OALib Journal期刊

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匹配条件: “F Hashemi” ,找到相关结果约144707条。
Comparative Study on Application of Bimetallic Pt-Based Alloy Electrocatalysts in Advanced Chlor-Alkali Electrolysis  [PDF]
F Farzami, E Joudaki, S. J Hashemi
Engineering (ENG) , 2011, DOI: 10.4236/eng.2011.38102
Abstract: Application of an oxygen-depolarized cathode will contribute to energy saving in chlor-alkali electrolysis. For this purpose, the development of high-performance cathode with the best electrocatalyst is essential. Using bimetallic Pt-based alloy electrocatalysts including PtPd and PtAg carbon-supported in oxygen-depolarized cathode chlor-alkali cell has been shown to have the high cell performance. This study presents application of PtRu carbon supported electrocatalyst oxygen-depolarized cathode and performance comparison of cells with carbon-supported PtRu, PtPd and PtAg electrocatalysts cathodes using the same DSA-Cl2 anode. Results show that there are quite similarity between the effects of various factors on the caustic current efficiency (CCE) in a zero-gap oxygen-depolarized chlor-alkali cells employing carbon-supported PtPd, PtRu and PtAg electrocatalysts. Besides, it seems that the PtPd/C electrocatalyst cathode has relatively higher performance than the other cathodes with PtAg/C and PtRu/C electrocatalysts in zero-gap chlor-alkali cells.
Some fixed point theorems for multi-valued contractions in quasi-metric spaces
S. F. Hashemi
International Journal of Mathematical Analysis , 2012,
Results of photorefractive keratectomy for high Myopia in Noor Clinic of Tehran
Hashemi SH,Fatehi F
Tehran University Medical Journal , 2000,
Abstract: Many studies have shown the effectiveness of photorefractive keratectomy (PRK) in correction of vision in low and moderate Myopia. To evaluate the results of 193-nm exeimer laser photorefractive keratectomy for highly Myopic eyes, we reviewed refractive outcome of 43 eyes of 30 patients. Most eyes were treated with 1-step operation, using a 6 mm optical zone. 43 eyes were treated for Myopia, which were between -6.40 and -16.90 diopters. The mean pre-operative refraction was -9.50 D. All eyes were followed for at least 12 months. At 12tht month visit, 30.2% and 60.5% of eyes achieved correction within 1 and 2 D of attempted correction, respectively. At this time, 62.7% of eyes obtained 20/40 visual acuity or better uncorrected. At 1 year, 13% and 8% of eyes lost 3 and 4 lines of best-corrected visual acuity, respectively. Also 13% of eyes lost 2 lines. 12 months after PRK, 5 eyes developed corneal haze grade 2 and 2 eyes, grade 3 (0-5 scale). There was much undercorrection seen in this group compared with patients undergoing PRK for low and moderate Myopia. Photorefractive keratectomy for high Myopia, though effective, is not a safe and accurate procedure and is less predictable and stable than performing it for low and moderate Myopia.
Effects of monotherapy versus combination therapy on overall and disease-free survival in high-grade astrocytoma
Amouzegar Hashemi F.,Hashemi E.,Haddad P.,Kazemian A.
Tehran University Medical Journal , 2007,
Abstract: Background: The standard treatment for high-grade astrocytoma (grades 3 and 4) is surgery followed by radiotherapy (post-op RT). Adjuvant chemotherapy increases disease-free survival (DFS) and overall survival (OS). There are several drugs used for this purpose, each of which have shown benefits and shortcomings. The superiority of combination therapies such as PVC (procarbazine, CCNU and vincristine) over single agents such as BCNU (carmustine) and CCNU (lumostin) has not been definitively established. Single agent CCNU could be a very convenient treatment, as it only involves oral prescription every six weeks. Thus, in this study, we compare CCNU alone with PCV to establish any potential superiority with regard to DFS and OS."nMethods: From 2003-2006, patients with high-grade astrocytoma who had undergone surgery and radiotherapy in the Cancer Institute of Imam Khomeini Hospital, Tehran, Iran, were randomized to CCNU alone or PCV. Chemotherapy was repeated every six weeks for six cycles. Six weeks after the end of sixth cycle, a CT scan was performed. New neurologic signs and symptoms or increases in the previous signs and symptoms and/or new masses in imaging and/or growth of the residual tumor (> 25%) and/or enhancement of any inactive mass from the previous imaging was considered a recurrence. DFS was considered to be the duration from the end of RT to the date of recurrence or last follow-up. OS was taken as the duration from the end of RT to date of death or last follow-up."nResults: After informed consent, of the 70 patients included in this study, 38 were treated with PCV and 32 were treated with CCNU. The mean age was 44 years, ranging from 16 to 78 years, and 51 of the patients were male. Nineteen patients had grade 3 anaplastic astrocytoma and 51 patients had grade 4 glioblastoma multiforme. There were no significant differences with regard to patient age, gender and pathology between the CCNU and PCV groups. DFS and OS were 26 and 27 months, respectively, in the CCNU group and 29 and 34 months, respectively, in the PCV group. By log-rank test, the difference between CCNU and PCV was not statistically significant with regard to the length of DFS and OS."nConclusion: Although no significant differences were found, a trend toward better survival could be seen in patients treated with PCV. Further studies with more patients and longer follow-up are needed to definitively resolve this issue.
Dynamics of Income Distribution — A Diffusion Analysis  [PDF]
Fariba Hashemi
Theoretical Economics Letters (TEL) , 2011, DOI: 10.4236/tel.2011.12008
Abstract: The study is motivated by the observation that the distribution of income across countries varies as a function of time. It would not be unreasonable to assume that there exists a statistical equilibrium distribution of income with a certain mean and variance, towards which the ensemble of countries considered tend to converge, and there is a speed of adjustment towards this said equilibrium. In order to quantify this process, the evolution through time of income around its trend is modeled using a classic stochastic differential equation. The model describes the diffusion of shocks across space, via an income adjustment process with noise. The dynamics rely on two opposing flows: (i) a factor equalization process, and (ii) a counteracting diffusion process. It is hypothesized that these flows follow simple evolutionary laws that can be described with five parameters — parameters that can be estimated from historical data with some accuracy. The dynamic behavior of the model is analytically derived. Both the extent and speed of adjustment of income are analyzed. An empirical application of the proposed model to the evolution of the distribution of income for 25 countries in the European Union tests the validity of the proposed method and suggests that diffusion may be a preferable technique for the analysis of income dynamics.
On a Theme by Williamson: A Stochastic Model for the Evolution of Global Labor Markets since 1830  [PDF]
Fariba Hashemi
Modern Economy (ME) , 2011, DOI: 10.4236/me.2011.24065
Abstract: The cross-sectional distribution of wages has so far been neglected compared to the study of income differences across countries over time. We propose a stochastic model, built on the theory of diffusion processes, to describe the evolution of global labor markets since 1830. The model is applied to empirical data collected by Williamson, in order to describe the level and variation of cross-country wages. The empirical application validates the proposed method.

