371 research outputs found
Scattered light mapping of protoplanetary disks
High-contrast scattered light observations have revealed the surface
morphology of several dozens of protoplanetary disks at optical and
near-infrared wavelengths. Inclined disks offer the opportunity to measure part
of the phase function of the dust grains that reside in the disk surface which
is essential for our understanding of protoplanetary dust properties and the
early stages of planet formation. We aim to construct a method which takes into
account how the flaring shape of the scattering surface of an (optically thick)
protoplanetary disk projects onto the image plane of the observer. This allows
us to map physical quantities (scattering radius and scattering angle) onto
scattered light images and retrieve stellar irradiation corrected (r^2-scaled)
images and dust phase functions. We apply the method on archival polarized
intensity images of the protoplanetary disk around HD 100546 that were obtained
with VLT/SPHERE in R'-band and VLT/NACO in H- and Ks-band. The brightest side
of the r^2-scaled R'-band polarized intensity image of HD 100546 changes from
the far to the near side of the disk when a flaring instead of a geometrically
flat disk surface is used for the r^2-scaling. The decrease in polarized
surface brightness in the scattering angle range of ~40-70 deg is likely a
result of the dust phase function and degree of polarization which peak in
different scattering angle regimes. The derived phase functions show part of a
forward scattering peak which indicates that large, aggregate dust grains
dominate the scattering opacity in the disk surface. Projection effects of a
protoplanetary disk surface need to be taken into account to correctly
interpret scattered light images. Applying the correct scaling for the
correction of stellar irradiation is crucial for the interpretation of the
images and the derivation of the dust properties in the disk surface layer.Comment: Accepted for publication in A&A, 6 pages, 3 figure
Response to letter regarding âEvidence of natural occurence of the banned antibiotic chloramphenicol in herbs and grassâ
# The Author(s) 2011. This article is published with open access at Springerlink.com We were surprised to read that the natural occurrence of chloramphenicol (CAP) was reported as long ago as 2003 by Hanekamp et al. [1]. We missed that information, probably because their findings were not published in a peer-reviewed journal. In our paper [2], we did not claim to be the first to suggest the natural occurrence of CAP; on the contrary, we included several references from earlier studies. We stated that our paper was the first to describe the detection of CAP in plant materials, sample material which had not been addressed before. Furthermore, there is an important issue which is not raised by Hanekamp et al. and that is the issue of âcriteria for confirmation of the identity of a compoundâ. InEU legislation, viz. Commission Decision 2002/657/EC, it i
Comprehensive screening and quantification of veterinary drugs in milk using UPLCâToF-MS
Ultra-performance liquid chromatography combined with time-of-flight mass spectrometry (UPLCâToF-MS) has been used for screening and quantification of more than 100 veterinary drugs in milk. The veterinary drugs represent different classes including benzimidazoles, macrolides, penicillins, quinolones, sulphonamides, pyrimidines, tetracylines, nitroimidazoles, tranquillizers, ionophores, amphenicols and non-steroidal anti-inflammatory agents (NSAIDs). After protein precipitation, centrifugation and solid-phase extraction (SPE), the extracts were analysed by UPLCâToF-MS. From the acquired full scan data the drug-specific ions were extracted for construction of the chromatograms and evaluation of the results. The analytical method was validated according to the EU guidelines (2002/657/EC) for a quantitative screening method. At the concentration level of interest (MRL level) the results for repeatability (%RSDâ<â20% for 86% of the compounds), reproducibility (%RSDâ<â40% for 96% of the compounds) and the accuracy (80â120% for 88% of the compounds) were satisfactory. Evaluation of the CCÎČ values and the linearity results demonstrates that the developed method shows adequate sensitivity and linearity to provide quantitative results. Furthermore, the method is accurate enough to differentiate between suspected and negative samples or drug concentrations below or above the MRL. A set of 100 samples of raw milk were screened for residues. No suspected (positive) results were obtained except for the included blind reference sample containing sulphamethazine (88Â ÎŒg/l) that tested positive for this compound. UPLCâToF-MS combines high resolution for both LC and MS with high mass accuracy which is very powerful for the multi-compound analysis of veterinary drugs. The technique seems to be powerful enough for the analysis of not only veterinary drugs but also organic contaminants like pesticides, mycotoxins and plant toxins in one single method
Moderate hyperventilation during intravenous anesthesia increases net cerebral lactate efflux
BACKGROUND:: Hyperventilation is known to decrease cerebral blood flow (CBF) and to impair cerebral metabolism, but the threshold in patients undergoing intravenous anesthesia is unknown. The authors hypothesized that reduced CBF associated with moderate hyperventilation might impair cerebral aerobic metabolism in patients undergoing intravenous anesthesia. METHODS:: Thirty male patients scheduled for coronary surgery were included in a prospective, controlled crossover trial. Measurements were performed under fentanyl-midazolam anesthesia in a randomized sequence aiming at partial pressures of carbon dioxide of 30 and 50 mmHg. Endpoints were CBF, blood flow velocity in the middle cerebral artery, and cerebral metabolic rates for oxygen, glucose, and lactate. Global CBF was measured using a modified Kety-Schmidt technique with argon as inert gas tracer. CBF velocity of the middle cerebral artery was recorded by transcranial Doppler sonography. Data were presented as mean (SD). Two-sided paired t tests and one-way ANOVA for repeated measures were used for statistical analysis. RESULTS:: Moderate hyperventilation significantly decreased CBF by 60%, blood flow velocity by 41%, cerebral oxygen delivery by 58%, and partial pressure of oxygen of the jugular venous bulb by 45%. Cerebral metabolic rates for oxygen and glucose remained unchanged; however, net cerebral lactate efflux significantly increased from -0.38 (2.18) to -2.41(2.43) ÎŒmol min 100 g. CONCLUSIONS:: Moderate hyperventilation, when compared with moderate hypoventilation, in patients with cardiovascular disease undergoing intravenous anesthesia increased net cerebral lactate efflux and markedly reduced CBF and partial pressure of oxygen of the jugular venous bulb, suggesting partial impairment of cerebral aerobic metabolism at clinically relevant levels of hypocapnia. Copyrigh
