615 research outputs found
Statistical hadronization of charmed quarks at SPS and RHIC
Production of open and hidden charm hadrons in heavy ion collisions is
considered within the statistical coalescence model. The charmed
quark-antiquark pairs are assumed to be created at the initial stage of the
reaction in hard parton collisions. The number of these pairs is conserved
during the evolution of the system. At the hadronization stage, the charmed
(anti)quarks are distributed among open and hidden charm hadrons in accordance
with the laws of statistical mechanics.
The model is in agreement with the experimental data on J/psi to Drell-Yan
ratio in Pb+Pb collisions at SPS. This agreement can be reached only if a
rather strong enhancement of the open charm production in central Pb+Pb
collisions is assumed. A possible mechanism of the charm enhancement is
discussed.
At the top RHIC energy, the model predicts an increase of J/psi to Drell-Yan
ratio in more central nucleus-nucleus collisions with respect to less central
ones.Comment: Presented at 16th International Conference "Quark Matter", Nantes
(France), July 18-24, 2002; 4 pages, LaTeX, 2 PS-figure
Heavy Flavor Enhancement as a Signal of Color Deconfinement
We argue that the color deconfinement in heavy ion collisions may lead to
enhanced production of hadrons with open heavy flavor (charm or bottom). We
estimate the upper bound of this enhancement.Comment: 7 pages, LaTeX, 3 PS-figure
Statistical Coalescence Model with Exact Charm Conservation
The statistical coalescence model for the production of open and hidden charm
is considered within the canonical ensemble formulation. The data for the J/psi
multiplicity in Pb+Pb collisions at 158 A GeV are used for the model prediction
of the open charm yield which has not yet been measured in these reactions.Comment: 7 pages, Late
Dual embedding of the Lorentz-violating electrodinamics and Batalin-Vilkovisky quantization
Modifications of the electromagnetic Maxwell Lagrangian in four dimensions
have been considered by some authors. One may include an explicit massive term
(Proca) and a topological but not Lorentz-invariant term within certain
observational limits.
We find the dual-corresponding gauge invariant version of this theory by
using the recently suggested gauge embedding method. We enforce this
dualisation procedure by showing that, in many cases, this is actually a
constructive method to find a sort of parent action, which manifestly
establishes duality. We also use the gauge invariant version of this theory to
formulate a Batalin-Vilkovisky quantization and present a detailed discussion
on the excitation spectrum.Comment: 8 page
FGFR1 and PROKR2 rare variants found in patients with combined pituitary hormone deficiencies.
The genetic aetiology of congenital hypopituitarism (CH) is not entirely elucidated. FGFR1 and PROKR2 loss-of-function mutations are classically involved in hypogonadotrophic hypogonadism (HH), however, due to the clinical and genetic overlap of HH and CH; these genes may also be involved in the pathogenesis of CH. Using a candidate gene approach, we screened 156 Brazilian patients with combined pituitary hormone deficiencies (CPHD) for loss-of-function mutations in FGFR1 and PROKR2. We identified three FGFR1 variants (p.Arg448Trp, p.Ser107Leu and p.Pro772Ser) in four unrelated patients (two males) and two PROKR2 variants (p.Arg85Cys and p.Arg248Glu) in two unrelated female patients. Five of the six patients harbouring the variants had a first-degree relative that was an unaffected carrier of it. Results of functional studies indicated that the new FGFR1 variant p.Arg448Trp is a loss-of-function variant, while p.Ser107Leu and p.Pro772Ser present signalling activity similar to the wild-type form. Regarding PROKR2 variants, results from previous functional studies indicated that p.Arg85Cys moderately compromises receptor signalling through both MAPK and Ca(2) (+) pathways while p.Arg248Glu decreases calcium mobilization but has normal MAPK activity. The presence of loss-of-function variants of FGFR1 and PROKR2 in our patients with CPHD is indicative of an adjuvant and/or modifier effect of these rare variants on the phenotype. The presence of the same variants in unaffected relatives implies that they cannot solely cause the phenotype. Other associated genetic and/or environmental modifiers may play a role in the aetiology of this condition
Open charm and charmonium production at relativistic energies
We calculate open charm and charmonium production in reactions at
= 200 GeV within the hadron-string dynamics (HSD) transport approach
employing open charm cross sections from and reactions that are
fitted to results from PYTHIA and scaled in magnitude to the available
experimental data. Charmonium dissociation with nucleons and formed mesons to
open charm ( pairs) is included dynamically. The 'comover'
dissociation cross sections are described by a simple phase-space model
including a single free parameter, i.e. an interaction strength , that
is fitted to the suppression data for collisions at SPS
energies. As a novel feature we implement the backward channels for charmonium
reproduction by channels employing detailed balance. From our
dynamical calculations we find that the charmonium recreation is comparable to
the dissociation by 'comoving' mesons. This leads to the final result that the
total suppression at = 200 GeV as a function of centrality
is slightly less than the suppression seen at SPS energies by the NA50
Collaboration, where the 'comover' dissociation is substantial and the backward
channels play no role. Furthermore, even in case that all directly produced
mesons dissociate immediately (or are not formed as a mesonic state),
a sizeable amount of charmonia is found asymptotically due to the + meson channels in central collisions of at =
200 GeV which, however, is lower than the yield expected from binary
scaling of collisions.Comment: 42 pages, including 14 eps figures, discussions extended and
references added, to be published in Phys. Rev.
