masoud derakhshan

Melatonin is involved in regulation of circadian rhythm and alleviation of sleep disorders, such as insomniadue to jet lag and shift work, as it plays a major role in synchronization of the sleep/wake cycle This study is devoted to extraction and determination of melatonin in Pistacia atlantica using anultrasound-assisted solid-liquid extraction (SLE) combined with UV-Vis Spectroscopy. The volume and type of extractionsolvent, sonication time, and extraction temperature on the extraction efficiency were optimized. Under optimum conditions, use of 30 mL of ethanol and 30 min sonication time caused to achieve the limit ofdetection (LOD) of 0.047 ppm. The method accuracy was confirmed according to the calculation of recovery using standardaddition method that, exhibited the successful applicability of the present method for real sample analysis. In addition, theobtained results were compared to those using gas chromatography/Mass spectroscopy (GC/MS). Combination of SLE andUV-Vis leads to greater sensitivity and lower cost for accurate and repeatable extraction of melatonin from Pistacia atlanticawith acceptable recovery and RSD% (1.04%). Therefore, we efficiently extracted and purified of melatonin from an inexpensive source (Pistacia atlanticafruit). The extracted melatonin can be replaced synthetic drugs.

We have first demonstrated that Debreu’s view regarding the publication of The Theory of Games and Economic Behavior by von Neumann and Morgenstern in 1944 as the birth of modern mathematical economics is not convincing. In this paper, we have proposed the hypothesis that the coordinated research programs in the 1930’s, initiated by the Econometric Society and the Cowles Commission for Research in Economics with the objective of unifying economic theory, mathematics and statistics, can be regarded as the beginning of modern mathematical economics as well as econometrics. We have argued that this unification has failed to satisfactorily bridge the gap between mathematical economics and the real world economic issues. However, contrary to Marshall's view that mathematics is not an engine of inquiry in economics but is only a shorthand language, we have established in this paper that the application of mathematics in modern mathematical economics can, under certain conditions, produce economic results of value.

Economists were interested in economic stabilization policies as early as the 1930’s but the formal applications of stability theory from the classical control theory to economic analysis appeared in the early 1950’s when a number of control engineers actively collaborated with economists on economic stability and feedback mechanisms. The theory of optimal control resulting from the contributions of mathematicians Lev Semenovich Pontryagin and Richard Ernest Bellman in the late 1950’s was first applied successfully to models of economic growth in the 1960’s by the economists who were interested in discovering the optimality properties of economic growth trajectories. It is shown that the collaborations of control engineers with econometricians in the 1970’s on the computation of optimal state and control trajectories in econometric models were the earliest attempts to demonstrate the possibility of applying deterministic, stochastic and adaptive optimal control to the numerical solution of optimal economic policies. We have explained why the collaborations of control engineers with econometricians on formulating and computing optimum system design in macroeconomic optimal planning models failed and why the economic applications of optimal control theory have proved to be more productive in the analysis of optimality conditions in mathematical economics and not in the computation of optimal trajectories in econometric models.

We have shown that the reliance on foreign investment within the framework of oil contracts with international oil companies has not been and will not be productive in the transfer and development of technology in Iranian upstream oil industry unless the following conditions are satisfied: i) adequate growth in the propositional and prescriptive knowledge related to oil industry to create a satisfactory absorption capacity، and ii) the active role of regulatory institutions for supervising، managing and enhancing efficiency in the market for technology to secure an effective utilization of the absorption capacity. It is emphasized that a careful identification of players in the market for oil technology transfer and development، and the realization of the processes of weakening and strengthening positions of international oil companies and service oil companies in this market، respectively، is the prerequisite in the design of optimum oil technology policies in Iran. Despite the importance of contractors in the recognition of the necessity of technological development in the chain of oil operations and conveying that to technology developers، we have noted that the scarcity of financial resources for investment in the transfer and development of technology as well as the shortcomings in the optimum utilization of the absorption capacity in Iran imply that the regulatory institutions in the market for oil technology should become more efficient and assume more active role in managing this market. It is shown that these institutions can direct the process of the transfer and development of oil technology along with the national strategies in industrial development by prioritizing the technologies which are consistent with the objectives of oil sector and at the same time having spillover effects to certain key industries in the national economy.

This paper examines critically the contributions of Cournot، Jevons and Walras as the founders of classical mathematical economics from a methodological standpoint. Advances in different economic schools and doctrines in the 19th century produced an environment of multi-dimensionality in economic analysis which was regarded by the pioneers of classical mathematical economists as a chaotic state. We have demonstrated that the formation of this new discipline، known equivalently as pure or scientific economics، was a response to this so-called chaotic state. We have also shown that the erroneous logic of abstraction in the sense of reducing a multi-dimensional economic system to a one-dimensional mechanical framework as the methodological basis of classical mathematical economics has been the origin of serious shortcomings in mathematical treatment of economics. Based on the writings of Jevons and Walras we have provided evidences to support the claim that advances in Marxian economics can be considered as the prime motive in the development of classical mathematical economics.

