Selective laser sintering of porous tissue engineering scaffolds from poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide)/carbonated hydroxyapatite nanocomposite microspheres

This study focuses on the use of bio-nanocomposite microspheres, consisting of carbonated hydroxyapatite (CHAp) nanospheres within a poly(L: -lactide) (PLLA) matrix, to produce tissue engineering (TE) scaffolds using a modified selective laser sintering (SLS) machine. PLLA microspheres and PLLA/CHAp nanocomposite microspheres were prepared by emulsion techniques. The resultant microspheres had a size range of 5-30 mum, suitable for the SLS process. Microstructural analyses revealed that the CHAp nanospheres were embedded throughout the PLLA microsphere, forming a nanocomposite structure. A custom-made miniature sintering platform was installed in a commercial Sinterstation((R)) 2000 SLS machine. This platform allowed the use of small quantities of biomaterials for TE scaffold production. The effects of laser power; scan spacing and part bed temperature were investigated and optimized. Finally, porous scaffolds were successfully fabricated from the PLLA microspheres and PLLA/CHAp nanocomposite microspheres. In particular, the PLLA/CHAp nanocomposite microspheres appeared to be promising for porous bone TE scaffold production using the SLS technique.     

Effects of partial substitutions of cerium and aluminum on the hydrogenation properties of La(0.65−x)CexCa1.03Mg1.32Ni(9−y)Aly alloy

Hydrogen in metal hydrides could be one of the promising energy storage mediums to address the intermittent nature of renewable energy. To convert the hydrogen energy to electricity, the storage system has to be coupled with a fuel cells system. Hence, it is important to design a hydrogen storage system that meets the operating requirements for a fuel cell system. In this work, the effects of partial substitution of both cerium and aluminum on the hydrogenation properties of La_(0.65−x)Ce_xCa_1.03Mg_1.32Ni_(9−y)Al_y alloys were investigated simultaneously using factorial design. Both Ce and Al additions greatly improved the reversibility of hydrogen storage capacity. However, the maximum hydrogen storage capacity and absorption kinetics can be reduced by the additions. As Ce and Al gave opposite effects on the absorption and desorption plateaus, they could be used to tune the properties of the alloys to the desired operating conditions for fuel cell applications.     

The relationship between price, amounts of saturated and trans fats, and nutrient content claims on margarines and oils.

PURPOSE: Modifications to the amount and type of fat in the diet are recommended as strategies to help reduce heart disease risk. Individuals can choose from a variety of margarines and oils to alter their intakes of different types of fats, and nutrient content claims on product labels (e.g., 'low in saturated fat') can help them quickly identify healthful products. However, margarines and oils vary in price. METHODS: To examine the relationship between the price and amounts of saturated and trans fats in margarines and oils, and the relationship between price and the presence of nutrient content claims, price and label information were recorded for margarines (n=229) and oils (n=342) sold in the major supermarkets within the Greater Toronto Area. RESULTS: Linear regression analysis revealed a negative relationship between the price and amounts of saturated fat and trans fats in margarines, but not in oils. Margarines with a nutrient content claim were significantly more expensive than were those without a claim. CONCLUSIONS: The findings for margarines are of particular concern for lower income groups for whom budgetary constraints result in the purchase of lower priced foods, and also raise important questions about the usefulness of nutrient content claims in guiding food selections.     

A radio frequency identification and sensor-based system for the transportation of food

The damage caused by the degeneration of the quality of perishable products usually results in a great loss to transportation enterprises. To improve the delivery system for perishable products, a real-time monitoring and online decision support system with Radio frequency identification (RFID), a sensor network and a decision rule base has been developed in this study. First of all, the value degeneration process is described, using several mathematical models for handing different ways of perishing. Based on the mathematical models, and data from RFID and the sensor network, the quality of the goods can be predicted by the forecast module. When something abnormal occurs, the warning function will send an alarm signal to the users, then, the rule-based decision module will provide the user with suggestions as how to cope with the abnormality. The results from the simulation have shown that the monitoring and decision support system is an efficient tool for reducing the transportation losses of perishable products for the enterprises in cold chain.     

