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Tetanus is an important disease which created by tetanospasmin toxin of Clostridium tetani. In this study we surveyed six important factors including LF, KF, MLD, pH, OD and total protein assay of Harvard 52 (H52), G5 (HG5) and 49205 (H49205) strains of the bacterium to determine which of them were more suitable for use in vaccine production. The mentioned strains were seperatedly reactivated in thioglycolate medium, 2ml of this suspension was used to inoculate the Muller-Miller medium of each of sixteen 500 ml Erlenmeyer flasks (7,6 and 3 flasks for H52, HG5 and H49205 respectively), where the fermentation runs were performed. Over a period of seven days of experiment, several tests for evaluation of the six mentioned factors on samples of medium cultures were carried out. Results revealed that H52 strain had significantly lower values in LF and OD compared to strains HG5 & H49205 (P

Aim: Addiction is an important social and health problem in many Middle Eastern countries. Studies show that opium is the most commonly used substance after tobacco in many countries, especially in Iran. Opium is obtained from the seeds of the Papaver somniferum plant and contains more than 40 different alkaloids, the most important of which are morphine, codeine, papaverine, noscapine, and thebaine. Various studies show that morphine, which is one of the most important substances in opium, increases the production of free radicals in the body and reduces the antioxidant capacity. Opium consumption has various adverse health effects on the body. Therefore, long-term use of this combination can be related to some pathological consequences, including neurological disorders, liver toxicity, kidney dysfunction, oxidative stress, and apoptosis. Most drugs are metabolized by liver hepatocytes and excreted by kidney cells. Therefore, opium consumption can directly cause damage to liver cells. Free radicals play an important role in liver diseases. The increase of free radicals and on the other hand the decrease of antioxidants in the body caused liver toxicity. Oxidative stress is caused by an imbalance between the production of free radicals and their neutralization inside the body by antioxidant defense mechanisms. Oxidative stress is produced in various diseases, consumption of toxic substances, and old age, since it is not possible to investigate the effect of opium on human liver cells, and no study has been conducted in this field. The liver is the most important organ that is directly responsible for the metabolism and excretion of opium. Therefore, in this study, the effects of opium on oxidative stress markers in HepG2 cell line were determined. Material and methods: Human liver cancer cell lines (HepG2) were used in this experimental study. At first, the cell line was placed in a 25 ml flask in the culture medium. DMEM (Dulbecco's modified Eagle's medium) containing 10% FBS (Fetal bovine serum), and 1% penicillin and streptomycin antibiotics were incubated in a 37°C incubator with 5% CO2. The cells were treated with different concentrations of opium (0-100ug/ml) for 24 hours. Then IC50 was determined and then a lower concentration, IC50, and a higher concentration (three concentrations in total) were used for further studies. The lipid peroxidation was measured by thiobarbituric acid method. The total oxidant was measured using xylenol orange. The amount of total antioxidants was determined by the FRAP (Ferric Reducing/Antioxidant Power) method. The catalase, glutathione peroxidase, and superoxide dismutase enzyme activities were measured by colorimetry methods. the data was entered into SPSS software (Version 20) and analyzed using ANOVA and Tukey statistical tests. P less than 0.05 was considered a significant level. Results: Statistical analysis results indicated a significant difference in the amount of oxidative stress factors compared with control (p<0.001). In the group receiving opium with a dose of 60 and 70 mg/ml compared to the control group, the amount of TOS and MDA increased significantly (p<0.001), while the amount of TAC decreased (p<0.001). Also, the activity of catalase, glutathione peroxidase, and superoxide dismutase enzymes decreased in opium-treated groups (p<0.001). Conclusion: The results of this research showed that opium had a lethal effect on HepG2 cells. Also, opium caused an increase in oxidative stress in this cell line, which indicates the vulnerability of the liver against this compound. The results of this study show that although opium has analgesic effects, it can seriously damage the liver tissue. [ABSTRACT FROM AUTHOR]

