فهرست مطالب

Sciences, Islamic Republic of Iran - Volume:30 Issue:4, 2019
  • Volume:30 Issue:4, 2019
  • تاریخ انتشار: 1398/08/10
  • تعداد عناوین: 6
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  • A. Allameh*, F. Ani, M. Shams, Ghahfarokhi, M. Razzaghi, Abyaneh Pages 305-313

    The present study was designed to examine the effects of Lactobacillus plantaraum and L. paracasei on the growth and aflatoxin-producing ability of Aspergillus parasiticus. In these experiments, direct and indirect interactions of two different probiotic lactobacilli with A. parasiticus was examined.A co-culture system which supported both fungal growth and probiotic bacteria showed the inhibitory actions of the lactobacilli on A. parasiticus growth. Disk Diffusion Assay was developed to examine the anti-fungal action of the probiotic cell free extract.  The probiotic extracts were also applied in a micro-dilution assay to evaluate the anti-fungal and anti-aflatoxin properties of the probiotic extracts. The results showed that direct interaction of the bacteria with A. parasiticus in a spot-culture method (two-layer semi-solid/solid culture) caused a clear zone of inhibition of A. parasiticus growth. Fungal growth inhibition was found to be dependent on the concentration of the probiotic extracts added to A. parasiticus culture (micro dilution assay). The inhibitory effects of the probiotic extracts was further confirmed using Disc Diffusion Assay by showing that discs loaded with 50 or 100 µl of extracts resulted in a significant (4-5 folds) inhibition in A. parasiticus growth. The extract prepared from the probiotics inhibited the fungal growth and at higher levels. Accordingly, the probiotic extract (50% v/v) could significantly suppress aflatoxin levels in mycelia and fungal culture media.  In conclusion, probiotic bacteria and their cell-free extracts produced under optimized condition exhibit anti-fungal and anti-mycotoxin effects provided that these bacteria undergo screening and selection prior totheir application.

    Keywords: Probiotic bacteria, Anti-fungal, Screening, Aflatoxin inhibition
  • A. Mollahosseini*, M. Konh Pages 315-323

    In this work, we successfully developed electromembrane extraction via preparation of an electrospun flat membrane based on device. The polyurethane-membrane was prepared by electrospinning method and used in EME. Affecting parameters on membrane preparation were optimized by Taguchi design. The developed method was used for extraction of phthalates as typical molecules and the proposed method was used to determine phthalates in water samples. The applied voltage, extraction time, distance of electrodes and agitation rate were selected as the main factors in EME and optimized using response surface methodology based on a central composite design. Under optimum conditions, calibration curves were obtained in the range of 0.5-5000 ng mL-1 with R2>0.990. The repeatabilities were less than 12% and 14% for intra-day and inter-day, respectively. The limits of detection were found to be 0.03 and 0.02 ng mL-1 and limits of quantification were obtained 0.09 and 0.06 for bis (2- ethylhexyl phthalate), and dimethyl phthalate, respectively.

    Keywords: Central composite design, Eectrospinning, Flat membrane, Gas-chromatography, Phthalates
  • M. Najafi*, E. Marzbanpour Pages 325-330

    In this paper, we calculate the second virial coefficient for binary mixtures of Ar with CH4 and CO in order to evaluate the performance of equations of state (EOSs). The investigated EOSs are van der Waals (vdW), Redlich-Kwong (RK), Peng-Robinson (PR), Carnahan-Starling–van der Waals (CS-vdW) and Guggenheim-van der Waals (G-vdW) based on van der Waals model. In our work, we also use Dieterici model of EOS consists of Dieterici (D) and Dieterici-Carnahan-Starling (DCS). In this study, the ability of these EOSs to predict second virial coefficients of binary mixtures is illustrated and since these models represent two different physical attitudes of contribution of interaction between molecules to thermodynamic functions, therefor from this view point, a comparison between the two models of equations of state is also reported.

    Keywords: Van der Waals model, Dieterici model, Second virial coefficient, Binary mixture
  • M. Ghavidel, Syooki* Pages 331-353

    The excellent preservation of the acritarchs, their great abundance, diversity and good stratigraphic control permit establishment of a detailed Middle and Late Cambrian acritarch biozonation. A total of 56 palynomorph species form the basis of 10 local acritarch assemblage zones. Assemblage zones I-II occur in the lower and middle parts of the Member C of the Mila Formation and suggest Early-mid Middle Cambrian; assemblages zones III-IV appears in the upper part of the Member C of the Mila Formation and the lower part of Ilebeyk Formation and encompass latest Middle and earliest Late Cambrian; acritarch assemblage zones V-IX occur in the middle and upper parts of the Ilebeyk Formation and characterize Late Cambrian; finally, acritarch assemblage zone X appears in the basal part of the Zardkuh Formation and proves to have an early Tremadocian age. Amongst the Late Cambrian acritarch assemblages of Laurentia only the two cosmopolitan species of Timofeevia phosphoritica and Vulcanisphaera turbata are shared with coeval strata in the High Zagros Mountains.Iranian acritarch assemblages show a marked Gondwanan paleobiogeographical affinity, share a high proportion of taxa with typical Baltican and North Africa–Gondwanan assemblages, and are different from known Laurentian microphytoplankton suites. These results are in general agreement with paleogeographical models that place Avalonia, Baltica, and the North African part of Gondwana, at relatively high southern paleolatitudes, whereas Laurentia occupies a sub-equatorial position. Four new acritarch species, namely Leiosphaeridia iranense, Navifusa reticulata, Ooidium zagrosensis, and Veryhachium ilebeykensis are described.

    Keywords: Acritarch biozonation, Middle-Late Cambrian, Mila Formation, Ilebeyk Formation, High Zagros Mountains
  • B. Babayar, Razlighi* Pages 355-362

    In this paper we reduce a free boundary problem from heat transfer to a weakly Singular Volterra  integral equation of the first kind. Since the first kind integral equation is ill posed, and an appropriate method for such ill posed problems is based on wavelets, then we apply the Chebyshev wavelets to solve the integral equation. Numerical implementation of the method is illustrated by two benchmark problems originated from heat transfer. The behavior of the initial and free boundary heat functions along the position axis during the time have been shown through some three dimensional plots. The convergence of the method is pointed in the end of section 2. The numerical examples show the accuracy and applicability of the method from application and programming points of views.

    Keywords: Volterra integral equation of the first kind, Heat equation, Numerical solution, Second kind Chebyshev wavelets, Free boundary
  • * M. R. Ghalani, M. R. Zadkarami Pages 363-369

    In this paper, a multivariate fundamental skew probit (MFSP) model is used to model correlated ordinal responses which are constructed from the multivariate fundamental skew normal (MFSN) distribution originate to the greater flexibility of MFSN. To achieve an appropriate VC structure for reaching reliable statistical inferences, many types of variance covariance (VC) structures are considered to model MFSN. Simulation methods are used to find the properties of the parameters estimate. The Schizophrenia Collaborative Study data invokes the proposed MFSN model. The results confirm that the first-order autoregressive (AR(1)) structure substantially enhances the estimation of the parameters. Furthermore, over time the drugs effect the schizophrenia treatment, noticeably.

    Keywords: Ordinal response, Multivariate fundamental skew probit, Variance covariance structures