110 research outputs found
Dual-stage triterpenoids from an African medicinal plant targeting the malaria parasite
Sixteen triterpenoids (1–16), previously isolated from the aerial parts of the African medicinal plant
Momordica balsamina or obtained by derivatization, were evaluated for their activity against liver stages
of Plasmodium berghei, measuring the luminescence intensity in Huh-7 cells infected with a firefly lucif erase-expressing P. berghei line, PbGFP-Luccon. Toxicity of compounds (1–16) was assessed on the same
cell line through the fluorescence measurement of cell confluency. The highest activity was displayed
by a derivative bearing two acetyl residues, karavoate B (7), which led to a dose-dependent decrease
in the P. berghei infection rate, exhibiting a very significant activity at the lowest concentration employed
(1 lM) and no toxicity towards the Huh-7 cells. It is noteworthy that, in previous studies, this compound
was found to be a strong inhibitor of blood-stages of Plasmodium falciparum, thus displaying a dual-stage
antimalarial activity.info:eu-repo/semantics/publishedVersio
Supramolecular Amino Acid Based Hydrogels: Probing the Contribution of Additive Molecules using NMR Spectroscopy
Supramolecular hydrogels are composed of self-assembled solid networks that restrict the flow of water. l-Phenylalanine is the smallest molecule reported to date to form gel networks in water, and it is of particular interest due to its crystalline gel state. Single and multi-component hydrogels of l-phenylalanine are used herein as model materials to develop an NMR-based analytical approach to gain insight into the mechanisms of supramolecular gelation. Structure and composition of the gel fibres were probed using PXRD, solid-state NMR experiments and microscopic techniques. Solution-state NMR studies probed the properties of free gelator molecules in an equilibrium with bound molecules. The dynamics of exchange at the gel/solution interfaces was investigated further using high-resolution magic angle spinning (HR-MAS) and saturation transfer difference (STD) NMR experiments. This approach allowed the identification of which additive molecules contributed in modifying the material properties
Study of dimuon production in Indium-Indium collisions with the NA60 experiment
The NA60 experiment at the CERN-SPS is devoted to the study of dimuon
production in heavy-ion and proton-nucleus collisions. We present preliminary
results from the analysis of Indium-Indium collisions at 158 GeV per nucleon.
The topics covered are low mass vector meson production, J/psi production and
suppression, and the feasibility of the open charm measurement from the dimuon
continuum in the mass range below the J/psi peak.Comment: Contribution at XXXXth Rencontres de Moriond, "QCD and High Energy
Hadronic Interactions
Halogen effects on the solid-state packing of phenylalanine derivatives and the resultant gelation properties
Phenylalanine is an important amino acid both biologically, essential to human health, and industrially, as a building block of artificial sweeteners. Our interest in this particular amino acid and its derivatives lies with its ability to form gels in a number of solvents. We present here the studies of the influence of halogen addition to the aromatic ring on the gelation properties and we analyse the crystal structures of a number of these materials to elucidate the trends in their behaviour based on the halogen addition to the aromatic group and the interactions that result
Evidence for radial flow of thermal dileptons in high-energy nuclear collisions
The NA60 experiment at the CERN SPS has studied low-mass dimuon production in
158 AGeV In-In collisions. An excess of pairs above the known meson decays has
been reported before. We now present precision results on the associated
transverse momentum spectra. The slope parameter Teff extracted from the
spectra rises with dimuon mass up to the rho, followed by a sudden decline
above. While the initial rise is consistent with the expectations for radial
flow of a hadronic decay source, the decline signals a transition to an
emission source with much smaller flow. This may well represent the first
direct evidence for thermal radiation of partonic origin in nuclear collisions.Comment: Accepted for publication in Physical Review Letter
Meson Production in In-In Collisions and the Puzzle
The NA60 experiment measured dimuon production in In-In collisions at 158
AGeV. This paper presents a high statistics measurement of with
the specific objective to provide insight on the puzzle, i.e. the
