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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Nanochemistry Research
- نوع مقاله: Journal Article
- کلمات کلیدی: Palladium nanoparticles,Magnetic nanoparticles,Heck reaction,Hyperbranched polymers,Sonogashira coupling reaction,Suzuki–Miyaura cross-couplings reaction
- چکیده:
- چکیده انگلیسی: This study offers an exclusive class of magnetic nanoparticles supported hyperbranched polyglycerol (MNP/HPG) that was functionalized with citric acid (MNP/HPG-CA) as a host immobilization of palladium nanoparticles. The MNP/HPG-CA/Pd catalyst was fully characterized using some different techniques such as thermogravimetric analysis (TGA), x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), inductively coupled plasma (ICP) and x-ray photoelectron spectroscopy (XPS). The new catalytic system showed high activity for the Suzuki–Miyaura cross-coupling and Heck reaction under mild and green conditions. Besides, the MNP/HPG-CA/Pd was found to be a convenient catalyst for copper-free Sonogashira coupling reaction in water as a green solvent at room temperature. Moreover, the catalyst could be recovered easily and reused several times without significant loss of reactivity. Ease of preparation, oxygen insensitive, phosphine-free, air- and moisture-stable, and high reusability of this immobilized palladium catalyst are the noteworthy advantages of this catalytic system.
- انتشار مقاله: 31-05-1394
- نویسندگان: Mina Amini,Marzieh Hajjari,Amir Landarani-Isfahani,Valiollah Mirkhani,Majid Moghadam,Sharam Tangestaninejad,Iraj Mohammadpoor-Baltork,Mohammad Ahmadi
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Nanoanalysis
- نوع مقاله: Journal Article
- کلمات کلیدی: Fullerene,Gate voltage,Coulomb blockade,Island length,Single Electron Transistor
- چکیده:
- چکیده انگلیسی: The Graphene based single electron transistor (SET) as a coulomb blockade device need to be explored .It is a unique device for high-speed operation in a nano scale regime. A single electron transfers via the coulomb barriers, but its movement may be prevented by coulomb blockade, so its effect is investigated in this research. The conditions of coulomb blockade and its controlling factors such as material, temperature, gate voltage and island length are investigated. At first, the coulomb blockade on fullerene SET as a nano transistor with new material is modeled and compared with experimental data of silicon SET. The comparison study indicates that the coulomb blockade range of fullerene SET is lower than the silicon one. On the other hand, the analysis demonstrates that, temperature and gate voltage play direct associations with zero current SET. In addition, island length and its material effect on coulomb blockade and desired current are achieved by decreasing the coulomb blockade range.
- انتشار مقاله: 13-02-1396
- نویسندگان: Vahideh KhademHosseini,Mohammad Taghi Ahmadi,Saeid Afrang,Razali Ismail
- مشاهده
- جایگاه : پژوهشی
- مجله: Middle East Journal of Cancer
- نوع مقاله: Journal Article
- کلمات کلیدی:
- چکیده:
- چکیده انگلیسی: Background: Pancreatic cancer is a major worldwide health problem. Little is known about the etiology of pancreatic cancer, which is an important cause of cancer mortality in developed countries. This study evaluates the importance of amounts of trace elements in pancreatic cancer etiology and diagnostics.Methods: Atomic absorption spectrometry was used to estimate zinc, selenium, copper, cadmium and lead concentrations in 80 patients with pancreatic cancer admitted to various hospitals in Tehran Province over an 18-month period and in 100 control subjects.Results: There were significantly lower levels (P0.05)of zinc in patients' sera(63.12±26.45 μg/dl) compared with controls (107.05±30.23 μg/dl). The mean concentration of cadmium in patients (3.10±1.05 μg/l) was higher than in healthy subjects(1.52±0.88 μg/l; P0.05).Conclusion: In this study and by analyzing data from recent major reported series, we have found that cadmium is a plausible pancreatic carcinogen. This study also suggests a significant relationship between zinc metabolism and pancreatic cancer.
