We used infrared absorption spectroscopy to study the effects of ion irradiation on the morphology/porosity of amorphous water ice. Thin icy films (about 0.25 μm) of amorphous water were irradiated ...with 200 keV protons at 15 K. Both the behaviour of the OH dangling bond feature and the ability to trap carbon monoxide (CO) were used to investigate the evolution of icy samples after ion irradiation. We show that the intensity of the OH dangling bond feature decreases after ion irradiation and that the amount of absorbed carbon monoxide decreases as the fluence of impinging ions increases. The results obtained indicate that the porosity of amorphous water ice decreases after ion irradiation. Furthermore, icy mixtures such as H2O:CO2, H2O:CO, and H2O:CH4 were irradiated with 200 keV H+, 30 and 200 keV He+ ions. Also in these cases, the intensity of the OH dangling bond band decreases after ion irradiation. However, when a second molecular species is present in the ice sample, this decrease is slower. Here we present the experimental results and discuss their relevance to our understanding of the properties of interstellar water ice. In particular, we suggest that, because of cosmic ion bombardment, water ice in interstellar grain mantles is compact in structure.
Context. Methyl formate (HCOOCH3) is a complex organic molecule detected in hot cores and hot corinos. Gas-phase chemistry fails to reproduce its observed abundance, which usually varies between 10-7 ...and 10-9 with respect to H2. Aims. Laboratory experiments were performed in order to investigate a solid-state route of methyl formate formation, to obtain an estimate of the amount that can be formed, and to verify whether it can account for the observed abundances. Methods. Several solid samples (16 K) of astrophysical interest were analyzed by infrared spectroscopy in the 4400-400 cm-1 range. The infrared spectral characteristics of frozen methyl formate were studied by deriving their band strength values. The effects produced upon warm-up of the samples were analyzed comparing the spectra taken at different temperatures. In order to study the formation and destruction mechanism of methyl formate in the interstellar ices, a binary mixture of methanol (CH3OH) and carbon monoxide (CO) ice and a sample of pure methanol were irradiated at 16 K with 200 keV protons. Methyl formate was identified through its fundamental mode (CH3 rocking) at about 1160 cm-1. Results. We present the mid-infrared methyl formate ice spectrum showing both the amorphous (16 K) and the crystalline (110 K) structure. We report novel measurements of the band strength values of the six main methyl formate bands. We prove the formation and the destruction of methyl formate after irradiation of CH3OH and a CO:CH3OH mixture. Extrapolating our results to the interstellar medium conditions we found that the production timescale of methyl formate agrees well with the evolutionary time of molecular clouds. The comparison with the observational data indicates that the amount of methyl formate formed after irradiation can account for the observed abundances. Conclusions. The present results allow us to suggest that gas phase methyl formate observed in dense molecular clouds is formed in the solid state after cosmic ion irradiation of icy grain mantles containing CO and CH3OH and released to the gas phase after desorption of icy mantles.
Sulphur appears to be depleted by an order of magnitude or more from its elemental abundance in star-forming regions. In the last few years, numerous observations and experiments have been performed ...in order to understand the reasons behind this depletion without providing a satisfactory explanation of the sulphur chemistry towards high-mass star-forming cores. Several sulphur-bearing molecules have been observed in these regions, and yet none are abundant enough to make up the gas-phase deficit. Where, then, does this hidden sulphur reside? This paper represents a step forward in our understanding of the interactions among the various S-bearing species. We have incorporated recent experimental and theoretical data into a chemical model of a hot molecular core in order to see whether they give any indication of the identity of the sulphur sink in these dense regions. Despite our model producing reasonable agreement with both solid-phase and gas-phase abundances of many sulphur-bearing species, we find that the sulphur residue detected in recent experiments takes up only ∼6 per cent of the available sulphur in our simulations, rather than dominating the sulphur budget.
