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Search Results: 1 - 10 of 191546 matches for " DUSAN D. STANOJEVIC "
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Lead and silver extraction from waste cake from hydrometallurgical zinc production
Journal of the Serbian Chemical Society , 2008,
Abstract: This paper presents the experimental results of the extraction of lead and silver from a lead–silver waste cake obtained in the process of hydrometallurgical zinc production. While controlling the pH value, the lead–silver cake was leached at a temperature close to boiling point in different concentrations of aqueous calcium chloride solutions. The experiments were performed applying different ratios between the mass of cake and the volume of the leaching agent under different durations of the process. It was concluded that at the optimal process parameters (pH 2.0–2.5; CaCl2 concentration, 3.6 mol dm-3; temperature, 95 °C; solid/liquid ratio, 1:5), the leaching efficiency of lead and silver could reach the approximate value of 94 %. Applying the same optimal process parameters, the method was applied to the leaching of a lead–silver cake in a magnesium chloride solution, but with significantly lower efficiencies. The results show that leaching of lead and silver in a calcium chloride solution could be a prospective method for increasing the recovery of lead and silver during hydrometallurgical zinc production.
Predicting the Evolution of Sex on Complex Fitness Landscapes
Dusan Misevic,Roger D. Kouyos,Sebastian Bonhoeffer
PLOS Computational Biology , 2009, DOI: 10.1371/journal.pcbi.1000510
Abstract: Most population genetic theories on the evolution of sex or recombination are based on fairly restrictive assumptions about the nature of the underlying fitness landscapes. Here we use computer simulations to study the evolution of sex on fitness landscapes with different degrees of complexity and epistasis. We evaluate predictors of the evolution of sex, which are derived from the conditions established in the population genetic literature for the evolution of sex on simpler fitness landscapes. These predictors are based on quantities such as the variance of Hamming distance, mean fitness, additive genetic variance, and epistasis. We show that for complex fitness landscapes all the predictors generally perform poorly. Interestingly, while the simplest predictor, ΔVarHD, also suffers from a lack of accuracy, it turns out to be the most robust across different types of fitness landscapes. ΔVarHD is based on the change in Hamming distance variance induced by recombination and thus does not require individual fitness measurements. The presence of loci that are not under selection can, however, severely diminish predictor accuracy. Our study thus highlights the difficulty of establishing reliable criteria for the evolution of sex on complex fitness landscapes and illustrates the challenge for both theoretical and experimental research on the origin and maintenance of sexual reproduction.
Saturated-liquid heat capacity of organic compounds: new empirical correlation model
Journal of the Serbian Chemical Society , 2004,
Abstract: A new saturated-liquid heat capacity model is recommended. This model is tested and compared with the known polynomial and quasi-polynomial models on 39 sets with 1453 experimental heat capacity data. The obtained results indicate that the new model is better then the existing models, especially near the critical point.
A simplified approach to the vibrational self-relaxation of simple molecules through convolution of their velocities
Journal of the Serbian Chemical Society , 2000,
Abstract: A theoretical approach has been developed for computing collisional self-relaxation probabilities of the first excited level in the lowest vibrational mode of simple molecules. The bending (n2) vibration in triatomic molecules, in which the average translational and rotational velocities are of the same order of magnitude, was examined. The approach was based on the assumption that both the velocities should be taken into account as a convolution of the corresponding Maxwell's distribution functions. The model was checked for the SO2 molecule in the temperature range from 130-1100 K. The calculated temperature dependence curve (the Landau-Teller plot) exhibits a minimum at about 150 K. The data obtained is discussed in relation to some experimental results. The comparison indicates that the problem was treated in correct manner. Some additional aspects of the relaxation, like intermolecular interactions and the steric factor, are also briefly considered. It is believed that this approach offers quite a good basis for further improvements of theoretical treatments.
