Solving Super-Synchronous Vibration On A Double Suction Pump

Case Stud

Applications of Monte Carlo methods to special radiotherapeutic techniques

Monte Carlo (MC) methods are considered one of the most powerful and precise approaches to study and solve medical physics issues. They, indeed, can be applied in all the situations where to use deterministic algorithms is infeasible or impossible. Surprising improvements in computer technology have promoted a wide diffusion of this technique, giving rise to the born of several Monte Carlo codes, such as the GEANT4 toolkit. In this paper we show some of the applications we developed using GEANT4. In particular, the simulation of two different radiotherapy techniques, such as proton/ion therapy and stereotactic radiosurgery will be discussed. In the first case we show the main features of our last public version of the GEANT4 Hadrontherapy program, also discussing the issues related to the nuclear fragmentation. In the second case, we show the procedures followed for the simulation of a Gamma Knife device, in order to validate the Treatment Planning System (TPS) used for the dose computation

Natural and CVD type diamond detectors as dosimeters in hadrontherapy applications

Abstract Diamond is potentially a suitable material for use as radiation dosimeter; the wide band gap results in low dark currents and low sensitivity to visible light, the high carrier mobility can give rapid response, the very high density of strong bonds in the crystal structure make diamond very resistent to radiation damage; moreover it is tissue equivalent. The more recent advances in the synthesis of polycrystalline diamond by chemical vapour deposition (CVD) techniques have allowed the synthesis of material with electronic properties suitable for dosimetric application. In this paper we will report the results obtained in the study of the response of a natural diamond dosimeter and a CVD one irradiated with 62 AMeV proton beams to demonstrate their possible application in protontherapy

Robustness of pet radiomics features: Impact of co-registration with mri

Radiomics holds great promise in the field of cancer management. However, the clinical application of radiomics has been hampered by uncertainty about the robustness of the features extracted from the images. Previous studies have reported that radiomics features are sensitive to changes in voxel size resampling and interpolation, image perturbation, or slice thickness. This study aims to observe the variability of positron emission tomography (PET) radiomics features under the impact of co-registration with magnetic resonance imaging (MRI) using the difference percentage coefficient, and the Spearman’s correlation coefficient for three groups of images: (i) original PET, (ii) PET after co-registration with T1-weighted MRI and (iii) PET after co-registration with FLAIR MRI. Specifically, seventeen patients with brain cancers undergoing [11C]-Methionine PET were considered. Successively, PET images were co-registered with MRI sequences and 107 features were extracted for each mentioned group of images. The variability analysis revealed that shape features, first-order features and two subgroups of higher-order features possessed a good robustness, unlike the remaining groups of features, which showed large differences in the difference percentage coeffi-cient. Furthermore, using the Spearman’s correlation coefficient, approximately 40% of the selected features differed from the three mentioned groups of images. This is an important consideration for users conducting radiomics studies with image co-registration constraints to avoid errors in cancer diagnosis, prognosis, and clinical outcome prediction

Can a leader be seen as too ethical? The curvilinear effects of ethical leadership

Ethical leadership predicts important organizational outcomes such as decreased deviant and increased organizational citizenship behavior (OCB). We argued that due to the distinct nature of these two types of employee behaviors, ethical leadership decreases deviance in a linear manner (i.e., more ethical leadership leading to less deviance), but we expected ethical leadership to reveal a curvilinear relationship with respect to OCB. Specifically, we expected that, at lower levels, ethical leadership promotes OCB. However, at high levels, ethical leadership should lead to a decrease in these behaviors. We also examined a mechanism that explains this curvilinear pattern, that is, followers’ perceptions of moral reproach. Our predictions were supported in three organizational field studies and an experiment. These findings offer a better understanding of the processes that underlie the workings of ethical leadership. They also imply a dilemma for organizations in which they face the choice between limiting deviant employee behavior and promoting OCB

CATANA protontherapy facility: The state of art of clinical and dosimetric experience

After nine years of activity, about 220 patients have been treated at the CATANA Eye Protontherapy facility. A 62MeV proton beam produced by a Superconducting Cyclotron is dedicated to radiotherapy of eye lesions, as uveal melanomas. Research and development work has been done to test different dosimetry devices to be used for reference and relative dosimetry, in order to achieve dose delivering accuracy. The follow-up results demonstrated the efficacy of proton beams and encouraged us in our activity in the fight against cancer

Molecular basis for the lack of enantioselectivity of human 3-phosphoglycerate kinase

Non-natural l-nucleoside analogues are increasingly used as therapeutic agents to treat cancer and viral infections. To be active, l-nucleosides need to be phosphorylated to their respective triphosphate metabolites. This stepwise phosphorylation relies on human enzymes capable of processing l-nucleoside enantiomers. We used crystallographic analysis to reveal the molecular basis for the low enantioselectivity and the broad specificity of human 3-phosphoglycerate kinase (hPGK), an enzyme responsible for the last step of phosphorylation of many nucleotide derivatives. Based on structures of hPGK in the absence of nucleotides, and bound to l and d forms of MgADP and MgCDP, we show that a non-specific hydrophobic clamp to the nucleotide base, as well as a water-filled cavity behind it, allows high flexibility in the interaction between PGK and the bases. This, combined with the dispensability of hydrogen bonds to the sugar moiety, and ionic interactions with the phosphate groups, results in the positioning of different nucleotides so to expose their diphosphate group in a position competent for catalysis. Since the third phosphorylation step is often rate limiting, our results are expected to alleviate in silico tailoring of l-type prodrugs to assure their efficient metabolic processing