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Purpose/objective(s): Flash radiotherapy, the delivery of high radiation dose (> 10 Gy) at ultrahigh dose rates (> 37 Gy/s), has been shown to reduce significantly normal tissue toxicity compared to conventional irradiation, while maintaining tumor control probability at similar level. Great excitement has since ensued about the transformative potential of FLASH radiotherapy. At present, important FLASH research employs complex accelerator technologies of limited accessibilities. Here, we study the feasibility of a novel self-shielded x-ray irradiation cabinet system, as an enabling technology to enhance the preclinical research capabilities of the radiation research community.Materials/methods: The proposed system employs two commercially available high capacity 150 kVp fluoroscopy x-ray sources, RAD-44 or G-1592 tubes, with rotating anode technology in a parallel-opposed arrangement. Simulation was performed using a simulation toolkit. Simulated dosimetric properties of the x-ray beam for both FLASH and conventional dose-rate irradiations were characterized in terms of output, uniformity and symmetry as a function of SSD, beam current, exposure time, and external filters. Dose and dose rate from a single kV x-ray fluoroscopy source at various depths in solid water phantom were verified with measurements using radiographic films.Results: The parallel-opposed x-ray sources can deliver doses up to 67 Gy to a 20-mm thick water equivalent medium at FLASH dose-rates of 40 - 240 Gy/s. A uniform depth dose rate within ± 5% deviation is achieved over 8-12 mm in central region of the phantom. Conventional dose-rate irradiation (≤ 0.1 Gy/s) can also be achieved by reducing the tube current and increasing the distance between the phantom and tubes. Either the RAD-44 or G-1592 x-ray source can be used to deliver FLASH and conventional dose-rate irradiations with the field larger than 25 mm and up to 200 mm in length, respectively. These field dimensions are well suitable for small animal and cell culture irradiations. For FLASH irradiation using parallel-opposed source arrangement, entrance and exit doses can be increased by 30% compared to the dose at the phantom center. Beam angling can be employed to reduce the high surface doses by minimizing the beams overlap at the phantom surfaces. For a 10 × 10 mm2 field, for example, 26degree beam angle from vertical axis reduces the entrance dose by 39%, while maintaining FLASH dose rate of 118 Gy/s spanning in 8 mm thickness.Conclusion: It is feasible to achieve FLASH dose rate irradiation with kV x-rays using rotating anode x-ray sources in the parallel-opposed arrangement. The system is amendable to self-shielding and readily deployable. Availability of both FLASH and conventional dose rate irradiations in the same platform enables effective comparative research. A cabinet FLASH irradiation system will greatly enhance research in the regular laboratory setting to elucidate the important biological mechanism of the FLASH effect. [ABSTRACT FROM AUTHOR]

BackgroundEvidence suggests a relationship between exposure to trauma during childhood and functional impairments in psychotic patients. However, the impact of age at the time of exposure has been understudied in early psychosis (EP) patients.MethodTwo hundred and twenty-five patients aged 18–35 years were assessed at baseline and after 2, 6, 18, 24, 30 and 36 months of treatment. Patients exposed to sexual and/or physical abuse (SPA) were classified according to age at the time of first exposure (Early SPA: before age 11 years; Late SPA: between ages 12 and 15 years) and then compared to patients who were not exposed to such trauma (Non-SPA). The functional level in the premorbid phase was measured with the Premorbid Adjustment Scale (PAS) and with the Global Assessment of Functioning (GAF) scale and the Social and Occupational Functioning Assessment Scale (SOFAS) during follow-up.ResultsThere were 24.8% of patients with a documented history of SPA. Late SPA patients were more likely to be female (p = 0.010). Comparison with non-SPA patients revealed that: (1) both Early and Late SPA groups showed poorer premorbid social functioning during early adolescence, and (2) while patients with Early SPA had poorer functional level at follow-up with lower GAF (p = 0.025) and lower SOFAS (p = 0.048) scores, Late SPA patients did not.ConclusionOur results suggest a link between exposure to SPA and the later impairment of social functioning before the onset of the disease. EP patients exposed to SPA before age 12 may present long-lasting functional impairment, while patients exposed at a later age may improve in this regard and have a better functional outcome. [ABSTRACT FROM AUTHOR]

In this paper, considering a more realistic model for the carbon nanotube (CNT) conveying viscous fluid which is embedded in a visco-elastic medium, the effect of viscosity of the medium surrounding the CNT has been investigated. By taking into account the influence of the fluid viscosity and using the Navier-Stokes equations, the governing equation of motion has been derived and a new analytical technique based on the power series is presented for its vibration analysis. The frequency equation of the system is obtained by applying the boundary conditions. The influence of the medium parameters and the fluid viscosity on the natural frequencies of the CNT has been studied. The results show that the medium damping has a marked effect on the natural frequencies and the critical fluid velocity. Furthermore, by increasing the fluid viscosity, the natural frequencies and the critical fluid velocity increase. There is a good agreement between the results obtained through the proposed method and the data reported in the literature. The two main advantages of the proposed method are the applicability of the method to all kinds of the boundary conditions and its rapid convergence. [ABSTRACT FROM PUBLISHER]