Investigation of field output factors using IAEA-AAPM TRS-483 code of practice recommendations and Monte Carlo simulation for 6 MV photon beams

Introduction: This study aims to experimentally determine field output factors using the methodologies suggested by the IAEA-AAPM TRS-483 for small field dosimetry and compare with the calculation from Monte Carlo (MC) simulation. Methods: The IBA-CC01, Sun Nuclear EDGE and IBA-SFD detectors were employed to determine the uncorrected and the corrected field output factors for 6 MV photon beams. Measurements were performed at 100 cm source to axis distance, 10 cm depth in water, and the field sizes ranged from 1 × 1 to 10 × 10 cm2. The use of field output correction factors proposed by the TRS-483 was utilised to determine field output factors. The measured field output factors were compared to that calculated using the egs_chamber user code. Results: The decrease in the percentage standard deviation of the measured three detectors was observed after applying the field output correction factors. Measured field output factors using CC01 and EDGE detectors agreed with MC values within 3% for field sizes down to 1 × 1 cm2, except the SFD detector. Conclusions: The corrected field output factors agree with the calculation from MC, except the SFD detector. CC01 and EDGE are suitable for determining field output factors, while the SFD may need more implementation of the intermediate field method.

Lightning Return-Stroke Transmission Line Modelling Based on the Derivative of Heidler Function and CN Tower Data

One of the most important parameters in a lightning flash that is of interest to researchers is the lightning return-stroke current as it causes most of the destructions and disturbances in electrical and telecommunication networks. In most cases, the lightning return-stroke current can not be directly measured and current characteristics are determined from measured electric and magnetic fields through the use of lightning return-stroke models. The main objective of this work is the development of a lightning return-stroke model for an elevated object. Also, an important objective is the correlation of the wavefront parameters (peak, maximum rate of rise and risetime) of the return-stroke current with the wavefront parameters of its associated lightning electromagnetic pulse (LEMP), measured 2 km north of the tower. The developed field-current parameter relationships for CN Tower lightning return strokes are compared with those obtained from measurements conducted at the Peissenberg Tower in Germany. A 3-section transmission line (TL) model of the CN Tower, along with the derivative of the modified Heidler function, is used to simulate the measured current derivative signal. Then, the spatial-temporal distribution of the lightning current along the CN Tower and the lightning channel, during the lightning return-stroke phase, is determined. The presented model simulates the measured current derivative signal instead of the current as has been used by other researchers. The use of the derivative of the modified Heidler function to simulate the lightning current derivative proved to be superior than simulating the lightning current. For the quantitative assessment of the proposed model, a comparison between the simulated field, obtained through the usage of Maxwell’s equations and the simulated current, and the measured field is performed. The developed 3-section TL model based on the measured current derivative and the derivative of the modified Heidler function produced a simulated magnetic field that is much closer to the measured field in comparison with previous models. The developed field-current parameter relationships as well as the experimentally verified lightning return-stroke model can contribute to solving the inverse-source problem, one of the most challenging problems in lightning research, where the lightning current characteristics are estimated based on the characteristics of the measured LEMP.

Lightning Return-Stroke Transmission Line Modelling Based on the Derivative of Heidler Function and CN Tower Data

One of the most important parameters in a lightning flash that is of interest to researchers is the lightning return-stroke current as it causes most of the destructions and disturbances in electrical and telecommunication networks. In most cases, the lightning return-stroke current can not be directly measured and current characteristics are determined from measured electric and magnetic fields through the use of lightning return-stroke models. The main objective of this work is the development of a lightning return-stroke model for an elevated object. Also, an important objective is the correlation of the wavefront parameters (peak, maximum rate of rise and risetime) of the return-stroke current with the wavefront parameters of its associated lightning electromagnetic pulse (LEMP), measured 2 km north of the tower. The developed field-current parameter relationships for CN Tower lightning return strokes are compared with those obtained from measurements conducted at the Peissenberg Tower in Germany. A 3-section transmission line (TL) model of the CN Tower, along with the derivative of the modified Heidler function, is used to simulate the measured current derivative signal. Then, the spatial-temporal distribution of the lightning current along the CN Tower and the lightning channel, during the lightning return-stroke phase, is determined. The presented model simulates the measured current derivative signal instead of the current as has been used by other researchers. The use of the derivative of the modified Heidler function to simulate the lightning current derivative proved to be superior than simulating the lightning current. For the quantitative assessment of the proposed model, a comparison between the simulated field, obtained through the usage of Maxwell’s equations and the simulated current, and the measured field is performed. The developed 3-section TL model based on the measured current derivative and the derivative of the modified Heidler function produced a simulated magnetic field that is much closer to the measured field in comparison with previous models. The developed field-current parameter relationships as well as the experimentally verified lightning return-stroke model can contribute to solving the inverse-source problem, one of the most challenging problems in lightning research, where the lightning current characteristics are estimated based on the characteristics of the measured LEMP.