Fisheries tourism is one of the types of tourism that has not received much attention in Iran, despite its good status. The benefits of the tourism industry with the high potential of the fisheries and fishing industry can provide an ideal option to connect the two industries in order to leave the difficult conditions of the fishery areas and move toward development. The first step in planning for fisheries tourism development is to accurately identify the potentials and fisheries' attractions to absorb tourists. Thus, the present study aimed to identify the tourists' attractions of fisheries using a qualitative methodology with an exploratory approach. This research was applied in terms of purpose, and is descriptive and survey in terms of nature and method. The statistical population of this study was relevant subject experts. Using the purposeful snowball sampling method, 23 experts were selected to determine the panel of the experts based on their subject expertise, experiences, and the theoretical adequacy principle. In three rounds, the attractiveness and attractive fisheries activities for tourism were identified using the Delphi technique. In the first round of Delphi, 30 attractions and attractive activities for fisheries tourism were introduced by experts. After the removal of the less important items in the second and third round of Delphi, finally, the consensus was reached about 12 attractions of fisheries tourism, in three categories of fishing and fishery, fisheries industries, and coastal aquaculture. [ABSTRACT FROM AUTHOR]

In this paper, we investigate weighted composition, Volterra and Integral operators on second derivative Hardy spaces. Some equivalent conditions for boundedness of the operators will be given using the boundedness on the Hardy spaces. Also we give a criteria for compactness of weighted composition operators. [ABSTRACT FROM AUTHOR]

Mixture of experts (ME), as one of the most popular neural network-based ensemble learning methods, consists of a number of experts and a gating network. ME is based on the divide and conquer strategy in which the input space is decomposed into some subspaces by managing the gating network. Moreover, the experts are encouraged to specialize in these subspaces. In this paper, a hybrid ensemble system based on the ME method, which is named semi-explicit mixture of experts (SEME) is proposed which consists of two steps. In the first step, a greedy algorithm is proposed which aggregates the randomness and heuristic properties to decompose the input space to the some local subspaces and consider a center corresponding to each subspace. In the second step, the ME algorithm by applying a distance-based gating network is used to encourage the experts into the created subspaces and keep the interaction and cooperation between the experts. The proposed method is evaluated on 19 classification benchmark datasets. Based on the simulation results, the average of improvements in the classification results on these datasets shows that SEME improves 5.45 % , 8.46 % , 5.52 % , 5.4 % and 3.95 % better than Bagging, AdaBoost, random forests (RF), forests of local trees (FLT) and ME, respectively. [ABSTRACT FROM AUTHOR]

In recent years, a nanoparticle-based strategy has shown that non-denatured protein toxins can be used to enhance the appropriate immune response. Once the toxin reacts between the nanoparticles and the protein (toxin), it loses its toxicity because it does not attach to its ligand at the cell surface. The results of the nanoparticle and toxin complex show that the nanoparticles facilitate the internal release of the toxin. Clostridium perfringens beta toxin is produced by Clostridium perfringens type B and C, and diarrhea is the most important disease caused in newborn lambs. When beta toxin forms a complex with nanoparticles, the reaction between the toxin and the nanoparticle leads to the formation of a new form of nanoparticle in which the toxin loses its lethality due to its involvement; therefore, it becomes a toxoid. The nanoparticles used in this research are of poly lactic-co-glycolic acid (PLGA) type, one of the most developed biodegradable polymers. This study aimed to isolate and purify Clostridium perfringens beta toxin and produce its complex with PLGA nanoparticles to form a non-toxic structure. In this study, Clostridium perfringens beta toxin type B was isolated using ammonium sulfate precipitation and gel filtration chromatography. Toxin assay was performed in vivo (lethal dose [LD50]) and in vitro by sodium dodecyl sulphate-polyacrylamide gel electrophoresis at each stage, and the quantity of purified toxin was calculated to be 10 mg/ml. Afterward, the beta toxin antigen was used as the basis for the preparation of nanotoxoid candidates with nanoparticle formulation. Moreover, the PLGA polymer and water-oil-water methods were used to fabricate nanoparticles. Under optimal conditions, nanoparticles without antigen with an average size of 100 nm and zeta potential of -23.28 mV, as well as nanoparticles containing antigen with an average size of 120 nm and zeta potential of -18.2 mV, were prepared. When nanoparticles are injected into mice with the beta toxin, the toxin becomes a toxoid with no toxicity effects, and it cannot bind to its receptors and reveal its effects. In this study, the mice showed mild symptoms in one case, and none of them died. The beta and PLGA toxin model could also be applied as a candidate to study the release and immunization of the target animal. In order to achieve antigen regulation using natural polymers, it is recommended to conduct a comparative study between nanoparticles based on natural polymers. [ABSTRACT FROM AUTHOR]

