5,047 research outputs found
The formation of CO through consumption of gas-phase CO on vacuum-UV irradiated water ice
[Abridged] Observations of protoplanetary disks suggest that they are
depleted in gas-phase CO. It has been posed that gas-phase CO is chemically
consumed and converted into less volatile species through gas-grain processes.
Observations of interstellar ices reveal a CO component within HO ice
suggesting co-formation. The aim of this work is to experimentally verify the
interaction of gas-phase CO with solid-state OH radicals above the sublimation
temperature of CO. Amorphous solid water (ASW) is deposited at 15 K and
followed by vacuum-UV (VUV) irradiation to dissociate HO and create OH
radicals. Gas-phase CO is simultaneously admitted and only adsorbs with a short
residence time on the ASW. Products in the solid state are studied with
infrared spectroscopy and once released into the gas phase with mass
spectrometry. Results show that gas-phase CO is converted into CO, with an
efficiency of 7-27%, when interacting with VUV irradiated ASW. Between 40 and
90 K, CO production is constant, above 90 K, O production takes over.
In the temperature range of 40-60 K, the CO remains in the solid state,
while at temperatures 70 K the formed CO is released into the gas
phase. We conclude that gas-phase CO reacts with solid-state OH radicals above
its sublimation temperature. This gas-phase CO and solid-state OH radical
interaction could explain the observed CO embedded in water-rich ices. It
may also contribute to the observed lack of gas-phase CO in planet-forming
disks, as previously suggested. Our experiments indicate a lower water ice
dissociation efficiency than originally adopted in model descriptions of
planet-forming disks and molecular clouds. Incorporation of the reduced water
ice dissociation and increased binding energy of CO on a water ice surfaces in
these models would allow investigation of this gas-grain interaction to its
full extend.Comment: Accepted for publication in Astronomy & Astrophysic
A teratocarcinoma-like human embryonic stem cell (hESC) line and four hESC lines reveal potentially oncogenic genomic changes
The first Swiss human embryonic stem cell (hESC) line, CH-ES1, has shown features of a malignant cell line. It originated from the only single blastomere that survived cryopreservation of an embryo, and it more closely resembles teratocarcinoma lines than other hESC lines with respect to its abnormal karyotype and its formation of invasive tumors when injected into SCID mice. The aim of this study was to characterize the molecular basis of the oncogenicity of CH-ES1 cells, we looked for abnormal chromosomal copy number (by array Comparative Genomic Hybridization, aCGH) and single nucleotide polymorphisms (SNPs). To see how unique these changes were, we compared these results to data collected from the 2102Ep teratocarcinoma line and four hESC lines (H1, HS293, HS401 and SIVF-02) which displayed normal G-banding result. We identified genomic gains and losses in CH-ES1, including gains in areas containing several oncogenes. These features are similar to those observed in teratocarcinomas, and this explains the high malignancy. The CH-ES1 line was trisomic for chromosomes 1, 9, 12, 17, 19, 20 and X. Also the karyotypically (based on G-banding) normal hESC lines were also found to have several genomic changes that involved genes with known roles in cancer. The largest changes were found in the H1 line at passage number 56, when large 5 Mb duplications in chromosomes 1q32.2 and 22q12.2 were detected, but the losses and gains were seen already at passage 22. These changes found in the other lines highlight the importance of assessing the acquisition of genetic changes by hESCs before their use in regenerative medicine applications. They also point to the possibility that the acquisition of genetic changes by ESCs in culture may be used to explore certain aspects of the mechanisms regulating oncogenesis
A teratocarcinoma-like human embryonic stem cell (hESC) line and four hESC lines reveal potentially oncogenic genomic changes
The first Swiss human embryonic stem cell (hESC) line, CH-ES1, has shown features of a malignant cell line. It originated from the only single blastomere that survived cryopreservation of an embryo, and it more closely resembles teratocarcinoma lines than other hESC lines with respect to its abnormal karyotype and its formation of invasive tumors when injected into SCID mice. The aim of this study was to characterize the molecular basis of the oncogenicity of CH-ES1 cells, we looked for abnormal chromosomal copy number (by array Comparative Genomic Hybridization, aCGH) and single nucleotide polymorphisms (SNPs). To see how unique these changes were, we compared these results to data collected from the 2102Ep teratocarcinoma line and four hESC lines (H1, HS293, HS401 and SIVF-02) which displayed normal G-banding result. We identified genomic gains and losses in CH-ES1, including gains in areas containing several oncogenes. These features are similar to those observed in teratocarcinomas, and this explains