Radiocarbon Production Events and their Potential Relationship with the Schwabe Cycle.

Extreme cosmic radiation events occurred in the years 774/5 and 993/4 CE, as revealed by anomalies in the concentration of radiocarbon in known-age tree-rings. Most hypotheses point towards intense solar storms as the cause for these events, although little direct experimental support for this claim has thus far come to light. In this study, we perform very high-precision accelerator mass spectrometry (AMS) measurements on dendrochronological tree-rings spanning the years of the events of interest, as well as the Carrington Event of 1859 CE, which is recognized as an extreme solar storm even though it did not generate an anomalous radiocarbon signature. Our data, comprising 169 new and previously published measurements, appear to delineate the modulation of radiocarbon production due to the Schwabe (11-year) solar cycle. Moreover, they suggest that all three events occurred around the maximum of the solar cycle, adding experimental support for a common solar origin.

Two-stage approach for risk estimation of fetal trisomy 21 and other aneuploidies using computational intelligence systems.

OBJECTIVE: To estimate the risk of fetal trisomy 21 (T21) and other chromosomal abnormalities (OCA) at 11-13 weeks' gestation using computational intelligence classification methods. METHODS: As a first step, a training dataset consisting of 72 054 euploid pregnancies, 295 cases of T21 and 305 cases of OCA was used to train an artificial neural network. Then, a two-stage approach was used for stratification of risk and diagnosis of cases of aneuploidy in the blind set. In Stage 1, using four markers, pregnancies in the blind set were classified into no risk and risk. No-risk pregnancies were not examined further, whereas the risk pregnancies were forwarded to Stage 2 for further examination. In Stage 2, using seven markers, pregnancies were classified into three types of risk, namely no risk, moderate risk and high risk. RESULTS: Of 36 328 unknown to the system pregnancies (blind set), 17 512 euploid, two T21 and 18 OCA were classified as no risk in Stage 1. The remaining 18 796 cases were forwarded to Stage 2, of which 7895 euploid, two T21 and two OCA cases were classified as no risk, 10 464 euploid, 83 T21 and 61 OCA as moderate risk and 187 euploid, 50 T21 and 52 OCA as high risk. The sensitivity and the specificity for T21 in Stage 2 were 97.1% and 99.5%, respectively, and the false-positive rate from Stage 1 to Stage 2 was reduced from 51.4% to ∼1%, assuming that the cell-free DNA test could identify all euploid and aneuploid cases. CONCLUSION: We propose a method for early diagnosis of chromosomal abnormalities that ensures that most T21 cases are classified as high risk at any stage. At the same time, the number of euploid cases subjected to invasive or cell-free DNA examinations was minimized through a routine procedure offered in two stages. Our method is minimally invasive and of relatively low cost, highly effective at T21 identification and it performs better than do other existing statistical methods. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Dosimetry using Gafchromic XR-RV2 radiochromic films in interventional radiology.

Patient dose measurements of local entrance dose to the skin have been carried out using radiochromic film (Gafchromic XR-RV2) in a sample of interventional procedures. The major aim of the work was to measure patient entrance dose from such examinations using Gafchromic XR-RV2. Forty-five various interventional procedures (including nefrostomies and urinary stenting, biliary stenting and percutaneous transhepatic biliary drainage (PTBD) and aorta stent grafting) were evaluated. Maximum entrance doses were 537 ± 119 mGy in nephrostomies, 943 ± 631 mGy in biliary stenting and PTBD and 2425 ± 569 mGy in aorta stent grafting. Results indicate that all patients undergoing aorta stent grafting received skin dose above 1500 mGy, which means that there is an increasing potential to suffer radiation-induced skin injuries. The film provides dose mapping, the position of the skin area with highest dose and can be used for immediate qualitative and as well as for quantitative assessment of patient skin dose.