Modeling controlled nutrient release from polymer coated fertilizers: diffusion release from single granules

A comprehensive model describing the complex and "non-Fickian" (mathematically nonlinear) nature of the release from single granules of membrane coated, controlled release fertilizers (CRFs) is proposed consisting of three stages: i. a lag period during which water penetrates the coating of the granule dissolving part of the solid fertilizer in it ii. a period of linear release during which water penetration into and release out occur concomitantly while the total volume of the granules remains practically constant; and iii. a period of "decaying release", starting as the concentration inside the granule starts to decrease. A mathematical model was developed based on vapor and nutrient diffusion equations. The model predicts the release stages in terms of measurable geometrical and chemophysical parameters such as the following: the product of granule radius and coating thickness, water and solute permeability, saturation concentration of the fertilizer, and its density. The model successfully predicts the complex and "sigmoidal" pattern of release that is essential for matching plant temporal demand to ensure high agronomic and environmental effectiveness. It also lends itself to more complex statistical formulations which account for the large variability within large populations of coated CRFs and can serve for further improving CRF production and performance.     

HEXTRAN–SMABRE calculation of the VVER-1000 coolant transient-1 benchmark

The VVER-1000 coolant transient benchmark is intended for validation of couplings of the thermal hydraulic codes and three-dimensional neutron kinetic core models. It concerns switching on a main coolant pump when the other three main coolant pumps are in operation. The problem is based on an experiment performed in Kozloduy NPP in Bulgaria. In addition to the real plant transient, an extreme scenario concerning a control rod ejection after switching on a main coolant pump was calculated. At VTT the three-dimensional advanced nodal code HEXTRAN is used for the core dynamics, and the system code SMABRE as a thermal hydraulic model for the primary and secondary loop. The parallelly coupled HEXTRAN–SMABRE code has been in production use since early 1990s, and it has been extensively used for analyses of VVER NPPs. The SMABRE input model is based on the standard VVER-1000 input used at VTT. The whole core calculation is performed with HEXTRAN. Also the core model is based on earlier VVER-1000 models. Nuclear data for the calculation were specified in the benchmark. The paper outlines the input models used for both codes. Calculated results are introduced both for the coupled core system with inlet and outlet boundary conditions and for the whole plant model. Parametric studies have been performed for selected parameters.     

Degradation in soybean oil,sunflower oil and partially hydrogenated fats after food frying,monitored by conventional and unconventional methods

This paper aims to study discontinuous deep frying of potatoes, milanesas (breaded bovine Semimembranosus muscle) and churros (flour, water, milk, lemon and salt) in soybean oil, sunflower oil and partially hydrogenated fats, monitored by conventional and unconventional methods. With the exception of partially hydrogenated fat after 80.5 h of deep-frying churros, all the oils exceeded 25% of total polar compounds (TPC) and the content of polymeric and dimerized triacylglycerols were higher than 10%, prevailing thermal alterations. For none of the samples the percentage of free fatty acids exceeded 2% of oleic acid. The losses of tocopherols during frying reached 76.0%. Little significant alterations occurred in the fatty acids composition, iodine index calculated, saponification index and formation of trans isomers after frying. The rapid tests used to determine TPC, malondialdehyde and alkenals have proved to be viable alternatives to monitor the quality of frying oils.     

Aggregation Properties of Albumin in Interacting with Magnetic Fluids

In this study, interactions of Fe₃O₄ magnetic nanoparticles with serum albumin biomolecules in aqueous solutions were considered. The studies were conducted with the laser correlation spectroscopy and optical analysis of dehydrated films. It was shown that the addition of magnetite to an albumin solution at low concentrations of up to 10⁻⁶ g/L led to the formation of aggregates with sizes of up to 300 nm in the liquid phase and an increase in the number of spiral structures in the dehydrated films, which indicated an increase in their stability. With a further increase in the magnetite concentration in the solution (from 10⁻⁴ g/L), the magnetic particles stuck together and to albumin, thus forming aggregates with sizes larger than 1000 nm. At the same time, the formation of morphological structures in molecular films was disturbed, and a characteristic decrease in their stability occurred. Most stable films were formed at low concentrations of magnetic nanoparticles (less than 10⁻⁴ g/L) when small albumin–magnetic nanoparticle aggregates were formed. These results are important for characterizing the interaction processes of biomolecules with magnetic nanoparticles and can be useful for predicting the stability of biomolecular films with the inclusion of magnetite particles.     

