373 research outputs found
Anomalous dispersion of optical phonons at the neutral-ionic transition: Evidence from diffuse X-ray scattering
Diffuse X-ray data for mixed stack organic charge-transfer crystals
approaching the neutral-ionic phase transition can be quantitatively explained
as due to the softening of the optical phonon branch. The interpretation is
fully consistent with vibrational spectra, and underlines the importance of
electron-phonon coupling in low-dimensional systems with delocalized electrons.Comment: 4 pages, 4 figure
Towards a regional ocean forecasting system for the IBI (Iberia-Biscay-Ireland area): developments and improvements within the ECOOP project framework
The regional ocean operational system remains a key element in downscaling from large scale (global or basin scale) systems to coastal ones. It enables the transition between systems in which the resolution and the resolved physics are quite different. Indeed, coastal applications need a system to predict local high frequency events (inferior to the day) such as storm surges, while deep sea applications need a system to predict large scale lower frequency ocean features. In the framework of the ECOOP project, a regional system for the Iberia-Biscay-Ireland area has been upgraded from an existing V0 version to a V2. This paper focuses on the improvements from the V1 system, for which the physics are close to a large scale basin system, to the V2 for which the physics are more adapted to shelf and coastal issues. Strong developments such as higher regional physics resolution in the NEMO Ocean General Circulation Model for tides, non linear free surface and adapted vertical mixing schemes among others have been implemented in the V2 version. Thus, regional thermal fronts due to tidal mixing now appear in the latest version solution and are quite well positioned. Moreover, simulation of the stratification in shelf areas is also improved in the V2
On the Crystal and Magnetic Behavior of ScFe4Al8 Single Crystal
Nuclear and magnetic properties of the ScFe4Al8 single crystal were found to exhibit unparalleled complexity
of nuclear and magnetic structures. Our previous neutron measurements revealed presence of two modulation
vectors, both along [", ", 0], however with dfferent critical temperatures. Recent experiments forced us to revise
our knowledge of the structural ordering in the sample. So far, the crystal structure of this alloy, being of
ThMn12-type, has never been questioned
Neutron Laue and X-ray diffraction study of a new crystallographic superspace phase in n-nonadecane-urea
International audienceAperiodic composite crystals present long-range order without translational symmetry. These materials may be described as the intersection in three dimensions of a crystal which is periodic in a higher-dimensional space. In such materials, symmetry breaking must be described as structural changes within these crystallographic superspaces. The increase in the number of superspace groups with the increase in the dimension of the superspace allows many more structural solutions. This is illustrated in n-nonadecane-urea, revealing a fifth higher-dimensional phase at low temperature
Potentiation of PBD Dimers by Lipophilicity Manipulation
Background & Introduction: Pyrrolobenzodiazepine (PBD) dimers are highly potent DNA cross-linking agents used as warheads in Antibody Drug Conjugates (ADCs) for cancer therapy. We propose to investigate the correlation existing between the lipophilicity of those molecules and their activity (both in vitro and in vivo) as well as any effect observed during conjugation. /
Materials and Methods: Reaction progress was monitored by Thin-Layer Chromatography (TLC) using Merck Kieselgel 60 F254 silica gel, with a fluorescent indicator on aluminium plates. Visualisation of TLC was achieved with UV light or iodine vapour unless otherwise stated. Flash chromatography was performed using Merck Kieselgel 60 F254 silica gel. /
Results: We have successfully designed and synthesized a novel PBD warhead (SG3312) with enhanced physicochemical properties. The warhead also displayed increased potency in vitro. After overcoming some epimerization issues, the synthesis of enantiomerically pure payload was achieved (SG3259) and fulfilled our criteria for a simplified and more efficient conjugation. No addition of propylene glycol was required, and high DAR and excellent monomeric purity were achieved. /
Conclusion: The ADC (Herceptin-maia-SG3259) has been shown to release the active warhead (SG3312) upon exposure to Cathepsin B and demonstrated encouraging activity both in vitro and in vivo
Phase Transition in a One-Dimensional Extended Peierls-Hubbard Model with a Pulse of Oscillating Electric Field: I. Threshold Behavior in Ionic-to-Neutral Transition
Photoinduced dynamics of charge density and lattice displacements is
calculated by solving the time-dependent Schr\"odinger equation for a
one-dimensional extended Peierls-Hubbard model with alternating potentials for
the mixed-stack organic charge-transfer complex, TTF-CA. A pulse of oscillating
electric field is incorporated into the Peierls phase of the transfer integral.
The frequency, the amplitude, and the duration of the pulse are varied to study
the nonlinear and cooperative character of the photoinduced transition. When
the dimerized ionic phase is photoexcited, the threshold behavior is clearly
observed by plotting the final ionicity as a function of the increment of the
total energy. Above the threshold photoexcitation, the electronic state reaches
the neutral one with equidistant molecules after the electric field is turned
off. The transition is initiated by nucleation of a metastable neutral domain,
for which an electric field with frequency below the linear absorption peak is
more effective than that at the peak. When the pulse is strong and short, the
charge transfer takes place on the same time scale with the disappearance of
dimerization. As the pulse becomes weak and long, the dimerization-induced
polarization is disordered to restore the inversion symmetry on average before
the charge transfer takes place to bring the system neutral. Thus, a
paraelectric ionic phase is transiently realized by a weak electric field. It
is shown that infrared light also induces the ionic-to-neutral transition,
which is characterized by the threshold behavior.Comment: 24 pages, 11 figure
[89Zr]Oxinate4 for long-term in vivo cell tracking by positron emission tomography
Purpose 111In (typically as [111In]oxinate3) is a gold standard
radiolabel for cell tracking in humans by scintigraphy. A long
half-life positron-emitting radiolabel to serve the same purpose
using positron emission tomography (PET) has long
been sought. We aimed to develop an 89Zr PET tracer for cell
labelling and compare it with [111In]oxinate3 single photon
emission computed tomography (SPECT).