Highly conductive multi-walled carbon nanotube/polydimethylsiloxane (MWCNT/PDMS) nanocomposite for microfluidic applications

Conductive materials are required for sensing and actuation purposes in microfluidic devices. Electrical and mechanical properties of aligned CNTs/PDMS nanocomposites fabricated in AC and quasi-AC electric fields were measured. Field emission scanning electron microscope and elemental mapping were used to evaluate the microstructural properties of fabricated specimens. Results showed that nanocomposite properties were dependent on CNT concentration. A homogenized and nonagglomerated composite was obtained using a quasi-AC electric field with the voltage of 1075 V zero to peak at a frequency of 100 Hz and current of 35 milliamps when applied to suspension for 2 hours at 80 °C. The aligned nanocomposite with 1 wt% of CNT exhibited an electrical conductivity, Young’s modulus, and tensile strength of 10-6 S/cm, 7.23 MPa, and 1.02 MPa, respectively.

Different Morphs of Heterostylous Plant (Tirpitzia Sinensis) Associated With Floral Characters Have Various Adaptation Strategies to Pollinator to Ensure Reproductive Success

Background: Heterostylous plants are commonly associated with pollinators promoting disassortative pollination. How different morphs adapt to pollinators to ensure reproductive success and whether floral characters (such as pistil, stamen and nectar traits) are relevant to this process remain unclear. Results: Tirpitzia sinensis is distylous flowers. Its floral characters were measured. Field observation of effective pollinator and pollination efficiency to different morphs was conducted, and breeding systems were examined by hand pollination treatments. Our results showed that L-morph produced more but smaller pollen grains per anther than S-morph. T. sinensis secreted more nectar at night as a possible adaptation to hawkmoths (Macroglossum spp.) active at dusk. L-morph produced much nectar due to its large secretion volume at night. The nectar was rich in sucrose. The sucrose/hexose ratio was higher in the nectar of S-morph than in that of L-morph. S-morph had higher visit rate but lower pollination efficiency of hawkmoths compared with L-morph. T. sinensis was self-incompatible. Seed sets in nature did not differ between morphs. Conclusions: Our findings suggest that L-morph increases its pollination efficiency through outstanding stigma, many pollen grains per anther, and high amount of nectar. S-morph attracts many hawkmoths to pollinate due to its high sucrose/hexose ratio in its nectar.

Technical aspects of the electrophoresis stage in the comet assay.

Inter- and intralaboratory variability of results is still a serious issue in the comet assay. There are several technical conditions of procedure, which may critically affect the results and electrophoresis terms were identified as main. A comparative assessment of the expected and actual field strength in five electrophoretic tanks and the contribution of the revealed differences to the variability in DNA damage carried out. Only for one tank, the measured field strength coincided with the expected 1 V/cm, while for four it ranged from 0.6 to 2.0 V/cm. The values of DNA damage assessed in the same samples of mouse kidney cells differed between tanks up to 4.7-fold for induced and up to 10-fold for spontaneous DNA damage. High local variations in the field strength and solution temperature across the platform as well as in %DNA in the tail of identical cell samples within electrophoresis runs also revealed. These variations were reduced by recirculation of electrophoresis solution. The results show that discrepancy between the estimated and the actual field strength can be reason of inter-laboratory variation of the comet assay results. Recirculation of the solution during electrophoresis will be useful to control of intra-laboratory and intra-assay variations.

Reduced Embedded Magnetic Field in Type-II Superconductor of Finite Dimension

This work maps the magnetic field within a type-II superconductor of finite dimension that is magnetically flux-pinned. The measured field is lower in magnitude than anticipated from the frozen image model and changes shape dependent on the field-cooled image location. A proposed refined model more accurately reflects the measured field.