683 research outputs found
Recommended from our members
OAO1.01. Are complementary therapies and integrative care cost-effective? A comprehensive systematic review of economic evaluations
Systematic Analysis of 22 Microlensing Parallax Candidates
We attempt to identify all microlensing parallax events for which the
parallax fit improves \Delta\chi^2 > 100 relative to a standard microlensing
model. We outline a procedure to identify three types of discrete degeneracies
(including a new one that we dub the ``ecliptic degeneracy'') and find many new
degenerate solutions in 16 previously published and 6 unpublished events. Only
four events have one unique solution and the other 18 events have a total of 44
solutions. Our sample includes three previously identified black-hole (BH)
candidates. We consider the newly discovered degenerate solutions and determine
the relative likelihood that each of these is a BH. We find the lens of event
MACHO-99-BLG-22 is a strong BH candidate (78%), event MACHO-96-BLG-5 is a
marginal BH candidate (37%), and MACHO-98-BLG-6 is a weak BH candidate (2.2%).
The lens of event OGLE-2003-BLG-84 may be a Jupiter-mass free-floating planet
candidate based on a weak 3 sigma detection of finite-source effects. We find
that event MACHO-179-A is a brown dwarf candidate within ~100 pc of the Sun,
mostly due to its very small projected Einstein radius, \tilde r_E = 0.23+-0.05
AU. As expected, these microlensing parallax events are biased toward lenses
that are heavier and closer than average. These events were examined for
xallarap (or binary-source motion), which can mimic parallax. We find that 23%
of these events are strongly affected by xallarap.Comment: 69 Pages, 10 Figures, 24 Tables, Submitted to Ap
Alternative mechanism for bacteriophage adsorption to the motile bacterium Caulobacter crescentus
2D and 3D cryo-electron microscopy, together with adsorption kinetics assays of ÏCb13 and ÏCbK phage-infected Caulobacter crescentus, provides insight into the mechanisms of infection. ÏCb13 and ÏCbK actively interact with the flagellum and subsequently attach to receptors on the cell pole. We present evidence that the first interaction of the phage with the bacterial flagellum takes place through a filament on the phage head. This contact with the flagellum facilitates concentration of phage particles around the receptor (i.e., the pilus portals) on the bacterial cell surface, thereby increasing the likelihood of infection. Phage head filaments have not been well characterized and their function is described here. Phage head filaments may systematically underlie the initial interactions of phages with their hosts in other systems and possibly represent a widespread mechanism of efficient phage propagation
Time delays for 11 gravitationally lensed quasars revisited
We test the robustness of published time delays for 11 lensed quasars by
using two techniques to measure time shifts in their light curves.
We chose to use two fundamentally different techniques to determine time
delays in gravitationally lensed quasars: a method based on fitting a numerical
model and another one derived from the minimum dispersion method introduced by
Pelt and collaborators. To analyse our sample in a homogeneous way and avoid
bias caused by the choice of the method used, we apply both methods to 11
different lensed systems for which delays have been published: JVAS B0218+357,
SBS 0909+523, RX J0911+0551, FBQS J0951+2635, HE 1104-1805, PG 1115+080, JVAS
B1422+231, SBS 1520+530, CLASS B1600+434, CLASS B1608+656, and HE 2149-2745
Time delays for three double lenses, JVAS B0218+357, HE 1104-1805, and CLASS
B1600+434, as well as the quadruply lensed quasar CLASS B1608+656 are confirmed
within the error bars. We correct the delay for SBS 1520+530. For PG 1115+080
and RX J0911+0551, the existence of a second solution on top of the published
delay is revealed. The time delays in four systems, SBS 0909+523, FBQS
J0951+2635, JVAS B1422+231, and HE 2149-2745 prove to be less reliable than
previously claimed.
