Showing papers by "Islamic Azad University published in 2003"

Mineral trioxide aggregate (MTA) and calcium hydroxide as pulp-capping agents in human teeth: a preliminary report.

Abstract: Aim To compare mineral trioxide aggregate (MTA) with calcium hydroxide when used as pulp-capping materials in human teeth. Methodology Eleven pairs of maxillary third molars in subjects between 20 and 25 years of age were subjected to mechanical pulp exposure. The exposed pulps were capped with MTA or calcium hydroxide, covered with ZOE and restored with amalgam. A total of 14 teeth were extracted after periods of 1 week (two molars) 2 months (three molars), 3 months (five molars), 4 months (two molars) and 6 months (two molars). Results Histological evaluation demonstrated less inflammation, hyperaemia and necrosis plus thicker dentinal bridge and more frequent odontoblastic layer formation with MTA than calcium hydroxide. Conclusions Although the results favour the use of MTA, more studies with larger samples and a longer follow up are suggested.

General Solution for Mechanical and Thermal Stresses in a Functionally Graded Hollow Cylinder due to Nonaxisymmetric Steady-State Loads

Abstract: In this paper the general theoretical analysis of two-dimensional steady-state thermal stresses for a hollow thick cylinder made of functionally graded material is developed. The temperature distribution is assumed to be a function of radial and circumferential directions with general thermal and mechanical boundary conditions on the inside and outside surfaces. The material properties, except Poisson's ratio, are assumed to depend on the variable r and they are expressed as power functions of r The separation of variables and complex Fourier series are used to solve the heat conduction and Navier equations.

Thermal buckling of functionally graded cylindrical shell

Abstract: In this article, the thermal buckling loads of cylindrical shells of functionally graded material are considered. Derivation of equations are based on the first-order shell theory and the Sanders kinematic equations. The derived equilibrium and stability equations for the functionally graded cylindrical shell are identical with the equations for homogeneous shells expressed in the form of forces and moments per unit length. Assuming that the material properties vary linearly through the thickness direction, the system of fundamental partial differential equations in terms of the displacement components is established. Buckling analysis of functionally graded cylindrical shells under two types of thermal loads with simply supported boundary conditions are carried out. Results are obtained in the analytical form. The results are validated with the known data in the literature.

Functionally Graded Cylindrical Shell Thermal Instability Based on Improved Donnell Equations

Abstract: The thermal instability of cylindrical shells of functionally graded material is considered. The derivation of equations is based on first-order shell theory and the complete Sanders kinematic equations. The resulting equilibrium and the stability equations contain the rotations in the x and θ directions and the transverse shear force in the θ direction, in addition to the conventional Donnell equations. When it is assumed that the material properties vary linearly through the thickness direction, the system of fundamental partial differential equations in terms of the displacement components is is established. Instability analysis of functionally graded cylindrical shells under two types of thermal loads with simply supported boundary conditions is carried out. Results are obtained in analytical form. The results are validated with the known data in the literature.

Cross-tolerance between morphine- and nicotine-induced conditioned place preference in mice.

Abstract: The acquisition of morphine and nicotine conditioned place preference (CPP) and cross-tolerance between the response of two drugs was studied in mice. A biased CPP paradigm was used to study the effect of the agents. Morphine (5 mg/kg) and nicotine (1 mg/kg) induced CPP. Naloxone (0.5, 1 and 2 mg/kg), but not mecamylamine (0.025, 0.05 and 0.1 mg/kg), induced conditioned place aversion (CPA). Both antagonists reversed CPP induced by morphine and nicotine. Administration of one daily dose of morphine (12.5, 25 or 50 mg/kg) for 3 days or nicotine (0.5, 1 or 2 mg/kg) three times a day for 12 days, in order to develop tolerance to the drugs, reduced the conditioning induced by morphine (5 mg/kg) or nicotine (1 mg/kg). CPA-induced by naloxone was reduced in animals, which were rendered tolerant to morphine (50 mg/kg) or nicotine (2 mg/kg). Mecamylamine, however, which did not induce any response in the nontolerant mice, elicited CPP in the tolerant animals. It is concluded that there may be a cross-tolerance between morphine- and nicotine-induced CPP.