- انتشار مقاله: 06-07-1392
- نویسندگان: Leila Farzin,Mohammad Esmail Moassesi,Fattaneh Sajadi,Mohammad Amin Ahmadi Faghih
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Water Sciences Research
- نوع مقاله: Journal Article
- کلمات کلیدی: scour,Spur dike,Triangular vanes,River banks
- چکیده:
- چکیده انگلیسی: The main purpose of this paper was to evaluate the performance of the triangular vanes located on the bed and their effect on the bed topography considering different flow conditions. For this purpose, tests were carried out on a straight flume for different flow conditions (five Froude numbers of 0.18, 0.20, 0.22, 0.24 and 0.26) by installing a series of triangular vanes at a space of 4Le (Le is the effective length of the structure) and considering a 30 degrees angleto the upstream bank. At the end of each test, the bed topography was measured by the laser distance measurer. The results showed that the geometric dimension of the scour hole for the rectangular spur dikes was larger than the triangular vanes. On average, the length and depth of the scour hole for the rectangular spur dikes were 1.3 and 1.5 timesin comparison to the triangular vanes, respectively. In addition, the maximum scour depth considering the triangular vanes was about 40% farther from the bank in comparison to the case with the rectangular spur dikes, that was an advantage for the triangular vanes.
- انتشار مقاله: 02-04-1394
- نویسندگان: Nushin Najafi Birgani,Mahmood Shafai Bejestan,Mohammad Bahrami Yarahmadi
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Ultrafine Grained and Nanostructured Materials
- نوع مقاله: Journal Article
- کلمات کلیدی: Mechanical properties,Metal Matrix Composites,3D printing,ultrasonic additive manufacturing,microstructural features,microstructure evolution
- چکیده:
- چکیده انگلیسی: Recently, high-performance lightweight materials with outstanding mechanical properties have opened up their way to some sophisticated industrial applications. As one of these systems, aluminum matrix composites/nanocomposites (AMCs) offer an outstanding combination of relative density, hardness, wear resistance, and mechanical strength. Until now, several additive manufacturing methods have been developed for fabrication of 3D metallic components among them, selective laser melting (SLM), electron beam melting (EBM), laser metal deposition (LMD), Wire+Arc additive manufacturing (WAAM), and ultrasonic additive manufacturing (UAM) are of prime significance. Unlike other methods, in ultrasonic additive manufacturing, the ultrasonic waves are used instead of applying the sintering process. This technique is well-known for its ability to produce 3D components by repeating the alternative welding and machining procedures at low temperatures. This is why it can overcome the technological issues arisen from the high-temperature sintering. The present review strives to provide an inclusive introduction to the principles of ultrasonic additive manufacturing method and recent advances in ultrasonic additive manufacturing of aluminum matrix composites/nanocomposites. Also, the challenges of this new emerging technique, i.e. its dependence to the applied weld power, is addressed in the paper. The authors attempt to give some perspectives to the researchers for further investigations in this new-emerging field.
- انتشار مقاله: 09-07-1398
- نویسندگان: Mir Saman Safavi,Abolfazl Azarniya,Mohammad Farshbaf Ahmadipour,Mogalahalli Venkatesh Reddy
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Teaching Language Skills
- نوع مقاله: Journal Article
- کلمات کلیدی: listening Comprehension,EFL Learners,Scaffolding,Collaborative dialogue,expert peer,co-equal peer
- چکیده:
- چکیده انگلیسی: This study investigated the comparative effects of audio-visually prompted collaborative dialogue on the listening comprehension development of symmetrical, asymmetrical, and asymmetrical teacher-fronted EFL learner groups. Besides, it explored the attitude of the participants of the groups concerning the effectiveness of collaborative dialogue for their listening comprehension improvement. The participants of the study were 120 Iranian female EFL learners who were conveniently chosen from several English language institutes and put into three experimental and one control groups, each with 30 learners. In the first experimental group, coequal learners engaged in collaborative dialogue. In the second experimental group, the expert peer(s) and less knowledgeable peers applied collaborative dialogue, and in the third experimental group, in addition to the peers, the teacher was involved in collaborative dialogue with the group members. As for the control group, the collaborative dialogue was abandoned and the participants worked individually. Quantitative and qualitative analyses revealed that collaborative dialogue in asymmetrical teacher-fronted, asymmetrical peer and symmetrical peer groups were respectively the most effective procedures for listening comprehension development of the EFL learners. Also, it was found that the participants of the asymmetrical teacher fronted group had a more positive attitude towards the efficacy of audio-visually prompted collaborative dialogue compared with asymmetrical and symmetrical peer groups. The findings underscore the cognitive and affective efficiency of a more knowledgeable source, either a teacher or a peer, in asymmetrical dyadic interactions for the less knowledgeable partners' ZPD sensitive development.