difference in the inverse slopes and absolute yields measured by NA49 and
NA50 in the kaon and lepton channel, respectively. Transverse momentum
distributions were studied as a function of centrality. The slope parameter
shows a rapid increase with centrality, followed by a saturation. Variations of
with the fit range of the order of 15 MeV were observed, possibly as a
consequence of radial flow. The meson yield normalized to the number of
participants increases with centrality and is consistently higher than the
yield measured by the NA49 experiment at any centrality.Comment: 4 Pages, 2 Figures. Proceedings of the 20 International
Conference on Ultra-Relativistic Nucleus Nucleus Collision
Photoproduction at collider energies: from RHIC and HERA to the LHC
We present the mini-proceedings of the workshop on ``Photoproduction at
collider energies: from RHIC and HERA to the LHC'' held at the European Centre
for Theoretical Studies in Nuclear Physics and Related Areas (ECT*, Trento)
from January 15 to 19, 2007. The workshop gathered both theorists and
experimentalists to discuss the current status of investigations of high-energy
photon-induced processes at different colliders (HERA, RHIC, and Tevatron) as
well as preparations for extension of these studies at the LHC. The main
physics topics covered were: (i) small- QCD in photoproduction studies with
protons and in electromagnetic (aka. ultraperipheral) nucleus-nucleus
collisions, (ii) hard diffraction physics at hadron colliders, and (iii)
photon-photon collisions at very high energies: electroweak and beyond the
Standard Model processes. These mini-proceedings consist of an introduction and
short summaries of the talks presented at the meeting
Low Mass Dimuon Production in Indium-Indium Collisions at the CERN SPS
NA60 is a fixed-target experiment at the CERN SPS which measured dimuon
production in nucleus-nucleus and proton-nucleus collisions. In this paper we
report on a precision measurement of low-mass muon pairs in 158 AGeV
indium-indium collisions. A significant excess of pairs is observed above the
yield expected from neutral meson decays. The excess can be isolated by
subtraction of expected sources, thanks to the excellent mass resolution and
large sample size.Comment: 4 pages, 3 figures, Contribution at XLIst Rencontres de Moriond, "QCD
and High Energy Hadronic Interactions
First Measurement of the rho Spectral Function in High-Energy Nuclear Collisions
We report on a precision measurement of low-mass muon pairs in 158 AGeV
indium-indium collisions at the CERN SPS. A significant excess of pairs is
observed above the yield expected from neutral meson decays. The unprecedented
sample size of 360 000 dimuons and the good mass resolution of about 2% allow
us to isolate the excess by subtraction of the decay sources. The shape of the
resulting mass spectrum is consistent with a dominant contribution from
pi+pi-->rho-->mu+mu- annihilation. The associated space-time averaged rho
spectral function shows a strong broadening, but essentially no shift in mass.
This may rule out theoretical models linking hadron masse
Thermal dileptons at SPS energies
Clear signs of excess dileptons above the known sources were found at the SPS
since long. However, a real clarification of these observations was only
recently achieved by NA60, measuring dimuons with unprecedented precision in
158A GeV, In-In collisions. The excess mass spectrum in the region M<1 GeV is
consistent with a dominant contribution from pi+pi- -> rho -> mu+mu-
annihilation. The associated rho spectral function shows a strong broadening,
but essentially no shift in mass. In the region M>1 GeV, the excess is found to
be prompt, not due to enhanced charm production. The inverse slope parameter
Teff associated with the transverse momentum spectra rises with mass up to the
rho, followed by a sudden decline above. While the initial rise, coupled to a
hierarchy in hadron freeze-out, points to radial flow of a hadronic decay
source, the decline above signals a transition to a low-flow source, presumably
of partonic origin. The mass spectra show at low transverse momenta the steep
rise towards low masses characteristic for Planck-like radiation. The
polarization of the excess referred to the Collins Soper frame is found to be
isotropic. All observations are consistent with the interpretation of the
excess as thermal radiation.Comment: Prepared for 20th International Conference on Ultra-Relativistic
Nucleus-Nucleus Collisions: Quark Matter 2008 (QM2008), Jaipur, India, 4-10
Feb. 200
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