121 research outputs found
Preoperative Acute Normovolaemic Hemodilution (ANH) in combination with Hypotensive Epidural Anaesthesia (HEA) during knee arthroplasty surgery. No effect on transfusion rate. A randomized controlled trial [ISRCTN87597684]
BACKGROUND: Hypotensive epidural anaesthesia (HEA) combines a high epidural anaesthesia, performing a sympathetic blockade, with low-dose iv-infusion of epinephrine to stabilize circulation in the conscious patient. Mean artery blood pressure is reduced to 45–50 mmHg and hereby a reduced blood loss. In this study we have combined HEA with preoperative acute normovolaemic hemodilution (ANH) in attempt to further reduce the blood loss and need for blood transfusion in total knee arthroplasty surgery (TKR). METHODS: Twenty-eight patients scheduled for TKR are randomised to ANH or no hemodilution (non-ANH). Both groups are anaesthetized with HEA. ANH is established with predonation of 20 % of the total blood volume, and replacement with equal volume of HAES 6 %. Blood re-transfusion is completed within 6 h. RESULTS: A mean of 877 ml blood was predonated (19.7 % of the total blood volume). Blood loss was, except from the intraoperative loss, significantly higher in ANH group. The total loss was 1306 mL (ANH) vs. 1026 mL (non-ANH), p < 0.05. Except from the first hour postoperatively, hematocrit was identical in between groups postoperatively. The amount of blood transfusion was identical 386 ml (ANH) vs. 343 ml (non-ANH) (ns). 50 % went through surgery without receiving blood (ANH) vs. 58 % (non-ANH). No renal, neurological or cardiopulmonary complications were registered. CONCLUSIONS: These data suggest no benefits in combining HEA and ANH in TKR surgery. Probably because of the reduced viscosity of the blood after ANH, there is an increased postoperative blood loss. The need for homologous blood transfusion was identical
Consensus report on 25 years of searches for damped Ly galaxies in emission: Confirming their metallicity-luminosity relation at
Starting from a summary of detection statistics of our recent X-shooter
campaign, we review the major surveys, both space and ground based, for
emission counterparts of high-redshift damped Ly absorbers (DLAs)
carried out since the first detection 25 years ago. We show that the detection
rates of all surveys are precisely reproduced by a simple model in which the
metallicity and luminosity of the galaxy associated to the DLA follow a
relation of the form, , and the DLA cross-section follows a relation of the form
. Specifically, our spectroscopic campaign
consists of 11 DLAs preselected based on their equivalent width of SiII
to have a metallicity higher than [Si/H] > -1. The targets have
been observed with the X-shooter spectrograph at the Very Large Telescope to
search for emission lines around the quasars. We observe a high detection rate
of 64% (7/11), significantly higher than the typical 10% for random,
HI-selected DLA samples. We use the aforementioned model, to simulate the
results of our survey together with a range of previous surveys: spectral
stacking, direct imaging (using the `double DLA' technique), long-slit
spectroscopy, and integral field spectroscopy. Based on our model results, we
are able to reconcile all results. Some tension is observed between model and
data when looking at predictions of Ly emission for individual targets.
However, the object to object variations are most likely a result of the
significant scatter in the underlying scaling relations as well as
uncertainties in the amount of dust which affects the emission.Comment: 25 pages (7 of which in appendix), accepted for publication in MNRA
The Optically Unbiased GRB Host (TOUGH) survey. IV. Lyman-alpha emitters
We report the results of a spectroscopic search for Lyman-alpha emission from
gamma-ray burst host galaxies. Based on the well-defined TOUGH sample of 69
X-ray selected Swift GRBs, we have targeted the hosts of a subsample of 20 GRBs
known from afterglow spectroscopy to be in the redshift range 1.8-4.5. We
detect Lya emission from 7 out of the 20 hosts, with the typical limiting
3sigma line flux being 8E-18 erg/cm2/s, corresponding to a Lya luminosity of
6E41 erg/s at z=3. The Lya luminosities for the 7 hosts in which we detect Lya
emission are in the range (0.6-2.3)E42 erg/s corresponding to star-formation
rates of 0.6-2.1 Msun/yr (not corrected for extinction). The rest-frame Lya
equivalent widths (EWs) for the 7 hosts are in the range 9-40A. For 6 of the 13
hosts for which Lya is not detected we place fairly strong 3sigma upper limits
on the EW (<20A), while for others the EW is either unconstrained or has a less
constraining upper limit. We find that the distribution of Lya EWs is
inconsistent with being drawn from the Lya EW distribution of bright Lyman
break galaxies at the 98.3% level, in the sense that the TOUGH hosts on average
have larger EWs than bright LBGs. We can exclude an early indication, based on
a smaller, heterogeneous sample of pre-Swift GRB hosts, that all GRB hosts are
Lya emitters. We find that the TOUGH hosts on average have lower EWs than the
pre-Swift GRB hosts, but the two samples are only inconsistent at the 92%
level. The velocity centroid of the Lya line is redshifted by 200-700 km/s with
respect to the systemic velocity, similar to what is seen for LBGs, possibly
indicating star-formation driven outflows from the host galaxies. There seems
to be a trend between the Lya EW and the optical to X-ray spectral index of the
afterglow (beta_OX), hinting that dust plays a role in the observed strength
and even presence of Lya emission. [ABRIDGED]Comment: ApJ accepted (v2: minor changes in the Subject headings and reference
list
On the mass-metallicity relation, velocity dispersion and gravitational well depth of GRB host galaxies
We analyze a sample of 16 absorption systems intrinsic to long duration GRB
host galaxies at for which the metallicities are known. We
compare the relation between the metallicity and cold gas velocity width for
this sample to that of the QSO-DLAs, and find complete agreement. We then
compare the redshift evolution of the mass-metallicity relation of our sample
to that of QSO-DLAs and find that also GRB hosts favour a late onset of this
evolution, around a redshift of . We compute predicted stellar
masses for the GRB host galaxies using the prescription determined from QSO-DLA
samples and compare the measured stellar masses for the four hosts where
stellar masses have been determined from SED fits. We find excellent agreement
and conclude that, on basis of all available data and tests, long duration
GRB-DLA hosts and intervening QSO-DLAs are consistent with being drawn from the
same underlying population. GRB host galaxies and QSO-DLAs are found to have
different impact parameter distributions and we briefly discuss how this may
affect statistical samples. The impact parameter distribution has two effects.
