D meson nuclear modification factors in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV with the ALICE detector

The measurement of D meson production provides key tests for parton energy-loss models, which predict that charm quarks should experience less in-medium energy loss than light quarks and gluons. The ALICE experiment has measured the production of prompt D^(0), D^(+) and D^(*+) mesons in pp and Pb-Pb collisions at the LHC at sqrt(s) = 7 and 2.76 TeV and at sqrt(s_NN) = 2.76 TeV, respectively, via the exclusive reconstruction of their hadronic decay. The pT-differential production yields in the range 2 < pT < 16 GeV/c at central rapidity, |y| < 0.5, were used to calculate the nuclear modification factor. A suppression of a factor 3 to 4 for transverse momenta larger than 5 GeV/c in the 20% most central collisions was observed. Preliminary results in an extended pT-range, using the data sample collected during the 2011 Pb-Pb run, together with the first measurement of D^(+)_(s) nuclear modification factor will be shown

Tethering surface tension to organic synthesis: a quest for chemoselectivity

The development of chemoselective processes is of utmost importance for the future of synthetic organic chemistry and has been described as ‘one of the greatest obstacles to complex molecule synthesis.’ This dissertation was written with this main objective in mind, which was pursued from two perspectives. Development of surface-tension driven droplet devices towards parallel and chemoselective synthesis of substituted 2H-chromen-2-ones was at first investigated on a sub-millimolar scale (Chapters 1-3). Multi-droplet sorting devices were manufactured and key parameters such as droplet composition, substrate temperature and orientation were optimised. Test reactions in aqueous propylene glycol (PG) were conducted in batch conditions, affording 3,6-disubstituted coumarins references via Knoevenagel condensation of 5-substituted salicyladehydes with activated methylene compounds and acid-promoted intramolecular cyclisation. Reactivity transposition onto droplets was thoroughly investigated, leading to a three-pair reagent (3x3) chemical sorter. Product quantification method by 1H-NMR spectroscopy was successfully implemented in micro-liter sized droplets, proving how chemoselectivity can be achieved following such unconventional, synthetic methodology. The second project studied chemoselective formation of 2-alkenyl tertiary anilines and 1,1,2-trimethylindolinium hexafluorophosphates via charged aza-Claisen rearrangement and thermal cyclisation of quaternary N-allylated ammonium salts (Chapter 4-6). In the latter case, early attempts of the reaction were unsuccessful due to decomposition catalysed by the bromide anion, but a switch to a non-nucleophilic anion (PF6-) allowed the ring closure to occur. Compound library synthesis was carried out to assess the synthetic methodology robustness. Key strengths and limitations were identified and ammonium substrate regiochemical effects were examined and discussed. Finally, interesting research avenues were suggested to broaden substrate scope studies and, most importantly, to link structural connectivity analysis of ammonium salts with modulation of their surface properties

Open charm hadron production via hadronic decays at STAR

Heavy quarks are a unique probe to study the medium produced in ultra-relativistic heavy ion collisions. The dominant process of charm quark production at RHIC is believed to be initial gluon fusion which can be calculated in the perturbative QCD. The upper limit of FONLL calculation seems to be in good agreement with charm cross section measurements at mid-rapidity in $p+p$ collisions at $\sqrt{s_{NN}}$ = 200 GeV provided by STAR. The same measurement in Au+Au collisions at equal energy reveals the number-of-binary-collisions scaling of charm cross section indicating that charm production is dominated by initial hard scatterings. In this article, we report the measurements of $D^{0}$, $D^{*}$ in $p+p$ at 0.6 GeV/$c < p_T < 6$ GeV/$c$ and $D^0$ in Au+Au collisions at 0.2 GeV/$c < p_T < 5$ GeV/$c$ via hadronic decays $D^{0}\rightarrow K^-\pi^+,\ D^{*+}\rightarrow D^0\pi^+\rightarrow K^-\pi^+\pi^+$ at mid-rapidity $|y|<1$. {abstract}Comment: 4 pages, 4 figures, Hard Probes 2012 proceeding

Heavy flavour production at LHC

The Large Hadron Collider (LHC) will open a new era in high energy physics. The expected large cross section for heavy flavour production in proton-proton collisions at $\sqrt{s}$ = 14 TeV will allow detailed studies of the production mechanisms and an extensive test of Quantum Chromodynamics. Since charm and beauty has been proposed as a good probe to study hot and dense QCD matter, the understanding of the production mechanisms in elementary proton-proton collisions is of primary importance as a reference for studies in heavy-ion collisions. In the early phase of LHC operation the experiments will focus on the investigation of the heavy flavour production mechanisms.Comment: 7 pages, 10 figures. Invited overview talk presented at the Europhysics Conference on High Energy Physics, Krakow, Poland, 16-22 July 2009. Proceedings to be published in Proceedings of Scienc

Laugier-Hunziker Syndrome: An Uncommon Cause of Oral Pigmentation and a Review of the Literature

Laugier-Hunziker syndrome is a rare benign condition characterized by diffuse oral hyperpigmentation associated with pigmentation of the nails. The syndrome must be included in the differential diagnosis of diffuse oral pigmentation to exclude other conditions with systemic implications. We describe a 43-year-old white woman with the clinical and histological features of Laugier-Hunziker syndrome associated with toenail pigmentation. The correct clinical identification avoids the need for detailed investigations and treatment. We also review the potential causes of oral pigmentation

