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Novel ultrafast x-ray sources based on high harmonic generation and at x-ray free electron lasers are opening up new opportunities to resolve complex ultrafast processes in condensed phase systems with exceptional temporal resolution and atomic site specificity. In this perspective, we present techniques for resolving charge localization, transfer, and separation processes in organic semiconductors and organic photovoltaic devices with time-resolved soft x-ray spectroscopy. We review recent results in ultrafast soft x-ray spectroscopy of these systems and discuss routes to overcome the technical challenges in performing time-resolved x-ray experiments on photosensitive materials with poor thermal conductivity and low pump intensity thresholds for nonlinear effects.

The development of ultra-thin flat liquid sheets capable of running in vacuum has provided an exciting new target for X-ray absorption spectroscopy in the liquid and solution phases. Several methods have become available for delivering in-vacuum sheet jets using different nozzle designs. We compare the sheets produced by two different types of nozzle; a commercially available borosillicate glass chip using microfluidic channels to deliver colliding jets, and an in-house fabricated fan spray nozzle which compresses the liquid on an axis out of a slit to achieve collision conditions. We find in our tests that both nozzles are suitable for use in X-ray absorption spectroscopy with the fan spray nozzle producing thicker but more stable jets than the commercial nozzle. We also provide practical details of how to run these nozzles in vacuum.

Abstract Background Recurrent CT imaging is believed to significantly increase lifetime malignancy risk. We previously reported that high acuity, admitted trauma patients who received a whole-body CT in the emergency department (ED) had a history of prior CT imaging in 14% of cases. The primary objective of this study was to determine the CT imaging history for trauma patients who received a whole-body CT but were ultimately deemed safe for discharge directly home from the ED. Methods This was a retrospective cohort study conducted at an academic ED. All trauma patients who were discharged directly home from the ED after whole-body CT were analyzed. The decision to utilize whole-body CT was at the discretion of the caring physician during the study period. Clinical data for the most recent trauma visit was recorded in a structured fashion on a standardized data collection instrument utilizing the hospital system electronic medical record (EMR). Subsequently, study investigators reviewed a shared, electronic radiological archive for the 6-hospital system to evaluate prior CT exposure for each patient. Results 165 patients were in the study group. The mean age of the study group was 39+/− 16 years old, 40% were female and 64% were Hispanic. The most common mechanism of injury in our study group was motor vehicle crash (MVC) (66%). In our study group, 25% had at least one prior CT. The most common prior studies performed were: CT abdomen/pelvis (13%), CT head (9.1%), CT face (6.7%), and CT chest (1.8%). Within a multivariate logistic regression model we found that the large majority of patient characteristics and mechanisms of injury were not associated with a positive prior CT imaging history. Conclusion We found a positive history for prior CT for 25% of trauma patients who received whole-body CT scan but were discharged from the ED to home.

We experimentally investigate the impact of pulse shape on the dynamics of laser-generated plasma in rare gases. Fast-rising triangular pulses with a slower decay lead to early ionization of the gas and depose energy more efficiently than their temporally reversed counterparts. As a result, in both argon and krypton, the induced shockwave as well as the plasma luminescence are stronger. This is due to an earlier availability of free electrons to undergo inverse Bremsstrahlung on the pulse trailing edge. Our results illustrate the ability of adequately tailored pulse shapes to optimize the energy deposition in gas plasmas. [ABSTRACT FROM AUTHOR]