506 research outputs found
OA031-02. Regulatory T cells inhibit CD8 T cell proliferation in HIV-1 infection through CD39/adenosine pathway
International audiencen.
Shearmeter floats in the area of the WHOI Brazil Basin Tracer Release Experiment : technical and oceanographic data
Six drifting floats designed to measure shear were deployed in the vicinity of the Brazil Basin Tracer Release Experiment. The
one-year long time series of oceanographic conditions obtained by the floats are for direct comparison with long-term tracer
dispersion. The purpose of the tracer dispersion experiment was to study mixing of Antarctic Bottom Water at approximately 4000
m depth with less dense water above. Two of the floats returned shear records, one from about 1660 m depth and one from about
2800 m depth. Mean shear at 1660 m was 2.2 x 10 -3 s-1 with N = 1.1 cph, about 1.9 times the Garrett-Munk model amount.
Mean shear at 2800 m was 1.1 x 10-3 with N = 0.5 cph, about 2.2 times Garrett-Munk. There was no apparent depth structure to
the shear recorded by the near-bottom float moving over the mountainous seafloor. The two shear time series and the local tidal
velocities were not strongly correlated, but the tide and shear series did have some similarities. Some variability in the 1660-m
shear may be due to atmospheric forcing. Three floats deeper than 2800 m returned one-year long trajectories. Two trajectories were
persistently eastward.Funding was provided by the National Science Foundation under
Grant Nos. OCE-9416014 and OCE-9906685
New synchronization method for <i>Plasmodium falciparum</i>
<b>Background</b>: Plasmodium falciparum is usually asynchronous during in vitro culture. Although various synchronization methods are available, they are not able to narrow the range of ages of parasites. A newly developed method is described that allows synchronization of parasites to produce cultures with an age range as low as 30 minutes.
<b>Methods</b>: Trophozoites and schizonts are enriched using Plasmion. The enriched late stage parasites are immobilized as a monolayer onto plastic Petri dishes using concanavalin A. Uninfected erythrocytes are placed onto the monolayer for a limited time period, during which time schizonts on the monolayer rupture and the released merozoites invade the fresh erythrocytes. The overlay is then taken off into a culture flask, resulting in a highly synchronized population of parasites.
<b>Results</b>: Plasmion treatment results in a 10- to 13-fold enrichment of late stage parasites. The monolayer method results in highly synchronized cultures of parasites where invasion has occurred within a very limited time window, which can be as low as 30 minutes. The method is simple, requiring no specialized equipment and relatively cheap reagents.
<b>Conclusions</b>: The new method for parasite synchronization results in highly synchronized populations of parasites, which will be useful for studies of the parasite asexual cell cycle
Nanoengineered Astronomical Optics
We describe a technology for the fabrication of inexpensive and versatile
mirrors through the use of a new type of nanoengineered optical material
composed by the spreading of a self-assembling reflective colloidal film spread
at the surface of a liquid. These new reflecting liquids offer interesting
possibilities for astronomical instrumentation. For example, they can replace
mercury in conventional rotating liquid mirrors. The main advantages offered
include extremely low cost and, by coating a viscous liquid, the possibility of
tilting the mirror by a few tens of degrees. We also have coated ferromagnetic
liquids with these reflecting films. The resulting surfaces can be shaped by
the application of a magnetic field, yielding reflecting surfaces that can have
complicated shapes that can rapidly shift with time. These inexpensive and
versatile optical elements could have numerous scientific and technological
applications. Among possible astronomical applications, they could be used to
make large inexpensive adaptive mirrors exhibiting strokes ranging from
nanometers to several millimeters.Comment: Submitted to Astrophysical Journal Letters. 18 pages, 4 figure
Evaluation of electrothermal vaporization for sample introduction aiming at Cu isotopic analysis via multicollector-inductively coupled plasma mass spectrometry
