Scale-up of Thermally Dried Kefir Production as Starter Culture for Hard-Type Cheese Making: An Economic Evaluation

This paper concerns the effect of thermal-drying methodology on the investment cost for dried kefir cells production in order to be used as starter culture in cheese manufacturing. Kefir cells were produced at pilot plant scale using a 250-L bioreactor and whey as the main substrate. Kefir cells were subsequently dried in a thermal dryer at 38?°C and used as a starter culture in industrial-scale production of hard-type cheeses. The use of thermally dried kefir as starter culture accelerated ripening of cheeses by increasing both lipolysis and fermentation rate as indicated by the ethanol, lactic acid, and glycerol formation. Additionally, it reduced coliforms and enterobacteria as ripening proceeded. This constituted the basis of developing an economic study in which industrial-scale production of thermally dried kefir starter culture is discussed. The industrial design involved a three-step process using three bioreactors of 100, 3,000, and 30,000 L for a plant capacity of 300 kg of thermally dried kefir culture per day. The cost of investment was estimated at 238,000 €, which is the 46% of the corresponding cost using freeze-drying methodology. Production cost was estimated at 4.9 €/kg of kefir biomass for a 300-kg/day plant capacity, which is the same as with the corresponding cost of freeze-dried cells. However, the estimated added value is up to 10.8?×?10⁹ € within the European Union.     

On the singular set,the resolvent and Fermi's Golden Rule for finite volume hyperbolic surfaces

Consider a finite volume hyperbolic surface. Under perturbation the spectrum of the Laplace operator is unstable but the singular set is stable. We characterize the singular set in terms of the resolvent of the Laplace operator and extend Fermi's Golden Rule to the case of multiple eigenvalues. the date of receipt and acceptance should be inserted later     

The settling of suspensions promoted by rigid buoyant particles

When substantial numbers of buoyant particles are mixed with a sedimenting suspension of heavy particles, the two types of solids undergo rapid lateral segregation from each other. Streams 3–5 mm in diameter containing the less populous species form and flow through a concentrated continuum suspension of the more populous species. This buoyancy driven convection results in greatly enhanced sedimentation rates. A theory is developed on the premise that streams move in plug flow with all resistance to motion confined to a thin lubricating layer at the strean-continuum interface. The model is compared with experimental data and is shown to account correctly for the effect of each system parameter on the observed settling rates.     

On the student evaluation of university courses and faculty members’ teaching performance

Trying to determine higher education quality, one gets quickly to one of its significant dimensions, namely the quality of faculty members’ teaching. The latter and, overall, the quality of any university course should be certainly evaluated by their recipients, namely students. In this paper we develop a statistical framework based on Statistical Quality Control mainly, which can be used in order to exploit student evaluations as much as possible. More specifically we present two directions of data monitoring and analysis; the one uses control charts and the other hypotheses testing. The results that can be raised through both directions are crucial for any decision maker.     

Interfacial Impregnation Chemistry in the Synthesis of Cobalt Catalysts Supported on Titania

The interfacial chemistry of the impregnation step involved in the synthesis of cobalt catalysts supported on titania was investigated with regard to the mode of interfacial deposition of the aqua complex [Co(H₂O)₆]²⁺ on the “titania/electrolyte solution” interface, the structure of the inner‐sphere complexes formed, and their relative interfacial concentrations. Several methodologies based on the application of deposition experiments and electrochemical techniques were used in conjunction with diffuse‐reflectance spectroscopy and EPR spectroscopy. These suggested the formation of mononuclear/oligonuclear inner‐sphere complexes on deposition of the [Co(H₂O)₆]²⁺ ions at the “titania/electrolyte solution” interface. The joint application of semiempirical quantum‐mechanical calculations, stereochemical considerations, and modeling of the deposition data revealed the exact structure of these complexes and allowed their relative concentrations at various Co^II surface concentrations to be determined. It was found that the interface speciation depends on the Co^II surface concentration. Mononuclear complexes are formed at the compact layer of the “titania/electrolyte solution” interface for low and medium Co^II surface concentrations. Formation of mono‐hydrolyzed Ti₂O–TiO and the dihydrolyzed TiO–TiO disubstituted configurations is very probable. In the first configuration one water ligand of the [Co(H₂O)₆]²⁺ ion is substituted by a bridging surface oxygen atom and another by a terminal surface oxygen atom. In the second configuration two water ligands of the [Co(H₂O)₆]²⁺ ion are substituted by two terminal surface oxygen atoms. Binuclear and trinuclear inner‐sphere complexes are formed, in addition to the mononuclear ones, at relatively high Co^II surface concentrations.     

Determination of antiferromagnetic exchange coupling in the tetrahedral thiolate-bridged diferrous complex [Fe2(SEt)6]2-

Protein-bound iron-sulfur clusters and their synthetic analogues are characterized by tetrahedral metal sites, multiple oxidation levels, and exchange coupling. The recent attainment of several all-ferrous protein clusters and the presence of sulfide- and thiolate-bridged sites in the all-ferrous state of the nitrogenase P-cluster provides an imperative for determination of exchange coupling between tetrahedral Fe(II) sites with sulfur bridges. The cluster in the previously reported compound (Et(4)N)(2)[Fe(2)(SEt)(6)] is centrosymmetric with distorted tetrahedral coordination and a planar Fe(2)(mu-SEt)(2) bridge unit. The compound is diamagnetic at 4.2 K, indicating antiferromagnetic coupling. The lower limit J > 80 cm(-)(1) (H = JS(1).S(2)) is obtained by M?ssbauer spectroscopy. Analysis of magnetic susceptibility data affords J = 165 +/- 15 cm(-)(1). It is noteworthy that the J value of the diferrous pair obtained here is comparable to the J values reported for the mixed-valence state of plant-type Fe(2)S(2) ferredoxins. The near temperature independence of the quadrupole splitting (DeltaE(Q) = 3.25 mm/s at 4.2 K and 3.20 mm/s at 180 K) indicates that no excited orbital states are appreciably populated at temperatures less than 300 K. The paramagnetism arises solely from thermal population of the S = 1 state of the spin ladder. This work provides the only measure of antiferromagnetic coupling by Fe(II) pairs in a tetrahedral sulfur environment.     

On the analysis of the unsymmetric successive overrelaxation method when applied top-cyclic matrices

Summary A Determinantal Invariance, associated with consistently ordered weakly cyclic matrices, is given. The DI is then used to obtain a new functional equation which relates the eigenvalues of a particular block Jacobi iteration matrix to the eigenvalues of its associated Unsymmetric Successive Overrelaxation (USSOR) iteration matrix. This functional equation as well as the theory of nonnegative matrices and regular splittings are used to obtain convergence and divergence regions of the USSOR method.