Among the key strategies in higher education is to prioritize the development of the entrepreneurial university. In this regard, the University of Applied Sciences and Technology (UAST) is one of the main institutions involved in vocational higher education, especially in the agricultural sector, which aims to help graduates acquire the knowledge and skills they will require. To this end, the university needs to plan for and develop entrepreneurial educations in its training system. Accordingly, the present study aimed to strategically analyze entrepreneur UAST in the agricultural sector. The statistical sample included 19 individuals, who were presidents, deputies, and managers of a university or managers of agricultural applied science and technology centers. After interviews and reaching theoretical saturation, the strengths, weaknesses, threats, and opportunities of the agricultural applied sciences and technology centers were specified. The results of the SWOT matrix show that the aggressive strategy (SO) is the most appropriate strategy for the agricultural centers of UAST. The most important strategies within this approach included 'organizing and developing agricultural applied sciences and technology programs in a balanced manner'; 'designing and implementing a province-wide educational need assessment model for the agricultural sector'; 'developing agricultural modular curricula and getting involved in new labor market potentials with the aid of the executive agencies'; 'enhancing the quality of agricultural training components'; 'developing financial resources and the use of the existing potentials of the agricultural sector with no financial burden on the government'; 'basing decisions on research'; and 'setting policies based on the modern agricultural and natural resources' technology'. [ABSTRACT FROM AUTHOR]

The main goal of this paper is the investigation of boundedness and compactness of a class of product-type operators T u,v,φm from Besov spaces into nth weighted type spaces. [ABSTRACT FROM AUTHOR]

Background and Objective: Glucagon-like peptide 1 (GLP-1) has anti-diabetic, antioxidant and anti-inflammatory properties that change under different conditions. This peptide is known as a therapeutic target in diabetes and obesity. The aim of this study was to investigate the relationship between GLP-1 and oxidative stress in preterm infants. Methods: In this case-control study, 40 term and preterm infants (gestational age less than 37 weeks) were used. GLP-1 concentration was measured by ELISA. Total antioxidant capacity (TAC), total oxidant status (TOS) and uric acid concentration were measured. Findings: Serum GLP-1 level in preterm infants was significantly higher than term infants (p=0.003). Serum TAC level in preterm infants (973.16±235.53) was significantly lower than term infants (837.00±218.97) (p=0.006). Serum TOS level in preterm infants (65.46±33.52) was significantly higher than term infants (31.50±14.62) (p<0.001). Uric acid levels in preterm infants (5.83±1.73) were statistically higher than term infants (5.13±0.90) (p=0.02). Serum GLP-1 level in preterm infants was negatively and significantly correlated with TAC (p<0.001, r=-0.674) and positively and significantly correlated with TOS (p<0.001, r=0.754) and uric acid (p<0.001, r=0.633). Conclusion: The results showed that the levels of GLP-1, TOS and uric acid in preterm infants were higher than term infants and GLP-1 had a negative correlation with TAC capacity and a positive correlation with TOS and uric acid in these infants. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agricultural Science & Technology is the property of Tarbiat Modares University Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lean production system is a new management approach and a business strategy that results in the elimination of waste (costs and time) and improvement of the performance and overall value of an organization. The main objective of this study was to investigate factors influencing implementation of Lean Production Principle (LPP) and its relation with the performance of Small and Medium-sized Food Industry Enterprises (SMFIEs) in Khuzestan Province. This study was a kind of descriptive-correlation and causal-relation that was conducted through a survey technique. Statistical population of the study consisted of all managers in Small and Medium Enterprises (SMEs) in Khuzestan food industry (N= 307). By using Krejcie and Morgan's tables and stratified random sampling method, 170 person were selected as sample, of which 161 person completed the research questionnaires (return rate 94.7%). The results show that among the eight factors that influence the implementation of LPP, three variables of "customer relationship management", "human resource management", and "employees' empowerment" have the most direct effects on LPP and, ultimately, the highest total effect on SMFIEs performance. The implementation of LPP could explain about 31 percent of variances in SMFIEs performance. Conducting justification and education workshops not only enhances the knowledge of SMFIEs managers, but also helps implement the LPP and, subsequently, improves the performance of SMFIEs. [ABSTRACT FROM AUTHOR]

