Iranian Journal of science and Technology (A: Siences)
Volume:34 Issue: 3, Summer 2010

Nitric oxide (NO) is an important signalling molecule with diverse physiological functions inplants. In the last years, many advances have been obtained regarding NO synthesis and its physiological effects in plants. It was found to play a crucial role in plant growth and development, starting from germination to flowering, ripening of fruit and senescence of organs, respiratory metabolism, as well as plant response to abiotic and biotic stressors. However, the molecular mechanisms underlying its effects remain poorly understood. This review discusses some aspects related to NO in plants, such as chemical properties,synthesis pathways, antioxidant action, physiological and biochemical changes that occur in plants under normal conditions and the possible functions of NO under changing environmental conditions. The interaction of NO with plant hormones, and cross-talk with salicylic acid are also discussed. The elucidation of such aspects represents a challenge to future studies.

Using a new numerical model, the pump-to-signal relative intensity noise (RIN) transfer in singlepump fiber optical parametric amplifiers for low modulation frequencies is investigated. The model includes fiber loss, pump depletion, as well as the gain saturation, and therefore, it can describe the practical circumstances associated with various applications of fiber optical parametric amplifiers. The nonlinear dynamics of the RIN transfer for different pump and signal powers is studied. The impact of the input pump and signal powers and signal wavelength on the RIN transfer is also investigated. Finally, the model is compared to the available experimental data and a very good agreement is obtained.

In this paper, the Lorentzian version of Beltrami-Euler formula is investigated in 1n. Initially, the first fundamental form and the metric coefficients of generalized timelike ruled surface are calculated and by the help of the Christoffel Symbols, Riemann-Christoffel curvatures are obtained. Thus, the curvatures of spacelike and timelike tangential sections of generalized timelike ruled surface with timelike generating spaceand central ruled surface are found to be related to the determinant of the first fundamental form of the surface. In addition to this, the relation between the sectional curvature and the distribution parameter of this ruled surface is obtained. Finally, paying attention to the spacelike and timelike central ruled surface of the generalized timelike ruled surface one by one, four different types of Lorentzian Beltrami-Euler formulas areconstituted for generalized timelike ruled surface with timelike generating space.

A novel and safe method for nitration of phenols, anilines and other aromatic compounds has been found to be feasible with alumina sulfuric acid (ASA) as catalyst and Mg (NO3)2.6H2O as nitrating agent in neat water as solvent. The use of water makes this method compatible with the green chemistry approach.

Cesium content and some other more radiologically important mineral elements were measured by nuclear and non-nuclear analytical methods in Iranian daily diets.This study was extended to a few more similar functioning elements such as Sr, Rb, I, K, Mg and Ca as well. Though the 137Cs and other radionuclieds were not measured in these diets under planned regular investigation in this work, but in comparison with some other backgrounds, the contribution and the impact/effective amount of 137Cs in thedaily diet/total mixed diet may be estimated either by its own part concentrations or by the amount of intakes per person per day, if any of those, is in sufficient quantity of normal range. Nevertheless, the protective role of these minerals in human organs is the main issue of this assessment. The amount of 137Cs and other radionulides in the foodstuff depends upon direct contamination/exposure or via the mineral and organiccontent of the radionuclides in the soil and environment to be transferred to nutritive species. This effect is also considered.

Root and shoot osmotic and elastic properties of two species of Haloxylon aphyllum and H.persicum in response to water stress were studied. The main goal of the study was to determine if the tissues of two species utilize osmotic adjustment and/or enhance their elastic property during prolonged water stress condition. The results showed that although tissue elasticity of both species of haloxylon was enhanced due toapplication of repeated water stress cycles, this condition also increased the tissue osmotic potential. Therefore, this study concluded that haloxylon species utilize enhancement of elasticity rather than osmotic adjustment to maintain positive turgor and withstand drought.

This research is focused on facies distribution, palaeoecology and palaeoenvironment of the Guri Member of the Mishan Formation in Kuh-e Shur and Kuh-e Kurdeh sections at the Lar area, Fars province. The Guri Member is composed of limestone, marly limestone and marl and the thickness at Kuh-e Shur and Kuh-e Kurdeh is about 72 and 110 meters, respectively. Based on petrographical studies of 120 thin sections, 8 microfacies have been identified that are deposited in open shelf environment (inner and middle shelf).Palaeolatitudinal reconstructions based on skeletal grains suggests that carbonate sedimentation of Guri Member took place in tropical waters under oligotrophic conditions, a typical environment for photozoan assemblages. These biotic assemblages of the Guri Member belong to foralgal association and may be broadly defined as comprising heterozoan assemblages. An important factor controlling the spread of heterozoanassemblages during the Early Miocene in the study areas seem to be related to the palaeoecology and evolution of zooxanthellate corals.