112 research outputs found
Muon to electron conversion in the Littlest Higgs model with T-parity
Little Higgs models provide a natural explanation of the little hierarchy
between the electroweak scale and a few TeV scale, where new physics is
expected. Under the same inspiring naturalness arguments, this work completes a
previous study on lepton flavor-changing processes in the Littlest Higgs model
with T-parity exploring the channel that will eventually turn out to be the
most sensitive, \mu-e conversion in nuclei. All one-loop contributions are
carefully taken into account, results for the most relevant nuclei are provided
and a discussion of the influence of the quark mixing is included. The results
for the Ti nucleus are in good agreement with earlier work by Blanke et al.,
where a degenerate mirror quark sector was assumed. The conclusion is that,
although this particular model reduces the tension with electroweak precision
tests, if the restrictions on the parameter space derived from lepton flavor
violation are taken seriously, the degree of fine tuning necessary to meet
these constraints also disfavors this model.Comment: 26 pages, 7 figures, 4 tables; discussion improved, results
unchanged, one reference added, version to appear in JHE
Response to imatinib rechallenge in a patient with a recurrent gastrointestinal stromal tumor after adjuvant therapy: a case report
<p>Abstract</p> <p>Introduction</p> <p>Adjuvant imatinib improves recurrence-free survival of patients following resection of primary KIT-positive gastrointestinal stromal tumors. However, it is unknown whether patients who previously received adjuvant imatinib therapy will respond to imatinib rechallenge as treatment for recurrent disease. Here we present the first report documenting the benefits of imatinib rechallenge in a patient previously exposed to imatinib during adjuvant treatment.</p> <p>Case presentation</p> <p>A 51-year-old Asian woman with a wedge-resected primary gastric gastrointestinal stromal tumor at high risk of relapse underwent two years of adjuvant treatment with imatinib. Only 10 months after the completion of adjuvant imatinib treatment, a computed tomography scan revealed gastrointestinal stromal tumor recurrence in this patient, with multiple peritoneal nodules in the upper abdomen being detected. Our patient was rechallenged with imatinib 400 mg/day and had a partial response after one month of treatment. Imatinib rechallenge was well tolerated by our patient; the only adverse events she experienced were grade 1 edema, anemia and fatigue. Our patient maintained a partial response two years and six months after the imatinib rechallenge. However, computed tomography scans three months later showed that our patient had disease progression.</p> <p>Conclusions</p> <p>This case report demonstrates that a patient with a gastrointestinal stromal tumor who had previously received adjuvant imatinib therapy responded to imatinib rechallenge as treatment for her recurrent disease. These results indicate that imatinib sensitivity can be maintained in a patient with previous exposure to adjuvant imatinib therapy.</p
Top Partner Discovery in the channel at the LHC
In this paper we study the discovery potential of the LHC run II for heavy
vector-like top quarks in the decay channel to a top and a boson. Despite
the usually smaller branching ratio compared to charged-current decays, this
channel is rather clean and allows for a complete mass reconstruction of the
heavy top. The latter is achieved in the leptonic decay channel of the
boson and in the fully hadronic top channel using boosted jet and jet
substructure techniques. To be as model-independent as possible, a simplified
model approach with only two free parameters has been applied. The results are
presented in terms of parameter space regions for evidence or
discovery for such new states in that channel.Comment: 24 pages, 8 figures, version 2 updated to JHEP 01 (2015) 08
Event-related alpha suppression in response to facial motion
This article has been made available through the Brunel Open Access Publishing Fund.While biological motion refers to both face and body movements, little is known about the visual perception of facial motion. We therefore examined alpha wave suppression as a reduction in power is thought to reflect visual activity, in addition to attentional reorienting and memory processes. Nineteen neurologically healthy adults were tested on their ability to discriminate between successive facial motion captures. These animations exhibited both rigid and non-rigid facial motion, as well as speech expressions. The structural and surface appearance of these facial animations did not differ, thus participants decisions were based solely on differences in facial movements. Upright, orientation-inverted and luminance-inverted facial stimuli were compared. At occipital and parieto-occipital regions, upright facial motion evoked a transient increase in alpha which was then followed by a significant reduction. This finding is discussed in terms of neural efficiency, gating mechanisms and neural synchronization. Moreover, there was no difference in the amount of alpha suppression evoked by each facial stimulus at occipital regions, suggesting early visual processing remains unaffected by manipulation paradigms. However, upright facial motion evoked greater suppression at parieto-occipital sites, and did so in the shortest latency. Increased activity within this region may reflect higher attentional reorienting to natural facial motion but also involvement of areas associated with the visual control of body effectors. © 2014 Girges et al
Evidence against a Human Cell-Specific Role for LRP6 in Anthrax Toxin Entry
The role of the cellular protein LRP6 in anthrax toxin entry is controversial. Previous studies showed that LRP6 was important for efficient intoxication of human M2182 prostate carcinoma cells but other studies performed with cells from gene-knockout mice demonstrated no role for either LRP6 or the related LRP5 protein in anthrax toxin entry. One possible explanation for this discrepancy is that LRP6 may be important for anthrax toxin entry into human, but not mouse, cells. To test this idea we have investigated the effect of knocking down LRP6 or LRP5 expression with siRNAs in human HeLa cells. We show here that efficient knockdown of either LRP6, LRP5, or both proteins has no influence on the kinetics of anthrax lethal toxin entry or MEK1 substrate cleavage in these cells. These data argue against a human-specific role for LRP6 in anthrax toxin entry and suggest instead that involvement of this protein may be restricted to certain cell types independently of their species of origin
Effective Lagrangian approach to neutrinoless double beta decay and neutrino masses
Neutrinoless double beta () decay can in general produce
electrons of either chirality, in contrast with the minimal Standard Model (SM)
extension with only the addition of the Weinberg operator, which predicts two
left-handed electrons in the final state. We classify the lepton number
violating (LNV) effective operators with two leptons of either chirality but no
quarks, ordered according to the magnitude of their contribution to \znbb
decay. We point out that, for each of the three chirality assignments, and , there is only one LNV operator of the corresponding type
to lowest order, and these have dimensions 5, 7 and 9, respectively. Neutrino
masses are always induced by these extra operators but can be delayed to one or
two loops, depending on the number of RH leptons entering in the operator.