Numerical solution of linear Fredholm and volterra integral equation of the second kind by using Legendre wavelets

Abstract: Uses the continuous Legendre wavelets on the interval [0,1) in the manner of M. Razzaghi and S. Yousefi, to solve the linear second kind integral equations. We use quadrature formula for the calculation of inner products of any functions, which are required in the approximation for the integral equations. Then, we reduced the integral equation to the solution of linear algebraic equations.

Novel Gadolinium PVC-Based Membrane Sensor Based on Omeprazole as an Antibiotic

Abstract: A novel gadolinium ion-selective electrode based on the antibiotic omeprazole as membrane carrier was prepared. The electrode has a linear dynamic range between 1.0×10−1 and 1.0×10−5 M, with a Nernstian slope of 19.3 ± 0.3 mV decade−1 and a detection limit of 5.0×10−6 M. The potentiometric response is independent of the pH of the solution in the pH range 4.0–10.0. The electrode possesses the advantages of short conditioning time, fast response time and especially, very good selectivity over a large number of other cations. The electrode can be used for at least 2 months without any considerable divergence in potentials. It was used as an indicator electrode in potentiometric titration of Gd(III) ions with EDTA.

Effect of Mn2+, Co2+, Ni2+, and Cu2+ on horseradish peroxidase: activation, inhibition, and denaturation studies.

Abstract: The effects of transition metal ions (M2+) such as Mn2+, Co2+, Ni2+, and Cu2+ on the functional and structural stabilities of horseradish peroxidase (HRP) were investigated with respect to reversible chemical denaturation, Michaelis-Menten kinetics, chemical modification and time-dependent catalytic activity. Conformational Gibbs free energy (ΔG°(H2O)) as a structural stability criterion and transition concentrations of metal ions ([M2+]1/2) were estimated using a two-state chemical denaturation model. Activation and inhibitory concentration ranges for each metal ion were specified by the steady-state enzyme kinetics. Results of a pH-profile method confirmed by chemical modification indicate that a histidine residue interacts in the activation concentration range, whereas carboxylic residues (Asp and Glu) contribute to interaction in the inhibitory concentration range. Incubation of the enzyme with the metal ion at activation concentration leads to long-term functional stability of peroxidase. Thus, such metal ions as potent effectors induced the enhancement of conformational and functional stabilities of horseradish peroxidase.

Interaction of metal ions with caffeine and theophylline: stability and structural features.

Abstract: The interactions of caffeine and theophylline with divalent cadmium, mercury, strontium and barium ions were studied in aqueous solution and physiological pH Fourier transform infrared spectroscop

Thallium-DNA Complexes in Aqueous Solution. Major or Minor groove Binding

Abstract: Thallium (Tl) binds to the major and minor grooves of B-DNA in the solid state (Howerton et al., Biochemistry 40 10023–10031, 2001). The aim of this study was to examine the binding of Tl(I) cation with calf-thymus DNA in aqueous solution at physiological pH, using constant concentration of DNA (12.5 mM) and various concentrations of metal ions (0.5 to 20 mM). UV-visible and FTIR spectroscopic methods were used to determine the cation binding site, the binding constant and DNA structural variations in aqueous solution. Direct Tl bindings to guanine and thymine were evident by major spectral changes of DNA bases with overall binding constant of K = 1.40 × 10 M−1 and little perturbations of the backbone phosphate group. Both major and minor groove bindings were observed with no alteration of the B-DNA conformation. At low metal concentration (0.5 mM), the number of cations bound were 10 per 1000 nucleotides, while at higher cation concentration (10 mM), this increased to 30 cations per 1000 nucleot...