Physics with the ALICE experiment

ALICE experiment at LHC collects data in pp collisions at $\sqrt{s}$=0.9, 2.76 and 7 TeV and in PbPb collisions at 2.76 TeV. Highlights of the detector performance and an overview of experimental results measured with ALICE in pp and AA collisions are presented in this paper. Physics with proton-proton collisions is focused on hadron spectroscopy at low and moderate $p_T$. Measurements with lead-lead collisions are shown in comparison with those in pp collisions, and the properties of hot quark matter are discussed.Comment: Presented at the Conference of the Nuclear Physics Division of the Russian Academy of Science, 11-25.11.2011, ITEP, Moscow. 16 pages, 14 figure

Model and parameter dependence of heavy quark energy loss in a hot and dense medium

Within the framework of the Langevin equation, we study the energy loss of heavy quark due to quasi-elastic multiple scatterings in a quark-gluon plasma created by relativistic heavy-ion collisions. We investigate how the initial configuration of the quark-gluon plasma as well as its properties affect the final state spectra and elliptic flow of D meson and non-photonic electron. We find that both the geometric anisotropy of the initial quark-gluon plasma and the flow profiles of the hydrodynamic medium play important roles in the heavy quark energy loss process and the development of elliptic flow. The relative contribution from charm and bottom quarks is found to affect the transverse momentum dependence of the quenching and flow patterns of heavy flavor decay electron; such influence depends on the interaction strength between heavy quark and the medium.Comment: 16 pages, 7 figure

Rapid System to Detect Variants of SARS-CoV-2 in Nasopharyngeal Swabs

Currently, the reference method for identifying the presence of variants of SARS-CoV-2 is whole genome sequencing. Although it is less expensive than in the past, it is still time-consuming, and interpreting the results is difficult, requiring staff with specific skills who are not always available in diagnostic laboratories. The test presented in this study aimed to detect, using traditional real-time PCR, the presence of the main variants described for the spike protein of the SARS-CoV-2 genome. The primers and probes were designed to detect the main deletions that characterize the different variants. The amplification targets were deletions in the S gene: 25-27, 69-70, 241-243, and 157-158. In the ORF1a gene, the deletion 3675-3677 was chosen. Some of these mutations can be considered specific variants, while others can be identified by the simultaneous presence of one or more deletions. We avoided using point mutations in order to improve the speed of the test. Our test can help clinical and medical microbiologists quickly recognize the presence of variants in biological samples (particularly nasopharyngeal swabs). The test can also be used to identify variants of the virus that could potentially be more diffusive as well as not responsive to the vaccine

SARS-CoV-2 infection serology: a useful tool to overcome lockdown?

The outbreak of 2019 novel coronavirus disease (Covid-19) caused by SARS-CoV-2 has spread rapidly, inducing a progressive growth in infected patients number. Social isolation (lockdown) has been assessed to prevent and control virus diffusion, leading to a worldwide financial and political crisis. Currently, SARS-CoV-2 RNA detection in nasopharyngeal swab takes place by real-time PCR (RT-qPCR). However, molecular tests can give some false-negative results. In this context, serological assays can be useful to detect IgG/IgM antibodies, to assess the degree of immunization, to trace the contacts, and to support the decision to re-admit people at work. A lot of serological diagnostic kits have been proposed on the market but validation studies have not been published for many of them. The aim of our work was to compare and to evaluate different assays analytical performances (two different immunochromatographic cards, an immunofluorescence chromatographic card, and a chemiluminescence-automated immunoassay) on 43 positive samples with RT-qPCR-confirmed SARS-CoV-2 infection and 40 negative control subjects. Our data display excellent IgG/IgM specificities for all the immunocromatographic card tests (100% IgG and 100% IgM) and for the chemiluminescence-automated assay (100% IgG and 94% IgM); IgG/IgM sensitivities are moderately lower for all methods, probably due to the assay viral antigen's nature and/or to the detection time of nasopharyngeal swab RT-qPCR, with respect to symptoms onset. Given that sensitivities (around 94% and 84% for IgG and IgM, respectively) implicate false-negative cases and given the lack of effective vaccines or treatments, the only currently available procedure to reduce SARS-CoV-2 transmission is to identify and isolate persons who are contagious. For this reason, we would like to submit a flowchart in which serological tests, integrated with nasopharyngeal swab RT-qPCR, are included to help social and work activities implementation after the pandemic acute phase and to overcome lockdown

Jet-like correlations of heavy-flavor particles - from RHIC to LHC

Measurements at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory have revealed strong modification of the jet structure in high-energy heavy-ion collisions, which can be attributed to the interaction of hard scattered partons with the hot and dense QCD matter. The study of heavy-quark (charm and bottom) production in such collisions provides key tests of parton energy-loss models and, thus, yields profound insight into the properties of the produced matter. The high-pT yield of heavy-flavor decay electrons exhibits an unexpected large suppression. Since those single electrons have contributions from charm and bottom decays an experimental method is needed to investigate them separately. Heavy-flavor particle correlations provide information about the underlying production mechanism. In this contribution, a review on recent measurements on azimuthal correlations of single electrons and open charmed mesons at RHIC and perspectives of such measurements at the CERN-Large Hadron Collider (LHC) are presented. Moreover, it has been shown that next-to-leading-order (NLO) QCD processes, such as gluon splitting, become important at LHC energies. It will be demonstrated how this contribution can be determined through the measurement of the charm content in jets.Comment: 8 pages, 6 figures, Proceedings of the 27th Winter Workshop on Nuclear Dynamics, Winter Park, Colorado, USA. To be published in Journal of Physics: Conference Series (JPCS