Poly(2‐hydroxyethyl methacrylate) nanocomposites: From a nonionic gel to pH sensitivity

2‐Hydroxyethyl methacrylate (HEMA)‐clay nanocomposites were prepared via in situ free radical polymerization using montmorillonite (MMT) as a crosslinker. The structure and surface morphology of the nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction, and scanning electron microscopy. It was found that exfoliated or highly expanded intercalated nanocomposite structure was obtained. The swelling degree was determined in distilled water and various pH buffered solutions. The highest swelling capacity in distilled water was observed for the nanocomposite sample prepared with the MMT amount of 10 % (w). It was seen that the diffusion mechanism was Fickian type in distilled water and also in various pH‐buffered solutions. It is interesting that the swelling degree of nanocomposites in alkaline pH values increased by the increasing of MMT in the polymer structure. This result supports the possibility of future applications of the novel nanocomposite in systems for the controlled released of drugs. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Biochemical and thermal properties of β-galactosidase enzymes produced by artisanal yoghurt cultures

β-Galactosidases, produced by pure and mixed cultures of Streptococcus thermophilus 95/2 (St 95/2) and Lactobacillus delbrueckii ssp bulgaricus 77 (Lb 77) isolated from the Toros mountain region of Turkey, were characterised with respect to their biochemical and thermal properties. Optimum pH and temperature for maximum activity were determined and these enzymes were stable in the pH range 7–9 and in the temperature range 20–37 °C, retaining 80–90% of their initial activities. The inactivation energies of β-galactosidase from Lb 77, St 95/2 and mixed culture (Lb 77 and St 95/2) were 51.3, 44.0 and 48.3 kcal mol⁻¹, respectively. Moreover, thermodynamic (ΔG, ΔS, ΔH) and kinetic constants (K_m and V_max) were determined and effects of metal ions were investigated. As a result, these enzymes could be considered as potential candidates for lactose hydrolysis of milk and milk products.     

Compatibilization of low‐density polyethylene/plasticized starch blends by reactive compounds and electron beam irradiation

Blends based on various compositions of low‐density polyethylene (LDPE) and plasticized starch (PLST) were prepared by melt extrusion and molding in the form of sheets under hot press. The rheology properties during mixing were studied in terms of torque and temperature against mixing time. The structural properties of LDPE/PLST blends before and after electron beam irradiation was characterized by IR spectroscopy, tensile mechanical testing, and scanning electron microscopy (SEM). The torque‐time curves during the mixing process showed that the values of torque in the first region of mixing for pure LDPE or LDPE/PLST blends are higher in the presence of the compatibilizer PEMA than that in the presence of EVA. In addition, the stability of mixing was attained after a short time in the presence of PEMA. The IR spectroscopy suggests that the compatibilization by EVA and PEMA compounds proceeds through the formation of hydrogen bonding during mixing and this compatibility was improved after electron beam irradiation. The stress–strain curves of pure LDPE and its blends with PLST showed the behavior of tough polymers with yielding properties. The SEM micrographs of the fracture surfaces give supports to the effect of EVA and PEMA as compatibilizers and the effect of electron beam irradiation. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Challenges and possibilities for achieving household food security in the Western Sudan region: the role of female farmers

This paper investigates the role of women in achieving household food security in the Western Region of Sudan, an area much affected by the impacts of drought and civil conflicts. The study is based on a quantitative survey and qualitative focus group discussions, supported by personal observations made during fieldwork. Additionally, the study draws upon secondary data that is publicly available. Results demonstrate that women play a major role in producing and providing food for their households in this high-risk climate and conflict area, while men are more likely to migrate seasonally and even permanently. In addition, women are responsible for food preparation, processing, and food preservation and are wholly responsible for attending to household garden plots. They therefore contribute more to household food security than men, though this contribution is not recognized in official statistics. The study findings indicate that the main problems women face as food producers and providers are a lack of access to the full package of improved production methods (improved seeds, fertilizers, modern farming methods, credit services, pesticides, appropriate technologies, and marketing facilities), in addition to gender disparities and gender-biased traditions. The impacts of natural crises and civil conflicts are gendered and therefore the responses to these crises must be gender responsive. Holistic and strategic policies and plans that take gender issues into account are thus needed in order to achieve food security.     