The preoperative cardiology consultation: Indications and risk modification
Background The cardiologist is regularly consulted preop-eratively by anaesthesiologists. However, insights into the efficiency and usefulness of these consultations are unclear. Methods This is a retrospective study of 24,174 preoperatively screened patients â„18 years scheduled for elective non-cardiac surgery, which resulted in 273 (1%) referrals to the cardiologist for further preoperative evaluation. Medical charts were reviewed for patient characteristics, main reason for referring, requested diagnostic tests, interventions, adjustment in medical therapy, 30-day mortality and major adverse cardiac events. Results The most common reason for consultation was the evaluation of a cardiac murmur (95 patients, 35%). In 167 (61%) patients, no change in therapy was initiated by the cardiologist. Six consultations (2%) led to invasive interventions (electrical cardioversion, percutaneous coronary intervention or coronary artery bypass surgery). On average, consultation delayed clearance for surgery by two weeks. Conclusion In most patients referred to the cardiologist after being screened at an outpatient anaesthesiology clinic, echocardiography is performed for ruling out specific conditions and to be sure that no further improvement can be made in the patientâs health. In the majority, no change in therapy was initiated by the cardiologist. A more careful consideration about the potential benefits of consulting must be made for every patient
Argon does not affect cerebral circulation or metabolism in male humans
Objective: Accumulating data have recently underlined argoĆs neuroprotective potential. However, to the best of our knowledge, no data are available on the cerebrovascular effects of argon (Ar) in humans. We hypothesized that argon inhalation does not affect mean blood flow velocity of the middle cerebral artery (Vmca), cerebral flow index (FI), zero flow pressure (ZFP), effective cerebral perfusion pressure (CPPe), resistance area product (RAP) and the arterio-jugular venous content differences of oxygen (AJVDO2), glucose (AJVDG), and lactate (AJVDL) in anesthetized patients.
Materials and methods: In a secondary analysis of an earlier controlled cross-over trial we compared parameters of the cerebral circulation under 15 minutes exposure to 70%Ar/30%O2versus 70%N2/30%O2in 29 male patients under fentanyl-midazolam anaesthesia before coronary surgery. Vmca was measured by transcranial Doppler sonography. ZFP and RAP were estimated by linear regression analysis of pressure-flow velocity relationships of the middle cerebral artery. CPPe was calculated as the difference between mean arterial pressure and ZFP. AJVDO2, AJVDG and AJVDL were calculated as the differences in contents between arterial and jugular-venous blood of oxygen, glucose, and lactate. Statistical analysis was done by t-tests and ANOVA.
Results: Mechanical ventilation with 70% Ar did not cause any significant changes in mean arterial pressure, Vmca, FI, ZFP, CPPe, RAP, AJVDO2, AJVDG, and AJVDL.
Discussion: Short-term inhalation of 70% Ar does not affect global cerebral circulation or metabolism in male humans under general anaesthesia
Exploring dust around HD142527 down to 0.025" / 4au using SPHERE/ZIMPOL
We have observed the protoplanetary disk of the well-known young Herbig star
HD 142527 using ZIMPOL Polarimetric Differential Imaging with the VBB (Very
Broad Band, ~600-900nm) filter. We obtained two datasets in May 2015 and March
2016. Our data allow us to explore dust scattering around the star down to a
radius of ~0.025" (~4au). The well-known outer disk is clearly detected, at
higher resolution than before, and shows previously unknown sub-structures,
including spirals going inwards into the cavity. Close to the star, dust
scattering is detected at high signal-to-noise ratio, but it is unclear whether
the signal represents the inner disk, which has been linked to the two
prominent local minima in the scattering of the outer disk, interpreted as
shadows. An interpretation of an inclined inner disk combined with a dust halo
is compatible with both our and previous observations, but other arrangements
of the dust cannot be ruled out. Dust scattering is also present within the
large gap between ~30 and ~140au. The comparison of the two datasets suggests
rapid evolution of the inner regions of the disk, potentially driven by the
interaction with the close-in M-dwarf companion, around which no polarimetric
signal is detected.Comment: 11 pages, 7 figures, accepted for publication in A
Fully automated screening of veterinary drugs in milk by turbulent flow chromatography and tandem mass spectrometry
There is an increasing interest in screening methods for quick and sensitive analysis of various classes of veterinary drugs with limited sample pre-treatment. Turbulent flow chromatography in combination with tandem mass spectrometry has been applied for the first time as an efficient screening method in routine analysis of milk samples. Eight veterinary drugs, belonging to seven different classes were selected for this study. After developing and optimising the method, parameters such as linearity, repeatability, matrix effects and carry-over were studied. The screening method was then tested in the routine analysis of 12 raw milk samples. Even without internal standards, the linearity of the method was found to be good in the concentration range of 50 to 500 ”g/L. Regarding repeatability, RSDs below 12% were obtained for all analytes, with only a few exceptions. The limits of detection were between 0.1 and 5.2 ”g/L, far below the maximum residue levels for milk set by the EU regulations. While matrix effectsâion suppression or enhancementâare obtained for all the analytes the method has proved to be useful for screening purposes because of its sensitivity, linearity and repeatability. Furthermore, when performing the routine analysis of the raw milk samples, no false positive or negative results were obtained
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