BACKGROUND AND OBJECTIVE: The main and effective treatment for diabetes is the use of insulin and synthetic drugs and herbal medicines, which may be accompanied by several side effects. Given that GLP-1 secretion is reduced in diabetic patients compared to healthy individuals, the aim of this study was to determine the simultaneous effect of resveratrol and probiotics on insulin secretion and glucagon-like peptide (GLP-1) and to evaluate insulin resistance in diabetic rats. METHODS: In this experimental study, 40 adult male Wistar rats weighing approximately 250-300 g were used. Animals were randomly divided into 5 groups: control group, diabetic group (using 65 mg/kg streptozotocin and 110 mg/kg nicotinamide intraperitoneally), diabetic group treated with probiotics (50×109 bacteria/kg body wt-1 daily by dissolving in water), diabetic group treated with resveratrol (10 mg/kg by gavage method) and diabetic group treated with probiotics and resveratrol (co-administration group). After four weeks, the animals were sacrificed and pancreatic tissue and blood samples were isolated for histopathological tests and biochemical tests. Blood glucose, insulin resistance, pancreatic GLP-1 as well as pancreatic histopathology were assessed. FINDINGS: The co-administration group compared with the diabetic group caused a 42% reduction in serum glucose levels (p<0.001) and a 30% reduction in insulin resistance (p<0.001). The co-administration group also caused a 23.5% increase in insulin levels (p<0.001) and an 88% increase in GLP-1 (p<0.05). The co-administration group improved the histology of the pancreas. CONCLUSION: The results of the study showed that resveratrol and probiotics are effective in controlling diabetes by increasing the levels of GLP-1 and insulin and decreasing insulin resistance. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agricultural Science & Technology is the property of Tarbiat Modares University Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effect of cooling rate after annealing at 900 °C on the microstructure and hardness of high entropy alloys was investigated using two typical samples with the chemical composition of Co16Cr14.5Fe29Mn11.5Ni29 and Co11.5Cr7Fe27Mn27Ni27(Nb0.08C0.5) (at%). The microstructural characterisation and hardness measurements were carried out by optical microscopy, scanning electron microscopy, wavelength-dispersive X-ray spectroscopy, electron back scattered diffraction, X-ray diffraction technique and Vickers hardness testing. A face centred cubic crystal structure matrix was observed in both alloys before and after annealing and regardless of cooling conditions. SEM analyses revealed an extensive precipitation in Co11.5Cr7Fe27Mn27Ni27 (Nb0.08C0.5) alloy after annealing. It was also found that air/furnace cooling can enhance grain growth-coarsening just in Co16Cr14.5Fe29Mn11.5Ni29. However, the hardness results generally showed insignificant hardness variations in both alloys after water-quenching, air-cooling and furnace-cooling. The results suggested that the hardness is mainly controlled by solid solution strengthening. [ABSTRACT FROM AUTHOR]

