2,445 research outputs found
Heavy flavours in AA collisions: production, transport and final spectra
A multi-step setup for heavy-flavour studies in high-energy nucleus-nucleus
(AA) collisions --- addressing within a comprehensive framework the initial
Q-Qbar production, the propagation in the hot medium until decoupling and the
final hadronization and decays --- is presented. The initial hard production of
Q-Qbar pairs is simulated using the POWHEG pQCD event generator, interfaced
with the PYTHIA parton shower. Outcomes of the calculations are compared to
experimental data in pp collisions and are used as a validated benchmark for
the study of medium effects. In the AA case, the propagation of the heavy
quarks in the medium is described in a framework provided by the relativistic
Langevin equation. For the latter, different choices of transport coefficients
are explored (either provided by a perturbative calculation or extracted from
lattice-QCD simulations) and the corresponding numerical results are compared
to experimental data from RHIC and the LHC. In particular, outcomes for the
nuclear modification factor R_AA and for the elliptic flow v_2 of D/B mesons,
heavy-flavour electrons and non-prompt J/\psi's are displayed.Comment: 16 pages, 21 figure
HEP Applications Evaluation of the EDG Testbed and Middleware
Workpackage 8 of the European Datagrid project was formed in January 2001
with representatives from the four LHC experiments, and with experiment
independent people from five of the six main EDG partners. In September 2002
WP8 was strengthened by the addition of effort from BaBar and D0. The original
mandate of WP8 was, following the definition of short- and long-term
requirements, to port experiment software to the EDG middleware and testbed
environment. A major additional activity has been testing the basic
functionality and performance of this environment. This paper reviews
experiences and evaluations in the areas of job submission, data management,
mass storage handling, information systems and monitoring. It also comments on
the problems of remote debugging, the portability of code, and scaling problems
with increasing numbers of jobs, sites and nodes. Reference is made to the
pioneeering work of Atlas and CMS in integrating the use of the EDG Testbed
into their data challenges. A forward look is made to essential software
developments within EDG and to the necessary cooperation between EDG and LCG
for the LCG prototype due in mid 2003.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
Conference (CHEP03), La Jolla, CA, USA, March 2003, 7 pages. PSN THCT00
Drug release mechanisms of chemically cross-linked albumin microparticles: effect of the matrix erosion
Albumin (BSA) microparticles were developed as a biotechnological alternative for drug delivery. Vitamin B12 (Vit-B12) was used as a model drug. The microparticles were obtained from maleic anhydride-functionalized BSA and N′,N′-dimethylacrylamide (DMAAm) in a W/O emulsion without and with PVA. The microparticles produced at 15 min of stirring without PVA showed the best results in terms of size, homogeneity, and sphericity. In such a case, BSA played a role as a surface active agent, replacing PVA. For longer stirring times, BSA was unable to act as an emulsifier.
These microparticles showed an uncommon release profile, consisting of a two-step release mechanism, at the pH range studied. Considering that a two-step release mechanism is occurring, the experimental data were adjusted by applying modified power law and Weibull equations in order to describe release mechanism n and release rate constant k, respectively. Each one of the release stages was related to a specific value of n and k. The second stage was driven by a super case II transport mechanism, as a result of diffusion, macromolecular relaxation, and erosion. A third model, described by Hixson–Crowell, confirmed the erosion mechanism.
