In this paper, the effect of surface curvature on calibration coefficients of the hole-Drilling method has been studied. Firstly, an FE simulation of the drilling process has been modeled for a flat surface. Then, the simulation has been implemented on a cylinder with different diameters and the calibration coefficients have been extracted. In all analyses, the stain-gauge rosette and hole diameter remain constant and mesh removal in the drilling simulation was achieved in eight increments. The comparison of simulation results and standard published calibration coefficients data for a flat surface show an acceptable error equal to 2.8 variation of errors between 0.6 to 6.2.

Background and Aim: coronal seal is as important as the quality of root canal therapy in treatment success. This study aimed to compare the coronal microleakage of canals filled with Resilon and gutta percha with a glass ionomer coronal barrier.Materials and Methods: In this experimental study, the crowns of 64 single-rooted human premolar teeth were cut at the level of CEJ. Root canals were prepared using rotary ProTaper files. The teeth were randomly divided into 4 experimental groups (n=14) and 2 positive and negative control groups (n=8). Root canals of experimental group specimens were filled with gutta percha (groups 1 and 2) or Resilon (groups 3 and 4) using lateral condensation technique. The roots of negative control specimens were filled and all teeth surfaces were sealed with sticky wax. Root canals of positive controls were filled without the application of sealer. Glass ionomer coronal barrier was placed at the orifices in groups 2 and 4. Microleakage of Streptococcus faecalis was evaluated during 90 days. Data were analyzed using Chi square, Log-Rank and Tukey’s tests.Results: The degree of microleakage was less in groups with GI coronal barrier. However, this difference was not statistically significant (P>0.05). Time to microleakage in gutta percha+ coronal barrier and Resilon+ coronal barrier groups was significantly less than that in gutta percha and Resilon groups, respectively (P=0.03).Conclusion: Within the limitations of this study, microleakage occurred in all groups but glass ionomer acted as an effective barrier.

Introduction: External resorption of cervical area is one of the worst side effects of bleaching in non vital teeth. One method for inhibition is placing a coronal plug into the canal's entrance. Therefore sealing ability of 3 materials including Super EBA, MTA and Glass Ionomer were examined in this research as coronal plug before bleaching procedure.Methods and Materials: Seventy single canal anterior teeth were chosen by simple randomization. After access cavity preparation, the canals were cleaned and shaped. Five teeth were used as positive control and five as negative control. Other sixty teeth were filled with gutta-percha and sealer using lateral condensation method. In the next step, 3mm of gutta percha was removed from the coronal part and a thickness of 2mm of one of the materials (GI, Super EBA, MTA) was placed as coronal plug. Then the teeth were bleached 3 times with an interval of 72h, using Sodium Perborate and 3% H2O2.Then the access cavities were completely cleaned and filled with 2% methylene blue for 24h. The sample teeth were washed, dried and sectioned and dye penetration was measured using magnifying glass and cullies. Data was analyzed by ANOVA and LSD tests.Results: The average dye penetration was 3.23mm in MTA, 5.42mm in Super EBA and 1.76mm in GI group (p value = 0.018).Conclusion: Based on the results obtained from this study, glass ionomer was the best material for secondary seal before bleaching. Sealing ability of MTA was lower than GI, and of Super EBA was the least.

The large and small coronal Mass Ejections (CMEs) and mini-CMEs are observed by the Extreme Ultra Violet Imager (EUVI) on the Solar Terrestrial Relation Observatory (STEREO). These eruption events are usually associated with dimming and wave-like brightenings. Here, the images of the full sun on 26 Apr 2008 with STEREO spacecraft (behind) with the cadences of 10 minutes and 150 seconds and pixel size of 1.59 arc second in pass band 195 and 171 Å were analyzed. The velocities of the large and small wave-like brightening were 221 km.s-1 and 6 km.s-1, respectively. The zernike moments of events and non-events were computed and these features were fed to the Support Vector Machine (SVM) classifier. Using this method, 697 mini-CMEs on three different regions of solar corona were detected. The number of mini-CMEs was increased when the CMEs occurred. The average velocity of mini-dimmings was 13.8 km.s-1.

