215 research outputs found
Pamela: development of the RF system for a non-relativistic non-scaling FFAG
The PAMELA project(Particle Accelerator For MEdical
Applications) currently consists of the design of a particle
therapy facility. The project, which is in the design phase,
contains Non-Scaling FFAG, particle accelerator capable
of rapid beam acceleration, giving a pulse repetition rate of
1kHz, far beyond that of a conventional synchrotron. To
realise the repetition rate, a key component of the accelerator
is the rf accelerating system. The combination of a high
energy gain per turn and a high repetition rate is a significant
challenge. In this paper, options for the rf system of
the proton ring and the status of development are presented
Precipitated iron: a limit on gettering efficacy in multicrystalline silicon
A phosphorus diffusion gettering model is used to examine the efficacy of a standard gettering process on interstitial and precipitated iron in multicrystalline silicon. The model predicts a large concentration of precipitated iron remaining after standard gettering for most as-grown iron distributions. Although changes in the precipitated iron distribution are predicted to be small, the simulated post-processing interstitial iron concentration is predicted to depend strongly on the as-grown distribution of precipitates, indicating that precipitates must be considered as internal sources of contamination during processing. To inform and validate the model, the iron distributions before and after a standard phosphorus diffusion step are studied in samples from the bottom, middle, and top of an intentionally Fe-contaminated laboratory ingot. A census of iron-silicide precipitates taken by synchrotron-based X-ray fluorescence microscopy confirms the presence of a high density of iron-silicide precipitates both before and after phosphorus diffusion. A comparable precipitated iron distribution was measured in a sister wafer after hydrogenation during a firing step. The similar distributions of precipitated iron seen after each step in the solar cell process confirm that the effect of standard gettering on precipitated iron is strongly limited as predicted by simulation. Good agreement between the experimental and simulated data supports the hypothesis that gettering kinetics is governed by not only the total iron concentration but also by the distribution of precipitated iron. Finally, future directions based on the modeling are suggested for the improvement of effective minority carrier lifetime in multicrystalline silicon solar cells
Conceptual design of a nonscaling fixed field alternating gradient accelerator for protons and carbon ions for charged particle therapy
Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.The conceptual design for a nonscaling fixed field alternating gradient accelerator suitable for charged particle therapy (the use of protons and other light ions to treat some forms of cancer) is described.EPSR
Clarifying the role of three-dimensional transvaginal sonography in reproductive medicine: an evidenced-based appraisal
This overview describes and illustrates the clinical applications of three-dimensional transvaginal sonography in reproductive medicine. Its main applications include assessment of uterine anomalies, intrauterine pathology, tubal patency, polycystic ovaries, ovarian follicular monitoring and endometrial receptivity. It is also useful for detailed evaluation of failed and/or ectopic pregnancy. Three-dimensional color Doppler sonography provides enhanced depiction of uterine, endometrial, and ovarian vascularity
Ammonium cations with high pK a in perovskite solar cells for improved high-temperature photostability
Phenethylammonium (PEA+) and butylammonium (BA+) are widely used in three-dimensional (3D) perovskites to form two-dimensional perovskites at film surfaces and grain boundaries (GBs) for defect passivation and performance enhancement. Here we show that these cations are unstable with 3D formamidinium (FA+)-containing perovskites under high-temperature light soaking. PEA+ and BA+ are found to deprotonate to amines, which then react with FA+ to produce (phenethylamino)methaniminium (PEAMA+) and (butylamino)methaniminium (BAMA+), respectively, severely limiting device high-temperature photostability. Removing these cations greatly improves the photostability but compromises device efficiency by leaving non-fully passivated surfaces and GBs. Ammonium cations with a high acid dissociation constant (pK a), including PEAMA+ (pK a = 12.0) and BAMA+ (pK a = 12.0), can replace PEA+ or BA+ for passivation and are stable with FA-based perovskites due to their resistance to further deprotonation. P–i–n structure solar cells with PEAMA+ additive maintained over 90% of their initial efficiency after light soaking at open circuit and 90 °C for 1,500 hours
Reproducibility of fetal heart volume by 3D-sonography using the XI VOCAL method
<p>Abstract</p> <p>Background</p> <p>To assess the reliability of fetal heart volume measurement by three-dimensional sonography (3DUS) using the eXtended Imaging Virtual Organ Computer-aided AnaLysis (XI VOCAL) method.</p> <p>Methods</p> <p>This reliability study enrolled 30 pregnant women with singleton healthy pregnancies between 19 and 34 weeks of gestation. All volume acquirements were performed with a convex volumetric transducer (C3-7ED) coupled to an Accuvix XQ sonography device (Medison, Korea). The XI VOCAL 10 planes was the method of choice for volumetric measurement. 3D datasets were analyzed by two observers (EQSB and HJFM); fetal heart volume was measured twice by the first and once by the second observer to calculate intra and interobserver reproducibility. Statistical analysis used pareated Student's t test (p) and calculated Intraclass correlation coefficients (ICC). Bland-Altman plots were also constructed.</p> <p>Results</p> <p>We observed an excellent intra- and interobserver reliability for fetal cardiac volume assessed by XI VOCAL. For the intraobserver the ICC was 0.998 (95% CI: 0.997; 0.999), with mean of differences of 0.12 cm<sup>3 </sup>(95% limits of agreement: -0.84; +0.84; p = 0.130). For interobserver the ICC was 0.899 (95%CI: 0.996; 0.998), mean of differences 0.05 cm<sup>3 </sup>(95% limits of agreement: -0.84; +0.84; p = 0.175).</p> <p>Conclusion</p> <p>Fetal cardiac volume assessed by 3DUS using XI VOCAL method is highly reproducible between 19 to 34 gestational weeks.</p
Transfer of thawed frozen embryo versus fresh embryo to improve the healthy baby rate in women undergoing IVF : the E-Freeze RCT
Peer reviewedPublisher PD
Endometrial scratching in women undergoing IVF/ICSI : an individual participant data meta-analysis
Funding No specific funding was sought for this project. The sponsor of this project is the University Medical Center Utrecht (UMC Utrecht), Utrecht, the Netherlands. The sponsor was not involved in the study design, data interpretation, or writing of the manuscript.Peer reviewedPublisher PD
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