Context. Solid carbon dioxide (CO2) is one of the most abundant species detected in icy grain mantles in dense molecular clouds. Its identification is based on the comparison between astronomical and ...laboratory spectra. In the past 30 yr the profile of solid CO2 infrared absorption bands has been extensively studied experimentally, however, the debate on the structure (amorphous versus crystalline) of CO2 samples obtained in laboratory by the thin-film technique is still open. Aims. The aim of this work is to investigate if the presence of the double peak feature in the profile of the CO2 bending mode band is related to the crystalline or amorphous structure of the sample. Methods. We performed new laboratory experiments depositing CO2 under ultra high vacuum (UHV) conditions at 17 K. We investigated, using infrared transmission spectroscopy, the influence of various experimental parameters on the profile of the CO2 bands, namely deposition rate, sample thickness, annealing, and presence of H2O, CH3OH or CO co-deposited with CO2. Results. We found that, within experimental uncertainties, under UHV conditions the profile of the CO2 bands in pure solid samples does not depend on the deposition rate or the sample thickness in the ranges investigated. In all cases the bending mode band profile shows a double peak (at 660 and 655 cm-1). The spectra also show the Fermi resonance features that cannot be active in crystalline samples. On the other hand, when a small fraction of H2O or CH3OH is co-deposited with CO2 the double peak is not observed while it is observed when a CO2:CO mixture is considered. Furthermore, we measured the density of solid CO2 and the refractive index (at 543.5 nm) at 17 K and at 70 K: ρ(17 K)= 1.17 g cm-3, ρ(70K)= 1.49 g cm-3, n(17K)= 1.285, and n(70K)= 1.372. Conclusions. Our experimental results indicate that the presence of the double peak in the profile of the bending mode band is not an indication of a crystalline structure of the sample and they do not exclude the presence of amorphous solid CO2 in space.
Context. The simultaneous detection of organic molecules of the form C2HnO, such as ketene (CH2CO), acetaldehyde (CH3CHO), and ethanol (CH3CH2OH), toward early star-forming regions offers hints of a ...shared chemical history. Several reaction routes have been proposed and experimentally verified under various interstellar conditions to explain the formation pathways involved. Most noticeably, the non-energetic processing of C2H2 ice with OH-radicals and H-atoms was shown to provide formation routes to ketene, acetaldehyde, ethanol, and vinyl alcohol (CH2CHOH) along the H2O formation sequence on grain surfaces in translucent clouds. Aims. In this work, the non-energetic formation scheme is extended with laboratory measurements focusing on the energetic counterpart, induced by cosmic rays penetrating the H2O-rich ice mantle. The focus here is on the H+ radiolysis of interstellar C2H2:H2O ice analogs at 17 K. Methods. Ultra-high vacuum experiments were performed to investigate the 200 keV H+ radiolysis chemistry of predeposited C2H2:H2O ices, both as mixed and layered geometries. Fourier-transform infrared spectroscopy was used to monitor in situ newly formed species as a function of the accumulated energy dose (or H+ fluence). The infrared spectral assignments are further confirmed in isotope labeling experiments using H218O. Results. The energetic processing of C2H2:H2O ice not only results in the formation of (semi-) saturated hydrocarbons (C2H4 and C2H6) and polyynes as well as cumulenes (C4H2 and C4H4), but it also efficiently forms O-bearing COMs, including vinyl alcohol, ketene, acetaldehyde, and ethanol, for which the reaction cross-section and product composition are derived. A clear composition transition of the product, from H-poor to H-rich species, is observed as a function of the accumulated energy dose. Furthermore, the astronomical relevance of the resulting reaction network is discussed.
Ruxolitinib is beneficial in patients with myelofibrosis (MF) and polycythemia vera (PV). Information on ruxolitinib adherence is scant. The Ruxolitinib Adherence in Myelofibrosis and Polycythemia ...Vera (RAMP) prospective multicenter study (NCT06078319) included 189 ruxolitinib-treated patients. Patients completed the Adherence to Refills and Medications Scale (ARMS) and Distress Thermometer and Problem List (DTPL) at the earliest convenience, after registration in the study, and at later timepoints. At week-0, low adherence (ARMS > 14) and high distress (DT ≥ 4) were declared by 49.7% and 40.2% of patients, respectively. The main reason for low adherence was difficult ruxolitinib supply (49%), intentional (4.3%) and unintentional (46.7%) non-take. In multivariable regression analysis, low adherence was associated to male sex (
p
= 0.001), high distress (
p
< 0.001), and treatment duration ≥ 1 year (
p
= 0.03). Over time, rates of low adherence and high distress remained stable, but unintentional non-take decreased from 47.9% to 26.0% at week-48. MF patients with stable high adherence/low distress were more likely to obtain/maintain the spleen response at week-24. Low adherence to ruxolitinib represents an unmet clinical need that require a multifaceted approach, based on reason behind it (patients characteristics and treatment duration). Its recognition may help distinguishing patients who are truly refractory and those in need of therapy optimization.
