281 research outputs found
On hypercharge flux and exotics in F-theory GUTs
We study SU(5) Grand Unified Theories within a local framework in F-theory
with multiple extra U(1) symmetries arising from a small monodromy group. The
use of hypercharge flux for doublet-triplet splitting implies massless exotics
in the spectrum that are protected from obtaining a mass by the U(1)
symmetries. We find that lifting the exotics by giving vacuum expectation
values to some GUT singlets spontaneously breaks all the U(1) symmetries which
implies that proton decay operators are induced. If we impose an additional
R-parity symmetry by hand we find all the exotics can be lifted while proton
decay operators are still forbidden. These models can retain the gauge coupling
unification accuracy of the MSSM at 1-loop. For models where the generations
are distributed across multiple curves we also present a motivation for the
quark-lepton mass splittings at the GUT scale based on a Froggatt-Nielsen
approach to flavour.Comment: 38 pages; v2: emphasised possibility of avoiding exotics in models
without a global E8 structure, added ref, journal versio
Wavefunctions and the Point of E8 in F-theory
In F-theory GUTs interactions between fields are typically localised at
points of enhanced symmetry in the internal dimensions implying that the
coefficient of the associated operator can be studied using a local
wavefunctions overlap calculation. Some F-theory SU(5) GUT theories may exhibit
a maximum symmetry enhancement at a point to E8, and in this case all the
operators of the theory can be associated to the same point. We take initial
steps towards the study of operators in such theories. We calculate
wavefunctions and their overlaps around a general point of enhancement and
establish constraints on the local form of the fluxes. We then apply the
general results to a simple model at a point of E8 enhancement and calculate
some example operators such as Yukawa couplings and dimension-five couplings
that can lead to proton decay.Comment: 46 page
Gauge coupling flux thresholds, exotic matter and the unification scale in F-SU(5) GUT
We explore the gauge coupling relations and the unification scale in F-theory
SU(5) GUT broken down to the Standard Model by an internal U(1)Y gauge flux. We
consider variants with exotic matter representations which may appear in these
constructions and investigate their role in the effective field theory model.
We make a detailed investigation on the conditions imposed on the extraneous
matter to raise the unification scale and make the color triplets heavy in
order to avoid fast proton decay. We also discuss in brief the implications on
the gaugino masses.Comment: 20 pages, 3 figures, references and extended comments on KK
thresholds effects adde
Adding Bupivacaine to High-potassium Cardioplegia Improves Function and Reduces Cellular Damage of Rat Isolated Hearts after Prolonged, Cold Storage
Background
Bupivacaine retards myocardial acidosis during ischemia. The authors measured function of rat isolated hearts after prolonged storage to determine whether bupivacaine improves cardiac protection compared with standard cardioplegia alone.
Methods
After measuring cardiac function on a Langendorff apparatus, hearts were perfused with cardioplegia alone (controls), cardioplegia containing 500 microm bupivacaine, or cardioplegia containing 2 mm lidocaine; were stored at 4 degrees C for 12 h; and were then reperfused. Heart rate and left ventricular developed pressures were measured for 60 min. Maximum positive rate of change in ventricular pressure, oxygen consumption, and lactate dehydrogenase release were also measured.
Results
All bupivacaine-treated, four of five lidocaine-treated, and no control hearts beat throughout the 60-min recovery period. Mean values of heart rate, left ventricular developed pressure, maximum positive rate of change in ventricular pressure, rate-pressure product, and efficiency in bupivacaine-treated hearts exceeded those of the control group (P < 0.001 at 60 min for all). Mean values of the lidocaine group were intermediate. Oxygen consumption of the control group exceeded the other groups early in recovery, but not at later times. Lactate dehydrogenase release from the bupivacaine group was less than that from the control group (P < 0.001) but did not differ from baseline.