East Asian Economic Growth—An Evolutionary Perspective  [PDF]
Fariba Hashemi
Journal of Service Science and Management (JSSM) , 2011, DOI: 10.4236/jssm.2011.43033
The High Performing Asian Economies have been the fastest growing economies anywhere, anytime. This phenomenal growth experience has stimulated extensive research on its determinants. What is less known however, is dynamics of the distribution of income. This paper considers a statistical model to describe convergence of cross-country incomes across the High Performing Asian Economies. The empirical results illustrate that diffusion is a potential technique for the analysis of spatial dynamics of economic growth.
Stochastic Convergence in Regional Economic Activity  [PDF]
Fariba Hashemi
Journal of Mathematical Finance (JMF) , 2011, DOI: 10.4236/jmf.2011.13016
Abstract: A stochastic model is presented, based on a double process of temporal drift and random disturbance, to fit the evolution of cross-country distribution of income and economic activity. Instead of assuming a steady state as is standard practice, a long run stationary equilibrium distribution is hypothesized, around which economic activity fluctuates. An empirical application comparing dynamics of growth in Asia and Europe tests the validity of the proposed method. In particular, results point out that the distribution of income and economic activity is approaching a long run equilibrium at a faster rate in the case of Asia, and that the dispersion of the distribution is shrinking over time above all in the case of Europe. Main implications are supportive of the convergence hypothesis, and suggest that diffusion may be a potential technique for the analysis of growth dynamics.
Industry dynamics in biotechnology  [PDF]
Fariba Hashemi
Advances in Bioscience and Biotechnology (ABB) , 2012, DOI: 10.4236/abb.2012.31006
Abstract: The field of modern biotechnology is thought to have largely begun in 1980, when the United States Supreme Court ruled that a genetically-modified microorganism could be patented. The growth of the Biotechnology industry has stimulated extensive research on its determinants. One of the areas which has attracted a fair amount of attention is the distribution of firm size within an industry. What is less known however, is the dynamics of firm size. This paper considers a statistical model to describe the spatial dynamics of firm size across the biotechnology industry. It is found that firm size fluctuates around its long run stationary equilibrium according to a temporal drift and random disturbance. The empirical results illustrate that diffusion is a potential technique for the analysis of spatial dynamics of firm size.
Industry Dynamics in Pharmaceuticals  [PDF]
Fariba Hashemi
Pharmacology & Pharmacy (PP) , 2012, DOI: 10.4236/pp.2012.31001
Abstract: Pharmaceuticals is a relatively large and mature industry, and of growing significance. The industry has stimulated extensive research on determinants of its growth and development. Specifically, the distribution of firm size has attracted significant attention, due to tis relevance as an indicator of degree of industrial concentration. A large part of this literature has focused, since the early contributions, on the explanation of the shape of firm size distribution in the industry at a given point in time by reference to steady state arguments. The dynamics in question have been relatively neglected however. The main objective of this paper is to help fill this gap. It is shown that interesting issues arise when one considers how firm structure evolves over time, rather than simply attending to equilibrium implications of processes. Information on the shape and time-evolution of the size distribution of firms over an extended period of time can be used to make inferences about an underlying process; specifically, on which characteristics lead to which kinds of dynamics. To that end, we propose a diffusion model to examine the spatial dynamics of firm size. Instead of assuming a steady state as is standard practice, we consider that firm size fluctuates around its long run stationary equilibrium, according to a double process of temporal drift and random disturbance. An empirical application to real data from the Pharmaceutical industry helps fill a second gap in the literature, as only a few diffusion studies have employed real statistical data when analyzing firm size dynamics. Our empirical application confirms results presented elsewhere and offers some new insights.

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