First any metallicity gradient will shift the measured metallicity away from
the metallicity in the centre of the galaxy, second the path of the sightline
through different parts of the potential well of the dark matter halo will
cause different velocity fields to be sampled. We report evidence suggesting
that this second effect may have been detected.Comment: 11 pages, 6 figures, 6 tables. Accepted for publication in MNRAS Main
Journal. For the definitive version visit http://mnras.oxfordjournals.org
The evolution of field early-type galaxies to z~0.7
We have measured the Fundamental Plane (FP) parameters for a sample of 30
field early-type galaxies (E/S0) in the redshift range 0.1<z<0.66. We find
that: i) the FP is defined and tight out to the highest redshift bin; ii) the
intercept \gamma evolves as d\gamma/dz=0.58+0.09-0.13 (for \Omega=0.3,
\Omega_{\Lambda}=0.7), or, in terms of average effective mass to light ratio,
as d\log(M/L_B)/dz=-0.72+0.11-0.16, i.e. faster than is observed for cluster
E/S0 -0.49+-0.05. In addition, we detect [OII] emission >5\AA in 22% of an
enlarged sample of 42 massive E/S0 in the range 0.1<z<0.73, in contrast with
the quiescent population observed in clusters at similar z. We interpret these
findings as evidence that a significant fraction of massive field E/S0
experiences secondary episodes of star-formation at z<1.Comment: ApJ Letters, in pres
The high A_V Quasar Survey: A z=2.027 metal-rich damped Lyman-alpha absorber towards a red quasar at z=3.21
To fully exploit the potential of quasars as probes of cosmic chemical
evolution and the internal gas dynamics of galaxies it is important to
understand the selection effects behind the quasar samples and in particular if
the selection criteria exclude foreground galaxies with certain properties
(most importantly a high dust content). Here we present spectroscopic follow-up
from the 10.4-m GTC telescope of a dust-reddened quasar, eHAQ0111+0641, from
the extended High A_V Quasar (HAQ) survey. We find that the z=3.21 quasar has a
foreground Damped Lyman-alpha Absorber (DLA) at z=2.027 along the line of
sight. The DLA has very strong metal lines due to a moderately high metallicity
(with an inferred lower limit of 25% of the solar metallicity), but a very
large gas column density along the line-of-sight in its host galaxy. This
discovery is further evidence that there is a dust bias affecting the census of
metals, caused by the combined effect of dust obscuration and reddening, in
existing samples of z>2 DLAs. The case of eHAQ0111+0641 illustrates that dust
bias is not only caused by dust obscuration, but also dust reddening.Comment: 7 pages, 4 figures. Accepted for publication in A&A. A few typos have
been correcte
Extinction curve template for intrinsically reddened quasars
We analyze the near-infrared to UV data of 16 quasars with redshifts ranging
from 0.71 2.13 to investigate dust extinction properties. The
sample presented in this work is obtained from the High Quasar (HAQ)
survey. The quasar candidates were selected from the Sloan Digital Sky Survey
(SDSS) and the UKIRT Infrared Deep Sky Survey (UKIDSS), and follow-up
spectroscopy was carried out at the Nordic Optical Telescope (NOT) and the New
Technology Telescope (NTT). To study dust extinction curves intrinsic to the
quasars, from the HAQ survey we selected 16 cases where the Small Magellanic
Cloud (SMC) law could not provide a good solution to the spectral energy
distributions (SEDs). We derived the extinction curves using Fitzpatrick &
Massa 1986 (FM) law by comparing the observed SEDs to the combined quasar
template from Vanden Berk et al. 2001 and Glikman et al. 2006. The derived
extinction, , ranges from 0.2-1.0 mag. All the individual extinction
curves of our quasars are steeper (-2.7) than that of the SMC, with a
weighted mean value of . We derive an `average quasar extinction
curve' for our sample by fitting SEDs simultaneously by using the weighted mean
values of the FM law parameters and a varying . The entire sample is well
fit with a single best-fit value of . The `average quasar
extinction curve' deviates from the steepest Milky Way and SMC extinction
curves at a confidence level . Such steep extinction curves
suggest a significant population of silicates to produce small dust grains.
Moreover, another possibility could be that the large dust grains may have been
destroyed by the activity of the nearby active galactic nuclei (AGN), resulting
in steep extinction curves.Comment: 8 pages, 4 figures, 1 tabl
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