Conclusions
Adding bupivacaine to a depolarizing cardioplegia solution reduces cell damage and improves cardiac function after prolonged storage. Metabolic inhibition may contribute to this phenomenon, which is not entirely explained by sodium channel blockade
What do People Value when they Negotiate? Mapping the Domain of Subjective Value in Negotiation
Four studies provide support for the development and validation of a framework for understanding the range of social psychological outcomes valued subjectively as consequences of negotiations. Study 1 inductively elicited and coded elements of subjective value among students, community members, and negotiation practitioners, revealing 20 categories that negotiation theorists in Study 2 sorted to reveal four underlying dimensions: Feelings about Instrumental Outcomes, the Self, Process, and Relationship. Study 3 proposed a new Subjective Value Inventory (SVI) questionnaire and confirmed its 4-factor structure, and Study 4 presents convergent, discriminant, and predictive validity data for this SVI. Results suggest the SVI is a promising tool to systematize and encourage research on the subjective outcomes of negotiation
Gauge sector statistics of intersecting D-brane models
In this article, which is based on the first part of my PhD thesis, I review
the statistics of the open string sector in T^6/(Z_2xZ_2) orientifold
compactifications of the type IIA string. After an introduction to the
orientifold setup, I discuss the two different techniques that have been
developed to analyse the gauge sector statistics, using either a saddle point
approximation or a direct computer based method. The two approaches are
explained and compared by means of eight- and six-dimensional toy models. In
the four-dimensional case the results are presented in detail. Special emphasis
is put on models containing phenomenologically interesting gauge groups and
chiral matter, in particular those containing a standard model or SU(5) part.Comment: 51 pages, 29 figures; v2: ref. added, version to appear in Fortsch.
Phys; v3: ref. adde
Rare variants in tenascin genes in a cohort of children with primary vesicoureteric reflux
Primary vesicoureteral reflux (PVUR) is the most common malformation of the kidney and urinary tract and reflux nephropathy is a major cause of chronic kidney disease in children. Recently, we reported mutations in tenascin XB (TNXB) as a cause of PVUR with joint hypermobility
Yukawa hierarchies at the point of in F-theory
We analyse the structure of Yukawa couplings in local SU(5) F-theory models
with enhancement. In this setting the symmetry is broken down to
SU(5) by a 7-brane configuration described by T-branes, all the Yukawa
couplings are generated in the vicinity of a point and only one family of
quarks and leptons is massive at tree-level. The other two families obtain
their masses when non-perturbative effects are taken into account, being
hierarchically lighter than the third family. However, and contrary to previous
results, we find that this hierarchy of fermion masses is not always
appropriate to reproduce measured data. We find instead that different T-brane
configurations breaking to SU(5) give rise to distinct hierarchical
patterns for the holomorphic Yukawa couplings. Only some of these patterns
allow to fit the observed fermion masses with reasonable local model parameter
values, adding further constraints to the construction of F-theory GUTs. We
consider an model where such appropriate hierarchy is realised and
compute its physical Yukawas, showing that realistic charged fermions masses
can indeed be obtained in this case.Comment: 46 pages + appendices, 5 figures. v2, added references and typos
corrected, version accepted on JHEP. v3, typos correcte
Confocal microscopy analysis reveals that only a small proportion of extracellular vesicles are successfully labelled with commonly utilised staining methods
Assessing genuine extracellular vesicle (EV) uptake is crucial for understanding the functional roles of EVs. This study measured the bona fide labelling of EVs utilising two commonly used fluorescent dyes, PKH26 and C5-maleimide-Alexa633. MCF7 EVs tagged with mEmerald-CD81 were isolated from conditioned media by size exclusion chromatography (SEC) and characterised using Nanoparticle Tracking Analysis (NTA), Transmission Electron Microscopy (TEM), MACsPlex immunocapture assay and immunoblots. These fluorescently tagged EVs were subsequently stained with C5-maleimide-Alexa633 or PKH26, according to published protocols. Colocalisation of dual-labelled EVs was assessed by confocal microscopy and quantified using the Rank-Weighted Colocalisation (RWC) algorithm. We observed strikingly poor colocalisation between mEmerald-CD81-tagged EVs and C5-Maleimide-Alexa633 (5.4%â±â1.8) or PKH26 (4.6%â±â1.6), that remained low even when serum was removed from preparations. Our data confirms previous work showing that some dyes form contaminating aggregates. Furthermore, uptake studies showed that maleimide and mEmerald-CD81-tagged EVs can be often located into non-overlapping subcellular locations. By using common methods to isolate and stain EVs we observed that most EVs remained unstained and most dye signal does not appear to be EV associated. Our work shows that there is an urgent need for optimisation and standardisation in how EV researchers use these tools to assess genuine EV signals
Supersymmetric Higgs and Radiative Electroweak breaking
We review the mechanism of radiative electroweak symmetry breaking taking
place in SUSY versions of the standard model. We further discuss different
proposals for the origin of SUSY-breaking and the corresponding induced
SUSY-breaking soft terms. Several proposals for the understanding of the little
hierarchy problem are critically discussed.Comment: To be published in Comptes Rendus de l'Academie des Science
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