This study adopted a survey approach to address and determine the effects of educational system components on strengthening the teamwork behavior of students in the agricultural higher education system of Iran. The statistical population consisted of all agricultural students in five universities of Iran. A sample of 291 students was selected using random stratified sampling method with proportional allocation. A structured questionnaire was used to collect data. The data were analyzed by structural simulation technique using Smart PLS software. The results showed that there was a positive and significant relationship between teamwork behavior of students and the components of the higher education system, which included the teacher, student, curriculum, and the learning environment. The results also showed that the curriculum component had the most impact compared to other components. Also, the presented Applied Structural Equation Model is a strong theoretical model for predicting the teamwork behavior of the students. [ABSTRACT FROM AUTHOR]

At the colleges of agriculture in Iran, lecture is used as a dominated teaching method. Team learning is one of the most commonly used educational methods in the present erea. The aim of this study was to compare the Team Member Teaching Design (TMTD) and the regular lecture method on the academic achievement and teamwork behavior of agricultural students. A within-subject design was followed for two courses in which students first attended a series of lectures and then participated in team teaching. Differences between lecture and team teaching methods were examined for their academic achievement and teamwork. The study samples were taken of Agricultural Extension and Education Department of the University of Tehran during the academic year of 2017-2018. The mean scores of academic achievement and the teamwork behavior of students were compared. In compared coursess, the effect of TMTD method on the academic achievement of students was shown. The results of means comparison tests indicated a significant difference between the two methods of teaching in the field of academic achievement and the strengthening of the teamwork behavior of students. The paper further discusses team method implementation and its implication for teaching and proffers the way forward for an effective use of teaching methods for better results in the classroom teaching and learning process. [ABSTRACT FROM AUTHOR]

Occupational injuries have several psychological, economic, social, and institutional consequences. Agriculture is a high-risk industry, but occupational injuries are mainly rooted in the behavior of farmers. The present study was conducted using the qualitative approach and the grounded theory method. The study population included members of the Faculty of Agricultural Science and Occupational Health of the School of Medical Science, agricultural experts, occupational health experts, and farmers who were selected through snowball sampling in Kermanshah province in western Iran. The data was collected through interviews. The findings showed that cognitive, personal management, cultural, organizational and economic factors affect agricultural occupational health behavior. In the research model, healthy growers, healthy products, and healthy society were the consequences of the use of appropriate strategies for agricultural occupational health behavior. Designing a native model of healthy behavior to promote occupational health is a step towards reducing injuries among farmers. [ABSTRACT FROM AUTHOR]

Considering the importance of investment in renewable energies and the numerous uses of this technology in the agriculture sector, the present research was conducted with the aim of investigating the factors affecting the decision-making process in renewable energies investment in the agricultural sector in Iran. This study is a non-experimental survey research in which structural equations modeling method was used for data analysis (LISREL 8.72). The statistical population consisted of 130 investors of active companies in the area of renewable energies in the agriculture sector throughout Iran. Using Krejcie and Morgan Table as well as simple random sampling method, 97 (n= 97) individuals were chosen as the sample size. The main data collection instrument was questionnaire, whose validity was confirmed by a panel of experts. To measure the reliability of the research tool, 30 copies of the questionnaire were completed by active investors in the area of renewable energies as well as the experts of Iranian Renewable Energy and Energy Efficiency Organization. Then, Cronbach Alpha coefficient was calculated by SPSS 22 for different sections of the completed questionnaire, which showed a good reliability. Based on the results, since the calculated Composite Reliability (CR) index was larger than 0.6 and the Average Variance Extracted (AVE) was larger than 0.5 for each of the five external and internal latent studied variables, the latent variables had convergent and divergent validity. The results indicated that among the studied variables, knowledge of renewable energy technology, a priori beliefs, market policy preferences, institutional pressure, and attitude toward radical technological innovations had the greatest impact on the renewable energies investment decision-making process in the agriculture sector, respectively. [ABSTRACT FROM AUTHOR]