Hyporheic exchange and fulvic acid redox reactions in an Alpine stream/wetland ecosystem, Colorado Front Range

The influence of hyporheic zone interactions on the redox state of fulvic acids and other redox active species was investigated in an alpine stream and adjacent wetland, which is a more reducing environment. A tracer injection experiment using bromide (Br-) was conducted in the stream system. Simulations with a transport model showed that rates of exchange between the stream and hyporheic zone were rapid (alpha approximately 10(-3) s(-1)). Parallel factor analysis of fluorescence spectra was used to quantifythe redox state of dissolved fulvic acids. The rate coefficient for oxidation of reduced fulvic acids (lambda = 6.5 x 10(-3) s(-1)) in the stream indicates that electron-transfer reactions occur over short time scales. The rate coefficients for decay of ammonium (lambda = 1.2 x 10(-3) s(-1)) and production of nitrate (lambda = -1.0 x 10(-3) s(-1)) were opposite in sign but almost equal in magnitude. Our results suggest that fulvic acids are involved in rapid electron-transfer processes in and near the stream channel and may be important in determining ecological energy flow at the catchment scale.     

Ant search based control optimisation strategy for a class of chaotic system

In this paper the authors propose a logistic mapping using chaotic model to describe the time-variable pest population. Two kinds of fuzzy rule embedded control strategies are investigated, three segment control and five segment control. They are designed to reduce the pest population. The simulation results show that the objective function is non-convex and anomalous along the control parameters. To find the optimal parameter combinations we develop an ant search approach. By imitating the food hunting and nest moving behaviours of Pachycondyla apicalis ants, this method can adaptively and effectively explore solution areas and arrive at the optimal solution. When we compared the performance curves with the one without control strategy, the method is better and can be used for a wide range of pest control problems in real life.     

Early alliance, alliance ruptures, and symptom change in a nonrandomized trial of cognitive therapy for avoidant and obsessive-compulsive personality disorders.

Participants were 30 adult outpatients diagnosed with avoidant personality disorder or obsessive-compulsive personality disorder who enrolled in an open trial of cognitive therapy for personality disorders. Treatment consisted of up to 52 weekly sessions. Symptom evaluations were conducted at intake, at Sessions 17 and 34, and at the last session. Alliance variables were patients' first alliance rating and "rupture-repair" episodes, which are disruptions in the therapeutic relationship that can provide corrective experiences and facilitate change. Stronger early alliances and rupture-repair episodes predicted more improvement in symptoms of personality disorder and depression. This work points to potentially important areas to target in treatment development for these personality disorders. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

具有恶化效应和学习效应的单机成组调度问题

讨论了一类具有恶化效应和学习效应的单机成组调度问题, 其中工件的加工时间为开工时间和组内工序的函数. 通过对问题性质的分析以及多项式时间算法的描述, 得出如下结论: 在单机成组调度问题中, 即便工件的加工时间同时受恶化效应和学习效应的制约, 极小化完工时间问题以及极小化总资源消耗的问题仍是多项式时间可解的.     

Glass Surface Layer Density by Neutron Depth Profiling

Several lithium-disilicate ( Li₂O∙2SiO₂ ) glass samples were synthesized, polished and subjected to static leach tests for varying periods of time in an HCl solution (pH 4) at 90°C. The presence of an alteration layer on the leached specimens was independently confirmed using infrared spectroscopy. These samples were then analyzed with neutron depth profiling (NDP), and for all exposure times between 1 and 20 h, a leached layer was detected by NDP. The residual concentration of ⁶Li in the alteration layer was observed to be approximately 10% of the bulk glass value. The 7.5 h and 17.5 h samples were cross-sectioned using focused ion beam milling, and the thickness of the alteration layer on the samples was measured directly using scanning electron microscopy to be 9.8 and 22.9 μm, respectively. The areal density of the gel layers — determined by deconvolution of the NDP spectra — was coupled with the SEM measurement to give densities of 1.46 ± 0.08 g/cm³ for the 7.5 h specimen and 1.46 ± 0.05 g/cm³ for the 17.5 h specimen. This preliminary work shows that NDP can be used to determine the average density of gel layers formed owing to leaching of alkali-silicate glass.