282 research outputs found
Scalar Dark Matter Models with Significant Internal Bremsstrahlung
There has been interest recently on particle physics models that may give
rise to sharp gamma ray spectral features from dark matter annihilation.
Because dark matter is supposed to be electrically neutral, it is challenging
to build weakly interacting massive particle models that may accommodate both a
large cross section into gamma rays at, say, the Galactic center, and the right
dark matter abundance. In this work, we consider the gamma ray signatures of a
class of scalar dark matter models that interact with Standard Model dominantly
through heavy vector-like fermions (the vector-like portal). We focus on a real
scalar singlet S annihilating into lepton-antilepton pairs. Because this
two-body final-state annihilation channel is d-wave suppressed in the chiral
limit, we show that virtual internal bremsstrahlung emission of a gamma ray
gives a large correction, both today and at the time of freeze-out. For the
sake of comparison, we confront this scenario to the familiar case of a
Majorana singlet annihilating into light lepton-antilepton pairs, and show that
the virtual internal bremsstrahlung signal may be enhanced by a factor of (up
to) two orders of magnitude. We discuss the scope and possible generalizations
of the model.Comment: 25 pages, 10 figures, typos corrected, added references, matching
version accepted by JCA
Signatures from Scalar Dark Matter with a Vector-like Quark Mediator
We present a comprehensive study of a model where the dark matter is composed
of a singlet real scalar that couples to the Standard Model predominantly via a
Yukawa interaction with a light quark and a colored vector-like fermion. A
distinctive feature of this scenario is that thermal freeze-out in the early
universe may be driven by annihilation both into gluon pairs at one-loop ()
and by virtual internal Bremsstrahlung of a gluon (). Such a dark
matter candidate may also be tested through direct and indirect detection and
at the LHC; viable candidates have either a mass nearly degenerate with that of
the fermionic mediator or a mass above about 2 TeV.Comment: 30 pages, 10 figures. Matches published versio
Top-philic Vector-Like Portal to Scalar Dark Matter
We investigate the phenomenology of scalar singlet dark matter candidates
that couple dominantly to the Standard Model via a Yukawa interaction with the
top quark and a colored vector-like fermion. We estimate the viability of this
vector-like portal scenario with respect to the most recent bounds from dark
matter direct and indirect detection, as well as to dark matter and vector-like
mediator searches at colliders. Moreover, we take QCD radiative corrections
into account in all our theoretical calculations. This work complements
analyses related both to models featuring a scalar singlet coupled through a
vector-like portal to light quarks, and to scenarios in which the dark matter
is a Majorana singlet coupled to the Standard Model through scalar colored
particles (akin to simplified models inspired by supersymmetry). Our study puts
especially forward the complementarity of different search strategies from
different contexts, and we show that current experiments allow for testing dark
matter masses ranging up to 700 GeV and mediator masses ranging up to 6 TeV.Comment: 15 pages, 11 figures; version accepted by PR
Il corpo violato, il corpo liberato: autodistruzione e catarsi in La Muñeca menor di Rosario Ferré
La teoria sull’auto-riconoscimento dell’universo femminile elaborata da Hélène Cixous nel saggio La Risa de la Medusa (1975) unitamente ai meccanismi di alienazione postcoloniale analizzati da Franz Fanon ne I Dannati della terra (1961) hanno, a mio avviso, ispirato Rosario Ferré nell’elaborazione delle strategie letterarie adottate nel racconto La Muñeca menor. L’intento di Ferré è quello di demistificare e rovesciare il sistema patriarcale vigente attraverso una scrittura autobiografica, sovversiva e iraconda. La ribellione che caratterizza le eroine femminili de La Muñeca menor si compie attraverso la catarsi e la consunzione dei loro corpi. La loro autodistruzione liberatoria apre la strada a una vera e propria decolonizzazione dell’anima. La scrittrice portoricana si prefigge di mettere in luce attraverso il racconto le ripercussioni emotive generate dai processi coloniali. Ferré teorizza inoltre una nuova cosmogonia in cui le donne portoricane, doppiamente vittime del sistema coloniale e patriarcale, possano rivestire un ruolo attivo e partecipativo.The theory of self-recognition of the female universe elaborated by Hélène Cixous in the essay The laugh of the Medusa1975) together with the mechanisms of postcolonial alienation analyzed by Franz Fanon in The Damned of the Earth (1961) have, in my opinion, inspired Rosario Ferré in the elaboration of the literary strategies adopted in her short story La Muñeca menor. Ferré’s intention is to demystify and overturn the patriarchal system in force through an autobiographical, subversive, and angry writing. The rebellion of the female heroines is accomplished through catharsis and the consumption of their bodies. Their liberating self-destruction opens the way to a real decolonization of the soul. The Puerto Rican author aims to highlight in the short story the emotional repercussions generated by colonial processes. Rosario Ferré also theorizes a new cosmogony in which Puerto Rican women, doubly victims of the colonial and patriarchal system, can play a more active and participatory role