If we wish to derive an estimate of H_0 based on time delays in
gravitationally lensed quasars, we need to obtain more robust light curves for
most of these systems in order to achieve a higher accuracy and robustness on
the time delays
I. Flux and color variations of the quadruply imaged quasar HE 0435-1223
aims: We present VRi photometric observations of the quadruply imaged quasar
HE 0435-1223, carried out with the Danish 1.54m telescope at the La Silla
Observatory. Our aim was to monitor and study the magnitudes and colors of each
lensed component as a function of time. methods: We monitored the object during
two seasons (2008 and 2009) in the VRi spectral bands, and reduced the data
with two independent techniques: difference imaging and PSF (Point Spread
Function) fitting.results: Between these two seasons, our results show an
evident decrease in flux by ~0.2-0.4 magnitudes of the four lensed components
in the three filters. We also found a significant increase (~0.05-0.015) in
their V-R and R-i color indices. conclusions: These flux and color variations
are very likely caused by intrinsic variations of the quasar between the
observed epochs. Microlensing effects probably also affect the brightest "A"
lensed component.Comment: 10 pages, 8 figure
A Multi-Compartment, Single and Multiple Dose Pharmacokinetic Study of the Vaginal Candidate Microbicide 1% Tenofovir Gel
Background: Tenofovir (TFV) gel is being evaluated as a microbicide with pericoital and daily regimens. To inhibit viral replication locally, an adequate concentration in the genital tract is critical. Methods and Findings: Forty-nine participants entered a two-phase study: single-dose (SD) and multi-dose (MD), were randomized to collection of genital tract samples (endocervical cells [ECC], cervicovaginal aspirate and vaginal biopsies) at one of seven time points [0.5, 1, 2, 4, 6, 8, or 24 hr(s)] post-dose following SD exposure of 4 mL 1% TFV gel and received a single dose. Forty-seven were randomized to once (QD) or twice daily (BID) dosing for 2 weeks and to collection of genital tract samples at 4, 8 or 24 hrs after the final dose, but two discontinued prior to gel application. Blood was collected during both phases at the seven times post-dose. TFV exposure was low in blood plasma for SD and MD; median C max was 4.0 and 3.4 ng/mL, respectively (Câ€29 ng/mL). TFV concentrations were high in aspirates and tissue after SD and MD, ranging from 1.2Ă10 4 to 9.9Ă10 6 ng/mL and 2.1Ă10 2 to 1.4Ă10 6 ng/mL, respectively, and did not noticeably differ between proximal and distal tissue. TFV diphosphate (TFV-DP), the intracellular active metabolite, was high in ECC, ranging from 7.1Ă10 3 to 8.8Ă10 6 ng/mL. TFV-DP was detectable in approximately 40% of the tissue samples, ranging from 1.8Ă10 2 to 3.5Ă10 4 ng/mL. AUC for tissue TFV-DP was two logs higher after MD compared to SD, with no noticeable differences when comparing QD and BID. Conclusions: Single-dose and multiple-dose TFV gel exposure resulted in high genital tract concentrations for at least 24 hours post-dose with minimal systemic absorption. These results support further study of TFV gel for HIV prevention. Trial registration: ClinicalTrials.gov NCT00561496. © 2011 Schwartz et al
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses VII. Time delays and the Hubble constant from WFI J2033-4723
Gravitationally lensed quasars can be used to map the mass distribution in
lensing galaxies and to estimate the Hubble constant H0 by measuring the time
delays between the quasar images. Here we report the measurement of two
independent time delays in the quadruply imaged quasar WFI J2033-4723 (z =
1.66). Our data consist of R-band images obtained with the Swiss 1.2 m EULER
telescope located at La Silla and with the 1.3 m SMARTS telescope located at
Cerro Tololo. The light curves have 218 independent epochs spanning 3 full
years of monitoring between March 2004 and May 2007, with a mean temporal
sampling of one observation every 4th day. We measure the time delays using
three different techniques, and we obtain Dt(B-A) = 35.5 +- 1.4 days (3.8%) and
Dt(B-C) = 62.6 +4.1/-2.3 days (+6.5%/-3.7%), where A is a composite of the
close, merging image pair. After correcting for the time delays, we find R-band
flux ratios of F_A/F_B = 2.88 +- 0.04, F_A/F_C = 3.38 +- 0.06, and F_A1/F_A2 =
1.37 +- 0.05 with no evidence for microlensing variability over a time scale of
three years. However, these flux ratios do not agree with those measured in the
quasar emission lines, suggesting that longer term microlensing is present. Our
estimate of H0 agrees with the concordance value: non-parametric modeling of
the lensing galaxy predicts H0 = 67 +13/-10 km s-1 Mpc-1, while the Single
Isothermal Sphere model yields H0 = 63 +7/-3 km s-1 Mpc-1 (68% confidence
level). More complex lens models using a composite de Vaucouleurs plus NFW
galaxy mass profile show twisting of the mass isocontours in the lensing
galaxy, as do the non-parametric models. As all models also require a
significant external shear, this suggests that the lens is a member of the
group of galaxies seen in field of view of WFI J2033-4723.Comment: 14 pages, 12 figures, published in A&
Microlensing Evidence for Super-Eddington Disc Accretion in Quasars
Microlensing by the stellar population of lensing galaxies provides an
important opportunity to spatially resolve the accretion disc structure in
strongly lensed quasars. Disc sizes estimated this way are on average larger
than the predictions of the standard Shakura-Sunyaev accretion disk model.
