Atomic Energy Council

Abstract Background HVL in diagnostic X-ray machine is an important property that is used to define the penetrating ability of an X-ray beam and hence can be used to determine the component of beam hardness. Purpose The purpose of the study was to assess the effect of HVL on the dose output of diagnostic X-ray machine and to determine the different corrective actions for the cases which did not comply the established dose limits. Material and Methods The study utilized the findings of the radiation safety inspections conducted between 2021–2022 by Atomic Energy Council to investigate different Half value layer (HVL) ranges for diagnostic X-ray machines. A number of 64 X-ray machines were selected for the study based on a set criterion. Results A total of 26 X-ray machines failed the HVL test though produced different descriptions of measured dose output. Fifteen (15) X-ray machines produced doses within the permissible range of 0.025 mGy/mAs – 0.080 mGy/mAs, eight (08) X-ray machines produced doses below the lower limit of the dose range of 0.025 mGy/mAs, while three (03) X-ray machines produce doses above the upper limit of the dose range of 0.080 mGy/mAs. The other 38 X-ray machines passed the HVL test but failed the dose output test. These were classified in different HVL groups that exceeded the recommended regulatory limit, that is, moderate (5), high (19), very high (10) and extreme high (4) X-ray machines. The corrective action made was either adding or removing filter plates to enhance or minimize the filtration for machines that failed the HVL test and the ones that passed HVL test but failed the dose output test respectively. However, this should only be after a conclusive investigation of checking the accuracy of tube current (mA), timer (s) and tube potential (kVp) parameters. Conclusion Therefore, the corrective action for HVL should not be done in isolation from other machine dose contributing parameters like tube current potential parameters and exposure time. The regulatory body recommends that HVL tests should be part of the acceptance and commissioning tests for the new machines and done routinely for the machines in use as specified in the quality control program for each facility.

In this work, a novel device concept for improving the efficiency and field operation of conventional InAs/GaAs quantum dot (QD) based intermediate band solar cell (IBSC) with the feature of current constraint (CC-QD-IBSC) was proposed and evaluated from both theoretical simulations and experimental demonstrations. The advantages of the proposed device concept including increasing efficiency, obtaining higher suitability for operation under concentrated photovoltaic (CPV) condition and more robust efficiency stability against intermediate band fluctuation were rigorously identified using the detailed balance theorem by comparing with conventional InAs/GaAs QD-IBSC. Furthermore, a hybrid molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD) shuttle growth of the proposed CC-QD-IBSC were adopted in this work for better preserving QD induced intermediate band feature and overcoming practical growth difficulties. By introducing a InGaP top cell for constraining the current of InAs/GaAs QD-IBSC, the short circuit current density of CC-QD-IBSC decreased to 13.0mA/cm2 under 1 sun illumination, a near 50 % reduction compared to the conventional InAs/GaAs QD-IBSC. On the contrary, by well adjusting the regrowth interface between MBE and MOCVD, we managed to reach the highest conversion efficiency of 22.8 % measured at an UL certified laboratory under light concentration ratio of 93 suns for the proposed CC-QD-IBSC with well-functioning QD and IB feature. It is our belief that our results pave the road for developing techniques geared towards higher efficiency and more practical field applications.

In this paper, a bidirectional converter with multi-mode control strategies is proposed for a battery energy storage system (BESS). This proposed converter, which is composed of a half-bridge-type dual-active-bridge (HBDAB) converter and an H-bridge inverter, is able to operate the BESS with different power conditions and achieve the DC–AC function for lower input DC voltage applications. For the HBDAB converter, the variable-frequency control (VFC) and phase-shift control (PSC) are both adopted to achieve zero-voltage switching over a wider power range and the battery module balance control capability for BESS, respectively. In addition, the interleaved configuration is used to reduce the current ripple and increase the overall current rating. For the H-bridge inverter, the unipolar control mode (UCM) and totem-pole control mode (TPCM) are adopted to manage the real and reactive current control under different AC grid conditions. The UCM offers a reduction in current ripple for real and reactive power control. The TPCM is able to eliminate switching losses and achieve higher conversion efficiency for pure real power control. Considering applications for battery energy storage systems, the principle of operation and voltage gain analysis are described. Finally, computer simulations and hardware experimental results from a prototype system are presented to verify the performance of the proposed converter with the different control strategies.

To enhance the electrochemical capability of graphite felt (GF) electrodes in vanadium redox flow batteries (VRFBs), we prepare nitrogen-doped tungsten carbide nanowires (N-WC NWs), which are grown on the GF surface via a two-step route. In the first step, we use a hydrothermal process using tungstic acid (H2WO4) as a precursor, and the WO3 NWs are deposited on the GF surface. Subsequently, the grown WO3 NWs are simultaneously carbonized and N-doped using melamine as the source of nitrogen and carbon. Compared to pristine GF, the prepared N-WC NWs-GF electrode exhibits an apparent electrocatalytic effect on the VO2+/VO2+ and V3+/V2+ redox reaction. The presence of a negatively charged density on the nitrogen atom encourages the vanadium ions’ absorption. The nanowire structure exposes more active sites for the vanadium ions’ redox reactions. Hence, the prepared N-WC NWs-GF electrode demonstrates the optimal electrochemical activity with energy and voltage efficiencies of 74.8% and 78.9%, respectively, which are much greater than those of the 59.8% and 63.2% attained from pristine GF at 100 mA cm–2. Moreover, the N-WC NWs-GF presented good stability and durability in acidic electrolyte during long-term operations for 100 cycles at a higher current density of 100 mA cm–2.