Implementation of Conservation Agriculture (CA) project is a process of multi-participation that involves actors from agricultural researchers and scientists, extension agents, private consulting firms, pioneer farmers, rural cooperatives, family members, peer farmers, etc. The social interactions between farmers and actors drive the CA development. Therefore, this study analyzes the social network structures and characteristics of various actors by social network analysis in seven processes of applying CA in Iran. The research sample was composed of farmers who participated in the CA project in three provinces of Fars, Golestan, and Khuzestan (n= 133). The research instrument was a questionnaire that was designed as a matrix. The findings showed that pioneer farmers, CA farmers, and family members were the main actors in the farmers' social network. It can be concluded that these actors were the main social power in applying CA principles by farmers and they constituted the main centrality of the farmers' social network. It means that farmers are more likely to interact with local actors, and they interact less with the government and the actors outside the rural community. Therefore, it can be recommended that social power should be identified and project management should be organized through them in attempts to implement CA. [ABSTRACT FROM AUTHOR]

The current research aimed to explore application of social network theory toward sustainable aquaculture system through Institutional Scientific Collaboration Network study conducted by interviews with key informants and follow-up organizational surveys at Alborz Watershed scale. The study was descriptive and explanatory, using social network analysis as a most analytical tool to systematically describe certain aspects of the social diversity and complexity of institutional scientific collaboration network. The needed data for social network analysis related to scientific collaborations in the form of research and scientific consulting, technical support, and implementation of joint project networks and was collected through a questionnaire. Research results revealed that the number of central actors in research and scientific consulting network was less than the other two networks. In this study, some powerful organizations such as the Institute of Ecology of the Caspian Sea and Shahid Rajai and Shahid Bahonar Reproduction Center had satisfactory research and scientific consultancy cooperation, as well as technical support for joint projects with other organizations, such as the Provincial Department of Fisheries, and Research Center for Agriculture and Natural Resources, which reflected dynamics of the organizations in the network. These three organizations can play a key role in the distribution of information, knowledge, and intersectoral cooperation among different institutions and can take responsibility of this process. If so, these organizations can develop a sustainable aquaculture in the basin of the Alborz Dam, based on scientific principles and in an interactive and dynamic path and, consequently, activate the implementation of projects and conducting scientific and executive studies by these organizations within the network. Although the approach is developed and tested using empirical social network data in the basin of Alborz watershed, the results can generally be useful for other regions and scales as well. Also, research finding could help in improving sustainable management through strengthening of intuitional scientific collaboration network and providing better understanding of the scientific needs and real interactions of diverse actors. [ABSTRACT FROM AUTHOR]

The natural environmental beauty preservation has become one of the most important human concerns in the present century, so that visual pollution is considered as a major obstacle to achievement of peace of mind and optimal perfection. In this respect, rural people have a major role in preserving the beauty of the natural environment. The purpose of this study was to analyze factors affecting the aesthetic behavior of Iranian villagers towards the natural environment. This study was descriptive-correlational and causal-relational and was conducted through a survey technique. Statistical population of this study consisted of all villagers in Kermanshah Province (as an indicator example of Iran) (N= 517,786). By using Krejcie and Morgan’s sample size table and stratified random sampling method, 385 people were selected as a sample. Research instrument included a questionnaire with approved validity by a panel of experts in the field of agricultural extension and education; and reliability of its items was obtained by a pilot study and calculation of Cronbach's alpha (0.64≥ α ≥0.82). Based on the findings, the causal model of factors affecting the aesthetic behavior of villagers was drawn. Results of this causal analysis indicated that ‘place attachment’ (β= 0.275) and ‘environmental aesthetic attitudes’ (β= 0.260) had highest effects on villagers' environmental aesthetic behavior, respectively. Therefore, by focusing on these two variables, the villagers' aesthetic behavior can be enhanced. [ABSTRACT FROM AUTHOR]