A new method for Cu isotopic analysis was developed using a commercially available electrothermal vaporization (ETV) device coupled to multicollector-inductively coupled plasma mass spectrometry (MC-ICP-MS). The method demonstrated potential for the isotopic analysis of microsamples (e.g., 5 mu L) in a biological context. For example, Cu isotopic analysis of NIST 3114 (diluted to 1 mg L-1 Cu) using self-bracketing provided average delta Cu-65 values of 0.00 +/- 0.17%0 (2SD, n = 10) and internal precision values of 712 ppm. In order to achieve this level of accuracy and precision, it is critical to properly deal with the short transient signals generated by the ETV-MC-ICP-MS, which implies using point by point calculations and time lag detector correction (TDC), as well as a criterion to reject potential outliers. The results of this technique were compared with the results obtained via femtosecond-laser ablation-MC-ICPMS using the same pre-treated serum samples. No significant differences were observed among the results obtained in both cases, while external precision was 0.26%0 for ETV-MC-ICP-MS and 0.24%0 for fs-LA-MC-ICP-MS, expressed as median value of 2SD (n = 27), further proving the usefulness of the approach proposed in this context, as the use of ETV results in a more straightforward approach
Target identification of hits using a concerted chemogenomic, biophysical and structural approach
Mycobacterium phenotypic hits are a good reservoir for new chemotypes for the treatment of tuberculosis. However, the absence
of defined molecular targets and modes of action could lead to failure in drug development. Therefore, a combination of
ligand-based and structure-based chemogenomic approaches followed by biophysical and biochemical validation have been used to
identify targets for Mycobacterium tuberculosis phenotypic hits. Our approach identified EthR and InhA as targets for several hits,
with some showing dual activity against these proteins. From the 35 predicted EthR inhibitors, eight exhibited an IC50 below 50
ÎĽM against M. tuberculosis EthR and three were confirmed to be also simultaneously active against InhA. Further hit validation was
performed using X-ray crystallography yielding eight new crystal structures of EthR inhibitors. Although the EthR inhibitors attain
their activity against M. tuberculosis by hitting yet undefined targets, these results provide new lead compounds that could be
further developed to be used to potentiate the effect of EthA activated pro-drugs, such as ethionamide, thus enhancing their
bactericidal effect.GM is grateful to the European Molecular Biology Laboratory and Marie Sklodowska-Curie Actions for funding this work. VM and MB
acknowledge Bill & Melinda Gates Foundation [subcontract by the Foundation for the National Institutes of Health (NIH)]
(OPP1024021). VM and MS acknowledge the European Community’s Seventh Framework Programme [grant number 260872]. GP
would like to acknowledge the Wellcome Trust and the European Molecular Biology Laboratory for funding. JPO was funded by the
member nation states of the European Molecular Biology Laboratory. TLB acknowledges The Wellcome Trust for funding and
support (grant number 200814/Z/16/Z)
New Chandra observations of the jet in 3C273. I. Softer X-ray than radio spectra and the X-ray emission mechanism
The jet in 3C273 is a high-power quasar jet with radio, optical and X-ray
emission whose size and brightness allow a detailed study of the emission
processes acting in it. We present deep Chandra observations of this jet and
analyse the spectral properties of the jet emission from radio through X-rays.
We find that the X-ray spectra are significantly softer than the radio spectra
in all regions of the bright part of the jet except for the first bright "knot
A", ruling out a model in which the X-ray emission from the entire jet arises
from beamed inverse-Compton scattering of cosmic microwave background photons
in a single-zone jet flow. Within two-zone jet models, we find that a
synchrotron origin for the jet's X-rays requires fewer additional assumptions
than an inverse-Compton model, especially if velocity shear leads to efficient
particle acceleration in jet flows.Comment: 11 pages, 5 figures, emulateapj. Accepted by Ap
Assay development and inhibition of the Mt-DprE2 essential reductase from Mycobacterium tuberculosis
Skyrmions and spirals in MnSi under hydrostatic pressure
The archetype cubic chiral magnet MnSi is home to some of the most
fascinating states in condensed matter such as skyrmions and a non-Fermi liquid
behavior in conjunction with a topological Hall effect under hydrostatic
pressure. Using small angle neutron scattering, we study the evolution of the
helimagnetic, conical and skyrmionic correlations with increasing hydrostatic
pressure. We show that the helical propagation vector smoothly reorients from
to at intermediate pressures. At
higher pressures, above the critical pressure, the long-range helimagnetic
order disappears at zero magnetic field. Nevertheless, skyrmion lattices and
conical spirals form under magnetic fields, in a part of the phase diagram
where a topological Hall effect and a non-Fermi liquid behavior have been
reported. These unexpected results shed light on the puzzling behavior of MnSi
at high pressures and the mechanisms that destabilize the helimagnetic
long-range order at the critical pressure
- …