16 research outputs found
Anarchy and Neutrino Physics
The neutrino sector of a seesaw-extended Standard Model is investigated under
the anarchy hypothesis. The previously derived probability density functions
for neutrino masses and mixings, which characterize the type I-III seesaw
ensemble of complex random matrices, are used to extract
information on the relevant physical parameters. For and , the
distributions of the light neutrino masses, as well as the mixing angles and
phases, are obtained using numerical integration methods. A systematic
comparison with the much simpler type II seesaw ensemble is also performed to
point out the fundamental differences between the two ensembles. It is found
that the type I-III seesaw ensemble is better suited to accommodate
experimental data. Moreover, the results indicate a strong preference for the
mass splitting associated to normal hierarchy. However, since all permutations
of the singular values are found to be equally probable for a particular mass
splitting, predictions regarding the hierarchy of the mass spectrum remains out
of reach in the framework of anarchy.Comment: 1+22 pages, 8 figures, typos fixed, added referenc
Phénoménologie des neutrinos dans une théorie de matrices aléatoires
Le mĂ©canisme permettant dâexpliquer lâorigine de la masse des neutrinos demeure, encore aujourdâhui, un mystĂšre complet dont la rĂ©solution est susceptible de modifier considĂ©rablement la structure du modĂšle standard en physique des particules Ă©lĂ©mentaires. Dans la littĂ©rature, plusieurs candidats potentiels sont donc proposĂ©s afin de combler cette lacune et, ainsi, faire la lumiĂšre sur certaines des propriĂ©tĂ©s les plus Ă©tranges des neutrinos. Parmi ceux-ci, les mĂ©canismes seesaw de type I, II et III constituent sans doute les approches les plus attrayantes et les plus Ă©tudiĂ©es. Cependant, bien que ces mĂ©canismes offrent un cadre de travail simple et Ă©lĂ©gant pour expliquer la faible masse des neutrinos (lâordre de grandeur), ceux-ci nâoffrent aucune prĂ©diction sur les paramĂštres fondamentaux caractĂ©risant le phĂ©nomĂšne dâoscillation, soit les angles de mĂ©lange, les phases complexes et la hiĂ©rarchie des masses. Afin dâobtenir des prĂ©dictions concrĂštes sur la phĂ©nomĂ©nologie des neutrinos, certaines hypothĂšses de travail supplĂ©mentaires doivent donc ĂȘtre formulĂ©es pour contraindre la structure des matrices de masse obtenue. Dans ce travail, lâhypothĂšse anarchique propre au secteur des neutrinos est adoptĂ©e. Les matrices de masse gĂ©nĂ©rĂ©es par les trois mĂ©canismes seesaw dans la limite des basses Ă©nergies sont traitĂ©es dans le contexte dâune thĂ©orie de matrices alĂ©atoires, ce qui permet de dĂ©finir et dâanalyser de nouveaux ensembles matriciels alĂ©atoires appelĂ©s ensembles seesaw. Un cadre thĂ©orique unifiĂ© est donc prĂ©sentĂ© pour la construction de ces ensembles. GrĂące au formalisme Ă©laborĂ©, qui repose sur les outils traditionnels relevant de la thĂ©orie des matrices alĂ©atoires, les densitĂ©s de probabilitĂ© jointes caractĂ©risant ces ensembles sont obtenues de façon analytique. Une Ă©tude dĂ©taillĂ©e de leurs propriĂ©tĂ©s est alors rĂ©alisĂ©e, ce qui permet dâextraire les tendances dominantes propres Ă ces mĂ©canismes de masse et dâanalyser leurs consĂ©quences pour le secteur des neutrinos du modĂšle standard Ă©tendu. En ce qui concerne le spectre de masse, les rĂ©sultats obtenus indiquent que les mĂ©canismes seesaw de type I et de type III sont plus adĂ©quats pour reproduire les observations expĂ©rimentales. De plus, une forte prĂ©fĂ©rence pour la diffĂ©rence de masses associĂ©e Ă la hiĂ©rarchie normale est observĂ©e. En contrepartie, il est Ă©galement dĂ©montrĂ© que pour une diffĂ©rence de masses donnĂ©e entre les trois gĂ©nĂ©rations, toutes les permutations des masses sont Ă©quiprobables, ce qui rend hors de portĂ©e toute prĂ©diction concernant la hiĂ©rarchie du spectre (normale ou inverse) sous lâhypothĂšse anarchique. En ce qui concerne les variables du groupe de symĂ©trie (les angles de mĂ©lange et les phases complexes), on constate, dâune part, que la notion de mĂ©lange quasi-maximal est naturellement favorisĂ©e et, dâautre part, que la matrice PMNS peut ĂȘtre dĂ©crite comme une matrice unitaire gĂ©nĂ©rique tirĂ©e au hasard dâun ensemble matriciel caractĂ©risĂ© par la mesure de Haar du groupe de Lie correspondant. Par ailleurs, il est Ă©galement dĂ©montrĂ© que ces conclusions sont indĂ©pendantes du mĂ©canisme de masse considĂ©rĂ©.The neutrino mass generation mechanism remains, to this day, a complete mystery which is likely to play an important role in understanding the foundations of the Standard Model of particle physics. In an effort to fill this gap and, ultimately, shed some light on some of the most intriguing properties of neutrinos, many theoretical models are proposed in the literature. Among