Abstract We present JWST MIRI MRS observations of the edge-on protoplanetary disk around the young subsolar-mass star Tau 042021, acquired as part of the Cycle 1 GO program “Mapping Inclined Disk ...Astrochemical Signatures.” These data resolve the mid-IR spatial distributions of H 2 , revealing X-shaped emission extending to ∼200 au above the disk midplane with a semiopening angle of 35° ± 5°. We do not velocity-resolve the gas in the spectral images, but the measured semiopening angle of the H 2 is consistent with a magnetohydrodynamic wind origin. A collimated, bipolar jet is seen in forbidden emission lines from Ne ii , Ne iii , Ni ii , Fe ii , Ar ii , and S iii . Extended H 2 O and CO emission lines are also detected, reaching diameters of ∼90 and 190 au, respectively. Hot molecular emission is not expected at such radii, and we interpret its extended spatial distribution as scattering of inner disk molecular emission by dust grains in the outer disk surface. H i recombination lines, characteristic of inner disk accretion shocks, are similarly extended and are likely also scattered light from the innermost star–disk interface. Finally, we detect extended polycyclic aromatic hydrocarbon (PAH) emission at 11.3 μ m cospatial with the scattered-light continuum, making this the first low-mass T Tauri star around which extended PAHs have been confirmed, to our knowledge. MIRI MRS line images of edge-on disks provide an unprecedented window into the outflow, accretion, and scattering processes within protoplanetary disks, allowing us to constrain the disk lifetimes and accretion and mass-loss mechanisms.
Abstract Purpose Our study evaluated brain natriuretic peptide (BNP) changes over time after adjuvant radiotherapy (RT) in women with left-sided breast cancer investigating its correlation with heart ...dosimetric parameters. Methods Forty-three patients underwent clinical cardiac examination, electrocardiogram (ECG), echocardiography and BNP measurement before RT (T0) and 1 (T1), 6 (T6) and 12 months (T12) after. After T12 cardiac assessment was performed annually in each patient. Mean values and standard deviation (SD) of BNP, left ventricular ejection fraction (LVEF), V20, V25, V30, V45 and mean dose were calculated. Normalized BNP (BNPn) was calculated as follows: BNPnT1 = BNPT1/BNPT0, BNPnT6 = BNPT6/BNPT0, BNPnT12 = BNPT12/BNPT0. Absolute BNP and BNPn values were used for data analysis. Results Median follow-up from the end of RT to the last check-up was 87 months (range 37–120 months). Minimum follow-up was 74 months except for two patients, who died at respectively 37 and 47 months after RT. In all patients LVEF did not change significantly ( p = 0.22) after RT. BNP increased significantly ( p < 0.001), particularly 1 and 6 months after RT. It slightly decreased after 12 months. BNP did not correlate with V20, V25, V30, V45, mean dose and MHD. All BNPn correlated significantly ( p < 0.05) with V20, V25, V30, V45, mean dose and MHD. Four patients had a cardiac event; in the only subject who developed myocardial infarction, V20, V25, V30 and V45 were the highest and BNP increased from T1 and persisted high even at T12. Conclusion Our results confirm that BNP could be a useful minimally invasive marker of early RT related cardiac impairment.
We present new experimental results on thermal and ion irradiation processing of frozen ammonia-carbon dioxide mixtures. Some mixtures were deposited at low temperatures (
T
16 K). Upon warming up to ...160 K, complex chemical reactions occur leading to the formation of new molecules and, in particular, of ammonium carbamate. We also show that the same species are produced when water is the dominant species in the ternary mixture with ammonia and carbon dioxide. The samples have been irradiated with 144 keV S
9+
ions at 16 K and 50 K. Also in this case, new chemical species are formed as
e.g.
ammonium formate, CO and OCN
−
. The results are discussed in the light of their relevance to the chemical evolution of ices in the interstellar medium and in the solar system. In particular, we suggest searching for them among the gas phase species sublimating from grains around young stellar objects and from the cometary nuclei approaching the Sun.
We present new experimental results on thermal and ion irradiation processing of frozen ammonia-carbon dioxide mixtures.
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