The Effect of Inflation on Government Revenue and Expenditure: The Case of the Islamic Republic of Iran

Abstract: This paper provides an empirical analysis of the government budget deficit, money supply growth and inflation in the Islamic Republic of Iran. We use a simultaneous equation system to examine the effect of inflation on government revenue and expenditure, using quarterly data. Our major finding has been that the government budget deficit will increase in the inflationary condition. In addition, the deficit will increase money supply and this tends to increase inflation in Iran.

Thermal and mechanical instability of an imperfect shallow spherical cap

Abstract: In this article, the thermal and mechanical buckling loads of a cap of a shallow spherical shell of isotropic material and geometrically imperfect shell are considered The equilibrium and stability equations are based on Donnell-Mushtari-Velasov (DMV) theory and are derived using the variational method The Sander's nonlinear strain-displacement relations are used The shell is under external pressure for mechanical loading and uniform temperature rise and radial temperature difference for thermal loadings A simply supported boundary condition is assumed The solutions for thermal and mechanical buckling loads are obtained using the stability equations and the Galerkin method One-term approximation for the middle-plane shell displacement is considered The expressions for the thermal and mechanical buckling loads are obtained analytically and are given by closed-form solutions

Chemical Composition of the Essential Oil of Stachys byzanthin C. Koch. from Iran

Abstract: The chemical composition of the oil obtained by hydrodistillation of the aerial parts of Stachys byzanthina C. Koch, was investigated by GC and GC/MS analysis. Twenty-four components representing 88.5% of the total oil were identified, of which sesquiterpenes—alpha;-copaene (16.5%), spathulenol 16.1%), β-caryophyllene (14.3%) and β-cubebene (12.6%)—were the major components.

Prevalence of oral leukoplakia and lichen planus in 1167 Iranian textile workers.

Abstract: Objective: To evaluate the prevalence of oral precancerous lesions in textile workers. Materials and methods: A cross-sectional study was undertaken to assess a total of 1167 textile factory workers randomly selected from a total of 6947. An overall 97 women and 1070 men aged 18–69 years (mean=31.8 years) were studied. Regular smoking during the past 6 months was considered as the smoker group. Leukoplakia lesions were classified in accordance to Axell criteria [Axell T, Pindborg JJ, Smith CJ and Van-der-waal I (1996). J Oral Pathol Med25: 49]. Results: The results showed that 115 workers (9.9%) had red and white lesions. Among these 43 positive detections (3.7%) had leukoplakia and six cases (0.5%) had lichen planus. The smoking habits of the workers were limited to cigarette smoking. There was a statistically significant positive correlation between tobacco smoking and oral leukoplakia (P < 0.001). Conclusion: There was a statistically significant positive correlation between tobacco smoking and leukoplakia in this relatively young cohort with generally mild tobacco use. The prevalence of leukoplakia had an inverse relationship with the level of education.

Cytogenetic study of some rapeseed (Brassica napus L.) cultivars and their hybrids

Abstract: Meiotic study was performed in 22 Brassica napus cultivars considering chiasma frequency and distribution as well as chromosome pairing. All cultivars possessed n = 19 chromosome number (4x) and showed a deviant course of prophase-I meiosis with synezetic knot and post pachytene diffuse stage. Chromosome stickiness occurred in most of the cultivars from early prophase to late telophase-II leading to the formation of laggard chromosomes and micronuclei. The cultivars studied differed significantly in chiasma frequency and distribution as well as bivalent formation indicating their genomic differences. Cluster analysis and ordination based on principal components analysis grouped those cultivars showing meiotic similarities. Some of the cultivars showed the occurrence of unreduced meiocytes and pollen grains.

Model of age estimation based on dental factors of unknown cadavers among Iranians.

Abstract: Two hundred and ten cadavers ranging in age from 25 to 60 were studied. Thirty subjects from each five-year interval were selected, and data were collected using the mandibular anterior and premolar teeth after extraction. Sections ranging from 0.5 to 1.0 mm were measured by a stereo microscope with a precision of 0.1 mm. The following factors were determined: attrition, periodontosis, root resorption, secondary dentine apposition, cementum apposition, and translucency of the root. Statistical analysis used the sum of ranks of the dental factors as an independent variable in a linear regression model to estimate the age of the cadaver. Among the different mandibular teeth, the sum of ranks of the first premolar factors had the best correlation coefficient with age. The sum of the dental factors presented a better model than each of the factors alone. The first premolar is recommended as the first step in the estimation of age.

