Simulations of Beam Quality in a 13 MeV PET Cyclotron

Simulation of the trajectories of negative hydrogen ion (H−) beam in a 13 MeV PET cyclotron (DECY-13) were carried out by using the Runge-Kutta (RK4) approximation method and Scilab 5.4.1. The magnetic and electric fields were calculated using Opera-3d/TOSCA softwares at 1 mm resolution. The cyclotron is of a fourth-harmonics type, meaning that the acceleration occurs four times per cycle, with a radiofrequency (RF) field of 77.66 MHz frequency and 40 kV amplitude. The calculations and simulations show that the maximum distance between the ion source and the puller is about 6 mm, while the maximum width of the beam at 13 MeV is about 10 mm, and the initial phase between the RF field and the beam ranges from -10° to 10°, with a yield of about 10% of the beam from the ion source getting accelerated to 13 MeV.Received: 12 March 2015; Revised:30 June 2015; Accepted: 01 July 201

Optimization of Ion Source Head Position in the Central Region of DECY-13 Cyclotron

Optimization of the ion source head position of the DECY-13 Cyclotron in the central region has been carried out based on simulation process using a particle tracking program written in Scilab 5.2.1. The simulated particle was the H- ion that was accelerated in DECY-13 Cyclotron. The input for the program were the magnetic field and the electric field in the central region that were calculated by Opera-3D software package and TOSCA module. The optimized position of ion source head position is in a radius of 2 cm relative to the zero point of the magnet and at a distance of 4 mm relative to the puller. This result can be useful for determining the configuration of the parts in the central region when it is tested for generating the first ion beam in the future

Simulations of Beam Quality in a 13 MeV PET Cyclotron

Simulation of the trajectories of negative hydrogen ion (H−) beam in a 13 MeV PET cyclotron (DECY-13) were carried out by using the Runge-Kutta (RK4) approximation method and Scilab 5.4.1. The magnetic and electric fields were calculated using Opera-3d/TOSCA softwares at 1 mm resolution. The cyclotron is of a fourth-harmonics type, meaning that the acceleration occurs four times per cycle, with a radiofrequency (RF) field of 77.66 MHz frequency and 40 kV amplitude. The calculations and simulations show that the maximum distance between the ion source and the puller is about 6 mm, while the maximum width of the beam at 13 MeV is about 10 mm, and the initial phase between the RF field and the beam ranges from -10° to 10°, with a yield of about 10% of the beam from the ion source getting accelerated to 13 MeV.Received: 12 March 2015; Revised:30 June 2015; Accepted: 01 July 201

Decision Tree for Prognostic Classification of Multivariate Survival Data and Competing Risks

Non

Design and Development of Scene Recognition and Classification Model Based on Human Pre-attentive Visual Attention

Recent works on scene classification still utilize the advantages of generic feature of Convolutional Neural Network while applying object-ontology technique that generates limited amount of object regions. Human can successfully recognize and classify scene effortlessly within short period of time. By utilizing this idea, we present a novel approach of scene classification model that built based on human pre-attentive visual attention. We firstly utilize saliency model to generate a set of high-quality regions that potentially contain salient objects. Then we apply a pre-trained Convolutional Neural Network model on these regions to extract deep features. Extracted features of every region are then concatenated to a final features vector and feed into one-vs-all linear Support Vector Machines. We evaluate our model on MIT Indoor 67 dataset. The result proved that saliency model used in this work is capable to generate high-quality informative salient regions that lead to good classification output. Our model achieves a better average accuracy rate than a standard approach that classifies as one whole image

Soil carbon storage of various species in Marudu Bay Mangrove Forest, Sabah

Soil, forest and atmosphere are potential carbon storage in the terrestrial ecosystem. However, little is known regarding the carbon storage of this ecosystem, particularly belowground. This study was conducted in the Marudu Bay mangrove forest, Sabah with the aim of quantifying carbon storage in soil for four dominant species in the study area. A total of 60 samples were collected at different species sites. Multiple linear regression and Pearson's correlations analysis were employed in this study. The average soil carbon storage in Marudu Bay mangrove forest was 89.98 t/ha with 35.5% from Rhizophora apiculata, 28.9% from Nypa fruticans, 27.15% from Bruguiera parviflora and 8.44% from Avicennia alba. Soil carbon storage was significantly affected by carbon content and sampling depth

Transient and sustained incentive effects on electrophysiological indices of cognitive control in younger and older adults

Preparing for upcoming events, separating task-relevant from task-irrelevant information and efficiently responding to stimuli all require cognitive control. The adaptive recruitment of cognitive control depends on activity in the dopaminergic reward system as well as the frontoparietal control network. In healthy aging, dopaminergic neuromodulation is reduced, resulting in altered incentive-based recruitment of control mechanisms. In the present study, younger adults (18–28 years) and healthy older adults (66–89 years) completed an incentivized flanker task that included gain, loss, and neutral trials. Event-related potentials (ERPs) were recorded at the time of incentive cue and target presentation. We examined the contingent negative variation (CNV), implicated in stimulus anticipation and response preparation, as well as the P3, which is involved in the evaluation of visual stimuli. Both younger and older adults showed transient incentive-based modulation of CNV. Critically, cue-locked and target-locked P3s were influenced by transient and sustained effects of incentives in younger adults, while such modulation was limited to a sustained effect of gain incentives on cue-P3 in older adults. Overall, these findings are in line with an age-related reduction in the flexible recruitment of preparatory and target-related cognitive control processes in the presence of motivational incentives