234 research outputs found
Fault Prognosis in Particle Accelerator Power Electronics Using Ensemble Learning
Early fault detection and fault prognosis are crucial to ensure efficient and
safe operations of complex engineering systems such as the Spallation Neutron
Source (SNS) and its power electronics (high voltage converter modulators).
Following an advanced experimental facility setup that mimics SNS operating
conditions, the authors successfully conducted 21 fault prognosis experiments,
where fault precursors are introduced in the system to a degree enough to cause
degradation in the waveform signals, but not enough to reach a real fault. Nine
different machine learning techniques based on ensemble trees, convolutional
neural networks, support vector machines, and hierarchical voting ensembles are
proposed to detect the fault precursors. Although all 9 models have shown a
perfect and identical performance during the training and testing phase, the
performance of most models has decreased in the prognosis phase once they got
exposed to real-world data from the 21 experiments. The hierarchical voting
ensemble, which features multiple layers of diverse models, maintains a
distinguished performance in early detection of the fault precursors with 95%
success rate (20/21 tests), followed by adaboost and extremely randomized trees
with 52% and 48% success rates, respectively. The support vector machine models
were the worst with only 24% success rate (5/21 tests). The study concluded
that a successful implementation of machine learning in the SNS or particle
accelerator power systems would require a major upgrade in the controller and
the data acquisition system to facilitate streaming and handling big data for
the machine learning models. In addition, this study shows that the best
performing models were diverse and based on the ensemble concept to reduce the
bias and hyperparameter sensitivity of individual models.Comment: 25 Pages, 13 Figures, 5 Table
Multi-module based CVAE to predict HVCM faults in the SNS accelerator
We present a multi-module framework based on Conditional Variational
Autoencoder (CVAE) to detect anomalies in the power signals coming from
multiple High Voltage Converter Modulators (HVCMs). We condition the model with
the specific modulator type to capture different representations of the normal
waveforms and to improve the sensitivity of the model to identify a specific
type of fault when we have limited samples for a given module type. We studied
several neural network (NN) architectures for our CVAE model and evaluated the
model performance by looking at their loss landscape for stability and
generalization. Our results for the Spallation Neutron Source (SNS)
experimental data show that the trained model generalizes well to detecting
multiple fault types for several HVCM module types. The results of this study
can be used to improve the HVCM reliability and overall SNS uptim
Analytic fluid theory of beam spiraling in high-intensity cyclotrons
Using a two-dimensional fluid description, we investigate the nonlinear radial-longitudinal dynamics of intense beams in isochronous cyclotrons in the nonrelativistic limit. With a multiscale analysis separating the time scale associated with the betatron motion and the slower time scale associated with space-charge effects, we show that the longitudinal-radial vortex motion can be understood in the frame moving with the charged beam as the nonlinear advection of the beam by the E×B velocity field, where E is the electric field due to the space charge and B is the external magnetic field. This interpretation provides simple explanations for the stability of round beams and for the development of spiral halos in elongated beams. By numerically solving the nonlinear advection equation for the beam density, we find that it is also in quantitative agreement with results obtained in particle-in-cell simulations
Increased chromosomal radiosensitivity in asymptomatic carriers of a heterozygous BRCA1 mutation
Background: Breast cancer risk increases drastically in individuals carrying a germline BRCA1 mutation. The exposure to ionizing radiation for diagnostic or therapeutic purposes of BRCA1 mutation carriers is counterintuitive, since BRCA1 is active in the DNA damage response pathway. The aim of this study was to investigate whether healthy BRCA1 mutations carriers demonstrate an increased radiosensitivity compared with healthy individuals.
Methods: We defined a novel radiosensitivity indicator (RIND) based on two endpoints measured by the G2 micronucleus assay, reflecting defects in DNA repair and G2 arrest capacity after exposure to doses of 2 or 4 Gy. We investigated if a correlation between the RIND score and nonsense-mediated decay (NMD) could be established.