Background and purposeHistone deacetylase (HDAC) inhibitors (HDIs) can modulate the epithelial-mesenchymal transition (EMT) progression and inhibit the migration and invasion of cancer cells. Emerging as a novel class of anti-cancer drugs, HDIs are attracted much attention in the field of drug discovery. This study aimed to discern the underlying mechanisms of Honokiol in preventing the metastatic dissemination of gastric cancer cells by inhibiting HDAC3 activity/expression.Experimental approachClinical pathological analysis was performed to determine the relationship between HDAC3 and tumor progression. The effects of Honokiol on pharmacological characterization, functional, transcriptional activities, organelle structure changes, and molecular signaling were analyzed using binding assays, differential scanning calorimetry, luciferase reporter assay, HDAC3 activity, ER stress response element activity, transmission electron microscopy, immune-blotting, and Wnt/β-catenin activity assays. The in vivo effects of Honokiol on peritoneal dissemination were determined by a mouse model and detected by PET/CT tomography.Key resultsHDAC3 over-expression was correlated with poor prognosis. Honokiol significantly abolished HDAC3 activity (Y298) via inhibition of NFκBp65/CEBPβ signaling, which could be reversed by the over-expression of plasmids of NFκBp65/CEBPβ. Treatments with 4-phenylbutyric acid (a chemical chaperone) and calpain-2 gene silencing inhibited Honokiol-inhibited NFκBp65/CEBPβ activation. Honokiol increased ER stress markers and inhibited EMT-associated epithelial markers, but decreased Wnt/β-catenin activity. Suppression of HDAC3 by both Honokiol and HDAC3 gene silencing decreased cell migration and invasion in vitro and metastasis in vivo.Conclusions and implicationsHonokiol acts by suppressing HDAC3-mediated EMT and metastatic signaling. By prohibiting HDAC3, metastatic dissemination of gastric cancer may be blocked.Graphical abstractConceptual model showing the working hypothesis on the interaction among Honokiol, HDAC3, and ER stress in the peritoneal dissemination of gastric cancer. Honokiol targeting HDAC3 by ER stress cascade and mitigating the peritoneal spread of gastric cancer. Honokiol-induced ER stress–activated calpain activity targeted HDAC3 and blocked Tyr298 phosphorylation, subsequently blocked cooperating with EMT transcription factors and cancer progression. The present study provides evidence to demonstrate that HDAC3 is a positive regulator of EMT and metastatic growth of gastric cancer cells. The findings here imply that overexpressed HDAC3 is a potential therapeutic target for honokiol to reverse EMT and prevent gastric cancer migration, invasion, and metastatic dissemination.• Honokiol significantly abolished HDAC3 activity on catalytic tyrosine 298 residue site. In addition, Honokiol-induced ER stress markedly inhibited HDAC3 expression via inhibition of NFκBp65/CEBPβ signaling.• HDAC3, which is a positive regulator of metastatic gastric cancer cell growth, can be significantly inhibited by Honokiol.• Opportunities for HDAC3 inhibition may be a potential therapeutic target for preventing gastric cancer metastatic dissemination.

Power systems all over the world have been under development towards microgrids integrated with renewable energy-based distributed generation. Due to the intrinsic nature of output power fluctuations in renewable energy-based power generation, the use of proper energy storage systems and integrated real-time power and energy control schemes is an important basis of sustainable development of renewable energy-based distributed systems and microgrids. The aim of this paper is to investigate the characteristics and application features of an integrated compound energy storage system via simulation and a small-scale hardware system implementation. This paper first discusses the main components, working principles and operating modes of the proposed compound energy storage system. Then, a detailed design example composed of supercapacitors, batteries, and various controllers used in two typical application scenarios, peak demand shaving and power generation smoothing, of a grid-connected microgrid is systematically presented. Finally, an experimental setup with proper power converters and control schemes are implemented for the verification of the proposed control scheme. Both simulation and implementation results prove that the proposed scheme can effectively realize desired control objectives with the proposed coordinated control of the two energy storage devices.

Despite the dynamic threats to the nuclear security of the East and Central African region, and the decision of the Government of Uganda to embark on a nuclear power programme, there was not much put in place as a coordination and cooperation mechanisms among the stakeholders in the nuclear security activities. This work confirmed the need in Uganda for the major nuclear security stakeholder agencies with roles and mandates for nuclear security including the regulator, security and intelligence agencies, police, border control, transport control, customs agencies and others to work together as necessary in the different nuclear security activities in order to strengthen the national nuclear security regime. In view of the findings of the researcher’s research thesis, and in line with international nuclear security legal framework, principles and IAEA guidance, recommendations are generated towards developing the most effective model for coordination of inter-agency action for nuclear security in Uganda.

The study utilizes the energy-flux-vector method to analyze the heat transfer characteristics of natural convection in a wavy-wall porous square cavity with a partially-heated bottom surface. The effects of the modified Darcy number, modified Rayleigh number, modified Prandtl number, and length of the partially-heated bottom surface on the energy-flux-vector distribution and mean Nusselt number are examined. The results show that when a low modified Darcy number with any value of modified Rayleigh number is given, the recirculation regions are not formed in the energy-flux-vector distribution within the porous cavity. Therefore, a low mean Nusselt number is presented. The recirculation regions do still not form, and thus the mean Nusselt number has a low value when a low modified Darcy number with a high modified Rayleigh number is given. However, when the values of the modified Darcy number and modified Rayleigh number are high, the energy flux vectors generate recirculation regions, and thus a high mean Nusselt number is obtained. In addition, in a convection-dominated region, the mean Nusselt number increases with an increasing modified Prandtl number. Furthermore, as the length of the partially-heated bottom surface lengthens, a higher mean Nusselt number is presented.