Microstructure and geotechnical properties of St. Peter sandstone in Clayton, Iowa

The St. Peter Sandstone is significantly different from the minerals and rocks which have been studied extensively in mining. It is brittle and characterized by an unusually high friction angle. On the other hand it is friable, and it is nearly cohesionless. The scarcity of the ground control techniques for this particular mining environment has created many difficulties for mine operators. This research aims to establish a fundamental understanding of the basic mechanical and strength properties of the St. Peter Sandstone for engineering design and scientific research. The specific objectives are 1) characterizing the strength of the St. Peter Sandstone, and 2) elucidating the strength mechanics by scientific evidences. The study is essential for developing safe and reliable ground control techniques for mining under this sandstone condition. In this study, extensive conventional rock mechanics testing, as well as a detailed particle structure including optical and scanning electron microscopies studies was carried out on St. Peter Sandstone. An appropriate sample preparation technique for St. Peter Sandstone is proposed. The optimum specimen size for characterizing St. Peter Sandstone was determined. The mechanical behavior of St. Peter Sandstone was investigated under triaxial compressive condition. The results indicated that confining pressure will significantly increase the strength and change the mechanical behavior of St. Peter Sandstone from brittle to ductile. The particle structure of St. Peter Sandstone was studied in terms of porosity, particle size distribution, and density. It was demonstrated that the mechanical and strength properties of the St. Peter Sandstone are fundamentally governed by its particle structure. The systematic presence of Hertzian fractures on the St. Peter Sandstone particle structures were obtained, identified and demonstrated. The finding provides direct evidence to resolve outstanding issues regarding the depositional environment of the St. Peter Sandstone. It was indicated that Hertzian fractures were not the product of eolian action. The contact surface of St. Peter‘s sand grains was investigated. It was found that the majority of contact surfaces are smooth. Hence, the high friction angle of St. Peter Sandstone cannot be attributed to “penetrative surfaces” as hypothesized by locked sand theory --Abstract, page iii

Agrobacterium-mediated transformation of plants: Basic principles and influencing factors

Transformation is an important topic in plant biology and transgenic plants have become a major focus in plant research and breeding programs. Agrobacterium-mediated transformation as a practical and common method for introducing specific DNA fragments into plant genomes is well established and the number of transgenic plants produced using this method is increasing. Despite the popularity of the method, low efficiency of transformation is a major challenge for scientists. Modification of differentgenetic and environmental aspects of transformation method may lead to better understanding of the system and result in high efficiency transformation. In this review, we deal with recent genetic findingsas well as different environmental factors which potentially influence Agrobacterium-mediated transformation

The Use of Hedging Devices in English and Persian Abstracts of Persian Literature and Civil Engineering MA/MS Theses of Iranian Writers

AbstractThe present study compared and contrasted the frequency of incidence of hedges in 40 MA/MS abstracts of Persian Literature and Civil Engineering theses written both in Persian and English against the taxonomy of hedges proposed by Salager-Meyer (1994). Running Chi-square analyses, it was found that, firstly, there were no significant differences in the frequency of incidence of hedges used in the abstracts written both in English and Persian in both disciplines and secondly, discipline had no effect on the frequency of incidence of hedges. Thirdly, Iranian graduate students made relatively lower use of hedges compared with their English speaking counterparts

Effect of Phentolamine as Reversal of Soft-Tissue Anesthesia on Post-Endodontic Pain in Patients with Symptomatic Irreversible Pulpitis: A Randomized Clinical Trial

Introduction: Phentolamine mesylate (OraVerse) is mostly used to reverse soft tissue anesthesia after dental procedures. The aim of the present study was to evaluate the effect of the injection of OraVerse on postoperative pain after root canal treatment in patients with symptomatic irreversible pulpitis. Methods and Materials: In this randomized single-blind clinical trial study, 100 patients (50 per group) with symptomatic irreversible pulpitis in the first or second mandibular molars, randomly received either OraVerse or sham treatment after a single-visit root canal therapy. Each patient recorded their pain score, using a Heft Parker visual analogue scale, before and after 6, 12, 24, 36, 48, and 72 h of the treatment. They also monitored their soft-tissue anesthesia every 15 min for 5 h. Data were analyzed by t-test and repeated measured ANOVA statistical tests. The level of significance was set at 0.05. Results: Patients who received phentolamine had significantly higher pain scores at 6- and 12-h postoperative intervals compared with those receiving sham treatment (P=0.01 and P=0.00 respectively). Consumption of analgesics in OraVerse group was significantly higher than that of the sham group (P=0.48). Conclusion: Although phentolamine accelerated the reversal of normal soft tissue sensation after the dental visit, it increased postoperative pain in patients suffering from symptomatic irreversible pulpitis, which may limit phentolamine administration in this group.Keywords: Anesthesia; Inferior Alveolar Nerve; Lidocaine; Phentolamine Mesylate; Postoperative Pai