Results: We found significantly increased radiosensitivity in the cohort of healthy BRCA1 mutation carriers compared with healthy controls. In addition, our analysis showed a significantly different distribution over the RIND scores (p = 0.034, Fisher’s exact test) for healthy BRCA1 mutation carriers compared with non-carriers: 72 % of mutation carriers showed a radiosensitive phenotype (RIND score 1–4), whereas 72 % of the healthy volunteers showed no radiosensitivity (RIND score 0). Furthermore, 28 % of BRCA1 mutation carriers had a RIND score of 3 or 4 (not observed in control subjects). The radiosensitive phenotype was similar for relatives within several families, but not for unrelated individuals carrying the same mutation. The median RIND score was higher in patients with a mutation leading to a premature termination codon (PTC) located in the central part of the gene than in patients with a germline mutation in the 5′ end of the gene.
Conclusions: We show that BRCA1 mutations are associated with a radiosensitive phenotype related to a compromised DNA repair and G2 arrest capacity after exposure to either 2 or 4 Gy. Our study confirms that haploinsufficiency is the mechanism involved in radiosensitivity in patients with a PTC allele, but it suggests that further research is needed to evaluate alternative mechanisms for mutations not subjected to NMD
EMSY overexpression disrupts the BRCA2/RAD51 pathway in the DNA-damage response: implications for chromosomal instability/recombination syndromes as checkpoint diseases
EMSY links the BRCA2 pathway to sporadic breast/ovarian cancer. It encodes a nuclear protein that binds to the BRCA2 N-terminal domain implicated in chromatin/transcription regulation, but when sporadically amplified/overexpressed, increased EMSY level represses BRCA2 transactivation potential and induces chromosomal instability, mimicking the activity of BRCA2 mutations in the development of hereditary breast/ovarian cancer. In addition to chromatin/transcription regulation, EMSY may also play a role in the DNA-damage response, suggested by its ability to localize at chromatin sites of DNA damage/repair. This implies that EMSY overexpression may also repress BRCA2 in DNA-damage replication/checkpoint and recombination/repair, coordinated processes that also require its interacting proteins: PALB2, the partner and localizer of BRCA2; RPA, replication/checkpoint protein A; and RAD51, the inseparable recombination/repair enzyme. Here, using a well-characterized recombination/repair assay system, we demonstrate that a slight increase in EMSY level can indeed repress these two processes independently of transcriptional interference/repression. Since EMSY, RPA and PALB2 all bind to the same BRCA2 region, these findings further support a scenario wherein: (a) EMSY amplification may mimic BRCA2 deficiency, at least by overriding RPA and PALB2, crippling the BRCA2/RAD51 complex at DNA-damage and replication/transcription sites; and (b) BRCA2/RAD51 may coordinate these processes by employing at least EMSY, PALB2 and RPA. We extensively discuss the molecular details of how this can happen to ascertain its implications for a novel recombination mechanism apparently conceived as checkpoint rather than a DNA repair system for cell division, survival, death, and human diseases, including the tissue specificity of cancer predisposition, which may renew our thinking about targeted therapy and prevention
Sensitivity to musical emotion is influenced by tonal structure in congenital amusia
Emotional communication in music depends on multiple attributes including psychoacoustic features and tonal system information, the latter of which is unique to music. The present study investigated whether congenital amusia, a lifelong disorder of musical processing, impacts sensitivity to musical emotion elicited by timbre and tonal system information. Twenty-six amusics and 26 matched controls made tension judgments on Western (familiar) and Indian (unfamiliar) melodies played on piano and sitar. Like controls, amusics used timbre cues to judge musical tension in Western and Indian melodies. While controls assigned significantly lower tension ratings to Western melodies compared to Indian melodies, thus showing a tonal familiarity effect on tension ratings, amusics provided comparable tension ratings for Western and Indian melodies on both timbres. Furthermore, amusics rated Western melodies as more tense compared to controls, as they relied less on tonality cues than controls in rating tension for Western melodies. The implications of these findings in terms of emotional responses to music are discussed
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Accelerator Physics Code Web Repository
In the framework of the CARE HHH European Network, we have developed a web-based dynamic acceleratorphysics code repository. We describe the design, structure and contents of this repository, illustrate its usage, and discuss our future plans, with emphasis on code benchmarking
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