Nowadays, a paradigm shift can be observed from economic and technical investments to social-behavioral dimensions in order to increase efficiency of exploiting water resources. The purpose of the present study was to identify and analyze factors affecting Farmers Active Participation in Water Conservation (FAPWC). In this regard, a theoretical framework was developed for analyzing farmers participatory behavior. This study was a descriptivecorrelational and causal relationship research which was conducted through a survey technique. The statistical population of the study included irrigated farmers in southern regions of West Azerbaijan Province in Iran. A sample of 378 irrigated farmers was selected using proportional stratified random sampling method. Data were collected using eight 5-point Likert-type scales. Validity of the scales was confirmed by a panel of experts, and their reliability was demonstrated by Cronbach’s Alpha coefficients which ranged between 0.60- 0.89, indicating internal consistency of the study scales. Parametric tests were used to analyze the data. The results of this study showed that the variables of moral norms of water conservation, social pressures, place attachment, social responsibility towards consequences of activities, quality of agricultural extension services, and satisfaction of water resources management had significant impacts on FAPWC. Moreover, the independent variables could predict 43.6% of variance changes in FAPWC. An attempt was made to examine the factors affecting FAPWC beyond the psychological individual-based (micro) analyses in order to develop the research framework and consider factors such as the effect of farmers’ social environments and, consequently, present policy implications at micro- and macro-levels separately. [ABSTRACT FROM AUTHOR]

Employing laser wigglers and accelerators provides the potential to dramatically cut the size and cost of X-ray light sources. Owing to recent technological developments in the production of high-brilliance electron beams and high-power laser pulses, it is now conceivable to make steps toward the practical realisation of laser-pumped X-ray free-electron lasers (FELs). In this regard, here the head-on collision of a relativistic dense electron beam with a linearly polarized laser pulse as a wiggler is studied, in which the laser wiggler can be realised using a conventional quantum laser. In addition, an external guide magnetic field is employed to confine the electron beam against self-fields, therefore improving the FEL operation. Conditions allowing such an operating regime are presented and its relevant validity checked using a set of general scaling formulae. Rigorous analytical solutions of the dynamic equations are provided. These solutions are verified by performing calculations using the derived solutions and well known Runge-Kutta procedure to simulate the electron trajectories. The effects of self-fields on the FEL gain in this configuration are estimated. Numerical calculations indicate that in the presence of self-fields the sensitivity of the gain increases in the vicinity of resonance regions. Besides, diamagnetic and paramagnetic effects of the wiggler-induced self-magnetic field cause gain decrement and enhancement for different electron orbits, while these diamagnetic and paramagnetic effects increase with increasing beam density. The results are compared with findings of planar magnetostatic wiggler FELs. [ABSTRACT FROM AUTHOR]

The readiness for self-directed learning among the students and its role in improving life-long learning skills has been emphasized recently. The present descriptive study aimed at analyzing the self-directed learning skills possessed by the students of agriculture at Tarbiat Modares University, Tehran, Iran (N= 414). As far as methodological design is concerned, the study has utilized Krejcie and Morgan's (1970) table, and stratified random sampling technique, through which 201 students were selected as sample (n= 201). From this, 193 students filled and returned the research instrument (Return rate= 96%). A set of open ended questionnaires was developed, which was considered to be the main tool for the collection of required data. This prepared questionnaire was validated by a panel of experts of agricultural extension and education, subsequently; its reliability was also checked and confirmed by Cronbach's Alpha coefficient (0.78-0.83). The results showed that the students could perceive the range of ‘moderate to high' for all dimensions underlying self-directed learning skills. Based upon another part of results, the students with different educational levels, majors and grade point averages had different self-directed learning skills. It can be concluded that readiness for self-directed learning is a crucial factor for all students and should be taken into consideration in education planning with regard to each field. It is necessary to state that the educational system seeks to develop such skills to promote self-management, selfmonitoring, and self-motivating as well as SDL skills among the students. [ABSTRACT FROM AUTHOR]