Spicules are intermittently rising above the surface of the Sun eruptions,EUV jets are now also reported immediately above surface layers. The orientation of spicules is a valuable parameter in the absence of direct magnetic field measurements with a sufficient spatial resolution in the chromospheric region because it is presumably determined by the confined flow of plasma, which should occur along the magnetic field lines, especially where the solar magnetic field pressure dominates the gas pressure. Of course, all these measurements suffer from the overlapping effect of spicules seen along each line of sight, the effect of which will be more critical when we look near the solar limb. In the case of macrospicules as well imaged by AIA of the SDO mission using the 304 filter recording the emissions of the HeII, resonance line, an additional effect arises due to the optical thickness of the line, especially on disk and also above the limb in the inner chromospheric shell. The primary purpose of this paper is to determine automatically and objectively the apparent tilt angle of spicules, using the best available highly processed observations, from the Solar Optical Telescope (SOT) limb imaging experiment by using an H CaII line, onboard Hinode mission. Furthermore, the Hough transform is applied to the resulting images for making a statistical analysis of spicule orientations in different regions around the solar limb, from the pole to the equator. A technique for the automatic detection off-limb spicules was implemented, and statistical measurements were conducted to determine the tilt angle for spicules at different heliocentric angles. We apply and develop a method with the following steps: (1) To increase the visibility of spicules, a radial logarithmic scale is applied,(2) To enhance linear features, while the Madmax operator is used. We investigated in more detail the apparent inclination of spicules and found the statistically average values for different locations around the solar limb for tilt angle. The results show a large difference of spicule apparent tilt angles in (i) the solar pole regions, (ii) the equatorial regions, (iii) the active regions, and (iv) the coronal hole regions. Analytically, during the minimum solar magnetically activity, from the equator to the poles, the inclination angles of the spicules are getting smaller and their lengths increase. As a result, the chromosphere thickness in this case is thicker than that of the solar maximum activities. When the spicules in the polar coronal holes are significantly inclined, the chromosphere and even transition regions thickness is thinner. Numerically, spicules are visible in a radial direction in the polar regions with a tilt angle <200. The tilt angle is even reduced to 10 degrees inside the coronal hole with open magnetic field lines and at the lower latitude, the tilt angle reaches values over 50 degrees. Usually, around an active region, they show a wide range of apparent angle variations from-60 to +60 degrees, which is in close resemblance to the rosettes that are made of dark mottles and fibrils in projection on the solar disk. However, large-scale activities with short life-time do not play a significant role in the thickness of the chromosphere, and they are removed for long term measurements by averaging. Therefore, this study considers the most statistical population of spicules in the minimum (and maximum) solar activity in the polar regions, and in lower latitude, to be considered as their inclination angles. While at the maximum laps of solar cycle, the opposite result will be expected, and fully confirmed, and give us a topological reason for the chromospheric prolateness at minimum activities.

I was asked to give a brief review of the black hole-string correspondence [1] as a warm-up for a longer SITP-group discussion of a recent paper by Chen, Maldacena, and Witten [2]. Here are my notes in written form.

There are issues in organizations that require new theoretical formulation. Hence, metaphorical theorizing is used in the study of organizations to interpret them and understand their complexities. In this method, the organization is likened to an entity and one of the key features of that entity is generalized to the organization. It should be borne in mind that most organizational theories are based on a positivist paradigm that focuses on knowledge and data in an attempt to discover the nomothetic of social systems. This article is an attempt to build a theory based on interpretive paradigm that puts the organizational black hole theory forward in a metaphorical way. The black hole theory of the organization has been adopted from the cosmic black hole metaphor. In the first step, the key features of the organizational black hole were summarized in accordance with the researcher's interpretation, taking into account the one-on-one correspondence and adopting the cosmic black hole characteristics. In the second step, the definition of the organizational black hole was presented based on key features, and in the third step the overall framework of the theory was formulated. In addition, by analyzing the characteristics of the organizational black hole theory, it was found that this theory falls under the interpretative paradigm. Finally, how one can test the theory in terms of falsifiability or utility is discussed.

Introduction: Providing adequate coronal seal of temporary filling materials is critical for the success of root canal therapy. The aim of this in vitro study was to compare coronal seal ability of three restorative materials over different periods of time.Materials and Methods: Ninety-eight molar teeth were selected. Once access cavities were prepared, teeth were divided randomly into three time groups (1 day, 1 week, and 4 weeks). Each group was then subdivided into three groups of 10 teeth. Each subgroup was restored using one of three restorative materials including Coltosol, Cavizol and Zonalin and then incubated in distilled water at 37oC. The samples were then immersed in 2% methylene blue dye. After rinsing and drying, teeth were sectioned longitudinally and examined for dye penetration. Kruskal-Wallis and Mann Whitney U tests were used to analyze the data.Results: All experimented materials showed increasing leakage from the 1st day to the 4th week. Zonalin showed more leakage than Coltosol and Cavizol at each time interval (P<0.05), but there was no significant difference between Coltosol and Cavizol.Conclusion: Coltosol and Cavizol are suitable temporary materials for up to 1 week.