261 research outputs found

    From Dimensional Reduction of 4d Spin Foam Model to Adding Non-Gravitational Fields to 3d Spin Foam Model

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    A Kaluza-Klein like approach for a 4d spin foam model is considered. By applying this approach to a model based on group field theory in 4d (TOCY model), and using the Peter-Weyl expansion of the gravitational field, reconstruction of new non gravitational fields and interactions in the action are found. The perturbative expansion of the partition function produces graphs colored with su(2) algebraic data, from which one can reconstruct a 3d simplicial complex representing space-time and its geometry; (like in the Ponzano-Regge formulation of pure 3d quantum gravity), as well as the Feynman graph for typical matter fields. Thus a mechanism for generation of matter and construction of new dimensions are found from pure gravity.Comment: 11 pages, no figure, to be published in International Journal of Geometric Methods in Modern Physic

    Quality management of cut carnation 'Tempo' with 1- MCP

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    Water relation and chlorophyll content are two important factors on the postharvest quality of cut flowers. 1-MCP (1–methylcyclopropene), as a gaseous inhibitor of ethylene action, significantly delayed the wilting ofcut carnation (Dianthus caryophyllus L.). The effects of 1-MCP depends on concentration, time duration and temperature. In this study, the effect of different 1-MCP concentrations (0, 20, 40, 60, 80 and 100 nl l-1) andtime durations (3, 6 and 9 h) on the vaselife, water uptake, loss of fresh weight and chlorophyll index of cut carnation 'Tempo' which is an ethylene-sensitive flower, were evaluated. The effects of 1-MCP concentrations and interaction between 1-MCP concentration and time duration on the vaselife, water uptake, loss of chlorophyll index and loss of fresh weight, were significant at 1% levels of probability. Also the effect of time duration on the loss of chlorophyll index and loss of fresh weight was significant at 5%and on the water uptake was significant at 1% of probability. Treatment with 60 nl l-1 1-MCP for 3 h with 16.47 days vaselife, 2.57 ml g-1 fresh weight, 2.41 ml g-1 water uptake and 2.667 loss of chlorophyll index wasbetter than other treatments

    Identify Challenges of Evaluating Students' Academic Performance E-Courses

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    This study was performed aims to Identification challenges of evaluating Virtual College students' perceptions of electronics courses. Statistical population was consisted of all students of Virtual University. For samples, 140 students were selected using stratified random sampling. Research instrument, researcher made questionnaire was a valid and reliable. The obtained data were analyzed. The mean, standard deviation, variance analysis and paired t-tests to measure t. The results showed that the greatest challenges to the evaluation of students' views of electronic Respectively Technical problems with mean 3/71 , Pedagogical difficulties, with a mean 3/20, And Mental health problems with an average of 3.Also, the students' perspective. In the terms different And various disciplines. There was a difference. In the particular challenges of of evaluation. Yet from the perspective of students And in terms different academic, technical problems as the most important challenge of evaluating students' academic performance was introduced

    The southern Zagros collisional orogen: new insights from transdimensional‐trees inversion of seismic noise

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    Imaging and resolving the lateral continuity of 3‐D crustal structures enhances our ability to interpret seismicity, and to understand how orogens are created. We apply a Bayesian, hierarchical inversion approach based on a transdimensional trees‐structured wavelet parameterisation to recover phase‐velocity maps at 2‐40 second periods. We then invert phase‐velocity dispersion to constrain a 3‐D shear‐velocity model of the crust beneath south‐central Iran. Together with accurate earthquake centroid depths and focal mechanisms, the pattern of 3‐D velocity variations supports recent suggestions that most large earthquakes in the Zagros occur within the lower sedimentary cover, or close to the sediment‐basement interface. Furthermore, we find evidence for Arabian basement underthrusting beneath central Iran, although only in one location does it appear to generate earthquakes. Our new 3‐D tomographic model clarifies and throws new light on the crustal structure of the SE Zagros and its relation to seismicity and active faulting

    The Southern Zagros Collisional Orogen: New Insights From Transdimensional Trees Inversion of Seismic Noise

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    Imaging and resolving the lateral continuity of 3-D crustal structures enhances our ability to interpret seismicity, and to understand how orogens are created. We apply a Bayesian, hierarchical inversion approach based on a transdimensional trees-structured wavelet parameterisation to recover phase-velocity maps at 2-40 second periods. We then invert phase-velocity dispersion to constrain a 3-D shear-velocity model of the crust beneath south-central Iran. Together with accurate earthquake centroid depths and focal mechanisms, the pattern of 3-D velocity variations supports recent suggestions that most large earthquakes in the Zagros occur within the lower sedimentary cover, or close to the sediment-basement interface. Furthermore, we fi nd evidence for Arabian basement underthrusting beneath central Iran, although only in one location does it appear to generate earthquakes. Our new 3-D tomographic model clarifi es and throws new light on the crustal structure of the SE Zagros and its relation to seismicity and active faulting.NERC Horizon 2020 Petroleum Institute Research Centr

    Machine Learning for Determining Interactions between Air Pollutants and Environmental Parameters in Three Cities of Iran