REBTAM: reliable energy balance traffic aware data reporting algorithm for object tracking in multi-sink wireless sensor networks

Recently, Multi-sink Wireless Sensor Networks (WSNs) have received more and more attention due to their significant advantages over the single sink WSNs such as improving network throughput, balancing energy consumption, and prolonging network lifetime. Object tracking is regarded as one of the key applications of WSNs due to its wide real-life applications such as wildlife animal monitoring and military area intrusion detection. However, many object tracking researches usually focus on how to track the location of objects accurately, while few researches focus on data reporting. In this work, we propose an efficient data reporting method for object tracking in multi-sink WSNs. Due to the limited energy resource of sensor nodes, it seems especially important to design an energy efficient data reporting algorithm for object tracking in WSNs. Moreover, the reliable data transmission is an essential aspect that should be considered when designing a WSN for object tracking application, where the loss of data packets will affect the accuracy of the tracking and location estimation of a mobile object. In addition, congestion in WSNs has negative impact on the performance, namely, decreased throughput, increased per-packet energy consumption and delay, thus congestion control is an important issue in WSNs. Consequentially, this paper aims to achieve both minimum energy consumption in reporting operation and balanced energy consumption among sensor nodes for WSN lifetime extension. Furthermore, data reliability is considered in our model where the sensed data can reach the sink node in a more reliable way. Finally, this paper presents a solution that sufficiently exerts the underloaded nodes to alleviate congestion and improve the overall throughput in WSNs. This work first formulates the problem as 0/1 Integer Linear Programming problem, and proposes a Reliable Energy Balance Traffic Aware greedy Algorithm in multi-sink WSNs (REBTAM) to solve the optimization problem. Through simulation, the performance of the proposed approach is evaluated and analyzed compared with the previous work which is related to our topic such as DTAR, NBPR, and MSDDGR protocols.     

Implementing and sustaining lean processes: the dilemma of societal culture effects

Lean processes allow the elimination of waste and the resulting improvements in productivity. However, implementing and sustaining lean processes are easier in some organisations than in others. There may be societal culture differences, as the successes in initial implementation in Japan have not been followed by global success. As organisations accelerate their lean efforts to gain or maintain competitive advantage, studying societal cultural effects seems timely. Understanding of the societal culture that the firm or subsidiary is operating in would be useful in determining how lean processes should lead the effort. Using the cultural dimensions developed by Hofstede, we examine the interconnection of societal culture and lean processes. For example, a societal emphasis on individualism is positively associated with a high level of lean process adoption, in terms of individual employee involvement, individual creativity and firm efficiency. A societal emphasis on high uncertainty avoidance is positively associated with a high level of lean process adoption, in terms of control and standardisation, efficiency and long-term philosophy. A societal emphasis on high power distance is positively associated with a high level of lean process adoption, in terms of control and standardisation, and efficiency. A long-term orientation in the society will be positively associated with a high level of lean process adoption, in terms of all of the dimensions. A societal emphasis on femininity will be positively associated with a high level of lean process adoption, in terms of employee involvement, creativity and long-term philosophy.     

Solving comprehensive dynamic job shop scheduling problem by using a GRASP-based approach

There are many dynamic events like new order arrivals, machine breakdowns, changes in due dates, order cancellations, arrival of urgent orders etc. that makes static scheduling approaches very difficult. A dynamic scheduling strategy should be adopted under such production circumstances. In the present study an event driven dynamic job shop scheduling mechanism under machine capacity constraints is proposed. The proposed method makes use of the greedy randomised adaptive search procedure (GRASP) by also taking into account orders due dates and sequence-dependent set-up times. Moreover, order acceptance/rejection decision and Order Review Release mechanism are integrated with scheduling decision in order to meet customer due date requirements while attempting to execute capacity adjustments. We employed a goal programming-based logic which is used to evaluate four objectives: mean tardiness, schedule unstability, makespan and mean flow time. Benchmark problems including number of orders, number of machines and different dynamic events are generated. In addition to event-driven rescheduling strategy, a periodic rescheduling strategy is also devised and both strategies are compared for different problems. Experimental studies are performed to evaluate effectiveness of the proposed method. Obtained results have proved that the proposed method is a feasible approach for rescheduling problems under dynamic environments.     

Optimizing the physical properties of calcium nanoferrites to be suitable in many applications

Calcium nano ferrite with composition CaGd_xEr_yFe_2?x?yO₄ (x?=?y?=?0.0, x?=?0.025, y?=?0.05) was prepared by citrate gel auto combustion method. The prepared samples showed orthorhombic phase structure and the crystallite sizes were found in the range of 32.1–35.3 nm. Detailed observation via the Field Emission Scanning Electron Microscopy (FESEM) showed that the calcium ferrite nano-particles were spherical and capsule like formation shape. The hysteresis loop confirms the magnetic behavior of the investigated samples, which is then discussed on the basis of super exchange interactions. Magnetic parameters such as saturation magnetization, coercivity, and retentivity were obtained. Greater than six-fold increase in coercivity (≈2085 Oe) was observed in calcium nanoferrites compared to the doped samples (≈360 Oe). The CaFe₂O₄-type structure includes edge- and corner sharing BO₆ octahedral, constituting a very unique network similar to perovskite-related nanoparticles. This structural network leads to an improvement in the physical properties of the investigated samples. Great efforts have been made to synthesize pure nanoferrite samples without any secondary phases even after the substitution of low soluble rare earth ions. Special attention should be given to calcium ferrite nanoparticles which are suitable candidates to be used in the manufacturing of bone-like scaffolds, hyperthermia treatment of cancer and biological activity.