New X-ray Selected Pre-Main Sequence Members of the Serpens Molecular Cloud

The study of young stars no longer surrounded by disks can greatly add to our understanding of how protoplanetary disks evolve and planets form. We have used VLT/FLAMES optical spectroscopy to confirm the youth and membership of 19 new young diskless stars in the Serpens Molecular Cloud, identified at X-ray wavelengths. Spectral types, effective temperatures and stellar luminosities were determined using the optical spectra and optical/near-IR photometry. Stellar masses and ages were derived based on PMS evolutionary tracks. The results yield remarkable similarities for age and mass distribution between the diskless and disk-bearing stellar populations in Serpens. We discuss the important impli- cations these similarities may have on the standard picture of disk evolution.Comment: Accepted for publication at the Astronomical Journal. 21 pages, 7 figures and 5 table

Woord en daad. De zoektocht van Derk Roelfs Mansholt naar een betere samenleving.

In deze studie is de zoektocht naar Derk Roelfs Mansholt (1842-1921) naar een betere samenleving in kaart gebracht. De Groninger herenboer Mansholt, die zich gedreven heeft beziggehouden met het zoeken naar oplossingen voor de grote politieke en sociale vraagstukken van zijn tijd, wordt in de historiografie gerangschikt onder de pioniers van de socialistische beweging. Dit is een karakterisering die op de maatschappijhervormer Mansholt van toepassing is, maar waarbij ook het gevaar bestaat dat de karakteristieken die niet passen binnen de omschrijving, over het hoofd worden gezien. Dit geldt des te meer voor een figuur als de radicale maatschappijhervormer Mansholt wiens activiteiten zich binnen maar even zo goed aan de rand van en zelfs buiten de socialistische beweging hebben afgespeeld. Nogal wat historici neigen er bovendien toe de geschiedenis van de vroeg-socialistische beweging te zeer als een soort van aanloopperiode tot de latere 'moderne' geschiedenis van het socialisme te beschouwen. ... Zie: Samenvatting

A comprehensive motion analysis - consequences for high precision image-guided radiotherapy of esophageal cancer patients

Background and purpose When treating patients for esophageal cancer (EC) with photon or proton radiotherapy (RT), breathing motion of the target and neighboring organs may result in deviations from the planned dose distribution. The aim of this study was to evaluate the magnitude and dosimetric impact of breathing motion. Results were based on comparing weekly 4D computed tomography (4D CT) scans with the planning CT, using the diaphragm as an anatomical landmark for EC. Material and methods A total of 20 EC patients were included in this study. Diaphragm breathing amplitudes and off-sets (changes in position with respect to the planning CT) were determined from delineated left diaphragm structures in weekly 4D CT-scans. The potential dosimetric impact of respiratory motion was shown in several example patients for photon and proton radiotherapy. Results Variation in diaphragm amplitudes were relatively small and ranged from 0 to 0.8 cm. However, the measured off-sets were larger, ranging from -2.1 to 1.9 cm. Of the 70 repeat CT-scans, the off-set exceeded the ITV-PTV margin of 0.8 cm during expiration in 4 CT-scans (5.7%) and during inspiration in 13 CT-scans (18.6%). The dosimetric validation revealed under- and overdosages in the VMAT and IMPT plans. Conclusions Despite relatively constant breathing amplitudes, the variation in the diaphragm position (off-set), and consequently tumor position, was clinically relevant. These motion effects may result in either treatments that miss the target volume, or dose deviations in the form of highly localized over- or underdosed regions

Organ sparing potential and inter-fraction robustness of adaptive intensity modulated proton therapy for lung cancer