Efficient and Selective Hydrosilylation of Carbonyl Compounds Catalyzed by Iron Acetate and N‐Hydroxyethylimidazolium Salts

Aromatic aldehydes, along with aryl alkyl, heteroaryl alkyl, and dialkyl ketones were efficiently reduced to their corresponding primary and secondary alcohols, respectively, in high yields, using the commercially available and inexpensive polymeric silane, polymethylhydrosiloxane (PMHS), as reducing agent. The reaction is catalyzed by in situ generated iron complexes containing hydroxyethyl‐functionalized NHC ligands. Turnover frequencies up to 600 h⁻¹ were obtained.     

Characterization and evaluation of the spoilage potential of Lactococcus piscium isolates from modified atmosphere packaged meat

A total of 222 psychrotrophic lactococci isolated from use-by day, modified atmosphere packaged (MAP) meat were identified to the species level by numerical analyses of EcoRI and ClaI ribopatterns and phylogenetic sequence analyses of 16S, rpoA and pheS genes. In addition, their meat spoilage potential was studied. The majority of the isolates (n=215) were identified as Lactococcus piscium, while seven isolates belonged to Lactococcus raffinolactis. L. piscium was shown to be adapted to growing in a variety of MAP meat products including broiler, turkey, pork, and minced meat from beef and pork, where they belonged to the predominating microbiota at the end of the storage. Numerical analyses of EcoRI and ClaI ribopatterns, and phylogenetic sequence analyses of rpoA and pheS genes were shown to be reliable tools in species level identification of meat lactococci. The spoilage potential of L. piscium was evaluated by inoculating representative isolates to MAP pork stored at 6 °C for 22 days. Development of spoilage population was monitored using a culture-independent T-RFLP approach. The sensory shelf life of pork inoculated with L. piscium was shortened compared to the uninoculated control. Alongside with the inoculated L. piscium isolates, Leuconostoc spp. present as initial contaminants in the samples thrived. This shows that even though lactococci were inoculated at higher levels compared to the natural microbiota, they did not occupy the niche and prevent the growth of other lactic acid bacteria.     

An efficient group key management protocol using code for key calculation: CKC

This paper presents a new group key management protocol, CKC (Code for Key Calculation) for secure IP multicast. In this protocol which is based on logical key hierarchy, only the group key needs to be sent to new member at join. Then, using the group key current members and the new member calculate the necessary keys by node codes and one-way hash function. A?node code is a random number assigned to each node to help users calculate necessary keys. Again, at leave server just sends the new group key to the remaining members. By this key, members calculate necessary keys using node codes and one-way hash function. The security of the keys is based on one-wayness of hash function. The results show that CKC reduces computational and communication overhead, and message size largely at join without increasing them at leave.     

Hierarchical Structuring in Block Copolymer Nanocomposites through Two Phase‐Separation Processes Operating on Different Time Scales

Tailoring the size and surface chemistry of nanoparticles allows one to control their position in a block copolymer, but this is usually limited to one‐dimensional distribution across domains. Here, the hierarchical assembly of poly(ethylene oxide)‐stabilized gold nanoparticles (Au‐PEO) into hexagonally packed clusters inside mesostructured ultrathin films of polystyrene‐block‐poly(methyl methacrylate) (PS‐b‐PMMA) is described. A close examination of the structural evolution at different nanoparticle filling fractions and PEO ligand molecular weights suggests that the mechanism leading to this structure‐within‐structure is the existence of two phase separation processes operating on different time scales. The length of the PEO ligand is shown to influence not only the interparticle distances but also the phase separation processes. These conclusions are supported by novel mesoscopic simulations, which provide additional insight into the kinetic and thermodynamic factors that are responsible for this behavior.     

Effect of 2-propanol and water contents on the crystallization and particle size of titanium dioxide synthesized at low-temperature

Two series of titanium dioxide, TiO₂, powder were prepared at a temperature of 50 °C without any catalyst. The effects of 2-propanol and water contents on the formation of crystalline powder mixture of anatase and brookite were systematically studied. The characteristics of produced powder were determined by employing X-ray diffraction, transmission electron microscopy, nitrogen adsorption test and Fourier transform infrared spectroscopy.