Vit-B12 diffusion kinetics in aqueous solutions (i.e., without the microparticles) follows a one-step process, being k dependent on the pH, confirming that the two-step release mechanism is a characteristic profile of the developed microparticles. The microparticles released only 2.70% of their initial drug load at pH 2, and 58.53% at pH 10
Optimasi Sistem Keamanan Transfer Data dengan Mengaplikasikan Konsep Terhubung Pelangi pada Graf
Pada era digital saat ini, inovasi teknologi berkembang semakin pesat. Hal ini seiring dengan tujuan manusia untuk mencapai Sustainable Development Goals (SDGs). Salah satu komponen pendukung berbasis teknologi yang diperlukan dalam pencapaian SDGs tersebut adalah sistem komunikasi publik secara digital, yang selanjutnya disebut sistem komunikasi digital. Dalam hal ini, sistem transfer data merupakan salah satu bentuk sistem komunikasi digital yang sering digunakan oleh masyarakat. Dapat dilihat dengan jelas, cakupan sistem komunikasi digital sangat luas, masif, dan terbuka. Oleh karena itu, keamanan pada sistem transfer data merupakan hal yang sangat penting dalam sistem komunikasi digital saat ini. Untuk menjaga keamanan data yang ditransfer, pengirim data akan menggunakan sandi (password) pada data tersebut. Namun untuk mengantisipasi bocornya sandi tersebut, maka pengirim data perlu memasang sandi secara berlapis. Banyaknya lapisan sandi pada data tersebut dapat ditentukan dengan konsep terhubung pelangi pada graf. Konsep ini dikembangkan oleh Chartrand dkk. pada tahun 2008 untuk mengatasi kelemahan dalam pengamanan pengiriman informasi antar agen rahasia Amerika Serikat. Artikel ini merupakan hasil studi literatur. Untuk memudahkan pemahaman, pembahasan dalam artikel ini dimulai dengan pemaparan tentang terminologi graf dan konsep terhubung pelangi pada graf. Selanjutnya, dalam artikel dibahas tentang bilangan terhubung pelangi dari beberapa kelas graf dan hasil operasi graf yang merepresentasikan kompleksitas sistem jaringan komunikasi
Concentração de nutrientes minerais em acessos da Etiópia de Coffea arabica.
O sucesso do manejo nutricional em plantas depende de diversos fatores, como características químicas, biológicas e físicas do solo, além da influência do genótipo. Apesar do manejo agronômico visando à adequação do solo para a cultura do cafeeiro estar bem estabelecido, pouco se sabe sobre o efeito do genótipo na absorção e acúmulo de nutrientes minerais. Tradicionalmente, o melhoramento genético do cafeeiro foca-se em características morfológicas, resistência a doenças e na produtividade; dessa forma, a exigência nutricional foi deixada em plano secundário ao longo deste processo. Com a necessidade cada vez maior de variedades que apresentem boa produtividade com impactos menores ao meio ambiente, a introgressão de características de genótipos silvestres é uma relevante estratégia para incremento da eficiência nutricional. Neste contexto, o presente trabalho tem como objetivo caracterizar a concentração de nutrientes em 12 acessos silvestres de Coffea arabica provenientes da Etiópia, identificando genótipos de cafeeiro que apresentam acumulação diferencial de nutrientes minerais (N, P, K, Ca, Mg, Cu, Zn, B e Mn) com relação a três tecidos: folhas, caule e raiz. Entre os acessos da Etiópia, destacou-se a concentração diferencial de P em folhas do acesso CAF032, e o acúmulo em raiz de N (CAF009), Zn (CAF131) e Mn (CAF023). Bourbon teve acúmulo diferencialmente menor de P no caule e maior de Ca na raiz e Catuaí Vermelho apresentou concentração diferencial de Mg no caule. O presente trabalho é uma importante contribuição na definição de genótipos silvestres de Coffea arabica com potencial de introgressão de características relacionadas à eficiência nutricional
A new measurement of J/psi suppression in Pb-Pb collisions at 158 GeV per nucleon
We present a new measurement of J/psi production in Pb-Pb collisions at 158
GeV/nucleon, from the data sample collected in year 2000 by the NA50
Collaboration, under improved experimental conditions with respect to previous
years. With the target system placed in vacuum, the setup was better adapted to
study, in particular, the most peripheral nuclear collisions with unprecedented
accuracy. The analysis of this data sample shows that the (J/psi)/Drell-Yan
cross-sections ratio measured in the most peripheral Pb-Pb interactions is in
good agreement with the nuclear absorption pattern extrapolated from the
studies of proton-nucleus collisions. Furthermore, this new measurement
confirms our previous observation that the (J/psi)/Drell-Yan cross-sections
ratio departs from the normal nuclear absorption pattern for semi-central Pb-Pb
collisions and that this ratio persistently decreases up to the most central
collisions.Comment: 19 pages, 10 figures. Submitted to Eur. Phys. J.