Radiative corrections to vectorlike portal dark matter
A massive real scalar dark matter particle can couple to Standard Model
leptons or quarks through a vector-like fermionic mediator , a scenario
known as the Vector-like portal. Due to helicity suppression of the
annihilation cross section into a pair of SM fermions, it has been shown in
previous works that radiative corrections, either at one-loop or through
radiation of gauge bosons, may play a significant role both in determining the
relic abundance and for indirect detection. All previous works considered the
limit of massless final state quarks or leptons. In this work, we focus on a
technical issue, which is to reliably determine the annihilation cross sections
taking into account finite fermion masses. Following previous works in the
framework of simplified supersymmetric dark matter scenarios, and building on
an analogy with Higgs decay into fermions, we address the issue of infrared and
collinear divergences that plagues the cross section by adopting an effective
operator description, which captures most of the relevant physics and give
explicit expressions for the annihilation cross sections. We then develop
several approximations for the differential and total cross sections, which
simplify greatly their expressions, and which can then be used in various
phenomenological studies of similar models. Finally, we describe our method to
compute the final gamma-ray spectrum, including hadronisation of the heavy
fermions, and provide some illustrative spectra for specific dark matter
candidates.Comment: 25 pages, 12 figures. One extra figure. Conclusions unchanged.
Version published in PR
Candida albicans infections in renal transplant recipients: effect of caspofungin on polymorphonuclear cells.
This study aimed to compare the caspofungin immunomodulating activities against Candida albicans on polymorphonuclear cells (PMNs) from renal transplant recipients (RTRs) and healthy subjects (HSs). RTR PMNs showed a significantly reduced fungicidal activity compared with that of HS PMNs. Addition of caspofungin to RTR PMNs significantly potentiated the yeast intracellular killing rate, achieving values similar to those observed for HS PMNs. These data show that caspofungin is suitable for invasive candidiasis treatment in patients with immune system-impaired components
A best-practice position statement on pregnancy after kidney transplantation: focusing on the unsolved questions. The Kidney and Pregnancy Study Group of the Italian Society of Nephrology
Kidney transplantation (KT) is often considered to be the method best able to restore fertility in a woman with chronic kidney disease (CKD). However, pregnancies in KT are not devoid of risks (in particular prematurity, small for gestational age babies, and the hypertensive disorders of pregnancy). An ideal profile of the potential KT mother includes “normal” or “good” kidney function (usually defined as glomerular filtration rate, GFR ≥ 60 ml/min), scant or no proteinuria (usually defined as below 500 mg/dl), normal or well controlled blood pressure (one drug only and no sign of end-organ damage), no recent acute rejection, good compliance and low-dose immunosuppression, without the use of potentially teratogen drugs (mycophenolic acid and m-Tor inhibitors) and an interval of at least 1–2 years after transplantation. In this setting, there is little if any risk of worsening of the kidney function. Less is known about how to manage “non-ideal” situations, such as a pregnancy a short time after KT, or one in the context of hypertension or a failing kidney. The aim of this position statement by the Kidney and Pregnancy Group of the Italian Society of Nephrology is to review the literature and discuss what is known about the clinical management of CKD after KT, with particular attention to women who start a pregnancy in non-ideal conditions. While the experience in such cases is limited, the risks of worsening the renal function are probably higher in cases with markedly reduced kidney function, and in the presence of proteinuria. Well-controlled hypertension alone seems less relevant for outcomes, even if its effect is probably multiplicative if combined with low GFR and proteinuria. As in other settings of kidney disease, superimposed preeclampsia (PE) is differently defined and this impairs calculating its real incidence. No specific difference between non-teratogen immunosuppressive drugs has been shown, but calcineurin inhibitors have been associated with foetal growth restriction and low birth weight. The clinical choices in cases at high risk for malformations or kidney function impairment (pregnancies under mycophenolic acid or with severe kidney-function impairment) require merging clinical and ethical approaches in which, beside the mother and child dyad, the grafted kidney is a crucial “third element”
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