Apoptosis induction by Pleurotus sajor-caju (Fr.) Singer extracts on colorectal cancer cell lines
Pleurotus sajor-caju (PSC) is an edible mushroom used in food supplements, presenting antitumor properties
through induction of cell death pathways. The PSC potential against colorectal cancer was analyzed by exposing
HCT116wt cells to different PSC extracts. The PSC n-hexane extract (PSC-hex) showed the highest cytotoxicity
effect (IC50 value 0.05 mg/mL). The observed cytotoxicity was then associated to apoptosis-promoting and cell
cycle-arrest pathways. PSC-hex was able to induce apoptosis related to breakdown of mitochondrial membrane
potential and ROS generation. The absence of cytotoxicity in HTC116-p53 and HTC116-Bax cells, alongside with
an increase in p53, Bax and Caspase-3 expression, and decrease in Bcl-2 expression, supports that the proapoptotic
effect is probably induced through a p53 associated pathway. PSC-hex induced cell cycle arrest at G2/
M in HCT116wt without cytotoxicity in HTC116-p21 cells. These findings suggest that a p21/p53 cell cycle regulation
pathway is probably disrupted by compounds present on PSC-hex. Identification of the major components
was then performed with ergosta-5,7,22-trien-3β-ol representing 30.6% of total weight. In silico docking
studies of ergosta-5,7,22-trien-3β against Bcl-2 were performed and results show a credible interaction with the
Bcl-2 hydrophobic cleft. The results show that PSC-hex can be used as supplementary food for adjuvant therapy
in colorectal carcinoma.The authors thank Dr. Larsen (Institut National de la Santé et de la
Recherche Médicale) for the gift of HCT116-Bax, HCT116-p21 and
HCT116-p53 cells. The authors are grateful to the Foundation for Science
and Technology (FCT, Portugal) and FEDER under Programme PT2020
for financial support to CIMO (UID/AGR/00690/2013) and L. Barros
contract. T.C. Finimundy thanks CAPES Foundation, Ministry of
Education of Brazil (CAPES fellow, process number 88881.134581/
2016–01). This work is supported by a grant from Coordenação de
Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Fundaçãoinfo:eu-repo/semantics/publishedVersio
Multifunctions of Pleurotus sajor-caju (Fr.) Singer: a highly nutritious food and a source for bioactive compounds
A study with Pleurotus sajor-caju was conducted to: evaluate the nutritional and chemical composition of the fruiting bodies; optimize the preparation of bioactive phenolic extracts; and characterize the optimized extract in terms of bioactive compounds and properties. P. sajor-caju revealed an equilibrated nutritional composition with the presence of hydrophilic (sugars and organic acids) and lipophilic (tocopherols and PUFA) compounds. p-Hydroxybenzoic, p-coumaric and cinnamic acids were identified in the extract obtained with ethanol (30 g/l ratio) at 55 °C for 85 min. This extract showed antioxidant properties (mainly reducing power and lipid peroxidation inhibition), antibacterial activity against MRSA and MSSA and cytotoxicity against NCI-H460, MCF-7 and HeLa. Furthermore, as the extract showed capacity to inhibit NO production in Raw 264.7 macrophages, molecular docking studies were performed to provide insights into the anti-inflammatory mechanism of action, through COX-2 inhibition by the phenolic acids identified.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and FEDER under Program PT2020 for financial support to CIMO (UID/AGR/00690/2013) and for L. Barros and R. Calhelha contracts. T.C. Finimundy thanks CAPES Foundation, Ministry of Education of Brazil (CAPES fellow, process number 88881.134581/2016-01). To Xunta de Galicia for financial support for the post-doctoral researcher of M.A. Prieto.info:eu-repo/semantics/publishedVersio
The reaction in ion-ion collisions
We study the threshold -meson production in the process , which appears as a possible important mechanism in high energy
nuclei-nuclei collisions. The isotopic invariance of the strong interaction and
the selection rules due to P-parity and total angular momentum result in a
general and model independent parametrization of the spin structure of the
matrix element in terms of three partial amplitudes. In the framework of
one-pion exchange model these amplitudes can be derived in terms of the two
threshold partial amplitudes for the process . We predict the
ratio of cross sections for meson production in - and -collisions and the polarization properties of the -meson, in
, as a function of a single parameter, which
characterizes the relative role of transversal and longitudinal -meson
polarizations in the process .Comment: 10 pages 3 figure
Charmonium from Statistical Hadronization of Heavy Quarks -- a Probe for Deconfinement in the Quark-Gluon Plasma
We review the statistical hadronization picture for charmonium production in
ultra-relativistic nuclear collisions. Our starting point is a brief reminder
of the status of the thermal model description of hadron production at high
energy. Within this framework an excellent account is achieved of all data for
hadrons built of (u,d,s) valence quarks using temperature, baryo-chemical
potential and volume as thermal parameters. The large charm quark mass brings
in a new (non-thermal) scale which is explicitely taken into account by fixing
the total number of charm quarks produced in the collision. Emphasis is placed
on the description of the physical basis for the resulting statistical
hadronization model. We discuss the evidence for statistical hadronization of
charmonia by analysis of recent data from the SPS and RHIC accelerators.
Furthermore we discuss an extension of this model towards lower beam energies
and develop arguments about the prospects to observe medium modifications of
open and hidden charm hadrons. With the imminent start of the LHC accelerator
at CERN, exciting prospects for charmonium production studies at the very high
energy frontier come into reach. We present arguments that, at such energies,
charmonium production becomes a fingerprint of deconfinement: even if no
charmonia survive in the quark-gluon plasma, statistical hadronization at the
QCD phase boundary of the many tens of charm quarks expected in a single
central Pb-Pb collision could lead to an enhanced, rather than suppressed
production probability when compared to results for nucleon-nucleon reactions
scaled by the number of hard collisions in the Pb-Pb system.Comment: review article, 27 pages, Landoldt review volume "Relativistic Heavy
Ion Physics", Reinhard Stock, edito
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