Background: The aim of this study was to compare adaptive intensity modulated proton therapy (IMPT) robustness and organ sparing capabilities with that of adaptive volumetric arc photon therapy (VMAT). Material and methods: Eighteen lung cancer patients underwent a planning 4DCT (p4DCT) and 5 weekly repeated 4DCT (r4DCT) scans. Target volumes and organs at risk were manually delineated on the three-dimensional (3D) average scans of the p4DCT (av_p4DCT) and of the r4DCT scans (av_r4DCT). Planning target volume (PTV)-based VMAT plans and internal clinical target volume (ICTV)-based robust IMPT plans were optimized in 3D on the av_p4DCT and re-calculated on the av_r4DCTs. Re-planning on av_r4DCTs was performed when indicated and accumulated doses were evaluated on the av_p4DCT. Results: Adaptive VMAT and IMPT resulted in adequate ICTV coverage on av_r4DCT in all patients and adequate accumulated-dose ICTV coverage on av_p4DCT in 17/18 patients (due to a shrinking target in one patient). More frequent re-planning was needed for IMPT than for VMAT. The average mean heart dose reduction with IMPT compared with VMAT was 4.6 Gy (p = .001) and it was >5 Gy for five patients (6, 7, 8, 15, and 22 Gy). The average mean lung dose reduction was 3.2 Gy (p < .001). Significant reductions in heart and lung V5 Gy were observed with IMPT. Conclusion: Robust-planned IMPT required re-planning more often than VMAT but resulted in similar accumulated ICTV coverage. With IMPT, heart and lung mean dose values and low dose regions were significantly reduced. Substantial cardiac sparing was obtained in a subgroup of five patients (28%)

Woord en daad. De zoektocht van Derk Roelfs Mansholt naar een betere samenleving.

In deze studie is de zoektocht naar Derk Roelfs Mansholt (1842-1921) naar een betere samenleving in kaart gebracht. De Groninger herenboer Mansholt, die zich gedreven heeft beziggehouden met het zoeken naar oplossingen voor de grote politieke en sociale vraagstukken van zijn tijd, wordt in de historiografie gerangschikt onder de pioniers van de socialistische beweging. Dit is een karakterisering die op de maatschappijhervormer Mansholt van toepassing is, maar waarbij ook het gevaar bestaat dat de karakteristieken die niet passen binnen de omschrijving, over het hoofd worden gezien. Dit geldt des te meer voor een figuur als de radicale maatschappijhervormer Mansholt wiens activiteiten zich binnen maar even zo goed aan de rand van en zelfs buiten de socialistische beweging hebben afgespeeld. Nogal wat historici neigen er bovendien toe de geschiedenis van de vroeg-socialistische beweging te zeer als een soort van aanloopperiode tot de latere 'moderne' geschiedenis van het socialisme te beschouwen. ... Zie: Samenvatting.

Necessity of manually adjusting automatic deformed CTVs on repeat CT scan to evaluate CTV coverage in IMPT for lung cancer

Background/Introduction: Manual CTV adjustment after deformable CTV registration on repeat-CT scans (rCT) is time consuming and may delay decisions on whether or not to perform plan adaptations. Our aim was to investigate if omitting such manual CTV adjustments would alter the decisions and/or impact the overall adequacy of treatment. Methodology: Seventeen lung cancer patients underwent a 4D planning-CT (pCT0) and 3-5 weekly 4D rCTs. In total 82 4D-average rCTs were available. Robustly optimized IMPT plans were established on the pCT0 aiming for a CTV D98 ≥ 57 Gy. The plans were evaluated on all rCTs including setup and range error scenarios. CTVs were deformed (intensity based deformable registration) from pCT0 to the rCTs (CTVauto) and manually adjusted by a clinician (CTVman). When rCT CTVauto and/or CTVman D98 &lt; 56.5 Gy (worst case scenario dose) the IMPT plan was adapted. Results: On average, CTVman was smaller than CTVauto (Δ volume in weeks 1-5: -4%, -6%, -9%, -11% and -15% (p &lt; 0.001), respectively. The average CTVauto D98 and CTVman D98 on all rCTs were 55.17 Gy and 55.13 Gy (p = 0.767), respectively. Omitting CTVman on all 82 rCTs would result in 3 ‘unnecessary' plan adjustments and 1 ‘skipped' plan adjustment. In the latter single case, the weekly rCTs dose deformed and summed in the CTV on pCT0 was adequate despite the skipped plan adaptation (58.1 Gy). Conclusions: In 17 lung cancer patients, omitting manual adjustments of deformed CTVs on weekly rCTs did not impact adequate CTV coverage of IMPT treatment