11 research outputs found
Selection of high-z supernovae candidates
Deep, ground based, optical wide-field supernova searches are capable of
detecting a large number of supernovae over a broad redshift range up to z~1.5.
While it is practically unfeasible to obtain spectroscopic redshifts of all the
supernova candidates right after the discovery, we show that the magnitudes and
colors of the host galaxies, as well as the supernovae, can be used to select
high-z supernova candidates, for subsequent spectroscopic and photometric
follow-up.
Using Monte-Carlo simulations we construct criteria for selecting galaxies in
well-defined redshift bands. For example, with a selection criteria using B-R
and R-I colors we are able to pick out potential host galaxies for which z>0.85
with 80% confidence level and with a selection efficiency of 64-86%. The method
was successfully tested using real observations from the HDF.
Similarly, we show that that the magnitude and colors of the supernova
discovery data can be used to constrain the redshift. With a set of cuts based
on V-R and R-I in a search to m_I~25, supernovae at z~1 can be selected in a
redshift interval sigma_z <0.15.Comment: 33 pages, 13 figures, accepted for publication in PASP (March 2002
issue
Tentative detection of the gravitational magnification of type Ia supernovae
The flux from distant type Ia supernovae (SN) is likely to be amplified or
de-amplified by gravitational lensing due to matter distributions along the
line-of-sight. A gravitationally lensed SN would appear brighter or fainter
than the average SN at a particular redshift. We estimate the magnification of
26 SNe in the GOODS fields and search for a correlation with the residual
magnitudes of the SNe. The residual magnitude, i.e. the difference between
observed and average magnitude predicted by the "concordance model" of the
Universe, indicates the deviation in flux from the average SN. The linear
correlation coefficient for this sample is r=0.29. For a similar, but
uncorrelated sample, the probability of obtaining a correlation coefficient
equal to or higher than this value is ~10%, i.e. a tentative detection of
lensing at ~90% confidence level. Although the evidence for a correlation is
weak, our result is in accordance with what could be expected given the small
size of the sample.Comment: 7 pages, 2 figure
The Galaxy Population of Cl1601+42 at z=0.54
Photometric redshifts are used to determine the rest frame luminosity
function (LF) of both early-type and late-type galaxies to M_B ~ -17.6 for the
cluster Cl1601+42 at z = 0.54. The total LF shows a steep faint-end slope alpha
\~ -1.4, indicating the existence of a numerous population of dwarf galaxies.
Luminous galaxies, with M_B < -19.5 are mostly red, early-type galaxies, with a
LF best described by a Gaussian. Faint galaxies are predominantly blue,
late-type galaxies, well fitted by a Schechter function with alpha ~ -1.7.
Compared to clusters at lower redshift, the steepening of the faint end starts
at brighter magnitudes for Cl1601+42, which may indicate a brightening of
todays dwarf population relative to the giant population with increasing
redshift. Early-type galaxies are centrally concentrated, and dominate the core
region, implying that the radial gradient of early-type galaxies seen in local
clusters is already established at z ~ 0.5. Bright, late-type galaxies are
rare, consistent with a decrease in star formation in field galaxies as they
are accreted on to the cluster, while faint, blue galaxies are evenly
distributed across the cluster, except for a depletion in the core region. The
blue fraction is f_B ~ 0.15, which is somewhat lower than the Butcher-Oemler
average at z ~ 0.5. The value of f_B is found to increase with limiting
magnitude and with radius from the centre.Comment: 19 pages, 12 figures, accepted by MNRA
Examina och utbildning inom svensk odontologisk forskning : lägesrapport
En internationell utvärdering visade för några år sedan att Sverige riskerar
att förlora sin position som världsledande nation inom odontologisk forskning.
För att få en uppfattning om förändringarna inom forskarutbildningen
och den postdoktorala meriteringen samlades data för 1990–2001 in från
fakulteterna, Statistiska Centralbyrån samt Högskoleverket. Avsikten var att
undersöka antalet forskarutbildade tandläkare, mångfalden bland doktoranderna
och de som disputerat samt deras nuvarande anställningsform.
Materialet jämfördes sedan med tidigare data.
I medeltal avlade 25 personer per år doktorsexamen åren 1990–2001.
Antalet har minskat under senare år. En majoritet av dem som avlade doktorsexamen
hade odontologisk bakgrund. Relativt få har meriterat sig för en fortsatt
akademisk karriär. 32 studerande påbörjade forskarutbildning åren 1991–2001.
Andelen doktorander med annan akademisk grundexamen än odontologisk ökar.
Sedan 1999 har forskningsvolymen minskat med motsvarande en hel fakultets
forskningsvolym. Vi drar därför slutsatsen att kunskapsutvecklingen inom
svensk odontologi riskerar att stagnera samt att fakulteternas behov av lärare till
högre akademiska tjänster liksom folktandvårdens behov av handledare inom
specialistutbildningen inte kommer att kunna tillgodoses i framtiden
Functionalized lipid nanoparticles for subcutaneous administration of mRNA to achieve systemic exposures of a therapeutic protein
Lipid nanoparticles (LNPs) are the most clinically advanced delivery system for RNA-based drugs but have predominantly been investigated for intravenous and intramuscular administration. Subcutaneous administration opens the possibility of patient self-administration and hence long-term chronic treatment that could enable messenger RNA (mRNA) to be used as a novel modality for protein replacement or regenerative therapies. In this study, we show that subcutaneous administration of mRNA formulated within LNPs can result in measurable plasma exposure of a secreted protein. However, subcutaneous administration of mRNA formulated within LNPs was observed to be associated with dose-limiting inflammatory responses. To overcome this limitation, we investigated the concept of incorporating aliphatic ester prodrugs of anti-inflammatory steroids within LNPs, i.e., functionalized LNPs to suppress the inflammatory response. We show that the effectiveness of this approach depends on the alkyl chain length of the ester prodrug, which determines its retention at the site of administration. An unexpected additional benefit to this approach is the prolongation observed in the duration of protein expression. Our results demonstrate that subcutaneous administration of mRNA formulated in functionalized LNPs is a viable approach to achieving systemic levels of therapeutic proteins, which has the added benefits of being amenable to self-administration when chronic treatment is required
Spitzer Observations of Massive, Red Galaxies at High Redshift
International audienceWe study massive galaxies at z~1-3.5 using HST optical imaging, ground-based near-IR imaging, and Spitzer observations at 3-24 mum. From Ks-selected galaxies in the ~=130 arcmin2 GOODS-S field, we identify 153 distant red galaxies (DRGs) with (J-Ks)Vega>=2.3. This sample is approximately complete in stellar mass for passively evolving galaxies above 1011 Msolar and z~4-6 mag) starbursts (at zmed~1.7). Very few DRGs (=1011 Msolar have specific star formation rates (SFRs per unit mass) including the reradiated far-IR emission that range from 0.2 to 10 Gyr-1. Based on the X-ray luminosities and rest-frame near-IR colors, roughly one-quarter of the DRGs contain AGNs, implying that the growth of supermassive black holes coincides with the formation of massive galaxies. At 1.5=1011 Msolar have an integrated specific SFR less than the global value and more than an order of magnitude lower than that for massive DRGs. At