No abstract

Reported here is the first on‐demand electrochemical epoxidation incorporated into the standard nano‐electrospray ionization mass spectrometry (nanoESI‐MS) workflow for double‐bond identification. The capability lies in a novel tunable electro‐epoxidation of double bonds, where onset of the reaction can be controlled by simply tuning the spray voltage. On‐demand formation of mono‐/multiple epoxides is achieved at different voltages. The electro‐epoxidized products are then fragmented by tandem MS to generate diagnostic ions, indicating the double bond position(s). The process is completed within seconds, holding great potential for high‐throughput analysis. The rapid switch‐on/off electro‐epoxidation of a single sample, the low sample consumption, the demonstrated applicability to complex lipids containing multiple double bonds, and the advantage of not requiring extra apparatus make this method attractive for use in lipid‐related biological studies.

In this prospective, randomized controlled study, nHFOV significantly reduced the need for IMV as compared with nCPAP in preterm infants with moderate-severe RDS without increase in adverse effects.

We present a proof of principle study of proton radiography and proton computed tomography (pCT) based on time-resolved dose measurements. We used a prototype, two-dimensional, diode-array detector capable of fast dose rate measurements, to acquire proton radiographic images expressed directly in water equivalent path length (WEPL). The technique is based on the time dependence of the dose distribution delivered by a proton beam traversing a range modulator wheel in passive scattering proton therapy systems. The dose rate produced in the medium by such a system is periodic and has a unique pattern in time at each point along the beam path and thus encodes the WEPL. By measuring the time dose pattern at the point of interest, the WEPL to this point can be decoded. If one measures the time–dose patterns at points on a plane behind the patient for a beam with sufficient energy to penetrate the patient, the obtained 2D distribution of the WEPL forms an image. The technique requires only a 2D dosimeter array and it uses only the clinical beam for a fraction of second with negligible dose to patient. We first evaluated the accuracy of the technique in determining the WEPL for static phantoms aiming at beam range verification of the brain fields of medulloblastoma patients. Accurate beam ranges for these fields can significantly reduce the dose to the cranial skin of the patient and thus the risk of permanent alopecia. Second, we investigated the potential features of the technique for real-time imaging of a moving phantom. Real-time tumor tracking by proton radiography could provide more accurate validations of tumor motion models due to the more sensitive dependence of proton beam on tissue density compared to x-rays. Our radiographic technique is rapid (~100 ms) and simultaneous over the whole field, it can image mobile tumors without the problem of interplay effect inherently challenging for methods based on pencil beams. Third, we present the reconstructed pCT images of a cylindrical phantom containing inserts of different materials. As for all conventional pCT systems, the method illustrated in this work produces tomographic images that are potentially more accurate than x-ray CT in providing maps of proton relative stopping power (RSP) in the patient without the need for converting x-ray Hounsfield units to proton RSP. All phantom tests produced reasonable results, given the currently limited spatial and time resolution of the prototype detector. The dose required to produce one radiographic image, with the current settings, is ~0.7 cGy. Finally, we discuss a series of techniques to improve the resolution and accuracy of radiographic and tomographic images for the future development of a full-scale detector.