the high malignancy. The CH-ES1 line was trisomic for chromosomes 1, 9, 12, 17, 19, 20 and X. Also the karyotypically (based on G-banding) normal hESC lines were also found to have several genomic changes that involved genes with known roles in cancer. The largest changes were found in the H1 line at passage number 56, when large 5 Mb duplications in chromosomes 1q32.2 and 22q12.2 were detected, but the losses and gains were seen already at passage 22. These changes found in the other lines highlight the importance of assessing the acquisition of genetic changes by hESCs before their use in regenerative medicine applications. They also point to the possibility that the acquisition of genetic changes by ESCs in culture may be used to explore certain aspects of the mechanisms regulating oncogenesis
Mixed-Integer MPC Strategies for Fueling and Density Control in Fusion Tokamaks
Model predictive control (MPC) is promising for fueling and core density
feedback control in nuclear fusion tokamaks, where the primary actuators,
frozen hydrogen fuel pellets fired into the plasma, are discrete. Previous
density feedback control approaches have only approximated pellet injection as
a continuous input due to the complexity that it introduces. In this letter, we
model plasma density and pellet injection as a hybrid system and propose two
MPC strategies for density control: mixed-integer (MI) MPC using a conventional
mixed-integer programming (MIP) solver and MPC utilizing our novel modification
of the penalty term homotopy (PTH) algorithm. By relaxing the integer
requirements, the PTH algorithm transforms the MIP problem into a series of
continuous optimization problems, reducing computational complexity. Our novel
modification to the PTH algorithm ensures that it can handle path constraints,
making it viable for constrained hybrid MPC in general. Both strategies perform
well with regards to reference tracking without violating path constraints and
satisfy the computation time limit for real-time control of the pellet
injection system. However, the computation time of the PTH-based MPC strategy
consistently outpaces the conventional MI-MPC strategy
Sound localization with bilateral bone conduction devices
Purpose To investigate sound localization in patients bilaterally fitted with bone conduction devices (BCDs). Additionally, clinically applicable methods to improve localization accuracy were explored. Methods Fifteen adults with bilaterally fitted percutaneous BCDs were included. At baseline, sound localization, (un)aided pure-tone thresholds, device use, speech, spatial and qualities of hearing scale (SSQ) and York hearing-related quality of life (YHRQL) questionnaire were measured. Settings to optimize sound localizing were added to the BCDs. At 1 month, sound localization was assessed again and localization was practiced with a series of sounds with visual feedback. At 3 months, localization performance, device use and questionnaire scores were determined again. Results At baseline, one patient with congenital hearing loss demonstrated near excellent localization performance and four other patients (three with congenital hearing loss) localized sounds (quite) accurately. Seven patients with acquired hearing loss were able to lateralize sounds, i.e. identify whether sounds were coming from the left or right side, but could not localize sounds accurately. Three patients (one with congenital hearing loss) could not even lateralize sounds correctly. SSQ scores were significantly higher at 3 months. Localization performance, device use and YHRQL scores were not significantly different between visits. Conclusion In this study, the majority of experienced bilateral BCD users could lateralize sounds and one third was able to localize sounds (quite) accurately. The localization performance was robust and stable over time. Although SSQ scores were increased at the last visit, optimizing device settings and a short practice session did not improve sound localization
Verkenning herstel kleinschalige lijnvormige infrastructuur Heuvelland
Kalkgraslanden en hellingbossen zijn voorbeelden van soortenrijke natuur in het Limburgse Heuvelland. In het kader van OBN is een verkennend overzicht van natuurwaarden van lijnvormige elementen gemaakt, met een visie op mogelijk herstel van natuur in bermen, heggen en houtwallen. Deze inventarisatie is tot stand gekomen dankzij de inzet van: RAVON, Vlinderstichting, Stichting Anemoon, Floron, Zoogdierenvereniging VZZ, EIS Nederland, en Alterr
Kan de Knoflookpad op termijn van de Intensive Care af?
In 2001 werd het landelijk Beschermingsplan Knoflookpad opgesteld. Wat is er sindsdien gedaan om de stand van de Knoflookpad te verbeteren en tot welke resultaten heeft dat geleid? Wat betekent dit voor de toekomst? Waar liggen de kansen voor de Knoflookpad? In een drietal artikelen komen achtereenvolgens aan bod: de historie van de Knoflookpad in Nederland, waarom en hoe in 2010 werd overgegaan tot bijplaatsing en herintroductie en tot slot welke scenario’s er zijn voor de toekomst van de Knoflookpad
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