Methods [89Zr]Oxinate4 was synthesised and its uptake and
efflux were measured in vitro in three cell lines and in human
leukocytes. The in vivo biodistribution of eGFP-5T33 murine
myeloma cells labelled using [89Zr]oxinate4 or [111In]oxinate3
was monitored for up to 14 days. 89Zr retention by living
radiolabelled eGFP-positive cells in vivo was monitored by
FACS sorting of liver, spleen and bone marrow cells followed
by gamma counting.
Results Zr labelling was effective in all cell types with yields
comparable with 111In labelling. Retention of 89Zr in cells
in vitro after 24 h was significantly better (range 71 to
>90 %) than 111In (43–52 %). eGFP-5T33 cells in vivo
showed the same early biodistribution whether labelled with
111In or 89Zr (initial pulmonary accumulation followed by
migration to liver, spleen and bone marrow), but later translocation
of radioactivity to kidneys was much greater for 111In.
In liver, spleen and bone marrow at least 92 % of 89Zr
remained associated with eGFP-positive cells after 7 days
in vivo.
Conclusion [89Zr]Oxinate4 offers a potential solution to the
emerging need for a long half-life PET tracer for cell tracking
in vivo and deserves further evaluation of its effects on survival
and behaviour of different cell types
Epidemiological risk of African horse sickness in donkeys in Burkina Faso
African horse sickness (AHS) virus causes severe epidemics when transmitted to horses by Culicoides vectors. A cross-sectional study was carried out in five areas of Burkina Faso to determine the seroprevalence of AHS virus in donkeys and to identify potential risk factors. A total of 460 sera were collected in 15 villages. A blocking enzyme-linked immunosorbent assay (ELISA) was carried out to detect AHS virus antibodies. The overall apparent seroprevalence was 72.6% indicating that the donkeys were infected with AHS virus. A multivariate logistic regression analysis was performed to determine the factors affecting the seroprevalence level. A significant effect between geographical areas was observed, confirming the role of the agroecological zone in the occurrence of AHS. Similarly, age and animal weight had significant effects on seroprevalence, whereas sex, coat color and herd size had not. This study highlighted the active circulation of AHS virus in donkeys in Burkina Faso
The chemopreventive polyphenol Curcumin prevents hematogenous breast cancer metastases in immunodeficient mice
Dissemination of metastatic cells probably occurs long before diagnosis of the primary tumor. Metastasis during early phases of carcinogenesis in high risk patients is therefore a potential prevention target. The plant polyphenol Curcumin has been proposed for dietary prevention of cancer. We therefore examined its effects on the human breast cancer cell line MDA-MB-231 in vitro and in a mouse metastasis model. Curcumin strongly induces apoptosis in MDA- MB- 231 cells in correlation with reduced activation of the survival pathway NF kappa B, as a consequence of diminished I kappa B and p65 phosphorylation. Curcumin also reduces the expression of major matrix metalloproteinases (MMPs) due to reduced NF kappa B activity and transcriptional downregulation of AP-1. NF kappa B/p65 silencing is sufficient to downregulate c-jun and MMP expression. Reduced NF kappa B/AP-1 activity and MMP expression lead to diminished invasion through a reconstituted basement membrane and to a significantly lower number of lung metastases in immunodeficient mice after intercardiac injection of 231 cells (p=0.0035). 68% of Curcumin treated but only 17% of untreated animals showed no or very few lung metastases, most likely as a consequence of down-regulation of NF kappa B/AP-1 dependent MMP expression and direct apoptotic effects on circulating tumor cells but not on established metastases. Dietary chemoprevention of metastases appears therefore feasible. Copyright (c) 2007 S. Karger AG, Basel
Transiting exoplanets from the CoRoT space mission VIII. CoRoT-7b: the first Super-Earth with measured radius
We report the discovery of very shallow (DF/F = 3.4 10-4), periodic dips in
the light curve of an active V = 11.7 G9V star observed by the CoRoT satellite,
which we interpret as due to the presence of a transiting companion. We
describe the 3-colour CoRoT data and complementary ground-based observations
that support the planetary nature of the companion. Methods. We use CoRoT color
information, good angular resolution ground-based photometric observations in-
and out- of transit, adaptive optics imaging, near-infrared spectroscopy and
preliminary results from Radial Velocity measurements, to test the diluted
eclipsing binary scenarios. The parameters of the host star are derived from
optical spectra, which were then combined with the CoRoT light curve to derive
parameters of the companion. We examine carefully all conceivable cases of
false positives, and all tests performed support the planetary hypothesis.
Blends with separation larger than 0.40 arcsec or triple systems are almost
excluded with a 8 10-4 risk left. We conclude that, as far as we have been
exhaustive, we have discovered a planetary companion, named CoRoT-7b, for which
we derive a period of 0.853 59 +/- 3 10-5 day and a radius of Rp = 1.68 +/-
0.09 REarth. Analysis of preliminary radial velocity data yields an upper limit
of 21 MEarth for the companion mass, supporting the finding.
CoRoT-7b is very likely the first Super-Earth with a measured radius.Comment: Accepted in Astronomy and Astrophysics; typos and language
corrections; version sent to the printer w few upgrade
- …