- انتشار مقاله: 16-05-1399
- نویسندگان: Shima Beheshti,Mohammad Ahmadi Safa
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Teaching Language Skills
- نوع مقاله: Journal Article
- کلمات کلیدی: EFL Teachers,Language Assessment Literacy,assessment literacy
- چکیده:
- چکیده انگلیسی: Language assessment literacy (LAL), mainly defined as knowledge and skills of language assessment, in the last two decades, has started to receive the attention it deserves. As one of the significant findings, based on a plethora of research, many second language (L2) teachers have been indicated to be professionally incompetent in terms of LAL. To investigate the status of LAL among Iranian English teachers, the present study was conducted. Three hundred and nine English teachers participated in answering a questionnaire. Besides, 24 teachers were interviewed based on a semi-structured interview. Both qualitative and quantitative data analysis and interpretation techniques were employed to find answers to the research questions which sought to investigate the features of language assessment literacy in language teachers' perceptions. The findings indicated that, overall, LAL is of concern to Iranian L2 (English) teachers. However, they also agree that their current level of both knowledge and practice in terms of LAL is not ideal. Furthermore, it was found that, as the teachers perceive it, assessment promotes learning and teaching; the nature of teacher-learner relationships affects evaluation; and, testing and assessment are seen as challenging notions due to their mathematical concepts and statistics. The findings will contribute to a more profound perception of LAL and better planning and executing the programs for L2 teachers regarding the issue.
- انتشار مقاله: 22-06-1398
- نویسندگان: Mohammad Reza Shah Ahmadi,Saeed Ketabi
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Rehabilitation Sciences and Research
- نوع مقاله: Journal Article
- کلمات کلیدی: Endurance test,Abdominal muscles,Visual feedback,Verbal encouragement
- چکیده:
- چکیده انگلیسی: Background: Abdominal muscles are one of the most important componentsthat provide trunk stability. It has been reported that abdominal musclesendurance can be decreased in patients with low back pain. Tests that canbe used for the assessment of abdominal muscles endurance; include supineisometric chest raise (SICR) and supine double straight-leg raise (SDSLR) tests.The aim of this study is to investigate the effects of visual feedback and verbalencouragement on endurance tests of deep abdominal muscles.Methods: In this two-factor mixed design study, a convenient sample of 40asymptomatic (healthy) participants (20 males and females each) aged between20-35 years was selected. Each subject performed the SICR and SDSLR tests under4 conditions: no feedback, visual feedback, verbal encouragement, and combinedvisual feedback and verbal encouragement. The tests were terminated when thesubject was no longer able to maintain a position. Furthermore, each test wasrepeated twice with 5 min interval and the average time was recorded for analysis.Results: Endurance test time was improved significantly when 2 types of feedbackwere given during the tests (P<0.01). However, combined visual feedback andverbal encouragement had superior effect on endurance test time compared tovisual feedback or verbal encouragement alone (P=0.01).Conclusion: The incorporation of verbal encouragement and visual feedback isan important factor in improving holding time during endurance tasks. Thismay have important implications on endurance training and rehabilitationprogrammes of abdominal muscles.