Articles 14 and 15 of the Grand Policies of Resilient Economy emphasize the following two principles: i) «Enhancing the strategic reserves of Iranian oil and gas … and improving the production capacities …» and ii) Observing the “maximum efficient rate of recovery (within IOR/EOR programs). Hence، oil contracts are optimum upon the satisfaction of these two principles. An emphasis is also given، in the introduction to the Grand Policies of the Resilient Economy، as to the necessity of «an economy based on knowledge and technology، founded on [the principles of] justice، endogenously driven with outward-looking approach، dynamic and progressive.» The application of these four requirements in designing optimum oil contracts may provide four other principles، namely، improving technical-managerial capability of NIOC، securing the inter-generational interests in exploitation of oil reservoirs، transforming NIOC to a national-international oil company، and attaining a competitive status in the global oil market. From the above-mentioned six principles، this paper examines optimum oil contracts by using MER and IOR/EOR principles only، with a brief reference to NIOC technical-managerial improvement. We have shown that the structural conflicts between the objectives of IOCs and NIOC، i. e.، the profit maximization within the principles of profit-seeking corporations، and the economic value maximization of reservoirs within the framework of securing long-term national interests، will make it impossible to conclude an optimum contract with IOCs satisfying the requirements of the resilient economy. This paper concludes that the only contracts which are compatible with the principles of resilient economy are technical and managerial support and cooperation contracts with oil service companies.

After reviewing briefly the Iranian oil contracts from Reuter and D’Arcy concessions to buy-back contracts, we have examined the desired properties of oil contracts as follows: sovereignty and ownership over oil resources, national rights and interests in the chain of oil operations, transfer of technical knowledge and skills, and finally improvement in Government revenues resulting from oil production. An evaluation of oil contracts over a period of 140 years since Reuter’s concession in 1872 reveals the fact that the main attention of Governments has always been focused on gaining higher foreign exchange revenues. In principle, the sovereignty and ownership of oil resources have not usually been a conflicting issue amongst Governments and IOCs due to the fact that the permanent sovereignty over natural resources is well-recognized in international law. However, the point of prime significance is the identification of the impact of this property on the process of oil operations by IOCs, which depends entirely on the knowledge and expertise of NIOC. The other two properties are, more or less, emphasized in all oil contracts, yet without producing any tangible results due to the lack of endogenous efforts to advance technical knowledge and skills in oil industry as well as a change of Government’s outlook to the role and status of oil in economic development. Otherwise, contracts with IOCs cannot be expected to enhance technical and managerial capabilities of NIOC towards becoming a national-international oil company.

We first define and briefly examine the “imitative” and “indigenal” approaches in conventional economic theories from an Islamic Economic perspective. We then review briefly the concepts of “indigenous” and “indigenization” in the humanities and social sciences from the points of view expressed by Imam Khomeini (ره) and the Supreme Leader. We have subdivided the “indigenal approach” into “comparative” and “foundational” approaches. It is shown that in the comparative approach, a critical analysis of the underlying assumptions in economic theories, and specifying the shortcomings of the logic of abstraction employed in economic theorization particularly in identification of economic players and their status in conventional economic theories, can be productive. However, this approach suffers from the lack of adequate potentialities for successful theorization in Islamic Economics, hence cannot be used as a basis for economic policy formations. The paper concludes by proposing the foundational approach as the only solution to indigenization of economics as well as the necessary condition in building Islamic-Iranian model of economic progress.

Optimality conditions for consumption behavior with liquidity constraints are obtained using the functional recurrence equation in Bellman’s dynamic programming and the generalized Hamiltonian function in Pontryagin’s maximum principle. The rejection of Hall’s random walk hypothesis is then established for liquidity constrained consumers. An explicit mathematical relation is formulated which demonstrates the effects of liquidity constraints on consumption، which implies that under certain conditions the liquidity constraint may shift the optimal consumption profile forward even when the rate of time preference exceeds the interest rate. Our analysis is further developed to time-varying interest rates. Using the Kuhn-Tucker conditions، we have shown the interactions between the timevarying interest rate، the utility discount rate and the severity of liquidity constraints. It is shown، using the coefficient of absolute risk aversion، that how the time-varying interest rate may affect optimal consumption through intertemporal elasticity of substitution. Simultaneous effects of the pure preference parameters، interest rates variations and the liquidity constraints on optimal consumption path are mathematically formulated. Limitations in optimal control applications in modeling optimal consumption with liquidity constraints in a stochastic environment are briefly examined.

In this paper, we first consider the role of rational expectations, the Lucas critique and the policy ineffectiveness debate in economic applications of optimal control theory. The problem of time-inconsistency in optimal control of macro-economic models with rational expectations will then be analyzed. The impact of reputation and the stochastic environment on the problem of inconsistency in dynamic choice together with the question of how can the developments in optimal control of macroeconomic models with forward-looking expectations contribute to the practice of econometric model building are the other topics which are discussed. We have adopted a historical approach in this paper, and the scope of our analysis is confined to the basic contributions made in the 20th Century.

Securing the interests of the present and the future generations in nonrenewable hydrocarbon reserves are of prime significance in Iranian oil and gas policy formulations. Despite the massive volume of the initial oil in place (IOIP), the rate of natural depletion is rather low due to the specific properties of Iranian oil reservoirs. This implies the vital importance of enhanced oil recovery (EOR) programs. Moreover, the Iranian giant andsuper-giants oil fields have now reached their second-half of their long-life production profile, which adds further importance to the EOR considerations. According the available research work done in this regard