A new masking method for spatial domain watermarking of three-dimensional triangle meshes

Abstract: We examine a new masking scheme for three-dimensional mesh watermarking in the spatial domain. The masking factor at each point is defined based an estimate of the average difference between the position of connected vertices to a vertex. We test the proposed watermarking scheme by embedding a random binary sequence and applying different attacks, such as additive random noise, compression by MPEG-4 SNHC, and mesh simplification, which shows that the proposed masking scheme can improve the robustness of the spatial domain watermarking scheme.

The prevalence of nursing caries in 18 to 60 months old children in Qazvin

Abstract: The study was carried out to establish the prevalence of Nursing Caries and its relation and caustive factors in children aged 18 to 60 months coming to Health Care Center weighing more than 2.5 kg. A total of 544 children (314 boys and 230 girls) were included in this study. The prevalence of Nursing Caries in girls was 23.5%, in boys 16.5% and in both sexes 19.5%. In affected children dmft was 3.8 times more than the unaffected children and DMFT of their mothers was higher too. Bottle feeding specially during sleep showed statistically significant increase in nursing caries and so did the duration of feeding with mother's milk. The results agree with those obtained in similar populations and showed that the prevalence of nursing caries is anxiously high.

MHD activity at low q(a) in Iran Tokamak 1 (IR-T1)*

Abstract: An attempt is made to explain the behaviour of the magneto-hydrodynamic (MHD) instabilities observed at low values of the edge safety factor q(a) on the basis of experimental results obtained on the Iran Tokamak 1 (IR-T1). For the poloidal-magnetic-field fluctuations observed at the Mirnov coils, Mirnov-coil analysis shows that both the m = 2/n = 1 and the m = 3/n = 2 mode are unstable, and that nonlinearly the 2/1 mode further destabilizes the 3/2 mode. Estimates are given for the characteristic growth time of the m = 2 mode, τg, and the related rate of island growth, dW/dt. The experimentally determined value of τg is found to be larger than the linear theoretical one, and the difference is explained by qualitative arguments. The experimental and theoretical estimates of dW/dt, on the other hand, are found to be in reasonable agreement with each other.

Kinetic spectrophotometric method for the determination of rhodium by its catalytic effect on the oxidation of O-toluidine blue by periodate in micellar media

Abstract: A simple kinetic spectrophotometric method was developed for the determination of ultra trace amounts of Rh(III). The method is based on the catalytic effect of rhodium(III) on the oxidation of o-Toluidine blue by periodate in micellar media. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of o-Toluidine blue at 628 nm with a fixed-time method. The decrease in the absorbance of o-Toluidine blue is proportional to the concentration of Rh(III) in the concentration range 1.0–400.0 ng/mL, with a fixed time of 0.5–4.5 min from initiation of the reaction. The limit of detection is 0.2 ng/mL Rh(III). The relative standard deviation for the determination of 0.020 and 0.100 μg/mL Rh(III) was 2.2 and 1.5%, respectively. The method was applied to the determination of rhodium in water.

Reaction Between 5-Isopropylidene-2,2-dimethyl-1,3-dioxane-4,6-dione and tert-Butyl Isocyanide in the Presence of Primary or Secondary Amines

Abstract: 5-Isopropylidene-2,2-dimethyl-1,3-dioxane-4,6-dione (the condensation product of Meldrum’s acid and acetone) reacts smoothly with tert-butyl isocyanide in the presence of primary or secondary amines to produce N-tert-butyl-2,2-dimethylbutyramide derivatives and/or 1-tert-butyl-4,4-dimethyl-2,5-dioxopyrrolidine-3-carboxamides in good yields.