J/psi azimuthal anisotropy relative to the reaction plane in Pb-Pb collisions at 158 GeV per nucleon
The J/ azimuthal distribution relative to the reaction plane has been
measured by the NA50 experiment in Pb-Pb collisions at 158 GeV/nucleon. Various
physical mechanisms related to charmonium dissociation in the medium created in
the heavy ion collision are expected to introduce an anisotropy in the
azimuthal distribution of the observed J/ mesons at SPS energies. Hence,
the measurement of J/ elliptic anisotropy, quantified by the Fourier
coefficient v of the J/ azimuthal distribution relative to the
reaction plane, is an important tool to constrain theoretical models aimed at
explaining the anomalous J/ suppression observed in Pb-Pb collisions. We
present the measured J/ yields in different bins of azimuthal angle
relative to the reaction plane, as well as the resulting values of the Fourier
coefficient v as a function of the collision centrality and of the
J/ transverse momentum. The reaction plane has been estimated from the
azimuthal distribution of the neutral transverse energy detected in an
electromagnetic calorimeter. The analysis has been performed on a data sample
of about 100 000 events, distributed in five centrality or p
sub-samples. The extracted v values are significantly larger than zero
for non-central collisions and are seen to increase with p.Comment: proceedings of HP08 conference corrected a typo in one equatio
The dependence of the anomalous J/psi suppression on the number of participant nucleons
The observation of an anomalous J/psi suppression in Pb-Pb collisions by the NA50 Collaboration can be considered as the most striking indication for the deconfinement of quarks and gluons at SPS energies. In this Letter, we determine the J/psi suppression pattern as a function of the forward hadronic energy E-ZDC measured in a Zero Degree Calorimeter (ZDC). The direct connection between EZDC and the geometry of the collision allows us to calculate, within a Glauber approach, the precise relation between the number of participant nucleons N-part and E-ZDC. Then, we check if the experimental data can be better explained by a sudden or a smooth onset of the anomalous J/psi suppression as a function of the number of participants. (C) 2001 Elsevier Science B.V. All rights reserved.info:eu-repo/semantics/publishedVersio
INFN What Next: Ultra-relativistic Heavy-Ion Collisions
This document was prepared by the community that is active in Italy, within
INFN (Istituto Nazionale di Fisica Nucleare), in the field of
ultra-relativistic heavy-ion collisions. The experimental study of the phase
diagram of strongly-interacting matter and of the Quark-Gluon Plasma (QGP)
deconfined state will proceed, in the next 10-15 years, along two directions:
the high-energy regime at RHIC and at the LHC, and the low-energy regime at
FAIR, NICA, SPS and RHIC. The Italian community is strongly involved in the
present and future programme of the ALICE experiment, the upgrade of which will
open, in the 2020s, a new phase of high-precision characterisation of the QGP
properties at the LHC. As a complement of this main activity, there is a
growing interest in a possible future experiment at the SPS, which would target
the search for the onset of deconfinement using dimuon measurements. On a
longer timescale, the community looks with interest at the ongoing studies and
discussions on a possible fixed-target programme using the LHC ion beams and on
the Future Circular Collider.Comment: 99 pages, 56 figure
Final results of magnetic monopole searches with the MACRO experiment
We present the final results obtained by the MACRO experiment in the search
for GUT magnetic monopoles in the penetrating cosmic radiation, for the range
. Several searches with all the MACRO sub-detectors
(i.e. scintillation counters, limited streamer tubes and nuclear track
detectors) were performed, both in stand alone and combined ways. No candidates
were detected and a 90% Confidence Level (C.L.) upper limit to the local
magnetic monopole flux was set at the level of cm
s sr. This result is the first experimental limit obtained in
direct searches which is well below the Parker bound in the whole range
in which GUT magnetic monopoles are expected.Comment: 12 pages, Latex, 9 figures and 2 Table
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