Analysing the observational data on microlensing variability allows to suggest
that some fraction of lensed quasars (primarily, smaller-mass objects) are
accreting in super-Eddington regime. Super-Eddington accretion leads to
formation of an optically-thick envelope scattering the radiation formed in the
disc. This makes the apparent disc size larger and practically independent of
wavelength. In the framework of our model, it is possible to make
self-consistent estimates of mass accretion rates and black hole masses for the
cases when both amplification-corrected fluxes and radii are available.Comment: 11 pages, 5 figures; typo corrected in formula 1
The biosocial event : responding to innovation in the life sciences
Innovation in the life sciences calls for reflection on how sociologies separate and relate life processes and social processes. To this end we introduce the concept of the âbiosocial eventâ. Some life processes and social processes have more mutual relevance than others. Some of these relationships are more negotiable than others. We show that levels of relevance and negotiability are not static but can change within existing relationships. Such changes, or biosocial events, lie at the heart of much unplanned biosocial novelty and much deliberate innovation. We illustrate and explore the concept through two examples â meningitis infection and epidemic, and the use of sonic âteen deterrentsâ in urban settings. We then consider its value in developing sociological practice oriented to critically constructive engagement with innovation in the life sciences
Microlens OGLE-2005-BLG-169 Implies Cool Neptune-Like Planets are Common
We detect a Neptune mass-ratio (q~8e-5) planetary companion to the lens star
in the extremely high-magnification (A~800) microlensing event
OGLE-2005-BLG-169. If the parent is a main-sequence star, it has mass M~0.5
M_sun implying a planet mass of ~13 M_earth and projected separation of ~2.7
AU. When intensely monitored over their peak, high-magnification events similar
to OGLE-2005-BLG-169 have nearly complete sensitivity to Neptune mass-ratio
planets with projected separations of 0.6 to 1.6 Einstein radii, corresponding
to 1.6--4.3 AU in the present case. Only two other such events were monitored
well enough to detect Neptunes, and so this detection by itself suggests that
Neptune mass-ratio planets are common. Moreover, another Neptune was recently
discovered at a similar distance from its parent star in a low-magnification
event, which are more common but are individually much less sensitive to
planets. Combining the two detections yields 90% upper and lower frequency
limits f=0.37^{+0.30}_{-0.21} over just 0.4 decades of planet-star separation.
In particular, f>16% at 90% confidence. The parent star hosts no Jupiter-mass
companions with projected separations within a factor 5 of that of the detected
planet. The lens-source relative proper motion is \mu~7--10 mas/yr, implying
that if the lens is sufficiently bright, I<23.8, it will be detectable by HST
by 3 years after peak. This would permit a more precise estimate of the lens
mass and distance, and so the mass and projected separation of the planet.
Analogs of OGLE-2005-BLG-169Lb orbiting nearby stars would be difficult to
detect by other methods of planet detection, including radial velocities,
transits, or astrometry.Comment: Submitted to ApJ Letters, 9 text pages + 4 figures + 1 tabl
- âŠ