A Survey on the Knowledge and Attitude of Iranian Endodontists toward Evidence Based Dentistry in 2017

Objectives Dentists make clinical decisions about dental cares on a daily basis. Thus, the best scientific evidence should be used to maximize the probability of successful patient care outcomes. The aim of this study was to evaluate the knowledge and attitude of endodontists towards evidence-based dentistry in Iran in 2017. Methods First a questionnaire was designed by the researchers. To evaluate the quality of the questionnaire, it was sent to six experts and they were asked to comment on each question. After collecting the questionnaires via e-mail, for each question, the statistics were determined by the expert and the reliability of the questionnaire was determined using the Cronbach's alpha coefficient. The target population of this cross-sectional study was the Iranian endodontists. Data were analyzed by SPSS software, and the frequency and descriptive indexes were used to evaluate the study variables (α=0.05). Results The mean score of knowledge of endodontists about evidence-based dentistry was 63.43±13.7 (out of 100) and the mean score of their attitude towards evidence-based dentistry was 62.22±18.5. Conclusion The results of this study revealed low level of knowledge and attitude of endodontists towards evidence-based dentistry, which is consistent with the results of studies conducted in other countries

Arabidopsis RecQl4A suppresses homologous recombination and modulates DNA damage responses

The DNA damage response and DNA recombination are two interrelated mechanisms involved in maintaining the integrity of the genome, but in plants they are poorly understood. RecQ is a family of genes with conserved roles in the regulation of DNA recombination in eukaryotes; there are seven members in Arabidopsis. Here we report on the functional analysis of the Arabidopsis RecQl4A gene. Ectopic expression of Arabidopsis RecQl4A in yeast RecQ-deficient cells suppressed their hypersensitivity to the DNA-damaging drug methyl methanesulfonate (MMS) and enhanced their rate of homologous recombination (HR). Analysis of three recQl4A mutant alleles revealed no obvious developmental defects or telomere deregulation in plants grown under standard growth conditions. Compared with wild-type Arabidopsis, the recQl4A mutant seedlings were found to be hypersensitive to UV light and MMS, and more resistant to mitomycin C. The average frequency of intrachromosomal HR in recQl4A mutant plants was increased 7.5-fold over that observed in wild-type plants. The data reveal roles for Arabidopsis RecQl4A in maintenance of genome stability by modulation of the DNA damage response and suppression of HR.

Seasonal Variations in Carnosic Acid Content of Rosemary Correlates with Anthocyanins and Soluble Sugars

Seasonal variations may influence the quality and quantity of biologically active ingredients in medicinal plants. Rosemary (Rosmarinus officinalis L.) a member of the Lamiaceae family, contains valuable antioxidant, anticancer and antibacterial substances, including Carnosic acid (CA). Here, the fluctuations of important active compounds present in rosemary leaf extracts collected in Golestan, Iran were studied during the year of 2012-2013. Plant phenolics, flavonoids, ascorbates, anthocyanins and soluble sugars were analyzed spectrophotometrically, while CA content was measured by High Performance Liquid Chromatography (HPLC). The highest amounts of total flavonoids occurred in autumn; while CA, phenolics, ascorbic acids and soluble sugars were greatest in winter, probably due to regional high precipitation and subtle winters. Most of the above indicated active compounds were low in early summer. Furthermore, total anthocyanins and soluble sugars showed significant positive correlations with CA over the year. These data suggest that rosemary extracts from the collected leaves in winter contain greater amounts of biologically active compounds; and can be used for standardization of plant materials harvested throughout a year