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    Air pollution, as one of the most significant environmental challenges, has adversely affected the global economy, human health, and ecosystems. Consequently, comprehensive research is being conducted to provide solutions to air quality management. Recently, it has been demonstrated that environmental parameters, including temperature, relative humidity, wind speed, air pressure, and vegetation, interact with air pollutants, such as particulate matter (PM), NO2, SO2, O3, and CO, contributing to frameworks for forecasting air quality. The objective of the present study is to explore these interactions in three Iranian metropolises of Tehran, Tabriz, and Shiraz from 2015 to 2019 and develop a machine learning-based model to predict daily air pollution. Three distinct assessment criteria were used to assess the proposed XGBoost model, including R squared (R2), Root Mean Squared Error (RMSE), and Mean Absolute Error (MAE). Preliminary results showed that although air pollutants were significantly associated with meteorological factors and vegetation, the formulated model had low accuracy in predicting (R2PM2.5 = 0.36, R2PM10 = 0.27, R2NO2 = 0.46, R2SO2 = 0.41, R2O3 = 0.52, and R2CO = 0.38). Accordingly, future studies should consider more variables, including emission data from manufactories and traffic, as well as sunlight and wind direction. It is also suggested that strategies be applied to minimize the lack of observational data by considering second-and third-order interactions between parameters, increasing the number of simultaneous air pollution and meteorological monitoring stations, as well as hybrid machine learning models based on proximal and satellite data

    Loop expansion in Yang-Mills thermodynamics

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    We argue that a selfconsistent spatial coarse-graining, which involves interacting (anti)calorons of unit topological charge modulus, implies that real-time loop expansions of thermodynamical quantities in the deconfining phase of SU(2) and SU(3) Yang-Mills thermodynamics are, modulo 1PI resummations, determined by a finite number of connected bubble diagrams.Comment: 15 pages, 2 figures, v5: discussion of much more severely constrained nonplanar situation included in Sec.

    Effects of the COVID-19 pandemic on food security and agriculture in Iran: a survey

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    The consequences of COVID-19 on the economy and agriculture have raised many concerns about global food security, especially in developing countries. Given that food security is a critical component that is affected by global crises, beside the limited studies carried out on the macroimpacts of COVID-19 on food security in Iran, this paper is an attempt to address the dynamic impacts of COVID-19 on food security along with economic and environmental challenges in Iran. For this purpose, a survey was conducted with the hypothesis that COVID-19 has not affected food security in Iran. To address this fundamental hypothesis, we applied the systematic review method to obtain the evidence. Various evidences, including indices and statistics, were collected from national databases, scientific reports, field observations, and interviews. Preliminary results revealed that COVID-19 exerts its effects on the economy, agriculture, and food security of Iran through six major mechanisms, corresponding to a 30% decrease in the purchasing power parity in 2020 beside a significant increase in food prices compared to 2019. On the other hand, the expanding environmental constraints in Iran reduce the capacity of the agricultural sector to play a crucial role in the economy and ensure food security, and in this regard, COVID-19 forces the national programs and budget to combat rising ecological limitations. Accordingly, our study rejects the hypothesis that COVID-19 has not affected food security in Iran

    Avocado (Persea americana) pulp improves cardiovascular and autonomic recovery following submaximal running: a crossover, randomized, double-blind and placebo-controlled trial

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    Previous studies have demonstrated that regular avocado consumption presents advantageous effects on cardiovascular system. However, little attention has been paid to the use of avocado as a dietary supplement, in particular, for individuals involved in physical exercise training. Therefore, this study aims to evaluate the effect of acute avocado pulp intake on cardiovascular and autonomic recovery subsequent to moderate exercise. Using a crossover, randomized, double-blind and placebo-controlled trial design, 16 healthy female adults underwent two protocols: Avocado pulp (600 mg in capsule) and placebo (600 mg starch in capsule). After the ingestion of Avocado pulp or placebo, the subjects were seated for 60 min at rest, followed by running on a treadmill at a submaximal level and then remained seated for 60 min during recovery from the exercise. Heart rate (HR), heart rate variability (HRV) [rMSSD, SD1, HF (ms2)] and skin conductance were evaluated before and during exercise, as well as during recovery. HR, systolic blood pressure, HRV and skin conductance recovered faster when subjects were given avocado pulp prior to exercise. In conclusion, avocado pulp improved cardiovascular and autonomic recovery after exercise, suggesting a reduced risk of cardiovascular events after exertion. The current results support the beneficial effects of ingestion of avocado prior to submaximal treadmill running

    Breast conserving surgery versus mastectomy: cancer practice by general surgeons in Iran

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    BACKGROUND: There appear to be geographical differences in decisions to perform mastectomy or breast conserving surgery for early-stage breast cancer. This study was carried out to evaluate general surgeons' preferences in breast cancer surgery and to assess the factors predicting cancer practice in Iran. METHODS: A structured questionnaire was mailed to 235 general surgeons chosen from the address list of the Iranian Medical Council. The questionnaire elicited information about the general surgeons' characteristics and about their work experience, posts they have held, number of breast cancer operations performed per year, preferences for mastectomy or breast conserving surgery, and the reasons for these preferences. RESULTS: In all, 83 surgeons returned the completed questionnaire. The results indicated that only 19% of the surgeons routinely performed breast conserving surgery (BCS) and this was significantly associated with their breast cancer case load (P < 0.01). There were no associations between BCS practice and the other variables studied. The most frequent reasons for not performing BCS were uncertainty about conservative therapy results (46%), uncertainty about the quality of available radiotherapy services (32%), and the probability of patients' non-compliance in radiotherapy (32%). CONCLUSION: The findings indicate that Iranian surgeons do not routinely perform BCS as the first and the best treatment modality. Further research is recommended to evaluate patients' outcomes after BCS treatment in Iran, with regard to available radiotherapy facilities and cultural factors (patients' compliance)
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