疏水表面,液体弹珠是通过颗粒层阻隔内部液体与载体的微观接触,构建类似于莱顿弗罗斯特液滴的结构来实现微量液体在固体或液体表面不润湿且稳定存在的目的.目前的研究已经证明液体弹珠拥有独特优越的物理性能,如液体弹珠表面的颗粒层将固-液接触转化为固-固和固-气接触,因此具有不粘的特性,与载体表面的摩擦很小,在很小的外力作用下就可以实现灵活移动且不污染弹珠内的液体和载体.当表面颗粒呈多层且致密分布时也并非完全阻隔外界环境,在很大程度上能够减缓内部液体的蒸发且具有良好的气体渗透性,而且液体弹珠具有较好的稳固性,往往能够承受30％的可逆线性弹性形变,这些性能使液体弹珠可以作为理想的数字微流体平台.液体弹珠的原材料十分丰富,从而决定了其性状具有灵活的可调控性,所用颗粒的疏水性和形状会直接影响液体弹珠的力学性能,例如棒状颗粒包裹的液体弹珠具有更大的刚度,链状颗粒包裹的液体弹珠具有优越的弹性性能.颗粒的化学性质可以按需赋予液体弹珠不同的响应特性,从而衍生出多种操控手段,主要方式包括静电力、磁力、自推进、光辐射、温度、超声等,完成液体弹珠的精确移动、定位、颗粒层开启和关闭以及释放内部液体的操作.以上特性使液体弹珠能够应用于各种工程中,在细胞组织和微生物的培养以及微型化学反应器方面具有很好的应用前景,同时还被广泛应用于传感器、制药和精密仪器等领域,例如光电传感、污水检测、微型胶囊制备、构建纳米复合透镜以及精准电化学沉积等.同时液体弹珠制备方法较简单,无需复杂仪器设备,具有很高的经济效益.本文结合近年来液体弹珠相关研究的发展现状介绍了液体弹珠的制备方法、结构特点、材料和不同于纯液滴的性质主要包括有效表面张力、力学稳定性和蒸发速率,归纳了几种主流操作控制液体弹珠移动和释放的手段并分析优势与不足,总结了目前液体弹珠在工程上的主要应用并对其未来的发展趋势和应用前景进行展望.     

Quantifying characteristic growth dynamics in a semi-arid grassland ecosystem by predicting short-term NDVI phenology from daily rainfall: a simple four parameter coupled-reservoir model

Predicting impacts on phenology of the magnitude and seasonal timing of rainfall pulses in water-limited grassland ecosystems concerns ecologists, climate scientists, hydrologists, and a variety of stakeholders. This report describes a simple, effective procedure to emulate the seasonal response of grassland biomass, represented by the satellite-based normalized difference vegetation index (NDVI), to daily rainfall. The application is a straightforward adaptation of a staged linear reservoir that simulates the pulse-like entry of rainwater into the soil and its redistribution as soil moisture, the uptake of water by plant roots, short-term biomass development, followed by the subsequent transpiration of water through foliage. The algorithm precludes the need for detailed, site specific information on soil moisture dynamics, plant species, and the local hydroclimate, while providing a direct link between discrete rainfall events and consequential biomass responses throughout the growing season. We applied the algorithm using rainfall data from the Central Plains Experimental Range to predict vegetation growth dynamics in the semi-arid shortgrass steppe of North America. The mean annual rainfall is 342 mm, which is strongly bifurcated into a dominantly ‘wet’ season, where during the three wettest months (May, June and July) the mean monthly rainfall is approximately 55 mm month^?1; and a ‘dry’ season, where during the three driest months (December, January and February), the mean monthly rainfall is approximately 7 mm month^?1. NDVI data from the Moderate Resolution Imaging Spectroradiometer (MODIS) MOD13Q1 16 day, 250 m × 250 m product were used as a proxy for grassland phenology for the period-of-record 2000–2013. Allowing for temporal changes in basic parameters of the response function over the growing season, the predicted response of the model tracks the observed NDVI metric with correlation coefficients exceeding 0.92. A two-stage series reservoir is preferred, whereby the characteristic time for transfer of a rainfall event to the peak response of NDVI decreases from 24 days (early growing season) to 12 days (late growing season), while the efficiency of a given volume of rainfall to produce a correspondingly similar amount of aboveground biomass decreases by a factor of 40% from April to October. Behaviours of the characteristic time of greenup and loss of rainfall efficiency with progression of the growing season are consistent with physiological traits of cool-season C₃ grasses versus warm-season C₄ grasses, and with prior research suggesting that early season production by C₃ grasses is more responsive to a given amount of precipitation than mid-summer growth of C₄ shortgrasses. Our model explains >90% of seasonal biomass dynamics. We ascribe a systematic underprediction of observed early season greenup following drought years to a lagged or ‘legacy’ effect, as soil inorganic nitrogen, accumulated during drought, becomes available for future plant uptake.     

Electrical properties of natural-fiber-reinforced low density polyethylene composites: A comparison with carbon black and glass-fiber-filled low density polyethylene composites

The electrical properties of sisal fiber-low density polyethylene (LDPE) and coir fiber-LDPE composites have been studied. The dielectric constant progressively increases with increase of fiber loading and decreases with increase of frequency in the case of all composites. The dielectric constant of sisal-LDPE composites has been studied as a function of fiber length. Volume resistivity values decrease with fiber content. The increase of dielectric constant with fiber loading is more predominant at low frequencies in both the sisal fiber-LDPE and coir fiber-LDPE composites. The results of the natural-fiber-filled composites were compared to those of the carbon and glass-fiber-filled LDPE composites. The dielectric constant of carbon-black-loaded LDPE composites increases with carbon content, and the increase is sharper at high carbon content. This is associated with the network formation of carbon black in LDPE matrix. © 1997 John Wiley & Sons, Inc.