Saturated-liquid heat capacity calculation of alkanes
Journal of the Serbian Chemical Society , 2005,
Abstract: An empirical model for the calculation of the heat capacity of alkanes is recommended. This model was tested and compared to known models (Luriaa Benson and Rizickaa Domalski) using 68 sets with 1155 literature experimental heat capacity data of 39 alkanes. The obtained results indicate that the newmodel is slightly better tha the existing models, especially near the critical point.
New values of the polarity factor
Journal of the Serbian Chemical Society , 2000,
Abstract: New values of the polarity factor c for 96 substances are proposed. Estimation procedure is tested on the values of this factor from the original work of Halm and Stiel.
Saturated-liquid heat capacity: new polynomial models and review of the literature experimental data
Journal of the Serbian Chemical Society , 2003,
Abstract: In this paper a review of selected literature experimental data for saturated-liquid heat capacities was presented. Two-, three- and four-parameter polynomial correlation models are tested on those data. Obtained results lead to the conclusion that correlation quality depends on the number of parameters, and slightly on the type of models. The best two-, three- and four-parameter models were proposed.
Field exposed water in a nanopore: liquid or vapour?
Dusan Bratko,Christopher D. Daub,Alenka Luzar
Physics , 2008, DOI: 10.1039/b809072f
Abstract: We study the behavior of ambient temperature water under the combined effects of nanoscale confinement and applied electric field. Using molecular simulations we analyze the thermodynamic causes of field-induced expansion at some, and contraction at other conditions. Repulsion among parallel water dipoles and mild weakening of interactions between partially aligned water molecules prove sufficient to destabilize the aqueous liquid phase in isobaric systems in which all water molecules are permanently exposed to a uniform electric field. At the same time, simulations reveal comparatively weak field-induced perturbations of water structure upheld by flexible hydrogen bonding. In open systems with fixed chemical potential, these perturbations do not suffice to offset attraction of water into the field; additional water is typically driven from unperturbed bulk phase to the field-exposed region. In contrast to recent theoretical predictions in the literature, our analysis and simulations confirm that classical electrostriction characterizes usual electrowetting behavior in nanoscale channels and nanoporous materials.
Water-mediated ordering of nanoparticles in electric field
Dusan Bratko,Christopher D. Daub,Alenka Luzar
Physics , 2008, DOI: 10.1039/b809135h
Abstract: Interfacial polar molecules feature a strongly anisotropic response to applied electric field, favoring dipole orientations parallel to the interface. In water, in particular, this effect combines with generic orientational preferences induced by spatial asymmetry of water hydrogen bonding under confined geometry, which may give rise to a Janus interface. The two effects manifest themselves in considerable dependence of water polarization on both the field direction relative to the interface, and the polarity (sign) of the field. Using molecular simulations, we demonstrate strong field-induced orientational forces acting on apolar surfaces through water mediation. At a field strength comparable to electric fields around a DNA polyion, the torques we predict to act on an adjacent nanoparticle are sufficient to overcome thermal fluctuations. These torques can align a particle with surface as small as 1 nm2. The mechanism can support electrically controlled ordering of suspended nanoparticles as a means of tuning their properties, and can find application in electro-nanomechanical devices.
Primary colorectal lymphoma: An overview
Goran Z Stanojevic,Milica D Nestorovic,Branko R Brankovic,Miroslav P Stojanovic
World Journal of Gastrointestinal Oncology , 2011,
Abstract: Lymphomas represent common hematological malignancies with increasing incidence in recent years. The major site of extranodal non-Hodgkin lymphoma is the gastrointestinal tract. Involvement of the large intestine is rare in comparison to the stomach or small bowel. The disease appears later in life, predominantly in the male population. Complaints are nonspecific, requiring a high index of suspicion in order to establish the diagnosis. The treatment varies from chemotherapy alone to multimodal therapies combining surgery, chemotherapy and radiotherapy. The small number of patients with various histological subtypes and different stage at presentation results in unclear protocol for the treatment of primary colorectal lymphoma. The purpose of this paper is to review current data on primary lymphoma of the colon and rectum while analyzing reported case series and published material on the subject.
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