Nutritional characterization of carbohydrates and proximal composition of cooked tropical roots and tubers produced in Costa Rica

Tropical roots and tubers (TRT) are important staple foods in the tropics. TRT are produced by small farmers and have received only limited attention. The objective of this paper was to evaluate nutritionally important carbohydrate fractions and proximal composition of cooked cassava (Manihot esculenta), cocoyam- or tannia- (Xantosoma sp) and yam (Dioscorea alata) grown in Costa Rica. Twenty boiled samples of each TRT were analyzed for proximal composition, following AOAC protocols. Carbohydrate fractions (dietary fiber, available and resistant starch) and alpha-amylolysis rate were assessed by enzymatic methods. All TRT analyzed consisted mainly of water and carbohydrates, representing moderate dietary fiber and energy sources. They show a low protein level and contain no fat. Moisture, protein, ashes and dietary fiber contents vary significantly (p<0.01) among the three species. In terms of their proximal composition, these locally grown TRT differ from TRTs cultivated in the South Pacific area, but appear similar to other Latin American varieties. In all samples most of the dietary fiber (84-88%) is insoluble; available starch ranges between 74 and 84% of the dry matter, whereas resistant starch content varied between 0.7 and 1.7%. Amylolysis rate was similar for cassava and cocoyam, whereas a significantly slower digestion (p<0.01) was recorded for yam. Compared to values reported in the literature for other starchy foods and to gelatinized potato starch, used as reference sample, the studied TRT showed intermediate amylolysis rates. It is concluded that consumption of these TRT may be promoted in Costa Rica and other countries with a similar nutritional situation.     

Energy-efficient scheduling for a flexible flow shop using an improved genetic-simulated annealing algorithm

The traditional production scheduling problem considers performance indicators such as processing time, cost, and quality as optimization objectives in manufacturing systems; however, it does not take energy consumption or environmental impacts completely into account. Therefore, this paper proposes an energy-efficient model for flexible flow shop scheduling (FFS). First, a mathematical model for a FFS problem, which is based on an energy-efficient mechanism, is described to solve multi-objective optimization. Since FFS is well known as a NP-hard problem, an improved, genetic-simulated annealing algorithm is adopted to make a significant trade-off between the makespan and the total energy consumption to implement a feasible scheduling. Finally, a case study of a production scheduling problem for a metalworking workshop in a plant is simulated. The experimental results show that the relationship between the makespan and the energy consumption may be apparently conflicting. In addition, an energy-saving decision is performed in a feasible scheduling. Using the decision method, there could be significant potential for minimizing energy consumption.     

Adaptive control for the discrete-time parametric-strict-feedback form

The design of a state feedback controller for a class of SISO non-linear discrete-time systems is proposed. Namely, an alternative adaptive scheme is stated for the parametric-strict-feedback form. The control objective is to achieve tracking of a reference signal. Backstepping control is combined with a parameter estimator based on an orthogonalization process which overcomes the drawback of over-parameterization. Without assuming any growth conditions on the non-linearities, global boundedness and convergence are obtained in the closed loop system.     

Electrostatic actuation as a self-testing method for silicon pressure sensors

The aim of this work is to investigate the possibility of using electrostatic forces to actuate the membrane of a pressure sensor in order to create self-testing features in the system. It is shown that the electrostatic pressure is small compared with the external pressure, unless large voltages or electrical charges are used. The interrelation between electrostatic forces and externally applied pressure is calculated for different electrical drive modes of the capacitor, in the case of a uniform membrane and for a MESA-type membrane.     

‘Generation rent’ and the emotions of private renting: self-worth,status and insecurity amongst low-income renters

Abstract

The UK private-rented sector is increasingly accommodating a diverse range of households, many of whom are young people struggling to access other forms of housing. For those at the bottom end of the sector, who typically have limited economic resources, it is a precarious housing tenure due to its expense and insecurity, yet few studies have explored qualitatively the emotional consequences of this for well-being. We address this gap in the ‘generation rent’ literature by focusing attention on those voices that have been less prominent in the literature. Informed by the theoretical lens of ‘residential alienation’, our study illustrates the emotional toll of private renting upon low-income groups in a national context where state regulation is more limited. In doing so, we add nuance to the literature surrounding socio-economic differentiation within the UK private-rented sector. Our arguments are also relevant to an international audience given global concerns about housing precarity and the politics of housing.     

Aflatoxins and ochratoxin A in Brazilian paprika

Seventy paprika samples collected in the city of São Paulo, Brazil, from January to April 2006 were analysed for aflatoxins and ochratoxin A (OTA) using an immunoaffinity column clean-up and HPLC-FLD. For aflatoxins, the limit of quantification (LOQ) were 0.23, 0.23, 0.45 and 0.45 μg/kg for AFB₁, AFB₂, AFG₁ and AFG₂, respectively. For OTA the LOQ was 0.80 μg/kg. Aflatoxins were found in 82.9% of samples and AFB₁ was detected in 61.4% at levels ranging from 0.5 to 7.3 μg/kg with mean concentration of 3.4 μg/kg. OTA was found in 85.7% at levels ranging from 0.24 to 97.2 μg/kg with mean concentration of 7.0 μg/kg.     

Effect of the type of nylon chain‐end on the compatibilization of PP/PP‐GMA/nylon 6 blends

Polyamide and polypropylene (PP) are two important classes of commercial polymers; however, their direct mixing leads to incompatible blends with poor properties. Polypropylene functionalized with glycidyl methacrylate (PP‐GMA) was used as a compatibilizer in blends of PP and nylon 6, because of the possible reaction of ? NH₂ and ? COOH groups with the epoxide group of GMA. Two types of nylon 6 with different ratios between ? NH₂ and ? COOH groups were used. The one with higher concentration of ? COOH groups was less compatible with PP in a binary blend. When PP‐GMA was used as a compatibilizer, a better dispersion of nylon in the PP matrix was obtained together with better mechanical properties for both nylons used in this work. © 2001 Society of Chemical Industry     

Thermal stability of modified end‐capped poly(lactic acid)

The influence of functional end groups on the thermal stability of poly(lactic acid) (PLA) in nitrogen‐ and oxygen‐enriched atmospheres has been investigated in this article using differential scanning calorimetry, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). Functional end groups of PLA were modified by succinic anhydride and l ‐cysteine by the addition–elimination reaction. PLA was synthesized by azeotropic condensation of l ‐lactic acid in xylene and characterized by nuclear magnetic resonance. The values of the activation energies determined by TGA in nitrogen and oxygen atmospheres revealed that the character of functional end groups has remarkable influence on the thermal stability of PLA. Moreover, DMA confirmed the strong influence of functional end groups of PLA on polymer chains motion. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41105.