Dataset Information

Establishing nonlinearity thresholds with ultraintense X-ray pulses.

ABSTRACT: X-ray techniques have evolved over decades to become highly refined tools for a broad range of investigations. Importantly, these approaches rely on X-ray measurements that depend linearly on the number of incident X-ray photons. The advent of X-ray free electron lasers (XFELs) is opening the ability to reach extremely high photon numbers within ultrashort X-ray pulse durations and is leading to a paradigm shift in our ability to explore nonlinear X-ray signals. However, the enormous increase in X-ray peak power is a double-edged sword with new and exciting methods being developed but at the same time well-established techniques proving unreliable. Consequently, accurate knowledge about the threshold for nonlinear X-ray signals is essential. Herein we report an X-ray spectroscopic study that reveals important details on the thresholds for nonlinear X-ray interactions. By varying both the incident X-ray intensity and photon energy, we establish the regimes at which the simplest nonlinear process, two-photon X-ray absorption (TPA), can be observed. From these measurements we can extract the probability of this process as a function of photon energy and confirm both the nature and sub-femtosecond lifetime of the virtual intermediate electronic state.

SUBMITTER: Szlachetko J

PROVIDER: S-EPMC5020491 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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Establishing nonlinearity thresholds with ultraintense X-ray pulses.

Szlachetko Jakub J Hoszowska Joanna J Dousse Jean-Claude JC Nachtegaal Maarten M Błachucki Wojciech W Kayser Yves Y Sà Jacinto J Messerschmidt Marc M Boutet Sebastien S Williams Garth J GJ David Christian C Smolentsev Grigory G van Bokhoven Jeroen A JA Patterson Bruce D BD Penfold Thomas J TJ Knopp Gregor G Pajek Marek M Abela Rafael R Milne Christopher J CJ

Scientific reports 20160913

X-ray techniques have evolved over decades to become highly refined tools for a broad range of investigations. Importantly, these approaches rely on X-ray measurements that depend linearly on the number of incident X-ray photons. The advent of X-ray free electron lasers (XFELs) is opening the ability to reach extremely high photon numbers within ultrashort X-ray pulse durations and is leading to a paradigm shift in our ability to explore nonlinear X-ray signals. However, the enormous increase in ...[more]

PMID: 27620067

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Project description:Context and objectiveStandards for clinical practice guidelines require explicit statements regarding how values and preferences influence recommendations. However, no cancer screening guideline has addressed the key question of what magnitude of benefit people require to undergo screening, given its harms and burdens. This article describes the development of a new method for guideline developers to address this key question in the absence of high-quality evidence from published literature.Summary of methodThe new method was developed and applied in the context of a recent BMJ Rapid Recommendation clinical practice guideline for colorectal cancer (CRC) screening. First, we presented the guideline panel with harms and burdens (derived from a systematic review) associated with the CRC screening tests under consideration. Second, each panel member completed surveys documenting their views of expected benefits on CRC incidence and mortality that people would require to accept the harms and burdens of screening. Third, the panel discussed results of the surveys and agreed on thresholds for benefits at which the majority of people would choose screening. During these three steps, the panel had no access to the actual benefits of the screening tests. In step four, the panel was presented with screening test benefits derived from a systematic review of clinical trials and microsimulation modelling. The thresholds derived through steps one to three were applied to these benefits, and directly informed the panel's recommendations.ConclusionWe present the development and application of a new, four-step method enabling incorporation of explicit and transparent judgements of values and preferences in a screening guideline. Guideline panels should establish their view regarding the magnitude of required benefit, given burdens and harms, before they review screening benefits and make their recommendations accordingly. Making informed screening decisions requires transparency in values and preferences judgements that our new method greatly facilitates.

Dataset Information

Establishing nonlinearity thresholds with ultraintense X-ray pulses.

Publications

Establishing nonlinearity thresholds with ultraintense X-ray pulses.

Similar Datasets

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