- انتشار مقاله: 25-10-1396
- نویسندگان: Morteza Taghipour,Salman Nazary-Moghadam,Mohammad Reza Pourahmadi,Fatemeh Rajabzadeh,Afsun Nodehi-Moghadam
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Rehabilitation in Civil Engineering
- نوع مقاله: Journal Article
- کلمات کلیدی: Artificial Neural Networks,Scour estimation,Water level regulation,Error back propagation
- چکیده:
- چکیده انگلیسی: Scour in the downstream of hydraulic structures is a phenomenon which usually occurs due to exceeding the velocity or shear stress from a critical level. In this paper by using the laboratory data by Borman- Jouline and De-Agostino research, it was tried to get more accurate equations in order to calculate the maximum depth of scour in the downstream of the water level regulation structures. Comparing these equations with the results of the other researchers showed that these equations are much more accurate. After that Artificial neural networks (ANNs) with learning algorithm of error back propagation (BP) were used to estimate maximum water scour depth, and the model which has seven neurons in its hidden layer was produced as the most appropriate model. Finally by using statistical parameters, the ANN model was compared with optimized equations. The results of this study showed high correlation between artificial neural network and proposed equation.
- انتشار مقاله: 09-06-1394
- نویسندگان: Saeed Farzin,Mohammad Hosein Ahmadi,Rasol Rajabpur,Forough Alizadeh Sanami,Kiuomars Asaii
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Plant Physiology and Breeding
- نوع مقاله: Journal Article
- کلمات کلیدی: Water use efficiency,SPAD,Canopy temperature,Gas exchange variables,Grain filling period,Terminal water deficit
- چکیده: تنش آب از تنشهای عمده غیر زنده کشاورزی در سراسر جهان است. به منظور ارزیابی واکنشهای فتوسنتزی و عملکرد دانه 25 ژنوتیپ گندم در شرایط کمبود آب (پس از گلدهی) یک پژوهش دو ساله (سالهای 1389 تا 1391) به صورت طرح کرتهای خرد شده در قالب بلوکهای کامل تصادفی با سه تکرار انجام شد. حساسترین عامل تبادل گازی به تنش کم آبی، هدایت روزنهای بود (62 درصد کاهش) و به دنبال آن فتوسنتز خالص با 42 درصد کاهش قرار داشت. همچنین کمبود آب عملکرد دانه را 45 درصد کاهش داد. فتوسنتز خالص و هدایت روزنهای با عملکرد دانه همبستگی معنیدار داشتند. محتوای کلروفیل زیادتر با فتوسنتز خالص بیشتر در شرایط کمبود آب همراه بود. دوام بیشتر سطح سبز برگها با عملکرد دانه بیشتر مرتبط بود. ژنوتیپهایی که فتوسنتز خالص و هدایت روزنهای بیشتری داشتند، از عملکرد دانه بیشتری برخوردار بودند (رقمهای زرین و دریا). بنابراین فتوسنتز خالص و هدایت روزنهای به عنوان شاخصهای مناسب برای انتخاب ژنوتیپهای برتر در شرایط تنش کمبود آب در انتهای فصل شناخته شدند.
- چکیده انگلیسی: Water stress is one of the major abiotic stresses in agriculture worldwide. In order to assess photosynthesis response and grain yield of 25 wheat genotypes under water deficit (post-anthesis stress) conditions, a 2-year study (2010-12) was carried out as a split-plot arrangement using randomized complete block design with three replications. The most sensitive gas exchange variable to water deficit was found to be mesophyll conductance (gm) (62% reduction), followed by photosynthesis rate (Pn) (42% reduction). Water deficit also reduced grain yield by an average of 45%. Pn and gm were significantly correlated with grain yield under both conditions. Higher chlorophyll content was associated with higher Pn under water deficit conditions. Maintenance of greater green leaf area during grain filling period was related to greater grain yield. Genotypes with higher Pn and gm were those with optimum grain yield (i.e. cvs. Zarrin and Darya), hence, Pn and gm were found to be the appropriate indices for screening wheat genotypes under the terminal water deficit conditions.
- انتشار مقاله: 07-06-1394
- نویسندگان: Mohammad Javad Ahmadi-Lahijani,Yahya Emam
- مشاهده