Then, the comparison of the decay rate and neutrino masses
should indicate the effective scenario at work, which confronted with the LHC
searches should also eventually decide on the specific model elected by nature.
We also list the SM additions generating these operators upon integration of
the heavy modes, and discuss simple realistic examples of renormalizable
theories for each case.Comment: Accepted for publication. Few misprints corrected and new references
adde
Lepton flavor violation in the Simplest Little Higgs model
The flavor sector of Little Higgs models based on product groups, notably the
Littlest Higgs with T parity (LHT), has been extensively studied and some
amount of fine tuning was found to be required to meet the experimental
constraints. However, no such attention has been paid to other classes of
models. Here we analyze the phenomenology of flavor mixing in the lepton sector
of a simple group model, the Simplest Little Higgs (SLH). We obtain the Feynman
rules of the SLH in the 't Hooft-Feynman gauge up to the necessary order and
calculate the leading contributions to the rare processes mu -> e gamma, mu ->
eee and mu-e conversion in nuclei. We find results comparable to those of the
LHT model, because in both cases they arise at the one-loop level. These
require the flavor alignment of the Yukawa couplings of light and heavy leptons
at the per cent level or an effective scale of around 10 TeV.Comment: 41 pages, 8 figures; minor changes and one reference added, version
to appear in JHE
Supersymmetric contributions to and decays in SCET
We study the decay modes and using Soft Collinear Effective Theory. Within Standard Model and
including the error due to the SU(3) breaking effect in the SCET parameters we
find that BR and BR
corresponding to
solution 1 and solution 2 of the SCET parameters respectively.For the decay
mode , we find that BR and BR corresponding to solution 1 and
solution 2 of the SCET parameters respectively. We extend our study to include
supersymmetric models with non-universal A-terms where the dominant
contributions arise from diagrams mediated by gluino and chargino exchanges. We
show that gluino contributions can not lead to an enhancement of the branching
ratios of and . In
addition, we show that SUSY contributions mediated by chargino exchange can
enhance the branching ratio of by about 14% with
respect to the SM prediction. For the branching ratio of , we find that SUSY contributions can enhance its value by about 1% with
respect to the SM prediction.Comment: 25 pages,5 figures, version accepted for publicatio
Helicobacter pylori Counteracts the Apoptotic Action of Its VacA Toxin by Injecting the CagA Protein into Gastric Epithelial Cells
Infection with Helicobacter pylori is responsible for gastritis and gastroduodenal ulcers but is also a high risk factor for the development of gastric adenocarcinoma and lymphoma. The most pathogenic H. pylori strains (i.e., the so-called type I strains) associate the CagA virulence protein with an active VacA cytotoxin but the rationale for this association is unknown. CagA, directly injected by the bacterium into colonized epithelium via a type IV secretion system, leads to cellular morphological, anti-apoptotic and proinflammatory effects responsible in the long-term (years or decades) for ulcer and cancer. VacA, via pinocytosis and intracellular trafficking, induces epithelial cell apoptosis and vacuolation. Using human gastric epithelial cells in culture transfected with cDNA encoding for either the wild-type 38 kDa C-terminal signaling domain of CagA or its non-tyrosine-phosphorylatable mutant form, we found that, depending on tyrosine-phosphorylation by host kinases, CagA inhibited VacA-induced apoptosis by two complementary mechanisms. Tyrosine-phosphorylated CagA prevented pinocytosed VacA to reach its target intracellular compartments. Unphosphorylated CagA triggered an anti-apoptotic activity blocking VacA-induced apoptosis at the mitochondrial level without affecting the intracellular trafficking of the toxin. Assaying the level of apoptosis of gastric epithelial cells infected with wild-type CagA+/VacA+ H. pylori or isogenic mutants lacking of either CagA or VacA, we confirmed the results obtained in cells transfected with the CagA C-ter constructions showing that CagA antagonizes VacA-induced apoptosis. VacA toxin plays a role during H. pylori stomach colonization. However, once bacteria have colonized the gastric niche, the apoptotic action of VacA might be detrimental for the survival of H. pylori adherent to the mucosa. CagA association with VacA is thus a novel, highly ingenious microbial strategy to locally protect its ecological niche against a bacterial virulence factor, with however detrimental consequences for the human host
- …