the many candidates, the type I, type II and type III seesaw mechanisms may very well be the most attractive and the most studied propositions. However, despite the fact that these mechanisms provide a simple and elegant framework for explaining the smallness of neutrino masses (the order of magnitude), no prediction can be made on the fundamental parameters governing neutrino oscillations (the mixing angles, the CP-violating phases and the mass differences). Thus, to obtain concrete results regarding neutrino phenomenology, additional working assumptions must be made in order to constrain the structure of the corresponding mass matrices. In this work, the anarchy hypothesis relevant to the neutrino sector is investigated. The mass matrices generated by the three seesaw mechanisms in the low-energy limit are studied within the framework of random matrix theory, which leads to the development and the analysis of the seesaw ensembles. A unified and precise theoretical formalism, based on the usual tools of random matrix theory, is presented for the construction of these new random matrix ensembles. Using this formalism, the joint probability density functions characterizing these ensembles are obtained analytically, thus paving the way for a detailed study of their properties. This study is then carried out, revealing the underlying trends in these ensembles and, thereby, offering a thorough analysis of their consequences for the neutrino sector of the seesaw-extended Standard Model. Regarding the mass spectrum, it is found that the type I and type III seesaw mechanisms are better suited to accommodate experimental data. Moreover, the results indicate a strong preference for the mass splitting associated to normal hierarchy. However, since all permutations of the masses are found to be equally probable for a particular mass splitting between the three generations, predictions concerning the hierarchy of the mass spectrum (normal or inverted) remains out of reach in the framework of anarchy. Regarding the group variables (the mixing angles an CP-violating phases), it is found that near-maximal mixing is naturally favored by these ensembles and, that the PMNS matrix can be described as a generic unitary matrix drawn at random from a matrix ensemble characterized by the Haar measure of the corresponding Lie group. Furthermore, these conclusions are found to be independent of the mass mechanism considered
Paramétrisation du champ de pion dans une extension quasi-BPS du modÚle de Skyrme
Le modĂšle de Skyrme, dont la premiĂšre apparition remonte au milieu du 20iĂšme siĂšcle, est maintenant interprĂ©tĂ© comme une thĂ©orie efficace de la chromodynamique quantique dans la limite des basses Ă©nergies. Dans ce modĂšle, une description des noyaux atomiques les plus stables sâavĂšre possible Ă lâaide dâune structure solitonique qui possĂšde une charge topologique conservĂ©e. Ce prĂ©sent travail sâappuie sur une rĂ©cente extension du modĂšle de Skyrme original suggĂ©rĂ©e par Marleau et coll., câest-Ă -dire le modĂšle de Skyrme quasi-BPS, et propose lâĂ©tude de deux hypothĂšses de dĂ©part (ansatz) pour la paramĂ©trisation du champ mĂ©sonique. Les rĂ©sultats obtenus Ă partir de ces deux hypothĂšses de dĂ©part ont Ă©tĂ© comparĂ©s et analysĂ©s selon deux approches principales, la premiĂšre favorisant un dĂ©veloppement perturbatif des Ă©quations de champs (qui permet des solutions analytiques) et la seconde sâappuyant sur un algorithme de recuit simulĂ© pour obtenir des solutions numĂ©riques complĂštes du modĂšle au niveau classique
Probability Density Functions for CP-Violating Rephasing Invariants
The implications of the anarchy principle on CP violation in the lepton
sector are investigated. A systematic method is introduced to compute the
probability density functions for the CP-violating rephasing invariants of the
PMNS matrix from the Haar measure relevant to the anarchy principle. Contrary
to the CKM matrix which is hierarchical, it is shown that the Haar measure, and
hence the anarchy principle, are very likely to lead to the observed PMNS
matrix. Predictions on the CP-violating Dirac rephasing invariant and
Majorana rephasing invariant are also obtained. They correspond to
and
respectively, in
agreement with the experimental hint from T2K of
(or ) for the
normal (or inverted) hierarchy.Comment: 1+15 pages, 2 figure
Optimization of culture conditions for porcine corneal endothelial cells
Purpose : To optimize the growth condition of porcine corneal endothelial cells (PCEC), we evaluated the effect of coculturing with a feeder layer (irradiated 3T3 fibroblasts) with the addition of various exogenous factors, such as epidermal growth factor (EGF), nerve growth factor (NGF), bovine pituitary extract (BPE), ascorbic acid, and chondroitin sulfate, on cell proliferation, size, and morphology.
Methods : PCEC cultures were seeded at an initial cell density of 400 cells/cm2 in the presence or absence of 20,000 murine-irradiated 3T3 fibroblast/cm2 in the classic media Dulbecco's Modified Eagle's Medium (DMEM) supplemented with 20% fetal bovine serum (FBS). Mean cell size and bromodeoxyuridine incorporation was assessed at various passages. Growth-promoting factors were studies by seeding PCEC at 8,000 cells/cm2 in DMEM with 20% FBS or Opti-MEM I supplemented with 4% FBS and one of the following additives: EGF (0.5, 5, 25 ng/ml), NGF (5, 20, 50 ng/ml), BPE (25, 50, 100, 200 ÎŒg/ml), ascorbic acid (10, 20, 40 ÎŒg/ml) and chondroitin sulfate (0.03, 0.08, 1.6%), alone or in combination. Cell number, size and morphology of PCEC were assessed on different cell populations. Each experiment was repeated at least twice in three sets. In some cases, cell cultures were maintained after confluence to observe post-confluence changes in cell morphology.
Results : Co-cultures of PCEC grown in DMEM 20% FBS with a 3T3 feeder layer improved the preservation of small polygonal cell shape. EGF, NGF, and chondroitin sulfate did not induce proliferation above basal level nor did these additives help maintain a small size. However, chondroitin sulfate did help preserve a good morphology. BPE and ascorbic acid had dose-dependent effects on proliferation. The combination of BPE, chondroitin sulfate, and ascorbic acid significantly increased cell numbers above those achieved with serum alone. No noticeable changes were observed when PCEC were cocultured with a 3T3 feeder layer in the final selected medium.
Conclusions : Improvements have been made for the culture of PCEC. The final selected medium consistently allowed the growth of a contact-inhibited cell monolayer of small, polygonal-shaped cells
Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases
The production of peroxide and superoxide is an inevitable consequence of
aerobic metabolism, and while these particular "reactive oxygen species" (ROSs)
can exhibit a number of biological effects, they are not of themselves
excessively reactive and thus they are not especially damaging at physiological
concentrations. However, their reactions with poorly liganded iron species can
lead to the catalytic production of the very reactive and dangerous hydroxyl
radical, which is exceptionally damaging, and a major cause of chronic
inflammation. We review the considerable and wide-ranging evidence for the
involvement of this combination of (su)peroxide and poorly liganded iron in a
large number of physiological and indeed pathological processes and
inflammatory disorders, especially those involving the progressive degradation
of cellular and organismal performance. These diseases share a great many
similarities and thus might be considered to have a common cause (i.e.
iron-catalysed free radical and especially hydroxyl radical generation). The
studies reviewed include those focused on a series of cardiovascular, metabolic
and neurological diseases, where iron can be found at the sites of plaques and
lesions, as well as studies showing the significance of iron to aging and
longevity. The effective chelation of iron by natural or synthetic ligands is
thus of major physiological (and potentially therapeutic) importance. As
systems properties, we need to recognise that physiological observables have
multiple molecular causes, and studying them in isolation leads to inconsistent
patterns of apparent causality when it is the simultaneous combination of
multiple factors that is responsible. This explains, for instance, the
decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference
Glucosamine-Anchored Graphene Oxide Nanosheets: Fabrication, Ultraviolet Irradiation, and Electrochemical Properties
Glucosamine-Anchored Graphene Oxide Nanosheets: Fabrication, Ultraviolet Irradiation, and Electrochemical Properties
A biofunctionalized graphene oxide
(GO) nanosheet with improved physicochemical properties is useful
for electrocatalysis and sensor development. Herein, a new class of
functionalized GO with a chemically anchored biomolecule glucosamine
is developed. Structural and chemical analyses confirm the glucosamine
anchoring. Ultraviolet irradiation transforms the surface chemistry
of GO. Glucosamine-anchored GO nanosheets exhibit improved cyclic
voltammetric and amperometric sensing activity toward the model redox
probe, rutheniumÂ(II) and <i>N</i>-acetylneuraminic acid,
respectively. The biomolecular anchoring and ultraviolet irradiation
helped to tune and enhance the properties of GO, which may find multiple
applications in optimizing sensor platforms